RELATED APPLICATIONS

The present application claims priority to Japanese Patent Application No. 2018-083656 filed Apr. 25, 2018, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

Field

The invention relates to a cooling apparatus of a vehicle driving system.

Description of the related art

There is known a hybrid vehicle driven by a vehicle driving system including an internal combustion engine and a motor. The vehicle driving system of the hybrid vehicle comprises a battery for storing electric power to be supplied to the motor. The hybrid vehicle comprises a cooling apparatus including water circulation passages, through which cooling water flows for cooling the internal combustion engine, the motor, and the battery, thereby preventing temperatures of the internal combustion engine, the motor, and the battery from increasing excessively.

In general, a temperature of a hybrid system including the motor and the battery should be maintained at a temperature lower than the temperature of the internal combustion engine. Accordingly, the cooling apparatus of the hybrid vehicle comprises a water circulation passage, through which the cooling water flows for cooling the hybrid system in addition to a water circulation passage, through which the cooling water flows for cooling the internal combustion engine.

Hereinafter, the temperature of the hybrid system will be referred to as “the hybrid system temperature”, the temperature of the internal combustion engine will be referred to as “the engine temperature”, the water circulation passage, in which the cooling water flows for cooling the hybrid system will be referred to as “the hybrid system water circulation passage”, and the water circulation passage, in which the cooling water flows for cooling the internal combustion engine will be referred to as “the engine water circulation passage”.

There is also known a cooling apparatus including a heat pump as means for cooling the cooling water flowing through the hybrid system water circulation system (for example, see JP 2014-234094 A as to the heat pump for cooling the cooling water).

A radiator for cooling the cooling water is provided in the engine water circulation passage, and a radiator for cooling the cooling water is provided in the hybrid system water circulation passage. These radiators are generally provided at a front area of an engine compartment provided at a front portion of the vehicle. Hereinafter, the radiator provided in the engine water circulation passage will be referred to as “the engine radiator”, and the radiator provided in the hybrid system water circulation passage will be referred to as “the hybrid system radiator”.

The heat pump includes an outside air heat exchanger for discharging heat of cooling medium to the outside air. Similar to the engine radiator and the hybrid system radiator, the outside air heat exchanger is provided at the front area of the engine compartment.

The engine compartment is spatially limited. When the engine radiator, the hybrid system radiator, and the outside air heat exchanger are provided at the front are of the engine compartment, sizes of the engine radiator, the hybrid system radiator, and the outside air heat exchanger should be small.

When the sizes of the engine radiator, the hybrid radiator, and the outside air heat exchanger are small, abilities of the engine radiator and the hybrid system radiator for cooling the cooling water and an ability of the outside air heat exchanger for cooling the cooling medium are low.

Accordingly, even when the heat pump is employed as the means for cooling the cooling water flowing through the hybrid system water circulation passage for increasing an ability of the cooling apparatus to cool the cooling water, a degree of increasing of the ability of the cooling apparatus to cool the cooling water, may be relatively small.

SUMMARY

The invention has been made for solving above-mentioned problems. An object of the invention is to provide a cooling apparatus of the vehicle driving system configured to cool the cooling water for cooling the hybrid system and having an increased ability to cool the cooling water.

A cooling apparatus of a vehicle driving system (200) for driving a vehicle (100) according to the invention comprises an engine water circulation passage (20), an engine radiator (13), a hybrid system water circulation passage (50), a hybrid system radiator, and a heat pump (70).

Cooling water flows in the engine water circulation passage (20) as engine cooling water for cooling an internal combustion engine (110) of the vehicle driving system (200). The engine radiator (13) is configured to cool the engine cooling water by outside air. The cooling water flows in the hybrid system water circulation passage (50) as hybrid system cooling water for cooling a hybrid system including at least one of a battery (120) and a motor (111,112) of the vehicle driving system (200). The hybrid system radiator (43) is configured to cool the hybrid system cooling water by the outside air. The heat pump (70) is configured to cool the hybrid system by cooling medium, the heat pump (70) including a condenser (73) for exchanging heat between the cooling medium and the engine cooling water.

The cooling apparatus according to the invention further comprises an electronic control unit (90). The electronic control unit (90) is configured to flow the engine cooling water in the engine water circulation passage (20) through the engine radiator (13) to cool the internal combustion engine (110) by the engine cooling water (see processes of steps1140and1150inFIG. 11) when an engine cooling condition is satisfied, the engine cooling condition being a condition that a process of cooling the internal combustion engine (110) by the engine cooling water is requested (see a determination “Yes” at a step1110inFIG. 11).

The electronic control unit (90) is further configured to activate the heat pump (70) to cool the hybrid system by the cooling medium (see a process of a step1340inFIG. 13) when a heat pump activation condition is satisfied, the heat pump activation condition being a condition that a process of cooling the hybrid system by the cooling medium of the heat pump (70) is requested (see a determination “Yes” at a step1330inFIG. 13).

The electronic control unit (90) is further configured to activate the heat pump (70) to cool the hybrid system by the cooling medium and flow the engine cooling water in the engine water circulation passage through the condenser (73) to cool the cooling medium by the engine cooling water at the condenser (73) (see processes of steps1240,1250,1270, and1280inFIG. 12and the process of the step1340inFIG. 13) when an engine water circulation condition is satisfied, the engine water circulation condition being a condition that the heat pump activation condition is satisfied, and the engine cooling condition is not satisfied (see the determination “Yes” at the step1110inFIG. 11, a determination “Yes” at a step1170inFIG. 11, a determination “Yes” at a step1210inFIG. 12, and the determination “Yes” at the step1340inFIG. 13).

According to the invention, when the engine water circulation condition is satisfied, the heat of the cooling medium absorbing from the hybrid system, is discharged to the engine cooling water at the condenser. Therefore, the cooling medium is cooled by the engine cooling water at the condenser. When the engine water circulation condition is satisfied, the process of cooling the internal combustion engine is not requested. Thus, a temperature of the internal combustion engine is relatively low. Therefore, the heat of the engine cooling water discharged from the cooling medium, is discharged to the internal combustion engine while the engine cooling water flows through the engine water circulation passage. When the heat of the engine cooling water is discharged to the internal combustion engine, a temperature of the engine cooling water decreases. The engine cooling water having a decreased temperature flows through the condenser and thus, the cooling medium is cooled by the engine cooling water at the condenser continuously.

When the heat of the cooling medium is discharged to the internal combustion engine via the engine cooling water, the cooling medium can be cooled if the heat pump has no outside air heat exchanger. In addition, when the heat pump has no outside air heat exchanger, the larger engine radiator and the larger hybrid system radiator can be provided in the engine compartment and thus, the higher abilities of the engine radiator and the hybrid radiator to cool the cooling water, can be accomplished. According to the invention, the cooling ability of the cooling apparatus may be increased.

On the other hand, when the heat pump is provided with an outside air heat exchanger, the cooling medium is cooled by the outside air heat exchanger and the internal combustion engine. Thus, the ability of the heat pump to cool the cooling medium is increased. According to the invention, the cooling ability of the cooling apparatus may be increased further.

According to an aspect of the invention, the engine water circulation condition may include a condition relating to a temperature of the cooling medium flowing into the condenser (73).

According to another aspect of the invention, the electronic control unit (90) may be further configured to stop flowing the engine cooling water in the engine water circulation passage (20) (see a process of a step1290inFIG. 12) when a temperature of the engine cooling water flowing into the condenser (73) is equal to or higher than the temperature of the cooling medium flowing into the condenser (73) even while the engine water circulation condition is satisfied (see a determination “No” at a step1210inFIG. 12).

When the temperature of the engine cooling water flowing into the condenser is higher than or equal to a temperature of the cooling medium flowing into the condenser while the engine water circulation condition is satisfied, the heat of the cooling medium may not be discharged to the engine cooling water even by flowing the engine cooling water in the engine water circulation passage through the condenser. If the heat of the cooling medium is not discharged to the engine cooling water, the cooling medium is not cooled. When the cooling medium is not cooled by the engine cooling water at the condenser, a flow of the engine cooling water in the engine water circulation passage is needless. Therefore, the needless flow of the engine cooling water may be prevented by stopping flowing the engine cooling water in the engine water circulation passage when the temperature of the engine cooling water flowing into the condenser is equal to or higher than the temperature of the cooling medium flowing into the condenser.

According to further another aspect of the invention, the engine water circulation condition may include a condition that the temperature of the cooling medium flowing into the condenser (73) is higher than a predetermined cooling medium temperature.

When the temperature of the cooling medium flowing into the condenser is high, the cooling medium is desirably cooled by the engine cooling water at the condenser to improve the ability of the heat pump to cool the hybrid system. According to this aspect, the engine water circulation condition includes the condition that the temperature of the cooling medium flowing into the condenser is higher than the predetermined cooling medium temperature. Therefore, when the temperature of the cooling medium flowing into the condenser is higher than the predetermined cooling medium temperature, the engine cooling water is forced to flow in the engine water circulation passage through the condenser. Thereby, the cooling medium is cooled by the engine cooling water at the condenser.

According to further another aspect of the invention, the engine water circulation condition may include a condition that a temperature of the internal combustion engine (110) is lower than an engine warmed temperature.

When the temperature of the internal combustion engine is higher than or equal to the engine warmed temperature, the internal combustion engine operates under a desired state, for example, that an amount of emission included in an exhaust gas discharged from the internal combustion engine is small. According to this aspect of the invention, the engine water circulation condition includes the condition that the temperature of the internal combustion engine is lower than the engine warmed temperature. Therefore, when the temperature of the internal combustion engine is lower than the engine warmed temperature while the engine water circulation condition is satisfied, the engine cooling water is forced to flow in the engine water circulation passage. Thereby, the heat of the engine cooling water absorbing from the cooling medium of the heat pump is likely to transfer to the internal combustion engine. Thus, the temperature of the internal combustion engine increases. Therefore, the temperature of the internal combustion engine is relatively high when the internal combustion engine starts operating later. Thus, the internal combustion engine can operate under the desired state when the internal combustion engine starts operating later.

According to further another aspect of the invention, the heat pump activation condition may include a condition that a temperature of the hybrid system cooling water, which is cooled by the hybrid system radiator (43) without the heat pump (70), is equal to or higher than a predetermined water temperature.

When the temperature of the hybrid system cooling water is high, the hybrid system cooling water may be insufficiently cooled only by the hybrid system radiator and as a result, the hybrid system may be insufficiently cooled. According to this aspect of the invention, the heat pump activation condition includes the condition that the temperature of the hybrid system cooling water, which is cooled by the hybrid system radiator without the heat pump, is equal to or higher than the predetermined water temperature. Therefore, when the temperature of the hybrid system cooling water, which is cooled by the hybrid system radiator without the heat pump, is equal to or higher than the predetermined water temperature, the hybrid system is cooled by the heat pump. In general, the ability of the heat pump to cool the hybrid system is larger than the ability of the hybrid system radiator to cool the hybrid system. Thus, according to this aspect of the invention, the hybrid system may be sufficiently cooled even when the hybrid system cooling water may be insufficiently cooled by the hybrid system radiator.

According to further another aspect of the invention, the heat pump (70) may include an evaporator (71a) for exchanging heat between the cooling medium and the hybrid system cooling water (seeFIG. 2). In this case, the electronic control unit (90) may be further configured to activate the heat pump (70) to cool the hybrid system cooling water by the cooling medium at the evaporator (71a) and flow the hybrid system cooling water in the hybrid water circulation passage (50) to cool the hybrid system by the hybrid system cooling water when the engine water circulation condition is satisfied.

The hybrid system cooling water flows in the hybrid system water circulation passage for cooling the hybrid system. According to this aspect of the invention, the heat pump cools the hybrid system cooling water at the evaporator. Thus, the conventional hybrid system water circulation passage can be used.

According to further another aspect of the invention, the heat pump (70) may be configured to cool the hybrid system directly by the cooling medium (seeFIG. 23). When the heat pump is configured to cool the hybrid system cooling water by the cooling medium, the evaporator needs to be provided in the heat pump. According to this aspect of the invention, the heat pump is configured to cool the hybrid system by the cooling medium directly. Thus, a design of the heat pump can be simplified.

According to further another aspect of the invention, the heat pump (70) may include an outside air heat exchanger (72) for exchanging the heat between the cooling medium and the outside air (seeFIG. 2).

In this case, the cooling medium may be cooled by the engine cooling water and the outside air at the condenser and the outside air heat exchanger, respectively when the engine circulation water condition is satisfied. Thus, the ability of cooling the cooling medium is increased, compared to when the cooling medium is cooled only by the outside air heat exchanger.

In the above description, for facilitating understanding of the present invention, elements of the present invention corresponding to elements of an embodiment described later are denoted by reference symbols used in the description of the embodiment accompanied with parentheses. However, the elements of the present invention are not limited to the elements of the embodiment defined by the reference symbols. The other objects, features and accompanied advantages of the present invention can be easily understood from the description of the embodiment of the present invention along with the drawings.

