JPH02123902A - Damping device for electric automobile - Google Patents

Abstract

PURPOSE:To obtain a damping device excellent in responding property and high in efficiency of collecting energy by applying regeneration damping action increasing according to a brake pedal tread force during a lagging period till the machine type damping device starts functioning, and by setting a regeneration damping force to be of a maximum value, at the starting point of machine type damping action. CONSTITUTION:By the output of a hydraulic sensor 34, it is discriminated whether the tread force of a brake pedal 30 exceeds critical hydraulic pressure Po or not. At the initiation of damping, the output S of a pedal stroke sensor 32 is multiplied by maximum regenerative-damping torque Tm, and along with the increment of the tread force of the brake pedal 30, the stroke sensor output S is increased till it approximates '1', and vehicle deceleration due to the regenerative braking of a regenerative damping controlling circuit 22 increasing according to the pedal tread force is obtained. In the meantime, when the hydraulic pressure P of master cylinder 28 comes to the critical hydraulic pressure Po, then regenerative damping torque T retains the maximum regenerative-damping torque Tm, and a brake flag is switched to '1'. As a result, the characteristic of a mechanical damping force added to constant regenerative-damping torque after the critical hydraulic pressure Po is set, and energy together with the damping of high responding property can be efficiently collected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a braking device for an electric vehicle, and particularly to a braking device that combines mechanical braking and regenerative braking.

[Prior Art] Electric vehicles, which use electric current supplied from a battery to drive a motor as a power source for the vehicle, are being put into practical use, and conventional internal combustion engine vehicles are being used because of their clean characteristics, such as not producing exhaust gas. Various alternative uses have been proposed.

However, this electric vehicle has a problem in that the distance traveled per charge is short, and efforts are being made to improve energy efficiency in all parts.

In this type of electric vehicle, the main braking action is a mechanical braking device, usually a hydraulic II + driving device.
Since such a hydraulic braking system alone simply consumes kinetic energy as heat, it is well known that in electric vehicles, it is practical to use regenerative braking in conjunction with the hydraulic braking system to recover energy. has been made into

Japanese Patent Application Laid-Open No. 59-209004 discloses a combined braking device that combines a hydraulic brake and regenerative braking, in which the amount of regenerative braking is adjusted according to the brake oil pressure so that the braking forces of both systems are optimally applied. It's changing.

In addition, in Utility Model Application No. 63-29301, regenerative braking control is performed in accordance with the amount of drive of the brake pedal.

However, in any of these conventional devices,
Hydraulic braking and regenerative braking are performed in cooperation with each other in the entire depression range of the brake pedal, and as a result, only a small amount of regenerative braking can be obtained during light load braking operations.
There was a problem with low energy recovery efficiency.

Furthermore, there is a problem in that the braking characteristics of conventional hydraulic brakes do not necessarily exhibit good responsiveness due to various delays.

FIG. 7 shows the deceleration characteristics of only the hydraulic brake and the ideal deceleration characteristics, with the horizontal axis plotting the brake pedal depression force F and the vertical axis plotting the deceleration g.

Characteristic 101 is a braking characteristic using only hydraulic brakes,
It has an initial delay with respect to the ideal characteristic 102.

In other words, until the brake pedal depression force reaches Fo,
This critical pedal force F without any deceleration occurring. After exceeding , a deceleration as shown by characteristic 101 occurs.

The ideal characteristic 102 indicates a characteristic in which the deceleration increases at the same time as the brake pedal depression force F is generated, and it is understood that this delay in reaching the critical depression force Fo significantly reduces the responsiveness for the braking action.

The above-mentioned delay is caused by, for example, a delay due to the spring or friction of the mask cylinder, a delay in the wheel-and-linda, play or deflection of the bushing rod, accumulated force in the return spring of the brake pedal, etc., and it is actually extremely difficult to reduce this delay. It is.

A conventional device that intensively performs regenerative braking in the delayed state at the beginning of the brake pedal depression described above was developed in 1984.
It is known as 369.

According to this conventional device, a certain regenerative braking operation is performed at the initial stage of depression of the brake pedal and during light braking.

Therefore, this conventional device has the advantage that even when sufficient hydraulic braking force is not applied during initial braking and light braking, this can be compensated for by regenerative braking.

[Problems to be Solved by the Invention] However, in the conventional device described above, since regenerative braking is applied at a constant value, a relatively large regenerative braking force is applied at the initial stage of depression of the brake pedal, and the regenerative braking force is applied at a relatively large amount in response to the amount of depression of the brake pedal. There was a problem that good brake feeling could not be expected.

As a result, the conventional regenerative braking function is suppressed to a relatively low level, resulting in the problem that the efficient energy recovery function necessary for an electric vehicle cannot be achieved.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to make the electrical regenerative braking action work with sufficient efficiency during the delay in the mechanical braking action, and to improve the responsiveness of the braking action. The object of the present invention is to provide a braking device with high energy recovery efficiency.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a regenerative braking action that increases in accordance with the brake pedal depression force during a delay period until the mechanical braking device starts to take effect, and By setting the regenerative braking force to approximately the maximum value at the starting point for the type braking operation, it is possible to obtain a braking device with excellent responsiveness and high energy recovery efficiency.

[Operation] Therefore, when the brake pedal is depressed, the mechanical braking device does not produce a braking action until a certain pedal force is reached due to the various mechanical delays described above, but on the other hand, according to the present invention, during this delay period, By allowing the regenerative braking to work to its maximum capacity, and by making the pedal force-regenerative braking force characteristic almost linear, it is possible to obtain a good brake feeling that corresponds to the brake pedal depression force, and furthermore, the mechanical braking force After the starting point, the regenerative braking force is kept at a nearly constant value, which allows the initial regenerative braking and the subsequent combined braking force to be connected continuously, resulting in good brake feeling and strong brake force over the entire brake pedal depression range. It becomes possible to obtain a braking operation with high energy recovery efficiency.

[Example] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a braking device for an electric vehicle according to the present invention. As is well known, an electric vehicle includes a drive motor 10 such as an AC induction motor, and the rotation of this motor 10 is caused by a reduction gear 12 and a Drive wheel 1 through the differential device that is not
4.16.

A motor control circuit 18 is provided to drive and control the drive motor 10, and causes the motor 10 to output a desired power running torque using well-known vector control or the like.

The rotational speed of the motor 10 is detected by a rotation sensor 20, and a regenerative braking control circuit 22 outputs a regenerative braking signal to the motor control circuit 18 together with a brake pedal depression force detection signal, which will be described later.

Therefore, according to the present invention, the motor 10 can be switched to the regenerative braking operation by a signal from the regenerative braking control circuit 22 to provide a desired regenerative braking force, and the energy at this time can be recovered.

On the other hand, the driving wheel 14.16 and the non-driving wheel 24.26
A mechanical braking force such as a hydraulic brake is applied to the wheels, and for this purpose, the hydraulic braking force from the mask cylinder 28 is supplied to the hydraulic cylinders of each wheel.

In order to generate a desired hydraulic pressure in the mask cylinder, the depression force of the brake pedal 30 is applied to the master cylinder 28, and the desired hydraulic braking force is obtained by the depression force of the brake pedal 30.

In this embodiment, the depression force of the brake pedal 30 is taken into the regenerative braking control circuit 22, and for this reason, in the embodiment, the stroke of the brake pedal 30 is detected by the stroke sensor 32 and sent as a stroke signal S to the regenerative braking control circuit 22. Supplied.

Further, in this embodiment, the depression force of the brake pedal 30 can be detected as the oil pressure of the hydraulic cylinder 28, and the oil pressure signal δ is sent to the regenerative braking control circuit 22 from the oil pressure sensor 34 provided on the output side of the mask cylinder 28. supplied to

Therefore, according to the present invention, the regeneration 1 motion control circuit 22
The maximum regenerative braking force can be commanded to the motor 10 before the hydraulic brake 1 starts to apply, and this regenerative braking force has a characteristic of increasing according to the pedal force so that it reaches its maximum value at the time when the hydraulic brake starts to apply. can give.

FIG. 2 shows the braking control action in the first embodiment of the present invention, in which it is determined in step 201 whether or not a brake operation has been performed. A switch may be provided to detect the initial movement of the brake pedal.

When no brake operation is performed, the regenerative braking @11 control circuit 22 always sets the brake flag to O (step 202).

On the other hand, when a brake operation is performed, the brake flag is determined in step 203, and since the brake flag is "0" at the start point of braking as described above, the maximum regenerative braking torque Tm is calculated in step 204. Ru.

This maximum regenerative torque Tm is predetermined based on the rotational speed of the motor 10 at this time, and the maximum regenerative braking torque allowed for the motor 10 at the current vehicle speed is determined, thereby preventing the motor from overheating, etc. In order to do this, from now on.”
It is not preferable to apply the second regenerative braking torque.

Next, control according to the pedal force is started so that this 'maximum regenerative braking torque Tm is obtained as a regenerative braking torque at the starting point of the hydraulic brake.

In the embodiment, the depression force of the brake pedal 30 is determined based on the output of the oil pressure sensor 34.

In the embodiment, the hydraulic pressure at which the mechanical or hydraulic brake starts to work is P. In step 205, the output of the oil pressure sensor 34 is the critical oil pressure P. A determination is made as to whether or not the value has been exceeded.

At the beginning of braking, this oil pressure is of course P. At this time, in step 206, the regenerative braking torque T
is set to a value according to the output S of the pedal stroke sensor 32. That is, in step 206, the output S of the pedal stroke sensor 32 is multiplied by the maximum regenerative braking torque Tm obtained in the step 204, and as the depression force of the brake pedal 30 increases, the output S of the pedal stroke sensor 32 is sequentially multiplied until it approaches this stroke sensor output SG rlJ. As a result, vehicle deceleration due to regenerative braking is obtained, which increases sequentially in accordance with the pedal depression force as shown in FIG.

On the other hand, in step 205, the pedal depression force, in the embodiment, the hydraulic pressure P of the master cylinder 28 is the critical hydraulic pressure P. When reaching , the regenerative braking torque T maintains the maximum regenerative braking torque Tm at this time (step 206).

Then, in step 207, the brake flag is switched to "1".

As described above, a series of braking operations are carried out at critical oil pressure P, as shown in FIG. Thereafter, the characteristic is that the mechanical braking force is added to the constant regenerative braking torque, and after the brake pedal 30 is depressed, a highly responsive braking operation that uses both mechanical braking and regenerative braking can be performed with extremely quick response. can.

Further, according to the present invention, the regenerative braking torque is already at its maximum value at the start point of mechanical braking, and sufficient regenerative braking is performed even in the initial stage of braking or in a light braking state to effectively recover energy. be able to.

During such a series of braking operations, after the oil pressure exceeds the critical oil pressure Po, the brake flag is already set to "1" in normal step 203, so from this point on, the regenerative braking torque Tm will be the same as when the critical oil pressure passes. The torque is fixed, and control based on this fixed maximum regenerative braking torque Tm is performed in steps 209 to 211.

That is, from this point on, depending on whether the oil pressure exceeds the critical oil pressure Po, the maximum regenerative braking torque Tm fixed in steps 210 and 211, respectively, or the torque obtained by multiplying this by the pedal stroke S is used for the regenerative braking operation.

As described above, according to the present invention, it is possible to use sufficiently large regenerative braking before mechanical braking is started, thereby achieving excellent responsiveness and increasing energy recovery efficiency.

FIG. 4 shows the characteristics when the output of the oil pressure sensor 34 is used to detect the depression force on the brake pedal 30, and similarly to FIG. The braking characteristics shown are obtained.

Compared to the characteristic 110 in FIG. 3 in which regenerative braking is performed with the pedal stroke S, the starting point of characteristic 120 in FIG. can do.

The brake hydraulic pressure delay in the embodiment shown in FIG. 4 is caused by a delay in the activation of the mask cylinder 28, rather than the pedal stroke itself.

FIG. 5 shows a flowchart of a second embodiment of the present invention. In this second embodiment, the amplification degree G in the electrical signal processing of the regenerative braking control circuit 22 is controlled, and the During the first braking operation after the start of the brake pedal, gain control is performed to smoothly connect the characteristics after the critical pedal force with the characteristics before that.

That is, as shown in FIG. 6, the critical pedal force F for the characteristic 101 of only mechanical braking. Below, the property is 1
As shown by 31 and 132, different slopes are determined depending on the two positions, and this slope may be different from the slope 101 of mechanical braking.

Therefore, in such a case, an unpleasant brake feeling will occur due to the difference in slope before and after the critical pedal force Fo.

In the second embodiment, this slope can be adjusted to match the slope of the mechanical braking only characteristic 101, and finally the characteristics before and after the critical pedal force Fo can be corrected to have the same slope as shown by 140.141.

In FIG. 5, when the ignition switch is turned on and the vehicle starts running, the G flag, which determines whether gain control has been performed, is set to "0" in step 301, and the amplifier is turned on. Gain G is the initial value G. stipulated by.

Steps 302 to 309 are substantially the same as steps 201 to 208 in the first embodiment, so a detailed explanation will be omitted.

However, in the second embodiment, in step 307, the gain G of the amplifier is multiplied to obtain the regenerative braking torque T, and in the initial state, this G is set to a predetermined value Go.

In step 309, the brake flag is set to "1" and the critical pedal force F is set. 1 when exceeds step 310
In step 311, the G flag is determined. Normally, in this state, the G flag is "0", and in step 311, the current G flag is changed.

In the embodiment, this newly set gain G is the stroke S that increases the maximum regenerative braking l・lux Tm to the critical pedal force.
(Generally, S. takes a different value depending on the difference in the device and its deterioration.) This is made to correspond to the value divided by S. and used as the amplifier gain G during subsequent braking operations.

After this gain change is completed, the G flag is switched to "1" in step 312.

In step 310, if the G flag is already "1", steps 311 and 312 are skipped and control is continued.

In step 304, when the brake flag is "1", that is, the brake pedal depression force is the critical depression force F.
. When the value exceeds the maximum regenerative braking torque Tm, the process proceeds to step 313, and control based on the determined maximum regenerative braking torque Tm is performed in steps 314 and 315. This control is similar to steps 210 and 211 of the first embodiment, so Detailed explanation will be omitted.

Of course, in this embodiment, the given gain G is used in the calculation in step 315.

Therefore, according to the present invention, in the first control, the brake feeling feels strange before and after the critical pedal force Fo, but after that, the characteristic 140.14 in FIG.
As shown by 1, continuity is achieved by gain control before and after the critical pedal force Fo.

[Effects of the Invention] As explained above, according to the present invention, a braking operation using both mechanical braking and regenerative braking is performed in an electric vehicle, and the regenerative braking is utilized up to its maximum braking torque in the delayed portion of mechanical braking. As a result, it is possible to provide a quick response to the operation of the brake pedal, and to efficiently recover energy through regenerative braking.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing a preferred embodiment of the braking device for an electric vehicle according to the present invention, FIG. 2 is a flowchart 1 of the first embodiment of the braking device according to the present invention, and FIG. Fig. 4 is a braking characteristic diagram using brake oil pressure, Fig. 5 is a flowchart showing the braking operation in the second embodiment of the present invention, and Fig. 6 is a braking characteristic diagram in the second embodiment. Braking characteristic diagram FIG. 7 is a characteristic diagram comparing the braking characteristic of conventional mechanical braking only and the ideal characteristic. 10...Motor 18...Motor control circuit 22...Regenerative braking control circuit 30...Brake pedal 32...Pedal stroke sensor 34...
oil pressure sensor

Claims (1)

[Scope of Claims] A mechanical braking device that applies mechanical braking force to an electric vehicle when a brake pedal is depressed; a depression force sensor that detects the depression force of the brake pedal; and a regenerative braking force that is applied to the electric vehicle according to the depression force of the brake pedal. a regenerative braking control device that provides a mechanical braking force, the regenerative braking control circuit controls the braking force to vary up to the maximum regenerative braking force according to the brake pedal depression force that generates the mechanical braking force, and A braking device for an electric vehicle, characterized in that it is configured to maintain a substantially constant maximum regenerative braking force from the moment it is generated.