Electric vehicle control method and electric vehicle control device

Abstract

An aspect of the present invention is an electric vehicle control method which distributes required torque between front torque and rear torque and which has a reduced power consumption mode and a driving performance mode as control modes for adjusting the distribution of the required torque. In this electric vehicle control method, in the case of the reduced power consumption mode, the required torque is largely distributed to one of either the front torque or the rear torque, while in the case of the driving performance mode, the front torque or the rear torque to which the required torque is largely distributed in the reduced power consumption mode is reduced. Also, the temperature of a front drive system or a rear drive system is obtained, and the output of the front or rear torque is limited by setting an upper limit value on the distributed front or rear torque according to the temperature of the front or rear drive system. Additionally, when the control mode is the reduced power consumption mode, after the upper limit value is lowered, the control mode is switched to the driving performance mode before the output of the front or rear torque is limited to the upper limit value.

Description

Control method for electric vehicle and control device for electric vehicle

[0001] The present invention relates to a control method for an electric vehicle and a control device for an electric vehicle.

[0002] JP2020-082988A discloses a driving mode control device for a vehicle that drives the front wheels with engine power and the rear wheels with motor generator power, and switches between two-wheel drive and four-wheel drive by adjusting the distribution of driving power between the engine and the motor generator. The configuration of this driving mode control device is intended to stabilize the behavior of a hybrid vehicle, which reduces power consumption, by narrowing the operating range in four-wheel drive mode and widening the operating range in two-wheel drive mode.

[0003] Four-wheel drive electric vehicles may adjust the torque (driving force) distribution between the front and rear wheels. Specifically, the torque distribution is adjusted to reduce power consumption by essentially making the electric vehicle two-wheel drive, or to improve driving performance by making the electric vehicle four-wheel drive.

[0004] The torque distribution that reduces power consumption essentially drives the electric vehicle in a two-wheel drive state as described above, so either the front-wheel drive system or the rear-wheel drive system operates intensively. For example, when using front-wheel two-wheel drive to reduce power consumption, the electric motor and inverter that drive the front wheels operate intensively. As a result, depending on the driving situation, either the front-wheel drive system or the rear-wheel drive system may overheat.

[0005] Furthermore, when there is a risk that an electric motor, inverter, or the like may overheat, the output torque is limited to prevent damage due to overheating. For example, when there is a risk that an electric motor driving the front wheels may overheat, an output limit is imposed on the torque allocated to the front wheels from the required torque. When an output limit is imposed to protect against overheating, a portion of the torque that should be output by the front and rear wheels as a whole is cut, and the electric vehicle is not driven with the required torque.

[0006] In other words, when a four-wheel drive electric vehicle is driven with torque distribution that suppresses power consumption, depending on the driving situation, the electric vehicle may not be driven with the required torque in order to protect the drive system from overheating.

[0007] The present invention aims to provide a control method for an electric vehicle and a control device for an electric vehicle that can protect the drive system from overheating and drive at the required torque, even when adjusting the torque distribution to a distribution that suppresses power consumption.

[0008] One aspect of the present invention is a control method for an electric vehicle that allocates required torque between front torque, which is torque generated on the front wheels, and rear torque, which is torque generated on the rear wheels, and has control modes for adjusting the allocation of required torque, including a power consumption reduction mode that prioritizes reducing power consumption and a driving performance mode that prioritizes driving performance. In this control method for an electric vehicle, in the power consumption reduction mode, the required torque is allocated more to either the front torque or the rear torque, and in the driving performance mode, the front torque or the rear torque to which the required torque is allocated more in the power consumption reduction mode is reduced. Also, the temperature of one of the drive systems, either a front drive system that drives the front wheels or a rear drive system that drives the rear wheels, corresponding to the front torque or the rear torque to which the required torque is allocated more in the power consumption reduction mode, is obtained. For the front torque or the rear torque to which the required torque is allocated more in the power consumption reduction mode, an upper limit is set according to the temperature of the corresponding drive system, thereby limiting the front torque or the rear torque to which the required torque is allocated more in the power consumption reduction mode. When the control mode is the power consumption reduction mode, after the upper limit value is lowered, the control mode is switched to the driving performance mode before the front torque or rear torque to which a large amount of the requested torque is allocated in the power consumption reduction mode is limited to this upper limit value.

[0009] FIG. 1 is an explanatory diagram showing the configuration of an electric vehicle. FIG. 2 is a block diagram showing the configuration of a controller related to torque distribution. FIG. 3 is a block diagram showing the configuration of a torque distribution unit. FIG. 4 is a block diagram showing the configuration of an output limit calculation unit. FIG. 5 is a schematic graph showing the mode of output limiting based on the temperature of the front motor. FIG. 6 is a schematic graph showing the mode of output limiting based on the temperature of the front inverter. FIG. 7 is a flowchart showing a case where the power consumption reduction mode is canceled and the control mode is switched to a driving performance mode. FIG. 8 is a flowchart showing a case where the power consumption reduction mode is returned to. FIG. 9 is a graph showing a schematic diagram of the temperature and torque of each motor and the vehicle speed changes in an electric vehicle of a comparative example. FIG. 10 is a graph showing a schematic diagram of the temperature and torque of each motor and the vehicle speed changes in an electric vehicle according to this embodiment. FIG. 11 is a graph showing a schematic diagram of the temperature and torque of each motor and the vehicle speed changes when the electric vehicle according to this embodiment returns to the power consumption reduction mode.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] 1 is an explanatory diagram showing the configuration of an electric vehicle 100. The electric vehicle 100 is an electric four-wheel drive vehicle that uses an electric motor to drive front wheels 22 and rear wheels 32, which are drive wheels. The electric vehicle 100 also generates a front torque T ｆ and a rear torque T ｒ Therefore, depending on the torque distribution, the electric vehicle 100 may be in a substantially two-wheel drive state.

[0012] As shown in FIG. 1 , the electric vehicle 100 includes a front drive system 11 , a rear drive system 12 , a battery 13 , and a controller 14 .

[0013] The front drive system 11 is a system that drives front wheels 22 by a front motor 21. In addition to the front motor 21 and the front wheels 22, the front drive system 11 also includes a front inverter 23, a rotation sensor 24, a current sensor 25, and the like.

[0014] The front motor 21 is, for example, a three-phase AC synchronous motor, and is driven by AC power input from a front inverter 23. The output torque of the front motor 21 (front torque T ｆ ) generates torque (driving force) on the front wheels 22. Furthermore, the front motor 21 generates so-called regenerative torque when its drive shaft is rotated by the front wheels 22. This allows the front motor 21 to recover the kinetic energy of the electric vehicle 100 as electrical energy.

[0015] The front wheels 22 are a pair of drive wheels located at the front of the electric vehicle 100. The front wheels 22 are connected to the front motor 21 via a front reduction gear 26 and a drive shaft 27. In this embodiment, the front wheels 22 consist of a right front wheel and a left front wheel. However, since the right front wheel and the left front wheel are connected by the drive shaft 27 and driven integrally, in this embodiment, the right front wheel and the left front wheel are not distinguished from each other and are collectively referred to as the front wheels 22. Furthermore, the front wheels 22 are first drive wheels in comparison with the rear wheels 32, which are other drive wheels.

[0016] The front inverter 23 includes two pairs of switching elements for each phase of the front motor 21. The front inverter 23 opens and closes these switching elements in response to a PWM (Pulse Width Modulation) signal input from the controller 14. As a result, the front inverter 23 converts DC power supplied from the battery 13 into AC power and inputs it to the front motor 21 to drive the front motor 21. The switching elements constituting the front inverter 23 are, for example, power semiconductor elements such as insulated gate bipolar transistors (IGBTs) and metal oxide semiconductor field effect transistors (MOS-FETs). During regenerative control, the front inverter 23 converts AC power generated by the front motor 21 into DC power and inputs it to the battery 13.

[0017] The rotation sensor 24 detects the rotor phase α of the front motor 21. ｆ Detect the rotor phase α ｆ is a so-called electrical angle [rad]. The rotation sensor 24 is, for example, a resolver or an encoder. The detected rotor phase α ｆ is input to the controller 14.

[0018] The current sensor 25 detects the currents (hereinafter referred to as three-phase currents) i flowing through the respective phases of the front motor 21. ｕｆ , i ｖｆ , i ｗｆ The three-phase current i of the front motor 21 is detected. ｕｆ , i ｖｆ , i ｗｆ is input to the controller 14.

[0019] The rear drive system 12 is a system that drives rear wheels 32 using a rear motor 31, and is configured symmetrically to the front drive system 11. Therefore, in addition to the rear motor 31 and rear wheels 32, the rear drive system 12 also includes a rear inverter 33, a rotation sensor 34, a current sensor 35, a rear reduction gear 36, a drive shaft 37, etc. These components that make up the rear drive system 12 function in the same way as the components of the front drive system 11. In other words, the rear wheels 32 are a pair of drive wheels located at the rear of the electric vehicle 10. The rear wheels 32 consist of a right rear wheel and a left rear wheel, but in this embodiment, these are not distinguished and the right rear wheel and the left rear wheel are collectively referred to as the rear wheels 32. The rear wheels 32 are second drive wheels in comparison with the front wheels 22, which are other drive wheels. The rotor phase of the rear drive system 12 detected by the rotation sensor 34 is α ｒ The current flowing through each phase of the rear motor 31 detected by the current sensor 35 is i ｕｒ , i ｖｒ , i ｗｒ is.

[0020] The battery 13 is provided in common to the front drive system 11 and the rear drive system 12, and supplies power to drive the front motor 21 and the rear motor 31. During regenerative control, the battery 13 is charged by the regenerative power generated by the front motor 21 and the rear motor 31.

[0021] The controller 14 is a control device for the electric vehicle 100. The controller 14 is configured by one or more computers including, for example, a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 14 is also programmed to control the front motor 21, the rear motor 31, and the like at a predetermined control period. For example, the controller 14 acquires various vehicle variables and generates PWM signals for driving the front motor 21 and the rear motor 31 based on these vehicle variables. The controller 14 then inputs the generated PWM signals to the front inverter 23 and the rear inverter 33, respectively, to drive the front motor 21 and the rear motor 31 in accordance with the vehicle variables.

[0022] The vehicle variables are parameters that represent the control state of the electric vehicle 10. As described above, the controller 14 controls the rotor phase α of the front motor 21, for example. ｆ and three-phase current i ｕｆ , i ｖｆ , i ｗｆ and the rotor phase α of the rear motor 31 ｒ and three-phase current i ｕｒ , i ｖｒ , i ｗｒ is acquired as a vehicle variable.

[0023] The controller 14 also detects, for example, the accelerator opening A ＰＯ , and the DC voltage V of the battery 13 ｄｃ etc. are acquired as vehicle variables. ＰＯ is a parameter that represents the amount of accelerator pedal operation by the driver. ＰＯ , and the DC voltage V of the battery 13 ｄｃ is detected appropriately as needed, for example, by using a sensor (not shown).

[0024] In addition, the controller 14 monitors the acceleration occurring in the electric vehicle 100, the temperature of the front drive system 11, the temperature of the rear drive system 12, and the gradient of the road surface on which the electric vehicle 100 is traveling (hereinafter referred to as the road surface gradient ψ ｒｏａｄ) are acquired as vehicle variables.

[0025] More specifically, the controller 14 calculates the acceleration in the front-rear direction caused by acceleration / deceleration as the acceleration occurring in the electric vehicle 100 (hereinafter referred to as the front-rear acceleration Ac １ ), and the lateral acceleration caused by turning (hereinafter referred to as lateral acceleration Ac ２ The longitudinal acceleration Ac １ and lateral acceleration Ac ２ is detected appropriately as needed, for example, by using an acceleration sensor (not shown).

[0026] The controller 14 determines the temperature of the front drive system 11 by calculating the temperature θ of the front motor 21. ｆ－ＭＯＴ , and the temperature θ of the front inverter 23 ｆ－ＩＮＶ The temperatures of the various parts of the front drive system 11 are acquired, such as the temperature of the permanent magnets in the rotor and the temperature of the stator coils that make up the stator. More realistically, the temperatures of the front motor 21 are acquired individually for each part that makes up the front motor 21, such as the temperature of the permanent magnets in the rotor and the temperature of the stator coils that make up the stator. However, in this embodiment, for the sake of simplicity, the temperatures of these parts are referred to as the temperature θ of the front motor 21. ｆ－ＭＯＴ Similarly, for the front inverter 23, for example, the temperature of each switching element can be acquired, but in this embodiment, for simplicity, the temperature of each part constituting the front inverter 23 is represented by the temperature θ ｆ－ＩＮＶ In this embodiment, the temperatures of the front motor 21, the front inverter 23, and other components of the front drive system 11 are simply referred to as the temperature of the front drive system 11. The temperature θ of the front motor 21 ｆ－ＭＯＴ and the temperature θ of the front inverter 23 ｆ－ＩＮＶ is detected as needed using a temperature sensor (not shown), or is estimated by calculation using vehicle variables.

[0027] The controller 14 calculates the temperature θ of the rear motor 31 as the temperature of the rear drive system 12 in the same manner as the temperature of the front drive system 11. ｒ－ＭＯＴ and the temperature θ of the rear inverter 33 ｒ－ＩＮＶThe temperature θ of the rear motor 31 can be obtained. ｒ－ＭＯＴ and the temperature θ of the rear inverter 33 ｒ－ＩＮＶ is detected as needed using a temperature sensor (not shown), or is estimated by calculation using vehicle variables.

[0028] The controller 14 calculates the road surface gradient ψ based on, for example, information about a planned travel route registered in advance in a car navigation system and the current position of the electric vehicle 100 identified by a GPS (Global Positioning System). ｒｏａｄ can be obtained.

[0029] In principle, the controller 14 of this embodiment acquires vehicle variables directly using various sensors, but the controller 14 can acquire some or all of the vehicle variables from another controller (computer) not shown.

[0030] Furthermore, the controller 14 can acquire new vehicle variables by performing calculations using the acquired vehicle variables. For example, the controller 14 can acquire the rotational angular velocity ω of the front motor 21. ｍｆ [rad / s], and the rotational angular velocity ω of the rear motor 31 ｍｒ [rad / s]. ｍｆ is the mechanical angular velocity, and the rotor phase α ｆ and dividing the result by the number of pole pairs of the front motor 21. Similarly, the rotational angular velocity ω of the rear motor 31 ｍｒ is the mechanical angular velocity, and the rotor phase α ｒ and dividing the result by the number of pole pairs of the rear motor 31. In this embodiment, the controller 14 also calculates the rotational angular velocity ω ｍｆ By converting [rad / s], the vehicle speed V [km / h] of the electric vehicle 100 is obtained.

[0031] 2 is a block diagram showing the configuration of the controller 14 related to torque distribution. As shown in FIG. 2, the controller 14 includes a required torque calculation unit 41 and a torque distribution unit 42.

[0032] The required torque calculation unit 41 calculates the output torque (hereinafter referred to as required torque T ｒｅｑ In this embodiment, the required torque calculation unit 41 calculates the accelerator opening A ＰＯ and the rotational angular velocity ω of the front motor 21 ｍｆ Based on this, the required torque T ｒｅｑ The required torque calculation unit 41 calculates, for example, the accelerator opening A ＰＯ and the rotational angular velocity ω of the front motor 21 ｍｆ and the required torque T ｒｅｑ and the accelerator opening A ＰＯ and the rotational angular velocity ω of the front motor 21 ｍｆ The required torque T ｒｅｑ Calculate the following.

[0033] The torque distribution unit 42 calculates the required torque T ｒｅｑ Based on this, the front torque T ｆ The front torque command value T ｆ ＊ and rear torque T ｒ The rear torque command value T ｒ ＊ The controller 14 calculates the front torque command value T ｆ ＊ and rear torque command value T ｒ ＊ Based on this, the front motor 21 generates a front torque T ｆ and causes the rear motor 31 to output the rear torque Tr. ｒｅｑ Front torque T ｆ and rear torque T ｒ to be allocated to.

[0034] In this embodiment, the electric vehicle 100 has a front torque T ｆ and rear torque T ｒ Required torque T ｒｅｑ The control mode for adjusting the distribution of power, i.e., torque distribution, includes two control modes: a power consumption reduction mode and a driving performance mode.

[0035] The power consumption reduction mode is a control mode in which the torque distribution unit 42 performs torque distribution that prioritizes reduction in power consumption (electricity cost). Specifically, when the control mode is the power consumption reduction mode, the torque distribution unit 42 reduces power consumption by adjusting the torque distribution so that the electric vehicle 100 is in a two-wheel drive state (or a state close to that) in which the electric vehicle 100 is driven by either the front wheels 22 or the rear wheels 32. In this embodiment, when the control mode is the power consumption reduction mode, the torque distribution unit 42 adjusts the torque distribution so that the electric vehicle 100 is in a two-wheel drive state (or a state close to that) in which the electric vehicle 100 is driven by either the front wheels 22 or the rear wheels 32. ｒｅｑ Rear torque T ｒ Front torque T ｆ In other words, in this embodiment, the torque distribution in the power consumption reduction mode is, in principle, ｆ : T ｒ 100:0. However, the torque distribution unit 42 further adjusts the torque distribution in the power consumption reduction mode based on the vehicle speed V.

[0036] The driving performance mode is a control mode in which the torque distribution unit 42 distributes torque with priority given to driving performance. Specifically, when the control mode is the driving performance mode, the torque distribution unit 42 adjusts the torque distribution so that the electric vehicle 100 is in a four-wheel drive state (or a state close to that), thereby improving the driving performance of the electric vehicle 100. Therefore, when the control mode is the driving performance mode, the torque distribution unit 42 adjusts the torque distribution so that the electric vehicle 100 is in a four-wheel drive state (or a state close to that), thereby improving the driving performance of the electric vehicle 100. ｒｅｑ Front torque T ｆ The rear torque is distributed to ｒ In this embodiment, the torque distribution in the driving performance mode is, in principle, ｆ : T ｒ = 50:50. However, the torque distribution unit 42 １ , lateral acceleration Ac ２ , and road surface gradient ψ ｒｏａｄ The torque distribution in the driving performance mode is further adjusted based on the above.

[0037] The control mode related to torque distribution is set by the driver using a control switch or the like (not shown). In this embodiment, the control mode is set to the power consumption reduction mode as a general rule. When the driving performance mode is explicitly set using the control switch or the like, the control mode is set to the driving performance mode.

[0038] However, even when the power consumption reduction mode is selected, the torque distribution unit 42 (controller 14) may automatically and forcibly cancel the power consumption reduction mode. That is, the torque distribution unit 42 may switch the control mode from the power consumption reduction mode to the driving performance mode. This is because the front torque T ｆ and rear torque T ｒ The sum of these torques (hereinafter referred to as total torque ΣT) is the required torque T ｒｅｑ , while protecting the front drive system 11 from overheating.

[0039] This automatic and forced change in control mode is, in principle, temporary. When the risk of damage to the front drive system 11 due to overheating has decreased, the torque distribution unit 42 (controller 14) automatically returns the control mode to the power consumption reduction mode. In other words, if the torque distribution unit 42 automatically switched the control mode to the driving performance mode without the driver's selection, and it is no longer necessary to maintain the driving performance mode, the torque distribution unit 42 automatically switches the control mode from the temporarily set driving performance mode back to the original power consumption reduction mode.

[0040] The torque distribution unit 42 automatically switches the control mode based on the temperature of the front drive system 11 or the rear drive system 12. In this embodiment, when the control mode is the power consumption reduction mode, the front drive system 11 operates intensively, and there is a risk of overheating depending on the driving situation. For this reason, the torque distribution unit 42 automatically switches the control mode based on the temperature of the front drive system 11. Furthermore, it is the front motor 21 and the front inverter 23 of the front drive system 11 that are particularly at risk of overheating when in the power consumption reduction mode. Therefore, the torque distribution unit 42 automatically switches the control mode based on the temperature θ of the front motor 21 in particular. ｆ－ＭＯＴ and the temperature θ of the front inverter 23 ｆ－ＩＮＶ The above automatic control mode switching is performed based on the above.

[0041] As described above, the selection of the power consumption reduction mode causes the electric vehicle 100 to be substantially in a two-wheel drive state, and the selection of the driving performance mode causes the electric vehicle 100 to be in a four-wheel drive state. Therefore, in this embodiment, switching the control mode related to torque distribution corresponds to switching between two-wheel drive and four-wheel drive. However, the power consumption reduction mode does not necessarily mean that the electric vehicle 100 must be in a two-wheel drive state strictly or always. In the power consumption reduction mode, for example, T ｆ : T ｒ The torque distribution may be adjusted to 80:20 or similar.

[0042] Fig. 3 is a block diagram showing the configuration of the torque distribution unit 42. As shown in Fig. 3, the torque distribution unit 42 includes a first torque distribution calculation unit 51, a second torque distribution calculation unit 52, an output limit calculation unit 53, a torque distribution selection unit 54, and a rate limiter 55.

[0043] The first torque distribution calculation unit 51 calculates the required torque T ｒｅｑ and the vehicle speed V, the first front torque command value T ｆ１ ＊ and the first rear torque command value T ｒ１ ＊ The first front torque command value T ｆ１ ＊ and the first rear torque command value Tｒ１ ＊ is the required torque T ｒｅｑ The front torque T when distributing the torque in the power consumption reduction mode ｆ and rear torque T ｒ That is, the first torque distribution calculation unit 51 calculates a torque command value for the power consumption reduction mode.

[0044] As described above, in this embodiment, the torque distribution in the power consumption reduction mode is T ｆ : T ｒ ≈100:0, the first front torque command value T ｆ１ ＊ is approximately the required torque T ｒｅｑ and the first rear torque command value T ｒ１ ＊ is approximately zero. However, the first torque distribution calculation unit 51 corrects this in accordance with the vehicle speed V to obtain a first front torque command value T ｆ１ ＊ and the first rear torque command value T ｒ１ ＊ In the following, the first front torque command value T ｆ１ ＊ and the first rear torque command value T ｒ１ ＊ is the torque command value (T ｆ１ ＊ , T ｒ１ ＊ )

[0045] The second torque distribution calculation unit 52 calculates the required torque T ｒｅｑ , longitudinal acceleration Ac １ , lateral acceleration Ac ２ , and road surface gradient ψ ｒｏａｄ Based on this, the second front torque command value T ｆ２ ＊ and the second rear torque command value T ｒ２ ＊ The second front torque command value T ｆ２ ＊ and the second rear torque command value T ｒ２ ＊ is the required torque T ｒｅｑFront torque T when distributing in the torque distribution of the driving performance mode ｆ and rear torque T ｒ That is, the second torque distribution calculation unit 52 calculates a torque command value for the driving performance mode.

[0046] As described above, in this embodiment, the torque distribution in the driving performance mode is, in principle, T ｆ : T ｒ = 50:50, the second front torque command value T ｆ２ ＊ and the second rear torque command value T ｒ２ ＊ is roughly the required torque T ｒｅｑ However, the second torque distribution calculation unit 52 calculates the longitudinal acceleration Ac １ , lateral acceleration Ac ２ , and road surface gradient ψ ｒｏａｄ By correcting this in accordance with the second front torque command value T ｆ２ ＊ and the second rear torque command value T ｒ２ ＊ In the following, the second front torque command value T ｆ２ ＊ and the second rear torque command value T ｒ２ ＊ is the torque command value (T ｆ２ ＊ , T ｒ２ ＊ )

[0047] The output limit calculation unit 53 calculates the front torque T based on the temperature of the front drive system 11 or the temperature of the rear drive system 12 to protect the front drive system 11 from damage due to overheating. ｆ or rear torque T ｒ In this embodiment, when the control mode is the power consumption reduction mode, the front drive system 11 operates intensively, and depending on the driving situation, there is a risk of overheating. For this reason, the output limit calculation unit 53 calculates the output limit to be imposed on the temperature θ of the front motor 21. ｆ－ＭＯＴ and the temperature θ of the front inverter 23 ｆ－ＩＮＶBased on this, for overheat protection, the distributed front torque T ｆ The upper limit value (hereinafter referred to as upper limit torque UL ＦＴ (called "(x,y)") is calculated.

[0048] Upper limit torque UL ＦＴ is a variable value, and the temperature θ of the front motor 21 ｆ－ＭＯＴ and the temperature θ of the front inverter 23 ｆ－ＩＮＶ Specifically, the upper limit torque UL ＦＴ is substantially equal to the maximum output torque of the front motor 21 when there is no risk of the front motor 21 or the front inverter 23 exceeding their heat resistance temperature. ｆ－ＭＯＴ is likely to exceed the heat resistance temperature of the front motor 21, or the temperature θ of the front inverter 23 ｆ－ＩＮＶ If there is a risk that the upper limit torque UL ＦＴ The temperature θ of the front motor 21 decreases to a value smaller than the maximum output torque of the front motor 21. ｆ－ＭＯＴ and the temperature θ of the front inverter 23 ｆ－ＩＮＶ Upper limit torque UL based on ＦＴ The setting method will be described in detail later.

[0049] Upper limit torque UL ＦＴ is the distributed front torque T ｆ In addition, in this embodiment, the upper limit torque UL ＦＴ is used as a criterion for automatically and forcibly canceling the power consumption reduction mode and switching the control mode from the power consumption reduction mode to the driving performance mode. ＦＴ is used as a criterion for automatically returning the control mode to the power saving mode.

[0050] The torque distribution selection unit 54 selects a torque command value for the power consumption reduction mode (T ｆ１ ＊ , T ｒ１ ＊) or the torque command value (T ｆ２ ＊ , T ｒ２ ＊ ) and outputs it. In this way, torque distribution selection unit 54 selects the torque distribution to be applied in the control of electric vehicle 100.

[0051] When the driving performance mode is set by the driver, the torque distribution selection unit 54 selects the torque command value for the driving performance mode (T ｆ２ ＊ , T ｒ２ ＊ ) is selected. As a result, torque distribution selection unit 54 sets the torque distribution of electric vehicle 100 to the torque distribution of the driving performance mode. In this case, the control mode is the driving performance mode.

[0052] When the power consumption reduction mode is set by the driver, or when the driving performance mode is not explicitly selected, the torque distribution selection unit 54 selects the torque command value for the power consumption reduction mode (T ｆ１ ＊ , T ｒ１ ＊ ) is selected. As a result, torque distribution selection unit 54 sets the torque distribution of electric vehicle 100 to that of the power consumption reduction mode. In this case, the control mode is the power consumption reduction mode. Note that "when the driving performance mode is not explicitly selected" refers to cases where the control mode is initially set or automatically set, so that the driver does not need to set either the power consumption reduction mode or the driving performance mode, or where the driving performance mode can be set using an operation button (not shown) but the operation button is not operated. In other words, even if the power consumption reduction mode is not set by the driver, the power consumption reduction mode may be automatically selected when the driver has not set the driving performance mode.

[0053] Furthermore, in this embodiment, when the control mode is the power consumption reduction mode, the torque distribution selector 54 selects the upper limit torque UL ＦＴIn response to a change in the vehicle speed, the control mode may be automatically and forcibly switched to the driving performance mode.

[0054] Specifically, the torque distribution selection unit 54 adjusts the upper limit torque UL according to the change in temperature of the front drive system 11. ＦＴ After the decrease in the front torque T ｆ The output of the upper limit torque UL ＦＴ Before the vehicle is restricted to the above range, the control mode is switched to the driving performance mode.

[0055] In this embodiment, the criterion for determining whether to cancel the power consumption reduction mode and switch to the driving performance mode is the upper limit torque UL ＦＴ The torque distribution selection unit 54 selects the upper limit torque UL ＦＴ The first threshold TH １ Set the upper limit torque UL ＦＴ is the first threshold TH １ When the first threshold TH is equal to or lower than the threshold TH, the power consumption reduction mode is cancelled and the driving performance mode is switched to. １ is a threshold value for determining whether to cancel the power saving mode (power saving mode cancellation threshold value).

[0056] As described above, when there is a risk that the front motor 21 or the front inverter 23 will exceed its heat resistance temperature, the upper limit torque UL ＦＴ decreases from the maximum output torque of the front motor 21. １ is set to detect the possibility that the front motor 21 or the front inverter 23 may exceed its heat-resistant temperature. １ is set to a value in the range lower than the maximum output torque of the front motor 21, for example, a value close to the maximum output torque. １ The specific value of is determined in advance by experiment, simulation, or the like.

[0057] Furthermore, in this embodiment, when the control mode is automatically and forcibly switched from the power consumption reduction mode to the driving performance mode, the torque distribution selection unit 54 may automatically return the control mode to the power consumption reduction mode.

[0058] Specifically, the upper limit torque UL is set according to the temperature of the front drive system 11. ＦＴ When it is determined that the temperature rises and there is no longer any risk that the front motor 21 or the front inverter 23 will exceed their heat resistance temperature, the torque distribution selector 54 automatically returns the control mode to the power consumption reduction mode.

[0059] In this embodiment, the torque distribution selection unit 54 selects the upper limit torque UL ＦＴ The second threshold TH ２ Set the upper limit torque UL ＦＴ is the second threshold TH ２ When the second threshold value TH is reached, the control mode is returned to the power consumption reduction mode. ２ is a threshold value that serves as a condition for returning to the power saving mode (power saving mode return threshold value). ２ is the first threshold TH １ The second threshold value TH is set to a value equal to or less than the maximum output torque of the front motor 21. ２ is the first threshold TH １ This allows the automatic switching and restoration of the control mode to have hysteresis, thereby suppressing hunting. In other words, it becomes difficult for the switching and restoration of the control mode to be repeated in a short period of time. ２ The specific value of is determined in advance by experiment, simulation, or the like.

[0060] The rate limiter 55 is a front torque T ｆ and rear torque T ｒ Specifically, the rate limiter 55 limits the rate of change of the torque command value (T ｆ１ ＊ , T ｒ１ ＊ ) or the torque command value (T ｆ２ ＊ , T ｒ２ ＊ ) per unit time. ｆ and rear torque T ｒChange smoothly.

[0061] In this embodiment, the rate limiter 55 functions when the control mode is switched from the power consumption reduction mode to the driving performance mode, and when the control mode is subsequently returned to the power consumption reduction mode. That is, in this embodiment, the rate limiter 55 essentially functions to limit the front torque T ｆ and rear torque T ｒ As a result, even when starting to travel or while traveling, the control mode is switched smoothly without causing vibrations or the like in electric vehicle 100.

[0062] Fig. 4 is a block diagram showing the configuration of the output limit calculation unit 53. As shown in Fig. 4, the output limit calculation unit 53 includes a first limit calculation unit 61, a second limit calculation unit 62, and an upper limit torque calculation unit 63.

[0063] The first limit calculation unit 61 calculates the temperature θ of the front motor 21. ｆ－ＭＯＴ Based on this, the front torque T ｆ (hereinafter referred to as the first upper limit torque Lim １ The first upper limit torque Lim is calculated. １ In order to prevent the front motor 21 from overheating, the front torque T ｆ This is a limiter that should be imposed on

[0064] The second limiting calculation unit 62 calculates the temperature θ of the front inverter 23. ｆ－ＩＮＶ Based on this, the front torque T ｆ (hereinafter referred to as the second upper limit torque Lim ２ The second upper limit torque Lim is calculated. ２ In order to prevent the front inverter 23 from overheating, the front torque T ｆ This is a limiter that should be imposed on

[0065] The upper limit torque calculation unit 63 calculates the first upper limit torque Lim １ and the second upper limit torque Lim ２ The smaller of these is the front torque T ｆ The final upper limit torque UL to be imposed on ＦＴThis prevents both the front motor 21 and the front inverter 23 from overheating.

[0066] FIG. 5 shows the temperature θ of the front motor 21. ｆ－ＭＯＴ 5 is a schematic graph showing the output limitation based on the temperature θ of the front motor 21. ｆ－ＭＯＴ is sufficiently low so that overheat protection is not required, the first upper limit torque Lim １ Therefore, in order to protect the front motor 21 from overheating, the front motor 21 is required to generate the maximum possible front torque T ｆ can be output.

[0067] Temperature θ of the front motor 21 ｆ－ＭＯＴ However, when the temperature rises from a temperature that is low enough that overheat protection is not required, the temperature θ ｆ－ＭＯＴ is temperature A １ When the torque exceeds the first upper limit Lim １ is the temperature θ of the front motor 21 ｆ－ＭＯＴ According to the line L １ Therefore, the temperature θ of the front motor 21 is set to gradually decrease along the ｆ－ＭＯＴ is temperature A １ When the torque exceeds the limit, the front torque T ｆ is limited.

[0068] In particular, in this embodiment, the temperature θ of the front motor 21 ｆ－ＭＯＴ is temperature A ２ When this occurs, the first upper limit torque Lim １ Therefore, the temperature θ of the front motor 21 ｆ－ＭＯＴ is temperature A ２ If the temperature exceeds this value, the front motor 21 will no longer be able to output torque in order to protect the front motor 21 from overheating. １ , A ２ and Line L １ The shape of the front motor 21 is determined in advance depending on the specific heat dissipation characteristics of the front motor 21.

[0069] On the other hand, the first upper limit torque Lim１ When the temperature θ of the front motor 21 is 0%, ｆ－ＭＯＴ When the temperature θ of the front motor 21 decreases, ｆ－ＭＯＴ is temperature B ２ When the torque is lower than the first upper limit torque Lim １ is the temperature θ of the front motor 21 ｆ－ＭＯＴ According to the line L ２ The temperature of the front motor 21 is set to gradually increase along the ｆ－ＭＯＴ Line L ２ along the temperature B １ When the first upper limit torque Lim １ is set to return to 100%.

[0070] Temperature B ２ is at least at temperature A ２ The temperature is set to the following value: ２ Also, the line L ２ is Line L １ However, in this embodiment, the temperature B ２ is at least at temperature A ２ is set to a value smaller than ２ is Line L １ As a result, the first upper limit torque Lim １ is the temperature θ of the front motor 21 ｆ－ＭＯＴ In this way, the first upper limit torque Lim １ The reason for providing hysteresis to the first upper limit torque Lim １ The final upper limit torque UL ＦＴ This is because the control mode is switched based on the above.

[0071] For example, the temperature θ of the front motor 21 ｆ－ＭＯＴ When the control mode is switched, the temperature θ of the front motor 21 ｆ－ＭＯＴ is temperature A １ When the power consumption reduction mode is exceeded, the control mode is soon forcibly switched from the power consumption reduction mode to the driving performance mode. Then, as a result of the control mode being switched to the driving performance mode, the distributed front torque Tｆ When the load on the front motor 21 is reduced, the temperature θ ｆ－ＭＯＴ will begin to show a downward trend.

[0072] At this time, the first upper limit torque Lim １ When the torque limiter 1 does not have the hysteresis, the first upper limit torque Lim １ is Line L １ The temperature θ of the front motor 21 increases along the ｆ－ＭＯＴ is temperature A １ and the first upper limit torque Lim １ When the front torque T ｆ increases, and the load on the front motor 21 increases. As a result, the temperature θ ｆ－ＭＯＴ is essentially the temperature A １ Therefore, the first upper limit torque Lim １ If the above-described hysteresis is not provided, even if the control mode returns to the power consumption reduction mode, the control mode may be forcibly switched back to the driving performance mode immediately thereafter.

[0073] That is, the first upper limit torque Lim １ The reason for providing the hysteresis to temperature B is to suppress hunting associated with the automatic switching and restoration of the control mode. １ , B ２ and Line L ２ The shape of the groove is determined in advance by experiment, simulation, or the like.

[0074] The first upper limit torque Lim １ Line L １ The temperature θ of the front motor 21 increases while the temperature θ ｆ－ＭＯＴ When the line L ２ Until you reach the upper point, or line L １ Until it returns to the upper point, the first upper limit torque Lim １ is the temperature θ of the front motor 21 ｆ－ＭＯＴ is maintained at the value when the line L １along the first upper limit torque Lim １ decreases, and the temperature θ of the front motor 21 ｆ－ＭＯＴ is the temperature T at point α α After that, the temperature θ of the front motor 21 starts to decrease. ｆ－ＭＯＴ When the temperature θ of the front motor 21 further decreases, ｆ－ＭＯＴ is the temperature T β Then, line L ２ The first upper limit torque Lim at point α is １ This is to suppress hunting associated with automatic switching and recovery of the control mode.

[0075] Similarly, the first upper limit torque Lim １ Line L ２ The temperature θ of the front motor 21 increases along the ｆ－ＭＯＴ When the line L starts to rise, １ Until you reach the upper point, or line L ２ Until it returns to the upper point, the first upper limit torque Lim １ is the temperature θ of the front motor 21 ｆ－ＭＯＴ is maintained at the value at which it began to rise.

[0076] FIG. 6 shows the temperature θ of the front inverter 23. ｆ－ＩＮＶ 6 is a schematic graph showing the output limitation based on the second upper limit torque Lim ２ is the first upper limit torque Lim １ Based on the same principle, the value is set according to the characteristics of the front inverter 23.

[0077] Temperature θ of the front inverter 23 ｆ－ＩＮＶ When the second upper limit torque Lim ２ The temperature C at which the temperature starts to decrease from 100% １ , second upper limit torque Lim ２ The lowest temperature C to set to 0% ２ , and the shape of the line therebetween is set in advance depending on the heat resistance temperature of the front inverter 23 (particularly the switching element). ｆ－ＩＮＶ When the second upper limit torque Lim２ The temperature D at which the temperature starts to rise from 0% ２ and the second upper limit torque Lim ２ Temperature D at which the １ , and the shape of the line therebetween are determined in advance by experiment, simulation, or the like so as to suppress hunting associated with the automatic switching and return of the control mode.

[0078] The following describes the automatic switching and returning of the control mode in the electric vehicle 100 configured as described above. Note that in the following, it is assumed that the driving performance mode is not set by the driver and the control mode is, in principle, the power consumption reduction mode.

[0079] 7 is a flowchart for canceling the power consumption reduction mode and switching the control mode to the driving performance mode. As shown in FIG. 7, in step S10, the first torque distribution calculation unit 51 calculates the torque command value (T ｆ１ ＊ , T ｒ１ ＊ In step S11, the second torque distribution calculation unit 52 calculates the torque command value (T ｆ２ ＊ , T ｒ２ ＊ In step S12, the temperature θ of the front motor 21 is calculated. ｆ－ＭＯＴ and the temperature θ of the front inverter 23 ｆ－ＩＮＶ Then, in step S13, the output limit calculation unit 53 calculates the temperature θ of the front motor 21. ｆ－ＭＯＴ and the temperature θ of the front inverter 23 ｆ－ＩＮＶ Based on this, the upper limit torque UL ＦＴ Calculate the following.

[0080] Then, in step S14, the torque distribution selection unit 54 selects the upper limit torque UL ＦＴ is the first threshold TH １ In step S14, the upper limit torque UL ＦＴ is the first threshold TH １ If it is determined that the front torque command value Tｆ ＊ and rear torque command value T ｒ ＊ The torque command value to be output as the torque command value for the power consumption reduction mode (T ｆ１ ＊ , T ｒ１ ＊ ) to the torque command value (T ｆ２ ＊ , T ｒ２ ＊ ) In step S16, the rate limiter 55 performs rate limit processing to smooth this switching.

[0081] As a result, the torque distribution control mode is set to the front torque T ｆ is the upper limit torque UL ＦＴ The control mode is automatically and forcibly switched to the driving performance mode before the requested torque T ｒｅｑ From front torque T ｆ As a result, the load on the front drive system 11 is reduced, and the heat generated therefrom is suppressed. Therefore, the front drive system 11 is appropriately protected from overheating. Also, in the driving performance mode, the required torque T ｒｅｑ The front torque is just right. ｆ and rear torque T ｒ Therefore, even if the control mode is switched as described above, the electric vehicle 100 can ｒｅｑ can continue to output.

[0082] In step S14, the upper limit torque UL ＦＴ is the first threshold TH １ If it is determined that the torque command value (T ｆ１ ＊ , T ｒ１ ＊) is the front torque command value T ｆ ＊ and rear torque command value T ｒ ＊ As a result, the power consumption reduction mode is continued.

[0083] 8 is a flowchart for returning to the power consumption reduction mode. As shown in FIG. 8, even after the automatic switch from the power consumption reduction mode to the driving performance mode, the torque command value (T ｆ１ ＊ , T ｒ１ ＊ ) continues to be calculated. Also, in step S21, the torque command value (T ｆ２ ＊ , T ｒ２ ＊ Similarly, in step S22, the temperature θ of the front motor 21 is calculated. ｆ－ＭＯＴ and the temperature θ of the front inverter 23 ｆ－ＩＮＶ is acquired, and in step S23, the upper limit torque UL ＦＴ is calculated.

[0084] Then, in step S24, the torque distribution selection unit 54 selects the upper limit torque UL ＦＴ is set as the second threshold TH ２ In step S24, the upper limit torque UL ＦＴ is the second threshold TH ２ If it is determined that the front torque command value T ｆ ＊ and rear torque command value T ｒ ＊ The torque command value to be output as the torque command value for the power consumption reduction mode (T ｆ１ ＊ , T ｒ１ ＊ ) In step S26, the rate limiter 55 performs rate limit processing to smooth this switching.

[0085] As a result, the torque distribution control mode is switched to the power consumption reduction mode when the possibility of the front drive system 11 overheating decreases. Therefore, the period during which the control mode is forcibly switched to the driving performance mode is minimized, and power consumption is also reduced as long as there is no risk of the front drive system 11 overheating.

[0086] 9 is a graph showing the temperature and torque of each motor and the transition of vehicle speed V in the electric vehicle of the comparative example. The electric vehicle of the comparative example continues the power consumption reduction mode unless the driving performance mode is set by the driver. Furthermore, in the electric vehicle of the comparative example, when overheat protection of the front drive system 11 becomes necessary, the front torque T distributed according to the torque distribution in the power consumption reduction mode is ｆ (First front torque command value T ｆ１ ＊ ) is the upper limit torque UL ＦＴ For simplicity, the temperature θ of the front motor 21 is limited by ｆ－ＭＯＴ The necessity of overheat protection is determined by the accelerator opening A ＰＯ is constant, and as a result, the required torque T ｒｅｑ is also assumed to be constant.

[0087] As shown in FIG. 9A, in the electric vehicle of the comparative example, the temperature θ of the front motor 21 decreases as the power consumption reduction mode continues. ｆ－ＭＯＴ rises, and temperature A １ , as shown in FIG. 9B, ＦＴ Then, the upper limit torque UL ＦＴ is the required torque T ｒｅｑ Front torque T distributed from ｆ When the front torque T ｆ is the upper limit torque UL ＦＴ This forcibly reduces the load on the front motor 21, suppressing heat generation therein. As a result, the front motor 21 is protected from overheating.

[0088] However, the front torque ｆis the upper limit torque UL ＦＴ By limiting the front torque to ｆ and rear torque T ｒ The total torque ΣT is the sum of the required torque T ｒｅｑ Therefore, when protecting the front motor 21 from overheating, the electric vehicle of the comparative example requires the required torque T ｒｅｑ As a result, as shown in FIG. 9C, in the electric vehicle of the comparative example, the output of the front torque T ｆ is the upper limit torque UL ＦＴ When the vehicle speed V starts to be limited to , the vehicle speed V decreases.

[0089] 10A and 10B are graphs showing the temperature and torque of each motor and the transition of vehicle speed in the electric vehicle 100 according to this embodiment. As in the electric vehicle of the comparative example, in the electric vehicle 100 according to this embodiment, the temperature θ ｆ－ＭＯＴ rises, and temperature A １ , as shown in FIG. 10(B), ＦＴ begins to decrease.

[0090] After that, in the electric vehicle of the comparative example, the front torque T ｆ is the upper limit torque UL ＦＴ However, in the electric vehicle 100 of this embodiment, the front torque T ｆ is the upper limit torque UL ＦＴ Before being limited to the upper limit torque UL ＦＴ is the first threshold TH １ When the following timing occurs, the control mode is switched from the power consumption reduction mode to the driving performance mode. ｆ decreases, and the rear torque T ｒ As a result, the load on the front motor 21 is forcibly reduced, and heat generation therein is suppressed, thereby protecting the front motor 21 from overheating.

[0091] Furthermore, in the electric vehicle 100 of this embodiment, the front torque T ｆ is the upper limit torque UL ＦＴThe control mode is switched to the driving performance mode before the total torque ΣT is limited to the required torque T ｒｅｑ Therefore, as shown in FIG. 9C, in the electric vehicle 100 of this embodiment, the vehicle speed V is maintained.

[0092] 11A and 11B are graphs showing the temperature and torque of each motor and the transition of vehicle speed when the electric vehicle 100 of this embodiment returns to the power consumption reduction mode. ｆ－ＭＯＴ For example, temperature B ２ When the torque is sufficiently reduced to the level below the upper limit torque UL, as shown in FIG. ＦＴ begins to recover (rise). ＦＴ is the second threshold TH ２ When the torque requirement T ｒｅｑ The front torque T ｆ and rear torque T ｒ Therefore, as described above, even when the control mode returns to the power consumption reduction mode, the total torque ΣT is ｒｅｑ Therefore, in the electric vehicle 100 of this embodiment, the vehicle speed V is maintained even when the control mode returns to the power consumption reduction mode.

[0093] In the above embodiment, the upper limit torque UL ＦＴ The first threshold TH １ and the second threshold TH ２ is set, and the upper limit torque UL ＦＴ However, the present invention is not limited to this. A similar threshold value can be set for the temperature of the front drive system 11, and the temperature of the front drive system 11 can be used as a criterion for automatically switching the control mode. However, as in the above embodiment, the temperatures of multiple parts of the front drive system 11 can be detected and the upper limit torque UL can be calculated by combining these temperatures. ＦＴWhen determining the upper limit torque UL ＦＴ It is simple and straightforward to use the upper limit torque UL as a criterion for automatically switching the control mode. ＦＴ When the above is used as a criterion for judgment, automatic switching of the control mode can be performed particularly accurately.

[0094] Furthermore, the automatic control mode switching control according to the above embodiment is particularly suitable for driving situations where the front drive system 11 is under high load. This is because, when the front drive system 11 is operating intensively in the power consumption reduction mode and the temperature of the front drive system 11 is already rising, there is a greater risk that the front drive system 11 will exceed its heat resistance temperature in driving situations where it is under even higher load.

[0095] Specifically, the automatic control of switching the control mode according to the above embodiment is particularly suitable when the electric vehicle 100 is traveling uphill, when the electric vehicle 100 is towing another vehicle, or when the electric vehicle 100 is traveling uphill while towing another vehicle. That is, when the control mode is the power consumption reduction mode and the electric vehicle is traveling uphill, the upper limit torque UL ＦＴ After the decrease in the front torque T ｆ The output of the upper limit torque UL ＦＴ It is preferable to automatically and forcibly switch the control mode to the driving performance mode as in the above embodiment before the upper limit torque UL is limited to . Also, when the control mode is the power consumption reduction mode and the vehicle is traveling while towing another vehicle, the upper limit torque UL ＦＴ After the decrease in the front torque T ｆ The output of the upper limit torque UL ＦＴ It is preferable that the control mode be automatically and forcibly switched to the driving performance mode as in the above embodiment before the control mode is restricted to the driving performance mode.

[0096] Whether the electric vehicle 100 is traveling on an uphill road or not can be determined by the road surface gradient ψ ｒｏａｄ Whether or not the electric vehicle 100 is towing another vehicle or the like can be determined based on the setting of a towing switch or the like (not shown), the load of the other vehicle or the like on the towing portion, or the like.

[0097] [Modification] In the above embodiment, the electric vehicle 100 is in a two-wheel drive state using the front wheels 22 in the power consumption reduction mode, but this is not limited to this. The electric vehicle 100 may be in a two-wheel drive state (or T) using the rear wheels 32 in the power consumption reduction mode. ｆ : T ｒ Therefore, in terms of automatic control of switching between control modes, the electric vehicle 100 that is in a two-wheel drive state using the front wheels 22 in the power consumption reduction mode is substantially equivalent to the electric vehicle of the modified example that is in a two-wheel drive state using the rear wheels 32 in the power consumption reduction mode. Therefore, the electric vehicle of the modified example can be configured as follows. That is, in the power consumption reduction mode, the required torque T ｒｅｑ Front torque T ｆ Rear torque T ｒ In the driving performance mode, the required torque T ｒｅｑ The temperature of the rear drive system 12 that drives the rear wheels 32 is acquired. The allocated rear torque T ｒ On the other hand, the upper limit value UL according to the temperature of the rear drive system 12 ＲＴ By setting the rear torque T ｒ When the control mode is the power consumption reduction mode, this upper limit value UL ＲＴ After the decrease in the rear torque T ｒ The output is at the upper limit UL ＲＴ In other words, the electric vehicle of this modified example is the electric vehicle 100 of the above embodiment, in which the roles of the front wheels 22 and the front drive system 11 and the rear wheels 32 and the rear drive system 12 are interchanged.

[0098] However, when comparing a two-wheel drive state (front-wheel drive) using the front wheels 22 with a two-wheel drive state (rear-wheel drive) using the rear wheels 32, the two-wheel drive state (front-wheel drive) using the front wheels 22 allows for more stable driving on any road surface, including slippery road surfaces, regardless of the driver's skill. For this reason, it is particularly preferable to configure the electric vehicle 100 so that, in the power consumption reduction mode, the vehicle is in the two-wheel drive state using the front wheels 22, as in the above embodiment.

[0099] As described above, the control method for the electric vehicle according to the above embodiment and the modified example is ｒｅｑ is a front torque T ｆ and a rear torque T ｒ and the required torque T ｒｅｑ In this control method for an electric vehicle, the control modes for adjusting the distribution of the required torque T ｒｅｑ is the front torque T ｆ or rear torque T ｒ In the driving performance mode, the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ In addition, in the power consumption reduction mode, the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ In the power consumption reduction mode, the temperature of one of the drive systems corresponding to the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ The upper limit (UL) according to the temperature of the corresponding drive system is ＦＴ or UL ＲＴ ) is set, the required torque T ｒｅｑFront torque T ｆ or rear torque T ｒ When the control mode is the power consumption reduction mode, the upper limit (UL ＦＴ or UL ＲＴ ) is reduced, the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ is this upper limit (UL ＦＴ or UL ＲＴ ), the control mode is switched to the driving performance mode.

[0100] In this way, when the control mode is the power consumption reduction mode, the upper limit value (UL ＦＴ or UL ＲＴ ) decreases, the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ The output is the upper limit (UL ＦＴ or UL ＲＴ ), the control mode is switched to the driving performance mode, so that the required torque T ｒｅｑ The front drive system 11 or the rear drive system 12 to which a large amount of torque is allocated is reliably protected from overheating, and the total torque ΣT is ｒｅｑ That is, according to the control methods for electric vehicles according to the above-described embodiments and modifications, electric vehicle 100 and the electric vehicles according to the modifications can protect the drive system from overheating and drive at the required torque, even when adjusting the torque distribution to a distribution that suppresses power consumption.

[0101] More specifically, for example, in the control method for the electric vehicle according to the above embodiment, the required torque T ｒｅｑ is a front torque T ｆ and a rear torque T ｒ and the required torque T ｒｅｑThe control method for the electric vehicle 100 has a power consumption reduction mode that prioritizes reduction in power consumption and a driving performance mode that prioritizes driving performance as control modes for adjusting the distribution of the required torque T ｒｅｑ is rear torque T ｒ Front torque T ｆ In the driving performance mode, the required torque T ｒｅｑ is the front torque T ｆ The temperature of the front drive system 11 that drives the front wheels 22 is acquired, and the allocated front torque T ｆ On the other hand, an upper limit value (upper limit torque UL ＦＴ ) to set the front torque T ｆ When the control mode is the power consumption reduction mode, the output of the upper limit value (upper limit torque UL ＦＴ ) decreases, and then the front torque T ｆ The output is the upper limit (upper limit torque UL ＦＴ ), the control mode is switched to the driving performance mode.

[0102] In this way, when the control mode is the power consumption reduction mode, the upper limit value (upper limit torque UL ＦＴ ) decreases, and then the front torque T ｆ The output is the upper limit (upper limit torque UL ＦＴ ), the control mode is switched to the driving performance mode, so that the front drive system 11 is reliably protected from overheating and the total torque ΣT is reduced to the required torque T ｒｅｑ That is, according to the control method for an electric vehicle according to the above embodiment, even when the torque distribution is adjusted to a distribution that suppresses power consumption, the electric vehicle 100 can protect the drive system from overheating and drive at the required torque.

[0103] In the control method for the electric vehicle according to the above embodiment, the temperature of the front drive system 11 is calculated based on the front torque T ｆ The temperature θ of the electric motor (front motor 21) that generates ｆ－ＭＯＴ, the temperature θ of the inverter (front inverter 23) that drives this motor ｆ－ＩＮＶ , or the motor temperature (θ ｆ－ＭＯＴ ) and inverter temperature (θ ｆ－ＩＮＶ ) are both.

[0104] In the front drive system 11, the parts that are particularly prone to overheating are the front motor 21 and the front inverter 23. For this reason, as described above, the temperature of the front drive system 11 is determined as the temperature θ ｆ－ＭＯＴ and the temperature θ of the front inverter 23 ｆ－ＩＮＶ By acquiring the temperatures and automatically switching the control mode based on these temperatures, the front drive system 11 can be protected from overheating with particular accuracy.

[0105] In the control method for the electric vehicle according to the above embodiment, the upper limit value (upper limit torque UL ＦＴ ) to the first threshold value TH １ is set in advance. Then, the upper limit value (upper limit torque UL ＦＴ ) is the first threshold TH １ The control mode is switched from the power consumption reduction mode to the driving performance mode when the following conditions are met:

[0106] In this way, the upper limit torque UL ＦＴ If this is used as the criterion for automatic control mode switching control, the control mode can be easily and particularly accurately switched from power consumption reduction mode to driving performance mode even if the front drive system 11 has multiple parts that need to be monitored for overheating protection.

[0107] In the control method for the electric vehicle according to the above embodiment, when switching the control mode, the front torque T ｆ and rear torque T ｒ Limit the rate of change of

[0108] In this way, when the control mode is switched, the rate limiter 55 limits the front torque T ｆ and rear torque T ｒBy limiting the rate of change of the control mode, automatic and forced switching of the control mode is performed smoothly without causing vibrations or the like in the electric vehicle 100.

[0109] In the control method for an electric vehicle according to the above embodiment, after the control mode is switched from the power consumption reduction mode to the driving performance mode, the upper limit value (upper limit torque UL ＦＴ ) rises, the control mode is switched from the driving performance mode to the power consumption reduction mode.

[0110] In this way, after the control mode is automatically and forcibly switched to the driving performance mode, the upper limit torque UL ＦＴ If the power consumption reduction mode is restored when it is determined that the front drive system 11 is no longer at risk of overheating due to an increase in the temperature, the period during which the control mode is forcibly switched to the driving performance mode is minimized. As a result, power consumption is likely to be reduced as long as there is no risk of the front drive system 11 overheating.

[0111] In the control method for the electric vehicle according to the above embodiment, the upper limit value (upper limit torque UL ＦＴ ) to the second threshold TH ２ is set in advance, and the upper limit value (upper limit torque UL ＦＴ ) is the second threshold TH ２ When this occurs, the control mode is returned to the power consumption reduction mode.

[0112] In this way, the upper limit torque UL ＦＴ If this is used as the criterion for determining whether to return to the power consumption reduction mode, the control mode can be returned to the power consumption reduction mode easily and particularly accurately even if the front drive system 11 has multiple parts that need to be monitored for overheat protection.

[0113] In the control method for an electric vehicle according to the above embodiment, when the control mode is the power consumption reduction mode and the vehicle is traveling on an uphill road, the upper limit value (upper limit torque UL ＦＴ ) decreases, and then the front torque T ｆ The output is the upper limit (upper limit torque UL ＦＴ ), the control mode is switched to the driving performance mode.

[0114] Driving on an uphill road in the power consumption reduction mode places a higher load on the front drive system 11 than when driving on a flat road. For this reason, for example, when driving on an uphill road after high-speed driving in the power consumption reduction mode and the temperature of the front drive system 11 has already risen, the front drive system 11 is particularly likely to overheat. For this reason, as described above, if automatic and forced switching control of the control mode is performed, especially when driving on an uphill road, the electric vehicle 100 will not be able to reduce the required torque T ｒｅｑ This makes it possible to output a sufficient amount of power while more reliably protecting the front drive system 11 from overheating.

[0115] In the control method for the electric vehicle according to the above embodiment, when the control mode is the power consumption reduction mode and the vehicle is traveling while towing another vehicle, after the upper limit value is lowered, the front torque T ｆ The output is the upper limit (upper limit torque UL ＦＴ ), the control mode is switched to the driving performance mode.

[0116] Towing in a state in which the control mode is the power consumption reduction mode places a particularly high load on the front drive system 11. For this reason, for example, when towing is attempted in a state in which the temperature of the front drive system 11 has already risen after high-speed driving in the power consumption reduction mode, or when high-speed driving is performed while towing another vehicle in the power consumption reduction mode, the front drive system 11 is particularly likely to overheat. For this reason, as described above, if automatic and forced switching control of the control mode is performed, particularly when towing, the electric vehicle 100 will not be able to reduce the required torque T ｒｅｑ This makes it possible to output a sufficient amount of power while more reliably protecting the front drive system 11 from overheating.

[0117] The control device for an electric vehicle according to the above embodiment and modification is ｒｅｑ is a front torque T ｆ and a rear torque T ｒ and the required torque T ｒｅｑThe control device for an electric vehicle has a power consumption reduction mode that prioritizes reduction in power consumption and a driving performance mode that prioritizes driving performance as control modes for adjusting the distribution of the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ In the driving performance mode, the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ In addition, in the power consumption reduction mode, the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ In the power consumption reduction mode, the temperature of one of the drive systems corresponding to the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ The upper limit (UL) according to the temperature of the corresponding drive system is ＦＴ or UL ＲＴ ) is set, the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ When the control mode is the power consumption reduction mode, the upper limit (UL ＦＴ or UL ＲＴ ) is reduced, the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ is this upper limit (UL ＦＴ or UL ＲＴ ), the control mode is switched to the driving performance mode.

[0118] In this way, when the control mode is the power consumption reduction mode, the upper limit value (UL ＦＴ or UL ＲＴ) decreases, the required torque T ｒｅｑ Front torque T ｆ or rear torque T ｒ The output is the upper limit (UL ＦＴ or UL ＲＴ ), the control mode is switched to the driving performance mode, so that the required torque T ｒｅｑ The front drive system 11 or the rear drive system 12 to which a large amount of torque is allocated is reliably protected from overheating, and the total torque ΣT is ｒｅｑ That is, according to the control methods for electric vehicles according to the above-described embodiments and modifications, electric vehicle 100 and the electric vehicles according to the modifications can protect the drive system from overheating and drive at the required torque, even when adjusting the torque distribution to a distribution that suppresses power consumption.

[0119] More specifically, the control device for the electric vehicle according to the above embodiment calculates the required torque T ｒｅｑ is a front torque T ｆ and a rear torque T ｒ and the required torque T ｒｅｑ The control device (controller 14) for the electric vehicle 100 has a power consumption reduction mode that prioritizes reduction in power consumption and a driving performance mode that prioritizes driving performance as control modes for adjusting the distribution of the required torque T ｒｅｑ Rear torque T ｒ Front torque T ｆ In the driving performance mode, the required torque T ｒｅｑ Front torque T ｆ In addition, the control device (controller 14) acquires the temperature of the front drive system 11 that drives the front wheels 22, and calculates the front torque T ｆ On the other hand, an upper limit value (upper limit torque UL ＦＴ ) to set the front torque T ｆWhen the control mode is the power consumption reduction mode, the control device (controller 14) limits the output of the upper limit value (upper limit torque UL ＦＴ ) decreases, and then the front torque T ｆ The output is the upper limit (upper limit torque UL ＦＴ ), the control mode is switched to the driving performance mode.

[0120] In this way, when the control mode is the power consumption reduction mode, the upper limit value (upper limit torque UL ＦＴ ) decreases, and then the front torque T ｆ The output is the upper limit (upper limit torque UL ＦＴ ), the control mode is switched to the driving performance mode, so that the front drive system 11 is reliably protected from overheating and the total torque ΣT is reduced to the required torque T ｒｅｑ That is, according to the control device for an electric vehicle according to the above embodiment, even when the torque distribution is adjusted to a distribution that suppresses power consumption, the electric vehicle 100 can protect the drive system from overheating and drive at the required torque.

[0121] The above describes embodiments of the present invention, but the configurations described in the above embodiments and each modified example only show some of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

Claims

1. The required torque is distributed into front torque which is the torque generated on the front wheels and rear torque which is the torque generated on the rear wheels, and as control modes for adjusting the distribution of the required torque, there are a power consumption suppression mode that prioritizes suppression of power consumption and a running performance mode that prioritizes running performance. A control method for an electric vehicle, comprising: In the power consumption suppression mode, the required torque is distributed more to either the front torque or the rear torque. In the running performance mode, the front torque or the rear torque to which the required torque is distributed more in the power consumption suppression mode is reduced. Of the front drive system that drives the front wheels or the rear drive system that drives the rear wheels, the temperature of one drive system corresponding to the front torque or the rear torque to which the required torque is distributed more in the power consumption suppression mode is acquired. By setting an upper limit value according to the temperature of the corresponding drive system for the front torque or the rear torque to which the required torque is distributed more in the power consumption suppression mode, the front torque or the rear torque to which the required torque is distributed more in the power consumption suppression mode is restricted. When the control mode is the power consumption suppression mode, after the upper limit value starts to decrease according to the temperature of the drive system, before the front torque or the rear torque to which the required torque is distributed more in the power consumption suppression mode is restricted to the upper limit value, by switching the control mode to the running performance mode, the total torque which is the sum of the front torque and the rear torque is maintained at the required torque. After switching the control mode from the power consumption suppression mode to the running performance mode, when the upper limit value increases, the control mode is switched from the running performance mode to the power consumption suppression mode. A control method for an electric vehicle.

2. A control method for an electric vehicle according to Claim 1, comprising: In the power consumption suppression mode, the required torque is distributed more to the front torque than to the rear torque. In the running performance mode, compared with the power consumption suppression mode, the required torque is distributed less to the front torque. The temperature of the front drive system that drives the front wheels is acquired. By setting the upper limit value according to the temperature of the front drive system with respect to the allocated front torque, the output of the front torque is restricted. When the control mode is the power consumption suppression mode, after the upper limit value decreases and before the output of the front torque is restricted to the upper limit value, the control mode is switched to the running performance mode. A control method for an electric vehicle.

3. A control method for an electric vehicle according to claim 2, wherein the temperature of the front drive system is the temperature of the motor that generates the front torque, the temperature of the inverter that drives the motor, or both the temperature of the motor and the temperature of the inverter. A control method for an electric vehicle.

4. A control method for an electric vehicle according to claim 2, wherein a first threshold value that is a switching condition from the power consumption suppression mode to the running performance mode is set in advance with respect to the upper limit value, and when the upper limit value becomes less than or equal to the first threshold value, the control mode is switched from the power consumption suppression mode to the running performance mode. A control method for an electric vehicle.

5. A control method for an electric vehicle according to claim 2, wherein when switching the control mode, the change rates of the front torque and the rear torque are restricted. A control method for an electric vehicle.

6. A control method for an electric vehicle according to claim 1, wherein a second threshold value that is a return condition to the power consumption suppression mode is set in advance with respect to the upper limit value, and when the upper limit value becomes greater than or equal to the second threshold value, the control mode is returned to the power consumption suppression mode. A control method for an electric vehicle.

7. A control method for an electric vehicle according to claim 2, wherein when the control mode is the power consumption suppression mode and the vehicle is running on an uphill road, after the upper limit value decreases and before the output of the front torque is restricted to the upper limit value, the control mode is switched to the running performance mode. A control method for an electric vehicle.

8. A control method for an electric vehicle according to any one of claims 2 to 7, wherein when the control mode is the power consumption suppression mode and the vehicle is running while towing another vehicle, after the upper limit value decreases and before the output of the front torque is restricted to the upper limit value, the control mode is switched to the running performance mode. A control method for an electric vehicle.

9. The required torque is distributed into front torque, which is the torque generated at the front wheels, and rear torque, which is the torque generated at the rear wheels. As control modes for adjusting the distribution of the required torque, there are a power consumption suppression mode that prioritizes suppression of power consumption and a running performance mode that prioritizes running performance. A control device for an electric vehicle having these modes is provided. In the power consumption suppression mode, the required torque is distributed more to either the front torque or the rear torque. In the running performance mode, the front torque or the rear torque to which the required torque is distributed more in the power consumption suppression mode is reduced. Of the front drive system that drives the front wheels or the rear drive system that drives the rear wheels, the temperature of one of the drive systems corresponding to the front torque or the rear torque to which the required torque is distributed more in the power consumption suppression mode is acquired. By setting an upper limit value according to the temperature of the corresponding drive system for the front torque or the rear torque to which the required torque is distributed more in the power consumption suppression mode, the front torque or the rear torque to which the required torque is distributed more in the power consumption suppression mode is limited. When the control mode is the power consumption suppression mode, after the upper limit value starts to decrease according to the temperature of the drive system, before the front torque or the rear torque to which the required torque is distributed more in the power consumption suppression mode is limited to the upper limit value, by switching the control mode to the running performance mode, the total torque, which is the sum of the front torque and the rear torque, is maintained at the required torque. After switching the control mode from the power consumption suppression mode to the running performance mode, when the upper limit value increases, the control mode is switched from the running performance mode to the power consumption suppression mode. A control device for an electric vehicle.