JP4665390B2 - Brake control device for vehicle - Google Patents

Description

  The present invention relates to a vehicle braking control device.

  2. Description of the Related Art Conventionally, as a braking control device for a vehicle equipped with ABS and EBD, there is a control device that recovers regenerative energy generated in a vehicle using a motor as a drive source (see Patent Document 1).

In this control device, the brake hydraulic pressure generated by the depressing force of the brake pedal is detected by using a hydraulic pressure sensor, and the brake controller includes a hydraulic pressure sensor, a wheel speed sensor, a foot brake switch, a parking brake switch, an engine speed sensor, and a shift range sensor. The braking force is controlled by the hydraulic unit based on the output signal. Specifically, when the required braking force calculated based on the input signal is smaller than the threshold value, regenerative braking is performed by the motor, and when the required braking force is greater than the threshold value, braking is performed by increasing the brake hydraulic pressure.
JP 2001-268704 A

  However, in the above-described conventional technology, since the braking force by the hydraulic pressure is generated after the motor generates the maximum torque, the hydraulic braking force is generated compared to the time until the regenerative braking force by the drive motor is generated. There is a problem that the time until the start is slow, the idle running distance due to this delay increases, and the braking performance decreases.

  In view of the above problems, an object of the present invention is to provide a vehicle braking control device that prevents a decrease in braking performance.

The present invention includes a wheel speed detecting means for detecting a wheel speed of a front wheel of a vehicle and a wheel speed of a rear wheel, a drive motor for driving the rear wheel, and a regenerative control means for regeneratively braking the drive motor when the vehicle is decelerated. A hydraulic brake that generates braking force on the front and rear wheels in response to the hydraulic pressure generated by the driver's depression of the brake pedal, and a rear wheel slip that is generated when the load on the front wheel increases during braking during forward traveling. A hydraulic pressure reducing means for restricting an increase in brake hydraulic pressure of a rear wheel to suppress, and when the driver's pedal force is equal to or less than a predetermined pedal force, a pseudo wheel speed smaller than the detected rear wheel speed is calculated, and the driving When the pedaling force of the person is larger than the predetermined pedaling force, the vehicle is provided with a pseudo wheel speed calculating means for using the detected rear wheel speed as a pseudo wheel speed, and the hydraulic pressure reducing means is based on the pseudo wheel speed when a predetermined condition is satisfied. Z Depressurizing the pressure of the rear wheel hydraulic brakes Te, the regenerative control means increases the regenerative torque by the drive motor in response to hydraulic pressure reduction amount of the hydraulic reducing means.

  In the present invention, the delay of the braking force of the hydraulic braking is suppressed while maintaining the braking force as the total vehicle, and the idling distance is not extended, so that the braking performance can be prevented from being lowered.

  FIG. 1 shows a system configuration diagram of a hybrid vehicle including an engine and a motor to which the present invention is applied as drive sources.

  In this hybrid vehicle, the power of the engine 1 is transmitted to the front wheels 4a via the transmission 2 and the front differential gear 3a. The drive motor 5 drives the rear wheel 4b via the rear differential gear 3b.

  Here, the engine 1 is suitably a high-efficiency engine such as a gasoline engine or a diesel engine that can change the opening / closing timing of the intake valve. The transmission 2 uses an automatic transmission with a torque converter having high transmission efficiency. It is preferable that the drive motor 5 is brake regenerative as a generator during braking, and a highly efficient motor, for example, an embedded permanent magnet synchronous motor or a switched reluctance motor is used. The battery 6 that supplies power to the drive motor 5 uses a nickel hydride battery, a lithium ion battery, or a capacitor in terms of output and charge capacity.

  The structure of the hydraulic system related to braking is that the brake pedal 7, a booster 8 that doubles the pedal force generated in the brake pedal 7 by the negative pressure of the engine 1, and the hydraulic pressure of the booster 8 is distributed to the front and rear wheel brakes. The hydraulic control valve 9 includes front and rear wheel hydraulic brakes 10 and 11 that generate a braking force according to the distributed hydraulic pressure.

  The hydraulic control valve 9 constitutes a hydraulic pressure reducing means in the present application, and is provided with a pressure increasing / decreasing solenoid valve. The hydraulic control valve 9 detects whether or not it is likely to be locked based on the slip ratio of the wheel. When this state is detected, the brake hydraulic pressure of the wheel is released and the braking force is reduced to suppress the wheel lock.・ Brake system) and EBD (Electric Brake Force Distribution) that regulates the increase in brake hydraulic pressure of the rear wheels in order to suppress the rear wheel slip that occurs when the load on the front wheels increases during braking while traveling forward Is configured.

Further, the hydraulic control valve 9 requires a control means for detecting the slip state of each wheel and issuing a command for reducing the brake hydraulic pressure, and it is necessary to detect at least the rotational state of each wheel in order to detect the slip. . In this embodiment, the control device is integrated with a regenerative control device 12 to be described later. However, the hydraulic control valve 9 includes a control device that executes independent ABS and EBD, and each wheel is connected via the regenerative control device 12. The status signal may be received.
The front and rear wheel brakes 10 and 11 easily dissipate heat generated during braking, and the brake caliper is preferably an opposed piston type as a disc brake in order to prevent a reduction in braking performance. A drum brake may be used when the vehicle weight is light.

  The hybrid vehicle further includes a regenerative braking control device 12 that integrally controls the vehicle, a drive motor controller 13 that controls the drive motor 5, and a battery controller 14 that detects a storage state of the battery 6.

The regenerative braking control device 12 receives from the battery controller 14 the output signals of wheel speed sensors 15 and 16 that detect the rotational speed of each wheel installed on each of the front wheels 4a and the rear wheels 4b, the state of charge SOC of the battery, and the like. Based on these, an open / close signal is transmitted to the control valve 9 and a regenerative torque command value or a drive torque command value is transmitted to the drive motor controller 13.
In the present application, the outputs of the wheel speed sensors 15 and 16 correspond to braking state signals.

  FIG. 2 shows a configuration of the regenerative braking control device 12, a failure diagnosis device 17 for diagnosing a failure of the regenerative braking control device 12 based on the wheel speed, and a pseudo wheel speed (pseudo braking using the detected wheel speed). A regenerative control device (regeneration control means) 18 that calculates and outputs a state signal) to the drive motor controller 13, and an EBD (hydraulic reduction) that electrically distributes the front and rear wheels of the braking force based on the detected wheel speed or the pseudo wheel speed. Means) 19. A method for calculating the pseudo wheel speed will be described later.

  The drive motor controller 13 includes a CPU, a ROM, an interface, and the like, and controls the drive torque of the drive motor 5 based on a regenerative torque command value input to the interface. Torque control of the drive motor 5 is performed by controlling the amount of power supplied from the battery 6.

  The battery controller 14 detects the current and voltage of the battery 6, calculates the storage state of the battery 6 and the input / output possible power, and outputs the calculation result to the regenerative braking control device 12.

  The flowchart of FIG. 3 is a flowchart for explaining the control content performed by the regenerative braking control device 12. This control is performed at regular time intervals, for example, every 10 msec.

  First, disconnection of each sensor is detected in step 1 (S1 in FIG. 3, the same applies hereinafter), and a short circuit of each sensor is detected in step 2. In the subsequent step 3, system failure diagnosis is performed based on the detection results in steps 1 and 2. The disconnection and short circuit of each sensor causes a voltage drop by causing a current to flow through each sensor, and a failure is determined based on whether or not the voltage drop is a normal value. Also, when a failure is diagnosed by the drive motor controller 13 or the battery controller 14, it is determined that the system is broken.

  If it is determined in step 3 that the system has failed, the process proceeds to step 8, and if not, the process proceeds to step 4. In step 4, the operating state of the ABS is determined. If the ABS is operating, the process proceeds to step 8, and if the operation is stopped, the process proceeds to step 5. As a method for determining the operation of the ABS, the regenerative braking control device 12 calculates the slip ratio of each wheel, and when the calculated slip ratio exceeds a predetermined slip ratio, it is determined that the ABS is operating. Alternatively, the operation signal of the ABS control device included in the EBD 19 may be input to the regenerative braking control device 12 for determination.

  In step 5, the SOC of the battery 6 is read. As an SOC calculation method, the SOC is calculated from the integrated value of the power supplied from the battery 6. At this time, deterioration of the battery 6 may be taken into consideration. The battery 6 is deteriorated by measuring several points of current value and voltage value when the battery 6 is charged / discharged, calculating current-voltage characteristics from the measurement result, and obtaining the slope as the internal resistance. This internal resistance is considered as deterioration when calculating the SOC.

  Further, the SOC of the battery 6 may be calculated from the input / output possible power of the battery 6. As for the power that can be input and output, first, the internal resistance and the open circuit voltage are calculated from the slope of the current-voltage characteristic described above. Next, the maximum charge / discharge current when the battery 6 is charged / discharged to the upper / lower limit voltage is calculated from the internal resistance and the open voltage, and the input / output possible power is calculated from the product of the upper / lower limit voltage and the maximum charge / discharge current. The relationship between the input / output available power and the SOC is previously mapped, and the SOC is calculated from the calculated input / output available power using the map. The SOC can be calculated with higher accuracy by detecting the temperature of the battery 6 and mapping the input / output power as a function of the SOC and the temperature of the battery 6.

  In step 6, it is determined whether the read SOC is larger than a predetermined threshold value C1. If it is below the predetermined threshold value C1, the regenerative torque of the drive motor 5 can be increased and the regenerative braking force can be increased. If it is larger, the process proceeds to step 8; In step 7, the pseudo wheel speed is calculated. A method for calculating the pseudo wheel speed will be described later.

  In the subsequent step 9, a control valve pressure reduction signal for reducing the hydraulic pressure supplied to the rear wheel brake by the EBD 19 is created from the calculated pseudo wheel speed, and a braking force corresponding to the hydraulic pressure reduction is generated by the regenerative torque. Thus, a torque command value is transmitted to the drive motor controller 14. In step 10, the hydraulic pressure of the rear wheel hydraulic brake is reduced based on the pressure reduction signal calculated in step 9.

  Detected in step 8, which proceeds when it is determined in step 3 that the system has failed, in step 4, when it is determined that the ABS is operating, or in step 6, where it is determined that the SOC is greater than the predetermined threshold C1 The wheel speed is transmitted to the EBD 19. In the subsequent step 11, failure processing of the hydraulic brakes 10 and 11 is performed by self-diagnosis of the EBD 19. In step 12, the regenerative braking control in the regenerative braking control device 12 is stopped and the braking is performed only with the hydraulic brake.

  FIG. 4 is a diagram for explaining the flow from the calculation of the pseudo wheel speed to the generation of the braking force, which corresponds to Step 7, Step 9 and Step 10 described above.

  First, the rear wheel speed VwR detected by the rear wheel speed sensor 16 is multiplied by a gain K to decelerate to obtain a rear wheel pseudo wheel speed. The gain K is calculated by obtaining the gain correction value R1 from the estimated pedal effort and multiplying the gain correction value R1 by the reference gain Ki.

  Here, the pedaling force is estimated by calculating the vehicle body speed Vb from the average value of the front left and right wheel speeds (VwFR, VwFL) and the rear left and right wheel speeds (VwRR, VwRL), and the slip ratio SwFR (front right wheel). ), SwFL (front left wheel), SwRR (rear right wheel), and SwRL (rear left wheel) are calculated from the following equations.

算出した前輪のスリップ率から前輪の平均スリップ率を求め、平均スリップ率からタイヤで発生している前輪制動力を線形計算により求める（図５参照）。ここで傾きａは予め実験等により算出しておく。傾きａは好ましくは、路面の摩擦係数により補正される。そして求めた前輪制動力からブレーキ踏力を線形計算により演算する（図６参照）。ここで傾きｂは予め実験等により算出しておく。なお、踏力推定計算は、ＡＢＳが作動しないスリップ率の場合にのみ演算されるため、前輪スリップ率と前輪制動力とはほぼ比例関係が成立する。

The average slip ratio of the front wheels is obtained from the calculated slip ratio of the front wheels, and the front wheel braking force generated in the tire is obtained from the average slip ratio by linear calculation (see FIG. 5). Here, the inclination a is calculated in advance through experiments or the like. The slope a is preferably corrected by the friction coefficient of the road surface. Then, the brake depression force is calculated by linear calculation from the obtained front wheel braking force (see FIG. 6). Here, the inclination b is calculated in advance through experiments or the like. Since the pedaling force estimation calculation is calculated only when the slip rate is such that the ABS does not operate, the front wheel slip rate and the front wheel braking force are substantially proportional.

  The gain correction value R1 is calculated from a table (FIG. 7) showing the relationship between the preset gain correction value R1 and the pedal effort. The correction value R1 approaches 1.0 as the pedal effort increases, and becomes 1 above a predetermined value. That is, in the region where the pedal effort is low, the correction value R1 is set to be smaller than 1 and set to be lower than the wheel speed at which the rear wheel side pseudo wheel speed is detected.

  However, the intercept R2 changes according to the SOC according to the table (FIG. 8) showing the relationship between the SOC and the intercept R2. That is, when the SOC is 100%, the intercept R2 is 1, and the correction value R1 is 1 regardless of the pedaling force. Note that the table shown in FIG. 8 is preferably corrected according to the degree of deterioration of the battery 6.

  The reference gain Ki is a value at which the control of the EBD 19 is most stable when regeneration is performed in a state where the SOC is sufficiently small, and is calculated beforehand by an experiment or the like.

  Based on the rear wheel side pseudo wheel speed calculated by the gain K and the detected front wheel speed, the EBD 19 performs PWM control on the rear wheel hydraulic valve of the control valve. That is, when the gain K is smaller than 1, the brake hydraulic pressure of the rear wheel is controlled to be reduced. A braking force is generated in the rear wheel hydraulic brake 11 by the hydraulic pressure adjusted by the rear wheel hydraulic valve.

  On the other hand, the deviation between the detected rear wheel speed and the front wheel speed is calculated, and in the motor EBD control, the target motor regeneration torque is calculated so that the difference becomes 0 (zero). Therefore, by executing the control using the pseudo wheel speed described above, the hydraulic pressure of the hydraulic brake is reduced and the deceleration of the wheel speed of the rear wheel is reduced. In addition, the regenerative braking amount of the drive motor 5 is increased and the total braking force as the vehicle is secured.

A block diagram of the motor EBD control is shown in FIG. The PID control as the deviation e _n of the rear wheel speed and the front wheel speed for calculating a change amount Δm of target rear-wheel regenerative torque m.

  When the rear wheel speed is lower than the front wheel side, the target rear wheel regenerative torque m is set smaller. When the rear wheel speed is higher than the front wheel side, the target rear wheel regenerative torque m is set. Set larger. In this way, regenerative energy is obtained without reducing the total braking performance. In the PID control described above, gain correction is performed based on the vehicle body speed. The gain correction is set from FIG. 10, FIG. 11, and FIG. 12, which show the relationship between the vehicle body speed Vb, the proportional band PB%, the integration time Ti (sec), and the differential time Td (sec). As shown in the figure, the proportional band PB% gradually increases with the increase in the vehicle speed, and the integration time Ti decreases at a constant rate with the increase in the vehicle speed. On the other hand, the differential time Td increases in proportion to the vehicle body speed at or above a predetermined vehicle body speed.

Variation Δm of target rear-wheel regenerative torque is calculated by subtracting the previous value m _n-1 of the target rear-wheel regenerative torque from the target rear-wheel regenerative torque m _n can be calculated by the following equation.

図４に戻り、演算された目標後輪回生トルクの変化量Δｍは駆動モータコントローラ１３に入力され、駆動モータ５をベクトル制御して回生トルクが発生する。そして、後輪油圧ブレーキ１１の制動力と駆動モータ５の回生トルクの加算値が車両の後輪制動力となる。

Returning to FIG. 4, the calculated change amount Δm of the target rear wheel regenerative torque is input to the drive motor controller 13, and the regenerative torque is generated by vector control of the drive motor 5. The added value of the braking force of the rear wheel hydraulic brake 11 and the regenerative torque of the drive motor 5 becomes the rear wheel braking force of the vehicle.

  Although the present embodiment has been described as a hybrid vehicle in which the engine 1 is installed as a front wheel side drive source, the present invention can also be applied to a hybrid vehicle motor in which the front wheel drive source is a motor.

  Therefore, in the vehicle braking control apparatus of the present invention, a driving motor that drives at least one of the front wheels and the rear wheels of the vehicle as driving wheels, regenerative braking control means that regeneratively brakes the driving motor when the vehicle decelerates, The regenerative control, comprising: a hydraulic brake that generates a braking force on the front and rear wheels in accordance with a hydraulic pressure generated by a depression force that depresses a brake pedal; and a hydraulic pressure reduction unit that reduces a hydraulic pressure of the hydraulic brake in accordance with a braking state of a vehicle. The means outputs a pseudo braking state signal to the hydraulic pressure reduction means when a predetermined condition is satisfied, and increases the regenerative torque by the drive motor in accordance with a difference in wheel speeds of the front and rear wheels. The reducing means reduces the hydraulic brake braking force delay in accordance with the input pseudo braking state signal, suppresses the delay of the hydraulic braking braking force, and Without having to extend the, it is possible to prevent the deterioration of the braking performance.

  Further, a wheel speed detecting means for detecting the wheel speed of the front wheel and the wheel speed of the rear wheel is provided, and the regenerative control means is configured so that the detected wheel speed of the front wheel and the wheel speed of the rear wheel are the same. Since the regenerative torque is increased or decreased, accurate braking force control by the drive motor is possible, and the braking performance can be improved.

  The regeneration control means outputs a pseudo braking state signal that increases the difference between the detected wheel speed of the front wheel and the wheel speed of the rear wheel to the hydraulic pressure reducing means, and the hydraulic pressure reducing means outputs the pseudo braking state signal. Accordingly, since the hydraulic pressure of the hydraulic brake of the drive wheel is reduced, the delay of the braking force of the hydraulic braking is suppressed, the idling distance is not extended, and the deterioration of the braking performance can be prevented.

  Since the regenerative control means includes pedal force estimating means for estimating the driver's pedaling force from the wheel speed of the driven wheel, a hydraulic sensor can be dispensed with and the cost can be reduced.

  Wheel speed detection means for detecting the wheel speed of the front wheel and the wheel speed of the rear wheel is provided, and when the driver's pedaling force is less than or equal to a predetermined pedaling force, the pseudo braking state signal is the wheel speed obtained by detecting the wheel speed of the driving wheel. When the driver's pedaling force is larger than the predetermined pedaling force, the pseudo braking state signal is the same as the detected wheel speed of the driving wheel, so stable braking is possible even during sudden deceleration with a large pedaling force. It can be carried out.

If the difference between the wheel speed and the vehicles of the vehicle speed from the wheel speed and the rear wheel of the prior SL front wheel is greater than a predetermined value, for the same wheel speed detecting a wheel speed of the driving wheels, when the ABS is active Also, stable braking performance can be ensured.

  Since the braking performance can be improved, the present invention is useful for a hybrid vehicle.

It is a block diagram of the hybrid vehicle system of this invention. It is a block diagram of the regenerative braking control apparatus of this invention. It is a flowchart explaining the control content of a regenerative braking control apparatus. It is a figure explaining the flow from calculation of pseudo wheel speed to generation of braking force. It is a figure which shows the relationship between a slip ratio and front-wheel braking force. It is a figure which shows the relationship between front-wheel braking force and brake pedal effort. It is a map which shows the relationship between gain correction value R1 and pedal effort. It is a table which shows the relationship between intercept R2 and SOC. It is a block diagram of EBD control. It is a figure which shows the relationship between the proportional band PB and the vehicle body speed Vb. It is a figure which shows the relationship between integration time Ti and vehicle body speed Vb. It is a figure which shows the relationship between differentiation time Td and vehicle body speed Vb.

Explanation of symbols

1 Engine 2 Transmission 3 Differential Gear 4 Front Wheel 5 Drive Motor 6 Battery 7 Brake Pedal 8 Booster 9 Control Valve 10 Front Wheel Hydraulic Brake 11 Rear Wheel Hydraulic Brake 12 Regenerative Braking Controller 13 Drive Motor Controller 14 Battery Controllers 15 and 16 Wheel Speed Sensor 17 Failure diagnosis device 18 Regeneration control device 19 EBD

Claims (6)

Wheel speed detecting means for detecting the wheel speed of the front wheel and the wheel speed of the rear wheel of the vehicle;
A drive motor for driving the rear wheel ;
Regenerative control means for regeneratively braking the drive motor during vehicle deceleration;
A hydraulic brake that generates a braking force on the front and rear wheels according to a hydraulic pressure generated by a pedaling force of a driver depressing a brake pedal;
Oil pressure reducing means for restricting an increase in the brake oil pressure of the rear wheel in order to suppress a rear wheel slip caused by an increase in a load on the front wheel during braking during forward traveling ;
When the driver's pedaling force is less than or equal to a predetermined pedaling force, a pseudo wheel speed smaller than the detected rear wheel speed is calculated, and when the driver's pedaling force is larger than the predetermined pedaling force, the detected rear wheel speed is simulated. Pseudo wheel speed calculation means for making the wheel speed;
With
The hydraulic pressure reducing means reduces the hydraulic pressure of the hydraulic brake of the rear wheel based on the pseudo wheel speed when a predetermined condition is satisfied,
The regenerative control means increases the regenerative torque by the drive motor corresponding to the hydraulic pressure reduction of the hydraulic pressure reducing means .
A braking control device for a vehicle characterized by the above. A battery for supplying electric power to the drive motor and charging electric power regenerated by the drive motor;
The pseudo wheel speed is set according to a wheel speed of the rear wheel , a pedaling force that is a force by which a driver depresses a brake pedal, and an SOC of the battery.
The vehicle braking control apparatus according to claim 1. Before SL regenerative control means comprises a wheel speed of the wheel speed and the rear wheel of the detected front wheel increases or decreases the regenerative torque of the drive motor to be identical,
The braking control apparatus for a vehicle according to claim 1 or 2. The pseudo wheel speed calculating means, the pseudo wheel speed calculated to increase the difference between the wheel speeds of the wheel speed and the rear wheel of the detected front wheel,
The hydraulic reducing means reduces the oil pressure of the hydraulic brake of the rear wheel in accordance with the prior Ki擬 similar wheel speed,
The vehicle braking control device according to claim 1, wherein the vehicle braking control device is a vehicle braking control device. The regenerative control means includes pedal force estimating means for estimating the driver's pedaling force from the wheel speed of the front wheels.
The vehicle braking control apparatus according to claim 1. Establishment condition of the predetermined condition, ABS is actuated Orazu, and supplies power to the drive motor, SOC of the battery to charge the electric power driving motor is power is below a predetermined value,
The braking control device according to claim 1.

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