JP3270646B2 - Vehicle electronically controlled suspension - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension device.

[0002]

2. Description of the Related Art In order to achieve a good balance between ride comfort and controllability of a vehicle, suspension characteristics are normally kept in a soft state, while switching to a hard state is performed in a driving situation in which controllability is important such as turning. Electronically controlled suspensions are known (Mitsubishi Motors Technical Review 199
3 NO.5 "Development of electronically controlled suspension for large buses"). As one of the controls, there is a technique for switching the suspension characteristics to hard when a brake is operated in order to suppress a brake dive of a vehicle body.

In such an anti-dive control, in order to enhance the convergence of pitching due to swing back after braking, the suspension characteristics are not returned to soft when the brake is released, but are switched to hard after a predetermined time has elapsed. (Japanese Utility Model Laid-Open No. 62-181414).

[0004]

By the way, in such a conventional example, when the brake pedal is depressed, the suspension characteristics are switched to hard even at the time of gentle braking which does not require the brake dive control, so that the riding comfort of the vehicle deteriorates. But,
As a countermeasure, adding a sensor such as a brake pressure or longitudinal acceleration to detect slow braking of the vehicle has a problem that the system becomes complicated. In addition, anti-dive control is started when the brakes are activated in the control to increase the convergence of pitching.However, even when the vehicle shifts from braking midway to re-acceleration without stopping, the suspension characteristics are hardened for a certain period after the brake is released. However, there is a problem that the riding comfort is degraded during that time.

An object of the present invention is to solve such a problem by a simple method.

[0006]

According to a first aspect of the present invention, as shown in FIG. 8, an actuator a for switching at least one of at least one of a spring constant and a damping force as a suspension characteristic of a vehicle, and an operation state of a brake. Means b for detecting and means c for controlling the actuator so that the suspension characteristics are switched to hard when the brake is actuated and the suspension characteristics are returned to soft when the brake is released
And means d for detecting the vehicle speed, and means e for prohibiting the control of the actuator accompanying the brake operation when it is determined that the vehicle is running at high speed based on the vehicle speed.

In the second invention, as shown in FIG. 8, an actuator a for switching at least one of at least one of a spring constant and a damping force as suspension characteristics of a vehicle, a means b for detecting an operating state of a brake, Switch the suspension characteristics to hard when the brake is activated,
Means c for controlling the actuator to return the suspension characteristics to soft when the brake is released, means d for detecting the vehicle speed, and means for delaying the control for returning the suspension characteristics to the software by a delay time corresponding to the vehicle speed when the brake is released. f is provided.

[0008]

According to the first aspect of the invention, when the brake is operated during normal running, the suspension characteristics are switched to hard, so that the brake dive of the vehicle body is suppressed. Since the control for suppressing the brake dive is not performed, the riding comfort at the time of gentle braking can be secured well.

According to the second aspect of the present invention, the suspension characteristics are switched to hard when the brakes are actuated, so that the brake dive of the vehicle body is suppressed, and when the brakes are released, the return of the suspension characteristics to soft is delayed by the delay time. The convergence of pitching can be improved. Since the delay time changes according to the vehicle speed when the brake is released,
By setting it longer on the low speed side and shorter on the high speed side, the hard state of the suspension characteristics will not be maintained more than necessary,
Deterioration of ride comfort can be minimized.

[0010]

1 and 2, reference numeral 20 denotes a vehicle body as a sprung system of the vehicle, 1a to 1d denote tires as unsprung systems of the vehicle, and air springs 2a to 2f and shock absorbers 7a to 7f. Interposed. Although not shown, the shock absorbers 7a to 7f include a damping force variable mechanism (including an actuator) that switches between a hard and soft stage by opening and closing the orifice of the piston.

The air springs 2a to 2f are connected to the air reservoir 3 via leveling valves 4a to 4c for controlling air supply and exhaust so as to maintain a desired vehicle height. Since there is one leveling valve 4c on the rear wheel side, the left and right air springs 2c, 2e and 2d, 2f communicate with each other. , 8b.

The sub-tanks 5a to 5d are connected to the air springs 2a to 2f via the switching valves 6a to 6f, respectively. When the opening and closing of the valves 6a to 6f are controlled, the substantial air volume changes. The spring constant of ２2f is switched between two stages (hard and soft). 1 is an overall system configuration diagram, and FIG. 2 is a configuration diagram of a front wheel side representing a suspension for one wheel.

A vehicle speed sensor 17 for detecting the running speed of the vehicle, a lateral acceleration sensor 14 for detecting the lateral acceleration of the vehicle body, and a vertical acceleration sensor for the vehicle body are provided as detecting means necessary for performing various controls according to the running conditions of the vehicle. A vertical acceleration sensor 15 for detecting acceleration, a steering angle sensor 11 for detecting a steering angle of a steering wheel, a foot brake switch 12 for detecting a braking state of a vehicle, a back lamp switch 16 and a side brake switch 13, manual control and automatic control A mode changeover switch 10 for selecting control is provided.

A controller 9 controls rolls, brake dives, pitching and bouncing of the vehicle body based on input signals from these sensors and switches.
The functional block configuration for performing the anti-dive control can be represented by a means 30 for processing an input signal from the foot brake switch 12 and a means 31 for processing an input signal from the vehicle speed sensor 17 as shown in FIG. Means 32 for determining a driving situation in which anti-dive control should not be performed from the vehicle speed signal, means 33 for determining a drive timing for switching the suspension characteristic from the brake signal in a driving situation in which anti-dive control should be performed, and Means 34 for outputting a control signal to the switching valves 6a to 6f of the air springs 2a to 2f, and means 35 for outputting a control signal to the damping force variable mechanism of the shock absorbers 7a to 7f are also provided.

FIG. 4 is a flowchart for explaining the anti-dive control, which is repeatedly executed at a predetermined control cycle. First, after the initialization of step 1, the brake signal B from the foot brake switch 12 and the detection signal V of the vehicle speed sensor 17 are read in step 2. In step 3, the vehicle speed signal V
Is zero (when stopped), step 9 and step 1
0, and the switching valves 6a- of all the air springs 2a-2f
6f is "open" and the damping force variable mechanisms of all the shock absorbers 7a to 7f are switched to the "soft" state.

If the vehicle speed signal V is not zero, step 4
To compare the vehicle speed signal V with a predetermined value Vt (a vehicle speed value for distinguishing between high-speed running and normal running, for example, set at 50 to 60 km / h). When V> Vt (during high-speed running), anti-dive control is performed. It is determined that it should not be performed, and the process proceeds to steps 9 and 10.

If V> Vt is not satisfied (during normal running), the routine proceeds to step 5, where it is determined whether or not the brake signal B is ON (during braking). When the brake signal B is turned on, the switching valves 6a and 6b of the front wheel side air springs 2a and 2b are "closed" and the switching valves 6c to 6f of the rear wheel side air springs 2c to 2f are set to "closed" in steps 6 to 8. Open ", the damping force variable mechanisms of all the shock absorbers 7a to 7f are switched to the" hard "state. Brake signal B
Is off, go to step 9 and step 10,
The switching valves 6a to 6f of all the air springs 2a to 2f are "opened" and the damping force variable mechanisms of all the shock absorbers 7a to 7f are returned to the "soft" state.

With such a configuration, the vehicle speed V becomes equal to the predetermined value V
When the brake is activated during normal traveling below t, the suspension characteristics are switched to hard, so that the nose dive of the vehicle body is suppressed. However, when the vehicle speed V exceeds a predetermined value Vt, the brake is activated. However, since the suspension characteristics are kept soft and the anti-dive control is not performed, the riding comfort at the time of gentle braking can be secured well. In addition, since a simple method for judging gentle braking from the vehicle speed V is not required, it is not necessary to add a sensor for brake pressure, longitudinal acceleration, and the like, so that the system is not complicated and the cost is advantageous.

The suspension characteristics may be such that all the air springs 2a to 2f are hard and all the shock absorbers 7a to 7f are hard. The brake signal B does not need to rely on the foot brake switch 12, but may be an operation signal including an auxiliary brake (for example, a stop lamp lighting signal) as long as it detects the braking state of the vehicle.

FIG. 5 shows a functional block diagram relating to the anti-dive control of the control unit 9 as another embodiment, in which means 30 for processing an input signal from the foot brake switch 12 and a signal from the vehicle speed sensor 17 are provided. A means 31 for processing an input signal; a means 36 for determining the necessity of anti-dive control based on a brake signal and a vehicle speed signal; a means 37 for obtaining a delay time corresponding to a vehicle speed signal from a data map as shown in FIG. Means 38 for determining a start time and a stop time for switching suspension characteristics from a brake signal and a delay time in a driving situation in which dive control is to be performed, and outputs a control signal to the switching valves 6a to 6f of the air springs 2a to 2f based on the determination result. And outputs a control signal to the damping force variable mechanism of the shock absorbers 7a to 7f. It provided with a means 35.

The components other than the control unit 9 are the same as those in the above-described embodiment, and therefore, are denoted by the same reference numerals, and redundant description will be omitted. FIG. 7 is a flowchart illustrating the anti-dive control of the control unit 9, which is repeatedly executed at a predetermined control cycle. Step 2 after initialization of Step 1
Reads the brake signal B from the foot brake switch 12 and the detection signal V from the vehicle speed sensor 17. In step 3, the delay time Td according to the vehicle speed V is obtained from the data map.
Ask for.

If the vehicle speed signal V is not zero in steps 4 to 6, the vehicle speed signal V is changed to a predetermined value Vt (a vehicle speed value for distinguishing between high-speed running and normal running, for example, 50 to 60).
If the brake signal B is turned on (during braking operation) when V> Vt is not satisfied (during normal running), the process proceeds to steps 7 to 9 to switch the front-wheel-side air springs 2a and 2b. The valves 6a and 6b are "closed", the switching valves 6c to 6f of the rear wheel side air springs 2c to 2f are "open", and the damping force variable mechanisms of all the shock absorbers 7a to 7f are switched to a "hard" state. In step 10, the flag is set to 1.

If the vehicle speed signal V is zero (stop) at step 4, V> Vt (at high speed running) at step 5, and the brake signal B is off (at brake release) at step 6,
In any case, the process proceeds to step 11, and if the flag is zero, the process returns to step 2. If the flag is not zero, the process proceeds to step 12, and when the timer counts the elapse of the delay time Td obtained in step 3, in steps 13 and 15, all air springs 2
The switching valves 6a to 6f a to 2f are "opened", and the damping force variable mechanisms of all the shock absorbers 7a to 7f are returned to the "soft" state. Then, in step 15, the flag is cleared to 0.

With such a configuration, the vehicle speed V becomes the predetermined value V
When the vehicle is running at a high speed exceeding t, even if the brake is operated, the anti-dive control is not performed. During normal running at a vehicle speed V equal to or lower than the predetermined value Vt, when the brake is actuated, the suspension characteristics are switched to hard, so that the brake dive is suppressed. When the brake is released from this state, the return of the suspension characteristics to the software is delayed by the delay time Td at that time, so that the convergence of pitching can be improved.
The delay time Td depends on the vehicle speed V when the brake is released.
Since it is set longer on the low speed side and shorter on the high speed side, the hard state of the suspension characteristics is not held longer than necessary, and the deterioration of the riding comfort is minimized. Further, since the control is simple without the addition of sensors, the system can be realized at low cost.

[0025]

According to the first aspect of the invention, an actuator for switching at least one of at least one of a spring constant and a damping force as a suspension characteristic of a vehicle, a means for detecting an operating state of a brake, Switching the suspension characteristics to hardware and controlling the actuator to return the suspension characteristics to soft when the brake is released, means for detecting the vehicle speed, and prohibiting the actuator control accompanying the brake operation when determining that the vehicle is running at high speed from the vehicle speed Since the anti-dive control is not performed even when the brake is operated during high-speed running, the riding comfort at the time of gentle braking can be ensured satisfactorily.
Also, since the control is simple, it can be realized at low cost.

According to the second aspect of the present invention, an actuator for switching at least one of a spring constant and a damping force in two or more steps as a suspension characteristic of a vehicle, a means for detecting an operation state of a brake, Means for controlling the actuator so that the suspension characteristics are restored to soft when the brake is released, means for detecting the vehicle speed, and means for delaying the control for returning the suspension characteristics to software by a delay time corresponding to the vehicle speed. Is provided, the convergence of pitching after braking can be improved while minimizing deterioration of ride comfort. Also, since the control is simple, it can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an entire system showing an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a suspension for one wheel.

FIG. 3 is a block diagram of an anti-dive control system.

FIG. 4 is a flowchart illustrating anti-dive control.

FIG. 5 is a block diagram showing another embodiment.

FIG. 6 is a data map of a delay time.

FIG. 7 is a flowchart illustrating anti-dive control.

FIG. 8 is a diagram corresponding to claims of the present invention.

[Explanation of symbols]

 1a-1d Tire 2a-2f Air spring 4a-4c Leveling valve 5a-5d Sub-tank 6a-6f Switching valve 7a-7f Shock absorber 9 Control unit 14 Lateral acceleration sensor 17 Vehicle speed sensor

Continuation of the front page (72) The inventor Masami Hagiwara Nissan Diesel Industry Co., Ltd., the first place of Oji-Chome, Ageo City, Saitama Prefecture (56) References JP-A-60-85010 (JP, A) JP, A) JP-A-61-249889 (JP, A) JP-A-63-49508 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60G 1/00-25/00

Claims (2)

(57) [Claims] An actuator for switching at least one of a spring constant and a damping force in two or more steps as a suspension characteristic of a vehicle, a means for detecting an operation state of a brake, and a suspension characteristic being hard-switched when the brake is operated, A means for controlling the actuator to return the suspension characteristics to soft when the brake is released, a means for detecting the vehicle speed, and a means for prohibiting the control of the actuator accompanying the brake operation when determining that the vehicle is running at high speed from the vehicle speed are provided. Vehicle suspension device. 2. An actuator for switching at least one of a spring constant and a damping force as a suspension characteristic of a vehicle in two or more stages, a means for detecting an operation state of a brake, and a suspension characteristic being hard-switched when the brake is activated, Providing means for controlling the actuator so that the suspension characteristics return to soft when the brake is released, means for detecting the vehicle speed, and means for delaying the return control of the suspension characteristics to software by a delay time corresponding to the vehicle speed when the brake is released A suspension device for a vehicle.