WO2022024578A1

WO2022024578A1 - Egr system

Info

Publication number: WO2022024578A1
Application number: PCT/JP2021/023079
Authority: WO
Inventors: 衛吉岡; 海翔曹; 崇別所; 伸二河井
Original assignee: 愛三工業株式会社
Priority date: 2020-07-27
Filing date: 2021-06-17
Publication date: 2022-02-03

Abstract

This EGR system comprises an EGR valve (14) that adjusts the flow rate of an EGR gas in an EGR passage (12), an EGR cooler (13) including a heat exchanger (32) that conducts heat exchange between the EGR gas flowing through the EGR passage (12) and engine cooling water in order to cool the EGR gas, a bypass passage (16) that allows the EGR gas to bypass the heat exchanger (32) of the EGR cooler (13), a bypass valve (17) that opens and closes the bypass passage (16), and an EGR gas distributor (15) that is made of resin and is provided downstream of the EGR cooler (13) and the bypass passage (16). The bypass valve (17) includes a valve body (21) and an actuator (22) that is configured so as to change from opening the valve body (21) to closing the valve body (21) when the temperature of the EGR gas or the temperature of the cooling water is equal to or greater than a first prescribed value.

Description

EGR system

The technology disclosed in this specification relates to an EGR system configured to flow a part of the exhaust gas discharged from the engine to the exhaust passage as EGR gas to the intake passage through the EGR passage and return it to the engine.

Conventionally, as this kind of technology, for example, the technology "exhaust heat recovery device" described in Patent Document 1 below is known. This exhaust heat recovery device is a heat exchanger that exchanges heat between the exhaust gas and the medium (cooling water) in an exhaust system such as an internal combustion engine (engine), and a bypass path in which the exhaust gas bypasses the heat exchanger. It is provided with a (bypass passage) and a valve body (bypass valve) that opens and closes the bypass passage. The bypass valve has a valve body that opens the bypass passage from the closed state against the urging force of the urging body (spring) when the flow rate of the exhaust gas exceeds the predetermined value, and the temperature of the cooling water exceeds the predetermined value. It includes a temperature-operated (temperature-sensitive) actuator that opens the valve body, and the valve body opens when at least one of the exhaust gas flow rate and the cooling water temperature exceeds a predetermined value. There is.

International Publication No. 2006/090725

However, in the exhaust heat recovery device described in Patent Document 1, the bypass valve opens when the exhaust gas has a large flow rate or the cooling water is at a high temperature, and the exhaust gas bypasses the heat exchanger. If a resin exhaust component is provided downstream of the exhaust component, there is a risk of melting damage due to high heat in the exhaust component.

Here, the same configuration as the exhaust heat recovery device described above is embodied in an EGR system in which a part of the exhaust gas discharged from the engine to the exhaust passage is passed as EGR gas to the intake passage through the EGR passage and returned to the engine. can do. This EGR system is provided in an EGR passage, and has an EGR cooler having a heat exchanger using engine cooling water as a medium, a bypass passage that bypasses the EGR cooler, a bypass valve that opens and closes the bypass passage, and an EGR cooler and a bypass. A resin EGR passage or a resin EGR gas distributor constituting the downstream EGR passage downstream from the passage is provided. In this EGR system, when the EGR gas is hot or the cooling water is hot, the bypass valve opens and the hot EGR gas bypasses the EGR cooler (heat exchanger) and flows through the bypass passage, and the downstream EGR There is a risk that the EGR passages or EGR gas distributors made of resin that constitute the passages will flow to the EGR passages or EGR gas distributors made of resin, and the EGR passages or EGR gas distributors will be melted due to high heat. Further, in the downstream EGR passage, if EGR gas flows during unwarming, condensed water may be generated inside.

This disclosure technique was made in view of the above circumstances, and the purpose is to reduce the high temperature EGR gas flowing from the exhaust passage to the EGR passage to an appropriate temperature in the above-mentioned EGR system, and to make the resin. The purpose is to allow the gas to flow into the downstream EGR passage and suppress the melting damage of the downstream EGR passage and the generation of condensed water in the downstream EGR passage.

(1) In order to achieve the above object, the aspect of the present invention is configured so that a part of the exhaust gas discharged from the engine to the exhaust passage is passed as EGR gas to the intake passage through the EGR passage and returned to the engine. In the EGR system, an EGR valve for adjusting the flow rate of EGR gas in the EGR passage and a heat exchanger that exchanges heat between the EGR gas and the cooling water of the engine to cool the EGR gas flowing in the EGR passage. An EGR cooler including, a bypass passage for bypassing a part of EGR gas flowing to the heat exchanger of the EGR cooler in the EGR passage, a bypass valve for opening and closing the bypass passage, and a downstream of the EGR cooler and the bypass passage. The downstream EGR passage is composed of a resin material, and the bypass valve is provided when the temperature of the valve body and the EGR gas, the temperature of the downstream EGR passage, or the temperature of the cooling water becomes equal to or higher than the first predetermined value. The purpose is to include an actuator configured to close the valve body from the open state.

According to the configuration of (1) above, the valve body of the bypass valve is opened by the actuator when EGR is executed in which the temperature of the EGR gas, the temperature of the downstream EGR passage, or the temperature of the cooling water becomes less than the first predetermined value. It becomes. At this time, a part of the EGR gas flowing from the exhaust passage to the EGR passage flows to the bypass passage, and the rest flows to the heat exchanger. Then, these two flows merge at the downstream EGR passage and flow through the downstream EGR passage. Therefore, even if a high-temperature EGR gas flows from the exhaust passage to the EGR passage, the EGR gas flowing through the bypass passage among the EGR gas is heated by the heat exchanger and merges with the EGR gas whose temperature has dropped. EGR gas that has dropped to an appropriate temperature flows to the downstream EGR passage. On the other hand, when the temperature of the EGR gas, the temperature of the downstream EGR passage, or the temperature of the cooling water becomes equal to or higher than the first predetermined value after the engine is warmed up, the valve body of the bypass valve is closed from the opened state by the actuator. Therefore, almost all of the EGR gas flowing from the exhaust passage to the EGR passage flows to the heat exchanger of the EGR cooler, heat is exchanged by the heat exchanger and the temperature drops to an appropriate temperature, and the EGR gas having an appropriate temperature flows to the downstream EGR passage. Flow to.

(2) In order to achieve the above object, it is preferable that the actuator operates in response to a change in temperature in the configuration of the above (1).

According to the configuration of (2) above, in addition to the operation of the configuration of (1) above, the actuator of the bypass valve operates in response to a change in temperature, so that it is not necessary to electrically control the bypass valve and the bypass is bypassed. The configuration for the valve is simplified.

(3) In order to achieve the above object, in the configuration of the above (1), it is preferable that the actuator is configured to open the valve body under the condition that the EGR valve is fully closed.

According to the configuration of (3) above, in addition to the operation of the configuration of (1) above, when the actuator of the bypass valve opens the valve body under the condition that the EGR valve is fully closed, the valve body closes. When present, the flow of condensed water accumulated downstream of the bypass valve upstream of the bypass valve is allowed.

(4) In order to achieve the above object, in any of the above configurations (1) to (3), the heat exchanger includes an outlet through which the EGR gas flows, and the bypass passage is adjacent to the outlet of the heat exchanger. The bypass valve further includes a plate-like valve body and a rotating shaft that rotates the valve body, and the valve body and the rotating shaft are located at the outlet of the bypass passage. Correspondingly arranged, the valve body is configured to open and close the outlet of the bypass passage by rotating the rotating shaft, and the rotating shaft is provided with a sealing member for preventing leakage of EGR gas to the outside. The bypass valve is placed in a position where the valve body is parallel to the axial direction of the heat exchanger or tilted downstream toward the heat exchanger when the valve body closes the outlet of the bypass passage. At the time of opening the valve that opens the outlet of the bypass passage, it is preferable that the valve body is arranged at a position that blocks a part of the flow path area of the outlet of the heat exchanger and narrows the flow path area.

According to the configuration of (4) above, in addition to the action of any of the configurations (1) to (3) above, when the bypass valve is closed, almost all of the EGR gas flowing from the exhaust passage to the EGR passage exchanges heat. It flows into the vessel, is cooled, flows out from its outlet, flows along the valve body of the bypass valve, and flows toward the downstream EGR passage. On the other hand, when the bypass valve is opened, the valve body blocks a part of the flow path area at the outlet of the heat exchanger and the flow path area becomes narrow. Therefore, the flow rate of the cooled EGR gas flowing out of the heat exchanger decreases as the flow path area at the outlet of the heat exchanger becomes narrower, and the ratio of the flow rate of the uncooled EGR gas flowing out of the bypass passage to the flow rate decreases. The amount increases, and the temperature of the EGR gas flowing to the downstream EGR passage becomes high.

(5) In order to achieve the above object, in the configuration of (4) above, a gap is provided between the boundary portion between the outlet of the heat exchanger and the outlet of the bypass passage and the valve body or the rotating shaft, and the gap is provided. Is preferably configured to be larger when the valve body is opened than when the valve body is closed.

According to the configuration of the above (5), in addition to the action of the configuration of the above (4), the gap between the boundary portion and the valve body or the rotating shaft is larger than that at the time of opening the valve body of the bypass valve when the valve body is closed. As the size becomes smaller, the EGR gas in the bypass passage is less likely to leak to the outlet side of the heat exchanger through the gap. On the other hand, the gap becomes larger when the valve body is opened than when the valve is closed, so that the condensed water discharged from the outlet of the heat exchanger easily flows into the gap. Further, since a part of the flow path area at the outlet of the heat exchanger is blocked by the valve body, the scattering of the condensed water discharged from the outlet is suppressed.

(6) In order to achieve the above object, in any of the above configurations (1) or (3) to (5), the bypass valve further includes a valve closing spring that urges the valve body in the valve closing direction. The actuator includes a stator including a coil, a rotor rotatably arranged at the center of the stator, a drive shaft rotatably connected to the rotor via a screw mechanism, and a drive shaft. It is equipped with a shaft spring that urges in the axial direction, and the rotation shaft and the drive shaft of the actuator are connected via a link in order to rotate the rotation shaft of the bypass valve, and the shaft spring links the drive shaft and the rotation shaft. It is preferable that the valve body is configured to urge the valve body in the valve closing direction.

According to the configuration of (6) above, in addition to the action of any of the configurations (1) or (3) to (5) above, the bypass valve has a valve closing spring that urges the valve body in the valve closing direction. Including, the actuator includes a shaft spring that urges the valve body in the valve closing direction via the link and the rotating shaft of the drive shaft. Therefore, the urging force of the valve closing spring and the urging force of the shaft spring always act on the valve body of the bypass valve in the valve closing direction, and the valve closing of the valve body is assisted.

(7) In order to achieve the above object, in the configuration of the above (6), the disconnection detecting means for detecting the disconnection of the coil and the EGR control means for controlling the recirculation of the EGR gas are further provided, and EGR It is preferable that the control means changes at least one of the condition for starting the opening of the EGR valve and the maximum opening degree in order to control the recirculation of the EGR gas according to the detection result of the disconnection detecting means.

According to the configuration of (7) above, in addition to the operation of the configuration of (6) above, when the disconnection of the coil of the actuator is detected by the disconnection detecting means, the EGR valve is used to control the recirculation of the EGR gas. At least one of the valve opening start condition and the maximum opening degree is changed by the EGR control means. Therefore, if the actuator does not operate normally due to the disconnection of the coil, the condition for starting the valve opening of the EGR valve is changed, so that the EGR gas does not flow to the EGR cooler before warming up, and the maximum opening of the EGR valve is changed. As a result, a large amount of high-temperature EGR gas does not flow into the downstream EGR passage.

(8) In order to achieve the above object, in any of the above configurations (1) to (3), the EGR cooler includes a housing, and at least a part of the bypass passage is provided integrally with the housing of the EGR cooler. It is preferable that the bypass valve is provided in a bypass passage integrally provided with the housing of the EGR cooler, and a cooling water passage through which cooling water flows is provided around the bypass valve.

According to the configuration of (8) above, in addition to the operation of any of the configurations (1) to (3) above, a bypass valve is provided in the bypass passage provided integrally with the housing of the EGR cooler, and is around the bypass valve. Is provided with a cooling water passage through which cooling water flows. Therefore, when the actuator of the bypass valve operates in response to a change in temperature, the actuator operates in response to a change in the temperature of the cooling water flowing through the cooling water passage, and the valve body of the bypass valve operates as cooling water. It will open and close according to the temperature change of.

(9) In order to achieve the above object, in any one of the above (1) to (3) or the configuration of (8), the EGR valve includes a housing made of an aluminum material, and the bypass valve is an EGR valve. It is preferable that it is provided integrally with the housing of.

According to the configuration of the above (9), in addition to the action of any one of the above (1) to (3) or the configuration of (8), the housing of the EGR valve is formed of an aluminum material, so that the thermal conductivity is good. .. Further, the bypass valve is provided integrally with the housing of the EGR valve. Therefore, when the actuator of the bypass valve operates in response to a change in temperature, the valve body of the bypass valve opens and closes in response to the change in temperature of the housing of the EGR valve.

(10) In order to achieve the above object, in any of the configurations (1) to (9) above, when the EGR cooler is mounted on the vehicle, the bypass passage is vertically downward with respect to the EGR cooler. It is preferably arranged so that its upstream side inclines vertically downward toward the exhaust passage.

According to the configuration of (10) above, in addition to the action of any of the configurations (1) to (9) above, the bypass passage is vertically downward with respect to the EGR cooler when the EGR cooler is mounted on the vehicle. Since it is arranged on the side, the condensed water generated by the EGR cooler can flow down to the bypass passage due to its own weight. Further, since the upstream side of the bypass passage is inclined downward in the vertical direction toward the exhaust passage, the condensed water flowing down to the bypass passage can flow down to the exhaust passage due to its own weight.

(11) In order to achieve the above object, in any of the above configurations (1) to (10), it is preferable that the EGR cooler and the bypass passage are adjacent to each other via a partition wall.

According to the configuration of (11) above, in addition to the action of any of the configurations (1) to (10) above, the EGR cooler and the bypass passage are adjacent to each other via the partition wall, so that the EGR cooler and the bypass passage are connected to each other. Heat exchange is possible through the partition wall between them.

(12) In order to achieve the above object, in the configuration of the above (11), the partition wall includes a main wall portion in contact with the heat exchanger and a downstream wall portion extending downstream from the heat exchanger, and the downstream wall portion. Is preferably provided with at least one communication hole that communicates from the EGR cooler to the bypass passage.

According to the configuration of the above (12), in addition to the action of the configuration of the above (11), the condensed water flowing out from the heat exchanger by the EGR cooler has its own weight from the communication hole to the bypass passage at the downstream wall portion of the partition wall. Makes it easier to flow down.

(13) In order to achieve the above object, in the configuration of the above (12), the communication hole is arranged at a position facing the valve body of the bypass valve, and when the bypass valve is closed, the valve body and the downstream wall portion are connected to each other. It is preferable to function as a relief hole to avoid interference.

According to the configuration of the above (13), in addition to the action of the configuration of the above (12), the communication hole functions as a relief hole for avoiding interference between the valve body and the downstream wall portion when the bypass valve is closed. Even if the valve body operates excessively during valve operation, it does not come into contact with the downstream wall.

(14) In order to achieve the above object, in any of the above configurations (11) to (13), the EGR cooler is provided with a plurality of fins adjacent to the partition wall and parallel to the flow direction of the EGR gas. It is preferable to be.

According to the configuration of (14) above, in addition to the action of any of the configurations (11) to (13) above, in the EGR cooler, a plurality of fins parallel to the flow direction of the EGR gas are adjacent to the partition wall. Is provided. Therefore, the heat of the EGR gas flowing through the bypass passage is transferred to the fins through the partition wall, the fins are warmed, and the condensed water adhering to the fins is warmed.

(15) In order to achieve the above object, in any of the above configurations (11) to (14), the bypass passage is provided with a plurality of fins in contact with the partition wall and parallel to the flow direction of the EGR gas. Is preferable.

According to the configuration of (15) above, in addition to the action of any of the configurations (11) to (14) above, a plurality of fins parallel to the flow direction of EGR gas are adjacent to the partition wall in the bypass passage. Is provided. Therefore, the heat of the EGR gas flowing through the bypass passage is transferred to the partition wall through the fins, and the EGR cooler is warmed.

(16) In order to achieve the above object, in any of the above configurations (1) to (15), a sub-bypass passage for bypassing the EGR gas flowing to the bypass valve in the bypass passage is further provided, and the sub-bypass passage is provided. Is preferably provided with a sub-bypass valve that opens when the outside air temperature becomes less than the second predetermined value.

According to the configuration of (16) above, in addition to the operation of any of the configurations (1) to (15) above, a sub-bypass passage for bypassing the EGR gas flowing to the bypass valve is provided in the bypass passage, and the sub-bypass passage is provided. The sub-bypass valve provided in the bypass passage opens when the outside air temperature becomes less than the second predetermined value. Therefore, even when the bypass valve is closed, when the outside air temperature becomes less than the second predetermined value, the sub-bypass valve is opened and the EGR gas flows to the downstream side through the bypass passage and the sub-bypass passage. It merges with the EGR gas cooled by the EGR cooler, and the temperature of the EGR gas flowing to the downstream EGR passage increases.

(17) In order to achieve the above object, in any of the above configurations (1) to (16), temperature detection for detecting the temperature of the downstream EGR passage or the temperature of the EGR gas flowing through the downstream EGR passage. Further, the means and the first control means for controlling the EGR valve based on the detection value of the temperature detecting means are further provided, and in the first control means, the temperature detected by the temperature detecting means is the allowable heating temperature of the downstream EGR passage. When the temperature exceeds the above, it is preferable to forcibly control the EGR valve to the fully closed position or the intermediate opening degree.

According to the configuration of (17) above, in addition to the action of any of the configurations (1) to (16) above, the temperature of the downstream EGR passage detected by the temperature detecting means or the EGR gas flowing through the downstream EGR passage. When the temperature of the EGR passage exceeds the allowable heating temperature of the downstream EGR passage, the first control means forcibly controls the EGR valve to the fully closed position or the intermediate opening degree. Therefore, the flow of EGR gas in the EGR passage is immediately cut off or reduced, and excessive heating exceeding the allowable heating temperature of the downstream EGR passage is immediately stopped.

(18) In order to achieve the above object, in any of the above configurations (1) to (17), temperature detection for detecting the temperature of the downstream EGR passage or the temperature of the EGR gas flowing through the downstream EGR passage. Further, the means and the second control means for controlling the EGR valve based on the detection value of the temperature detection means are further provided, and the second control means is downstream when the temperature detected by the temperature detection means is equal to or higher than the third predetermined value. When the temperature is lower than the heat resistant temperature of the EGR passage, it is preferable to control the EGR valve to a normal opening degree.

According to the configuration of (18) above, in addition to the action of any of the configurations (1) to (17) above, the temperature of the downstream EGR passage detected by the temperature detecting means or the EGR gas flowing through the downstream EGR passage. When the temperature of the EGR valve is equal to or higher than the third predetermined value and is lower than the heat resistant temperature of the downstream EGR passage, the second control means controls the EGR valve to a normal opening degree. Therefore, the flow rate of the EGR gas flowing through the EGR passage is appropriately adjusted, and the flow rate of the EGR gas flowing to the downstream EGR passage is suppressed to a flow rate that does not exceed the heat resistant temperature.

(19) In order to achieve the above object, in the configuration of the above (3), the actuator operates electrically to detect the temperature of the downstream EGR passage or the temperature of the EGR gas flowing through the downstream EGR passage. Further, a temperature detecting means and a third control means for controlling the bypass valve based on the detection value of the temperature detecting means are further provided. It is preferable to control the actuator so that the bypass valve is closed when the allowable temperature is exceeded.

According to the configuration of the above (19), in addition to the action of the configuration of the above (3), the temperature of the downstream EGR passage detected by the temperature detecting means or the temperature of the EGR gas flowing through the downstream EGR passage is the temperature of the downstream EGR passage. When the heating allowable temperature is exceeded, the third control means controls the actuator so as to close the bypass valve. Therefore, most of the EGR gas flowing through the EGR passage is cooled by the EGR cooler without flowing to the bypass passage, and then flows to the downstream EGR passage.

(20) In order to achieve the above object, it is preferable that the bypass valve is configured to be closed when the actuator is turned off and not operated in the configuration of the above (19).

According to the configuration of (20) above, in addition to the operation of the configuration of (19) above, the bypass valve is closed when the actuator is turned off and not operated, so that the bypass valve is bypassed even if the actuator fails and does not operate. The valve is kept closed.

According to the configuration (1) above, in the EGR system, the high-temperature EGR gas flowing from the exhaust passage to the EGR passage can be lowered to an appropriate temperature and flowed to the downstream EGR passage made of a resin material. It is possible to suppress the melting damage of the downstream EGR passage and the generation of condensed water in the downstream EGR passage.

According to the configuration of (2) above, in addition to the effect of the configuration of (1) above, the product cost as an EGR system can be suppressed.

According to the configuration of the above (3), in addition to the effect of the configuration of the above (1), when the bypass valve is closed, the condensed water accumulated downstream from the bypass valve is completely closed to the EGR valve. Under the conditions, it can flow upstream from the bypass valve by its own weight.

According to the configuration of (4) above, in addition to the effect of the configuration of (1) or (3) above, when the bypass valve is closed, the valve body of the bypass valve can be cooled with cooled EGR gas. The rotating shaft can be cooled via the valve body, and the sealing member provided on the rotating shaft can be protected from heat damage of the EGR gas. Further, when the bypass valve is opened, the warm-up of the downstream EGR passage can be promoted by the amount of the increase in the bypass flow rate ratio.

According to the configuration of (5) above, in addition to the effect of the configuration of (4) above, when the valve body of the bypass valve is closed, the gap is narrowed to allow the EGR gas from the bypass passage to the heat exchanger side. Leakage can be suppressed, and a decrease in the cooling efficiency of EGR gas due to the heat exchanger can be suppressed. Further, when the valve body is opened, a large amount of condensed water discharged from the outlet of the heat exchanger can be discharged to the bypass passage through the gap by widening the gap.

According to the configuration of (6) above, in addition to the effect of any of the configurations (1) or (3) to (5) above, even if the actuator should fail, the valve body of the bypass valve is closed. It is possible to block the flow of EGR gas in the bypass passage, prevent the uncooled high temperature EGR gas from flowing to the downstream EGR passage, and suppress heat damage in the downstream EGR passage. ..

According to the configuration of (7) above, in addition to the effect of the configuration of (6) above, when the coil of the actuator of the bypass valve is broken and the actuator does not operate normally, the bypass valve cannot be controlled appropriately. Correspondingly, by controlling the flow of EGR gas to the downstream EGR passage, it is possible to suppress the generation of condensed water in the EGR cooler and the generation of heat damage in the downstream EGR passage. can.

According to the configuration of (8) above, in addition to the effect of any of the configurations (1) to (3) above, even when the bypass valve is attached to the housing of the EGR cooler having a poor heat transfer coefficient, the actuator of the bypass valve is used. Operates in response to changes in the temperature of the cooling water, so that it is not necessary to electrically control the bypass valve, and the configuration related to the bypass valve can be simplified.

According to the configuration of (9) above, in addition to the effect of any one of the above (1) to (3) or the configuration of (8), a cooling water passage for flowing cooling water of the engine is provided in the housing of the EGR valve. Can open and close the bypass valve according to the temperature change of the cooling water.

According to the configuration of (10) above, in addition to the effect of any of the configurations (1) to (9) above, the condensed water generated in the EGR passage or the EGR cooler is discharged to the exhaust passage through the bypass passage by its own weight. be able to.

According to the configuration of (11) above, in addition to the effect of any of the configurations (1) to (10) above, the heat of the EGR gas flowing through the bypass passage can be released to the EGR cooler by that amount on the downstream side. The temperature of the EGR gas flowing to the EGR passage can be lowered, and the melting damage of the downstream EGR passage can be suppressed more reliably.

According to the configuration of the above (12), in addition to the effect of the configuration of the above (11), the condensed water generated in the EGR passage, the EGR cooler, etc. can be efficiently flowed to the bypass passage by its own weight and discharged to the exhaust passage. can do.

According to the configuration of (13) above, in addition to the effect of the configuration of (12) above, even if the valve body operates excessively in the bypass valve, it is possible to prevent the valve body or the downstream wall portion from being damaged. can.

According to the configuration of (14) above, in addition to the effect of any of the configurations (11) to (13) above, the condensed water generated by the EGR cooler can be efficiently evaporated.

According to the configuration of (15) above, in addition to the effect of any of the configurations (11) to (14) above, heat dissipation of the bypass passage can be promoted, and in addition, the temperature rise of the EGR cooler is promoted. Can be done.

According to the configuration of (16) above, in addition to the effect of any of the configurations (1) to (15) above, even if the bypass valve is closed in a low temperature environment where the outside air temperature is below the freezing point. The EGR gas flowing to the downstream EGR passage can warm the downstream EGR passage, and the melting damage of the downstream EGR passage and the generation of condensed water in the downstream EGR passage can be suppressed.

According to the configuration of (17) above, in addition to the effect of any of the configurations (1) to (16) above, even if the temperature of the EGR gas flowing to the downstream EGR passage becomes higher than necessary, the EGR gas can be used. By stopping the flow or reducing the weight, it is possible to surely prevent the melting damage of the downstream EGR passage.

According to the configuration of (18) above, in addition to the effect of any of the configurations (1) to (17), the EGR gas is recirculated to the engine through the downstream EGR passage and the downstream EGR passage is melted. And the generation of condensed water in the downstream EGR passage can be suppressed.

According to the configuration of (19) above, in addition to the effect of the configuration of (3) above, when the temperature of the EGR gas flowing to the downstream EGR passage exceeds the allowable heating temperature of the downstream EGR passage, the temperature of the EGR gas is lowered. By controlling the bypass valve so as to be allowed to do so, it is possible to suppress the melting damage of the downstream EGR passage and the generation of condensed water in the downstream EGR passage.

According to the configuration of (20) above, in addition to the effect of the configuration of (19) above, even if the actuator of the bypass valve fails, the flow of EGR gas in the bypass passage can be blocked, and the EGR passage on the downstream side is melted. The loss can be suppressed.

A schematic configuration diagram showing an engine system according to the first embodiment. FIG. 6 is a cross-sectional view showing an EGR cooler, a bypass passage, a bypass valve (valve open state), and a part of the EGR valve cut along the longitudinal direction thereof according to the first embodiment. FIG. 3 is a cross-sectional view showing an EGR cooler, a bypass passage, a bypass valve (valve closed state), and a part of the EGR valve cut along the longitudinal direction thereof according to the first embodiment. FIG. 2 is a cross-sectional view showing a part of the EGR cooler and the bypass passage in FIGS. 2 and 3 according to the first embodiment. FIG. 6 is a cross-sectional view showing a specific example of a bypass valve and a valve open state according to the first embodiment. FIG. 6 is a cross-sectional view showing a specific example of a bypass valve and a closed state according to the first embodiment. A graph showing the opening / closing characteristics of the bypass valve according to the first embodiment. A flowchart showing the contents of the first EGR control according to the first embodiment. A flowchart showing the contents of the second EGR control according to the second embodiment. An EGR allowable opening degree map referred to in order to obtain an EGR allowable opening degree according to a cooling water temperature according to a second embodiment. A flowchart showing the contents of the third EGR control according to the third embodiment. The graph which shows the change of the opening degree of the EGR valve after the start of EGR according to the 3rd Embodiment. The graph which shows the change of the wall temperature after the start of EGR according to the 3rd Embodiment. FIG. 5 is a cross-sectional view according to FIG. 5, which is a specific example of a bypass valve and shows a valve open state according to a fourth embodiment. FIG. 6 is a cross-sectional view according to FIG. 6, which is a specific example of the bypass valve and shows a closed state according to the fourth embodiment. FIG. 2 is a cross-sectional view according to FIG. 2 showing an EGR cooler, a bypass passage, a bypass valve (valve open state), and a part of the EGR valve according to the fifth embodiment. FIG. 5 is a cross-sectional view according to FIG. 3 showing an EGR cooler, a bypass passage, a bypass valve (valve closed state), and a part of the EGR valve according to the fifth embodiment. FIG. 6 is a cross-sectional view according to FIG. 3 showing an EGR cooler, a bypass passage, a bypass valve (valve closed state), and a part of the EGR valve according to the sixth embodiment. FIG. 6 is a cross-sectional view according to FIG. 3 showing an EGR cooler, a bypass passage, a bypass valve (valve closed state), and a part of the EGR valve according to the sixth embodiment. FIG. 7 is a cross-sectional view showing an EGR cooler, a bypass passage, a bypass valve (valve open state), and a part of the EGR valve cut along the longitudinal direction thereof according to the seventh embodiment. FIG. 7 is a cross-sectional view showing an EGR cooler, a bypass passage, a bypass valve (valve closed state), and a part of the EGR valve cut along the longitudinal direction thereof according to the seventh embodiment. FIG. 8 is a cross-sectional view showing an EGR cooler, a bypass passage, a bypass valve (valve open state), and a part of the EGR valve cut along the longitudinal direction thereof according to the eighth embodiment. FIG. 8 is a cross-sectional view showing an EGR cooler, a bypass passage, a bypass valve (valve closed state), and a part of the EGR valve cut along the longitudinal direction thereof according to the eighth embodiment. FIG. 9 is a cross-sectional view showing an EGR cooler, a bypass passage, a bypass valve (valve open state), and a part of the EGR valve cut along the longitudinal direction thereof according to the ninth embodiment. FIG. 10 is a cross-sectional view showing an EGR cooler, a bypass passage, a bypass valve (valve open state), and a part of the EGR valve cut along the longitudinal direction thereof according to the tenth embodiment. FIG. 24 is a cross-sectional view according to FIG. 24 showing an EGR cooler, a bypass passage, and a bypass valve (valve open state) according to the eleventh embodiment. FIG. 26 is a sectional view taken along line BB of FIG. 26 showing heat radiation fins according to the eleventh embodiment. FIG. 24 is a cross-sectional view according to FIG. 24 showing an EGR cooler, a bypass passage, and a bypass valve (valve open state) according to a twelfth embodiment. FIG. 6 is a schematic configuration diagram showing an engine system according to a thirteenth embodiment. FIG. 28 is a cross-sectional view according to FIG. 28 showing an EGR cooler, a bypass passage, and a bypass valve (valve closed state) according to the thirteenth embodiment. A flowchart showing the contents of the fourth EGR control according to the thirteenth embodiment. The flowchart which shows the content of the bypass valve switching control which concerns on 14th Embodiment. A front view showing an EGR cooler in which a bypass passage and a bypass valve are integrally provided according to the fifteenth embodiment. A rear view showing an EGR cooler according to a fifteenth embodiment. FIG. 15 is a cross-sectional view showing the EGR cooler cut along the longitudinal direction thereof when the valve body of the bypass valve is fully closed according to the fifteenth embodiment. FIG. 15 is an enlarged cross-sectional view showing a portion of the EGR cooler, which is enclosed by a one-dot chain line square in FIG. 35, according to the fifteenth embodiment. FIG. 15 is a cross-sectional view according to FIG. 35 showing an EGR cooler when the valve body of the bypass valve is half-opened according to the fifteenth embodiment. FIG. 15 is an enlarged cross-sectional view showing a portion of the EGR cooler, which is enclosed by a one-dot chain line square in FIG. 37, according to the fifteenth embodiment. FIG. 15 is a cross-sectional view according to FIG. 35 showing an EGR cooler when the valve body of the bypass valve is fully opened according to the fifteenth embodiment. FIG. 19 is an enlarged cross-sectional view showing a portion of the EGR cooler, which is enclosed by a two-dot chain line square in FIG. 39, according to the fifteenth embodiment. FIG. 5 is a cross-sectional view showing a configuration of a valve assembly provided corresponding to an outlet of a bypass passage according to a fifteenth embodiment. FIG. 5 is a flowchart showing the contents of opening / closing control of the bypass valve according to the fifteenth embodiment. A target bypass opening degree map referred to in order to obtain a target bypass opening degree according to various parameters according to the fifteenth embodiment. 15th embodiment, an EGR start permit water temperature map referred to for obtaining an EGR start permit water temperature according to an intake air temperature. FIG. 5 is a graph showing the difference between the cooler flow rate ratio and the bypass flow rate ratio when the bypass valve is half-opened and fully opened according to the fifteenth embodiment. 16th embodiment shows the relationship between the part of the EGR cooler, the outlet portion of the bypass passage adjacent to the outlet of the heat exchanger, the valve body (fully closed state) of the bypass valve, and the rotation shaft. Sectional view. 16th embodiment shows the relationship between the part of the EGR cooler, the outlet portion of the bypass passage adjacent to the outlet of the heat exchanger, and the valve body (valve open state) and the rotating shaft of the bypass valve. Sectional view. 17 is a cross-sectional view according to FIG. 46 showing a state in which the valve body of the bypass valve is fully closed, which is a part of the EGR cooler according to the 17th embodiment. FIG. 17 is a cross-sectional view according to FIG. 47 showing a state in which the valve body is opened, which is a part of the EGR cooler according to the 17th embodiment. FIG. 18 is a cross-sectional view according to FIG. 48 showing a state in which the valve body of the bypass valve is fully closed, which is a part of the EGR cooler according to the eighteenth embodiment. A cross-sectional view according to FIG. 49 showing a state in which the valve body of the bypass valve is opened, which is a part of the EGR cooler according to the eighteenth embodiment. FIG. 19 is a cross-sectional view according to FIG. 41 showing a configuration of a valve assembly of a bypass valve according to a nineteenth embodiment. FIG. 52 is a cross-sectional view according to FIG. 52 showing a configuration of a valve assembly of a bypass valve according to a twentieth embodiment. FIG. 2 is a perspective view showing an EGR cooler including an actuator and a link as viewed from the rear side according to the 21st embodiment. 21st embodiment is a rear view which is an EGR cooler and which shows the state of the actuator and the link when the bypass valve is operated to open (fully open), according to FIG. 34. 21st embodiment is a rear view which is an EGR cooler and which shows the state of the actuator and the link when the bypass valve is operated to close (fully closed), according to FIG. 34. FIG. 21 is a cross-sectional view showing an actuator when the bypass valve is fully opened according to the 21st embodiment, cut along the axial direction thereof. FIG. 21 is a cross-sectional view showing an actuator when the bypass valve is fully closed according to the 21st embodiment, cut along the axial direction thereof. 21. A cross-sectional view according to FIG. 40 showing a part of the EGR cooler when the valve body of the bypass valve is fully opened according to the 21st embodiment. 21. A cross-sectional view according to FIG. 36 showing a part of the EGR cooler when the valve body of the bypass valve is fully closed according to the 21st embodiment. FIG. 21 is an enlarged cross-sectional view showing a part of a screwed state of a male screw and a female screw in a state where the valve body is fully opened according to the 21st embodiment. FIG. 21 is an enlarged cross-sectional view showing a part of a screwed state of a male screw and a female screw in a “butted fully closed state” according to the 21st embodiment. A time chart showing an energization pattern for each coil when the upper coil and the lower coil of the actuator are normal according to the 21st embodiment. A time chart showing an energization pattern for each coil when the upper coil and the lower coil of the actuator are normal according to the 21st embodiment. A time chart showing an energization pattern for each coil when the lower coil of the actuator is disconnected according to the 21st embodiment. A time chart showing an energization pattern for each coil when the lower coil of the actuator is disconnected according to the 21st embodiment. The flowchart which concerns on 21st Embodiment and shows the content of the coil disconnection correspondence control. 22nd Embodiment is a flowchart which shows the content of the coil disconnection correspondence control. The water temperature / opening degree map referred to in accordance with the 22nd embodiment for obtaining the EGR start permitted water temperature (solid line) and the EGR maximum opening degree (broken line) according to the final actual bypass opening degree. A perspective view showing an EGR cooler including an actuator and a link as viewed from the rear side according to the 23rd embodiment. A rear view according to FIG. 56 showing the state of the actuator and the link when the bypass valve is operated to be closed (fully closed) in the EGR cooler according to the 23rd embodiment. A rear view according to FIG. 55 showing the state of the actuator and the link when the bypass valve is operated to open (fully open) the EGR cooler according to the 23rd embodiment. A front view showing an EGR cooler including an actuator and a link according to the 24th embodiment. Top view showing the EGR cooler of FIG. 73 as viewed from the direction of the arrow according to the 24th embodiment. FIG. 74 is a sectional view taken along line CC of FIG. 74 showing an EGR cooler according to the 24th embodiment. FIG. 73 is a sectional view taken along line DD of FIG. 73 showing a part of the EGR cooler according to the 24th embodiment. A front view showing a state in which the bimetal of the actuator has cooled and shrunk according to the 24th embodiment. A front view showing a state in which the bimetal of the actuator is stretched by heating and the open end thereof is rotated in the circumferential direction according to the 24th embodiment. A table showing the opening / closing characteristics of the bypass valve with respect to the EGR flow rate and the cooling water temperature according to the 24th embodiment. A table showing the opening / closing characteristics of the bypass valve with respect to the cooling water temperature according to the 24th embodiment. A front view showing an EGR cooler including an actuator and a link according to a 25th embodiment. FIG. 81 is a sectional view taken along line EE of FIG. 81 showing an EGR cooler in a state in which the valve body of the bypass valve is fully closed according to the 25th embodiment. FIG. 25 is a cross-sectional view according to FIG. 82 showing an EGR cooler 13 in a state where the valve body of the bypass valve is opened according to the 25th embodiment. The table which shows an example of the control content of the bypass valve fully open or fully closed corresponding to the condition of the Encopa temperature and the cooling water temperature at the time of restarting and after restarting EGR according to the 25th embodiment. A table showing an example of control contents of energization (on) or non-energization (off) of the biometal corresponding to the conditions of the encopa temperature and the cooling water temperature at the time of resuming and after resuming the EGR according to the 25th embodiment. FIG. 6 is a cross-sectional view showing an EGR cooler, a bypass passage and a bypass valve (valve closed state) and a part of the EGR valve cut along the longitudinal direction thereof according to another embodiment. An enlarged cross-sectional view according to FIG. 36 showing a part of the EGR cooler according to another embodiment. FIG. 5 is a cross-sectional view according to FIG. 52 showing a configuration of a valve assembly of a bypass valve according to another embodiment. FIG. 11 is a cross-sectional view according to FIG. 41 showing a configuration of a valve assembly of a bypass valve according to another embodiment.

Hereinafter, some embodiments in which the EGR system is embodied in a gasoline engine system will be described.

<First Embodiment>
First, the first embodiment will be described in detail with reference to the drawings.

[About the engine system]
FIG. 1 shows a gasoline engine system of this embodiment (hereinafter, simply referred to as “engine system”) by a schematic configuration diagram. The engine system mounted on the automobile includes an engine 1 having a plurality of cylinders. The engine 1 is a 4-cylinder, 4-cycle reciprocating engine and includes well-known configurations such as a piston and a crankshaft. The engine 1 is provided with an intake passage 2 for introducing intake air into each cylinder and an exhaust passage 3 for deriving exhaust gas from each cylinder of the engine 1. The intake passage 2 is provided with an air cleaner 9, a throttle device 4, and an intake manifold 5 from the upstream side thereof. Further, the exhaust manifold 6 and the catalyst 7 are provided in the exhaust passage 3 in order from the upstream side thereof. In addition, this engine system comprises a high pressure loop type exhaust gas recirculation device (EGR device) 11.

The throttle device 4 is arranged in the intake passage 2 upstream of the intake manifold 5, and by driving the butterfly type throttle valve 4a to open and close with a variable opening according to the accelerator operation of the driver, the amount of intake air flowing through the intake passage 2 Is designed to be adjusted. The intake manifold 5 is mainly composed of a resin material and is arranged in the intake passage 2 directly upstream of the engine 1. One surge tank 5a into which the intake air is introduced and the intake air introduced in the surge tank 5a are used in the engine 1. It includes a plurality of (four) branch pipes 5b branched from the surge tank 5a for distribution to each cylinder. For example, a three-way catalyst is built in the catalyst 7 in order to purify the exhaust gas.

The engine 1 is provided with a fuel injection device (not shown) for injecting fuel corresponding to each cylinder. The fuel injection device is configured to inject fuel supplied from a fuel supply device (not shown) into each cylinder of the engine 1. In each cylinder, a combustible air-fuel mixture is formed by the fuel injected from the fuel injection device and the intake air introduced from the intake manifold 5.

The engine 1 is provided with an ignition device (not shown) corresponding to each cylinder. The igniter is configured to ignite the combustible mixture in each cylinder. The combustible air-fuel mixture in each cylinder explodes and burns due to the ignition operation of the ignition device, and the exhaust gas after combustion is discharged from each cylinder to the outside via the exhaust manifold 6 and the catalyst 7. At this time, the piston (not shown) moves up and down in each cylinder, and the crankshaft (not shown) rotates to obtain power to the engine 1.

[About the EGR system]
The EGR system of this embodiment includes the EGR device 11 described above. The EGR device 11 is configured to flow a part of the exhaust gas discharged from each cylinder of the engine 1 to the exhaust passage 3 as an exhaust gas recirculation gas (EGR gas) to the intake passage 2 and return the exhaust gas to each cylinder of the engine 1. .. The EGR device 11 includes an exhaust gas recirculation passage (EGR passage) 12 for flowing EGR gas from the exhaust passage 3 to the intake passage 2, and an exhaust gas recirculation cooler (EGR cooler) 13 for cooling the EGR gas flowing through the EGR passage 12. , The exhaust gas recirculation valve (EGR valve) 14 provided downstream from the EGR cooler 13 in order to adjust the flow rate of the EGR gas flowing through the EGR passage 12, and the EGR gas flowing through the EGR passage 12 are distributed to each cylinder of the engine 1. Therefore, an exhaust gas recirculation gas distributor (EGR gas distributor) 15 for distributing EGR gas to each branch pipe 5b of the intake manifold 5 is provided. The EGR gas distributor 15 is provided in the EGR cooler 13, the bypass passage 16, and the EGR passage 12 downstream of the EGR valve 14. The EGR passage 12 includes an inlet 12a and an outlet 12b. The inlet 12a of the EGR passage 12 is connected to the exhaust passage 3 upstream of the catalyst 7, and the outlet 12b of the passage 12 is connected to the EGR gas distributor 15. In this embodiment, the EGR gas distributor 15 is made of a resin material, is located downstream of the EGR cooler 13 and the bypass passage 16, and constitutes the final stage (part) of the downstream EGR passage in the disclosed technique. There is. In the EGR passage 12, the EGR valve 14 is provided adjacent to the EGR cooler 13 downstream of the EGR cooler 13. The EGR cooler 13 is configured to exchange heat between the EGR gas and the cooling water of the engine 1 in order to cool the EGR gas flowing through the EGR passage 12.

In this EGR device 11, when the EGR valve 14 is opened, a part of the exhaust gas flowing through the exhaust passage 3 flows through the EGR passage 12 as EGR gas, and passes through the EGR cooler 13, the EGR valve 14, and the EGR gas distributor 15. It is distributed to each branch pipe 5b of the intake manifold 5, and further distributed to each cylinder of the engine 1 to be circulated.

In this embodiment, a bypass passage 16 is provided between the EGR valve 14 and the EGR cooler 13. The bypass passage 16 is a passage for bypassing a part of the EGR gas flowing to the EGR cooler 13 in the EGR passage 12. The bypass passage 16 is provided with a bypass valve 17 for opening and closing the passage 16.

The EGR gas distributor 15 is mainly composed of a resin material, has a horizontally long shape as a whole, and has a plurality of branch pipes of the intake manifold 5 in the longitudinal direction (left-right direction in FIG. 1) as shown in FIG. Arranged so as to cross 5b. In this embodiment, the EGR gas distributor 15 is branched from one gas chamber 15a in which the EGR gas introduced from the outlet 12b of the EGR passage 12 collects, and the gas chamber 15a, and the EGR is branched from the gas chamber 15a to each branch pipe 5b. It includes a plurality (4) gas distribution passages 15b for distributing gas.

2 and 3 show a cross-sectional view of the EGR cooler 13, the bypass passage 16, the bypass valve 17, and a part of the EGR valve 14 cut along the longitudinal direction thereof. FIG. 2 shows a state in which the bypass valve 17 is opened, and FIG. 3 shows a state in which the bypass valve 17 is closed. As shown in FIGS. 2 and 3, the inlet flange 18a of the EGR valve 14 is connected to the outlet flange 31d of the EGR cooler 13. With the EGR cooler 13 mounted on the vehicle, the bypass passage 16 is arranged vertically upward with respect to the EGR cooler 13 and the EGR valve 14 from the EGR cooler 13 to the housing 18 of the EGR valve 14. In FIGS. 2 and 3, arrow A1 indicates the flow of cooling water, arrow A2 indicates the flow of hot EGR gas, and arrow A3 indicates the flow of cooled EGR gas (same below).

FIG. 4 shows a part of the EGR cooler 13 and the bypass passage 16 in FIGS. 2 and 3 by a cross-sectional view. As shown in FIG. 4, the EGR cooler 13 introduces the EGR gas from the housing 31, the heat exchanger 32 provided in the housing 31, the introduction port 33 for introducing the EGR gas into the housing 31, and the housing 31. Includes a derivation port 34 for derivation. In this embodiment, the EGR cooler 13 is obliquely arranged in the EGR passage 12 so that the EGR gas flows diagonally upward. In this diagonally arranged state, the outlet port 34 is arranged at a position higher in the vertical direction than the introduction port 33.

The housing 31 includes a main body portion 31a in which the heat exchanger 32 is provided, an introduction portion 31b between the main body portion 31a and the introduction port 33, a lead-out portion 31c between the main body portion 31a and the outlet port 34, and an outlet flange. Including 31d. The introduction unit 31b has an introduction space 35 inside thereof. The derivation unit 31c has a derivation space 36 inside thereof. The heat exchanger 32 includes a water passage 41 through which cooling water flows and a gas passage 42 arranged in the water passage 41 through which EGR gas flows. The gas passage 42 is composed of a plurality of small gas passages 42A having a flat shape. Each small gas passage 42A is provided with a plurality of internal fins 44 so as to be in contact with the inner wall thereof. The water passage 41 is composed of an internal space of the main body portion 31a, and both ends of the internal space in the axial direction are closed by

partition walls

43A and 43B. The main body 31a is formed with an intake port 38 for taking cooling water into the water passage 41 and an outlet 39 for taking out the cooling water from the water passage 41. The plurality of small gas passages 42A are arranged in parallel with each other via the gaps constituting the water passage 41. The openings at both ends of each small gas passage 42A are arranged so as to penetrate the

partition walls

43A and 43B, and communicate with the introduction space 35 and the lead-out space 36, respectively. A part of the bypass passage 16 is integrally formed in the EGR cooler 13. The EGR cooler 13 and the bypass passage 16 are adjacent to each other via the partition wall 46. As shown in FIGS. 2 to 4, the partition wall 46 includes a main wall portion 46a in contact with the heat exchanger 32 and a downstream wall portion 46b extending downstream from the heat exchanger 32. The downstream wall portion 46b includes a wall portion 46ba integrally formed with the housing 31 of the EGR cooler 13, and a wall portion 46bb integrally formed with the housing 18 of the EGR valve 14.

[Bypass valve]
In this embodiment, as shown in FIGS. 2 and 3, the bypass valve 17 is integrally attached to the housing 18 of the EGR valve 14 and opens and closes the bypass passage 16 provided in the housing 18. In this embodiment, the housing 18 of the EGR valve 14 is made of an aluminum material. The bypass valve 17 includes a valve body 21 and an actuator 22 configured to close the valve body 21 from the open state when the temperature of the cooling water of the engine 1 becomes equal to or higher than the first predetermined value. In this embodiment, the first predetermined value is set to a temperature in the range of "40 ° C. or higher and lower than 65 ° C.". In this embodiment, the bypass valve 17 is configured by a thermowax valve. 5 and 6 show a specific example of the bypass valve 17 in a cross-sectional view. FIG. 5 shows the bypass valve 17 in the valve open state, and FIG. 6 shows the bypass valve 17 in the valve closed state. As shown in FIGS. 5 and 6, the bypass valve 17 seals the casing 23, the thermowax 24 built in the casing 23, and the thermowax 24 in addition to the valve body 21, and expands the thermowax 24. And a diaphragm 25 that can be deformed according to shrinkage. The valve body 21 has a shaft shape, one end thereof is fixed to the diaphragm 25, and the other end portion is provided so as to be reciprocating with respect to the casing 23. In this embodiment, the actuator 22 is composed of a thermowax 24 and a diaphragm 25, and is configured to operate in response to a change in temperature. When the temperature of the bypass valve 17 is low, the thermowax 24 contracts as shown in FIG. 5, and the valve body 21 is pulled into the casing 23 via the diaphragm 25 to open the valve. That is, the bypass passage 16 is opened. On the other hand, when the temperature of the bypass valve 17 is high, the thermowax 24 expands as shown in FIG. 6, so that the valve body 21 protrudes from the casing 23 via the diaphragm 25 and closes. That is, the bypass passage 16 is closed.

In this embodiment, the housing 18 of the EGR valve 14 is formed with a cooling water passage (not shown) through which the cooling water of the engine 1 flows, and the cooling water heats or cools the housing 18. There is. In this embodiment, since the bypass valve 17 is attached to the housing 18 of the EGR valve 14, when the temperature of the cooling water is low, the housing 18 and the bypass valve 17 cannot be warmed, as shown in FIG. The bypass valve 17 opens. When the bypass valve 17 opens, as shown in FIG. 2, most of the EGR gas introduced from the introduction port 33 of the EGR cooler 13 flows through the bypass passage 16, and the remaining EGR gas flows through the EGR cooler 13 (heat). It flows through the exchanger 32) and joins at the EGR valve 14, respectively. The merged EGR gas further flows to the EGR gas distributor 15, is distributed to each cylinder of the engine 1 via the intake manifold 5, and is recirculated. On the other hand, when the temperature of the cooling water is high, the housing 18 and the bypass valve 17 are warmed, and the bypass valve 17 is closed as shown in FIG. When the bypass valve 17 is closed, as shown in FIG. 3, all of the EGR gas introduced from the introduction port 33 of the EGR cooler 13 flows to the EGR cooler 13 (heat exchanger 32) to be cooled, and further EGR. It flows to the valve 14 and the EGR gas distributor 15, is distributed to each cylinder of the engine 1 via the intake manifold 5, and is recirculated.

FIG. 7 shows the opening / closing characteristics of the bypass valve 17 graphically. In this graph, the horizontal axis shows the cooling water temperature THW, and the vertical axis shows the opening degree of the bypass valve 17. As can be seen from this graph, the bypass valve 17 is fully opened when the cooling water temperature THW is less than "40 ° C." and is fully opened when the cooling water temperature THW is "65 ° C." or higher due to the characteristics of the thermowax 24. It is fully closed, and the opening between fully open and fully closed is in the range of "40 ° C" or more and less than "65 ° C".

[About the electrical configuration of the engine system]
Next, an example of the electrical configuration of the engine system will be described. In FIG. 1, various sensors and the like 81 to 88 provided in this engine system constitute an operating state detecting means for detecting an operating state of the engine 1. The water temperature sensor 81 provided in the engine 1 detects the temperature (cooling water temperature) THW of the cooling water flowing inside the engine 1 and outputs an electric signal according to the detected value. The rotation speed sensor 82 provided in the engine 1 detects the rotation angle (crank angle) of the crankshaft of the engine 1 and uses the change in the crank angle (crank angle speed) as the rotation speed (engine rotation speed) NE of the engine 1. Detects and outputs an electric signal according to the detected value. The air flow meter 83 provided in the vicinity of the air cleaner 9 detects the intake air amount Ga flowing through the air cleaner 9, and outputs an electric signal according to the detected value. The intake pressure sensor 84 provided in the surge tank 5a detects the intake pressure PM in the intake passage 2 (surge tank 5a) downstream of the throttle device 4, and outputs an electric signal according to the detected value. The throttle sensor 85 provided in the throttle device 4 detects the opening degree (throttle opening degree) TA of the throttle valve 4a and outputs an electric signal corresponding to the detected value. The oxygen sensor 86 provided in the exhaust passage 3 between the inlet 12a of the EGR passage 12 and the catalyst 7 detects the oxygen concentration Ox in the exhaust and outputs an electric signal according to the detected value. The intake air temperature sensor 87 provided at the inlet of the air cleaner 9 detects the temperature (intake air temperature) THA of the outside air sucked into the air cleaner 9, and outputs an electric signal according to the detected value. The wall temperature sensor 88 provided in the EGR gas distributor 15 detects the wall temperature (wall temperature) THDW of the EGR gas distributor 15 and outputs an electric signal according to the detected value. The wall temperature sensor 88 corresponds to an example of the temperature detection means in this disclosed technique.

This engine system further includes an electronic control unit (ECU) 90 that controls the system. Various sensors and the like 81 to 88 are connected to the ECU 90, respectively. Further, in addition to the EGR valve 14, an injector (not shown) and an ignition coil (not shown) are connected to the ECU 90. The ECU 90 corresponds to an example of the first control means in this disclosure technique. As is well known, the ECU 90 includes a central processing unit (CPU), various memories, an external input circuit, an external output circuit, and the like. A predetermined control program related to various controls is stored in the memory. The CPU executes fuel injection control, ignition timing control, EGR control, and the like based on a predetermined control program based on the detection signals of various sensors and the like 81 to 88 input via the input circuit.

In this embodiment, the ECU 90 controls the EGR valve 14 according to the operating state of the engine 1 in the EGR control. Specifically, the ECU 90 controls the EGR valve 14 to be fully closed when the engine 1 is stopped, idle operation, and deceleration operation, and obtains a target EGR opening degree according to the operating state at other times. , The EGR valve 14 is controlled to the target EGR opening degree. At this time, when the EGR valve 14 is opened, it is discharged from the engine 1 to the exhaust passage 3, and a part of the exhaust gas is used as EGR gas in the EGR passage 12, the EGR cooler 13, the EGR valve 14, and the EGR gas distributor 15. It flows to the intake passage 2 (intake manifold 5) via the above, and is distributed to each cylinder of the engine 1 to be circulated.

[About the first EGR control]
In this embodiment, the opening and closing of the bypass passage 16 by the bypass valve 17 is switched depending on the temperature of the cooling water flowing through the housing 18 of the EGR valve 14, but may not be switched depending on the temperature of the EGR gas. That is, the bypass valve 17 may not close from the valve open state, and the high temperature EGR gas may continue to flow to the EGR valve 14 and the EGR gas distributor 15. Therefore, when the EGR is started when the cooling water temperature is low and the water temperature is low and the engine 1 is operated under conditions of high rotation and high load, the high temperature EGR gas flows into the resin EGR gas distributor 15. , The distributor 15 may be melted by heat. Therefore, in this embodiment, in order to prevent the EGR gas distributor 15 from being melted when the temperature of the EGR gas becomes higher than necessary, the ECU 90 performs the following first EGR control. It has become.

FIG. 8 shows the contents of the first EGR control by a flowchart. When the process shifts to this routine, in step 100, the ECU 90 takes in the wall temperature THDW of the EGR gas distributor 15 based on the detection value of the wall temperature sensor 88.

Next, in step 110, the ECU 90 determines whether or not the wall temperature THDW is equal to or higher than the allowable heating temperature of the EGR gas distributor 15. "120 ° C." is an example. If the determination result is affirmative, the ECU 90 shifts the process to step 120, and if the determination result is negative, the ECU 90 shifts the process to step 140.

In step 120, the ECU 90 executes a forced EGR cut on the assumption that the EGR gas distributor 15 may be melted because the wall temperature THDW is "120 ° C." or higher. That is, the ECU 90 controls the EGR valve 14 to be fully closed.

Next, in step 130, the ECU 90 sets the forced EGR cut flag XEGRC to "1" and returns the process to step 100.

On the other hand, in step 140 after shifting from step 110, the ECU 90 determines whether or not the forced EGR cut flag XEGRC is "1", that is, whether or not the forced EGR cut has already been executed. If the determination result is affirmative, the ECU 90 shifts the process to step 150, and if the determination result is negative, the ECU 90 shifts the process to step 180.

In step 150, the ECU 90 determines whether or not the wall temperature THDW is "100 ° C." or higher. If the determination result is affirmative, the ECU 90 assumes that the wall temperature THDW is "100 ° C." or higher and there is still a risk of melting damage to the EGR gas distributor 15, and the process proceeds to step 120. If this determination result is negative, the process proceeds to step 160, assuming that the EGR gas distributor 15 is not likely to be melted.

In step 160, the ECU 90 releases the forced EGR cut. That is, the ECU 90 releases the fully closed control of the EGR valve 14.

Next, in step 170, the ECU 90 sets the forced EGR cut flag XEGRC to "0" and returns the process to step 100.

On the other hand, in step 180 after shifting from step 140, the ECU 90 executes normal EGR control and returns the process to step 100. The normal EGR control is to control the EGR valve 14 based on the target EGR opening degree calculated according to the operating state of the engine 1.

According to the first EGR control described above, when the wall temperature THDW (temperature) detected by the wall temperature sensor 88 (temperature detection means) exceeds the allowable heating temperature of the EGR gas distributor 15, the ECU 90 EGR The valve 14 is forcibly controlled to be fully closed. Specifically, in the first EGR control, the ECU 90 avoids melting damage of the resin EGR gas distributor 15 when the wall temperature THDW of the EGR gas distributor 15 becomes a high temperature of "120 ° C." or higher. It is designed to perform a forced EGR cut in order to do so. According to this first EGR control, even if the bypass valve 17 made of the thermowax valve remains open (open failure), the wall temperature THDW may become a high temperature of "120 ° C." or higher. Therefore, the forced EGR cut will be executed. Therefore, this first EGR control functions as a fail-safe when the bypass valve 17 opens and fails.

[About the action and effect of the EGR system]
As described above, according to the configuration of the EGR system in this embodiment, when the EGR in which the temperature of the cooling water is lower than the first predetermined value (40 ° C.) is executed, the valve body 21 of the bypass valve 17 is the thermowax 24. The actuator 22 is opened by the actuator 22. At this time, a part of the EGR gas flowing from the exhaust passage 3 to the EGR passage 12 flows to the bypass passage 16, and the rest flows to the heat exchanger 32. Then, these two flows merge at the downstream EGR valve 14, and further flow to the EGR gas distributor 15 via the downstream EGR passage 12. Therefore, even if a high temperature EGR gas flows from the exhaust passage 3 to the EGR passage 12, the EGR gas flowing through the bypass passage 16 among the EGR gas is heat exchanged by the heat exchanger 32 with the EGR gas whose temperature has dropped. The temperature drops due to the confluence of the EGR gas, and the EGR gas whose temperature has dropped to an appropriate temperature flows to the EGR gas distributor 15. On the other hand, when the temperature of the cooling water reaches the first predetermined value (65 ° C.) or higher after the engine 1 is warmed up, the valve body 21 of the bypass valve 17 is closed from the open state by the actuator 22 composed of the thermowax 24. Therefore, almost all of the EGR gas flowing from the exhaust passage 3 to the EGR passage 12 flows to the heat exchanger 32 of the EGR cooler 13, is heat exchanged by the heat exchanger 32, drops to an appropriate temperature, and is an EGR gas having an appropriate temperature. Flows to the EGR gas distributor 15 after passing through the EGR valve 14 and the EGR passage 12. Therefore, in the EGR system, the high-temperature EGR gas flowing from the exhaust passage 3 to the EGR passage 12 can be lowered to an appropriate temperature and flowed to the resin EGR gas distributor 15 (downstream side EGR passage), and the EGR can be flown. It is possible to suppress the melting damage of the gas distributor 15 and the generation of condensed water in the EGR gas distributor 15.

According to the configuration of this embodiment, since the actuator 22 of the bypass valve 17 is composed of the thermowax 24 and the diaphragm 25 and operates in response to a change in temperature, it is not necessary to electrically control the bypass valve 17. The configuration of the bypass valve 17 is simplified. Therefore, the product cost as an EGR system can be suppressed.

According to the configuration of this embodiment, since the housing 18 of the EGR valve 14 is formed of an aluminum material, its thermal conductivity is good. Further, the bypass valve 17 is provided integrally with the housing 18 of the EGR valve 14, and the actuator 22 thereof is composed of the thermowax 24 and the diaphragm 25, and operates in response to a change in temperature. Therefore, the valve body 21 of the bypass valve 17 opens and closes according to the temperature change of the housing 18 of the EGR valve 14. Therefore, when the housing 18 of the EGR valve 14 is provided with a cooling water passage through which the cooling water of the engine 1 flows, the bypass valve 17 can be opened and closed according to the temperature change of the cooling water.

According to the configuration of this embodiment, since the EGR cooler 13 and the bypass passage 16 are adjacent to each other via the partition wall 46, heat exchange is possible between the EGR cooler 13 and the bypass passage 16 via the partition wall 46. .. Therefore, the heat of the EGR gas flowing through the bypass passage 16 can be released to the EGR cooler 13, and the temperature of the EGR gas flowing to the EGR gas distributor 15 can be lowered by that amount, and the EGR gas distributor 15 is melted. The loss can be suppressed more reliably.

According to the configuration of this embodiment, in the first EGR control, the wall temperature THDW of the EGR gas distributor 15 detected by the wall temperature sensor 88 exceeds the allowable heating temperature (120 ° C.) of the EGR gas distributor 15. If so, the ECU 90 forcibly controls the EGR valve 14 to be fully closed, that is, executes a forced EGR cut. Therefore, the flow of EGR gas in the EGR passage 12 is immediately cut off, and excessive heating exceeding the allowable heating temperature of the EGR gas distributor 15 is immediately stopped. Therefore, even if the temperature of the EGR gas flowing to the EGR gas distributor 15 becomes higher than necessary, the EGR gas distributor 15 can be reliably prevented from being melted by stopping the flow of the EGR gas.

<Second Embodiment>
Next, the second embodiment will be described in detail with reference to the drawings. In the following description, the components equivalent to those in the first embodiment are designated by the same reference numerals, the description thereof will be omitted, and the differences will be mainly described.

This embodiment is different from the "first EGR control" of the first embodiment in the content of the "second EGR control" executed by the ECU 90. In this embodiment, the ECU 90 corresponds to an example of a second control means in this disclosure technique.

[Second EGR control]
FIG. 9 shows the contents of the second EGR control by a flowchart. When the process shifts to this routine, in step 200, the ECU 90 sets the cooling water temperature THW and the engine rotation speed based on the detection values of the water temperature sensor 81, the rotation speed sensor 82, the throttle sensor 85, the intake air temperature sensor 87 and the wall temperature sensor 88. The NE, intake air temperature THA, engine load KL, and wall temperature THDW are taken in, respectively. The ECU 90 can obtain the engine load KL based on the throttle opening TA or the intake pressure PM.

Next, in step 210, the ECU 90 determines whether or not the EGR start permission condition is satisfied. The ECU 90 can determine the establishment of the EGR start permission condition based on the various parameters THW and THA taken in. If the determination result is affirmative, the ECU 90 shifts the process to step 220, and if the determination result is negative, the ECU 90 shifts the process to step 290.

In step 220, the ECU 90 obtains a target EGR opening degree TEGR according to the intake air temperature THA, the cooling water temperature THW, the engine speed NE, and the engine load KL. The ECU 90 can obtain a target EGR opening TEGR according to various parameters THA, THW, NE, and KL by referring to a predetermined target EGR opening map (not shown), for example.

Next, in step 230, the ECU 90 determines whether or not the wall temperature THDW of the EGR gas distributor 15 is less than the heat resistant temperature of the EGR gas distributor 15, "140 ° C.". "140 ° C" is an example. If the determination result is affirmative, the ECU 90 shifts the process to 240, and if the determination result is negative, the ECU 90 shifts the process to step 340.

In step 240, the ECU 90 determines whether or not the forced EGR cut flag XEGRC is “0”. As will be described later, this flag XEGRC is set to "1" when the forced EGR cut is executed. If the determination result is affirmative, the ECU 90 shifts the process to 250, and if the determination result is negative, the ECU 90 shifts the process to step 310.

In step 250, the ECU 90 determines whether or not the wall temperature THDW is equal to or higher than the allowable heating temperature of the EGR gas distributor 15. "120 ° C." is an example. If the determination result is affirmative, the ECU 90 shifts the process to 260, and if the determination result is negative, the ECU 90 shifts the process to step 280.

In step 260, the ECU 90 obtains the EGR allowable opening degree TEGRMX according to the cooling water temperature THW. The ECU 90 can obtain the EGR allowable opening degree TEGRMX according to the cooling water temperature THW, for example, by referring to the EGR allowable opening degree map as shown in FIG. In this map, when the cooling water temperature THW is less than "40 ° C", the EGR allowable opening TEGRMX is "40 (%)", and the cooling water temperature THW is "65 ° C" or more. In the range where the EGR allowable opening TEGRMX is fully opened at "100 (%)" and the cooling water temperature THW is "40 ° C" or more and less than "65 ° C", the EGR allowable opening TEGRMX is "40 (%)". The opening is between the opening and the full opening of "100%".

Next, in step 270, the ECU 90 determines whether or not the target EGR opening degree TEGR is smaller than the EGR allowable opening degree TEGRMX. If the determination result is affirmative, the ECU 90 shifts the process to 280, and if the determination result is negative, the ECU 90 shifts the process to step 300.

In step 280, the ECU 90 controls the EGR valve 14 to the target EGR opening degree TEGR, and returns the process to step 200.

When shifting from step 270 to step 300, the ECU 90 sets the EGR allowable opening TEGRMX to the target EGR opening TEGR, and shifts the process to step 280.

On the other hand, in step 340 after shifting from step 230, the ECU 90 sets the target EGR opening TEGR to "0" for forced EGR cut.

Next, in step 350, the ECU 90 sets the forced EGR cut flag XEGRC to "1" and shifts the process to step 280.

Further, in step 310 after shifting from step 240, the ECU 90 determines whether or not the wall temperature THDW of the EGR gas distributor 15 is less than "130 ° C.". "130 ° C" is an example. If the determination result is affirmative, the ECU 90 shifts the process to 320, and if the determination result is negative, the ECU 90 shifts the process to step 340.

In step 320, the ECU 90 releases the forced EGR cut that has already been executed. That is, the ECU 90 ends the control for forcibly closing the EGR valve 14.

Next, in step 330, the ECU 90 sets the forced EGR cut flag XEGRC to "0" and shifts the process to step 280.

On the other hand, in step 290 after shifting from step 210, the ECU 90 sets the target EGR opening degree TEGR to "0" and shifts the process to step 280.

According to the second EGR control described above, the ECU 90 determines the EGR when the wall temperature THDW detected by the wall temperature sensor 88 (temperature detection means) exceeds the heat resistant temperature (140 ° C.) of the EGR gas distributor 15. The valve 14 is forcibly controlled to be fully closed (forced EGR cut). Further, the ECU 90 distributes EGR gas when the wall temperature THDW detected by the wall temperature sensor 88 (temperature detecting means) is equal to or higher than the third predetermined value (the allowable heating temperature (120 ° C.) or more and less than 130 ° C. of the EGR gas distributor 15). When the temperature becomes lower than the heat resistant temperature (140 ° C.) of the vessel 15, the EGR valve 14 is controlled to a normal opening degree.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, unlike the first EGR control of the first embodiment, the second EGR control obtains the following actions and effects. That is, when the wall temperature THDW of the EGR gas distributor 15 detected by the wall temperature sensor 88 exceeds the heat resistant temperature (140 ° C.) of the EGR gas distributor 15, the ECU 90 forcibly fills the EGR valve 14. Control to close, i.e. perform a forced EGR cut. Therefore, the flow of EGR gas in the EGR passage 12 is immediately cut off, and excessive heating exceeding the heat resistant temperature (140 ° C.) of the EGR gas distributor 15 is immediately stopped. Therefore, even if the temperature of the EGR gas flowing to the EGR gas distributor 15 becomes higher than necessary, the EGR gas distributor 15 can be reliably prevented from being melted by stopping the flow of the EGR gas. Further, when the wall temperature THDW detected by the wall temperature sensor 88 is equal to or higher than the third predetermined value (120 ° C. or higher and lower than 130 ° C.) and lower than the heat resistant temperature (140 ° C.) of the EGR gas distributor 15, the ECU 90 performs EGR. The valve 14 is controlled to a normal opening degree. Therefore, the flow rate of the EGR gas flowing through the EGR passage 12 is appropriately adjusted, and the flow rate of the EGR gas flowing to the EGR gas distributor 15 is suppressed to a flow rate that does not exceed the heat resistant temperature (140 ° C.). Therefore, it is possible to suppress the melting damage of the EGR gas distributor 15 and the generation of condensed water in the EGR gas distributor 15 while recirculating the EGR gas to the engine 1 via the EGR gas distributor 15. In this case, unlike the first EGR control, the forced EGR cut is not executed, so that the effect of EGR (for example, the fuel consumption reduction effect) can be obtained in the engine 1.

<Third Embodiment>
Next, the third embodiment will be described in detail with reference to the drawings.

This embodiment is different from the "first EGR control" and the "second EGR control" of each of the above-described embodiments in terms of the content of the "third EGR control" executed by the ECU 90.

[Third EGR control]
FIG. 11 shows the contents of the third EGR control by a flowchart. The third EGR control shown in FIG. 11 is different from the second EGR control shown in FIG. 9 in that the process of step 250 is omitted.

When the process shifts to this routine, the ECU 90 executes the processes of steps 200 to 240, and if the determination result of step 240 is affirmative, the process proceeds to step 260, and the determination result of step 240 is negative. If so, the process proceeds to step 310. That is, in the flowchart of FIG. 11, the process of step 250 shown in FIG. 9, that is, the determination of whether or not the wall temperature THDW is “120 ° C.” or higher is omitted, and the process proceeds from step 240 to step 260. Other processing contents are the same as those of the second EGR control shown in FIG.

According to the third EGR control described above, when the wall temperature THDW of the EGR gas distributor 15 is less than "140 ° C.", the ECU 90 determines whether the wall temperature THDW is "120 ° C." or higher. Regardless of this, by controlling the EGR valve 14 to the EGR allowable opening TEGRMX according to the cooling water temperature THW, the wall temperature THDW is suppressed to an EGR gas flow rate that does not exceed the heating allowable temperature "120 ° C". ing.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, unlike the second EGR control in the second embodiment, the ECU 90 has the ECU 90 regardless of whether the wall temperature THDW is “120 ° C.” or higher. By controlling the EGR valve 14 to the EGR allowable opening degree TEGRMX according to the cooling water temperature THW, the wall temperature THDW is suppressed to an EGR gas flow rate that does not exceed "120 ° C.". FIG. 12 graphically shows the change in the opening degree of the EGR valve 14 after the start of EGR. FIG. 13 also graphically shows the change in the wall temperature THDW after the start of EGR. In FIGS. 12 and 13, the thick line shows the case of the second EGR control of the second embodiment, and the broken line shows the case of the third EGR control of the present embodiment. As shown in FIGS. 12 and 13, in the third embodiment, the opening degree of the EGR valve 14 during a predetermined period from the start of EGR (time t1) to time t2 is the target EGR in the case of the second EGR control. Since the EGR allowable opening TEGRMX is controlled to be lower than the opening TEGR, the flow rate of the EGR gas flowing to the EGR gas distributor 15 is suppressed by that amount, and the wall temperature THDW of the EGR gas distributor 15 is increased even after the time t2. It can be suppressed to less than "120 ° C". On the other hand, in the second embodiment, the opening degree of the EGR valve 14 is controlled to the target EGR opening degree TEGR larger than the EGR allowable opening degree TEGRMX from the time of EGR start (time t1), and the wall temperature THDW becomes higher after the time t2 elapses. When the temperature becomes "120 ° C." or higher, the EGR allowable opening degree TEGRMX is controlled to be lower than the target EGR opening degree TEGR. Therefore, the flow rate of the EGR gas flowing to the EGR gas distributor 15 increases by the amount controlled to the target EGR opening degree TEGR for the predetermined period, and the wall temperature THDW of the EGR gas distributor 15 increases by that amount to "120 ° C." Will be exceeded once. In this embodiment, the effect of the EGR gas in the engine 1 (for example, the effect of reducing fuel consumption) is reduced by the amount of the decrease in the flow rate of the EGR gas as described above, but the wall temperature THDW is suppressed to less than "120 ° C". Therefore, it is possible to reliably prevent the EGR gas distributor 15 from being melted.

<Fourth Embodiment>
Next, the fourth embodiment will be described in detail with reference to the drawings.

This embodiment differs from each of the above embodiments in that the structure of the bypass valve 17 made of a thermowax valve is different.

[Bypass valve]
14 and 15 show specific examples of the bypass valve 17 of this embodiment by a cross-sectional view according to FIGS. 5 and 6. FIG. 14 shows the bypass valve 17 in the valve open state, and FIG. 15 shows the bypass valve 17 in the valve closed state. In the bypass valve 17 made of a thermowax valve, when the thermowax 24 is excessively expanded, the valve body 21 protrudes excessively, the tip of the bypass valve 17 hits the wall portion 46bb, and the valve body 21 or the wall portion 46bb may be damaged. .. Therefore, in this embodiment, even if the valve body 21 tries to protrude excessively, the damage to the valve body 21 or the wall portion 46bb is alleviated.

That is, in this embodiment, as shown in FIGS. 14 and 15, the cap 26 slidable with respect to the valve body 21 is attached to the tip of the valve body 21 of the bypass valve 17 so as not to fall off. A cushioning spring 27 is provided between the cap 26 and the valve body 21.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the operation and effect are different from those of each embodiment in the difference in the configuration of the bypass valve 17. That is, in this embodiment, as shown in FIG. 14, when the bypass valve 17 is opened, the cap 26 is attached to the tip of the casing 23, and the spring 27 is extended in the cap 26. On the other hand, as shown in FIG. 15, when the bypass valve 17 is closed, the cap 26 abuts against the wall portion 46bb as the valve body 21 expands, but the spring 27 in the cap 26 contracts, so that the cap 26 contracts. By that amount, the impact of the end of the cap 26 on the wall portion 46bb is alleviated. Therefore, in the bypass valve 17, even if the thermowax 24 excessively expands and the valve body 21 tries to protrude excessively, the damage due to the abutment between the valve body 21 and the wall portion 46bb can be alleviated.

<Fifth Embodiment>
Next, the fifth embodiment will be described in detail with reference to the drawings.

This embodiment is different from the first embodiment in that the structure is related to the bypass valve 17 made of a thermowax valve.

[Bypass valve]
16 and 17 show a part of the EGR cooler 13, the bypass passage 16, the bypass valve 17, and the EGR valve 14 by a cross-sectional view according to FIGS. 2 and 3. FIG. 16 shows a state in which the bypass valve 17 is opened, and FIG. 17 shows a state in which the bypass valve 17 is closed. Also in this embodiment, even if the thermowax 24 is excessively expanded and the valve body 21 is excessively projected, the valve body 21 or the wall portion 46bb is not damaged.

That is, in this embodiment, as shown in FIGS. 16 and 17, a relief hole 47 for avoiding interference with the valve body 21 is provided in the wall portion 46bb of the partition wall 46 to which the tip of the valve body 21 of the bypass valve 17 abuts. Is formed.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the operation and effect are different from those of each embodiment in the difference of the configuration related to the bypass valve 17. That is, in this embodiment, as shown in FIG. 17, when the bypass valve 17 is closed, the tip of the valve body 21 penetrates the relief hole 47, so that the valve body 21 excessively protrudes when the valve is closed. However, the tip end portion of the valve body 21 does not hit the wall portion 46bb of the downstream wall portion 46b. Therefore, in the bypass valve 17, even if the thermowax 24 is excessively expanded and the valve body 21 is excessively projected, it is possible to prevent the valve body 21 or the wall portion 46bb from being damaged.

<Sixth Embodiment>
Next, the sixth embodiment will be described in detail with reference to the drawings.

This embodiment differs from each of the above embodiments in that the configuration is related to the bypass valve 17 including the thermowax valve.

[Bypass valve]
18 and 19 show a part of the EGR cooler 13, the bypass passage 16, the bypass valve 17, and the EGR valve 14 by a cross-sectional view according to FIG. 18 and 19 show a state in which the bypass valve 17 is closed when the cooling water temperature THW becomes “65 ° C.” or higher. As shown in FIGS. 18 and 19, in this embodiment, the bypass passage 16 is provided with a sub-bypass passage 48 for bypassing the EGR gas flowing to the bypass valve 17. The sub-bypass passage 48 is arranged at a position exposed to the outside air. The sub-bypass passage 48 is provided with a sub-bypass valve 49 made of a thermowax valve that opens when the outside air temperature becomes less than the second predetermined value. In this embodiment, the second predetermined value is set to a temperature in the range of "-10 ° C. or higher and lower than 5 ° C.". The basic configuration of the sub-bypass valve 49 is the same as that of the bypass valve 17 shown in FIGS. 5 and 6. The sub-bypass valve 49 is attached to the sub-bypass passage 48 via the heat insulating layer 50 so as not to transfer the heat transferred to the housing 18 of the EGR valve 14 to the thermowax. FIG. 18 shows a state in which the sub-bypass valve 49 is opened, and FIG. 19 shows a state in which the sub-bypass valve 49 is closed. The sub-bypass valve 49 operates in response to a change in the outside air temperature. That is, the sub-bypass valve 49 opens as shown in FIG. 18 when the outside air temperature becomes less than "-10 ° C", and as shown in FIG. 19 when the outside air temperature becomes "5 ° C" or higher. It is designed to close the valve.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the operation and effect are different from those of each embodiment in the difference of the configuration related to the bypass valve 17. That is, in this embodiment, the bypass passage 16 is provided with a sub-bypass passage 48 that bypasses the EGR gas flowing to the bypass valve 17. Further, the sub-bypass valve 49 provided in the sub-bypass passage 48 is opened when the outside air temperature becomes less than the second predetermined value (-10 ° C.). Therefore, even when the bypass valve 17 is closed, when the outside air temperature becomes less than the second predetermined value, the sub-bypass valve 49 opens and EGR to the downstream side through the bypass passage 16 and the sub-bypass passage 48. The gas flows, and the EGR gas merges with the EGR gas cooled by the heat exchanger 32 of the EGR cooler 13, and the temperature of the EGR gas flowing to the EGR gas distributor 15 (downstream EGR passage) increases. Therefore, even if the bypass valve 17 is closed in a low temperature environment where the outside air temperature is below the freezing point, the EGR gas distributor 15 is warmed by the EGR gas flowing to the EGR gas distributor 15 (downstream EGR passage). It is possible to suppress the generation of condensed water in the distributor 15.

<7th Embodiment>
Next, the seventh embodiment will be described in detail with reference to the drawings.

This embodiment is different from each of the above embodiments in terms of the arrangement and structure of the bypass valve 17 in the bypass passage 16.

[Bypass valve]
20 and 21 show a cross-sectional view of the EGR cooler 13, the bypass passage 16, the bypass valve 17, and a part of the EGR valve 14 cut along the longitudinal direction thereof. FIG. 20 shows a state in which the bypass valve 17 is opened, and FIG. 21 shows a state in which the bypass valve 17 is closed. In this embodiment, the bypass valve 17 is attached directly to the bypass passage 16 in the EGR cooler 13 rather than in the housing 18 of the EGR valve 14. In this case, the housing 31 and the bypass passage 16 of the EGR cooler 13 are each made of a thin SUS plate, the heat transfer coefficient is poor, and the heat of the cooling water of the engine 1 flowing to the heat exchanger 32 is difficult to transfer. The bypass valve 17 cannot be operated according to the temperature of the cooling water. Therefore, in this embodiment, in order to allow the cooling water of the engine 1 to flow around the bypass valve 17, the bypass valve 17 is provided with an adapter 51 including a cooling water passage 51a through which the cooling water flows. The adapter 51 is made of a metal having a good heat transfer coefficient. Other configurations are the same as the configurations of the above-described embodiments.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the operation and effect are different from those of each embodiment in the difference in the arrangement and structure of the bypass valve 17. That is, in this embodiment, the bypass valve 17 is provided in the bypass passage 16 provided integrally with the housing 31 of the EGR cooler 13, and the adapter 51 including the cooling water passage 51a through which the cooling water flows is provided around the bypass valve 17. It will be provided. Therefore, when the actuator 22 of the bypass valve 17 operates in response to a change in temperature, the actuator 22 operates in response to a change in the temperature of the cooling water flowing through the cooling water passage 51a, and the bypass valve 17 operates. The valve body 21 opens and closes according to a change in the temperature of the cooling water. Therefore, even when the bypass valve 17 is attached to the housing 31 of the EGR cooler 13 having a poor heat transfer coefficient, the actuator 22 of the bypass valve 17 operates in response to a change in the temperature of the cooling water, so that the bypass valve 17 is electrically operated. It is not necessary to control the bypass valve 17, and the configuration of the bypass valve 17 can be simplified.

<8th Embodiment>
Next, the eighth embodiment will be described in detail with reference to the drawings.

[About the arrangement of bypass passages]
This embodiment differs from each of the above embodiments in that the bypass passage 16 is arranged with respect to the EGR cooler 13. That is, FIGS. 22 and 23 show a cross-sectional view of the EGR cooler 13, the bypass passage 16, and a part of the bypass valve 17 and the EGR valve 14 cut along the longitudinal direction thereof. FIG. 22 shows a state in which the bypass valve 17 is opened, and FIG. 23 shows a state in which the bypass valve 17 is closed. As shown in FIGS. 22 and 23, in this embodiment, when the EGR valve 14 and the EGR cooler 13 are mounted on the vehicle, the bypass passage 16 is vertically downward with respect to the EGR valve 14 and the EGR cooler 13. It is arranged so that the upstream side of the bypass passage 16 is inclined downward in the vertical direction toward the exhaust passage 3 of the engine 1. In this respect, the bypass passage 16 is different from each of the above-described embodiments provided on the upper side of the EGR valve 14 and the EGR cooler 13 in the vertical direction. In this embodiment, the bypass valve 17 made of a thermowax valve is attached to the housing 18 of the EGR valve 14 corresponding to the bypass passage 16 as in the first to sixth embodiments. In FIGS. 22 and 23, arrow A4 indicates the flow of condensed water.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the operation and effect are different from those of each embodiment in the difference in the arrangement of the bypass passage 16 with respect to the EGR cooler 13. That is, in this embodiment, in the state where the EGR cooler 13 is mounted on the vehicle, the bypass passage 16 is arranged on the lower side in the vertical direction with respect to the EGR cooler 13, so that the condensed water generated by the EGR cooler 13 is the same. Due to its own weight, it can flow down to the bypass passage 16. Further, since the upstream side of the bypass passage 16 is inclined downward in the vertical direction toward the exhaust passage 3, the condensed water flowing down to the bypass passage 16 can flow down to the exhaust passage 3 due to its own weight. Therefore, the condensed water generated in the EGR passage 12, the EGR cooler 13, and the like can be discharged to the exhaust passage 3 through the bypass passage 16 by its own weight.

<9th embodiment>
Next, the ninth embodiment will be described in detail with reference to the drawings.

[Bypass valve arrangement]
This embodiment differs from the eighth embodiment in that the configuration of the EGR cooler 13 and the arrangement of the bypass valve 17 including the thermowax valve are different. That is, FIG. 24 shows a cross-sectional view of the EGR cooler 13, the bypass passage 16, and the bypass valve 17 cut along the longitudinal direction thereof. FIG. 24 shows a state in which the bypass valve 17 is opened. In this embodiment, the bypass passage 16 is formed integrally with the housing 31 made of SUS of the EGR cooler 13 from the inlet side to the outlet side thereof. Also in this embodiment, the EGR cooler 13 and the bypass passage 16 are adjacent to each other via the partition wall 46. The partition wall 46 includes a main wall portion 46a in contact with the heat exchanger 32 and a downstream wall portion 46b extending downstream from the heat exchanger 32. The bypass valve 17 is attached to the housing 31 of the EGR cooler 13 at a rising portion having a steep slope on the outlet side of the bypass passage 16. Further, in this embodiment, in the downstream wall portion 46b of the partition wall 46, a plurality of communication holes communicating with the bypass passage 16 from the outlet side of the EGR cooler 13 in order to drain the condensed water flowing on the outlet side of the EGR cooler 13. 53 is provided. Further, in this embodiment, in order to allow the cooling water of the engine 1 to flow around the bypass valve 17, the bypass valve 17 is provided with an adapter 51 including a cooling water passage 51a through which the cooling water flows. The adapter 51 is made of a metal having a good heat transfer coefficient.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the operation and effect are different from those of the eighth embodiment in the difference between the configuration of the EGR cooler 13 and the arrangement of the bypass valve 17. That is, in this embodiment, the condensed water flowing out from the heat exchanger 32 on the outlet side of the EGR cooler 13 tends to flow down from the communication hole 53 to the bypass passage 16 at the downstream wall portion 46b of the partition wall 46 due to its own weight. .. Therefore, the condensed water generated in the EGR passage 12 or the EGR cooler 13 or the like can be efficiently flowed to the bypass passage 16 by its own weight, and can be discharged to the exhaust passage 3.

<10th Embodiment>
Next, the tenth embodiment will be described in detail with reference to the drawings.

[Bypass valve arrangement]
This embodiment differs from the ninth embodiment in the arrangement of the bypass valve 17 composed of the thermowax valve. That is, FIG. 25 shows a cross-sectional view of the EGR cooler 13, the bypass passage 16, and the bypass valve 17 cut along the longitudinal direction thereof. FIG. 25 shows a state in which the bypass valve 17 is opened. In this embodiment, the bypass valve 17 is attached to the housing 31 of the EGR cooler 13 corresponding to near the outlet of the heat exchanger 32. In this embodiment, the communication hole 53 is formed in the partition wall 46 (downstream wall portion 46b) near the outlet of the heat exchanger 32. The communication hole 53 is arranged at a position facing the tip of the valve body 21 of the bypass valve 17, and functions as a relief hole for avoiding interference between the tip of the valve body 21 extending when the bypass valve 17 is closed and the downstream wall portion 46b. It is designed to do.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, it has the following actions and effects in addition to the actions and effects of the ninth embodiment. That is, in this embodiment, the communication hole 53 functions as a relief hole for avoiding interference between the tip of the valve body 21 and the downstream wall portion 46b when the bypass valve 17 is closed, so that the valve body 21 is excessively used when the valve is closed. Even if it protrudes, the tip end portion of the valve body 21 does not abut (contact) with the downstream wall portion 46b. Therefore, in the bypass valve 17, even if the thermowax 24 is excessively expanded and the valve body 21 is excessively projected (operated), it is possible to prevent the valve body 21 or the downstream wall portion 46b from being damaged.

<11th Embodiment>
Next, the eleventh embodiment will be described in detail with reference to the drawings.

[About heat dissipation fins]
This embodiment differs from the ninth embodiment in the configuration on the outlet side of the EGR cooler 13. That is, FIG. 26 shows the EGR cooler 13, the bypass passage 16, and the bypass valve 17 in a cross-sectional view according to FIG. 24. FIG. 27 shows the heat radiating fin 55 with a sectional view taken along the line BB of FIG. 26. As shown in FIGS. 26 and 27, in the lead-out space 36 on the outlet side of the EGR cooler 13, a plurality of heat radiation fins 55 adjacent to the partition wall 46 (downstream wall portion 46b) and parallel to the flow direction of the EGR gas are provided. It will be provided. The lower side of the heat radiating fins 55 is connected to the downstream wall portion 46b, and the upper side of the heat radiating fins 55 is not connected to the housing 31 of the EGR cooler 13 and is separated. Other configurations are the same as those of the ninth embodiment.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, it has the following actions and effects in addition to the actions and effects of the ninth embodiment. That is, in this embodiment, in the EGR cooler 13, a plurality of heat radiation fins 55 parallel to the flow direction of the EGR gas are provided adjacent to and connected to the downstream wall portion 46b of the partition wall 46. Therefore, the heat of the EGR gas flowing through the bypass passage 16 is transmitted to the heat radiation fin 55 via the downstream wall portion 46b, the heat radiation fin 55 is warmed, and the condensed water adhering to the heat radiation fin 55 is warmed. Therefore, the condensed water generated by the EGR cooler 13 can be efficiently evaporated.

<12th Embodiment>
Next, the twelfth embodiment will be described in detail with reference to the drawings.

[About heat dissipation fins]
This embodiment is different from the eleventh embodiment in that the heat radiation fins 56 are arranged. That is, FIG. 28 shows the EGR cooler 13, the bypass passage 16, and the bypass valve 17 in a cross-sectional view according to FIG. 24. As shown in FIG. 28, a plurality of heat radiation fins 56 which are in contact with the partition wall 46 (main wall portion 46a) and are parallel to the flow direction of the EGR gas in the middle portion of the bypass passage 16 and directly below the heat exchanger 32. Is provided. The upper side of the heat radiation fins 56 is connected to the main wall portion 46a, and the lower side of the heat radiation fins 56 is connected to the housing 31 of the EGR cooler 13. In this embodiment, the communication hole is not provided in the downstream wall portion 46b of the partition wall 46.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the operation and effect are different from those of the eleventh embodiment in the following points. That is, in this embodiment, a plurality of heat radiation fins 56 parallel to the flow direction of the EGR gas are provided adjacent to and connected to the partition wall 46 (main wall portion 46a) in the bypass passage 16. Therefore, the heat of the EGR gas flowing through the bypass passage 16 is transmitted to the main wall portion 46a via the heat radiation fins 56, and the EGR cooler 13 is warmed. Therefore, the heat dissipation of the bypass passage 16 can be promoted, and in addition, the temperature rise of the EGR cooler 13 can be promoted.

<13th Embodiment>
Next, the thirteenth embodiment will be described in detail with reference to the drawings.

This embodiment is different from each of the above embodiments in terms of the configuration of the bypass valve 17 and the content of EGR control.

[About the engine system]
FIG. 29 shows a schematic configuration diagram of the engine system of this embodiment. FIG. 30 shows the EGR cooler 13, the bypass passage 16, and the bypass valve 19 in a cross-sectional view according to FIG. 28. The arrangement of the EGR cooler 13, the bypass passage 16 and the bypass valve 19 (valve closed state) in this embodiment is the same as that of the twelfth embodiment except that there is no heat radiation fin. In this embodiment, the bypass valve 19 is configured by a solenoid valve and is controlled by the ECU 90. The actuator 22 of the bypass valve 19 is composed of an electrically operated solenoid 29. In another embodiment, the bypass valve 17 made of a thermowax valve can be replaced with a bypass valve 19 having a solenoid as an actuator to implement this embodiment. In this embodiment, the bypass valve 19 is configured to be closed (normally closed) when the actuator 22 (solenoid 29) is turned off and not operated.

[Fourth EGR control]
FIG. 31 shows the contents of the fourth EGR control by a flowchart. As shown in FIG. 31, the fourth EGR control omits the processing of

steps

260, 270 and 300, and instead adds the processing of

steps

400 and 410 between

steps

250 and 280. The content is different from the second EGR control shown in 9.

When the process shifts to this routine, the ECU 90 executes the processes of steps 200 to 250, and if the determination result of step 250 is affirmative, the process proceeds to step 400 and the determination result of step 250 is negative. If so, the process proceeds to step 410.

Then, in step 400, the ECU 90 closes the bypass valve 19, and then shifts the process to step 280.

On the other hand, in step 410, the ECU 90 opens the bypass valve 19, and then shifts the process to step 280.

According to the fourth EGR control described above, the ECU 90 executes a forced EGR cut when the wall temperature THDW detected by the wall temperature sensor 88 exceeds the heat resistant temperature (140 ° C.) of the EGR gas distributor 15. Therefore, the EGR valve 14 is controlled to be fully closed. On the other hand, the ECU 90 closes the bypass valve 19 when the detected wall temperature THDW exceeds the allowable heating temperature of "120 ° C." of the EGR gas distributor 15 when the forced EGR cut is not executed. In addition to controlling the actuator 22 (solenoid 29), normal EGR control is executed. In this embodiment, the ECU 90 corresponds to an example of the third control means of the present disclosure technique.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, when the wall temperature THDW of the EGR gas distributor 15 detected by the wall temperature sensor 88 exceeds the allowable heating temperature (120 ° C.) of the EGR gas distributor 15. The ECU 90 controls the actuator 22 (solenoid 29) so as to close the bypass valve 19. Therefore, most of the EGR gas flowing through the EGR passage 12 does not flow to the bypass passage 16 but is cooled by the EGR cooler 13 and then flows to the EGR gas distributor 15. Therefore, when the temperature of the EGR gas flowing through the EGR passage 12 to the EGR gas distributor 15 exceeds the allowable heating temperature of the EGR gas distributor 15, the bypass valve 19 is controlled to close so as to lower the temperature of the EGR gas. It is possible to suppress the melting damage of the EGR gas distributor 15 and the generation of condensed water in the EGR gas distributor 15.

According to the configuration of this embodiment, the bypass valve 19 is closed when the actuator 22 (solenoid 29) is turned off and not operated, so that the bypass valve 19 is closed even if the solenoid 29 fails and does not operate. It is kept in a state. Therefore, even if the actuator 22 (solenoid 29) of the bypass valve 19 fails, the flow of EGR gas in the bypass passage 16 can be blocked, and the EGR gas distributor 15 (downstream EGR passage) is suppressed from being melted. can do.

<14th Embodiment>
Next, the 14th embodiment will be described in detail with reference to the drawings.

This embodiment is different from the thirteenth embodiment in that in addition to the fourth EGR control in the thirteenth embodiment, the bypass switching control for switching the opening and closing of the bypass valve 19 is executed.

When the engine 1 is cold (when not warmed up), the bypass valve 19 is opened in order to allow a part of the EGR gas flowing from the EGR passage 12 to the EGR cooler 13 to flow to the bypass passage 16 to detour. After that, when the warm-up of the engine 1 is completed, the bypass valve 19 is closed in order to allow almost all of the EGR gas to flow to the EGR cooler 13. However, even if the warm-up is completed once, the condensed water CW may stay in the vicinity of the outlet of the bypass passage 16 or the like as shown in FIG. 30 at low temperature. Therefore, in this embodiment, the following bypass valve switching control is executed in order to discharge the condensed water CW accumulated in the vicinity of the outlet of the bypass passage 16 after the bypass valve 19 is closed. ..

[Bypass valve switching control]
FIG. 32 shows the contents of the bypass valve switching control in this embodiment by a flowchart. When the process shifts to this routine, in step 500, the ECU 90 sets the cooling water temperature THW and engine rotation based on the detection values of the water temperature sensor 81, the rotation speed sensor 82, the throttle sensor 85, the intake air temperature sensor 87 and the wall temperature sensor 88. The number NE, intake temperature THA, engine load KL, and wall temperature THDW are taken in, respectively.

Next, in step 510, the ECU 90 determines whether or not there is a valve opening request to the bypass valve 19. If the determination result is affirmative, the ECU 90 shifts the process to step 520, and if the determination result is negative, the ECU 90 shifts the process to step 530.

In step 520, the ECU 90 opens the bypass valve 19 and then returns the process to step 500.

On the other hand, in step 530, the ECU 90 determines whether or not the cooling water temperature THW is less than "80 ° C.". "80 ° C" is an example. If the determination result is affirmative, the ECU 90 shifts the process to step 540, and if the determination result is negative, the ECU 90 shifts the process to step 550.

In step 540, the ECU 90 determines whether or not the EGR is cut, that is, whether or not the EGR is stopped. If the determination result is affirmative, the ECU 90 shifts the process to step 520, and if the determination result is negative, the ECU 90 shifts the process to step 550.

Then, in step 550 after shifting from step 530 or step 540, the ECU 90 closes the bypass valve 19 and returns the process to step 500.

According to the above-mentioned bypass valve switching control, the ECU 90 forcibly opens the bypass valve 19 on condition that the EGR cut is executed when the bypass valve 19 is closed. That is, in this embodiment, the actuator 22 (solenoid 29) of the bypass valve 19 is configured to open the valve body 21 under the condition that the EGR valve 14 is fully closed.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the following actions and effects can be obtained in addition to the actions and effects of the thirteenth embodiment. That is, the actuator 22 (solenoid 29) of the bypass valve 19 opens the valve body 21 of the bypass valve 19 under the condition that the EGR cut is executed (the EGR valve 14 is fully closed). Therefore, when the valve body 21 of the bypass valve 19 is opened under the condition that the EGR valve 14 is fully closed, it accumulates downstream of the bypass valve 19 (on the outlet side of the bypass passage 16) when the valve body 21 is closed. The flow of the condensed water CW upstream from the bypass valve 19 is allowed. Therefore, when the bypass valve 19 is closed, the condensed water CW accumulated in the bypass passage 16 downstream of the bypass valve 19 is transferred to the bypass passage 16 upstream of the bypass valve 19 by its own weight when the EGR cut is executed. It can be flushed and discharged to the exhaust passage 3.

<15th Embodiment>
Next, the fifteenth embodiment will be described in detail with reference to the drawings.

In this embodiment, the arrangement of the bypass passage 16 with respect to the EGR cooler 13, the configuration of the bypass valve 60, and the opening / closing control of the bypass valve 60 are different from those of the eighth to fourteenth embodiments. FIG. 33 shows a front view of an EGR cooler 13 in which a bypass passage 16 and a bypass valve 60 are integrally provided. FIG. 34 also shows the EGR cooler 13 with a rear view. FIG. 35 shows a cross-sectional view of the EGR cooler 13 cut along its longitudinal direction when the valve body 61 of the bypass valve 60 is fully closed. FIG. 36 shows an enlarged cross-sectional view of the portion of the EGR cooler 13 surrounded by the alternate long and short dash line square X1 in FIG. 35. FIG. 37 shows a cross-sectional view of the EGR cooler 13 when the valve body 61 of the bypass valve 60 is half-opened, according to FIG. 35. FIG. 38 shows the portion of the EGR cooler 13 surrounded by the one-dot chain line square X2 in FIG. 37 by an enlarged cross-sectional view. FIG. 39 shows a cross-sectional view of the EGR cooler 13 when the valve body 61 of the bypass valve 60 is fully opened, according to FIG. 35. FIG. 40 shows the portion of the EGR cooler 13 surrounded by the one-dot chain line square X3 in FIG. 39 by an enlarged cross-sectional view.

[About the configuration of the EGR cooler]
As shown in FIGS. 33 to 40, in the EGR cooler 13 of this embodiment, the bypass passage 16 is the EGR cooler 13 in a state of being mounted on the vehicle, similarly to the EGR cooler 13 of the eighth to 14th embodiments. It is arranged on the lower side in the vertical direction with respect to the above, and is provided so that the upstream side of the EGR cooler 13 and the bypass passage 16 is inclined downward in the vertical direction toward the exhaust passage 3 of the engine 1. Further, the heat exchanger 32 includes an inlet 32a into which the EGR gas flows in and an outlet 32b in which the EGR gas flows out. The bypass passage 16 also includes an inlet 16a through which the EGR gas flows in and an outlet 16b through which the EGR gas flows out. The outlet 16b of the bypass passage 16 is arranged adjacent to the outlet 32b of the heat exchanger 32. In this embodiment, the valve body 61 and the rotating shaft 62 of the bypass valve 60 are arranged in the housing 31 of the EGR cooler 13 corresponding to the outlet 16b of the bypass passage 16. In FIGS. 33 to 40, for convenience, the illustration of the inlet and outlet of the cooling water is omitted, and the illustration of the heat exchanger 32 and the bypass valve 60 is simplified.

[Bypass valve configuration]
As shown in FIGS. 35 to 40, the bypass valve 60 of this embodiment includes a valve body 61 having a substantially square plate shape and a rotating shaft 62 that rotates the valve body 61, and one side of the valve body 61 is included. The side is fixed to the rotating shaft 62, and the other side of the valve body 61 facing the one side is configured as a swing type swinging around the rotating shaft 62. Further, as shown in FIG. 34, the bypass valve 60 includes an actuator 63 that electrically operates to rotate the rotating shaft 62. The actuator 63 includes a drive shaft 63a that can reciprocate in the axial direction, and the tip end portion of the drive shaft 63a is driven and connected to the rotating shaft 62 via a link 64. Then, when the drive shaft 63a of the actuator 63 reciprocates in the axial direction, the rotating shaft 62 rotates in one direction or the opposite direction via the link 64, and the rotation of the rotating shaft 62 causes the valve body 61 to rotate. It is configured to open and close the exit 16b of the bypass passage 16.

In this embodiment, as shown in FIGS. 35 and 36, when the valve body 61 of the bypass valve 60 closes the outlet 16b of the bypass passage 16 when the valve is closed (when fully closed), the valve body 61 is a heat exchanger. It is arranged so as to be substantially parallel to the direction (axial direction) of the axis L1 of the 32, and the valve body 61 is arranged at a position where the flow path directly downstream of the outlet 32b of the heat exchanger 32 is fully opened. Further, as shown in FIGS. 37 and 38, when the valve body 61 is half-opened (when the valve is opened) with the outlet 16b of the bypass passage 16 half-opened, the valve body 61 is at the outlet 32b of the heat exchanger 32. It is placed at a position that blocks a part of the flow path directly downstream and narrows the flow path area. Further, as shown in FIGS. 39 and 40, when the valve body 61 fully opens the outlet 16b of the bypass passage 16 (when the valve is opened), the valve body 61 is one of the outlets 32b of the heat exchanger 32. It is arranged at a position where the portion is further blocked and the flow path area of the outlet 32b is further narrowed.

[Valve assembly constituting the bypass valve and its assembly procedure]
Here, with respect to the housing 31 of the EGR cooler 13, it is conceivable to perform spot welding on a part of the housing 31 and then finish the entire fastening by brazing. The reason for adopting this procedure is that if welding is performed after brazing, the brazed portion melts and a fastening defect occurs. Further, the rotary shaft 62 constituting the bypass valve 60 is generally provided with a rubber lip seal in order to prevent gas leakage. In this case, the lip seal cannot be brazed in the state of being assembled to the rotary shaft 62, and it is necessary to retrofit the rotary shaft 62 to which the lip seal is assembled after finishing the housing 31 of the EGR cooler 13. Become. Here, in order to fasten the valve body 61 to the rotary shaft 62 after assembling the rotary shaft 62 to the housing 31, a fastening window must be provided in the housing 31. Further, after the valve body 61 is fastened to the rotating shaft 62, it becomes necessary to close the fastening window with a lid or the like. In this case, it is difficult to weld the lid, and a seal with a gasket is required, which leads to an increase in manufacturing cost. Therefore, in this embodiment, the following configurations are proposed for the valve assembly constituting the bypass valve 60 and the assembly procedure thereof.

FIG. 41 shows a cross-sectional view of the configuration of the valve assembly 65 provided corresponding to the outlet 16b of the bypass passage 16. As shown in FIG. 41, a bearing case 66 is provided in the housing 31 of the EGR cooler 13 constituting the bypass passage 16. The bearing case 66 includes a tubular portion 66a, a bottom portion 66b of the tubular portion 66a, and a flange portion 66c provided on the outer periphery of the bottom portion 66b. The flange portion 66c of the bearing case 66 is fixed to the housing 31 via bolts 67. A gasket 68 for preventing gas leakage is provided at a portion where the flange portion 66c of the bearing case 66 abuts on the housing 31. A ball bearing 69 is provided inside the tubular portion 66a of the bearing case 66. A rotary shaft 62 is rotatably supported by the ball bearing 69. The base end portion 62a of the rotating shaft 62 penetrates the bottom portion 66b of the bearing case 66 and is arranged in the vicinity of the outlet 16b of the bypass passage 16. A valve body 61 is fixed to the base end portion 62a via a screw 70. Between the ball bearing 69 and the bottom 66b, a lip seal 71 for preventing gas leakage is provided on the rotating shaft 62. The lip seal 71 is formed of a flexible material such as rubber. The lip seal 71 corresponds to an example of a seal member in this disclosure technique. Further, a lever 72 for rotating the rotating shaft 62 is fixed to the tip of the rotating shaft 62. The lever 72 can rotate integrally with the rotating shaft 62 and the valve body 61. Further, a valve closing spring 73 for urging the valve body 61 in the valve closing direction is provided on the outer periphery of the tubular portion 66a. The valve closing spring 73 is interposed between the bearing case 66 and the lever 72, and rotates and urges the valve body 61 in the valve closing direction via the rotating shaft 62.

The valve assembly 65 described above can be assembled by the following procedure. That is, (1) First, the inside of the ball bearing 69 is press-fitted to the outer circumference of the rotating shaft 62. (2) The lip seal 71 is press-fitted into the inner circumference of the tubular portion 66a of the bearing case 66. (3) The outer circumference of the ball bearing 69 is press-fitted into the inner circumference of the tubular portion 66a, and the base end portion 62a of the rotating shaft 62 is passed through the lip seal 71 and the bottom portion 66b of the bearing case 66. (4) After fixing the valve body 61 to the base end portion 62a of the rotating shaft 62 with a screw 70, the head of the screw 70 is spot-welded. (5) A valve closing spring 73 is attached to the outer periphery of the tubular portion 66a of the bearing case 66, and a lever 72 is attached to the tip of the rotating shaft 62 and fixed to form a sub valve assembly. Here, the lever 72 can be fixed to the rotating shaft 62 by tightening, welding, or caulking a nut. (6) The assembly of the valve assembly 65 is completed by fixing the bearing case 66 of the sub-valve assembly to the housing 31 via the gasket 68 with bolts 67.

[Bypass valve open / close control]
Next, the opening / closing control of the bypass valve 60 configured as described above will be described. FIG. 42 shows the control contents by a flowchart. The engine system of this embodiment adopts the engine system shown in FIG. 29, the bypass valve 19 in FIG. 29 is replaced with the bypass valve 60 of the present embodiment, and the actuator 63 is used to control the bypass valve 60. It shall be controlled.

When the process shifts to the routine shown in FIG. 42, in step 600, the ECU 90 determines the engine rotation speed NE, the engine load KL, based on the detection values of the water temperature sensor 81, the rotation speed sensor 82, the throttle sensor 85, and the intake air temperature sensor 87. The cooling water temperature THW and the intake temperature THA are taken in, respectively.

Next, in step 610, the ECU 90 obtains the target bypass opening TECBV according to the engine speed NE, the engine load KL, the cooling water temperature THW, and the intake air temperature THA. The ECU 90 can obtain the target bypass opening degree TECBV corresponding to various parameters NE, KL, THW, and THA by referring to the target bypass opening degree map shown in FIG. 43, for example. As shown in FIG. 43, this target bypass opening degree map covers three intake air temperature ranges in which the intake air temperature THA (which is also the outside air temperature) is “-10 ° C. or lower”, “0 ° C.”, and “25 ° C. or higher”. For each of these intake air temperature ranges, the cooling water temperature THW is defined in four cooling water temperature ranges of "less than 40 ° C", "40 ° C", "60 ° C" and "80 ° C or higher". Then, the target bypass opening degree TECBV corresponding to the engine load KL and the engine speed NE is set for each of the 12 combination regions combined in each intake air temperature range and each cooling water temperature range. In this map, the target bypass opening degree TECBV is set to increase as the engine 1 rotates at a lower speed and has a lighter load. Further, in this map, the lower the intake air temperature THA, the larger the target bypass opening TECBV is set. The target bypass opening TECBV is set to be large. Further, in this map, the target bypass opening TECBV is set to increase as the cooling water temperature THW decreases. However, when the cooling water temperature THW becomes "less than 40 ° C." which is the EGR starting water temperature, The target bypass opening TECBV is set to be "0".

Next, in step 620, the ECU 90 obtains the EGR start permitted water temperature SEGRTHW according to the intake air temperature THA. The ECU 90 can obtain the EGR start permitted water temperature SEGRTHW according to the intake air temperature THA, for example, by referring to the EGR start permitted water temperature map shown in FIG. 44. This map is set so that the lower the intake air temperature THA from "25 ° C" to "-15 ° C", the higher the EGR start permitted water temperature SEGRTHW is from "40 ° C" to "85 ° C", and the intake temperature THA becomes. When the temperature rises above "25 ° C", the EGR start permitted water temperature SEGRTHW is set to "40 ° C".

Next, in step 630, the ECU 90 determines whether or not the EGR start permitted water temperature SEGRTHW is lower than the cooling water temperature THW. If the determination result is affirmative, the ECU 90 shifts the process to step 640, and if the determination result is negative, the ECU 90 shifts the process to step 660.

In step 640, the ECU 90 determines whether or not the cooling water temperature THW is lower than "100 ° C.". If the determination result is affirmative, the ECU 90 shifts the process to step 650, and if the determination result is negative, the ECU 90 shifts the process to step 660.

In step 650, the ECU 90 sets the target bypass opening degree TECBV as the final target bypass opening degree FTECBV.

On the other hand, in step 660 after shifting from step 630 or step 640, the ECU 90 sets "0%" as the final target bypass opening degree FTECBV.

Then, in step 670 after shifting from step 650 or step 660, the ECU 90 controls the bypass valve 60 to the final target bypass opening degree FTECBV.

According to the above-mentioned open / close control of the bypass valve 60, the ECU 90 controls the bypass valve 60 to be fully closed under the condition that the cooling water temperature THW is equal to or lower than the EGR start permitted water temperature SEGRTHW, and the cooling water temperature THW starts EGR. Under the condition that the permitted water temperature is higher than SEGRTHW and the temperature is 100 ° C. or higher, the bypass valve 60 is controlled to be fully closed even if the intake air temperature THA (outside air temperature) is low, and the cooling water temperature THW permits EGR start. Under the condition that the water temperature is higher than SEGRTHW and lower than 100 ° C., the bypass valve 60 is controlled to the target bypass opening degree TECBV.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, it is possible to obtain the same action and effect as the action and effect of the eighth to fourteenth embodiments. In addition, according to the configuration of the EGR cooler 13 of this embodiment, the outlet 16b of the bypass passage 16 is arranged adjacent to the outlet 32b of the heat exchanger 32, and the valve body 61 and the rotating shaft 62 of the bypass valve 60 are bypassed. It is arranged corresponding to the exit 16b of the passage 16. Further, in the bypass valve 60, when the valve body 61 closes the outlet 16b of the bypass passage 16 (when the valve is closed), the valve body 61 is arranged substantially parallel to the axial direction of the heat exchanger 32. Therefore, when the bypass valve 60 is fully closed, almost all of the EGR gas flowing from the exhaust passage 3 to the EGR passage 12 flows to the heat exchanger 32 to be cooled, flows out from the outlet 32b, and flows along the valve body 61 of the bypass valve 60. It flows toward the EGR valve 14 and the EGR gas distributor 15 (downstream EGR passage). Therefore, when the bypass valve is fully closed, the valve body 61 of the bypass valve 60 can be cooled with the cooled EGR gas, and the rotary shaft 62 can be cooled via the valve body 61. As a result, the lip seal 71 provided on the rotating shaft 62 can be protected from the heat damage of the EGR gas. On the other hand, when the bypass valve 60 is half-opened or fully opened (when the valve is opened), the valve body 61 blocks a part of the flow path area of the outlet 32b of the heat exchanger 32, and the flow path area becomes narrow. Therefore, the flow rate of the cooled EGR gas flowing out from the outlet 32b of the heat exchanger 32 decreases by the amount that the flow path area of the outlet 32b of the heat exchanger 32 becomes narrower, and the flow rate of the cooled EGR gas with respect to the flow rate decreases from the outlet 16b of the bypass passage 16. The ratio of the flow rate of the uncooled EGR gas flowing out (bypass flow rate ratio) increases, and the temperature of the EGR gas flowing to the EGR valve 14 and the EGR gas distributor 15 (downstream EGR passage) increases. Therefore, when the bypass valve 60 is half-opened or fully opened, warm-up of the EGR valve 14 and the EGR gas distributor 15 (downstream EGR passage) can be promoted by the amount that the bypass flow rate ratio increases.

FIG. 45 shows the ratio of the flow rate of EGR gas flowing through the heat exchanger 32 (cooler flow rate ratio) and the bypass flow rate ratio to the total flow rate of EGR gas flowing to the downstream EGR passage when the bypass valve 60 is half-opened and fully opened. The difference between the above is shown by a graph. As shown in FIG. 45, when half-opened, the cooler flow rate ratio is "75%" and the bypass flow rate ratio is "25%". On the other hand, when fully open, the cooler flow rate ratio is "60%" and the bypass flow rate ratio is "40%". As described above, it can be seen that the bypass flow rate ratio is increased by about 15% at the time of full opening as compared with the time of half opening.

Here, according to the open / close control of the bypass valve 60 in this embodiment, the ECU 90 closes the EGR valve 14 and EGR to the EGR cooler 13 under the condition that the cooling water temperature THW is equal to or lower than the EGR start permitted water temperature SEGRTHW. Gas does not flow and the bypass valve 60 is controlled to be fully closed. Further, the ECU 90 fully closes the bypass valve 60 even if the intake air temperature THA (outside air temperature) is low under the condition that the cooling water temperature THW is higher than the EGR start permitted water temperature SEGRTHW and the temperature is as high as 100 ° C. or higher. To control. Therefore, the EGR valve 14 is opened, and all of the EGR gas flowing to the EGR cooler 13 can be cooled by the heat exchanger 32, and the temperature of the EGR gas is lowered to the EGR gas distributor 15 (downstream EGR passage). Can be shed. Further, the ECU 90 controls the bypass valve 60 to the target bypass opening degree TECBV under the condition that the cooling water temperature THW is higher than the EGR start permitted water temperature SEGRTHW and lower than 100 ° C. Therefore, the bypass flow rate ratio in the EGR gas flowing to the EGR gas distributor 15 (downstream EGR passage) can be increased, the temperature of the EGR gas can be raised, and the EGR gas distributor 15 can be appropriately warmed up. can do.

Further, according to the configuration of the EGR cooler 13 of this embodiment, the valve assembly 65 is provided by adopting the above-mentioned assembly procedure. That is, the bearing case 66 of the sub-valve assembly formed by assembling

various parts

61, 62, 66, 69, 70 to 73 is finally fixed to the housing 31 via the gasket 68 with bolts 67, whereby the valve assembly 65 I tried to complete the assembly of. Therefore, although the gasket 68 and the bolt 67 are required to fix the bearing case 66 to the housing 31, the valve assembly 65 is provided to the housing 31 without providing an assembly window and without welding. This makes it possible to reduce the manufacturing cost of the EGR cooler 13.

<16th Embodiment>
Next, the 16th embodiment will be described in detail with reference to the drawings.

This embodiment is different from the fifteenth embodiment in the configuration of the swing type bypass valve 60. In the 16th embodiment, the outlet 16b of the bypass passage 16 is arranged adjacent to the outlet 32b of the heat exchanger 32, and the valve assembly 65 of the bypass valve 60 is arranged corresponding to the outlet 16b of the bypass passage 16. That is, the valve assembly 65 is arranged in the vicinity of the outlet 32b of the heat exchanger 32 and the outlet 16b of the bypass passage 16. Therefore, the rotating shaft 62 of the valve assembly 65 is arranged along one end edge 46c of the partition wall 46 between the heat exchanger 32 and the bypass passage 16. Here, a slight gap may be formed between one end edge 46c of the partition wall 46 and the rotating shaft 62. If this gap becomes large, the EGR gas blocked by the bypass passage 16 may leak to the outlet 32b side of the heat exchanger 32 through the gap when the valve body 61 is fully closed. As a result, the leaked EGR gas may reduce the cooling efficiency of the EGR gas cooled by the heat exchanger 32. On the other hand, if the gap becomes large, the condensed water flowing out of the heat exchanger 32 can be discharged to the bypass passage 16 through the gap. Therefore, in this embodiment, the bypass valve 60 is configured as follows.

[Bypass valve configuration]
46 and 47 show a portion of the EGR cooler 13 at the outlet 16b of the bypass passage 16 adjacent to the outlet 32b of the heat exchanger 32, and the valve body 61 and the rotating shaft 62 of the bypass valve 60. The relationship is shown in cross-sectional view. FIG. 46 shows a state in which the valve body 61 of the bypass valve 60 is fully closed, and FIG. 47 shows a state in which the valve body 61 is fully opened. In this embodiment, a gap 59 is provided between the boundary portion 58 between the outlet 32b of the heat exchanger 32 and the outlet 16b of the bypass passage 16 and the rotating shaft 62. The gap 59 is configured to be larger when the valve body 61 is opened than when the valve body 61 is closed (fully closed). Here, the boundary portion 58 is composed of one end edge 46c of the partition wall 46.

That is, in this embodiment, as shown in FIGS. 46 and 47, one end edge 46c of the partition wall 46 is flat, and the rotation shaft 62 is arranged adjacent to the one end edge 46c. A notch 62b having an arcuate cross section is formed in a part of the rotating shaft 62, and the notch 62b is displaced with respect to the boundary portion 58 (one end edge 46c) as the rotating shaft 62 rotates. It has become. Specifically, as shown in FIG. 46, when the valve body 61 is fully closed, the notch 62b is displaced so that the gap 59 between the rotating shaft 62 and the boundary portion 58 (one end edge 46c) is minimized. On the other hand, as shown in FIG. 47, when the valve body 61 is opened, the notch 62b is displaced so that the gap 59 between the rotating shaft 62 and the boundary portion 58 (one end edge 46c) is maximized. The valve body 61 is fixed in a state where its base is housed in the rotating shaft 62. Further, the valve body 61 has a tip end side projecting radially from the rotation shaft 62 to open and close the outlet 16b of the bypass passage 16. Here, the tip of the valve body 61 is inclined according to the inclination of the housing 31.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the following actions and effects can be obtained in addition to the actions and effects of the fifteenth embodiment. That is, in this embodiment, the gap 59 between the boundary portion 58 (one end edge 46c) between the outlet 32b of the heat exchanger 32 and the outlet 16b of the bypass passage 16 and the rotating shaft 62 is the valve body of the bypass valve 60. It is configured so that it is larger when the valve is opened than when the valve is closed. Therefore, as shown in FIG. 46, this gap 59 becomes smaller when the valve body 61 is closed than when the valve is opened, so that the EGR gas in the bypass passage 16 passes through the gap 59 in the heat exchanger 32. It becomes difficult to leak to the side of the outlet 32b. Therefore, when the valve body 61 is closed, by narrowing the gap 59, it is possible to suppress the leakage of EGR gas due to the gap 59 from the bypass passage 16 to the side of the heat exchanger 32, and the EGR by the heat exchanger 32 can be suppressed. It is possible to suppress a decrease in gas cooling efficiency. On the other hand, as shown in FIG. 47, this gap 59 becomes larger when the valve body 61 is opened than when the valve is closed, so that the condensed water discharged from the outlet 32b of the heat exchanger 32 (indicated by a white circle in FIG. 47). ) Makes it easier to flow into the gap 59. Further, since a part of the flow path area of the outlet 32b of the heat exchanger 32 is blocked by the valve body 61, the scattering of the condensed water discharged from the outlet 32b is suppressed. Therefore, when the valve body 61 is opened, by widening the gap 59, a large amount of condensed water discharged from the outlet 32b of the heat exchanger 32 can be discharged to the bypass passage 16 through the gap 59. Here, when the valve body 61 is opened, the EGR gas flowing out of the bypass passage 16 joins the EGR gas cooled by the heat exchanger 32, so that the EGR gas leaks from the gap 59 to the outlet 32b side of the heat exchanger 32. Due to the EGR gas, the decrease in the cooling efficiency of the EGR gas cooled by the heat exchanger 32 does not become a problem.

<17th Embodiment>
Next, the 17th embodiment will be described in detail with reference to the drawings.

[Bypass valve configuration]
This embodiment differs from the 16th embodiment in that the swing type bypass valve 60 is configured. FIG. 48 shows a state in which the valve body 61 of the bypass valve 60, which is a part of the EGR cooler 13, is fully closed, by a cross-sectional view according to FIG. 46. FIG. 49 shows a state in which the valve body 61 is a part of the EGR cooler 13 and the valve body 61 is opened by a cross-sectional view according to FIG. 47. Also in this embodiment, the bypass valve 60 is provided with a gap 59 between the boundary portion 58 between the outlet 32b of the heat exchanger 32 and the outlet 16b of the bypass passage 16 and the rotating shaft 62. The gap 59 is configured to be larger when the valve body 61 is fully closed than when the valve body 61 is fully closed.

That is, as shown in FIGS. 48 and 49, even in this embodiment, the one end edge 46c of the partition wall 46 is flat, and the one end edge 46c constitutes the boundary portion 58. Then, the rotation shaft 62 is arranged adjacent to the boundary portion 58. In this embodiment, a notch is not formed in a part of the rotary shaft 62, and the rotary shaft 62 constituting the swing type bypass valve 60 has a predetermined gap 59 with respect to the boundary portion 58 (one end edge 46c). Placed through. The base side of the valve body 61 is fixed to the rotating shaft 62, and the base end 61a thereof slightly protrudes in the radial direction of the rotating shaft 62. Further, the valve body 61 has a tip end side projecting radially from the rotation shaft 62 to open and close the outlet 16b of the bypass passage 16. Here, the tip of the valve body 61 is inclined at an acute angle according to the inclination of the housing 31, and the base end 61a of the valve body 61 is also inclined at an acute angle. Then, as shown in FIG. 48, when the valve body 61 is fully closed, the gap 59 between the rotating shaft 62 and the boundary portion 58 is closed by the base end 61a of the valve body 61. On the other hand, as shown in FIG. 49, when the valve body 61 is opened, the valve body 61 rotates together with the rotating shaft 62, so that the base end 61a of the valve body 61 rotates and the boundary portion 58 (one end edge 46c). ), The gap 59 is opened.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the same operation and effect as those of the 16th embodiment can be obtained, although there are some differences from the configuration of the 16th embodiment.

<18th Embodiment>
Next, the eighteenth embodiment will be described in detail with reference to the drawings.

[Bypass valve configuration]
This embodiment differs from that of the 16th and 17th embodiments having a swing type configuration in that the bypass valve 60 has a butterfly type configuration. FIG. 50 shows a state in which the valve body 61 of the bypass valve 60, which is a part of the EGR cooler 13, is fully closed, by a cross-sectional view according to FIG. 48. FIG. 51 shows a state in which the valve body 61 of the bypass valve 60, which is a part of the EGR cooler 13, is opened, by a cross-sectional view according to FIG. 49. Also in this embodiment, the bypass valve 60 is provided with a gap 59 between the boundary portion 58 between the outlet 32b of the heat exchanger 32 and the outlet 16b of the bypass passage 16 and the valve body 61. The gap 59 is configured to be larger when the valve body 61 is opened than when the valve body 61 is closed (fully closed).

That is, as shown in FIGS. 50 and 51, in this embodiment, the rotation shaft 62 is arranged adjacent to the boundary portion 58 (one end edge 46c of the partition wall 46). Since the bypass valve 60 of this embodiment has a butterfly type configuration, the rotating shaft 62 is arranged with respect to the boundary portion 58 (one end edge 46c) at a predetermined interval. The intermediate portion of the valve body 61 is fixed to the rotating shaft 62, and one end side 61b and the other end side 61c of the valve body 61 project in the radial direction of the rotating shaft 62, respectively. Further, the valve body 61 has one end side 61b in contact with the one end edge 46c of the partition wall 46, and the other end side 61c in contact with the inclined inner wall of the housing 31. Here, the one end side 61b of the valve body 61 is inclined at an acute angle according to the inclined one end edge 46c of the partition wall 46, and the other end side 61c of the valve body 61 is inclined at an acute angle according to the inclination of the housing 31. .. Then, as shown in FIG. 50, when the valve body 61 is fully closed, the one end side 61b of the valve body 61 comes into contact with the boundary portion 58 (one end edge 46c), and the rotary shaft 62 and the boundary portion 58 (one end edge 46c) come into contact with each other. There is no gap 59 between them. On the other hand, as shown in FIG. 51, when the valve body 61 is opened, the valve body 61 rotates together with the rotating shaft 62 between the one end side 61b of the valve body 61 and the boundary portion 58 (one end edge 46c). There is a gap 59 in the space.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, although the types of the bypass valve 60 are different from those of the 16th and 17th embodiments, the same operations and effects as those of the 16th and 17th embodiments can be obtained. Can be done.

<19th Embodiment>
Next, the 19th embodiment will be described in detail with reference to the drawings.

[Bypass valve valve assembly configuration and valve assembly assembly procedure]
This embodiment is different from the swing type bypass valve 60 of the fifteenth embodiment in that the configuration of the valve assembly 65 according to the butterfly type bypass valve 60 and the procedure for assembling the valve assembly 65 are different. FIG. 52 shows the configuration of the valve assembly 65 of the bypass valve 60 by a cross-sectional view according to FIG. 41. In the valve assembly 65 shown in FIG. 52, the same components as those shown in FIG. 41 are designated by the same reference numerals, description thereof will be omitted, and different points will be mainly described (the same applies in the following description). .).

As shown in FIG. 52, the housing 31 of the EGR cooler 13 includes an outer cylinder portion 31e protruding outward. On the outer periphery of the outer cylinder portion 31e, a plurality (four) press-fitting surface 31ea forming a flat surface are arranged at equal angular intervals in the circumferential direction. Since these press-fitting surface 31ea are formed by cutting the outer periphery of the outer cylinder portion 31e, the portion thereof appears to be concave in FIG. 52. As will be described later, this press-fitting surface 31ea is for positioning the side of the housing 31 with a positioning jig when the sub-valve assembly including the rotary shaft 62 and the valve body 61 is press-fitted inside the outer cylinder portion 31e. Used for. The bearing case 66 includes a tubular portion 66a and a bottom portion 66b, and does not include a flange portion. The bearing case 66 is press-fitted and fixed to the inside of the outer cylinder portion 31e of the housing 31. A rotary shaft 62 is rotatably supported on the tubular portion 66a of the bearing case 66 via a ball bearing 69, and the outer periphery of the rotary shaft 62 is sealed via a lip seal 71. Inside the housing 31, the valve body 61 is fixed to the base end portion 62a of the rotating shaft 62 via a screw 70. A lever 72 is fixed to the tip of the rotating shaft 62. A cylindrical spring guide 74 is provided on the outer periphery of the outer cylinder portion 31e of the housing 31. On the outer periphery of the spring guide 74, a valve closing spring 73 for urging the valve body 61 in the valve closing direction is provided between the spring guide 74 and the lever 72.

The procedure for assembling the valve assembly 65 described above is as follows. That is, (1) the inside of the ball bearing 69 is press-fitted to the outer circumference of the rotating shaft 62. (2) The lip seal 71 is press-fitted into the inside of the tubular portion 66a of the bearing case 66. (3) The outside of the ball bearing 69 into which the rotating shaft 62 is press-fitted is press-fitted into the inside of the tubular portion 66a. (4) The rotating shaft 62 is passed through the lip seal 71 and the bottom portion 66b of the bearing case 66, the valve body 61 is fixed to the base end portion 62a of the rotating shaft 62 with a screw 70, and then the head of the screw 70 is spot welded. do. In this way, the assembly of the sub-valve assembly of the bypass valve 60 is completed. (5) The bearing case 66 constituting the sub-valve assembly is press-fitted into the outer cylinder portion 31e of the housing 31 and fixed. At this time, the bearing case 66 can be easily press-fitted into the outer cylinder portion 31e by utilizing the recess of the press-fitting receiving surface 31ea formed on the outer periphery of the outer cylinder portion 31e of the housing 31. (6) A tubular spring guide 74 is attached to the outer periphery of the outer cylinder portion 31e of the housing 31, and a valve closing spring 73 is attached to the outer periphery of the spring guide 74. (7) By fixing the lever 72 to the tip of the rotating shaft 62, the assembly of the valve assembly 65 is completed. The lever 72 can be fixed to the rotating shaft 62 by tightening, welding or caulking a nut.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, although the configuration of the valve assembly 65 of the bypass valve 60 is slightly different from that of the fifteenth embodiment, the same operation and effect as those of the fifteenth embodiment can be obtained. .. Further, according to the configuration of this embodiment, the valve assembly 65 is provided by adopting the above-mentioned assembly procedure. That is, after the bearing case 66 of the sub-valve assembly to which

various parts

61, 62, 66, 69, 71 are assembled is press-fitted into the outer cylinder portion 31e of the housing 31 and fixed, the remaining various parts 72 to 74 are assembled. This completes the assembly of the valve assembly 65. Therefore, in order to fix the bearing case 66 to the housing 31, the valve assembly 65 can be provided to the housing 31 without providing an assembly window and without welding, and the manufacturing cost of the EGR cooler 13 can be provided. Can be suppressed.

<20th Embodiment>
Next, the twentieth embodiment will be described in detail with reference to the drawings.

[Bypass valve valve assembly configuration and valve assembly assembly procedure]
This embodiment differs from the 19th embodiment in the configuration of the valve assembly 65 according to the bypass valve 60 and the procedure for assembling the valve assembly. FIG. 53 shows the valve assembly 65 with a cross-sectional view according to FIG. 52. As shown in FIG. 53, the housing 31 of the EGR cooler 13 includes a long cylinder portion 31g having an outer cylinder portion 31e projecting outward from the housing 31 and an inner cylinder portion 31f fitted into the housing 31. An opening 31fa through which EGR gas flows is formed in the inner cylinder portion 31f corresponding to the outlet 16b of the bypass passage 16. The bearing case 66 includes a tubular portion 66a and a bottom portion 66b. The bearing case 66 is press-fitted and fixed to the inside of the outer cylinder portion 31e of the housing 31. A rotary shaft 62 is rotatably supported on the tubular portion 66a of the bearing case 66 via a ball bearing 69, and the outer periphery of the rotary shaft 62 is sealed via a lip seal 71. In the inner cylinder portion 31f of the housing 31, the valve body 61 is fixed to the base end portion 62a of the rotating shaft 62 via a screw 70. A lever 72 is fixed to the tip of the rotating shaft 62. A valve closing spring 73 is provided on the outer periphery of the outer cylinder portion 31e of the housing 31 between the lever 72 and the outer cylinder portion 31e.

The procedure for assembling the valve assembly 65 described above is as follows. That is, (1) the inside of the ball bearing 69 is press-fitted to the outer circumference of the rotating shaft 62. (2) The lip seal 71 is press-fitted into the inside of the tubular portion 66a of the bearing case 66. (3) The outside of the ball bearing 69 to which the rotating shaft 62 is assembled is press-fitted inside the tubular portion 66a. (4) The rotating shaft 62 is passed through the bottom portion 66b of the bearing case 66, the valve body 61 is fixed to the base end portion 62a of the rotating shaft 62 with a screw 70, and the head of the screw 70 is spot-welded. This forms a sub-valve assembly. (5) The bearing case 66 of the sub valve assembly is press-fitted into the outer cylinder portion 31e of the housing 31. (6) A valve closing spring 73 is mounted on the outside of the outer cylinder portion 31e of the housing 31. (7) The lever 72 is attached and fixed to the tip of the rotating shaft 62, and the valve closing spring 73 is engaged with the lever 72. This completes the assembly of the valve assembly 65 of the bypass valve 60.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the same operation and effect as those of the 19th embodiment can be obtained, although there are some differences in the configuration from the 19th embodiment.

<21st Embodiment>
Next, the 21st embodiment will be described in detail with reference to the drawings.

In this embodiment, the configuration is different from that of the fifteenth embodiment in terms of the configuration of the bypass valve 60 and the control for dealing with coil disconnection. FIG. 54 shows a perspective view of the EGR cooler 13 including the actuator 63 and the link 64 as viewed from the rear side. 55 and 56 show the EGR cooler 13 in a rear view according to FIG. 34. FIG. 55 shows the state of the actuator 63 and the link 64 when the bypass valve 60 is operated to open (fully open), and FIG. 56 shows the actuator when the bypass valve 60 is operated to close (fully closed). The state of 63 and the link 64 are shown. In this embodiment, the bypass valve 60 has the same configuration as that shown in FIGS. 35 to 41, but the actuator 63 and the link 64 have different configurations. The actuator 63 and the link 64 of this embodiment will be described below.

[About the configuration of actuators and links]
The actuator 63 of this embodiment is configured to operate electrically to rotate the rotating shaft 62. As shown in FIGS. 54 to 56, the actuator 63 includes a drive shaft 63a that can reciprocate in the axial direction, and the tip of the drive shaft 63a is driven and connected to the rotating shaft 62 via a link 64. In this embodiment, the lever 72 is integrally rotatably fixed to the tip of the rotating shaft 62. The base end of the lever 72 is fixed to the rotating shaft 62, and an elongated hole 72a is formed at the tip of the lever 72. The link 64 is configured by movably connecting the tip of the drive shaft 63a to the elongated hole 72a. In this bypass valve 60, the drive shaft 63a of the actuator 63 reciprocates in the axial direction, so that the rotating shaft 62 rotates in one direction and the opposite direction, and the valve body 61 opens and closes the outlet 16b of the bypass passage 16. It is designed to do.

FIG. 57 shows a cross-sectional view of the actuator 63 when the bypass valve 60 is fully opened, cut along the axial direction thereof. FIG. 58 shows a cross-sectional view of the actuator 63 when the bypass valve 60 is fully closed, cut along the axial direction thereof. FIG. 59 is a cross-sectional view according to FIG. 40 showing a part of the EGR cooler 13 when the valve body 61 of the bypass valve 60 is fully opened. FIG. 60 is a cross-sectional view according to FIG. 36 showing a part of the EGR cooler 13 when the valve body 61 of the bypass valve 60 is fully closed.

As shown in FIGS. 57 and 58, the actuator 63 is provided in the housing 941 and the housing 941, and has an inner shaft portion 942 including a lower end portion (one end portion) and an upper end portion (the other end portion) and an inner shaft portion 942. A drive shaft 63a integrally provided so as to be coaxial with the lower end portion of the housing 941 is provided in the housing 941 corresponding to the proximal end side of the inner shaft portion 942, and the inner shaft portion 942 and the drive shaft 63a reciprocate in the axial direction. It includes a step motor 944 for moving the inner shaft portion 942 and a shaft spring 945 for urging the inner shaft portion 942 and the drive shaft 63a in a direction away from the step motor 944. The inner shaft portion 942 is arranged so as to penetrate the center of the housing 941, and a male screw 946 is provided at the upper end portion.

The housing 941 includes an outer housing 961 that covers the outside of the actuator 63, an inner housing 962 that is arranged inside the outer housing 961, and a bearing housing 963 that is arranged inside the lower part of the inner housing 962. The upper portion of the inner housing 962 constitutes a stator 971 of the step motor 944, and a pair of upper layer coils 972A and lower layer coils 972B are provided on the outer periphery thereof. The bearing housing 963 includes a thrust bearing portion 963a that reciprocally supports the inner shaft portion 942 in the thrust direction at the center thereof, and the periphery of the thrust bearing portion 963a is hollow. Inside the stator 971, a rotor 973 constituting the step motor 944 is arranged. The outer housing 961 is formed with a connector 961a projecting upward. The connector 961a is provided with terminals 974 connected to the

coils

972A and 972B. A flange 961b is formed in the lower portion of the outer housing 961. As shown in FIGS. 54 to 56, a bracket 75 is provided on the outside of the housing 31 of the EGR cooler 13. The actuator 63 is fixed to the bracket 75 via bolts or the like (not shown) via its flange 961b.

The rotor 973 includes a rotor main body 973a and a magnet 973b provided on the outer periphery of the rotor main body 973a. A sleeve 975 extending downward is provided at the lower end of the rotor main body 973a, and a radial bearing 976 is provided between the outer circumference of the sleeve 975 and the inner housing 962. The rotor 973 is rotatably supported inside the stator 971 by a radial bearing 976. At the center of the rotor body 973a, a female screw 947 screwed into the male screw 946 of the inner shaft portion 942 is provided. A predetermined backlash 949 (see FIGS. 61 and 62) is provided between the male screw 946 and the female screw 947 in the axial direction of the inner shaft portion 942.

As shown in FIGS. 57 and 58, in this embodiment, when the drive shaft 63a and the inner shaft portion 942 reciprocate inside the bearing housing 963, the base portion 63ab of the drive shaft 63a is moved inward. A lip seal 951 for sealing between the bearing housing 963 and the bearing housing 963 is provided to prevent foreign matter and moisture from entering. In this embodiment, around the inner shaft portion 942, a cylindrical outer shaft 952 that includes an outer peripheral portion 952c that can contact the lip seal 951 and extends from the base portion 63ab of the drive shaft 63a along the inner shaft portion 942 is provided. Be done. In this embodiment, the outer diameter of the outer peripheral portion 952c of the outer shaft 952 is set to be the same as the maximum outer diameter of the drive shaft 63a.

The actuator 63 is provided with an inner space 953 that is divided inside the housing 941 by sealing between the outer shaft 952 and the bearing housing 963 with a lip seal 951. The upper end portion 952a (one end portion) of the outer shaft 952 is arranged so as to face the inner space 953. Then, in order to communicate the inner space 953 to the atmosphere, the housing 941 (outer housing 961, inner housing 962 and bearing housing 963) is provided with an atmospheric passage 954 (scheme is shown by a two-dot chain line). Note that, unlike the conventional actuator, the actuator 63 of this embodiment is not provided with a stopper or a contact portion for defining an initial position as a reference for the inner shaft portion 942.

That is, the step motor 944 constituting the actuator 63 described above has a screw mechanism with respect to the stator 971 including the upper layer coil 972A and the lower layer coil 972B, the rotor 973 rotatably arranged at the center of the stator 971, and the rotor 973. A drive shaft 63a movably connected in the axial direction via (male screw 946 and female screw 947) and a shaft spring 945 for urging the drive shaft 63a in the axial direction are provided. Then, in order to rotate the rotary shaft 62 of the bypass valve 60, the rotary shaft 62 and the drive shaft 63a of the actuator 63 are connected via the link 64. The shaft spring 945 is configured to urge the valve body 61 in the valve closing direction via the link 64 and the rotating shaft 62 by urging the drive shaft 63a in the axial direction.

The actuator 63 configured as described above converts the rotational motion into the stroke motion of the inner shaft portion 942 and the drive shaft 63a via the male screw 946 and the female screw 947 by driving the step motor 944 to rotate the rotor 973. The rotating shaft 62 is rotated via the lever 72. That is, as shown in FIGS. 56 and 58, the actuator 63 rotates the rotor 973 in one direction from a state in which the drive shaft 63a protrudes from the housing 941 and the lever 72 is pushed down. As a result, due to the screwing relationship between the male screw 946 and the female screw 947, the inner shaft portion 942 and the drive shaft 63a make a stroke movement in the upward direction of FIG. 58, which is the thrust direction, against the urging force of the shaft spring 945. As a result, as shown in FIGS. 54, 55 and 57, the inner shaft portion 942 is immersed in the housing 941, the lever 72 is pulled up by the drive shaft 63a, and the valve body 61 is as shown in FIG. 59. It will be fully open.

On the other hand, as shown in FIGS. 54, 55 and 57, the actuator 63 rotates the rotor 973 in the opposite direction from the state where the drive shaft 63a is immersed in the housing 941 and the lever 72 is pulled up. As a result, due to the screwing relationship between the male screw 946 and the female screw 947, the inner shaft portion 942 and the drive shaft 63a make a stroke movement in the downward direction of FIG. 57, which is the thrust direction, in cooperation with the urging force of the shaft spring 945. As a result, as shown in FIGS. 56 and 58, the drive shaft 63a protrudes from the housing 941, the lever 72 is pushed down by the drive shaft 63a, and the valve body 61 is fully closed as shown in FIG. 60.

FIG. 61 shows a part of the screwed state of the male screw 946 and the female screw 947 in a state where the valve body 61 of the bypass valve 60 is fully opened by an enlarged cross-sectional view. FIG. 62 shows a part of the screwed state of the male screw 946 and the female screw 947 in the “butted fully closed state” described later by an enlarged cross-sectional view. As shown in FIGS. 61 and 62, the male screw 946 has a male screw thread 946a spirally connected in the axial direction of the inner shaft portion 942. The male thread 946a includes a first male thread surface 946aa facing away from the step motor 944 (downward) and a second male thread surface 946ab located on the opposite side (upper side) of the first male thread surface 946aa. .. Further, the female thread 947 has a female thread 947a spirally connected in the axial direction of the inner shaft portion 942. The female thread 947a includes a first female thread surface 947aa facing away from the step motor 944 (downward) and a second female thread surface 947ab located on the opposite side (upper side) of the first female thread surface 947aa. .. Then, as shown in FIGS. 61 and 62, there is a predetermined backlash 949 (play) between the male screw 946 and the female screw 947 in the axial direction of the inner shaft portion 942.

In the bypass valve 60 of this embodiment, when the valve body 61 is opened or closed, the valve body 61 is urged in the valve closing direction by the urging force of the valve closing spring 73. Further, the drive shaft 63a of the actuator 63 is urged by the urging force of the shaft spring 945 in the direction in which the drive shaft 63a protrudes from the housing 941, that is, in the direction in which the valve body 61 is closed. Therefore, as shown in FIG. 61, the first male thread surface 946aa of the male thread 946 provided on the inner shaft portion 942 is in contact with the second female thread surface 947ab of the female thread 947 provided on the rotor main body 973a. Become. On the other hand, from the state where the valve body 61 is fully closed, "butting control" is executed in which the drive shaft 63a is abutted against the lever 72 by tightening with the rotor main body 973a. As a result, as shown in FIG. 62, the first female thread surface 947aa of the female thread 947a and the second male thread surface 946ab of the male thread 946a are engaged with each other, and the inner shaft portion 942 and the drive shaft are engaged by the shaft spring 945. The 63a is maximally urged in the direction away from the step motor 944 (valve closing direction) (fully engaged urging state). In this fully engaged urged state, the fully engaged urged state is maintained even if a force in the direction opposite to the urging direction acts on the inner shaft portion 942 and the drive shaft 63a. As a result, the valve body 61 of the bypass valve 60 is maintained in the fully closed state. However, if the rotor body 973a of the actuator 63 is further tightened from the fully engaged urged state, "step-out" occurs in the step motor 944, and step-out is performed by a maximum of "2 steps" to the valve opening side. Also in this case, the inner shaft portion 942 and the drive shaft 63a are kept in a fully engaged urging state by the urging force of the shaft spring 945, and the valve body 61 of the bypass valve 60 is kept in a fully closed state.

According to the bypass valve 60 described above, the valve body 61 is urged in the valve closing direction by the valve closing spring 73, and the drive shaft 63a of the actuator 63 is pushed out in the protruding direction (lever 72 and the rotating shaft 62) by the shaft spring 945. It is urged in the direction of closing the valve body 61). Here, the urging force of the valve closing spring 73 is set stronger than the urging force of the shaft spring 945 of the actuator 63. Further, when the valve body 61 is fully closed, the ECU 90 "butts and controls" the actuator 63, so that the male thread 946a of the male thread 946 and the female thread 947a of the female thread 947 are engaged with each other, and the drive shaft 63a (inner shaft portion) is engaged. The movement of 942) is locked. Here, in the configuration in which the urging force of the valve closing spring 73 of the bypass valve 60 does not act on the drive shaft 63a of the actuator 63, when the actuator 63 is stepped out, it is slightly between the male screw 946 and the female screw 947 (maximum 0. There is a gap (about 084 mm). Therefore, wear may occur between the male screw 946 and the female screw 947 due to vibration. On the other hand, according to the configuration of the actuator 63 of this embodiment, the male screw 946 and the female screw 947 are engaged with each other to lock the movement of the drive shaft 63a (inner shaft portion 942) at the time of step-out, so that the male screw 946 is locked. There is no slight gap between the male screw 946 and the female screw 947, and there is no risk of wear due to vibration between the male screw 946 and the female screw 947.

[About disconnection of actuator coil]
In the actuator 63 of this embodiment, when one of the upper coil 972A and the lower coil 972B is disconnected, the drive shaft 63a is operated by the other to rotate the rotary shaft 62, and the valve body 61 is driven in the valve closing direction. And it can be fully closed. At this time, although the controllability of the actuator 63 is reduced, the valve closing spring 73 assists the movement of the valve body 61 in the valve closing direction, so that the bypass valve 60 is controlled to be fully closed only by the upper layer coil 972A or the lower layer coil 972B. be able to.

FIGS. 63 and 64 show the energization patterns for the

coils

972A and 972B when the upper coil 972A and the lower coil 972B of the actuator 63 are normal by a time chart. FIG. 63 shows the case where the pole S1 of the upper layer coil 972A is energized, and FIG. 64 shows the case where the pole S2 of the lower layer coil 972B is energized. In FIG. 64, a thick line arrow between each pole N of the rotor 973 and a pole S2 of the lower coil 972B indicates a case where the magnetic force is strong, and a broken line arrow indicates a case where the magnetic force is weak. In FIGS. 63 and 64, (a) shows a plurality of poles N in the rotor 973, (b) shows the on / off of the upper layer coil 972A which becomes the poles S1 and S3, and (c) shows the poles S2 and S4. The on / off of the lower layer coil 972B is shown.

When each

coil

972A and 972B is normal, the rotation direction of the rotor 973 of the step motor 944 is changed by repeating "pole S1 → pole S2 → pole S3 → pole S4" which is an energization pattern for each

coil

972A and 972B. It can be controlled in the direction corresponding to the closing of the valve body 61. As shown in FIGS. 63 and 64, when the energization of the

coils

972A and 972B is switched from the pole S1 of the upper coil 972A to the pole S2 of the lower coil 972B, the magnetic force of the pole S2 with respect to each pole N of the rotor 973 is ". It changes repeatedly from "strong" to "weak". Therefore, the rotor 973 rotates in the direction corresponding to the closing of the valve body 61 due to the attractiveness difference of the magnetic force.

FIGS. 65 and 66 show the energization patterns for the

coils

972A and 972B when the lower coil 972B of the actuator 63 is disconnected by a time chart. FIG. 65 shows the case where the pole S1 of the upper layer coil 972A is energized, and FIG. 66 shows the case where the pole S3 of the upper layer coil 972A is energized. In FIG. 66, the solid arrow between each pole N of the rotor 973 and the pole S3 of the upper coil 972A indicates a case where the magnetic force is medium. The names of (a) to (c) in FIGS. 65 and 66 are the same as those in FIGS. 63 and 64.

When the lower layer coil 972B is disconnected, the rotation direction of the rotor 973 of the step motor 944 corresponds to the closing of the valve body 61 by repeating the "pole S1 → pole S3 →" which is the energization pattern for the upper layer coil 972A. It can be controlled in the direction. As shown in FIGS. 65 and 66, when the energization of the upper coil 972A is switched from the pole S1 to the pole S3, the magnetic force of the pole S3 with respect to each pole N of the rotor 973 is always "medium" and uniform. There is no difference in magnetic force attraction. However, the rotor 973 can be rotated in the direction corresponding to the valve closing of the valve body 61 by the cooperation between the urging force of the shaft spring 945 of the actuator 63 and the urging force of the valve closing spring 73 of the valve assembly 65.

[Control for coil disconnection]
Next, coil disconnection correspondence control for dealing with disconnection of each

coil

972A and 972B of the actuator 63 will be described. FIG. 67 shows the control contents by a flowchart. In this embodiment, the same engine system as in the fifteenth embodiment is adopted, and the bypass valve 60 (actuator 63) of this embodiment is controlled instead of the bypass valve 19 shown in FIG. 29.

When the process shifts to this routine, in step 700, the ECU 90 determines whether or not the upper coil 972A of the actuator 63 is disconnected. In this embodiment, the ECU 90 can detect the disconnection of the upper coil 972A and the lower coil 972B by monitoring the presence or absence of normal energization of the

coils

972A and 972B when controlling the actuator 63. It has become. In this embodiment, the ECU 90 corresponds to an example of the disconnection detecting means of the disclosed technology. If the determination result of step 700 is affirmative, the ECU 90 shifts the process to step 710, and if the determination result is negative, the ECU 90 shifts the process to step 760.

In step 710, the ECU 90 determines whether or not the lower coil 972B of the actuator 63 is disconnected. If the determination result is affirmative, the ECU 90 shifts the process to step 720, and if the determination result is negative, the ECU 90 shifts the process to step 740.

In step 720, the ECU 90 changes the EGR start permitted water temperature SEGRTHW related to EGR control from "40 ° C" to "65 ° C". That is, the ECU 90 changes the EGR valve 14 in a direction of delaying the timing condition for starting the valve opening. The ECU 90 is configured to start EGR when the cooling water temperature THW reaches the EGR start permitted water temperature SEGRTHW in a separately provided program for EGR control (the same applies hereinafter).

Next, in step 730, the ECU 90 guards the opening degree of the EGR valve 14 to be equal to or less than a predetermined upper limit opening degree. That is, the ECU 90 limits the opening degree of the EGR valve 14 to a predetermined upper limit opening degree or less in a separately provided EGR control program. That is, the ECU 90 changes in the direction of reducing the maximum opening degree of the EGR valve 14.

On the other hand, in step 740, which is a transition from step 710, the ECU 90 controls the valve body 61 of the bypass valve 60 to be fully closed by energizing the lower coil 972B of the actuator 63.

Next, in step 750, the ECU 90 changes the EGR start permitted water temperature SEGRTHW related to EGR control from "40 ° C" to "65 ° C" as in step 720, and then returns the process to step 700.

On the other hand, in step 760 after shifting from step 700, the ECU 90 determines whether or not the lower coil 972B of the actuator 63 is disconnected. If the determination result is affirmative, the ECU 90 shifts the process to step 770, and if the determination result is negative, the ECU 90 shifts the process to step 790.

In step 770, the ECU 90 controls the valve body 61 of the bypass valve 60 to be fully closed by energizing the upper coil 972A of the actuator 63.

Next, in step 780, the ECU 90 changes the EGR start permitted water temperature SEGRTHW related to EGR control from "40 ° C" to "65 ° C" as in step 720, and then returns the process to step 700.

Further, in the transition from step 760 to step 790, the normal opening / closing control of the bypass valve 60 is executed, and after the normal EGR control is executed, the process is returned to step 700.

In the coil disconnection correspondence control described above, the ECU 90 monitors the presence or absence of disconnection in the upper layer coil 972A and the lower layer coil 972B constituting the step motor 944 of the actuator 63. When the disconnection of the upper layer coil 972A or the lower layer coil 972B is detected, the ECU 90 drives the step motor 944 (actuator 63) only by the normal lower layer coil 972B or the upper layer coil 972A, and the valve body of the bypass valve 60. The 61 is controlled to be fully closed, and the EGR start permitted water temperature SEGRTHW in the EGR control is changed from "40 ° C" to "65 ° C". also. When both the upper layer coil 972A and the lower layer coil 972B are detected to be disconnected, it is difficult for the ECU 90 to drive the step motor 944 (actuator 63), so EGR control is executed as follows. That is, the ECU 90 changes the EGR start permitted water temperature SEGRTHW in the EGR control from "40 ° C" to "65 ° C". This change is effective when both

coils

972A and 972B are disconnected when the valve body 61 of the bypass valve 60 is near fully closed. Further, the ECU 90 guards the EGR valve 14 to a predetermined upper limit opening or less. This guard is effective when both

coils

972A and 972B are disconnected when the valve body 61 of the bypass valve 60 is in the vicinity of full opening. In this way, the ECU 90 changes at least one of the valve opening start and the maximum opening degree of the EGR valve 14 in order to control the recirculation of the EGR gas according to the disconnection detection result of the

coils

972A and 972B. There is. Here, the ECU 90 corresponds to an example of the EGR control means of this disclosed technology.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the following actions and effects can be obtained unlike the 20th embodiment. That is, according to the configuration of this embodiment, the bypass valve 60 includes a valve closing spring 73 that urges the valve body 61 in the valve closing direction, and the actuator 63 connects the drive shaft 63a via the link 64 and the rotary shaft 62. A shaft spring 945 for urging the valve body 61 in the valve closing direction is included. Therefore, the urging force of the valve closing spring 73 and the urging force of the shaft spring 945 always act on the valve body 61 of the bypass valve 60 in the valve closing direction, and the valve closing of the valve body 61 is assisted. Therefore, even if the actuator 63 should fail, the valve body 61 of the bypass valve 60 can be closed, the flow of the EGR gas in the bypass passage 16 is blocked, and the high temperature EGR gas that is not cooled is the EGR gas. It is possible to prevent the flow to the distributor 15 (downstream EGR passage), and it is possible to suppress heat damage to the EGR gas distributor 15.

According to the configuration of this embodiment, when the disconnection of the

coils

972A and 972B of the actuator 63 is detected by the ECU 90, the EGR start permitted water temperature SEGRTHW (EGR valve 14 is opened) in order to control the recirculation of the EGR gas. At least one of the valve start condition) and the upper limit opening (maximum opening) is changed by the ECU 90. Therefore, when the actuator 63 does not operate normally due to the disconnection of each

coil

972A and 972B, the EGR start permitted water temperature SEGRTHW is changed, so that the EGR gas does not flow to the EGR cooler 13 before warming up, and the EGR valve 14 By changing the upper limit opening, a large amount of high temperature EGR gas does not flow to the EGR gas distributor 15 (downstream side EGR passage).

That is, in this embodiment, when only the upper layer coil 972A is disconnected, the actuator 63 is operated by energizing the lower layer coil 972B to control the valve body 61 of the bypass valve 60 to be fully closed and the EGR start permission water. The temperature SEGRTHW is changed from "40 ° C" to "65 ° C". That is, by changing the direction of delaying the timing condition for starting the valve opening of the EGR valve 14, the EGR gas is prevented from flowing to the EGR cooler 13 before warming up. When only the lower layer coil 972B is disconnected, the actuator 63 is operated by energizing the upper layer coil 972A to control the valve body 61 of the bypass valve 60 to be fully closed, and the EGR start permitted water temperature is the same as described above. Change SEGRTHW from "40 ° C" to "65 ° C". Further, when both the upper coil 972A and the lower coil 972B are disconnected, the EGR start permitted water temperature SEGRTHW is changed from "40 ° C" to "65 ° C" without operating the actuator 63, and the EGR valve 14 is used. The opening is guarded to be equal to or less than the predetermined upper limit opening. That is, by limiting the maximum opening degree of the EGR valve 14 so as not to be fully opened, a large amount of high temperature EGR gas is prevented from flowing into the EGR gas distributor 15. Therefore, if the

coils

972A and 972B of the actuator 63 of the bypass valve 60 are disconnected and the actuator 63 does not operate normally and the bypass valve 60 cannot be controlled appropriately, the EGR gas distributor 15 ( By controlling the flow of EGR gas to the downstream EGR passage), it is possible to suppress the generation of condensed water in the EGR cooler 13 and the generation of heat damage in the EGR gas distributor 15. ..

According to the configuration of this embodiment, it is assumed that the ECU 90 executes "butting control" in which the drive shaft 63a is abutted against the lever 72 by tightening the actuator 63 by the rotor main body 973a from the state where the valve body 61 is fully closed. .. In this case, the first female thread surface 947aa of the female thread 947a of the actuator 63 and the second male thread surface 946ab of the male thread 946a are engaged with each other, and the inner shaft portion 942 (drive shaft 63a) is stepped by the shaft spring 945. It is in a state of being maximally urged (fully engaged urging state) in a direction away from the motor 944 (valve closing direction). In this fully engaged urging state, the fully engaged urging state is maintained even if a force in the direction opposite to the urging direction acts on the inner shaft portion 942 (drive shaft 63a). Therefore, the valve body 61 of the bypass valve 60 can be locked to the fully closed state, and even if a high pressure for opening the valve body 61 acts on the valve body 61, the valve body 61 is fully closed. It can be kept closed and the leakage of EGR gas to the downstream side of the valve body 61 can be suppressed.

<22nd Embodiment>
Next, the 22nd embodiment will be described in detail with reference to the drawings.

[Control for coil disconnection]
This embodiment differs from the 21st embodiment in the content of the coil disconnection correspondence control regarding the actuator 63. FIG. 68 shows the contents of the coil disconnection correspondence control of this embodiment by a flowchart. In the flowchart of FIG. 68, the process of step 800 is provided before step 700, the process of step 810 is provided instead of step 720, and the process of step 820 is provided instead of step 730. Is different. Hereinafter, processing different from the flowchart of FIG. 67 will be mainly described.

When the process shifts to this routine, in step 800, the ECU 90 takes in the final target bypass opening degree FTECBV and the actual bypass opening degree (actual bypass opening degree) ECBV step. The final target bypass opening degree FTECBV can be obtained by opening / closing control of the bypass valve 60 shown in FIG. 42 described above. The actual bypass opening degree ECBV step can be obtained from the command value of the ECU 90 for the actuator 63 (step motor 944).

Next, the ECU 90 executes the determination of step 700 and step 710, and if the determination result of step 700 is negative, the process shifts to step 760 and the processes of steps 760 to 790 are executed. If the determination result of step 710 is negative, the ECU 90 shifts the process to step 740 and executes the processes of

step

740 and 750.

On the other hand, if the determination result in step 710 is affirmative, the ECU 90 stores the actual bypass opening ECBV step as the final actual bypass opening FECBV step in step 810.

Next, in step 820, the ECU 90 calculates the EGR start permitted water temperature SEGRTHW according to the final actual bypass opening FECBV step and the EGR maximum opening EGRMAX step for the EGR valve 14. The ECU 90 obtains the EGR start permitted water temperature SEGRTHW (solid line) and the EGR maximum opening EGRMAX step (broken line) according to the final actual bypass opening FECBV step, for example, by referring to the water temperature / opening map shown in FIG. Can be done. In FIG. 69, the horizontal axis indicates the final actual bypass opening degree FECBV step, and the vertical axis indicates the EGR start permitted water temperature SEGRTHW and the EGR maximum opening degree EGRMAX step. In this water temperature / opening map, the EGR start permitted water temperature SEGRTHW decreases from "65 ° C" to "40 ° C" as the final actual bypass opening FECBV step changes from fully closed (0%) to fully open (100%). Become. Further, in this water temperature / opening degree map, as the final actual bypass opening degree FECBV step changes from fully closed to fully open, the EGR maximum opening degree EGRMAX step becomes lower toward the predetermined value R1. After that, the ECU 90 returns the process to step 800.

According to the coil disconnection correspondence control described above, when both the upper layer coil 972A and the lower layer coil 972B are detected to be disconnected, the ECU 90 opens the actual bypass opening ECBV step immediately before the disconnection, unlike the 21st embodiment. The degree FECBV step is set, and the EGR start permitted water temperature SEGRTHW in EGR control is calculated according to the same opening FECBV step, and the EGR maximum opening EGRMAX step of the EGR valve 14 is calculated. That is, when both the upper coil 972A and the lower coil 972B are disconnected, the ECU 90 changes the EGR start permitted water temperature SEGRTHW and the EGR maximum opening EGRMAX step according to the actual bypass opening ECBV step immediately before the coil disconnection. ing.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the following actions and effects can be obtained unlike the 21st embodiment. That is, when both the upper layer coil 972A and the lower layer coil 972B are disconnected, the ECU 90 changes the EGR start permitted water temperature SEGRTHW and the EGR maximum opening EGRMAX step according to the actual bypass opening degree ECBV step. Therefore, the suitable EGR start permitted water temperature SEGRTHW and the EGR maximum opening EGRMAX step can be obtained according to the actual bypass opening ECBV step immediately before the coil disconnection (the opening of the valve body 61 of the actual bypass valve 60). The overheating of the EGR gas flowing to the EGR gas distributor 15 (downstream EGR passage) can be precisely suppressed, the generation of condensed water in the EGR cooler 13 can be precisely suppressed, and the heat in the EGR gas distributor 15 can be suppressed. It is possible to precisely suppress the occurrence of harm.

<23rd Embodiment>
Next, the 23rd embodiment will be described in detail with reference to the drawings.

This embodiment differs from the 21st embodiment in the configuration of the actuator 63 and the link 64 of the bypass valve 60. FIG. 70 shows a perspective view of the EGR cooler 13 including the actuator 63 and the link 64 as viewed from the rear side. FIG. 71 shows the state of the actuator 63 and the link 64 when the bypass valve 60 is operated to be closed (fully closed) in the EGR cooler 13 by a rear view according to FIG. 56. FIG. 72 shows the state of the actuator 63 and the link 64 in the EGR cooler 13 when the bypass valve 60 is operated to open (fully open) by a rear view according to FIG. 55. In this embodiment, the configurations of the actuator 63 and the link 64 are different from those of the 21st and 22nd embodiments. The actuator 63 and the link 64 of this embodiment will be described below.

[About the configuration of actuators and links]
The actuator 63 of this embodiment is configured to operate electrically to rotate the rotating shaft 62. As shown in FIGS. 70 to 72, the actuator 63 includes a drive shaft 63b that can reciprocate in the axial direction, and the tip of the drive shaft 63b is driven and connected to the rotating shaft 62 via a link 64. In this embodiment, the tip of the drive shaft 63b is always in contact with the lever 76 in order to rotate the lever 76. The base end of the lever 76 is fixed to the rotation shaft 62, and a receiving plate 76a parallel to the axial direction of the rotation shaft 62 is formed on the tip end side of the lever 76. The link 64 is configured by constantly pressing the receiving plate 76a with the tip of the drive shaft 63b. In this bypass valve 60, the drive shaft 63b of the actuator 63 reciprocates in the axial direction, so that the rotating shaft 62 rotates in one direction and the opposite direction, and the valve body 61 opens and closes the outlet 16b of the bypass passage 16. It is designed to do. In the valve assembly 65 of the actuator 63 and the bypass valve 60 in the 21st embodiment, the valve closing spring 73 for urging the valve body 61 in the valve closing direction is assembled to the lever 76, and the drive shaft 63a of the actuator 63 is housed. A shaft spring 945 was provided to urge the valve body 61 in a direction protruding from 941 (a direction in which the valve body 61 is closed). On the other hand, in this embodiment, in order to keep the receiving plate 76a of the lever 76 in contact with the tip of the drive shaft 63b, a valve closing spring 73 for urging the valve body 61 in the valve closing direction is assembled to the lever 76. At the same time, a shaft spring 945 for urging the drive shaft 63b of the actuator 63 in the direction protruding from the housing 941 (the direction in which the valve body 61 is opened) is provided. Further, the urging force of the valve closing spring 73 is set to be larger than the urging force of the shaft spring 945 of the actuator 63.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, since the valve opening spring urges the valve body 61 in the valve opening direction, the valve closing spring 73 urges the valve body 61 in the valve closing direction. Although there are differences from the embodiment, almost the same operation and effect as those of the 21st embodiment can be obtained.

<24th Embodiment>
Next, the 24th embodiment will be described in detail with reference to the drawings.

This embodiment differs from the 21st to 23rd embodiments in the configuration of the actuator 77 of the bypass valve 60 and the link 64. FIG. 73 shows a front view of the EGR cooler 13 including the actuator 77 and the link 64. FIG. 74 shows the EGR cooler 13 of FIG. 73 with a top view seen from the direction of arrow Y1. FIG. 75 shows the EGR cooler 13 with a cross-sectional view taken along the line CC of FIG. FIG. 76 shows a part of the EGR cooler 13 with a cross-sectional view taken along the line DD of FIG. 73. This embodiment differs from the 21st to 23rd embodiments in the configuration of the actuator 77 of the bypass valve 60 and the link 64. The actuator 77 and the link 64 of this embodiment will be described below.

[About the configuration of actuators and links]
As shown in FIGS. 73 and 74, the valve assembly 65, the actuator 77 and the link 64 of the bypass valve 60 are provided in the housing 31 on the front side of the EGR cooler 13. Further, the actuator 77 is the housing 31 of the EGR cooler 13, and is provided at a position corresponding to (overlapping) both the heat exchanger 32 and the bypass passage 16.

The actuator 77 of this embodiment has a built-in spiral bimetal 78, and the bimetal 78 contracts and expands due to the heat transferred from the EGR cooler 13, and the open end thereof is displaced (rotated) in the circumferential direction of the bypass valve 60. It is configured to rotate the lever 79. FIG. 77 is a front view showing a state in which the bimetal 78 of the actuator 77 has cooled and contracted. FIG. 78 shows a front view showing a state in which the bimetal 78 of the actuator 77 is expanded by heating and the open end 78a thereof is rotated in the circumferential direction. In this embodiment, the open end 78a reciprocates in the circumferential direction due to the contraction and expansion of the bimetal 78, so that the rotation shaft 62 rotates in one direction and the opposite direction, and the valve body 61 exits the bypass passage 16. It is designed to open and close 16b. As shown in FIG. 77, when the bimetal 78 is contracted, the lever 79 is in the state shown by the two-dot chain line in FIG. 73, and the valve body 61 is in the valve open state shown by the two-dot chain line in FIG. 75. As the bimetal 78 further cools and contracts, the valve body 61 rotates to the fully open position. On the other hand, as shown in FIG. 78, when the bimetal 78 is stretched by heating, the lever 79 rotates to the state shown by the solid line in FIG. 73, and the valve body 61 is in the fully closed state shown by the solid line in FIG. 75. ..

As shown in FIG. 76, in the actuator 77 of this embodiment, the open end 78a of the spiral bimetal 78 is driven and connected to the rotating shaft 62 of the valve assembly 65 via the link 64. The open end 78a of the bimetal 78 is connected to the lever 79 in order to rotate the lever 79. The base end of the lever 79 is fixed to the rotating shaft 62, and an arm 79a having a substantially L-shaped cross section is provided at the tip of the lever 79. In this embodiment, the open end 78a of the bimetal 78 constantly presses the tip of the arm 79a, and the open end 78a and the lever 79 form a link 64. The valve assembly 65 of this embodiment conforms to the configuration of the valve assembly 65 of the 19th embodiment shown in FIG. 52. In this embodiment, the valve assembly 65 of the bypass valve 60 is provided with a valve opening spring 80 that urges the valve body 61 in the valve opening direction instead of the valve closing spring 73. Also in this embodiment, the rotational force acting on the lever 79 from the open end 78a when the bimetal 78 becomes hot, that is, the force for closing the valve body 61 is larger than the urging force of the valve opening spring 80. Set large enough.

In this embodiment, the actuator 77 is provided in the housing 31 of the EGR cooler 13 at a position corresponding to (overlapping) both the heat exchanger 32 and the bypass passage 16, so that the opening / closing characteristic of the bypass valve 60 is EGR. It will change according to the EGR flow rate flowing through the cooler 13 and the temperature of the cooling water circulating in the EGR cooler 13. FIG. 79 shows the opening / closing characteristics of the bypass valve 60 of this embodiment with respect to the EGR flow rate and the cooling water temperature. In this table, for example, when the cooling water temperature THW is "40 ° C." and the EGR flow rate is "low", the valve body 61 of the bypass valve 60 is "fully open". When the cooling water temperature THW is "40 ° C." and the EGR flow rate is "medium", the valve body 61 is "fully open". When the cooling water temperature THW is "40 ° C." and the EGR flow rate is "high", the valve body 61 is "half open". When the cooling water temperature THW is "60 ° C" or "80 ° C", it is as shown in the same table.

Here, as a inverse proportion, it is assumed that the actuator 77 is provided in the housing 31 of the EGR cooler 13 at a position corresponding only to the heat exchanger 32. In this case, the opening / closing characteristics of the bypass valve 60 will change depending only on the cooling water temperature. FIG. 80 shows the opening / closing characteristics of the bypass valve 60 of this embodiment with respect to the cooling water temperature. In this table, when the cooling water temperature THW is "40 ° C", the valve body 61 of the bypass valve 60 is "fully open", and when it is "60 ° C", the valve body 61 is "starting to close" and "80". In the case of "° C.", the valve body 61 is "fully closed".

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the following actions and effects can be obtained unlike the fifteenth embodiment. That is, the actuator 77 is composed of a bimetal 78, and the opening / closing characteristics of the bypass valve 60 are configured to be changed according to the EGR flow rate and the cooling water temperature in the EGR cooler 13. Therefore, unlike the bypass valve 60 provided with the electric actuator 63, it is not necessary to electrically control the electric wiring to the actuator 77 and the actuator 77, and the configuration of the bypass valve 60 can be simplified. can.

<25th Embodiment>
Next, the 25th embodiment will be described in detail with reference to the drawings.

This embodiment is different from the 24th embodiment in that the actuator 91 of the bypass valve 60 and the link 64 are configured. Hereinafter, the points different from those of the 24th embodiment will be mainly described. In the 24th embodiment, since the actuator 77 is made of the bimetal 78, heat is transferred to the bimetal 78, and it takes time for the open end 78a to rotate, and the operation responsiveness of the actuator 77 is not good. In addition, the bimetal 78 could not be heated by energization. Further, it is conceivable to bring the entire lower surface of the bimetal 78 into contact with the heater to directly heat it, but it is also difficult to directly heat the entire bimetal 78 because sliding wear occurs between the bimetal 78 and the heater.

Therefore, in this embodiment, in order to enhance the operation responsiveness of the actuator, the actuator 91 is configured not with the bimetal 78 but with a "biometal" that can be operated by directly energizing and heating. Biometal is a fibrous actuator that is tension-contracted-relaxed and stretched by itself and is characterized by flexible and quiet movement. Biometal is usually soft and supple, but when the temperature is raised by energization (for example, 60 to 70 ° C.), it becomes hard and shrinks with a strong force. When the power is turned off, it softens again and extends to its original length. The biometal also operates by changing the atmospheric temperature, shrinks when the atmospheric temperature is about 70 ° C. or higher, and expands when the atmospheric temperature is lower than about 70 ° C. The internal structure of the biometal has a stable structure, excellent durability and stable operating characteristics.

[About the configuration of actuators and links]
FIG. 81 shows a front view of the EGR cooler 13 including the actuator 91 and the link 64 of this embodiment. FIG. 82 is an EGR cooler 13 in a state where the valve body 61 of the bypass valve 60 is fully closed, and is shown by a sectional view taken along line EE of FIG. 81. FIG. 83 shows a cross-sectional view of the EGR cooler 13 in a state where the valve body 61 of the bypass valve 60 is opened, according to FIG. 82.

As shown in FIGS. 81 to 83, in this embodiment, the valve assembly 65, the actuator 91, and the link 64 of the bypass valve 60 are provided in the housing 31 on the front side of the EGR cooler 13. The actuator 91 of this embodiment includes a rod-shaped biometal 92, and a positive electrode 93 is provided at one end (base end) of the biometal 92. The positive electrode 93 is supported by the bracket 95 via the insulating material 94. The bracket 95 is fixed to the housing 31. The other end (tip) of the biometal 92 is fixed to the tip of the lever 96 constituting the valve assembly 65. The tip of the biometal 92 conducts to the housing 31 via the lever 96, the rotating shaft 62, and the like, and is electrically grounded. Then, when the biometal 92 is energized and heated via the positive electrode 93, the biometal 92 contracts from the stretched state, and the lever 96 of the valve assembly 65 rotates.

FIG. 82 shows a state in which the biometal 92 of the actuator 91 has shrunk due to energization and heating. FIG. 83 shows a state in which the biometal 92 of the actuator 91 is stretched by non-energization. In the bypass valve 60 of this embodiment, the lever 96 rotates in one direction and the opposite direction due to the contraction and expansion of the biometal 92, and the valve body 61 passes through the outlet 16b of the bypass passage 16 via the rotation shaft 62. It is designed to open and close. As shown in FIG. 82, when the biometal 92 is contracted, the lever 96 is in the state shown by the solid line in FIG. 81, and the valve body 61 is in the fully closed state. On the other hand, as shown in FIG. 83, when the biometal 92 is stretched due to non-energization, the lever 96 rotates to the state shown by the two-dot chain line in FIG. 81, and the valve body 61 is in the valve open state.

As shown in FIGS. 81 to 83, in this actuator 91, the tip 92a of the rod-shaped biometal 92 is driven and connected to the rotating shaft 62 of the valve assembly 65 via the link 64. In this embodiment, the tip 92a of the biometal 92 is connected to the lever 96 in order to rotate the lever 96. The base end of the lever 96 is fixed to the rotating shaft 62, and the arm 96a is provided at the tip of the lever 96. In this embodiment, the tip 92a of the biometal 92 is fixed to the arm 96a, so that the link 64 is formed by the tip 92a of the biometal 92 and the lever 96. The valve assembly 65 of this embodiment has the same configuration as the valve assembly 65 of the 24th embodiment, although the shape of the lever 96 is different. In this valve assembly 65, when the biometal 92 expands due to non-energization at a low temperature, the valve body 61 is opened via the lever 96 and the rotary shaft 62, and the valve body 61 is opened by the valve opening spring 80. It is urged in the valve opening direction. On the other hand, in this valve assembly 65, when the temperature is high or the biometal 92 contracts due to energization heating, the valve body 61 is closed via the lever 96 and the rotary shaft 62 against the urging force of the valve opening spring 80. To.

In the EGR system of this embodiment, when the outside air temperature is extremely low, if the EGR cut in which the EGR valve 14 is fully closed becomes long, the EGR passage 12 and the EGR gas distributor 15 will be cooled in the Encopa. Here, in the actuator 77 using the bimetal 78 in the 24th embodiment, it is difficult to responsively restart the bypass valve 60 in the fully closed state when the EGR is restarted from the EGR cut. On the other hand, in the actuator 91 using the biometal 92 of the present embodiment, when the atmospheric temperature of the encopa is extremely low, the biometal 92 is in an extended state and the valve body 61 is opened. Therefore, when the EGR is restarted, the high temperature EGR gas can flow to the EGR valve 14 and the EGR gas distributor 15 through the bypass passage 16. On the other hand, in the actuator 91 using the biometal 92 of the present embodiment, when the outside air is at a normal temperature and the engine 1 is in a completely warmed state, the biometal 92 is in a contracted state and the valve body 61 is closed. Therefore, when the EGR is restarted, the flow of the EGR gas in the bypass passage 16 can be cut off, and only the EGR gas cooled by the heat exchanger 32 can flow to the EGR valve 14 and the EGR gas distributor 15.

FIG. 84 shows an example of the control contents of the bypass valve 60 fully opened or fully closed corresponding to the conditions of the encopa temperature and the cooling water temperature at the time of restarting the EGR and after restarting. In FIG. 85, the control content shown in FIG. 84 is performed to carry out the energization (on) or de-energization of the biometal 92 corresponding to the conditions of the encopa temperature and the cooling water temperature at the time of restarting and after restarting the EGR. An example of the control content of (OFF) is shown in the table. In FIG. 85, when both the encopa temperature and the cooling water temperature are “70 ° C.” or higher, the bypass valve 60 can be fully closed even when the biometal 92 is not energized.

[About the action and effect of the EGR system]
According to the configuration of the EGR system of this embodiment described above, the following actions and effects can be obtained unlike the 24th embodiment. That is, in this embodiment, since the actuator 77 is made of the biometal 92, the biometal 92 can be responsively contracted by energization, and the valve body 61 of the bypass valve 60 can be responsively closed from the valve open state. can. Therefore, the flow (merging) of the EGR gas from the bypass passage 16 into the EGR gas flowing out from the heat exchanger 32 can be stopped with good responsiveness. As a result, the temperature of the EGR gas flowing from the EGR cooler 13 to the EGR gas distributor 15 (downstream EGR passage) can be rapidly lowered. Further, the biometal 92 contracts as the ambient temperature rises without being energized, and the valve body 61 of the bypass valve 60 can be closed from the valve open state. Therefore, even when it becomes difficult to energize the biometal 92 due to a failure, the valve body 61 of the bypass valve 60 can be closed, and the fail-safe function can be exhibited in the event of an energization failure.

Note that this disclosure technique is not limited to each of the above-described embodiments, and a part of the configuration may be appropriately modified and implemented within a range that does not deviate from the purpose of the disclosure technique.

(1) In each of the above embodiments, the

bypass valves

17, 19, and 60 are configured to open or close according to the temperature of the cooling water, but the bypass valve is opened or closed according to the temperature of the EGR gas. It can also be configured to valve.

(2) In the first to twelfth embodiments, the thermowax 24 is used as the actuator 22 that operates in response to a change in temperature for the bypass valve 17, but bimetal or shape memory is used instead of the thermowax 24. Alloys can also be used.

(3) In the 14th embodiment, the bypass valve 19 made of a solenoid valve is provided on the outlet side of the bypass passage 16, and the bypass valve 19 is EGR cut in order to drain the condensed water accumulated on the downstream side of the bypass valve 19. It was configured to open the valve on condition of the execution of. On the other hand, as shown in FIG. 86, a bypass valve 20 made of a diaphragm type valve is provided on the inlet side of the bypass passage 16, and the EGR cut is used to drain the condensed water CW accumulated on the downstream side of the bypass valve 20. It can also be configured to open on condition of execution. FIG. 86 is a cross-sectional view showing the EGR cooler 13, the bypass passage 16, and the bypass valve 20 (valve closed state) cut along the longitudinal direction thereof.

(4) In the first and second embodiments, when the wall temperature THDW (temperature) detected by the wall temperature sensor 88 (temperature detection means) exceeds the allowable heating temperature of the EGR gas distributor 15, EGR Although the valve 14 is forcibly controlled to be fully closed, it can also be configured to be controlled to an intermediate opening degree (opening between fully closed and fully open) instead of being controlled to be fully closed. In this case, the flow of EGR gas in the EGR passage is reduced, and excessive heating exceeding the allowable heating temperature of the downstream EGR passage is immediately stopped. Therefore, it is possible to reliably prevent melting damage of the downstream EGR passage.

(5) In each of the above-described embodiments, the EGR gas is configured to be distributed to each branch pipe 5b of the intake manifold 5 via the EGR gas distributor 15 constituting the downstream EGR passage. On the other hand, it is also possible to introduce the EGR gas from the downstream EGR passage into the surge tank of the intake manifold without providing the EGR gas distributor. In this case, the wall temperature sensor can be provided in the downstream EGR passage made of the resin material.

(6) In the fifteenth embodiment, as shown in FIGS. 35 and 36, the valve body 61 is configured to be arranged parallel to the axial direction of the heat exchanger 32 when the bypass valve 60 is closed. .. On the other hand, as shown in FIG. 87, when the bypass valve 60 is closed, the valve body 61 may be arranged at a position inclined toward the downstream side of the heat exchanger 32. In this case, as shown in FIG. 87, the plate area of the valve body 61 is larger than that of the valve body 61 of the fifteenth embodiment. Therefore, when the valve body 61 is opened, the area where the valve body 61 blocks the flow path area of the outlet 32b of the heat exchanger 32 becomes large, and the flow rate of the EGR gas flowing out from the outlet 32b can be further reduced. Further, since the swing angle of the valve body 61 between the valve closing time and the valve opening time is smaller than that of the fifteenth embodiment, the movement amount (stroke amount) of the drive shaft 63a of the actuator 63 is reduced. be able to. In addition, when the bypass valve 60 is closed, the EGR gas cooled through the heat exchanger 32 is likely to hit the valve body 61, so that the lip seal (seal member) is easily cooled via the valve body 61. FIG. 87 is an enlarged cross-sectional view according to FIG. 36 showing a part of the EGR cooler 13.

(7) In the eighteenth embodiment, as shown in FIG. 52, a plurality of press-fitting surfaces 31ea forming a flat surface are provided on the outer periphery of the outer cylinder portion 31e. These press-fitting receiving surfaces 31ea are formed by flatly cutting the outer periphery of the outer cylinder portion 31e, and the portion thereof has a concave shape. On the other hand, as shown in FIG. 88, a claw 74a is provided on the inner circumference of the spring guide 74 so that the claw 74a is engaged with the concave press-fitting surface 31ea of the outer cylinder portion 31e. You can also. In this case, it is possible to prevent the spring guide 74 from coming off. FIG. 88 is a cross-sectional view according to FIG. 52 showing the configuration of the valve assembly 65 of the bypass valve 60.

(8) In the fifteenth embodiment, as shown in FIG. 41, the bypass valve 60 is embodied in a valve assembly 65 having a swing type valve body 61. On the other hand, as shown in FIG. 89, the valve assembly 65 having the same configuration as that of FIG. 41 can be embodied as a bypass valve 60 having a butterfly type valve body 61. FIG. 89 is a cross-sectional view according to FIG. 41 showing the configuration of the valve assembly 65 of the bypass valve 60.

(9) In the engine system of each of the above embodiments, the inlet 12a of the EGR passage 12 is configured to be connected to the exhaust passage 3 upstream of the catalyst 7, but the inlet of the EGR passage is connected to the exhaust passage downstream of the catalyst. It can also be configured as follows.

This disclosure technology can be applied to gasoline engines and diesel engines mounted on vehicles.

1 Engine 2 Intake passage 3 Exhaust passage 5 Intake manifold (intake passage)
12 EGR passage 13 EGR cooler 14 EGR valve 15 EGR gas distributor (downstream EGR passage)
16 Bypass passage 16b Outlet 17 Bypass valve 18 Housing 19 Bypass valve 20 Bypass valve 21 Valve body 22 Actuator 31 Housing 32 Heat exchanger 32b Outlet 46 Partition wall 46a Main wall 46b Downstream wall 48 Sub bypass passage 49 Sub bypass valve 51a Cooling Water passage 53 Communication hole 55 Heat dissipation fin 56 Heat dissipation fin 58 Boundary part 59 Gap 60 Bypass valve 61 Valve body 63 Actuator

63a Drive shaft

63b Drive shaft 64 Link 71 Lip seal (seal member)
73 Valve closing spring 77 Actuator 88 Wall temperature sensor (temperature detection means)
90 ECU (1st control means, 2nd control means, 3rd control means, EGR control means, disconnection detection means)
91 Actuator 945 Shaft spring 946 Male thread 947 Female thread 971 Stator 972A Upper layer coil 972B Lower layer coil 973 Rotor

Claims

In the EGR system configured to flow a part of the exhaust gas discharged from the engine to the exhaust passage as EGR gas to the intake passage through the EGR passage and return it to the engine.
An EGR valve for adjusting the flow rate of the EGR gas in the EGR passage, and
An EGR cooler including a heat exchanger that exchanges heat between the EGR gas and the cooling water of the engine in order to cool the EGR gas flowing through the EGR passage.
A bypass passage for bypassing a part of the EGR gas flowing to the heat exchanger of the EGR cooler in the EGR passage.
A bypass valve for opening and closing the bypass passage and
The EGR cooler and the downstream EGR passage downstream of the bypass passage are made of a resin material.
The bypass valve includes a valve body and an actuator.
The actuator is characterized in that the valve body is configured to close from an open state when the temperature of the EGR gas, the temperature of the downstream EGR passage, or the temperature of the cooling water becomes equal to or higher than a first predetermined value. EGR system.
In the EGR system according to claim 1,
The actuator is an EGR system characterized in that it operates in response to a change in temperature.
In the EGR system according to claim 1,
The EGR system is characterized in that the actuator is configured to open the valve body under the condition that the EGR valve is fully closed.
In the EGR system according to any one of claims 1 to 3.
The heat exchanger includes an outlet from which the EGR gas flows out, and the bypass passage includes an outlet arranged adjacent to the outlet of the heat exchanger and from which the EGR gas flows out.
The bypass valve further includes a plate-shaped valve body and a rotating shaft that rotates the valve body, and the valve body and the rotating shaft are arranged so as to correspond to the outlet of the bypass passage. , The valve body is configured to open and close the outlet of the bypass passage by rotating the rotating shaft.
The rotating shaft is provided with a sealing member for preventing the EGR gas from leaking to the outside.
The bypass valve is located at a position where the valve body is parallel to the axial direction of the heat exchanger or tilted downstream toward the heat exchanger when the valve body closes the outlet of the bypass passage. Arranged, the valve body is arranged at a position where the valve body blocks a part of the flow path area of the outlet of the heat exchanger and narrows the flow path area when the valve body opens the outlet of the bypass passage. EGR system characterized by that.
In the EGR system according to claim 4,
A gap is provided between the boundary portion between the outlet of the heat exchanger and the outlet of the bypass passage and the valve body or the rotating shaft, and the gap is larger than that when the valve body is closed. An EGR system characterized in that it is configured to be larger when the valve is opened.
In the EGR system according to any one of claims 1 or 3 to 5.
The bypass valve further includes a valve closing spring that urges the valve body in the valve closing direction.
The actuator includes a stator including a coil, a rotor rotatably arranged at the center of the stator, a drive shaft rotatably connected to the rotor via a screw mechanism in the axial direction, and the drive. Equipped with a shaft spring that urges the shaft in the axial direction,
In order to rotate the rotating shaft of the bypass valve, the rotating shaft and the driving shaft of the actuator are connected via a link.
The EGR system is characterized in that the shaft spring is configured to urge the valve body in the valve closing direction via the link and the rotating shaft.
In the EGR system according to claim 6,
The disconnection detecting means for detecting the disconnection of the coil and the disconnection detecting means.
Further provided with an EGR control means for controlling the recirculation of the EGR gas, the EGR control means is further provided.
The EGR control means is characterized in that at least one of a valve opening start condition and a maximum opening degree of the EGR valve is changed in order to control the recirculation of the EGR gas according to the detection result of the disconnection detection means. EGR system to do.
In the EGR system according to any one of claims 1 to 3.
The EGR cooler includes a housing and
At least a portion of the bypass passage is provided integrally with the housing of the EGR cooler.
The bypass valve is provided in the bypass passage provided integrally with the housing of the EGR cooler.
An EGR system characterized in that a cooling water passage through which the cooling water flows is provided around the bypass valve.
In the EGR system according to any one of claims 1 to 3 or 8.
The EGR valve includes a housing made of aluminum material.
The EGR system is characterized in that the bypass valve is provided integrally with the housing of the EGR valve.
In the EGR system according to any one of claims 1 to 9.
When the EGR cooler is mounted on a vehicle, the bypass passage is arranged vertically downward with respect to the EGR cooler, and the upstream side thereof is inclined vertically downward toward the exhaust passage. EGR system.
In the EGR system according to any one of claims 1 to 10.
An EGR system characterized in that the EGR cooler and the bypass passage are adjacent to each other via a partition wall.
In the EGR system according to claim 11,
The partition wall includes a main wall portion in contact with the heat exchanger and a downstream wall portion extending downstream from the heat exchanger, and the downstream wall portion includes at least one communicating from the EGR cooler to the bypass passage. An EGR system characterized in that two communication holes are provided.
In the EGR system according to claim 12,
The communication hole is arranged at a position facing the valve body of the bypass valve, and functions as a relief hole for avoiding interference between the valve body and the downstream wall portion when the bypass valve is closed. EGR system.
In the EGR system according to any one of claims 11 to 13.
The EGR system is characterized in that the EGR cooler is provided with a plurality of fins adjacent to the partition wall and parallel to the flow direction of the EGR gas.
In the EGR system according to any one of claims 11 to 14,
The EGR system is characterized in that the bypass passage is provided with a plurality of fins in contact with the partition wall and parallel to the flow direction of the EGR gas.
In the EGR system according to any one of claims 1 to 15,
Further provided with a sub-bypass passage for bypassing the EGR gas flowing to the bypass valve in the bypass passage.
The EGR system is characterized in that the sub-bypass passage is provided with a sub-bypass valve that opens when the outside air temperature becomes less than a second predetermined value.
In the EGR system according to any one of claims 1 to 16.
A temperature detecting means for detecting the temperature of the downstream EGR passage or the temperature of the EGR gas flowing through the downstream EGR passage, and
Further provided with a first control means for controlling the EGR valve based on the detection value of the temperature detecting means.
The first control means forcibly controls the EGR valve to a fully closed position or an intermediate opening degree when the temperature detected by the temperature detecting means exceeds the allowable heating temperature of the downstream EGR passage. Characterized EGR system.
In the EGR system according to any one of claims 1 to 17.
A temperature detecting means for detecting the temperature of the downstream EGR passage or the temperature of the EGR gas flowing through the downstream EGR passage, and
Further provided with a second control means for controlling the EGR valve based on the detection value of the temperature detecting means.
The second control means controls the EGR valve to a normal opening degree when the temperature detected by the temperature detecting means is equal to or higher than the third predetermined value and is lower than the heat resistant temperature of the downstream EGR passage. Characterized EGR system.
In the EGR system according to claim 3,
The actuator operates electrically and
A temperature detecting means for detecting the temperature of the downstream EGR passage or the temperature of the EGR gas flowing through the downstream EGR passage, and
Further provided with a third control means for controlling the bypass valve based on the detection value of the temperature detecting means.
The third control means is characterized in that the actuator is controlled so as to close the bypass valve when the temperature detected by the temperature detecting means exceeds the allowable heating temperature of the downstream EGR passage. EGR system to do.
In the EGR system of claim 19,
The EGR system is characterized in that the bypass valve is configured to be closed when the actuator is turned off and not operated.