Hybrid vehicle control method and device

Abstract

A control device for a hybrid vehicle is provided that suppresses temporary increases and decreases in the system maximum torque during the driving mode transition process to eliminate a feeling of being pushed forward. A vehicle ECU 201 of a hybrid vehicle has a setting unit 210 that sets a first battery upper limit power when the discharge time exceeds a predetermined time and a second battery upper limit power that is greater than the first battery upper limit power and for a discharge time equal to or less than the predetermined time as the maximum value of the driving battery output from the battery 110, a relaxation power calculation unit 211 that calculates a relaxation power that increases the maximum value of the driving battery output from the first battery upper limit power to the second battery upper limit power in a driving mode in which the vehicle is driven using the engine as a power source, and a maximum motor drive shaft torque calculation unit 212 that suppresses temporary increases and decreases in maximum motor drive shaft torque during the driving mode transition process by changing the maximum value of the driving battery output between the first battery upper limit power and the second battery upper limit power using the relaxation power.

Description

[Technical field]

[0001] The present invention relates to a control technique for a hybrid vehicle having a parallel driving mode and a series driving mode. [Background technology]

[0002] Generally, a hybrid vehicle is equipped with a motor (electric motor), a generator (electric generator), and an engine (internal combustion engine), and a driving mode such as a series driving mode, a parallel driving mode, an EV mode, etc. is appropriately selected depending on the driving situation. In the series driving mode, the motor is used as a power source for driving the vehicle, and the engine is used as a power source for the generator. In the parallel driving mode, the motor and the engine are used as power sources for driving the vehicle. Patent Document 1 discloses an example of a control technique for the engine and the generator in the parallel driving mode. Patent Document 2 discloses a control technique for a hybrid vehicle equipped with an engine clutch and a motor clutch, and when it is determined that motor assist is necessary in parallel driving, the driving force until the motor clutch is connected is assisted by power running of the generator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-093777 A [Patent Document 2] Patent No. 7010391 Summary of the Invention [Problem to be solved by the invention]

[0004] When the accelerator is depressed to about WOT (Wide Open Throttle) during steady driving in the parallel driving mode with engine drive only, the control device connects the motor clutch to connect the motor to the drive shaft, and releases the engine clutch to switch to series driving mode. This increases the engine speed to ensure the generator generates electricity, and increases the drive shaft torque according to the driver's request.

[0005] When the motor clutch is engaged in the parallel driving mode, the system transitions to a clutch release mode in which the engine clutch is released. When the clutch release mode starts, the maximum value of the battery power supplied to the motor (upper battery power limit) is increased from the maximum long-term dischargeable power (long-term SOP (State Of Power)) to the short-term SOP. The long-term SOP is the maximum power applied when discharging for a period longer than a specified time, and the short-term SOP is applied when discharging for a period shorter than a specified time and is a maximum power greater than the long-term SOP. Therefore, the long-term SOP is applied in the parallel driving mode, which is mainly selected for steady driving, and the short-term SOP is applied in the series driving mode, which requires acceleration response.

[0006] However, when the battery upper limit power increases from the long-time SOP to the short-time SOP when the parallel driving mode is switched to the clutch release mode, the maximum value of the drive shaft torque by the motor increases in a step-like manner. Also, when the clutch release mode is switched to the series driving mode and the engine speed increases, the required power generation temporarily decreases. For this reason, the system maximum torque, which is the sum of the maximum engine drive shaft torque and the maximum motor drive shaft torque, increases when the parallel driving mode is switched to the clutch release mode and decreases when the series driving mode is switched to. Such a temporary increase or decrease in the system maximum torque when the driving mode is switched to the clutch release mode is felt as a pushing sensation when the user's required torque exceeds the system limit, and deteriorates the driving feeling. In particular, when the time required to switch from the parallel driving mode to the clutch release mode is long due to the connection and disconnection of the motor clutch, the time in the parallel driving mode using the long-time SOP becomes relatively long, and the fluctuation in the system maximum torque is easily felt.

[0007] The present invention has been devised in consideration of the above circumstances, and an object of the present invention is to provide a control method and device for a hybrid vehicle that can suppress temporary increases and decreases in system maximum torque during the driving mode transition process, thereby eliminating the feeling of being pushed forward. [Means for solving the problem]

[0008] BooksAccording to one embodiment of the invention, a control device for a hybrid vehicle having a motor, a generator, an engine, and a battery that exchanges power between the motor and the generator, and having a plurality of driving modes including a parallel driving mode in which the motor and the engine are used as a power source for driving the vehicle, and a series driving mode in which the motor is used as a power source for driving the vehicle and the engine is used as a power source for the generator, includes a setting unit that sets a first battery upper limit power when the discharge time exceeds a predetermined time, and a second battery upper limit power that is greater than the first battery upper limit power for a discharge time equal to or less than the predetermined time, as a maximum value of a driving battery output from the battery, and a relaxation power calculation unit that calculates a relaxation power that increases the maximum value of the driving battery output from the first battery upper limit power in the direction of the second battery upper limit power from the first battery upper limit power in a driving mode in which the vehicle is driven using the engine as a power source, a maximum motor drive shaft torque calculation unit that calculates a maximum motor drive shaft torque that increases or decreases depending on the drive battery output, a maximum engine drive shaft torque calculation unit that calculates a maximum engine drive shaft torque output by driving the engine, and a system maximum torque calculation unit that calculates a system maximum torque by adding up the maximum motor drive shaft torque and the maximum engine drive shaft torque; A temporary increase or decrease in maximum motor drive shaft torque during a travel mode transition process is suppressed by varying a maximum value of the drive battery output between the first battery upper limit power and the second battery upper limit power by the relaxation power. Control Unit The present invention is characterized by comprising: Furthermore, according to one embodiment of the present invention, in the parallel driving mode from the start of the driving mode transition process until the ratio of the engine output to the system maximum torque is reduced, the relaxation power can be set as the first relaxation power according to the following formula: first relaxation power = (second battery upper limit power) - (first battery upper limit power) - (rotation synchronization upper limit output). Furthermore, according to one embodiment of the present invention, from the start of the decrease in the ratio of the engine output to the system maximum torque during the traveling mode transition process, the second relaxed power can be set according to the following formula: second relaxed power = (first relaxed power) + (target generated power) - (generator requested generated power). According to one embodiment of the present invention, the relaxation power is calculated by the following formula: relaxation power=(rotation synchronous output margin)+(required power generation reduction amount); Rotation synchronous output margin=max{0kW, (2nd battery upper limit power)-(1st battery upper limit power)-(rotation synchronization upper limit output)}; Required power generation reduction amount = max {0kW, (Target generated power) - (Generator required generated power) It can be set by: Also, according to one embodiment of the present invention, in the parallel running mode in which the motor clutch between the motor and the drive shaft is in a disengaged state from the start of the running mode transition process, the first relaxation power can be set. According to one embodiment of the present invention, From the start of the driving mode transition process, The second damping power may be set after a motor clutch is engaged and an engine clutch between the engine and the drive shaft begins to open. Furthermore, according to one embodiment of the present invention, when it is predicted that the user requested output will exceed the system maximum torque, the control unit can start mitigation control of the maximum value of the driving battery output using the mitigation power. According to one embodiment of the present invention, there is provided a method for controlling a hybrid vehicle including a motor, a generator, an engine, and a battery which transfers electric power between the motor and the generator, and having a plurality of driving modes including a parallel driving mode in which the motor and the engine are used as a power source for driving the vehicle, and a series driving mode in which the motor is used as a power source for driving the vehicle and the engine is used as a power source for the generator, wherein a control device of the hybrid vehicle sets, as a maximum value of a driving battery output from the battery, a first battery upper limit power when a discharge time exceeds a predetermined time, and a second battery upper limit power which is greater than the first battery upper limit power and for a discharge time equal to or less than the predetermined time, and calculates a relaxation power for increasing the maximum value of the driving battery output from the battery in a driving mode in which the engine is used as a power source, calculating a maximum motor drive shaft torque that increases or decreases depending on an output of the drive battery, calculating a maximum engine drive shaft torque that is output by driving the engine, and calculating a system maximum torque by adding up the maximum motor drive shaft torque and the maximum engine drive shaft torque; The maximum value of the drive battery output is changed between the first battery upper limit power and the second battery upper limit power by the relaxation power, thereby suppressing a temporary increase or decrease in the maximum motor drive shaft torque during the driving mode transition process. Effect of the Invention

[0009] According to one embodiment of the present invention, by increasing the maximum value of the driving battery output toward the second battery upper limit power by the relaxation power, it is possible to suppress a temporary increase or decrease in the system maximum torque during the driving mode transition process. Furthermore, according to one embodiment of the present invention, it is possible to calculate the relaxation power in the parallel running mode before the engine output ratio is reduced. Moreover, according to one embodiment of the present invention, it is possible to calculate the mitigation power after the engine output ratio is reduced. Moreover, according to one embodiment of the present invention, the mitigation power can be calculated regardless of whether the driving mode is switched. Furthermore, according to one embodiment of the present invention, the first and second relaxation powers can be set in accordance with the motor clutch engagement process and the engine clutch release process. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram illustrating a schematic configuration of a drive system in a hybrid vehicle according to an embodiment of the present invention. [Diagram 2] 1 is a block diagram illustrating a schematic configuration of a control system in a hybrid vehicle according to an embodiment of the present invention. [Diagram 3] 4 is a schematic time chart illustrating a breakdown of torque fluctuations in a hybrid vehicle according to an embodiment of the present invention; [Figure 4] 1 is a schematic time chart illustrating a breakdown of torque fluctuation in the background art for comparison with the present embodiment; [Diagram 5] 5 is a schematic time chart illustrating the fluctuation of maximum motor drive shaft torque in FIGS. 3 and 4. [Figure 6] 4 is a block diagram illustrating a calculation process of a relaxation power in a control system of a hybrid vehicle according to the present embodiment. FIG. [Figure 7A] 4 is a time chart illustrating a portion of the operation of a hybrid vehicle according to one embodiment of the present invention. [Figure 7B]7B is a time chart illustrating another portion of the operation of the hybrid vehicle shown in FIG. 7A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 1. Vehicle configuration An example of the configuration and control system of a hybrid vehicle (hereinafter, also simply referred to as a "vehicle") according to one embodiment of the present invention will be described with reference to FIGS. 1 and 2.

[0012] 1, a hybrid vehicle 100 according to an embodiment of the present invention has an engine 101, a motor 102, and a generator 103, which are interconnected with a drive shaft 105 and drive wheels 106 by a power transmission mechanism 104. The power transmission mechanism 104 is made up of an engine clutch 107, a motor clutch 108, a differential gear 109, and other gear mechanisms, and may be a transaxle that integrates these. Note that the engine clutch 107 may be included in a transmission (not shown).

[0013] The engine 101 is an internal combustion engine that uses gasoline or diesel as fuel. The crankshaft of the engine 101 is gear-connected to the shaft of the generator 103 and to the engine clutch 107. This allows the torque of the engine 101 to be transmitted to the generator 103, and the torque of the generator 103 to the engine 102 and the engine clutch 107. By engaging the engine clutch 107, the torque of the engine 101 or the generator 103 can be transmitted to the drive shaft 105. Also, by disengaging the engine clutch 107, the engine 101 can be used exclusively for generating electricity for the generator 103.

[0014] The motor 102 is connected to a differential gear 109 via a motor clutch 108, and the torque of the motor 102 is transmitted to a drive shaft 105. As is well known, the motor 102 functions as a generator during regeneration, and the generator 103 can function as a motor during power running.

[0015] Furthermore, the hybrid vehicle 100 includes a battery 110, a control unit 200 (control device), various operation amount sensors such as an accelerator opening sensor (not shown), a vehicle speed sensor for detecting the traveling speed V, and various sensors for detecting the engine rotation speed, the axle rotation speed, the motor rotation speed, etc. The control unit 200 controls the engine 101, the motor 102, the generator 103, the engine clutch 107, and the motor clutch 108, and executes various controls including the traveling control according to this embodiment, which will be described later.

[0016] If the hybrid vehicle 100 is a plug-in hybrid (PHEV) type, the battery 110 may be charged by power supplied from a commercial household power source or a quick-charging power source at a charging station by providing an external charging unit (not shown), or may be supplied to home appliances by providing an external power supply unit (not shown). The control system will be described below with reference to FIG. 2.

[0017] 2, the control unit 200 includes a vehicle ECU (Electronic Control Unit) 201, an MCU (Motor Control Unit) 202, an engine (ENG) ECU 203, a transmission ECU 204, a GCU (Generator Control Unit) 205, a BMU (Battery Control Unit) 206, and other control units. The vehicle ECU 201 is connected to the MCU 201, the engine ECU 203, the transmission ECU 204, the GCU 205, and the BMU 202, and realizes the control function according to this embodiment.

[0018] Here, it is assumed that the vehicle ECU 201 realizes the functions of a setting unit 210, a relaxed power calculation unit 211, a maximum motor drive shaft torque calculation unit 212, a maximum engine drive shaft torque calculation unit 213, and a system maximum torque calculation unit 214. The setting unit 210 sets a long-term SOP (first battery upper limit power), a short-term SOP (second battery upper limit power), and other data described later, and outputs them to the relaxed power calculation unit 211. As described later, the long-term SOP is a relatively small battery upper limit power that is longer than a predetermined time, and is applied to the parallel driving mode. The short-term SOP is a battery upper limit power that is shorter than a predetermined time but larger than the long-term SOP, and is applied to the series driving mode and the clutch release mode. By applying the short-term SOP, it is possible to improve the acceleration response.

[0019] As described later, the relaxed power calculation unit 211 calculates the relaxed power to be added to the long-term SOP and outputs it to the maximum motor drive shaft torque calculation unit 212. The maximum motor drive shaft torque calculation unit 212 adds the relaxed power to the long-term SOP and further adds the required power generation to calculate the maximum motor drive shaft torque. The maximum engine drive shaft torque calculation unit 213 calculates the maximum engine drive shaft torque. The system maximum torque calculation unit 214 adds the maximum motor drive shaft torque and the maximum engine drive shaft torque thus calculated to calculate the system maximum torque. According to this embodiment, by changing the magnitude of the relaxed power to be added to the short-term SOP side from the long-term SOP, the maximum motor drive shaft torque can be changed smoothly from the start of the clutch release mode, and as a result, the occurrence of a temporary increase or decrease in the system maximum torque can be avoided. The control operation according to this embodiment will be described in detail below.

[0020] 2. Control Action The control method according to this embodiment will be described in detail below with reference to Figures 3 to 6. Figure 3 illustrates a sequence of this embodiment, and Figure 4 illustrates a sequence of the background art for comparison. These sequences show a driving mode transition process in which the vehicle transitions from the parallel driving mode to the series driving mode via the clutch release mode. This driving mode transition process starts when the vehicle transitions to a driving mode in which the vehicle runs using the engine as a power source, but may also start at a time t0 when the accelerator is depressed to approximately full throttle (WOT) during parallel driving with the motor clutch disengaged.

[0021] In Fig. 3 and Fig. 4, the maximum system torque T SYS_MAX is the maximum engine drive shaft torque T ENG_MAX and maximum motor drive shaft torque T MOT_MAX That is, T SYS_MAX =T ENG_MAX +T MOT_MAX It is.

[0022] Here, the maximum engine drive shaft torque T ENG_MAX teeth T ENG_MAX = Maximum possible torque (MMAX) x reduction ratio x engine output ratio It can be expressed as Maximum motor drive shaft torque T MOT_MAX teeth T MOT_MAX = (Upper battery power limit + Required power generation - Power consumption of auxiliary equipment - Power loss) x Axle angular speed Therefore, the maximum motor drive shaft torque T MOT_MAX increases or decreases depending on the battery upper limit power and the required power generation.

[0023] The battery upper limit power is the upper limit of the dischargeable power of the battery 110. In the parallel driving mode, a long-term SOP is used, while in the series driving mode and the clutch release mode, a short-term SOP is used to improve acceleration response during power generation increase.

[0024] The required power generation is normally consistent with the target power generation. The target power generation at WOT is 0 kW in parallel driving mode, and is the vehicle drive power (+ battery charging) in series driving mode. In clutch release mode, the target power generation is a value obtained by interpolating the value in parallel driving mode and the value in series driving mode according to the engine output ratio. However, it temporarily drops during power assist by generator 103 (times t1 to t2 in FIG. 3) and while the engine speed Ne is increasing in series driving mode (after time t3 in FIG. 3). Also, an increase in the target power generation may result in a power generation shortage relative to the required power generation.

[0025] According to this embodiment, the temporary reduction or shortage of the required generated power is compensated for by the relaxation power, and the generated power is increased so as to compensate for the reduction in the maximum engine drive shaft torque in the clutch release mode (reduction in the engine output ratio). In other words, the difference between the target generated power and the required generated power is offset by raising the battery upper limit power by the relaxation power, and the target generated power is increased according to the reduction ratio of the engine output. As a result, the maximum motor drive shaft torque T MOT_MAX This allows the system maximum torque T SYS_MAX This eliminates the temporary increase or decrease in torque, enabling a smooth transition from parallel driving to series driving even when the user-requested torque exceeds the system limit torque.

[0026] According to the background art shown in FIG. 4, the battery upper limit power is increased stepwise from the long-time SOP to the short-time SOP at time t1, and the maximum motor drive shaft torque T MOT_MAX 4. Furthermore, the maximum motor drive shaft torque T MOT_MAX As a result, the maximum system torque T SYS_MAX changes as shown by reference numeral 20 throughout the driving mode transition process, and increases and decreases significantly especially at time t1 and immediately thereafter at reference numeral 21, and at time t3 after reference numeral 22, causing a so-called pushing sensation.

[0027] In contrast, according to the present embodiment, as shown in FIG. 3, the relaxation power PWR is applied to the SOP 301 for a long time throughout the process of transitioning the driving mode from the parallel driving mode to the series driving mode. BST The following is the mitigation power PWR for long-term SOP301. BST The "addition" to the above will be expressed as "relaxation to the short-term SOP" as appropriate.

[0028] <Relief power> FIG. 5 illustrates a comparison between the background art and the present embodiment with respect to maximum motor drive shaft torque. BST is set between the difference between the long-term SOP and the short-term SOP as follows: In parallel driving mode, the relaxation value PWR is set between t0 and t1. B is set to (302); Between time points t1 and t2 when the mode is switched to the clutch release mode, the power requirement is increased so as to compensate for the decrease 11 in the power generation requirement during the power running assistance of the generator 103 (302A); From time t2 to t3, the relaxation value PWR B is set to (302B); After time t3 when the mode is changed to the series driving mode, the engine speed Ne is increased so as to compensate for the decrease 12 in the requested power generation while the engine speed Ne is increasing (302C).

[0029] As described later, even if an increase in the target power output causes a power output shortfall between the target power output and the required power output, the mitigation power PWR is set to compensate for the power output shortfall. BST Increase.

[0030] As shown in FIG. 6, the relaxation power calculation unit 211 calculates the relaxation power PWR which changes from the time t0 in the parallel running mode to the time in the series running mode. BST is calculated using the following formula: Relaxation power PWR BST = Rotation-synchronous output margin PWR MRG + Required power reduction amount PWR dGEN

[0031] Here, the rotation-synchronous output margin PWR MRG teeth, PWR MRG =max{0kW, Short-time SOP-Long-time SOP-Upper limit output for rotation synchronization} It can be expressed as:

[0032] Here, the rotation synchronization upper limit output is the upper limit of the power used for rotation synchronization when the motor clutch is connected or disconnected, and is set to a fixed value smaller than the difference between the short-term SOP and the long-term SOP. Therefore, this margin power PWR MRG (= Short-time SOP - Long-time SOP - Rotation synchronous upper limit output) relaxation power PWR BST If a motor clutch is not installed, the power can be set based on the power for adjusting the rotation speed Ne in the series running mode.

[0033] Also, the required power reduction amount PWR dGEN teeth, PWR dGEN =max{0kW, target power generation - generator required power generation} and the target generated power = engine required power generation output - generator loss power.

[0034] Mitigation power PWR for the long-term SOP described above BST (= rotation synchronous output margin PWR MRG + Required power reduction amount PWR dGEN ) is distributed as follows through the parallel driving mode, clutch release mode and series driving mode:

[0035] [Table 1]

[0036] As mentioned above, the mitigation power PWR BST By varying the SOP and relaxing the SOP for a long period of time, it is possible to prevent an increase or decrease in the system maximum torque, which limits the required drive shaft torque during mode transitions, and eliminate the pushing sensation that previously occurred.

[0037] 3. Working Example Hereinafter, the operation of the hybrid vehicle to which the control method according to one embodiment of the present invention is applied will be described with reference to the operations (a) to (k) in FIG. 7A and FIG. 7B.

[0038] First, it is assumed that the vehicle is running steadily in parallel running mode (PR) with the motor clutch 108 in a disengaged state (b). During this parallel running, when the accelerator opening AP increases beyond a predetermined value at time t0 and exceeds the system maximum torque (a), the control unit 200 turns off the request to disengage the motor clutch 108 (disengagement prohibited) (c) and starts rotation synchronization of the motor clutch 108 (e). As described above, the control unit 200 calculates the rotation synchronization output margin PWR MRG (= Short-time SOP - Long-time SOP - Rotation synchronous upper limit output) relaxation power PWR BST to increase the upper battery power limit (i) and the maximum motor drive shaft torque (j).

[0039] When rotation synchronization is completed at time t1, the control unit 200 connects the motor clutch 108 (d) and transitions to a clutch release mode (CLO) (b). In the clutch release mode, the engine 101 output ratio and the generator 103 assist ratio each decrease from 1 to 0 over a predetermined time period in order to release the engine clutch 107 (g). Here, it is assumed that the generator assist ratio becomes 0 between time t1 and t2.

[0040] In response to the decrease in the output ratio of the engine 101, the target generated power increases to the target value for the series running mode (SR) (h), and together with the engine output ratio, the maximum engine drive shaft torque 401 decreases to 0 [Nm] (k).

[0041] Furthermore, the generator 103 shifts from power assist to power generation in response to the decrease in the assist ratio, and the required power generation starts to increase from time t2 (h). However, there is a period during which the required power generation falls below the target power generation, and there is a power generation decrease indicated by the shaded area. Specifically, when the engine 101 reaches the maximum engine output (actual rotation speed Ne) at the maximum possible torque MMAX, the required power generation cannot be generated any more. Therefore, an increase in the target power generation creates a power generation shortage between the required power generation and the target power generation. According to this embodiment, the control unit 200 adjusts the relaxed power PWR to make up for the power generation shortage. BST by increments 302A, 302B (i).

[0042] Furthermore, when the mode transitions to the series running mode after time t3, the target Ne of the engine 101 rises, causing a difference with the actual Ne, and the required power generation is reduced by adjusting the rotation of the generator 103, causing a power generation shortage. According to this embodiment, the control unit 200 adjusts the mitigation power PWR to compensate for the power generation shortage. BST by increment 302C (i).

[0043] In this way, by relaxing the battery upper limit power from the long-time SOP to the short-time SOP by the relaxation power, the maximum motor drive shaft torque increases accordingly. Therefore, the system maximum torque 407 added to the maximum engine drive shaft torque 401 forms a smooth curve without temporary increases and decreases, and the pushing sensation that occurred with the conventional maximum motor drive shaft torque 13 and required drive shaft torque 20 can be eliminated.

[0044] The vehicle ECU 201 of the control unit 200 includes a processor such as a CPU (Central Processing Unit), a ROM (Read-only memory) that stores a control program executed by the processor, a RAM (Random access memory) as an operating area for the control program, an interface with peripheral circuits, etc. The control method according to this embodiment can be implemented by executing a program on the processor of the vehicle ECU 201. [Explanation of symbols]

[0045] 100 Hybrid Vehicles 101 Engine 102 Motor 103 Generator 104 Power transmission mechanism 105 Drive shaft 106 Drive Wheel 107 Engine clutch 108 Motor clutch 109 Differential Gear 110 Battery 200 Control section 201 Vehicle ECU 210 Setting section 211 Mitigation Power Calculation Unit 212 Maximum motor drive shaft torque calculation unit

Claims

1. A control device for a hybrid vehicle including a motor, a generator, an engine, and a battery that exchanges electric power between the motor and the generator, the control device having a plurality of drive modes including a parallel drive mode in which the motor and the engine are used as a power source for driving the vehicle, and a series drive mode in which the motor is used as a power source for driving the vehicle and the engine is used as a power source for the generator, a setting unit that sets, as a maximum value of a driving battery output from the battery, a first battery upper limit power when a discharge time exceeds a predetermined time, and a second battery upper limit power that is greater than the first battery upper limit power and when the discharge time is equal to or shorter than the predetermined time; a relaxation power calculation unit that calculates a relaxation power for increasing a maximum value of the driving battery output from the first battery upper limit power toward the second battery upper limit power in a traveling mode in which the vehicle travels using the engine as a power source; a maximum motor drive shaft torque calculation unit that calculates a maximum motor drive shaft torque that increases or decreases depending on the drive battery output; a maximum engine drive shaft torque calculation unit that calculates a maximum engine drive shaft torque output by driving the engine; a system maximum torque calculation unit that calculates a system maximum torque by adding the maximum motor drive shaft torque and the maximum engine drive shaft torque; a control unit that suppresses a temporary increase or decrease in a maximum motor drive shaft torque during a travel mode transition process by changing a maximum value of the drive battery output between the first battery upper limit power and the second battery upper limit power using the relaxation power; A control device for a hybrid vehicle comprising:

2. In the parallel driving mode before the ratio of the engine output to the system maximum torque is reduced from the start of the driving mode transition process, the relaxation power is expressed by the following formula: First mitigation power=(Second battery upper limit power)−(First battery upper limit power)−(Rotation synchronization upper limit output) 2. The control device for a hybrid vehicle according to claim 1, wherein the first relaxation power is set by:

3. From the start of the decrease in the ratio of the engine output to the system maximum torque in the traveling mode transition process, the relaxation power is calculated based on the following formula: Second relaxation power = (The first mitigation power)+(Target power generation)−(Generator requested power generation) 3. The control device for a hybrid vehicle according to claim 2, wherein the second relaxation power is set by:

4. The relaxation power is expressed by the following formula: Mitigation power = (rotation synchronous output margin) + (required power generation reduction amount); RPM output margin=max {0 kW, (second battery upper limit power) - (first battery upper limit power) - (rotation synchronization upper limit output)}; Required power generation reduction amount=max {0 kW, (Target generated power) - (Generator required generated power) 2. The control device for a hybrid vehicle according to claim 1, wherein the control device is set by:

5. 3. The control device for a hybrid vehicle according to claim 2, wherein the first relaxation power is set in the parallel running mode in which a motor clutch between the motor and the drive shaft is in a disengaged state from the start of the running mode transition process.

6. 4. The control device for a hybrid vehicle according to claim 3, wherein a motor clutch between the motor and the drive shaft is connected from the start of the driving mode transition process, and after an engine clutch between the engine and the drive shaft starts to be released, the second relaxation power is set.

7. The control device for a hybrid vehicle described in any one of claims 1 to 6, characterized in that the control unit starts mitigation control of the maximum value of the driving battery output using the mitigation power when it is predicted that the user requested output will exceed the system maximum torque.

8. A control method for a hybrid vehicle including a motor, a generator, an engine, and a battery that exchanges electric power between the motor and the generator, the hybrid vehicle having a plurality of drive modes including a parallel drive mode in which the motor and the engine are used as a power source for driving the vehicle, and a series drive mode in which the motor is used as a power source for driving the vehicle and the engine is used as a power source for the generator, The control device for the hybrid vehicle, a first battery upper limit power when a discharge time exceeds a predetermined time and a second battery upper limit power when a discharge time is equal to or shorter than the predetermined time and is greater than the first battery upper limit power, calculating a relaxation power for increasing a maximum value of the driving battery output from the first battery upper limit power toward the second battery upper limit power in a traveling mode in which the vehicle travels using the engine as a power source; Calculating a maximum motor drive shaft torque that increases or decreases depending on the drive battery output; Calculating a maximum engine drive shaft torque output by driving the engine; Calculating a system maximum torque by adding the maximum motor drive shaft torque and the maximum engine drive shaft torque; a maximum value of the driving battery output is changed between the first battery upper limit power and the second battery upper limit power by the relaxation power, thereby suppressing a temporary increase or decrease in a maximum motor drive shaft torque during a traveling mode transition process. A method for controlling a hybrid vehicle.

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