Vehicle control system

Abstract

To suppress a vehicular pitch motion possibly caused by motor lock protection control.SOLUTION: A vehicular control apparatus is capable of traveling on a motor as a drive source. The control apparatus includes: a lock determination part for determining a motor lock state of a motor; a torque control part for performing motor lock protection control for repeatedly increasing and decreasing motor torque in a case where the motor is determined to be locked or likely to be locked; and a suspension control part for performing, in a case where the motor lock protection control is performed, control to increase attenuation power of a shock absorber of an active suspension as compared to before the aforementioned control is performed.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle, and more particularly to a control device that performs motor lock protection control and suspension control for a vehicle.

Background Art

[0002] Conventionally, battery electric vehicles (BEVs) having a motor as a power source (drive source) for driving wheels and hybrid vehicles (HEVs) having both an engine and a motor as drive sources are known. In such electric vehicles, generally, a three-phase AC motor is used.

[0003] In an electric vehicle, for example, when the vehicle is on an uphill road and the accelerator pedal is lightly depressed, the motor driving force and the vehicle horizontal load are balanced and the vehicle speed becomes zero (or almost zero), and the rotor of the motor cannot rotate. Such a state is called a "motor lock state".

[0004] When the motor is in the locked state, there is a possibility that a high current may concentrate and flow in a coil of a specific phase among the U-phase, V-phase, and W-phase coils arranged in the stator of the three-phase AC motor. If such a state continues, there is a risk that the coil of the specific phase and the switching element in the inverter corresponding thereto may burn out due to overheating.

[0005] In order to avoid such a situation where the motor coil or the like burns out, motor lock protection control is performed. In the motor lock protection control, the torque of the motor is repeatedly increased and decreased to rotate the rotor of the motor at a very low speed to avoid the motor lock state. In Patent Document 1, this motor lock protection control is described as "torque reduction control", and a control device that executes a first torque reduction control and a second torque reduction control that reduces the torque to a predetermined torque lower than that is disclosed.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2010-11546 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In motor lock protection control, periodic increases and decreases in torque can induce pitch motion in the vehicle. This may lead to a deterioration in the vehicle's ride comfort.

[0008] The objective of the present invention is to suppress vehicle pitch motion that may occur due to motor lock protection control. [Means for solving the problem]

[0009] The vehicle control device according to the present invention is a vehicle control device capable of running using a motor as a drive source, and is characterized by comprising: a lock determination unit that determines the motor lock state of the motor; a torque control unit that performs motor lock protection control by repeatedly increasing or decreasing the torque of the motor when it is determined that the motor is in the motor lock state or is likely to be in that state; and a suspension control unit that, when the motor lock protection control is being performed, performs control to increase the damping force of the shock absorber of the active suspension compared to before the motor lock protection control was performed. [Effects of the Invention]

[0010] According to the present invention, when motor lock protection control is performed, the damping force of the shock absorber is increased, thereby suppressing the pitch motion of the vehicle. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic block diagram showing the configuration related to the vehicle's control system. [Figure 2] This is a flowchart showing the processing of the control unit. [Figure 3]This diagram illustrates the vehicle state when motor lock protection control and damping force enhancement control are performed. [Figure 4] This diagram illustrates the vehicle state when only motor lock protection control is performed. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the embodiments described herein. The present invention is applicable to vehicles capable of running using a motor as a driving source, and is applicable to, for example, electric vehicles, hybrid vehicles, plug-in hybrid vehicles, etc. In the following description, a hybrid vehicle will be used as an example.

[0013] Figure 1 is a schematic block diagram showing the configuration of the control device 12 of the vehicle 10. In Figure 1, mechanical connections are shown with thick solid lines, power lines with thin solid lines, and signal lines with dotted lines. The vehicle 10 is a hybrid vehicle. In Figure 1, some components of the hybrid vehicle, such as the battery, DC / DC converter, engine, and MG1, are omitted. Details of the hybrid vehicle are described in Patent Document 1, and the configuration and control (including motor lock state determination and motor lock protection control) described in that document can be applied to the embodiments described below.

[0014] In this embodiment, an active suspension 26 is employed for each wheel 30 in the hybrid vehicle described in Patent Document 1. The active suspension 26 is a suspension with an electronically controlled variable damping mechanism. Specifically, the active suspension 26 includes a spring, a shock absorber (damper), and an actuator. This actuator, for example, makes the damping force generated by the shock absorber variable and is controlled by a suspension control ECU 18.

[0015] Vehicle 10 is a front-wheel drive vehicle. In another embodiment, vehicle 10 may be a hybrid vehicle, electric vehicle, etc., which is a four-wheel drive vehicle equipped with an electric drive mechanism on the rear wheels.

[0016] Vehicle 10 comprises an engine (not shown), two three-phase AC synchronous motor generators MG1 and MG2 (MG1 not shown), and a gear mechanism 24. Hereafter, MG2 will also be referred to as motor 22 as appropriate. The rotating shafts of the engine, MG1, and MG2 are connected to the gear mechanism 24. The gear mechanism 24 is connected to the axle of the wheel 30.

[0017] MG1 and MG2 are electrically connected to their respective inverters (the inverter for MG1 is not shown), and each inverter is electrically connected to a battery (not shown) via a DC / DC converter (not shown). The battery is a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery.

[0018] The inverter 20 of MG2 is electrically connected to the motor control ECU 16 and is controlled based on the control signals transmitted from the motor control ECU 16. The same applies to the inverter (not shown) of MG1. The engine is controlled by the engine control ECU (not shown).

[0019] Vehicle 10 is equipped with a control device 12. The control device 12 includes a hybrid control ECU 14, a motor control ECU 16, a suspension control ECU 18, and an engine control ECU (not shown). The motor control ECU 16, suspension control ECU 18, and engine control ECU are electrically connected to the hybrid control ECU 14, and the hybrid control ECU 14 has the function of comprehensively controlling these ECUs and managing the battery, etc.

[0020] Note that an ECU (Electronic Control Unit) is configured to include, for example, a microcomputer. The ECU includes a processor such as a CPU, a memory, and an input / output interface. The memory includes a RAM (Random Access Memory), a ROM (Read Only Memory), a non-volatile storage device (e.g., flash memory), and the like. By the processor using the RAM to perform processing according to programs and data stored in the ROM and non-volatile storage device in advance, the ECU realizes various controls and various functions. Note that the ECU may be configured to include a plurality of integrated or physically separated computers.

[0021] In the following description, the hybrid control ECU 14 functions as a lock determination unit 15 that determines the motor locked state of the motor 22 (MG2). Also, the motor control ECU 16 functions as a torque control unit, and the suspension control ECU 18 functions as a suspension control unit. Note that the lock determination unit 15 may be realized by the motor control ECU 16.

[0022] For example, when the vehicle 10 starts from a stopped state or is traveling at a low speed, normally, power is supplied from the battery to the MG2 via the converter and the inverter 20, and the driving force of the MG2 is output to the wheels 30 via the gear mechanism 24 and the axle to travel. When the remaining capacity of the battery is low and there is a charging requirement, the power from the engine is input to the rotating shaft of the MG1 to generate electricity, and the generated power is used to charge the battery.

[0023] Also, for example, during normal driving when the vehicle 10 is traveling at a substantially constant and stable speed, the driving force of the engine is output to the wheels 30 via the gear mechanism 24 and the axle to travel. At this time, for example, when the accelerator pedal is temporarily depressed greatly and rapid acceleration occurs, power is also output from the MG1 or the MG2 to assist the power of the engine.

[0024] Furthermore, for example, during regenerative braking when the vehicle 10 is decelerated, power is transmitted from the wheels 30 to the rotating shaft of the MG2 via the axle and gear mechanism 24, causing the MG2 to function as a generator. The electricity generated by the MG2 is used to charge the battery via the inverter 20 and DC / DC converter.

[0025] The following describes the control system when a motor lock occurs during so-called EV driving, where the vehicle is driven using only motor 22 (MG2) to output wheel drive force, or during series hybrid driving, where the vehicle is driven using only motor 22 (MG2) but power from the engine is also input to MG1 to generate electricity.

[0026] Figure 2 is a flowchart showing the processing of the control device 12. The flow in Figure 2 is executed each time, for example, event S10 (switching between the brake pedal and the accelerator pedal) occurs. In S10, the driver of vehicle 10 switches from the brake pedal to the accelerator pedal. For example, this occurs when vehicle 10 is on an incline, a situation in which the motor driving force and the vehicle's horizontal load are balanced, which can cause a state in which the motor rotor cannot rotate (motor lock state).

[0027] In S12, the lock determination unit 15 determines whether the motor 22 is in a motor lock state (or a state in which it could occur). That is, it determines whether a high current is concentrated in a specific phase coil (or a state in which it could occur). If the result of S12 is No, the active suspension 26 is set to normal control (normal mode) (S24), and the process shown in Figure 2 is terminated.

[0028] On the other hand, if S12 is Yes, the process proceeds to S14. In S14, the torque control unit 16 performs motor lock protection control. In motor lock protection control, the torque of the motor 22 is repeatedly increased or decreased. Figure 3 shows an example of increasing or decreasing the motor torque.

[0029] Next, in S16, the suspension control unit 18 performs control to increase the damping force of the active suspension 26 for each wheel 30 (referred to as damping force enhancement control or motor lock protection coordinated mode). That is, if motor lock protection control is being performed, the suspension control unit 18 performs control to increase the damping force of the shock absorber of the active suspension 26 compared to before the control was performed. Figure 3 shows an example of a state in which the damping force of the shock absorber has been increased. For example, the suspension control unit 18 increases the damping force of the shock absorber of the active suspension 26 to the maximum for each of the four wheels 30.

[0030] Next, in S18, the lock determination unit 15 determines whether the motor lock state of the motor 22 (or a state in which it could occur) has been resolved. That is, it determines whether the concentration of high current on a specific phase coil (or a state in which it could occur) has been resolved. For example, the motor lock state is resolved when the vehicle starts on an incline and the speed increases, or when the accelerator pedal is pressed again to the brake pedal. If S18 is No, the unit waits for the motor lock state of the motor 22 to be resolved.

[0031] On the other hand, if S18 is Yes, the process proceeds to S20. In S20, the torque control unit 16 terminates the motor lock protection control.

[0032] Then, in S22, the hybrid control ECU 14 checks whether the vehicle speed (vehicle speed) of the vehicle 10 has reached a predetermined speed (constant speed). If S22 is No, it waits for the vehicle speed to reach a constant speed. If S22 is Yes, it proceeds to S24. In S24, the suspension control unit 18 terminates the damping force enhancement control of the active suspension 26 of each wheel 30 and returns to normal control (normal mode). This means that once a predetermined vehicle speed that can be judged as starting acceleration is reached, the damping force enhancement control of the active suspension 26 is terminated. Then, the process shown in Figure 2 is completed.

[0033] According to the embodiment described above, as shown in Figure 3, when motor lock protection control is performed, the damping force enhancement control of the active suspension 26 is performed, thereby suppressing the pitch motion of the vehicle. Figure 4 is a schematic diagram showing the fluctuations in the vehicle pitch angle and vehicle longitudinal G (G is gravitational acceleration) when only motor lock protection control is performed (when the damping force enhancement control of the active suspension is not performed). As can be seen by comparing Figures 3 and 4, by performing damping force enhancement control of the active suspension 26, fluctuations in the vehicle pitch angle and fluctuations in vehicle longitudinal G can be suppressed.

[0034] In motor lock protection control that increases or decreases the torque of the drive motor, a larger increase / decrease rate (shorter increase / decrease cycle) shortens the time of the increase / decrease execution cycle, making it easier to release the phase current concentration state, which is advantageous from the standpoint of component protection. However, increasing the increase / decrease rate directly leads to an increase in the amount of vehicle oscillation, and if the periodic increase / decrease of torque excites vehicle pitch motion associated with the extension and contraction of the vehicle's front and rear suspension strokes, the vibrations transmitted to the seat and occupants are amplified, causing discomfort to the occupants. However, according to the embodiment described above, since the damping force of the suspension is increased simultaneously with the motor lock protection control, vehicle oscillation can be reduced even at high increase / decrease rates. This makes it possible to achieve both component protection performance and vehicle ride comfort.

[0035] The embodiments described above are thought to be achievable with a general variable damping mechanism for active suspension, and can be realized simply by changing the control without altering the vehicle's mechanical or electrical specifications. [Explanation of Symbols]

[0036] 10 Vehicle, 12 Control device, 14 Hybrid control ECU, 15 Lock detection unit, 16 Motor control ECU (torque control unit), 18 Suspension control ECU (suspension control unit), 20 Inverter, 22 Motor, 24 Gear mechanism, 26 Active suspension, 30 Wheels.

Claims

[Claim 1] A control device for a vehicle capable of running using a motor as a driving source, A lock determination unit for determining the motor lock state of the motor and A torque control unit that performs motor lock protection control by repeatedly increasing or decreasing the torque of the motor when it is determined that the motor is in a motor lock state or is likely to be in such a state, The system includes a suspension control unit that, when the motor lock protection control is being performed, controls the damping force of the shock absorber of the active suspension to be higher than before the motor lock protection control was performed. A vehicle control device characterized by the following features.

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