JPH10338013A - Ground load control device - Google Patents

Abstract

(57) [Problem] To provide a contact load control device capable of continuously increasing the contact load of each wheel for a desired time. SOLUTION: A vertical inertial force is generated in the vehicle body by the extension acceleration of an actuator provided between the vehicle body and the axle,
A phase difference between the left and right actuators is used to increase the ground contact load of the tire by the reaction force of the inertia force and to contract immediately after reaching the extension limit of the relative distance between the vehicle body and the axle in the vertical direction. To be performed continuously and repeatedly. According to this, the load due to the inertial force on the ground contact surface is intermittently intermittent, so that the generation limit of the grip force of the tire can be raised over a desired time, and the left and right actuators raise the vehicle body. Since it is possible to cause a shift in the timing at which the thrust to be generated is generated, power to be supplied to the actuator can be saved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact load control device capable of increasing the contact load by generating acceleration in at least one of a sprung mass and a unsprung mass.

[0002]

2. Description of the Related Art A linear sliding actuator capable of actively changing a stroke is provided between a vehicle body and an axle, and a distribution of a ground contact load of each tire according to a motion state of the vehicle at that time is a predetermined target. An active suspension system (active suspension device) in which the stroke of the actuator is feedback-controlled to obtain a value has already been put to practical use.

A conventional active suspension system as proposed in Japanese Patent Publication No. Sho 60-500662, for example, basically employs the thrust of a hydraulic actuator (such as the thrust force of a hydraulic actuator so as to suppress a change in the attitude of a vehicle body during traveling). Stroke), the tire follows the unevenness of the road surface so as to suppress the change of the center of gravity of the sprung mass during straight traveling, and the front and rear axles between the front and rear axles to suppress pitching during braking or acceleration. Generally, the amount of load movement is controlled, and the amount of load movement between the tires is controlled so as to suppress rolling during turning.

[0004]

However, in the conventional active suspension system as described above, the load distribution of each wheel according to the behavior of the vehicle at that time can be optimized within the range of the total weight of the vehicle. It was not possible to increase the margin of grip force totally.

An inertial force is generated in the sprung mass or the unsprung mass by the acceleration when the vertical relative distance between the vehicle body and the axle is expanded and contracted by the actuator, and the apparent wheel weight is determined by the reaction force of the inertial force. It is conceivable to increase the contact load by increasing the contact load. However, since the operation time of the actuator within the stroke limit of the suspension is extremely short, the increase in the contact load due to this is only instantaneous.

[0006] In view of such findings, a main object of the present invention is to provide a contact load control device capable of continuously increasing the contact load of each wheel for a desired time.

[0007]

In order to achieve the above object, according to the present invention, a vertical inertial force is generated in a vehicle body by the extension acceleration of an actuator provided between the vehicle body and an axle. The ground contact load of the tire shall be increased by the reaction force of the force, and the movement of contracting immediately after reaching the extension limit of the vertical relative distance between the vehicle body and the axle, the movement of the left wheel actuator and the right wheel. The operation is repeated continuously with a phase difference between the actuator and the actuator. According to this, the load due to the inertial force on the ground contact surface is intermittently intermittent, so that the generation limit of the grip force of the tire can be raised over a desired time, and the left and right actuators raise the vehicle body. Since it is possible to cause a shift in the timing at which the thrust to be generated is generated, power to be supplied to the actuator can be saved. In particular, by making the operation time during the return exercise longer than the operation time during the load increase exercise, it is possible to suppress a decrease in the grounding load due to the acceleration during the return exercise. In addition, by adding cushion control to gradually reduce the speed near the limit of the stroke, in the case of an active suspension device using a suspension spring, the spring reaction force is attenuated, and the spring can be prevented from being pushed up by residual energy.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of the present invention will be described below in detail with reference to embodiments shown in the accompanying drawings.

FIG. 1 schematically shows a schematic configuration of a main part of an active suspension system to which the present invention is applied. Tire 1
The upper and lower suspension arms 2 and 3
It is supported so that it can move up and down. A linear actuator 5 driven by hydraulic pressure is provided between the lower suspension arm 3 and the vehicle body 4.

The linear actuator 5 is of a cylinder / piston type, and uses a servo valve 10 to supply hydraulic oil supplied from a variable displacement hydraulic pump 9 to oil chambers 7 and 8 above and below a piston 6 inserted into the cylinder. To generate a vertical thrust on the piston rod 11,
As a result, the relative distance between the center (axle) of the tire 1 and the vehicle body 4 can be freely changed.

The oil discharged from the pump 9 is stored in an accumulator 12 for removing the pump pulsation and securing the oil amount in a transient state. Are supplied via servo valves 10 provided individually.

An unload valve 13, an oil filter 14, a check valve 15, a pressure regulating valve 16, an oil cooler 17, and the like are connected to the hydraulic circuit, similarly to a known active suspension system.

The servo valve 10 provides a control signal issued from an electronic control unit (ECU) 18 to a solenoid 10a via a servo valve driver 19, so that the hydraulic pressure and direction applied to the hydraulic actuator 5 are continuously adjusted. The vehicle body 4 and the piston rod 1 are controlled.
1, a load sensor 20 provided between the vehicle body 4 and the lower suspension arm 3, a sprung acceleration sensor 22 for detecting a vertical acceleration on the vehicle body, and a vertical sensor on the tire side. Control is performed according to a control algorithm shown in FIG. 2 based on a signal obtained by processing a signal of the unsprung acceleration sensor 23 for detecting acceleration by the ECU 18.

The ECU 18 inputs the signal of the longitudinal acceleration sensor 27 to the sudden braking determination section 28 (step 1), and determines from this value whether or not the current state is under a predetermined sudden braking state (step 2). . If it is determined that the vehicle is suddenly braking, a temporary target load is internally generated with reference to the signals from the sprung acceleration sensor 22 and the unsprung acceleration sensor 23 input to the target load calculating unit 24 (step S1). 3),
The deviation between this value and the signal (actual load) of the load sensor 20 is calculated (step 4), and this difference is processed by the stabilization calculation unit 25. Then, the displacement limit comparison calculation unit 26 refers to the signal of the stroke sensor 21. The servo valve driver 19 is controlled so that the control within the stroke limit of the actuator 5 is performed.
Is adjusted (step 5). Based on the adjusted signal, the servo valve 10 is driven so that the target load and the actual load become equal, a stroke is generated in the actuator 5, and the vertical acceleration in the direction of increasing the tire contact load is calculated as the sprung mass and the vertical acceleration. It is generated in at least one of the unsprung mass (step 6). As a result, the grip force of the tire temporarily increases, so that the locking limit is raised and the braking distance is shortened.

Next, the principle of the present invention will be described. FIG.
M2: sprung mass M1: unsprung mass Z2: sprung coordinates Z1: unsprung coordinate Kt: tire spring constant Fz: actuator thrust, and if the downward direction is the positive direction, the sprung mass M2 and the unsprung mass The equations of motion of the mass M1 are given by the following equations, respectively. However, the * mark in the equation represents the first derivative, and the ** mark represents the second derivative. M2 · Z2 ^** =-Fz M1 · Z1 ^** + Kt · Z1 = Fz

Accordingly, the tire contact load W is given by the following equation. W = −Kt · Z1 = −Fz + M1 · Z1 ^** = M2 · Z2 ^** + M1 · Z1 ^**

That is, since the ground contact load W is the sum of the sprung inertia force and the unsprung inertial force, the expansion / contraction acceleration of the actuator 5 is controlled to control the at least one of the sprung mass and the unsprung mass. Is changed, the contact load W can be changed. Therefore, by controlling the extension acceleration of the actuator 5, it is possible to temporarily increase the contact load W for each tire. When a 1-ton thrust is generated in the actuator 5 with a suspension stroke of 200 mm, about 0.2
Can be activated for seconds.

In general, a suspension spring for supporting the weight of the vehicle and a damper for generating a damping force are used together in order to save energy consumption of the actuator (see FIG. 4). In this case, Ks: Spring constant C: damping coefficient of damper Assuming that, the equations of motion of the sprung mass M2 and the unsprung mass M1 are given by the following equations, respectively. M2 · Z2 ^** + C · (Z2 ^* −Z1 ^* ) + Ks · (Z2-Z1)
= −Fz M1 · Z1 ^** + C · (Z1 ^* −Z2 ^* ) + Ks · (Z1−Z2)
+ Kt.Z1 = Fz

Accordingly, the tire contact load W is given by the following equation. W = −Kt · Z1 = −Fz + M1 · Z1 ^** + C · (Z1 ^* −Z2 ^* ) + Ks · (Z
1−Z2) = M2 · Z2 ^** + M1 · Z1 ^**

That is, it is understood that the ground load W can be changed by controlling the expansion and contraction acceleration of the actuator in the same manner as described above.

Now, as described above, the actuator 5
The apparent applied load generated by the extension acceleration of the actuator 5 disappears when the stroke end of the piston rod 11 of the actuator 5 is reached. Therefore, in the present invention, the reciprocating motion of contracting immediately after the piston rod 11 reaches the extension limit is repeated, so that the reaction force load due to the inertial force applied to the ground contact surface is periodically intermittent (FIG. 5).
reference).

On the other hand, in order to simultaneously extend the actuators 5 provided on each of the left wheel and the right wheel, an extremely large power is required. In addition, at least the section where the load exercise is performed is shifted left and right. Thus, at the time of contraction, only a small amount of power is required for the gravity of the vehicle body to descend, so that the required supply power can be saved.

In FIG. 5, for example, when the control for increasing the ground contact load is started when the vehicle height is substantially in the neutral position, the cushion control is first performed based on the signal of the stroke sensor 21 in accordance with the possible extension stroke of the actuator 5 for the right front wheel. (To be described later) is set, and up to that point, the extension motion is applied at an acceleration that is equal to or less than the maximum acceleration determined in consideration of the ability of the actuator and the effect on the occupant and a required load is obtained. Here, since the sprung mass is generally much larger than the unsprung mass, the force of the actuator 5 is applied to the contact surface of the right front wheel as a reaction force of the sprung inertial weight (see FIG. 6A). .

If the mechanical stroke end of the actuator 5 reaches the mechanical stroke end at the same speed, a large impact force is generated. Therefore, a cushion control for gradually reducing the speed from near the stroke end is added to buffer. In particular, when this cushion control is applied to an active suspension device (the model in FIG. 4) that also uses a suspension spring, the spring reaction force of the suspension spring can be attenuated, so that the suspension spring can be suppressed from being pushed up by residual energy.

When the expansion limit is reached, the contraction movement is immediately started. At this time, since the unsprung mass is overwhelmingly small, if the acceleration of the contraction movement is large, the contact load is reduced. Therefore, the operation time during the contraction movement is set longer than the operation time during the extension movement (Td> T).
s). Immediately before reaching the contraction-side stroke end, the same cushion control as described above is added. At the same time as the right front wheel turns to the contraction motion, the extension motion of the left front wheel actuator starts. The force of the actuator 5 is applied to the contact surface of the left front wheel as a reaction force of the sprung inertia weight as described above (see FIG. 6B).

By repeating this reciprocating motion with a phase difference of Tf time between the left and right actuators, the control for increasing the contact load can be substantially continued for a desired time.

FIG. 6 conceptually shows the distribution of the contact load (= grip force) of the tire. The contact load in the range of the static load is represented by a solid circle, and the contact load increased by the stroke control of the actuator 5. Is represented by a two-dot chain line circle. FIG. 6 shows a case where the ground contact load of the front wheels is increased as compared with the normal case. For example, in the case of sudden braking on a downhill road, the rear wheel load tends to decrease. It is sufficient to increase the contact load of the rear wheel by the above method.

In the above embodiment, the case where the ground contact load at the time of braking is increased has been described. However, according to the present invention, an optimum load distribution can be obtained according to the vehicle motion state and the road surface state at that time. As described above, each actuator is individually controlled, and it is needless to say that the present invention is equally applicable not only to lock prevention during braking, but also to control for increasing traction during acceleration and cornering force during turning.

Further, in the above-described embodiment, the actuator using the hydraulically driven cylinder device as the actuator is shown, but this may be achieved by using other electric thrust generating means such as a linear motor or a voice coil, or by using a cam mechanism. The same effect can be obtained even if acceleration is generated using a spring or a spring means.

In addition, the sensor used can be simplified without departing from the gist of the present invention. For example,
The position detection signal can also be obtained by integrating the output difference between the unsprung and unsprung acceleration sensors in the second order, so that the stroke sensor can be eliminated. Since the force generated by the actuator can be obtained by calculating the output values of the lower and sprung acceleration sensors, the load sensor can be eliminated. Furthermore, a state estimator can be configured based on signals from the load sensor and the displacement sensor, and both unsprung and sprung accelerations can be obtained indirectly. Also for the ECU,
Needless to say, any of digital, analog, and hybrid can be realized.

[0031]

As described above, according to the present invention, one or both of the sprung mass and the unsprung mass are directly controlled by the thrust generated by the actuator to control one or both of the sprung mass and the unsprung mass. By generating an inertial force and acting on the ground contact surface, control for increasing the ground contact load of the tire beyond the range of the vehicle weight can be continuously continued regardless of the stroke length of the suspension device. In addition, by shifting the timing at which the left and right actuators generate a thrust for raising the vehicle body, power supplied to the actuators can be saved. Therefore, according to the present invention, the continuation of the state in which the grip force limit of the tire is further increased according to the running conditions can be realized with relatively small power supply, and a great effect is obtained in improving the vehicle mobility. .

[Brief description of the drawings]

FIG. 1 is a schematic system configuration diagram of an active suspension device to which the present invention is applied.

FIG. 2 is a control flowchart of the present invention.

FIG. 3 is a model diagram for explaining the principle of the present invention.

FIG. 4 is a model diagram of a general active suspension device.

FIG. 5 is a conceptual graph showing changes in the stroke of the suspension with respect to time.

FIG. 6 is a conceptual ground load distribution diagram at the time of sudden braking.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tire 2 Upper suspension arm 3 Lower suspension arm 4 Body 5 Actuator 6 Piston 7.8 Oil chamber 9 Hydraulic pump 10 Servo valve 11 Piston rod 12 Accumulator 13 Unload valve 14 Oil filter 15 Check valve 16 Pressure control valve 17 Oil cooler Reference Signs List 18 electronic control unit (ECU) 19 servo valve driver 20 load sensor 21 stroke sensor 22 sprung acceleration sensor 23 unsprung acceleration sensor 24 target load calculation unit 25 stabilization calculation unit 26 displacement limit comparison calculation unit 27 longitudinal acceleration sensor 28 rapid braking Judgment unit

Claims (3)

[Claims] 1. An unsprung mass and an unsprung mass based on acceleration generated in at least one of a sprung mass and an unsprung mass by an actuator that actively changes a vertical relative distance between a vehicle body and an axle. The actuator of the left wheel changes the contact load of the tire by the reaction force of the inertia force of at least one of the mass and the movement of extending and contracting the vertical distance between the vehicle body and the axle. A phase difference between the actuator and the actuator of the right wheel to continuously and repeatedly perform the operation. 2. The operation time during the return movement is made longer than the operation time during the load increasing movement.
2. The contact load control device according to item 1. 3. The contact load control device according to claim 1, wherein a cushion section for gradually reducing the movement speed is provided near the limit of both the extension and contraction strokes.