JPH05270387A - Brake control device for electric automobile - Google Patents

Abstract

PURPOSE:To enable realization of suitable ABS control even at a low mu (coeffi cient of friction) road. CONSTITUTION:A regeneration brake force command value Tr is corrected by means of a brake force correction value dT at 210 in a state, when ABS control is executed, a hydraulic brake force command value Tb is held at the same value as a preceding hydraulic brake force command value Tb1. At 200, the brake force correction value dT is a negative value when a wheel lock tendency is detected, and a positive value when a wheel speed is restored. When the brake force correction value dT is high, the regeneration brake force command value Tr is a command value expressing powering torque. Since, during ABS control, torque of a motor for drive is used in a state to contain the powering torque side, a total brake force being a sum of hydraulic brake forces is controllable to a low value and coping with a low mu road is practicable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking control device for an electric vehicle, and more particularly to an improvement of means for avoiding wheel lock (sliding).

[0002]

2. Description of the Related Art Conventionally, various electric vehicles equipped with a motor as a drive source have been developed. As a vehicle braking means, mechanical braking is generally known in which hydraulic pressure or the like is applied to wheels. However, in an electric vehicle, regenerative braking by regenerating a drive motor is further possible.

Further, in the case of a vehicle traveling on a road surface,
A state where the wheels are slipping (wheel locking tendency) may occur. That is, the vehicle body speed may exceed the wheel speed due to factors such as the road surface condition. The continuation of such a state is not preferable for safe driving of the vehicle. Therefore, a so-called anti-lock brake system (ABS) has been conventionally developed in gasoline vehicles and the like. It is preferable to mount ABS also in an electric vehicle.

By the way, the problem of wheel slippage occurs not only in a vehicle traveling on a road surface but also in an electric vehicle traveling on a rail. In FIG.
According to Japanese Patent Laid-Open No. 141354/1989, a configuration of a brake system used for an electric vehicle and capable of coping with sliding is shown.

In the vehicle according to this conventional example, a main motor 10 as a drive source and an overhead wire 12 for transmitting electric power are a pantograph 1.
4 and the main circuit controller 16 are connected. The pantograph 14 is arranged on the vehicle lid, and the overhead line 12
Abut. The main circuit controller 16 is a pantograph 14
The main motor 10 is driven by the electric power supplied via the. As a result, the wheels 18 connected to the main motor 10 rotate.

Further, this conventional example has a brake system composed of an air brake and an electric brake. First, the brake receiver 22 determines the distribution of the electric braking force and the air braking force according to the brake command from the driver's cab 20. The brake receiver 22 is the main circuit controller 16
To m, the main circuit control device 16 operates the main motor 10 in the regenerative mode. The output of the main circuit control device 16 is detected by the electric braking force detection device 26, and the detection result mf is input to the brake receiver 22 via the signal holding device 28. As a result, the electric braking force is feedback-controlled. Further, the brake receiver 22 provides the air braking device 30 and the distribution m of the air braking force to mechanically brake the wheels 18.

In this conventional example, the sliding of the wheel 18 is detected by the sliding detecting device 32. Sliding detector 3
When detecting the sliding of the wheels 18 from the output of the speed generator 24, the signal holding device 28 holds mf at a lower value. Then, the electric braking force distribution m by the brake receiver 22 is temporarily reduced. That is, in this conventional example, the electric braking force is reduced while the air braking force is maintained substantially constant during the sliding.

[0008]

By the way, since the electric vehicle is capable of mechanical braking and regenerative braking as described above, it is possible to apply a system as shown in FIG. That is, when the wheel lock tendency is detected, the total braking force can be maintained by controlling the regenerative braking force while maintaining the mechanical braking force substantially constant. However, an electric vehicle does not run on a rail like an electric vehicle, but the road surface condition relating to running changes remarkably. Therefore, depending on the road surface condition, there is a possibility that the wheel lock tendency cannot be quickly escaped.

The present invention has been made to solve the above problems, and realizes a device capable of avoiding a lock and quickly braking regardless of the road surface condition. The purpose is to do.

[0010]

In order to achieve such an object, the braking control device of the present invention changes the torque of the drive motor from the range of the regenerative mode to the power running mode when the wheel lock tendency is detected. It is characterized in that it is provided with a means for avoiding a wheel lock tendency by controlling in a range.

[0011]

In the present invention, the torque of the drive motor during so-called ABS operation is controlled in the range of the power running mode in addition to the range of the regenerative mode. Therefore, by controlling the drive motor in the power running mode, it is possible to cope with a road surface situation in which even if the regenerative torque is set to 0, it is not possible to quickly escape from the wheel lock tendency, and it is possible to brake more quickly while avoiding locking.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an electric vehicle equipped with a braking control device according to an embodiment of the present invention. The electric vehicle shown in this figure has drive motors 36a to 36d as drive sources for the respective wheels 34a to 34d. Among the four motors, the motors 36a and 36b related to the front wheels 34a and 34b are motor controllers 38.
and the other two, namely the rear wheels 34c,
The motors 36c and 36d related to 34d are controlled by a motor controller 38b.

The motor controllers 38a and 38b are
It operates according to a command from the ECU 40 and controls the drive torque and regenerative braking torque of the motors 36a and 36b or the motors 36c and 36d. That is, when a torque command is issued from the ECU 40, the motor controllers 38a and 38b control the electric power supplied to the motors 36a and 36b or the motors 36c and 36d while monitoring the state of the battery 42.

When powering the motors 36a to 36d,
The ECU 40 determines the torque command value according to the depression of an accelerator pedal (not shown), and the motor controller 38a
And 38b. As a result, drive torque is generated according to the amount of depression of the accelerator pedal.

When regenerating the motors 36a to 36d, the ECU 40 detects the depression of the brake pedal 44 by the brake switch 46, and further detects the depression amount by the pedal force sensor 48. Further, the ECU 40
Determines a torque command value according to the pedaling force, and gives a command to the motor controllers 38a and 38b. As a result, a regenerative braking torque is generated according to the depression amount of the brake pedal 44. As a result, regenerative braking means is realized.

The electric vehicle shown in this figure is provided with not only regenerative braking means but also hydraulic braking means as braking means. The hydraulic braking means is composed of a hydraulic transmission mechanism and respective control means associated therewith.

First, the brake pedal 44 has a booster 5
0s are connected. Booster 50 is brake pedal 4
The pressure generated by stepping in 4 is increased and input to the brake master cylinder 52. Brake master cylinder 5
Piping 5 from each hydraulic chamber 2 to the front wheels 34a, 34b side
In addition, a pipe 56 is drawn out to the rear wheels 34c and 34d.

A stroke simulator 60a and a solenoid valve 62a are connected to the front wheel side pipe 54 via a solenoid valve 58a. Similarly, the stroke simulator 60b and the solenoid valve 62b are also connected to the rear wheel side pipe 56 via the solenoid valve 58b.
Are connected. Therefore, when the solenoid valves 58a and 58b are off, the amount of fluid in the brake master cylinder 52 is equal to that of the stroke simulators 60a and 6b.
0b and is not transmitted to the wheel cylinders 64a to 64d provided on the wheels 34a to 34d, respectively. However, since the stroke of the brake pedal 44 is simulated by the stroke simulators 60a and 60b, the feeling does not change.

When the solenoid valves 58a and 58b are on, simulation by the stroke simulators 60a and 60b is not performed. If the solenoid valves 62a and 62b are on, the hydraulic pressure of the brake master cylinder 52 is the wheel cylinder 64a. ~ 64d
In addition, hydraulic braking is performed.

Further, in this embodiment, a pump unit 66 is provided as a means for generating hydraulic pressure in the wheel cylinders 64a to 64d while the solenoid valves 58a and 58b are off. Pump unit 6
6 is a reservoir 68, a pump 70, an accumulator 7
2, a hydraulic pressure sensor 74 and an electronic circuit 76, and the output of the pump 70 is connected to the linear valves 78a and 78b. The braking oil stored in the reservoir 68 is pressure-fed by the pump 70, accumulated in the accumulator 72, and then pressure-fed to the linear valves 78a and 78b. The pressure on the output side of the accumulator 72 is the hydraulic pressure sensor 74.
The electronic circuit 76 controls the operation of the pump 70 according to the detection result. Linear valves 78a and 78
b is a wheel cylinder 64a-6a via solenoid valves 62a and 62b in response to a command from the ECU 40.
Supply hydraulic pressure to 4d. Hydraulic pressure sensors 80a and 80b are provided on the output side of the linear valves 78a and 78b, and the ECU 40 feedback-controls the linear valves 78a and 78b according to the detection values of the hydraulic pressure sensors 80a and 80b. By this control, the wheel cylinder 64
The hydraulic pressure in a to 64d can be linearly controlled.

The characteristic operation of this embodiment is the operation when the wheels 34a to 34d tend to lock. FIG. 2 shows the operation of the ECU 40 in that case.

Immediately after the operation is started (100), the ECU 40 inputs the speed V _W of each wheel 34a to 34d, the state of the brake switch 46 and the pedaling force (output of the pedaling force sensor 48) F _{0 applied} to the brake pedal 44. (11
0). Incidentally, the rotational speed of the motor 36 a to 36 d, may be input as the wheel speeds V _W.

Next, the ECU 40 calculates the estimated vehicle speed V _O based on the information input in step 110 (120). Further, the ECU 40 determines that the wheel speed deviation dV
= Calculates the V _O -V _W and the wheel acceleration deviation _{dG = dV O dV W (130} ). The ECU 40 further determines whether or not the brake pedal 44 is depressed based on the information input in step 110 (140). If the result of this determination is that the pedal is not stepped on, the operation shown in this figure is terminated (240) and the process returns to step 100. When the brake pedal 44 is stepped on, the ECU 40 proceeds to the operation of step 150.

In step 150, the required braking force T is calculated based on the pedaling force F _{0 applied} to the brake pedal 44.
_O is calculated. Further, the ECU 40 determines the distribution of the regenerative braking force and the hydraulic braking force according to a predetermined rule, and according to this distribution, the regenerative braking force specified value T _r and the hydraulic braking force command value T
Calculate _b (160). FIG. 3 shows an example of the braking force distribution in this embodiment. As shown in this figure, the ECU 40 controls the pedal force F _{O of the} brake pedal 44.
When is less than a predetermined value, only regenerative braking is used, and when it exceeds a predetermined value, hydraulic braking is used.

At this time, if the wheels 34a to 34d are not in the lock tendency and it is not necessary to execute the ABS control described later, the command value T obtained in step 160 is obtained.
_{r as it is} to the motor controllers 38a and 38b, and command value T _{b as it is} to the linear valves 78a and 78b,
You can output each. Therefore, after executing step 160, the ECU 40 first determines whether or not ABS control is currently being executed (170), and further, according to a predetermined control start condition (180), whether or not the condition for starting ABS control is satisfied. It is determined (190). When the ABS control is not currently performed and the ABS control start condition is not satisfied, the ECU 40 proceeds to step 230 and outputs the command values _Tr and _{Tb as} they are. On the contrary, AB
If the S control is being executed or the starting condition is satisfied, the process proceeds to step 200.

In step 200, the braking force correction value dT is calculated. The correction value dT is generated, for example, according to the evaluation function W _S = K ₁ dV + K ₂ dG (see Japanese Patent Laid-Open No. 3-50059). The correction value dT thus obtained is a negative value when the wheels 34 tend to lock and the braking force needs to be weakened, and conversely, a positive value when the speed of the wheels 34 is restored and the braking force is insufficient. Becomes

The correction value dT obtained by the calculation is added to the regenerative braking force command value in step 210. That is, dT is added to the previous regenerative braking force command value T _rl to _obtain the current regenerative braking force command value T _r . The hydraulic braking force command value T _b is kept of the last hydraulic braking force command value T _bl (220). Thereafter, the set command values _Tr and _Tb are output (230).

As described above, in this embodiment, the hydraulic braking force is maintained at a predetermined value and the regenerative braking force is corrected by the correction value dT during the ABS control. The point to be noted in this embodiment is that, as a result of the correction of the regenerative braking force command value by the correction value dT,
This command value may be a command value indicating the power running side. However, also in this case, the total braking force of regeneration and hydraulic pressure should be a positive value. Next, regarding this point,
This will be described with reference to FIGS. 4 and 5.

FIG. 4 shows an example of behavior during ABS control in this embodiment. As shown in this figure, assume that the hydraulic braking force starts increasing after the regenerative braking force reaches the maximum value, and the ABS control is started when the hydraulic braking force reaches a certain value. Wheels 3 subject to ABS control
The braking force applied to 4 (herein represented by the FL wheel and the FR wheel) is the sum of the hydraulic braking force and the regenerative braking force, and fluctuates with the same waveform as the control of the regenerative braking force after the ABS control is started. ..

FIG. 5 shows another example of the behavior of the braking force during ABS control in this embodiment. In the example shown in this figure, after the start time t ₀ of the ABS control (time t
₁ ), an example in which the vehicle has changed from a road surface with a high coefficient (high μ road) to a road surface with a low coefficient of friction (low μ road). On the high μ road, the ABS control is performed in a state where the total braking force of the hydraulic braking force and the regenerative braking force is relatively high, but on the low μ road, the total braking force must be set to a smaller value.
Therefore, in the present embodiment, the torque generated by the motors 36a to 36d is not the regenerative torque but the torque on the power running side,
As a result, the total braking force is reduced below the hydraulic braking force value.

Therefore, according to the present embodiment, it is possible to realize an effective ABS even on a low μ road where the wheel lock cannot be avoided even if the regenerative braking force is set to 0. Thereby, braking can be performed more quickly and with a shorter braking distance. Furthermore, since the regenerative braking force can be controlled for each wheel, a total of two hydraulic braking systems, that is, the front wheel side and the rear wheel side are sufficient.

[0032]

As described above, according to the present invention,
When the tendency to lock the wheels is detected, the torque of the drive motor can be controlled within the range of the power running mode by adding the torque of the drive motor to the range of the powering mode while keeping the mechanical braking force at a predetermined value. It is possible to reduce the braking distance to a predetermined value that can correspond to the road, and to shorten the braking distance.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an electric vehicle equipped with a braking control device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a flow of operation of an ECU in this embodiment.

FIG. 3 is a diagram showing a braking force distribution in this embodiment.

FIG. 4 is a diagram showing an example of behavior during ABS control in this embodiment.

FIG. 5 is a diagram showing another example of behavior during ABS control in this embodiment.

FIG. 6 is a block diagram showing a configuration of a braking control device for an electric vehicle according to a conventional example.

[Explanation of symbols]

34a~34d wheel 36a~36d motor 38a, 38b motor controller 40 ECU 44 pipe brake pedal 46 brake switch 48 depressing force sensor 52 brake master cylinder 54, 56 64a-64d wheel cylinder V _W wheel speed F _O pedaling force V _O estimated vehicle speed dV Wheel speed deviation dG Wheel acceleration deviation T _O Required braking force T _r Regenerative braking force command value T _b Hydraulic braking force command value dT Braking force correction value T _rl Previous regenerative braking force command value T _bl Previous hydraulic braking force command value t ₀ ABS control start time point t ₁ High μ road to low μ road

Claims (1)

[Claims] 1. A means for detecting a wheel lock tendency, a means for generating a necessary braking force by regeneration of a drive motor and mechanical braking of a wheel when the wheel lock tendency is not detected, and a wheel lock tendency is detected. If a wheel lock tendency is detected in the braking control device for the electric vehicle, which includes means for controlling the regenerative braking force to prevent the wheels from being locked while maintaining the mechanical braking force at a predetermined value. A braking control device for an electric vehicle, comprising means for avoiding a wheel lock tendency by controlling a torque of a drive motor from a range of a regenerative mode to a range of a power running mode.