JP3395435B2 - Regenerative braking control 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 regenerative braking control device mounted on an electric vehicle for controlling regenerative braking torque.

[0002]

2. Description of the Related Art Generally, hydraulic braking and regenerative braking are used as braking means for electric vehicles. Of these, the control of the regenerative braking force can be realized as the control of the output torque of the motor. First, when the required braking force is given as the amount of depression of the brake pedal by the vehicle operator, more specifically, the stroke of the brake pedal or the hydraulic pressure in the brake master cylinder, the required braking force is the maximum regenerative braking torque Tmax, that is, The maximum value of the regenerative braking torque allowed to be output from the motor is compared. When the required braking force exceeds the maximum regenerative braking torque Tmax,
The regenerative braking force is controlled with the maximum regenerative braking torque Tmax as a target value (torque command value). When the required braking force does not exceed the maximum regenerative braking torque Tmax, the maximum regenerative braking torque Tmax is divided according to the required braking force, and the torque command value is determined accordingly. By such control, it is possible to obtain the regenerative braking force according to the depression amount of the brake pedal.

Further, since regenerative braking is a braking method in which braking energy is recovered from a traveling motor by regenerating electric power to an on-vehicle battery, in controlling the braking force on the drive wheel side, regenerative braking is performed against hydraulic braking force. The system is preferably configured so that the braking force acts preferentially. As a result, the travelable distance per charge of the battery can be extended, and a more economical electric vehicle can be realized. For that purpose, for example, a differential pressure valve may be provided between the master cylinder and the wheel cylinder on the drive wheel side. This differential pressure valve has a shallow depression of the brake pedal, so the pressure of the brake fluid in the master cylinder (master cylinder fluid pressure)
While the pressure difference of the brake fluid (wheel cylinder fluid pressure) in the wheel cylinder on the drive wheel side is low, the closed state is maintained and the differential pressure is maintained. While the differential pressure valve is closed
If only the above-described regenerative braking is executed, the braking energy can be efficiently regenerated. In addition, the differential pressure valve is designed to open when the differential pressure increases and approaches the maximum regenerative braking torque Tmax equivalent value. Then, after the regenerative braking torque reaches the maximum regenerative braking torque Tmax, the difference between the required braking force and the regenerative braking torque is realized as the hydraulic braking force, so that it is possible to prevent the braking force from being excessive or insufficient.

The maximum regenerative braking torque Tmax is, for example,
As shown in FIG. 5 , it depends on the motor rotational speed RMOT (see Japanese Patent Laid-Open No. 5-176406). In this figure, the maximum regenerative braking torque Tmax is constant in the medium-low speed region where the rotation speed RMOT is N2 or more and N3 or less, and the motor output is limited by the torque (constant torque region), but N3 or more and N4 or more. In the following high speed range, the product of the maximum regenerative braking torque Tmax and the rotational speed RMOT is constant, and the limitation is imposed not by torque but by power (constant power range). Further, in the region where the rotational speed RMOT is N1 or less, the maximum regenerative braking torque Tmax is set to 0 in order to initially introduce the master cylinder hydraulic pressure generated according to the depression of the brake pedal, for example, with the proportioning characteristic. In the region where the rotation speed RMOT is N1 or more and N2 or less, therefore, the maximum regenerative braking torque Tmax sharply falls as the rotation speed RMOT decreases. In order to determine the torque command value with reference to such control characteristics, the rotational speed RMO
A means for directly or indirectly detecting T, for example, a rotation sensor such as a resolver is required.

[0005]

When controlling the regenerative braking torque according to such characteristics, it is preferable to smooth the torque command value in order to improve the brake feeling in the extremely low speed range.

For example, consider a case where rattling of a mechanical system or torsional vibration of a vehicle system occurs. The influence of this vibration or the like appears in the output of the rotation sensor in the form of vibration or the like. Even if the output of the rotation sensor slightly vibrates, the control and the feeling are greatly affected in the rotation speed region where the maximum regenerative braking torque Tmax is constant or in the rotation speed region where the change of the maximum regenerative braking torque Tmax is gentle. Absent. However, in the example of FIG. 5 , in a region where the maximum regenerative braking torque Tmax changes abruptly according to the change in the rotational speed RMOT, such as in the region where the rotational speed RMOT is N1 or more and N2 or less, the output of the rotation sensor and the rotation When vibrations appear in the detected value of several RMOT, vibrations also appear in the torque command value and accordingly vibrations in the motor torque. In order to prevent such a phenomenon, low-pass filtering (so-called smoothing) may be applied to the torque command value. As a result, it is possible to remove a relatively high frequency component of the vibration of the torque command value, which causes deterioration of the brake feeling. But,
This alone may cause a new discomfort problem. That is, when the torque command value is set when the brake pedal is started to be pressed or when the brake pedal is started to be released, the response of the regenerative braking force to the depression of the brake pedal becomes dull, and a feeling of strangeness appears.

The present invention has been made to solve the above problems, and pays attention to the motor rotation speed and the brake pedal depressing speed to execute regenerative braking control so that the brake pedal is operated. An object of the present invention is to provide a regenerative braking device that does not feel discomfort and has a good brake feeling even in a transitional state such as when the driver starts to depress or starts to depress.

[0008]

In order to achieve such an object, the first structure of the present invention includes means for detecting the rotational speed of the traveling motor and a region where the maximum regenerative torque is constant.
So that no predetermined revolution speed and the maximum regenerative braking torque characteristic is realized, and means for determining in accordance with a torque command value indicating the required regenerative braking torque to the rotation speed of the traveling motor, traveling on the basis of the torque command value And a means for controlling the regenerative braking torque of the motor, in a regenerative braking control device mounted on an electric vehicle, wherein the rotational speed of the traveling motor is the maximum regenerative torque in the above rotational speed vs. maximum regenerative braking torque characteristic.
It is on the lower rotation side than a certain range and the maximum regenerative braking torque
Means for determining whether or not it belongs to a rotation speed region that changes according to changes in the rotation speed, and means for allowing time variation of the torque command value when it is determined that the rotation speed region does not belong, as compared with other rotation speed regions And are provided.

According to a second aspect of the present invention, a means for directly or indirectly detecting the depression amount of the brake pedal and a torque command value indicating a required regenerative braking torque are determined according to the depression amount of the brake pedal. And a means for controlling the regenerative braking torque of the traveling motor on the basis of the torque command value, in a regenerative braking control device mounted on an electric vehicle, a change over time in which the depression amount of the brake pedal exceeds a predetermined level. A means for determining whether or not it is shown, and a means for allowing time variation of the torque command value when it is decided that it is shown, as compared with a case where it is decided not to show it. To do .

[0010]

In the first configuration of the present invention, the maximum regenerative braking torque is constant with respect to the detected rotational speed of the traveling motor.
Is on the lower rotation side than the range of
It is determined whether or not the dynamic torque belongs to the fluctuating region.
As a result, when it is determined that the torque command value does not belong, the time variation of the torque command value is allowed as compared with other rotational speed regions. For example, small annealing is performed as compared with other rotation speed regions. Therefore, even if the time variation of the torque command value is allowed, the time variation of the torque command value is allowed in the rotation speed range in which the brake feeling is not deteriorated due to the vibration of the motor rotation speed detection value. Therefore, the responsiveness of the regenerative braking force to the depression of the brake pedal in the transient state is improved, and the discomfort is reduced.

In the second configuration of the present invention, first, the depression amount of the brake pedal is detected directly or indirectly. When the amount of depression of the brake pedal shows a time change exceeding a predetermined amount, the time variation of the torque command value is allowed as compared with the case where it is not shown. For example, the moderation is reduced when the vehicle operator is depressing the brake pedal. Therefore, the responsiveness of the regenerative braking force to the depression of the brake pedal in the transient state is improved, and the discomfort is reduced.

[0012]

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the configuration of an electric vehicle suitable for implementing the present invention. The electric vehicle shown in this figure is a front-wheel drive vehicle, and front wheels Wf are driven by an AC motor 10. Electric power for driving the motor 10 is supplied to the motor 10 from a battery (not shown) via the inverter 12. The inverter 12 is a circuit that converts the DC power supplied from the battery into AC power and then supplies the AC power to the motor 10. The operation of the inverter 12 is controlled by the EV-ECU 16 based on the output of the resolver 14 and the like. For example, when the vehicle operator depresses the accelerator pedal, the EV-ECU 16 determines the torque command value according to the amount of depressing and referring to the rotation speed (or rotor position) of the motor 10 detected by the resolver 14. It This torque command value indicates the power running torque to be output from the motor 10. EV-ECU16
Controls the electric power conversion operation in the inverter 12 based on the determined torque command value, thereby controlling the current flowing through the motor 10 so that the torque command value is realized as the power running torque.

The electric vehicle shown in this figure has a hydraulic (for example, hydraulic) braking mechanism as a braking means. First, when the vehicle operator depresses a brake pedal (not shown), hydraulic pressure is generated in the master cylinder 18. On the other hand, a wheel cylinder 20 is provided on each of the brake wheels of the front wheels Wf and the rear wheels Wr. Therefore, when the hydraulic pressure generated in the master cylinder 18 in response to the depression of the brake pedal (hereinafter, master cylinder hydraulic pressure) is transmitted to the wheel cylinder 20, the hydraulic braking force acts on the front wheels Wf and the rear wheels Wr. To do.

The hydraulic braking mechanism shown in this figure includes various valves interposed between the master cylinder 18 and the wheel cylinder 20. The proportioning and bypass (P & B) valve 22 has a function of proportionally reducing the master cylinder hydraulic pressure and then bypassing it to the wheel cylinder 20 side. In addition, anti-brake system (AB
The valve 24 for S) controls the wheel cylinder 2 under the control of the ABS-ECU 26 in order to prevent the front wheel Wf from locking.
The hydraulic pressure at 0 (hereinafter, wheel cylinder hydraulic pressure) is changed according to a predetermined waveform. Further, the mechanical valve 28 is a valve for generating a difference between the master cylinder hydraulic pressure and the wheel cylinder hydraulic pressure as necessary, and can be used for regenerative priority control and control of front and rear wheel braking force distribution. Each relief valve 30 is provided in parallel with the corresponding mechanical valve 28, and opens in response to a command from the EV-ECU 16. When the relief valve 30 is opened, the master cylinder hydraulic pressure is immediately introduced to the wheel cylinder 20 side.

More specifically, the mechanical valve 28 substantially shuts off the hydraulic passage while the master cylinder hydraulic pressure is low (for example, the master cylinder hydraulic pressure is greatly proportionally reduced and introduced to the wheel cylinder 20 side). When the differential pressure before and after the master cylinder hydraulic pressure rises above a predetermined valve opening value as the master cylinder hydraulic pressure rises, the mechanical valve 28 opens and the wheel cylinder hydraulic pressure starts to rise. After that, the differential pressure across the mechanical valve 28 is maintained while the master cylinder hydraulic pressure continues to rise. When the master cylinder hydraulic pressure starts to drop, the differential pressure across the mechanical valve 28 also drops accordingly. The differential pressure before and after that is 0
Then, as the master cylinder hydraulic pressure decreases, the wheel cylinder hydraulic pressure starts to decrease.

Therefore, even if the vehicle operator depresses the brake pedal, the hydraulic braking force does not act while the depression is shallow, and when the depression becomes deep, the hydraulic braking force reduced by the valve opening value is obtained. Start to work. When the vehicle operator depresses the brake pedal, the hydraulic braking force starts to be reduced when the depression becomes shallow.

In the regeneration priority control in this embodiment, the hydraulic braking force is cut off within the limit corresponding to the valve opening value, while the difference between the required braking force (stepping amount of the brake pedal) and the hydraulic braking force is regenerated. Based on the idea that it will be covered by braking force,
Has been realized. Further, the braking force distribution between the front and rear wheels can be optimized by appropriately setting or controlling the valve opening value of each mechanical valve 28. In implementing the present invention, any valve that can be used when controlling the hydraulic braking force according to the master cylinder hydraulic pressure can be used. Therefore, a proportioning valve or the like may be used instead of the above mechanical valve 28 (generally a differential pressure valve).

FIG. 2 shows the entire procedure of the regenerative braking control executed in this embodiment. The procedure shown in this figure is a procedure executed by the EV-ECU 16.

When executing the regenerative braking control, the EV
-ECU 16 first determines whether regenerative braking is being executed (100). For example, the EV-ECU 16 should not perform the regenerative braking when the acceptability of the battery (not shown) is significantly reduced and the battery cannot be charged with the regenerative power from the motor 10. to decide. Specifically, the regenerative torque amount to be output by the motor 10 is set to 0 (102), and the regenerative torque amount is used as a torque command value to control the motor 10 (104).

When regenerative braking is possible, E
The V-ECU 16 sets the rotational speed RMOT of the motor 10 by the resolver 14 (106), the master cylinder hydraulic pressure by the hydraulic sensor 32 provided on the master cylinder 18 side as viewed from the mechanical valve 28 (108), and the mechanical valve 28 by the mechanical valve 28. As seen, the hydraulic pressure sensor 34 provided on the wheel cylinder 20 side indicates the wheel cylinder hydraulic pressure (11
0), respectively. The EV-ECU 16 subtracts the wheel cylinder hydraulic pressure from the detected master cylinder hydraulic pressure to obtain the differential pressure P across the mechanical valve 28 on the front wheel Wf side.
Is calculated (112). Further, in step 112, the master cylinder hydraulic pressure change amount ΔP is calculated by subtracting the differential pressure P calculated when the previous step 112 was executed from the differential pressure P calculated this time.

The EV-ECU 16 further executes step 1
The characteristics shown in FIG. 5 are referred to by the motor rotation speed RMOT detected in 06, and the maximum regenerative braking torque T
I asked Mel the max. The EV-ECU 16 proceeds to step 112.
If the differential pressure P calculated in step 2 exceeds the valve opening value equivalent value,
The regenerative torque amount, that is, the torque command value related to the regenerative braking is calculated, and if it does not exceed, the regenerative torque amount is calculated by dividing the maximum regenerative braking force torque Tmax with the differential pressure P (114). Therefore, the amount of regenerative torque is Tmax ×
It is given by P / Pk (Pk: valve opening value of the mechanical valve 28). The regenerative torque amount calculated in this way is used for motor control (104) after being subjected to a smoothing process (116).

FIG. 3 shows the contents of the processing executed in step 116 in the first embodiment of the present invention. The process shown in this figure is a process of performing low-pass filtering (moderation) on the regenerative torque amount T determined in step 114. Further, in the present embodiment, in this smoothing processing, according to the motor rotation speed RMOT detected in step 104 and the absolute value | ΔP | of the master cylinder hydraulic pressure change amount calculated in step 112,
The annealing amount is being switched.

[0025] That is, as described above, when the motor rotational speed RMOT belongs to the rotational speed region of the region or around the N1 or N2 or less in FIG. 5, the twist of the backlash or the vehicle system of the mechanical system There is a possibility that the output of the resolver 14 will vibrate due to the vibration, and this vibration will cause the regenerative torque amount T to vibrate. The smoothing process for relaxing the time change of the regenerative torque amount T is effective in preventing the deterioration of the brake feeling due to this vibration, but on the other hand, the vehicle operator is just stepping on or depressing the brake pedal. Under the situation, the response of the regenerative braking torque to the operation of the brake pedal becomes dull. In the present embodiment, these problems are solved or reduced by switching the filter coefficient of the regression type low-pass filter according to the detected value of the motor rotation speed RMOT and the detected value of the absolute value | ΔP | of the master cylinder hydraulic pressure change amount. is doing.

First, at step 200 in FIG. 3, the motor rotation speed RMO detected at step 106.
T is compared with a predetermined threshold value RMOT0. The threshold RMOT0, for example, is set to a slightly higher rotational speed than the rotational speed N2 in FIG. When it is determined in step 200 that RMOT <RMOT0, it can be considered that the motor rotation speed RMOT is in the region of N1 or more and N2 or less shown in FIG. 5 or a region in the vicinity thereof, and conversely, RMOT ≧ RMOT0. If determined, it can be considered not to be in such an area. Also, step 2
00, when RMOT ≧ RMOT0 is determined,
The EV-ECU 16 further compares the absolute value | ΔP | of the master cylinder hydraulic pressure change amount with a predetermined threshold value ΔP0 (202). This threshold value ΔP0 is set so that it can be determined whether or not the vehicle operator is in a transitional state in which he or she is just stepping on or returning the brake pedal. When it is determined in step 202 that | ΔP | <ΔP0, it can be considered that the brake pedal is not in the transitional state, and conversely, when | ΔP | ≧ ΔP0 is determined, the transition is just about to occur. Can be considered a state.

Therefore, these steps 200 and 202
In accordance with the result of the determination in step 1, the regression type low-pass filtering using different filter coefficients A to C is executed (204, 206, or 208), so that the level of the motor rotation speed RMOT or the depression state of the brake pedal is not adjusted. It is possible to add benefits. Steps 204, 20
6 or 208, the regenerative torque amount T ₀ after the smoothing
Is set to the regenerative torque amount T in step 210 and used for the motor control in step 104, and when step 116 is executed next, step 204,
It is subjected to processing in 206 or 208. In addition, when the processing shown in step 204, 206, or 208 is expressed by a mathematical expression, the following expression (1), (2), or (3), respectively,
It becomes an expression like. However, A to C are filter coefficients, and have a relationship of C <B <A.

[0028]

## EQU1 ## _Tn = _Tn-1 + (T- _Tn-1 ) / A (1) _Tn = _Tn-1 + (T- _Tn-1 ) / B ... (2) _Tn = Tn _-1 + (T-Tn _-1 ) / C (3) As described above, according to the present embodiment, the motor rotation speed RMOT.
Since the moderation amount is switched according to the value of, the brake feeling can be improved in the rotational speed range where the influence of rattling of the mechanical system and torsional vibration of the vehicle system becomes apparent. It is possible to improve the responsiveness of the regenerative braking torque to the brake operation by reducing the amount of smoothing in the rotation speed region where the influence of such a phenomenon does not become apparent. Further, even if the motor rotation speed RMOT is high, the absolute value of the master cylinder hydraulic pressure change amount | ΔP
When | is small, the moderation amount is set to be slightly large, so that it is possible to preferably eliminate the influence of vibration and the like even in a region where the motor rotational speed RMOT is high, and when the brake pedal depressing speed is high. It can reduce the disguise and reduce the feeling of strangeness.

FIG. 4 shows E in the second embodiment of the present invention.
The content of the smoothing process executed by the V-ECU 16 is shown. This embodiment is different from the above-described first embodiment in that instead of steps 204-208, steps 204A-
208A is being executed. Step 204A
208A, the following equations (4)-
As a result of (6), the regenerative torque amount T is smoothed.
However, in using these equations, step 1
The regenerative torque amount T calculated in 14 is used as T _n . Further, for example, N _A is set to 64, N _B is set to 20, and N _C is set to a score of 2.

[0030]

[Equation 2] Thus, by using the moving average calculation instead of the regression type low pass filtering in the first embodiment,
The same effect as the first embodiment can be obtained.

[0031]

[0032]

In the above description, the depression amount of the brake pedal by the vehicle operator is detected as the hydraulic pressure on the master cylinder 18 side of the mechanical valve 28 by the hydraulic sensor 32, but instead of this, the stroke of the brake pedal is detected. You may make it detect directly. However, since the master cylinder hydraulic pressure detected by the brake sensor 32 can be used for the differential pressure calculation in step 112, and further for the regenerative torque amount calculation in step 114, the master cylinder hydraulic pressure which is the detection output of the hydraulic pressure sensor 32 is used. This simplifies the system configuration. Further, the wheel speed or the like may be used instead of the motor rotation speed RMOT.
In addition, in each of the above-described embodiments, the motor rotation speed RM
Determination of OT and absolute value of master cylinder hydraulic pressure change |
Although the determination regarding ΔP | or the master cylinder hydraulic pressure change speed P ^· is executed together, the present invention is not limited to an example in which both are executed together. For example, a configuration including only switching of the smoothing amount according to the motor rotation speed RMOT,
The present invention can also be implemented as a configuration including only the switching of the smoothing amount according to the absolute value | ΔP | of the master cylinder hydraulic pressure change amount or the master cylinder hydraulic pressure change speed P ^· .

[0034]

As described above, according to the first configuration of the present invention, the detected value of the rotation speed of the traveling motor is on the lower rotation side than the region where the maximum regenerative braking torque is constant, and the maximum regeneration is performed.
When the braking torque does not belong to the range that changes with the change in the rotation speed, the time change of the torque command value is allowed as compared to the other rotation speed range, so even if the time change of the torque command value is allowed, the motor Time variation of the torque command value is allowed in the rotational speed range where the brake feeling is not deteriorated due to the vibration of the rotational speed detection value.Therefore, the regenerative braking force against the depression of the brake pedal in the transient state is Responsiveness is improved and discomfort is reduced.

According to the second configuration of the present invention, when the amount of depression of the brake pedal shows a time change exceeding a predetermined degree, the time variation of the torque command value is allowed as compared with the case where it is not shown. Therefore, the responsiveness of the regenerative braking force to the depression of the brake pedal in the transient state is improved, and the discomfort is reduced.

[0036]

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a system configuration of an electric vehicle.

FIG. 2 is a flowchart showing an entire regenerative braking control procedure.

FIG. 3 is a flowchart showing a flow of a smoothing process according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing a flow of a smoothing process according to a second embodiment of the present invention.

FIG. 5 is a diagram showing an example of a motor speed vs. maximum regenerative braking torque characteristic.

[Explanation of symbols]

10 motors, 12 inverters, 16 EV-EC
U, 18 master cylinder, 20 wheel cylinder, 2
8 mechanical valve, 32, 34 oil pressure sensor, Wf front wheel,
Wr rear wheel, RMOT motor rotation speed, ΔP master cylinder hydraulic pressure change amount, P · master cylinder hydraulic pressure change speed, Tn regenerative torque amount after annealing at time n, T
Regenerative torque amount to output, A to C, NA to NC filter coefficient.

Claims (2)

(57) [Claims] 1. A means for detecting the rotational speed of a traveling motor and a regenerative braking torque required to realize a predetermined rotational speed vs. maximum regenerative braking torque characteristic including a region where the maximum regenerative torque is constant. A regenerative braking control device mounted on an electric vehicle, comprising: a means for determining a torque command value according to the number of revolutions of a traveling motor; and a means for controlling a regenerative braking torque of a traveling motor based on the torque command value. , The speed of the traveling motor is lower than the range where the maximum regenerative torque is constant in the above-mentioned rotational speed vs. maximum regenerative braking torque characteristics.
It is on the rotation side and the maximum regenerative torque fluctuates according to the fluctuation of the rotation speed.
Means for determining whether or not it belongs to a rotation speed range, and, when it is determined that the rotation speed range does not belong, a means for permitting a time variation of the torque command value compared to other rotation speed ranges. Regenerative braking control device. 2. A means for directly or indirectly detecting the depression amount of the brake pedal, a means for determining a torque command value indicating a required regenerative braking torque according to the depression amount of the brake pedal, and a torque command value. And a means for controlling the regenerative braking torque of the traveling motor based on the above, and in the regenerative braking control device mounted on the electric vehicle, it is determined whether or not the depression amount of the brake pedal shows a time change exceeding a predetermined degree. And a means for permitting the time variation of the torque command value in the case of being determined to be present, as compared with the case of not being shown.