JP5506632B2 - Brake device for vehicle - Google Patents

Description

  The present invention relates to a vehicle brake device, and more particularly to a vehicle brake device that performs regenerative cooperative braking.

  In electric vehicles and hybrid vehicles, a motor (electric motor) is connected to the drive wheels or all wheels, and the motor can be used as a generator during braking so that braking can be performed by regenerative braking. The regenerative cooperative braking combined with the hydraulic brake (hydraulic braking) is performed because the necessary braking force is not always obtained only by the regenerative braking due to the battery capacity or the like. Some automobiles use regenerative braking to the maximum extent in terms of energy efficiency even if the braking force distribution is slightly disrupted during normal braking.

  However, if the braking force, which is the sum of regenerative braking and hydraulic braking, is significantly biased at any of the front, rear, left, and right wheels, the wheels with a high braking load on the tire tend to lock, and ABS or skid prevention devices (hereinafter referred to as ABS) In particular, there is a risk that it will operate earlier than the start of operation of the ABS when regenerative braking is not performed. Further, depending on the situation, it is conceivable that the above-described uneven distribution of the braking force may adversely affect the turning state of the vehicle. Further, when operating the ABS, it is preferable to control mainly by the hydraulic brake. In that case, the ratio of the regenerative braking to the hydraulic brake is reduced or made zero. This would be against the intention of use.

  Therefore, the front and rear wheel speed difference is used to determine the bias of the front and rear braking force distribution, the turning state is determined using the steering angle signal, etc., and excessive regenerative braking braking torque is suppressed. Various techniques have been proposed (see, for example, Patent Documents 1, 2, and 3).

JP 2008-56151 A JP 2006-204073 A JP 2006-246657 A

  On the other hand, if an excessive bias occurs in the braking force distribution of each wheel due to excessive use of regenerative braking, there is a risk that the braking stability of the vehicle will deteriorate. For example, when a motor is connected to the front wheels, excessive use of regenerative braking promotes an understeer tendency, and conversely, the rear wheels are oversteered. In the case of ABS, the operating sound, vibration, etc. may cause discomfort to the occupant, and it is necessary to prevent an increase in the operating frequency of ABS caused by excessive use of regenerative braking.

  In many ABSs, the amount of tire slip is controlled independently on all four wheels, but when a motor is connected to one or both of the front and rear axles, torque is distributed to the left and right wheels. Therefore, it is not appropriate to use the regenerative braking in such a case for the ABS control. Also, if the motor regenerative braking torque remains at the start of the ABS operation, when the regenerative braking torque is increased or decreased, the drive train will be via an inertia or a torsional element, and the responsiveness to increase or decrease the braking force. However, there is a problem that it becomes disadvantageous compared with the case where ABS control is performed only by a hydraulic brake.

In order to solve such a problem, perform regenerative cooperative braking, and suppress frequent operation of the ABS due to excessive use of regenerative braking, in the present invention, a vehicle (1 Friction braking means (2a, 3a, 8, 22) for friction braking each wheel of the front wheel (2) and rear wheel (3)), and a motor (5) connected to at least one of the front wheel and the rear wheel And a braking force distribution means (6) for distributing and controlling the braking forces of the friction braking means and the regenerative braking means during braking. Wheel speed detecting means (9) for detecting each wheel speed of each wheel, and wheel speed calculating means (12.13) for specifying the maximum value and the minimum value of each wheel speed based on each wheel speed. ) And the vehicle speed that determines the vehicle speed of the vehicle And a constant means (26), the brake force distribution means obtains a relative slip rate of the difference between the maximum value and the minimum value of the wheel speeds divided by the vehicle speed, the greater said relative slip rate It was assumed to reduce the ratio of regenerative braking by extent the regenerative braking means.

  According to this, for example, the relative slip ratio can be obtained based on the difference between the maximum value of each wheel speed and the vehicle body speed and the difference between the minimum value of each wheel speed and the vehicle body speed, and the magnitude of the relative slip ratio. By performing control that suppresses the magnitude of regenerative braking as the value of R is larger, it is possible to prevent regenerative braking from being excessively effective without monitoring the amount of load movement in the front-rear direction and the left-right direction of the vehicle. When slip occurs, there is a high possibility that the ABS will operate. In such a case, if the regenerative braking remains large, the ABS may operate frequently. In the case of ABS operation, the frequency of ABS operation due to regenerative braking can be reduced by controlling the distribution of regenerative braking to be small in advance.

In particular, the wheel speed calculation means may set the minimum value of the wheel speed at the wheel connected to the motor as the minimum value to be specified and the maximum value of the wheel speed at all wheels as the maximum value to be specified. . According to this, since the magnitude of regenerative braking is suppressed with reference to the wheel to which the motor is connected, the regenerative braking is performed even when the wheel to which the motor is not connected becomes locked due to overcoming a step or moving a load. By suppressing the braking and suppressing the regenerative braking unnecessarily, it is possible to prevent leaving from the purpose of using the regenerative braking as much as possible.

Further, the motor (5, 45) is connected to the front wheel and the rear wheel, and the regenerative braking means regeneratively brakes the front wheel and regenerative braking means (21) for the front wheel that regeneratively brakes the front wheel. Rear wheel regenerative braking means (41), and the wheel speed calculating means includes a front wheel minimum value that is a minimum value of the wheel speed of the front wheel and a rear wheel minimum value that is a minimum value of the wheel speed of the rear wheel. The braking force distribution means obtains a front wheel relative slip ratio obtained by dividing the difference between the maximum value and the minimum front wheel value by the vehicle body speed, and the front wheel regenerative braking increases as the front wheel relative slip ratio increases. The ratio of the regenerative braking of the front wheels by the means is reduced, and the difference between the maximum value and the rear wheel minimum value is divided by the vehicle body speed to obtain the rear wheel relative slip ratio , and the larger the rear wheel relative slip ratio is, the larger the rear wheel relative slip ratio is. In the rear wheel regenerative braking means That may reduce the ratio of regenerative braking of the rear wheel. According to this, since the regenerative control of the front and rear wheels can be performed independently, the regenerative braking can be suppressed even earlier when the regenerative braking becomes excessive.

  Further, the vehicle has anti-lock control means (24) for preventing the wheels from being locked by increasing / decreasing each friction braking force of each wheel, and the braking force distribution means is effectively controlled by the anti-lock control means. In such a case, the magnitude of the regenerative braking may be set to a preset minimum value regardless of the magnitude of the relative slip ratio. According to this, even when the lock tendency cannot be detected before the operation of the anti-lock control means (ABS) by the calculation of the relative slip ratio, the regenerative torque is quickly reduced to shift to the anti-lock control by friction braking. Can do.

  The braking force distribution means may include regenerative braking force suppression amount regulating means (18) that regulates fluctuations in the regenerative braking force suppression amount. According to this, the fluctuation | variation of the vehicle by the increase / decrease in the braking force (torque) of regenerative braking can be suppressed.

  As described above, according to the present invention, as the relative slip ratio is increased, the regenerative braking is controlled so that the load movement amount in the front-rear direction and the left-right direction of the vehicle is not monitored. The regenerative braking can be prevented from being excessively effective, the ABS operation due to the regenerative braking can be prevented, and the regenerative braking can be effectively performed.

It is a principal part systematic diagram of the brake system of the motor vehicle to which this invention was applied. It is a control block diagram based on this invention. It is a figure which shows the relationship of the coefficient R with respect to relative slip ratio SP. It is a map which shows the relationship of the braking force of a front wheel and a rear wheel. It is a figure corresponding to the principal part of FIG. 2 which shows 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of a main part of a brake system of an automobile to which the present invention is applied.

  The automobile shown in FIG. 1 has a pair of left and right front wheels 2 disposed on the front side of the vehicle 1 and a pair of left and right rear wheels 3 disposed on the rear side of the vehicle 1. An electric motor 5 is mechanically connected to the front wheel axle 4 connected to the left and right front wheels 2. The differential mechanism is not shown.

  In addition, by providing a control circuit using a CPU, various control of the vehicle is performed and a control unit 6 as a braking force distribution means is provided. A battery 7 serving as a power source is connected to the control unit 6, and a motor 5 is electrically connected. In the case of an electric vehicle, this configuration may be maintained. However, in the case of a hybrid vehicle, an output shaft of an engine (internal combustion engine) (not shown) is connected to the front wheel axle 4.

  Each wheel of the front wheel 2 and the rear wheel 3 is provided with a known disc brake as friction braking means for friction-braking each wheel, and the calipers 2a and 3a of each disc brake are connected via a known brake pipe. A brake fluid pressure generator 8 is connected. The brake fluid pressure generator 8 is configured by a hydraulic circuit that can distribute the brake pressure by increasing or decreasing the brake pressure for each wheel.

  Each wheel speed sensor 9 is provided as a wheel speed detecting means for detecting the wheel speed corresponding to each wheel of the front wheel 2 and the rear wheel 3, and the brake pedal 11 operated by the driver has an operation amount thereof. A displacement sensor 11a for detecting (depression amount) is provided. Each detection signal of each wheel speed sensor 9 and displacement sensor 11 a is input to the control unit 6.

  The control unit 6 determines that a braking command has been issued when the output signal of the displacement sensor 11a of the brake pedal 11 increases from 0, and performs control during braking. In the illustrated example, the braking is performed by regenerative cooperative control in which regenerative braking and hydraulic braking are performed, and therefore, it is assumed to be brake-by-wire.

  Next, the control unit 6 will be described with reference to FIG. As the wheel speeds, the signals of the left front wheel speed WFL, the right front wheel speed WFR, the left rear wheel speed WRL, and the right rear wheel speed WRR are the maximum value specifying circuit 12 and the vehicle speed estimation as the vehicle speed determining means. In addition to being input to the circuit 26, the front wheel speeds WFL and WFR are input to the minimum value specifying circuit 13. The maximum value specifying circuit 12, the minimum value specifying circuit 13, and the vehicle body speed estimating circuit 26 constitute wheel speed calculating means.

  The maximum value specifying circuit 12 specifies the maximum value Wmax of each wheel speed WFL / WFR / WRL / WRR and outputs it to the differentiator 14. The vehicle body speed estimation circuit 26 estimates the vehicle body speed using a known method based on the wheel speeds WFL, WFR, WRL, and WRR, and outputs the estimated pseudo vehicle body speed to the lower limit value setting circuit 16. Here, the maximum value Wmax may be used as the vehicle body speed Vv of the vehicle 1. This is based on the premise that the braking control according to the present invention is before the operation of the ABS (anti-lock control means), and in this case, the slip amount of each of the wheels 2 and 3 is not large. This is because the maximum wheel speed can be set to the pseudo vehicle speed. This can simplify the circuit. The vehicle body speed Vv may be an average value or a vehicle speed obtained from a ground sensor (not shown) instead of the maximum value Wmax.

  The minimum value specifying circuit 13 specifies the minimum value Wmin of each front wheel speed WFL / WFR and outputs it to the differentiator 14. The difference unit 14 obtains a wheel speed difference ΔW between the maximum value Wmax and the minimum value Wmin and outputs the difference to the divider 15. Thereby, it can respond to both the front-back wheel speed difference of the front wheel 2 and the rear wheel 3, and the left-right wheel speed difference.

  On the other hand, the vehicle body speed Vv corresponding to the maximum value Wmax from the maximum value specifying circuit 12 is input to the lower limit value setting circuit 16. The lower limit value setting circuit 16 is preset with a lower limit value WL corresponding to the minimum detection limit value (a value greater than 0) by each wheel speed sensor 9, and when the input vehicle speed Vv is less than or equal to the lower limit value WL. When the vehicle body speed Vv (= WL) into which the lower limit value WL is substituted is larger than the lower limit value WL, the vehicle body speed Vv is output to the divider 15.

  The divider 15 outputs the result obtained by dividing the wheel speed difference ΔW by the vehicle body speed Vv to the percentage converter 17. The percentage converter 17 converts the value of ΔW (= (Wmin−Wmax) / Vv) into a percentage and outputs the relative slip ratio SP to the backlash processing circuit 18 as a relative slip ratio SP. The wheel corresponding to the minimum value Wmin (the absolute value of the slip ratio) of the front wheel 2 (motor drive wheel) has the maximum braking force load, and the maximum value Wmax of all the wheels 2 and 3 (the absolute value of the slip ratio is the minimum). Wmin / Vv−Wmax / Vv = ΔW / Vv, which is obtained by dividing both values by the vehicle body speed, is interpreted as a relative load (slip rate difference) of the braking force. The relative slip ratio SP corresponds to a value obtained by converting this slip ratio difference into a percentage. Although percentages are used, the present invention is not limited to this, and the magnification may be set as appropriate based on the slip ratio difference.

  The backlash processing circuit 18 has both a temporary peak hold function and a noise processing function. For example, by processing an input waveform (for example, amplitude 10) with a backlash cutoff width (for example, 8), the input value becomes a dead zone up to half (4) of the cutoff width. When the input value becomes more than half of the cut-off width, the output waveform is generated so as to follow the input waveform. When the input value is inverted, the input value is changed in the opposite direction by the cut-off width (8) from the inversion start point. Until it fluctuates, the output value corresponding to the start of inversion of the input value is held, and thereafter, the output waveform is offset by half (4) of the cutoff width to follow the input value. The blocking width is preferably 5 to 8%.

  The signal backlash processed by the backlash circuit 18 in this way is input to the regenerative braking coefficient setting circuit 19. The regenerative braking coefficient setting circuit 19 obtains a coefficient R for reducing regenerative braking. A method of obtaining the coefficient R will be described with reference to FIG.

  FIG. 3 shows an example of the relationship of the coefficient R to the relative slip ratio SP. As shown in the figure, the relative slip ratio SP is between 0% and SP1 {(− x) + (x / 2)}%. Then, the coefficient R remains 1, and the coefficient R changes in proportion to the relative slip ratio SP between the relative slip ratio SP1 and SP2 {(−2x) + (x / 2)}. The slip ratio SP2 becomes 0, and becomes 0 when the relative slip ratio SP is larger than SP2. Here, x is a backlash cutoff width. For example, when the backlash cutoff width is 8%, SP1 is −4% and SP2 is −12%.

  The coefficient R thus obtained is output to the regenerative cooperative control circuit 20. The regenerative cooperative control circuit 20 determines the magnitude of the braking force based on the detection value (braking operation amount FB) from the displacement sensor 11a, and the magnitude is set by the coefficient R for the braking force. The regenerative braking is prioritized and the shortage is set as hydraulic braking, the regenerative braking command value Fa is output to the regenerative braking control circuit 21 as regenerative braking means, and the hydraulic braking command value Fb is output to the hydraulic braking control circuit 22. Output. The regenerative braking force of the motor 5 is generated with a magnitude corresponding to the output from the regenerative braking control circuit 21, and the brake pressure for the caliper 2 a is controlled by the brake hydraulic pressure generator 8 according to the output from the hydraulic braking control circuit 22. A hydraulic braking force (friction braking force) is generated.

  At this time, the braking force is distributed as shown in FIG. That is, the area indicated by hatching on the left side of the boundary A in the figure is a portion where the regenerative braking acts, and the boundary A is a delimiter having the maximum regenerative braking width B determined by the rating of the motor 5 and the like. The region on the right side is a portion where hydraulic braking is applied to the front wheels. The size of regenerative braking when the partition A is the coefficient R = 1, and the width B decreases as the coefficient R decreases, for example, as the partition C indicated by the two-dot chain line in FIG. That is, when the braking is started, regenerative braking is applied to the front wheel to reach the break A, but when the coefficient R becomes a value that decreases from 1 and the regenerative braking area is narrowed to break C, the ratio of the hydraulic braking Increases and regenerative braking is suppressed. The maximum width B of the regenerative braking is increased or decreased depending on other vehicle parameters such as the remaining battery level.

  When the relative slip ratio SP increases, there is a possibility that the ABS may operate. When the above-mentioned separation remains A, if the ratio of regenerative braking with respect to the entire braking force is large, the accuracy of ABS control will be increased. There is a risk of lowering. On the other hand, the ratio of the regenerative braking is reduced by reducing the coefficient, and the coefficient is set to 0 when the relative slip ratio SP is large. Therefore, the ratio of the regenerative braking in the entire braking force according to the increase of the relative slip ratio SP. The frequency of occurrence of ABS due to regenerative braking can be reduced.

  In addition, when the rear wheel that does not perform regenerative braking is locked due to overcoming a step or moving a load during turning, the relative slip ratio is detected when the minimum wheel speed of any one of the wheels is detected. SP increases and regenerative braking decreases. On the other hand, even if the rear wheels that do not perform regenerative braking are locked by setting the smallest wheel speed among the front wheels subject to regenerative braking as shown in this example to the minimum wheel speed, Thus, the relative slip ratio SP is not increased, and regenerative braking can be prevented from being suppressed unnecessarily, and braking control utilizing regenerative braking to the maximum can be performed.

  Next, a second embodiment will be described with reference to FIG. The second embodiment is configured such that regenerative braking can be performed for each of the front and rear wheels, whereas the above embodiment has a structure in which regenerative braking is performed only on the front wheels. The same parts as those in FIG. 2 are given the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 5, the rear wheel speeds WRL and WRR are input to the rear wheel minimum value specifying circuit 33. The circuit configuration and control procedure from the minimum value specifying circuit 33 to the subtractor 34, the divider 35, the lower limit value setting circuit 36, the percentage converter 37, the backlash processing circuit 38, and the regenerative braking coefficient setting circuit 39 are the above minimum values. The circuit configuration and control procedure from the specific circuit 13 to the subtractor 14, the divider 15, the lower limit setting circuit 16, the percentage converter 17, the backlash processing circuit 18, and the regenerative braking coefficient setting circuit 19 may be the same. Note that the maximum value Wmax of the maximum value specifying circuit 12 and the minimum value Wminr of the rear wheel minimum value specifying circuit 33 are input to the subtractor 34, and the vehicle body speed Vv is input to the lower limit value setting circuit 36.

  Thus, like the coefficient R of the above embodiment, the front wheel regenerative braking coefficient Rf and the rear wheel regenerative braking coefficient Rr are set, and the front wheel coefficient Rf and the rear wheel coefficient Rr are set in the regenerative cooperative control. The magnitudes of regenerative braking and hydraulic braking for each of the front wheels and the rear wheels corresponding to the braking force requested by the driver are input to the circuit 20.

  Thereby, the regenerative braking control circuit 21 applies the front wheel regenerative braking to the motor 5, and the rear wheel regenerative braking control circuit 41 connects the rear wheel regenerative braking to the rear wheel 3. In contrast, each can be controlled independently. Similarly for hydraulic braking, front wheel hydraulic braking is controlled by the brake fluid pressure generator 8 to control the front wheel 2 (caliper 2a), and rear wheel hydraulic braking is controlled by the brake fluid pressure generator 48 to the rear wheel. 3 (caliper 3a) can be performed independently. In this way, since the regenerative control of the front and rear wheels 2 and 3 can be performed independently, the regenerative braking can be suppressed even earlier when the regenerative braking becomes excessive.

  Also, an ABS device 24 (FIG. 2) as a known antilock control means is provided, and its activation signal is input to the regenerative braking coefficient setting circuit 19, and in the regenerative braking coefficient setting circuit 19, When the ABS activation signal is input, the coefficient R is set to a value (for example, zero) corresponding to the necessary minimum regeneration amount. As a result, even if the lock tendency cannot be detected before the ABS is activated by calculating the relative slip ratio SP, the regenerative torque can be quickly reduced to shift to ABS control by hydraulic braking (friction braking).

  Further, the control unit 6 may be provided with a backlash processing circuit 18 as a regenerative braking force suppression amount regulating means for regulating fluctuations in the regenerative braking force suppression amount. For example, the relative slip ratio SP is processed by the backlash processing circuit 18 to suppress excessive fluctuation of the value output to the regenerative braking coefficient setting circuit 19. Thereby, the fluctuation | variation of the vehicle by the big increase / decrease in the braking force (torque) of regenerative braking can be suppressed. Here, the backlash process is selected as means for suppressing the fluctuation amount of the output signal without initial phase delay with respect to the input signal, but the present invention is not limited to this.

1 Vehicle 2a, 3a Caliper (Friction braking generating means)
5 Motor 8 Brake fluid pressure generator (Friction braking generator)
9 Wheel speed sensor (wheel speed detection means)
12 Maximum value identification circuit (wheel speed calculation means / body speed determination means)
13 Minimum value specifying circuit (wheel speed calculation means)
18 Backlash processing circuit (regenerative braking force suppression amount regulating means)
21 Regenerative braking control circuit (regenerative braking means / regenerative braking means for front wheels)
22 Hydraulic braking control circuit (friction braking generating means)
24 ABS device (anti-lock control means)
26 Vehicle speed estimation circuit (vehicle speed determination means)
41 Regenerative braking control circuit (regenerative braking means for rear wheels)
45 motor

Claims (5)

Friction braking means for frictionally braking the front and rear wheels of the vehicle; regenerative braking means for generating regenerative braking by a motor connected to at least one of the front and rear wheels; and the friction braking means during braking. A braking device for a vehicle having braking force distribution means for distributing and controlling each braking force with the regenerative braking means,
Wheel speed detection means for detecting each wheel speed of each wheel;
Wheel speed calculating means for specifying the maximum value and the minimum value of each wheel speed based on each wheel speed;
Vehicle body speed determining means for determining the vehicle body speed of the vehicle,
The brake force distribution means, the relative slip ratio of the difference divided by the vehicle speed of the maximum value and the minimum value of the wheel speeds calculated, the ratio of the regenerative braking by the regenerative braking means the greater said relative slip rate The brake device for vehicles characterized by reducing . The wheel speed calculation means sets the minimum value of the wheel speed in the wheel connected to the motor as the specified minimum value, and sets the maximum value of the wheel speed in all wheels as the specified maximum value. The vehicle brake device according to claim 1. The motor is connected to the front wheel and the rear wheel;
The regenerative braking means includes a front wheel regenerative braking means for regeneratively braking the front wheel, and a rear wheel regenerative braking means for regeneratively braking the rear wheel,
The wheel speed calculation means respectively identifies a front wheel minimum value that becomes a minimum value of the wheel speed of the front wheel and a rear wheel minimum value that becomes a minimum value of the wheel speed of the rear wheel,
The braking force distribution means obtains a front wheel relative slip ratio obtained by dividing a difference between the maximum value and the front wheel minimum value by the vehicle body speed, and the front wheel regenerative braking means increases the front wheel regenerative braking ratio as the front wheel relative slip ratio increases. while decreasing the ratio of braking, the maximum value and the rear wheel the difference between the minimum value and the search of wheels relative slip rate was divided by the vehicle speed and the rear wheel relative slipping after the higher rate is larger wheel regenerative braking means The vehicle brake device according to claim 1, wherein a regenerative braking ratio of the rear wheel is reduced . Anti-lock control means for preventing locking of each wheel by increasing or decreasing each friction braking force of each wheel;
The braking force distribution means sets the magnitude of the regenerative braking to a preset minimum value regardless of the magnitude of the relative slip ratio when the control by the antilock control means becomes effective. The vehicle brake device according to any one of claims 1 to 3.   5. The vehicle brake device according to claim 1, wherein the braking force distribution unit includes a regenerative braking force suppression amount regulation unit that regulates fluctuations in the regenerative braking suppression amount. 6.

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