JP3156358B2 - Electric vehicle braking system - 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 performs both mechanical braking and regenerative braking.

[0002]

2. Description of the Related Art Since an electric vehicle is a vehicle driven by a motor, a regenerative brake in addition to a mechanical brake can be used as a braking means. FIG.
No. 201 discloses an electric vehicle having a mechanical brake and a regenerative brake.

The driving source of the electric vehicle shown in FIG. 1 is a three-phase AC motor 10. The shaft output of the motor 10 is transmitted to the wheels 12 via a shaft (not shown) to rotate the wheels 12. The driving power is supplied from the battery 14 to the motor 10 via the power converter 16. The power converter 16 is configured as, for example, an inverter circuit, and converts DC power from the battery 10 into three-phase AC power.

[0004] The output torque of the motor 10 is
6 can be controlled by controlling the operation. The control unit 18 is a member for this control, and includes an output torque calculation unit 20 and a motor control unit 22. The control unit 18 controls the number of rotations of the motor 10
The output torque calculator 20 calculates a torque command value based on the detected motor rotation speed and the detected accelerator amount or brake amount. The accelerator amount refers to the amount of depression of the accelerator pedal, and the brake amount refers to the amount of depression of the brake pedal. The motor control unit 22 gives a current command to the electric power converter 1 so that the motor 10 generates a torque corresponding to the command value based on the obtained torque command value.
6 is controlled. In the case where an induction motor is used as the motor 10 and an inverter circuit is used as the power converter 16, this control is performed as vector control for dividing the current of the motor 10 into a current for excitation and a current for torque. This is executed as PWM control.

As described above, since the output torque of the motor 10 can be controlled, it is possible to generate a power running torque according to the accelerator amount and to generate a regenerative brake torque according to the brake amount. That is, at the time of braking, with described below the mechanical brake, the motor 10
A regenerative brake by regenerating the energy of the battery 14 into the battery 14 can be used.

The mechanical brake includes a brake master cylinder 28 for generating a hydraulic pressure corresponding to the depression of a brake pedal 26 and a pipe 30 for transmitting the hydraulic pressure to the wheels 12. Therefore, in this example, the mechanical brake
It is constituted by a so-called hydraulic brake. In addition, 3 in the figure
Reference numeral 2 denotes a brake amount detector, and its output is input to the controller 18 as a brake amount. Reference numeral 34 denotes a brake switch that is turned on by depressing a brake pedal, and the output is input to the control unit 18.

As described above, in an electric vehicle, mechanical braking and regenerative braking can be used together.

Further, a technique called field weakening control for driving the motor 10 with high efficiency is also known. In this control, in consideration of the rise time constant of the excitation component current being larger than the torque component current, the excitation component current is set small in advance (field weakening), and the output torque is controlled exclusively by controlling the torque component current. Method.

[0009]

However, when a relatively large brake torque is required, the rise of the regenerative brake torque may be delayed in an electric vehicle that performs field weakening control. FIG. 6 illustrates this problem.

[0010] First, when the brake switch is turned on at time _{t 0 (A} 3), the mechanical brake torque begins to occur in response to this _{(t 1, B} 3). Difference time t ₀ and time t _1, the hydraulic generation, due to mechanical time delay caused by transmission or the like. Control unit at time t _1, i.e. to obtain a torque command value according to the regenerative braking in synchronization with the beginning effectiveness of mechanical brake <br/> key (C _3). If the regenerative brake torque is generated with good response to the torque command value, the mechanical brake torque and the regenerative brake torque act in a predetermined distribution determined by the control unit.

When a large brake torque is required in the state where the field weakening control is being performed, it is necessary to temporarily increase the excitation component current from the value of the field weakening. By doing so, a large value can be obtained as the regenerative braking torque. But,
Although torque current rises good response, the rise delays by (D ₃₎ of the exciting component _current, the exciting component current and the rise of the regenerative braking torque determined by the product of the torque current is delayed (E _3), the machine braking torque _against, t 4 -t ₂
Will be delayed. Such a delay is not preferable in that it takes time to obtain the necessary break torque, and the brake feeling changes.

According to the present invention, in a case where it is necessary to increase an exciting component current for braking, for example, when field weakening control is performed, the regenerative brake torque is started up with good responsiveness as much as the mechanical brake torque. With the goal.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a drive motor which starts increasing an exciting current of a drive motor after a brake signal is generated and before a mechanical brake torque is generated. Means for increasing the torque current in synchronization with the generation of the mechanical brake torque, and generating the regenerative brake torque with a rising time constant close to the mechanical brake torque.

A second aspect of the present invention is characterized in that the torque current is temporarily increased to substantially the maximum value from the time when the mechanical brake torque is generated until the time when the regenerative brake torque approaches the target value.

[0015]

In the present invention, the excitation current of the drive motor starts rising after the generation of the brake signal and before the generation of the mechanical brake torque. The torque current that determines the rise of the regenerative brake torque is increased in synchronization with the generation of the mechanical brake torque. Therefore, the regenerative braking torque determined by the product of the exciting current and the torque current rises relatively quickly since the exciting current has already increased to some extent at the time when the torque current starts to increase. Thus, the responsiveness of the regenerative brake torque is improved.

According to the second aspect of the present invention, the above-described torque current temporarily increases to almost the maximum value.
Therefore, the increase of the regenerative brake torque is promoted, and the responsiveness is further improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the device configuration of the present invention is sufficient for the configuration of FIG. 5 described above. Therefore, a case will be described below in which the present invention is implemented with the apparatus configuration in FIG. 5, but the present invention is not limited to this apparatus configuration.

FIG. 1 shows a flow of the operation of the control unit 18 in the first embodiment of the present invention. FIG. 2 shows the behavior of torque in this embodiment.
The operation shown in FIG. 1 is sequentially repeated in control unit 18.

As shown in FIG. 1, the controller 18 first determines whether or not the brake switch 34 has been turned on (1.
00). If the time t ₀ a previously since the brake switch 34 does not brake pedal 26 is depressed is off, the control unit 18 first b. After setting the flag to 0 (102), the field weakening control is executed (104). b.
The flag is a flag indicating whether or not the brake pedal 26 is depressed, and the contents of the field weakening may be the same as those in the related art. Time t ₀ the previous run cycle is such content.

After the above operation is repeated, it is assumed that the brake switch 34 is turned on at a certain point. This time t
₀ , it is determined in step 100 that the brake switch 34 is on, so the control unit 18 sets b. f
The process proceeds to step 106 for determining whether or not lag = 1. At this point, the brake switch 34 has been turned off in the immediately preceding execution cycle, and b. flag
= 0, steps 108 and 110
Is executed. Step 108 the control unit 18 inside the counter is set to _{t 0,} in step 110 b. fl
ag = 1 is set. The control unit 18 commands the power converter 16 so that the excitation current after the initial setting becomes the maximum value (112). However, the excitation current command value is
Further, a first-order lag term (differential term) is added to provide a feedforward (magnetic flux feedforward) function. Depending on the command of step 112, as indicated by D ₁ in FIG. 2, the exciting component current starts to increase. At this point the machine is still
Mechanical brake torque has not started to rise (11
4), the control unit 18 instructs the power converter 16 to 0 as a torque component current (116). Therefore, at this time, the torque current is maintained at zero.

Thereafter, until the time t _{1 at} which the mechanical brake torque (B ₁ ) rises, the above-described step 112,
The cycle including 116 is repeated. In this state,
The torque component current is held at 0 while the excitation component current increases. However, b. Steps 108 and 110 are not performed because flag = 1. It reaches the time _{t 1} (11
4) The control unit 18 issues a command relating to the torque component current to the current converter 16 according to the required regenerative braking torque. Then, torque current increases as shown in D ₁ in FIG. 2, a regenerative braking torque determined by the product of the exciting component current and torque current increases as shown in E _1.

[0022] Thus, in this embodiment, increase the brake switch 34 is started up simultaneously exciting component current and to turn on, already exciting component current at the time point t ₁ launch torque current to some extent and is leading to the target value regenerative braking torque is at an early time point t ₃ to time t _4. Therefore, the responsivity of the regenerative braking torque is improved by t ₄ -t ₃ despite performing the field weakening control.

FIG. 3 shows a flow of the operation of the control unit 18 in the second embodiment of the present invention. FIG. 4 shows the behavior of torque in this embodiment.
This embodiment is different from the first embodiment in that the control unit 18 executes steps 120 to 124 instead of step 108, and as a result, as shown in FIG. Is remarkable.

[0024] That is, before time t ₂ when the mechanical brake torque rises enough after reaching the time t _1, the control unit 18 issues a current command to the torque component current is maximized (122). As a result, the torque current temporarily increases to the maximum value. Further, after time t _2, the control unit 18, so that the product of the exciting component current becomes a value corresponding to the regenerative braking torque as a target, determines a command value of the torque current (124). Command value calculated in step 124, as shown in FIG. 4D _2, complementarily decreased growth curve of the exciting component current.

[0025] Such control as shown in FIG. 4E _2, already so that the regenerative braking torque reaches the target value at time t _2. Therefore, compared to the conventional example of FIG.
Only ₄ -t _2, only _t 3 -t ₂ compared with the first embodiment of FIG. 2, the response of the regenerative braking torque is improved.

The application of the present invention is not limited to an electric vehicle that performs field weakening control. That is, the present invention is applied to a vehicle that needs to increase the exciting current at the time of braking. For example, in the high-speed rotation range of the induction motor, the maximum regenerative torque decreases with an increase in the rotation speed. There is a control method in the same way. When this method is adopted, the exciting component current is smaller at a relatively high rotation speed belonging to the high-speed rotation region than at a lower rotation speed belonging to the same rotation region. Therefore, when shifting from the relatively high rotation speed to the lower rotation speed, the response of the regenerative braking torque can be improved by the method of the present invention.

[0027]

As described above, according to the present invention,
After the brake signal is generated, the excitation current is started to increase before the mechanical brake torque is generated, and the excitation current is increased to some extent at the time when the torque current increases, so that the regenerative brake torque determined by the product of the excitation current and the torque current It rises quickly and the responsivity of the regenerative brake torque improves.

According to the second aspect of the present invention, since the torque current is temporarily increased to almost the maximum value, the increase in the regenerative braking torque is promoted, and the responsiveness is further improved.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a control flow according to a first embodiment of the present invention.

FIG. 2 is a time chart showing the behavior of the torque in this embodiment. FIG. 2A ₁ shows the state of the brake switch, FIG. 2B ₁ shows the behavior of the mechanical brake torque, and FIG. 2C ₁
Is the command value of the regenerative braking torque, FIG. 2D ₁ is the behavior of the exciting component current and torque current, the behavior of the Figure 2E ₁ regenerative braking torque, illustrates respectively.

FIG. 3 is a flowchart illustrating a control flow according to a second embodiment of the present invention.

FIG. 4 is a time chart showing the behavior of the torque in this embodiment. FIG. 4D ₂ shows the behavior of the exciting component current and the torque component current, and FIG. 4E ₂ shows the behavior of the regenerative braking torque.

FIG. 5 is a block diagram illustrating a configuration of an electric vehicle.

6A and 6B are time charts showing a problem of the conventional field weakening control. FIG. 6A ₃ shows a state of a brake switch, FIG. 6B ₃ shows a behavior of a mechanical brake torque, and FIG.
₃ a command value of the regenerative braking torque, Figure 6D ₃ behavior of the exciting component current and torque current, FIG. 6E ₃ behavior regenerative braking torque, illustrates respectively.

[Explanation of symbols]

 10 Motor 18 Control unit 26 Brake pedal 34 Brake switch

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60L 7/24 B60L 7/14

Claims (2)

(57) [Claims] 1. A means for generating a mechanical brake torque in response to generation of a brake signal, and a means for applying a mechanical brake torque to a drive motor.
By controlling the exciting current value and the torque current value,
Kitoruku can be generated, in the braking device for an electric vehicle and means for generating in synchronization with regenerative braking torque to the generation of the mechanical braking torque, the drive prior to the occurrence of the generation after the mechanical brake torque of the brake signal Means to start increasing the excitation current of the drive motor and increase the torque current of the drive motor in synchronization with the generation of mechanical brake torque, and to generate regenerative brake torque with a startup time constant close to the mechanical brake torque A braking device for an electric vehicle, comprising: 2. The braking device for an electric vehicle according to claim 1, wherein the torque current is temporarily increased to substantially a maximum value from a point in time when the mechanical braking torque is generated to a point in time when the regenerative braking torque approaches a target value. A braking device for an electric vehicle.