JP2005351194A - Egr system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EGR system capable of increasing an amount of recirculation of exhaust gas when a load is low relative to the engine rotation speed. <P>SOLUTION: A cooling water inlet of an EGR cooler 1 is connected to an inlet flow passage 4 for supplying cooling water to a water jacket of an engine 3, a cooling water outlet of the EGR cooler 1 is connected to an outlet flow passage 5 for feeding the cooling water from the water jacket of the engine 3, a flow adjustment valve 9a is incorporated on a water jacket inlet side of the engine 3, and a control unit 8 capable of expanding/reducing the opening of the flow adjustment valve 9a based on the rotation speed and the load of the engine 3 is provided. When the load gets low relative to the rotation speed of the engine 3, the control unit 8 reduces the opening of the flow adjustment valve 9a to increase the supply of the cooling water to the EGR cooler 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an EGR device.

  Conventionally, in an internal combustion engine with a supercharger to which exhaust gas recirculation (EGR) is applied, an EGR pipe into which an EGR cooler (water-cooled tubular heat exchanger) is incorporated into the exhaust gas diverted from the engine exhaust path The fuel is fed to the engine intake path by the road, and the generation of NOx is reduced by reducing the combustion temperature (for example, see Patent Document 1 and Non-Patent Document 1).

  FIG. 5 shows a cooling water circulation system as an example of a conventional EGR device, in which the cooling water inlet of the EGR cooler 1 is connected to an inlet flow path 4 for supplying cooling water from the water pump 2 to the water jacket of the engine 3. The cooling water outlet of the EGR cooler 1 is connected to the outlet flow path 5 for sending the cooling water from the water jacket of the engine 3.

  That is, the exhaust gas diverted from the engine exhaust path is cooled by the cooling water flowing through the EGR cooler 1.

A thermostat 6 and a radiator 7 are attached to the outlet flow path 5. When the temperature of the cooling water sent from the engine 3 is high, the cooling water returns to the water pump 2 through the radiator 7. On the contrary, when the temperature is low, Return to the water pump 2 without passing through the radiator 7.
Japanese Patent Laid-Open No. 9-256915 “Engine Anatomy” Working Vehicles 25 POTO PUBLISHING, April 5, 2004, p33-35

  However, in the EGR device shown in FIG. 5, the cooling water discharge amount of the water pump 2 increases or decreases according to the rotational speed of the engine 3, and the cooling water flow path of the EGR cooler 1 is connected in parallel to the water jacket of the engine 3. Therefore, the ratio of the cooling water supplied to the EGR cooler 1 and the cooling water supplied to the water jacket of the engine 3 is uniquely determined by the difference in pressure loss between the EGR cooler 1 and the water jacket of the engine 3. It will be decided.

  For this reason, when the vehicle is running normally and the load on the engine 3 is low, if the amount of exhaust gas recirculation is increased more than before, the amount of cooling water supplied to the EGR cooler 1 is relatively short. When the capacity of the water pump 2 is increased in anticipation of an increase in the exhaust gas recirculation amount, the amount of cooling water supplied to the water jacket of the engine 3 becomes excessive.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an EGR device that can increase the amount of exhaust gas recirculation when the load is low with respect to the engine speed.

  In order to achieve the above object, according to the first aspect of the present invention, the cooling water inlet of the EGR cooler is connected to an inlet flow path for supplying cooling water to the water jacket of the engine, and the cooling water outlet of the EGR cooler is Connected to the outlet flow path for sending cooling water from the engine water jacket, at least one of the water jacket inlet side, water jacket outlet side, EGR cooler cooling water inlet side, and EGR cooler cooling water outlet side A flow control valve is incorporated.

  The invention described in claim 2 is provided with a control means capable of expanding and reducing the opening of the flow rate adjusting valve based on the engine speed and the engine load.

  In the first aspect of the invention, the degree of opening of the flow rate adjustment valve is appropriately expanded and reduced so that the ratio of the cooling water supplied to the EGR cooler and the cooling water supplied to the water jacket of the engine is in an optimum state. To.

  In the second aspect of the present invention, when the engine load becomes lower than the engine speed, the control means enlarges or reduces the opening of the flow rate adjustment valve, and increases the amount of cooling water supplied to the EGR cooler. To do.

  According to the EGR device of the present invention, the following excellent effects can be obtained.

  (1) When the load is low with respect to the engine speed, the amount of cooling water supplied to the EGR cooler can be increased to increase the amount of exhaust gas recirculation, thereby achieving more effective NOx reduction. it can.

  (2) Since the ratio of the cooling water supplied to the water jacket of the engine can be increased when the load is high with respect to the engine speed, the cooling performance of the engine can be ensured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a cooling water flow system according to a first example of an embodiment of the EGR apparatus of the present invention. In the figure, the same reference numerals as those in FIG. 5 denote the same parts.

  This EGR device assumes that the pressure loss of the EGR cooler 1 is larger than that of the water jacket of the engine 3, and the opening degree command becomes smaller as the load becomes lower than the rotation speed with the rotation speed and load of the engine 3 as parameters. A control unit (ECU: Electronic Control Unit) 8 in which a smaller map is set in advance, and a flow rate adjusting valve 9 a incorporated in the water jacket inlet side of the engine 3 and remotely operated by the control unit 8 are provided.

  Due to the presence of the flow rate adjusting valve 9a, the ratio of the cooling water supplied to the EGR cooler 1 and the cooling water supplied to the water jacket of the engine 3 is not uniquely determined.

  The control unit 8 is configured to expand and contract the opening of the flow rate adjusting valve 9a based on the detected value obtained by the accelerator opening sensor 10, the engine rotation sensor 11, and the map described above.

  In other words, the lower the load with respect to the rotational speed of the engine 3, the smaller the opening of the flow rate adjusting valve 9 a, and apparently the inflow of cooling water into the water jacket of the engine 3 is suppressed to cool the EGR cooler 1. Even if the water supply amount is increased and the capacity of the water pump 2 is not increased, the amount of exhaust gas recirculation can be increased more than ever.

  On the contrary, as the load increases with respect to the rotational speed of the engine 3, the opening degree of the flow rate adjusting valve 9 a increases, and apparently the inflow of cooling water into the water jacket of the engine 3 increases. Performance is ensured.

  The control unit 8 is not particularly required to be an independent configuration only for the EGR device, and a normal in-vehicle ECU can be used.

  FIG. 2 shows a cooling water flow system according to a second example of the embodiment of the EGR apparatus of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same parts.

  This EGR device assumes that the pressure loss of the water jacket of the engine 3 is larger than that of the EGR cooler 1, and the opening degree command becomes smaller as the load becomes lower than the rotation speed with the rotation speed and load of the engine 3 as parameters. A control unit 12 in which a map to be enlarged is set in advance, and a flow rate adjusting valve 9b incorporated in the cooling water inlet side of the EGR cooler 1 and remotely operated by the control unit 12 are provided.

  Due to the presence of the flow regulating valve 9b, the ratio of the cooling water supplied to the EGR cooler 1 and the cooling water supplied to the water jacket of the engine 3 is not uniquely determined.

  The control unit 12 is configured to expand or contract the opening of the flow rate adjusting valve 9a based on the detected value obtained by the accelerator opening sensor 10, the engine rotation sensor 11, and the map described above.

  That is, the lower the load with respect to the rotational speed of the engine 3, the larger the opening of the flow rate adjusting valve 9 b, and apparently the amount of cooling water supplied to the EGR cooler 1 increases and the capacity of the water pump 2 increases. Even without this, the amount of exhaust gas recirculation can be increased more than ever.

  On the contrary, as the load increases with respect to the rotational speed of the engine 3, the opening degree of the flow rate adjusting valve 9b is reduced, and apparently the inflow of cooling water to the EGR cooler 1 is suppressed. Secured.

  The control unit 12 does not need to have an independent configuration especially for the EGR device alone, and a normal in-vehicle ECU can be used.

  FIG. 3 shows a third example of the cooling water flow system according to the embodiment of the EGR apparatus of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components.

  This EGR device assumes that the pressure loss of the EGR cooler 1 is larger than that of the water jacket of the engine 3, and incorporates a flow control valve 9 c remotely operated by the control unit 8 on the water jacket outlet side of the engine 3. Yes.

  Due to the presence of the flow rate adjusting valve 9c, the ratio of the cooling water supplied to the EGR cooler 1 and the cooling water supplied to the water jacket of the engine 3 is not uniquely determined.

  That is, the lower the load with respect to the rotational speed of the engine 3, the smaller the opening degree of the flow rate adjusting valve 9 c and the greater the flow resistance of the water jacket of the engine 3, thereby suppressing the inflow of cooling water into the water jacket. .

  As a result, the amount of cooling water supplied to the EGR cooler 1 increases, and the amount of exhaust gas recirculation can be increased more than before without increasing the capacity of the water pump 2.

  On the contrary, as the load increases with respect to the rotational speed of the engine 3, the opening degree of the flow rate adjusting valve 9c increases, the flow resistance of the water jacket of the engine 3 decreases, and the flow of cooling water into the water jacket increases. Therefore, the cooling performance of the engine 3 is ensured.

  FIG. 4 shows a cooling water flow system of a fourth example of the embodiment of the EGR device of the present invention, and in the figure, the parts denoted by the same reference numerals as those in FIG. 2 represent the same items.

  This EGR device assumes that the water jacket of the engine 3 has a larger pressure loss than the EGR cooler 1, and incorporates a flow rate adjusting valve 9d remotely operated by the control unit 12 on the cooling water outlet side of the EGR cooler 1. It is out.

  Due to the presence of the flow rate adjusting valve 9d, the ratio of the cooling water supplied to the EGR cooler 1 and the cooling water supplied to the water jacket of the engine 3 is not uniquely determined.

  That is, as the load decreases with respect to the rotational speed of the engine 3, the opening degree of the flow rate adjusting valve 9d increases and the flow path resistance of the EGR cooler 1 decreases, so that the amount of cooling water supplied to the EGR cooler 1 apparently increases. Even if the capacity of the water pump 2 is not increased, the amount of exhaust gas recirculation can be increased more than ever.

  On the contrary, as the load increases with respect to the rotational speed of the engine 3, the opening degree of the flow rate adjusting valve 9 d decreases and the flow resistance of the EGR cooler 1 increases, and apparently the inflow of cooling water to the EGR cooler 1 flows. Therefore, the cooling performance of the engine 3 is ensured.

  It should be noted that the EGR apparatus of the present invention is not limited to the above-described embodiment, and it goes without saying that modifications can be made without departing from the scope of the present invention.

  The EGR device of the present invention can be applied to various internal combustion engines including a diesel engine for vehicles.

It is a conceptual diagram which shows the 1st example of embodiment of the EGR apparatus of this invention. It is a conceptual diagram which shows the 2nd example of embodiment of the EGR apparatus of this invention. It is a conceptual diagram which shows the 3rd example of embodiment of the EGR apparatus of this invention. It is a conceptual diagram which shows the 4th example of embodiment of the EGR apparatus of this invention. It is a conceptual diagram which shows an example of the conventional EGR apparatus.

Explanation of symbols

1 EGR cooler 3 Engine exhaust path 8 Control unit (control means)
9a Flow adjustment valve 9b Flow adjustment valve 9c Flow adjustment valve 9d Flow adjustment valve 10 Control unit (control means)

Claims (2)

  The cooling water inlet of the EGR cooler is connected to an inlet flow path for supplying cooling water to the engine water jacket, the cooling water outlet of the EGR cooler is connected to an outlet flow path for sending cooling water from the engine water jacket, An EGR apparatus comprising a flow rate adjusting valve incorporated in at least one of a water jacket inlet side, a water jacket outlet side, a cooling water inlet side of the EGR cooler, and a cooling water outlet side of the EGR cooler.   The EGR device according to claim 1, further comprising a control unit that can expand and contract the opening of the flow rate adjustment valve based on the engine speed and the engine load.

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