JP4968163B2 - Vehicle motor control device - Google Patents

Description

  The present invention relates to a vehicle motor control device, and more particularly to a vehicle motor control device that controls torque of a motor to prevent overheating of an inverter when a motor that drives the vehicle is locked.

  An electric vehicle or a hybrid vehicle is a vehicle that can be driven by the output of a motor that is a prime mover. These automobiles are electrically connected to a motor, and are equipped with an inverter that converts electric power from direct current to alternating current and supplies it to the motor. By controlling the operation of a plurality of switching elements provided in the inverter, the torque output from the motor and the rotational speed are adjusted, and the vehicle travels.

  In such an automobile, an alternating current flows through each switching element of the inverter when the motor rotates during normal driving. However, when the motor is locked and the rotation of the motor stops, a large direct current flows only in a specific switching element of the inverter. For this reason, the specific switching element may increase in temperature due to a sudden increase in heat loss and cause thermal destruction. Here, the locked state is a state in which the running resistance torque is greater than the output torque of the motor. For example, the motor may be locked when running on an uphill or when a wheel is fitted in a recess. There is.

  In the following Patent Document 1, there is described a control technique for controlling a motor so that the maximum torque that can be output by the motor is intermittently output when the motor is in a locked state. Specifically, when the motor is locked, the motor is controlled so as to repeatedly output a maximum torque and a torque lower than this torque.

  In Patent Document 1 below, the number of times that the motor has output the maximum torque is counted, and when the count value reaches the allowable number, the motor is controlled so as to intermittently output the torque gradually reduced from the maximum torque. Control techniques are described. With this control technique, the maximum torque can be effectively utilized within a range where a specific switching element of the inverter does not reach the allowable temperature.

JP 2007-129801 A

  When the motor is in the locked state, the power performance necessary for the escape from the locked state can be ensured for a predetermined time by performing motor control that intermittently outputs the maximum torque as in Patent Document 1 described above. However, when the automobile cannot escape from the locked state of the motor and the time elapses, the temperature of the specific switching element may rise and reach an allowable temperature. On the other hand, in order to prevent the temperature of a specific switching element from reaching the allowable temperature, if the motor is controlled so as to intermittently output the torque gradually decreased from the maximum torque, the automobile may escape from the state. It becomes difficult.

  An object of the present invention is to secure a power performance required for escape from a locked state for a long time while suppressing a temperature rise of a specific switching element of an inverter when a motor driving a vehicle is in a locked state. An object of the present invention is to provide a vehicular motor control device.

  In the present invention, when the motor that drives the vehicle is locked, in order to prevent overheating of the inverter, the torque is output so that the maximum torque that the motor can output and a low torque lower than this torque are repeatedly output. In the vehicle motor control device to be controlled, each time the maximum torque is output, phase detection means for measuring the electrical angle of each of the three phases and detecting the phase through which the largest current flows among the three phases, and the current maximum A phase detection means for determining whether or not a phase detected by the phase detection means at the time of torque output and a phase detected by the detection means at the time of the previous maximum torque output are in phase with the phase detection means. When it is determined that there is a temperature increase suppression means for suppressing a temperature increase of the switching element of the inverter corresponding to the phase.

  Moreover, the temperature rise suppression means can make the length of the output time of the maximum torque output this time shorter than the length of the output time of the maximum torque output last time.

  Further, the temperature rise suppression means may make the value of the low torque output after the maximum torque output this time smaller than the value of the low torque output before the maximum torque output this time. it can.

  Further, the temperature rise suppression means further shortens the period when the low torque is subsequently reduced from the maximum torque output this time, compared with the period when the low torque is subsequently reduced from the maximum torque output. be able to.

  Moreover, it has a cooling means which circulates a cooling medium and cools an inverter, and a temperature rise suppression means can increase the cooling capacity of a cooling means.

  The cooling means has a heat radiating fan that radiates the heat of the cooling medium, and the temperature rise suppressing means can increase the cooling capacity of the cooling means by increasing the number of rotations of the heat radiating fan.

  Furthermore, the temperature raising means can increase the cooling capacity of the cooling means by increasing the circulation flow rate of the cooling medium.

  According to the vehicle motor control device of the present invention, when the motor for driving the vehicle is in the locked state, the power necessary for the escape from the locked state while suppressing the temperature rise of the specific switching element of the inverter. Performance can be secured for a long time.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a vehicle motor control device according to the present invention will be described with reference to the drawings. As an example, an electric vehicle driven by electricity is cited, and a vehicle motor control device mounted on the vehicle will be described. The present invention is not limited to an electric vehicle, and can be applied to a vehicle that travels with the output of an engine and a motor, that is, a vehicle motor control device mounted on a hybrid vehicle.

  First, the configuration of an electric vehicle 10 equipped with a vehicle motor control device 30 according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a schematic configuration of an electric vehicle 10 according to the present embodiment.

  The electric vehicle 10 has a motor 12 as a prime mover. Drive wheels 16 are connected to the motor 12 via a power transmission mechanism 14. The power transmission mechanism 14 includes a speed reduction mechanism (not shown) that reduces the rotational speed of the output shaft of the motor 12 and a differential mechanism (not shown) that absorbs the rotational difference between the left and right drive wheels 16. The power of the motor 12 is transmitted to the drive wheels 16 via the power transmission mechanism 14, and the electric vehicle 10 travels.

  The motor 12 is electrically connected to the battery 20 via the inverter 18. The motor 12 and the inverter 18 are connected via a three-phase AC cable 22. On the other hand, the inverter 18 and the battery 20 are connected via a DC cable 24.

  The battery 20 is a chargeable / dischargeable secondary battery, and is composed of, for example, a nickel metal hydride battery or a lithium ion battery. Of course, instead of the battery 20, a chargeable / dischargeable battery other than the secondary battery, for example, a capacitor may be used.

  The electric power stored in the battery 20 is converted from direct current to alternating current by the inverter 18 and then supplied to the motor 12 to drive the motor 12. Further, the electric power generated by the motor 12 during regeneration is converted from alternating current to direct current by the inverter 18 and then sent to the battery 20 for storage. Thus, the motor 12 can function as an electric motor and a generator.

  The inverter 18 will be described in detail with reference to FIG. FIG. 2 is an electric circuit diagram connecting the motor 12, the inverter 18, and the battery 20.

  In the circuit in the inverter 18, a U-phase arm 25, a V-phase arm 26, and a W-phase arm 27 are provided in parallel between a positive electrode bus and a negative electrode bus connected to the battery 20. Switching element 18a and switching element 18b are connected in series to U-phase arm 25, switching element 18c and switching element 18d are connected in series to V-phase arm 26, and switching element 18e is connected to W-phase arm 27. And the switching element 18f are connected in series. The switching elements 18a to 18f are composed of, for example, an IGBT (Insulated Gate Bipolar Transistor), a power transistor, a thyristor, or the like.

  An intermediate point of each phase arm 25, 26, 27 is connected to each phase end of each phase coil of motor 12. That is, the intermediate point of the U-phase arm 25 is connected to one end of the U-phase coil of the motor 12, the intermediate point of the V-phase arm 26 is connected to one end of the V-phase coil of the motor 12, and the intermediate point of the W-phase arm 27. The point is connected to one end of the W-phase coil of the motor 12. The motor 12 is configured such that the other end of each phase coil of the motor 12 is commonly connected to the midpoint.

  Further, in the circuit in the inverter 18, a capacitor 19 is provided in parallel to each phase arm 25, 26, 27 between the positive and negative buses connected to the battery 20. Capacitor 19 smoothes the DC voltage supplied from battery 20 into inverter 18.

  The operation of the inverter 20 will be described. DC power is supplied from the battery 20 to the phase arms 25, 26, 27. When DC power is supplied to each phase arm 25, 26, 27, switching elements 18 a to 18 f are turned on / off according to a PWM (pulse width modulation) control signal from vehicle motor control device 30 described later. . Thereby, inverter 20 converts electric power from direct current to three-phase alternating current, and drives motor 12.

  Returning to the description of FIG. 1, the electric vehicle 10 includes a vehicle motor control device (hereinafter simply referred to as a control device) 30 that controls the motor 12 based on the driver's request and the state of the vehicle. The control device 30 is composed of a microcomputer.

  The control device 30 is connected to an ignition switch 32, an accelerator pedal 34, a brake pedal 36, a shift lever 38, and the like which are operated by the driver, and a signal indicating a driver's request is input from these. The control device 30 flows through a vehicle speed sensor 40 that detects the traveling speed of the vehicle, a rotation angle sensor 42 that detects the rotational position of a rotor (not shown) of the motor 12, and a cable 22 for three-phase alternating current. A current detection sensor 44 for detecting a current is connected, and a signal indicating the state of the vehicle is input from these. In addition, various sensors (not shown) that detect the state of the battery 20 are connected to the control device 30. The various sensors are sensors that detect the temperature, current, and voltage of the battery 20, and signals indicating the state of the vehicle are also input from these sensors. The control device 30 determines the driver's request based on the above-described signal indicating the driver's request, determines the vehicle state based on the above-described signal indicating the vehicle state, and determines the driver's request and the vehicle state. A control signal is output to the inverter 18 so as to operate the motor 12 applied to the above.

  Next, the cause of the thermal destruction of the inverter 18 will be described with reference to FIG. FIG. 3 is a diagram showing a waveform of a three-phase alternating current supplied to the motor 12. The waveform is a sine wave, and the U phase, V phase, and W phase each have a phase difference of 120 degrees. The electrical angle of the waveform of the three-phase alternating current is determined according to the rotation angle of the rotor of the motor 12. When the motor 12 is locked, the rotational speeds of the motor 12 and the drive wheels 16 are zero, that is, the rotation stops, even though a torque command is output from the control device 30 to the inverter 18. Stopping the rotation of the motor 12 means that the rotation angle of the rotor is fixed at a constant angle. At this time, the waveform of the three-phase alternating current stops at the electrical angle corresponding to the fixed rotation angle, and the current of the electrical angle flows continuously. That is, a direct current flows. This direct current also flows through the switching elements 18a to 18f of the inverter 18, and if the value is large, there is a high possibility that the element will generate heat due to heat loss of the element itself and cause thermal destruction. In view of this, the present invention secures the power performance required for escape from the locked state for a long time while suppressing the temperature rise of a specific inverter element of the inverter 18 by the control operation of the control device 30 described below. Yes.

  A method of adjusting the torque of the motor 12 when the motor 12 is locked will be described with reference to FIG. The upper graph in FIG. 4 shows the relationship between the torque of the motor 12 and time, and the lower graph shows the relationship between the temperature of a specific switching element of the inverter 18 and time.

  In the upper graph of FIG. 4, when the motor 12 is locked at time t = 0, the control device 30 controls the torque so as to intermittently output the maximum torque Tmax that the motor 12 can output. The change in torque due to this control will be described in detail below.

  First, from time t0 to time t1, the torque increases from 0 to the maximum torque Tmax. The torque maintains the maximum torque Tmax during a predetermined period dt1 from time t1 to time t2. After time t2 when the predetermined period dt1 has elapsed, the torque gradually decreases from the maximum torque Tmax. Note that the predetermined period dt1 is set to be shorter than the time until the temperature of the element rises and reaches the allowable temperature when the current corresponding to the maximum torque Tmax continuously flows to the specific switching element.

  At the time t1, the electrical angle of each of the three phases is measured, and the phase through which the largest current flows among the three phases is detected. Specifically, the electrical angle is measured by the rotation angle sensor 42 or the current detection sensor 44, and the target phase is detected by fitting the electrical angle to the waveform shown in FIG. This detected phase is used when determining whether or not it is in phase with the phase detected at time t4 next indicating the maximum torque Tmax.

  Then, the torque decreases from the maximum torque Tmax to the low torque T1 over a predetermined period dt3 from time t2 to time t3. When it is determined that the torque has reached the low torque T1 at the time t3, the torque increases from the low torque T1 to the maximum torque Tmax from the time t3 to the time t4. Here, the torque control described in paragraphs 0031 to this paragraph is referred to as control for intermittently outputting the normal maximum torque Tmax.

  At time t4, the electrical angle of each of the three phases is measured, and the phase through which the largest current flows among the three phases is detected. When the detected phase and the phase detected at the time t1 are in phase, the control device 30 determines that only the temperature of the specific switching element rises to reach the allowable temperature, and The content of the intermittent output of the maximum torque Tmax is changed. On the other hand, if the phase in which the maximum current detected at the time t4 flows and the phase in which the maximum current detected at the time t1 are different are specified by switching the switching element that increases in temperature. Only the temperature of the switching element can be prevented from rising. Therefore, the control for intermittently outputting the normal maximum torque Tmax is continuously performed. In FIG. 4, the case where the phase through which the maximum current flows is the same at time t1 and time t4 will be described next.

  The predetermined period dt2 from time t4 to time t5 in which the maximum torque Tmax is maintained is changed so as to be shorter than the predetermined period dt1. After the time t5 when the predetermined period dt2 has elapsed, the torque gradually decreases from the maximum torque Tmax toward the low torque T2. At this time, the predetermined period dt4 from time t5 to time t6 in which the torque decreases from the maximum torque Tmax to the low torque T2 is changed to be shorter than the predetermined period dt3. Further, the value of the low torque T2 is changed so as to be smaller than the value of the low torque T1.

  When it is determined that the torque has reached the low torque T2 at the time t6, the torque increases from the low torque T2 to the maximum torque Tmax from the time t6 to the time t7. At time t7, the electrical angle of each of the three phases is measured, and the phase through which the largest current flows among the three phases is detected. When the detected phase and the phase detected at the time t4 are in phase, the control device 30 determines that only the temperature of the specific switching element rises and reaches the allowable temperature. The torque is controlled in the same manner as the control content described in paragraph 0035. That is, as shown in the figure, the control is performed such that the period during which the maximum torque Tmax is output is dt2, the period during which the torque decreases from the maximum torque Tmax to the low torque is dt4, and the low torque is T2. On the other hand, when the phase in which the largest current flows among the three phases and the phase detected at the time t4 are different at the time t7, the switching element that rises in temperature is switched to switch the specific switching element. Only the temperature can be prevented from rising. For this reason, although not shown in figure, the control apparatus 30 performs control which outputs the normal maximum torque Tmax intermittently.

  The lower graph of FIG. 4 shows the temperature characteristics of a specific switching element corresponding to the torque control described above. The control device 30 has a predetermined allowable temperature Thlim as the temperature of the switching element. The control device 30 intermittently outputs the maximum torque Tmax within the range where the temperature of the switching element does not reach the allowable temperature Thlim by controlling the torque described above.

  In the torque control described above, the control for intermittently outputting the normal maximum torque Tmax is performed until time t4, and the content of the control for intermittently outputting the maximum torque Tmax is changed after time t4. As a result, the temperature characteristics of the switching element also change. That is, since the period during which the maximum torque Tmax is output is shortened from dt1 to dt2, the degree of the temperature rise of the switching element during that period is reduced. Further, since the period during which the maximum torque Tmax is reduced to the low torque is shortened from dt3 to dt4, and the low torque is reduced from T1 to T2, the degree of the temperature drop of the switching element is increased. In this way, by changing the content of the control for intermittently outputting the maximum torque Tmax from the control for intermittently outputting the normal maximum torque Tmax, the temperature rise of the specific switching element is suppressed, and the temperature is allowed. The temperature Thlim is never reached.

  Therefore, according to this embodiment, as long as the temperature of the switching element does not reach the allowable temperature Thlim, it is possible to cause the motor 12 to output the maximum torque Tmax intermittently for a long time. As a result, the power performance can be secured for a long time by maximizing the ability of the motor 12 while preventing overheating of the switching element.

  Next, a control operation in which the control device 30 controls the torque of the motor 12 when the motor 12 is locked will be described with reference to FIG.

  First, the control device 30 determines whether or not the motor 12 is in a locked state (step S01). When the motor 12 is in the locked state, the control device 30 controls the torque so as to intermittently output the maximum torque Tmax (step S02). On the other hand, when the motor 12 is not in the locked state, this control operation ends.

  When control for intermittently outputting the maximum torque Tmax is performed, the control device 30 causes the phase in which the maximum current flows when the Nth maximum torque Tmax is output and the phase in which the maximum current flows when the N−1th maximum torque Tmax is output. Is in phase with each other (step S03). That is, each time the maximum torque Tmax is output, the phase through which the maximum current flows is detected, and the phase detected when the current (Nth) maximum torque Tmax is output and the previous (N-1) time when the maximum torque Tmax is output. It is determined whether or not the detected phase is in phase. When these phases are in phase, control device 30 controls the torque so as to suppress the temperature rise of the switching element (steps S04 to S06). On the other hand, when those phases are not in phase, control device 30 returns to step S01.

  The torque control in steps S04 to S06 will be described. First, the output period of the maximum torque Tmax is shortened from Td1 to Td2 shorter than this (step S04). Next, the period from the maximum torque Tmax to the low torque is shortened from Td3 to a shorter Td4 (step S05). Then, the low torque is reduced from T1 to T2 smaller than this (step S06). Then, it returns to step 01 and repeats the control operation mentioned above.

  According to the control device 30 according to the present embodiment, when the torque is controlled so that the motor 12 is locked and the maximum torque Tmax is intermittently output, it is detected every time the maximum torque Tmax is output. It is determined whether or not the phase in which the maximum current flows is the same as the phase in which the maximum current flows when the previous maximum torque Tmax is output. When the phases are different, control is performed to intermittently output the normal maximum torque Tmax. On the other hand, when the phases are the same, control for suppressing the temperature rise of the switching element is performed even when the maximum torque Tmax is intermittently output. Thereby, the power performance required for escape from the locked state can be ensured for a long period of time without the temperature of the switching element reaching the allowable temperature.

  Next, another means for suppressing the temperature rise of the switching element will be described with reference to FIG. FIG. 6 is a diagram showing a schematic configuration of a cooling device 50 that cools the motor 12 and the inverter 18.

  The cooling device 50 includes a pump 52, a radiator 54 that radiates heat of the cooling liquid that is a cooling medium, and a cooling channel 56 through which the cooling liquid flows. A radiator fan 58 that sends air to the radiator 54 is attached to the radiator 54. The heat radiating fan 58 is an electric fan, and a drive motor (not shown) drives the heat radiating fan 58 in an adjustable manner. By driving the radiating fan 58, air is sent to the radiator 54, and the coolant is effectively radiated. The cooling flow path 56 connects the pump 52, the inverter 18, the motor 12, and the radiator 54 in this order. The pump 52 is an electric pump, and a drive motor (not shown) drives the pump 52 so as to be adjustable. By driving the pump 52, the coolant flows so as to circulate through the cooling flow path 56.

  In the cooling device 50 configured as described above, the control device 30 increases the cooling capacity of the cooling device 50 when suppressing the temperature rise of the switching element. Specifically, the control device 30 increases the rotational speed of the heat radiating fan 58 and increases the circulating flow rate of the coolant. As a result, the amount of heat dissipated by the cooling liquid by the heat radiating fan 58 increases and the amount of heat absorbed by the cooling liquid by the inverter 18 increases. As a result, the inverter 18 can be further cooled, and the temperature rise of the switching element in the inverter 18 can be suppressed. In order to suppress the temperature rise of the switching element, the control device 30 may perform only one of the operations of increasing the number of rotations of the heat radiating fan 58 and increasing the circulating flow rate of the coolant.

It is a figure showing the schematic structure of the electric vehicle concerning this embodiment. It is an electric circuit diagram which connects a motor, an inverter, and a battery. It is a figure which shows the waveform of the three-phase alternating current supplied to a motor. It is a timing chart for demonstrating the method of adjusting the torque of a motor, when a motor will be in a locked state. It is a flowchart which shows an example of the control action which adjusts the torque of a motor when a motor will be in a locked state. It is a figure which shows schematic structure of the cooling device which cools a motor and an inverter.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Electric vehicle, 12 Motor, 18 Inverter, 18a-18f Switching element, 30 Vehicle motor control apparatus (control apparatus).

Claims (6)

For vehicles that control the torque to repeatedly output the maximum torque that the motor can output and a lower torque lower than this torque to prevent overheating of the inverter when the motor that drives the vehicle is locked In the motor control device,
Phase detection means for measuring the electrical angle of each of the three phases and detecting the phase in which the largest current flows among the three phases each time the maximum torque is output;
In-phase determination means for determining whether or not the phase detected by the phase detection means at the time of the current maximum torque output and the phase detected by the detection means at the time of the previous maximum torque output;
When it is determined by the in-phase determining means that the phase is in-phase, the temperature increase suppressing means for suppressing the temperature increase of the switching element of the inverter corresponding to the phase;
I have a,
The temperature increase suppression means makes the length of the output time of the maximum torque output this time shorter than the length of the output time of the maximum torque output last time . The vehicle motor control device according to claim 1 ,
The temperature rise suppression means is characterized in that the value of the low torque output after the maximum torque output this time is made smaller than the value of the low torque output before the maximum torque output this time. A vehicle motor control device. The vehicle motor control device according to claim 1 or 2 ,
The temperature rise suppression means further makes the period when the low torque is subsequently reduced from the maximum torque output this time shorter than the period when the low torque is subsequently reduced from the maximum torque output. A motor control device for a vehicle that is characterized. In the motor controller for vehicles according to any one of claims 1 to 3 ,
A cooling means for circulating the cooling medium to cool the inverter;
The vehicle temperature control means increases the cooling capacity of the cooling means. The vehicle motor control device according to claim 4 ,
The cooling means has a heat radiating fan that radiates the heat of the cooling medium,
A vehicle motor control device characterized in that the temperature rise suppression means increases the cooling capacity of the cooling means by increasing the rotational speed of the heat radiating fan. The vehicle motor control device according to claim 4 or 5 ,
The vehicle temperature control means increases the circulating flow rate of the cooling medium to increase the cooling capacity of the cooling means.

Images