Vehicular air conditioning device

Abstract

The present invention suppresses the restart of an engine caused by a temperature drop of a heater core. This vehicular air conditioning device includes: a heater core that is connected to a cooling pipe of an engine; a water pump that circulates cooling water inside the cooling pipe; a pump motor that drives the water pump; and a control system that comprises a processor and a memory communicably connected to each other, and controls the pump motor according to the temperature of the heater core. The control system causes the pump motor to operate when the temperature of the heater core drops to a threshold value after the engine is stopped.

Description

Vehicle air conditioning system

[0001] The present disclosure relates to a vehicle air conditioning system.

[0002] In a vehicle, coolant heated by the engine passes through a heater core, causing heat exchange between the air in the vehicle cabin and the coolant, thereby warming the air (see Patent Documents 1 to 4).

[0003] Japanese Patent Application Publication No. 2021-041807 Japanese Patent Application Publication No. 2020-196317 Japanese Patent Application Publication No. 2011-148439 Japanese Patent Application Publication No. 2011-116366

[0004] In a vehicle air conditioning system that circulates engine-heated coolant through a heater core to heat the air, the pump stops operating when the engine is stopped. In this case, the heater core temperature drops because heated coolant is no longer supplied to the heater core. To raise the heater core temperature, the engine must be restarted.

[0005] However, restarting the engine simply to raise the heater core temperature results in the engine being operated unnecessarily when it should have been stopped, resulting in unnecessary consumption of energy for restarting the engine. For this reason, there is a need to suppress engine restarts due to a drop in heater core temperature.

[0006] An object of the present invention is to suppress restarting of the engine due to a drop in heater core temperature.

[0007] In one embodiment, a vehicle air conditioning system includes a heater core connected to an engine's cooling pipe, a water pump that circulates coolant inside the cooling pipe, a pump motor that drives the water pump, and a control system that has a processor and memory that are communicatively connected to each other and controls the pump motor in accordance with the temperature of the heater core, and the control system operates the pump motor when the temperature of the heater core drops to a threshold value after the engine is stopped.

[0008] In one embodiment of the vehicle air conditioning system, when the heater core temperature drops to a threshold value after the engine is stopped, the control system operates the pump motor to drive the water pump, thereby supplying the heater core with heated coolant water that is heated by the heat emitted from the engine, thereby raising the heater core temperature above the threshold value, thereby preventing the engine from restarting due to a drop in the heater core temperature.

[0009] 1 is a diagram showing an example of the configuration of a hybrid vehicle equipped with an air conditioning system of a first embodiment; FIG. 2 is a diagram showing an example of the configuration of an air conditioning system of the first embodiment; FIG. 3 is a diagram simply showing the basic structure of a control unit of the first embodiment; FIG. 4 is a timing chart showing an example of the operation status of a water pump of the first embodiment; FIG. 5 is a flowchart showing an example of water pump control of the first embodiment; FIG. 6 is a flowchart showing an example of water pump control of the first embodiment; FIG. 7 is a diagram showing an example of the configuration of an air conditioning system of a second embodiment;

[0010] Hereinafter, a first embodiment, a second embodiment, and modifications of the present invention will be described in detail with reference to the drawings. In the following description, identical or substantially identical configurations and elements will be designated by the same reference numerals and repeated description will be omitted.

[0011] First Embodiment Fig. 1 is a diagram showing an example of the configuration of a hybrid vehicle 10 equipped with an air conditioning system 11 according to a first embodiment. As shown in Fig. 1, the hybrid vehicle 10 is an example of a vehicle and is equipped with a powertrain 16 including an engine 12 and a transmission 14. The powertrain 16 has an output shaft 18. Rear wheels 25 are connected to the output shaft 18 via a propeller shaft 22 and a rear differential 24. A front differential 19 is incorporated into the transmission 14. Front wheels 20 are connected to the front differential 19. The hybrid vehicle 10 may be configured as a series, parallel, or series-parallel hybrid vehicle.

[0012] 2, the air conditioning system 11 includes the engine 12, a heater core 52, a temperature sensor 53, a water pump 42, a drive unit 30, and a control system 60. The air conditioning system 11 is an example of a vehicle air conditioner. The hybrid vehicle 10 is further provided with a pipe 44 and a radiator 54.

[0013] <<Engine>> The engine 12 includes a crankshaft 17, a throttle valve, an injector, an ignition device, etc. An engine control unit 64 is connected to the throttle valve, the injector, the ignition device, etc. of the engine 12. The engine control unit 64 controls the operation of the throttle valve, the injector, the ignition device, etc., thereby controlling the operation of the engine 12. The engine 12 outputs power from the crankshaft 17. The power of the crankshaft 17 is transmitted to an output shaft 18. The control system 60 is provided so as to be able to switch between the engine 12 and a traction motor 28, which will be described later.

[0014] The output shaft 18 extends from the transmission 14 toward the rear of the vehicle. A switching clutch 26, a traction motor 28, and the like are provided inside the transmission 14. The switching clutch 26 is, for example, an electromagnetic clutch. The switching clutch 26 is provided so as to be able to switch between engagement and disengagement of the crankshaft 17 and the output shaft 18. In other words, the switching clutch 26 switches between running by the engine 12 and running by the traction motor 28. The traction motor 28 is an electric motor. The traction motor 28 is capable of power running and regenerative running, and during regenerative running, converts motive power into electric power to charge the battery via an inverter.

[0015] <<Drive Unit>> The drive unit 30 has a belt mechanism unit 32, an ISG (Integrated Starter Generator) 36, and a clutch unit 38. In the drive unit 30, the ISG 36 drives the water pump 42 via the belt mechanism unit 32 when the clutch unit 38 is in a disengaged state.

[0016] <<<Belt Mechanism>>> The path located between the ISG 36 and the water pump 42, through which power is transmitted from the ISG 36 to the water pump 42, is referred to as the power transmission path K. The belt mechanism 32 is an example of a transmission part provided on the power transmission path K. In other words, the belt mechanism 32 transmits power from the ISG 36 to the water pump 42. The belt mechanism 32 includes, as an example, a pulley 33, a pulley 34, and a belt 35. The pulley 33 is provided on a connecting shaft 39 of the ISG 36. The pulley 34 is provided on a rotating shaft 43 of the water pump 42. The belt 35 is looped around the pulleys 33 and 34.

[0017] <<<ISG>>> The ISG 36 is an example of a pump motor that drives the water pump 42. The ISG 36 drives the water pump 42 when the engine 12 is stopped. Specifically, the ISG 36 has a stator wound with a stator coil, a rotor rotatably housed within the stator, and a connecting shaft 39 fixed to the rotor. The ISG 36 functions as both a generator and an electric motor. In other words, the ISG 36 not only functions as a generator that generates electricity using the power of the engine 12, but also as an electric motor that rotates the crankshaft 17 when the engine 12 is started.

[0018] <<<Clutch Unit>>> The clutch unit 38 is provided so as to be able to connect and disconnect the crankshaft 17 and the connecting shaft 39. In other words, the clutch unit 38 is provided so as to be able to connect and disconnect the engine 12 and the ISG 36. In this way, the clutch unit 38 is used when switching between transmitting power from the ISG 36 to the engine 12 and cutting off the transmission of power from the ISG 36 to the engine 12. The clutch unit 38 is an electromagnetic clutch. The clutch unit 38 controls the transmission and cut-off of power transmission by a control system 60, which will be described later. Specifically, the clutch unit 38 releases the connection between the crankshaft 17 and the connecting shaft 39 when no excitation current is flowing. Furthermore, the clutch unit 38 connects and disconnects the crankshaft 17 and the connecting shaft 39 when an excitation current is flowing.

[0019] <<Water Pump>> The water pump 42 has a rotating shaft 43. The rotating shaft 43 receives driving force from the connecting shaft 39 via the belt mechanism 32. Note that, as an example, the water pump 42 is driven by the engine 12 when the engine 12 is running, regardless of whether the clutch 38 is engaged or disengaged. Furthermore, when the clutch 38 is in the disengaged state, the water pump 42 is driven by power transmitted from the ISG 36 via the belt mechanism 32. The water pump 42 pressurizes the coolant W inside the pipe 44 to deliver the coolant W. In other words, the coolant W is circulated by receiving the pressurizing force of the water pump 42.

[0020] <<Piping>> The pipe 44 is an example of a cooling pipe through which coolant W flows to cool the engine 12. The pipe 44 starts at the water pump 42 and has an upstream flow path 45, a first flow path 46, a second flow path 47, and a downstream flow path 48. The upstream flow path 45 extends downstream from the water pump 42 via the engine 12. The coolant W is heated in the upstream flow path 45 by receiving heat emitted from the engine 12.

[0021] The downstream end of the upstream flow path 45 branches into a first flow path 46 and a second flow path 47. The downstream end of the first flow path 46 and the downstream end of the second flow path 47 merge into a downstream flow path 48. The downstream end of the downstream flow path 48 is connected to the water pump 42. This allows the coolant W to circulate inside the pipe 44.

[0022] <<Heater Core>> The heater core 52 is connected to the first flow path portion 46. The heater core 52 is located inside the passenger compartment of the hybrid vehicle 10. The heater core 52 has fins. The fins transfer heat from the coolant W in the first flow path portion 46 to the outside. That is, the heater core 52 heats the air A1 with the heat supplied from the coolant W. The air A1 is an example of a gas.

[0023] Specifically, when air A1 in the vehicle cabin is sent to the heater core 52 by a blower fan or the like, the air A1 comes into contact with the first flow path portion 46 and the fins, thereby removing heat from the coolant W. In other words, the air A1 becomes heated air A2 and flows into the vehicle cabin. The flow of air A2 into the vehicle cabin warms the interior of the vehicle cabin.

[0024] <<Temperature Sensor>> The temperature sensor 53 measures the temperature of the heater core 52. In the present embodiment, as an example, the temperature of the heater core 52 is directly measured using the temperature sensor 53, but the temperature of the heater core 52 does not have to be measured directly. For example, if there is a correlation between the temperature of the coolant W upstream of the heater core 52 in the first flow path section 46 and the temperature of the heater core 52, the temperature of the coolant W may be measured by a temperature sensor, and the temperature of the heater core 52 may be determined using a correlation coefficient. The temperature sensor 53 transmits information about the temperature of the heater core 52 to a vehicle control unit 62, which will be described later.

[0025] <<Radiator>> The radiator 54 is provided in the second flow path portion 47 and is located outside the vehicle cabin. The radiator 54 has fins. The fins transfer heat from the coolant W in the second flow path portion 47 to the outside. While the hybrid vehicle 10 is running, the radiator 54 cools the coolant W by removing heat from the coolant W using air sent to the second flow path portion 47 and the fins.

[0026] <<Control System>> The control system 60 has two driving modes for the hybrid vehicle 10: an engine mode in which the hybrid vehicle 10 is driven using the engine 12, and an electric mode in which the hybrid vehicle 10 is driven using the traction motor 28. The control system 60 is capable of switching between the engine mode and the electric mode. The control system 60 engages the clutch unit 38 when starting the engine 12. The control system 60 also disengages the clutch unit 38 when the engine 12 is stopped.

[0027] The control system 60 is, for example, composed of a plurality of electronic control units. Examples of the plurality of electronic control units include a vehicle control unit 62, an engine control unit 64, a motor control unit 66, and a battery control unit. The vehicle control unit 62, the engine control unit 64, the motor control unit 66, and the battery control unit are communicatively connected to each other via an in-vehicle network 68 such as a CAN (Controller Area Network). The vehicle control unit 62 outputs control signals to the engine control unit 64, the motor control unit 66, and the battery control unit.

[0028] 3, the vehicle control unit 62, the engine control unit 64, and the motor control unit 66 each have a microcontroller 72 equipped with a processor 73, a main memory 74, etc. The main memory 74 is an example of a memory. A predetermined program is stored in the main memory 74.

[0029] The processor 73 and the main memory 74 are connected to each other so that they can communicate with each other. The processor 73 reads a predetermined program from the main memory 74, expands it, and executes it, thereby executing the program. Note that multiple processors 73 may be incorporated into the microcontroller 72. Also, multiple main memories 74 may be incorporated into the microcontroller 72.

[0030] The vehicle control unit 62, the engine control unit 64, and the motor control unit 66 each include, for example, an input circuit 76, a drive circuit 77, a communication circuit 78, an external memory 79, and a power supply circuit 81. The input circuit 76 converts signals input from various sensors into signals that can be input to the microcontroller 72. The drive circuit 77 generates drive signals for various devices such as the engine 12, the ISG 36, and the clutch unit 38, based on signals output from the microcontroller 72.

[0031] The communication circuit 78 converts signals output from the microcontroller 72 into communication signals directed to other control units. The communication circuit 78 also converts communication signals received from other control units into signals that can be input to the microcontroller 72. The power supply circuit 81 supplies a stable power supply voltage to the microcontroller 72, input circuit 76, drive circuit 77, communication circuit 78, external memory 79, etc. The external memory 79 is made up of a non-volatile memory, etc. Programs, various data, etc. are stored in the external memory 79.

[0032] 2, the control system 60 switches the driving mode of the hybrid vehicle 10 from the engine mode to the electric mode, and after the engine 12 is stopped, controls the ISG 36 in accordance with the temperature of the heater core 52. Specifically, after the engine 12 is stopped, when the temperature of the heater core 52 drops to a threshold value, the control system 60 disengages the clutch unit 38 and causes the ISG 36 to drive the water pump 42. The threshold value will be described later.

[0033] 2 and 4, the first threshold value T2, the second threshold value T3, and the third threshold value T1 set in the control system 60 will be described. The temperature of the heater core 52 is referred to as the heater core temperature T (°C). The control system 60 has preset therein the first threshold value T2, the second threshold value T3, and the third threshold value T1 for the heater core temperature T. The first threshold value T2, the second threshold value T3, and the third threshold value T1 are threshold values ​​used in the control system 60 to determine whether or not various operations are required.

[0034] The first threshold value T2 is an example of a threshold value used to determine whether or not operation of the water pump 42 is required using the ISG 36. When the engine 12 is stopped and the heater core temperature T drops to the first threshold value T2 while the hybrid vehicle 10 is running, the control system 60 determines that operation of the water pump 42 is required and operates the ISG 36.

[0035] The second threshold T3 is set as a temperature higher than the first threshold T2. The second threshold T3 is used to determine whether to stop the water pump 42 using the ISG 36. If the heater core temperature T becomes higher than the second threshold T3 after decreasing to the first threshold T2, the control system 60 determines that operation of the water pump 42 is unnecessary and stops the ISG 36. Note that if the heater core temperature T is higher than the first threshold T2 and lower than the second threshold T3, the control system 60 continues operation of the water pump 42.

[0036] The third threshold T1 is set to a temperature lower than the first threshold T2. The third threshold T1 is used to determine whether or not the engine 12 needs to be operated. In the hybrid vehicle 10, after the heater core temperature T has dropped to the first threshold T2, the heater core temperature T may fall below the third threshold T1 while the ISG 36 is operating. For example, if the coolant W is circulated for a long period of time in the electric mode, the coolant W is not heated, and the temperature of the coolant W will fall over time. Here, the control system 60 engages the clutch unit 38 and controls the engine 12 to restart when the heater core temperature T falls below the third threshold T1 while the ISG 36 is operating after the heater core temperature T has dropped to the first threshold T2.

[0037] [Operation of First Embodiment] <Water Pump Control: Flowchart> The procedure for executing water pump control will now be described. Figures 5A, 5B, and 5C are flowcharts showing an example of the procedure for executing water pump control. The flowcharts shown in Figures 5A, 5B, and 5C are connected via terminals indicated by the symbols A, B, and C, respectively. Each step of the water pump control shown in Figures 5A, 5B, and 5C is executed by processor 73 constituting control system 60. Note that for each configuration and threshold of hybrid vehicle 10, reference should be made to Figures 1 to 4, and individual figure numbers will be omitted.

[0038] 5A, the control system 60 proceeds to step S10 and sets the driving mode of the hybrid vehicle 10 to the engine mode. For example, if the remaining battery charge of the battery pack is low, the control system 60 sets the driving mode to be driven by the engine 12. At this time, the clutch unit 38 is engaged. Then, the control system 60 proceeds to step S12.

[0039] In step S12, the control system 60 starts the engine 12. Specifically, the ISG 36 operates as a starter motor to start the engine 12. When the engine 12 starts, the water pump 42 begins operating. Then, the control system 60 proceeds to step S14.

[0040] In step S14, the control system 60 starts measuring the heater core temperature T using the temperature sensor 53, and proceeds to step S16. In step S16, the control system 60 determines whether to switch from the engine mode to the electric mode. For example, if the load during driving is smaller than a set load, the control system 60 determines to switch to the electric mode. If the control system 60 determines to switch to the electric mode (S16: Yes), the control system 60 proceeds to step S18. If the control system 60 determines not to switch to the electric mode (S16: No), the control system 60 repeats step S16.

[0041] In step S18, the control system 60 stops the engine 12 and proceeds to step S20. In step S20, the control system 60 disengages the clutch unit 38 and proceeds to step S22. In step S22, the control system 60 determines whether the heater core temperature T is equal to or lower than a first threshold value T2. If the heater core temperature T is equal to or lower than the first threshold value T2 (S22: Yes), the control system 60 proceeds to step S24. If the heater core temperature T is higher than the first threshold value T2 (S22: No), the control system 60 repeats step S22.

[0042] In step S24, the control system 60 uses the ISG 36 to start the operation of the water pump 42. Then, the control system 60 proceeds to step S26. In step S26, the control system 60 determines whether the heater core temperature T is higher than the first threshold value T2. If the heater core temperature T is higher than the first threshold value T2 (S26: Yes), the control system 60 proceeds to step S28. If the heater core temperature T is equal to or lower than the first threshold value T2 (S26: No), the control system 60 proceeds to step S32.

[0043] In step S28, the control system 60 determines whether the heater core temperature T is higher than the second threshold value T3. If the heater core temperature T is higher than the second threshold value T3 (S28: Yes), the control system 60 proceeds to step S30. If the heater core temperature T is equal to or lower than the second threshold value T3 (S28: No), the control system 60 repeats step S28. In step S30, the control system 60 stops the operation of the ISG 36, thereby stopping the operation of the water pump 42, and proceeds to step S22.

[0044] In step S32, the control system 60 determines whether the heater core temperature T is equal to or lower than the third threshold value T1. If the heater core temperature T is equal to or lower than the third threshold value T1 (S32: Yes), the control system 60 proceeds to step S34. If the heater core temperature T is higher than the third threshold value T1 (S32: No), the control system 60 repeats step S32.

[0045] In step S34, the control system 60 stops the operation of the ISG 36, thereby stopping the operation of the water pump 42, and proceeds to step S36. In step S36, the control system 60 engages the clutch unit 38, and proceeds to step S38. In step S38, the control system 60 uses the ISG 36 to start the engine 12. When the engine 12 starts, the water pump 42 begins operating. Then, the process ends.

[0046] Note that control system 60 may proceed to step S16 without terminating the process in step S38. When the process proceeds from step S38 to step S16, control of water pump 42 is repeatedly performed. Here, when control system 60 acquires information indicating that hybrid vehicle 10 has finished traveling, the control system may terminate the water pump control program using the information as a trigger.

[0047] <Water Pump Control: Timing Chart> The water pump control described above will be explained using a timing chart. FIG. 4 is a timing chart showing an example of control of the water pump 42. For each component of the hybrid vehicle 10, please refer to FIGS. 1, 2, and 3, and individual figure numbers will be omitted. The intervals between times t1 to t9 shown in FIG. 4, i.e., the lengths of time, are merely examples, and control does not necessarily have to be performed exactly as shown. In reality, there is a time lag between when the control system 60 transmits a control signal to a controlled object and when the controlled object starts operating; however, FIG. 4 shows a timing chart that omits this time lag.

[0048] As shown in Figure 4, the clutch 38 is engaged until just before time t1. The ISG 36 is not operating. The engine 12 is operating, and the water pump 42 is not operating. The heater core temperature T is, for example, T = TA. Note that the temperature TA is, for example, higher than the second threshold value T3.

[0049] At time t1, the water pump 42 is stopped as the engine 12 is stopped. Also at time t1, the clutch unit 38 is disengaged. The water pump 42 is stopped from time t1 to time t2. That is, no coolant W is supplied to the heater core 52. As a result, the heater core temperature T drops from the temperature TA. When the heater core temperature T reaches the first threshold value T2 at time t2, the control system 60 activates the ISG 36, thereby starting the water pump 42.

[0050] During the period from time t2 to time t4, the water pump 42 operates, and the coolant W that has passed through the engine 12 is supplied to the heater core 52. As a result, the heater core temperature T becomes higher than the first threshold value T2. Note that the water pump 42 continues to operate in order to maintain the heater core temperature T at a temperature higher than the first threshold value T2.

[0051] When the heater core temperature T reaches the second threshold value T3 at time t4, the control system 60 stops the operation of the ISG 36. This stops the water pump 42. Then, since the coolant W is no longer circulating, the heater core temperature T drops below the second threshold value T3. Note that the controls from time t5 to time t6 are performed in the same manner as the controls from time t2 to time t4. Therefore, a description of the controls from time t5 to time t6 will be omitted.

[0052] When the heater core temperature T reaches the first threshold value T2 at time t7, the control system 60 operates the ISG 36 to start the water pump 42. Then, from time t7 to time t8, the water pump 42 continues to operate, supplying the coolant W to the heater core 52. For this reason, the heater core temperature T may become higher than the first threshold value T2.

[0053] When the engine 12 is stopped, there is no new heat source for the coolant W. Therefore, the temperature of the coolant W decreases due to the circulation of the coolant W or the blowing of air A1 through the heater core 52. In other words, the longer the engine 12 is stopped and the longer the time the coolant W is circulated, the lower the temperature of the coolant W. Therefore, even if the water pump 42 continues to operate, there is a possibility that the heater core temperature T will fall below the first threshold value T2 at a certain point. Figure 4 shows a state in which the heater core temperature T does not reach the second threshold value T3 but falls to the first threshold value T2 between time t7 and time t8.

[0054] At time t8, the control system 60 determines that it is difficult to increase the heater core temperature T even by circulating the coolant W, and stops the ISG 36, thereby stopping the water pump 42. Note that the time from time t8 to time t9 corresponds, for example, to a preparation time or waiting time for restarting the engine 12.

[0055] When the heater core temperature T reaches the third threshold value T1 at time t9, the control system 60 engages the clutch unit 38 and operates the ISG 36. This restarts the engine 12 and operates the water pump 42. When the engine 12 restarts, the engine 12 heats the coolant W. The heated coolant W is then supplied to the heater core 52 by the water pump 42. This causes the heater core temperature T to rise above the third threshold value T1. In this embodiment, the engine 12 is stopped at time t1 and restarted at time t9. The time from time t1 to time t9 is designated dT1. The time dT1 is the time during which the engine 12 is stopped.

[0056] [Comparative Example] The dashed-dotted line G1 in FIG. 4 represents the heater core temperature T in a hybrid vehicle that is a comparative example of this embodiment. The dotted line G2 in FIG. 4 represents the engine speed in the hybrid vehicle of the comparative example. In the hybrid vehicle of the comparative example, the water pump remains stopped after the engine is stopped. Therefore, if the heater core temperature T drops to the third threshold value T1 at time t3, the engine must be restarted to operate the water pump. In other words, in the hybrid vehicle of the comparative example, the time dT2 from time t1 to time t3 is the engine stop time. Time dT2 is shorter than time dT1.

[0057] Summary of First Embodiment As described above, in the air conditioning system 11, when the temperature of the heater core 52 drops to the first threshold value T2 after the engine 12 is stopped, the control system 60 operates the ISG 36 to drive the water pump 42. As a result, the coolant W heated by the heat emitted from the engine 12 is supplied to the heater core 52, and the temperature of the heater core 52 becomes higher than the first threshold value T2, thereby preventing the engine 12 from restarting due to a drop in the temperature of the heater core 52. In other words, the time dT1, which is the stop time of the engine 12 shown in FIG. 4 , can be made longer than the time dT2 in the comparative example described above, and the electric mode can be continued.

[0058] In the air conditioning system 11, when the temperature of the heater core 52 drops to the first threshold value T2 and then rises above the second threshold value T3, the control system 60 stops the ISG 36. This stops the water pump 42 and stops the supply of coolant W to the heater core 52. This prevents the heater core 52 from being heated more than necessary, thereby reducing the amount of energy consumed to heat the heater core 52.

[0059] The longer the coolant W circulates while the engine 12 is stopped, the lower the temperature of the coolant W tends to be. In other words, if the temperature of the heater core 52 does not reach the first threshold T2 despite the coolant W circulating, it is considered that the coolant W does not have the heat quantity required to heat the heater core 52. In the air conditioning system 11, after the temperature of the heater core 52 has dropped to the first threshold T2, the control system 60 starts the engine 12 when the temperature of the heater core 52 falls below the third threshold T1 while the ISG 36 is operating. This allows the coolant W to be heated by heat emitted from the engine 12, thereby raising the temperature of the heater core 52 to at least the first threshold T2.

[0060] In the air conditioning system 11, when the driving mode is switched from the electric mode to the engine mode, the control system 60 engages the clutch unit 38 and operates the engine 12 using the ISG 36. On the other hand, when the driving mode is switched from the engine mode to the electric mode, the control system 60 stops the engine 12. Furthermore, when the temperature of the heater core 52 drops to the first threshold T2 after the engine 12 is stopped, the control system 60 disengages the clutch unit 38 and drives the water pump 42 using the ISG 36. In this way, the ISG 36 can be used not only as a drive source for restarting the engine 12 but also as a drive source for the water pump 42, so there is no need to provide a drive source separate from the ISG 36 to drive the water pump 42.

[0061] In the air conditioning system 11, the control system 60 switches from the engine mode to the electric mode, and after the engine 12 is stopped, operates the ISG 36 when the temperature of the heater core 52 drops to the first threshold T2. This eliminates the need to operate the engine 12 to heat the heater core 52. In other words, the air conditioning system 11 can extend the time in the electric mode compared to a system not having this configuration.

[0062] Second Embodiment An air conditioning system 90 according to a second embodiment will be described below. Components that are the same as or similar to those in the first embodiment are designated by the same reference numerals, and duplicate descriptions will be omitted. Individual reference numerals will be omitted for the configurations shown in Figures 1 to 4. The air conditioning system 90 is an example of a vehicle air conditioning device.

[0063] As shown in FIG. 6 , in the air conditioning system 90, the drive source for operating the water pump 42 is different from that in the air conditioning system 11 of the first embodiment. Specifically, in the air conditioning system 90, a drive motor 94 drives the water pump 42. The drive motor 94 is an example of a pump motor, and is operated by being supplied with electric power. The drive motor 94 is also controlled by the control system 60. In the air conditioning system 90, as an example, the crankshaft 17 and the connecting shaft 39 of the ISG 36 are connected by a belt mechanism 32.

[0064] The engine 12 is provided with a starter motor 92. The starter motor 92 is an electric motor that cranks the crankshaft 17 using power supplied from a battery. The starter motor 92 is used when starting the engine 12. The ISG 36 is used when restarting the engine 12.

[0065] In the air conditioning system 90, when the temperature of the heater core 52 drops to the first threshold value T2 after the engine 12 is stopped, the control system 60 operates the drive motor 94 to drive the water pump 42. As a result, the coolant W heated by the heat emitted from the engine 12 is supplied to the heater core 52, causing the temperature of the heater core 52 to rise above the first threshold value T2, thereby preventing the engine 12 from restarting due to a drop in the temperature of the heater core 52. In other words, the electric mode can be continued.

[0066] Furthermore, in the air conditioning system 90, when the temperature of the heater core 52 drops to the first threshold value T2 and then rises above the second threshold value T3, the control system 60 stops the drive motor 94. This stops the water pump 42, and the supply of coolant W to the heater core 52 is stopped. This prevents the heater core 52 from being heated more than necessary, thereby reducing the amount of energy consumed to heat the heater core 52. In this way, a drive motor 94 separate from the ISG 36 may be used as the drive source for the water pump 42.

[0067] [Modifications] The present invention is not limited to the first and second embodiments, and it goes without saying that various modifications are possible without departing from the spirit of the invention.

[0068] The vehicle is not limited to the hybrid vehicle 10, but may be a vehicle that has an engine 12 but does not have a traction motor 28. In such a vehicle, the drive motor 94 may be operated when the temperature of the heater core 52 drops to a threshold value after the engine 12 is stopped.

[0069] The second threshold value T3 does not have to be set in the air conditioning system 11. In other words, in the air conditioning system 11, even if the temperature of the heater core 52 reaches the second threshold value T3, the operation of the drive unit 30 may continue. The second threshold value T3 does not have to be set in the air conditioning system 90 either.

[0070] In the air conditioning systems 11 and 90, a gear mechanism including a plurality of gears may be used instead of the belt mechanism 32. Also, instead of the belt mechanism 32, a transmission unit that transmits power using a chain and sprockets may be used.

[0071] 11...air conditioning system (an example of a vehicle air conditioning device), 12...engine, 17...crankshaft, 32...belt mechanism section (an example of a transmission section), 28...travel motor, 36...ISG (an example of a pump motor), 38...clutch section, 42...water pump, 44...piping (an example of a cooling piping), 52...heater core, 60...control system, 73...processor, 74...main memory (an example of a memory), 90...air conditioning system (an example of a vehicle air conditioning device), 94...drive motor (an example of a pump motor), K...power transmission path, T1...third threshold, T2...first threshold (an example of a threshold), T3...second threshold, W...coolant

Claims

1. An air conditioning system for a vehicle comprising: a heater core connected to an engine cooling pipe; a water pump for circulating coolant inside the cooling pipe; a pump motor for driving the water pump; and a control system having a processor and memory communicatively connected to each other, and for controlling the pump motor in accordance with a temperature of the heater core, wherein the control system operates the pump motor when the temperature of the heater core drops to a threshold value after the engine is stopped.

2. A vehicle air conditioning system as described in claim 1, wherein the control system is set with a first threshold value and a second threshold value higher than the first threshold value as the threshold value, and the control system stops the pump motor when the temperature of the heater core drops to the first threshold value and then becomes higher than the second threshold value.

3. A vehicle air conditioning system as described in claim 1, wherein the control system is set with a first threshold value and a third threshold value lower than the first threshold value as the threshold value, and the control system starts the engine when the temperature of the heater core falls below the third threshold value while the pump motor is operating after the temperature of the heater core falls to the first threshold value.

4. A vehicle air conditioning system as described in claim 1, further comprising: a transmission unit provided in a power transmission path between the pump motor and the water pump; and a clutch unit capable of engaging and disengaging the transmission unit and the crankshaft of the engine, wherein the control system engages the clutch unit when the engine is operated, and disengages the clutch unit and drives the water pump using the pump motor when the temperature of the heater core has dropped to a threshold value after the engine is stopped.

5. An air conditioning system for a vehicle as described in claim 1, wherein the control system is capable of switching between an engine mode in which the vehicle is driven using the engine and an electric mode in which the vehicle is driven using a traction motor, and the control system operates the pump motor when the temperature of the heater core drops to the threshold value after switching from the engine mode to the electric mode and the engine is stopped.

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