JP2012196082A - Electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a torque shock caused by change of a sign of a drive force for traveling.SOLUTION: A value of a slow variation treating flag FO is checked (S110) which takes a value 1 when the slow variation treatment is performed for slowly varying required torque when the sign of the required torque to be output to a drive shaft, when the flag FO is a value 1, frequency fc2 higher than ordinarily used frequency fc1 is set (S130) as carrier frequency fc that switches the transistor of a boost converter. Switching of the transistor of the boost converter is performed at the carrier frequency fc to which the frequency fc2 is set. Thus, voltage to the more boosting side than the boost converter is stabilized, the controllability of a motor driven by the power of the boosting side is increased, to allow the slow variation treatment at a high preciseness. As a result, the torque shock caused by looseness of a gear occurring when the sign of the required torque changes is suppressed.

Description

  The present invention relates to an electric vehicle, and more specifically, an electric motor that inputs and outputs driving power, an inverter that drives the electric motor, a rechargeable secondary battery, a battery voltage system and an inverter to which the secondary battery is connected. Is connected to the drive voltage system to which the voltage is connected, and the switching element is switched to boost the voltage of the drive voltage system to a voltage higher than the voltage of the battery voltage system to transfer power between the drive voltage system and the battery voltage system. The present invention relates to an electric vehicle that includes a converter and controls a boost converter and an inverter so as to travel with a driving force required for traveling.

  Conventionally, in this type of technology, in a device that boosts the voltage of a battery by a converter composed of two IGBT elements as a switching element and a reactor and supplies the boosted voltage to an inverter that drives a motor, the IGBT decreases as the inductance of the reactor decreases. A device that changes the carrier frequency so that the frequency at which the element is switched (carrier frequency) has been proposed (see, for example, Patent Document 1). In this apparatus, the reactor is prevented from being overheated by increasing the carrier frequency as the reactor inductance decreases.

JP 2010-098819 A

  In an electric vehicle that boosts the voltage of the battery with the converter and supplies it to the motor inverter as in the above-described device, the switching frequency (carrier frequency) of the switching element of the converter is changed in order to improve energy efficiency. Is desired. The lower the carrier frequency, the smaller the switching loss, so energy efficiency can be improved by lowering the carrier frequency. However, the lower the carrier frequency, the lower the voltage stability on the boost side. It may decrease and cause a torque shock. When switching from deceleration to acceleration or switching from acceleration to deceleration, the direction of torque action in a gear mechanism such as a differential gear changes, resulting in torque shock due to gear backlash. In order to suppress this, when the sign of the driving force changes, a gradual change process is performed to make the change in the driving force slower than usual, but when the carrier frequency is low and the controllability of the motor decreases, the gradual change process is performed. Despite this, a torque shock due to gear backlash occurs.

  The electric vehicle of the present invention is mainly intended to suppress torque shock that may occur when the sign of the driving force for travel changes.

  The electric vehicle of the present invention employs the following means in order to achieve the main object described above.

The electric vehicle of the present invention is
An electric motor that inputs and outputs driving power, an inverter that drives the electric motor, a chargeable / dischargeable secondary battery, a battery voltage system to which the secondary battery is connected, and a drive voltage system to which the inverter is connected A boost converter that boosts the voltage of the drive voltage system to a voltage higher than the voltage of the battery voltage system by switching a switching element connected to the battery, and transfers power between the drive voltage system and the battery voltage system; In an electric vehicle comprising: control means for controlling the step-up converter and the inverter so as to travel with the driving force required for traveling,
The control means is means for performing switching of the switching element of the step-up converter using a larger frequency than when the sign of the driving force is not changed when the sign of the driving force is changed. is there,
It is characterized by that.

  In the electric vehicle according to the present invention, when the sign of the driving force required for driving is changed, the voltage of the driving voltage system is boosted to a voltage higher than the voltage of the battery voltage system, and power is generated between the driving voltage system and the battery voltage system. Switching of the switching element of the step-up converter that transmits and receives is performed using a larger frequency than when the sign of the driving force for traveling is not changed. As a result, the stability of the voltage of the drive voltage system is made higher than when the sign of the driving force for traveling is not changed, and the controllability of the electric motor by the inverter is increased. Torque shocks caused by gear backlash can be suppressed. That is, torque shock that can occur when the sign of the driving force for travel changes can be suppressed.

It is a block diagram which shows the outline of a structure of the electric vehicle 20 as one Example of this invention. 2 is a configuration diagram of an electric drive system centered on a motor 32 and an inverter 34. FIG. 4 is a flowchart showing an example of a carrier frequency setting process routine executed by the electronic control unit 50. FIG. 11 is a configuration diagram showing an outline of a configuration of a hybrid vehicle 120 according to a modification. FIG. 11 is a configuration diagram showing an outline of a configuration of a hybrid vehicle 220 of a modified example.

  Next, the form for implementing this invention is demonstrated using an Example.

  FIG. 1 is a configuration diagram showing an outline of a configuration of an electric vehicle 20 as an embodiment of the present invention. As shown in the figure, an electric vehicle 20 according to the embodiment includes, for example, a motor 32 that is configured as a synchronous generator motor and that can input and output power to a drive shaft 22 that is connected to drive wheels 26a and 26b via a differential gear 24. An inverter 34 for driving the motor 32, a battery 36 configured as, for example, a lithium ion secondary battery, a power line (hereinafter referred to as a high voltage system power line) 42 to which the inverter 34 is connected, and a battery 36 are connected. Connected to a power line (hereinafter referred to as a battery voltage system power line) 44 and adjusts the voltage VH of the high voltage system power line 42 within the range of the voltage VL of the battery voltage system power line 44 and the maximum allowable voltage VHmax. And a booster converter that exchanges power between the high voltage system power line 42 and the battery voltage system power line 44. It comprises a chromatography motor 40, the electronic control unit 50 that controls the whole vehicle, the. Here, as the maximum allowable voltage VHmax, a voltage that is predetermined as a voltage equal to or lower than the withstand voltage of the capacitor 46 described later can be used.

  The motor 32 is configured as a well-known synchronous generator motor including a rotor in which a permanent magnet is embedded and a stator around which a three-phase coil is wound, and generates a counter electromotive voltage with rotation. The inverter 34 is connected in parallel in the reverse direction to the transistors T11 to T16 as the six switching elements and the transistors T11 to T16 as shown in the block diagram of the electric drive system centering on the motor 32 and the inverter 34 in FIG. And six diodes D11 to D16. The transistors T11 to T16 are arranged in pairs so as to be on the source side and the sink side with respect to the positive electrode bus and the negative electrode bus of the high voltage system power line 42, and each of the connection points between the paired transistors. The three-phase coils (U-phase, V-phase, W-phase) of the motor 32 are connected to each other. Therefore, by controlling the ratio of the on-time of the transistors T11 to T16 while the voltage is applied to the inverter 34, a rotating magnetic field can be formed in the three-phase coil, and the motor 32 can be driven to rotate. A smoothing capacitor 46 is connected to the positive and negative buses of the high voltage power line 42.

  As shown in FIG. 2, the boost converter 40 is configured as a boost converter including two transistors T31 and T32, two diodes D31 and D32 connected in parallel in opposite directions to the transistors T31 and T32, and a reactor L. . The two transistors T31 and T32 are connected to the positive bus of the high voltage system power line 42 and the negative bus of the high voltage system power line 42 and the battery voltage system power line 44, respectively, and the reactor L is connected to the connection point. Has been. Further, the positive terminal and the negative terminal of the battery 36 are connected to the reactor L, the negative bus of the high voltage system power line 42 and the battery voltage system power line 44, respectively. Therefore, by turning on and off the transistors T31 and T32, the power of the battery voltage system power line 44 is boosted and supplied to the high voltage system power line 42, or the power of the high voltage system power line 42 is stepped down to reduce the battery voltage. Or can be supplied to the system power line 44. A smoothing capacitor 48 is connected to the reactor L, the negative bus of the high voltage system power line 42 and the battery voltage system power line 44.

  The electronic control unit 50 is configured as a microprocessor centered on the CPU 52, and includes a ROM 54 that stores a processing program, a RAM 56 that temporarily stores data, and an input / output port (not shown) in addition to the CPU 52. . The electronic control unit 50 is attached to the rotational position of the rotor of the motor 32 from the rotational position detection sensor 32 a that detects the rotational position of the rotor of the motor 32, or to a connection line (power line) between the motor 32 and the inverter 34. Phase current from a current sensor (not shown), voltage Vb between terminals from a voltage sensor (not shown) installed between terminals of the battery 36, current sensor (not shown) attached to a power line connected to the output terminal of the battery 36 Charge / discharge current, battery temperature from a temperature sensor (not shown) attached to the battery 36, voltage of the capacitor 46 from the voltage sensor 46a attached between terminals of the capacitor 46 (voltage of the high voltage system power line 42) VH and capacitor The voltage of the capacitor 48 from the voltage sensor 48a attached between the terminals of 48 ( The voltage of the battery voltage system power line 44) VL, the ignition signal from the ignition switch 60, the shift position SP from the shift position sensor 62 that detects the operation position of the shift lever 61, and the accelerator pedal position that detects the depression amount of the accelerator pedal 63 The accelerator opening Acc from the sensor 64, the brake pedal position BP from the brake pedal position sensor 66 for detecting the depression amount of the brake pedal 65, the vehicle speed V from the vehicle speed sensor 68, and the like are input via the input port. From the electronic control unit 50, switching control signals to the transistors T11 to T16 of the inverter 34, switching control signals to the transistors T31 and T32 of the boost converter 40, and the like are output via an output port. The electronic control unit 50 also calculates the rotational speed Nm of the motor 32 based on the rotational position of the rotor of the motor 32 from the rotational position detection sensor 32a.

  The electric vehicle 20 of the embodiment configured in this way is driven and controlled by a drive control routine (not shown). In the drive control, a required torque Tr * to be output to the drive shaft 22 is set according to the accelerator opening Acc from the accelerator pedal position sensor 64 and the vehicle speed V from the vehicle speed sensor 68, and the set required torque Tr * is set to the motor. 32 is set as the torque command Tm * to be output from 32, and the voltage required to drive the motor 32 at the operating point consisting of the set torque command Tm * and the rotation speed Nm is set to the target voltage VH of the high voltage system power line 42. * Is set as *, and the step-up converter controls the switching of the transistors T11 to T16 of the inverter 34 so that the motor 32 is driven by the set torque command Tm * and the voltage VH of the high-voltage power line 42 becomes the target voltage VH *. Forty transistors T31 and T32 are subjected to switching control. When the vehicle is decelerated by traveling off while traveling, a required torque Tr * (negative torque) is set as a braking force in accordance with the amount of depression of the brake pedal 65 and the vehicle speed V, and of the set required torque Tr * Torque that can be output within the rated value range of the motor 32 is set as the torque command Tm *, and the voltage required to drive the motor 32 at the operating point consisting of the set torque command Tm * and the rotation speed Nm is increased. The target voltage VH * of the voltage system power line 42 is set, and the transistors T11 to T16 of the inverter 34 are switched and controlled so that the motor 32 is driven by the set torque command Tm *, and the voltage VH of the high voltage system power line 42 is The transistors T31 and T32 of the boost converter 40 are subjected to switching control so that the target voltage VH * is obtained. Of the required torque Tr * as the braking force, the braking torque that is insufficient for the braking torque output from the motor 32 controls the hydraulic brake device so that the corresponding braking force is output from a hydraulic brake device (not shown). Then, when the vehicle speed decreases, processing for replacing the braking force by the motor 32 with the braking force by the hydraulic brake device is performed in order to smoothly stop the vehicle without causing a shock to the vehicle.

  Further, in the electric vehicle 20 of the embodiment, when the sign of the required torque Tr * changes, that is, when the acceleration torque changes to the deceleration torque (negative value torque), or conversely, the deceleration torque. When the torque is changed from the torque to the acceleration torque, in order to suppress the torque shock that may be caused by the backlash of the differential gear 24, the required torque Tr * is set while the required torque Tr * is within a predetermined torque range including the value 0. It is changed by a slow change process. Specifically, the target torque T * to be output to the drive shaft 22 in accordance with the accelerator opening Acc from the accelerator pedal position sensor 64, the brake position BP from the brake pedal position sensor 66, and the vehicle speed V from the vehicle speed sensor 68. When the target torque T * is set to the required torque Tr * and the sign of the required torque Tr * changes, a unit time (for example, 8 msec) is required until the required torque Tr * falls within a predetermined torque range including the value 0. Etc.) is set as a new required torque Tr *, which is obtained by changing the previous required torque Tr * in the direction of the target torque T * by the rate value Tr1 used during normal operation, and the required torque Tr * has a value of 0. When the torque is within the predetermined torque range, the required torque Tr * up to that time is increased every unit time (for example, 8 msec). Setting the torque is changed by preparative value Tr2 in the direction of the target torque T * as the new requested torque Tr *. As described above, the sign of the required torque Tr * is changed by the gradual change process, so that the torque shock that may be caused by the backlash of the differential gear 24 can be suppressed.

  Next, the operation of the electric vehicle 20 of the embodiment configured as described above, particularly when setting the switching frequency (carrier frequency) of the transistors T31 and T32 of the boost converter 40 when the sign of the required torque Tr * changes. The operation will be described. FIG. 3 is a flowchart showing an example of a carrier frequency setting process routine executed by the electronic control unit 50. This routine is repeatedly executed every predetermined time.

  When the carrier frequency setting process routine is executed, first, the CPU 52 of the electronic control unit 50 first performs a gradual change process that indicates whether or not the gradual change process that is executed when the sign of the required torque Tr * changes. Processing for inputting the flag F0 is executed (step S100). In the embodiment, the slow change process flag F0 is set to a value of 1 when the execution starts in the slow change process executed when the sign of the required torque Tr * changes, and is set to a value of 0 when the slow change process ends. Can be stored by writing to a predetermined address in the RAM 56 of the electronic control unit 50 when the electronic control unit 50 executes the gradual change process. In step S100 of this routine, the predetermined address is stored. The slow change processing flag F0 can be input by reading from.

  Next, the value of the slow change process flag F0 is checked (step S110). When the slow change process flag F0 is 0, the slow change process that is executed when the sign of the required torque Tr * changes is not executed. Therefore, the normally used frequency fc1 is set to the switching frequency (carrier frequency) fc of the transistors T31 and T32 of the boost converter 40 (step S120), and this routine is terminated. On the other hand, when the gradual change processing flag F0 is 1, it is determined that the gradual change processing that is executed when the sign of the required torque Tr * changes is being executed, and the frequency is higher than the normally used frequency fc1. fc2 is set to the carrier frequency fc (step S130), and this routine ends. When the carrier frequency fc is set, the electronic control unit 50 uses the carrier frequency fc in which the transistors T31 and T32 of the boost converter 40 are set so that the voltage VH of the high voltage system power line 42 becomes the target voltage VH *. Control switching. The lower the carrier frequency fc, the smaller the switching loss. Therefore, the energy efficiency of the vehicle can be improved by keeping the normally used frequency fc1 low. While the slow change process executed when the sign of the required torque Tr * changes, the carrier frequency fc for switching the transistors T31 and T32 of the boost converter 40 is higher than the normally used frequency fc1. By switching the transistors T31 and T32 of the boost converter 40 using the frequency fc2, the voltage VH of the high voltage system power line 42 is stabilized, the controllability of the motor 32 is increased, and the slow change process is performed with high accuracy. Can be done. As a result, torque shock due to gear backlash in the differential gear 24 can be suppressed.

  According to the electric vehicle 20 of the embodiment described above, when the slow change process for slowly changing the required torque Tr * is executed when the sign of the required torque Tr * to be output to the drive shaft 22 changes, By switching the transistors T31 and T32 of the boost converter 40 using the frequency fc2 higher than the normally used frequency fc1 as the carrier frequency fc for switching the transistors T31 and T32 of the converter 40, a high voltage system on the boost side from the boost converter 40 is obtained. The voltage VH of the power line 42 is stabilized, the controllability of the motor 32 is increased, and the gradual change process can be performed with high accuracy. As a result, torque shock due to gear backlash in the differential gear 24 can be suppressed.

  In the embodiment, the present invention is applied to the electric vehicle 20 including the motor 32 that can input and output power to the drive shaft 22 connected to the drive wheels 26a and 26b and the inverter 34 for driving the motor 32. As exemplified in the hybrid vehicle 120 of the modified example of FIG. 4, an engine 122 and a motor 124 connected to the drive shaft 22 via a planetary gear mechanism 126, a motor 32 capable of inputting and outputting power to the drive shaft 22, The motor 32 may be applied to the hybrid vehicle 120 including the motor 32, and the motor 32 is attached to the drive shaft 22 and the rotation shaft of the motor 32 is connected to the rotation shaft of the motor 32 via the clutch 229 as illustrated in the hybrid vehicle 220 of the modified example of FIG. The engine 122 is connected, and the power from the engine 122 is output to the drive shaft 22 through the rotation shaft of the motor 32. It may alternatively be applied to a hybrid vehicle 220 for outputting power from the motor 32 to the drive shaft 22 as well as.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. In the embodiment, the motor 32 corresponds to an “electric motor”, the inverter 34 corresponds to an “inverter”, the battery 36 corresponds to a “secondary battery”, the boost converter 40 corresponds to a “boost converter”, and is electronically controlled. The unit 50 corresponds to “control means”.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is the same as that of the embodiment described in the column of means for solving the problem. Therefore, the elements of the invention described in the column of means for solving the problems are not limited. That is, the interpretation of the invention described in the column of means for solving the problems should be made based on the description of the column, and the examples are those of the invention described in the column of means for solving the problems. It is only a specific example.

  As mentioned above, although the form for implementing this invention was demonstrated using the Example, this invention is not limited at all to such an Example, In the range which does not deviate from the summary of this invention, it is with various forms. Of course, it can be implemented.

  The present invention can be used in the manufacturing industry of electric vehicles.

  20 electric vehicle, 22 drive shaft, 24 differential gear, 26 battery, 26a, 26b drive wheel, 32 motor, 32a rotational position detection sensor, 34 inverter, 36 battery, 40 boost converter, 42 high voltage system power line, 44 battery voltage System power line, 46 capacitor, 46a voltage sensor, 48 capacitor, 48a voltage sensor, 50 electronic control unit, 52 CPU, 54 ROM, 56 RAM, 60 ignition switch, 61 shift lever, 62 shift position sensor, 63 accelerator pedal, 64 Accelerator pedal position sensor, 65 Brake pedal, 66 Brake pedal position sensor, 68 Vehicle speed sensor, 120, 220 Hybrid vehicle, 122 Engine, 124 Motor, 12 Planetary gear mechanism 229 clutch, D11-D16, D31, D32 diodes, L reactor, T11 to T16, T31, T32 transistor.

Claims (1)

An electric motor that inputs and outputs driving power, an inverter that drives the electric motor, a chargeable / dischargeable secondary battery, a battery voltage system to which the secondary battery is connected, and a drive voltage system to which the inverter is connected A boost converter that boosts the voltage of the drive voltage system to a voltage higher than the voltage of the battery voltage system by switching a switching element connected to the battery, and transfers power between the drive voltage system and the battery voltage system; In an electric vehicle comprising: control means for controlling the step-up converter and the inverter so as to travel with the driving force required for traveling,
The control means is means for performing switching of the switching element of the step-up converter using a larger frequency than when the sign of the driving force is not changed when the sign of the driving force is changed. is there,
The electric vehicle characterized by the above-mentioned.