JP2001315625A - Deceleration control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deceleration control device for a vehicle preventing worsening of drivability by stabilizing vehicle behavior when adding deceleration. SOLUTION: In performing control for adding deceleration according to the return operation of an accelerator, the higher the vehicle speed is and the higher the engine speed is, the smaller the change rate of rising time after starting to add deceleration is set to prevent the abrupt change of deceleration without abruptly applying large assist braking force in the case that the action of an engine brake is large. Deceleration control is performed by controlling a linear valve and a pressure reducing valve connected to each wheel cylinder from a hydraulic pressure source, by a control unit having a memory unit such as a table.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle deceleration control device for adding deceleration to a vehicle, and more particularly to a vehicle deceleration control device for detecting an accelerator operation state and adding deceleration to the vehicle in accordance with the operation state. The present invention relates to a deceleration control device.

[0002]

2. Description of the Related Art Hitherto, a deceleration control device has been proposed in which a braking force is applied when a driver releases the accelerator pedal to decelerate the vehicle. JP-A-9-
One of the technologies disclosed in Japanese Patent Publication No. 95222 is to apply a braking force to the main brake system via a deceleration control device when the accelerator pedal is in a deceleration range.

[0003] By adding such a deceleration control device, it is not necessary to frequently operate the brake pedal when the vehicle is gradually accelerated or decelerated, and it is possible to enhance the deceleration response and realize an easy drive. Have been.

[0004]

However, since the deceleration is added according to the opening degree of the accelerator pedal and the vehicle speed, the deceleration may change suddenly depending on the accelerator operation by the driver, and the vehicle behavior is unstable. And drivability may be degraded.

Accordingly, an object of the present invention is to provide a deceleration control device for a vehicle which stabilizes the behavior of the vehicle when deceleration is added and prevents deterioration of drivability.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, a vehicle deceleration control device according to the present invention includes an accelerator operation state detecting means for detecting an accelerator operation state of a driver, and a deceleration added to the vehicle. A deceleration control unit for a vehicle, comprising: a deceleration adding unit that performs the deceleration adding operation according to a detection result of the accelerator operation state detecting unit; The present invention is characterized in that control is performed to adjust the time rate of change when the deceleration added by the speed adding means increases.

According to the present invention, it is possible to prevent a sudden change in the deceleration by adjusting the time change rate when the deceleration increases. Therefore, the vehicle behavior at the time of adding the deceleration is stabilized, and the drivability does not deteriorate.

This adjustment control sets the rate of change with time when the deceleration increases when the vehicle speed is high as compared with when the vehicle speed is low. When the engine speed is high, the deceleration is lower than when the engine speed is low. It is preferable to decrease the rate of change with time when the value increases. When the vehicle speed is high, and when the accelerator operation is performed while the engine speed is high, the additional deceleration due to the so-called engine brake generated by the resistance caused by the decrease in the engine speed increases. In such a case, by setting the time change rate when the deceleration is increased to be smaller than in the other cases, it is possible to effectively suppress the addition of the excessive deceleration.

[0009]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In order to facilitate understanding of the description, the same constituent elements are denoted by the same reference numerals as much as possible in each drawing, and redundant description will be omitted.

FIG. 1 is a diagram showing a configuration of a deceleration control system including a deceleration control device (hereinafter, referred to as an embodiment) according to the present invention, and FIG. It is a figure showing composition of a system.

First, the structure of the braking system of the vehicle will be described with reference to FIG. In this vehicle, wheel cylinders 25 to 28 for wheel braking are provided on front wheels FR and FL and rear wheels RR and RL, respectively.
The vehicle is braked by driving the brake at .about.28.

A brake pedal 10 for operating the braking system is connected to a piston shaft of a master cylinder 11. The brake pedal 10 includes a brake stroke sensor 4 for detecting an operation state of the brake pedal.
0 is connected. A stroke simulator 15 is further connected to the master cylinder 11 on the side opposite to the brake pedal 10 so as to generate an appropriate repulsive force when the brake pedal 10 is operated.

Two hydraulic fluid lines extending from the master cylinder 11 are connected to respective wheel cylinders 25, 26 of a right front wheel FR and a left front wheel FL via solenoid valves 12, 13, respectively. This master cylinder 1
A master pressure sensor 38 (39) is arranged on a path from 1 to the solenoid valve 12 (13).

On the other hand, a hydraulic fluid line extending from the reservoir tank 16 is connected to a pump 17 driven by a motor 18, and a hydraulic fluid line extending from the pump 17 is connected to a wheel cylinder of each wheel via each linear valve 21a to 24a. 25-28. A pressure sensor 31 is provided between the pump 17 and a branch to each of the linear valves 21a to 24a.
And an accumulator 19 are arranged. Further, pressure reducing valves 21b to 24b are connected to the hydraulic fluid lines returning from the respective wheel cylinders 25 to 28 to the reservoir tank 16. Wheel cylinder pressure sensors 32 to 35 are attached to the wheel cylinders 25 to 28, respectively.

The deceleration control unit 100 constituting the control unit of the vehicle deceleration control device according to the present invention includes a brake stroke sensor 40 for detecting the opening of the brake pedal 10 described above, and an opening of the accelerator pedal 4 described later. In addition to the accelerator opening sensor 42 for detecting θa, the vehicle speed sensor 4
4. The output signals of the engine speed sensor 46, shift sensor 48, wheel cylinder pressure sensors 32 to 35, pressure sensor 31, and master pressure sensors 38 and 39 are also supplied.

Further, the deceleration control unit 100 has a memory unit 120 for storing tables and constants used for deceleration control.
Valves 21a to 24a and pressure reducing valve 2 connected to
1b to 24b and the solenoid valves 12 and 13 are respectively controlled.

Here, the basic operation of the braking system during braking will be described. Here, the hydraulic fluid sent from the reserve tank 16 is maintained at a predetermined pressure in the downstream pipe of the pump 17, and the accumulator 19 serves to maintain this pressure. And the pressure sensor 31
When the hydraulic pressure of the hydraulic fluid detected in step (1) is lower than the predetermined pressure, the pump 17 is driven by the motor 18 to raise the hydraulic fluid in the downstream pipe to the predetermined pressure.
When the brake pedal 10 is depressed, the piston shaft of the master cylinder 11 is pushed, and a hydraulic pressure (master pressure) corresponding to the operation amount is generated. Under normal conditions, the solenoid valve 12,
Reference numeral 13 denotes a shut-off state, and the master pressure is not directly transmitted to the wheel cylinder 25 of the right front wheel FR and the wheel cylinder 26 of the left front wheel FL. The operation amount of the master cylinder 11 is detected by the master pressure sensors 38 and 39, and the deceleration control unit 100 calculates the hydraulic pressure (wheel cylinder pressure) to be applied to each of the wheel cylinders 25 to 28 according to the operation amount. . And each linear valve 21a-24a,
By controlling the operation of the pressure reducing valves 21b to 24b, the wheel cylinder pressure transmitted to each of the wheel cylinders 25 to 28 (measured by the wheel cylinder pressure sensors 32 to 35) is adjusted to be the determined wheel cylinder pressure. In this way, by independently controlling the wheel cylinder pressure transmitted to each of the wheel cylinders 25 to 28, it is possible to independently control the braking force applied to each wheel.

When the braking system is abnormal, each solenoid valve 1
2 and 13 are made conductive, and the master pressure of the master cylinder 11 is transmitted to the wheel cylinder 25 of the right front wheel FR and the wheel cylinder 26 of the left front wheel FL via the solenoid valves 12 and 13, respectively. Apply braking.

In this embodiment, when the depressed accelerator pedal 4 is returned, a braking force is applied to generate deceleration, thereby providing an engine braking effect which tends to be insufficient particularly in a vehicle equipped with an automatic transmission. Perform assisted deceleration control. Hereafter, this is called Engine Brake Assist (EBA)
Called control. FIG. 3 is a diagram illustrating the state of the accelerator pedal 4. The accelerator opening θa indicates the opening of the accelerator pedal 4 from the fully closed position side, and is 0 on the fully closed position side. The opening degree θa0 is the fuel cutoff position (fuel cut position) of the accelerator pedal 4.

The EBA control according to this embodiment adjusts the rise of the deceleration to be added according to the engine speed and the vehicle speed. FIG. 4 is a flowchart showing the EBA control, and FIG. 5 is a graph showing an example of a correction coefficient F (V, Ne) of the time rate of change at the time of deceleration rising used in the control flow. This control is performed by the deceleration control unit 100, and is repeatedly executed at a predetermined timing from the time when the engine of the vehicle is driven. However, when the brake pedal 10 is operated, the braking torque is added according to the operation state of the brake pedal 10, so that the processing of this flowchart is not performed and the processing is skipped.

In step S1, the accelerator opening θa sent as an output signal of the accelerator opening sensor 42 attached to the accelerator pedal 4 and the vehicle speed sensor 4
The vehicle state V such as the vehicle speed V sent as the output signal of No. 4 and the gear position information sent from the shift sensor 48 is read.

In step S2, whether the EBA control condition is satisfied, that is, the returning operation of the accelerator pedal 4 is performed, and the accelerator pedal 4 is located closer to the fully closed position than the fuel cut position, that is, 0 ≦ θa It is determined whether or not <θa0. If the condition is not satisfied, the process proceeds to step S3, where a variable EBAfl indicating whether or not EBA control is being performed.
ag is set to 0, the subsequent processing is skipped, and the processing ends.

If it is determined in step S2 that the EBA control condition is satisfied, the process proceeds to step S4 to determine whether or not the variable EBAflag is 1, that is, whether or not EBA control is already being executed. Is determined. If the variable EBAflag is 0, together determined to be a case of future start EBA control, the process proceeds to step S5, first stores the current time t to the variable t ₀ representing the EBA control start time, the variable EBAflag Is set to 1 and the process moves to step S6.
If the variable EBAflag has already been set to 1, the process skips step S5 and proceeds to step S6.

In step S6, a steady-state value _GEBA of the reference deceleration to be added is calculated based on the vehicle speed V, the accelerator opening θa, and the shift state. Returning amount from Shitaei0 the G _EBA, for example, if the vehicle speed V is equal accelerator opening θa (θa0-θa)
May be set in proportion to. Furthermore, this steady value
Reference time Delta] t _a required to reach the G _EBA is calculated.

In step S7, the elapsed time Δt from time t ₀ is calculated.

[0026]

(Equation 1)

It is determined whether or not Δtx is exceeded. (The meaning of this Δtx will be described later.) Here, F (V, Ne) is a correction coefficient for the engine speed Ne and the vehicle speed V of the time rate of change at the start of deceleration, as shown in FIG. , Is set smaller as the vehicle speed V is higher and the engine speed Ne is higher. This correction coefficient may be stored in the memory unit 120 in the form of a map, or may be incorporated in the control program of the deceleration control unit 100 in the form of a mathematical expression.

If it is determined that .DELTA.t does not exceed .DELTA.tx, the flow shifts to step S8 to add the target deceleration to be added.
EBA (t)

[0029]

(Equation 2)

Is set. On the other hand, when it is determined that Δt exceeds Δtx, the process proceeds to step S9.
EBA (t) is set to G _EBA . That is, after starting the EBA control, the target deceleration EBA (t) is set to the reference rate of change (1 /
Δt _a ) is increased to the target value _GEBA at a change rate of F (V, Ne) times. That is, the change rate is set to be smaller than the reference change rate as the vehicle speed V becomes higher and the engine speed Ne becomes higher by the correction coefficient F (V, Ne).

In step S10, a braking torque to be applied to each wheel is obtained so as to obtain the target deceleration EBA (t) thus set, and a wheel cylinder pressure at which the braking torque is obtained is calculated. Each linear valve 21a to 24a
And controlling the pressure reducing valves 21b to 24b to adjust the hydraulic pressure acting on the wheel cylinders 25 to 28 of each wheel to the determined wheel cylinder pressure. When the accelerator pedal 4 is returned,
An engine control unit (not shown) reduces the supply of fuel and air to reduce the engine speed Ne, and this resistance produces an engine braking effect in which a braking force is generated, but the added braking torque assists this. Play a role. As a result, deceleration is added to the vehicle, and deceleration is performed. In the middle and high speed range, when the accelerator pedal 4 is returned from the fuel cutoff position to the fully closed position, the engine control unit cuts off the fuel supply to the engine, so that a larger deceleration can be obtained.

FIG. 6 is a time chart showing the time change of the deceleration at the rise of the additional deceleration. That is, when the vehicle speed V is low, that is, in FIG.
When F (V, Ne) is set to 1 (case A), the added deceleration EBA (t) has a constant rate of change ( _GEBA) from time t ₀ as shown by the solid line in FIG. / Δt _a ) and reaches _a steady-state value G _EBA at time ta after Δt _a, after which the steady-state value G _EBA
Is maintained in.

Whether the vehicle speed V is higher than this or the engine speed
If Ne is higher than this and the correction coefficient F (V, Ne) is set to b in FIG. 5 (case B), the added deceleration EB
A (t) is the case A from time t ₀ as shown by the broken line in FIG.
The rate of change of b times the rate of change _{b (G E BA / Δt a} ) = G EBA / Δt b with increasing Delta] t _b after time _{(Δt b = Δt a / b} ) time t _b at constant value G
_EBA is reached and thereafter maintained at this steady value G _EBA .

Further, when the vehicle speed V is higher than this or the engine speed Ne is higher than this, and the correction coefficient F (V, Ne) is set to c in FIG. 5 (case C), the added deceleration EBA (t) Figure 6 from the time t _0, as shown by the chain line of the rate of change of case a c times the change rate c (G _EBA / Δt
_a ) = Increase by G _EBA / Δt _c and after Δt _c time (Δt _c = Δt _a / c)
Reached at time t _b to the constant value G _EBA, then the steady-state value G _EBA
Is maintained in.

As described above, the higher the vehicle speed V and the higher the engine speed Ne, the smaller the time change rate at the start (when increasing) after the start of deceleration addition.
When the engine brake itself exerts a large force, a large assist braking force is not suddenly applied, and a sudden change in deceleration can be prevented. Therefore, the behavior of the vehicle does not deteriorate due to the addition of the deceleration that is not intended by the driver, and the drivability does not deteriorate. Further, by performing such EBA control, fine adjustment of the vehicle speed by operating the accelerator pedal 4 is facilitated, and drivability is improved.

In the above description, the embodiment in which deceleration is provided by directly controlling the braking system has been described. However, a configuration in which deceleration is applied by acting on the drive system may be employed. Here, the case where the correction coefficient of the time change rate of the deceleration is determined by both the vehicle speed V and the engine speed Ne has been described as an example,
It may be set so as to depend on only one of them.

[0037]

As described above, according to the present invention, when the deceleration is increased in the deceleration additional control according to the accelerator operation, the time change rate of the deceleration is adjusted according to the vehicle state such as the vehicle speed and the engine speed. By performing such control, rapid changes in deceleration can be suppressed, vehicle behavior can be stabilized, and deterioration of drivability can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a deceleration control device according to the present invention.

FIG. 2 is a diagram showing a configuration of a braking system of a vehicle equipped with the deceleration control device according to the present invention.

FIG. 3 is a diagram illustrating an accelerator pedal opening.

FIG. 4 is a flowchart illustrating deceleration control of the apparatus of FIG. 1;

FIG. 5 is a graph illustrating a correction coefficient F (V, Ne) in FIG. 4;

FIG. 6 is a timing chart showing an example of the control of FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Body, 4 ... Accelerator pedal, 10 ... Brake pedal, 11 ... Master cylinder, 16 ... Reservoir tank, 1
7 Pump, 19 Accumulator, 21a to 24a
Linear valves, 21b to 24b: pressure reducing valves, 25 to 28: wheel cylinders, 31: brake pressure sensors, 32 to 35: wheel cylinder pressure sensors, 42: accelerator opening degree sensors, 4
4 vehicle speed sensor, 46 engine speed sensor, 100
... deceleration control unit, 120 ... memory unit.

Claims (3)

[Claims] 1. An accelerator operation state detecting means for detecting an accelerator operation state of a driver, a deceleration adding means for adding deceleration to a vehicle, and the deceleration adding means according to a detection result of the accelerator operation state detecting means. A deceleration control device for adjusting deceleration to be added by the means, wherein the control unit performs control for adjusting a time change rate when the deceleration to be added by the deceleration adding means is increased. Vehicle deceleration control device to perform. 2. The deceleration control device for a vehicle according to claim 1, wherein the control unit sets the time rate of change when the deceleration increases when the vehicle speed is high as compared to when the vehicle speed is low. 3. The vehicle according to claim 1, wherein the control unit sets the rate of change with time when the deceleration increases when the engine speed is high as compared to when the engine speed is low. Deceleration control device.