Method and apparatus for warming up the internal combustion engine of a hybrid vehicle

Abstract

To warm-up a vicinity of an air-intake port of an internal combustion engine before starting the engine while effectively utilizing waste heat from an inverter 21, a motor generator 22 for running or the like.SOLUTION: A cooling device of a series hybrid vehicle comprises: a first cooling water circuit 1 for mainly cooling a water jacket 11 of an internal combustion engine; a second cooling water circuit 2 that cools an inverter 21, a motor generator 22 for running or the like; and a refrigeration cycle 3 constituting a vehicle interior air-conditioner. The refrigeration cycle 3, through which first cooling water circuit 1 is thermally connected to the second cooling water circuit 2, absorbs heat of cooling water in the second cooling water circuit 2, as vaporization heat in a chiller 37, and heats cooling water in the first cooling water circuit 1 as condensation heat in a capacitor 36 for warming-up an engine, where the heated cooling water is circulated in the air-intake port water jacket 16.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a warm-up promotion technology before starting an internal combustion engine that drives a motor generator for power generation in, for example, a series hybrid vehicle.

Background Art

[0002] When a so-called port injection type internal combustion engine is started in a cold state, fuel injected from a fuel injection valve toward an intake port adheres as a liquid film to the low-temperature intake port wall surface and flows into the combustion chamber through the intake valve as it is, resulting in an increase in unburned HC and CO. And during such starting, since the temperature of the catalyst provided in the exhaust system is low, sufficient exhaust purification performance by the catalyst cannot be obtained.

[0003] Patent Document 1 discloses a technology for warming up an engine by heating engine cooling water using a refrigeration cycle in a vehicle cabin air conditioner in a hybrid vehicle. Specifically, a warm-up cooling water circuit is formed in parallel with a heater core that forms part of an engine cooling water circuit, and a condenser of the refrigeration cycle is configured to exchange heat between the cooling water in the warm-up cooling water circuit and the refrigerant in the refrigeration cycle. In other words, the condenser is cooled by engine cooling water instead of outside air. As a result, the engine cooling water is warmed by the heat released from the condenser during operation of the refrigeration cycle.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] However, in the conventional configuration described above, the evaporator housed within the so-called air conditioning unit of the passenger compartment merely transfers heat obtained from the outside air to the engine coolant. This makes it difficult to efficiently promote engine warm-up, especially under conditions of low outside temperatures. Furthermore, it is not possible to effectively utilize the waste heat from drive mechanisms such as the inverter and motor generator in hybrid vehicles. [Means for solving the problem]

[0006] The warm-up method of this invention relates to a hybrid vehicle comprising: a first coolant circuit through which coolant flows around at least the intake port of an internal combustion engine; and a second coolant circuit through which another coolant circulates to cool a motor generator and inverter for vehicle operation. The first cooling water circuit and the second cooling water circuit are thermally connected via a refrigeration cycle using an electric compressor that constitutes the vehicle's air conditioning system. When warming up is required before starting the internal combustion engine, the refrigeration cycle is operated such that the refrigerant in the refrigeration cycle receives heat from the coolant in the second coolant circuit and dissipates heat to the coolant in the first coolant circuit. How to warm up the internal combustion engine of a hybrid vehicle And, In the first cooling water circuit described above, a branch passage is provided downstream of the electric water pump, allowing the water to flow around the intake port. During warm-up, the cooling water flows through this branch passage in parallel with the water jacket of the internal combustion engine around the intake port. The flow of cooling water in the water jacket and the branch passage is controlled by a control valve located on the outlet side of the water jacket and upstream of the point where it merges with the branch passage.

[0007] In this configuration, at least a portion of the waste heat generated from the motor generator and inverter used for vehicle propulsion is supplied to the cooling water in the first cooling water circuit via the refrigeration cycle. This warms the area around the intake port. [Effects of the Invention]

[0008] According to this invention, the waste heat from the motor generator and inverter used for vehicle operation can be effectively utilized to warm the area around the intake port of the internal combustion engine. Furthermore, since the temperature of the coolant in the second coolant circuit is generally higher than the ambient temperature, the engine can be warmed up efficiently. [Brief explanation of the drawing]

[0009] [Figure 1] A cooling circuit diagram of one embodiment of this invention. [Modes for carrying out the invention]

[0010] Hereinafter, an embodiment of this invention will be described in detail with reference to the drawings.

[0011] Figure 1 is a circuit diagram showing the overall configuration of a vehicle cooling system in one embodiment. The vehicle in this embodiment is a series hybrid vehicle in which an internal combustion engine drives a motor generator for power generation, and the generated electricity drives a motor generator for driving. The internal combustion engine is, for example, a four-stroke cycle spark-ignition internal combustion engine (a so-called gasoline engine), and has a port injection configuration in which fuel is injected from a fuel injector provided in the intake port of each cylinder toward the intake port.

[0012] One embodiment of the cooling system is broadly composed of three components: a first cooling water circuit 1 that cools the internal combustion engine by circulating cooling water, a second cooling water circuit 2 that cools the drive mechanism by circulating cooling water, and a refrigeration cycle 3 that constitutes the vehicle cabin air conditioning system. In this invention, "cooling water" broadly refers to a liquid-phase refrigerant.

[0013] The first cooling water circuit 1 is basically configured similarly to a typical water-cooled cooling system for an internal combustion engine, and has the water jacket 11 of the internal combustion engine (including the water jacket 11a on the cylinder block side and the water jacket 11b on the cylinder head side) as its main target for cooling. It is configured as a closed circuit that includes a radiator 12 that cools the cooling water, which has become hot after passing through the water jacket 11, by heat exchange with the outside air, and an electric water pump 13 that sends the cooling water that has been heated by the radiator 12 back to the water jacket 11. The radiator 12 is positioned in a location that can receive the airflow while the vehicle is running, such as at the front of the vehicle. Similar to a typical water-cooled cooling system for an internal combustion engine, it is equipped with a bypass passage 14 and a thermostat valve 15 for the cooling water to bypass the radiator 12 when the water temperature is low. The thermostat valve 15 may be of a type that responds mechanically to the cooling water temperature, or it may be of a type whose opening degree can be controlled electrically.

[0014] Furthermore, in this embodiment, the water jacket around the intake port is independent as the intake port water jacket 16, and the circuit is configured so that coolant flows in parallel with the water jacket 11 between the electric water pump 13 and the radiator 12. In other words, it has a branching passage that passes through the intake port water jacket 16. A control valve 17 is provided on the outlet side of the water jacket 11 so that the coolant circulates mainly through the intake port water jacket 16 when the intake port is warmed up. When the control valve 17 is fully closed, the entire amount of coolant discharged by the electric water pump 13 flows through the intake port water jacket 16.

[0015] The second cooling water circuit 2 cools several elements in the hybrid vehicle's drive mechanism that require cooling, such as the inverter 21, the traction motor generator 22, and the power generation motor generator 23, by circulating cooling water. It includes a second radiator 24 that exchanges heat between the cooling water circulating in the circuit and the outside air, and a second electric water pump 25 that circulates the cooling water. It is desirable to position the second radiator 24 in a location that can receive the airflow from the vehicle, such as the front of the vehicle. The cooling water flowing through the second cooling water circuit 2 is different from the cooling water flowing through the first cooling water circuit 1, that is, it is independent of the cooling water flowing through the first cooling water circuit 1. Note that the cooling water flowing through the first cooling water circuit 1 and the cooling water flowing through the second cooling water circuit 2 may be different types of cooling water, i.e., have different compositions, or they may each be coolants with the same composition.

[0016] Furthermore, the temperature of the coolant circulating in the second coolant circuit 2 is relatively lower than the temperature of the coolant circulating in the first coolant circuit 1. For example, while the internal combustion engine is running, the temperature of the coolant in the first coolant circuit 1 is maintained at around 70-90°C, while the temperature of the coolant in the second coolant circuit 2 is maintained at around 40-60°C. However, this relationship between the coolant temperatures of the two coolant circuits 1 and 2 is not essential to the present invention.

[0017] In the diagram, cooling water flows in series between the inverter 21, the drive motor generator 22, and the power generation motor generator 23, but it may also be configured so that the cooling water flows in parallel with each other. Furthermore, similar to the first cooling water circuit 1, a bypass passage and thermostat valve (not shown) may be provided to allow cooling water to flow by bypassing the second radiator 24 when the water temperature is low.

[0018] The refrigeration cycle 3 is configured as a closed circuit including: an electric compressor 31 that compresses a refrigerant into a high-temperature and high-pressure gaseous refrigerant; a condenser 32 located downstream of the electric compressor 31 that cools the high-temperature and high-pressure gaseous refrigerant through heat exchange with outside air to convert it into a liquid phase; an expansion valve 33 that depressurizes the refrigerant liquefied by the condenser 32; and an evaporator 34 located downstream of the expansion valve 33 that vaporizes the liquid-phase refrigerant through heat exchange with outside air. The condenser 32 is arranged, for example, side by side with the radiator 12 at the front portion of the vehicle body. The evaporator 34 is housed in an air conditioning unit for generating conditioned air for a vehicle cabin air conditioner. Outside air taken in by a blower (not shown) is cooled by passing through the evaporator 34.

[0019] Further, between the discharge side of the electric compressor 31 and the condenser 32, a cabin heating condenser 35 and an engine warming-up condenser 36 are further arranged in series. As an alternative to a general hot water type heater core for cabin heating, the cabin heating condenser 35 is housed in the air conditioning unit together with the evaporator 34, and heats the conditioned air by performing heat exchange with the high-temperature and high-pressure gaseous refrigerant discharged from the electric compressor 31. The proportion of conditioned air that passes through the cabin heating condenser 35 is controlled by the opening degree of an air mix door (not shown). In one embodiment, conditioned air always passes through the evaporator 34 to perform cooling and dehumidification.

[0020] The engine warming-up condenser 36 performs heat exchange between the high-temperature and high-pressure gaseous refrigerant discharged from the electric compressor 31 and the cooling water of the first cooling water circuit 1. That is, the cooling water in the first cooling water circuit 1 is heated by the condensation heat generated when the gaseous refrigerant is liquefied. In one embodiment, in the first cooling water circuit 1, a cooling water passage is connected to the engine warming-up condenser 36 at a position on the suction side of the electric water pump 13 and downstream of the thermostat valve 15.

[0021] In the illustrated example, in the refrigeration cycle 3, the condenser 36 for engine warm-up is located downstream of the condenser 35 for vehicle compartment heating. However, the condenser 36 for engine warm-up may alternatively be located upstream of the condenser 35 for vehicle compartment heating, or the condenser 35 for vehicle compartment heating and the condenser 36 for engine warm-up may be arranged in parallel.

[0022] The refrigeration cycle 3 further comprises a heat exchanger arranged in parallel with the evaporator 34, that is, a chiller 37. An expansion valve 38 for the chiller is provided at an inlet of the chiller 37. Refrigerant decompressed by the expansion valve 38 for the chiller passes through the chiller 37, and heat exchange is performed between the refrigerant and cooling water of the second cooling water circuit 2. That is, in the chiller 37, the refrigerant vaporizes similarly to in the evaporator 34, and the cooling water of the second cooling water circuit 2 is cooled by the heat of vaporization. In one embodiment, in the second cooling water circuit 2, a cooling water passage is connected to the chiller 37 at a position upstream of the second radiator 24 through which high-temperature cooling water flows after cooling an object to be cooled such as an inverter 21. It is preferable that the configuration is such that heat exchange in the chiller 37 can be stopped by, for example, controlling the expansion valve 38 for the chiller to be fully opened or fully closed.

[0023] As described above, the first cooling water circuit 1 and the second cooling water circuit 2 are each independently configured such that cooling water circulates therein separately, while being thermally connected via the refrigeration cycle 3 of the vehicle compartment air conditioner. Through operation of the refrigeration cycle 3, heat of the cooling water in the second cooling water circuit 2 can be transferred to the cooling water in the first cooling water circuit 1.

[0024] The operations of the aforementioned first cooling water circuit 1, second cooling water circuit 2 and refrigeration cycle 3 are controlled by a controller 41. In practice, the controller 41 is configured to include a plurality of controllers such as an engine controller and an air conditioner controller.

[0025] In series hybrid vehicles, the internal combustion engine is basically started when the battery's State of Charge (SOC) drops to a predetermined lower limit and stopped when the SOC recovers to a predetermined level. In other words, the internal combustion engine drives the power generation motor generator in response to power generation demands and generates electricity.

[0026] If the internal combustion engine is in a cold state and not in a warm-up restart state, warm-up control is performed before starting (before combustion operation begins) by transferring heat via the refrigeration cycle 3 described above in order to warm the area around the intake port. Specifically, the refrigeration cycle 3 is operated by the drive of the electric compressor 31, and the refrigerant absorbs the heat from the coolant in the second coolant circuit 2 through the action of the chiller expansion valve 38 and chiller 37. Then, heat is transferred from the refrigerant in the refrigerant cycle 3 to the coolant in the first coolant circuit 1 via the engine warm-up condenser 36. At this time, the control valve 17 of the first coolant circuit 1 is closed as appropriate, and the coolant, which has become hot due to the heat from the refrigeration cycle 3, is sent to the intake port water jacket 16 by the action of the electric water pump 13, warming the area around the intake port. Then, after passing through the intake port water jacket 16, the coolant circulates through the bypass passage 14 and passes through the engine warm-up condenser 36 again.

[0027] By warming the area around the intake port in this way before starting, the fuel properties are improved from the initial stages of starting, which can suppress transient increases in unburned HC and CO, for example.

[0028] In the above embodiment, the waste heat from the inverter 21 and other components in the second cooling water circuit 2 is effectively utilized to promote warming up around the intake port, thus eliminating the need for other heat sources. Furthermore, compared to conventional techniques that use outside air as a heat source to raise the cooling water temperature through a refrigeration cycle, a relatively higher temperature can be obtained from the heat source, allowing for efficient heating of the cooling water.

[0029] Incidentally, when warming up the intake port area using the refrigeration cycle 3, it is preferable to minimize the energy consumption (e.g., power consumption) associated with this. Therefore, in a preferred embodiment, it is desirable to detect the ambient temperature and reduce the power of the electric compressor 31 of the refrigeration cycle 3 as the ambient temperature increases. In other words, warming up is performed taking the ambient temperature into consideration, resulting in reduced energy consumption.

[0030] Alternatively, the cooling water temperature of the first cooling water circuit 1 or the temperature around the intake port is detected, and the higher this temperature, the lower the power of the electric compressor 31 of the refrigeration cycle 3 is reduced.

[0031] In other embodiments, the ambient temperature is detected, and the higher the ambient temperature, the lower the power of the electric water pump 13 in the first cooling water circuit 1. In other words, the amount of cooling water circulated is adjusted to take the ambient temperature into account.

[0032] Alternatively, the cooling water temperature of the first cooling water circuit 1 or the temperature around the intake port may be detected, and the higher this temperature, the lower the power of the electric water pump 13 in the first cooling water circuit 1 may be.

[0033] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the specific configurations of the first cooling water circuit 1, the second cooling water circuit 2, and the refrigeration cycle 3 can be changed as appropriate. For example, the intake port water jacket 16 may be configured to warm the area around the intake port as part of the water jacket 11b on the cylinder head side, rather than being a separate circuit. Furthermore, the present invention is not limited to the cooling system of the series hybrid vehicle described above, but can be broadly applied to any vehicle that has a second cooling water circuit for cooling an inverter or the like, including vehicles in which an internal combustion engine is the driving source. [Explanation of symbols]

[0034] 1…First cooling water circuit 2…Second cooling water circuit 3…Refrigeration cycle 11…Water Jacket 12…Radiator 13…Electric water pump 16…Intake port water jacket 21…Inverter 22… Motor generator for driving 23... Motor generator for power generation 24…2nd radiator 25…Second electric water pump 31… Electric compressor 32…Capacitor 33...Expansion valve 34... Evaporator 35...Condenser for vehicle interior heating 36… Engine warm-up condenser 37... Chiller 38... Expansion valve for chiller 41…Controller

Claims

1. In a hybrid vehicle comprising a first cooling water circuit through which cooling water circulates to at least the area around the intake port of an internal combustion engine, and a second cooling water circuit through which other cooling water circulates to cool the motor generator and inverter for vehicle operation, The first cooling water circuit and the second cooling water circuit are thermally connected via a refrigeration cycle using an electric compressor that constitutes the vehicle's air conditioning system. When warming up is required before starting the internal combustion engine, the refrigeration cycle is operated such that the refrigerant in the refrigeration cycle receives heat from the coolant in the second coolant circuit and dissipates heat to the coolant in the first coolant circuit. A method for warming up the internal combustion engine of a hybrid vehicle, In the first cooling water circuit described above, a branch passage is provided downstream of the electric water pump, allowing the water to flow around the intake port. During warm-up, the cooling water flows through this branch passage in parallel with the water jacket of the internal combustion engine around the intake port. The flow of cooling water in the water jacket and the branch passage is controlled by a control valve located on the outlet side of the water jacket and upstream of the point where it merges with the branch passage. A method for warming up the internal combustion engine of a hybrid vehicle.

2. In the above refrigeration cycle, heat exchange is performed between the refrigerant compressed by the electric compressor and the cooling water of the first cooling water circuit. Heat exchange is performed between the refrigerant, which has been depressurized through the expansion valve, and the cooling water of the second cooling water circuit. A method for warming up an internal combustion engine of a hybrid vehicle according to claim 1.

3. The system detects the outside temperature and reduces the power of the electric compressor as the outside temperature increases. A method for warming up an internal combustion engine of a hybrid vehicle according to claim 1.

4. The system detects the cooling water temperature in the first cooling water circuit or the temperature around the intake port, and reduces the power of the electric compressor as the temperature increases. A method for warming up an internal combustion engine of a hybrid vehicle according to claim 1.

5. The system detects the ambient temperature and reduces the power of the electric water pump in the first cooling water circuit as the ambient temperature increases. A method for warming up an internal combustion engine of a hybrid vehicle according to claim 1.

6. The system detects the coolant temperature in the first coolant circuit or the temperature around the intake port, and reduces the power of the electric water pump in the first coolant circuit as the temperature increases. A method for warming up an internal combustion engine of a hybrid vehicle according to claim 1.

7. A first coolant circuit through which coolant flows at least around the intake port of an internal combustion engine, A second cooling water circuit through which separate cooling water circulates to cool the motor generator and inverter for vehicle operation, A refrigeration cycle using an electric compressor that constitutes the vehicle's air conditioning system, In the above refrigeration cycle, a first heat exchanger performs heat exchange between the refrigerant compressed by the above electric compressor and the cooling water of the first cooling water circuit, A second heat exchanger performs heat exchange between the refrigerant, which has been depressurized through an expansion valve in the above refrigeration cycle, and the cooling water of the second cooling water circuit. A controller operates the refrigeration cycle such that, when warming up is required before starting the internal combustion engine, the refrigerant in the refrigeration cycle receives heat from the coolant in the second coolant circuit and dissipates heat to the coolant in the first coolant circuit. Equipped with, The first cooling water circuit described above has a branching passage that branches downstream of the electric water pump and flows around the intake port, and is configured so that the cooling water flows in parallel with the water jacket of the internal combustion engine through this branching passage. A control valve is provided at the outlet side of the water jacket and upstream of the confluence point with the branch passage, and the flow of cooling water in the water jacket and the branch passage is controlled by the opening of this control valve. A warm-up system for the internal combustion engine of a hybrid vehicle.

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