JP7530848B2 - Gear shift control method and gear shift control device - Google Patents

Description

The present invention relates to a gear shift control method and gear shift control device for an electric vehicle having multiple motors and at least one transmission.

Patent Document 1 describes an electric vehicle having a fuel cell and a transmission. In this electric vehicle, control is performed to shorten the gear change time by taking into account the response delay in the control of the fuel cell. More specifically, when upshifting, the electric vehicle of Patent Document 1 switches the motor, which is the drive source, into regenerative operation, thereby reducing the motor rotation speed to the rotation speed corresponding to the gear to which the gear is to be shifted. Patent Document 1 also describes adjusting the amount of power generated by the fuel cell before shifting to ensure the amount of regeneration by the motor.

International Publication No. 2017/060960

In electric vehicles that have two motors as drive sources, with at least one of the motors connected to the drive wheels via a transmission, it is desirable to shorten the gear change time. Specifically, when the clutch goes into neutral during gear change, the torque generated by the motor connected to the drive wheels via the transmission is no longer transmitted. This causes so-called torque loss during gear change, so it is desirable to have a short gear change time even in such electric vehicles.

However, regenerative control that generates more regenerative power than the battery can normally accept is not possible. For this reason, depending on the battery's charge rate, regenerative control to reduce the motor's rotation speed may not be sufficient, resulting in longer gear change times.

The present invention aims to provide a gear shift control method and a gear shift control method that can shorten the gear shift time more stably than before in an electric vehicle that has two motors as drive sources, at least one of which is connected to the drive wheels via a transmission.

One aspect of the present invention is a gear shift control method executed when shifting the transmission in an electric vehicle having a first motor and a second motor as drive sources driven by power supplied from a battery, with at least the first motor connected to drive wheels via a transmission. In this gear shift control method, the torque to be output by the first motor is compensated for by increasing the torque output by the second motor compared to before the start of gear shift control, thereby maintaining the output of the required driving force, which is the driving force required for the electric vehicle. In addition, when the clutch of the transmission is in neutral, the first motor is regeneratively controlled so that the rotation speed of the first motor is synchronized with the rotation speed corresponding to the gear to be shifted. Then, a part or all of the regenerative power generated by the regenerative control of the first motor is used to drive the second motor.

The present invention provides a gear shift control method and gear shift control device that can reduce gear shift time more stably than ever before in an electric vehicle that has two motors as drive sources, at least one of which is connected to a drive wheel via a transmission.

FIG. 1 is an explanatory diagram showing a schematic configuration of an electric vehicle. FIG. 2 is a flow chart of the gear shift control for upshifting. FIG. 3 is a shift diagram of an electric vehicle. FIG. 4 is an explanatory diagram showing types of synchronization time reduction control. FIG. 5 is an explanatory diagram showing the flow of power in the C1 control. FIG. 6 is an explanatory diagram showing the flow of power in the C2 control. FIG. 7 is an explanatory diagram showing the flow of power in the C3 control. FIG. 8 is an explanatory diagram showing the flow of power in the C4 control. FIG. 9 is a flowchart of the rotation speed synchronization control including the synchronization time reduction control. FIG. 10 is a timing chart showing the accelerator opening, vehicle speed, rear motor RPM, clutch position, rear motor operation mode, and torque during an upshift. FIG. 11 is a flowchart of the rotation speed synchronization control according to the second embodiment. FIG. 12 is a skeleton diagram showing the configuration of an electric vehicle according to a modified example.

The following describes an embodiment of the present invention with reference to the drawings.

[First embodiment]
Fig. 1 is an explanatory diagram showing a schematic configuration of an electric vehicle 100. As shown in Fig. 1, the electric vehicle 100 is driven by power supplied from a battery 10 (Batt). The electric vehicle 100 of this embodiment is a four-wheel drive vehicle in which front wheels 11 and rear wheels 12 are driven wheels. That is, the electric vehicle 100 of this embodiment is an electric four-wheel drive vehicle. In addition to the battery 10, the front wheels 11, and the rear wheels 12, the electric vehicle 100 is equipped with a front-wheel drive system FDS, a rear-wheel drive system RDS, and a controller 13 (CTRL).

The battery 10 is a so-called high-voltage battery, and is a common energy source for driving the front wheels 11 and the rear wheels 12. The battery 10 is also rechargeable. The battery 10 is connected to the front-wheel drive system FDS and the rear-wheel drive system RDS by a bus bar 16. The bus bar 16 has a line 16a for supplying power to the front-wheel drive system FDS and/or the rear-wheel drive system RDS, and a line 16b for receiving power from the front-wheel drive system FDS and/or the rear-wheel drive system RDS.

The battery 10 selectively supplies or receives power. For example, the battery 10 selectively supplies power to the front-wheel drive system FDS and receives power from the front-wheel drive system FDS. Similarly, the battery 10 selectively supplies power to the rear-wheel drive system RDS and receives power from the rear-wheel drive system RDS.

The front-wheel drive system FDS is a system that drives the front wheels 11. The front-wheel drive system FDS includes a front junction box 21 (FR_JB), a front inverter 22 (FR_INV), a front motor 23 (FR_MOT), and a front power transmission device 24.

The front junction box 21 distributes the high voltage supplied from the battery 10. The front junction box 21 also functions as a breaker that cuts off the high voltage supplied from the battery 10 in the event of an abnormality, etc. In this embodiment, the front junction box 21 includes a DC/DC converter that converts the voltage of the direct current power supplied from the battery 10 into a voltage for driving the front motor 23. In this embodiment, the front junction box 21 also includes a charger for supplying power (regenerative power) from the front wheel drive system FDS to the battery 10. In other words, the front junction box 21 is a so-called power delivery module (PDM).

The front inverter 22 converts the DC power supplied from the battery 10 via the front junction box 21 into AC power and supplies it to the front motor 23. When controlling the front motor 23 in a regenerative manner, the front inverter 22 converts the AC power supplied from the front motor 23 into DC power. This DC power is supplied to the battery 10 via the front junction box 21. As a result, the battery 10 is charged.

The front motor 23 is, for example, a three-phase AC motor. The front motor 23 is driven according to AC power input from the front inverter 22, and generates torque for driving the front wheels 11 on the rotating shaft 25 of the front motor 23. This torque is transmitted to the front wheels 11 by the front power transmission device 24, and generates driving force on the front wheels 11. In other words, the front motor 23 is the driving source for the front wheels 11. In addition, the operating modes of the front motor 23 include a torque control mode that controls the torque for generating driving force on the front wheels 11, and a regenerative control mode that generates a braking force on the front wheels 11.

The front power transmission device 24 generates a driving force for the front wheels 11 by transmitting the torque generated by the front motor 23 to the front wheels 11. When the front motor 23 is under regenerative control, the kinetic energy of the front wheels 11 is transmitted to the rotating shaft 25 of the front motor 23. The front power transmission device 24 includes a rotating shaft 26 and a drive shaft 27. The rotating shaft 26 is provided with a gear 28 and a gear 29. The gear 28 meshes with a gear 30 that is attached to the rotating shaft 25 of the front motor 23. The gear 29 is connected to a differential mechanism 31 that is attached to the drive shaft 27. This allows torque to be transmitted between the front motor 23 and the front wheels 11.

The rear-wheel drive system RDS is a system that drives the rear wheels 12. The rear-wheel drive system RDS includes a rear junction box 41 (RR_JB), a rear inverter 42 (RR_INV), a rear motor 43 (RR_MOT), and a rear power transmission device 44.

The rear junction box 41 is configured similarly to the front junction box 21, except that it is for the rear wheels 12. Similarly, the rear inverter 42 and rear motor 43 are configured similarly to the front inverter 22 and front motor 23. However, the regenerative control mode of the rear motor 43 includes a normal regenerative control mode for generating a braking force on the rear wheels 12, and a rotation speed control mode for regeneratively controlling the rear motor 43 for gear shifting, which will be described later.

The rear power transmission device 44 generates a driving force for the rear wheels 12 by transmitting the torque generated by the rear motor 43 to the rear wheels 12. When the rear motor 43 is operated in regenerative mode, the kinetic energy of the rear wheels 12 is transmitted to the rotating shaft 45 of the rear motor 43. The operation of the rear power transmission device 44 is similar to that of the front power transmission device 24. That is, like the front power transmission device 24, the rear power transmission device 44 includes a rotating shaft 46 and a drive shaft 47.

On the other hand, the rear power transmission device 44 has a transmission 51, which is not provided in the front power transmission device 24, on the rotating shaft 45 of the rear motor 43. The transmission 51 in this embodiment has a low gear 52 with a relatively small gear ratio and a high gear 53 with a relatively large gear ratio, and is capable of shifting between these two gear stages. In addition, the gear shift of the transmission 51 is performed by a clutch 54.

The clutch 54 is, for example, a clutch with a dog mechanism or a clutch with a synchro mechanism. The clutch 54 includes a sleeve 55 that can slide along the rotating shaft 45 between the low gear 52 and the high gear 53, and a hub 56 that slides integrally with the sleeve 55. The operation of the clutch 54, i.e., the gear shift control, is automatically performed by the controller 13.

In addition, since the transmission 51 is provided, the rotating shaft 46 has a gear 57 that meshes with the low gear 52, a gear 58 that meshes with the high gear 53, and a gear 59 that connects to a differential mechanism 60 interposed in the drive shaft 47. The low gear 52 and the gear 57 form a low gear train. The high gear 53 and the gear 58 form a high gear train. The torque transmitted to the rotating shaft 46 via the low gear 52 or the high gear 53 is transmitted to the drive shaft 47 via the gear 59 and the differential mechanism 60. In this way, torque is transmitted between the rear motor 43 and the rear wheel 12.

More specifically, when the hub 56 meshes with the hub of the low gear 52, the torque generated by the rear motor 43 on the rotating shaft 45 is transmitted to the rear wheel 12 via the low gear 52. On the other hand, when the hub 56 meshes with the hub of the high gear 53, the torque generated by the rear motor 43 on the rotating shaft 45 is transmitted to the rear wheel 12 via the high gear 53. Also, during the gear shifting process, a neutral (non-engaged) state occurs in which the hub 56 is not connected to either the low gear 52 or the high gear 53. The neutral state is a state in which the torque generated by the rear motor 43 on the rotating shaft 45 is not transmitted to the rear wheel 12.

Hereinafter, the position where the hub 56 is connected to the hub of the low gear 52 and the clutch 54 is engaged with the low gear 52 is referred to as the "low position (L)". The position where the hub 56 is engaged with the hub of the high gear 53 and the clutch 54 is engaged with the high gear 53 is referred to as the "high position (H)". Also, the position where the hub 56 is not connected to either the low gear 52 or the high gear 53 and the clutch 54 is not engaged is referred to as the "neutral position (N)". Also, shifting from the low gear 52 to the high gear 53 is referred to as an "upshift", and shifting from the high gear 53 to the low gear 52 is referred to as a "downshift".

When the clutch 54 is shifted from the low or high position to the neutral position, the torque of the rear motor 43 must be set to zero. When the clutch 54 is engaged with the low gear 52 or high gear 53 and the torque of the rear motor 43 is not zero, a pressing force is generated between the low gear 52 or high gear 53 and the hub 56 in a direction that promotes their connection. For this reason, when the torque of the rear motor 43 is not zero, the clutch 54 cannot be shifted to the neutral position. Therefore, for example, when upshifting, the torque of the rear motor 43 is set to zero while the clutch 54 remains engaged with the low gear 52. This eliminates the mutual pressing force in the direction in which the hub 56 and the hub of the low gear 52 are connected. As a result, the sleeve 55 can slide, and the clutch 54 can be shifted to the neutral position.

Furthermore, when the clutch 54 is shifted from the neutral position to the low position or the high position, it is necessary to roughly synchronize the rotation speed required for the gear to be engaged after the shift with the rotation speed N _R of the rear motor 43. This is because if there is a difference between the rotation speed required for the gear to be engaged after the shift and the rotation speed N _R of the rear motor 43, the hub 56 will not be connected to the gear after the shift. Hereinafter, the control for roughly matching the rotation speed N _R of the rear motor 43 with the rotation speed required for the gear to be engaged after the shift when the clutch 54 is in the neutral position will be referred to as rotation speed synchronization control.

The controller 13 is composed of one or more computers that comprehensively control each part of the electric vehicle 100, such as the battery 10, the front motor 23, and the rear motor 43. In this embodiment, the controller 13 includes a vehicle controller that controls the driving of the electric vehicle 100 and a battery controller that controls the operation of the battery 10. The computer that constitutes the controller 13 is composed of, for example, a central processing unit (CPU), a random access memory (RAM), and an input/output interface (I/O interface). In addition, the controller 13 is programmed to periodically execute control of each part at a predetermined control cycle.

The controller 13 can also obtain information (vehicle information) relating to the operating state and the like from each part of the electric vehicle 100 as necessary. For example, the controller 13 can obtain the charging rate (SOC (State Of Charge)) of the battery 10, the accelerator opening Apo (see FIG. 10) indicating the amount of accelerator pedal operation, and the vehicle speed V (see FIGS. 3 and 10) or the wheel speed (not shown). The controller 13 can also obtain the rotation speed (not shown) of the front motor 23, the rotation speed N _R of the rear motor 43 (see FIG. 10), and the position CL of the clutch 54 (see FIG. 10). The controller 13 can also obtain other vehicle information such as the temperature TempFR of the front motor 23 (see FIG. 12) and the temperature TempRR of the rear motor 43 (see FIG. 12).

Furthermore, the controller 13 can calculate the control parameters of the electric vehicle 100 using the various vehicle information described above. For example, the controller 13 uses the accelerator opening Apo to calculate the driver's requested driving force for the electric vehicle 100. In addition, the controller 13 can obtain or calculate the regenerative power PregenFR obtained when the front motor 23 is regeneratively controlled (hereinafter referred to as front regenerative power). Similarly, the controller 13 can obtain or calculate the regenerative power obtained when the rear motor 43 is regeneratively controlled.

The control that the controller 13 executes in relation to upshifting (hereafter referred to as upshift control) is described in detail below.

Figure 2 is a flowchart of the gear shift control for upshifting. As shown in Figure 2, in step S101, the controller 13 determines whether or not it is necessary to upshift the transmission 51. The timing of the upshift will be described in detail later.

When an upshift is required, torque compensation control is executed in step S102. Torque compensation control is a control that compensates for the torque to be output by the rear motor 43 by increasing the torque output by the front motor 23 compared to before control for an upshift (hereinafter referred to as upshift control) was started, thereby maintaining the required driving force. When torque compensation by this torque compensation control is completed, the torque of the rear motor 43 becomes zero, so that the clutch 54 can transition from the low position to the neutral position. Note that the output of the front motor 23 is usually limited by a rated torque. The limit by the rated torque of the front motor 23 in the torque compensation control will be described in detail later.

When the torque compensation control is completed, the controller 13 releases the clutch 54 in step S103. That is, step S103 causes the position of the clutch 54 to transition from the low position to the neutral position.

After that, in step S104, the controller 13 executes the rotation speed synchronization control. The rotation speed synchronization control performed here is for upshifting. Therefore, the rotation speed N _R of the rear motor 43 is reduced so that the rotation speed N R of the rear motor 43 matches the rotation speed required for the high gear 53 (hereinafter simply referred to as the rotation speed of the high gear 53). At this time, the controller 13 switches the control of the rear motor 43 to regenerative control, and applies a load to the rotary shaft 45 of the rear motor 43, thereby reducing the rotation speed _{N R of} the rear motor 43.

The rotation speed synchronization control when upshifting includes control (hereinafter referred to as synchronization time reduction control) for reducing the time required for the rotation speed _NR of the rear motor 43 to synchronize with the rotation speed of the high gear 53 (hereinafter referred to as synchronization time). The synchronization time is reduced by switching the control of the rear motor 43 to regenerative control, but the synchronization time reduction control referred to here reduces the synchronization time even more than when the control of the rear motor 43 is switched to regenerative control. In other words, the rotation speed synchronization control in step S104 is rotation speed synchronization control in which the synchronization time is reduced compared to the conventional case. The synchronization time reduction control will be described in detail later.

When the rotation speed N _R of the rear motor 43 is synchronized with the rotation speed of the high gear 53 by the above rotation speed synchronization control, the clutch 54 is able to mesh with the high gear 53. Therefore, in step S105, the controller 13 engages the clutch 54. That is, the clutch 54 transitions from the neutral position to the high position by step S103.

Then, in step S106, the controller 13 executes torque transition control. The torque transition control is a control that causes the torque that was compensated for by the front motor 23 through the torque compensation control to be output again to the rear motor 43. This completes the upshift, and the electric vehicle 100 is again driven by the front motor 23 and the rear motor 43.

Note that the torque compensation control in step S102 and the torque transition control in step S106 are both controls that change the torque distribution between the front motor 23 and the rear motor 43 (and thus the front wheels 11 and the rear wheels 12). Changing the torque distribution between the front motor 23 and the rear motor 43 in this way is generally sometimes referred to as "switching" the torque. However, as described above, the directionality and technical significance of the torque switching differs between steps S102 and S106. For this reason, in this embodiment, for the sake of distinction, the torque switching in step S102 is referred to as torque compensation, and the torque switching in step S106 is referred to as torque transition.

<Upshift timing and torque compensation control>
3 is a shift diagram of the electric vehicle 100. In FIG. 3, a solid line 71 indicates the relationship between the vehicle speed V and the maximum driving force [N] that the front motor 23 can generate alone on the electric vehicle 100 (front wheels 11). A two-dot chain line 72 indicates the maximum driving force that can be generated in the electric vehicle 100 by the front motor 23 and the rear motor 43 connected to the low gear 52. A dashed line 73 indicates the maximum driving force generated in the electric vehicle 100 by the front motor 23 and the rear motor 43 connected to the high gear 53. A thin solid curve R/L indicates the driving force that balances with the road load for the vehicle speed V. A dashed curve is a constant acceleration line that indicates the driving force for maintaining a constant acceleration for the vehicle speed V.

As shown in FIG. 3, the controller 13 monitors the vehicle speed V and determines whether an upshift is necessary based on whether the vehicle speed V exceeds a predetermined shifting vehicle speed V1. When the vehicle speed V exceeds the shifting vehicle speed V1, the controller 13 executes an upshift to switch the clutch 54 from the low position (L) to the high position (H). The shifting vehicle speed V1 is predetermined within the range where the two-dot chain line 72 and the one-dot chain line 73 overlap, for example.

Upshifts are also performed by torque compensation control along the constant acceleration line shown by the thin solid curve R/L or the dashed curve. This is to suppress changes in acceleration caused by upshifts and prevent or reduce vibrations caused by upshifts.

On the other hand, in torque compensation control, the front motor 23 is usually set to a rated torque as the upper limit of its output. Therefore, when torque compensation is performed for shifting, the rated torque of the front motor 23 is taken into consideration as follows.

The driving force range B1 in FIG. 3 represents the range in which the driving force (required driving force) of the electric vehicle 100 at the shifting vehicle speed V1 is equal to or less than the driving force A1 that the front motor 23 can output alone. When upshifting, if the driving force of the electric vehicle 100 is within this driving force range B1, the front motor 23 can compensate for all of the torque that should be output by the rear motor 43 within the rated torque range.

On the other hand, the driving force range B2 in FIG. 3 represents a range in which the driving force of the electric vehicle 100 at the shifting vehicle speed V1 is greater than the driving force A1 that the front motor 23 can output alone and is equal to or less than the upper limit A2 of the driving force that the front motor 23 and the rear motor 43 can output in cooperation with each other. When the driving force of the electric vehicle 100 is within this driving force range B2 when upshifting, the driving force of the electric vehicle 100 exceeds the driving force generated by the torque that the front motor 23 can output within the rated torque range. Therefore, when upshifting in the driving force range B2, the front motor 23 cannot compensate for the torque that the rear motor 43 should output within the normal rated torque range. Therefore, when upshifting in the driving force range B2, a state called "torque loss" or "driving force loss" occurs while the clutch 54 is in the neutral state. "Torque loss" or "driving force loss" is a state in which the driving force (torque) of the electric vehicle 100 is insufficient for the required driving force (required torque).

Therefore, in this embodiment, two types of rated torque, a first rated torque and a second rated torque, are defined as the rated torque of the front motor 23. The first rated torque is a normal rated torque when the front motor 23 is driven stably for a relatively long time. Upshifting in the driving force range B1 is performed within the range of this first rated torque. The second rated torque is a rated torque when the front motor 23 is driven for a relatively short time. That is, the first rated torque is a rated value of the output torque for normal long-term operation, whereas the second rated torque is a rated value of the output torque that is acceptable only for short-term driving. Therefore, the value of the second rated torque is greater than the first rated torque. Then, when upshifting in the driving force range B2, the controller 13 drives the front motor 23 within the range of the second rated torque, exceeding the first rated torque. As a result, even when upshifting in the driving force range B2, the torque to be output by the rear motor 43 is compensated for by the front motor 23. Hereinafter, compensating for the torque that the rear motor 43 should output by driving the front motor 23 within the range of the second rated torque will be referred to as "torque boost."

<Synchronization time reduction control>
As described above, when an upshift is performed within the driving force range B2, the torque boost is performed. Since the time during which the front motor 23 can be driven within the second rated torque range by the torque boost is limited, it is necessary to complete the rotation speed synchronization control as quickly as possible.

On the other hand, in the rotation speed synchronization control, the rear motor 43 is regeneratively controlled to shorten the synchronization time, but simply controlling the rear motor 43 regeneratively may not complete the rotation speed synchronization control within the time required to drive the front motor 23 within the range of the second rated torque. Regenerative control can usually be performed within a range in which the regenerative power generated does not exceed the power that the battery 10 can accept. For this reason, for example, when the battery 10 is close to being fully charged and the power that the battery 10 can accept is low, the regenerative braking force for the rear motor 43 becomes insufficient, and the synchronization time becomes long. For this reason, simply controlling the rear motor 43 regeneratively may result in the synchronization time exceeding the time required to drive the front motor 23 within the range of the second rated torque.

Therefore, in this embodiment, when an upshift accompanied by a torque boost is performed, the controller 13 performs synchronization time reduction control to reduce the synchronization time by enabling the rear motor 43 to be regeneratively controlled regardless of the charging rate of the battery 10. Specifically, in the synchronization time reduction control, at least a part or all of the regenerative power generated by the regenerative control of the rear motor 43 is used as a part or all of the power required to drive the front motor 23 accompanied by a torque boost. According to the synchronization time reduction control, the main recipient of the regenerative power generated by the regenerative control of the rear motor 43 is essentially the front motor 23. Therefore, by performing the synchronization time reduction control, the battery 10 does not need to receive all of the regenerative power generated by the rear motor 43. Therefore, according to the synchronization time reduction control, the rear motor 43 can be regeneratively controlled to the maximum extent almost regardless of the charging rate of the battery 10. As a result, the synchronization time is reduced to almost the minimum time that can be reached by the regenerative control of the rear motor 43 regardless of the charging rate of the battery 10.

In the following, the regenerative power generated by the regenerative control of the rear motor 43 is referred to as rear regenerative power P _regenRR . At least a portion of the power consumption of the front motor 23 that increases due to the torque boost is compensated for by the rear regenerative power P _regenRR . For this reason, in the following, the power of the rear regenerative power P _regenRR that is used to drive the front motor 23 is referred to as boost power P _boost .

Fig. 4 is an explanatory diagram showing types of synchronization time reduction control. As shown in Fig. 4, the synchronization time reduction control includes four control modes according to the relationship between the required driving force for the electric vehicle 100 and the electric power (hereinafter referred to as required electric power) _Pdrv required to generate this required driving force.

The first synchronization time reduction control (hereinafter referred to as C1 control) is a synchronization time reduction control when the required power P _drv is equal to the regenerative power (hereinafter referred to as rear regenerative power) P _regenRR generated by maximum regenerative control of the rear motor 43. FIG. 5 is an explanatory diagram showing the flow of power in the C1 control. As shown in FIG. 5, in the C1 control, the rear regenerative power P _regenRR is entirely used as the boost power P _boost . That is, P _drv = P _boost = P _regenRR . In this way, in the C1 control, the rear regenerative power P _regenRR is not stored in the battery 10. Therefore, according to the C1 control, the rear motor 43 can be regeneratively controlled at maximum efficiency regardless of the charging rate of the battery 10. As a result, the synchronization time is reduced in the C1 control compared to the case where the rear motor 43 is regeneratively controlled at an efficiency lower than maximum efficiency according to the charging rate of the battery 10.

The second synchronization time reduction control (hereinafter, referred to as C2 control) is a synchronization time reduction control when the required power _Pdrv is larger than the rear regenerative power PregenRR (see FIG. 4). FIG. 6 is an explanatory diagram showing the flow of power in the C2 control. As shown in FIG. 6, in the C2 control, the rear regenerative power _PregenRR is entirely used for _{the boost} power Pboost, as in the C1 control. However, in the C2 control, even if the rear regenerative power _PregenRR is entirely used for _{the boost} power Pboost, there is a shortage of the required power _Pdrv . Therefore, the shortage is made up for by the power Pout supplied from the battery 10. That is, _Pdrv = _Pboost + _Pout = _PregenRR + _Pout . In this way, in the C2 control, the rear regenerative power _PregenRR is not stored in the battery 10. Therefore, according to the C2 control, the rear motor 43 can be regeneratively controlled with maximum efficiency regardless of the charging rate of the battery 10. As a result, compared to a case where the rear motor 43 is regeneratively controlled at an efficiency lower than the maximum efficiency according to the charging rate of the battery 10, the synchronization time is reduced in the C2 control.

The third synchronization time shortening control (hereinafter, referred to as C3 control) is a synchronization time shortening control when the required power _Pdrv is smaller than the rear regenerative power _PregenRR (see FIG. 4). FIG. 7 is an explanatory diagram showing the flow of power in the C3 control. As shown in FIG. 7, in the C3 control, a part of the rear regenerative power _PregenRR is used as the required power _Pdrv . However, since the rear regenerative power _PregenRR exceeds the required power _Pdrv , the required power _Pdrv is entirely covered by the rear regenerative power _PregenRR . The surplus power ( _PregenRR - _Pdrv ) obtained by subtracting the required power _Pdrv required to drive the front motor 23 from the rear regenerative power _PregenRR becomes the substantial supply power _Pin to the battery 10. In this way, in the C3 control, at least a part of the rear regenerative power _PregenRR is used as _{the boost} power Pboost. That is, _PregenRR = _Pboost + _Pin = _Pdrv + _Pin . In this way, in the C3 control, the power that the battery 10 must receive in order to regeneratively control the rear motor 43 is reduced compared to when the battery 10 receives all of the rear regenerative power P _regenRR . Therefore, the C3 control increases the number of situations in which the rear motor 43 can be regeneratively controlled at approximately maximum efficiency. As a result, in the C3 control, there are more situations in which the synchronization time is reduced compared to when the rear motor 43 is regeneratively controlled at an efficiency lower than maximum efficiency depending on the charging rate of the battery 10.

In addition, in the above-described C3 control, when the required driving force increases, the amount of rear regenerative power P _regenRR used to drive the front motor 23 is increased, and the surplus power (P _in ) charged to the battery 10 is reduced. That is, in the C3 control, the rear regenerative power P _regenRR is preferentially used as boost power P _boost .

The fourth synchronization time shortening control (hereinafter referred to as C4 control) is a synchronization time shortening control when the required power _Pdrv is zero or negative (see FIG. 4). This C4 control is a control for dealing with a situation in which the required driving force decreases during an upshift. After the vehicle speed V exceeds the shifting vehicle speed V1 and the upshift control starts, if the accelerator is released or the brake is further applied before the upshift is completed, the C4 control is executed.

FIG. 8 is an explanatory diagram showing the flow of power in the C4 control. As shown in FIG. 8, in the C4 control, the required power P _drv is zero or negative, and the front motor 23 is regeneratively controlled. For this reason, the torque boost of the front motor 23 is not required. Therefore, the sum of the regenerative power (hereinafter referred to as the front regenerative power) P _regenFR generated by the regenerative control of the front motor 23 and the rear regenerative power P _regenRR is the power P _in supplied to the battery 10. That is, P _in =P _regenFR +P _regenRR . Therefore, the regenerative control of the front motor 23 and the rear motor 43 is limited to a range in which the supplied power P _in does not exceed the power that the battery 10 can accept. However, there is a degree of freedom in the distribution of the front regenerative power P _regenFR and the rear regenerative power P _regenRR within the range of the power that the battery 10 can accept. For this reason, in the C4 control, the rear regenerative power P _regenRR is maximized. That is, in the C4 control, priority is given to maximizing the efficiency of regenerative control of the rear motor 43 over the front motor 23. Therefore, in the C4 control, the synchronization time is minimized even in an irregular situation in which the required driving force decreases after the start of upshift control but before the completion of the upshift.

9 is a flowchart of the rotation speed synchronization control including the synchronization time reduction control. As shown in FIG 9, in step S201, it is determined whether the electric vehicle 100 is in a powering state depending on whether the required power _Pdrv is greater than zero.

When the electric vehicle 100 is in a powered state and normal upshift control can be executed, it is determined in step S202 whether the required power _Pdrv is equal to the rear regenerative power _PregenRR . On the other hand, when an irregularity such as the accelerator being released occurs after the start of the rotation speed synchronization control and it is determined in step S201 that the electric vehicle 100 is not in a powered state, the C4 control is executed in step S203.

When it is determined in step S202 that the required electric power _Pdrv is equal to the rear regenerative electric power _PregenRR , the C1 control is executed in step S204. On the other hand, when it is determined that the required electric power _Pdrv is not equal to the rear regenerative electric power _PregenRR , it is further determined in step S205 whether the required electric power _Pdrv is greater than the rear regenerative electric power _PregenRR .

When it is determined in step S205 that the required electric power _Pdrv is greater than the rear regenerative electric power _PregenRR , the C2 control is executed in step S206. On the other hand, when the required electric power _Pdrv is smaller than the rear regenerative electric power _PregenRR , the C3 control is executed in step S207.

Thus, when rotation speed synchronization control is performed by any of C1 control, C2 control, C3 control, or C4 control, in step S208, it is confirmed whether or not rotation speed synchronization has been completed. If rotation speed synchronization has not been completed, the above control is repeated.

The following describes the operation of upshift control of the electric vehicle 100 configured as described above.

FIG. 10 is a timing chart showing (A) accelerator opening Apo, (B) vehicle speed V, (C) rear motor rotation speed N _R , (D) clutch position CL, (E) rear motor operation mode, and (F) torque. In FIG. 10(C) and (D), "L", "N" and "H" represent the positions of the clutch 54. That is, "L" represents the low position, "H" represents the high position, and "N" represents the neutral position. In FIG. 10(C) to (F), the dashed line represents the result of upshift control of a comparative example that does not include torque boost and synchronization time reduction control. In FIG. 10(F), "T _FF " represents the torque of the front motor 23 (hereinafter referred to as "front torque"), and "T _FR " represents the torque of the rear motor 43 (hereinafter referred to as "rear torque").

As shown in Fig. 10(A), the accelerator is depressed at time t1, and as shown in Fig. 10(B), the vehicle speed V exceeds the shift vehicle speed V1 at the same time t1, making an upshift necessary. At this time, as shown in Fig. 10(D), the clutch 54 is in the low position ("L") at time t1, and as shown in Fig. 10(C), the rotation speed N _R of the rear motor 43 is also the rotation speed corresponding to the low gear 52. Also, as shown in Fig. 10(E), the clutch 54 is engaged in the low gear 52 at time t1, so the operation mode of the rear motor 43 is the torque control mode.

On the other hand, as shown in FIG. 10(F), since it is determined that an upshift is necessary at time t1, torque compensation control, which is the first stage of the upshift control, is started from time t1. Specifically, while the front torque T _FF and the rear torque T _FR are the same torque Σ/2 (1/2 of the required torque Σ) until time t1, the rear torque T _FR is gradually reduced to zero after time t1 in order to enable the clutch 54 to transition to the neutral position. On the other hand, in order to compensate for the driving force that is reduced by gradually reducing the rear torque T _FR , the front torque T _FF is gradually increased in accordance with the gradual reduction of the rear torque T _FR . Here, the increase amount β of the front torque T _FF is the first rated torque, and the increase amount γ is due to the torque boost within the range of the second rated torque. Therefore, the total increase amount β+γ of the front torque T _FF is equal to the decrease amount α of the rear torque T _FR .

In this way, when the rear torque _TFR reaches zero at time t2 while the front torque _TFF is being compensated for, the clutch 54 is shifted from the low position to the neutral position as shown in Fig. 10(D). Therefore, as shown in Fig. 10(E), after time t2, the operation mode of the rear motor 43 is switched to the rotation speed control mode, and the rear motor 43 is subjected to regenerative control. As a result, as shown in Fig. 10(C), the rotation speed N _R of the rear motor 43 is gradually reduced toward the rotation speed corresponding to the high gear 53.

Then, when the rotation speed N _R of the rear motor 43 reaches the rotation speed corresponding to the high gear 53 at time t3, the regenerative control of the rear motor 43 is terminated and the clutch 54 is transitioned to the high position. After that, when the clutch 54 is completely engaged with the high gear 53 at time t4, the operation mode of the rear motor 43 is switched from the rotation speed control mode to the torque control mode as shown in FIG. 10(E), and the torque transition control is executed. Specifically, in the torque transition control, the rear torque T _FR is gradually increased toward 1/2 of the required torque Σ, contrary to the torque compensation control. Therefore, the front torque T _FF is gradually decreased toward 1/2 of the required torque Σ. Then, when the front torque T _FF and the rear torque T _FR reach the same torque Σ/2 at time t7, the upshift control is completed.

When performing upshift control as described above, the rotation speed synchronization control performed from time t2 to time t3 includes synchronization time reduction control. Therefore, as shown in FIG. 10(F), the regenerative torque RT during the rotation speed synchronization control is the maximum regenerative torque RT2 that can be realized by the rear motor 43.

On the other hand, as shown by the dashed line in Fig. 10(F), in the comparative example that does not include the synchronization time reduction control, the regenerative torque of the rear motor 43 reaches an upper limit depending on the charging rate of the battery 10, and only the regenerative torque RT1 can be obtained, which is less than the maximum regenerative torque RT2. Therefore, as shown by the dashed line in Fig. 10(C), it takes time for the rotation speed N _R of the rear motor 43 to synchronize with the rotation speed corresponding to the high gear 53, and the rotation speed synchronization is completed at time t5. As a result, as shown in Fig. 10(D) and (E), the transition of the clutch 54 to the high position and the switching to the torque control mode are also delayed until time t6, and the completion of the upshift control is also delayed until time t8 as shown in Fig. 10(F).

Therefore, comparing the upshift control of this embodiment with that of the comparative example, in the comparative example, the time until the upshift control is completed varies depending on the charge rate of the battery 10. In contrast, in this embodiment, the synchronization time reduction control allows the upshift control to be completed more stably and in a shorter time than in the comparative example, regardless of the charge rate of the battery 10. And the upshift control is completed stably and in a shorter time. Therefore, although the execution time of the torque boost is limited, the upshift control of this embodiment allows the torque boost to be performed. Therefore, the upshift control of this embodiment has the advantage that no torque loss occurs compared to the comparative example in which the torque boost is not performed.

Note that FIG. 10 shows an example in which synchronization time reduction control is performed in upshift control accompanied by torque boost, but this is not limiting. In other words, the synchronization time can be reduced by the above-described synchronization time reduction control even in upshift control that does not involve torque boost.

As described above, the shift control method of the present embodiment is executed when upshifting the transmission 51 in the electric vehicle 100 having the first motor (rear motor 43) and the second motor (front motor 23) as drive sources driven by power supplied from the battery 10, and in which at least the first motor (rear motor 43) is connected to the drive wheels (rear wheels 12) via the transmission 51. In this shift control method, the torque (front torque T FF ) output by the second motor (front motor 23) is increased compared to before the control for the upshift is started, thereby compensating for the torque (rear torque T _FR ) that should be output by the first motor (rear motor 43), and the required drive force that is the drive force required for the electric vehicle 100 is maintained. In addition, when the clutch 54 of the transmission 51 is put into neutral, the first motor (rear _motor 43) is regeneratively controlled, so that the rotation speed N _R of the first motor (rear motor 43) is synchronized with the rotation speed corresponding to the gear (high gear 53) to which the shift is to be made. In addition, a part or all of the regenerative power (rear regenerative power P _regenRR ) generated by the regenerative control of the first motor (rear motor 43 ) is used to drive the second motor (front motor 23 ).

That is, in the shift control method of the present embodiment, when upshifting, torque compensation control and rotation speed synchronization control by regeneration control are executed, and in particular, when torque boost is executed in the torque compensation control, the regenerative power (rear regenerative power P _regenRR ) of the first motor (rear motor 43) is used to drive the second motor (front motor 23). As a result, in the shift control method of the present embodiment, it is possible to execute maximum regenerative control for rotation speed synchronization, regardless of the charging rate of the battery 10. As a result, the synchronization time of the rotation speed is kept shorter and more stable than in the past. That is, in the shift control method of the present embodiment, the shift time is shortened more stably than in the past. This effect is obtained regardless of whether or not the upshift is accompanied by a torque boost. And, by shortening the shift time of the upshift, the time during which torque loss occurs is reduced. The upshift is executed when the electric vehicle 100 is accelerating the electric vehicle 100 using both the front motor 23 and the rear motor 43, and running stability is particularly required. In this regard, if the upshift time is shortened and the time during which torque loss occurs is reduced, the running stability during upshifting is improved.

Furthermore, in the gear shift control method of this embodiment, regenerative power (rear regenerative power P _regenRR ) is used to drive the second motor (front motor 23) particularly when the torque (rear torque T _FR ) to be output by the first motor (rear motor 43) is compensated for within the range of a second rated torque, which is the rated torque when the second motor (front motor 23) is driven for a relatively short time, exceeding a first rated torque, which is the rated torque when the second motor (front motor 23) is driven for a relatively long time. In other words, when an upshift is performed in a situation where at least a torque boost is required, part or all of the regenerative power (rear regenerative power P _regenRR ) generated by the regenerative control of the first motor (rear motor 43) is used to drive the second motor (front motor 23).

Since the time that torque boost can be performed is limited, there is a particular need to stably shorten the gear change time when performing an upshift in a situation where torque boost is required. For this reason, as described above, if the rotation speed synchronization time is stably shortened when performing an upshift in a situation where torque boost is required, torque boost can be utilized stably. As a result, the time during which torque loss occurs is reduced. Therefore, according to the above-mentioned gear change control method, upshift control can be performed with particularly reduced torque loss, even in situations where torque loss would have occurred in the past.

Furthermore, in the shift control method of this embodiment, the C1 control is executed when the electric power (required electric power P _drv ) required for the second motor (front motor 23) to generate the required driving force is equal to the regenerative electric power (rear regenerative electric power P _regenRR ). In other words, while the regenerative control is being performed, the second motor (front motor 23) is driven by the regenerative electric power (rear regenerative electric power P _regenRR = boost electric power P _boost ) without using the electric power (P _out ) supplied from the battery 10. This C1 control makes it possible to perform the maximum regenerative control that can be realized by the first motor (rear motor 43) in the upshift control. As a result, the synchronization time for the rotation speed is minimized.

In addition, in the shift control method of this embodiment, the C2 control is executed when the electric power (required electric power P _drv ) required for the second motor (front motor 23) to generate the required driving force is greater than the regenerative electric power (rear regenerative electric power P _regenRR ). That is, the regenerative electric power (rear regenerative electric power P _regenRR ) is used to drive the second motor (front motor 23), and the insufficient electric power obtained by subtracting the regenerative electric power (rear regenerative electric power P _regenRR ) from the electric power (required electric power P _drv ) required for the second motor (front motor 23) to generate the required driving force is supplied from the battery 10 to the second motor (front motor 23). In a scene where this C2 control is executed, the maximum regenerative control that can be realized by the first motor (rear motor 43) in the upshift control can be executed. As a result, the synchronization time of the rotation speed is shortened to the minimum.

In addition, in the shift control method of this embodiment, when the electric power (required electric power P _drv ) required for the second motor (front motor 23) to generate the required driving force is smaller than the regenerative electric power (rear regenerative electric power P _regenRR ), the C3 control is executed. That is, the second motor (front motor 23) is driven by the regenerative electric power (rear regenerative electric power P _regenRR ) without using the electric power (P _out ) supplied from the battery 10, and the surplus electric power obtained by subtracting the electric power (required electric power P _drv ) required for driving the second motor (front motor 23) from the regenerative electric power (rear regenerative electric power P _regenRR ) is charged to the battery 10. In a scene where this C3 control is executed, the surplus electric power is charged to the battery 10, but the regenerative electric power (rear regenerative electric power P _regenRR ) generated by the rotation speed control is preferentially used to drive the second motor (front motor 23). For this reason, the regenerative control of the first motor (rear motor 43) is less affected by the charging rate of the battery 10 than in the past. As a result, with the C3 control, there are more situations in which maximum regenerative control that can be achieved by the first motor (rear motor 43) can be performed during upshift control, and the synchronization time for the rotation speeds is likely to be shortened.

In particular, in the above-described C3 control, when the required driving force increases, the amount of regenerative power (rear regenerative power P _regenRR ) used to drive the second motor (front motor 23) is increased, and the surplus power charged to the battery 10 is reduced. In this way, when the rear regenerative power P _regenRR is preferentially used as the boost power P _boost , the regenerative control of the first motor (rear motor 43) in particular tends to be the most efficient regenerative control. As a result, the synchronization time for the rotation speed is likely to be shortened.

Furthermore, in the gear shift control method of this embodiment, when the second motor (front motor 23) is regeneratively controlled after control for the upshift has been started (after time t1) and before control for the upshift has been completed (before time t7), C4 control is executed. That is, the regenerative power (rear regenerative power P _regenRR ) is not used to drive the second motor (front motor 23), and the regenerative power (rear regenerative power P _regenRR ) is charged to the battery 10. In this way, in an irregular situation in which the required driving force is reduced after the start of upshift control but before the completion of the upshift, the synchronization time for the rotation speed is likely to be minimized by executing the above-mentioned C4 control.

[Second embodiment]
In the first embodiment described above, the temperatures of the front motor 23 and the rear motor 43 are not taken into consideration. However, in order to perform torque boost more safely and reliably during upshifting, it is preferable to take the temperatures of the front motor 23 and the rear motor 43 into consideration. Also, it is preferable to be able to safely stop or interrupt the shift when a situation occurs in which it is not appropriate to perform torque boost after upshift control has started. The shift control method of the second embodiment described below is a shift control method that adds, to the shift control method of the first embodiment, (1) control that takes into consideration the temperature of the front motor 23, (2) control that takes into consideration the temperature of the rear motor 43, and (3) control that stops or interrupts the upshift.

Figure 11 is a flowchart of the rotation speed synchronization control according to the second embodiment. Of the controls included in the upshift control, the controls other than the rotation speed synchronization control are the same as those in the first embodiment. Note that the electric vehicle 100 according to the second embodiment is the same as the electric vehicle 100 of the first embodiment.

(1) Control Taking into Account the Temperature of the Front Motor As shown in FIG. 11, in the second embodiment, steps S301 to S306 are added between steps S201, S202 and S205 in the rotation speed synchronization control of the first embodiment in order to take into account the temperature TempFR of the front motor 23.

In step S301, the controller 13 acquires the temperature TempFR of the front motor 23, and determines whether the temperature TempFR of the front motor 23 is smaller than a predetermined first threshold value Th1. The first threshold value Th1 is a threshold value for determining whether or not the output torque of the front motor 23 should be limited due to temperature. The first threshold value Th1 is determined by adaptation based on experiments, simulations, etc.

In this embodiment, the first threshold Th1 is set to a temperature at which the front motor 23 can output a torque greater than the first rated torque and equal to or less than the second rated torque. In other words, the first threshold Th1 is the upper limit of the temperature at which the front motor 23 can output the output torque required during torque boost. Therefore, when the temperature TempFR of the front motor 23 is smaller than the first threshold Th1, torque boost can be performed in upshift control without temperature restrictions.

When the result of the determination in step S301 is that the temperature TempFR of the front motor 23 is lower than the first threshold value Th1, there is no need to limit the output torque of the front motor 23. Therefore, the controller 13 executes the processes from step S202 to step S207 in the same manner as in the first embodiment.

On the other hand, when the result of the judgment in step S301 is that the temperature TempFR of the front motor 23 is equal to or higher than the first threshold value Th1, it is necessary to limit the output torque of the front motor 23. For this reason, in step S302, the controller 13 reduces the upper limit of the power for driving the front motor 23 (hereinafter, FR upper limit power) to less than the FR reference upper limit power. This is to reduce the thermal load of the front motor 23. The FR reference upper limit power is the upper limit of the driving power in a situation where it is not necessary to limit the output torque due to temperature, that is, in a normal state. In other words, the FR reference upper limit power is, for example, the power that generates the first rated torque when the front motor 23 is driven within the range of the first rated torque, and the power that generates the second rated torque when the front motor 23 is driven within the range of the second rated torque. In this embodiment, the FR reference upper limit power is the power that generates the first rated torque, regardless of the driving mode of the front motor 23.

In addition, in this embodiment, the controller 13 sets the FR upper limit power according to the temperature TempFR of the front motor 23. For example, the higher the temperature TempFR of the front motor 23, the smaller the FR upper limit power becomes continuously or stepwise. However, the FR upper limit power can be set to a predetermined value.

In step S303, the controller 13 limits the rear regenerative power P _regenRR in accordance with the limitation of the FR upper limit power in step S302. That is, the regenerative control of the rear motor 43 generated in the rotation speed synchronization control is limited in accordance with the set FR upper limit power. In this embodiment, the smaller the FR upper limit power, the smaller the maximum value of the rear regenerative power P _regenRR (the absolute value of the regenerative torque RT2).

In step S304, the controller 13 acquires the temperature TempFR of the front motor 23, and further determines whether the temperature TempFR of the front motor 23 is smaller than a predetermined second threshold value Th2. The second threshold value Th2 is a threshold value for determining whether the front motor 23 should be stopped due to temperature. Therefore, the second threshold value Th2 is set to a value larger than the first threshold value Th1. The second threshold value Th2 is determined by adaptation based on experiments, simulations, etc.

When it is determined in step S304 that the temperature TempFR of the front motor 23 is less than the second threshold value Th2, the controller 13 executes the processes of steps S202 to S207 in the same manner as in the first embodiment, under the restrictions imposed in steps S302 and S303.

On the other hand, when it is determined in step S304 that the temperature TempFR of the front motor 23 is equal to or higher than the second threshold value Th2, in step S305, the controller 13 stops driving the front motor 23. Therefore, in step S306, the rear regenerative power P _regenRR is further limited. Specifically, since the front motor 23 is stopped, the rear regenerative power P _regenRR is limited to the power that can be accepted by the battery 10. Then, under these restrictions, the C4 control in step S203 is executed.

(2) Control Taking into Account the Temperature of the Rear Motor As shown in FIG. 11, in the second embodiment, steps S401 to S403 are added after steps S204, S206, S207, and S203 in the rotation speed synchronization control of the first embodiment in order to take into account the temperature TempRR of the rear motor 43.

In step S401, the controller 13 acquires the temperature TempRR of the rear motor 43, and further determines whether the temperature TempRR of the rear motor 43 is smaller than a third threshold value Th3. The third threshold value Th3 is a threshold value for determining whether or not a limit should be imposed on the output torque of the rear motor 43 due to temperature. The third threshold value Th3 is determined by adaptation based on experiments, simulations, etc.

When it is determined in step S401 that the temperature TempRR of the rear motor 43 is less than the third threshold value Th3, the process proceeds to step S501.

On the other hand, when it is determined in step S401 that the temperature TempRR of the rear motor 43 is equal to or higher than the third threshold value Th3, in step S402, the controller 13 limits the rear regenerative power P _regenRR (regenerative torque TR2). This limitation on the rear regenerative power P _regenRR is performed, for example, according to the temperature TempRR of the rear motor 43. In this embodiment, the controller 13 imposes a limitation such that the upper limit of the rear regenerative power P _regenRR becomes smaller as the temperature TempRR of the rear motor 43 becomes higher. This is to reduce the thermal load on the rear motor 34.

Then, in step S403, the controller 13 determines whether the temperature TempRR of the rear motor 43 is smaller than a fourth threshold value Th4. The fourth threshold value Th4 is a threshold value for determining whether the rear motor 43 should be stopped due to temperature. The fourth threshold value Th4 is determined by adaptation based on experiments, simulations, etc.

When the temperature TempRR of the rear motor 43 is smaller than the fourth threshold value Th4, the process proceeds to step S501. On the other hand, when the temperature TempRR of the rear motor 43 is greater than the fourth threshold value Th4, the process proceeds to step S502. Steps S501 and S502 are controls to stop or interrupt the upshift.

(3) Control to Stop or Interrupt Upshift In step S501, the controller 13 determines whether the elapsed time _Tsync after the start of the rotation synchronization control (after time t2) is less than the predetermined synchronization time τ. The predetermined synchronization time τ defines the upper limit of the normal synchronization time scheduled in the rotation synchronization control. Therefore, when the elapsed time _Tsync exceeds the predetermined synchronization time τ, there is a risk that the rotation speed synchronization, and therefore the upshift, will not be completed due to the occurrence of an unexpected event, etc. The predetermined synchronization time τ is determined by adaptation based on experiments, simulations, etc.

In step S501, when it is determined that the elapsed time _Tsync is less than the predetermined synchronization time τ, the controller 13 executes step S204 as in the first embodiment. On the other hand, when it is determined in step S501 that the elapsed time _Tsync is equal to or greater than the predetermined synchronization time τ, the process proceeds to step S502.

In step S502, the controller 13 stops or interrupts the upshift. Step S502 is executed when the temperature TempRR of the rear motor 43 becomes equal to or greater than the fourth threshold value Th4 and the rear motor 43 should be stopped, or when an unexpected event occurs in which the elapsed time _Tsync becomes equal to or greater than the predetermined synchronization time τ.

Note that stopping or interrupting the upshift in step S502 refers to terminating upshift control, including rotation speed synchronization, while leaving the clutch 54 in the neutral position, or reconnecting the clutch 54 to low gear 52. In particular, stopping the upshift refers to the controller 13 determining not to resume upshift control after step S502 is executed. Also, interrupting the upshift refers to the possibility that upshift control may be performed after step S502 is executed, for example, via a control routine not shown, at the discretion of the controller 13. In step S502, for example, either stopping or interrupting the upshift is selected depending on the cause and/or the extent of the cause.

As described above, in the gear shift control method of the second embodiment, when the temperature TempFR of the second motor (front motor 23) is equal to or higher than the predetermined first threshold value Th1, the output of the second motor (front motor 23) is reduced in step S302 compared to when the temperature TempFR of the second motor (front motor 23) is lower than the first threshold value. Furthermore, in step S303, the regenerative power (rear P _regenRR ) generated by the first motor (rear motor 43) is limited.

In this way, by limiting the drive of the front motor 23 and the rear motor 43 in the rotation speed control when necessary depending on the temperature TempFR of the front motor 23, upshift control including torque boost and synchronization time reduction control can be executed more safely and reliably. In particular, the thermal load on the front motor 23 is reduced.

In the gear shift control method of the second embodiment, the regenerative power (rear regenerative power P _regenRR ) in step 303 is limited based on the temperature TempFR of the second motor (front motor 23). This allows maximum regenerative control to be performed by the rear motor 43 in a situation where limitation is required due to the temperature TempFR of the front motor 23. Therefore, even in a situation where limitation due to the temperature TempFR of the front motor 23 is required, the synchronization time can be easily shortened.

In the shift control method of the second embodiment, the first threshold Th1 is set to a temperature at which the second motor (front motor 23) can output a torque greater than the first rated torque and equal to or less than the second rated torque. Therefore, when performing the upshift control of the first embodiment, it is particularly appropriate to determine whether or not a restriction based on the temperature TempFR of the front motor 23 is necessary.

In the gear shift control method of the second embodiment, when the temperature of the second motor (front motor 23) is equal to or higher than a second threshold Th2 that is set to a value higher than the first threshold Th1, in step S306, the regenerative power (rear regenerative power P _regenRR ) is limited to the power that can be charged to the battery 10. This allows the upshift to be completed even when it is unavoidable to stop the second motor (front motor 23). As a result, the electric vehicle 100 can be stopped safely.

In the gear shift control method of the second embodiment, when the temperature TempRR of the first motor (rear motor 43) is equal to or higher than a predetermined third threshold value Th3, the regenerative power (rear regenerative power P _regenRR ) is limited in step S402, thereby reducing the thermal load on the rear motor 34 when upshift control including the torque boost and synchronization time reduction control is performed.

The above describes an embodiment of the present invention, but the configurations described in the above embodiment merely show some of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

For example, in the first and second embodiments, the front wheel drive system FDS is not provided with a transmission, and only the rear wheel drive system RDS is provided with a transmission 51, but this is not limited to the above. For example, instead of providing the rear wheel drive system RDS with a transmission 51, the front wheel drive system FDS may be provided with a transmission. In this case, contrary to the first and second embodiments, the front motor 23 is the first motor, and the rear motor 43 is the second motor. Also, transmissions may be provided in both the front wheel drive system FDS and the rear wheel drive system RDS. Even in these cases, the same effects as those of the first and second embodiments are achieved. In this case, the motor connected to one of the transmissions that is to be upshifted is the first motor, and the motor connected to the other transmission that is not to be shifted is the second motor. For example, when upshifting the transmission of the front wheel drive system FDS, the front motor 23 is the first motor, and the rear motor 43 is the second motor. Conversely, when upshifting the transmission of the rear wheel drive system RDS, the rear motor 43 is the first motor and the front motor 23 is the second motor.

In addition, the electric vehicle 100 in the first and second embodiments is a four-wheel drive vehicle, but the present invention can also be applied to a two-wheel drive vehicle. Figure 12 is a skeleton diagram showing the configuration of a modified electric vehicle 600.

As shown in FIG. 12, in an electric vehicle 600, two motors, a first motor 602 and a second motor 603, are connected as drive sources to a pair of drive wheels 601. In the power transmission mechanism 604 of this electric vehicle 600, the first motor 602 is connected to a drive shaft 606 of the drive wheels 601 via a transmission 605. The second motor 603 is connected to the drive shaft 606 via a transmission 607.

The shift control method of the present invention can be suitably implemented in the electric vehicle 600 of the above modification, and the effects of the first and second embodiments can be obtained.

In addition, in the electric vehicle 100 of the first and second embodiments described above, the transmission 51 has a two-speed configuration with a low gear 52 and a high gear 53, but a transmission with three or more speeds can also be used.

100: Electric vehicle 10: Battery 11: Front wheel 12: Rear wheel 13: Controller 23: Front motor 43: Rear motor 51: Transmission 52: Low gear 53: High gear 54: Clutch

Claims (13)

1. A gear shift control method for an electric vehicle having a first motor and a second motor as drive sources, the first motor being driven by electric power supplied from a battery, and in which at least the first motor is connected to drive wheels via a transmission, the method comprising the steps of:
By increasing the torque output by the second motor compared to before the control for the upshift was started, the torque to be output by the first motor is compensated for, thereby maintaining a required driving force that is a driving force required for the electric vehicle;
When the clutch of the transmission is in neutral, the first motor is regeneratively controlled to synchronize the rotation speed of the first motor with the rotation speed corresponding to the gear to which the transmission is to be shifted;
A part or all of the regenerative power generated by the regenerative control of the first motor is used to drive the second motor.
Shift control method. 2. A gear shift control method according to claim 1,
The regenerative power is used to drive the second motor when the torque to be output by the first motor is compensated for within a range of a second rated torque, which is a rated torque when the second motor is driven for a relatively short time, exceeding a first rated torque, which is a rated torque when the second motor is driven for a relatively long time.
Shift control method. 3. The gear shift control method according to claim 1, further comprising the steps of:
When the electric power required for generating the required driving force by the second motor is equal to the regenerative electric power, the second motor is driven by the regenerative electric power without using the electric power supplied from the battery while the regenerative control is being performed.
Shift control method. A gear shift control method according to any one of claims 1 to 3,
When the electric power required for generating the required driving force by the second motor is greater than the regenerative electric power,
The regenerative electric power is used to drive the second motor, and
supplying, from the battery to the second motor, an amount of electric power that is a deficiency of electric power obtained by subtracting the regenerative electric power from electric power required for generating the requested driving force by the second motor;
Shift control method. A gear shift control method according to any one of claims 1 to 4,
When the electric power required for generating the required driving force by the second motor is smaller than the regenerative electric power,
The second motor is driven by the regenerative power without using the power supplied from the battery, and
Charging the battery with surplus power remaining after subtracting power required to drive the second motor from the regenerative power.
Shift control method. 6. A gear shift control method according to claim 5,
When the required driving force increases, an amount of the regenerative power used to drive the second motor is increased, and an amount of the surplus power charged to the battery is reduced.
Shift control method. A gear shift control method according to any one of claims 1 to 6,
When the second motor is subjected to regenerative control after the control for the upshift is started and before the control for the upshift is completed, the regenerative power is not used to drive the second motor, and the regenerative power is charged to the battery.
Shift control method. A gear shift control method according to any one of claims 1 to 7,
When the temperature of the second motor is equal to or higher than a predetermined first threshold value,
reducing an output of the second motor compared to when the temperature of the second motor is less than the first threshold; and
limiting the regenerative power generated by the first motor;
Shift control method. 9. A gear shift control method according to claim 8, comprising:
The method further includes limiting the regenerative power based on a temperature of the second motor. A gear shift control method according to claim 8 or 9, which is dependent on claim 2,
the first threshold value is set to a temperature at which the second motor can output a torque that is greater than the first rated torque and is equal to or smaller than the second rated torque;
Shift control method. A gear shift control method according to any one of claims 8 to 10,
When the temperature of the second motor is equal to or higher than a second threshold value that is set to a value greater than the first threshold value, the regenerative power is limited to a power that can be charged into the battery.
Shift control method. A gear shift control method according to any one of claims 1 to 11,
limiting the regenerative power when a temperature of the first motor is equal to or higher than a predetermined third threshold value;
Shift control method. A gear shift control device for an electric vehicle having a first motor and a second motor as drive sources, the first motor being driven by electric power supplied from a battery, and in which at least the first motor is connected to drive wheels via a transmission, the gear shift control device executing control when upshifting the transmission,
By increasing the torque output by the second motor compared to before the control for the upshift was started, the torque to be output by the first motor is compensated for, thereby maintaining a required driving force that is a driving force required for the electric vehicle;
When the clutch of the transmission is in neutral, the first motor is regeneratively controlled to synchronize the rotation speed of the first motor with the rotation speed corresponding to the gear to which the transmission is to be shifted;
A part or all of the regenerative power generated by the regenerative control of the first motor is used to drive the second motor.
Gear shift control device.

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