JP2632160B2 - Control system for automotive suspension - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an automobile suspension.

2. Description of the Related Art Japanese Patent Laid-Open Publication No. Sho-59-28139 discloses a vehicle suspension that uses a variable damping force damper to increase the damping force of a rear suspension during sudden start or rapid acceleration, thereby preventing a squat (body bottom descent). It is disclosed in Japanese Patent Application No. 60-116514.

Problems to be Solved by the Invention As described above, changes in vehicle body behavior such as a squat at the time of sudden start or sudden acceleration, a north dive at the time of control or a roll at the time of turning are predicted, and a damper damping force, a spring constant or Devices that control suspension variable elements such as vehicle height to mitigate large changes in vehicle body behavior are generally referred to as semi-active suspensions. , Nose dive, roll, etc., only control corresponding to changes in vehicle body posture. However, the stability of the vehicle body behavior is greatly affected by the condition of the running road surface, for example, whether the friction coefficient of the road surface (hereinafter referred to as road surface μ) is high or low. There is a problem that the control for the above problem is not performed at all.

Means for Solving the Problems The present invention is directed to a four-wheel drive vehicle equipped with the above semi-active suspension and interposing a visco clutch in a power transmission system between the front and rear wheels. The logic for determining whether the road surface μ is high or low based on the temperature is incorporated in a control unit that controls the semi-active suspension, and the control unit performs control to reduce the roll stiffness of the rear suspension when it is determined that the road is low μ. It is characterized by having such a configuration.

According to the above, when the temperature of the Visco clutch rises and becomes higher than the outside temperature by a set value or more, the control unit determines that the road is a low μ road, and reduces the damper damping force and the spring constant of the rear suspension. By reducing the roll stiffness by pressing the signal, the ground load of the rear wheel can always be sufficiently ensured, and the cornering characteristic moves to the understeer side by lowering the roll stiffness of the front wheel, and on low μ roads The running stability of
A significant improvement in safety can be achieved.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a perspective explanatory view schematically showing a main part of an automobile to which the present invention is applied in a perspective view.

In FIG. 1, reference numerals 1 and 1 denote front air suspensions, 2 and 2 denote rear air suspensions, 3 denotes an air compressor, and air control comprising a drive source (for example, an electric motor) of the air compressor, a high-pressure air tank, a low-pressure air tank, and the like. The high-pressure air stored in the high-pressure air tank by driving the air compressor is injected into the air suspension when the injection valve of the control valve 4 provided for each air suspension is opened, and the control valve 4 is discharged. When the valve is opened, the air in the air suspension is discharged into the low-pressure air tank, whereby the air suspension can be expanded and contracted to adjust the vehicle height. Reference numeral 5 denotes an actuator provided for each air suspension, and the operation of the actuator 5 can variably control the damping force of a damping force variable damper (not shown) provided in each air suspension unit and the spring constant of the air suspension. It has become.

The control valve 4 and the actuator 5 operate based on a command from the control unit 6, respectively.

The control unit 6 receives a vehicle height signal of a vehicle height sensor built in each air suspension and inputs the vehicle height signal from the vehicle height sensor. When the predetermined number of times is repeated a predetermined number of times or more within a predetermined time, it is determined that the road is a bad road, and a hard signal is issued to the actuator 5 to increase a damper damping force and a spring constant so as to improve a rough road running property. A vehicle speed signal of the vehicle speed sensor 7, an accelerator opening signal of the accelerator opening sensor 8, a brake pressure signal of the brake fluid pressure sensor 9, a steering angle signal of the steering angle sensor 10, and the like are input. Predicts changes in vehicle attitude, such as squats, nose dives, and rolls. 5, the damper damping force and the spring constant are hardened to prevent squat, the front air suspension 1, 1 actuator 5 is operated to harden it to prevent north dive, or left or right By controlling the actuator 5 of one of the air suspensions to increase the roll stiffness, a control for reducing the change in the posture of the vehicle body is performed. In addition, there is a restriction that the entire system is hardened at a high speed based on the vehicle speed signal.

The control unit 6 sends a signal to the control valve 4 based on a signal from the vehicle height sensor to independently inject or discharge air for each air suspension when the loading condition changes and the vehicle body posture becomes unbalanced. The vehicle height is adjusted to normalize the vehicle body posture, and a signal is transmitted to the control valve 4 based on a signal from a manual vehicle height change switch (not shown) to switch the vehicle height from a low normal vehicle height to a high vehicle height. Alternatively, vehicle height control is performed such that a signal is sent to the control valve 4 based on the above-described rough road determination to automatically switch to a high vehicle height.

Reference numeral 11 denotes a Visco clutch interposed in a driving force transmission system between front and rear wheels in a four-wheel drive type automobile. The Visco clutch 11 has a temperature sensor 12 for detecting an internal temperature (viscous liquid temperature). Is provided.

 Reference numeral 13 denotes an outside air temperature sensor that detects an outside air temperature.

The temperature signals of the temperature sensor 12 and the outside air temperature sensor 13 of the Visco clutch 11 are transmitted to the control unit 6 described above.
The control unit 6 determines the friction coefficient of the road surface, that is, the road surface μ based on the two temperature signals.

The visco clutch 11 is generally set in a viscous liquid such as silicon oil in a state in which a driven side of a plate rotated by a drive side shaft, for example, a front wheel side shaft, for example, a plate integrated with a rear wheel side shaft and a plate integral therewith. The both plates are provided with hole slits, and the rotational torque of the driving side is transmitted to the driven side by using the fluid resistance of the viscous liquid. Since it is conventionally known, a detailed description of the structure above is omitted.

If there is a relative rotation difference between the front and rear wheels, a shear force acts on the viscous liquid by slits and holes in each plate, and the resistance generated when trying to cut the viscous liquid, that is, the shear resistance, Since a viscous torque is generated and the torque is transmitted while trying to eliminate the rotational speed difference, if a large rotational speed difference continues for a long time, the viscous force is converted into heat and the temperature and pressure in the housing rise.

On the other hand, the rotation speed difference between the front and rear wheels naturally occurs at the time of cornering, but the rotation speed difference becomes extremely large when the front wheel or the rear wheel idles, and the road surface μ such as an icy snowy road or a wet road is reduced. When the temperature is low, slip occurs frequently, so that the temperature inside the housing of the visco clutch 11 rises significantly.

Therefore, as described above, the temperature sensor 12 for detecting the internal temperature of the Visco clutch 11 and the outside air temperature sensor for detecting the outside air temperature
13 and the control unit 6
13, the temperature Tc in the visco-clutch and the temperature Ta in the outside air are calculated as shown in the flowchart of FIG.
Is calculated, and when the difference exceeds a preset set value, it is determined that the road is a low μ road, and a signal is issued to the actuator 5 of the rear air suspensions 2, 2. By operating this, the damper damping force and the spring constant are reduced, and the roll rigidity is reduced, so that a sufficient ground load on the rear wheel can always be ensured.

In this way, even when the front wheels idle (slip) on a low μ road, the driving torque is accurately transmitted to the rear wheels via the Visco clutch 11, and stable running with the grip force of the rear tires is achieved. As well as ensuring that the rear wheel roll stiffness is lower than the front wheel roll stiffness, the vehicle shifts to a cornering characteristic in which the degree of understeer is increased, and the steering stability is significantly improved.

An outline of an example of the overall control mode of the semi-active suspension of the present invention is as shown in the flowchart of FIG. 3, and as can be seen from FIG. When it is determined that the road is a road, the reduction of the roll stiffness of the rear suspension is performed prior to the control for changes in the vehicle body posture such as a squat, a nose dive, and a roll.

In FIG. 3, the description of which of the front, rear, left, and right suspensions outputs the hard output with respect to the squat, the nose dive, and the roll is omitted, but this rolling is as described in the above description.

In the above description, the damper damping force variable control and the spring constant variable control include, for example, in the case of a hydraulic damper, changing the opening area of an orifice serving as an oil passage by opening and closing a solenoid valve to change the damping force, or as shown in the illustrated embodiment. In the case of an air suspension that uses the bulk elasticity of air as a spring, the air sealing section is divided into a main chamber and a sub-chamber, and an opening that can communicate both chambers is opened and closed by a solenoid valve, thereby effectively forming a spring. For example, the spring constant may be changed by changing the volume of the air enclosing portion that acts, or any conventionally known control means may be employed.

Although the illustrated embodiment shows an example in which an air suspension is used as the suspension, the present invention is not limited to the air suspension, and an arbitrary suspension having a damping force variable damper and a spring mechanism capable of changing a spring constant is used. Applicable to

Effect of the Invention As described above, according to the present invention, in a semi-active suspension of a four-wheel drive vehicle using a Visco clutch, logic for judging the road surface μ based on the temperature of the Visco clutch is provided in the control unit of the semi-active suspension. The control unit performs control to soften the damper damping force and spring constant of the rear suspension and reduce the roll rigidity when the control unit determines that the road is a low μ road based on the above logic.
With a simple configuration, accurate determination of the road surface μ can be made, the ground contact load of the drive wheels can be sufficiently secured on low μ roads such as icy and snowy roads and wet roads, and the cornering characteristics move to the understeer side to improve running stability. It can significantly improve safety, and can significantly improve safety.In addition, on snowy roads and gravel roads, rear uplift can be reduced and riding comfort can be improved, and it can have a great effect in practical use. is there.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, and is a perspective view schematically showing main parts of an automobile to which the present invention is applied, and FIG. 2 is an example of determination and control of a road surface friction coefficient according to the present invention. FIG. 3 is a flowchart schematically showing an example of the overall control mode of the semi-active suspension according to the present invention. 1,2 …… Air suspension, 5 …… Actuator,
6 Control unit 7 Speed sensor 8
... accelerator opening sensor, 9 ... brake fluid pressure sensor, 10
…… Steering angle sensor, 11… Visco clutch, 12… Temperature sensor, 13… Outside air temperature sensor.

Claims (1)

(57) [Claims] 1. A four-wheel drive vehicle using a visco clutch, which predicts changes in vehicle behavior such as a squat, a nose dive, and a roll, and controls variable elements of a suspension such as a damping force of a damper and a spring constant. For those equipped with a semi-active suspension variably controlled by a signal from the unit, the control unit incorporates logic to determine whether the road surface friction coefficient is high or low based on the temperature of the Visco clutch, and the road surface friction coefficient is A control device for a vehicle suspension, characterized in that the control unit performs control to reduce the roll stiffness of the rear suspension when it is determined to be low.