JP3508335B2 - Brake for electric vehicles - 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 device for an electric vehicle that combines a mechanical braking action and a regenerative braking action.

[0002]

2. Description of the Related Art A conventional braking device for an electric vehicle is disclosed, for example, in Japanese Patent Laid-Open No. 6-253406 shown in FIG. This is a brake pedal 81, a master cylinder 82 that applies hydraulic pressure to hydraulic braking means for each wheel (not shown) when the brake pedal is depressed, a stroke sensor 83 that measures the amount of depression of the brake pedal, and an electric vehicle. A drive motor 84 for running the vehicle, a motor control circuit 85 for controlling the drive motor, a regenerative braking control circuit 86 for controlling regenerative braking for braking while the drive motor 84 functions as a generator, and wheels using friction force. And a hydraulic control device 87 for controlling mechanical braking for braking.

This braking device for an electric vehicle obtains a total braking torque value during braking based on the amount of depression of the brake pedal detected by a stroke sensor 83 when the brake pedal 81 is depressed, and a hydraulic control device 87. Both the hydraulic control device 87 and the regenerative braking control circuit 86 are controlled so that the sum of the hydraulic braking torque value generated by the regenerative braking control circuit 86 and the regenerative braking torque value generated by the regenerative braking control circuit 86 becomes the total braking torque value. At the same time, the control device 88 controls to gradually increase the distribution amount of the hydraulic braking torque value as the brake pedal depressing speed increases.

[0004]

However, in such a conventional braking device for an electric vehicle, the hydraulic braking torque value is calculated based on the brake pedal depression amount and the brake pedal depression speed detected by the stroke sensor. Since it is a setting method, a special hydraulic control device for controlling the hydraulic pressure to an arbitrary set hydraulic braking torque value is required, and the cost is higher than that of the conventional hydraulic braking means. In addition, because the braking torque is generated by the total braking torque value calculated based on the amount of depression of the brake pedal, the conventional hydraulic system that hydraulically generates the braking torque according to the pedaling force of the brake pedal. There is a problem that the operation feeling equivalent to that of the braking means cannot be obtained.

In view of such conventional problems, the present invention provides a braking device for an electric vehicle that simplifies hydraulic control and obtains a braking torque equivalent to that obtained when braking is performed only by hydraulic braking means. Is intended.

[0006]

In order to achieve the above-mentioned object, the invention according to claim 1 is a mechanical braking means for mechanically braking a vehicle in response to a depression operation of a brake pedal, and a vehicle by a generator. A braking device for an electric vehicle comprising: a regenerative braking unit that charges a power storage device while braking the vehicle; and a deceleration detecting unit that detects a deceleration of the vehicle, the brake being applied when the brake pedal is depressed. All mechanical braking torque corresponding to the pedaling force of the pedal is once generated by the mechanical braking means and detected by the deceleration detecting means.
After the change in the deceleration of the vehicle converged, the mechanical braking by the mechanical braking unit and the regenerative braking by the regenerative braking unit are used together, and the mechanical braking torque value and the regenerative braking by the mechanical braking unit are combined. the sum of the regenerative braking torque value by means were to include a brake control means for controlling so as to be equal to the total braking torque value once caused Ri by said mechanical braking means.

As described above, only the mechanical braking is generated in the initial stage of braking, and the vehicle detected by the deceleration detecting means is detected.
After the deceleration change has converged, by using both mechanical braking and regenerative braking, the total braking torque according to the pedaling force of the brake pedal is equivalent to the feeling of operating with only general mechanical braking means. On the other hand, since the regenerative braking can be performed by using the regenerative braking means together with almost no change in the configuration of the conventional general mechanical braking means, energy recovery can be achieved and the machine to be generated. The braking torque can be kept to a minimum, wear of the mechanical braking means can be suppressed, and durability can be improved.

According to a second aspect of the present invention, the braking control means gradually reduces the mechanical braking torque value and changes in the mechanical braking torque value when the mechanical braking and the regenerative braking are used in combination. Based on the characteristics, the regenerative braking torque value is controlled so as to be gradually increased by the decreasing amount of the mechanical braking torque value. As a result, the distribution ratio between the mechanical braking torque and the regenerative braking torque changes smoothly, so that the mechanical braking torque value and the regenerative braking torque value and the regenerative braking torque are prevented, while preventing the occurrence of a shock due to the relative delay in the operation response. The sum of the braking torque value and the total braking torque value can be accurately maintained.

According to a third aspect of the present invention, the regenerative braking torque value when the mechanical braking means and the regenerative braking means are used together is set based on the state of charge of the power storage device. As a result, a more appropriate regenerative braking torque value is set based on the state of charge of the power storage device, and regenerative braking with higher charging efficiency can be performed.

According to a fourth aspect of the present invention, the mechanical braking means is hydraulic braking means, and the mechanical braking torque is hydraulic braking torque. Thereby, the braking torque can be generated with a simple configuration, and the braking torque value can be easily controlled.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
~ It demonstrates based on FIG. First, the configuration of the first embodiment is shown in FIG. In this embodiment, the engine
The driving force generated by 101 and the motor 102 that generates the driving force to assist the engine when the vehicle accelerates, and regeneratively brakes when decelerating or braking the front wheels 104a, 104b or 104b via the transmission 103. While being transmitted to the rear wheel 105a, 105b or both, the pedaling force from the brake pedal 106 is transmitted to the actuator 109 via the booster 107 and the master cylinder 108, and the actuator 109
Hydraulic pressure through front brake wheel cylinders 110a, 110
b and rear wheel brake wheel cylinders 111a and 111b convert to braking torque. In addition, the electric vehicle motor 10
2 Motor control circuit 112 that controls driving and regenerative braking
And a power storage device 113 using a storage battery, a capacitor, etc.
And a configuration in which these are collectively controlled by the controller 114. The controller 114 includes a stop lamp switch 115 and wheel speed sensors 116a to 116d.
The signal from is input.

As described above, the motor for an electric vehicle is used as it is without changing the structure of the hydraulic braking means such as the front / rear wheel brake wheel cylinders conventionally used. This actuator 10
9 is the same as that used in the anti-lock brake system, and is composed of the hydraulic circuit shown in FIG.
That is, the pressure increasing valves 21a, 21b,
21c and pressure reducing valves 22a, 22b, 22c are provided, and the opening / closing operation is controlled by passing an on / off pulse current to each valve. Specifically, by opening the pressure increasing valve 21a and closing the pressure reducing valve 22a, the pressure increasing mode in which the hydraulic pressure from the master cylinder 108 is directly transmitted to the wheel cylinder is set, and the pressure increasing valve 21a is closed to reduce the pressure. By opening the valve 22a, the pressure in the wheel cylinder is released to the reservoir 23a to reduce the pressure, and by closing the pressure increasing valve 21a and the pressure reducing valve 22a respectively, the hydraulic pressure of the wheel cylinder is maintained. It becomes a mode. By controlling each valve in this way, the hydraulic pressure can be controlled in three modes: pressure increase, pressure decrease, and holding.

FIG. 3 shows the pressure reduction characteristics of the hydraulic pressure in the wheel cylinder with respect to time when the pressure reduction signal from the controller 114 is input to the actuator 109. According to this figure, the hydraulic pressure in the wheel cylinder gradually decreases after the pressure reduction signal is turned on, and the hydraulic pressure in the wheel cylinder is ΔP during the time Δt when the pressure reduction signal is on. Only the pressure will be reduced.

Next, the operation of the braking device for an electric vehicle will be described with reference to FIG. FIG. 4 shows (a) hydraulic braking torque,
It is the figure which respectively showed the time chart with respect to (b) regenerative braking torque and (c) deceleration. First, when the brake pedal 106 is depressed at time t ₁ , the actuator 1
09 becomes the pressure increasing mode, and the hydraulic pressure corresponding to the pedaling force of the brake pedal 106 is directly transmitted to the wheel cylinder. As a result, hydraulic braking torque is generated, and deceleration is generated in the vehicle body. As shown in FIG. 4 (c) , the deceleration of the vehicle body is generated almost simultaneously with the hydraulic braking torque, and converges to a value commensurate with the hydraulic braking torque generated by the pedaling force of the brake pedal 106 and the frictional force on the road surface. And stable.

Here, the deceleration of the vehicle body is determined by the wheel speed sensor 11
The velocity signals obtained by 6a to 116d can be estimated by differentiating them with respect to time and adding filtering or the like to them. In this case, the absolute value of the deceleration of the vehicle body is not required, but it is necessary to determine the time t ₂ indicating that the change in the deceleration has converged in the processing in the controller 114. Absolute accuracy of the speed sensors 116a-116d is not required.

During the period e until the controller 114 detects that the deceleration of the vehicle body has converged and is stable, the actuator 109 is kept in the pressure increasing mode to perform braking by the conventional hydraulic braking alone. Similar to the case, it is possible to obtain the braking torque according to the pedaling force of the brake pedal 106. In this way, the required braking torque (total braking torque) is once generated, and then the regenerative operation is started after time t ₂ .

Time t₂First, from the actuator 109
By inputting the pressure reduction signal to the
The mode is switched to the hydraulic braking torque by a predetermined amount d.₁Only
Decrease gradually. This decompression signal is input and finally
Hydraulic braking torque T to be set_OThe following (1) ~
From equation (3), the wheel cylinder pressure reduction characteristics shown in FIG.
It is calculated in correspondence with (ΔP / Δt).   [Hydraulic braking torque T_O] = [Constant] x [Wheel cylinder hydraulic pressure]               × [Wheel cylinder cross-sectional area] × [Brake pad friction coefficient]               × [Rotor effective radius] (1)   [Wheel cylinder hydraulic pressure] = [hydraulic pressure before pressure reduction]-[pressure reduction amount] (2)   [Decompression amount] = (ΔP / Δt) × [Decompression signal input time] (3) Next, as shown in Fig. 4 (b), it decreases after the pressure reduction signal is input.
Hydraulic braking torque d ₁Regenerative braking torque equal to d₂
Generated by motor 102 and motor control circuit 104
And the total braking torque T_aAs shown in equation (4),
Formula braking torque T _OAnd regenerative braking torque T_gWill be the sum of
To set. [Total braking torque T_a] = [Hydraulic braking torque T_O] + [Regenerative braking torque T_g]                                                           ... (4) Reduction of hydraulic braking torque and generation of regenerative braking torque
Continuous decompression signal input or intermittent decompression signal pulse.
Target regenerative braking torque T_gRepeat until
Then do it.

As a result, the total braking torque T _a becomes equal to the braking torque when braking is performed only by hydraulic braking. still,
The regenerative braking torque to be generated is set so that the energy recovery efficiency is high, that is, the charging state of the power storage device is close to the appropriate charging state. As a method of detecting the state of charge of the power storage device, as shown in FIG. 5, an overcharge state detection voltage of the power storage device, an overdischarge state detection voltage, and a voltage in an intermediate state thereof, which are predetermined from the rating, are used. The state of charge is detected from the terminal voltage of the power storage device with reference to the prescribed state-of-charge table.

Then, at time t ₄ when the value of the regenerative braking torque to be generated reaches the target value T _g , the reduction of the hydraulic braking torque and the increase of the regenerative braking torque are stopped, and both braking torques are distributed at a constant ratio. Braking is performed while holding in this state. However, the amount of increase d ₂ of the regenerative braking torque is determined by the motor 10
The regenerative capacity of 2 is within the limit, and the reduction amount d ₁ of the hydraulic braking torque is also within the limit commensurate with this.

Next, when the brake pedal is stopped at time t ₅ , it is determined that the brake operation has stopped because the stop lamp switch has been turned off, and the regenerative braking is stopped. . This allows
When the brake pedal is stopped, the total braking torque T _a disappears. Then, when the brake pedal is stepped on again, hydraulic braking torque corresponding to the stepping force is generated again. Since the same braking operation is performed thereafter, it is possible to perform repeated operations such as pumping braking.

In addition, exceptionally, the deceleration of the vehicle body may not be obtained as a stable deceleration as shown in FIG. 4 (c). This is the case where the rotational speed of the wheels changes in small steps, for example, when the antilock brake is activated, and the deceleration of the vehicle body changes oscillatingly, and it may not be possible to detect that the braking torque is stable. . Therefore, regenerative braking is prohibited during the operation of the antilock brake. Here, since the number of times the antilock brake is activated during normal traveling is very small compared to the number of times energy is regenerated, it is not necessary to dare to perform regenerative braking.

As described above, according to the present embodiment, only hydraulic braking is generated at the initial stage of braking to decelerate the vehicle.
After the change of the degree has converged, by using both hydraulic braking and regenerative braking, the total braking torque according to the pedaling force of the brake pedal can be operated with the same operation feeling as when braking with only general hydraulic braking. Obtainable. Also, without changing the configuration of the conventional general hydraulic braking means,
Since regenerative braking can be performed by using regenerative braking means such as a motor for an electric vehicle together, energy recovery can be achieved and the hydraulic braking torque generated can be kept to a minimum, and the durability of the hydraulic braking means can be reduced. It is possible to improve the property and suppress the wear of the brake shoes and the like.

Further, since the distribution ratio between the mechanical braking torque and the regenerative braking torque changes smoothly, it has the effect of preventing the occurrence of shock due to the relative delay in the operation response of both braking means, and the mechanical type Since the control is performed based on the characteristic of the braking torque, the total sum of the mechanical braking torque value and the regenerative braking torque value can be accurately maintained at the total braking torque value.

By setting the regenerative braking torque value according to the state of charge of the power storage device, regenerative braking with high energy recovery efficiency can be performed. Next, a second embodiment for obtaining the deceleration of the vehicle body using the vehicle speed sensor will be described. In this embodiment, as shown in FIG. 6, the vehicle speed sensor 61 is arranged on the transmission 103 side in the structure of the first embodiment. The vehicle speed sensor 61 measures the rotational speed of the drive wheels to approximately detect the vehicle speed, and the detected vehicle speed signal is subjected to differential processing and subjected to filter processing to obtain the vehicle deceleration. There is.

After that, as in the first embodiment, the hydraulic braking is operated until the deceleration of the vehicle is stabilized, and the controller 114 detects that the hydraulic braking torque is stable, and then the regenerative braking is performed. To start the operation. Since the vehicle speed sensor 61 is arranged on the transmission 103 side to measure the deceleration in this way, the same effect as that of the first embodiment can be obtained and, for example, the drive that connects between the wheel and the transmission. The speed of the vehicle can be measured stably without depending on the mechanical twist of the shaft or vibration caused by backlash.
It is possible to more accurately determine the start time of regenerative braking.

Next, a third embodiment for obtaining the deceleration of the vehicle body from the acceleration sensor will be described. In the present embodiment, as shown in FIG. 7, the acceleration sensor 71 is arranged on the vehicle body in the configuration of the first embodiment. The deceleration of the vehicle body is directly measured by the acceleration sensor 71, and the controller 114 determines that the hydraulic braking torque has stabilized, as in the first embodiment, and then the regenerative operation is started.

Since the acceleration sensor 71 is arranged on the vehicle body in this way, the same effect as that of the first embodiment can be obtained, and the signal detected by the acceleration sensor 71 is subjected to differentiation processing, filtering processing, and the like. Since the deceleration of the vehicle can be directly obtained without performing the deceleration, the deceleration can be measured more quickly.

[0028]

As described above, according to the first aspect of the present invention, the braking torque corresponding to the pedaling force of the brake pedal can be operated with a feeling equivalent to that obtained by braking with only a general mechanical braking means. It is possible to obtain a stable braking torque according to the pedaling force of the brake pedal, while using the regenerative braking means together with almost no change to the structure of the conventional general mechanical braking means. Since the regenerative braking can be performed by, the energy can be recovered and the mechanical braking torque to be generated can be kept to the minimum, so that the mechanical braking means can be prevented from wearing and the durability can be improved.

According to the second aspect of the present invention, since the distribution ratio of the mechanical braking torque and the regenerative braking torque changes smoothly, the occurrence of shock due to the relative delay in the operation response of both braking means is prevented. While preventing, the total sum of the mechanical braking torque value and the regenerative braking torque value can be accurately maintained at the total braking torque value. According to the invention of claim 3,
Since the regenerative braking torque value is set based on the state of charge of the power storage device, a more appropriate regenerative braking torque value is set,
Regenerative braking with higher charging efficiency can be performed.

According to the fourth aspect of the invention, by braking using hydraulic pressure, the braking torque can be generated with a simple structure, and the braking torque value can be easily controlled.

[Brief description of drawings]

FIG. 1 is a system configuration diagram according to a first embodiment.

FIG. 2 is a hydraulic circuit diagram of a hydraulic actuator.

FIG. 3 is a pressure reduction characteristic diagram of a hydraulic actuator.

FIG. 4 is a time chart diagram of hydraulic braking torque, regenerative braking torque, and deceleration common to each embodiment.

FIG. 5 is a diagram showing characteristics of a charge state of a power storage device.

FIG. 6 is a system configuration diagram according to a second embodiment.

FIG. 7 is a system configuration diagram according to a third embodiment.

FIG. 8 is a diagram showing an example of a conventional braking device for an electric vehicle.

[Explanation of symbols]

102 Electric vehicle motor 106 brake pedal 108 Master cylinder 110a, 110b Front brake wheel cylinder 111a, 111b Rear brake wheel cylinder 112 Motor control circuit 113 power storage device 114 controller

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-284607 (JP, A) JP-A-2-146903 (JP, A) Actual development Sho-58-143401 (JP, U) JP-B-40- 5858 (JP, B1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60L 7/24

Claims (4)

(57) [Claims] 1. An electric vehicle, comprising: mechanical braking means for mechanically braking the vehicle in response to depression of a brake pedal; and regenerative braking means for charging a power storage device while braking the vehicle by a generator. In the braking device, a deceleration detecting means for detecting the deceleration of the vehicle is provided , and when the brake pedal is stepped on, all the braking torque corresponding to the pedaling force of the brake pedal is once generated by the mechanical braking means, It is detected by the deceleration detecting means.
After the change in the deceleration of the issued vehicle has converged, the mechanical braking by the mechanical braking means and the regenerative braking by the regenerative braking means are used together, and the mechanical braking torque value and the regenerative braking by the mechanical braking means are combined. A braking device for an electric vehicle, comprising: braking control means for controlling a total sum of regenerative braking torque values by the braking means to be equal to a total braking torque value once generated by the mechanical braking means. 2. The braking control means gradually reduces the mechanical braking torque value when the mechanical braking and the regenerative braking are used in combination, and the regenerative braking is performed based on a change characteristic of the mechanical braking torque value. The braking device for an electric vehicle according to claim 1, wherein the braking means controls the regenerative braking torque value to gradually increase by a decreasing amount of the mechanical braking torque value. 3. The electric motor according to claim 1, wherein the regenerative braking torque value when the mechanical braking means and the regenerative braking means are used in combination is set based on the state of charge of the power storage device. Vehicle braking system. 4. The braking device for an electric vehicle according to claim 1, wherein the mechanical braking means is a hydraulic braking means, and the mechanical braking torque is a hydraulic braking torque. .