JP4631452B2 - EGR cooling system for vehicles - Google Patents

Description

  The present invention relates to an EGR cooling system for a vehicle, and more specifically, EGR cooling for a vehicle in which the cooling effect of EGR gas can always be maintained in a stable state by metering the flow rate of the refrigerant pumped to the EGR cooler. About the system.

  2. Description of the Related Art Conventionally, a technique for correcting an exhaust gas recirculation amount (EGR amount) of an exhaust gas recirculation (hereinafter referred to as EGR) device to a reduction side based on an engine coolant temperature detected as an engine temperature of an engine is known ( For example, see Patent Document 1).

  When the EGR gas is cooled by the EGR cooler for NOx reduction or fuel efficiency improvement, the EGR gas is usually cooled by engine cooling water. When the traveling wind and the engine load are stable, such as during steady running, the engine cooling water is stable within approximately 80 to 90 ° C., and the outflow temperature of the EGR cooler is also substantially stable.

  In this way, when the EGR cooler is cooled by the engine cooling water, a predetermined amount or more of heat is constantly received from the engine combustion chamber, which is a heat source, and the excess heat is radiated by the radiator. For this reason, if the EGR cooler is too cold, the amount of heat radiation can be reduced and the engine cooling water can be warmed. On the other hand, if the EGR cooler is too warm, the entire amount of engine cooling water is pumped to the radiator to cool the EGR cooler. Can do. That is, the temperature of the engine cooling water can be controlled to a desired value (cooling water temperature when creating the EGR control map).

JP 2000-104627 A

  However, in order to further reduce NOx and improve fuel efficiency, it is conceivable that another cooling water having a temperature lower than that of the engine cooling water is used as the cooling water for the EGR cooler. In such a case, if the water pump that pumps the cooling water is always driven, the EGR gas may be excessively cooled under the operation condition with a small amount of EGR gas.

  Further, when the EGR gas is cooled by a cooling system that does not always have a stable heat source such as combustion heat in the engine combustion chamber, the EGR cooler is a heat source when the EGR is in an ON state.

  However, when the EGR is in an OFF state or an engine stopped state (in the case of a hybrid vehicle, during EV travel using only the motor as a travel drive source), the water pump is excessively cooled if the water pump is always driven. There has been a problem that the temperature of the gas discharged from the EGR cooler cannot always be controlled to a stable temperature.

  The present invention has been made in view of the above, and by adjusting the flow rate of the refrigerant pressure-fed to the EGR cooler, the EGR cooling of the vehicle capable of constantly maintaining the cooling effect of the EGR gas in a stable state. The purpose is to provide a system.

In order to solve the above-described problems and achieve the object, an EGR cooling system for a vehicle according to claim 1 of the present invention does not receive the heat supply from the combustion chamber of the engine and supplies the EGR gas of the exhaust gas recirculation device. In a vehicle EGR cooling system including a cooling system that is cooled by an EGR cooler, the EGR cooler is disposed in the circuit of the cooling system, and a variable displacement pump that varies a flow rate of a refrigerant that is pumped to the EGR cooler; Variable displacement pump control means for adjusting the discharge amount of the variable displacement pump based on at least one of the temperature of the refrigerant and the temperature of the EGR gas that has passed through the EGR cooler, and the vehicle includes an engine and a motor. It is a hybrid vehicle that can be driven by at least one, and the cooling system includes a dedicated radiator, an inverter, and the motor. No is a cooling system for a hybrid electric appliances, cooling water radiated by the radiator, after cooling the inverter, and is characterized in that cooling the EGR cooler.

According to a second aspect of the present invention, in the EGR cooling system for a vehicle according to the first aspect, the cooling water radiated by the radiator cools the EGR cooler and then cools the motor. It is characterized by this.

A vehicle EGR cooling system according to a third aspect of the present invention is the vehicle EGR cooling system according to the first or second aspect , wherein when the required EGR cooling performance is low in the light load region of the engine, the variable displacement pump A correction means for correcting the discharge amount to be smaller than normal is provided.

According to the EGR cooling system of a vehicle according to the present invention, the flow rate of the refrigerant pumped into the EGR cooler by metering the variable displacement pump, it is possible to maintain the cooling effect of the EGR gas stably at any time.
In addition, the cooling effect of the EGR gas can be constantly maintained in a stable state by using the cooling system for hybrid electric equipment.
Moreover, in an electric device of a hybrid vehicle, since the inverter has the highest temperature, the cooling efficiency of the inverter is lowered by cooling the inverter with cooling water radiated by a radiator and then cooling the EGR cooler. The EGR gas can be cooled by the EGR cooler. As a result, the EGR gas temperature can be sufficiently reduced without degrading the performance of the hybrid vehicle.

Further, according to the EGR cooling system of a vehicle according to the present invention, it is possible to adjust the cooling performance of the EGR cooler by metering in accordance with the discharge amount of the variable displacement pump to the load of the engine. In the prior art, a bypass passage and a bypass valve were required for suppressing overcooling of the EGR cooler, etc. However, in the present invention, the discharge capacity of the refrigerant can be adjusted by a variable displacement pump, so these bypass passages are unnecessary. And cost can be reduced. In addition, by providing a variable displacement pump capable of metering the refrigerant discharge capacity, it is possible to improve the durability of the pump and reduce the energy consumption of the pump that always discharges the refrigerant at a constant capacity without changing the refrigerant discharge capacity. Reduction can be achieved.

  Embodiments of an EGR cooling system for a vehicle according to the present invention will be described below in detail with reference to the drawings. In addition, although the example which applied this invention to the diesel hybrid vehicle is demonstrated, this invention is not limited by this Example.

  FIG. 1 is a schematic diagram showing an EGR cooling system according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing a schematic configuration of a diesel hybrid vehicle. First, a schematic configuration of a diesel hybrid vehicle will be described with reference to FIG. As shown in FIG. 2, a diesel hybrid vehicle (hybrid vehicle) 10 is provided with a diesel engine (hereinafter simply referred to as an engine) 11 as a travel drive source.

  The driving force generated by the engine 11 is transmitted to the drive wheels 13 through a stepped transmission (hereinafter referred to as MMT (multi-mode manual transmission)) 12, a differential gear 15 and a drive shaft 14 that can be automatically shifted. It is like that.

  The MMT 12 electrically and automatically controls a gear shift operation by an actuator in accordance with a traveling state. Between the engine 11 and the MMT 12, there is provided a clutch 12a that performs contact and separation of power transmission, and the contact and separation operation is electrically and automatically controlled by an actuator according to the running state.

  A motor generator (electric motor) 17 in which a drive system gear unit (gear train) is integrated is connected to a battery 20 that is a chargeable / dischargeable secondary battery via an inverter 19 and functions as a motor that is a travel drive source. Power running operation mode, and a regenerative operation mode that functions as a generator.

  Whether motor generator 17 is operated in the power running mode or the regenerative operation mode is determined in consideration of the state of charge (SOC) of battery 20. The battery charge state amount SOC is calculated by a predetermined battery state monitor computer.

  Next, the outline of the engine 11 and the EGR cooling system will be described with reference to FIG. The intake passage 21 of the engine 11 includes an air flow meter (not shown) that detects the intake air amount and a throttle valve 24 that adjusts the intake air amount. The engine 11 is water-cooled, and a radiator 23 is disposed in an engine coolant passage 22 that communicates with a water jacket (not shown) in the engine 11. The engine cooling water is circulated through the engine cooling water passage 22 by a water pump 22 a driven by the engine 11.

  Further, the exhaust passage 30 of the engine 11 is driven by rotating a turbine section (not shown) using exhaust gas pressure to drive a coaxial compressor section (not shown) to increase the intake air amount. A turbocharger 26 that assists engine torque is provided. An intercooler 28 is provided in the intake passage 21 between the turbocharger 26 and the intake manifold 21a for cooling the intake air that has been supercharged and heated. The fresh air that has passed through the intercooler 28 and the throttle valve 24 is introduced into the intake manifold 21a.

  The engine 11 includes an EGR device 35 that recirculates a part of the exhaust gas to the intake system. The EGR passage 36 of the EGR device 35 is provided with an EGR cooler 37 that cools the EGR gas and an EGR valve 38 that adjusts the flow rate of the EGR gas. That is, a part of the exhaust gas discharged from the exhaust manifold 30a of the engine 11 is recirculated to the intake manifold (intake system) 21a through the EGR cooler 37 and the EGR valve 38 of the EGR passage 36.

  The temperature of the EGR gas that has passed through the EGR cooler 37 is detected by an outgas temperature sensor 37a disposed downstream of the EGR cooler 37, and is monitored by an electronic control unit (hereinafter referred to as ECU) not shown.

  The cooling system 40 for hybrid electrical equipment connected to the EGR cooler 37 includes a dedicated radiator 42, an inverter 19, and a motor generator (motor) 17. It is connected by an EGR cooler cooling water passage 41 so that water (refrigerant) can circulate.

  In this embodiment, the bypass passage 39 and the bypass valve 39a for bypassing the cooling water are provided for the case where the introduction of the cooling water to the EGR cooler 37 is unnecessary, but these may be provided if necessary. Good.

  The inverter 19 is disposed on the downstream side of the radiator 42 and on the upstream side of the EGR cooler 37. That is, the cooling water radiated by the radiator 42 circulates in the order of the inverter 19, the EGR cooler 37, the motor generator 17, and the radiator 42. In the electric device of the diesel hybrid vehicle 10, the inverter 19 has the highest temperature. Therefore, by disposing the inverter 19 at the above position, the cooling water cools the inverter 19 and then cools the EGR cooler 37.

  Thus, the EGR gas can be cooled by the EGR cooler 37 without reducing the cooling efficiency of the inverter 19. As a result, the EGR gas temperature can be sufficiently reduced without degrading the performance of the diesel hybrid vehicle 10.

  Further, an electric variable water pump (variable capacity pump) 44 that makes the flow rate of the cooling water pumped to the EGR cooler 37 variable is disposed downstream of the inverter 19. A water temperature sensor 46 that detects the temperature of the cooling water that has passed through the inverter 19 is disposed downstream of the variable water pump 44.

  The variable water pump 44 is discharged by the ECU (variable capacity pump control means) based on at least one of the temperature of the cooling water detected by the water temperature sensor 46 and the temperature of the EGR gas detected by the outgas temperature sensor 37a. It is configured to be metered in quantity. Here, as shown in FIG. 3, an example in which the discharge amount of the variable water pump 44 (denoted as variable W / P in FIG. 3) is adjusted based on the gas output temperature of the EGR cooler 37 will be described.

  For example, when the outlet gas temperature of the EGR cooler 37 is low, the discharge amount of the variable water pump 44 is adjusted to be small to reduce the amount of cooling heat, while when the outlet gas temperature of the EGR cooler 37 is high, the variable water pump is adjusted. The amount of cooling heat is increased by adjusting the discharge amount of the pump 44 to be high.

  As a result, even in a cooling system that does not receive a stable heat supply from the combustion chamber of the engine 11, the temperature of the EGR gas supplied to the engine 11 can be adjusted to a stable value, and the engine is always under stable conditions. 11 can be driven.

  Further, the variable water pump 44 has a smaller discharge amount than the normal time (normal load) when the EGR cooling required performance (capability required for cooling the EGR gas) is low in the light load region of the engine 11. In this way, the ECU (correction means) is configured to make corrections.

For example, the corrected discharge amount is
Discharge amount after correction = (Discharge amount at normal load) × Correction coefficient K
As shown in FIG. 4, when the load (torque) of the engine 11 is small, as shown in FIG. 4, the correction coefficient K is set to a small value so that the discharge amount becomes smaller than that at the normal load. On the other hand, when the load on the engine 11 is large, the value of the correction coefficient K is set large so that the discharge amount is corrected to be larger than that at the normal load. Here, FIG. 4 is a map showing the characteristics of the correction coefficient K for correcting the discharge amount of the variable water pump 44.

  Thus, the cooling performance of the EGR cooler 37 can be adjusted by adjusting the discharge amount of the variable water pump 44 according to the load of the engine 11. In addition, by providing a variable water pump 44 that can regulate the cooling water discharge capacity, the durability of the pump is improved compared to a pump that always discharges the cooling water at a constant capacity without making the cooling water discharge capacity variable. And energy consumption can be reduced.

  In the prior art, a bypass passage, a bypass valve, and the like are necessary for suppressing overcooling of the EGR cooler. In the present invention, the variable water pump 44 can adjust the discharge amount of the cooling water. A passage or the like can be omitted, and the cost can be reduced.

  In the above embodiment, the present invention is applied to a diesel hybrid vehicle. However, the present invention may be applied to other hybrid vehicles or vehicles using only an internal combustion engine as a travel drive source. The refrigerant for cooling the EGR cooler 37 may be other than water, for example, a cooling liquid obtained by adding a rust inhibitor or an antioxidant to an antifreeze liquid.

  As described above, the EGR cooling system for a vehicle according to the present invention can maintain the cooling effect of the EGR gas in a constantly stable state by adjusting the flow rate of the refrigerant pumped to the EGR cooler. In particular, the present invention is suitable for a hybrid vehicle including a cooling system for hybrid electric equipment including a dedicated radiator, an inverter, and a motor.

It is a schematic diagram which shows the EGR cooling system which concerns on the Example of this invention. It is a mimetic diagram showing a schematic structure of a diesel hybrid vehicle. It is a map which shows the example which adjusts the discharge amount of a variable water pump based on the outgas temperature of an EGR cooler. It is a map which shows the characteristic of the correction coefficient K which correct | amends the discharge amount of a variable water pump.

Explanation of symbols

10 Diesel hybrid vehicle (hybrid vehicle)
11 Diesel engine (engine)
17 Motor generator (motor)
19 Inverter 35 EGR device 36 EGR passage 37 EGR cooler 37a Outgas temperature sensor 40 Cooling system for hybrid electric equipment 41 EGR cooler cooling water passage 42 Radiator 44 Variable water pump (variable capacity pump)
46 Water temperature sensor

Claims (3)

In an EGR cooling system for a vehicle having a cooling system that cools EGR gas of an exhaust gas recirculation device by an EGR cooler without receiving heat supply from an engine combustion chamber,
A variable displacement pump in which the EGR cooler is disposed in the circuit of the cooling system, and the flow rate of the refrigerant pumped to the EGR cooler is variable;
Variable displacement pump control means for adjusting the discharge amount of the variable displacement pump based on at least one of the temperature of the refrigerant and the temperature of the EGR gas that has passed through the EGR cooler;
With
The vehicle is a hybrid vehicle that can be driven by at least one of an engine and a motor,
The cooling system is a cooling system for a hybrid electric device including a dedicated radiator, an inverter, and the motor.
The cooling water radiated by radiator, EGR cooling system of a vehicle, characterized in that after cooling the inverter, cooling the EGR cooler. 2. The vehicle EGR cooling system according to claim 1, wherein the cooling water radiated by the radiator cools the EGR cooler and then cools the motor. 3.   3. A correction means for correcting the discharge amount of the variable displacement pump to be smaller than normal when the required EGR cooling performance is low in the light load region of the engine. The vehicle EGR cooling system described in 1.

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