JP2009278840A - Regenerative braking control unit of electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform regenerative braking regulation in accordance with a braking slip of a driving wheel, so as not to exceedingly deviate a distribution of a braking force in front and rear wheels from an ideal distribution, even under any degree of required deceleration. <P>SOLUTION: A distribution rate in the braking force of driving wheels (rear wheels) is determined to value constant an approximate to an ideal distribution characteristic of the braking force in the front and rear wheels in the case of small slipping as shown in α of the distribution characteristic of the braking force in the front and rear wheels, when the slipping degree Slip of the driving wheels (rear wheels) amounts to a small value on braking; and as constant in the value approximate to the ideal distribution characteristic of the braking force in the front and rear wheels, in the case of large slipping as shown in β of the distribution characteristic of the braking force in the front and rear wheels, as the slipping degree Slip of the driving wheels (rear wheels) amounts to a larger value on braking. A regenerative braking force is regulated in the driving wheels (rear wheels) in accordance with the slipping degree Slip, based on the distribution rate in the braking force of the driving wheels (rear wheels). When giving a comment on a case where the degree of slipping is small, therefore, an operating point moves from A3 to A5, B3 to B5 when regulating the regenerative braking force, thereby minimizing deviation from the ideal distribution characteristic of the braking force in the front and rear wheels irrespective of the level of deceleration. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes an engine and a motor / generator mounted as a prime mover, and an electric vehicle equipped with only an electric motor as a prime mover, or a hybrid vehicle capable of electric travel using only the motor / generator, or hybrid travel using the engine and / or motor / generator. A regenerative braking control device for an electric vehicle such as an automobile, especially when a driving wheel regeneratively braked by a motor / generator generates a braking slip, the braking slip of the driving wheel is prevented to prevent the turning behavior from becoming unstable. The present invention relates to a regenerative braking restriction technique for solving the problem.

As a regenerative braking restriction technique when the driving wheel during regenerative braking generates a braking slip, for example, as described in Patent Document 1, for example,
The driving wheel during regenerative braking generates braking slip because the wheel speed of the other rear wheel or front wheel, which is the driving wheel, is relatively lower than the wheel speed of the front wheel or rear wheel, which is the driven wheel that is not driven. Therefore, a technique has been proposed in which the regenerative braking force is limited according to the wheel speed deviation of the driving wheel speed (the driving wheel braking slip amount) with respect to the driven wheel speed.
In this proposed technique, the regenerative braking force is more strongly limited as the wheel speed deviation (drive wheel braking slip amount) is larger, and the braking slip of the drive wheel during regenerative braking is prevented by limiting the braking force. .
JP 2006-246657 A

  However, this conventional driving wheel regenerative braking restriction technology increases the degree of restriction of the regenerative braking force as the above wheel speed deviation (drive wheel braking slip amount) increases, but the degree of restriction of the regenerative braking force is reduced to the wheel speed deviation ( The driving wheel braking slip amount) is unambiguously determined, resulting in problems as described below.

Referring to FIG. 10, A is the regenerative braking force before the restriction at the time of requesting a large deceleration with the brake pedal strongly depressed, and B is the regenerative braking before the restriction at the time of a request for a small deceleration with a reduced brake pedal depression force. Each power is shown.
If the same wheel speed deviation (driving wheel braking slip amount) occurs at the time of requesting large deceleration and small deceleration, the regenerative braking forces A and B are respectively determined by this wheel speed deviation (driving wheel braking slip amount). Only the same regenerative braking force limit amount A2, B2 determined uniquely is limited, and the regenerative braking force A1, B1 after the limit is reduced.
Then, these regenerative braking force limits (decreases) A2 and B2 are supplemented by friction braking force by a hydraulic brake or the like, respectively.

However, the regenerative braking force A, B is limited only by the regenerative braking force limit amount A2, B2, which is uniquely determined by the wheel speed deviation (drive wheel braking slip amount), both when requesting large deceleration and when requesting small deceleration. In the case where the wheel speed deviation (drive wheel braking slip amount) is the same, the regenerative braking force limit amounts A2 and B2 are the same as shown in FIG. 10 when the large deceleration is requested and when the small deceleration is requested.
For this reason, in the case of an electric vehicle in which only the front wheels or the rear wheels are motor-driven and the other is a driven wheel, there is a possibility that not all brake pedal depression forces (required deceleration) will provide an appropriate front-rear wheel braking force distribution.

  For example, as shown in FIG. 11, when the rear wheel (driving wheel) achieves a large deceleration request with the limited previous braking force A while regeneratively braking the rear wheel (driving wheel) at point A3, the rear wheel (driving wheel) performs braking slip. If the regenerative braking force A is reduced by the regenerative braking force limit amount A2 that is uniquely determined by the braking slip amount and the rear wheel (drive wheel) is to be regeneratively braked with the regenerative braking force A1 after limitation, The braking is performed at point A4 on the corresponding equal deceleration front and rear wheel braking force distribution characteristic line.

  When small deceleration is requested, as shown in the figure, the rear wheel (driving wheel) is regeneratively braked at point B3, while the limited deceleration braking force B is used to achieve the small deceleration request, the rear wheel ( The drive wheel) generates the same braking slip as when a large deceleration is requested, and the regenerative braking force B is reduced by the regenerative braking force limit amount B2 (= A2) that is uniquely determined by this braking slip amount. When regenerative braking is applied to the rear wheels (drive wheels) at B1, braking is performed at point B4 on the corresponding constant deceleration front and rear wheel braking force distribution characteristic line.

As is clear from the comparison of the operation points A4 and B4 after regenerative braking restriction in Fig. 11, the operation point becomes B4 when regenerative braking is restricted at the time of a small deceleration request, and the front and rear wheels that simultaneously brake and lock the front and rear wheels Although it is located on the braking force ideal distribution characteristic line and the front and rear wheel braking force distribution is appropriate,
When regenerative braking is restricted at the time of a large deceleration request, the operating point becomes A4 point, which is greatly deviated from the front and rear wheel braking force ideal distribution characteristic line, and the front and rear wheel braking force distribution is not appropriate.

In this way, regardless of the brake pedal depression force (required deceleration), the regenerative braking force limit amount is uniquely determined according to the braking slip amount of the driving wheel and the regenerative braking force is limited (driving wheel braking slip amount). If the two are the same, the regenerative braking force limit amount is the same whether the required deceleration is large or small)
As described above, when the regenerative braking restriction during the request for small deceleration is performed, the regenerative braking restriction mode is such that the operating point is located near the front / rear wheel braking force ideal distribution characteristic line and the front / rear wheel braking force distribution becomes appropriate. ,
When the large deceleration is requested, the regenerative braking force limit amount is not sufficient, and the front and rear wheel braking force distribution including the friction braking force becomes an excessive distribution of the driving wheel braking force, so that the driving wheel is ahead of the driven wheel. Brake lock occurs beyond the tire limit performance, and vehicle behavior becomes unstable.

  That is, as in the case of FIG. 11, when the rear wheel is a driving wheel and the front wheel is a driven wheel, the rear wheel exceeds the tire limit performance before the front wheel, and a braking lock is generated. This is not preferable because the behavior of the vehicle becomes unstable as compared with the case where the front wheel is braked before the rear wheel.

On the contrary, the regenerative braking restriction mode in which the operating point is located near the front and rear wheel braking force ideal distribution characteristic line and the front and rear wheel braking force distribution becomes appropriate when regenerative braking is restricted during a large deceleration request. Then
When the rear wheel is the driving wheel and the front wheel is the driven wheel, the operating point is located in the front wheel tip lock area than the front and rear wheel braking force ideal distribution characteristic line when regenerative braking is restricted while requesting small deceleration, Although the above problem of instability in vehicle behavior does not occur,
The above operating point is located farther than necessary from the front / rear wheel braking force ideal distribution characteristic line and is located in the front wheel tip lock region, and the regenerative braking force limit is excessive, reducing the fuel efficiency improvement effect due to regenerative braking. Cause problems.

The present invention is based on the fact that the above problem occurs as long as the regenerative braking force limit amount is determined according to the driving wheel braking slip amount,
Instead, the braking force distribution ratio of the regenerative braking drive wheel corresponds to a constant front and rear wheel braking force distribution characteristic that approximates the front and rear wheel braking force ideal distribution characteristic that changes according to the driving wheel braking slip amount. As a configuration to perform regenerative braking restriction control at the time of driving wheel braking slip,
It is an object of the present invention to propose a regenerative braking control device for an electric vehicle that can solve the above-mentioned problems of trade-off.

For this purpose, the regenerative braking control device for an electric vehicle according to the present invention, as claimed in claim 1,
At least a motor / generator is mounted as a prime mover, and the front wheel or rear wheel as a driving wheel is driven or regeneratively braked by the motor / generator, and the regenerative braking force is driven to the rear wheel or the front wheel speed that is the driven wheel. In an electric vehicle that is limited according to the wheel speed deviation of
The regenerative braking force is limited so that the driving wheel braking force distribution ratio corresponds to a constant front and rear wheel braking force distribution characteristic that approximates the front and rear wheel braking force ideal distribution characteristic in a practical range. It is what.

According to the configuration of the present invention,
When limiting the regenerative braking force of the front wheel or the rear wheel as the driving wheel according to the deviation of the wheel speed of the driving wheel with respect to the wheel speed of the rear wheel or the front wheel which is the driven wheel,
In order to limit the regenerative braking force so that the driving wheel braking force distribution ratio corresponds to a constant front and rear wheel braking force distribution characteristic that approximates the front and rear wheel braking force ideal distribution characteristic in the practical range,
Appropriate front / rear wheel braking force distribution with the operating point located close to the front / rear wheel braking force ideal distribution characteristic line when regenerative braking is restricted while requesting large deceleration and when regenerative braking is restricted while requesting small deceleration Can be.

For this reason, when regenerative braking is restricted during a large deceleration request, the rear wheel exceeds the tire limit performance before the front wheel, causing a braking lock, and the above problem that the behavior of the vehicle becomes unstable does not occur.
The regenerative braking force limit amount is unnecessarily increased when the regenerative braking is restricted during the small deceleration request, and the above-described problem that the fuel efficiency improvement effect due to the regenerative braking is reduced does not occur.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 shows a power train of a front engine / rear wheel drive hybrid vehicle (electric vehicle) equipped with a regenerative braking control device according to an embodiment of the present invention, along with its control system,
1 is an engine as a prime mover, 2FL and 2FR are left and right front wheels (left and right driven wheels), and 3RL and 3RR are left and right rear wheels (right and left drive wheels), respectively.
In the power train of the hybrid vehicle shown in FIG. 1, an automatic transmission 4 is arranged in tandem at the rear of the engine 1 in the vehicle front-rear direction in the same manner as a normal rear wheel drive vehicle, and the engine 1 (specifically, the crankshaft 1a) A motor / generator 6 serving as a second prime mover is provided in connection with the shaft 5 that transmits the rotation to the input shaft 4a of the automatic transmission 4.

The motor / generator 6 includes an annular stator 6a fixed in the housing and a rotor 6b disposed concentrically with a predetermined air gap in the stator 6a. Acts as an electric motor) or as a generator (generator), and is disposed between the engine 1 and the automatic transmission 4.
The motor / generator 6 is connected to the center of the rotor 6b through the shaft 5, and this shaft 5 is used as a motor / generator shaft.

The first clutch 7 is inserted between the motor / generator 6 and the engine 1, more specifically, between the motor / generator shaft 5 and the engine crankshaft 1a, and the engine 1 and the motor / generator 6 are connected by the first clutch 7. Combine in a detachable manner.
Here, it is assumed that the first clutch 7 is capable of continuously changing the transmission torque (clutch engagement) capacity. For example, the first clutch 7 continuously controls the clutch hydraulic oil flow rate and the clutch operation hydraulic pressure with a proportional solenoid to transmit the transmission torque (clutch engagement). ) Consists of wet multi-plate clutch with variable capacity.

The motor / generator 6 and the automatic transmission 4 are directly coupled to each other by direct coupling of the motor / generator shaft 5 and the transmission input shaft 4a.
The automatic transmission 4 is similar to the known planetary gear set type automatic transmission, except that the torque converter is excluded from this, and instead the motor / generator 6 is directly coupled to the transmission input shaft 4a. ,
By selectively engaging or releasing a plurality of speed change friction elements (clutch, brake, etc.), the transmission system path (speed stage) is determined by a combination of engagement and release of these speed change friction elements.

Accordingly, the automatic transmission 4 shifts the rotation from the input shaft 4a with a gear ratio corresponding to the selected shift speed, and outputs it to the output shaft 4b.
This output rotation is distributed and transmitted to the left and right rear wheels 3RL and 3RR by the differential gear device 8, and is used for traveling of the vehicle.
However, it goes without saying that the automatic transmission 4 is not limited to the stepped type as described above, and may be a continuously variable transmission.

In the hybrid vehicle, the second clutch 9 that detachably couples the motor / generator 6 and the drive wheels 3RL and 3RR is necessary.
In this embodiment, the second clutch 9 is not added to the automatic transmission 4 or after the automatic transmission 4, and a new configuration is not adopted.
Instead, among the above-described shift friction elements existing in the automatic transmission 4, as the second clutch 9, a shift friction element for selecting a forward shift stage or a shift friction element for selecting a reverse shift stage is used.

Incidentally, in the automatic transmission 4 used as the second clutch 9, the existing transmission friction element for selecting the forward shift stage or the shift friction element for selecting the reverse shift stage is originally transmitted torque capacity similarly to the first clutch 7 described above. The (clutch engagement capacity) can be continuously changed.
As described above, when the existing shift friction element for selecting the forward shift stage or the shift friction element for selecting the reverse shift stage is used as the second clutch 9 in the automatic transmission 4, the second clutch 9 will be described below. In addition to fulfilling the mode selection function, the automatic transmission is put into a power transmission state by shifting to the corresponding gear stage when engaged to fulfill this function, and a dedicated second clutch is unnecessary, which is very advantageous in terms of cost. It is.

The power train mode selection function described above with reference to FIG. 1 will be described below.
In the power train shown in FIG. 1, when the electric driving (EV driving) mode used at low load and low vehicle speed including when starting from a stopped state is required, the first clutch 7 is disengaged and the automatic shifting is performed. The machine 4 is brought into a power transmission enabled state by engaging the second clutch 9.

When the motor / generator 6 is driven in this state, only the output rotation from the motor / generator 6 reaches the transmission input shaft 4a, and the automatic transmission 4 changes the rotation to the input shaft 4a to the selected shift speed. The speed is changed according to the speed and output from the transmission output shaft 4b.
The rotation from the transmission output shaft 4b then reaches the rear wheels 3RL and 3RR via the differential gear device 8, and the vehicle can be electrically driven (EV traveling) only by the motor / generator 6.

When the hybrid travel (HEV travel) mode used for high speed travel or heavy load travel is required, the first clutch 7 is engaged and the automatic transmission 4 can be transmitted power by engaging the second clutch 9. To.
In this state, the output rotation from the engine 1, or both the output rotation from the engine 1 and the output rotation from the motor / generator 6 reach the transmission input shaft 4a, and the automatic transmission 4 is connected to the input shaft 4a. Is rotated according to the selected gear position and output from the transmission output shaft 4b.
The rotation from the transmission output shaft 4b then reaches the rear wheels 3RL and 3RR via the differential gear device 8, and the vehicle can be hybrid-run (HEV-run) by both the engine 1 and the motor / generator 6.

  In such HEV traveling, if the engine 1 is operated with the optimum fuel efficiency and the energy becomes surplus, the surplus energy is converted into electric power by operating the motor / generator 6 as a generator by this surplus energy, and this generated power is converted into electric power. By accumulating power to be used for driving the motor of the motor / generator 6, the fuel consumption of the engine 1 can be improved.

Hereinafter, a control system for the engine 1, the motor / generator 6, the first clutch 7, and the second clutch 9 constituting the power train of the hybrid vehicle described above will be schematically described with reference to FIG.
This control system includes an integrated controller 11 that performs integrated control of the operating point of the power train. The operating point of the power train includes the target engine torque tTe, the target motor / generator torque tTm, and the target engagement capacity of the first clutch 7. It is defined by tTc1 (first clutch engagement pressure command value tPc1) and target engagement capacity tTc2 (second clutch engagement pressure command value tPc2) of the second clutch 9.

In the integrated controller 11, in order to determine the operating point of the power train,
A signal from the engine speed sensor 12 for detecting the engine speed Ne;
A signal from the motor / generator rotation sensor 13 for detecting the motor / generator rotation speed Nm,
A signal from the input rotation sensor 14 for detecting the transmission input rotation speed Ni;
A signal from the output rotation sensor 15 that detects the transmission output rotation speed No,
A signal from the accelerator opening sensor 16 for detecting the accelerator pedal depression amount (accelerator opening APO);
A signal from a storage state sensor 17 that detects a storage state SOC (carryable power) of a battery 31 that stores power for the motor / generator 6;
A signal from the master cylinder hydraulic pressure sensor 18 that detects the master cylinder hydraulic pressure Pm according to the brake pedal depression force,
Signals from a wheel speed sensor group 21 that individually detect the wheel speeds Vw of the left and right front wheels (left and right driven wheels) 2FL and 2FR and the left and right rear wheels (right and left drive wheels) 3RL and 3RR are input.

  The integrated controller 11 is a driving mode in which the driving force of the vehicle desired by the driver can be realized from the accelerator opening APO, the battery storage state SOC, and the transmission output rotational speed No (vehicle speed VSP) among the above input information. (EV mode, HEV mode) is selected, and target engine torque tTe, target motor / generator torque tTm, first clutch target engagement capacity tTc1, and second clutch target engagement capacity tTc2 are calculated.

  The target engine torque tTe is supplied to the engine controller 32. The engine controller 32 realizes the target engine torque tTe based on the engine speed Ne from the engine speed Ne detected by the sensor 12 and the target engine torque tTe. Therefore, the engine 1 is controlled so that the engine torque becomes the target engine torque tTe by the throttle opening control and the fuel injection amount control.

  The target motor / generator torque tTm is supplied to the motor / generator controller 33. The motor / generator controller 33 converts the electric power of the battery 31 from DC to AC by the inverter 34, and the motor / generator 6 under the control of the inverter 34. And the motor / generator torque is controlled so that the motor / generator torque matches the target motor / generator torque tTm.

When the target motor / generator torque tTm is such that the motor / generator 6 requires regenerative braking action, the motor / generator controller 33 is connected to the battery storage state SOC detected by the sensor 17 via the inverter 34 (can be taken out) In relation to the electric power), a power generation load is applied to the motor / generator 6 so that the battery 31 is not overcharged.
The electric power generated by the regenerative braking by the motor / generator 6 is AC-DC converted and the battery 31 is charged.

When the braking force is insufficient with only the regenerative braking of the motor / generator 6, the integrated controller 11 uses the brake braking command value Tf as a regenerative cooperative brake control command to supplement the insufficient braking force with the hydraulic brake system. Supply to 35.
When there is no regenerative cooperative brake control command (when the friction braking force command value Tf = 0), the brake controller 35 receives a signal from the master cylinder hydraulic pressure sensor 18 that detects the master cylinder hydraulic pressure Pm according to the brake pedal depression force. Originally, the brake fluid pressure of each wheel brake unit is controlled to a fluid pressure corresponding to the master cylinder fluid pressure Pm with a fixed front and rear wheel friction braking force distribution ratio that cannot be changed,
When receiving the regenerative cooperative brake control command (friction braking force command value Tf> 0) from the integrated controller 11, the brake controller 35 is configured to apply the friction braking force command value Tf (> 0) to each wheel brake unit by the hydraulic brake system. The brake hydraulic pressure is controlled to a hydraulic pressure corresponding to the friction braking force command value Tf with a fixed front and rear wheel friction braking force distribution ratio that cannot be changed.

  The first clutch target engagement capacity tTc1 is supplied to the first clutch controller 36. The first clutch controller 36 detects the first clutch engagement pressure command value tPc1 corresponding to the first clutch target engagement capacity tTc1 and the sensor 19. The first clutch 7 is engaged via the first clutch engagement pressure control unit 37 so that the engagement pressure Pc1 of the first clutch 7 becomes the first clutch engagement pressure command value tPc1 by comparison with the engagement pressure Pc1 of the first clutch 7. The engagement capacity of the first clutch 7 is controlled by controlling the pressure.

The second clutch target engagement capacity tTc2 is supplied to the transmission controller 38,
The transmission controller 38 compares the second clutch engagement pressure command value tPc2 corresponding to the second clutch target engagement capacity tTc2 with the engagement pressure Pc2 of the second clutch 9 detected by the sensor 20, and The engagement capacity of the second clutch 9 is controlled by controlling the engagement pressure of the second clutch 9 via the second clutch engagement pressure control unit 39 so that the engagement pressure Pc2 becomes the second clutch engagement pressure command value tPc2.

  The transmission controller 38 selects a gear suitable for the current driving state based on the planned shift map from the transmission output rotation speed No (vehicle speed VSP) detected by the sensor 15 and the accelerator opening APO detected by the sensor 16. It is assumed that an automatic shift from the current gear to this preferred gear is also performed.

The above is an outline of the normal control executed by the control system of FIG.
In this embodiment, the integrated controller 11 in FIG. 1 executes the control program shown in FIG. 2 during a deceleration request by depressing a brake pedal (not shown), and the regenerative braking control targeted by the present invention is as follows: Assumed to be performed.

In step S11, the vehicle target deceleration Gs desired by the driver is calculated from the master cylinder hydraulic pressure Pm detected by the sensor 18 (may be a brake pedal depression stroke).
In the next step S12, the target total braking force Tb of the vehicle necessary for generating the target deceleration Gs is obtained by searching a planned target braking force map or by calculation based on the vehicle model.

In the next step S13, based on the wheel speed Vw detected by the wheel speed sensor group 21, the wheel speed deviation between the two is calculated by subtracting the driving wheel speed (rear wheel speed) from the driven wheel speed (front wheel speed). The wheel speed deviation is defined as the braking slip amount Slip of the drive wheel (rear wheel).
When calculating the driving wheel (rear wheel) braking slip amount Slip, as clearly shown in FIG. 3, the right wheel speed is calculated by subtracting the right driving wheel speed (right rear wheel speed) from the right driven wheel speed (right front wheel speed). While calculating the deviation, the left wheel speed deviation is calculated by subtracting the left driving wheel speed (left rear wheel speed) from the left driven wheel speed (left front wheel speed), and the larger of the right wheel speed deviation and the left wheel speed deviation. One wheel speed deviation is selected (indicated by MAX) to be the braking slip amount Slip of the driving wheel (rear wheel).

In step S14, the driving wheel (rear wheel) braking force distribution ratio BTOr is retrieved from the driving wheel (rear wheel) braking slip amount Slip based on the map illustrated in FIG. ) Subtract the braking force distribution ratio BTOr to calculate the driven wheel (front wheel) braking force distribution ratio BTOf.
Here, the driving wheel (rear wheel) braking force distribution ratio BTOr is made smaller as the driving wheel (rear wheel) braking slip amount Slip increases, as is apparent from FIG.
When the driving wheel (rear wheel) braking slip amount Slip is less than the first set slip amount Slip1, the driving wheel (rear wheel) braking force distribution ratio BTOr is set, and the driving wheel (rear wheel) braking slip amount Slip is the first amount. Keep the upper limit when the set slip amount is Slip1.
Note that the upper limit value of the driving wheel (rear wheel) braking force distribution ratio BTOr is such that the front and rear wheel braking force distribution characteristics are represented by α in FIG. It is made to correspond to a value that becomes a constant distribution ratio that approximates the ideal front / rear wheel braking force distribution characteristic shown in the figure.

As shown in FIG. 4, when the driving wheel (rear wheel) braking slip amount Slip is not less than the first set slip amount Slip1 and less than the second set slip amount Slip2, the driving wheel (rear wheel) braking slip amount Slip is As the value increases, the driving wheel (rear wheel) braking force distribution ratio BTOr is gradually reduced from the upper limit.
This decrease in the driving wheel (rear wheel) braking force distribution ratio BTOr changes the ideal distribution characteristic of the front and rear wheel braking force from the one shown in FIG. 6 to a more gentle one as the driving wheel (rear wheel) braking slip amount Slip increases. Accordingly, the reduced driving wheel (rear wheel) braking force distribution ratio BTOr keeps approximating the front and rear wheel braking force distribution characteristics with respect to the changed front and rear wheel braking force ideal distribution characteristics.

When the driving wheel (rear wheel) braking slip amount Slip is equal to or larger than the second set slip amount Slip2, the driving wheel (rear wheel) braking force distribution ratio BTOr is set, and the driving wheel (rear wheel) braking slip amount Slip is the second setting slip amount Slip2. Keep the lower limit when the set slip amount is Slip2.
Here, the lower limit value of the driving wheel (rear wheel) braking force distribution ratio BTOr is as shown in FIG.
Preferably, the value should correspond to the fixed front and rear wheel friction braking force distribution ratio of the hydraulic friction brake, which cannot be changed, as described above with respect to the brake controller 35 of FIG.
Therefore, the front and rear wheel braking force distribution characteristics determined by the driving wheel (rear wheel) braking force distribution ratio BTOr and the driven wheel (front wheel) braking force distribution ratio BTOf obtained from the calculation are the driving wheel (rear wheel) braking slip amount. As the number of slips increases, the α characteristic in FIG. 6 changes toward the β characteristic.

In step S15 in FIG. 2, the allowable maximum regenerative braking force Tmmax determined from the battery storage state SOC (capable power to be taken out) detected by the sensor 17 and the motor / generator rotation speed Nm detected by the sensor 13 is obtained by map search or the like.
In the next step S16, the target total braking force Tb obtained in step S12 is multiplied by the driven wheel (front wheel) braking force distribution ratio RTOf obtained in step S14 to calculate the friction braking force Tbff of the driven wheel (front wheel). To do.

In step S17, the driven wheel (front wheel) friction braking force Tbff obtained in step S16 is set to the fixed front and rear wheel friction braking force distribution ratio RTOmecha, which is described above for the brake controller 35 in FIG. Multiply to calculate the friction braking force Tbrf of the drive wheel (rear wheel).
In step S18, the target total braking force Tb obtained in step S12 is multiplied by the driving wheel (rear wheel) braking force distribution ratio RTOr obtained in step S14 to calculate the total braking force Tbr of the driving wheel (rear wheel). To do.

  In step S19, the driving wheel (rear wheel) friction braking force Tbrf (negative value) obtained as described above in step S17 and the driving wheel (rear wheel) total braking force Tbr (determined as described above in step S18). (Negative value) and whether or not Tbrf> Tbr, that is, whether or not | Tbrf | <| Tbr |, is checked whether regenerative braking of the drive wheels (rear wheels) is possible.

When it is determined in step S19 that the regenerative braking of the driving wheel (rear wheel) is possible, in step S20,
The difference obtained by subtracting the driving wheel (rear wheel) friction braking force Tbrf from the driving wheel (rear wheel) total braking force Tbr is the driving wheel (rear wheel) regenerative braking force Tbrm, and this is set as the target motor / generator torque tTm. Instruct the motor / generator controller 33 like
The sum of the driven wheel (front wheel) friction braking force Tbff and the driving wheel (rear wheel) friction braking force Tbrf obtained in step S16 and step S17 is output to the brake controller 35 as shown in FIG. 1 as the friction braking force command value Tf. .

When it is determined in step S19 that the regenerative braking of the driving wheel (rear wheel) is impossible, in step S21,
The drive wheel (rear wheel) regenerative braking force Tbrm = 0 is set as a target motor / generator torque tTm, and the motor / generator controller 33 is commanded as shown in FIG.
The sum of the driven wheel (front wheel) friction braking force Tbff and the driving wheel (rear wheel) friction braking force Tbrf obtained in step S16 and step S17 is output to the brake controller 35 as shown in FIG. 1 as the friction braking force command value Tf. .

The calculation procedure of the driving wheel (rear wheel) regenerative braking force Tbrm, driven wheel (front wheel) friction braking force Tbff and driving wheel (rear wheel) friction braking force Tbrf is shown in a block diagram as shown in FIG. Become.
That is, from the target total braking force Tb of the vehicle, the driving wheel (rear wheel) braking force distribution ratio BTOr and the driven wheel (front wheel) braking force distribution ratio BTOf according to the driving wheel (rear wheel) braking slip amount Slip,
A driven wheel (front wheel) friction braking force Tbff (= Tb × RTOf) is calculated, and a driving wheel (rear wheel) total braking force Tbr (= Tb × RTOr) is calculated.
Next, from the driven wheel (front wheel) friction braking force Tbff and the fixed front and rear wheel friction braking force distribution ratio RTOmecha of the hydraulic friction brake,
Calculate the driving wheel (rear wheel) friction braking force Tbrf (= Tbff x RTOmecha)
A difference value obtained by subtracting the driving wheel (rear wheel) friction braking force Tbrf from the driving wheel (rear wheel) total braking force Tbr is used as the driving wheel (rear wheel) regenerative braking force Tbrm (= Tbr−Tbrf).

In the above-described embodiment, the regenerative braking force Tbrm of the driving wheel (rear wheel) is limited according to the deviation of the driving wheel (rear wheel) speed from the driven wheel (front wheel) speed (driving wheel braking slip amount Slip). On the occasion
When the driving wheel (rear wheel) braking slip amount Slip is less than the first set slip amount Slip1 (see FIG. 4), the driving wheel (rear wheel) braking force distribution ratio BTOr is shown, and the front and rear wheel braking force distribution characteristics are shown in FIG. And an upper limit value that gives a constant front and rear wheel braking force distribution characteristic approximated to the front and rear wheel braking force ideal distribution characteristic at the time of small slip as exemplified by α,
When the driving wheel (rear wheel) braking slip amount Slip is equal to or larger than the second set slip amount Slip2 (see FIG. 4), the driving wheel (rear wheel) braking force distribution ratio BTOr is shown, and the front and rear wheel braking force distribution characteristics are shown in FIG. And an upper limit value that gives a constant front and rear wheel braking force distribution characteristic corresponding to the unchangeable front and rear wheel friction braking force distribution ratio of the hydraulic friction brake as illustrated by β in FIG.
As the drive wheel (rear wheel) braking slip amount Slip increases from the first set slip amount Slip1 to the second set slip amount Slip2, the change in the ideal distribution characteristic of the front and rear wheel braking force accompanying this change in slip amount is accommodated. , Reduce the driving wheel (rear wheel) braking force distribution ratio BTOr from the upper limit to the lower limit,
Since the regenerative braking force is limited based on the driving wheel (rear wheel) braking force distribution ratio BTOr, the following effects can be obtained.

That is, the upper limit value of the driving wheel (rear wheel) braking force distribution ratio BTOr when the driving wheel (rear wheel) braking slip amount Slip is less than the first set slip amount Slip1, as indicated by α in FIG. With a distribution ratio corresponding to a constant front / rear wheel braking force distribution ratio that approximates the front / rear wheel braking force ideal distribution at the time of small slip,
When regenerative braking is restricted while a large deceleration is requested, the regenerative braking force A is limited by the regenerative braking force limit A2 and reduced to the regenerative braking force A1 after the restriction as shown in FIG. When braking is limited, even with the same drive wheel (rear wheel) braking slip amount Slip, as shown in the figure, the regenerative braking force B is limited by the regenerative braking force limit amount B2, which is different from the above A2, and the regenerative braking after limiting Reduced to power B1.

As shown in FIG. 6 showing the movement of the operating point under the same conditions as in FIG. 11, the operating point moves from point A3 to point A5 on the front and rear wheel braking force distribution characteristics α when regenerative braking is restricted during a large deceleration request. However, when regenerative braking is restricted during a small deceleration request, the operating point moves from point B3 to point B5 on the same front and rear wheel braking force distribution characteristic α.
Therefore, even when regenerative braking is restricted while requesting large deceleration and when regenerative braking is restricted while requesting small deceleration, the front and rear wheel braking force distribution that approximates the ideal distribution characteristic line for front and rear wheels when the small slip is applied Located on the line α, the front and rear wheel braking force distribution becomes appropriate,
Therefore, the slip force ratio A1: A2 at the time of regenerative braking restriction during a large deceleration request shown in FIG. 7 and the braking force ratio B1: B2 at the time of regenerative braking restriction at a small deceleration request are kept the same. The time regenerative braking force limit control is performed.

For this reason, when regenerative braking is restricted during a large deceleration request, the rear wheel exceeds the tire limit performance before the front wheel, causing a braking lock, and the above problem that the behavior of the vehicle becomes unstable does not occur.
The regenerative braking force limit amount is unnecessarily increased when the regenerative braking is restricted during the small deceleration request, and the above-described problem that the fuel efficiency improvement effect due to the regenerative braking is reduced does not occur.

Further, as the driving wheel (rear wheel) braking slip amount Slip increases, the driving wheel (rear wheel) braking force distribution ratio BTOr corresponds to the characteristic β of FIG. 6 from the upper limit value corresponding to the characteristic α of FIG. To lower it towards the lower limit,
The driving wheel (rear wheel) braking force distribution ratio BTOr follows the front / rear wheel braking force ideal distribution characteristic (not shown) that moves in the same direction as the driving wheel (rear wheel) braking slip amount Slip increases. Will decline,
Regardless of the magnitude of the driving wheel (rear wheel) braking slip amount Slip, the regenerative braking limit operating point is located on a certain front and rear wheel braking force distribution line that approximates the slip front and rear wheel braking force ideal distribution characteristic line. Thus, the front and rear wheel braking force distribution can be constantly made appropriate, and the above-described operation and effect can be achieved regardless of the magnitude of the driving wheel (rear wheel) braking slip amount Slip.

In this embodiment, as described above with reference to FIG. 3, the right wheel speed deviation obtained by subtracting the right driving wheel speed (right rear wheel speed) from the right driven wheel speed (right front wheel speed) and the left driven wheel speed ( The driving wheel (rear wheel) braking slip amount Slip is the larger of the left wheel speed deviation obtained by subtracting the left driving wheel speed (left rear wheel speed) from the left front wheel speed.
Drive wheel (rear wheel) braking slip amount Slip The left or right drive wheel (left or right rear wheel) with a large slip slip restricts regenerative braking for slip prevention, making slip prevention even more reliable You can do it.

As described above, the lower limit value of the driving wheel (rear wheel) braking force distribution ratio BTOr to be set when the driving wheel (rear wheel) braking slip amount Slip is equal to or larger than the second set slip amount Slip2 (see FIG. 4). When the hydraulic friction brake has a value corresponding to the front and rear wheel friction braking force distribution ratio RTOmecha that cannot be changed,
A reduction in unnecessary driving wheel (rear wheel) braking force distribution ratio BTOr can be avoided, and the amount of regenerative braking force restriction can be increased unnecessarily, thereby preventing a reduction in fuel efficiency improvement effect due to regenerative braking. it can.

In the above description, the case where the hydraulic friction brake cannot change the front and rear wheel friction braking force distribution ratio RTOmecha has been described. In this case, as shown in FIG. 8, the regenerative braking force limit obtained as described above is used. The front and rear wheel braking force ratio, that is, the front wheel braking force Fr that is the front wheel friction braking force Tbff itself and the rear wheel braking force Rr that is the sum of the rear wheel regenerative braking force Tbrm and the rear wheel friction braking force Tbrf Wheel braking force ratio Fr: Rr
Since the front-rear wheel friction braking force distribution ratio RTOmecha (= Tbff / Tbrf) of the hydraulic friction brake cannot be changed, it deviates from the front-rear wheel braking force ratio C: D before the regenerative braking force limit, and the drive wheel (rear wheel) There is a concern that the braking force becomes too large.

To solve this problem, a friction brake that cannot change the front and rear wheel friction braking force distribution ratio RTOmecha is used as a friction brake, and the front wheel friction braking force Tbff, the rear wheel regenerative braking force Tbrm, and the rear wheel friction braking force are as follows. Find Tbrf.
First, the target front and rear wheel braking force distribution ratio corresponding to the driving wheel (rear wheel) braking force distribution ratio RTOr, which becomes smaller as the driving wheel (rear wheel) slip amount Slip becomes larger, from α in FIG. 6 according to the slip amount Slip. The friction braking force Tbff of the driven wheel (front wheel) and the braking force target value Tbr of the driving wheel (rear wheel) are obtained from (changes to β).

Next, when the driving wheel (rear wheel) braking force target value Tbr can be covered by the allowable maximum regenerative braking force Tmmax (step S15), the driving wheel (rear wheel) regenerative braking force Tbrm is used as the driving wheel braking force target value Tbr. And the drive wheel (rear wheel) friction braking force Tbrf to zero,
If the drive wheel (rear wheel) braking force target value Tbr cannot be covered by the allowable maximum regenerative braking force Tmmax, the drive wheel (rear wheel) regenerative braking force Tbrm is set to the same value as the allowable maximum regenerative braking force Tmmax. The front and rear wheel friction braking force distribution ratio RTOmecha of the friction brake is changed so that the deficiency (Tbr-Tmmax) of the wheel (rear wheel) braking force is compensated by the driving wheel (rear wheel) friction braking force Tbrf.

  In this case, as shown in FIG. 9, before and after the front wheel braking force Fr, which is the front wheel friction braking force Tbff itself, and the rear wheel braking force Rr, which is the sum of the rear wheel regenerative braking force Tbrm and the rear wheel friction braking force Tbrf. The wheel braking force ratio Fr: Rr does not deviate from the front and rear wheel braking force ratio C: D before the regenerative braking force limit, and the concern that the driving wheel (rear wheel) braking force becomes too large can be avoided.

1 is a diagrammatic plan view showing a power train of a front engine / rear wheel drive hybrid vehicle including a regenerative braking control device according to an embodiment of the present invention, together with its control system. FIG. 3 is a flowchart showing a main routine of regenerative braking control executed by an integrated controller in FIG. FIG. 3 is a block diagram showing a calculation process of a driving wheel braking slip amount obtained in the main routine of FIG. FIG. 3 is a change characteristic diagram of a drive wheel braking force distribution ratio obtained in the main routine of FIG. FIG. 3 is a block diagram showing calculation processing of front wheel (driven wheel) friction braking force, rear wheel (driving wheel) friction braking force, and rear wheel (driving wheel) regenerative braking force obtained in the main routine of FIG. FIG. 6 is a front / rear wheel braking force distribution diagram used to explain regenerative braking restriction control of the embodiment shown in FIGS. FIG. 6 is an explanatory diagram showing a relationship between a regenerative braking force and a friction braking force (regenerative braking force limit amount) after performing the regenerative braking restriction control of the embodiment shown in FIGS. When the hydraulic friction brake cannot change the front-rear wheel friction braking force distribution ratio, the rear wheel regenerative braking force when the regenerative braking restriction control of the embodiment shown in FIGS. FIG. 5 is an explanatory diagram showing a relationship with front wheel friction braking force. Rear wheel regenerative braking force, rear wheel friction braking force, and front wheel friction when the regenerative braking restriction control of the embodiment shown in FIGS. 1 to 5 is performed while changing the front-rear wheel friction braking force distribution ratio of the hydraulic friction brake It is explanatory drawing which shows the relationship with braking force. It is explanatory drawing which shows the relationship between the regenerative braking force after performing the conventional regenerative braking limitation control, and friction braking force (regenerative braking force limitation amount). It is a front-rear wheel braking force distribution diagram used to explain conventional regenerative braking restriction control.

Explanation of symbols

1 engine (motor)
2FL, 2FR Left and right front wheels (left and right driven wheels)
3RL, 3RR Left and right rear wheels (left and right drive wheels)
4 Automatic transmission
6 Motor / generator (motor)
7 First clutch
9 Second clutch
11 Integrated controller
12 Engine rotation sensor
13 Motor / generator rotation sensor
14 Transmission input rotation sensor
15 Transmission output rotation sensor
16 Accelerator position sensor
17 Storage state sensor
18 Master cylinder hydraulic pressure sensor
21 Wheel speed sensor group
31 battery
32 Engine controller
33 Motor / generator controller
34 Inverter
35 Brake controller
36 1st clutch controller
37 1st clutch engagement pressure control unit
38 Transmission controller
39 Second clutch engagement pressure control unit

Claims (6)

At least a motor / generator is mounted as a prime mover, and the front wheel or rear wheel as a driving wheel is driven or regeneratively braked by the motor / generator, and the regenerative braking force is driven to the rear wheel or the front wheel speed that is the driven wheel. In an electric vehicle that is limited according to the wheel speed deviation of
The regenerative braking force is limited so that the driving wheel braking force distribution ratio corresponds to a constant front and rear wheel braking force distribution characteristic that approximates the front and rear wheel braking force ideal distribution characteristic in a practical range. A regenerative braking control device for an electric vehicle. In the regenerative braking control device for an electric vehicle according to claim 1,
As the deviation of the driving wheel speed with respect to the driven wheel speed, the larger one of the deviation of the right driving wheel speed with respect to the right driven wheel speed and the deviation of the left driving wheel speed with respect to the left driven wheel speed is used. A regenerative braking control device for an electric vehicle. In the regenerative braking control device for an electric vehicle according to claim 1 or 2,
The regenerative braking control device for an electric vehicle, wherein the driving wheel braking force distribution ratio is set to be smaller as the deviation of the driving wheel speed from the driven wheel speed is larger. 4. The electric vehicle according to any one of claims 1 to 3, wherein the electric vehicle realizes a deceleration request by a combined brake of a friction brake whose front and rear wheel friction braking force distribution ratio cannot be changed and a regenerative brake by the motor / generator. In the regenerative braking control device for an electric vehicle according to item 1,
A regenerative braking control device for an electric vehicle, wherein a lower limit value of the driving wheel braking force distribution ratio is a distribution ratio corresponding to a front and rear wheel friction braking force distribution ratio that cannot be changed. 5. The electric vehicle according to any one of claims 1 to 4, wherein the electric vehicle realizes a deceleration request by a combined brake of a friction brake whose front and rear wheel friction braking force distribution ratio cannot be changed and a regenerative brake by the motor / generator. In the regenerative braking control device for an electric vehicle according to item 1,
A difference value obtained by subtracting the driving wheel friction braking force obtained from the unchangable front and rear wheel friction braking force distribution ratio from the driving wheel braking force target value obtained from the driving wheel braking force distribution ratio is obtained as a driving wheel regeneration control. A regenerative braking control device for an electric vehicle, characterized in that it is configured to be determined as power. 5. The electric vehicle according to any one of claims 1 to 4, wherein the electric vehicle realizes a deceleration request by a combined brake of a friction brake capable of changing a front and rear wheel friction braking force distribution ratio and a regenerative brake by the motor / generator. In the regenerative braking control device for an electric vehicle according to item 1,
From the target front and rear wheel braking force distribution ratio corresponding to the driving wheel braking force distribution ratio, the friction braking force of the driven wheel and the braking force target value of the driving wheel are obtained,
If this driving wheel braking force target value can be covered by the allowable maximum regenerative braking force, the driving wheel regenerative braking force is set to the same value as the driving wheel braking force target value, and the driving wheel braking force target value is covered by the allowable maximum regenerative braking force. If not, the driving wheel regenerative braking force is set to the same value as the allowable maximum regenerative braking force, and the front and rear wheel friction braking force distribution ratio of the friction brake is set to compensate for the deficiency of the driving wheel braking force with the driving wheel friction braking force. A regenerative braking control device for an electric vehicle characterized by being configured to change.

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