JPH0568362B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a support device for a shock absorber that changes the spring constant of a suspension bush for upper support of a shock absorber during running to improve ground contact when running on rough roads. (Prior art) Conventionally, suspension bushes for atspa support that support automobile shock absorbers on the vehicle body have a fixed spring constant determined by the hardness of the rubber itself or a fixed spring constant determined by embedding a metal body in the rubber. Therefore, the vibration absorption and shock absorption characteristics of an automobile determined by the suspension springs and bushings are constant. Therefore, if the spring constant of the bushings is determined with emphasis on ride comfort, the ride comfort and road holding on paved roads will be Even if both conditions are good, when the vehicle is driven on a rough road, the vibrations are further increased due to the subsequent impact, resulting in poor road holding. This tendency not only appears in pitching, rolling, and yawing, and not only reduces driving performance, but also reduces ride comfort on rough roads.
Although the ride comfort on rough roads and road holding were improved, the drawback was that the ride comfort on paved roads was significantly reduced. In order to solve this problem, a suspension system has been developed that can change the spring constant of the suspension bushing depending on the driving condition. An example of such a suspension system is the
There is an invention of a flexible bushing such as a tension rod described in Japanese Patent Publication No. 205432, and an invention of an adjustable suspension system for a vehicle described in Japanese Patent Application Laid-Open No. 53-26021. In the device described in the former publication, a liquid chamber is provided inside a flexible bush such as a tension rod that receives longitudinal force, and the liquid passage from the hydraulic pressure generating part of the brake device to the wheel cylinder is connected to this liquid chamber. It is connected to the. As a result, when the vehicle is braked, hydraulic pressure is supplied to the fluid chamber of the flexible bushing, thereby increasing the rigidity of the flexible bushing. In this way, the stability of the vehicle during braking is improved. The invention described in the latter publication also includes an automatic driving condition detector that automatically detects the driving conditions of the vehicle, and a valve operation command signal generator that adjusts the spring constant of the shock absorber according to the detection signal. are provided. With this configuration, the driving state of the vehicle can be detected and the spring constant can be set high when driving on a rough road. (Problems to be Solved by the Invention) However, among the above-mentioned conventional techniques, in the former flexible bushing such as a tension rod,
The spring constant of the flexible bushing can only be increased when the vehicle is braking, and the spring constant of the flexible bushing cannot be changed in other driving conditions. Therefore, it is not possible to improve road holding characteristics when driving on rough roads. Furthermore, in the latter adjustable suspension system for a vehicle, the spring constant of the shock absorber is set high even when a signal corresponding to driving on a rough road is instantaneously generated due to a difference in road level or the like. As a result, the spring constant of the shock absorber remains high even under normal road surface conditions after overcoming a bump or the like, resulting in a problem of worsening ride comfort. Therefore, an object of the present invention is to provide a shock absorber support structure that uses a relatively simple structure and can improve road holding characteristics when driving on rough roads without impairing ride comfort. . (Means for solving the problem) Therefore, in the invention according to claim 1 of the present application, in order to solve the above problem,
As shown in the figure, when installing a shock absorber for absorbing vibrations of a suspension spring installed between a support member of a car wheel and a car body, a suspension made of elastic material is placed between the upper end of the shock absorber 1 and the car body 2. Attach the bush 3 so that it can be elastically deformed,
The shock absorber 1 of the suspension bush 3 is supplied with pressure fluid from the outside into the suspension bush 3.
A fluid pressure chamber 4 is formed to change the spring constant in the vibration absorption direction, and a vehicle height or vertical acceleration detection sensor 5 generates an output corresponding to a change in the vehicle height or vertical acceleration when driving on a rough road. When the corresponding signal is integrated and the integrated value exceeds a predetermined reference value, it is determined that continuous driving on rough roads has occurred for a predetermined period of time or more, and the solenoid valve 6 is activated.
is activated to open the fluid pressure chamber 4 in the suspension bush 3.
A supporting device for a shock absorber has been created, which is characterized by being provided with a fluid pressure control device 7 which increases the spring constant in the direction of vibration absorption by the shock absorber 1 of the suspension bush 3 by supplying pressure fluid for a certain period of time to the shock absorber 1 of the suspension bush 3. Further, it may be used as a support device for a shock absorber as set forth in claim 1 (corresponding to claim 2), in which a hollow bag is built into the suspension bush as a fluid pressure chamber. Furthermore, the vehicle height or vertical acceleration detection sensor and the vehicle height or vertical acceleration detection sensor are connected via a time constant circuit to output from an integral circuit that receives two inputs from a differential amplifier. It is also possible to provide a support device for a shock absorber according to claim 1 or 2, which detects the shock absorber (corresponding to claim 3). (Function) In the shock absorber support device according to claim 1, a fluid pressure chamber is provided within the suspension bush that attaches the shock absorber to the vehicle body. On the other hand, a signal corresponding to driving on a rough road from a vehicle height or vertical acceleration detection sensor that generates an output corresponding to a change in vehicle height or vertical acceleration is integrated, and the integrated value is determined as a predetermined reference value. be compared. When the integral value exceeds the reference value, it is determined that continuous driving on rough roads has occurred for a predetermined period of time or more, and the solenoid valve is activated to supply pressure fluid to the fluid pressure chamber for a certain period of time, and the suspension bushing is The shock absorber has a higher spring constant in the direction of vibration absorption. Therefore, when a vehicle equipped with a shock absorber support device having such a configuration travels on a rough road, if the vehicle continues to travel on the rough road for a predetermined period of time or more, the integral value exceeds the reference value, and the fluid pressure decreases. Pressure fluid is supplied to the chamber. This increases the spring constant of the suspension bushing, ensuring good road holding characteristics on rough roads. Also,
This also prevents the problem of worsening ride comfort due to amplification of vibrations caused by driving on rough roads. Furthermore, since pressure fluid is supplied to the fluid pressure chamber only when driving on a rough road continues for a predetermined period of time, it is possible to avoid problems when a signal corresponding to driving on a rough road is instantaneously generated due to a bump in the road, etc. There is no need to increase the spring constant of the suspension bushings to worsen ride comfort. In this way, the support structure for the shock absorber can be obtained with a relatively simple structure, which can improve the road holding characteristics when traveling on rough roads without impairing ride comfort. (Example) Next, the configuration of an example of the present invention is shown in FIGS. 2 to 6.
This will be explained using figures. The rear end of the cylinder 9 at the lower end of the shock absorber 8 is installed between the wheel support member of the automobile and the vehicle body to absorb vibrations of a suspension spring, and the rear end portion of the cylinder 9 is attached to the wheel support member through a nut bolt joint (not shown). The tip of the piston rod 10 at the upper end of the shock absorber 8 is connected to a suspension bush, in this case, support plates 13 and 14, with an upper spring receiving member 11 and a spacer 12 inserted into the stepped part.
A suspension bush 16 is attached to the support plate 13 of a suspension bush 16 with a rubber elastic member 15 bonded therebetween by a nut 18 via a bearing 17, and the support plate 14 of the suspension bush 16 is attached to the vehicle body 21 via a bolt 19 and a nut 20. installed on. Also, the piston rod 1 of the shock absorber 8
The upper spring receiving member 11 attached to 0
A coiled suspension spring 23 for absorbing automobile vibration and shock is inserted in a compressed state between the lower spring receiving member 22 attached to the cylinder 9,
A dust boof 25 for the shock absorber 8 is attached to the tip of a bound stopper 24 vulcanized and bonded to the lower surface of the upper spring receiving member 11. Suspension bush 16 installed in this way
Four hollow parts 26 are formed in the elastic member 15 at equal intervals on the circumference, and a hollow bag body 27 made of a stretchable material such as rubber is built into the hollow parts 26. A hose 30 for supplying pressure fluid, for example, pressure oil, is connected to the bag body 27 via a mouthpiece 28 attached to the support plate 14 of the suspension bush 16 and a hose clamp 29. FIG. 5 shows a hydraulic circuit that supplies pressure oil to each hollow bag body 27, in which each hollow bag body 27 is connected to each other by a hose 30 and has a spring return opening/closing solenoid valve 31 and a spring return direction switching. Each solenoid valve 31, 3 is connected to a reservoir tank 34 connected to an engine-driven hydraulic pump 33 via a solenoid valve 32 or to a hydraulic pump 33 via a relief valve (not shown).
It is connected or disconnected by the on/off operation of step 2. That is, the following Table 1 is a truth table showing pressure changes in the hollow bag body 27 built in the suspension bush 16 controlled by the hydraulic circuit in FIG.

[Table] When both the solenoid valves 31 and 32 are energized, the valve positions are switched from V ₁ to V ₂ and pressure oil is supplied to the hollow bag body 27 from the hydraulic pump 33, so that the hollow bag body 27 is heated. As the pressure increases, the spring constant of the suspension bush 16 in the direction of vibration absorption by the shock absorber 8 (hereinafter referred to as the spring constant of the suspension bush 16) increases. Next, when the directional solenoid valve 32 is de-energized in this state, the valve position of the solenoid valve 32 changes from V ₂ to
_V1 , the hollow bag body 27 communicates with the reservoir tank 34, the pressure of the hollow bag body 27 decreases, and the spring constant of the suspension bush 16 decreases. Next, when the open/close solenoid valve 31 is de-energized in this state, the valve position of the solenoid valve 31 is switched from V ₂ to V ₁ and the hollow bag 27 is sealed, and the pressure in the hollow bag 27 is reduced to a sealed state. At the same time, the spring constant of the suspension bushing 16 is also maintained at the spring constant at the time of sealing, which means that the directional solenoid valve 32
The same applies when the on-off solenoid valve 31 is in a de-energized state while the valve is in an energized state. FIG. 6 shows an electric circuit for controlling each of the solenoid valves 31 and 32 according to the truth table. The output from the differential amplifier IC ₁ , which has two inputs as the cylinder e ₁ and the charging voltage e ₂ of the capacitor C ₁ via the resistor R _{1, is connected to the integrating circuit via the diode D 1 ,} in this case, the resistor R ₂ is input to an integrating circuit 36 consisting of a capacitor _C2 and an operational amplifier _IC2 . The output e ₃ from the integrating circuit 36 is input to a comparator IC 3 whose reference voltage is the output e ₄ from the setter 37 set corresponding to rough road detection, and the output e ₅ from _{the comparator IC 3 is} the output It is input to a first monostable circuit 38 that generates a pulse output e ₆ of a constant width at the rising edge of the signal, and a second monostable circuit 39 that generates a pulse output e ₇ of a constant width at the falling edge of the output signal, and is input to a direction switching electromagnetic circuit. The valve 32 is operated by the output from the first drive circuit 40 which receives the output from the first monostable circuit 38, and the opening/closing solenoid valve 31 is operated by the output from the first monostable circuit 38 and the second monostable circuit 39. It is operated by the output via the exclusive OR circuit EX/OR which takes the output as input and the second drive circuit 41. Next, the operation of this embodiment will be explained according to the operation diagram shown in FIG. In the supporting device for the shock absorber 8 configured in this way, when the automobile is running on a paved road, there is almost no change in the output from the sensor 35, so there is no output from the differential amplifier IC ₁ , and therefore,
Output e ₃ from integration circuit 36 and comparator IC ₃
The output from the monostable circuits 38, 39 and the drive circuits 40, 41 is also "L", and each solenoid valve 31, 32 is in a non-conducting state, and the suspension bush 1
The spring constant of 6 is the pressure of the pressure oil sealed in the hollow bag body 27. In this case, the pressure is relatively low, so the spring constant is also low, and the ride comfort and road holding of the car are maintained well. , the height of the car temporarily changes due to a bag on the paved road while driving.Similarly, even if the car temporarily experiences vertical acceleration, the output from differential amplifier IC ₁ is temporary. Since it hardly appears as an output of the integrating circuit 36, neither of the electromagnetic valves 31 and 32 operates, and the ride comfort and road holding of the automobile are maintained well without being affected by the temporary stage. Next, if the car starts driving on a rough road in this condition,
When the output from the sensor 35 fluctuates and an output _e3 is generated from the integrating circuit 36, and the output _e3 exceeds the reference voltage _e4 on a rough road, that is, with a low spring constant, load holding etc. cannot be maintained well. In the case of a rough road, the output e ₅ is generated from the comparator IC ₃ , and the rise of the output e ₅ signal causes the generation of pulse outputs e ₆ and e ₈ from the first monostable circuit 38 and the exclusive OR circuit EX/OR. Both solenoid valves 3
1 and 32 become conductive at the same time, and the hollow bag body 27
The pressure oil from the hydraulic pump 33 produces a pulse output e ₆ ,
As a result of the supply for a certain period of time determined by the pulse width of _e8 , the pressure in the hollow bag body 27 increases, and as a result, the suspension bush 16
The spring constant of the high spring constant increases, and road holding when driving on rough roads is maintained well, and ride comfort is also suppressed from bouncing and maintained well on rough roads. This continues in a rough road driving condition where an output is generated from 36. Here, as shown in FIG. 7, e ₃ is a signal obtained by integrating only the positive part of the difference between signal e ₁ and signal e ₂ .
The value of does not exceed the value of the reference output _e4 unless the high-frequency signal of _e1 corresponding to driving on a rough road continues for a certain period of time. Therefore, the above-mentioned switching (increase) of the pressure in the hollow bag body 27 is performed only when the signal corresponding to driving on a rough road continues for a predetermined period of time or more. Further, the magnitude of the rising slope of the signal e ₃ shown in FIG. 7 changes depending on the characteristics of the integrating circuit 36. Depending on the magnitude of this rising slope, the time required for the signal e ₃ to exceed the reference value e ₄ when a signal e ₁ of a certain specific magnitude is input also changes. Therefore, by changing the characteristics of the integrating circuit 36, it is possible to adjust how long the spring constant of the suspension bushing 3 is increased when the vehicle continues to travel on rough roads. Next, when the car stops driving on a rough road in this state, the output fluctuation from the sensor 35 disappears, and the output from the differential amplifier IC ₁ also disappears, and the output e ₃ from the integrating circuit 36 becomes as shown in FIG. It decreases as shown in and becomes below the value of the reference output _e4 . As a result, the output from the comparator IC ₃ becomes "L" and falls, and the pulse output e ₇ is generated from the second monostable circuit 39, resulting in the output e ₈ from the exclusive OR circuit EX/OR. Therefore, only the opening/closing solenoid valve 31 becomes conductive for a certain period of pulse width, and the pressure oil in the hollow bag 27 of the suspension bush 16 returns to the reservoir tank 34, and the spring constant of the suspension bush 16 becomes suitable for driving on paved roads. value, and the ride comfort and road holding of the vehicle are maintained well. In addition, in this embodiment, two solenoid valves 31,
32, the pressure of the hollow bag body 27 is changed, but for example, by directly connecting the hollow bag body 27 to the hydraulic pump 33 and controlling the hydraulic pressure arbitrarily by using the relief valve as a solenoid valve, the spring of the suspension bush 16 can be changed. The constant can be changed arbitrarily, and the hollow bag body 27 can be formed in any number of parts, such as one part formed in a C-shape, and a computer can be used instead of the electric circuit shown in FIG. The solenoid valve can be controlled with. (Effects of the Invention) The present invention detects running on a rough road by detecting changes in the vehicle height or the output from a vertical acceleration detection sensor, and increases the pressure in the fluid pressure chamber in the suspension bushing when running on a rough road. By increasing the spring constant of the suspension bushing, it is possible to improve the road holding characteristics of the vehicle on rough roads while maintaining the ride comfort of the vehicle. That is, the present invention specifically limits the spring constant of the suspension bushing to the pressure control of the small volume fluid pressure chamber formed within the suspension bushing within a certain period of time without controlling the hydraulic pressure of the shock absorber itself. Therefore, within the control of the fluid pressure chamber, the stability of the vehicle is not compromised, and this allows for a relatively simple structure with excellent responsiveness, high precision, and high performance, and the best ride comfort and driving performance depending on the road surface condition. This has the effect of ensuring good road holding.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram clearly showing the configuration of the present invention,
FIG. 2 is a cutaway front view of one embodiment of the present invention, FIG. 3 is a detailed view of its main parts, FIG. FIG. 6 is its electric circuit diagram, and FIG. 7 is its operation diagram. 1...Shock absorber, 2...Vehicle body, 3...
...Suspension bush, 4...Fluid pressure chamber, 5...Vehicle height or vertical acceleration detection sensor, 6...Solenoid valve, 7...Fluid pressure control device.

Claims (1)

[Scope of Claims] 1. When installing a shock absorber for absorbing vibrations of a suspension spring installed between a support member of a wheel of an automobile and a vehicle body, a suspension bush made of an elastic material is provided between the upper end of the shock absorber and the vehicle body. It is attached to be elastically deformable, and a fluid pressure chamber is formed in the suspension bushing to change the spring constant in the direction of vibration absorption by the shock absorber of the suspension bushing by supplying pressure fluid from the outside, and the suspension bushing has a fluid pressure chamber that changes the spring constant in the direction of vibration absorption by the shock absorber of the suspension bushing. A signal corresponding to rough road driving from a vehicle height or vertical acceleration detection sensor that generates an output corresponding to a change in directional acceleration is integrated, and when the integrated value exceeds a predetermined reference value, it is detected continuously for a predetermined period of time or more. It is determined that the vehicle has been traveling on a rough road, and the solenoid valve is operated to supply pressure fluid to the fluid pressure chamber in the suspension bushing for a certain period of time, thereby increasing the spring constant in the direction of vibration absorption by the shock absorber of the suspension bushing. A support device for a shock absorber, characterized in that it is provided with a fluid pressure control device. 2. The shock absorber support device according to claim 1, wherein a hollow bag is built into the suspension bush as a fluid pressure chamber. 3. The vehicle height or vertical acceleration detection sensor and the vehicle height or vertical acceleration detection sensor are connected to two inputs via a time constant circuit, and an output from an integral circuit that receives the output from a differential amplifier is used to detect rough road driving. The shock absorber support device according to claim 1 or 2, wherein the shock absorber support device detects the shock absorber.