Abstract:
To carry out a start with good fuel economy without resulting in a power shortage or a forcefulness shortage. A hybrid automobile is structured which executes a start control method including a selection step of selecting one start method from among a start only by a motor, a start only by an engine, and a start by the motor and the engine in cooperation with each other and a control step of controlling the execution of the start by the start method selected.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of application No. PCT/JP2011/074161, filed on Oct. 20, 2011. Priority under 35 U.S.C. §119(a) and 35 U.S.C. §365(b) is claimed from Japanese Patent Application No. 2010-236608, filed on Oct. 21, 2010, the disclosure of which are also incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a start control method, a start control device, a hybrid vehicle, and a computer program. 
     BACKGROUND ART 
     A hybrid vehicle includes an engine and an electric motor. The hybrid vehicle can run by using the engine or the electric motor, or by using the engine and the electric motor in cooperation with each other. The hybrid vehicle described above starts by using the electric motor, and, when the vehicle reaches a certain speed, it runs with the engine instead of the electric motor. Exhaust gas emitted from the engine upon the start can be reduced. Thus, the fuel economy can be enhanced (see, for example, patent literature PTL1). 
     CITATION LIST 
     Patent Literature 
     PTL1: JP 2006-132448 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     As described above, the hybrid vehicle has an effect of reducing exhaust gas and fuel economy by using the electric motor upon the start. Conventionally, there are hybrid vehicles that can always start with the electric motor, so long as a battery can feed electric power to the electric motor. 
     The conventional hybrid vehicle starts by using the electric motor, if the battery can feed electric power to the electric motor, although the charged level is low. However, in this case, electric power becomes insufficient just after the start of the vehicle, and the electric motor cannot output required traction force. Therefore, a driver might feel a lack of power, or the vehicle might slow down. In addition, after the vehicle starts with the lack of electric power as described above, electric power for assisting the engine becomes also insufficient, so that a satisfactory effect of enhancing fuel economy cannot be attained. 
     The present invention is accomplished in view of the circumstance described above, and aims to provide a start control method, a start control device, a hybrid vehicle, and a computer program that can make the hybrid vehicle start with excellent fuel economy without a lack of electric power and lack of power. 
     Solution to Problem 
     One aspect of the present invention is directed to a start control method. The start control method in a start control device controlling a start of a hybrid vehicle that includes an engine, an electric motor, and a battery supplying electric power to the electric motor, and that can run by using the engine, by using the electric motor, or by using the engine and the electric motor in cooperation with each other, the start control method includes: a selecting step of selecting any one of starting modes, which are a starting mode using only the electric motor, a starting mode using only the engine, and a starting mode using the electric motor and the engine in cooperation with each other, according to a predetermined condition of the battery; and a control step of controlling the execution of the start in accordance with the selected starting mode. 
     For example, the predetermined condition is a condition involved with a charged state of the battery, a condition involved with a temperature of the battery, and a condition involved with both the charged state of the battery and the temperature of the battery. 
     The start control method may further includes a step of observing a change in the charged state or the temperature of the battery, wherein a reference point for the determination when the observation result is on the point of the process where the situation is changed from the situation in which the starting mode using only the electric motor is allowed to the situation in which the same starting mode is not allowed, and a reference point for the determination when the observation result is on the point of the process where the situation is changed from the situation in which the starting mode using only the electric motor is not allowed to the situation in which the same starting mode is allowed, are set to be different from each other. 
     Further, a state of a rising slope of a road surface where the hybrid vehicle starts may be added as the condition in addition to the predetermined condition, and the starting mode using only the electric motor may not be allowed, when a value indicating the rising slope exceeds a predetermined value even if the starting mode using only the electric motor is allowed according to the determination result in the process of the first step. 
     Another aspect of the present invention is directed to a start control device. The start control device includes a start control unit that executes the start control method according to the aspect of the present invention. 
     Still another aspect of the present invention is directed to a hybrid vehicle. The hybrid vehicle includes the start control device according to the aspect of the present invention. 
     The other aspect of the present invention is directed to a computer program. The computer program causes an information processing apparatus to implement a function of the start control device according to the aspect of the present invention. 
     Advantageous Effects of Invention 
     According to the present invention, the vehicle can start with excellent fuel economy without a lack of electric power and a lack of power. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating an example of a configuration of a hybrid vehicle according to a first embodiment of the present invention. 
         FIG. 2  is a block diagram illustrating an example of a configuration of functions realized by a hybrid ECU in  FIG. 1 . 
         FIG. 3  is a flowchart illustrating a start control process in a start control unit in  FIG. 2 . 
         FIG. 4  is a view illustrating a changeover determination reference point for a start control method in the start control by the start control unit in  FIG. 2 . 
         FIG. 5  is a block diagram illustrating an example of a configuration of a hybrid vehicle according to a second embodiment of the present invention. 
         FIG. 6  is a block diagram illustrating an example of a configuration of functions realized by a hybrid ECU in  FIG. 5 . 
         FIG. 7  is a flowchart illustrating a start control process in a start control unit according to the second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     A hybrid vehicle according to a first embodiment of the present invention will be described below with reference to  FIGS. 1 to 4 . 
       FIG. 1  is a block diagram illustrating an example of a configuration of a hybrid vehicle  1 . The hybrid vehicle  1  is one example of vehicles. The hybrid vehicle  1  is driven by an engine (internal combustion engine)  10  and/or an electric motor  13  through a transmission that is a semiautomatic transmission. At least staring, the hybrid vehicle  1  starts under one of starting modes including a starting mode using only the electric motor  13 , a starting mode using only the engine  10 , and a starting mode using the electric motor  13  and the engine  10  in cooperation with each other, selected according to at least a state of charge (hereinafter referred to as SOC) of the battery  15 . The semiautomatic transmission has a configuration same as a manual transmission, but can realize an automatic shift operation. 
     The hybrid vehicle  1  includes an engine  10 , an engine ECU (Electronic Control Unit)  11 , a clutch  12 , an electric motor  13 , an inverter  14 , a battery  15 , a transmission  16 , a motor ECU  17 , a hybrid ECU  18 , a wheel  19 , a key switch  20 , and a shift unit  21 . The transmission  16  has the above-mentioned semiautomatic transmission, and is operated by the shift unit  21  having a drive range (hereinafter referred to as D (Drive) range). 
     The engine  10  is one example of the internal combustion engine. It is controlled by the engine ECU  11  to burn gasoline, light gas oil, CNG (Compressed Natural Gas), LPG (Liquefied Petroleum Gas), or alternate fuel therein, thereby generating power for rotating a shaft. It then transmits the generated power to the clutch  12 . 
     The engine ECU  11  is a computer that works in conjunction with the motor ECU  17  in accordance with an instruction from the hybrid ECU  18 . It controls the engine  10 , i.e., controls the fuel injection amount or valve timing. For example, the engine ECU  11  is composed of a CPU (Central Processing Unit), ASIC (Application Specific Integrated Circuit), microprocessor (microcomputer), and DSP (Digital Signal Processor), and includes an operation unit, a memory, and an I/O (Input/Output) port. 
     The clutch  12  is controlled by the hybrid ECU  18 , and transmits a shaft output from the engine  10  to the wheel  19  via the electric motor  13  and the transmission  16 . Specifically, the clutch  12  mechanically connects the rotation shaft of the engine  10  and the rotation shaft of the electric motor  13  to transmit the shaft output of the engine  10  to the electric motor  13 , or cuts the mechanical connection between the rotation shaft of the engine  10  and the rotation shaft of the electric motor  13  to allow the rotation shaft of the engine  10  and the rotation shaft of the electric motor  13  to rotate with a different rotational speed, under the control of the hybrid ECU  18 . 
     For example, the clutch  12  mechanically connects the rotation shaft of the engine  10  and the rotation shaft of the electric motor  13 , when the hybrid vehicle  1  runs by the power from the engine  10 , by which the electric motor  13  generates electric power; when the engine  10  is assisted by the driving force of the electric motor  13 ; and when the engine  10  is started by the electric motor  13 . 
     For example, the clutch  12  cuts the mechanical connection between the rotation shaft of the engine  10  and the rotation shaft of the electric motor  13 , when the engine  10  is stopped or in an idling condition, and the hybrid vehicle  1  runs with the driving force of the electric motor  13 , or when the engine  10  is stopped or in an idling condition, the hybrid vehicle  1  reduces its speed, or runs on a downhill, and the electric motor  13  generates electric power (regenerates electric power). 
     The clutch  12  is different from a clutch that is operated by the driver&#39;s operation on a clutch pedal, and it is operated by the control of the hybrid ECU  18 . 
     The electric motor  13  is a so-called motor generator, and it generates power for rotating a shaft by electric power supplied from the inverter  14 , and supplies the shaft output to the transmission  16 . Alternatively, the electric motor  13  generates electric power by the power for rotating the shaft supplied from the transmission  16 , and supplies the electric power to the inverter  14 . When the hybrid vehicle  1  increases its speed, or runs with a constant speed, the electric motor  13  generates power for rotating the shaft, and supplies the shaft output to the transmission  16 , thereby allowing the hybrid vehicle  1  to run in cooperation with the engine  10 . For example, when the hybrid vehicle  1  runs without using power, such as in the case where the electric motor  13  is driven by the engine  10 , or in the case where the hybrid vehicle  1  reduces its speed or runs on a downhill, the electric motor  13  operates as a motor generator. In this case, the electric motor  13  generates electric power by the power for rotating the shaft supplied from the transmission  16 , and supplies the electric power to the inverter  14 , whereby the battery  15  is charged. 
     The inverter  14  is controlled by the motor ECU  17 , and it converts DC voltage from the battery  15  into AC voltage, or converts AC voltage from the electric motor  13  to DC voltage. When the electric motor  13  generates power, the inverter  14  converts the DC voltage from the battery  15  into AC voltage so as to supply the electric power to the electric motor  13 . When the electric motor  13  generates electric power, the inverter  14  converts the AC voltage from the electric motor  13  into DC voltage. Specifically, in this case, the inverter  14  functions as a rectifier or a voltage regulation device for feeding DC voltage to the battery  15 . 
     The battery  15  is a chargeable secondary battery. It feeds electric power to the electric motor  13  through the inverter  14  when the electric motor  13  generates power, or it is charged by the electric power generated from the electric motor  13  when the electric motor  13  generates electric power. 
     The transmission  16  has a semiautomatic transmission (not illustrated in the drawings) for selecting any one of plural gear ratios (transmission gear ratios) in accordance with a instruction signal to shift from the hybrid ECU  18 . It changes the transmission gear ratio, and transmits the shifted power of the engine  10  and/or the shifted power of the electric motor  13  to the wheel  19 . When the vehicle reduces its speed, or runs on the downhill, the transmission  16  transmits power from the wheel  19  to the electric motor  13 . In the semiautomatic transmission, the driver can manually change the gear position to an arbitrary gear number by operating the shift unit  21 . 
     The motor ECU  17  is a computer that works in conjunction with the engine ECU  11  in accordance with an instruction from the hybrid ECU  18 . It controls the electric motor  13  by controlling the inverter  14 . For example, the motor ECU  17  is composed of a CPU, ASIC, microprocessor (microcomputer), and DSP, and includes an operation unit, a memory, and an I/O port. 
     The hybrid ECU  18  is one example of a computer. It acquires accelerator opening information, brake operation information, vehicle speed information, gear position information acquired from the transmission  16 , and engine rotational speed information acquired from the engine ECU  11 , and controls the clutch  12  as well as supplies the instruction signal to shift to control the transmission  16  by referring to the acquired information. The hybrid ECU  18  issues an instruction to the motor ECU  17  to control the electric motor  13  and the inverter  14 , and issues an instruction to the engine ECU  11  to control the engine  10 , in order to realize a hybrid driving. In order to realize the hybrid driving, the hybrid ECU  18  acquires SOC information and temperature information from the battery  15 , and controls the engine ECU  11 , the clutch  12 , and the motor ECU  17 , thereby executing the start control. For example, the hybrid ECU  18  is composed of a CPU, ASIC, microprocessor (microcomputer), and DSP, and includes an operation unit, a memory, and an I/O port. 
     A computer program to be executed by the hybrid ECU  18  can preliminarily be installed to the hybrid ECU  18  that is a computer by storing the computer program beforehand into a non-volatile memory in the hybrid ECU  18 . 
     The engine ECU  11 , the motor ECU  17 , and the hybrid ECU  18  are interconnected with a bus in accordance with a standard such as CAN (Control Area Network). 
     The wheel  19  is a driving wheel that transmits driving force to a road surface. Although  FIG. 1  illustrates only one wheel  19 , the hybrid vehicle  1  actually includes plural wheels  19 . 
     The key switch  20  is turned ON or OFF by a driver who inserts a key into the key switch  20  upon starting the vehicle  1 . When the key switch  20  is turned ON, the respective units of the hybrid vehicle  1  are started, and when the key switch  20  is turned OFF, the respective units of the hybrid vehicle  1  are stopped. 
       FIG. 2  is a block diagram illustrating an example of a configuration of functions realized by the hybrid ECU  18  that executes a computer program. When the hybrid ECU  18  executes the computer program, a start control unit  30  and an observation data storage unit  31  are realized. 
     The start control unit  30  issues a start control instruction to the engine ECU  11 , the clutch  12 , and the motor ECU  14  based upon the SOC information and temperature information of the battery  15 . 
     A part of a memory area of the hybrid ECU  18  is allocated to the observation data storage unit  31 , and it stores the SOC information and the temperature information of the battery  15  for a certain period. 
     A process of the start control executed by the hybrid ECU  18 , which performs the computer program, will be described with reference to a flowchart in  FIG. 3 . The flowchart in  FIG. 3  corresponds to a process of one cycle, and it is supposed that the process is repeatedly executed, so long as the key switch  20  is turned ON. 
     The process described below is started, when the hybrid vehicle  1  is stopped with the accelerator not being turned ON (i.e., with the accelerator not being operated, i.e., not being depressed), in a state in which the key switch  20  is turned ON, the hybrid ECU  18  executes the computer program, and the hybrid ECU  18  realizes the start control unit  30 . 
     In step S 1 , the start control unit  30  determines whether the SOC and the temperature of the battery  15  are satisfactory or not. When it is determined that the SOC and the temperature of the battery  15  are not satisfactory in step S 1 , the process proceeds to step S 2 . On the other hand, when it is determined in step S 1  that the SOC and the temperature of the battery  15  are satisfactory, the process proceeds to step S 7 . 
     The condition that the SOC and the temperature of the battery  15  are satisfactory means the condition in which the SOC is higher than SOC (hereinafter referred to as SOC threshold value) that can feed electric power, by which torque necessary for starting the vehicle can be generated, to the electric motor  13 , and the temperature is lower than a certain temperature (hereinafter referred to as a temperature threshold value). On the other hand, the condition in which the SOC of the battery  15  is higher than the SOC threshold value, but the temperature is higher than the temperature threshold value, the condition in which the SOC of the battery  15  is lower than the SOC threshold value and the temperature is higher than the temperature threshold value, and the condition in which the SOC of the battery  15  is lower than the SOC threshold value and the temperature is lower than the temperature threshold value, are all unsatisfactory conditions. The reason why the temperature of the battery  15  is also determined is because, when the temperature of the battery  15  is high, electric power cannot be inputted and outputted due to the performance of the battery  15 , so that electric power corresponding to the SOC cannot be fed to the electric motor  13 , even if the SOC is satisfactory. 
     In step S 2 , the start control unit  30  determines whether the accelerator operation is applied or not. When it is determined that the accelerator operation is applied (accelerator ON: the operation of depressing the accelerator pedal is executed), the process proceeds to step S 3 . On the other hand, it is determined in step S 2  that the accelerator operation is not applied, the process returns to step S 1 . 
     In step S 3 , the start control unit  30  starts a process of engaging the clutch  12 . 
     Then, in step S 4 , the start control unit  30  determines whether the SOC and the temperature of the battery  15  are satisfactory or not. When it is determined in step S 4  that the SOC and the temperature of the battery  15  are not satisfactory, the process proceeds to step S 5 . On the other hand, when it is determined in step S 4  that the SOC and the temperature of the battery  15  are satisfactory, the process proceeds to step S 6 . 
     The criteria for determining the SOC and the temperature of the battery  15  in step S 4  are the criteria for determining whether assist driving is possible or not, and it may be looser (lower) than the criteria for determining whether driving of the electric motor  13  only is possible or not in step S 1 . As for the SOC, the criterion in step S 4  is set to be lower than the criterion in step S 1 . As for the temperature, the criterion in step S 4  is set to be higher than the criterion in step S 1 . 
     In step S 5 , the start control unit  30  starts to execute the starting mode using the engine  10 . Thus, the rotational speed of the engine  10  is increased to the rotational speed by which torque necessary for starting the vehicle can be output, and power from the engine  10  is transmitted to the wheel  19  through the clutch  12 . In this case, the electric motor  13  may control to execute regeneration in order to increase the SOC of the battery  15 , or the electric motor  13  may be free in order not to apply friction loss to the engine  10 . 
     In step S 6 , the start control unit  30  starts the assist starting mode in which the vehicle is started by using the engine  10  in cooperation with the electric motor  13 . With this process, the rotational speed of the electric motor  13  is increased to the rotational speed of the engine  10  (the rotational speed in the idling state), and power of the engine  10  and the electric motor  13  is transmitted to the wheel  19 . 
     In step S 7 , the start control unit  30  determines whether the accelerator operation is applied or not. When it is determined that the accelerator operation is applied (accelerator ON), the process proceeds to step S 8 . On the other hand, when it is determined in step S 7  that the accelerator operation is not applied, the process returns to step S 1 . 
     In step S 8 , the start control unit  30  disengages the clutch  12 , and then, the process proceeds to step S 9 . 
     In step S 9 , the start control unit  30  starts the starting mode by using the electric motor  13 . 
     When the process in step S 5 , step S 6 , or step S 9  is executed, the process for one cycle of the starting mode is finished, and the above-mentioned process is repeatedly executed for a predetermined period, for example. 
     Subsequently, a changeover determination reference point for a start control method in the start control by the start control unit  30  will be described with reference to  FIG. 4 . When acquiring the SOC information or the temperature information of the battery  15 , the start control unit  30  stores the acquired information into the observation data storage unit  31 . The start control unit  30  confirms whether the SOC of the battery  15  changes from low SOC to high SOC, or vice versa, and also confirms whether the temperature of the battery  15  changes from high temperature to low temperature, or vice versa, by referring to the observation data storage unit  31 . Thus, the reference point for the determination by the start control unit  30  in step S 1  and step S 4  in the flowchart illustrated in  FIG. 3  is set to be a different point according to the direction of the change in the SOC or the temperature as illustrated in  FIG. 4 . In  FIG. 4 , only one of the SOC change or the temperature change may be focused. 
     Effect 
     The hybrid vehicle  1  determines whether or not it can start only by using the electric motor  13  according to the predetermined condition of the battery  15 . When it is determined that the vehicle  1  cannot start only by using the electric motor  13 , the vehicle  1  selects either one of the starting mode using only the engine  10  and the starting mode using the electric motor  13  and the engine  10  in cooperation with each other, according to the predetermined condition of the battery  15 . Therefore, the vehicle  1  can start with excellent fuel economy without a lack of electric power and a lack of power. 
     Specifically, even if the vehicle  1  cannot start only by using the electric motor  13 , the vehicle  1  can select not only the starting mode using only the engine  10 , but also the assist starting mode that has excellent fuel economy compared to the starting mode using only the engine  10 . Accordingly, starting with excellent fuel economy can be realized. 
     The temperature of the battery  15  is observed. Therefore, when sufficient electric power cannot be outputted even with the sufficient SOC, the starting mode using the engine is selected, whereby the vehicle  1  can appropriately start without a lack of power. 
     The SOC of the battery  15  temporarily reduces a little just after the battery  15  feeds electric power to the electric motor  13 . Similarly, the temperature of the battery  15  temporarily increases a little just after the battery  15  feeds electric power to the electric motor  13 . Since the SOC or the temperature of the battery  15  varies in a short period as described above, the situation in which the starting mode is again returned from the assist starting mode to the engine starting mode just after the starting mode is changed from the engine starting mode to the assist starting mode might be repeated (this is referred to as a mode hunting). According to this operation, unnecessary control is generated; for example, the control in which the clutch  12  is changed from the disengaged state to the engaged state is repeated in a short period, and the control in which the rotational speed of the engine  10  and the rotational speed of the electric motor  13  are synchronized is repeated in a short period. In order to avoid this situation, the assist starting mode may be controlled to be continued just after the starting mode is changed from the engine starting mode to the assist starting mode, even if the SOC or the temperature of the battery  15  slightly changes toward the engine starting mode. 
     In view of this, the change in the SOC or the temperature of the battery  15  is observed, and the reference point for the determination when the observation result is on the point of the process where the situation is changed from the situation in which the starting mode using the electric motor  13  is allowed to the situation in which the same starting mode is not allowed, and the reference point for the determination when the observation result is on the point of the process where the situation is changed from the situation in which the starting mode using the electric motor  13  is not allowed to the situation in which the same starting mode is allowed, are set to be different from each other. Thus, the start control unit  30  can execute a precise control without causing the mode hunting in the control by the start control unit  30  even under the situation in which the SOC or the temperature of the battery  15  varies in a short period. 
     Second Embodiment 
     A hybrid vehicle  1 A according to a second embodiment of the present invention will be described with reference to  FIGS. 5 to 7 . As illustrated in  FIG. 5 , the hybrid vehicle  1 A includes a slope sensor  22  in addition to the configuration of the hybrid vehicle  1  illustrated in  FIG. 1 . 
       FIG. 6  is a block diagram illustrating an example of a configuration of functions realized by a hybrid ECU  18 A that executes a computer program. When the hybrid ECU  18 A executes the computer program, a start control unit  30 A and an observation data storage unit  31  are realized. 
     The start control unit  30 A acquires not only the SOC information and temperature information of the battery  15 , which are acquired by the start control unit  30  in the first embodiment, but also slope information from the slope sensor  22 . 
     A process of a start control executed by the hybrid ECU  18 A, which performs the computer program, will be described with reference to a flowchart in  FIG. 7 . The flowchart in  FIG. 7  corresponds to a process of one cycle, and it is supposed that the process is repeatedly executed, so long as the key switch  20  is turned ON. In “START”, the hybrid vehicle  1 A is stationary. 
     In the processes in the flowchart in  FIG. 7 , the processes in steps S 1  to S 9  are the same as those in the flowchart in  FIG. 3 , so that the description will not be repeated. The process in step S 20  will mainly be described. 
     In step S 1 , the start control unit  30 A determines whether the SOC and the temperature of the battery  15  are satisfactory or not. When it is determined that the SOC and the temperature of the battery  15  are not satisfactory in step S 1 , the process proceeds to step S 2 . On the other hand, when it is determined in step S 1  that the SOC and the temperature of the battery  15  are satisfactory, the process proceeds to step S 20 . 
     In step S 20 , the start control unit  30 A determines whether or not a road on which the hybrid vehicle  1 A currently stops has a rising slope less than a predetermined value based upon the slope information acquired from the slope sensor  22 . The predetermined value here represents a slope index of the rising slope, and it is represented as “X %”, for example. The value of X is appropriately set according to a climbing ability of the electric motor  13  in the hybrid vehicle  1 A. When it is determined in step S 20  that the road on which the hybrid vehicle  1 A currently stops has the rising slope less than the predetermined value based upon the slope information acquired from the slope sensor  22 , the process proceeds to step S 7 . On the other hand, when it is determined in step S 20  that the road on which the hybrid vehicle  1 A currently stops has the rising slope equal to or more than the predetermined value based upon the slope information acquired from the slope sensor  22 , the process proceeds to step S 2 . 
     Effect 
     The hybrid vehicle  1 A not only determines whether it can start only by using the electric motor or not depending upon the SOC or temperature of the battery  15 , but also determines whether the vehicle can start only by using the electric motor depending upon the slope of the road on which the hybrid vehicle  1 A is stopping. Therefore, the hybrid vehicle  1 A can start with excellent fuel economy without a lack of electric power and a lack of power according to the road environment. Specifically, when the hybrid vehicle  1 A is stopping on an uphill, torque is required for the start. Therefore, upon the start of the hybrid vehicle  1 A stopping on the uphill, the hybrid vehicle  1 A selects the assist starting mode or the engine starting mode, even if the starting mode using only the electric motor  13  is allowed according to the SOC condition or the temperature condition of the battery  15 . Thus, the hybrid vehicle  1 A can start with excellent fuel economy without a lack of electric power and a lack of power. 
     Other Embodiments 
     In the description of the flowchart described above, the boundary for the determination region may be modified. For example, “equal to or more than” can be changed to “more than”, and “less than” can be changed to “not less than.” 
     Upon the determination of the state of the battery  15 , only the SOC of the battery  15 , or only the temperature of the battery  15  may be used. 
     It is described that the engine  10  is the internal combustion engine. However, the engine  10  may be a thermal engine including an external combustion engine. 
     The computer program executed by the hybrid ECUs  18  and  18 A is installed beforehand in the hybrid ECUs  18  and  18 A in the above description. However, a removable media on which the computer program is stored (that stores the computer program) may be attached to a drive not illustrated, and the computer program read from the removable media may be stored on the non-volatile memory in the hybrid ECUs  18  and  18 A, or the computer program sent via a wired or wireless transfer medium may be received by a communication unit not illustrated, and stored in the non-volatile memory in the hybrid ECUs  18  and  18 A, whereby the computer program may be installed to the hybrid ECUs  18  and  18 A that are a computer. 
     The respective ECUs may be realized by an ECU having some of these functions or all of these functions. Alternatively, an ECU having classified functions of each ECU may newly be provided. 
     The computer program executed by the computer may be a computer program by which the process is executed in a time-series manner according to the order described in the present specification, or may be a computer program by which the process is executed simultaneously, or on a necessary timing when called. 
     The embodiment of the present invention is not limited to the above-mentioned embodiment, and various modifications are possible without departing from the scope of the present invention. 
     In the embodiments described above, the determination is made based upon the SOC and the temperature of the battery  15  in steps S 1  and S 4  in the flowchart in  FIG. 3  or in  FIG. 7 . However, the determination may be made based upon any one or more of other factors including the temperature of the inverter  14  and the temperature of cooling water of the inverter  14 . 
     In the embodiments described above, it is not supposed that the hybrid vehicle  1  is on a road having a descending slope upon the start. When the hybrid vehicle  1  is on the road with a descending slope, and the cause of No in the determination result in step S 1  mainly lies in the SOC of the battery  15 , the process may proceed to step S 7 . This is because the starting mode using only the electric motor  13  (step S 9 ) may be carried out with the clutch  12  being disengaged (step S 8 ), since the regenerative power generation is possible just after the hybrid vehicle  1  starts, even if the SOC of the battery  15  is lower than a prescribed value. However, when the cause of No in the determination result in step S 1  mainly lies in the temperature of the battery  15 , the regenerative power generation cannot be executed, so that the process has to proceed to step S 2 . On a descending slope that is almost flat, the regenerative power generation just after the start is not expected as described above. Therefore, it may be controlled such that a threshold value is set for an angle of the descending slope, and in case where the determination result in step S 1  is No, and its cause mainly lies in the SOC, not in the temperature of the battery  15 , only when the angle of the descending slope is not less than the threshold value, the process proceeds to step S 7 .