JPH03514A - Suspension for vehicle - Google Patents

Abstract

PURPOSE:To improve the quantities of head turning and stability compatibly by arranging so that respective actuators may be controlled in such a way that suspension members on the front wheel side are displaced upward or suspension members on the rear wheel side are displaced downward, as a car velocity increases. CONSTITUTION:When transfer from a stop condition to a travel condition is made, a car velocity V rising gradually is inputted into a controller 24 from a car velocity detector 25. This controller 24, in proportion to the car velocity V, makes a command value I to a front wheel pressure control valve 23F, come down gradually from a neutral value IN, and makes a command value I to a rear wheel pressure control valve 23R, increase gradually from the neutral value IN. Accordingly, oil pressure cylinders 21FL, 21FR on the front wheel side come down, and the upward force of the spring force of the spring of a suspension increases, a stroke dwindles. Conversely, the stroke of the rear wheel side extends. Accordingly, a roll center becomes high on the front wheel side, and low on the rear wheel side, and the quantities of head turning and stability can be compatible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vehicle suspension, and in particular, the roll center of the vehicle is improved by changing the vertical position of a suspension member provided on the vehicle body side with respect to the vehicle body. This invention relates to a vehicle suspension that can be adjusted according to driving conditions.

[Prior Art] As a conventional suspension structure, one having the configuration shown in FIG. 6 is known. This one shows a double wishbone type.

In the figure, 1 is a wheel, 2 is a vehicle body, and 3 is a suspension member provided on the vehicle body 2. An upper arm 4. is located between the knuckle (not shown) of one example wheel and the suspension member 3. A lower arm 5 is provided, the end of each arm 4, 50 on the wheel side is connected to the knuckle via a ball joint 6, and the end on the vehicle body side is connected to the suspension member 3 via a rubber bush 7. There is.

In such a suspension structure, the roll center height is determined by the upper arm 4. Point RC(
It is obtained as the height HRC of the roll center) from the road surface.

[Problem to be solved by the invention]

However, in such a conventional suspension structure, the instantaneous center IC moves with the stroke of the suspension, and the roll center RC also moves accordingly, changing its height HRC. Because the structure was such that the roll center does not change even if the vehicle speed or the longitudinal acceleration, which is the rate of change thereof, changes, the characteristics of turning performance and vehicle stability due to the roll center heights H and C are dependent on the vehicle speed and longitudinal acceleration. Good turning performance at medium to low speeds and limit turning (high G), which is required for normal vehicles.
There was a problem in that it was difficult to achieve both high stability during high speed and limit turning (high G). Furthermore, when a high-G turn is performed during acceleration/deceleration, skids and spins are likely to occur, resulting in unstable vehicle behavior.

This invention was made by focusing on the problems of conventional suspension engines, and improves turning performance by changing the roll center height of the vehicle according to changes in driving conditions such as vehicle speed and longitudinal acceleration. The first problem to be solved is to achieve both high vehicle stability. Also,
The second problem to be solved is to stabilize the vehicle behavior even when a high-G turn is made during acceleration/deceleration.

[Means to solve the problem]

In order to solve the first problem, the invention according to claim (1) includes a suspension member that is attached to the vehicle body so as to be able to move up and down, and an actuator that moves this suspension member up and down with respect to the road surface. It also includes a vehicle speed detector that detects vehicle speed, and control means that controls the operation of the actuator according to a detection signal from the vehicle speed detector, and this control means controls the front wheel suspension as the vehicle speed increases. It has at least one of a control mechanism that controls the actuator in a direction in which the member ascends, and a control mechanism that controls the actuator in a direction in which the suspension member on the rear wheel side descends as the vehicle speed increases. There is.

Further, in order to solve the second problem, the invention according to claim (2) includes a suspension member that is attached to the vehicle body so as to be able to move up and down, and an actuator that moves this suspension member up and down with respect to the road surface. and a longitudinal acceleration detector for detecting the longitudinal acceleration of the vehicle, and a control means for controlling the operation of the actuator according to a detection signal of the longitudinal acceleration detector, and the control means controls the increase in acceleration and deceleration. a control mechanism that controls the actuator in a direction in which the suspension member on the front wheel side rises as the acceleration/deceleration increases; and a control mechanism that controls the actuator in the direction that the suspension member on the rear wheel side descends as the acceleration/deceleration increases. , has at least one.

Furthermore, the first. In order to solve the second problem, an actuator that changes the roll center height of the suspension, a detector that detects a physical quantity related to vehicle speed, and an operation of the actuator is controlled according to a detection signal of this detector. The control means has a control mechanism for controlling the roll center of the suspension on the front wheel side to be higher than the roll center of the suspension on the rear wheel side in response to a change in the detection signal of the detector. ing.

[Effect]

In the invention set forth in claim (1), the control means controls the operation of the actuator in accordance with an increase in vehicle speed as a running state, thereby controlling the actuator at least in a direction in which the suspension member on the front wheel side rises. Or, the actuator is controlled in a direction in which the suspension member on the rear wheel side descends. As a result, the roll center height on the front wheel side becomes higher than the roll center height on the rear wheel side, so the higher the speed, the larger the amount of load transfer between the front wheels and the inner and outer wheels during a turn will be than that of the rear wheels. As a result, the steering characteristic becomes an understeer characteristic, and vehicle stability is improved. In addition, at medium and low speeds, there is no significant difference in the amount of load transfer between the front and rear wheels, so the steering characteristics become neutral.
Good retrospective performance can be obtained.

Further, in the invention set forth in claim (2), the control means controls the operation of the actuator according to an increase in longitudinal acceleration/deceleration as a running state, and thereby at least a direction in which the suspension member on the front wheel side rises. The actuator is controlled in the direction that the suspension member on the rear wheel side descends. Therefore, as the vehicle accelerates and decelerates more rapidly, the amount of load movement between the front wheels and the inner and outer wheels during the turn becomes larger than that of the rear wheels, and the vehicle stability is further improved.

Furthermore, in the invention set forth in claim (3), the control means controls the actuator so that the roll center of the front wheel suspension is higher than that of the rear wheel suspension in accordance with a change in a physical quantity related to the vehicle speed. Therefore, the same effect as described above can be obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

(First example) A first embodiment is shown in FIGS. 1 to 3.

FIG. 1 shows an embodiment of the present invention applied to a vehicle having a double wishbone type suspension for both the front and rear wheels (the figure shows the configuration as seen from the front side of the vehicle).

In the same figure, 11FL and 11FR are the front right wheel, 1
2 is a vehicle body, and 13 is a suspension member provided on the vehicle body 12 side. An upper arm 14 is disposed between the knuckle (not shown) on the wheel side and the suspension member 13, as in the conventional example described above. Lower arm 15
The wheel side end of each arm 14,15 is connected to the knuckle via a ball joint 16, and the vehicle body side end is connected to the suspension member 13 via a rubber bush 17. There is.

Further, the vehicle of this embodiment is provided with a roll center height control device 18 whose actuator is interposed between the vehicle body I2 and the suspension member 13. This roll center height control device 18 includes a member support shaft 20 provided at the bottom of the vehicle body 12, and hydraulic cylinders 21FL to 21RR (see FIG. 2) as actuators provided between the vehicle body 12 and the suspension member 13. , hydraulic source 22
Hydraulic cylinders 21FL to 2
It includes front and rear pressure control valves 23F and 23R that control the operation of the 1RR separately in the front and rear, a controller 24 that provides a command value I for the pressure control valves 23F and 23R, and a vehicle speed detector 25. Among these, the pressure control valves 23F, 23R and the controller 24 constitute a control means.

The member support shaft 20 hangs down from the bottom of the vehicle body 12 in an inverted T shape and supports the suspension member 13 in a vertically movable manner, and the stopper portion 2OA at the lower end supports the suspension member 13 with an insulator 21 in between.
The lowermost end position of the member 13 is restricted.

Each of the hydraulic cylinders 21FL to 21RR is a single-rod, single-acting cylinder, whose cylinder tube side is connected to the vehicle body 12, whose piston rod side is connected to the suspension member 13, and whose cylinder chamber R is connected to a front (or rear) pressure control valve. They are respectively connected to the output ports of 23F (or 23R). Note that a spring 21A having a predetermined spring constant is inserted between the piston and the tube on the piston rond side.

The front and rear pressure control valves 23F and 23R are connected to the front hydraulic cylinders 21FL and 21PR, and the rear hydraulic cylinder 2.
1RL and 21RR are one set each, and the equipment is equipped correspondingly to the two sets, and the supply and return boats are connected to hydraulic power source 2.
2, which is a conventionally well-known three-port electromagnetic proportional pressure reducing valve (see, for example, Japanese Patent Laid-Open No. 187609/1983). This pressure control valve 23F.

23R is supplied with a command value I in the form of a current value from the controller 24, so the output pressure changes in proportion to the value of this command value (■), and as a result, the cylinder pressure is controlled.

On the other hand, the vehicle speed detector 25 magnetically or optically detects the rotational speed of the vehicle transmission, propulsion shaft, etc. corresponding to the vehicle speed,
A vehicle speed signal (■) having a voltage amplitude value corresponding to the rotational speed is output to the controller 24.

Specifically, the controller 24, as shown in FIG.
Function generators 28F and 2 provided corresponding to the front and rear sides
8R and drive circuits 29F and 29R. The function generators 28F and 28R output a roll center height target value HIIC, which is a current value that changes in proportion to the input vehicle speed signal (2). Of these, the front function generator 28F
takes a value corresponding to the reference height target value H, when the vehicle speed ■=0, and as the vehicle speed increases, a predetermined proportional gain r-
Then, the height target value HRC, which decreases by J, is output to the drive circuit 29F. On the other hand, the rear function generator 28R calculates the vehicle speed ■
When = 0, the reference height target value H.

A height target value H, lc is output to the drive circuit 29R, which increases with a predetermined proportional gain "K," as the vehicle speed increases. These function generators 28F, 28
The characteristic of R corresponds to the characteristic of change in roll center height with respect to vehicle speed (2) shown in FIG. 3, which will be described later, with an opposite slope. On the other hand, the drive circuits 29F and 29R each amplify the input roll center height target value HRC and convert it into a command value ■ consisting of a current value, and convert the command value ■ to the corresponding pressure control valve 23.
It is designed to output to F23R.

Next, the operation of the first embodiment will be explained.

When the vehicle is in a stopped state, the detection signal ■ from the vehicle speed detector input to the controller 24 is zero, so the output signals (roll center height target value) of the front and rear function generators 28F and 28R HRC = HNO value is taken, and the command value I output to pressure control valves 23F and 23R is also its neutral value IN.
becomes. Therefore, each pressure control valve 23F, 23R has a corresponding hydraulic cylinder 21FL, 21FR, 21RL.
, 21RR cylinder pressure is controlled to neutral pressure PM according to neutral command value IN. Therefore, each cylinder 21FR~
In 21RR, the force related to cylinder pressure PM and spring 2
The 1A spring force is balanced and the stroke remains at a preset value. Therefore, the height of the roll center RC determined as described above is also maintained at a predetermined value.

Assume that the vehicle starts traveling from this stopped state and gradually increases the vehicle speed. Along with this, the vehicle speed detection signal ■ increases, so in proportion to this, the command value I for the front wheels gradually decreases from the neutral value IN, and the command value I for the rear wheels gradually decreases from the neutral value IN. increase

For this reason, the hydraulic cylinders 21FL and 21F on the front wheel side
The operating pressure of R also gradually decreases, and the upward force increases due to the spring force of the spring 21A, its stroke decreases, and the hydraulic cylinders 21RL and 21RL on the rear wheel side
In 21RR, on the contrary, the stroke gradually increases. Therefore, the suspension member 13 on the front wheel side rises with respect to the road surface, and the suspension member 13 on the rear wheel side
3 is lowered, so the instantaneous center on the front wheel side becomes higher as mentioned above, and the roll center height also rises as shown in Figure 4, and the instantaneous center on the rear wheel side becomes lower, as shown in the same figure. The roll center height also decreases.

'In this way, when the roll center height increases (or decreases) depending on the vehicle speed, the roll angle becomes smaller (or thicker).
Therefore, the roll rigidity becomes thicker (or smaller).

As a result, when turning at high speeds, the amount of load transfer between the inner and outer wheels is moderately thicker on the front wheel side than on the rear wheel side.
As a result, the total cornering power of the inner and outer wheels and the total maximum cornering force of the inner and outer wheels are moderately larger on the rear wheel side than on the front wheel side. In other words, the stability factor increases, the steering characteristics of the vehicle become understeer characteristics, and the vehicle stability improves.

In addition, there is no significant difference in the amount of load transfer between the front and rear wheels during turns in the medium and low speed range, so the total cornering power of the inner and outer wheels and the total maximum cornering force of the inner and outer wheels are Almost balanced between the side and rear wheel side. In other words, the stability factor is further reduced, the steering characteristics become closer to neutral characteristics, and good turning performance can be obtained.

Furthermore, in the arrangement of the upper arm I4 and the lower arm 15 in this embodiment, as the vehicle speed increases, the roll center height increases on the front wheel side, and the camber angle to the ground changes in a positive direction; In addition to the decrease in roll center height on the wheel side, the camber angle to the ground changes in a negative direction. As a result, there is a synergistic effect in that the stability in the high-speed, high-G region is further improved in terms of camber change.

Note that the change characteristics of the roll center height with respect to the vehicle speed in the present invention are not necessarily limited to those described above; for example, the roll center heights of the front and rear wheels are kept the same up to a medium to low speed range, When entering a predetermined high speed range, as in the first embodiment, a function is generated such that the roll center height of the front wheels is gradually or stepwise raised and that of the rear wheels is lowered gradually or stepwise. Vessel 28F, 2
The characteristics of 8R may be changed.

(Second Embodiment) Next, a second embodiment will be described based on FIGS. 4 and 5. Here, the same reference numerals are used for the same components as in the first embodiment.

The configuration of the second embodiment is almost the same as that of the first embodiment described above, but instead of using a vehicle speed detector, the longitudinal acceleration is detected by detecting the acceleration in the longitudinal direction of the vehicle, and the longitudinal acceleration is determined by a voltage value corresponding to the acceleration. A longitudinal acceleration detector 32 that outputs a signal G to the controller 24 is provided.

The longitudinal acceleration detector 32 is configured to take a positive signal G when the vehicle is accelerating, and a negative signal G when the vehicle is decelerating, for example.

Further, the controller 24 in the second embodiment is equipped with a function generator and a drive circuit on the front and rear wheels as in the first embodiment, but the roll center height with respect to the acceleration/deceleration G is The characteristics correspond to those shown in FIG. 5(a). In other words, in the acceleration state, the front and rear roll center heights Hll are kept at the same reference value H until the predetermined acceleration Gl.
8, and when the predetermined acceleration G1 is exceeded, the height HRC on the front wheel side increases in proportion to the increase in acceleration G1 (2 for the proportional gain).
is gradually raised, and the height HRC on the rear wheel side is gradually lowered. In addition, in the deceleration state, the proportional gain is changed to 3 until the predetermined deceleration G2, as in the case of acceleration, and the predetermined deceleration G2
After , the proportional gain is changed to another proportional gain of 4 (>K3). In addition, in FIG. 5(a), the characteristic of the roll center height HRc according to the conventional example of straight line Aμ is shown.

For this reason, for example, when an FR (front engine, rear drive) vehicle decelerates, the strokes of the front wheel side hydraulic cylinders 21FL and 21PR are reduced in accordance with the deceleration G, and the rear wheel side hydraulic cylinder 21RL is reduced. , 2
The stroke of 1RR is extended, the roll center height HRC on the front wheel side increases more than the reference value H, and the height HRC on the rear wheel side decreases. Therefore, when turning during such a deceleration state, the total cornering power of the inner and outer wheels and the total maximum cornering force of the inner and outer wheels relative to the rear wheels become larger than those of the front wheels. As a result, Figure 5 (
As shown in b), the stability factor of the vehicle is significantly increased compared to the conventional one (curve B in the figure).
Compared to conventional systems, the occurrence of rear skids, spins, etc. can be significantly reduced, and vehicle stability can be improved. This advantage is that the deceleration is G! This is particularly noticeable when making a critical turn (high G) in a state of deceleration.

Furthermore, when accelerating with an FR vehicle, the front and rear roll center heights HRC are not controlled in a relatively gentle acceleration state up to a predetermined acceleration G, and this allows cornering while accelerating. Improves good turning ability when performing. Then, when the vehicle enters a sudden acceleration state exceeding a predetermined acceleration G1, the height HRC is controlled in the same manner as during deceleration, and the stability factor is increased as shown in FIG. 5(b). This has the advantage of reliably preventing spins and the like caused by turns during rapid acceleration, and improving vehicle stability.

In each of the above embodiments, the controller is composed of a function generator and a drive circuit, but it goes without saying that it may be composed of a microcomputer storing equivalent software.

Furthermore, the mounting position of the hydraulic cylinder as the actuator of the present invention is not necessarily limited to that described in each of the above embodiments, for example, at the mounting point of the lower arm or upper arm to the suspension member, between each arm and the suspension member. It may also be configured such that the vertical position of the suspension member is changed by intervening therein.

Further, as the actuator in the suspension of the present invention, for example, a pneumatic cylinder may be used in addition to the hydraulic cylinder of each of the above embodiments. On the other hand, the hydraulic cylinder as an actuator is a combination of the single-acting cylinder and spring shown in each of the above embodiments, as well as
A double-acting cylinder that performs the same function may be used, and the stroke may be varied by controlling the pressure in both chambers of this cylinder.

Furthermore, although the suspension in each of the above embodiments has been described as having a double wishbone type, the present invention is not limited to those types, and the roll center height can be improved by changing the vertical position of the suspension member. It may be of a structure that allows adjustment of the height. Furthermore, in each of the embodiments described above, the roll center heights of both the front and rear wheels are individually controlled, but if necessary, only one of them may be controlled to simplify the structure.

〔Effect of the invention〕

As explained above, according to the invention set forth in claim (1), the suspension member is attached to the vehicle body so as to be movable up and down, and the actuator that moves the suspension member up and down with respect to the road surface is provided. ,
The actuator is controlled so that the front wheel suspension member moves up as the vehicle speed increases, or the rear wheel suspension member moves down as the vehicle speed increases.・Since there is no significant difference in the amount of load transfer between the front and rear wheels at the time of limit turning, good turning performance is maintained, and at high speeds.
At the time of limit turning, the amount of load movement between the inner and outer wheels on the front wheel side is much larger than that on the rear wheel side, so that high vehicle stability is ensured, and this has the effect of achieving both.

Further, according to the invention described in claim (2), since the above-mentioned control is performed for longitudinal acceleration, vehicle behavior such as skidding and spin during high-G turns in an acceleration/deceleration state is appropriately eliminated, and the vehicle The effect is improved stability.

Furthermore, according to the invention described in claim (3), the same effects as the inventions described in items (1) and (2) above can be obtained without moving the entire suspension member.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing a first embodiment of the present invention as seen from the front side of the vehicle, Fig. 2 is a block diagram of the controller of the first embodiment, and Fig. 3 is a diagram showing the front and back of the vehicle speed change in the first embodiment. Characteristic diagram of wheel side roll center height change, 4th
The figure is a schematic configuration diagram showing the second embodiment of the present invention as seen from the front side of the vehicle, and FIG. 5.degree. C.) is a characteristic diagram of changes in stability factor with respect to changes in acceleration/deceleration in the second embodiment, and FIG. 6 is a schematic diagram showing the conventional example as seen from the front side of the vehicle. In the figure, 12 is the vehicle body, 13 is the suspension member, and 14
15 is an upper arm, 15 is a lower arm, 18 is a roll center height control device, 20 is a member support shaft, 20A is a stopper portion, 21FL to 21RR are hydraulic cylinders (actuators), 23F and 23R are pressure control valves, 24 is a controller, 25 32 is a vehicle speed detector, and 32 is a longitudinal acceleration detector.

Claims (3)

[Claims] (1) It includes a suspension member attached to the vehicle body so as to be able to move up and down, an actuator that moves the suspension member up and down relative to the road surface, a vehicle speed detector that detects vehicle speed, and detection of this vehicle speed detector. control means for controlling the operation of the actuator in response to a signal; 1. A vehicle suspension comprising at least one of a control mechanism for controlling the actuator in a direction in which a suspension member on a rear wheel side is lowered in accordance with the lowering of the suspension member on the rear wheel side. (2) A suspension member attached to the vehicle body so as to be able to move vertically, an actuator that moves the suspension member vertically relative to the road surface, a longitudinal acceleration detector that detects the longitudinal acceleration of the vehicle, and a longitudinal acceleration detector that detects the longitudinal acceleration of the vehicle; control means for controlling the operation of the actuator according to a detection signal from an acceleration detector; A vehicle suspension comprising at least one of a mechanism and a control mechanism for controlling the actuator in a direction in which a suspension member on a rear wheel side is lowered as acceleration/deceleration increases. (3) comprising an actuator that changes the roll center height of the suspension, a detector that detects a physical quantity related to vehicle speed, and a control means that controls the operation of the actuator in accordance with a detection signal from the detector; The control means is characterized in that it has a control mechanism that controls the roll center of the front wheel suspension to be higher than the roll center of the rear wheel suspension in response to a change in the detection signal of the detector. Vehicle suspension.