JP3063368B2 - Electric vehicle braking control device - Google Patents

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 in 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 braking means for a vehicle, mechanical braking for applying hydraulic pressure or the like to wheels is generally known. In an electric vehicle, regenerative braking by regenerative driving of a driving motor is also possible. Further, when a motor is provided for each wheel, it is possible to generate a different driving torque or regenerative braking torque for each wheel.

[0003] In a vehicle traveling on a road surface, when braking,
A state where the wheels are sliding (wheel locking tendency) may occur. That is, the vehicle speed may exceed the wheel speed due to factors such as road surface conditions. It is not preferable that such a state continues for safe driving of the vehicle. Therefore, a so-called anti-lock brake system (ABS) has conventionally been developed for gasoline-powered vehicles and the like. It is preferable that an electric vehicle is also equipped with an ABS.

[0004] The problem of wheel slippage not only occurs in vehicles running on the road surface but also in electric vehicles running on rails. FIG.
Japanese Patent Application Laid-Open No. 141354/1989 discloses a configuration of a brake system used for an electric vehicle and capable of coping with gliding.

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 have a pantograph 1
4 and the main circuit controller 16. The pantograph 14 is arranged on the vehicle lid, and the overhead wire 12
Abut. The main circuit control device 16 includes a pantograph 14
The main motor 10 is driven by electric power supplied through the main motor. Thereby, 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 pneumatic braking force according to the brake command from the cab 20. The brake receiver 22 is connected to the main circuit controller 16.
, 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 brake 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 gives the air brake device 30 and the distribution m of the air brake 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
2 detects the sliding of the wheel 18 from the output of the speed generator 24 and causes the signal holding device 28 to hold mf at a lower value. Then, the electric braking force distribution m by the brake receiver 22 temporarily decreases. That is, in this conventional example, the electric braking force is reduced while the air braking force is maintained substantially constant during the skiing.

[0008]

Since the electric vehicle can perform mechanical braking and regenerative braking as described above, it is conceivable to apply a system as shown in FIG. That is, when the tendency to lock the wheels is detected, the total braking force can be controlled by operating the regenerative braking force while maintaining the mechanical braking force substantially constant. However, an electric vehicle does not travel on rails like an electric vehicle, and therefore may travel on a road surface (split μ road) having different friction coefficients μ for left and right wheels.

Here, consider an electric vehicle in which motors are provided on left and right wheels, respectively. AB in such an electric car
S is mounted, and the above-described control is executed individually for each of the left and right wheels. When a braking operation is performed while traveling on a split μ road in such an electric vehicle, the wheels on the low μ road side have the above-mentioned A to prevent wheel lock.
There is a possibility that a normal braking operation is performed for the wheels on the high-μ road side for the BS operation for braking.
At this time, the mechanical braking force applied to the wheels on the low μ road side is maintained at a certain value, and the mechanical braking force applied to the wheels on the high μ road side increases in accordance with the amount of depression of the brake pedal. May be deflected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is intended to suppress the deflection of a vehicle body when a braking operation is performed while traveling on a split μ road. The purpose is to increase safety.

[0011]

In order to achieve the above object, a braking control device according to a first aspect of the present invention detects whether or not the left and right wheels have a tendency to lock during braking. when either one of the left and right wheels are locking tendency least the to the other is not a locking tendency
Means for reducing the increasing gradient of the mechanical braking force acting on the other wheel to within a predetermined value, and controlling the regenerative braking force for each of the left and right wheels, so that the total braking force of the mechanical braking force and the regenerative braking force Means for setting a braking force necessary for avoiding the lock of the vehicle.

Further, in the braking control device according to the second aspect of the present invention, the total braking force of the mechanical braking force and the regenerative braking force
The driving motor is controlled in the regenerative region and the powering region when the braking force required to avoid locking is controlled .

[0013]

According to the first aspect of the present invention, at the time of braking, first, it is detected whether the left and right wheels have a tendency to lock. This detection is performed based on information such as a wheel speed and a vehicle speed. The mechanical braking force normally increases in response to the operation of the driver, but when one of the left and right wheels has a locking tendency detected and the other does not have a locking tendency, the mechanical braking force acts on at least the other wheel. increasing gradient of mechanical braking force is limited within a predetermined value.

The case where the tendency to lock the wheel occurs on only one of the right and left sides is, for example, the case where the vehicle is traveling on a split μ road. In this case, after the wheel having the lower friction coefficient has a tendency to lock, the wheel having the higher friction coefficient has a tendency to lock due to an increase in the braking force. In the present invention,
In the process in which one of the left and right wheels tends to lock and then the other wheel tends to lock, the increase of the braking force becomes slow due to the limitation of the increase gradient of the mechanical braking force. Therefore, the deflection of the vehicle body due to the difference between the left and right braking forces can be easily corrected by the steering of the driver, and the stability of the vehicle body is improved. Further, the braking force of the wheel having the tendency to lock is operated by controlling the regenerative braking force, and the braking distance is optimized.

According to a second aspect of the present invention, a mechanical braking force is provided.
And the total braking force of regenerative braking force is required to avoid locking each wheel
When the braking force is controlled to be low, the control area of the drive motor is extended to the power running side. As a result, the total braking force can be sufficiently reduced, particularly for the wheels on the low friction coefficient side, and it is possible to appropriately avoid locking.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments 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 one embodiment of the present invention. The electric vehicle shown in this figure has a driving motor 36-a-3 for each wheel 34-a-34-d as a driving source.
6-d. Of the four motors, the front wheel 34-
a, 34-b are controlled by a motor controller 38-a, and the other two motors 36-a and 36-b
That is, the motor 36-c related to the rear wheels 34-c and 34-d.
And 36-d are controlled by a motor controller 38-b.

[0017] Motor controllers 38-a and 38-b
Operates according to a command from the ECU 40, and the motor 36-
a and 36-b or the driving torque and regenerative braking torque of the motors 36-c and 36-d. That is, EC
When a torque command is issued from U40, the motor controllers 38-a and 38-b monitor the state of the battery 42 while checking the state of the motor 36-a and 36-b or the motor 36-b.
-Control the power supplied to c and 36-d.

When powering the motors 36-a to 36-d, the ECU 40 determines a torque command value according to depression of an accelerator pedal (not shown),
Give instructions to 8-a and 38-b. As a result, a driving torque corresponding to the amount of depression of the accelerator pedal is generated.

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

The electric vehicle shown in FIG. 1 is provided with hydraulic braking means in addition to regenerative braking means as braking means. The hydraulic braking means includes a hydraulic transmission mechanism and various control means associated therewith.

First, the booster 5 is connected to the brake pedal 44.
0 is linked. The booster 50 is the brake pedal 4
The pressure generated by the depression of step 4 is increased and input to the brake master cylinder 52. Brake master cylinder 5
From each hydraulic chamber 2, a pipe 54 to the front wheels 34-a and 34-b and a pipe 56 to the rear wheels 34-c and 34-d are drawn out.

A stroke simulator 60-a and a solenoid valve 62-a are connected to a pipe 54 on the front wheel side via a solenoid valve 58-a. Similarly,
A stroke simulator 60-b and a solenoid valve 62-b are also connected to the rear wheel side pipe 56 via a solenoid valve 58-b. Therefore, when the solenoid valves 58-a and 58-b are turned off, the fluid amount of the brake master cylinder 52 is consumed by the stroke simulators 60-a and 60-b, and the wheels 34-a and 60-b are consumed.
Wheel cylinders 6 provided for each of a to 34-d
4-a to 64-d are not transmitted. However, the stroke of the brake pedal 44 depends on the stroke simulator 6
Feeling does not change because it is simulated by 0-a and 60-b.

When the solenoid valves 58-a and 58-b are turned on, the stroke simulator 60-
No simulation is performed by a and 60-b. At this time, if the solenoid valves 62-a and 62-b are turned on, the hydraulic pressure of the brake master cylinder 52 is applied to the wheel cylinders 64-a to 64-d, and braking by the hydraulic pressure is performed.

Further, in this embodiment, a pump unit 66 is provided as means for generating hydraulic pressure in the wheel cylinders 64-a to 64-d when the solenoid valves 58-a and 58-b are off. I have. The pump unit 66 includes a reservoir 68, a pump 70, an accumulator 72, a hydraulic pressure sensor 74, and an electronic circuit 76. The output of the pump 70 is controlled by linear valves 78-a and 7
8-b. The brake oil stored in the reservoir 68 is pressure-fed by the pump 70, stored in the accumulator 72, and fed to the linear valves 78-a and 78-b. The pressure at the output side of the accumulator 72 is detected by a hydraulic pressure sensor 74, and the electronic circuit 76 controls the operation of the pump 70 according to the detection result. Linear valve 7
8-a and 78-b respond to a command from the ECU 40,
The hydraulic pressure is supplied to the wheel cylinders 64-a to 64-d via the solenoid valves 62-a and 62-b. A hydraulic pressure sensor 80 is provided at the output side of the linear valves 78-a and 78-b.
-A and 80-b are provided, and the ECU 40 performs feedback control of the linear valves 78-a and 78-b according to the detection values of the hydraulic sensors 80-a and 80-b. By this control, the wheel cylinders 64-a to 64-a to 64
The hydraulic pressure at −d can be linearly controlled.

The characteristic operation of this embodiment is the operation when the wheels 34-a to 34-d tend to lock. FIG. 2 shows the wheels 34-a and 34 of the ECU 40.
The control operation of -b (front wheel) is shown.

The operation shown in this figure is executed when the operator steps on the brake pedal 44 and turns on the brake switch 46. At this time, the depression force F ₀ of the brake pedal 44 is detected by the depression force sensor 48. In this embodiment, during normal braking, a necessary braking force is obtained by a braking force distribution as shown in FIG. That is, in the region pedal force F ₀ is small to obtain a braking force by the regenerative braking, after the regenerative braking force becomes the maximum value so that using together hydraulic braking.

For this reason, first, the ECU 40
It is determined whether or not -a and 34-b satisfy the ABS control condition (100, 102). ABS control conditions are:
This is a condition indicating that the wheel has a tendency to lock, and may be a conventionally known condition. If none left not in the ABS control, ECU 40 generates a braking force distribution shown in Figure 3 according to pedal force F _0. That is, in order to execute the above-described normal braking operation, the regenerative braking force command value _Tr and the hydraulic braking force command value _Tb are calculated (104), and the right front wheel 34 is operated.
Regenerative braking force command value T _r for -a (FR) and the regenerative braking force command value T _r for left front wheel 34-b of the (FL) is set to the regenerative braking force command value T _r calculated in step 104 (106) , Command values _Tr (FR), _Tr (FL) and _Tb are output (108). Command value _Tr (FR) and T
The output destination of _r (FL) is the motor controller 38-a, and the motor controller 38-a executes regenerative braking of the wheels 34-a and 34-b accordingly. Also,
Destination of command value T _b is the linear valve 78-a, and supplies the brake fluid to the opening control wheel cylinder 64-a and 64-b according to the linear valve 78-a is.

If it is determined in steps 100 and 102 that only one of the wheels 34-a and 34-b satisfies the ABS control condition, the ECU 40 determines that the pedaling force F
Pressure increase gradient dp '/ dt by ₀ and set pressure increase gradient dp / d
and t (110, 112). The pressure increase gradient dp' / dt by pedal force F _0, for example, as indicated by the broken line in FIG. 4 (b), refers to a hydraulic incremental gradient which occurs when not running ABS control. Set pressure increase gradient dp / dt
Is a sufficiently small value for the ECU 40 (for example, 50 to 100a
tm / sec). As a result of the comparison, d
When it is recognized that p '/ dt> dp / dt holds, it can be considered that the driver depresses the brake pedal 44 relatively steeply. It can be considered moderate.

In this embodiment, the wheels 34-a and 34-a
If only one of b are subject to ABS control, in accordance with the smaller one of the gradient dp' / dt and dp / dt described above, so that determining the hydraulic braking force command value T _b ( 114, 116). Furthermore, ECU
40 is the required braking force T of the wheel 34-a from the slip ratio and the like.
_o (FR) and required braking force T _o (FL) of wheel 34-b
It calculates the (118), taking the difference between this and the hydraulic braking force command value T _b to compute the command value T _r (FR) and T _r (FL) (120). Thereafter, the process proceeds to step 108.

Further, when the wheel 34-a and 34-b in step 100 and 102 are all were found to satisfy the ABS control condition, ECU 40 holds the conventional hydraulic braking force command value T _b (122) Step 1
Step 18 and subsequent steps are executed.

FIG. 4 shows an example of the behavior of this embodiment when the vehicle is traveling on the split μ road.

First, it is assumed that the operator depresses the brake pedal 44 as shown in FIG. In this embodiment, as shown in FIG. 3, the regenerative braking is first operated, and then the operation is shifted to the hydraulic braking. As a result, as shown in FIG. 4C, after the regenerative braking force reaches the maximum value, the hydraulic braking starts to function.

Here, it is assumed that the friction coefficient of the left half of the road surface on which the vehicle is traveling is relatively small and the friction coefficient of the right half is a sufficiently large value. Such a split μ
When a wheel lock occurs on a road, it is considered that the left wheel tends to lock first, and then the right wheel tends to lock. That is, in the example of the front wheel control shown in FIG. 2, the ABS control is first required for the left front wheel 34-b, and then the ABS control is performed for the right front wheel 34-a.
Control is required.

[0034] Here, the ABS control condition is satisfied at time t ₀ for the left front wheel 34-b. Before this, that is, at time t ₀ after the hydraulic braking starts to function.
Until the hydraulic pressure increases with the brake operation shown in FIG. 4 (a), but the time t ₀ Thereafter steps 110 and 1
12 with the slope selected. For example, the depression of the brake pedal 44 is sudden and dp '/ dt> dp /
When dt holds, the gradient of the oil pressure increase decreases from dp '/ dt to dp / dt by the control of the linear valve 62-a by the ECU 40 as shown in FIG. 4B.

Then, since the increase in the hydraulic braking force is lessened than before time t ₀ , excessive braking is prevented for the wheels 34-a which have not yet satisfied the ABS control conditions at this time. That is, the difference in the braking force with respect to the wheel 34-b showing the locking tendency gradually occurs to such an extent that the steering of the driver can easily avoid the deflection of the vehicle body.
As a result, the stability of the vehicle is improved. Thereafter, at time t ₁
When the ABS control condition of the front right wheel 34-a is satisfied at step 122, the command value _Tb is held in step 122,
As shown in FIG. 4B, the oil pressure increase gradient becomes 0, and the ABS control according to step 118 and the like is started for the wheel 34-a.

Furthermore, in this embodiment, as shown in step 118 and 120 in FIG. 2, the hydraulic braking force command value T _b in advance as the value determined in step 114 and 116 or 122, which the necessary braking force T _o (FR) or T _o (FL) to obtain the regenerative braking force command value _Tr (F
R) and _Tr (FL) are determined. That is, to execute the regenerative braking to the braking force required for ABS control hydraulic braking force command value T _b as a reference T _o (FR) or T _o (FL) is obtained. The second feature of this embodiment is that the range in which the command values _Tr (FR) and _Tr (FL) can take after shifting to the ABS control is not limited to the regeneration region.
It is in the point including the power running area.

For example, in the example of FIG. 4, the ABS control based on the command value _Tr (FL) in the powering region is executed for the wheel 34-b on the low friction coefficient side. That is, after the start of the ABS control (t ₀ ), at some point in time, the vehicle has shifted from the regeneration side to the power running side. Therefore, a small braking force that cannot be obtained by staying in the regenerative region, specifically, a braking force equal to or less than the hydraulic braking force can be obtained particularly for the wheel 34-b on the low friction coefficient side.

As is clear from the comparison between FIGS. 4B and 4C, the torque of the motor 36-b is reduced in parallel with the process of increasing the oil pressure, and the torque is reduced from the regenerative side to the power running side. Migrating.

[0039] those resulting because they Such behavior, by subtracting the hydraulic pressure braking force command value T _b obtains a command value T _r (FL) in step 120 from the necessary braking force T _o (FL) obtained in step 118 It is. By such an operation, FIG.
As shown in (d), the wheel 34-b on the low friction coefficient side
The wheel 34-b can be placed under the ABS immediately after the time t ₀ , even though the hydraulic pressure continues to increase. Further, a single hydraulic system may be used for the wheels.

Although the above description has been made with reference to the front wheels, the present invention may be applied to rear wheels.

[0041]

As described above, according to the first aspect of the present invention,
According to the present invention, when only one of the right and left wheels tends to lock, the increasing gradient of the mechanical braking force acting on at least the other wheel is limited to within a predetermined value. When driving on the road,
After either one of the left and right wheels has a tendency to lock, the other wheel has a tendency to lock, the braking force increases slowly, and the effect of preventing deflection of the vehicle body and improving the stability of the vehicle body can be obtained.

According to a second aspect of the present invention, a mechanical control is provided.
The total braking force of power and regenerative braking force is used to avoid locking each wheel
When the required braking force is controlled, the control area of the drive motor is expanded to the power running side, so that the total braking force can be reduced enough to avoid locking, especially for wheels with low friction coefficient, and braking The distance can be shortened.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a flow of an 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 a behavior during ABS control in this embodiment.

FIG. 5 is a block diagram showing a configuration of an electric vehicle braking control device according to a conventional example.

[Explanation of symbols]

34-a to 34-d Wheels 36-a to 36-d Motors 38-a, 38-b Motor controller 40 ECU 44 Brake pedal 46 Brake switch 48 Tread force sensor 52 Brake master cylinder 54, 56 Piping 64-A to 64- d Wheel cylinder F _O Pedal pressing force _Tr Regenerative braking force command value _Tb Hydraulic braking force command value _Tr (FR) Regenerative braking force command value for right front wheel _Tr (FL) Regenerative braking force command value for left front wheel dp / dt increase due to the depression force gradient dp' / dt set up pressure gradient T _o (FR) necessary braking force of the right front wheel T _o (FL) necessary braking force of the left front wheel

Continuation of the front page (56) References JP-A-60-32501 (JP, A) JP-A-64-7701 (JP, A) JP-A-49-87009 (JP, A) JP-A-2-250603 (JP) JP-A-1-306359 (JP, A) JP-A-61-218463 (JP, A) JP-A-59-114149 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B60T 8/34-8/58 B60L 7/00-7/28 B60L 15/00-15/42

Claims (2)

(57) [Claims] 1. A drive motor capable of individually driving left and right wheels, mechanical braking means provided on each of the left and right wheels to generate a mechanical braking force according to an operation of a driver, and regeneration of the drive motor. In an electric vehicle equipped with regenerative braking means for braking the left and right wheels, respectively, a means for detecting whether the left and right wheels have a tendency to lock during braking, and one of the left and right wheels having a tendency to lock. At least acts on the other wheel if the other is not prone to locking
Means to reduce the increasing gradient of the mechanical braking force to within a predetermined value, and controlling the regenerative braking force for each of the left and right wheels, so that the total braking force of the mechanical braking force and the regenerative braking force is required to avoid locking each wheel A braking control device comprising: 2. The braking control device according to claim 1, wherein the total braking force of the mechanical braking force and the regenerative braking force is such that each wheel is locked.
A braking control device, wherein a driving motor is controlled from a regenerative region to a powering region when the braking force required for avoidance is controlled.