Cooling system for hybrid vehicles

Abstract

To improve the cooling of hybrid vehicles equipped with an intercooler. [Solution] The hybrid vehicle 1 has a first cooling system 15 capable of cooling the electric powertrain 3, a second cooling system 16 that cools the internal combustion engine 2 independently of the first cooling system 15, and a cooling circuit 17 connected to the first cooling system 15. The cooling circuit 17 consists of an intercooler 4 and a first water jacket 7 connected in series. The hybrid vehicle 1 cools the cylinder head of the internal combustion engine 2 with the cooling water of the first cooling system 15, which is at a lower temperature than the cooling water of the second cooling system 16.

Description

Technical Field

[0001] The present invention relates to a cooling device for a hybrid vehicle. Background Art

[0002] For example, Patent Document 1 discloses a hybrid vehicle including an internal combustion engine for power generation that performs port injection, and a driving force generation unit that generates driving force transmitted to driving wheels, wherein a cylinder head of the internal combustion engine is warmed by circulating warm water warmed by the driving force generation unit or warm water warmed using a heater before the internal combustion engine is started.

[0003] Here, when the temperature of cooling water for cooling an intercooler is low, there is a risk that the temperature of intake air becomes excessively low when passing through the intercooler, resulting in generation of condensed water. In particular, when part of exhaust gas is recirculated into intake air, condensed water is more likely to be generated, so there is a risk that the possibility of unstable combustion in the internal combustion engine due to the generation of condensed water increases. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2023-115415 Summary of the Invention Problem to be Solved by the Invention

[0005] However, the hybrid vehicle of Patent Document 1 is not provided with a supercharger that pressurizes intake air of the internal combustion engine, and does not have an intercooler that cools intake air. That is, Patent Document 1 does not consider cooling of a hybrid vehicle having an intercooler.

[0006] Therefore, there is still room for further improvement regarding cooling of a hybrid vehicle having an intercooler. Means for Solving the Problem

[0007] The cooling system for a hybrid vehicle of the present invention comprises an internal combustion engine having a first water jacket for cooling the intake port of the cylinder head and a second water jacket independent of the first water jacket for cooling the portion of the cylinder head other than the intake port; an electric powertrain for converting electrical energy into mechanical energy; a supercharger for supercharging the internal combustion engine; an intercooler for cooling the intake air of the internal combustion engine, including EGR gas; a first cooling system for cooling the electric powertrain; a second cooling system for cooling the internal combustion engine independently of the first cooling system; and a cooling circuit connected to the first cooling system, which connects the first water jacket and the intercooler, wherein the cooling circuit is configured such that the intercooler and the first water jacket are adjacent to each other. [Effects of the Invention]

[0008] In the hybrid vehicle cooling system of the present invention, after the internal combustion engine has warmed up, the intake air passing through the intake port is cooled by the coolant of the first cooling system, thereby suppressing the temperature of the air-fuel mixture in the cylinder and suppressing knocking of the internal combustion engine. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram illustrating the general outline of the cooling system for a hybrid vehicle in a first embodiment to which the present invention is applied. [Figure 2] A schematic diagram illustrating the general outline of the cooling system for a hybrid vehicle in a second embodiment to which the present invention is applied. [Figure 3] A schematic diagram illustrating the general outline of the cooling system for a hybrid vehicle in a third embodiment to which the present invention is applied. [Modes for carrying out the invention]

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 is a schematic diagram illustrating the cooling system of a hybrid vehicle 1 in a first embodiment to which the present invention is applied.

[0011] In the first embodiment, the hybrid vehicle 1 is equipped with an internal combustion engine 2 for power generation, and the drive wheels (not shown) are driven by an electric motor 3a of an electric powertrain 3. In other words, the hybrid vehicle 1 is a series hybrid vehicle in which the internal combustion engine 2 is connected to a power-generating electric motor (power-generating motor generator) not shown, and all of the power from the internal combustion engine 2 is used for power generation.

[0012] The hybrid vehicle 1 includes an internal combustion engine 2, an electric powertrain 3, a water-cooled intercooler 4, a supercharger (not shown), and an EGR passage (not shown).

[0013] The internal combustion engine 2 is, for example, a spark-ignition in-line multi-cylinder internal combustion engine. The internal combustion engine 2 has a first water jacket 7 that cools the intake port (not shown) of the cylinder head (not shown), and a second water jacket 8 that cools at least the portion of the cylinder head other than the intake port, independently of the first water jacket 7. The second water jacket 8 may also include a portion that cools the intake port of the cylinder head.

[0014] The electric powertrain 3 is a drive system electrical component that converts electrical energy into mechanical energy, and includes an electric motor 3a as a traction motor that drives the drive wheels of the hybrid vehicle 1, and an inverter 3b that controls the power supplied to the electric motor 3a.

[0015] The intercooler 4 is a heat exchanger that cools the intake air of the internal combustion engine 2, which contains supercharged EGR gas. The intercooler 4 is located downstream of the connection point between the EGR passage and the intake passage (not shown) in the direction of intake air flow. The supercharger is located upstream of the intercooler 4 in the direction of intake air flow, and also downstream of the connection point between the EGR passage and the intake passage. The EGR passage recirculates a portion of the exhaust gas as EGR gas into the intake passage of the internal combustion engine 2. An EGR cooler 11 is positioned in the EGR passage to cool the EGR gas. The intercooler 4 is mounted in the hybrid vehicle 1 so as to be adjacent to the internal combustion engine 2.

[0016] The hybrid vehicle 1 includes a first cooling system 15 capable of cooling the electric powertrain 3, a second cooling system 16 that cools the internal combustion engine 2 independently of the first cooling system 15, and a cooling circuit 17 connected to the first cooling system 15.

[0017] The first cooling system 15 has a first radiator 21 and an electric first water pump 22, and cools the electric powertrain 3 by circulating relatively low-temperature coolant in the direction of arrow A in Figure 1. The operation of the first water pump 22 is controlled by a control unit 45, which will be described later. In the first cooling system 15, the flow rate of coolant flowing through the first radiator 21 is controlled by a first thermostat 23 that operates according to the temperature of the coolant, and the flow rate of coolant flowing through the electric powertrain 3 is controlled by a flow control valve 24.

[0018] The first thermostat 23 and the flow restriction valve 24 correspond to a flow restriction mechanism, and by closing each valve, the inflow of coolant to the first radiator 21 and the electric powertrain 3 is blocked, making it possible to circulate the coolant to the first water jacket 7 and the intercooler 4.

[0019] The flow control valve 24 is located upstream of the electric powertrain 3 in the direction of the flow of the cooling water in the first cooling system 15.

[0020] In the first cooling system 15, a water temperature sensor 25 detects the temperature (TWLT) of cooling water on the suction side of the first water pump 22. That is, the water temperature sensor 25 detects the water temperature (TWLT) of cooling water on the downstream side of the electric powertrain 3 and the cooling circuit 17. In other words, the water temperature sensor 25 detects the water temperature (TWLT) of cooling water at a predetermined preset position in the first cooling system 15.

[0021] The second cooling system 16 includes a second radiator 31 and a second water pump 32, circulates cooling water at a relatively high temperature in the direction of arrow B in FIG. 1 to cool the internal combustion engine 2 and the EGR cooler 11, and supplies cooling water to a heater core 33. The second water pump 32 is driven electrically or by the internal combustion engine 2; in the case of electric driving, the operation thereof is controlled by a control unit 45 described later. In the second cooling system 16, the flow rate of cooling water flowing through the second radiator 31 is controlled by a second thermostat 34 that operates in accordance with the temperature of the cooling water. Further, in the second cooling system 16, the flow rate of cooling water flowing through the heater core 33 is controlled by a heater core control valve 35. The opening and closing of the heater core control valve 35 is controlled by the control unit 45.

[0022] In the cooling circuit 17, an intercooler 4 and a first water jacket 7 are connected (arranged) in series. More specifically, the cooling circuit 17 is configured (arranged) such that the first water jacket 7 is located downstream of the intercooler 4 in the flow direction of cooling water. The cooling circuit 17 is connected to the first cooling system 15 so as to be parallel to the electric powertrain 3.

[0023] The hybrid vehicle 1 recirculates EGR gas to an intake passage through an EGR passage when the water temperature (TWLT) detected by the water temperature sensor 25 is higher than a predetermined preset EGR permission temperature T0. The EGR permission temperature T0 is a temperature at which condensed water will not be generated in the intercooler 4 even if EGR gas is recirculated to the intake passage, and is a value obtained, for example, through experiments using an actual machine.

[0024] The flow rate of EGR gas returned to the intake passage is controlled by opening and closing an EGR valve (not shown) located in the EGR passage using a control unit 45. The control unit 45 is a well-known digital computer equipped with a CPU, ROM, RAM, and an input / output interface.

[0025] Furthermore, if the water temperature (TWLT) detected by the water temperature sensor 25 is below a predetermined first temperature T1, the hybrid vehicle 1 shuts off the flow of coolant to the first radiator 21 and the electric powertrain 3. In other words, the first thermostat 23 is set so that coolant does not flow into the first radiator 21 when the temperature of the coolant in the first cooling system 15 is below the first temperature T1. The flow restriction valve 24 is opened and closed by the control unit 45, which acts as a control unit, and is controlled to close when the temperature of the coolant in the first cooling system 15 is below the first temperature T1. By closing the flow restriction valve 24, the hybrid vehicle 1 stops the flow of coolant to the electric powertrain 3.

[0026] The first temperature T1 may be the same as, for example, the EGR permission temperature T0, or it may be set to a higher temperature than the EGR permission temperature T0 in order to improve the combustion stability of the internal combustion engine 2.

[0027] In hybrid vehicles, internal combustion engines used for power generation recirculate a portion of the exhaust gas as EGR (Exhaust Gas Recirculation) into the intake passage to expand the combustion range at the stoichiometric air-fuel ratio and improve thermal efficiency. Furthermore, the technology of recirculating a portion of the exhaust gas as EGR into the intake passage is also well-known in turbocharged internal combustion engines. In turbocharged internal combustion engines, the intercooler is cooled by a relatively low-temperature cooling circuit, which is different from the relatively high-temperature cooling circuit used for cooling the internal combustion engine.

[0028] Here, when the coolant in the low-temperature cooling circuit that cools the intercooler is at a low temperature, the temperature of the intake air containing EGR gas passing through the intercooler becomes too low, which can cause condensation and potentially lead to unstable combustion in the internal combustion engine. Also, if the EGR gas is not recirculated into the intake passage until the temperature of the coolant in the low-temperature cooling circuit rises in order to avoid condensation in the intercooler, the fuel efficiency of the internal combustion engine may deteriorate.

[0029] Therefore, in the hybrid vehicle 1 of the first embodiment, the intake port of the cylinder head of the internal combustion engine 2 is cooled by the coolant of the first cooling system 15, which is at a lower temperature than the coolant of the second cooling system 16.

[0030] As a result, in the hybrid vehicle 1, after the internal combustion engine 2 has warmed up, the intake air passing through the intake port is cooled by the coolant of the first cooling system 15, suppressing the temperature of the air-fuel mixture in the cylinder and thus suppressing knocking of the internal combustion engine 2.

[0031] Furthermore, by suppressing knocking in the internal combustion engine 2, the hybrid vehicle 1 can expand the combustion range of the internal combustion engine 2 at its stoichiometric air-fuel ratio.

[0032] Furthermore, when the internal combustion engine 2 is cold, the hybrid vehicle 1 uses the coolant heated in the first water jacket 7 to accelerate the warming of the intercooler 4, thereby preventing condensation from forming and allowing the intercooler 4 to heat up quickly. As a result, the internal combustion engine 2 can heat up the intercooler 4 quickly, enabling earlier introduction of EGR gas and improving fuel efficiency.

[0033] The hybrid vehicle 1 can warm up the intercooler 4 by blocking the flow of coolant to the first radiator 21 and the electric powertrain 3 when the temperature of the coolant in the first cooling system 15 is lower than the first temperature T1, thereby warming up the intercooler 4 with the coolant that has been heated by the heat absorbed in the first water jacket 7. In other words, the hybrid vehicle 1 can supply the amount of heat dissipated by the coolant in the first water jacket 7 from the cylinder head side to the intercooler 4, thereby warming up the intercooler 4.

[0034] Other embodiments of the present invention will be described below. Note that components identical to those in the embodiments described above are denoted by the same reference numerals, and redundant descriptions are omitted.

[0035] A second embodiment of the present invention will be described using Figure 2. Figure 2 is a schematic explanatory diagram showing the outline of the cooling system of a hybrid vehicle 51 in a second embodiment to which the present invention is applied.

[0036] The hybrid vehicle 51 of the second embodiment has substantially the same configuration as the cooling system of the hybrid vehicle 1 of the first embodiment described above, but the intercooler 4 and the first water jacket 7 are connected in parallel in the cooling circuit 17, and it has an electric inflow restricting valve 52 that can block the inflow of cooling water from the cooling circuit 17 to the first cooling system 15. In other words, in the hybrid vehicle 51, the cooling circuit 17 has the first water jacket 7 and the intercooler 4 arranged in parallel. In the hybrid vehicle 51, the cooling water flows through the first water jacket 7 in the direction of arrow C in Figure 2.

[0037] The inflow restriction valve 52 corresponds to a cooling circuit restriction mechanism and is located upstream of the first water jacket 7 in the direction of coolant flow, and is positioned so as not to obstruct the flow of coolant toward the intercooler 4. The opening and closing of the inflow restriction valve 52 is controlled by the control unit 45, which acts as a control unit.

[0038] Furthermore, in the hybrid vehicle 51 of the second embodiment, if the water temperature (TWLT) detected by the water temperature sensor 25 is above a predetermined second temperature T2, the inflow restricting valve 52 is closed so that the inflow of coolant from the cooling circuit 17 to the first cooling system 15 is blocked.

[0039] The inflow restriction valve 52 may also be placed at position P, indicated by the dashed line in Figure 2. That is, the inflow restriction valve 52 may be placed downstream of the first water jacket 7 in the direction of the cooling water flow, and in a position that does not obstruct the flow of cooling water that has passed through the intercooler 4.

[0040] The hybrid vehicle 51 of this second embodiment can achieve substantially the same effects as the hybrid vehicle 1 of the first embodiment described above.

[0041] Furthermore, the hybrid vehicle 51 can prevent the amount of heat absorbed by the cooling water in the first water jacket 7 from increasing and impairing the cooling function of the first cooling system 15 by closing the inflow restriction valve 52 when the internal combustion engine 2 is operating at high output. In other words, the hybrid vehicle 51 can suppress excessive temperature rise of the electric powertrain 3 even when the internal combustion engine 2 is operating at high output, and can ensure the cooling of the electric powertrain 3.

[0042] A third embodiment of the present invention will be described using Figure 3. Figure 3 is a schematic explanatory diagram showing the outline of the cooling system of a hybrid vehicle 61 in the third embodiment to which the present invention is applied.

[0043] The hybrid vehicle 61 of the third embodiment has substantially the same configuration as the cooling system of the hybrid vehicle 1 of the first embodiment described above, but the cooling circuit 17 is configured such that the intercooler 4 is located downstream of the first water jacket 7.

[0044] In other words, in the hybrid vehicle 61, the cooling circuit 17 is configured such that the first water jacket 7 and the intercooler 4 are connected in series, with the intercooler 4 located downstream of the first water jacket 7 in the direction of coolant flow.

[0045] The hybrid vehicle 61 shuts off the flow of coolant to the first radiator 21 and the electric powertrain 3 if the water temperature (TWLT) detected by the water temperature sensor 25 is less than a predetermined first temperature T1.

[0046] Furthermore, in the hybrid vehicle 61, if the water temperature (TWLT) detected by the water temperature sensor 25 is less than a predetermined first temperature T1, the flow rate (discharge amount) of the first water pump 22 is reduced compared to when the cooling water temperature is at or above the first temperature T1. In other words, in the third embodiment, the first water pump 22 is controlled by the control unit 45, which acts as a control unit, to reduce the flow rate when the cooling water temperature of the first cooling system 15 is less than the first temperature T1.

[0047] The hybrid vehicle 61 of this third embodiment can achieve substantially the same effects as the hybrid vehicle 1 of the first embodiment described above.

[0048] Furthermore, the hybrid vehicle 61 can efficiently warm up and raise the temperature of the intercooler 4 with the coolant that has been heated by the heat received in the first water jacket 7. In other words, the hybrid vehicle 61 can efficiently supply the amount of heat that the coolant receives from the cylinder head side in the first water jacket 7 to the intercooler 4, thereby efficiently raising the temperature of the intercooler 4.

[0049] Although specific embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0050] For example, in the hybrid vehicles 1 and 51 of the first and second embodiments, if the water temperature (TWLT) detected by the water temperature sensor 25 is less than a predetermined first temperature T1, the flow rate (discharge amount) of the first water pump 22 may be reduced compared to when the cooling water temperature is equal to or greater than the first temperature T1.

[0051] For example, the flow control valve 24 only needs to be capable of blocking the inflow of cooling water into the electric powertrain 3, and may be positioned downstream of the electric powertrain 3 in the direction of the cooling water flow in the first cooling system 15.

[0052] For example, the flow control valve 24 may be a three-way valve positioned at a location where the path for supplying coolant to the electric powertrain 3 and the path for supplying coolant to the cooling circuit 17 diverge, or at a location where the path for coolant that has passed through the electric powertrain 3 and the path for coolant that has passed through the cooling circuit 17 merge.

[0053] For example, in hybrid vehicles 1, 51, and 61, the flow control valve 24 can be omitted. [Explanation of symbols]

[0054] 1…Hybrid vehicles 2…Internal combustion engine 3…Electric Powertrain 3a… Electric motor 3b...Inverter 4…Intercooler 7…First Water Jacket 8…Second Water Jacket 11…EGR cooler 15...1st cooling system 16…Second cooling system 17…Cooling circuit 21…Radiator No. 1 22…First water pump 23…First thermostat 24...Flow control valve 25…Water temperature sensor 31…Second radiator 32…Second water pump 34…Second thermostat 35…Heater control valve 45…Control Unit

Claims

1. An internal combustion engine having a first water jacket for cooling the intake port of the cylinder head, and a second water jacket that cools the portion of the cylinder head other than the intake port, independently of the first water jacket, An electric powertrain that converts electrical energy into mechanical energy, A supercharger that supercharges the above internal combustion engine, An intercooler that cools the intake air of the internal combustion engine containing EGR gas, A first cooling system for cooling the above-mentioned electric powertrain, A second cooling system that cools the internal combustion engine independently of the first cooling system described above, It has a cooling circuit connected to the first cooling system described above, and the first water jacket and the intercooler are connected to it. The cooling circuit described above is a cooling system for a hybrid vehicle, characterized in that the intercooler and the first water jacket are configured to be adjacent to each other.

2. The cooling circuit is characterized in that the intercooler and the first water jacket are arranged in series, as described in claim 1 for a hybrid vehicle cooling system.

3. The cooling circuit is characterized in that the intercooler and the first water jacket are arranged in parallel, as described in claim 1.

4. It has an EGR passage that recirculates a portion of the exhaust gas into the intake passage as EGR gas. The cooling system for a hybrid vehicle according to claim 1, characterized in that the supercharger supercharges the intake air of the internal combustion engine, which includes EGR gas.

5. The first cooling system described above includes a radiator and a flow path regulating mechanism that can block the inflow of coolant to the radiator and the electric powertrain, and circulate coolant to the first water jacket and the intercooler. The cooling system for a hybrid vehicle according to claim 1, characterized in that the flow path regulating mechanism blocks the inflow of coolant to the radiator and the electric powertrain when the temperature of the coolant in the first cooling system is lower than a preset first temperature.

6. The first cooling system described above includes a radiator and a flow path regulating mechanism that can block the inflow of coolant to the radiator and the electric powertrain, and circulate coolant to the first water jacket and the intercooler. The above cooling circuit is configured such that the intercooler is located downstream of the first water jacket in the direction in which the cooling water flows. The above flow path regulating mechanism blocks the flow of coolant to the radiator and the electric powertrain when the temperature of the coolant in the first cooling system is lower than a preset first temperature. The cooling system for a hybrid vehicle according to claim 2, characterized in that the water pump for circulating the coolant of the first cooling system reduces the flow rate of the pump when the temperature of the coolant of the first cooling system is lower than a preset first temperature.

7. The above-mentioned cooling circuit has a cooling circuit regulating mechanism that blocks the inflow of cooling water from the cooling circuit to the first cooling system. The cooling system for a hybrid vehicle according to claim 1, characterized in that the cooling circuit regulating mechanism blocks the inflow of cooling water from the cooling circuit to the first cooling system when the temperature of the cooling water in the first cooling system is above a preset second temperature.

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