JP2000134714A - Vehicle braking system - Google Patents

Abstract

(57) [Problem] To provide a vehicular braking system capable of controlling a slip state of drive wheels to an appropriate state by controlling regenerative braking torque. A is a rotational speed N _ma substantially zero electric motor for driving the driving wheels, that is not the vehicle running speed V _va approximately 0 (S4,6), the driving wheel is judged to have fallen into the locked state During the set time t _cr , the regenerative braking torque T _m is kept at the lower limit T _mmin (S7-9). After lapse of the set time, the regenerative braking torque T _m is returned to the upper limit value T _mmax commensurate with the brake pedal depression force at that time (S10),
It is determined whether the drive wheel is still in the locked state (S
4, 6), if in the locked state, it is reduced again to the lower limit. On the other hand, if the drive wheel is not in the locked state after the lapse of the set time, the regenerative braking torque is kept at the upper limit. Then, when the lock state is established again, the regenerative braking torque is reduced again to the lower limit value. By repeating this control, the driving wheels are prevented from being left in the locked state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle braking system including a regenerative braking device for applying a braking torque to driving wheels by regenerative braking of an electric motor that drives driving wheels of a vehicle.

[0002]

2. Description of the Related Art A vehicle braking system of this type is described, for example, in Japanese Patent Application Laid-Open No. Hei 8-98313. The vehicular braking system described in this publication includes a hydraulic brake device in addition to the regenerative brake device. 2. Description of the Related Art A hydraulic brake device is a type of friction braking device that presses a friction member against a brake rotating body, applies friction braking torque to the brake rotating body by a frictional force between the two, and brakes wheels that rotate with the brake rotating body. In the vehicle braking system, if the slip state of the wheels at the time of braking requires antilock control, the regenerative braking torque by the regenerative braking device becomes zero.
The anti-lock control is performed by controlling the hydraulic pressure of the brake cylinder of the hydraulic brake device.

[0003]

However, the regenerative braking torque applied to the driving wheels by the regenerative braking device, not only when the vehicle braking system does not include the friction braking device, but also when the vehicle braking system includes the friction braking device. In some cases, it is desirable to perform antilock control by the control of. Therefore, an object of the present invention is to provide a vehicle braking system capable of performing antilock control by controlling regenerative braking torque. According to the present invention, a vehicle braking system of the following aspects is obtained. Can be As in the case of the claims, each aspect is divided into sections, each section is numbered, and if necessary, the other sections are cited in a form in which the numbers are cited. This is to facilitate understanding of some of the technical features and combinations thereof described in this specification, and the technical features and combinations thereof described in this specification are limited to the following. Should not be interpreted as such. (1) In a vehicular braking system including a regenerative braking device that applies a braking torque to a driving wheel by regenerative braking of an electric motor that drives a driving wheel of a vehicle, a regenerative braking torque applied to the driving wheel by the regenerative braking device is reduced. An anti-lock control device for controlling a slip state of a drive wheel to an appropriate state by controlling the braking system is provided. If the anti-lock control device is provided in the vehicle braking system, the slip state of the drive wheels can be controlled to an appropriate state by controlling the regenerative braking torque. (2) In the state where the anti-lock control device is applying the maximum regenerative braking torque to be applied by the regenerative braking device at that time, the slip state of the drive wheel has reached a state requiring the anti-lock control. The vehicle braking system according to (1), further including a regenerative braking torque reducing unit configured to reduce the regenerative braking torque to the lower limit braking torque. As described above, if the regenerative braking torque is reduced to the lower limit braking torque when the slip state of the drive wheel reaches a state that requires anti-lock control, the drive wheel is locked or locked. It is possible to avoid being kept in a state. (3) The vehicle braking system according to the above mode (2), wherein the lower limit braking torque is predetermined. The lower limit braking torque can be set as in the following item, or can be set to another value such as 0. (4) The vehicular braking system according to (3), wherein the lower limit braking torque is predetermined so that the slip state of the drive wheels does not reach a state requiring antilock control even on ice. As described above, if the lower limit braking torque is set to such a value that the slip state of the drive wheels does not reach a state requiring antilock control even on ice, the vehicle is traveling on a road surface having any friction coefficient. Even in this case, the slip state can be recovered. (5) The vehicular braking system according to (2), wherein the antilock control device includes a lower limit braking torque setting unit that sets the lower limit braking torque according to a friction coefficient of a road surface on which the vehicle is currently traveling. . The deceleration of the vehicle at the time when the antilock control is performed is proportional to the road surface friction coefficient. Therefore, the lower limit braking torque setting means, for example,
The friction coefficient of the road surface was estimated based on the deceleration obtained as a differential value of the vehicle traveling speed or the deceleration detected by the acceleration sensor, and the relationship between the friction coefficient of the road surface and the lower limit braking torque was tabulated. The lower limit braking torque can be set from the lower limit braking torque table. (6) When the anti-lock control device is configured to reduce the regenerative braking torque to the lower limit braking torque by the regenerative braking torque reducing unit, and then, when the slip state of the drive wheel reaches a regenerative braking torque increasing required state. The vehicle braking system according to any one of (2) to (5), further including regenerative braking torque recovery means for recovering regenerative braking torque to the upper limit braking torque. If the regenerative braking torque recovery means is provided, the slip of the drive wheels is prevented from being excessively suppressed, and the slip state is controlled to an appropriate state. (7) The vehicle braking system according to any one of (1) to (6), wherein the proper state is a state in which the slip ratio of the drive wheel is within a proper range. When the slip ratio of the wheel is within a predetermined range, the friction coefficient of the road surface is most effectively used for braking. Therefore, if the regenerative braking torque is controlled so that the slip ratio is kept within the range, the vehicle braking distance can be reduced. (8) The antilock control device feeds back the regenerative braking torque applied to the drive wheel by the regenerative braking device to a magnitude at which the slip state of the drive wheel becomes a target state set within the appropriate state region. The vehicle braking system according to item (2), including feedback control means for controlling. In this way, if the regenerative braking torque is controlled by the feedback control means to a substantially continuously changing magnitude, it is possible to control the slip state of the drive wheels to an almost ideal state. (9) The vehicle braking system according to (8), wherein the antilock control device includes target state setting means for setting the target state to a state corresponding to a friction coefficient of a road surface on which the vehicle is currently traveling. (10) The appropriate state is a state in which the slip ratio of the drive wheel is within an appropriate range, and the target state is that the slip ratio of the drive wheel is such that the friction coefficient of the road surface on which the vehicle is actually running is substantially maximum. Size that is used only for
The vehicle braking system according to (9). (11) The vehicle braking system according to the mode (8), wherein the target state is predetermined. According to this aspect, it is possible to obtain antilock control means having a simple configuration. (12) The vehicle braking system according to the mode (11), wherein the target state is a state in which the slip ratio of the drive wheel has a predetermined magnitude. The predetermined slip ratio may be set, for example, to a value that maximizes a friction coefficient of a road surface on which the vehicle is expected to mainly travel, and a friction coefficient of an average value is maximized. May be set to a size used only for

[0004]

FIG. 1 shows a vehicle braking system according to an embodiment of the present invention. In the drawing, reference numeral 10 denotes an electric motor for driving a vehicle. Driving wheels 12 are connected to the electric motor 10 via a driving force transmission device.
The electric motor 10 is controlled by a motor control unit 16 via an inverter 14. A vehicle control unit 18 is connected to the motor control unit 16, and an accelerator pedal sensor 20, a brake switch 22, a tread force sensor 23, and a wheel speed sensor 24 are connected to the vehicle control unit 18.
The accelerator pedal sensor 20 detects an operation amount of an accelerator pedal (not shown), and the brake switch detects that a brake pedal (not shown) is operated from a release position. The pedaling force sensor 23 detects the pedaling force of the brake pedal using a load cell connected to the brake pedal.
Numeral 4 is for detecting the rotational speed (peripheral speed) of the drive wheel 12. The vehicle control unit 18 is also connected to wheel speed sensors (not shown) for detecting the rotational speeds of other drive wheels and driven wheels.

[0005] The vehicle control unit 18 includes a CP, a ROM, and a RAM.
And a computer having an I / O port, and based on signals from an accelerator pedal sensor 20, a brake switch 22, and a pedaling force sensor 23,
A control command is issued to the motor control unit 16. The control command includes a drive command for instructing the electric motor 10 to generate a drive torque, and a brake command for instructing the regenerative braking to apply the regenerative braking torque 12 to the drive wheels 12. The vehicle control unit 18 also performs a control based on signals from four wheel speed sensors including the wheel speed sensor 24.
The rotation speed of each wheel is calculated, and the running speed of the vehicle is estimated based on the rotation speed of each wheel. Since the control of the motor control unit 16 and the calculation of the rotational speed and the estimation of the traveling speed are well known, detailed description thereof will be omitted.

The vehicle controller 18 further monitors the slip ratio of the drive wheels 12 during braking based on the running speed of the vehicle and the rotation speed of the electric motor 10, and when the slip ratio exceeds an appropriate range, Anti-lock control is performed to control the slip ratio within an appropriate range by controlling the regenerative braking torque. Therefore, RO of the above-mentioned computer
M stores an antilock control routine represented by the flowchart shown in FIG. The PU executes this antilock control routine while using the RAM.

First, in S1, the accelerator pedal sensor
The accelerator pedal is depressed based on the signal from the
Not in the OFF state and the brake pedal is released.
Operated from the removal position to the operation position, and
Is changed to the ON state. Judgment is NO
If so, S1 is repeated and the brake pedal is depressed
Is waited, but if the determination is YES, in S2,
At that time, that is, at the start of depression of the brake pedal
Speed N of the electric motor 10_miIs read. This
Rotation speed N at the start of braking_miIs stored in the ROM
Set rotation speed N _mrIt is determined in S2 whether or not
If the determination is NO, the execution of this reaching is to S1.
Returning, if YES, S4 is executed.

In S4, it is determined whether or not the rotation speed _Nma of the electric motor at that time is substantially zero.
Usually, it is not 0 at this time, so it is determined in S5 whether the brake pedal is in the OFF state or whether the vehicle running speed _Vva at that time is equal to or lower than the set running speed _Vvr . At this time, since this determination is also NO,
Returning to S4, S4 and S5 are repeated. And
If the determination in S5 is YES, the process returns to S1, but before that, if the determination in S4 is YES, in S6, it is determined whether or not the vehicle traveling speed _Vva is substantially zero. If the determination is YES, the rotational speed of the electric motor 10 has also become substantially zero because the vehicle has almost stopped, and the execution of this routine returns to S1, but if the determination is NO. Means that the drive wheel 12 is in the locked state, and thus the anti-lock control is started.

[0009] In S7, the regenerative braking torque T _m of a motor 10 is set to the lower limit value T _mmin. Thereby, the command value from the vehicle control unit 18 to the motor control unit 16 is changed from the upper limit _Tmmax, which is the regenerative braking torque corresponding to the treading force detected by the treading force sensor 23, to the lower limit _Tmmin . Subsequently, in S8, the timer counter is set to 0.
Is a count-up is started from the count value t _ca of the timer counter is set count value at S9 t _cr
, That is, the elapse of the set time is awaited. After a lapse of the set time, the regenerative braking torque T _m of a motor 10 is returned to the upper limit value T _mmax, execution of the routine S4
And thereafter, the above-described control is repeated. And
When the determination at S5 or S6 becomes YES, the execution of this routine returns to S1, and the antilock control for one braking operation ends.

As is clear from the above description, in the antilock control according to the present routine, when the drive wheel 12 is in the locked state, the regenerative braking torque _Tm is _reduced to the lower limit _Tmmin.
After being kept at the lower limit T _mmin for a set time, it is determined whether or not the drive wheel 12 is in a locked state. If the drive wheel 12 is in the locked state, the regenerative braking torque T _m is again reduced to the lower limit. _Although it is reduced to T _mmin , if it is not in the locked state, the regenerative braking torque T _m is kept at the upper limit T _mmax, and when it is locked again, it is reduced to the lower limit T _mmin . That is, the command value of the regenerative braking torque T _m is alternately switched to the lower limit value T _mmin and the upper limit value T _mmax, whereby the drive wheel 12 is to be avoided can remain locked.

In the anti-lock control routine, the slip ratio calculated on the basis of the rotational speed of the drive wheels 12 and the running speed of the vehicle is replaced with the determination of the necessity of the anti-lock control in S4 and S6. It is also possible to determine whether or not the value exceeds the set upper limit slip ratio. Further, in S8 and S9, instead of keeping the regenerative braking torque _Tm at the lower limit _Tmmin for the set time, it is determined whether or not the slip ratio of the drive wheel 12 is lower than the set lower limit slip ratio. And the judgment is YE
When a S can also be so regenerative braking torque T _m is returned to the upper limit value upper limit value T _mmax.

Further, instead of determining whether the vehicle traveling speed is substantially zero in the determination of S5, the electric motor 10
May be determined whether or not the actual braking torque at has become substantially zero. Furthermore, the present invention is implemented in various modified and improved forms based on the knowledge of those skilled in the art, including the form described in the section [Problems to be Solved by the Invention, Problem Solving Means and Effects]. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a vehicle braking system according to an embodiment of the present invention.

FIG. 2 is a computer RO of the vehicle braking system.
5 is a flowchart illustrating an antilock control routine stored in M.

[Explanation of symbols]

10: Electric motor 12: Drive wheel 14: Inverter 16: Motor control unit 18: Vehicle control unit 2
0: accelerator pedal sensor 22: brake switch 23: pedal force sensor 24: wheel speed sensor

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Claims (1)

[Claims] 1. A vehicular braking system including a regenerative braking device that applies a braking torque to driving wheels by regenerative braking of an electric motor that drives driving wheels of a vehicle, wherein the regenerative braking device applies regenerative braking to the driving wheels. A braking system for a vehicle, comprising an anti-lock control device that controls a slip state of a drive wheel to an appropriate state by controlling a torque.