JP2017194024A - Water supply device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water supply device for an engine capable of being more easily installed in an engine.SOLUTION: There is provided the water supply device for an engine comprising a high temperature-side cooling liquid circuit for circulating cooling liquid through an engine body, a low temperature-side cooling liquid circuit for circulating the cooling liquid without passing through the engine body, and an EGR valve 42 for adjusting a flow rate of an EGR gas recirculated during air intake. The water supply device for an engine comprises: a first solenoid valve 57 and a second solenoid valve 68 switching the cooling liquid to be introduced to an EGR cooler between the high temperature cooling liquid flowing in the high temperature-side cooling liquid circuit and the low temperature-side cooling liquid flowing in the low temperature-side cooling circuit; a condensed water generation control portion 70 which switches cooling liquid from the high temperature cooling liquid to the low temperature cooling liquid by the first solenoid valve 57 and the second solenoid valve 68 in a high load operation of the engine, the cooling liquid being introduced to the EGR cooler, and controls an amount of condensed water generated in cooling the EGR gas by the EGR cooler through the adjustment of the flow rate of the EGR gas by the EGR valve 42.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an engine water supply apparatus that supplies condensed water generated by cooling of EGR gas in an EGR cooler to a combustion chamber.

  As is well known, the combustion state and emissions may be improved by supplying water to the combustion chamber of the engine and burning the fuel together with the supplied water. Such a water supply device that supplies water to the combustion chamber requires a mechanism that adjusts the amount of water supplied in accordance with the operating state of the engine.

  Conventionally, the apparatus of patent document 1 is known as an engine water supply apparatus. The water supply apparatus described in the document includes a water tank and a water addition valve. The water tank is a tank that stores condensed water generated by an EGR cooler that cools exhaust gas (EGR gas) recirculated during intake air, and is installed outside the engine body. The water addition valve is a valve that adds condensed water in the water tank into the intake air, and is installed in the intake port of the engine. In the water supply apparatus, the amount of condensed water added to the intake air by the water addition valve is controlled in accordance with the engine load, thereby adjusting the amount of condensed water supplied according to the operating condition of the engine.

Japanese Patent Laying-Open No. 2015-096713

  By the way, in many cases, new engine designs are carried out by using existing engine designs to some extent. However, if the conventional water supply device is added to an existing engine, the design of the engine has to be significantly changed. For example, the water tank provided in the conventional water supply device needs a certain volume, and in order to secure the installation space, the arrangement of parts around the engine may need to be significantly changed. In the case of the conventional water supply device, a mechanism for separating the condensed water from the EGR gas must be provided in the EGR cooler, and the EGR cooler of the existing engine cannot be used as it is. Further, in the conventional water supply apparatus, since the water addition valve is installed in the intake port, the structure of the engine body must be changed from that of the existing engine.

Thus, an engine equipped with a conventional water supply device requires a significant design change from the existing engine, and as a result, requires many new parts.
The present invention has been made in view of such circumstances, and a problem to be solved is to provide a water supply device for an engine that can be easily installed on the engine.

  An engine water supply device that solves the above-described problems is a high-temperature side cooling liquid circuit that circulates the cooling liquid through the engine body and a cooling liquid circuit that circulates the cooling liquid without passing through the engine main body as a cooling liquid circuit that circulates the cooling liquid. An EGR valve that adjusts the flow rate of EGR gas that is exhaust gas recirculated during intake air, and an EGR cooler that cools the EGR gas with coolant introduced from outside It is installed in the engine provided, and the condensed water generated by the cooling of the EGR gas in the EGR cooler is supplied to the engine combustion chamber together with the EGR gas. The water supply device includes a cooling liquid switching unit that switches a cooling liquid introduced into the EGR cooler between a cooling liquid flowing in the high temperature side cooling liquid circuit and a cooling liquid flowing in the low temperature side cooling liquid circuit; During the load operation, the coolant introduced into the EGR cooler by the coolant switching unit is switched from the coolant flowing through the high-temperature side coolant circuit to the coolant flowing through the low-temperature side coolant circuit, and the EGR valve A condensate generation control unit that controls the amount of condensate generated by cooling the EGR gas in the EGR cooler through adjustment of the flow rate.

  In an engine to which such a water supply device is applied, the coolant that circulates in the high-temperature side coolant circuit receives heat from the engine body that is combusted, and thus has a higher temperature than the coolant that circulates in the low-temperature side coolant circuit. Tend. On the other hand, the water in the EGR gas may be condensed by cooling with the EGR cooler, and the condensed water generated thereby is introduced into the combustion chamber of the engine together with the EGR gas.

  Here, when the coolant switching unit switches the coolant introduced into the EGR cooler from the higher temperature coolant flowing in the high temperature side coolant circuit to the lower temperature coolant circuit flowing in the low temperature side coolant circuit. The EGR gas in the EGR cooler is cooled to a lower temperature, and condensed water is likely to be generated. On the other hand, the amount of condensed water generated in the EGR cooler correlates with the flow rate of EGR gas passing through the EGR cooler. Therefore, by adjusting the flow rate of the EGR gas with the EGR valve, the amount of condensed water generated by the cooling of the EGR gas in the EGR cooler at this time, and thus the amount of condensed water supplied to the combustion chamber together with the EGR gas can be reduced. Can be controlled.

  In the engine water supply apparatus, the condensate generation control unit cools the coolant introduced into the EGR cooler through the high-temperature side coolant circuit by the coolant switching unit during a high load operation in which the combustion temperature tends to be high. By switching from the liquid to the cooling liquid flowing through the low-temperature side cooling liquid circuit, the EGR cooler facilitates the generation of condensed water. Further, the condensed water generation control unit at this time controls the amount of condensed water generated by the cooling of the EGR gas in the EGR cooler by adjusting the flow rate of the EGR gas by the EGR valve. Therefore, an appropriate amount of condensed water can be introduced into the combustion chamber, and the combustion temperature can be lowered by the heat of vaporization of the condensed water. In addition, if the engine has the two coolant circuits, the EGR valve, and the EGR cooler, the configuration of the engine main body and the EGR cooler is hardly changed, and the piping arrangement is changed with respect to the two coolant circuits. Such a water supply device can be added only by adding a valve mechanism or the like constituting the coolant switching unit. Therefore, according to the water supply device for the engine, a water supply device that can supply the condensed water generated by the cooling of the EGR gas in the EGR cooler to the combustion chamber and can control the supply amount of the condensed water is easier. Can be installed on the engine.

The figure which shows typically the structure of the intake-exhaust system of the engine provided with one Embodiment of the water supply apparatus. The figure which shows typically the structure of the cooling system of the engine provided with the water supply apparatus of the embodiment. The block diagram which shows the control structure of the water supply apparatus of the embodiment. The graph which shows the relationship between the temperature of EGR flow volume, the temperature of the cooling water which flows into an EGR cooler, and the EGR exit gas temperature in the engine to which the water supply apparatus is applied. The flowchart of the condensed water generation | occurrence | production control routine performed in the water supply apparatus.

Hereinafter, an embodiment of an engine water supply device will be described in detail with reference to FIGS.
As shown in FIG. 1, the engine E provided with the water supply device of the present embodiment includes an engine body 10 (cylinder head, cylinder block) provided with a combustion chamber 11 of each cylinder. Further, the engine E is provided with an intake passage 20 through which intake air flowing into the combustion chamber 11 of each cylinder flows, and an exhaust passage 30 through which the exhaust discharged from the combustion chamber 11 of each cylinder flows. Further, the engine E is also provided with an EGR passage 40 for recirculating a part of the exhaust gas flowing through the exhaust passage 30 into the intake air flowing through the intake passage 20. This figure shows a case where the engine E is an in-line four-cylinder engine, and the engine body 10 is provided with four combustion chambers 11.

  The engine body 10 is provided with a crank angle sensor 12 that outputs a pulsed crank signal in accordance with the rotation of the engine E. The engine speed NE is detected using the crank signal of the crank angle sensor 12.

  The intake passage 20 is provided with an air flow meter 21 for detecting the intake flow rate GA. A compressor 22 that compresses the intake air is provided in a portion of the intake passage 20 downstream of the air flow meter 21, and further, a portion of the intake passage 20 downstream of the compressor 22 has a high temperature due to compression by the compressor 22. Is provided with an intercooler 23 for cooling with a coolant introduced from the outside. A throttle valve 24 is provided in a portion of the intake passage 20 downstream of the intercooler 23. The intake passage 20 is branched toward the combustion chamber 11 of each cylinder at a portion downstream of the throttle valve 24. Further, an intake pressure sensor 25 for detecting the pressure of the intake air after compression by the compressor 22 (intake air pressure PA) and an intake air temperature sensor 26 for detecting the temperature of the intake air after the compression (intake air temperature THA) are provided in the intake passage 20. Is provided.

  The exhaust passage 30 is provided with a turbine 31 that drives the compressor 22 using the flow of exhaust gas flowing through the exhaust passage 30. A catalyst 32 that purifies harmful components in the exhaust is provided in a portion of the exhaust passage 30 downstream of the turbine 31.

  The EGR passage 40 connects a portion of the exhaust passage 30 upstream of the turbine 31 and a portion of the intake passage 20 downstream of the throttle valve 24 and upstream of the branching position to each combustion chamber 11. Is provided. The EGR passage 40 is provided with an EGR cooler 41 that cools exhaust gas (hereinafter referred to as EGR gas) that is recirculated into the intake air through the EGR passage 40 with a coolant introduced from the outside. . Furthermore, an EGR valve 42 that adjusts the flow rate of the EGR gas by changing the opening degree is provided in a portion of the EGR passage 40 on the downstream side of the EGR cooler 41.

  A spark plug 11a is provided in each combustion chamber 11 of each cylinder of the engine E. Each spark plug 11a is controlled by a knock control system (hereinafter referred to as KCS 11b). The KCS 11b gradually advances the ignition timing while monitoring the occurrence of knocking in the engine E. When the occurrence of knocking is confirmed, the KCS 11b delays the ignition timing until knocking does not occur. As a result, the KCS 11b advances the ignition timing to the limit at which knocking can be avoided, and increases the efficiency of the engine E as a heat engine.

  In FIG. 2, the structure of the cooling system of the engine E in which the water supply apparatus of this embodiment was provided is shown. In the cooling system of the engine E, as a coolant circuit for circulating the coolant, a high-temperature side coolant circuit 50 that circulates the coolant through the engine body 10, and the coolant is circulated without passing through the engine body 10. A low-temperature side coolant circuit 60 is provided.

  The high temperature side coolant circuit 50 is provided with a main pump 51 that is a mechanical pump that operates by the power of the engine E and sucks and discharges the coolant. An outlet passage 52 is connected to the discharge side of the main pump 51, and an inlet passage 53 is connected to the suction side of the main pump 51. The outlet passage 52 is branched in the middle, and one end of the branch is connected to the engine body 10 and the other end is connected to a sub-radiator 61 that cools the coolant by heat exchange with air. Yes.

  The high temperature side coolant circuit 50 passes through the inside of the engine body 10 through the inside of the engine body 10, among the coolant discharged from the main pump 51 to the outlet passage 52, and toward the engine body 10 at the branch point of the outlet passage 52. After that, it is provided so as to return to the main pump 51 through the inlet passage 53. The high temperature side coolant circuit 50 is provided with a first fluid temperature sensor 59 that detects the temperature of the coolant immediately after passing through the engine body 10 (hereinafter referred to as the engine outlet fluid temperature THW).

  The high temperature side coolant circuit 50 is branched into two passages, a radiator passage 54 and a bypass passage 55, at a portion downstream of the engine body 10. The radiator passage 54 is provided so that the coolant that has passed through the engine body 10 flows to the inlet passage 53 through the main radiator 56 that cools the coolant by heat exchange with air. On the other hand, the bypass passage 55 is provided so that the coolant that has passed through the engine body 10 flows through the inlet passage 53, bypassing the main radiator 56.

  Further, a device passage 58 is branched from a part of the bypass passage 55 in the high temperature side coolant circuit 50. The device passage 58 is provided so that the coolant divided from the bypass passage 55 is sent to the EGR cooler 41 described above, and the coolant that has passed through the EGR cooler 41 flows to the inlet passage 53. In the device passage 58, a part of the coolant that has passed through the EGR cooler 41 further flows through the throttle valve 24 and then into the inlet passage 53.

  On the other hand, the low-temperature-side coolant circuit 60 uses the coolant that has been discharged from the main pump 51 to the outlet passage 52 and is directed toward the sub-radiator 61 at the branch point of the outlet passage 52. After passing through, it is provided to return to the main pump 51 through the inlet passage 53. Such a low temperature side coolant circuit 60 is not completely independent of the high temperature side coolant circuit 50, and shares a part of the inlet passage 53, the main pump 51, and the outlet passage 52 with the high temperature side coolant circuit 50. Yes. Note that a sub pump 62 is provided in a portion downstream of the sub radiator 61 in the low temperature side coolant circuit 60 and upstream of the intercooler 23. The sub pump 62 is configured as an electric pump driven by power feeding. Then, the sub pump 62 sucks the coolant discharged from the main pump 51 into the outlet passage 52 through the sub radiator 61 and sends it out toward the intercooler 23 in accordance with driving. By adjusting the coolant discharge amount of the sub pump 62, the flow rate of the coolant in the high temperature side coolant circuit 50 and the low temperature side coolant circuit 60 is changed. The low-temperature side coolant circuit 60 is provided with a second liquid temperature sensor 63 that detects the temperature of the coolant immediately before flowing into the intercooler 23 (hereinafter referred to as IC inlet liquid temperature THL).

  The cooling system is provided with a thermo mechanism. The thermo mechanism includes a temperature sensing unit 64, a first thermo valve 65, and a second thermo valve 66. The temperature sensing unit 64 is provided at a connection portion of the main pump 51 in the inlet passage 53. Further, the first thermo valve 65 is provided in a portion on the downstream side of the main radiator 56 in the radiator passage 54 of the high temperature side coolant circuit 50. Further, the second thermo valve 66 is provided in a portion downstream of the sub radiator 61 in the low temperature side coolant circuit 60 and upstream of the sub pump 62. The temperature sensing unit 64 operates according to the temperature of the coolant passing through the temperature sensing unit 64 to drive the first thermo valve 65 and the second thermo valve 66. Specifically, when the temperature of the coolant is lower than a specified temperature, the temperature sensing unit 64 closes the first thermo valve 65 and the second thermo valve 66 and passes through the main radiator 56 and the sub radiator 61. The cooling water flow is stopped. Then, when the temperature of the coolant becomes equal to or higher than a specified temperature, the temperature sensing unit 64 closes the first thermo valve 65 and the second thermo valve 66, and cools the cooling water through the main radiator 56 and the sub radiator 61. Allow flow.

  The water supply device of the present embodiment includes a coolant switching unit that switches between the coolant flowing through the high temperature side coolant circuit 50 and the coolant flowing through the low temperature side coolant circuit 60, and switching the coolant introduced into the EGR cooler 41. Prepare for such a cooling system. The coolant switching unit includes a first electromagnetic valve 57, an extraction passage 67, and a second electromagnetic valve 68.

  The first electromagnetic valve 57 is provided in a portion upstream of the branch portion of the device passage 58 in the bypass passage 55 of the high temperature side coolant circuit 50. The first electromagnetic valve 57 is opened when energization is stopped, and allows the coolant to flow from the engine body 10 to the bypass passage 55 and the device passage 58. On the other hand, the first electromagnetic valve 57 is closed in response to energization, and prohibits the flow of the coolant from the engine body 10 to the bypass passage 55 and the device passage 58.

  The take-out passage 67 is provided downstream of the sub pump 62 in the low-temperature side coolant circuit 60 and upstream of the intercooler 23 and the EGR cooler 41. The second electromagnetic valve 68 is provided in such an extraction passage 67. The second electromagnetic valve 68 is closed when the energization is stopped, and the flow of the coolant through the extraction passage 67 is blocked. On the other hand, the second solenoid valve 68 opens in response to energization, and allows the coolant to flow through the take-out passage 67.

  Here, when the first electromagnetic valve 57 is opened and the second electromagnetic valve 68 is closed, the coolant of the high-temperature side coolant circuit 50 that has passed through the engine main body 10 through the device passage 58 (hereinafter referred to as high-temperature coolant). Are introduced into the EGR cooler 41. On the other hand, when the first solenoid valve 57 is closed and the second solenoid valve 68 is opened, the coolant of the low-temperature side coolant circuit 60 that has passed through the sub-radiator 61 through the take-out passage 67 (hereinafter referred to as low-temperature coolant). Are introduced into the EGR cooler 41. The high-temperature coolant is a coolant that is warmed by the combustion heat of the engine E when passing through the engine body 10 after being discharged from the main pump 51, whereas the low-temperature coolant is after being discharged from the main pump 51. The coolant is cooled by the secondary radiator 61. For this reason, the low-temperature coolant is at a lower temperature than the high-temperature coolant. The engine outlet liquid temperature THW detected by the first liquid temperature sensor 59 corresponds to the temperature of the high-temperature coolant, and the IC inlet liquid temperature THL detected by the second liquid temperature sensor 63 is the temperature of the low-temperature side coolant. Corresponds to temperature.

  In FIG. 3, the control structure of the water supply apparatus of this embodiment is shown. As shown in the figure, the water supply device of the present embodiment includes a condensed water generation control unit 70. The condensed water generation control unit 70 receives detection signals from the crank angle sensor 12, the air flow meter 21, the intake pressure sensor 25, the intake temperature sensor 26, the first liquid temperature sensor 59, and the second liquid temperature sensor 63 described above. Yes. The condensed water generation control unit 70 obtains detection results of the engine speed NE, the intake flow rate GA, the intake pressure PA, the intake air temperature THA, the engine outlet liquid temperature THW, and the IC inlet liquid temperature THL from these detection signals. The condensed water generation control unit 70 controls the opening degree of the EGR valve 42 and the opening / closing of the first electromagnetic valve 57 and the second electromagnetic valve 68 based on the detection results.

  At the time of high load operation of the engine E provided with the water supply device of the present embodiment configured as described above, the intake air compression rate in the compressor 22 increases and the intake air temperature THA increases, so the combustion temperature is high. Therefore, knocking is likely to occur. Therefore, during high load operation, the combustion temperature is lowered by introducing a large amount of EGR gas to suppress the occurrence of knocking. However, if the amount of EGR gas introduced exceeds a certain level, combustion becomes unstable and misfire occurs. Therefore, there is a limit to the reduction of the combustion temperature due to the introduction of EGR gas, and the retard of the ignition timing by the KCS 11b is necessary for suppressing knocking, which may cause the efficiency of the engine E to deteriorate. Further, when the intake air temperature THA increases, the maximum mass of the intake air that can be introduced into the combustion chamber 11 decreases due to the thermal expansion of the intake air, so that the maximum output of the engine E also decreases.

  On the other hand, in the EGR cooler 41, when the EGR gas is cooled below the dew point, the moisture in the EGR gas is condensed. The condensed water generated in this way is introduced into the combustion chamber 11 together with the EGR gas during the intake air flowing through the intake passage 20. When condensed water is introduced into the combustion chamber 11, the combustion temperature decreases due to the heat of vaporization of the condensed water. Therefore, during high-load operation of the engine E where the combustion temperature tends to be high, condensate is generated by the EGR cooler 41, and the amount of the generated condensate is appropriately adjusted to suppress an increase in the combustion temperature. Thus, knocking can be suppressed and the output performance of the engine E can be improved.

  In the water supply device according to the present embodiment, the condensed water generation control unit 70 switches the coolant introduced into the EGR cooler 41 from the high-temperature coolant to the low-temperature coolant during high load operation of the engine E in which the combustion temperature increases. Thus, the EGR cooler 41 is likely to generate condensed water. Further, the condensed water generation control unit 70 adjusts the flow rate of the EGR gas introduced into the intake air by the EGR valve 42 (hereinafter referred to as the EGR gas flow rate), so that the EGR gas in the EGR cooler 41 at this time The amount of condensed water generated by cooling is controlled to an appropriate amount.

  FIG. 4 shows the temperature of the coolant introduced into the EGR cooler 41 (cooler internal temperature), the EGR gas flow rate, and the temperature of the EGR gas after passing through the EGR cooler 41 (hereinafter referred to as cooler outlet gas temperature). The relationship is shown. As shown in the figure, the cooler outlet gas temperature decreases as the cooler internal liquid temperature decreases and as the EGR gas flow rate decreases.

  When the amount of water vapor in the EGR gas exceeds the saturated water vapor amount of the EGR gas, the excess water vapor is condensed into water droplets. The saturated water vapor amount of the EGR gas decreases as the EGR gas becomes lower in temperature. Therefore, if the cooler outlet gas temperature is a temperature at which the water vapor amount in the EGR gas exceeds the saturated water vapor amount, that is, the dew point or less, condensed water is generated in the EGR cooler 41. The amount of condensed water generated when the EGR gas flow rate is constant increases as the cooler outlet gas temperature falls below the dew point. On the other hand, as described above, the cooler outlet gas temperature varies depending on the liquid temperature in the cooler and the EGR gas flow rate. Therefore, the amount of condensed water generated in the EGR cooler 41 can be controlled by adjusting the liquid temperature in the cooler and the EGR gas flow rate.

  The EGR gas flow rate can be controlled by the opening degree of the EGR valve 42. Further, in the water supply device of the present embodiment, the coolant introduced into the EGR cooler 41 by opening and closing the first solenoid valve 57 and the second solenoid valve 68, the high-temperature coolant flowing through the high-temperature side coolant circuit 50, and By switching between the low-temperature coolant flowing through the low-temperature-side coolant circuit 60, the liquid temperature in the cooler can be changed. Therefore, the generation of condensed water in the EGR cooler 41 through the switching of the cooling liquid by the cooling liquid switching unit (the first electromagnetic valve 57, the take-out passage 67, the second electromagnetic valve 68) and the adjustment of the EGR gas flow rate by the EGR valve 42. The amount can be controlled.

  FIG. 5 shows a processing procedure of a condensed water generation control routine executed by the condensed water generation control unit 70 in the water supply device of the present embodiment. The condensed water generation control unit 70 repeatedly executes the processing of this routine every prescribed control cycle while the engine E is in operation.

  When this routine is started, first, in step S100, detected values of the engine speed NE, the intake pressure PA, the intake air temperature THA, the engine outlet liquid temperature THW, and the IC inlet liquid temperature THL are read. In the subsequent step S101, the required water amount is calculated based on the engine speed NE, the intake pressure PA, the intake air temperature THA, and the like. The required amount of water is calculated using a map stored in the condensate generation control unit 70 in advance, and the calculated value is an EGR cooler 41 that is necessary to reduce the combustion temperature to a temperature at which knocking can be suppressed. The amount of condensed water is required to be generated. Outside the high-load operation region of the engine E, even if the condensed water is not supplied to the combustion chamber 11, the combustion temperature does not rise until knocking occurs, so the calculated value of the required water amount is “0”. .

  Subsequently, in step S102, it is determined whether or not the calculated value of the required water amount is larger than “0”. That is, it is determined whether or not it is necessary to supply condensed water to the combustion chamber 11 to suppress knocking.

  Here, when the required water amount is “0” (S102: NO), the process proceeds to step S120, and in step S120, the EGR is set so that an opening degree at which an EGR rate corresponding to the operating state of the engine E is obtained. Valve 42 is controlled. The EGR rate at this time is calculated from the engine speed NE, the intake air flow rate GA, the intake pressure PA, the engine outlet fluid temperature THW, etc., and the calculated value is the same as when the high temperature coolant is introduced into the EGR cooler 41. Condensed water is not generated in the cooler 41, and the value does not exceed the misfire limit, which is the upper limit value of the EGR rate at which misfire can be avoided. In step S122, the first electromagnetic valve 57 is opened and the second electromagnetic valve 68 is closed, so that the high-temperature coolant is introduced into the EGR cooler 41. Is terminated.

  On the other hand, when the calculated value of the required water amount is larger than “0” (S102: YES), the process proceeds to step S103, and when the low-temperature coolant is introduced into the EGR cooler 41 in step S103, the required water amount is obtained. An EGR gas flow rate (hereinafter, referred to as a required flow rate α) required for generating the condensed water of is calculated. The calculation of the required flow rate α here is performed based on the IC inlet liquid temperature THL. Then, in the subsequent step S104, it is determined whether or not the required flow rate α is equal to or less than the misfire limit flow rate that is the upper limit value of the EGR flow rate that can avoid misfire. The value of the misfire limit flow rate is obtained according to the engine speed NE, the intake flow rate GA, and the like.

  If the required flow rate α exceeds the misfire limit flow rate (S104: NO), the process proceeds to step S121, and the EGR valve 42 is controlled to be fully closed. In step S122, the first electromagnetic valve 57 is opened and the second electromagnetic valve 68 is closed, so that the high-temperature coolant is introduced into the EGR cooler 41. Is terminated.

  On the other hand, when the required flow rate α is equal to or less than the misfire limit flow rate (S104: YES), the process proceeds to step S110, and in step S110, the opening degree necessary for securing the EGR gas flow rate for the required flow rate α is obtained. The EGR valve 42 is controlled. In step S111, the first electromagnetic valve 57 is closed, the second electromagnetic valve 68 is opened, and the low temperature coolant is introduced into the EGR cooler 41. Is terminated.

Then, the effect | action of this embodiment comprised as mentioned above is demonstrated.
In the water supply device for the engine E of the present embodiment, in the operation region other than the high load operation region, the condensed water generation control unit 70 opens the first electromagnetic valve 57 and closes the second electromagnetic valve 68 to perform high temperature side cooling. The high temperature coolant flowing through the liquid circuit 50 is introduced into the EGR cooler 41. Further, the condensed water generation control unit 70 at this time controls the opening degree of the EGR valve 42 so as to obtain an EGR rate suitable for improving fuel efficiency and exhaust performance according to the operating state of the engine E. Note that the EGR rate at this time is a value at which condensed water is not generated in the EGR cooler 41. Therefore, it is possible to prevent the EGR cooler 41 from constantly generating condensed water and preventing the pipes and the like constituting the EGR passage 40 from being corroded.

  On the other hand, when the high-temperature coolant is introduced into the EGR cooler 41, the condensed water generation control unit 70 closes the first electromagnetic valve 57 and the second electromagnetic valve 57 in the high load operation region where the combustion temperature increases until knocking occurs. The electromagnetic valve 68 is opened so that the low temperature coolant flowing through the low temperature side coolant circuit 60 is introduced into the EGR cooler 41. As a result, the temperature of the coolant introduced into the EGR cooler 41 is lowered, and the EGR gas is cooled to a lower temperature by the EGR cooler 41. Therefore, the generation of condensed water in the EGR cooler 41 is promoted. . Further, the condensate generation control unit 70 at this time controls the EGR valve so that the amount of condensate generated in the EGR cooler 41 becomes an amount (required water amount) necessary for lowering the combustion temperature until knocking is suppressed. 42 is controlled.

  The condensed water generated in the EGR cooler 41 at this time is introduced into the intake air together with the EGR gas, and further sent to the combustion chamber 11 together with the intake air. And the combustion temperature is lowered by the heat of vaporization of the condensed water, and the occurrence of knocking is suppressed. As a result, the retarding of the ignition timing by the KCS 11b for suppressing knocking can be suppressed, and the efficiency and output performance of the engine E can be increased.

  However, when the EGR gas flow rate necessary for generating the required amount of condensed water exceeds the misfire limit flow rate, the condensed water generation control unit 70 opens the first electromagnetic valve 57 and closes the second electromagnetic valve 68. Thus, all of the low-temperature coolant flowing through the low-temperature-side coolant circuit 60 flows through the intercooler 23. In such a case, the condensed water generation control unit 70 stops the introduction of EGR gas by fully closing the EGR valve 42.

  In such a case, even if condensed water is generated by the EGR cooler 41 to the limit where misfire can be avoided, knocking cannot be suppressed, and retarding of the ignition timing by the KCS 11b is unavoidable. On the other hand, if the flow rate of the low-temperature coolant flowing through the intercooler 23 is increased, the intake air is cooled to a lower temperature in the intercooler 23, and the reduction of the filling rate of the intake air into the combustion chamber 11 due to thermal expansion is suppressed. Furthermore, if the introduction of EGR gas is stopped, the amount of fresh air introduced into the combustion chamber 11 is increased accordingly. Therefore, the decrease in the output of the engine E due to the retard of the ignition timing is compensated by the increase in the amount of fresh air introduced into the combustion chamber 11.

  In the water supply device of the present embodiment as described above, the cooling liquid introduced into the EGR cooler 41 is switched from the high-temperature cooling liquid to the low-temperature cooling liquid, and the EGR cooler 41 is condensed by adjusting the EGR gas flow rate by the EGR valve 42. By controlling the amount of water generated, water is supplied to the combustion chamber 11 during high-load operation of the engine E. If the engine controls the flow rate of EGR gas, the EGR valve 42 is provided from the beginning. In addition, in the case of an engine including two systems of coolant circuits, that is, a high temperature side coolant circuit 50 and a low temperature side coolant circuit 60, a pipe constituting the take-out passage 67 and two electromagnetic valves (57, 68) are added. It is possible to realize the switching of the cooling liquid only. Therefore, the water supply apparatus of this embodiment can be installed more easily than the conventional water supply apparatus which requires a water tank and a water addition valve as described above.

In addition, the said embodiment can also be changed and implemented as follows.
-In the above embodiment, even when the engine E is operating at a high load, if the EGR gas flow rate required for generating the required amount of condensed water exceeds the misfire limit flow rate, the introduction of the EGR gas is stopped. However, even at this time, the EGR gas may be introduced within a range not exceeding the misfire limit flow rate. In such a case, even if the amount is less than the required water amount, the condensed water is supplied to the combustion chamber 11 and the combustion temperature is lowered to a certain extent. Therefore, even if the ignition timing is retarded by the KCS 11b, the amount of retardation can be reduced to suppress a decrease in efficiency of the engine E due to the retardation of the ignition timing.

  -Although the water supply apparatus of the said embodiment was provided in the engine E with the supercharger which has the compressor 22 and the turbine 31, the water supply apparatus of the same embodiment is similarly provided also in the naturally aspirated engine be able to.

  In the above embodiment, the coolant introduced into the EGR cooler 41 is switched by the two electromagnetic valves (57, 68). However, the switching is performed by using another valve mechanism such as a three-way valve. You may make it perform.

  In the above embodiment, the high temperature side coolant circuit 50 and the low temperature side coolant circuit 60 are configured to share a part of the coolant circulation path, but these two coolant circuits are completely independent. A coolant circuit may be used. In the above-described embodiment, the coolant circuit that circulates the coolant that flows to the intercooler 23 is used as the low-temperature-side coolant circuit 60 that circulates the coolant without passing through the engine body 10. The liquid circuit may be used as a low temperature side cooling liquid circuit. For example, in a hybrid vehicle, a coolant circuit for cooling the inverter may be provided separately from the coolant circuit for cooling the engine body. In many cases, the coolant that circulates in the coolant circuit for cooling the inverter has a lower temperature than the coolant that circulates in the coolant circuit for cooling the engine body in which combustion is performed. Therefore, the EGR gas in the EGR cooler is switched by switching the coolant introduced into the EGR cooler from the coolant flowing in the coolant circuit for cooling the engine body to the coolant flowing in the coolant circuit for cooling the inverter. Thus, it is possible to promote the generation of condensed water in the EGR cooler. Then, by adjusting the flow rate of the EGR gas, the amount of condensed water generated in the EGR cooler can be controlled.

  E ... Engine, 10 ... Engine body, 11 ... Combustion chamber, 41 ... EGR cooler, 42 ... EGR valve, 50 ... High temperature side coolant circuit, 57 ... First solenoid valve (coolant switching unit), 60 ... Low temperature side cooling Liquid circuit, 67... Extraction passage (cooling liquid switching unit), 68... Second electromagnetic valve (cooling liquid switching unit), 70.

Claims (1)

As a coolant circuit for circulating the coolant, a high-temperature side coolant circuit that circulates the coolant through the engine body and a low-temperature side coolant circuit that circulates the coolant without passing through the engine body, and an intake air An EGR valve that adjusts the flow rate of EGR gas that is exhaust gas recirculated therein, and an EGR cooler that cools the EGR gas with a coolant introduced from outside, is installed in the engine, In an engine water supply device for supplying condensed water generated by cooling of the EGR gas to the combustion chamber of the engine together with the EGR gas,
A coolant switching unit that switches between the coolant that flows into the EGR cooler and the coolant that flows through the high-temperature side coolant circuit and the coolant that flows through the low-temperature side coolant circuit;
During the high load operation of the engine, the coolant introduced into the EGR cooler by the coolant switching unit is switched from the coolant flowing through the high temperature side coolant circuit to the coolant flowing through the low temperature side coolant circuit, A condensed water generation controller that controls the amount of condensed water generated by cooling the EGR gas in the EGR cooler through adjustment of the flow rate of the EGR gas by the EGR valve;
An engine water supply device comprising:

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