Air conditioner for vehicle

An air conditioner for a vehicle includes a cooling water circuit and a heater. The cooling water circuit allows a cooling water to circulate between an engine and a heater core in a heating operation. The engine is a power source of the vehicle. The heater core is configured to heat air using a heat of the cooling water. The heater is located downstream of the engine and upstream of the heater core in the cooling water circuit and is configured to heat the cooling water.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2015-249041 filed on Dec. 21, 2015. The entire disclosure of the application is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to air conditioners for a vehicle. Such air conditioners may include a heater core that is configured to heat air using the heat of cooling water for an engine that is a power source for the vehicle.

BACKGROUND ART

Hybrid vehicles are widely used in recent years due to societal demand requesting to improve fuel consumption and to reduce the exhaust gas. Such hybrid vehicles may include the engine and a motor as power sources. For example, the hybrid vehicles may improve the fuel consumption by operating EV mode that moves the vehicle by the motor while stopping the engine. However, the fuel consumption tends to deteriorate in winter since a time period in which the engine is operated becomes longer to generate a required amount of heat required for a heating operation of the air conditioners. The amount of heat may be an amount of heat from the cooling water for the engine.

Patent Literature 1 discloses a heater, which is a heat source other than the engine, configured to heat the cooling water. The heater includes a heat pump and an exhaust-heat recovery device. A rotational speed of a compressor for the heat pump based on a temperature of the cooling water, a temperature of the exhaust gas, and a load applied to the engine. As a result, power consumption of the heat pump is reduced.

PRIOR ART LITERATURES

Patent Literature

Patent Literature 1: JP 2007-283830 A

SUMMARY OF INVENTION

Patent Literature 1 does not explicitly disclose an arrangement of the engine, the heater core, and the heater in the cooling water circuit through which the cooling water circulates. However, for example, it may be considered to arrange the heater downstream of the engine and to arrange the heater downstream of the heater core. According to this arrangement, the cooling water flows into the engine after being heated in the heater. On the other hand, since the heated cooling water flows into the engine, a temperature of the cooling water in an inlet of the engine tends to be high. Therefore, the engine can be warmed, however the amount of heat transmitting from the engine to the cooling water reduces, and thus the amount of heat dissipated from the heated engine to the atmosphere may increase. That is, exhaust heat increases, and whereby the fuel consumption may deteriorate. In addition, a temperature of the cooling water in an outlet of the engine is required to be heated such that the temperature of the cooling water in the inlet of the engine becomes a specified temperature. Therefore, a temperature at which the warm-up operation for warming the engine is completed and the engine can be stopped is required to be set relatively high. Thus, in vehicles being operable in the EV-traveling mode, starting the EV-traveling mode delays, and therefore the fuel consumption effect in the EV-traveling mode may deteriorate.

It is an objective of the present disclosure to provide an air conditioner for a vehicle that includes a system including a heater core, which is configured to heat the air using the heat of the cooling water for an engine, and that can improve the fuel consumption of the vehicle.

An air conditioner for a vehicle in the present disclosure includes a cooling water circuit and a heater. The cooling water circuit allows a cooling water to circulate between an engine and a heater core in a heating operation. The engine is a power source of the vehicle. The heater core is configured to heat air using a heat of the cooling water. The heater is located downstream of the engine and upstream of the heater core in the cooling water circuit and is configured to heat the cooling water.

According to the above-specified configuration, the cooling water flowing out of the engine can be heated by the heater, and thus the heated cooling water can flow into the heater core. Accordingly, the temperature of the cooling water in the outlet of the engine is not necessarily increased such that the temperature of the cooling water in the inlet of the heater core becomes the specified temperature. As a result, the temperature of the cooling water, at which the warm-up operation is completed and the engine can be stopped, can be relatively low. Therefore, in the vehicle operable in the EV-traveling mode, the EV-traveling mode can be started promptly and can improve the fuel consumption.

Furthermore, the cooling water is heated in the heater, dissipates the heat in the heater core, and then flows into the engine. As a result, the temperature of the cooling water in the inlet of the engine can be relatively low. Therefore, the amount of heat transferring from the engine to the cooling water can be prevented from decreasing, and thus the amount of heat being dissipated from the engine to the atmosphere can be prevented from increasing. Thus, exhaust heat can be reduced, and the fuel consumption of the vehicle can be improved.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described hereinafter referring to drawings. In the embodiments, a part that corresponds to or equivalents to a part described in a preceding embodiment may be assigned with the same reference number, and a redundant description of the part may be omitted. When only a part of a configuration is described in an embodiment, another preceding embodiment may be applied to the other parts of the configuration. The parts may be combined even if it is not explicitly described that the parts can be combined. The embodiments may be partially combined even if it is not explicitly described that the embodiments can be combined, provided there is no harm in the combination.

First Embodiment

A first embodiment will be described referring toFIG. 1toFIG. 4. First, a schematic diagram of a control system in a hybrid vehicle will be described referring toFIG. 1.

The hybrid vehicle mounts an engine11, i.e., an internal combustion engine, and a motor generator12that serve as power sources of the hybrid vehicle. The motor generator12will be referred to as MG12hereinafter. When an output shaft, i.e., a crank shaft, of the engine11generates power, the power transmits to a transmission13through the MG12. An output shaft of the transmission13generates power, and the power transmits to wheels16, i.e., drive wheels, through a component such as a differential gear mechanism14or a wheel axis15. For example, the transmission13may be a variable transmission that includes a plurality of steps and shifts the steps one another to change a speed of the vehicle or may be a non-variable transmission (i.e., CVT) that changes the speed of the vehicle without shifting steps.

A rotary shaft of the MG12is connected to a power transmitting path, which is configured to transmit the power generated by the engine11to the wheels16, to be transmittable the power. The rotary shaft is located between the engine11and the transmission13in the power transmitting path. A crutch may be mounted to the power transmitting path between the engine11and the MG12to stop and start the transmission of the power. The crutch may be located between the MG12and the transmission13.

The engine11drives a generator17. The power generated by the generator17is stored in a high-pressure battery18. The MG12is operated by an inverter19. The inverter19is connected to the high-pressure battery18. Thus, the power is transferred between the MG12and the high-pressure battery18through the inverter19. The generator17is connected to a low-pressure battery21through a DC-DC converter20.

The high-pressure battery18and the low-pressure battery21are configured to store and supply the power and are in communication with each other through the DC-DC converter20. The DC-DC converter20is connected to a low-pressure load that consumes the power supplying thereto from the high-pressure battery18through the DC-DC converter20or the power supplying thereto from the low-pressure battery21.

The air conditioner for a vehicle in the present disclosure includes a heating device that is configured to perform a heating operation for heating a vehicle compartment. For example, the heating device may be a warm-water heating device22using the heat of the cooling water of the engine11. The warm-water heating device22includes a cooling water circuit23that is configured to be connected to a coolant water path (i.e., a water jacket) of the engine11and that allows the cooling water therethrough in the heating operation. The cooling water circuit23mounts an electric water pump24and a heater core25for the heating operation.

The cooling water circuit23mounts a heater that is configured to heat the cooling water. The heater is located downstream of the engine11and upstream of the heater core25in the cooling water circuit23. In the first embodiment, the heater may include a heat pump26and an exhaust-heat recovery device44. As shown inFIG. 1andFIG. 2, the heat pump26is located downstream of the engine11. The exhaust-heat recovery device44is located downstream of the heat pump26. The heater core25is located downstream of the exhaust-heat recovery device44.

As shown inFIG. 1, the electric water pump24is operated by the power from the low-pressure battery21. The electric water pump24is configured to circulate the cooling water in the cooling water circuit23. In the first embodiment, the cooling water flows through the engine11, the heat pump26, the exhaust-heat recovery device44, the heater core25in this order, and returns to the engine11after flowing out of the heater core25.

The heat pump26includes an electric compressor27, a heater28, an expansion valve29, and an exterior heat exchanger30. The electric compressor27is configured to compress a gas refrigerant having a low temperature and a low pressure to be a gas refrigerant having a high temperature and a high pressure. The heater28is configured to allow the high-temperature and high-pressure gas refrigerant to dissipate heat to be a high-pressure liquid refrigerant. The expansion valve29is configured to decompress and expand the high-pressure liquid refrigerant to be a low-temperature and low-pressure liquid refrigerant. The exterior heat exchanger30is configured to allow the low-temperature and low-pressure liquid refrigerant to absorb heat to be a low-temperature and low-pressure gas refrigerant.

The heater28of the heat pump26allows the refrigerant and the cooling water to exchange heat with each other therein and is configured to heat the cooling water using the heat of the refrigerant. The exhaust-heat recovery device44allows exhaust gas from the engine11and the cooling water to exchange heat with each other therein and is configured to heat the cooling water using the heat of the exhaust gas. On the other hand, the heater core25allows the cooling water and the air to exchange heat with each other therein and is configured to heat the air using the heat of the cooling water.

The heat pump26and the exhaust-heat recovery device44are arranged so as to improve the heat generation efficiency as a whole of the heating system. The operation efficiency of the heat pump26is improved as a temperature (i.e., an inlet temperature) of the cooling water flowing into the heat pump26falls. Therefore, the heat pump26is located close to the engine11, for example, may be located upstream of the exhaust-heat recovery device44. The operation efficiency of the exhaust-heat recovery device44is also improved as a temperature (i.e., an inlet temperature) of the cooling water flowing into the exhaust-heat recovery device44falls. The operation efficiencies may deteriorate due to the inlet temperatures. However, a degree of the deterioration in the operation efficiency of the exhaust-heat recovery device44is less than a degree of the deterioration in the operation efficiency of the heat pump26because a temperature of the exhaust gas is high. In addition, the exhaust-heat recovery device44uses free heat (i.e., the heat of the exhaust gas). On the other hand, the heat pump26uses a paid heat. For example, the paid heat may be heat generated by consuming the electric power. Therefore, the operation efficiency of the heat pump26is ignored considering the fuel consumption, and the exhaust-heat recovery device44is located downstream of the heat pump26.

The cooling water circuit23mounts an engine-outlet temperature sensor31that is configured to detect a temperature (i.e., an engine-outlet water temperature) of the cooling water flowing out of the engine11. A blower fan32, which is configured to blow warm air, is disposed near the heater core25. The cooling water circuit23further mounts an HER-inlet temperature sensor45and an EHR outlet temperature sensor. The EHR-inlet temperature sensor45is configured to detect a temperature (i.e., EHR-inlet water temperature) of the cooling water flowing into the exhaust-heat recovery device44. The EHR outlet temperature sensor46is configured to detect a temperature (i.e., EHR-outlet water temperature) of the cooling water flowing out of the exhaust-heat recovery device44.

An accelerator sensor34is configured to detect an opening degree of an accelerator. The opening degree of the accelerator is, i.e., an operation degree of a gas pedal. A shift switch35is configured to detect a location of a shift lever. A brake switch36is configured to detect an operation of the brake. Alternatively, a brake sensor may be disposed to detect the operation amount of the brake. A speed sensor37is configured to detect a speed of the vehicle. An acceleration sensor38is configured to detect a degree of the acceleration.

A hybrid ECU39is mounted as a controller that is configured to control the vehicle as a whole. Specifically, the hybrid ECU39is configured to read output signals from the above-described various sensors and switches and to determine an operation state of the vehicle based on the output signals. The hybrid ECU39is configured to send and receive control signals and data signals between the hybrid ECU39and an engine ECU40and between the hybrid ECU39and an air conditioning ECU42.

The engine ECU40is a controller that is configured to control an operation of the engine11. MG-ECU41is a controller that is configured to control the inverter19to control the MG12and to control the generator17and the DC-DC converter20. The air conditioning ECU42is a controller that is configured to control the warm-water heating device22. For example, the warm-water heating device22may include the electric water pump24, the electric compressor27, and the blower fan32.

The hybrid ECU39is configured to send the control signals and the data signals to the ECUs40,41,42and receives the control signals and the data signals from the ECUs40,41,42. Thus, the hybrid ECU39is configured to control the engine11, the MG12, the generator17, the DC-DC converter20, and the warm-water heating device22based on the operation state of the vehicle. In addition, the hybrid ECU39is also configured to send the control signals and the data signals to a power-source ECU43and receives the controls signals and the data signals from the power-source ECU43. The power-source ECU43is configured to monitor the high-pressure battery18.

The hybrid ECU39is configured to switch driving modes, for example, may be among an engine mode, an assist mode, and an EV mode. In the engine mode, the vehicle moves by operating the wheels16using only the power from the engine11. In the assist mode, the vehicle moves by operating the wheels16using both of the power from the engine11and the power from the MG12. In the EV mode, the vehicle moves by operating the wheels16using only the power from the MG12. For example, the hybrid ECU39may allow the EV mode to be started when the temperature of the cooling water in the outlet of the engine11becomes a warm-up stoppable temperature, at which the engine11is allowed to be stopped, or higher.

The hybrid ECU39is configured to set the driving mode to a power regeneration mode when braking the vehicle. For example, the hybrid ECU39may operate the power regeneration mode when generating the braking force while the gas pedal is not operated or while the brake pedal is operated. In the power regeneration mode, the power from the wheels16operates the MG12such that the MG12converts the kinetic energy of the vehicle into the electric energy to generate the regenerated power. The regenerated power, i.e., the regenerated electric power, is stored in the high-pressure battery18. As a result, time durations in which the assist mode and the EV mode are operated can be longer, and therefore the fuel consumption can be improved.

The output of the exhaust-heat recovery device44varies depending on, e.g., operation states of the engine11. The output is, in other words, an amount of heat used by the exhaust-heat recovery device44to heat the cooling water. Thus, in the first embodiment, the hybrid ECU39performs a heating control routine, which is described later, shown inFIG. 3to perform the following control.

The hybrid ECU39calculates the output of the exhaust-heat recovery device44based on the EHR-inlet water temperature detected by the EHR-inlet temperature sensor45and the EHR-outlet water temperature detected by the EHR-outlet temperature sensor46. The hybrid ECU39adjusts the output of at least one selected from a group of the heat pump26, the electric heater47, and a combustion heater49based on the output of the exhaust-heat recovery device44. In the present embodiment, the heater includes the exhaust-heat recovery device44and the heat pump26. That is, the hybrid ECU39adjusts the output of the heat pump26based on the output of the exhaust-heat recovery device44.

The heating control routine shown inFIG. 3, which is performed by the hybrid ECU39, will be described in detail hereinafter.

The heating control routine shown inFIG. 3is performed repeatedly at specific intervals while the hybrid ECU39is on. The heating control routine serves as an output controller.

When the heating control routine is started, the hybrid ECU39reads the EHR-inlet water temperature and the EHR-outlet water temperature at the section101. In the present embodiment, the temperature of the cooling water in the inlet of the exhaust-heat recovery device44detected by the EHR-inlet temperature sensor45is read as the EHR-inlet water temperature, and the temperature of the cooling water in the outlet of the exhaust-heat recovery device44detected by the EHR-outlet temperature sensor46is read as the EHR-outlet water temperature. Alternatively, for example, a shifting average value of the EHR-inlet water temperature detected by the EHR-inlet temperature sensor45from a specified period before may be obtained as the EHR-inlet water temperature. Similarly, a shifting average value of the EHR-outlet water temperature detected by the EHR-outlet temperature sensor46from a specified period before may be obtained as the EHR-outlet water temperature.

The heating control routine advances from the section101to the section102. In the section102, the hybrid ECU39calculates the EHR heating amount [kW] based on the EHR-inlet water temperature and the EHR-outlet water temperature. The EHR heating amount is, in other words, the output of the exhaust-heat recovery device44or the amount of heat used by the exhaust-heat recovery device44to heat the cooling water. Specifically, the hybrid ECU39calculates an EHR temperature difference between the EHR-inlet water temperature and the EHR-outlet water temperature, and then calculates the EHR heating amount based on the EHR temperature difference, a specific heat of the cooling water, and the flow rate of the cooling water by using the following formula F1.
EHR HEATING AMOUNT=EHR TEMPERATURE DIFFERENCE×SPECIFIC HEAT×FLOW RATE  (F1)

The flow rate of the cooling water used in the formula F1 may be a present value of the flow rate when the EHR-inlet water temperature and the EHR-outlet water temperature are the present values. Alternatively, the flow rate of the cooling water used in the formula F1 may be the shifting average value when the EHR-inlet water temperature and the EHR-outlet water temperature are the shifting average value.

The heating control routine advances to the section103after the section102. In the section103, the hybrid ECU39reads, as the engine-outlet water temperature, the present value of the cooling water in the outlet of the engine11detected by the engine-outlet temperature sensor31.

The heating control routine advances to the section104from the section103. In the section104, the hybrid ECU39, using a map or a formula, calculates a target inlet temperature of the heater core25based on the outside temperature, the inside temperature of the vehicle compartment, and the target inside temperature of the vehicle compartment. The target inlet temperature of the heater core25is, in other words, a target temperature of the cooling water to be heated. The target inlet temperature of the heater core25may be a target value of the heater-core-inlet water temperature, i.e., a target temperature of the cooling water flowing into the heater core25.

The heating control routine advances to the section105from the section104. In the section105, the hybrid ECU39calculates, using the following formula F2, a total amount of heat [kW] of the heater other than the engine11and the exhaust-heat recovery device44based on the target heater-core-inlet water temperature, the engine-outlet water temperature, the specific heat of the cooling water, the flow rate of the cooling water, and the EHR heating amount. The total amount of heat is a necessary amount to raise the heater-core-inlet water temperature to the target value. In the formula F2, the flow rate of the cooling water is the present value.
TOTAL AMOUNT OF HEAT=(TARGET HEATER-CORE-INLET WATER TEMPERATURE−ENGINE-OUTLET WATER TEMPERATURE)×SPECIFIC HEAT×FLOW RATE−EHR HEATING AMOUNT  (F2)

The heating control routine advances to the section106after the section105. In the section106, the hybrid ECU39sets the output of the heater other than the engine11and the exhaust-heat recovery device44. In the first embodiment, the heater includes only the heat pump26. Accordingly, the total amount of heat calculated in the section105becomes the output of the heat pump26, i.e., becomes the amount of heat used by the heat pump26to heat the cooling water. Thus, the output of the heat pump26is adjusted based on the output of the exhaust-heat recovery device44. For example, when the heater other than the engine11and the exhaust-heat recovery device44includes a plurality of devices, the total amount of heat calculated in the section105may be distributed to the plurality of devices and the outputs of the plurality of devices may be set.

The heating control routine advances to the section107after the section106. In the section107, the hybrid ECU39calculates, e.g., may be using a map or a formula, a target flow rate of the cooling water based on the engine-outlet water temperature. As shown inFIG. 4, the map or the formula used to calculate the target flow rate may be set such that the target flow rate decreases as the engine-outlet water temperature falls. The hybrid ECU39controls the electric water pump24such that the flow rate of the cooling water becomes the target flow rate. As a result, the hybrid ECU39decreases the engine-inlet water temperature by decreasing the flow rate of the cooling water circulating through the cooling water circuit23as the engine-outlet water temperature falls. The engine-inlet water temperature is, in other words, a temperature of the cooling water flowing into the engine11. Thus, the section107, including the above-described processes, serves as the flow rate controller.

The heater-core-outlet water temperature, i.e., a temperature of the cooling water flowing out of the heater core25, may be expressed by the following formula F3.
HEATER-CORE-OUTLET WATER TEMPERATURE=HEATER-CORE-INLET WATER TEMPERATURE−OUTPUT OF HEATER CORE/SPECIFIC HEAT/FLOW RATE  (F3)

As obvious from the formula F3, the heater-core-outlet water temperature falls by decreasing the flow rate of the cooling water when the output of the heater core and the heater-core-inlet water temperature are fixed. Here, no heater is arranged downstream of the heater core25. In other words, no heater is located between the heater core25and the engine11. Therefore, the engine-inlet water temperature becomes substantially the same as the heater-core-outlet water temperature or becomes lower than the heater-core-outlet water temperature. As a result, the engine-inlet water temperature can be decreased by decreasing the flow rate of the cooling water.

In the first embodiment, the heater, which heats the cooling water, is mounted to the cooling water circuit23downstream of the engine11and upstream of the heater core25. Specifically, the heater includes the heat pump26, the exhaust-heat recovery device44. The heat pump26is located downstream of the engine11, the exhaust-heat recovery device44is located downstream of the heat pump26, and the heater core25is located downstream of the exhaust-heat recovery device44.

According to the above-described configuration, the heater, i.e., the heat pump26and the exhaust-heat recovery device44, heats the cooling water from the engine11, and the heated cooling water, which is heated in the heater, flows into the heater core25. The cooling water heated in the heater has a temperature higher than the engine-outlet water temperature.

As a result, it is not necessary to increase the engine-outlet water temperature to a required temperature of the heater-core-inlet water temperature, and thus the warm-up stoppable temperature, at which the engine11is allowed to be stopped, can be relatively low. The required temperature is, in other words, the target heater-core-inlet water temperature. That is, the warm-up stoppable temperature can be set lower than the target heater-core-inlet water temperature. Therefore, when the EV mode in which the vehicle moves using the power from the MG12while stopping the engine11is operable in the vehicle, the EV mode is allowed to be performed promptly and thus the fuel consumption in the EV mode can be improved.

In addition, the cooling water is heated in the heater, dissipates the heat in the heater core25, and then flows into the engine11. Accordingly, the engine-inlet water temperature can become relatively low. As a result, the amount of heat transferring from the engine11to the cooling water can be reduced, and thus the amount of heat transferring from the engine11to the atmosphere can be prevented from increased. Therefore, the waste heat can be reduced, and thus the fuel consumption of the vehicle can be improved.

In the present embodiment, the hybrid ECU39adjusts the output of the heat pump26based on the output of the exhaust-heat recovery device44. As a result, a cause of the variation of the heater-core-inlet water temperature can be suppressed in a manner that the output of the heat pump26is adjusted based on the output of the exhaust-heat recovery device44, even when the output of the exhaust-heat recovery device44is changed, e.g., depending on the operation states of the engine11. Moreover, a cause of the waste heat generated by the heat pump26can be suppressed. That is, most of the energy, which is necessary to perform the heating operation, is provided by the heat from the engine11, i.e., by the heat of the exhaust gas, and the heat pump26ekes out the rest of the energy without being operated unnecessarily. Thus, the fuel consumption can be improved.

Furthermore, in the first embodiment, the hybrid ECU39calculates the output of the exhaust-heat recovery device44based on the EHR-inlet water temperature detected by the EHR-inlet temperature sensor45and the EHR-outlet water temperature detected by the EHR-outlet temperature sensor46. Accordingly, the output of the exhaust-heat recovery device44can be calculated with high accuracy based on the actual temperatures detected by the temperature sensors45and46.

In the first embodiment, the engine-inlet water temperature is decreased in a manner that the flow rate of the cooling water circulating through the cooling water circuit23as the engine-outlet water temperature falls. Accordingly, the amount of heat dissipated from the engine11, e.g., and from pipes that allow the cooling water to flow therethrough, can be reduced by increasing the amount of heat transferred from the engine11to the cooling water. As a result, the waste heat can be reduced, and thus the fuel consumption can be improved.

Second Embodiment

A second embodiment will be described hereafter referring toFIG. 5. In the second embodiment, parts different from the first embodiment will be described mainly.

In the second embodiment, at least one of the EHR-inlet temperature sensor45and the EHR-outlet temperature sensor46is omitted from the above-configuration of the first embodiment shown inFIG. 1. In addition, the hybrid ECU39operates a heating control routine shown inFIG. 5to estimate the output of the exhaust-heat recovery device44based on the output of the engine11. The output of the exhaust-heat recovery device44is, in other words, the amount of heat used by the exhaust-heat recovery device44to heat the cooling water.

In the heating control routine shown inFIG. 5, the section101of the heating control routine shown inFIG. 3is omitted, and the section102ais performed instead of the section102. Other sections are the same as those of the first embodiment shown inFIG. 3.

The heating control routine, which is performed by the hybrid ECU39in the second embodiment, shown inFIG. 5will be described in detail hereinafter. The heating control routine shown inFIG. 5may serve as the output controller.

In the heating control routine shown inFIG. 5, the hybrid ECU39estimates the EHR heating amount [kW], which is the output of the exhaust-heat recovery device44, based on the output of the engine11in the section102a. Specifically, the hybrid ECU39calculates EHR warm-up coefficient g(Pe) based on the engine output Pe, for example, by using a map or a formula. The engine output Pe is a time-averaged output of the engine11from a time point at which the engine11is started.

Subsequently, the hybrid ECU39calculates, e.g., by using a map or a formula, an exhaust-gas heat amount f(Ne, Te, Ke) based on an engine rotational speed Ne, an engine torque Te, and the engine-outlet water temperature Ke. The hybrid ECU39further calculates the EHR heating amount using the exhaust-gas heat amount f(Ne, Te, Ke) and the EHR warm-up coefficient g(Pe) by using the following formula F4.
EHR HEATING AMOUNT=f(NE,Te,Ke)×g(Pe)  (F4)

The heating control routine advances to the section103after the section102a. In the section103, the hybrid ECU39reads, as the engine-outlet water temperature, the current value of the temperature of the cooling water in the outlet of the engine11detected by the engine-outlet temperature sensor31. The heating control routine advances to the section104after the section103. In the section104, the hybrid ECU39calculates, e.g., by using the map or the formula, the target heater-core-inlet water temperature based on the outside temperature, the inside temperature inside the vehicle compartment, and the target inside temperature of the vehicle compartment.

The heating control routine advances to the section105after the section104. In the section104, the hybrid ECU39calculates the total amount of heat of the heater other than the engine11and the exhaust-heat recovery device44by using the target heater-core-inlet water temperature, the engine-outlet water temperature, the specific heat of the cooling water, and the flow rate of the cooling water. The heating control routine advances to the section106after the section105. In the section106, the hybrid ECU39sets the output of the engine11and the output of the heater other than the exhaust-heat recovery device44.

The heating control routine advances to the section107after the section106. In the section107, the hybrid ECU39calculates, e.g., by using the map or the formula, the target flow rate of the cooling water based on the engine-outlet water temperature.

In the second embodiment, the hybrid ECU39estimates the output of the exhaust-heat recovery device44based on the output of the engine11. Accordingly, at least one of the EHR-inlet temperature sensor45and the EHR-outlet temperature sensor46can be omitted, and thus the system can be provided with a low cost.

Third Embodiment

A third embodiment will be described hereafter referring toFIG. 6. In the third embodiment, parts different from the first embodiment will be described.

In the third embodiment, the hybrid ECU39operates a heating control routine shown inFIG. 6such that the operation states of the engine11is switched between being on and being off based on the output of the exhaust-heat recovery device44. The output of the exhaust-heat recovery device44is, in other words, the amount of heat used by the exhaust-heat recovery device44to heat the cooling water.

The heating control routine, which is operated by the hybrid ECU39in the third embodiment, shown inFIG. 6will be described in detail hereafter. The heating control routine shown inFIG. 6may serve as the output controller.

In the heating control routine shown inFIG. 6, the hybrid ECU39reads the EHR-inlet water temperature and the EHR-outlet water temperature in the section201. The section201corresponds to the section101shown inFIG. 3.

The heating control routine advances to the section202after the section201. In the section202, the hybrid ECU39calculates the EHR heating amount based on the EHR-inlet water temperature and the EHR-outlet water temperature.

The section202corresponds to the section102shown inFIG. 3.

The heating control routine advances to the section203after the section202. In the section203, the hybrid ECU39calculates, e.g., by using a map or a formula, the target amount of heat [kW] output by the heater core25based on the outside temperature, inside temperature inside the vehicle compartment, and the target inside temperature of the vehicle compartment.

The heating control routine advances to the section204after the section203. In the section204, the hybrid ECU39calculates, by using the following formula F5, the total amount of heat [kW] of the heater other than the exhaust-heat recovery device44based on the target amount of heat output by the heater core25and the EHR heating amount.
TOTAL AMOUNT OF HEAT=TARGET AMOUNT OF HEAT OUTPUT BY HEATER CORE−EHR HEATING AMOUNT  (F5)

The heating control routine advances to the section205after the section204. In the section205, the hybrid ECU39determines SOC that shows a remaining capacity of the high-pressure battery18. The SOC is defined by the following formula F6.
SOC=REMAINING CAPACITY/FULL-CHARGED CAPACITY×100   (F6)

The heating control routine advances to the section206after the section205. In the section206, the hybrid ECU39determines whether the EHR heating amount is a reference value or lower. The reference value may be calculated, e.g., by using a map or a formula, based on the speed of the vehicle and the SOC of the high-pressure battery18. The map or the formula with which the reference value is calculated is set such that the reference value rises as the speed of the vehicle increases and the SOC of the high-pressure battery18increases.

The heating control routine advances to the section207when the hybrid ECU39determines that the EHR heating amount is the reference value or lower in the section206. In the section207, the hybrid ECU39switches the engine11from being off to being on or continues to operate the engine11. On the other hand, the heating control routine advances to the section208when the hybrid ECU39determines that the EHR heating amount is larger than the reference value. In the section208, the hybrid ECU39switches the engine11from being on to being off or continues to stop the engine11. The sections206to208including the above-described processes may serve as the switching controller.

The heating control routine advances to the section209after the section208. In the section209, the hybrid ECU39sets the output of the heater other than the exhaust-heat recovery device44. The heater other than the exhaust-heat recovery device44includes the engine11and the heat pump26.

While the engine11is operated, the hybrid ECU39distributes the total amount of heat calculated in the section204to the engine11and the heat pump26and sets the output of the engine11and the output of the heat pump26. The output of the engine11is, in other words, the amount of heat used by the engine11to heat the cooling water. The output of the heat pump26is, in other words, the amount of heat used by the heat pump26to heat the cooling water. In this situation, the hybrid ECU39calculates, e.g., by using a map or a formula, the distribution rate based on the SOC of the high-pressure battery18, and then distributes the total amount of heat to the engine11and the heat pump26with the distribution rate and sets the outputs of the engine11and the heat pump26.

The map or the formula, with which the distribution rate is calculated, is set such that the ratio of the output of the heat pump26increases as the SOC of the high-pressure battery18increases, i.e., such that the ratio of the output of the engine11increases as the SOC of the high-pressure battery18decreases. Thus, the outputs of the engine11and the heat pump26are adjusted based on the SOC of the high-pressure battery18.

On the other hand, while the engine11is stopped, the total amount of heat calculated in the section204becomes the output of the heat pump26. The section209including the above-described processes may serve as the output controller.

The heating control routine advances to the section210after the section209. In the section210, the hybrid ECU39calculates the target flow rate of the cooling water based on the engine-outlet water temperature. The section210corresponds to the section107shown inFIG. 3.

In the third embodiment, the operation states of the engine11are switched between being on and being off based on the output of the exhaust-heat recovery device44. Specifically, the hybrid ECU39starts the engine11when determining the EHR heating amount, which is calculated as the output of the exhaust-heat recovery device44, to be the reference value or lower, and stops the engine11when determining the EHR heating amount to be larger than the reference value. Accordingly, the hybrid ECU39increases the output of the exhaust-heat recovery device44by starting the engine11when the output of the exhaust-heat recovery device decreases, e.g., while the engine11is stopped in heavy traffic. As a result, the output of the heat pump26can be prevented from being increased.

For example, the output of the heat pump26may be increased because the exhaust pipe of the engine11is cooled and therefore the exhaust-heat recovery device44starts serving as a radiator when the EV mode is operated for a long time, e.g., in the heavy traffic. Then, in the third embodiment, the operation states of the engine11are switched between being on and being off such that the amount of heat output from the exhaust-heat recovery device44is kept to be a specified value or higher. Conventionally, when a load applied to the engine11is low, e.g., in the heavy traffic, the EV mode is continued until the SOC of the high-pressure battery18becomes a lower limit value, and then the engine11is kept to be operated until the SOC of the high-pressure battery18increases to a specified value. However, the exhaust pipe of the engine11is cooled in this situation, therefore it is considered to switch the operation states of the engine11between being on and being off based on the output of the exhaust-heat recovery device44.

In the present embodiment, the engine11is started when the output of the exhaust-heat recovery device44falls such that the generator17, which is operated using the power from the engine11, generates power positively. Accordingly, the electric power consumed in the EV mode is recovered. In addition, a deterioration of the performance of the engine11, which is caused by operating the engine11mandatorily, can be suppressed, and the increase of the output of the heat pump26, which is caused when heat generation is increased, can be suppressed. As a result, the fuel consumption of the vehicle can be improved as compared with a case where the exhaust-heat recovery device44is located downstream of the heater core25.

It may be better to operate the engine11while the vehicle moves because the engine11generates power with low efficiency while the vehicle is stopped and because the volume of ram air is small therefore the exhaust pipe is hardly cooled while the vehicle is stopped. Accordingly, the reference value, which is compared with the output of the exhaust-heat recovery device44to start the engine11, is set small while the vehicle moves. In contrast, the reference value is set large such that the engine11is not started while the high-pressure battery18is not electrifiable, i.e., while the SOC of the high-pressure battery18is close to the upper limit value.

In addition, the outputs of the engine11and the heat pump26are adjusted based on the SOC of the high-pressure battery18in the third embodiment. Specifically, the ratio of the output of the heat pump26is increased as the SOC of the high-pressure battery18increases. In other words, the ratio of the output of the engine11is increased as the SOC of the high-pressure battery18decreases. Accordingly, when the SOC of the high-pressure battery18is low, the output of the engine11is increased such that the power generated by the generator17, which is operated by the power from the engine11, increases and that the amount of heat generated by the engine11is increased. As a result, the output of the heat pump26can be reduced while the SOC of the high-pressure battery18is increased. On the other hand, when the SOC of the high-pressure battery18is high, the output of the heat pump26can be increased without increasing the output of the engine11. Thus, sufficient amount of heat, which is required to perform the heating operation, can be provided with a small volume of fuel.

In the third embodiment, the hybrid ECU39calculates the output of the exhaust-heat recovery device44based on the EHR-inlet water temperature detected by the EHR-inlet temperature sensor45and the EHR-outlet water temperature detected by the EHR-outlet temperature sensor46. However, the output of the exhaust-heat recovery device44may be estimated based on the output of the engine11.

In the above-described first, second, and third embodiments, the exhaust-heat recovery device44is located downstream of the heat pump26. However, the heat pump26may be located downstream of the exhaust-heat recovery device44.

Fourth Embodiment

A fourth embodiment will be described hereafter referring toFIG. 7. In the fourth embodiment, parts different from the first embodiment will be described.

In the fourth embodiment, the heater includes the heat pump26, the exhaust-heat recovery device44, and the electric heater47. As shown inFIG. 7, the heat pump26, the exhaust-heat recovery device44, and the electric heater47are located downstream of the engine11and upstream of the heater core25. The heat pump26and the electric heater47are electric heat sources. The electric heater47heats the cooling water. For example, the electric heater47may be a PTC heater, a carbon heater, or a sheathed heater.

The heat pump26is located downstream of the engine11. The exhaust-heat recovery device44is located downstream of the heat pump26. The electric heater47is located downstream of the exhaust-heat recovery device44. The heater core25is located downstream of the electric heater47. That is, in the fourth embodiment, the electric heater47is added to the configuration of the first embodiment. In the fourth embodiment, the cooling water is allowed to flow through the engine11, the heat pump26, the exhaust-heat recovery device44, the electric heater47, and the heater core25in this order and then returns to the engine11from the heater core25.

The electric heater47can be operated stably since the electric heater47does not rely on the heater-core inlet water temperature, and therefore the heater-core inlet water temperature is easily controlled. Therefore, the electric heater47is located immediately upstream of the heater core25such that the heater-core-inlet water temperature becomes the target value with minimum output.

The fourth embodiment can obtain the same effects as the first embodiment since the heater is located downstream of the engine11and upstream of the heater core25.

In the fourth embodiment, the output of the electric heat source, i.e., the outputs of the heat pump26and the electric heater47, may be adjusted based on the output of the exhaust-heat recovery device44. Alternatively, the output of the electric heat source, i.e., the outputs of the heat pump26and the electric heater47, may be adjusted based on the SOC of the high-pressure battery18.

Fifth Embodiment

A fifth embodiment will be described hereafter referring toFIG. 8. In the fifth embodiment, parts different from the first embodiment will be described.

In the fifth embodiment, as shown inFIG. 8, the heater includes the exhaust-heat recovery device44and the electric heater47. The exhaust-heat recovery device44and the electric heater47are located downstream of the engine11and upstream of the heater core25. The exhaust-heat recovery device44is located downstream of the engine11. The electric heater47is located downstream of the exhaust-heat recovery device44. The heater core25is located downstream of the electric heater47. That is, in the fifth embodiment, the heat pump26is omitted from the configuration of fourth embodiment. In the fifth embodiment, the cooling water is allowed to flow through the engine11, the exhaust-heat recovery device44, the electric heater47, and the heater core25in this order and then returns to the engine11from the heater core25.

The fifth embodiment can provide the same effects as the first embodiment since the heater is located downstream of the engine11and upstream of the heater core25.

In the fifth embodiment, the output of the electric heater47may be adjusted based on the output of the exhaust-heat recovery device44. Alternatively, the output of the engine11and the output of the electric heater47may be adjusted based on the SOC of the high-pressure battery18.

Sixth Embodiment

A sixth embodiment will be described hereafter referring toFIG. 9. In the sixth embodiment, parts different from the first embodiment will be described.

In the sixth embodiment, the heater includes a heat storage device48, the exhaust-heat recovery device44, and the electric heater47. As shown inFIG. 9, the heat storage device48, the exhaust-heat recovery device44, and the electric heater47are located downstream of the engine11and upstream of the heater core25. For example, the heat storage device48may store the cooling water, which is heated in the engine11, while keeping the cooling water warm. The heat storage device48may supply the warm cooling water into the cooling water circuit23to heat the cooling water circulating through the cooling water when the engine-outlet water temperature is low. The heat storage device48is located downstream of the engine11. The exhaust-heat recovery device44is located downstream of the heat storage device48. The electric heater47is located downstream of the exhaust-heat recovery device44. The heater core25is located downstream of the electric heater47. That is, in the sixth embodiment, the heat storage device48is added to the configuration of the fifth embodiment. In the sixth embodiment, the cooling water is allowed to flow through the engine11, the heat storage device48, the exhaust-heat recovery device44, the electric heater47, and the heater core25in this order, and then returns to the engine11from the heater core25.

Here, a temperature of the cooling water stored in the heat storage device48may fall. Therefore, the heat storage device48is located closest to the engine11such that the cooling water flowing out of the heat storage device48can be heated by another device located downstream of the heat storage device48.

The sixth embodiment can provide the same effects as the first embodiment since the heater is located downstream of the engine11and upstream of the heater core25.

In the sixth embodiment, the output of the electric heater47may be adjusted based on the output of the exhaust-heat recovery device44. Alternatively, the output of the engine11and the output of the electric heater47may be adjusted based on the SOC of the high-pressure battery18.

Seventh Embodiment

A seventh embodiment will be described hereafter referring toFIG. 10. In the seventh embodiment, parts different from the first embodiment will be described.

In the seventh embodiment, the heater includes the exhaust-heat recovery device44and the combustion heater49. As shown inFIG. 10. the exhaust-heat recovery device44and the combustion heater49are located downstream of the engine11and upstream of the heater core25. For example, the combustion heater49may combust the fuel for the engine11and may heat the cooling water using the combustion heat. The exhaust-heat recovery device44is located downstream of the engine11. The combustion heater49is located downstream of the exhaust-heat recovery device44. The heater core25is located downstream of the combustion heater49. In the seventh embodiment, the cooling water is allowed to flow through the engine11, the exhaust-heat recovery device44, the combustion heater49, and the heater core25, and then returns to the engine11from the heater core25.

The combustion heater49can be operated stable without relying on the heater-core-inlet water temperature. Accordingly, the heater-core-inlet water temperature can be controller easily. Therefore, the combustion heater49is located immediately upstream of the heater core25such that the heater-core-inlet water temperature becomes the target value with minimum output.

The seventh embodiment can provide the same effects as the first embodiment since the heater is located downstream of the engine11and upstream of the heater core25.

In the seventh embodiment, the output of the combustion heater49may be adjusted based on the output of the exhaust-heat recovery device44.

In the fourth to seventh embodiments, the output of the exhaust-heat recovery device44may be calculated based on the EHR-inlet water temperature detected by the EHR-inlet temperature sensor45and the EHR-outlet water temperature detected by the EHR-outlet temperature sensor46. Alternatively, the output of the exhaust-heat recovery sensor44may be estimated based on the output of the engine11. In addition, the operation states of the engine11may be switched between being on and being off based on the output of the exhaust-heat recovery device44.

Eighth Embodiment

An eighth embodiment will be described hereafter referring toFIG. 11. In the eighth embodiment, parts different from the first embodiment will be described.

In the eighth embodiment, the heater includes the combustion heater49. As shown inFIG. 11, the combustion heater49is located downstream of the engine11and upstream of the heater core25. The combustion heater49is located downstream of the engine11. The heater core25is located downstream of the combustion heater49. In the eighth embodiment, the cooling water is allowed to flow through the engine11, the combustion heater49, and the heater core25, and then returns to the engine11from the heater core25.

The eight embodiment can provide the same effects as the first embodiment since the heater is located downstream of the engine11and upstream of the heater core25.

Other Embodiment

While the present disclosure has been described with reference to preferred embodiments thereof, it is to be understood that the disclosure is not limited to the preferred embodiments and constructions. The present disclosure is intended to cover various modification and equivalent arrangements within a scope of the present disclosure. It should be understood that structures described in the above-described embodiments are preferred structures, and the present disclosure is not limited to have the preferred structures. The scope of the present disclosure includes all modifications that are equivalent to descriptions of the present disclosure or that are made within the scope of the present disclosure.

In the fourth to eighth embodiments, the engine-inlet water temperature may be decreased by decreasing the flow rate of the cooling water, which circulates through the cooling water circuit23, as the engine-outlet water temperature decreases.

The heater, which is located downstream of the engine11and upstream of the heater core25, may include various devices. A quantity of the devices may not be limited. The devices included in the heater and the quantity of the devices may not be limited to the above-described examples and may be changed as required.

In the above-described embodiments, the hybrid ECU39operates the heating control routine. However, another ECU other than the hybrid ECU39may operate the heating control routine. For example, the another ECU may be at least one of the engine ECU40, the MG-ECU41, or the air conditioning ECU42. Alternatively, the hybrid ECU39may operate the heating control routine together with another ECU.

In the above-described embodiments, a part of or an entirety of functions operated by the ECU may be configured, as hardware, by one or more devices such as IC.

The present disclosure is not limited to be mounted to the vehicle having the above-described system shown inFIG. 1. For example, the vehicle may have various configurations including the engine, which is the power source for the vehicle, and the heater core, which is configured to heat air using the heat of the cooling water for the engine.