KR20000022751A - Methods for controlling a distribution of braking force - Google Patents

Abstract

PURPOSE: A method for controlling distribution of a braking force is provided to optimize the time to finish of distributing and controlling the braking force from the deceleration degree of a presumptive wheel by sensing the movement of a vehicle load toward a back wheel from a front wheel. CONSTITUTION: An initialization of a device is performed, and the speed of a vehicle wheel is output from a signal of a sensor of a vehicle wheel. The presumptive deceleration degree of a front wheel and a rear wheel are output from data such as the speed of the wheel and so on. Each mode of brake control such as anti-lock brake control, braking force distribution control and so on is judged from the output values. In case of the anti-lock brake control, anti-lock brake control process is performed, and if not, the judgement of control mode for a braking force distribution is performed. In case of the brake distribution control process, a distribution control process is performed, and if not, a generalized brake control process is performed.

Description

Methods for controlling a distribution of braking force}

The present invention relates to control of braking force distribution of a vehicle.

Conventionally, the end of the braking force distribution control is close to a stationary state at a low speed so that the vehicle hardly requires braking force distribution control, or the brake switch is changed from on to off, or the boosting pulse in the boost mode of the braking force distribution control. Is executed by determining whether or not n is output more than n times. However, in the case where the driver has applied the pumping brake, the braking force distribution control will continue regardless of whether the braking force distribution control is in good condition even if the brake switch is switched from on to off in order to press the brake pedal gently once again. There is a possibility.

The present invention is to optimize the end timing of the braking force distribution control by detecting the movement of the vehicle load from the front wheel to the rear wheel from the estimated wheel deceleration of the front wheel and the rear wheel.

1 is a schematic view of a brake control device.

2 is a diagram of a brake hydraulic system in four wheels;

3 is a flowchart of brake control.

4 is a time chart of deceleration when rushing down.

5 is a time chart of deceleration when not stepped on urgently.

6 is a flowchart of braking force distribution control start determination.

7 is a flowchart of a braking force distribution control process.

8 is a flowchart of braking force distribution control end determination.

9 is another flowchart of braking force distribution control termination determination.

<Description of the symbols for the main parts of the drawings>

1: left front wheel 2: right front wheel

3: left rear wheel 4: right rear wheel

11: brake pedal 12: master cylinder

13: main reservoir 14: wheel cylinder

20: hydraulic unit 21: first hydraulic circuit

22: second hydraulic circuit 23: inlet valve

24: outlet valve 25: pump

26: motor 27: auxiliary reservoir

28: check valve 30: electronic control device

31: wheel speed sensor 32: brake switch

41: main hydraulic circuit 42: auxiliary hydraulic circuit

43: return hydraulic circuit

The present invention provides a hydraulic unit having a main hydraulic circuit connected from the master cylinder to the wheel cylinder via the inlet valve, and an auxiliary hydraulic circuit connected from the wheel cylinder to the auxiliary reservoir via the outlet valve, and an electronic controller for controlling the hydraulic unit. In the brake hydraulic apparatus for a vehicle provided with a brake, the braking force distribution control method for controlling the braking force distribution control for controlling the inlet valve and the outlet valve of the rear wheel when the wheel deceleration of the rear wheel is smaller than the wheel deceleration of the front wheel. , or,

For a vehicle having a hydraulic unit having a main hydraulic circuit connected from the master cylinder to the wheel cylinder through the inlet valve and a secondary hydraulic circuit connected from the wheel cylinder to the auxiliary reservoir via the outlet valve, and an electronic control device for controlling the hydraulic unit. In the brake hydraulic system, the estimated wheel deceleration obtained from the present and previous cycles is compared, and the state in which the current estimated wheel deceleration is smaller than the previous estimated wheel deceleration is continued a predetermined number of times, and the wheel deceleration of the rear wheel is The braking force distribution control method is characterized in that the braking force distribution control for controlling the inlet valve and the outlet valve of the rear wheel is terminated when the front deceleration is smaller than the wheel deceleration.

Example

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1> Outline of vehicle brake hydraulic system

In the vehicle brake hydraulic system, as shown in FIG. 1, the hydraulic pressure generated in the hydraulic unit 20 is applied to each wheel cylinder 14 of the front wheel and the rear wheel, and each wheel (left front wheel 1, right front wheel ( 2) Brake control is performed on the left rear wheel (3) and the right rear wheel (4). For example, in the brake control of the braking force distribution control (EBD) or the anti-lock brake control (ABS), the electronic control device 30 is connected to the electronic control device 30 based on signals from the wheel speed sensor 31, the brake switch 32, or the like. By this, the hydraulic unit 20 is controlled to perform optimum brake control for the wheels. The electronic control apparatus 30 is provided with brake pedal step determination means for determining the step speed of the brake. In addition, the electronic control apparatus 30 may have the structure of a dedicated hard apparatus and general computer apparatuses, such as a microcomputer.

<2> Overview of the hydraulic unit

The example of the hydraulic unit 20 is shown in FIG. 2, and is provided with the hydraulic circuit of brake control, such as braking force distribution control EBD and anti-lock brake control ABS. In addition, FIG. 2 is an example of X piping, and the left front wheel 1 and the right rear wheel 4 are connected to one 1st hydraulic circuit 21, and the right front wheel to the 2nd independent hydraulic circuit 22 of the other. (2) and the left rear wheel 3 are connected.

The hydraulic unit 20 includes a main hydraulic circuit 41 connecting the wheel cylinders 14 of each wheel through the master cylinder 12 and the inlet valve 23, the wheel cylinders 14 and the outlet valves of each wheel ( An auxiliary hydraulic circuit 42 for connecting the auxiliary reservoir 27 to the auxiliary reservoir 27 and a return hydraulic circuit 43 for returning from the auxiliary reservoir 27 to the main hydraulic circuit 41 via the pump 25; The opening and closing of the inlet valve 23 and the outlet valve 24 are controlled to perform predetermined brake control on each wheel. In addition, the main reservoir 13 accumulates the brake fluid, the check valve 28 prevents backflow, and the motor 26 controls the driving of the pump 25.

The operation of the brake hydraulic device will be described below.

<1> Outline of brake control

The electronic control device 30 executes arithmetic processing of the brake control as shown in FIG. 3, for example, by signals from the wheel speed sensor 31, the brake switch 32, or the like. First, the device 30 is initialized (S1), and the wheel speed is calculated from the signal of the wheel speed sensor 31 (S2). The estimated wheel deceleration (value obtained from the wheel deceleration of the front two wheels) and the estimated wheel deceleration (the value obtained from the wheel deceleration of the rear two wheels) of the front wheel are calculated from information such as the wheel speed (S3, S4). ). The estimated vehicle body speed and the estimated vehicle body deceleration (value obtained from the front and rear four wheel decelerations) are calculated from information such as the wheel speed (S5, S6). From these calculations, the respective modes of brake control, such as anti-lock brake control and braking force distribution control, are determined (S7, S8). In the anti-lock brake control mode (S9), the anti-lock brake control process is performed (S11), otherwise (S9), the braking force distribution control mode is determined (S10). In the case of the braking force distribution control mode (S10), the braking force distribution control process (S12) is performed, otherwise (S10), the normal brake control process is performed (S13).

<2> normal brake control

In normal brake control (normal brake control), when the brake pedal 11 is pressed, brake oil pressure is generated in the master cylinder 12, the inlet valve 23 is open, and the outlet valve 24 is closed. Therefore, the brake hydraulic pressure generated by the master cylinder 12 is applied directly to the wheel cylinder 14, and brakes are applied to each of the wheels 1, 2, 3, and 4.

<3> anti-lock brake control

When the brake is applied to the wheel and the wheel is locked, the electronic controller 30 performs anti-lock brake control such as opening / closing control of the inlet valve 23 and the outlet valve 24 and driving control of the pump 25. do.

In the anti-lock brake control, the boosting, holding and depressurizing modes are repeated for each cycle, and the brake hydraulic pressure is controlled. In the boosting mode of one cycle, for example, the inlet valve 23 is opened and closed to control the outlet valve 24. To the closed state, the brake fluid of the wheel cylinder 14 is increased.

The braking force distribution control will be described below. 4 and 5 show time charts of estimated wheel deceleration and estimated body deceleration of the front and rear wheels when the braking force distribution control is performed.

<1> Time chart of deceleration when strongly stepped on

When the brake pedal 11 is pressed hard, for example, the estimated vehicle body deceleration gradually increases as shown in FIG. 4. On the other hand, the estimated wheel deceleration of the front wheel becomes large apart from the estimated body deceleration at t1, and is increased at t4 to coincide with the estimated body deceleration again (point B). The estimated wheel deceleration of the rear wheel sharply increases away from the estimated body deceleration at t2, is greater in line with the estimated wheel deceleration of the front wheel at t3 (point A), becomes the highest at t5, begins to decrease, and again at t6 This corresponds to the estimated wheel deceleration of the front wheel (point C). Further, the deceleration is a negative acceleration, and a large deceleration indicates that the absolute value is large.

In addition, when the brake is applied, the load movement of the vehicle occurs, the point B shows that the load on the front wheel is all moved, and the ground load on the front wheel is maximized, and the point C is the ground load on the rear wheel after the brake is released. Indicates a moved point.

<2> Time chart of deceleration when not stepped strongly

When the brake pedal 11 is strongly pressed, for example, as shown in FIG. 5, the estimated wheel deceleration of the front wheel is slightly larger than the estimated body deceleration at t1. Further, the estimated wheel deceleration of the rear wheel is slightly larger than the estimated body deceleration at t2, coincides with the estimated wheel deceleration of the front wheel at t3 (point A), and gradually increases from the estimated wheel deceleration of the front wheel. The estimated wheel deceleration of the rear wheel is further increased, and the difference between the estimated wheel deceleration of the front wheel becomes a predetermined value β at t4. At t5 (point B) again, the estimated body deceleration coincides with the estimated wheel deceleration of the front wheel, and then the magnitude is reversed.

As in the case of sudden stepping, at t6 (point C), the ground load is moved to the rear wheel after the brake is released.

<3> Start condition of braking force distribution control

The braking force distribution control that performs the brake control of the rear wheels determines the start thereof, for example, as shown in FIG. 6. First, the start condition is divided by the determination of the stepping amount of the brake pedal 11 such as the stepping strength and the speed, that is, the sudden stepping determination. The sudden stepping determination calculates the amount of change in the estimated body deceleration or the wheel deceleration, for example, the estimated body deceleration or the wheel deceleration for each cycle (for example, every 7 ms), and calculates the difference between the previous cycle and the present cycle. When the difference amount continues for a predetermined time [tau] or more than the predetermined value [Delta] [alpha], or a predetermined number of times has occurred, it is determined that it is strongly stepped on (S21). The predetermined value [Delta] [alpha] and the predetermined time [tau] or the predetermined number of times of the difference amount are 0.4G, 27 ms, or 4 times, for example.

Incidentally, the stepping of the brake pedal is not limited to this method, and for example, the stroke of the pedal may be detected and a sudden stepping judgment may be made from the rate of change.

<4> Start condition when stepped strongly

When the brake is strongly pressed, the estimated wheel deceleration of the front wheel is compared with the estimated wheel deceleration of the rear wheel, and it is examined whether the estimated wheel deceleration of the rear wheel is greater than the estimated wheel deceleration of the front wheel (S22). That is, the estimated wheel deceleration of the rear wheel becomes large at the same time as the load movement due to braking, and the estimated wheel deceleration of the front wheel, which is larger than the estimated wheel deceleration of the rear wheel, is smaller at the same time as the ground load of the front wheel increases, and both are equal. Check if it is (point A). When the estimated wheel deceleration of the rear wheel becomes larger than the estimated wheel deceleration of the front wheel, the process proceeds to step S26 for starting braking force distribution control. Otherwise, braking force distribution control is not started.

In this way, when the brake is strongly stepped on, it is necessary to perform the braking force distribution control before the boosting speed of the brake hydraulic pressure is increased and the load of the vehicle moves. In such a case, a sudden stepping determination is performed as the sudden brake power input determination, and the sudden stepping determination is performed to the point A where the influence of the wheel ground pressure due to the load movement is small.

<5> Start condition when it is not stepped strongly

If the stepping degree is not determined strongly (S21), the estimated wheel deceleration of the front wheel and the estimated wheel deceleration of the rear wheel are compared, and the estimated wheel deceleration of the rear wheel is greater than the estimated wheel deceleration of the front wheel. It is checked whether or not (S23). If the difference is greater than the estimated wheel deceleration of the front and rear wheels (point A), and the difference between the estimated wheel deceleration of the front wheel and the estimated wheel deceleration of the rear wheel is greater than or equal to the predetermined value (β) (S24). Then, the braking force distribution control is started (S26). Otherwise, braking force distribution control is not started.

In this way, when it is not strongly stepped on, there is no sudden change in the vehicle body deceleration, but the load movement is already started, and the braking force distribution control is performed up to the point B where the load has moved to the front wheel.

In addition, in step S23, the value of the estimated wheel deceleration of the front wheel and the estimated wheel deceleration of the rear wheel are compared, and instead of the condition for checking whether the estimated wheel deceleration of the rear wheel is greater than the estimated wheel deceleration of the front wheel. After the estimated wheel deceleration of the rear wheel becomes larger than the estimated wheel deceleration of the front wheel (point A), the condition may be sufficient until the estimated wheel deceleration of the front wheel becomes equal to the estimated body deceleration (point B).

<6> braking force distribution control (EBD)

The braking force distribution control (EBD) is to control the brake oil pressure of the wheel cylinder of the rear wheel and, for example, instead of the proportional control valve (P valve), press the rear wheel brake oil pressure low against the brake oil pressure of the front wheel. To control the hydraulic pressure of the wheel cylinder. In the anti-lock brake control device, even when the anti-lock brake control cannot be performed due to a failure of the motor or the pump, the rear wheel slip is prevented by the braking force distribution control.

For example, as shown in the flowchart of FIG. 7, the braking force distribution control process checks whether the braking force distribution control is started (checks whether the start flag is set) (S31), and the start flag is not set. The pressure is increased by normal brake control (S37). When the start flag is set, variables necessary for braking force distribution control such as slip ratio of the rear wheel with respect to the front wheel are calculated (S32). The control mode for increasing, maintaining, and depressurizing the brake hydraulic pressure is determined from the calculated variables and the like (S33). Next, it is checked whether the braking force distribution control is finished (S34), and when it is finished, normal brake control is performed (S37). If it is not finished, it is determined in steps S35 and S36 based on the result of the brake control mode determination obtained in step S33, and the pressure of the wheel cylinder of the rear wheel is increased (S38) or maintained (S39) or decompressed. It becomes (S40).

<7> End condition 1 of braking force distribution control

The end of the braking force distribution control is preferably terminated early when the vehicle returns safely. For example, as shown in FIG. 8, the braking force distribution control is stopped at a low speed such that the vehicle requires little braking force distribution control. It is determined whether or not close (S41). For that purpose, for example, it is determined whether the estimated vehicle body speed Vref is smaller than the predetermined value V0. If it is close to the stop state, the control proceeds to normal brake control (S46). The predetermined value V0 depends on conditions such as a vehicle and a road surface, but is set to 1 km or less, for example.

When the estimated vehicle body speed Vref is larger than the predetermined value V0, it is determined whether the brake switch SW is on or off (S42). When the brake switch is changed from on to off, it is considered that the brake operation is finished, and thus the braking force distribution control is terminated, and normal brake control is performed (S46).

When the brake switch is kept on, in the boost mode of the braking force distribution control mode, when the boost pulse is output n or more times, normal brake control is performed (S43). The number of times n is a state in which the braking force distribution control is not necessary and depends on the structure of the vehicle, the state of the road surface, and the like, but is about 8 times.

When the estimated wheel deceleration of the rear wheel becomes smaller than the estimated wheel deceleration of the front wheel, that is, when the point C is exceeded, the load from the front wheel is returned to the rear wheel to date and it can be determined that the locking tendency is avoided as a vehicle state. The brake control is performed (S4). In this way, if the movement of the load is used as the determination condition for the movement force distribution control, the braking force distribution control can be performed more accurately. In particular, even if the end condition is not met from step S41 to step S43, it can be terminated early in this step S44.

<8> End condition 2 of braking force distribution control

As an example other than the termination of the braking force distribution control, a check of the increase / decrease state of the estimated wheel deceleration is added to the step of FIG. 8 as shown in FIG. For example, when the boost pulse is not output n or more times in the boost mode (step S43), the estimated wheel deceleration of the front and rear wheels obtained in this cycle is smaller than the estimated wheel deceleration of the front and rear wheels obtained in the previous cycle. Check the operation (S431). If small, investigate how long the reduction in the estimated wheel deceleration continues. For example, it is checked whether this reduction occurs more than a predetermined number of times (S432). When a predetermined number of times or more occur, when the estimated wheel deceleration of the rear wheel becomes smaller than the estimated wheel deceleration of the front wheel (step S44), the braking force distribution control is terminated (step S46). For about 10 times. In addition, the estimated wheel deceleration reduction determination method can be considered in various ways, and it is also possible to appropriately combine the estimated wheel deceleration of each wheel in addition to the estimated wheel deceleration of all the wheels.

If the estimated wheel deceleration of the front and rear wheels is not less than the estimated wheel decelerations of the front and rear wheels obtained in the previous cycle (S431) or if it is not continued for a predetermined number of times (S432), the determination routine for stopping the braking force distribution control ends. , Return to the original control routine.

The present invention can obtain the following effects.

<1> From the estimated wheel deceleration of the front wheel and the rear wheel, the braking force distribution control is terminated by detecting the movement of the load of the vehicle from the front wheel to the rear wheel, whereby the end timing of the braking force distribution control can be further optimized.

As a result, for example, even when the driver applies the pumping brake, once the brake pedal is gently pressed again, the braking force distribution control is finished, so that the braking force of the rear wheel can be more effectively utilized.

Claims (2)

For a vehicle having a hydraulic unit having a main hydraulic circuit connected from the master cylinder to the wheel cylinder through the inlet valve and a secondary hydraulic circuit connected from the wheel cylinder to the auxiliary reservoir via the outlet valve, and an electronic control device for controlling the hydraulic unit. In the brake hydraulic system, The braking force distribution control method when the wheel deceleration of the rear wheel becomes smaller than the wheel deceleration of the front wheel, ending the braking force distribution control for controlling the inlet valve and the outlet valve of the rear wheel. For a vehicle having a hydraulic unit having a main hydraulic circuit connected from the master cylinder to the wheel cylinder through the inlet valve and a secondary hydraulic circuit connected from the wheel cylinder to the auxiliary reservoir via the outlet valve, and an electronic control device for controlling the hydraulic unit. In the brake hydraulic system, The estimated wheel deceleration obtained from the current and previous cycles is compared, and the current estimated wheel deceleration is smaller than the previous estimated wheel deceleration for a predetermined number of times, and the wheel deceleration of the rear wheel is also performed. And a braking force distribution control method for ending the braking force distribution control for controlling the inlet and outlet valves of the rear wheel when smaller.