Hybrid vehicle

Abstract

Hybrid vehicle (1), comprising: an internal combustion engine (2); a motor generator (5) which assists the power output of the internal combustion engine (2) under the condition that predetermined assistance conditions are met; a secondary battery (6A, 6B) that supplies power to the motor generator (5) and an electrical load (9); a control unit (25) that allows assistance from the motor generator (MG) under the condition that an assistance cost value, calculated on the basis of a change in fuel consumption before and after the fulfillment of the assistance conditions and the power consumption of the secondary battery (6A, 6B), is equal to or greater than a predetermined target assistance cost value, wherein the target assistance cost value is set high when the rotational speed of the internal combustion engine (2) becomes high; and a support cost value calculation unit (22) that specifies a plurality of drive torques of the motor generator (5) and calculates a support cost value that is incurred during the support by the drive of the motor generator (5) at each of the drive torques, wherein the control unit (25) controls the motor generator (5) to provide assistance at the drive torque that achieves the maximum assistance cost value among the majority of assistance cost values ​​calculated by the assistance cost value calculation unit (22), and wherein the support cost value calculation unit (22) determines the majority of drive torques of the motor generator (5) such that they are sequentially reduced starting from a predetermined torque limit.

Description

BACKGROUND OF THE INVENTION 1. Technical Field

[0001] The invention relates to a hybrid vehicle equipped with an internal combustion engine and a motor generator as power sources. 2. Background of the technology

[0002] A hybrid vehicle in which the drive of an internal combustion engine can be supported by the drive power of a motor-generator as needed is known. Such a hybrid vehicle is known from JP 2003-286 872 A, which aims to reduce the fuel consumption necessary for generating drive power while the vehicle is driving. The hybrid vehicle described in JP 2003-286 872 A selects a drive power source from among an internal combustion engine, a motor-generator, and a combination of both in order to minimize fuel consumption while the vehicle is driving.

[0003] German patent application DE 10 2009 008 474 A1 discloses a method for operating a hybrid system comprising an internal combustion engine and an electric machine with an associated energy storage device. In this method, a potential specific cost value is determined, representing the relationship between increased fuel consumption of the internal combustion engine and an additional charge quantity of the energy storage device. If the potential specific cost value is less than or equal to a cost threshold, it becomes a specific cost value. Furthermore, a potential specific savings value is determined, representing the relationship between reduced fuel consumption of the internal combustion engine and a smaller charge quantity of the energy storage device.If the potential specific savings value is greater than or equal to a savings threshold, the potential specific savings value becomes a specific savings value. Based on the existence of a specific cost value and / or a specific savings value, a future operating mode for the hybrid system is selected.

[0004] JP 4 512 056 B2 discloses a hybrid vehicle that calculates a plurality of possible combinations of drive patterns of an engine speed and an auxiliary speed when the vehicle is driven with the assistance described above, and that controls the internal combustion engine and the motor generator based on that drive pattern among the plurality of possibilities which minimizes fuel consumption during the assistance.

[0005] However, in the hybrid vehicles JP 2003-286 872 A and JP 4 512 056 B2, the discharge power of a secondary battery increases when the motor-generator provides assistance during an increase in the vehicle's electrical load. Consequently, the frequency of power generation cycles performed by the motor-generator also increases.

[0006] If the frequency of power generation events increases, assistance may not be possible, even if support from the engine-generator is necessary. For this reason, the amount of fuel consumed by the internal combustion engine increases in the hybrid vehicles described in JP 2003-286 872 A and JP 4 51 2056 B2, which can worsen fuel efficiency. SUMMARY OF THE INVENTION

[0007] The present invention was made in view of the circumstances described above and has the objective of providing a hybrid vehicle that is able to perform support by a motor generator in a situation with good efficiency and thereby suppress a deterioration in fuel efficiency.

[0008] The present invention comprises a setup comprising: an internal combustion engine; a motor-generator that assists the power output of the internal combustion engine under the condition that predetermined assistance conditions are met; a secondary battery that supplies power to the motor-generator and an electrical load; and a control unit that allows assistance from the motor-generator under the condition that an assistance cost value, calculated on the basis of a change in fuel consumption before and after the fulfillment of the assistance conditions and the power consumption of the secondary battery, is equal to or greater than a predetermined target assistance cost value, wherein the target assistance cost value is set high when the rotational speed of the internal combustion engine becomes high.Furthermore, a support cost value calculation unit is provided which specifies a plurality of drive torques of the motor generator and calculates a support cost value that is incurred during support by the drive of the motor generator at each of the drive torques, wherein the control unit controls the motor generator to perform the support at the drive torque that achieves the maximum support cost value among the plurality of support cost values ​​calculated by the support cost value calculation unit, and wherein the support cost value calculation unit specifies the plurality of drive torques of the motor generator such that they are sequentially reduced starting from a predetermined torque limit.

[0009] According to the invention, the motor generator can provide support in a situation with good efficiency, thereby suppressing the deterioration of fuel efficiency. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of a hybrid vehicle according to an embodiment of the present invention. Fig. Figure 2 is a representation of an example of a fuel consumption map. Fig. Figure 3 is a representation of a characteristic field for calculating a target support cost value. Fig. Figure 4 is a conceptual view of a calculation of the maximum support cost value in an embodiment of the present invention. Fig. Figure 5 is a flowchart that represents a sequence of a support control process carried out by the drive control device of the hybrid vehicle according to an embodiment of the present invention. Fig. Figure 6 is a flowchart that represents a sequence of a process for determining the fulfillment of a support condition, which is carried out by the drive control device of the hybrid vehicle according to an embodiment of the present invention. DESCRIPTION OF EXECUTION FORMS

[0010] The following describes embodiments of the present invention with reference to the drawings.

[0011] As in Fig. Figure 1 shows a vehicle 1 according to an embodiment of the present invention designed such that it comprises an engine 2 as an internal combustion engine, a transmission 3, a drive wheel 4, a motor generator (hereinafter referred to as "MG") as a motor generator, a main battery 6A and an auxiliary battery 6 as secondary batteries, a transmission control device 7, a battery control device 8 and a drive control device 10.

[0012] Vehicle 1 is a hybrid vehicle that uses engine 2 and MG 5 as drive power sources. This means that vehicle 1 moves by transmitting power generated by at least one of engine 2 and MG 5 to drive wheel 4 via transmission 3. Transmission 3 is, for example, a continuously variable transmission (CVT).

[0013] The MG 5, for example, is mechanically connected to a (not shown) crankshaft of engine 2 via a plurality of gears, belts, chains, or the like. The MG 5 can, for example, be an integrated starter generator (ISG) that, in addition to functioning as an AC generator, also performs the function of a starter motor.

[0014] The MG 5 is designed to assist the power of motor 2 under certain predefined conditions. Specifically, when these conditions are met, the MG 5 is designed to generate auxiliary torque, in addition to the power of motor 2, to assist the propulsion of vehicle 1. Furthermore, the MG 5 is designed to generate electricity using the power of motor 2.

[0015] The main battery 6A and the auxiliary battery 6B are designed as lead-acid batteries, lithium-ion batteries, or the like, and are configured to be charged with the current generated by the MG 5. In the present embodiment, the main battery 6A is designed as a lead-acid battery and the auxiliary battery 6B as a lithium-ion battery.

[0016] An electrical load 9, such as various electrical components located in the vehicle, is connected to the main battery 6A and the auxiliary battery 6B. The main battery 6A and the auxiliary battery 6B are designed to supply the stored electricity to the electrical load 9 and the MG 5.

[0017] The transmission control device 7 is designed as a computer unit equipped with a central processing unit (CPU), a working memory (RAM), a read-only memory (ROM), a flash memory, an input port and an output port.

[0018] The ROM of the transmission control unit 7 contains programs, along with various control constants and characteristic maps, that enable the computer unit to function as the transmission control unit 7. This means that when the CPU executes the program stored in the ROM of the transmission control unit 7, the computer unit functions as the transmission control unit 7. The transmission control unit 7 is connected to the drive control unit 10 and exchanges data with it.

[0019] The transmission control device 7 performs a control operation in which a transmission ratio in the transmission 3 is changed by controlling a (not shown) hydraulic control device in response to a shift operation detected by a (not shown) shift sensor and various types of information transmitted by the drive control device 10.

[0020] The battery control device 8 is designed as a computing unit equipped with a CPU, RAM, ROM, flash memory, input port and output port.

[0021] The battery control unit 8 calculates and manages, for example, the state of charge (SOC) and similar parameters of the main battery 6A and the auxiliary battery 6B by performing management of the main battery 6A and the auxiliary battery 6B. Furthermore, the battery control unit 8 is connected to the drive control unit 10 and exchanges data with it.

[0022] The drive control device 10 is designed as a computer unit equipped with a CPU, a RAM, a ROM, a flash memory, an input port and an output port.

[0023] An engine speed sensor 11, an accelerator pedal opening sensor 12, and a vehicle speed sensor 13 are connected to the drive control device 10. The engine speed sensor 11 detects an engine speed [rpm] that corresponds to the speed of the engine 2. The accelerator pedal opening sensor 12 detects the amount of depressurization of a (not shown) depressed accelerator pedal, i.e., the accelerator pedal opening. The vehicle speed sensor 13 detects the vehicle speed [km / h] of the vehicle 1.

[0024] The drive control unit 10 calculates the drive power required for vehicle 1, for example, based on the vehicle speed detected by the vehicle speed sensor 13 and the accelerator pedal opening detected by the accelerator pedal opening sensor 12. The drive control unit 10 calculates the power required by motor 2 based on the drive power required for vehicle 1.

[0025] The drive control device 10 calculates a target torque of the motor and a target speed of the motor on the basis of a characteristic map in which the power required by the motor and a motor operating point are specified, and controls the operation of the motor 2 depending on the target torque of the motor and the target speed of the motor.

[0026] The drive control device 10 is designed to include a torque limit setting unit 21, a support cost value calculation unit 22 and a control unit 25.

[0027] The torque limit setting unit 21 sets the torque limit [Nm] of the MG 5 so that a current with a value equal to or greater than a current limit does not flow through the power supply system of the vehicle 1. Since the auxiliary torque applied during assistance is set to be equal to or less than the torque limit, a current with a value equal to or greater than a current limit is prevented from flowing through the power supply system.

[0028] The support cost value calculation unit 22 is configured to include a battery power consumption calculation unit 23 and a fuel consumption calculation unit 24. The support cost value calculation unit 22 determines a plurality of auxiliary torques of the MG 5 and calculates a support cost value that is incurred during the support provided by the drive of the MG 5 for each of the auxiliary torques.

[0029] In particular, the support cost value calculation unit 22 determines a plurality of auxiliary torques of the MG 5, which are sequentially reduced from the torque limit set by the torque limit setting unit 21. That is, the support cost value calculation unit 22 reduces the auxiliary torque of the MG 5 stepwise from the torque limit according to a predetermined decrement over a predetermined number of samples.

[0030] When the auxiliary torque is sequentially reduced from the torque limit as described above, the battery power consumption calculation unit 23 calculates the battery power consumption [W] of the main battery 6A and the auxiliary battery 6B for each of the auxiliary torques. In particular, the battery power consumption calculation unit 23 calculates the battery power consumption during the support provided by the MG 5 based on each auxiliary torque of the MG 5, the MG speed, an efficiency map of the MG 5 and a power consumption of the electrical load 9.

[0031] The battery power consumption calculated by the battery power consumption calculation unit 23 is therefore a virtually determined battery power consumption.

[0032] The fuel consumption calculation unit 24 calculates the current fuel consumption [g / h] of engine 2 and the fuel consumption [g / h] of engine 2 during support by the MG 5.

[0033] In particular, the fuel consumption calculation unit 24 calculates the fuel consumption before support from the MG, referring to a value in Fig. 2 Fuel consumption map shown, based on the engine torque and the engine speed detected by the engine speed sensor 11.

[0034] The in Fig. The fuel consumption map shown represents the relationship between engine torque and engine speed on the one hand, and the fuel consumption determined in advance through experiments on the other, and is stored in advance in the ROM of the drive control unit 10. The fuel consumption map has a characteristic whereby fuel consumption increases with increasing engine torque and increasing engine speed. The thick solid line in the fuel consumption map represents optimal fuel efficiency.

[0035] If the auxiliary torque is sequentially reduced from the torque limit as described above, the fuel consumption calculation unit 24 also calculates the fuel consumption when assistance is provided by driving the MG 5 at each of the auxiliary torques, as the assistance fuel consumption occurring during the assistance.

[0036] In particular, the fuel consumption calculation unit 24 calculates the auxiliary fuel consumption for each of the auxiliary torques with reference to the one in Fig. 2 shows a fuel consumption map based on the engine torque and engine speed in response to each engine load occurring during support by the MG 5. In this case, the engine torque and engine speed can be determined, for example, by the drive control device 10 referencing a map that represents the ratio between the auxiliary torques of the MG 5 and the engine torque and engine speed, determined in advance through trials.

[0037] The support cost value calculation unit 22 calculates the support cost value [g / kWh] based on the current fuel consumption before support by the MG 5 and the fuel consumption during support and the battery power consumption.

[0038] In particular, assuming that the auxiliary torque of the MG 5 is sequentially reduced from the torque limit, the support cost calculation unit 22 calculates the support cost incurred when driving the MG 5 with each of the auxiliary torques, i.e., the support cost for each of the auxiliary torques. In the present embodiment, the predetermined number of samples described above is thus calculated as the support cost.

[0039] The support cost is expressed as fuel consumption (g / h / kW = g / kWh) per unit of battery power consumption. Specifically, the support cost is obtained by dividing the fuel consumption during support from the current fuel consumption—that is, the fuel consumption reduced due to support from the MG 5 (decrement)—by the battery power consumption [kW]. As described above, the auxiliary torque is calculated based on the change in fuel consumption before and after the support condition is met and the battery power consumption.

[0040] Control unit 25 sets a target support cost value based on a characteristic map derived from the engine speed. This is in Fig. The map shown in section 3 exemplifies a relationship between engine speed and the target support cost value. One of Fig. 3. A different characteristic map is determined in advance through testing and pre-stored in the ROM of the drive control device 10. In this characteristic map, the target support cost value increases with an increase in motor speed.

[0041] The control unit 25 allows the MG 5 to perform the support under the condition that the support cost value calculated by the support cost value calculation unit 22 is equal to or greater than the target support cost value set as described above.

[0042] The control unit 25 controls the MG 5 to provide assistance at that auxiliary torque which achieves the maximum assistance cost value among the majority of assistance cost values ​​calculated by the assistance cost value calculation unit 22, i.e. the predetermined number of samples of assistance cost values.

[0043] Fig. Figure 4 shows an example of the support cost value for each of the auxiliary torques which, when the torque limit setting unit 21 sets the torque limit to T1, are set to T2, T3, T4 and T5 when the support cost value calculation unit 22 reduces the auxiliary torque from a torque limit T1 to T2, T3, T4 and T5.

[0044] In the Fig. In example 4, the maximum support cost value is reached with an auxiliary torque set to T4. In the Fig. In the example shown in 4, the control unit 25 controls the MG 5 to provide support for the auxiliary torque T4 selected from the auxiliary torques T1, T2, T3, T4 and T5, which achieves the maximum support cost value.

[0045] In Fig. Figure 4 shows a target support cost value in a state where the motor speed is high and a target support cost value in a state where the motor speed is low. The former support cost value is set higher than the latter support cost value.

[0046] The following describes the sequence of a support control process carried out by the drive control device 10 of the present embodiment, with reference to the Fig. 5 described. The in Fig. The support control shown in 5 is repeatedly carried out by the drive control device 10 at predetermined time intervals.

[0047] The drive control device 10 performs a process to determine whether support conditions are met (step S1) or not. Subsequently, during this process, the drive control device 10 determines whether support is permitted or not (step S2). If support is not permitted, i.e., if it is determined that support is prohibited, the drive control device 10 terminates the support control.

[0048] If, on the other hand, it is determined that assistance is permitted, the drive control device 10 sets the torque limit of the MG 5 (step S3). Subsequently, the drive control device 10 reduces the auxiliary torque of the MG 5 stepwise by a predetermined decrement from the torque limit to a predetermined number of sample values ​​(step S4).

[0049] The drive control unit 10 then calculates the battery power consumption for each sampled auxiliary torque (step S5). Following this, the drive control unit 10 calculates a change in fuel consumption before and after the fulfillment of the support condition for each sampled auxiliary torque (step S6).

[0050] The drive control device 10 then calculates a support cost value for each auxiliary torque, assuming that the auxiliary torque of the MG 5 is sequentially reduced from the torque limit (step S7). The drive control device 10 then establishes a target support cost value with reference to the value in Fig. 3. The map shown is based on the engine speed (step S8).

[0051] The drive control device 10 then determines whether the maximum support cost value (hereinafter referred to as the "support cost maximum value") of the majority of support cost values ​​calculated in step S7 is equal to or greater than the target support cost value set in step S8 (step S9).

[0052] If it is determined that the maximum support cost is not equal to or greater than the target support cost, the drive control device 10 terminates the support control. Conversely, if it is determined that the maximum support cost is equal to or greater than the target support cost, the drive control device 10 controls the MG 5 to provide support at the auxiliary torque corresponding to the maximum support cost (step S10) and terminates the support control.

[0053] The following describes the process for determining whether the support condition is met in step S1 of the [document / document]. Fig. 5 support control shown with reference to Fig. 6 described.

[0054] The drive control device 10 determines whether a water temperature detected by a (not shown) water temperature sensor is higher than a specified value, thereby determining, for example, when to end the warm-up phase of the engine 2 (step S11). If it is determined that the water temperature is not higher than the specified value, the drive control device 10 disables assistance (step S27) and terminates the process for determining whether the assistance condition has been met.

[0055] If, on the other hand, it is determined that the water temperature is higher than the measured value, the drive control device 10 determines whether a bypass clutch is engaged or not, i.e., whether a bypass exists (step S12). If it is determined that no bypass exists, the drive control device 10 determines that the effect on fuel efficiency is low, prohibits assistance (step S27), and terminates the process for determining whether the assistance condition is met.

[0056] If, on the other hand, it is determined that a bridging condition exists, the drive control unit 10 determines whether the transmission control unit 7 has granted permission or not (step S13). If it is determined that the transmission control unit 7 has not granted permission, the drive control unit 10 determines that the effect on fuel efficiency is low, prohibits assistance (step S27), and terminates the process for determining whether the assistance condition has been met.

[0057] On the other hand, if it is determined that the transmission control device 7 has granted permission, the drive control device 10 determines whether a (not shown) gearshift lever is in an operating position “D” for forward travel or not (step S14).

[0058] If it is determined that the gear selector is not in the forward driving position “D”, the drive control device 10 determines that a driver does not intend to drive, prohibits assistance (step 27) and terminates the process of determining whether the assistance condition has been met.

[0059] On the other hand, if it is determined that the gearshift lever is in the operating position “D” for forward travel, the drive control device 10 determines whether the engine speed is lower than the specified value (step S15).

[0060] If it is determined that the motor speed is not lower than the specified value, that is to say, that the motor speed is equal to or higher than the specified value, the drive control device 10 prohibits assistance (step S27) and terminates the process for determining whether the assistance condition has been met.

[0061] On the other hand, if it is determined that the engine speed is lower than the specified value, the drive control device 10 determines a speed range with a low support efficiency and determines whether the vehicle speed is higher than a specified value or not (step S16).

[0062] If it is determined that the vehicle speed is equal to or lower than the specified value, the drive control device 10 determines a low vehicle speed range with low fuel efficiency, prohibits assistance (step S27) and terminates the process for determining whether the assistance condition has been met.

[0063] If, on the other hand, it is determined that the vehicle speed is higher than the specified value, the drive control unit 10 determines whether the state of charge of the main battery 6A is higher than a specified value or not (step S17). If it is determined that the state of charge of the main battery 6A is equal to or lower than the specified value, the drive control unit 10 prohibits assistance (step S27) in order to prioritize charging the main battery 6A and terminates the process for determining whether the assistance condition has been met.

[0064] If, on the other hand, it is determined that the state of charge of the main battery 6A is higher than the specified value, the drive control unit 10 determines whether the state of charge of the auxiliary battery 6B is higher than a specified value or not (step S18). If it is determined that the state of charge of the auxiliary battery 6B is equal to or lower than the determined value, the drive control unit 10 prohibits assistance (step S27) to prioritize charging the auxiliary battery 6B and terminates the process for determining whether the assistance condition has been met.

[0065] On the other hand, if it is determined that the state of charge of the auxiliary battery 6B is higher than the specified value, the drive control device 10 determines whether the temperature of the auxiliary battery 6B is within a usable temperature range or not (step S19).

[0066] If it is determined that the temperature of the auxiliary battery 6B is not within the usable temperature range, the drive control device 10 prohibits assistance (step S27) to avoid damage to the auxiliary battery 6B and terminates the process for determining whether the assistance condition is met.

[0067] On the other hand, if it is determined that the temperature of the auxiliary battery 6B is within the usable temperature range, the drive control device 10 determines whether a predetermined time has elapsed since the end of the previous support or not (step S20).

[0068] If it is determined that the predetermined time since the end of the previous support has not elapsed, the drive control device 10 prohibits support (step S27) and terminates the process for determining whether the support condition has been met.

[0069] Accordingly, by performing the support only once, continuous support is prohibited and discharge of the main battery 6A or the auxiliary battery 6B is prevented. This avoids a situation in which subsequent support cannot be performed.

[0070] On the other hand, if it is determined that the predetermined time has elapsed since the end of the previous support, the drive control device 10 determines whether the substrate temperature of the MG 5 is lower than a specified value or not (step S21).

[0071] If it is determined that the substrate temperature of MG 5 is equal to or higher than the specified value, the drive control device 10 prohibits support (step S27) and terminates the process for determining whether the support condition has been met.

[0072] If, on the other hand, it is determined that the substrate temperature of MG 5 is lower than the specified value, the drive control device 10 determines, based on the detection result of a (not shown) brake sensor, whether the driver is pressing down a brake pedal or not (step S22). If it is determined that the driver is pressing down the brake pedal, the drive control device 10 determines that the driver does not intend to accelerate, prohibits assistance (step S27), and terminates the process for determining whether the assistance condition has been met.

[0073] On the other hand, if it is determined that the driver is not pressing down the brake pedal, the drive control device 10 determines whether the temperature of a power metal oxide semiconductor field-effect transistor (MOSFET) is lower than a specified value (step S23).

[0074] If it is determined that the temperature of the power MOSFET is equal to or higher than the specified value, the drive control device 10 disables support (step S27) and terminates the process for determining whether the support condition is met. Conversely, if it is determined that the temperature of the power MOSFET is lower than the specified value, the drive control device 10 determines whether a coil temperature is lower than a specified value or not (step S24).

[0075] If it is determined that the coil temperature is equal to or higher than the specified value, the drive control device 10 prohibits assistance (step S27) and terminates the process for determining whether the assistance condition has been met. Conversely, if it is determined that the coil temperature is lower than the specified value, the drive control device 10 determines whether or not to charge one of the coils from the main battery 6A or the auxiliary battery 6B (step S25).

[0076] If it is determined that at least one of the main battery 6A and the auxiliary battery 6B is being charged, the drive control device 10 prohibits assistance (step S27) and terminates the process for determining whether the assistance condition has been met.

[0077] On the other hand, if it is determined that neither the main battery 6A nor the auxiliary battery 6B will be charged, the drive control device allows the assistance (step S26) and terminates the process of determining whether the assistance condition has been met.

[0078] In this document, the temperature of the auxiliary battery 6B mentioned above, the substrate temperature of the MG 5, the temperature of the power MOSFET and the coil temperature are each recorded by (not shown) temperature sensors.

[0079] As described above, the drive control device 10 according to the present embodiment allows assistance by the MG5, provided that the assistance cost value calculated on the basis of a change in fuel consumption before and after the fulfillment of the assistance conditions and battery power consumption is equal to or higher than the target assistance cost value.

[0080] Thus, according to the present embodiment, the drive control device 10 enables support by the MG5 in a situation with good efficiency, thereby avoiding the deterioration of fuel efficiency.

[0081] Furthermore, according to the present embodiment, as described above, the drive control device 10 allows assistance to be provided based on battery power consumption and not on the power consumption of the MG 5. Thus, if the vehicle's power consumption is high, the frequency of assistance can be reduced. Consequently, the degree of discharge of the main battery 6A and the auxiliary battery 6B can be reduced.

[0082] Furthermore, according to the present embodiment, the drive control device 10 controls the MG 5 to provide assistance with the auxiliary torque with the maximum assistance cost value below the assistance cost values ​​of the respective auxiliary torques, assuming that the auxiliary torque is sequentially reduced from the torque limit.

[0083] Thus, according to the present embodiment, the drive control device 10 can support the power of the motor 2 with the auxiliary torque at which the MG 5 provides the most effective support.

[0084] Although embodiments of the present invention have been described, it is apparent to those skilled in the art that modifications can be made without departing from the scope of the invention. All such modifications and equivalents are to be considered as being covered by the appended claims.

Claims

[1] Hybrid vehicle (1), comprising: an internal combustion engine (2); a motor generator (5) that assists the power output of the internal combustion engine (2) under the condition that predetermined assistance conditions are met; a secondary battery (6A, 6B) that supplies power to the motor generator (5) and an electrical load (9); a control unit (25) that allows assistance from the motor generator (MG) under the condition that an assistance cost value, calculated on the basis of a change in fuel consumption before and after the fulfillment of the assistance conditions and the power consumption of the secondary battery (6A, 6B), is equal to or greater than a predetermined target assistance cost value, wherein the target assistance cost value is set high when the rotational speed of the internal combustion engine (2) becomes high; and a support cost value calculation unit (22) that specifies a plurality of drive torques of the motor generator (5) and calculates a support cost value that is incurred during the support by the drive of the motor generator (5) at each of the drive torques, wherein the control unit (25) controls the motor generator (5) to provide assistance at the drive torque that achieves the maximum assistance cost value among the majority of assistance cost values ​​calculated by the assistance cost value calculation unit (22), and wherein the support cost value calculation unit (22) determines the majority of drive torques of the motor generator (5) such that they are sequentially reduced starting from a predetermined torque limit.

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