JP3523726B2 - Electric vehicle braking method and 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 method and a braking device for an electric vehicle, and more particularly to a combined use of regenerative braking and hydraulic braking.

[0002]

2. Description of the Related Art Conventionally, as a braking technique for an electric vehicle using both regenerative braking and hydraulic braking, for example, Japanese Patent Application Laid-Open No. 5-16 is available.
There is one disclosed in Japanese Patent No. 1210. In this technique, there are three types of braking modes, that is, modes 1 to 3, and one of them is selected by the initial determination,
Braking is performed in a predetermined mode, and the mode is changed during braking due to changes in the operating state.

Mode 1 is selected during a sudden braking when the regenerative braking system is not operating normally or when the regenerative braking system is operating normally. In this mode 1, no regenerative braking is performed on the rear wheels that are the driving wheels, and when the brake pedal is depressed, hydraulic braking is performed on the rear wheels and the rear wheels that are the driven wheels. The braking force distribution characteristics for the rear wheels and the front wheels in this case are shown in FIG.
As shown by the solid line in (a), the braking force of the front wheels is placed below the ideal distribution characteristic shown by the broken line.

Mode 2 is selected when the regenerative braking system is operating normally and during steering, not during sudden braking. In this mode 2, when the brake pedal is depressed, the hydraulic braking of the front wheels is performed concurrently with the regenerative braking of the rear wheels, and if the braking force of the rear wheels exceeds the regenerative limit during that time, the rear wheels will regenerate the hydraulic pressure. Brakes when used in combination with. The braking force distribution characteristic for the rear wheels and the front wheels in this mode 2 is also such that the braking force of the front wheels is weighted as shown by the solid line in FIG. 13 (b).

Mode 3 is a normal operating condition, that is,
This is selected when the regenerative braking system is operating normally, and neither during sudden braking nor during steering.When the brake pedal is depressed, only the rear wheels are regeneratively braked first, and the front wheels are hydraulically braked. Is not done. When the regenerative braking force of the rear wheels reaches a predetermined value P, hydraulic braking of the front wheels is started from that moment, and when the braking force of the rear wheels exceeds the regenerative limit, the rear wheels are braked by both regeneration and hydraulic pressure. It is a thing. The braking force distribution characteristic in mode 3 is
As shown in FIG. 13C, the braking force distribution above the ideal distribution characteristic, that is, the rear wheel braking force distribution is biased to exceed the ideal distribution characteristic. This is to utilize regenerative braking as much as possible to charge the battery and improve regenerative efficiency.

If a tendency of wheel locking on a low μ road is detected during braking in mode 3, mode 3 is selected.
Is changed to mode 2 and similarly, when a stronger wheel locking tendency on the low μ road is detected during braking by mode 2, the mode 2 is changed to mode 1.

[0007]

However, in mode 3 braking distribution, the braking force distribution of the rear wheels is biased so as to exceed the ideal distribution characteristic, as is apparent from FIG. 13 (c). Since the braking force is biasedly applied to the rear wheels, slipping or locking of the rear wheels is likely to occur when the command braking torque becomes large, so that the mode is changed to mode 2 or mode 1 and the regeneration efficiency is reduced. There is.

It is an object of the present invention to secure the running stability of a vehicle and to improve the energy recovery efficiency during regenerative braking.

[0009]

In order to solve the above problems, the braking method according to the first aspect of the present invention is connected to and driven by a motor whose energy source is a battery, at least during initial braking. , Prohibiting hydraulic braking of the drive wheel capable of hydraulic braking and regenerative braking by operating the brake pedal and hydraulic braking of driven wheels capable of hydraulic braking by operating the brake pedal, and regenerative braking of the driving wheel. When the regenerative braking force of the drive wheels reaches a predetermined value equal to or less than the maximum value, the regenerative braking force is held to start hydraulic braking of the driven wheels to maintain the regenerative braking force. The braking force distribution of the driven wheels and the driving wheels is continued until it matches a preset ideal distribution approximate characteristic.

The braking method according to the second invention is the first method.
In the invention, when the braking force distributions of the driven wheels and the driving wheels match the preset ideal distribution approximation characteristics, and the regenerative braking force of the driving wheels has the maximum value, the ideal distribution approximation characteristics are matched. Starts hydraulic braking of the drive wheels,
The subsequent braking force is secured.

In the braking method according to the third aspect of the present invention, at least during initial braking, the driving wheel is connected to a motor that uses a battery as an energy source for driving, and hydraulic braking and regenerative braking are possible by operating a brake pedal. Hydraulic braking and hydraulic braking of driven wheels that can be hydraulically braked by operating the brake pedal are prohibited, regenerative braking of the drive wheels is activated, and the regenerative braking force of the drive wheels is less than a predetermined value. When the value is reached, this regenerative braking force is held to start hydraulic braking of the driven wheels, and after the braking force distribution of the driven wheels and the driving wheels matches the preset ideal distribution approximation characteristic, The hydraulic braking of the drive wheels is started in accordance with this characteristic.

A braking device according to a fourth aspect of the present invention comprises a motor capable of regeneratively braking the drive wheel by driving the drive wheel using a battery as an energy source, and hydraulic braking means provided on the drive wheel and the driven wheel, respectively. A braking command value generated according to the operation of the brake pedal is input, and when the braking command value is smaller than a predetermined first set value, a regenerative braking force value having a value corresponding to the braking command value is output, Regenerative braking force determining means for outputting a predetermined constant value of the regenerative braking force value when the braking command value is greater than or equal to the first set value, and a braking force value corresponding to the braking command value and the regenerative braking force value. Hydraulic braking force value determining means for determining the hydraulic braking force value based on
The hydraulic braking force value is divided into a driving wheel hydraulic braking force value and a driven wheel hydraulic braking force value, and this distribution is such that the driving wheel braking force value and the driven wheel hydraulic braking force value approximate an ideal distribution characteristic. And a distribution means for performing the above.

In the braking device according to the fifth aspect of the present invention, the first set value is set smaller than the maximum regenerative braking force value determined by the motor.

In the braking device according to the sixth aspect of the present invention, the regenerative braking force value determining means sets the regenerative braking force to a value smaller than the maximum regenerative braking force value determined by the motor, corresponding to the first set value. The maximum regenerative braking force value is output when a power value is output and a braking command value equal to or greater than a second setting value that is set to be larger than the first setting value is input.

In the braking method according to the first aspect of the present invention, only the regenerative braking force is applied until the regenerative braking force of the driving wheels reaches a predetermined value equal to or less than the maximum value, and after the regenerative braking force reaches the predetermined value. , The hydraulic braking of the driven wheels is started while maintaining the regenerative braking force. With the regenerative braking force maintained at a predetermined value, the hydraulic braking of the driven wheels is increased until the braking force distributions of the driven wheels and the drive wheels match the preset ideal distribution approximate characteristics.

In the braking method according to the second aspect of the present invention, the braking force distribution between the braking force by the hydraulic braking of the driven wheels and the regenerative braking force of the driving wheels coincides with the ideal distribution approximation characteristic, and the driving is performed. When the regenerative braking force of the wheels has the maximum value, the hydraulic braking of the drive wheels is started so as to match the ideal distribution approximate characteristic. That is, the maximum regenerative braking force is exerted, and then the hydraulic braking forces of the driven wheels and the driving wheels are increased so as to match the ideal distribution approximate characteristics.

In the braking method according to the third aspect of the present invention, until the regenerative braking force of the drive wheels reaches a predetermined value less than the maximum value, only the regenerative braking force is actuated as in the first aspect of the invention, and the regenerative braking force is reduced. After reaching the predetermined value, the hydraulic braking of the driven wheels is started while maintaining the regenerative braking force, and the braking force distribution of the driven wheels and the driving wheels is maintained until the ideal distribution approximation characteristic is set in advance. Increase hydraulic braking of the driving wheels. The hydraulic braking force of the driven wheels and the drive wheels are increased so as to match the ideal distribution approximate characteristics while maintaining the regenerative braking force at a predetermined value even after the characteristics match the ideal distribution approximate characteristics.

In the braking device according to the fourth aspect of the present invention, the regenerative braking force determining means outputs the regenerative braking force value according to the operation of the brake pedal. The regenerative braking force determination means outputs a regenerative braking force value having a predetermined value when the braking command value is equal to or more than the first set value. The hydraulic braking force value is determined based on the regenerative braking force value and the braking force value corresponding to the braking command. That is,
When the regenerative braking force is insufficient, the braking force value that the hydraulic braking force bears is determined. The distribution means distributes the hydraulic braking force value to the driven wheel hydraulic braking force value and the driving wheel hydraulic braking force value. In this distribution, the driving wheel braking force, which is a combination of the braking force of the driving wheel due to the regenerative braking force value and the braking force of the driving wheel due to hydraulic braking, and the hydraulic braking force of the driven wheel, approximate the ideal distribution characteristic. To do so. Therefore, if the braking force of the driving wheels is sufficient with only the regenerative braking force value, hydraulic braking of the driving wheels is not performed, but with the regenerative braking force value alone, the braking force of the driving wheels is insufficient. In this case, hydraulic braking of the drive wheels is also performed.

In the braking device according to the fifth aspect of the present invention, the regenerative braking force value determining means regenerates a value smaller than the maximum regenerative braking force value when the braking command value greater than or equal to the first set value is input. The braking force value is output. Therefore, the regenerative braking force is
It is held at this value. It is desirable that the regenerative braking force has a value that does not significantly impair the running stability of the vehicle within a range of the braking force during the normal operation that is frequently used.

In the braking device according to the sixth aspect of the present invention, the regenerative braking force value determining means outputs the maximum regenerative braking force value when the braking command value equal to or more than the second set value is input and holds it. Therefore, the maximum regenerative braking force is obtained.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment will be described with reference to FIGS.
Shown in. The electric vehicle of this embodiment is a four-wheeled vehicle having a pair of front wheels 2, 2 and a pair of rear wheels 4, 4 as shown in FIG. The rear wheels 4, 4 are drive wheels driven by the motors 6, 6. The front wheels 2 and 2 are driven wheels that are not driven. The motors 6, 6 are supplied with electric power from a rechargeable battery 8 which is controlled by a power control unit, for example, an inverter 10, which controls the driving of the motors 6, 6. Further, the inverter 10 charges the battery 8 with the electric power generated by the regenerative braking of the motors 6, 6.

The inverter 10 is a system controller 1 composed of, for example, a microcomputer.
Controlled by 1. The system controller 11
A signal for controlling the drive state of the motors 6, 6 is supplied to the inverter 10 in accordance with an accelerator signal generated by operating an accelerator pedal (not shown), and in response to a regenerative brake command signal from a brake controller 13 described later,
A signal for controlling the state of regenerative braking is supplied to the inverter 10.

The rear wheels 4, 4 are provided with hydraulic braking means, for example hydraulic brakes 12, 12. The front wheels 2, 2 are also provided with hydraulic braking means, for example hydraulic brakes 14, 14.

These hydraulic brakes 12, 12, 14, 1
4 brakes the front wheels 2 and 2 and the rear wheels 4 and 4 by the hydraulic pressure supplied from the ABS (antilock brake system) hydro unit 16. The hydro unit 16 receives the control hydraulic pressure generated by the master cylinder 20 by operating the brake pedal 18 via the control valve unit 22. The braking state is also controlled by a control signal from an ABS ECU (anti-lock brake system electronic control unit) 24. The control valve unit 22 and the ABS ECU 24 are controlled by a control signal from the brake controller 13 configured by, for example, a microcomputer. These controls are individually performed for the hydraulic brakes 12, 12 and 14, 14.

The brake controller 13 receives the speed signals of the electric vehicle detected by the front wheel speed sensors 26, 26, that is, the speeds of the motors 6, 6, and also connects between the master cylinder 20 and the control valve unit 22. The detected value of the pressure change generated by the operation of the brake pedal 18 detected by the pressure sensor 28 provided in the oil passage, that is, the braking command value Bin is also input.

The brake controller 13 supplies the motor rotation speed (R) supplied from the system controller 11,
Based on (L), control valve unit 22, ABS ECU
A control signal is supplied to 24. The brake controller 13 also outputs a braking command value Bin from the pressure sensor 28, a speed signal from the front wheel speed sensors 26, 26, a signal (not shown) that detects the state of charge of the battery, and the motors 6 and 6. A regenerative braking command signal is supplied to the system controller 11 based on the signal that has detected the temperature.

Brake control performed by the brake controller 13 and the system controller 11 will be briefly described. As shown in FIG. 1, in the initial braking, the rear wheels 4 and 4 are braked only by regenerative braking until a predetermined braking force a smaller than the maximum regenerative braking force is reached. When a larger braking force is required, the regenerative braking force a of the rear wheels 4 and 4
Is maintained, and the hydraulic braking force of the front wheels 2, 2 is increased.
Then, the braking forces of the front wheels 2, 2 and the rear wheels 4, 4 are approximate characteristics β of the ideal distribution α between the braking force of the front wheels and the braking force of the rear wheels.
(Point b in FIG. 1), the braking force of the front wheels and the braking force of the rear wheels are increased along this approximate characteristic β.

This ideal distribution α is, in this embodiment,
As is clear from FIG. 1, the braking force of the rear wheels is represented by a curve that maintains a state in which the braking force of the rear wheels is somewhat larger than the braking force of the front wheels, and the approximate characteristic β is within the predetermined braking force range of the front wheels. It is represented by a straight line where the braking force of the rear wheels is smaller than the distribution α.

If the braking force of the rear wheels 4 and 4 reaches the maximum value of the regenerative braking, and the braking force of the rear wheels 4 and 4 necessary for matching the ideal distribution approximate characteristics can be alleviated by the regenerative braking. When it disappears, the shortage is borne by the hydraulic braking of the rear wheels 4, 4.

As described above, the regenerative braking force is kept at a constant value a less than the maximum value until it matches the approximate characteristic β of the ideal distribution.
A certain amount of regenerative energy is recovered.

In order to perform such control, in the control performed by the brake controller 13 and the system controller 11, as shown in FIG. 4, it is first determined whether the brake pedal is operated (step S2). This is performed, for example, by determining whether or not a switch (not shown) provided on the brake pedal 18 and turned on when the brake pedal 18 is operated is on. If the answer to this decision is no, then step S2 is repeated until yes.

If the answer to the step S2 is YES, that is, if the brake pedal 18 is operated, the brake controller 13 takes in the braking command value Bin obtained by the pressure sensor 28 (step S4). And
Based on the braking command value Bin, the hydraulic braking value BFi for the front wheels 2 and 2 is determined (step S6). This hydraulic braking value BFi is determined as follows. For example, the total value of the braking force values of the front wheels and the rear wheels corresponding to the braking command value Bin,
That is, the characteristic of the total braking force value Bin "is predetermined.
In the characteristic of "in", the characteristic of the braking force that the front wheels need to bear when regenerative braking is not used in order to realize the ideal approximate characteristic β is also determined. In this characteristic, the hydraulic braking value BFi and the braking command value Bin Is set so as to have a proportional relationship as shown in FIG. 5, for example, the hydraulic braking value BFi can be obtained by multiplying the braking command value Bin by a predetermined coefficient. Alternatively, the hydraulic braking value BFi corresponding to each braking command value Bin may be stored in the lookup table and the hydraulic braking value BFi may be read out.

Next, the running state of the electric vehicle is read (step S8). The running state means, for example, the front wheel speed sensor 1
4 and 14, the speed of the electric vehicle, that is, the speed of the motors 6 and 6, the state of charge of the battery 8, the motors 6 and 6
Temperature, etc. The maximum regenerative braking force BEmax that can be generated at the present time is determined from these read traveling states (step S10). As shown in FIG. 6, the maximum regenerative braking force BEmax
Is a function of speed, and the charging rate and the temperature of the batteries 8 and 8 are parameters, and the relationship between them is known in advance. Therefore, similar to the hydraulic braking value BFi, a calculation or a lookup table is used. Can be sought by.

Subsequently, the regenerative braking force value BE (Bin) corresponding to the braking command value Bin is obtained (step S12). That is, this regenerative braking force value BE (Bin) corresponds to the input braking command value Bin and corresponds to the regenerative braking force value BE as shown in FIG.
Output (Bin).

In FIG. 8, BE2 is the maximum regenerative braking force that can be output by the motors 6, 6, BE1 is a value smaller than BE2, and is in the range of the braking force during normal operation that is frequently used. The value is experimentally set to a value that does not significantly impair the running stability of the vehicle. In addition, this regenerative braking force value B
E1 is equal to the braking force value a shown in FIG.

Bin1 represents the braking command value Bin when the regenerative braking force BE1 is output, and the regenerative braking force value Bin 'proportional to the braking command value Bin from zero to Bin1 is the regenerative braking force value BE (Bin ) Is output. Note that this regenerative braking force value Bin 'is the total braking force value B in the section from zero to Bin1.
It is set to match "in".

Bin2 is the total braking force value Bi when the braking force value BF of the front wheels 2, 2 determined by BFi and the regenerative braking force value BE1 become the value of the point b of the approximate characteristic β shown in FIG.
n "(in this case, the braking force value of the rear wheel, that is, the regenerative braking force value Bi
This is a braking command value Bin corresponding to a value obtained by combining n ′ and the braking force value BF of the front wheels 2, 2. Braking command value Bin1 to Bin
Up to 2, BE1 is output as the regenerative braking force value BE (Bin).

As shown in FIG. 2, Bin3 is a braking command value Bin corresponding to the total braking force value Bin "when BF and the maximum regenerative braking force value BE2 cannot be borne. The braking command value Bin is Between Bin2 and Bin3, the regenerative braking force value B
As E (Bin), the total braking force value B corresponding to the braking command value Bin
The value obtained by subtracting the front wheel hydraulic braking force value BFi corresponding to the braking command value Bin from "in" is output. This value represents the braking force that regenerative braking bears in order to match the ideal distribution approximate characteristic. If the braking command value Bin is greater than or equal to Bin3, BE2 is output as the regenerative braking force value BE (Bin).

In order to determine the regenerative braking force value BE (Bin) in this way, the brake controller 13 determines whether the input braking command value Bin is Bin2 or more (step S14). If the answer to this determination is a note, it is determined whether the braking command value Bin is Bin1 or more (step S1).
6). If the answer to this decision is no, the regenerative braking force value B
The regenerative braking force value Bin 'is output as E (Bin) (step S18). If the answer to the determination in step S16 is YES, BE1 is output as the regenerative braking force value BE (Bin) (step S20).

If the answer in step S14 is no, it is determined whether the braking command value Bin is larger than Bin3 (step S22). If the answer is NO, the regenerative braking force value BE (Bin) is determined from the total braking force value Bin "corresponding to the braking command value Bin" to the front wheel hydraulic control when the regenerative braking corresponding to the braking command value Bin is off. A value obtained by subtracting the power value BFi is output (step S24), and if the answer in step S22 is YES, as the regenerative braking force value BE (Bin),
BE2 is output (step S26).

As described above, in this embodiment, since the regenerative braking force value BE (Bin) is determined by using the dichotomy method, the determination can be performed easily and quickly. A function generator that outputs a regenerative braking force value BE (Bin) as shown in FIG. 8 when the braking command value Bin is input using a lookup table may be used.

The regenerative braking force value BE determined in this way
It is determined whether (Bin) is larger than the actual maximum regenerative braking force value BEmax determined in step S10 (step S2
8). This is the regenerative braking force value BE depending on the running condition.
This is because it may not be possible to output (Bin). When the determination in step S28 is YES, the actual maximum regenerative braking force value BEmax determined in step S10 is set as the regenerative braking force value BEmax as the regenerative braking force (step S
30). If the determination in step S28 is no,
As the regenerative braking force, the actual maximum regenerative braking force value BE (Bin) determined in step S12 is set as the regenerative braking force value BEmax (step S32).

Next, from the total braking force value Bin "to the regenerative braking force value B
Emax is subtracted to determine the share BM of the hydraulic braking force value (step S36). It should be noted that the total braking force value Bin "is, when the braking command value Bin is input in step S4,
For example, it is determined by calculation or a look-up table.

Following this, the share BM of the hydraulic braking force value
Is determined to be equal to or greater than the front wheel hydraulic braking force value BFi when the regenerative braking is off (step S38). This is provided in order to determine whether the share BM of the hydraulic braking force value can be borne by only the hydraulic braking of the front wheels.

If the determination in step S38 is negative, that is, the hydraulic braking of the front wheels can be alleviated, the hydraulic braking force value BF of the front wheels is set as the share BM of the hydraulic braking force values (step S40). The hydraulic braking force value BR is set to zero (step S42).

If the determination in step S38 is yes,
That is, since the front wheel hydraulic braking force value BF cannot be borne by the front wheel hydraulic braking alone, the front wheel hydraulic braking force value BF is set to the front wheel hydraulic braking force value BFi (step S44). The front wheel hydraulic braking force value BFi is subtracted to determine the rear wheel hydraulic braking force value BR (step S
46). After determining the braking force values of the front and rear wheels in this way, these regenerative braking force values BE are output to the system controller 11, and the hydraulic braking force value BF of the front wheels and the hydraulic braking force value BR of the rear wheels are determined. , Control valve unit 22
To control this.

Therefore, for example, when the braking command value Bin is not more than Bin1 as shown in FIG. 2, the regenerative braking force value Bin 'corresponding to this is output as the regenerative braking force value BE in step S12. If BE (Bin) is smaller than BE (max), BM becomes zero in step S36, and the judgment in step S38 is naturally no, and step S4
0 and S42 are executed, but since BM is zero, the hydraulic braking force of the front wheels 2, 2 and the rear wheels 4, 4 is also zero. Therefore, the hydraulic braking of the front wheels 2, 2 and the rear wheels 4, 4 is not performed,
Only regenerative braking is performed. This period corresponds to the section from zero to a shown in FIG.

In the section where the braking command value Bin is from Bin1 to Bin2, BE1 is output as the regenerative braking force value BE in step S12. Assuming that BE (Bin) is smaller than BE (max), BM is determined as Bin "-BE1 in step S36. This value is, for example, Δ1 shown in FIG. 2. This Δ1 is clear from FIG. Since it is smaller than BFi, the determination in step S38 is NO and step S38
At 40, BM (= Bin "-BE1) is output as BF and BR is made zero by S42. Therefore, regenerative braking of the rear wheels and hydraulic braking of the front wheels 2 and 2 are performed. It corresponds to the section from a to b shown in 2.

In the section where the braking command value Bin is from Bin2 to Bin3, Bin "-BFi is output as the regenerative braking force value BE in step S12. If BE (Bin) is smaller than BE (max), step S36 is performed. Therefore, BM is determined to be BFi, so that the determination in step S38 becomes NO, BFi is output as BF in step S40, and BR is set to zero in step S42. The regenerative braking force whose value is larger than BE1 and the hydraulic braking of the front wheels 2 and 2 are performed.This period corresponds to the section from b to c shown in Fig. 1. In this section, the regenerative braking force value is Since it is increased from BE1 toward BE2, the regenerative efficiency is improved and it matches the ideal distribution approximation characteristic.

In the section where the braking command value Bin exceeds Bin3, BE2 is output as the regenerative braking force value BE (Bin) in step S12. If BE (Bin) is smaller than BE (max), BM is output as Bin "-BE2 in step S36. If this value is Δ2 in FIG. 2, this Δ2 is as shown in FIG. Since it is larger than BFi, the determination in step S38 becomes YES, and in step S44, BFi is output as BF and S4 is output.
BR is set to Bin "-BE2-BFi by 6. Therefore, regenerative braking of the rear wheels, hydraulic braking of the rear wheels, and front wheels 2, 2
Hydraulic braking is performed. This period corresponds to the section after c shown in FIG. In this section, the hydraulic braking of the rear wheels bears a portion of the braking force that the rear wheels bear that the rear wheels cannot bear in order to match the ideal distribution approximate characteristic.

As described above, in this embodiment, since the regenerative braking has a surplus after the distribution of the braking forces of the front wheels and the rear wheels matches the ideal approximate characteristic, the regenerative braking force is increased to the maximum regenerative braking force. By not using hydraulic braking on the rear wheels as much as possible, the regenerative efficiency is increased and the necessary braking force is secured. Then, when the maximum regenerative braking force alone cannot match the braking force of the rear wheels to the ideal distribution, the hydraulic braking force of the rear wheels is used to match the braking force of the rear wheels. Therefore, even in such a state, the required braking force can be secured and the ideal distribution approximate characteristic can be matched, and the energy can be recovered by the maximum regenerative braking.

The second embodiment will be described with reference to FIGS. 9 to 12. The second embodiment also has substantially the same configuration as that of the first embodiment, but as is clear from the comparison between FIG. 10 and FIG. 8, the regenerative braking force value BE (Bin)
When a predetermined regenerative braking force value BE1 that is smaller than the maximum regenerative braking force value is reached, the value is maintained thereafter and does not increase. For example, in a small electric vehicle or the like, the possibility of braking at the maximum regenerative braking force value is stochastically small, so the running stability of the vehicle is significantly impaired in the range of braking force during normal operation, which is frequently used. It is experimentally set to a value that does not exist.

Therefore, BE (Bi
The operation of the system controller 13 is the same as that of the first embodiment except that the determination routine of n) is simplified as shown in FIG. In the routine for determining BE (Bin), it is first judged whether the braking command value Bin is larger than a predetermined value Bin1 (step S50). If this determination is NO, the braking force value Bin 'proportional to the braking command value Bin at that time is output as the regenerative braking force value BE (Bin) (step S52). If the determination in step S50 is YES, the predetermined regenerative braking force value BE1 is set to the regenerative braking force value BE (Bin).
(Step S54).

Even in the case of such a configuration, as shown in FIG. 11, the regenerative braking force is first increased to a (= BE1). During this period, after step S12 of FIG. 4, if the determined regenerative braking force value is smaller than BEmax, steps S28, S32, S36, S38, S40, S4.
2, S44 is executed. Next, while maintaining this regenerative braking force, the hydraulic braking force of the front wheels is increased until it matches the ideal distribution approximation characteristic (see point b in FIG. 11). During this time,
Again, steps S28, S32, S36, S38, S
40, S42, and S44 are executed. After that, the braking force of the front wheels and the rear wheels is increased in accordance with the ideal distribution approximate characteristic. Since the regenerative braking force value of the rear wheels is fixed to BE1, the shortage is compensated by the hydraulic braking force of the rear wheels. Therefore, as shown in FIG. 12, the hydraulic braking force BR of the rear wheels is exerted after the ideal distribution approximate characteristic is matched. That is, steps S28, S32, S36, S38, S44, S4
6, S48 is executed.

In the second embodiment, when the braking command value Bin becomes Bin1 or more, the regenerative braking force value is held at the value BE1 which is less than the maximum regenerative braking force value. When importance is attached to, the retained regenerative braking force value may be the maximum regenerative braking force value. Further, in both of the above-described embodiments, it is determined whether the regenerative braking force value BE (Bin) determined in step S12 is equal to or less than the maximum regenerative braking force value BEmax that can be actually output depending on the running state, and the processing corresponding thereto To perform steps S28, S30, S32
However, these processes are unnecessary in some cases.

[0056]

As described above, in the braking method according to the first aspect, after the regenerative braking force reaches the predetermined value, the hydraulic braking of the driven wheels is started while maintaining the regenerative braking force. ,
It is possible to match the braking distribution between the driving wheels and the driven wheels to the ideal distribution approximate characteristic while attempting to recover the energy by regenerative braking, and it is possible to secure the necessary braking force while ensuring the running stability of the vehicle.

In the braking method according to the second aspect of the present invention, the braking force distribution between the braking force by the hydraulic braking of the driven wheels and the regenerative braking force of the driving wheels matches the ideal distribution approximation characteristic, and the driving wheels are When the regenerative braking force of is the maximum value, the hydraulic braking of the drive wheels is started so as to match the ideal distribution approximate characteristic. That is, since the maximum regenerative braking force is exerted and the hydraulic braking force of the driven wheel and the driving wheel is increased so as to match the ideal distribution approximate characteristic, the maximum energy can be recovered and the ideal A distribution approximation characteristic is obtained.

In the braking method according to the third aspect, after the regenerative braking force of the drive wheels reaches a predetermined value less than the maximum value, the hydraulic braking of the driven wheels is started while maintaining the regenerative braking force,
The hydraulic braking of the driven wheels is increased until the braking force distribution of the driven wheels and the driving wheels matches the preset ideal distribution approximate characteristic, and the regenerative braking force is maintained at the predetermined value even after the hydraulic pressure braking of the driven wheels matches the ideal distribution approximate characteristic. Since the hydraulic braking force of the driven wheels and the driving wheels is increased as it is, it is possible to recover the regenerative energy while maintaining the running stability.

In the braking device according to the fourth aspect, the regenerative braking force determination means outputs the regenerative braking force value of a predetermined value when the braking command value is equal to or more than the first set value, and the regenerative braking force value and the braking The hydraulic braking force value is determined based on the braking force value corresponding to the command, and the hydraulic braking force value is distributed by the distributing means to the driven wheel hydraulic braking force value and the driving wheel hydraulic braking force value. The distribution is such that the driving wheel braking force, which is the sum of the braking force of the driving wheel due to the regenerative braking force value and the braking force of the driving wheel due to hydraulic braking, and the hydraulic braking force of the driven wheels, approximate the ideal distribution characteristics. Have been to. Therefore, when the braking force of the drive wheels is sufficient with only the regenerative braking force value, hydraulic braking of the driving wheels is not performed, but with the regenerative braking force value alone, the braking force of the driving wheels is insufficient. In this case, hydraulic braking of the drive wheels is also performed, energy is recovered by regenerative braking, and the braking force that matches the ideal approximate characteristics can be distributed.

In the braking device according to the fifth aspect, the regenerative braking force value determining means, when the braking command value equal to or more than the first set value is input, the regenerative braking force value set to be smaller than the maximum regenerative braking force value. Output the power value. Therefore, the regenerative braking force is held at this value, so by properly selecting this value, the running stability of the vehicle will not be significantly impaired in the range of the braking force during normal operation that is frequently used. Can be

In the braking device according to the sixth aspect, the regenerative braking force value determining means outputs the maximum regenerative braking force value and holds it when a braking command value equal to or greater than the second set value is input. The maximum regenerative braking force can be obtained, and the energy recovery efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a front wheel braking force and a rear wheel braking force in an embodiment of a braking device according to the present invention.

FIG. 2 is a diagram showing braking forces of front wheels and rear wheels with respect to a braking command value in the first embodiment.

FIG. 3 is a block diagram of the first embodiment.

FIG. 4 is a flowchart of the first embodiment.

FIG. 5 is a diagram showing a relationship between a braking command value and a front wheel braking force value when regenerative braking is off in the first embodiment.

FIG. 6 is a diagram showing a relationship between a motor speed and a regenerative braking force value according to the first embodiment.

FIG. 7 is a flowchart of a routine for determining a regenerative braking force according to the first embodiment.

FIG. 8 is a diagram showing a relationship between a braking command value and a regenerative braking force value according to the first embodiment.

FIG. 9 is a flowchart of a routine for determining a regenerative braking force according to the second embodiment.

FIG. 10 is a diagram showing a relationship between a braking command value and a regenerative braking force value according to the second embodiment.

FIG. 11 is a diagram showing a braking force applied to a front wheel and a rear wheel according to the second embodiment.

FIG. 12 is a diagram showing braking forces of front wheels and rear wheels with respect to a braking command value in the second embodiment.

FIG. 13 is a diagram showing a relationship between a front wheel braking force and a rear wheel braking force in a conventional braking device.

[Explanation of symbols]

2 front wheel 4 rear wheel 6 motor 8 battery 11 system controller 12 rear wheel hydraulic brake (rear wheel hydraulic braking means) 13 brake controller (regenerative braking force determination means, hydraulic braking force value determination means, distribution means) 14 front wheel hydraulic brake ( Front wheel hydraulic braking means) 18 Brake pedal

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Ashikaga 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Meidensha Co., Ltd. (72) Inventor Yoshihiro Matsumura 2-70-58 Higashiuraga-cho, Yokosuka City, Kanagawa Prefecture ( 72) Inventor, Togo, No. 6-35, Nakamichi, Tarumi-ku, Kobe-shi, Hyogo (56) References JP-A 5-161210 (JP, A) JP-A 6-153313 (JP, A) JP-A 7-203602 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60L 7/24

Claims (6)

(57) [Claims] 1. At least at the time of initial braking, it is connected to a motor that uses a battery as an energy source to be driven, and is hydraulically braked on a drive wheel capable of being hydraulically and regeneratively braked by operating a brake pedal, and the brake. Prohibiting hydraulic braking of the driven wheels that can be hydraulically braked by operating the pedal, actuating regenerative braking of the drive wheels, and when the regenerative braking force of the drive wheels reaches a predetermined value equal to or less than the maximum value,
This regenerative braking force is retained to start hydraulic braking of the driven wheels, and the retention of the regenerative braking force is continued until the braking force distributions of the driven wheels and the driving wheels match the preset ideal distribution approximation characteristics. A method of braking an electric vehicle, characterized by: 2. The braking method for an electric vehicle according to claim 1, wherein the braking force distribution of the driven wheels and the driving wheels matches a preset ideal distribution approximation characteristic, and the regenerative braking force of the driving wheels is maximum. When the value is a value, the braking method for an electric vehicle is characterized in that the hydraulic braking of the drive wheels is started in conformity with the ideal distribution approximate characteristic and the braking force thereafter is secured. 3. At least at the time of initial braking, it is connected to a motor that uses a battery as an energy source to be driven, and hydraulic braking is performed on a drive wheel that can be hydraulically and regeneratively braked by operating a brake pedal, and the brake. Prohibiting hydraulic braking of the driven wheels that can be hydraulically braked by operating the pedal, actuating regenerative braking of the drive wheels, and when the regenerative braking force of the drive wheels reaches a predetermined value less than the maximum value,
The hydraulic braking of the driven wheels is started by holding this regenerative braking force, and after the braking force distribution of the driven wheels and the driving wheels matches the preset ideal distribution approximation characteristic, the characteristics are matched with this characteristic and A braking method for an electric vehicle, characterized by starting hydraulic braking of driving wheels. 4. A motor capable of driving a drive wheel using a battery as an energy source to regeneratively brake the drive wheel, hydraulic braking means provided on each of the drive wheel and the driven wheel, and a brake pedal in response to an operation of the brake pedal. When the generated braking command value is input and the braking command value is smaller than a predetermined first set value, a regenerative braking force value having a value corresponding to the braking command value is output, and the braking command value is the first value. A regenerative braking force determination means that outputs a predetermined constant value of the regenerative braking force value when it is equal to or greater than a set value, and a hydraulic braking force value based on the braking force value corresponding to the braking command value and the regenerative braking force value. A hydraulic braking force value determining means for determining, and the hydraulic braking force value is divided into a driving wheel hydraulic braking force value and a driven wheel hydraulic braking force value, in which the braking command value is equal to or more than the first set value. , The driving wheel braking force value and the And distribution means wheel braking force value and is performed to approximate the ideal distribution characteristic, a braking device for an electric vehicle equipped. 5. The braking device for an electric vehicle according to claim 4, wherein the first set value is set smaller than a maximum regenerative braking force value determined by the motor. . 6. The braking device for an electric vehicle according to claim 4, wherein the regenerative braking force value determining means sets a value smaller than a maximum regenerative braking force value determined by the motor, corresponding to the first set value. Output the regenerative braking force value
A braking device for an electric vehicle, which outputs the maximum regenerative braking force value when a braking command value equal to or larger than a second set value set to be larger than the first set value is input.