Electric vehicle driving control device

Abstract

To provide a travel control device of an electric vehicle which can suppress occurrence of shock in a vehicle, even when loss electric power having a restricted change rate is greatly lower than actual loss electric power.SOLUTION: A travel control device of an electric vehicle includes a change rate restriction determination part for determining whether battery output of a battery for driving is equal to or less a prescribed first predetermined value, and a change rate restriction part for setting loss electric power of a motor to be loss electric power having a restricted change rate so as to be smaller than an actual change rate, when the change rate restriction determination part determines that the battery output of the battery for driving is equal to or less the first predetermined value, wherein the change rate restriction determination part further determines whether the battery output of the battery for driving is equal to or less a prescribed second predetermined value smaller than the first predetermined value, and the change rate restriction part invalidates restriction of a change rate when the change rate restriction determination part determines that the battery output of the battery for driving is equal to or less than the second predetermined value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a cruise control device for an electric vehicle. [Background technology]

[0002] The upper limit of the drive shaft torque that can be used to drive an electric vehicle (hereinafter referred to as "upper limit drive shaft torque") is determined by the power that can be used to drive the vehicle (hereinafter referred to as "upper limit drive shaft motor power"), and even if the driver requests a drive shaft torque greater than the upper limit drive shaft torque, the drive shaft torque greater than the upper limit drive shaft torque cannot be output. Since the upper limit drive shaft motor power is the difference between the battery output of the drive battery and the power loss of the motor, the greater the power loss of the motor, the smaller the upper limit drive shaft motor power and the smaller the upper limit drive shaft torque. The power loss of the motor fluctuates greatly in the low rotation range and stabilizes once the low rotation range is exceeded. Therefore, even when the battery output of the drive battery, at which the motor is in the low rotation range, is smaller than a predetermined value, the power loss of the motor also fluctuates greatly.

[0003] Therefore, the inventors of the present application calculated an upper limit drive shaft torque as a loss power (hereinafter referred to as "virtual loss power") that limits the rate of change of the motor's loss power to be smaller than the actual rate of change when the battery output of the drive battery is below a predetermined value, and output the drive shaft torque requested by the driver within the range of this upper limit drive shaft torque (see, for example, Patent Application No. 2020-126408).

[0004] Incidentally, Patent Document 1 discloses a technology for changing the power loss in the drive system of an electric vehicle, but this power loss is generated in a power converter that performs orthogonal conversion of power, and is not directly related to the power loss of the motor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-013280 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the driving control device for an electric vehicle according to the above-mentioned patent application, when the virtual power loss falls far below the actual power loss, such as when the drive battery deteriorates and the temperature of the drive battery becomes low, the upper limit drive shaft torque (the drive shaft torque calculated as the motor can output) far exceeds the drive shaft torque that the electric vehicle can actually output, so that when the driver requests a drive shaft torque (for example, the upper limit drive shaft torque) that exceeds the drive shaft torque that can actually be output, the over-discharge threshold of the cells that make up the drive battery is exceeded and power is supplied from the drive battery to the motor. In this case, the battery protection control is activated and power is not supplied from the drive battery to the motor, but a shock (impact) may occur to the vehicle.

[0007] In consideration of the above-mentioned circumstances, at least one embodiment of the present invention aims to provide a driving control device for an electric vehicle that can suppress the occurrence of shock (impact) in the vehicle even if the loss power with the limited rate of change is significantly lower than the actual loss power. [Means for solving the problem]

[0008] (1) A travel control device for an electric vehicle according to at least one embodiment of the present invention is a travel control device for an electric vehicle in which power is supplied to a motor from a drive battery, the travel control device including: an upper limit drive shaft motor power calculation unit that calculates an upper limit drive shaft motor power which is the difference between the power supplied to the motor and the power loss of the motor; an upper limit drive shaft torque conversion unit that converts the upper limit drive shaft motor power calculated by the upper limit drive shaft motor power calculation unit into an upper limit drive shaft torque of the motor; a drive shaft torque output control unit that outputs a drive shaft torque requested by a driver within the range of the upper limit drive shaft torque converted by the upper limit drive shaft torque conversion unit; and a drive battery that converts the upper limit drive shaft motor power into an upper limit drive shaft torque. and a change rate limiting unit which, when the change rate limiting determination unit determines that the battery output of the driving battery is equal to or less than the first predetermined value, limits the change rate of the motor to a loss power smaller than an actual rate of change. The change rate limiting determination unit further determines whether the battery output of the driving battery is equal to or less than a predetermined second predetermined value which is smaller than the first predetermined value, and the change rate limiting unit further disables the limit on the change rate when the change rate limiting determination unit determines that the battery output of the driving battery is equal to or less than the second predetermined value.

[0009] According to the configuration of (1) above, when the battery output of the drive battery is equal to or lower than the second predetermined value, the actual upper limit drive shaft torque is calculated using the actual motor power loss, and the drive shaft torque requested by the driver is output within the range of the actual upper limit drive shaft torque. This prevents the drive battery from supplying power to the motor in excess of the over-discharge threshold of the drive battery, and also prevents the battery protection control from operating. As a result, even if the loss power with the limited rate of change falls significantly below the actual loss power, it is possible to prevent a shock (impact) from occurring in the electric vehicle.

[0010] (2) In some embodiments, in the configuration of (1) above, the change rate limiting determination unit further determines whether the charging rate of the driving battery is less than a predetermined third predetermined value, and the change rate limiting unit further enables the change rate limiting unit when it determines that the charging rate of the driving battery is less than the third predetermined value.

[0011] According to the configuration of (2) above, when the battery output of the driving battery is equal to or less than the second predetermined value but the charging rate of the driving battery is less than the third predetermined value, the motor's power loss is limited to be smaller than the actual rate of change. Therefore, when the electric vehicle is a hybrid vehicle and the battery output of the driving battery is equal to or less than the second predetermined value and the charging rate of the driving battery is less than the third predetermined value, the engine starts and charging of the driving battery begins. At this time, because a current flows through the driving battery in the charging direction, the driving battery is unlikely to be over-discharged (the operation of battery protection control is also suppressed).

[0012] In addition, in the region where the charging rate of the drive battery is less than the third predetermined value, the internal resistance of the drive battery is smaller than in the region where the charging rate is high (above the third predetermined value), so the drive battery is less likely to experience a voltage drop and is less likely to become over-discharged. Therefore, by activating the rate of change limit when it is determined that the charging rate of the drive battery is less than the third predetermined value, the motor power loss is limited to be smaller than the actual rate of change. This allows the drive shaft torque required of the motor to be closer to the driver's acceleration request.

[0013] (3) In some embodiments, in the configuration of (1) or (2) above, the first predetermined value is a power value for the motor to output a drive shaft torque requested by the driver when the electric vehicle starts moving.

[0014] According to the configuration of (3) above, when the battery output of the drive battery is smaller than the power value at which the motor is required by the driver when the electric vehicle starts, the change rate limiting unit limits the motor's power loss to a power loss rate smaller than the actual change rate. This reduces fluctuations in the upper limit drive shaft torque, and makes it possible to suppress vibrations of the electric vehicle when the electric vehicle starts, even if the battery output of the drive battery is smaller than the power value at which the motor is required to output the drive shaft torque required by the driver.

[0015] (4) In some embodiments, in any one of the configurations (1) to (3) above, the electric vehicle is a hybrid vehicle in which a generator is driven by an engine and electric power is supplied from the generator to the motor, and when the generator starts generating electric power by the engine at the time of starting the electric vehicle, the change rate limiting unit Regardless of the magnitude of the battery output of the driving battery, During the period from when the accelerator opening is 0 to when the generator outputs the generated power, the power loss of the motor is set to a power loss whose rate of change is limited to be smaller than the actual rate of change.

[0016] According to the configuration of (4) above, the change in the motor's power loss is small, and the changes in the upper limit drive shaft motor power and the upper limit drive shaft torque are also small (stable) from when the accelerator pedal position is 0 until the generator outputs the generated power. Therefore, from when the accelerator pedal position is 0 until the generator outputs the generated power, the drive shaft torque output from the motor is stable, and the front and rear G of the electric vehicle is also stable, making it possible to suppress shocks felt by the driver that are generated in the electric vehicle. Effect of the Invention

[0017] According to at least one embodiment of the present invention, even if the power loss with the suppressed rate of change falls significantly below the actual power loss, it is possible to suppress shock (impact) on the vehicle. [Brief description of the drawings]

[0018] [Figure 1] 1 is a block diagram showing a schematic configuration of a hybrid vehicle employing a cruise control device for an electric vehicle according to an embodiment; [Diagram 2] 2 is a block diagram showing a schematic configuration of a driving control device for the hybrid vehicle shown in FIG. 1. [Diagram 3] 3 is a block diagram showing a change rate limiting unit and a change rate limit determining unit shown in FIG. 2. [Figure 4] 4 is a diagram for explaining the rate of change in motor power loss limited by the rate of change limiter shown in FIG. 3. [Diagram 5] 4 is a diagram for explaining a second predetermined value and a third predetermined value at which the change rate limit determination unit shown in FIG. 3 disables the change rate limit unit. FIG. [Figure 6] 3 is a flowchart for explaining the operation of the driving control device for the hybrid vehicle shown in FIG. 2. [Figure 7] 4 is a diagram showing the battery output of the driving battery, the power loss of the motor, the cell voltage of the driving battery, and shock (impact) when the change rate limiting unit shown in FIG. 3 limits the rate of change in the power loss of the motor. FIG. [Figure 8] 4 is a diagram showing the battery output of the drive battery, the power loss of the motor, the cell voltage of the drive battery, and shock (impact) when the change rate limiting unit shown in FIG. 3 disables the limit on the change rate of the power loss of the motor. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a driving control device for an electric vehicle according to an embodiment will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative positions, etc. of components described as the embodiment or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0020] As shown in Fig. 1, a cruise control device 1 according to the embodiment is applied to an electric vehicle in which power is supplied from a drive battery 21 to a motor 31. The electric vehicle according to the embodiment is a hybrid vehicle (HV) that generates power by an engine 41, but is not limited to this and can also be applied to, for example, an electric vehicle (EV). The hybrid vehicle is, for example, a plug-in hybrid vehicle (PHEV, PHV), but is not limited to a plug-in hybrid vehicle.

[0021] [Electric vehicle configuration] The electric vehicle to which the driving control device 1 according to the embodiment is applied includes an engine 41, a generator 51, and accessories 61 in addition to a driving battery 21 and a motor 31.

[0022] The driving battery 21 is configured as a battery pack in which a plurality (a large number) of battery cells are housed in one container. The driving battery 21 configured in this manner is managed by a battery controller unit 23. For example, the battery controller unit 23 manages the battery output (SOPout) and charging rate (SOC (State Of Charge)) of the driving battery 21 and notifies the driving control device 1 of the battery output and charging rate, while stopping discharging of the driving battery 21 (for example, power supply to the motor 31) to protect the driving battery 21 when the battery cells constituting the driving battery 21 discharge beyond an over-discharge threshold (battery protection control).

[0023] The motor 31 converts the power supplied from the drive battery 21 into drive shaft torque to rotate and drive the tires (drive wheels) 71, and is controlled by the motor controller unit 33. For example, the motor controller unit 33 controls the motor 31 so that the motor 31 outputs the drive shaft torque requested (output) from the driving control device 1, and notifies the driving control device 1 of the actual power loss of the motor 31. The engine 41 drives the generator 51, and is controlled by the engine controller unit 43. The generator 51 generates power to charge the driving battery 21, is connected to the engine 41, and is controlled by the generator controller unit 53. For example, the engine controller unit 43 and the generator controller unit 53 control the engine 41 and the generator 51 so that the generator 51 generates the generated power requested by the driving control device 1.

[0024] The auxiliary device 61 is, for example, an electric heater, an electric air conditioner, and a DC-DC converter. Electric power (auxiliary power consumption) is supplied from the driving battery 21, and the auxiliary device 61 notifies the driving control device 1 of the auxiliary power consumption.

[0025] The driving control device 1 according to the embodiment described above is configured by, for example, a processor (not shown) configured by an arithmetic unit, a register for storing instructions and information, peripheral circuits, etc., memories (not shown) such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and an input / output interface (not shown).

[0026] [Configuration of driving control device 1] As shown in FIG. 2, the driving control device 1 according to the embodiment includes an upper limit drive shaft motor power calculation unit 11, an upper limit drive shaft torque conversion unit 13, and a drive shaft torque output control unit 15, as well as a change rate limit determination unit 17 (see FIG. 3) and a change rate limiting unit 19.

[0027] The upper limit drive shaft motor power calculation unit 11 is a part that calculates the upper limit drive shaft motor power, which is the difference between the power supplied to the motor 31 and the power loss of the motor 31. The power supplied to the motor 31 is the battery output (SOPout) of the drive battery 21 minus the power consumption of the accessories (not shown), but in a hybrid vehicle, the generated power is added in the supply power calculation unit 12.

[0028] The upper limit drive shaft torque conversion unit 13 converts the upper limit drive shaft motor power calculated by the upper limit drive shaft motor power calculation unit 11 into the upper limit drive shaft torque of the motor 31. The upper limit drive shaft torque is converted by the following Equation 1.

[0029]

number

[0030] The drive shaft torque output control unit 15 is a unit that outputs the drive shaft torque requested by the driver within the range of the upper limit drive shaft torque converted by the upper limit drive shaft torque conversion unit 13. The drive shaft torque requested by the driver is calculated by a driver requested drive shaft torque calculation unit 16 based on the vehicle speed and accelerator position (accelerator opening) of the electric vehicle.

[0031] As shown in FIG. 3, the change rate limit determination unit 17 is a part that determines whether or not the battery output (SOPout) of the driving battery 21 is equal to or less than a predetermined value (hereinafter referred to as a "first predetermined value").

[0032] The first predetermined value is a power value (battery output value) that specifies the range in which the power loss of the motor 31 varies greatly when the electric vehicle starts, and is, for example, a power value for the motor 31 to output the drive shaft torque requested by the driver when the electric vehicle starts. The first predetermined value is, for example, determined by a test that specifies the range in which a shock (impact) occurs when starting with the upper limit drive shaft torque that can be output by the actual power loss of the motor 31, but is not limited to this. The first predetermined value is, for example, a fixed value (see FIG. 5), but may be a variable value that varies depending on the vehicle speed and accelerator position, or the drive shaft torque requested by the driver.

[0033] The change rate limiting unit 19 is a part that, when the change rate limiting determination unit 17 determines that the battery output of the driving battery 21 is equal to or less than the first predetermined value, limits the power loss of the motor 31 to a power loss (virtual power loss) with a rate of change limited to be smaller than the actual rate of change. For example, when the change rate limiting determination unit 17 determines that the battery output of the driving battery 21 is equal to or less than the first predetermined value and the generator 51 starts generating power by the engine 41 when the electric vehicle starts moving, the change rate limiting unit 19 limits the power loss of the motor 31 to a power loss (virtual power loss) with a rate of change limited to be smaller than the actual rate of change from when the accelerator opening is 0 until the generator 51 outputs the generated power.

[0034] The rate of change (see FIG. 3) for limiting the loss power of the motor 31 to be smaller than the actual rate of change is limited so that the change in the loss power per unit time is equal to or less than a predetermined value. For example, as shown in FIG. 4, when the actual loss power increases by BkW in time A, time A is divided (n, n+1, n+2, . . . n+7), and the loss power is limited to change stepwise for each divided time (e.g., 10 msec). For example, when the generator 51 starts generating power by the engine 41 when the electric vehicle starts, the loss power per divided time is limited to be equal to or less than a predetermined value from when the accelerator opening is 0 until the generator 51 outputs the generated power. For example, in the example shown in FIG. 4, time A is the time from when the accelerator opening is 0 until the generator 51 outputs the generated power, and BkW is the loss power after the generated power is output.

[0035] The change rate limiting determination unit 17 further determines whether the battery output (SOPout) of the driving battery 21 is equal to or less than a predetermined value (hereinafter referred to as a "second predetermined value") that is smaller than the first predetermined value. The second predetermined value is a power value (battery output value) at which the battery cells constituting the driving battery 21 discharge beyond the overdischarge threshold due to the deviation between the loss power with the change rate limited and the actual loss power when the electric vehicle starts. The second predetermined value is given, for example, by a map (see FIG. 5) of the battery output (SOPout) and the state of charge (SOC). The second predetermined value is determined, for example, by a test that specifies a range in which a shock (impact) occurs due to battery protection control when the battery cells constituting the driving battery 21 discharge beyond the overdischarge threshold due to the deviation from the actual loss power when the electric vehicle starts with an upper limit drive shaft torque that can be output by the loss power of the motor 31 with the change rate limited, but the second predetermined value is not limited to this.

[0036] The above-mentioned change rate limiting section 19 further disables the limit on the change rate when the change rate limit determining section 17 determines that the battery output (SOPout) of the driving battery 21 is equal to or less than a second predetermined value.

[0037] The change rate limit determination unit 17 further determines whether the state of charge (SOC) of the driving battery 21 is less than a predetermined value (hereinafter referred to as a "third predetermined value"). The third predetermined value is given, for example, by a map (see FIG. 5) of battery output (SOPout) and state of charge (SOC), but is not limited to this. For example, when the electric vehicle is a hybrid vehicle, the third predetermined value is the state of charge at which charging of the driving battery begins when the engine starts, and is determined, for example, by the battery temperature and state of charge of the driving battery 21, but is not limited to this.

[0038] Furthermore, the above-mentioned change rate limiting unit 19 further enables the limit on the change rate when the state of charge (SOC) of the driving battery 21 is less than a third predetermined value.

[0039] [Operation of driving control device 1] 6, the driving control device 1 according to the embodiment first calculates the generated power that the driving control device 1 requests the generator 51 to generate based on the battery output (SOPout) of the driving battery 21 notified by the battery controller unit 23 (step S1). Next, the supply power calculation unit 12 calculates the power to be supplied to the motor 31 (step S2). As described above, the power supplied to the motor 31 is the battery output of the driving battery 21 minus the auxiliary power consumption, to which the generated power requested of the generator 51 is added.

[0040] Next, the change rate limiting determination unit 17 determines whether the battery output of the driving battery 21 notified from the battery controller unit 23 is equal to or less than a first predetermined value (step S31). If the battery output of the driving battery 21 is equal to or less than the first predetermined value (step S31: Yes), the change rate limiting unit 19 limits the change rate of the loss power of the motor 31 to a predetermined value or less (step S32), and sets the loss power (MTR loss power) of the motor 31 to a loss power with a limited change rate (virtual loss power) (step S33). If the battery output of the driving battery 21 is not equal to or less than the first predetermined value (step S31: No), that is, if it exceeds the first predetermined value, the change rate limiting unit 19 does not limit the change rate of the motor 31, and sets the loss power (MTR loss power) of the motor 31 to an actual loss power (MTR actual loss power).

[0041] Next, the change rate limit determination unit 17 determines whether the battery output of the driving battery 21 notified from the battery controller unit 23 is equal to or less than a second predetermined value (step S34). If the battery output of the driving battery 21 is equal to or less than the second predetermined value (step S34: Yes), the change rate limit unit 19 disables the limit on the change rate (step S35) and sets the loss power (MTR loss power) of the motor 31 to the actual loss power (MTR actual loss power) (step S36). If the battery output of the driving battery 21 exceeds the second predetermined value (step S34: No), the change rate limit unit 19 does not disable the limit on the change rate, and keeps the loss power (MTR loss power) of the motor 31 as the loss power with the limited change rate (virtual loss power).

[0042] Next, the change rate limit determination unit 17 determines whether the charging rate of the driving battery 21 notified from the battery controller unit 23 is less than a third predetermined value (step S37). If the charging rate of the driving battery 21 is less than the third predetermined value (step S37: Yes), the change rate limit unit 19 activates the change rate limit (step S38) and sets the motor loss power (MTR loss power) to the loss power with the change rate limited (step S39). If the charging rate of the driving battery 21 is equal to or greater than the third predetermined value (step S37: No), the change rate limit unit 19 does not activate the change rate limit and sets the motor loss power (MTR loss power) to the actual loss power (MTR actual loss power).

[0043] Next, the upper limit drive shaft motor power calculation unit 11 calculates the upper limit drive shaft motor power (step S4). The upper limit drive shaft motor power is the difference between the power supplied to the motor 31 and the power loss of the motor 31. The power supplied to the motor 31 is the power output from the above-mentioned supply power calculation unit 12, and the power loss of the motor 31 is the power loss output from the above-mentioned rate of change limiting unit 19.

[0044] Next, the upper limit drive shaft motor power is converted into the upper limit drive shaft torque of the motor 31 (step S5). The upper limit drive shaft torque is converted by the above-mentioned formula 1.

[0045] Next, the driver requested drive shaft torque calculation unit 16 calculates the drive shaft torque requested by the driver (step S6). The drive shaft torque requested by the driver is calculated based on the vehicle speed and accelerator position of the electric vehicle.

[0046] Next, the drive shaft torque output control unit 15 outputs the drive shaft torque requested by the driver within the range of the upper limit drive shaft torque (step S7). Thereafter, steps S1 to S7 are repeated to suppress shocks (impacts) when the electric vehicle starts moving.

[0047] [Effects of driving control device 1] [When the battery output of the driving battery 21 is equal to or lower than the first predetermined value] 7, when the battery output of the driving battery 21 is equal to or lower than a first predetermined value, the power loss of the motor 31 fluctuates greatly as shown by the two-dot chain line L1. Therefore, the upper limit drive shaft motor power, which is the difference between the power supplied to the motor 31 and the power loss of the motor 31, also fluctuates greatly, and the upper limit drive shaft torque of the motor 31 converted from the upper limit drive shaft motor power also fluctuates greatly as shown by the two-dot chain line L2.

[0048] The drive shaft torque required by the driver is determined by the speed of the electric vehicle and the accelerator opening, but the drive shaft torque that can be output from the motor 31 is limited within the range of the upper limit drive shaft torque of the motor 31. Therefore, even if the drive shaft torque required by the driver does not fluctuate greatly, if the upper limit drive shaft torque fluctuates greatly, the drive shaft torque output from the motor 31 also fluctuates greatly. This causes fluctuations in the front and rear G of the electric vehicle as shown by the two-dot chain line L3, causing a shock (impact) to the electric vehicle that the driver can feel.

[0049] Therefore, when the inventors of the present application determine that the battery output of the drive battery 21 is equal to or less than the first predetermined value, the power loss of the motor 31 is set to a power loss (virtual power loss) whose rate of change is limited to be smaller than the actual rate of change as shown by the solid line. When the power loss of the motor 31 is set to a power loss (virtual power loss) whose rate of change is limited to be smaller than the actual rate of change, the change in the power loss of the motor 31 is reduced, and the changes in the upper limit drive shaft motor power and the upper limit drive shaft torque are also reduced (stable). Therefore, the drive shaft torque output from the motor 31 is also stabilized, and the front-rear G of the electric vehicle is also stabilized, making it possible to suppress shocks that are generated in the electric vehicle and that the driver feels.

[0050] When the electric vehicle starts moving, if the battery output of the driving battery 21 does not reach a predetermined power generation threshold or if the battery temperature of the driving battery 21 does not reach a predetermined temperature threshold, the generator 51 starts generating power using the engine 41, but the response speed of the motor 31 is faster than that of the engine 41, so the amount of power generation cannot keep up. In this case, the power loss of the motor 31 also varies greatly, and the drive shaft torque output from the motor 31 also varies greatly. This causes a change in the longitudinal G of the electric vehicle, causing a shock (impact) to the electric vehicle that the driver can feel.

[0051] Therefore, the inventors of the present application set the loss power of the motor 31 to a loss power (virtual loss power) whose rate of change is limited to be smaller than the actual rate of change when the generator 51 starts generating power by the engine 41 when the electric vehicle starts moving, from when the accelerator opening is 0 (T1) until the generator 51 outputs the generated power (T2). In this way, the change in the loss power of the motor 31 becomes small from when the accelerator opening is 0 until the generator 51 outputs the generated power, and the changes in the upper limit drive shaft motor power and the upper limit drive shaft torque also become small (stable). Therefore, from when the accelerator opening is 0 until the generator 51 outputs the generated power, the drive shaft torque output from the motor 31 is stable, and the front and rear G of the electric vehicle is also stable, making it possible to suppress shocks that are generated in the electric vehicle and are felt by the driver.

[0052] [When the battery output of the driving battery 21 is equal to or lower than the second predetermined value] As shown in FIG. 8, when the battery output of the driving battery 21 is equal to or lower than the first predetermined value, even if the loss power of the motor 31 is set to the virtual loss power as shown by the two-dot chain line L4, if the virtual loss power is significantly lower than the actual loss power, as in the case where the driving battery 21 is deteriorated and the temperature of the driving battery 21 is low, the upper limit driving shaft torque (the driving shaft torque calculated as being able to be output by the motor 31) significantly exceeds the driving shaft torque that the electric vehicle can actually output. Therefore, when the driver requests a driving shaft torque (for example, the upper limit driving shaft torque) that exceeds the driving shaft torque that can actually be output, the driving battery 21 will exceed the over-discharge threshold of the battery cell that constitutes the driving battery 21 and power will be supplied from the driving battery 21 to the motor 31 (see the two-dot chain line L5 of the cell voltage). In this case, the battery protection control is activated, and power is not supplied from the driving battery 21 to the motor 31, but a large fluctuation occurs in the driving shaft torque as shown by the two-dot chain line L6. This causes a large fluctuation in the longitudinal G as shown by the two-dot chain line L7, causing a shock (impact) to the electric vehicle that the driver can feel.

[0053] Therefore, the inventors of the present application decided to disable the limit on the rate of change when the battery output of the driving battery 21 is equal to or less than the second predetermined value. Thus, when the battery output of the driving battery 21 is equal to or less than the second predetermined value, the actual upper limit drive shaft torque is calculated using the actual loss power of the motor 31, and the drive shaft torque requested by the driver is output within the range of the actual upper limit drive shaft torque. This prevents the power supplied from the driving battery 21 to the motor 31 beyond the over-discharge threshold of the battery cells constituting the driving battery 21, and also prevents the battery protection control from operating. As a result, even if the loss power with the rate of change limited is significantly lower than the actual loss power, it is possible to prevent a shock (impact) from occurring in the electric vehicle.

[0054] [When the charging rate of the driving battery 21 is less than the third predetermined value] When the electric vehicle is a hybrid vehicle and the state of charge (SOC) of the driving battery 21 is less than a third predetermined value, the engine starts and charging of the driving battery 21 begins. At this time, a current flows in the charging direction to the driving battery 21, so that the driving battery 21 is unlikely to enter an over-discharge state even if the motor power loss is limited to be smaller than the actual rate of change (the operation of the battery protection control is also suppressed).

[0055] Furthermore, in a region where the state of charge (SOC) of the driving battery 21 is less than the third predetermined value, the internal resistance of the driving battery 21 is smaller than in a region where the state of charge is high (above the third predetermined value), so the driving battery 21 is less likely to experience a voltage drop and is less likely to become over-discharged.

[0056] Therefore, the inventors of the present application decided to limit the motor power loss to a value smaller than the actual rate of change by activating the rate of change limit when it is determined that the state of charge (SOC) of the drive battery 21 is less than a third predetermined value. This allows the drive shaft torque required of the motor to be closer to the acceleration request of the driver.

[0057] The present invention is not limited to the above-described embodiment, and includes modifications to the above-described embodiment and appropriate combinations of these modifications. [Explanation of symbols]

[0058] 1 Driving control device 11 Upper limit drive shaft motor power calculation section 12 Supply power calculation section 13 Upper limit drive shaft torque converter 15 Drive shaft torque output control section 16 Driver required drive shaft torque calculation section 17 Change rate limit judgment section 19 Rate of change limiter 21 Drive battery 23 Battery Controller Unit 31 Motor 33 Motor controller unit 41 Engine 43 Engine controller unit 51 Generator 53 Generator Controller Unit 61 Auxiliary Machine 71 Tires (drive wheels)

Claims

1. A driving control device for an electric vehicle in which power is supplied from a driving battery to a motor, an upper limit drive shaft motor power calculation unit that calculates an upper limit drive shaft motor power, which is a difference between the power supplied to the motor and the power loss of the motor; an upper limit drive shaft torque conversion unit that converts the upper limit drive shaft motor power calculated by the upper limit drive shaft motor power calculation unit into an upper limit drive shaft torque of the motor; a drive shaft torque output control unit that outputs a drive shaft torque requested by a driver within the range of the upper limit drive shaft torque converted by the upper limit drive shaft torque conversion unit; a change rate limit determination unit that determines whether a battery output of the driving battery is equal to or less than a first predetermined value; a change rate limiting unit that limits a change rate of the power loss of the motor to a smaller value than an actual change rate when the change rate limiting determination unit determines that the change rate is equal to or less than the first predetermined value; Equipped with The change rate limit determination unit further determines whether or not the battery output of the driving battery is equal to or less than a second predetermined value that is smaller than the first predetermined value, The change rate limiting unit is further characterized in that, when the change rate limit determination unit determines that the battery output of the driving battery is equal to or less than the second predetermined value, the change rate limiting unit disables the limit on the change rate. A driving control device for an electric vehicle.

2. The change rate limit determination unit further determines whether or not the charging rate of the driving battery is less than a predetermined third predetermined value; The change rate limiting unit is further configured to enable the limit of the change rate when it determines that the charging rate of the driving battery is less than the third predetermined value. The driving control device for an electric vehicle according to claim 1.

3. The first predetermined value is a power value for the motor to output a drive shaft torque requested by the driver when the electric vehicle starts. The driving control device for an electric vehicle according to claim 1 or 2.

4. The electric vehicle is a hybrid vehicle in which a generator is driven by an engine and electric power is supplied from the generator to the motor, when the generator starts generating power by the engine when the electric vehicle starts moving, the change rate limiting unit limits the rate of change of the loss power of the motor to be smaller than an actual rate of change during a period from when the accelerator opening degree is 0 to when the generator outputs generated power, regardless of a magnitude of the battery output of the driving battery. The driving control device for an electric vehicle according to any one of claims 1 to 3.

Images