Abstract:
A control apparatus for a hybrid vehicle includes an engine for traveling, a motor for traveling, and a battery exchanging electric power with the motor. the control apparatus including: a heater is configured to perform heating inside a cabin of the hybrid vehicle by using the engine or an electric heat source as a heat source; and a controller is configured to operate the engine intermittently, the controller is configured to select the heat source for the heater, the controller is configured to determine whether or not a fuel for the engine is degraded when the engine is stopped, and the controller is configured to start the engine and select the engine as the heat source when the controller determines that the fuel is degraded.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The disclosure of Japanese Patent Application No. 2013-057487 filed on Mar. 21, 2013 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a control apparatus for a hybrid vehicle (HV), and more particularly to a control apparatus for a HV which includes an engine and a motor for traveling, a battery exchanging electric power with the motor, and a heater for heating the interior of the vehicle cabin by using the engine or an electric heat source as a heat source, and which runs with intermittent engine operation. 
         [0004]    2. Description of Related Art 
         [0005]    A control apparatus has been suggested for a HV that has as drive sources an internal combustion engine, to which fuel stored in a fuel tank is supplied, and an electric motor, to which electric power stored in a battery is supplied, the control apparatus storing history of each refueling time and each refueling amount for a plurality of fuel tank refueling operations and calculates the degree of degradation of the fuel in the fuel tank on the basis of the history (see, for example, Japanese Patent Application Publication No. 2009-255680 (JP 2009-255680A)). 
       SUMMARY OF THE INVENTION 
       [0006]    When a HV provided with a charger capable of charging a battery with electric power from an external power source is driven only short distances (short-distance running and battery charging are repeated), the fuel in the fuel tank is not consumed for a comparatively long period and the fuel can degrade. 
         [0007]    The control apparatus for a HV in accordance with the invention enhances the consumption of the degraded fuel. 
         [0008]    According to an aspect of the invention, a control apparatus for a HV including an engine for traveling, a motor for traveling, and a battery exchanging electric power with the motor. The control apparatus includes a heater configured to perform heating inside a cabin of the HV by using the engine or an electric heat source as a heat source, and a controller configured to drive the engine intermittently. The controller is configured to select the heat source for the heater. The controller is configured to determine whether or not a fuel for the engine is degraded when the engine is stopped, and the controller is configured to start the engine and select the engine as the heat source when the controller determines that the fuel is degraded. 
         [0009]    In the control apparatus for a HV according to the aspect of the invention, when the controller determines that the fuel for the engine is degraded, the controller starts the engine and selects the engine as the heat source of the heater. As a result, the consumption of the degraded fuel can be enhanced. In this case, the HV can be also provided with a charger capable of charging the battery by using electric power from an external electric power source. 
         [0010]    Further, in the control apparatus for a HV according to the aspect of the invention, when the controller determines that the fuel is degraded and the heater heats the cabin, the controller may extend a warm-up time of the engine longer in comparison with a case when the controller determines that the fuel is not degraded and the heater heats the cabin. Further, when the controller determines that the fuel for the engine is degraded and the heater heats the cabin, the controller may increase a revolution speed of the engine during warm-up higher in comparison with a case when the controller determines that the fuel is not degraded and the heater heats the cabin. In such cases, it is possible to enhance further the consumption of the degraded fuel and improve heating performance of the heater. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
           [0012]      FIG. 1  is a configuration diagram illustrating schematically the configuration of a HV of an embodiment of the invention; 
           [0013]      FIG. 2  is a flowchart illustrating an example of a processing routine executed by a HV electronic control unit (ECU) of the embodiment when fuel has degraded; 
           [0014]      FIG. 3  is a configuration diagram illustrating schematically the configuration of a HV  120  of a variation example; 
           [0015]      FIG. 4  is a configuration diagram illustrating schematically the configuration of a HV  220  of a variation example; and 
           [0016]      FIG. 5  is a configuration diagram illustrating schematically the configuration of a HV  320  of a variation example. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0017]    A mode for carrying out the invention is explained below on the basis of an embodiment thereof. 
         [0018]      FIG. 1  is a configuration diagram illustrating schematically the configuration of a HV  20  as an embodiment of the invention. As shown in the figure, the HV  20  according to the embodiment is provided with an engine  22  that receives the supply of fuel such as gasoline or light oil from a fuel tank  21  and outputs power; an engine ECU  24  that performs drive control of the engine  22 ; a planetary gear  30  in which a carrier is connected to a crankshaft  26  of the engine  22 ; and a ring gear is connected to a drive axle  36  linked by a differential gear  37  to drive wheels  38   a ,  38   b ; a motor MG 1  constituted, for example, as a synchronous motor generator and connected by a rotor to a sun gear of the planetary gear  30 ; a motor MG 2  constituted, for example, as a synchronous motor generator and connected by a rotor to the drive axle  36 ; inverters  41 ,  42  for driving the motors MG 1 , MG 2 ; a motor ECU  40  that performs drive control of the motors MG 1 , MG 2  by switch controlling switching elements (not shown in the figure) of the inverters  41 ,  42 ; a battery  50  that is configured, for example, as a lithium ion secondary battery and that exchanges electric power with the motors MG 1 , MG 2  via the inverters  41 ,  42 ; a battery ECU  52  that manages the battery  50 ; a heater  58  that performs heating inside a HV cabin by using as a heat source the engine  22  or an electric heat source (for example, a heat pump or an electric heater)  56 ; a charger  60  that is connected to an external power source such as a household power source and can charge the battery  50 ; and a hybrid ECU (referred to hereinbelow as HVECU)  70  that controls the entire vehicle. 
         [0019]    The engine ECU  24  is configured as a microprocessor centered on a central processing unit (CPU) (this configuration is not shown in the figure), and is provided, in addition to the CPU, with a read only memory (ROM) that stores a processing program, a random access memory (RAM) for temporarily storing data, input/output ports, and a communication port (this configuration is not shown in the figure). Signals from various sensors detecting the drive state of the engine  22  are inputted via the input port into the engine ECU  24 . Examples of the signals include a crank position θcr from a crank position sensor that detects the rotation position of the crankshaft  26 ; a cooling water temperature Tw from a water temperature sensor that detects the temperature of cooling water in the engine  22 ; a pressure Pin inside a cylinder from a pressure sensor attached inside a combustion chamber; a cam position θca from a cam position sensor that detects the rotation position of a camshaft that opens and closes an intake valve and an exhaust valve that perform intake and exhaust to and from the combustion chamber; a throttle position TP from a throttle position sensor that detects the position of a throttle valve; an intake air amount Qa from an air flow meter mounted on an intake pipe; an intake temperature Ta from a temperature sensor also mounted on the intake pipe; an air-fuel ratio AF from an air-fuel sensor mounted on an exhaust system; and an oxygen signal O 2  from an oxygen sensor also mounted on the exhaust system. A variety of control signals for driving the engine  22  are outputted from the engine ECU  24  via the output port. Examples of such signals include a drive signal to fuel injection valves, a drive signal to a throttle motor that adjusts the throttle valve position; a control signal to an ignition coil integrated with an igniter, and a control signal to a variable valve timing mechanism that can change the opening-closing timing of the intake valve. Further, the engine ECU  24  communicates with the HVECU  70  and performs drive control of the engine  22  by a control signal from the HVECU  70 . The engine ECU  24  also outputs, as necessary, data relating to the drive state of the engine  22  to the HVECU  70 . The engine ECU  24  also calculates the revolution speed of the crankshaft  26 , that is, the revolution speed Ne of the engine  22 , on the basis of a signal from the crank position sensor (not shown in the figure) mounted on the crankshaft  26 . 
         [0020]    The motor ECU  40  is configured as a microprocessor centered on a CPU (this configuration is not shown in the figure) and is provided, in addition to the CPU, with a ROM that stores a processing program, a RAM for temporarily storing data, input/output ports, and a communication port. Signals necessary for performing drive control of the motors MG 1 , MG 2  are inputted via the input port into the motor ECU  40 . Examples of such signals include revolution positions θm 1 , θm 2  from the revolution position detection sensors  43 ,  44  that detect the revolution positions of the rotors of the motors MG 1 , MG 2 , and phase currents applied to the motors MG 1 , MG 2 , which are detected by current sensors (not shown in the figure). Switching control signals to the switching elements (not shown in the figure) of the inverters  41 ,  42  are outputted via the output port from the motor ECU  40 . The motor ECU  40  also communicates with the HVECU  70 , performs drive control of the motors MG 1 , MG 2  by the control signals from the HVECU  70 . The motor ECU  40  also outputs, as necessary, data relating to the drive state of the motors MG 1 , MG 2  to the HVECU  70 . The motor ECU  40  also calculates the revolution angle speed ωm 1 , ωm 2  and revolution speed Nm 1 , Nm 2  of the motors MG 1 , MG 2  on the basis of the revolution positions θm 1 , θm 2  of the motors MG 1 , MG 2  from the revolution position detection sensors  43 ,  44 . 
         [0021]    The battery ECU  52  is configured as a microprocessor centered on a CPU (this configuration is not shown in the figure) and is provided, in addition to the CPU, with a ROM that stores a processing program, a RAM for temporarily storing data, input/output ports, and a communication port. Signals necessary for managing the battery  50  are inputted into the battery ECU  52 . Examples of such signals include a terminal voltage Vb from a voltage sensor  51   a  disposed between the terminals of the battery  50 , a charge-discharge current Ib from a current sensor  51   b  mounted on an electric power line connected to the output terminals of the battery  50 , and a battery temperature Tb from a temperature sensor  51   c  mounted on the battery  50 . The battery ECU  52  transmits, as necessary, data relating to the state of the battery  50  by communication to the HVECU  70 . In order to manage the battery  50 , the battery ECU  52  calculates an electric power storage ratio SOC, which is a ratio of the capacity of the electric power dischargeable from the battery  50  at this time to the total capacity on the basis of the integral value of the charge-discharge current Ib detected by the current sensor  51   b . The battery ECU  52  also calculates the input and output limits Win, Wout, which are allowable input and output electric power that may be charged into and discharged from the battery  50  on the basis of the calculated electric power storage ratio SOC and the battery temperature Tb. The input and output limits Win, Wout of the battery  50  can be set by setting the basic values of the input and output limits Win, Wout on the basis of the battery temperature Tb, setting an output limit correction factor and an input limit correction factor on the basis of the electric power storage ratio SOC of the battery  50 , and multiplying the basic values of the input and output limits Win, Wout, which have been set, by the input limit correction factor and an output limit correction factor, respectively. 
         [0022]    The heater  58  is provided with a heat exchanger that warms the air by using cooling water of the engine  22  or the electric heat source  56  as a heat source, and a blower that blows the air warmed up by the heat exchanger into the HV cabin (this configuration is not shown in the figure). 
         [0023]    The charger  60  is connected via a relay  62  to an electric power line  54  connecting the inverters  41 ,  42  with the battery  50 . The charger  60  is provided with an AC/DC converter  66  that converts AC power from an external electric power source that is supplied via an electric power supply plug  68  into DC power, and a DC/DC converter  64  that converts the voltage of the DC power from the AC/DC converter  66  and supplies the converted voltage to the electric power line  54 . 
         [0024]    The HVECU  70  is configured as a microprocessor centered on a CPU (this configuration is not shown in the figure) and is provided, in addition to the CPU, with a ROM that stores a processing program, a RAM for temporarily storing data, input/output ports, and a communication port. The following signals are inputted into the HVECU  70  via the input port: a connection detection signal from a connection detection sensor  69  that detects the connection of the electric power supply plug  68  to the external electric power supply, an ignition signal from an ignition switch  80 , a shift position SP from a shift position sensor  82  that detects the operation position of a shift lever  81 , an accelerator depression amount Acc from an accelerator pedal position sensor  84  that detects the depression amount of an accelerator pedal  83 , a brake pedal position BP from a brake pedal position sensor  86  that detects the depression amount of a brake pedal  85 , a vehicle speed V from a vehicle speed sensor  88 , and an ON/OFF signal from a fuel economy heating mode switch  89  that allows the user to indicate a fuel economy heating mode in which heating is forcibly performed with the heater  58  using the engine  22  as a heat source. The HVECU  70  outputs, via the output port, a control signal to the electric heat source  56 , a control signal to the heater  58 , and a display signal to the display unit  90  that displays various types of information. As mentioned hereinabove, the HVECU  70  is connected via the communication port to the engine ECU  24 , motor ECU  40 , and battery ECU  52  and exchanges various control signals and data with the engine ECU  24 , motor ECU  40 , and battery ECU  52 . 
         [0025]    In the HV  20  of the embodiment according to the invention, a required torque Tr* that should be outputted to the drive axle  36  is calculated on the basis of the vehicle speed V and the accelerator depression mount Acc corresponding to the amount of depression of the accelerator pedal by the driver. The drive control of the engine  22  and the motors MG 1 , MG 2  is performed such that the required power corresponding to the required torque Tr* is outputted to the drive axle  36 . The drive control of the engine  22  and the motors MG 1 , MG 2  can be performed in a torque conversion drive mode, a charge-discharge drive mode, and a motor drive mode. &lt;Torque conversion drive mode&gt; In this drive mode, the drive control of the engine  22  is performed such that the mechanical power matching the required power is outputted from the engine  22 , and the drive control of the motor MG 1  and the motor MG 2  is performed such that the entire mechanical power outputted from the engine  22  is subjected to torque conversion by the planetary gear  30 , the motor MG 1 , and the motor MG 2 , and the torque-converted power is outputted to the drive axle  36 . &lt;Charge-discharge drive mode&gt; In this drive mode, the drive control of the engine  22  is performed such that the mechanical power matching a sum of the required power and the electric power necessary for charging and discharging the battery  50  is outputted from the engine  22 . Further, the drive control of the motor MG 1  and the motor MG 2  is performed such that the required power is outputted to the drive axle  36  as the battery  50  is charged and discharged and also as the entire mechanical power outputted from the engine  22  or part of the outputted mechanical power is subjected to torque conversion by the planetary gear  30 , the motor MG 1 , and the motor MG 2 . &lt;Motor drive mode&gt; The drive control is performed such that the drive of the engine  22  is stopped and the power matching the required power from the motor MG 2  is outputted to the drive axle  36 . Further, both in the torque conversion drive mode and in the charge-discharge drive mode, the engine  22 , the motor MG 1 , and the motor MG 2  are controlled such that the required power is outputted to the drive axle  36  as the engine  22  is driven, and the two control modes are not substantially different from each other. Accordingly, the two modes will be together referred to hereinbelow as an engine drive mode. 
         [0026]    In the engine drive mode, the HVECU  70  sets the required torque Tr* which is required for traveling (should be outputted to the drive axle  36 ) on the basis of the accelerator depression amount Acc from the accelerator pedal position sensor  84  and the vehicle speed V from the vehicle speed sensor  88 . Traveling power Pdrv*, which is required for traveling, is then calculated by multiplying the required torque Tr*, which has been set, by the revolution speed Nr (for example, a revolution speed Nm 2  of the motor MG 2  or the revolution speed obtained by multiplying the vehicle speed V by a recalculation factor) of the drive axle  36 . Required power Pe*, which is required for the vehicle (should be outputted from the engine  22 ) is then set by subtracting charge-discharge required power Pb* (a positive value when the battery  50  is discharged) of the battery  50 , which is based on the power storage ratio SOC of the battery  50 , from the calculated traveling power Pdrv*. A target revolution speed Ne* and a target torque Te* of the engine  22  are then set by using an operation line (for example, a fuel economy optimum operation line) as a relationship between the revolution speed Ne and torque Te of the engine  22  at which the required power Pe* can be efficiently outputted from the engine  22 . A drive point constituted by the target revolution speed Ne* and target torque Te* based on the required power Pe* and operation line is referred to hereinbelow as a fuel economy drive point. A torque command Tm 1 *of the motor MG 1  is then set by revolution speed feedback control such that the revolution speed Ne of the engine  22  becomes the target revolution speed Ne* within the range of the input/output limits Win, Wout of the battery  50 . Also, a torque command Tm 2 * of the motor MG 2  is set by subtracting a torque acting upon the drive axle  36  via the planetary gear  30  when the motor MG 1  is driven according to the torque command Tm 1 * from the required torque Tr*. The target revolution speed Ne* and target torque Te*, which have been set, are transmitted to the engine ECU  24 , and the torque commands Tm 1 ,*, Tm 2 * are transmitted to the motor ECU  40 . The engine ECU  24  that has received the target revolution speed Ne* and target torque Te* performs the intake air amount control, fuel injection control, and ignition control of the engine  22  such that the engine  22  is driven at the target revolution speed Ne* and target torque Te*. The motor ECU  40  that has received the torque commands Tm 1 *, Tm 2 * performs switching control of the switching elements of the inverters  41 ,  42  such that the motors MG 1 , MG 2  are driven according to the torque commands Tm 1 *, Tm 2 *. Because of such control, the required torque Tr* can be outputted to the drive axle  36  to run the vehicle within the range of input/output limits Win, Wout of the battery  50 , while the engine  22  is driven with good efficiency. In the engine drive mode, when the stopping condition of the engine  22 , such as the condition of the required power Pe* of the engine  22  getting equal to or lower than a stop threshold Pstop, is fulfilled the drive of the engine  22  is stopped and a transition is made to the motor drive mode. The stop threshold Pstop is set as the upper limit of the range of the required power Pe* in which it is better to stop the drive of the engine  22 . 
         [0027]    In the motor drive mode, the HVECU  70  sets the required torque Tr* on the basis of the accelerator depression amount Acc and vehicle speed V and sets a value 0 for the torque command Tm 1 * of the motor MG 1 . Further, the torque command Tm 2 * of the motor MG 2  is set such that the required torque Tr* is outputted to the drive axle  36  within the range of input/output limits Win, Wout of the battery  50 , and the torque command that has been set is transmitted to the motor ECU  40 . The motor ECU  40  that has received the torque commands Tm 1 *, Tm 2 * performs switching control of the switching elements of the inverters  41 ,  42  such that the motors MG 1 , MG 2  are driven according to the torque commands Tm 1 *, Tm 2 *. Because of such control, the required torque Tr* can be outputted to the drive axle  36  to run the vehicle within the range of input/output limits Win, Wout of the battery  50  in a state in which the drive of the engine  22  is stopped. In such a motor drive mode, the required power Pe* of the engine  22  is calculated that is obtained by subtracting the charge-discharge required power Pb* of the battery  50  from the traveling power Prdrv* obtained by multiplying the required torque Tr* by the revolution speed Nr of the drive axle  36 . Further, the condition of the required power Pe* getting equal to or higher than a start threshold Pstart, which has been set as the lower limit of the range of the required power Pe* in which it is better to start the engine  22 , is established as the starting condition for the engine  22 . When such starting condition for the engine  22  is fulfilled, the engine  22  is started and a transition is made to the engine drive mode. 
         [0028]    In the HV  20  of the embodiment of the invention, where an actuation request signal is received from the heater  58 , heating inside the HV cabin is performed using the engine  22  or the electric heat source  56  as a heat source. In the embodiment, when the engine  22  is driven, a revolution speed Neh 1  (for example, 1200 rpm or 1300 rpm) that has been set to check the heating performance of the heater  58  when the engine  22  is used as a heat source is set as a heating target revolution speed Neh of the engine  22 . In this case, the engine  22  is driven when the HV travels in the engine drive mode or when the HV travels using power from the motor MG 2  while the engine  22  is warmed up (autonomous drive). The engine  22  is controlled such that the engine  22  is driven at a revolution speed equal to or higher than the heating target revolution speed Neh. Thus, when the HV travels in the engine drive mode, the engine  22  is driven at the fuel economy drive point or a drive point that has shifted from the fuel economy drive point. When the engine  22  is warmed up, the engine  22  is warmed up (autonomous drive) at the heating target revolution speed Neh. When the HV travels while the engine  22  is being warmed up, a temperature Twend 1  (for example, 40° C. or 50° C.) is set as a warm-up end water temperature Twend. It is assumed that when the cooling water temperature Tw of the engine  22  becomes equal to or higher than the warm-up end water temperature Twend, the engine  22  is stopped and a transition is made to the motor drive mode. When the HV travels in the motor drive mode, the electric heat source  56  is controlled to check the heating performance of the heater  58  using the electric heat source  56  as a heat source. 
         [0029]    The operation of the HV  20  of the embodiment according to the invention, in particular the control of the heater  58  performed when the fuel for the engine  22  has degraded is explained below.  FIG. 2  is a flowchart illustrating an example of a processing routine executed by the HVECU  70  of the embodiment when the fuel has degraded. This routine is executed when HVECU  70  determines that the fuel for the engine  22  is degraded when the engine  22  is stopped. Whether or not the fuel for the engine  22  has degraded can be determined, for example, on the basis of whether or not a predetermined period of time (for example, several months to about one year) has passed since the previous refueling. In the HV  20  of the embodiment, the battery  50  can be charged using electric power from an external electric power source such as a household electric power source. Therefore, when the HV is driven only short distances within the range of the electric power charged to the battery  50  (short-distance running and charging of the battery  50  are repeated), the fuel in the fuel tank  21  is not consumed for a comparatively long period and the fuel can degrade. Such a state is assumed in the embodiment. 
         [0030]    Where the fuel degradation processing routine is executed, the HVECU  70  initially displays on the display unit  90  a message prompting to switch on the fuel economy heating mode switch  89  (step S 100 ), and waits till the user switches on the fuel economy heating mode switch  89  (step S 110 ). 
         [0031]    Where the fuel economy heating mode switch  89  is switched on by the user, it is determined to actuate forcibly the heating with the heater  58  (step S 120 ) and the engine  22  is started, thereby switching (selecting) the heat source of the heater  58  from the electric heat source  56  to the engine  22  (step S 130 ). As a result, the consumption of the fuel (degraded fuel) in the fuel tank  21  can be enhanced. Further, the consumption of electric power from the battery  50  on the heating with the heater  58  can be inhibited. 
         [0032]    Then, a revolution speed Neh 2 , for degraded fuel, (for example, 1500 rpm or 1600 rpm) that is higher than the aforementioned revolution speed Neh 1 , for undegraded fuel, (for example, 1200 rpm or 1300 rpm) is set (step S 140 ) as the heating target revolution speed Neh of the engine  22  and a temperature Twend 2  (for example, 70° C. or 80° C.) that is higher than the aforementioned temperature Twend 1  (for example, 40° C. or 50° C.) is set (step S 150 ) as the warm-up end water temperature Twend, thereby ending the routine. The increase in the warm-up end water temperature Twend (setting the temperature Twend 2  for degraded fuel which is higher than the temperature Twend 1  for undegraded fuel) means that the warm-up time of the engine  22  is extended. 
         [0033]    Where the heating target revolution speed Neh and the warm-up end water temperature Twend of the engine  22  are thus set, when the cooling water temperature Tw of the engine  22  is lower than the warm-up end water temperature Twend, the engine  22  is warmed up (autonomously driven) at the heating target revolution speed Neh. When the cooling water temperature Tw of the engine  22  is equal to or higher than the warm-up end water temperature Twend, the engine  22  is controlled such that the engine  22  is stopped. As a result, heating with the heater  58  is forcibly performed by using the cooling water of the engine  22  as a heat source. When the engine  22  is warmed up, the revolution speed Ne of the engine  22  is increased (to the revolution speed Neh 2  for degraded fuel which is higher than the revolution speed Neh 1  for undegraded fuel), the warm-up end water temperature Twend of the engine  22  is increased (to the temperature Twend 2  for degraded which is higher than the temperature Twend 1  for undegraded) and the warm-up time is extended, thereby making it possible to enhance further the consumption of the fuel (degraded fuel) in the fuel tank  21  and increase the heating performance of the heater  58 . 
         [0034]    With the HV  20  of the above-described embodiment of the invention, where the degradation of the fuel for the engine  22  is detected when the drive of the engine  22  is stopped, the engine  22  is started and the heat source of the heater  58  is switched from the electric heat source  56  to the engine  22 . Therefore, the consumption of the fuel (degraded fuel) in the fuel tank  21  can be enhanced. Furthermore, when the fuel for the engine  22  is degraded, the revolution speed Neh 2  and the temperature Twend 2 , which are higher than the revolution speed Neh 1  and the temperature Twend 1  that are set when the fuel for the engine  22  is not degraded, are set as the heating target revolution speed Neh and warm-up end water temperature Twend of the engine  22 , and the control is performed such that the engine  22  is warmed up at the heating target revolution speed Neh till the cooling water temperature Tw of the engine  22  becomes equal to or higher than the warm-up end water temperature Twend. As a result, it is possible to enhance further the consumption of the fuel (degraded fuel) in the fuel tank  21  and increase the heating performance of the heater  58 . 
         [0035]    Further, in the HV  20  of the above-described embodiment of the invention, when the fuel for the engine  22  has degraded, the revolution speed Neh 2  and temperature Twend 2 , which are higher than the revolution speed Neh 1  and temperature Twend  1  that are set when the fuel for the engine  22  is not degraded, are set as the heating target revolution speed Neh and warm-up end water temperature Twend of the engine  22 . Alternatively, the revolution speed Neh 2 , which is higher than the revolution speed Neh 1  that is set when the fuel for the engine  22  is not degraded, may be set as the heating target revolution speed Neh of the engine  22 , but the temperature Twend 1  equal to that set when the fuel for the engine  22  is not degraded may be set as the warm-up end water temperature Twend. Further, the temperature Twend 2 , which is higher than the temperature Twend 1  that is set when the fuel for the engine  22  is not degraded, may be set at the warm-up end water temperature Twend of the engine  22 , but the revolution speed Neh 1  equal to that set when the fuel for the engine  22  is not degraded may be set as the heating target revolution speed Neh of the engine  22 . 
         [0036]    In the HV  20  of the above-described embodiment, where it is determined that the fuel for the engine  22  has degraded when the engine  22  is stopped, the engine  22  is started, thereby switching the heat source of the heater  58  from the electric heat source  56  to the engine  22 , and the revolution speed Neh 2  and temperature Twend 2 , which are higher than the revolution speed Neh 1  and temperature Twend 1  that are set when the fuel for the engine  22  is not degraded, are set as the heating target revolution speed Neh and warm-up end water temperature Twend of the engine  22 . Alternatively, the heat source of the heater  58  may be switched from the electric heat source  56  to the engine  22  to cause forcible heating. For example, the revolution speed Neh 1  and temperature Twend 1  equal to those set when the fuel for the engine  22  is not degraded may be set as the heating target revolution speed Neh and warm-up end water temperature Twend of the engine  22 . 
         [0037]    In the HV  20  of the above-described embodiment, where it is determined that the fuel for the engine  22  has degraded when the engine  22  is stopped, the engine  22  is immediately started, thereby switching the heat source of the heater  58  from the electric heat source  56  to the engine  22 . Alternatively, when it is indicated that preheating is to be performed for heating the inside of the HV in advance, that is, before the vehicle runs, after the degradation of the fuel for the engine  22  has been determined, the heat source of the heater  58  may be switched to the engine  22  by starting the engine  22 . In this case, the consumption of the fuel (degraded fuel) in the fuel tank  21  can be enhanced when the preheating is executed. In the preheating performed in such a case, the revolution speed Neh 2  and temperature Twend 2 , which are higher than the revolution speed Neh 1  and temperature Twend 1  that are set when the fuel for the engine  22  is not degraded, may be set as the heating target revolution speed Neh and warm-up end water temperature Twend of the engine  22 . Further, the revolution speed Neh 2 , which is higher than the revolution speed Neh 1  that is set when the fuel for the engine  22  is not degraded, may be set as the heating target revolution speed Neh of the engine  22 , but the temperature Twend 1  same as that set when the fuel for the engine  22  is not degraded may be set as the warm-up end water temperature Twend. Alternatively, the temperature Twend 2 , which is higher than the temperature Twend 1  that is set when the fuel for the engine  22  is not degraded, may be set as the warm-up end water temperature Twend of the engine  22 , but the revolution speed Neh 1  same as that set when the fuel for the engine  22  is not degraded may be set as the heating target revolution speed Neh of the engine  22 . Alternatively, the revolution speed Neh 1  and temperature Twend 1  same as those set when the fuel for the engine  22  is not degraded may be set as the heating target revolution speed Neh and the warm-up end water temperature Twend of the engine  22 . 
         [0038]    In the HV  20  of the embodiment of the invention, the power from the motor MG 2  is outputted to the drive axle  36  connected to the drive wheels  38   a ,  38   b . Alternatively, the power from the motor MG 2  may be outputted to an axle (axle connected to wheels  39   a ,  39   b  in  FIG. 3 ) other than the axle (axle connected to the drive wheels  38   a ,  38   b ) connected to the drive axle  36 , as exemplified by a HV  120  of the variation example shown in  FIG. 3 . 
         [0039]    In the HV  20  of the embodiment of the invention, the power from the engine  22  is outputted via the planetary gear  30  to the drive axle  36  connected to the drive wheels  38   a ,  38   b . Alternatively, a twin-rotor electric motor  230  may be provided which has an inner rotor  232  connected to the crankshaft of the engine  22  and an outer rotor  234  connected to the drive axle  36  connected to the drive wheels  38   a ,  38   b  and which transfers part of the mechanical power from the engine  22  to the drive axle  36  and converts the remaining mechanical power into electric power, as exemplified by a HV  220  of the variation example shown in  FIG. 4 . 
         [0040]    In the HV  20  of the embodiment of the invention, the power from the engine  22  is outputted via the planetary gear  30  to the drive axle  36  connected to the drive wheels  38   a ,  38   b , and the power from the motor MG 2  is also outputted to the drive axle  36 . Alternatively, the configuration may be used in which a motor MG is attached by a transmission  330  to the drive axle  36  connected to the drive wheels  38   a ,  38   b , and the engine  22  is connected by a clutch  329  to the rotating shaft of the motor MG, as exemplified by a HV  320  of the variation example shown in  FIG. 5 . With such a configuration, the power from the engine  22  may be outputted to the drive axle  36  via the rotating shaft of the motor MG and the transmission  330 , and the power from the motor MG may be outputted to the drive axle via the transmission  330 . 
         [0041]    The correspondence relationship between the main elements in the embodiment of the invention and the main elements of the invention that are set forth in the claims is explained below. The “engine  22 ” in the embodiment of the invention corresponds to the “engine” in the claims. The “motor MG 2 ” in the embodiment of the invention corresponds to the “motor” in the claims. The “electric heat source  56 ” in the embodiment of the invention corresponds to the “electric heat source” in the claims. The “heater  58 ” in the embodiment of the invention corresponds to the “heater” in the claims. The “HVECU  70 ” in the embodiment of the invention corresponds to the “controller” in the claims. 
         [0042]    The correspondence relationship between the main elements in the embodiment of the invention and the main elements of the invention that are set forth in the claims is merely an example for explaining a specific mode for carrying out the invention described in the claims. Therefore, no limitation is placed on the elements of the invention described in the claims. Thus, the invention described in the claims should be interpreted on the basis of the description thereof, and the embodiment is merely a specific example of the invention described in the claims. 
         [0043]    The mode for carrying out the invention is explained hereinabove by using the embodiment, but the invention is obviously not limited to the embodiment and can be implemented in a variety of forms without departing from the essence of the invention. 
         [0044]    The invention can be used in manufacturing industry of HVs.