JP4659857B2 - Electric vehicle motor control device - Google Patents

Description

  The present invention relates to a motor control device for an electric vehicle using a motor driven by an inverter circuit in which a plurality of switching elements are connected in a bridge configuration as a power source, and in particular, driving the switching elements when the motor is locked. The present invention relates to a motor control device for an electric vehicle that performs control accurately.

  Recently, electric vehicles (including electric wheelchairs) that use a motor as a power source have been developed and put into practical use as electric wheelchairs for the elderly and physically handicapped, as well as electric carts in golf courses and the like. In such an electric vehicle, control is performed so that the control device drives the motor so as to achieve a speed based on a speed command set based on the accelerator operation amount.

  When climbing by this type of electric vehicle, the running resistance is large, so if there are steps or obstacles in the middle of climbing, the motor may be locked even if the accelerator operation amount is maximized.

  When the motor is locked, a large current continuously flows only to a specific switching element among the switching elements of the inverter circuit that supplies current to the motor.

  If such a motor lock state continues for a long time, the temperature of a specific switching element to which a large current continues to be supplied rises above the maximum allowable temperature of the element, and the specific switching element is destroyed by heat. The In order to prevent thermal destruction of the switching element, various techniques for protecting the switching element when a locked state of the motor is detected have been proposed.

  Patent Document 1 calculates a time until the junction temperature of a transistor reaches a set upper limit temperature when a locked state of the motor is detected, sets it in a timer, and when the time measurement by the timer ends, a current command A technique for limiting the value is disclosed.

  Patent Document 2 considers that the motor is in a locked state when the motor rotation speed is 60 [rpm] or less, and changes the carrier frequency of the PWM (pulse width modulation) signal from the usual 10 [kHz] to 1.25 [kHz]. , The technology for reducing the switching loss and protecting the switching element is disclosed.

  Patent Document 3 discloses a technique for forcibly switching (commutating) a current supply target element among a plurality of switching elements when it is determined that the motor is in a locked state that does not substantially rotate when a driver acceleration request is made. Yes.

JP-A-9-56182 JP-A-9-70195 JP 2005-185000 A

  However, the technique according to Patent Document 1 requires a temperature sensor having high-precision temperature detection performance for detecting the junction temperature of the transistor element and its detection control device, and is expensive.

  Moreover, according to the technique according to Patent Document 2, a plurality of oscillators for switching the carrier frequency are required, and the cost is similarly high.

  Furthermore, according to the technique according to Patent Document 3, since the commutation is performed regardless of the motor phase, there is a concern that the drive control becomes complicated and the motor cannot be driven stably.

  By the way, according to the techniques disclosed in Patent Documents 1 and 2 described above, it is possible to limit the current and protect the switching element, but it is difficult to escape from the locked state because the driving torque is small. It is.

  Further, according to the technique disclosed in Patent Document 3 described above, in order to forcibly perform commutation regardless of the motor phase, current is supplied to the stator (motor coil) necessary to escape from the locked state. Since the average current value to the switching element to be reduced is reduced, the application of torque to the rotor by the motor coil is reduced, and a state in which sufficient driving torque for escaping the locked state cannot be obtained occurs. .

  The present invention has been made in consideration of such problems. When the motor of an electric vehicle is in a locked state, the electric motor can protect the switching element and ensure sufficient driving torque. An object of the present invention is to provide a motor control device for a vehicle.

  The motor control device for an electric vehicle according to the present invention includes the following features (1) to (5).

(1) An inverter circuit that converts DC power into AC power by a plurality of switching elements and supplies it to a wheel driving motor, and torque from a deviation between the rotational speed command of the motor and the actual rotational speed according to the accelerator operation amount A control device that calculates a command value, supplies a drive command value based on the actual rotational speed and the torque command value to the switching element to drive the motor, and a current that detects a current flowing through a power line of the inverter circuit Each of the switching elements is set with an instantaneous allowable current threshold and a continuous allowable current threshold that decreases from the instantaneous allowable current threshold according to a continuous energization time. The apparatus includes: a lock state determination unit that determines whether or not the motor is in a locked state based on the accelerator operation amount and the actual rotation speed of the motor; When the lock state determination unit determines that the lock state is in effect, the lock current flowing through the specific switching element that is in the continuous energization state is limited to a constant current value that does not exceed the instantaneous allowable current threshold at the initial period of continuous energization. Then, after the time when the constant current value is about to exceed the continuous allowable current threshold value, the upper limit of the current value when the current value is increased / decreased by releasing the limitation of the constant current value and repeating the increase / decrease of the current value. Control so that the peak value is less than or equal to the instantaneous allowable current threshold and greater than or equal to the continuous allowable current threshold, and control so that the average current value when the current value is increased or decreased does not exceed the continuous allowable current threshold And a drive command unit at the time of locking.

  According to the invention having the feature (1), when it is determined to be in the locked state, the current at the time of locking that flows through the specific switching element that is in the continuous energization state does not exceed the instantaneous allowable current threshold at the initial period of continuous energization. After the time when the current is limited to a constant current value and the constant current value is about to exceed the continuous allowable current threshold value, the constant current value is released and the current value is increased and decreased repeatedly. When the current upper peak value is less than the instantaneous allowable current threshold and greater than or equal to the continuous allowable current threshold, and the average current value when the current value is increased or decreased is equal to the continuous allowable current threshold. Since control is performed so that the current does not exceed the specified value, a specific switching element in which a large current flows when locked can be protected from overcurrent. It is possible to generate a click.

  By controlling in this way, even if the electric vehicle is locked on a slope or the like, it does not move backward on the slope or the like.

(2) In the invention having the feature (1), the lock-time drive command unit is a lock that flows to the specific switching element that is in a continuous energization state when the lock state determination unit determines that the lock state is in the locked state. At the initial stage of continuous energization, the current is limited to a constant current value that does not exceed the first allowable current threshold lower than the instantaneous allowable current threshold, and after the time when the constant current value attempts to exceed the continuous allowable current threshold, The restriction on the constant current value is released and the current value is repeatedly increased and decreased, and the current upper peak value when the current value is increased or decreased is equal to or less than the first allowable current threshold and equal to or greater than the continuous allowable current threshold. And the average current value when the current value is increased or decreased is controlled so as not to exceed the continuous allowable current threshold value.

  According to the invention having the feature (2), compared with the invention having the feature (1), the value of the large driving torque intermittently generated at the time of locking is slightly reduced, but the switching element is more marginal from the overcurrent. Can be protected.

(3) In the invention having the above feature (1) or (2), when the lock-time drive command unit increases or decreases the current value, the drive duty of the specific switching element is increased. When the current value is decreased when the current value is increased, the specific switching element is cut off and decreased so as not to exceed the instantaneous allowable current threshold value or a constant current value smaller than the instantaneous allowable current threshold value. Control can be performed with a simple configuration.

(4) In the invention having the above feature (3), the drive command unit at the time of locking is configured such that the average current value of the specific switching element at the time of lock is less than the continuous allowable current threshold. With the configuration in which the interruption time of the specific switching element is gradually increased when decreasing the average current value when the current value is increased or decreased with a simple configuration, the continuous allowable current threshold value is not exceeded. Control can be performed more reliably.

(5) In the invention having any one of the above characteristics (1) to (4), the apparatus further includes a temperature detector that detects a temperature of the inverter circuit, and decreases from the instantaneous allowable current threshold according to the energization time. By controlling the setting of the continuous allowable current threshold so as to vary according to the detected temperature of the inverter circuit, the temperature of the inverter circuit is detected instead of the temperature of the switching element itself, so the switching element is accurately detected with a simple configuration. Can be protected.

  According to the motor control device for an electric vehicle according to the present invention, when the motor of the electric vehicle is locked, the switching element can be protected and a sufficient driving torque can be generated.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a motor control device for an electric vehicle according to the present invention will be described with reference to FIGS.

  FIG. 1 shows a perspective configuration of a four-wheeled electric vehicle 12 equipped with a motor control device 10 for an electric vehicle according to this embodiment.

  The electric vehicle 12 is used as an electric wheelchair for an elderly person or a disabled person, and basically includes a front wheel 14, a rear wheel 16, a steering wheel 18 that changes the direction of the front wheel 14, and a rear wheel 16. A motor 20 to be driven and an operation unit 22 provided at the center of the steering 18 are provided. In the electric vehicle 12, the rider runs with the motor 20 rotated by the operation of the operation unit 22 in a state where his / her foot is placed on the step base 24 and the steering wheel 18 is steered, so that the direction of the front wheel 14 is changed. You can change corners and drive corners.

  The motor control device 10 of the electric vehicle according to this embodiment, which is arranged in a box 28 below the seat 26, includes a control device (control device body) 11, a motor 20, and an inverter as a driver for driving the motor 20. Circuit 30.

  The control device 11 is connected to the operation unit 22, obtains a rotation speed command Vmcom of the motor 20 based on a signal obtained from the operation unit 22, and performs rotation control of the motor 20 via the inverter circuit 30. The motor 20 is a DC brushless motor and can perform stepless speed control. Braking is performed by a combination of regenerative braking, reverse braking, electromagnetic brake braking, and manual friction braking. The drive system is a rear wheel direct drive system.

  Further, a battery (not shown) is mounted inside the box 28 of the electric vehicle 12, and a lead battery is mounted in this embodiment, and supplies power to each device.

  As shown in FIG. 2, the operation unit 22 is a console 31 provided at the center, a manual brake lever 32 provided on the left steering 18, and two traveling levers protruding from the left and right side surfaces of the console 31. And an accelerator 36.

  The accelerator 36 is configured to be interlocked with a gear or the like inside the console 31, and can travel by operating the accelerator 36.

  The console 31 includes various switches for traveling, and includes a speed setting unit 46 that is a speed setting knob, a monitor 48 that displays a traveling speed, and the like. The speed setter 46 is a knob that is rotated integrally with the potentiometer, and can be set so that the maximum speed limit Vmax for traveling increases as the knob is rotated clockwise. The maximum speed limit Vmax is set in a stepless manner, for example, 1 to 6 km / h when moving forward, and 1 to 2 km / h when moving backward.

  The accelerator 36 is an operation amount of an operation of pulling the lever forward (hereinafter referred to as an accelerator operation amount (so-called accelerator opening)). } In accordance with θ, the speed is set to be higher within the range of the maximum speed limit Vmax set by the speed setter 46. When the accelerator 36 is released, the accelerator 36 is returned to its original position by a restoring force of an elastic body (not shown), brakes are applied, the speed is reduced, and the accelerator 36 can be stopped.

  The accelerator operation amount θ is detected by the accelerator sensor 40 and supplied to the motor control device 10 of the electric vehicle.

  FIG. 3 is a block diagram showing a circuit configuration of the motor control device 10 of the electric vehicle according to this embodiment.

  The motor control device 10 of the electric vehicle includes the battery 52 described above, and converts the DC power of the battery 52 into AC power by the UVW three-phase bridge-connected switching elements 54 (54a to 54f) constituting the inverter circuit 30. And supplied to the motor 20 for driving the wheel. As the switching element 54, MOSFET or IGBT is adopted.

  A current detector 62 that detects a motor current Im flowing from the battery 52 to the inverter circuit 30 is inserted into a power supply line 53 between the battery 52 and the inverter circuit 30.

  The control device 11 that drives the inverter circuit 30 includes a microcomputer 60. The microcomputer 60 is a computer and includes a CPU (Central Processing Unit), a ROM (including EEPROM), a RAM (Random Access Memory), a RAM (Random Access Memory), an A / D converter, a D / A converter, and the like. It has an output device, a timer as timing means, and the like, and functions as various function realization units when the CPU reads and executes the program recorded in the ROM.

  In this embodiment, the microcomputer 60 includes a basic drive command unit 70 that supplies a drive command Dcom to a PWM (pulse width modulation) circuit 58 during normal running that is not locked, and the motor 20 detected by the speed detector 56. It functions as a lock state determination unit 72 that determines the lock state based on the actual rotation speed Vm and the like, and a lock-time drive command unit 74 that supplies a drive command Dcom for performing lock control when it is determined to be in the lock state.

  The basic drive command unit 70 calculates the rotation speed command Vmcom of the motor 20 according to the accelerator operation amount θ from the accelerator sensor 40 based on the setting of the maximum speed limit Vmax of the speed setting device 46, and the rotation speed command Vmcom and the speed The torque command value Trcom is calculated from the deviation from the actual rotational speed Vm detected by the detector 56, and the drive command Dcom based on the actual rotational speed Vm and the torque command value Trcom is switched via the PWM circuit 58 to the switching element of the inverter circuit 30. 54.

  The PWM circuit 58 supplies a drive signal having a duty corresponding to the drive command Dcom to each switching element 54. The switching element 54 is sequentially switched in accordance with the drive signal to generate a rotating magnetic field through the stator (field coil) of the motor 20 to rotate the rotor. The electric vehicle 12 travels when the rotational force of the rotor is transmitted to the rear wheels 16 through a speed reducer (not shown).

  The lock state determination unit 72 considers that the actual rotation speed Vm is equal to or less than a predetermined rotation speed (rotation speed to be regarded as a stop) Vms, for example, Vms = 50 [rpm] or less during the output of the drive command Dcom. When the state of the predetermined rotational speed Vms or less continues for a predetermined time Tstop or more, for example, Tstop = 3 [s] or more, it is determined that the motor 20 in which the electric vehicle 12 is not traveling by the wheels 14 and 16 is in the locked state.

  When it is determined that the motor 20 is in the locked state, control of the PWM circuit 58 is switched from control by the basic drive command unit 70 to control by the lock-time drive command unit 74 and the current limiter 64.

  When the motor 20 of the electric vehicle 12 is in the locked state, the drive command unit 74 and the current limiter 64 at the time of locking operate to protect the switching element 54 and generate (ensure) sufficient driving torque. .

  When the motor drive command unit 74 recognizes that the motor 20 is in a locked state, it outputs a drive command Dcom at the time of lock to a specific switching element 54 that supplies current to the motor 20 in the locked state. .

  The current limiter 64 determines the current that flows through the switching element 54 as the instantaneous allowable current threshold Iimaxth (the maximum allowable current value that is likely to cause element breakdown or the like when the current flowing through the switching element 54 exceeds this value even instantaneously) or this The margin is limited to a value that does not exceed the first allowable current threshold Iimaxth1, which is smaller than the instantaneous allowable current threshold Iimaxth.

  Since the current limiter 64 is configured by a hardware circuit using a comparator, the current flowing through the specific switching element 54 that supplies current to the motor 20 in the locked state is instantaneously (through the PWM circuit 58 ( Can be cut off at high speed).

  The current limiter 64 supplies the PWM circuit 58 with an element stop signal Sls for immediately interrupting the current flowing through the specific switching element 54. The current limit operation state signal Sla is supplied to the lock time drive command unit 74 during the period when the element stop signal Sls is being output. The lock-time drive command unit 74 supplies a current limit release signal Slr to the current limiter 64 under a predetermined condition described later.

  The inverter circuit 30 has a package configuration (unit configuration) in which a switching element 54 is attached to a radiator (heat radiating plate) in consideration of heat dissipation, and a temperature detector 33 that measures the package temperature Tp is integrally provided. ing. The package temperature Tp and the element temperature (actually the junction temperature) of the switching element 54 have a predetermined functional relationship, and the relationship is measured in advance and the functional relationship is stored in the ROM of the microcomputer 60 as a map or the like. The element temperature of the switching element 54 can be estimated by measuring the package temperature Tp.

  Therefore, when the package temperature Tp of the inverter circuit 30 is known, the continuous allowable current threshold Icth depending on the package temperature Tp (actually the junction temperature) of the switching element 54 can be calculated. A map or calculation formula for calculating is stored in the ROM of the microcomputer 60 as a threshold map (threshold reference table) 76 or the like.

  In addition to the program executed by the CPU, the ROM stores a threshold map 76 (threshold reference table) referred to by the CPU (various functional units).

  As shown in FIG. 4, the threshold map 76 is a table showing the threshold (current threshold) Ith of the current I [A] with respect to the elapse of time [s], and the instantaneous threshold of the switching element 54 described above is used as the current threshold Ith. The current threshold value Iimaxth, the first allowable current threshold value Iimaxth1, and the continuous allowable current threshold value Icth (average value) are stored.

  The continuous allowable current threshold Icth is considered in consideration of an increase in element temperature (in this embodiment, as described above, the element temperature is converted into the package temperature Tp and the element temperature is replaced with the package temperature Tp). It has a characteristic of decreasing as the package temperature Tp increases from the instantaneous allowable current threshold value Iimaxth of the continuous energization time of zero seconds.

  As shown in FIG. 5, the allowable current decreases exponentially when the package temperature Tp [° C.] becomes high. As shown in FIG. 6, the allowable current starts from a certain point in time with respect to the continuous energization time [s]. Decreases proportionally. Therefore, by detecting the package temperature Tp, the value of the continuous allowable current threshold Icth (see FIG. 4) at the time of temperature detection can be obtained.

  For example, even when the electric vehicle 12 is pressed against a wall or the like and the motor 20 is locked, it is necessary to ensure torque for a certain time (for example, 15 seconds) in the locked state (field of the stator of the motor 20). It is necessary to pass a current through the coil). The fixed time is referred to as a lock protection time Tpro shown in FIG. During the lock protection time Tpro, it is preferable that the switching element 54 is not destroyed and that as much driving torque as possible can be secured.

  Before describing the detailed operation of the motor control device 10 of the electric vehicle according to this embodiment that is basically configured and operates as described above, first, a comparative example for clarifying the significance of this operation. explain.

  Since the rotation of the motor 20 is stopped in the locked state, as shown in FIG. 7, the motor current Im (Im = Imlock) flows from the battery 52 only to the specific switching elements 54a and 54e when the rotation stops.

  As shown in FIG. 8, at the time t0 when this lock state is detected, for example, the drive torque of the motor 20 is increased by increasing the duty of the drive signal of the switching element 54e of the lower arm and increasing the motor current Im (Im = Imlock). Increase In this case, as shown in FIG. 8, the drive signal of the switching element 54a of the upper arm is turned on, but since it is connected in series, the motor having the same waveform as the switching element 54e of the lower arm is also connected to the switching element 54a of the upper arm. A current Im (Im = Imlock) flows.

  By such driving, as shown in FIG. 9, the basic duty motor current Imlock at the time of locking increases rapidly from the time of locking at the time t0 (t0 = 0) and becomes a constant current at the time t1. As shown at t2, when the basic duty motor current Imlock at the time of lock exceeds the continuous allowable current threshold value Icth, the switching elements 54a and 54e reach a breakdown failure. Therefore, in the comparative example, the lock holding time Tpro cannot be satisfied, and therefore it is necessary to limit the current value to the lock basic duty motor current Imlock 'or the like when the lock basic duty motor current Imlock is smaller. Therefore, the driving torque of the motor 20 becomes small.

  Therefore, the disadvantages of this comparative example are solved by the processing described below in this embodiment.

  Hereinafter, operation | movement of the motor control apparatus 10 of the electric vehicle which concerns on this embodiment is demonstrated based on the flowchart of FIG.

  In step S1 during travel of the electric vehicle 12, the accelerator operation amount θ corresponding to the operation of the accelerator 36 by the passenger is detected by the accelerator sensor 40, and the maximum speed limit Vmax set by the speed setter 46 is set as the basic drive command. It is detected by the unit 70 (FIG. 3).

  Next, in step S2, the basic drive command unit 70 calculates the rotational speed command Vmcom of the motor 20 based on the accelerator operation amount θ and the maximum speed limit Vmax.

  Next, in step S <b> 3, the basic drive command unit 70 calculates a deviation (Vm−Vmcom) between the calculated rotation speed command Vmcom and the actual rotation speed Vm of the motor 20 detected by the speed detector 56.

  In step S4, the basic drive command unit 70 calculates a torque command value Trcom such that the deviation (Vm−Vmcom) becomes zero by PID (proportional integral derivative) control.

  In step S <b> 5, the basic drive command unit 70 calculates a drive command Dcom, which is a drive duty, with reference to a map created in advance from the actual rotational speed Vm and the torque command value Trcom, and sets it in the PWM circuit 58.

  In step S6, the PWM circuit 58 outputs a drive signal having a duty corresponding to the drive command Dcom to the switching element 54.

  Next, in step S7, as described above, the lock state determination unit 72 determines that the actual rotational speed Vm is equal to or lower than the predetermined rotational speed Vms and is considered to be stopped during the output of the drive command Dcom. It is determined whether or not the motor 20 is in a locked state depending on whether or not it continues for a predetermined time Tstop.

  When it is determined that the lock state is not established, the process returns to step S1, and the control operation (traveling operation of the electric vehicle 12) by the basic drive command unit 70 is repeated.

  On the other hand, when the determination in step S7 is established, in step S8, the lock state determination unit 72 determines (determines) that the motor 20 is in the lock state and notifies the lock-time drive command unit 74. Thereby, the control to the PWM circuit 58 is switched from the control by the basic drive command unit 70 to the control by the lock-time drive command unit 74 and the current limiter 64, and the lock-time drive command unit 74 is in a locked state. At t0, first, a drive command Dcom for the lock basic duty motor current Imlock is output to the PWM circuit 58 (see t0 in FIG. 11).

  At this time, in step S9, the lock-time drive command unit 74 starts measuring the locked state from the time point t0 determined to be in the locked state, and detects the package temperature Tp of the inverter circuit 30 by the temperature detector 33. In S10, the continuous allowable current threshold Icth is calculated from the package temperature Tp and the elapsed time (time from the time point t0) of the locked state.

  Next, in step S11, the lock-time drive command unit 74 detects the lock-time basic duty motor current Imlock (the lock-time maximum duty motor current Imlockmax when step S12 described later is established) by the current detector 62.

  Next, in step S12, the lock-time drive command unit 74 determines that the detected lock-time basic duty motor current Imlock is smaller than the continuous allowable current threshold Icth and the current limiter 64 is not activated (element stop signal Sls). Is not output).

  When the determination in step S12 is established (see time point t10 in the time chart of FIG. 11), in step S13, the lock-time drive command unit 74 is locked until the current limiter 64 operates and outputs the element stop signal Sls. A drive command Dcom having a larger duty that causes the maximum duty motor current Imlockmax to flow is output (see time points t10 to t11).

  As shown in the time point t11 in FIG. 11 (and the subsequent time points t13, t15, t17, t19, and t21), the current limiter 64 has the maximum duty motor current Imlockmax at the time of locking detected by the current detector 62 as a first value. When an attempt is made to exceed the allowable current threshold value Iimaxth1, the element stop signal Sls is output to operate, and a current limit operation state signal Sla indicating the operation state is notified to the lock-time drive command unit 74.

  Next, in step S14, when the lock-time drive command unit 74 receives the current limit operation state signal Sla indicating that the current limiter 64 is in the operation state, in step S15, the lock-time basic drive motor current Imlock is locked. The DC power supply current Imlockdc at the time of locking is calculated from the integral value of the power supply time of the maximum duty motor current Imlockmax (see FIG. 11).

  Next, in step S16, the lock-time drive command unit 74 determines whether or not the lock-time DC energization current Imlockdc is lower than the continuous allowable current threshold value Icth (Imlockdc <Icth).

  If it is lower, the lock-time drive command unit 74 notifies the current limiter 64 of the current limit release signal S1r in step S17, so that the current limiter 64 releases the output of the element stop signal Sls. (In FIG. 11, time t12 and subsequent time points t14, t16, t18, t20, t22).

  Then, in the next step S11, the maximum duty motor current Imlockmax at the time of locking is detected, and the operations after step S12 are repeated.

  As shown in the explanatory diagrams of the embodiments of FIGS. 12 and 13, in the locked state, the basic duty motor current at the time of locking at the time t0 when the locked state is determined as compared to the explanatory diagrams of the comparative examples of FIGS. The same is true in that the motor current Im is increased by Imlock, but after the time point t10, under the condition that the continuous current limit threshold Icth is satisfied, the motor current Im is set to the maximum duty motor current Imlockmax at the time of lock when the motor current Im is large. As shown in FIG. 11, the motor current Im at the time of locking can be intermittently increased to the first allowable current threshold Iimaxth1, and the motor driving torque can be increased even in the locked state as shown in FIG. It can be. In FIG. 13, the period between time points t11 and t12 is a period in which the switching element 54a and the switching element 54e are cut off by the current limiter 64 (see also FIG. 11).

  At the time of locking, the limitation by the current limiter 64 may be an instantaneous allowable current threshold Iimaxth that is larger than the first allowable current threshold Iimaxth1. The allowable current threshold {instantaneous allowable current threshold Iimaxth or first allowable current threshold Iimaxth1} may be set in the current limiter 64 from the drive command unit 74 at the time of locking.

  As described above, the motor control device 10 for an electric vehicle according to the above-described embodiment converts the direct current power of the battery 52 into alternating current power by the plurality of switching elements 54 connected to the UVW three-phase bridge to drive the wheel. A torque command value Trcom is calculated from the deviation between the inverter circuit 30 supplied to the motor 20 and the rotational speed command Vmcom of the motor 20 corresponding to the accelerator operation amount θ and the actual rotational speed Vm, and the actual rotational speed Vm and the torque command value Trcom are calculated. Is supplied to the switching element 54 through the PWM circuit 58 to drive the motor 20, and a current detector 62 that detects the motor current Im flowing through the power line 53 of the inverter circuit 30 is provided.

  Each switching element 54 is set with an instantaneous allowable current threshold value Iimaxth and a continuous allowable current threshold value Icth that decreases from the instantaneous allowable current threshold value Iimaxth according to the continuous energization time of the direct current.

  The control device 11 uses the lock state determination unit 72 that determines whether or not the motor 20 is in a locked state based on the accelerator operation amount θ and the actual rotational speed Vm of the motor 20, and the lock state determination unit 72 When determined, the current at the time of locking flowing through the specific switching element 54 (54a, 54e) in which the direct current is continuously energized is instantaneous at the initial period of energization (time t0 to t10 in FIG. 11). After the time point t10 when the lockable basic duty motor current Imlock is a constant current value that does not exceed the allowable current threshold Iimaxth, and the lock basic duty motor current Imlock that is the constant current value attempts to exceed the continuous allowable current threshold icth Then, by releasing the restriction of the basic duty motor current Imlock at the time of locking, which is the constant current value, When the current value is increased or decreased repeatedly, the current upper peak value (the upper peak value of the maximum duty motor current Imlockmax at the time of locking) is equal to or less than the instantaneous allowable current threshold Iimaxth and equal to or greater than the continuous allowable current threshold Icth. And a lock-time drive command unit 74 that controls the DC current-carrying current Imlockdc at the lock, which is an average current value when the current value is increased or decreased, not to exceed the continuous allowable current threshold Icth.

  According to this embodiment, the specific switching element 54 (54a, 54e) in which a large current flows at the time of locking can be protected from an overcurrent, and a large driving torque can be generated intermittently even in the locked state.

  By controlling in this way, even if the electric vehicle 12 is locked on a hill or the like, the electric vehicle 12 does not move backward on the hill or the like.

  In this case, when the lock state determination unit 72 determines that the lock state driving command unit 74 is in the locked state, the lock state drive command unit 74 continuously outputs the lock state current flowing through the specific switching element 54 (54a, 54e) that is in the continuous energization state. At the initial energization (time points t0 to t10), the lock is limited to the basic duty motor current Imlock at the time of lock, which is a constant current value that does not exceed the first allowable current threshold Iimaxth1 lower than the instantaneous allowable current threshold Iimaxth. After time t11 when the current exceeds the allowable current threshold Itch, the peak value when the current value is increased or decreased by repeatedly releasing the restriction of the constant current value and increasing or decreasing the current value (the maximum duty motor current when locked) The upper peak value of Imlockmax) is equal to or less than the first allowable current threshold Iimaxth1, and the continuous allowable current threshold Icth is controlled to be equal to or greater than Icth, and the DC current Ilock current at lock, which is an average current value when the current value is increased or decreased, is controlled so as not to exceed the continuous allowable current threshold Icth. The value of the large drive torque generated at the time is slightly reduced corresponding to the difference between the instantaneous allowable current threshold Iimaxth and the first allowable current threshold Iimaxth1, but the switching elements 54 (54a, 54e) in the locked state are more reliably protected. can do.

  When the current value is increased or decreased, the lock-time drive command unit 74 drives the specific switching element 54e (including 54a as a result because it is connected in series). When the duty value is increased and increased (see time point t10 in FIG. 13), and the current value is decreased, the instantaneous allowable current threshold Iimaxth or the specific switching element 54 (54a and 54e) is cut off and decreased. It is possible to perform control with a simple configuration so as not to exceed the first allowable current threshold value Iimaxth1 as a constant current value smaller than the instantaneous allowable current threshold value Iimaxth.

  Further, the lock-time drive command unit 74 allows the lock-time DC energization current Imlockdc, which is an average current value of the specific switching elements 54 (54a, 54e) at the time of the lock, to be instantaneously allowed according to the continuous energization time of the DC current. The cutoff time (time t11 to t12, time t13 to t14, time t13 to t14) of the specific switching element 54 (54a) when the current value is decreased so as to be lower than the continuous allowable current threshold value Icth that decreases from the current threshold value Iimaxth. (3) By gradually increasing the length of the control), a simple configuration with a control in which the locked DC energization current Imlockdc, which is an average current value when the current value is increased or decreased, does not exceed the continuous allowable current threshold Icth, This can be done more reliably.

  Further, a temperature detector 33 for detecting the package temperature Tp of the inverter circuit 30 is provided, and the setting of the continuous allowable current threshold Icth that decreases from the instantaneous allowable current threshold Iimaxth according to the energization time is detected. By controlling so as to vary according to Tp, the package temperature Tp of the inverter circuit 30 is detected instead of the temperature of the switching element 54 itself, so that the switching element 54 can be accurately protected with a simple configuration. it can.

  The motor control device for an electric vehicle according to the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

It is a perspective view of an electric vehicle. It is a top view of an operation part. It is a block diagram which shows the circuit structure of the motor control apparatus of an electric vehicle. It is an illustration figure of a threshold value map. It is explanatory drawing of the allowable current of the switching element with respect to package temperature. It is explanatory drawing of the allowable electric current with respect to continuous energization time. It is explanatory drawing of a motor current flowing only into a specific switching element at the time of the lock in a comparative example. In a comparative example, it is explanatory drawing which increases the drive duty of a specific switching element after the lock state detection time. It is explanatory drawing of the electric current threshold in a comparative example, and the electric current at the time of a lock | rock. It is a flowchart with which operation | movement description of this embodiment is provided. It is explanatory drawing of the electric current threshold value concerning this embodiment, and the electric current at the time of a lock | rock. It is explanatory drawing of the peak current increase path | route in a locked state. It is explanatory drawing of the peak current increase method in a locked state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Motor control apparatus of electric vehicle 11 ... Control apparatus (control apparatus main body)
DESCRIPTION OF SYMBOLS 12 ... Electric vehicle 20 ... Motor 30 ... Inverter circuit 58 ... PWM circuit 62 ... Current detector 72 ... Lock state determination part 74 ... Locking drive command part 76 ...・ Threshold map

Claims (5)

An inverter circuit that converts DC power to AC power by a plurality of switching elements and supplies the AC power to a wheel driving motor;
A torque command value is calculated from a deviation between the rotational speed command of the motor and the actual rotational speed corresponding to the accelerator operation amount, and a drive command value based on the actual rotational speed and the torque command value is supplied to the switching element, A control device for driving the motor;
A current detector for detecting a current flowing in the power line of the inverter circuit,
Each of the switching elements is set with an instantaneous allowable current threshold and a continuous allowable current threshold that decreases from the instantaneous allowable current threshold according to a continuous energization time,
The controller is
A lock state determination unit that determines whether the motor is in a locked state based on the accelerator operation amount and the actual rotation speed of the motor;
When the lock state determination unit determines that the lock state is in effect, the current at the time of lock that flows through a specific switching element that is in a continuous energization state is limited to a constant current value that does not exceed the instantaneous allowable current threshold at the time of initial energization. Then, after the time when the constant current value is about to exceed the continuous allowable current threshold value, the upper limit of the current value when the current value is increased / decreased by releasing the limitation of the constant current value and repeating the increase / decrease of the current value. Control so that the peak value is less than or equal to the instantaneous allowable current threshold and greater than or equal to the continuous allowable current threshold, and control so that the average current value when the current value is increased or decreased does not exceed the continuous allowable current threshold A drive command section when locked,
A motor control device for an electric vehicle characterized by comprising: In the motor control device of the electric vehicle according to claim 1,
The drive command unit at the time of locking is
When the lock state determination unit determines that the lock state is established, the lock-time current flowing through the specific switching element that is in the continuous energization state is a first allowable current threshold value that is lower than the instantaneous allowable current threshold value in the initial period of continuous energization. After the time when the constant current value is about to exceed the continuous permissible current threshold, the constant current value is released and the current value is increased and decreased repeatedly. The current upper peak value when increasing / decreasing is controlled to be not more than the first allowable current threshold and not less than the continuous allowable current threshold, and the average current value when increasing / decreasing the current value is the continuous A motor control device for an electric vehicle, wherein control is performed so as not to exceed an allowable current threshold. In the motor control device of the electric vehicle according to claim 1 or 2,
The drive command unit at the time of locking is
When increasing or decreasing the current value, when increasing the current value, the drive duty of the specific switching element is increased to increase, and when decreasing the current value, the specific switching element is cut off and decreased. A motor control device for an electric vehicle. The motor control device for an electric vehicle according to claim 3,
The drive command unit at the time of locking is
The cut-off time of the specific switching element when the current value is decreased is gradually increased so that the average current value of the specific switching element at the time of locking is lower than the continuous allowable current threshold. A motor control device for an electric vehicle. In the motor control device of the electric vehicle according to any one of claims 1 to 4,
A temperature detector for detecting the temperature of the inverter circuit;
The motor control device for an electric vehicle, wherein the setting of the continuous allowable current threshold that decreases from the instantaneous allowable current threshold according to the energization time is varied according to the detected temperature of the inverter circuit.

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