JP3308413B2 - 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 electronic control suspension.

[0002]

2. Description of the Related Art In order to achieve a high level of comfort and operability of a vehicle at the same time, the spring constant of an air spring and the damping force of a shock absorber are usually kept in a soft state, while the operability during turning is maintained. An electronically controlled suspension is known that switches to a hard drive in driving situations where emphasis is placed (Mitsubishi Motors Technical Review 199
3 NO.5 "Development of electronically controlled suspension for large buses"
reference). During this so-called semi-active suspension control, there is a technique for reducing the roll angle of the vehicle body by switching the air spring and the shock absorber to hardware.

By changing the roll stiffness between the front wheel and the rear wheel, the load movement between the left and right wheels changes, and the grip balance (ie, the steering characteristic) between the front wheel and the rear wheel changes. When the roll rigidity distribution is increased, the vehicle tends to understeer, and when the roll rigidity distribution to the rear wheel side is increased, the vehicle tends to oversteer. Therefore, in order to improve the yaw characteristics of the vehicle in the active suspension, the distribution to the rear wheels is increased in the driving situation where the turning performance of the vehicle is required, and the distribution to the front wheels is increased in the driving situation where the convergence of the vehicle is required Is known (refer to MotorFan magazine 89/12, "Steer characteristic control of Nissan active suspension").

[0004]

However, in the former case (semi-active suspension), the control of the yaw characteristic is not taken into consideration, and in the latter case (active suspension), a complicated mechanism is required, so that the system is expensive. There was a problem of becoming.

An object of the present invention is to realize a reduction in roll and an improvement in yaw characteristics with a simple configuration in a semi-active suspension.

[0006]

According to the present invention, there is provided an actuator for switching at least two of at least one of a spring constant and a damping force as a suspension characteristic for each of front and rear wheels of a vehicle, as shown in FIG. Means for detecting the lateral acceleration of the vehicle and outputting a control signal for switching the suspension characteristics of the front and rear wheels to hardware by delaying the front wheel by a predetermined time when the lateral acceleration exceeds a predetermined value based on the detection signal. Means for outputting a control signal for switching the suspension characteristics of the front and rear wheels to software by delaying the front wheel side by a predetermined time when the lateral acceleration becomes equal to or less than a predetermined value,
Means for driving the actuator in accordance with these output signals.

[0007]

When the lateral acceleration exceeds a predetermined value, such as when the vehicle turns or changes lanes, initially only the suspension characteristics of the rear wheels are switched to hard, so the roll stiffness of the rear wheels is lower than that of the front wheels. As a result, the yaw characteristic tends to oversteer, and the turning performance of the vehicle is improved. When a predetermined time elapses in this state, the suspension characteristics of the front wheel are also switched to hardware with a delay to the rear wheel side, so that the roll accompanying the lateral acceleration exceeding the predetermined value can be efficiently suppressed. Thereafter, when the lateral acceleration becomes equal to or less than a predetermined value, the suspension characteristics are switched to software with a delay of a predetermined time on the front wheel side, so that the yaw characteristics tend to understeer, and the convergence of the vehicle is improved.

[0008]

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 rear left and right air springs 2c, 2e and 2d, 2f are in communication with each other. 8b are provided.

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 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.
A functional block configuration for performing the roll control is represented by a lateral acceleration sensor 14 and a vehicle speed sensor 17 as shown in FIG.
Means 31 and 31 for input processing of the detection signals, means 32 for determining the necessity of roll control from these processed signals (lateral acceleration and vehicle speed), and means for determining the drive pattern of roll control according to the elapsed time 33 and means 34 and 35 for outputting drive signals to the switching valves 6a to 6f of the air springs 2a to 2d and the damping force variable mechanism of the shock absorbers 7a to 7f based on the results.

FIG. 4 is a flowchart for explaining the roll control in the automatic mode, which is repeatedly executed at a predetermined control cycle. First, after initialization, the detection signal Gy of the lateral acceleration sensor and the detection signal V of the vehicle speed sensor are read (steps 1 and 2). When the vehicle speed signal V is zero (stop state), the switching valves 6a and 6b of all the air springs 2a to 2f are "opened",
The variable damping force mechanisms of all the shock absorbers 7a to 7f are switched to the "soft" state (step 3 → step 21 to step 22).

If the vehicle speed signal is not zero, a lateral acceleration threshold Gt corresponding to the vehicle speed signal V at that time is read from a data map as shown in FIG. 5 (step 4). This threshold Gt
And the absolute value of the lateral acceleration signal Gy, | Gy |> Gt
Then, the necessity of roll control is determined at the time, and the timer is turned on from that point, and the flag is set to 1 (steps 5 and 6).

[0015] Then, until the timer counts the passage of a predetermined time T _1, the front-wheel-side air springs 2a, selector valve 6a in 2b, and 6b "open", the rear-wheel-side air springs 2c
２2f are switched to “closed”, the damping force variable mechanism of the front wheel shock absorbers 7a and 7b is switched to “soft”, and the damping force variable mechanism of the rear wheel shock absorbers 7c to 7f is switched to “hard” ( Step 7 to Step 1
1).

[0016] When the timer counts a predetermined time elapses T _1, switching valve of the total air spring 2a to 2f 6 a to 6 f
Is closed, and the damping force variable mechanism of all the shock absorbers 7a to 7f is switched to "hard" (steps 12 and 13).

If the absolute value of the lateral acceleration | Gy | is equal to or smaller than the threshold value Gt, the state of the flag is checked (step 5 → step 14). When the flag is 0, it is determined that the roll control is not necessary, and the switching valves 6a to 6f of all the air springs 2a to 2f are "opened", and all the shock absorbers 7a to 7f
Is maintained in the "soft" state (step 14 → step 21, step 22).

[0018] If not flag = 0, the timer until counts a lapse of a predetermined period of time T _2, the front-wheel-side air springs 2a, selector valve 6a of 2b, 6b to "closed", the rear-wheel-side air springs 2c~2f The switching valves 6c to 6f are switched to the "open" state, the damping force variable mechanisms of the front wheel side shock absorbers 7a and 7b are switched to the "hard" state, and the variable damping mechanisms of the rear wheel side shock absorbers 7c to 7f are switched to the "soft" state (step 15). Step 19). When the timer counts the passage of a predetermined time T _2, the flag turns off the timer 0
(Step 15 → step 20). Then, 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 switched to "soft" (steps 21 and 22).

With such a configuration, the air springs 2a to 2f and all the shock absorbers 7a to 7f of the front and rear wheels are kept in a "soft" state at normal times including when the vehicle is stopped. Good riding comfort is obtained.

When turning or changing lanes, if the absolute value of the lateral acceleration | Gy | exceeds the threshold Gt, only the suspension characteristics on the rear wheel side are initially switched to hard.
As the roll rigidity on the rear wheel side is increased compared to the front wheel side,
The yaw characteristic tends to oversteer, and the turning performance of the vehicle is improved.

[0021] While continues until this condition is the predetermined time T ₁ is elapsed the predetermined time T ₁ is passed, because the suspension characteristic of the front wheel side behind the rear wheel side switched to hard, the lateral acceleration exceeds a predetermined value The accompanying roll can be suppressed efficiently.

Thereafter, when the lateral acceleration falls below a predetermined value,
Since only suspension characteristic of the rear wheel until a predetermined time T ₂ prior to the front wheel side has elapsed is switched to soft, turn yaw characteristics become understeer tendency, improved convergence of the vehicle (stability) is.

In this case, since the spring constant and the damping force of each of the front and rear wheels are controlled according to the elapsed time, a simple program is required. In addition, since an on-off system that does not require a complicated mechanism like an active suspension and controls suspension characteristics reliably can reduce the roll and improve the yaw characteristics at low cost. Note that a steering angle or a steering angular velocity may be used instead of the lateral acceleration as a parameter of the roll control.

[0024]

According to the present invention, an actuator for switching at least two of at least one of a spring constant and a damping force as a suspension characteristic for each of front and rear wheels of a vehicle, and a means for detecting a lateral acceleration of the vehicle Means for outputting a control signal for switching the suspension characteristics of each of the front and rear wheels to hardware by delaying the front wheel by a predetermined time when the lateral acceleration exceeds a predetermined value based on the detection signal; In other words, the vehicle has a means for outputting a control signal for delaying the front wheel side by a predetermined time and switching the suspension characteristics of the front and rear wheels to soft, and a means for driving the actuator according to these output signals. In some cases, such as at the beginning, the turning process of the initial stage and the convergence process of the finishing stage are improved, and the roll of the wheel continued during the It can be suppressed. Also easy to control,
Since no complicated mechanism is required, it is advantageous in terms of 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 a roll control system.

FIG. 4 is a flowchart illustrating roll control.

FIG. 5 is a lateral acceleration threshold map used for roll control.

FIG. 6 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 front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60G 17/015

Claims (1)

(57) [Claims] An actuator for switching at least one of a spring constant and a damping force as a suspension characteristic for each of front and rear wheels of a vehicle in two or more stages, means for detecting a lateral acceleration of the vehicle, before the lateral acceleration is delayed by a predetermined time front wheel exceeds a predetermined value based
A means for outputting a control signal for switching the suspension characteristics of each rear wheel to hardware, and similarly, when the lateral acceleration becomes a predetermined value or less, the front wheels are delayed by a predetermined time to switch the suspension characteristics of the front and rear wheels to soft. A suspension device for a vehicle, comprising: means for outputting a control signal; and means for driving an actuator according to the output signal.