JPH0370676A - Variable rigidity steering mount bush - Google Patents

Abstract

PURPOSE:To always obtain optimum steering support rigidity by restricting a relative movement for steering reaction force between a car body side and each intermediate support member and between a steering side and the intermediate support member through each free piston thereby changing a spring constant of each bush, in the above described, between the car body side and the intermediate support member and between the steering side and the intermediate support member. CONSTITUTION:A bush 3 is constituted of a mount structure part for supporting a steering housing 16 to a car body and an actuator part for variably generating support rigidity of the mount structure part. Here in the mount structure part, the first bush 31 is adhesively attached to the periphery of a car body side support member 30, further a steering side support member 33 is relatively turnably arranged inside an intermediate support member 32 with the first bush 31 mounted, while the second bush 34 is interposed between the support members 32, 33. While in the actuator part, two free pistons 45, 46 are interposed between the support members 32, 33. Each support member 30, 32, 33, between the members 30 and 32 and between the members 33 and 32, is restricted, thus a spring constant of each bush 31, 34 is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a variable rigidity steering mount bushing applied to a front or rear steering mechanism that variably controls the support rigidity for a vehicle body from the outside.

(Prior Art and Problems to Be Solved) Conventionally known steering mount bushings have a constant spring constant and can only have one fixed support rigidity.

Therefore, in order to improve vehicle stability performance and sound and vibration performance when going straight and turning with low lateral acceleration, the support rigidity has been changed to a low rigidity (
When the spring constant is set to +), the yaw rate change characteristic with respect to the lateral acceleration becomes as shown by the dotted line characteristic in Figure 9, and the higher the lateral acceleration, the greater the amount of front tire reversal. Since the cornering power characteristics of the tires are also reduced, the movement in the direction of the vehicle becomes slow, that is, the effectiveness of the steering becomes poor.

Incidentally, the amount of change in yaw rate is the difference in yaw rate before and after the additional turning of the rudder when a certain amount of additional turning of the rudder is performed during a turn, and this magnitude affects the degree of effectiveness of the rudder.

In addition, when the support rigidity is set to high stiffness (spring constant 2) in order to improve turning performance when turning with high lateral acceleration, the yaw rate change amount characteristic with respect to lateral acceleration
As shown in the dot-dashed line characteristics in the figure, the front tires move too much during straight running and turns with low lateral acceleration, resulting in poor vehicle stability, and the vibration transmission force is large, resulting in poor sound vibration performance such as shimmy.

That is, it is not possible to obtain the optimal steering support rigidity depending on the steering situation and vehicle situation when driving straight ahead or when turning.

On the other hand, by forming multiple fluid chambers in the steering mount bushing, installing valves between these multiple fluid chambers, and controlling the opening and closing of these valves from the outside, all of the multiple fluid chambers are communicated, resulting in low rigidity. There is a proposal to increase rigidity by blocking multiple liquid chambers.

However, in this case, the rigidity changes in stages, leading to a feeling of discomfort when steering, and if a large number of liquid chambers are formed in order to reduce the feeling of discomfort when steering, the structure becomes complicated, resulting in an increase in size and a significant increase in size. This results in increased costs.

The present invention has been made in view of the above-mentioned problems, and provides a variable rigidity steering mount bushing that supports a steering mechanism to a vehicle body without causing discomfort in steering, increase in size, or significant increase in cost. It is an object of the present invention to provide a steering mount bush that provides optimal steering support rigidity depending on steering conditions and vehicle conditions.

(Means for Solving the Problems) In order to solve the above problems, the variable rigidity steering mount bushing of the present invention has two bushes arranged in series, and the spring constant effect of the two bushes is restrained between the support members. It was used as a means to change by giving.

That is, a vehicle body side support member to which the vehicle body is fixed, a steering side support member fixed to the steering housing,
an intermediate support member disposed between the vehicle body side support member and the steering side support member; a first bushing interposed between the vehicle body side support member and the intermediate support member; and the steering side support member. A second bush disposed between the intermediate support member and at least the vehicle body side support member and the intermediate support member or the steering wheel side support member and the intermediate support member relative to the steering reaction force are adjusted to the oil pressure level of the external oil pressure. It is characterized by comprising a free piston provided between each member to apply restraint accordingly.

(Function) When the oil pressure level of the external oil pressure supplied to the free piston is zero, there is no restraint between each support member, and the relative movement of the vehicle body side support member, intermediate support member, and steering side support member against the steering reaction force is prevented. This is carried out with the deformation of both the first bushing and the second bushing, and the spring constant is the sum of both bushings, resulting in the lowest supporting rigidity.

When the hydraulic pressure level of the external hydraulic pressure supplied to the free piston is increased, the free piston provided between each member will respond to at least the steering reaction force of the vehicle body side support member and the intermediate support member or the steering side support member and the intermediate support member. Relative movement is restricted according to the oil pressure level of the external oil pressure, and the support rigidity gradually increases.

Then, the hydraulic pressure level of the external hydraulic pressure supplied to the free piston is set to the maximum hydraulic pressure, and, for example, the first or second
When restraint is given to integrate the steering side support member and the intermediate support member on the second bush side among the bushes, the first bush
Deformation of only the fuselage is allowed, and the support rigidity is the highest.

(Example) Embodiments of the present invention will be described below based on the drawings.

First, the configuration will be explained.

1 to 4 are diagrams showing a variable rigidity steering mount bushing 3 according to an embodiment, in which the rack tube 16 (steering housing) is rotated while receiving a steering reaction force from the vehicle body.
It is composed of a mount structure section that supports the mount structure, and a variable rigidity actuator section that makes the support rigidity variable.

The mount structure section includes a stem 30 (vehicle body side support member) fixed to the vehicle body 2 with a port 8, a first bush 31 glued to the outer periphery of the stem 30, and the first bush 31.
The first support member 32 (intermediate support member) into which is inserted
A second support member 33 (steering side support member) is provided inside the first support member 32 so as to be relatively rotatable, and a second support member 33 is interposed between the first support member 32 and the second support member 33. The second support member 33 is inserted into the outer periphery of the rack tube 16.

The first bushing 31 is arranged in a direction perpendicular to the rack axis so as to receive the steering reaction force F with a spring constant due to compression and tension deformation, and has a stem 35 on its outer surface. Further, the second bush 34 is arranged in the axial direction of the rack tube so as to receive the steering reaction force E with a spring constant due to shear deformation, and has stems 36 and 37 on its inner and outer surfaces.

The variable rigidity actuator section controls the relative movement of the first support member 32 and the second support member 33 in response to the steering reaction force using a hydraulic pressure P. A first free piston 45 is provided between the first support member 32 and the second support member 33 so as to be movable in the tube axial direction. Control oil pressure P is applied to the piston chamber 47 formed between the second free piston 46 and both pistons 45 and 46. An oil supply port 48 is formed in the first support member 32 to guide the hydraulic oil, and an oil groove 49 is formed in the first support member 32 to drain the hydraulic oil from the oil grooves 49 formed in the ends of both pistons 45 and 46. It has a discharge port 50, an oil seal 51 that keeps the first support member 32 and the second support member 33 in an oil-tight state, and a stop nut 52 that is screwed and fixed to the first support member 32.

FIG. 5 is a diagram showing the entire front steering system to which the variable rigidity steering mount bushing 3 of the embodiment is applied.

First, the front steering mechanism 1 is a mechanism that steers the front tires 7 according to the direction and magnitude of steering input by the driver, and includes a steering wheel 10, a steering shaft 11, a pinion 12, a rack gear 13, a side rod 14, a knuckle arm 15, It is configured with a rack tube 16.

The control hydraulic pressure generator 4 that generates the control hydraulic pressure PC to be supplied to the variable rigidity steering mount bushing 3 includes a hydraulic control valve 40, a reserve tank 41, and an oil pump 4.
2, an oil supply vibe 43 and an oil return vibe 44, the oil supply vibe 43 being connected to the oil supply port 48, and the oil return pipe 44 being connected to the oil discharge port 50.

The steering support rigidity controller 6, which applies the control current I to the hydraulic control valve 40, is configured by an electronic control circuit and receives the lateral acceleration Y from the lateral acceleration sensor 5. A control program is set to obtain the optimum support rigidity according to the magnitude of the lateral acceleration Y6 by increasing the support rigidity of the variable rigidity steering mount bush 3 in accordance with the increase in the lateral acceleration Y6.

Next, the effect will be explained.

First, the effect of changing the spring constant by the variable rigidity steering mount bushing 3 will be explained.

Control hydraulic pressure P supplied to a piston chamber 47 formed between the first free piston 45 and the second free piston 46.

When the oil pressure level is zero, both pot members 32 and 33
There is no restraint between the stem 30 and the first support member 3.
2 and the second support member 33 relative to the steering reaction force, or deformation of both the first and second shafts 31 and 34 arranged in series.

Therefore, as shown in the characteristics in Figure 6, the spring constant is the sum of both bushes 31.34,
The support rigidity is the lowest.

Control hydraulic pressure PC supplied to the piston chamber 47 formed between the first free piston 45 and the second free piston 46
When the oil pressure level of both port members 32,
The free pistons 45 and 46 provided between the support members 32 and 33 are pressed against the support members 32 and 33 by hydraulic pressure, so that the relative movement of the support members 32 and 33 relative to the steering reaction force F is controlled by the hydraulic pressure P. It will be restrained depending on the oil pressure level.

Therefore, as shown by the dotted line characteristics in FIG. 6, in the region where the steering reaction force F is smaller than the restraining force due to hydraulic pressure, the spring constant of the first bushing 31 is 2, and the steering reaction force F is less than the restraining force due to hydraulic pressure. If it exceeds K.

The characteristic shows a spring constant characteristic with a slope parallel to the control hydraulic pressure ρ. The support rigidity will gradually increase as the value increases.

Then, when the hydraulic pressure level of the control hydraulic pressure PC supplied to the piston chamber 47 formed between the first free piston 45 and the second free piston 46 is set to the maximum hydraulic pressure PCL/AX, the second bushing 34 is placed between the two bushings 34. Therefore, the support members 32 and 33 are constrained to become integrated.

Therefore, deformation of only the first bushing 31 is allowed, and as shown in the characteristics of FIG. 6, the spring constant is the maximum spring constant of 2, and the support rigidity is the highest.

Next, an example of variable support rigidity control using the variable rigidity steering mount bushing 3 will be described.

FIG. 7 is a flowchart showing the flow of the support stiffness variable control performed by the steering support stiffness controller 6, and each step will be explained below.

In step 70, the lateral acceleration Y6 is detected by the lateral acceleration sensor 5.
is loaded.

In step 71, the lateral acceleration Y read in step 7o. Based on , the lateral acceleration Y as shown in FIG. Lookup from the map and lateral acceleration Y to increase the spring constant according to the increase in. The optimum spring constant K for the read lateral acceleration Y6 is set by calculation using the spring constant calculation formula created by the function.

In step 72, the control oil pressure PC for obtaining the spring constant K set in step 71 is determined from the spring constant characteristic using the oil pressure as a parameter shown in FIG.

In step 73, a control flow control that provides the control oil pressure PC determined in step 72 is set based on the preset Po-I characteristic.

In step 74, the control current calculated in step 73 is output to the hydraulic control valve 40.

The above control operation is repeated at every predetermined control activation time.

Therefore, when the vehicle is running, in the steering support rigidity controller 6, the rack tube 16 of the front steering mechanism 1 is supported by the variable rigidity steering mount bushing 3, which supports the rack tube 16 relative to the vehicle body 2 in response to an increase in the lateral acceleration Ya generated in the vehicle. Control is performed to increase the rigidity, and the characteristic of the yaw rate change Δψ with respect to the lateral acceleration Y6 is the virtual acceleration Y, as shown by the solid line characteristic in FIG. On the side, a fixed spring constant approximates one characteristic, and high lateral acceleration Y. On the side, there is a variable spring constant K that approximates the fixed spring constant with two characteristics. shows the characteristics according to

As a result, when turning with high lateral acceleration, the support rigidity of the rack tube 16 of the front steering mechanism 1 becomes high, and the amount of reversal of the front tire 7 becomes small.
In addition, the cornering power characteristics of the front tire γ are also increased, making the movement in the direction more sensitive and the steering more effective.
Improves turning performance.

Furthermore, when traveling straight and turning with low lateral acceleration, the support rigidity of the rack tube 16 of the front steering mechanism 1 becomes low, suppressing the movement of the front tires 7 and improving vehicle stability. Improves sound vibration performance such as small shimmy.

As explained above, the variable rigidity steering mount bushing of the embodiment has two bushings 31.34 arranged in series, and the spring constant effect of the two bushings 31.34 is applied to both support members 32.33. Since it has a configuration in which changes are made by applying constraints between them, it has the characteristics listed below.

■ Since the support rigidity changes steplessly, the driver does not feel any discomfort when steering.

In particular, since the rigidity variable control is performed by the second bushing 34 which acts with a shearing force having a small spring constant, fine-grained rigidity variable control according to the driving situation is possible.

■ Compared to a mounting bush that forms multiple liquid chambers, it is more compact and has fewer parts, which is advantageous in terms of cost.

■ As above, lateral acceleration Y. By controlling the steering support rigidity to the optimum level according to the vehicle speed, it is possible to achieve both improved controllability when turning with high lateral acceleration and improvements in vehicle stability performance and sound and vibration performance when driving straight ahead and turning with low lateral acceleration. Optimal steering support rigidity can be obtained depending on the steering situation, vehicle situation, etc.

Although the embodiment has been described above based on the drawings, the specific configuration is not limited to this embodiment, and even if there is a design change within the scope of the gist of the present invention, it is included in the present invention. .

For example, in the embodiment, an example in which restraints are applied to both the support members 32 and 33 was shown, but even in an example in which restraints are applied to the stem 30 and the first support member 32, both support members 32, 33 and An example in which restraints are applied to both the stem 30 and the first support member 32 may also be used.

In addition, although the example shows an example of application to a binion rack type steering mechanism, it is of course applicable to other steering gear type mechanisms such as a recirculating pole type. It can be applied not only to steering mechanisms but also to rear steering mechanisms using hydraulic power cylinders, electric motor actuators, etc.

Further, in the embodiment, an example of control corresponding to lateral acceleration was shown as an example of variable control of support stiffness, but the present invention can also be applied to variable control of support stiffness based on other control information such as steering angle and vehicle speed.

(Effects of the Invention) As explained above, in the present invention, the variable rigidity steering mount bushing that supports the steering mechanism with respect to the vehicle body has two bushes arranged in series, and the springs by the two bushes are arranged in series. Since the constant effect is changed by applying restraint between the support members, it is possible to obtain the optimal steering support rigidity according to the steering situation and vehicle situation without causing discomfort in steering, increase in size, or significant cost. The effect of being able to provide a steering mount bushing is obtained.

[Brief explanation of drawings]

FIG. 1 is a side view showing a variable rigidity steering mount bushing according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional front view of the variable rigidity steering mount bushing taken along line I-r in FIG.
Figure 3 is a cross-sectional view according to Figure 2 ■-■, Figure 4 is a cross-sectional view according to Figure 1 ■
- A cross-sectional view using a curved line; Figure 5 is a diagram showing the entire system of the front steering to which the variable rigidity steering mount bushing of the embodiment is applied; Figure 6 is the flow of operation of variable support rigidity control in the steering support rigidity controller. 7 is a spring constant characteristic diagram of a variable rigidity steering mount bushing with oil pressure as a parameter. FIG. 8 is a spring constant control characteristic diagram for lateral acceleration.
FIG. 9 is a characteristic diagram of the amount of change in yaw rate with respect to lateral acceleration. 2...Vehicle body 3...Variable rigidity steering mount fish 8...
- Porto 16... Rack tube (steering housing) 30... Stem (vehicle body side support member) 31... First bush 32... First support member (intermediate support member) 33... Second support Member (steering side support member) 34...Second bushing 45...First free piston 46...Second free piston 47...Piston chamber 48...-Oil supply port 49...Oil groove 50 ... Oil discharge port 51 ... Oil seal 52 ... Stop Narato

Claims (1)

[Scope of Claims] 1) A vehicle body side support member to which the vehicle body is fixed, a steering side support member fixed to the steering housing, and an intermediate support disposed between the vehicle body side support member and the steering side support member. a first bush interposed between the vehicle body side support member and the intermediate support member; a second bush disposed between the steering side support member and the intermediate support member; and at least the vehicle body side. A free piston provided between each member to restrain the relative movement of the support member and the intermediate support member or the steering side support member and the intermediate support member against the steering reaction force according to the hydraulic pressure level of the external hydraulic pressure. A variable rigidity steering mount bush that features: