JP2576280B2 - Vehicle suspension control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle suspension control device used for a vehicle such as an automobile, and more particularly to a vehicle suspension control device that extends in the vehicle front-rear direction and is disposed between a wheel support member and a vehicle body. To variably control the rigidity of a suspension bush provided on a suspension arm that supports a longitudinal force applied to the suspension.

(Prior Art) Conventionally, as a device for variably controlling the rigidity of a suspension bush, for example, a control valve provided between a fluid-containing bush and a hydraulic pressure source as disclosed in Japanese Patent Application Laid-Open No. 63-231032 has been proposed. 2. Description of the Related Art There has been known an apparatus that controls the operation to control the supply and discharge of hydraulic pressure to and from a bush, thereby variably controlling the rigidity of the bush.

Further, as disclosed in Japanese Patent Application Laid-Open No. Sho 62-17440, there is also known one in which the damping characteristic of the bush is variably controlled by controlling the operation of a variable orifice for switching the communication state of two fluid chambers provided in the bush. Have been.

(Problems to be Solved by the Invention) However, in the former conventional example, since the hydraulic pressure is positively applied to variably control the rigidity of the bush, a power loss occurs to obtain the hydraulic pressure, and the economic efficiency is deteriorated. Cause problems.

Further, in the latter conventional example, since a mechanism for switching the communication state between two fluid chambers provided in a limited space must be provided, the structure is complicated and the degree of freedom in layout is greatly restricted. There is.

In any case, these conventional examples have a problem that the structure is complicated, the cost is high, and the reliability is liable to cause a problem.

(Means for Solving the Problems) The present invention has been made in view of the above points, and has a preview sensor for detecting the presence of a protrusion on a road surface in front of a vehicle, and a vehicle speed sensor for detecting a traveling speed of the vehicle. A bush made of an elastic body and provided in a suspension arm that extends in the vehicle front-rear direction and is disposed between the wheel supporting member and the vehicle body and that supports a vehicle front-rear direction force applied to the suspension; The oil chamber is provided at a position intersecting the arm axis, and is connected to an oil chamber through which hydraulic oil flows in and out, a hydraulic control device mounted on the vehicle, a return path opened to a reserve tank of the hydraulic control device, and the oil chamber. An oil path, and a control valve for controlling the communication of the oil path to be openable and closable when the preview sensor does not detect the protrusion. The inflow and outflow of hydraulic oil into and out of the oil chamber is regulated to increase the rigidity of the bush in the longitudinal direction of the vehicle, and when a protrusion is detected, the time until the wheel reaches the protrusion based on the vehicle speed detected by the vehicle speed sensor. After reaching the arrival point, the control valve is opened for a predetermined period of time to allow the hydraulic oil to flow into and out of the oil chamber to reduce the rigidity of the bush in the vehicle longitudinal direction. And a control means for controlling the control valve.

(Action) According to the present invention, the control valve for controlling the opening and closing of the communication of the oil path connecting the return path of the hydraulic control device mounted on the vehicle and the oil chamber in the bush provided on the suspension arm is provided. The operation is controlled by the control means, and when the control valve is closed, the inflow and outflow of hydraulic oil into and out of the oil chamber in the bush is prohibited, so that the bush characteristic has high rigidity against the longitudinal force applied to the suspension arm in the vehicle axial direction. When the control valve is opened, the oil chamber in the bush and the return path of the hydraulic control device communicate with each other, and the inflow and outflow of hydraulic oil to and from the oil chamber are free. It is possible to obtain a bush characteristic having low rigidity against an applied force in the vehicle longitudinal direction.

Further, since the control valve may be provided in an oil path connecting the return path of the hydraulic control device and the oil chamber in the bush,
It has a high degree of freedom in layout, does not complicate the structure, does not actively use hydraulic pressure, so there is no problem with power loss, and it is inexpensive and easy to use the existing hydraulic control device effectively. With such a configuration, the rigidity of the bush can be variably controlled.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a system configuration diagram of an embodiment using an active suspension as a hydraulic control device.

In FIG. 1, an oil pump 1 is provided to suck oil stored in a reserve tank 3 through an oil passage 2 and discharge the oil to a supply oil passage 4. An oil filter 9 and a check valve 10 are interposed in the supply oil passage 4, and the check valve 10 prohibits the flow of oil from a downstream side to an upstream side. An accumulator 11 for holding line pressure is connected to the supply oil passage 4 downstream of the check valve 10, and a suspension unit 12 is connected downstream of the accumulator 11. Although FIG. 1 shows one suspension unit 12 as a representative, the suspension unit 12 is provided for each wheel, and each suspension unit 12 has a return oil passage communicated with the reservoir tank 3. 6 is also connected.

Each suspension unit 12 has the same structure. A suspension spring 13 and a single-acting hydraulic actuator 14 are provided between the vehicle body 7 and the wheels 8, and are provided in a hydraulic chamber 15 of the hydraulic actuator 14. The hydraulic chamber of the hydraulic actuator 14 is controlled by a control valve 17 interposed between the communicating oil passage 16 and the supply oil passage 4 and the return oil passage 6.
The supply and discharge of hydraulic pressure to and from 15 are controlled. The control valve 17 controls the flow rate of oil flowing from the supply oil passage 4 to the discharge oil passage 6 to thereby control the hydraulic actuator 14.
Is controlled, and the valve opening is controlled in accordance with the supplied current value. For this reason, the control valve 17 can control the pressure in the hydraulic actuator 14 in proportion to the supplied current value, and the supporting force generated by the hydraulic actuator 14 increases as the supplied current value increases. It is increasing.

Further, an accumulator 20 is connected to an oil passage 16 communicating with a hydraulic chamber 15 of the hydraulic actuator 14 via a first orifice 19. The first orifice 19 exhibits a vibration damping effect, and the accumulator 20 is provided in the accumulator 20. Is filled with gas and exerts a gas spring action. Further, a second orifice 21 is provided between the accumulator 20 and the oil passage 16 in parallel with the first orifice 19, and a switching valve 22 is provided between the second orifice 21 and the accumulator 20. The communication between the second orifice 21 and the accumulator 20 is switched or cut off.
The first orifice 19 and the second orifice 21
The switching valve 22 constitutes a variable orifice means, and the second orifice 21 having a larger orifice diameter than the first orifice 19 is used. The switching valve 22 is normally turned off, and is in a shut-off state shown in the figure.

Further, a suspension arm 23 such as a trailing arm is provided between the vehicle body 7 and a wheel supporting member that rotatably supports the wheels 8 and is disposed below the hydraulic actuator 14 and disposed in the vehicle front-rear direction. The front end of the suspension arm 23 and the vehicle body 7 are pivotally connected via a rubber bush 24. As shown in FIGS. 2 and 3, the rubber bush 24 has a structure in which the inner cylinder 25 is supported on a bracket 7 on the vehicle body 7 side by support bolts 26.
27 and the outer cylinder 28 is a suspension arm
It is fixed at 23. An oil chamber 30 is provided at a position of the cylindrical rubber portion 29 provided between the inner cylinder 25 and the outer cylinder 28 at a position located forward of the inner cylinder 25, that is, at a position intersecting the arm axis of the suspension arm 23. The outer cylinder 28 is provided with a nipple 31 communicating with the oil chamber 30. A communication oil passage 32 is connected to the nipple 31, and the other end of the communication oil passage 32 is connected to the return oil passage 6 as shown in FIG. A two-position switching communication control valve 33 is provided in the communication oil passage 32, and the communication control valve 33 corresponds to the control valve of the present invention. Therefore, the spring constant of the rubber bush 24 is switched by opening and closing the communication control valve 33, and the rubber bush 24 has a characteristic in the vehicle front-rear direction as shown in FIG. 4 by opening and closing the communication control valve 33. It is changing.

The operations of the control valve 17, the switching valve 22, and the communication control valve 33 are controlled by a controller 40 constituted by a microcomputer. The controller 40 has a detection output of a sprung G sensor 41 that detects vertical acceleration acting on the vehicle body corresponding to each wheel,
A detection output of a vehicle height sensor 42 provided for each wheel and detecting a stroke amount of the wheel, a detection output of a preview sensor 43 for detecting that a protrusion is present on a road surface in front of the vehicle,
And a detection output of a vehicle speed sensor 44 for detecting a traveling speed of the vehicle. The controller 40 controls each control valve 17, each switching valve 22, and each communication control based on the detection outputs of these sensors. The operation state of the valve 3 is controlled for each vehicle. The controller 40 has a configuration corresponding to control means.

As the preview sensor 43, a sensor in which an ultrasonic sensor is arranged in front of the vehicle body and inclined downward is used, and the sprung G sensor 41 and the vehicle height sensor 42 detect vibration input to the vehicle body. It is provided for.

The control operation for the control valve 17 performed in the controller 40 is represented by a control block diagram shown in FIG. That is, the output of the sprung G sensor 41 is integrated by the integrator 45 and then multiplied by KI by the amplifier 46.
The output of 42 is differentiated by a differentiator 47, and then KP by an amplifier 48.
Multiplied. The outputs of the amplifiers 46 and 48 are input to an adder 49, and are added to the control amount for maintaining the vehicle height stored or calculated in the controller 40, and the output of the adder 49 is supplied to the control valve via a valve driving unit 50. 17 is output to the control valve
The operation of 17 is controlled, whereby the hydraulic actuator 14 expands and contracts so as to absorb the input vibration, and a soft ride is obtained.

On the other hand, the control operation of the switching valve 22 and the communication control valve 33 performed in the controller 40 is represented by a control flowchart shown in FIG.

Referring to the flowchart shown in FIG. 6, first, in step S1, the fluctuation frequency of the output of the vehicle height sensor 32 is calculated, and in the following step 2, it is determined whether the calculated fluctuation frequency corresponds to a high-frequency road surface. If it is determined that the road surface corresponds to the high-frequency road surface, the process proceeds to step S3, where the switching valve 22 and the communication control valve 33 are turned on to be opened, and the process returns.

When it is determined in step S2 that the fluctuating frequency does not correspond to the high-frequency road surface, the process proceeds to step S4, where it is determined whether there is a protrusion or a step on the road surface in front of the vehicle based on the output of the preview sensor 33. . If it is determined in step S4 that there is no protrusion or step, step
After the switching valve 22 and the communication control valve 33 are turned off and closed in S5, the process returns.

On the other hand, if it is determined in step S4 that there is a protrusion or a step, the process proceeds to step S5, and the time until the wheel reaches the protrusion or the step is calculated. This time is, as shown in FIG. 7, the distance between the protrusion and the step and the wheel on the road surface in front of the vehicle (L for front wheels, L + for rear wheels).
1) and the vehicle speed V detected by the vehicle speed sensor 44. In this case, if the preview sensor 43 detects the presence or absence of a protrusion or a step at a predetermined distance in front of the vehicle body, the above-described L value is a fixed value, and if the distance to the protrusion or the step can be detected. The above L value is a measured value.

Then, after the time until the wheel reaches the protrusion or the step is calculated in step S6, the process proceeds to step S7,
It is determined whether or not the time calculated in step S6 has elapsed. If the time has not elapsed, this determination is repeated, and when it is time for the wheel to reach a protrusion or a step, step S8 is performed.
Proceed to. Then, in step S8, for a predetermined time t, the switching valve 22 is turned on, the second orifice 21 and the accumulator 20 are communicated via the switching valve 22, the communication control valve 33 is turned on, and the oil in the rubber bush 24 is turned on. The chamber 30 and the return oil passage 6 are communicated, and after a lapse of a predetermined time t, the switching valve 22 and the communication control valve 33 return to the off state, and thereafter return.

Next, the operation of the above embodiment will be described. In a normal state in which the traveling road surface is not a high-frequency road (a state in which the fluctuation frequency is smaller than a predetermined value and no protrusion or step is detected), the switching valve 22 and the communication control valve 33 are turned off and the second Orifice 2 and accumulator
The communication with the oil chamber 20 and the communication between the oil chamber 30 of the rubber bush 24 and the return oil passage 6 are shut off. In this state, the pressure in the hydraulic actuator 14 is controlled by the control valve 17 driven by the controller 30, and the vibration input to the wheels 8 is absorbed by the operation of the hydraulic actuator 14, so that the riding comfort is improved. And in this state, the accumulator 20
And the hydraulic actuator 14 have a small orifice diameter.
The control valve is connected only by the orifice.
The amount of hydraulic oil controlled by the oil passage 19 flowing through the oil passage 19 passing through the first orifice 19 is small, and sufficient control can be performed even if a relatively small flow rate is used as the control valve 17.

By the way, the above-described vibration absorbing effect obtained by controlling the operation of the control valve 17 cannot exert a sufficient effect on high-frequency vibration. This is due to the fact that the frequency response of the control valve 17 is limited as shown in FIG. 8. Since the frequency response of the control valve 17 is limited, the hydraulic actuator 14 follows the high frequency vibration. It cannot be activated.

For this reason, in the above embodiment, the high frequency vibration is attenuated by the orifice and the accumulator 20 (gas spring). This is to attenuate the pressure fluctuation in the pressure chamber 15 of the hydraulic actuator 14 due to the vertical movement of the wheel 8 due to the road surface input due to the flow resistance of the orifice, but simply use the first orifice 19 and the accumulator 20. In this case, as shown by a solid line in FIG. 9, the transmission force to the vehicle body with respect to the pressure fluctuation of the pressure chamber 15 due to the road surface input increases as the frequency of the vibration increases, so that the vibration of the high-frequency Is input, a large vibration is transmitted particularly to the vehicle body, giving the occupant a large push-up feeling. Therefore, the above embodiment is
By controlling the operation of the switching valve 22 using a configuration in which the second orifice 21 is provided in parallel with the first orifice 19, the effect of the second orifice 21 absorbs the vibration input in the vertical direction, and the spring of the rubber bush 24 By switching the constant, the longitudinal vibration input is absorbed.

That is, in the above embodiment, when the fluctuation frequency of the vehicle height sensor output is equal to or higher than the predetermined value (when high-frequency vibration is continuously input), the switching valve 22 and the communication control valve
While turning on 33, the switching valve 22 communication control valve 33 is turned on for a predetermined time t when the vehicle goes over the protrusion (in the case where high-frequency vibration is input spontaneously). Then, by turning on the switching valve 22, the second
Since the orifice is opened and the orifice diameter of the second orifice 21 is larger than the first orifice 19, the substantial orifice diameter interposed between the hydraulic actuator 14 and the accumulator 20 is greatly increased. As a result, the damping force for high-frequency vibration is significantly reduced, and the vibration transmitting force to the vehicle body is also reduced, so that high-frequency vibration input can be efficiently attenuated. At the same time, the communication control valve 33 is turned on and the oil chamber 30 of the rubber bush 24 and the return oil passage 6 communicate with each other, so that the spring constant of the rubber bush 24 is reduced and high-frequency longitudinal vibration input is efficiently absorbed. be able to.

In particular, it is possible to greatly reduce the feeling of thrust when riding over a protrusion, and after a lapse of a predetermined time t, the switching valve 22 and the communication control valve 33 are turned off again, so that the damping force and the spring constant of the rubber bush 24 increase. Thus, the vibration after the protrusion can be efficiently converged. FIG. 10 shows the vertical acceleration generated in the vehicle body when riding over a protrusion, and it is clear that the above-described switching has improved the riding comfort.

According to the above embodiment, the operation of the hydraulic actuator 14 can efficiently absorb the relatively low frequency vibration, and at the same time, when the high frequency vibration is input, the first and second orifices 19 and 21 move the vertical direction. Vibration input
Further, the vibration input in the front-rear direction can be efficiently absorbed by the action of the rubber bush 24, and a good ride comfort can be obtained even when high-frequency vibration is input.

In addition, since a relatively small flow rate can be used as the control valve 17, there is an advantage that a good ride comfort can be ensured even for a high-frequency vibration input without increasing the cost.

In particular, regarding the switching of the spring constant of the rubber bush 24,
Since the return path of the hydraulic circuit of the active suspension is used without actively using hydraulic pressure, the structure is simple, economical and highly reliable, and the freedom of arrangement of the communication control valve 33 is large. Has the advantage of excellent versatility.

Note that the present invention is not limited to the above-described embodiment.For example, the control of the communication control valve 33 may be performed only based on the fluctuation frequency of the vehicle height sensor, or may be performed when a projection or a step using the preview sensor 33 is used. May be performed alone. Further, a control valve having an orifice or a variable orifice may be used, and a power steering device or a rear wheel steering device may be used as a hydraulic control device to variably control only the rigidity of the bush. Also,
It goes without saying that various modifications can be made without departing from the spirit of the present invention.

(Effects of the Invention) As described above in detail with the embodiment, according to the present invention, a simple configuration is provided between the wheel support member and the vehicle body to support the vehicle longitudinal force applied to the suspension. The function of variably controlling the rigidity of the bush provided on the suspension arm in the longitudinal direction of the vehicle is achieved. When the preview sensor detects that there is a protrusion on the road surface, the time until the wheel reaches the protrusion is calculated. However, when the protrusion on the road surface is taken over, the rigidity of the bush is reduced, and the feeling of pushing up when the vehicle goes over the protrusion can be greatly reduced. After a predetermined time has elapsed, the control valve is closed and the rigidity of the rubber bush is increased, so that the vibration in the vehicle longitudinal direction after riding over the protrusion can be efficiently converged, and a suspension device with extremely comfortable riding can be provided. The switching of the rigidity (spring constant) of the rubber bush is simple because the return path of the hydraulic control device is used without actively adjusting the pressure, such as increasing or decreasing the oil pressure. Since it is economical and excellent in reliability and has a large degree of freedom in arranging the control valve, there is an effect of providing a suspension control device having excellent versatility and extremely high commercial value.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a sectional view showing details of the rubber bush 24, and FIG.
FIG. 4 is a view showing a spring constant characteristic of the rubber bush 24, FIG. 5 is a control block diagram showing a control operation of the control valve 17, and FIG. 6 is a switching valve 22 and a communication control valve. FIG. 7 is a flowchart showing the control operation of 33, FIG. 7 is a principle diagram of detection of over-projection using the preview sensor 43,
FIG. 8 is a frequency response characteristic diagram of the control valve 17, FIG. 9 is a characteristic diagram of the vibration transmission force to the vehicle body with respect to the input vibration frequency, and FIG.
FIG. 10 is a characteristic diagram of the vertical acceleration generated in the vehicle body when riding over a protrusion. 1 ... Oil pump, 6 ... Return oil passage 14 ... Hydraulic actuator, 17 ... Control valve 23 ... Suspension arm 24 ... Rubber bushing, 30 ... Oil chamber 32 ... Communication oil passage, 33 ... Communication control Valve 40: Controller, 43: Preview sensor, 44: Vehicle speed sensor

Continued on the front page (72) Inventor Naohiro Kishimoto 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Hiroaki Yoshida 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Examiner in Industrial Co., Ltd. Masayuki Ogura (56) References Japanese Utility Model 1984-91910 (JP, U)

Claims (1)

(57) [Claims] 1. A preview sensor for detecting the presence of a protrusion on a road surface in front of a vehicle, a vehicle speed sensor for detecting a running speed of the vehicle, and extending in the front-rear direction of the vehicle and arranged between a wheel support member and the vehicle body and applied to a suspension. A bush made of an elastic body provided on a suspension arm for supporting a force in a vehicle front-rear direction, an oil chamber formed in the bush and arranged at a position intersecting an arm axis of the suspension arm, and into which hydraulic oil flows in and out; A hydraulic control device mounted on the hydraulic control device, an oil passage connecting the return chamber opened to the reserve tank of the hydraulic control device with the oil chamber, and a control valve for controlling the communication of the oil passage to be openable and closable. In addition, when the preview sensor does not detect the protrusion, the control valve is closed to restrict the inflow and outflow of hydraulic oil into and out of the oil chamber, and the bush is moved forward and backward of the vehicle. When the protrusion is detected, the time until the wheel reaches the protrusion is calculated based on the vehicle speed detected by the vehicle speed sensor, and during the predetermined time after reaching the same point, Control means for opening the control valve to allow the inflow and outflow of hydraulic oil into and out of the oil chamber and controlling the control valve so as to reduce the rigidity of the bush in the longitudinal direction of the vehicle. Suspension control device.