JPH0413568B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a shock absorber for a vehicle whose damping force can be freely adjusted.

(Prior Art) A conventional variable damping force shock absorber, as disclosed in, for example, Japanese Patent Laid-Open No. 58-194609, connects two upper and lower hydraulic chambers defined in a cylinder with a passage. The damping force was changed by changing the area of the passage using a rotary valve.

(Problem to be Solved by the Invention) However, in the conventional system, when changing the damping force of the shock absorber depending on the driving condition of the vehicle, the driving condition is detected by various sensors such as a vehicle speed sensor and a steering angle sensor.・It was configured to indirectly predict the damping force based on signals from the throttle sensor, etc., and control the rotary valve to provide an appropriate damping force. For this reason, in order to properly control the damping force with conventional methods, a large number of sensors are required, and the control circuit that receives the signals from these sensors and predicts the vehicle's driving condition becomes complex. It had some problems.

The present invention has been made in view of the above-mentioned problems, and provides a novel damping system that predicts vehicle running conditions based on pressure changes in the oil chamber in the shock absorber and enables highly responsive control. The object of the present invention is to provide a variable force shock absorber.

(Means for Solving the Problems) As a means for solving the above-mentioned problems, the present invention provides a piston 1 that is slidable with respect to the cylinder 11.
The piston is provided with first and second oil chambers 14 and 15 that house the oil chambers 1 and 2.
4 and 15, and a sliding member 19 whose passage area is changed by sliding displacement, and whose one end face receives pressure from the second oil chamber. The sliding member 19 is disposed on the other end surface side, receives the displacement of the sliding member 19 as stress, generates a voltage based on this stress, and expands and contracts based on the applied voltage to reduce the displacement. It is characterized by comprising a piezoelectric body 23 that transmits power to the moving member 19.

(Example) Next, an example of the present invention will be described based on the drawings. FIG. 1 is a sectional view of a variable damping force shock absorber according to an embodiment of the present invention, FIG. 2 is a schematic diagram of a vehicle control system using the shock absorber 1 shown in FIG. FIG. 2 shows a circuit diagram of the control circuit 2 shown in FIG.

In FIG. 1, reference numeral 1 denotes a variable damping force shock absorber, which consists of a piston rod 13 housed in a cylinder 11 so as to be slidable in the axial direction, and a piston 12 that is integrally fixed to the piston rod 13 by welding or the like. A first oil chamber 14 and a second oil chamber 15 which are partitioned and filled with hydraulic oil, and a throttle 16 provided on the piston 12 so as to communicate the first oil chamber 14 and the second oil chamber 15. are arranged respectively.

A central hole 17 and a side hole 1 are provided in the center of the piston 12.
8 is bored to form a communication path that communicates the first oil chamber 14 and the second oil chamber 15. This central hole 1
A slidable spool 19 that changes the passage area of the communication passage is inserted into the spool 7 in an oil-tight manner so as to be slidable in the axial direction. That is, the spool 19 has an annular groove 19a on the outer periphery, a central hole 19b in the center, and a communication hole 19c that communicates the two.
By moving a from a position where it communicates with the side hole 18 to a position where it is blocked, it acts as a so-called variable throttle that changes the passage area of the communication. Also, one end surface of the spool 19, that is, the lower end surface in the figure, receives pressure from the second oil chamber 15, and a portion of the spool 19 receives pressure from the spring 20 supported by the stopper 20.
is urged upward by. In addition, Stoppa 2
0 is press-fitted into the central hole 17 and fixed. On the other hand, the other end surface of the spool 19, that is, the upper end surface in the figure, has a protrusion 19 formed above the spool 19.
d, and projects into the inclusion chamber 27, which will be described later. The spool 19 is provided with a small hole 19e that communicates between the upper and lower end surfaces in order to reduce sliding resistance.

A laminated piezoelectric body 23 in which a large number of piezoelectric elements 23a and electrode plates (not shown) are alternately laminated is fixed in a space 22 formed by the casing 12a above the piston 12 and the piston rod 13. There is. This piezoelectric element 23a has an inverse piezoelectric effect in which it expands and contracts in the axial direction based on the voltage applied by the lead wire 24 in the piston rod 13, and also has a stress in the axial direction of the piezoelectric element 23a. It has a piezoelectric effect that generates an electromotive force based on the applied stress. For example, PbZrO ₃ ,
These include PZT elements whose main components are PbTiO ₃ and the like.

A plunger 25 slides vertically in a space 22 inside the casing 12a following the expansion and contraction of the piezoelectric body 23, and includes the plunger 25, the space 22, the upper end surface of the protrusion 19d of the spool 19, and the O-ring 26 for sealing. The enclosing chamber 27 is defined by the following. An incompressible fluid such as silicone oil is hermetically sealed in the filling chamber 27, and the ratio between the cross-sectional area of the plunger 25 and the cross-sectional area of the protrusion 19d of the spool 19 is determined based on the so-called Pascal's principle. The amount of minute displacement of the plunger 25 displaced by the piezoelectric body 23 is increased and transmitted to the spool 19. Further, the pressure in the enclosure chamber 27 is maintained at a pressure of about 10 to 20 kg/cm ³ by a spring 21.

Note that when no voltage is applied to the piezoelectric body 23, the spool 19 communicates with the first and second oil chambers 14 and 15 through a side hole 18 and a throttle 16.
When high voltage (approximately 500V) is applied, both oil chambers 1
4 and 15 are constructed so that the side holes 18 communicate with each other only through the aperture 16.

Further, 28 and 29 are O-rings for sealing. This prevents the silicone oil in the sealing chamber 27 from leaking to the outside.

Further, 2 is a control circuit which is electrically connected to the piezoelectric body 23 via a lead wire 24.

The operation of the variable damping force shock absorber will be explained based on the above configuration.

When no voltage is applied to the piezoelectric body 23 by the control circuit 2, the side hole 18 of the piston 12 and the groove 19a of the spool 19 are in communication, and the piston 12 and the piston rod 13 are connected to the cylinder 11.
The damping force generated when sliding inside is obtained as a resistance force of the hydraulic oil flowing through the side hole 18 and the throttle 16.

The control circuit 2 applies a high voltage (approx.
500V), the piezoelectric body 23 undergoes a slight elongation displacement (approximately 90μ), and this displacement causes the enclosure chamber 27 to expand by a ratio (approximately 25 times) of the cross-sectional area of the plunger 25 and the protrusion 19d of the spool 19. , and is transmitted to the spool 19 as a downward displacement (approximately 2 mm) in the figure. At this time, the side hole 18 and the spool 19
Since communication with the groove 19a is cut off, the damping force of the shock absorber 1 is obtained as a resistance force of the hydraulic oil flowing through the throttle 16. This resistance force becomes larger as the side hole 18 is closed compared to the case described above, so that the damping force of the shock absorber 1 increases.

As described above, the damping force of the shock absorber 1 is determined by controlling the voltage applied to the piezoelectric body 23 by the control circuit 2.
By turning it ON and OFF, you can obtain two types of damping force: hard and soft.

In the above explanation, the damping force of the shock absorber 1 is switched in two stages by controlling the voltage applied to the piezoelectric body 23 on and off, but the voltage applied to the piezoelectric body 23 It goes without saying that it is also possible to continuously change the damping force of the shock absorber 1 from soft to hard by continuously controlling the voltage from zero to a high voltage (approximately 500 V).

Next, the oil chambers 14, 1 in the shock absorber 1
The operation of the piezoelectric body 23 when detecting the running state of the vehicle based on the pressure change shown in FIG. 5 will be described.

During the operation of the shock absorber 1, for example, when the piston 12 is moving down inside the cylinder 11, the hydraulic oil in the second oil chamber 15 flows into the first oil chamber 15 through the side hole 18 of the piston 12 and the throttle 16. flows to At this time, the pressure in the second oil chamber 15 increases due to the operating resistance of the hydraulic oil, and a pressing force that presses the lower end surface of the spool 19 upward acts.

The plunger 25 that follows the piezoelectric body 23 and the spool 19 are configured so that their displacement is transmitted by the silicone oil in the enclosure chamber 27.
When a pressing force is applied from the lower end surface of the spool 19, the pressure in the filling chamber 27 changes in accordance with the pressing force. This pressure change causes a pressing force to act on the piezoelectric body 23 via the plunger 25.
3, voltage is generated due to piezoelectric effect. This voltage is connected to the control circuit 2 through a lead wire 24 and used to determine the running state.

In the above embodiment, since the displacement of the piezoelectric body 23 is minute, the displacement is magnified and transmitted to the spool 20 via the enclosure chamber 27. directly on spool 2
It goes without saying that if it is possible to open and close the side hole 18 of the piston 12 even if 0 is displaced, the sealing chamber 27 becomes unnecessary.

In addition, the center hole 17 and side hole 18 of the piston 12
Those skilled in the art will easily understand that if the passage area of the communication passage made of .

FIG. 2 is a schematic diagram of a vehicle control incorporating the above-mentioned shock absorber 1, where 2 is a control circuit, 3 is a wheel, and the shock absorber 1 is attached to each of the four wheels, both front and rear wheels. Each lead wire 24 is connected to the control circuit 2.

FIG. 3 is a circuit diagram of the control circuit 2.

The control circuit 2 turns 0N-OFF the output of the high-voltage power supply 201 and the high-voltage power supply 201 using the DC-DC converter.
resistors 203 and 204 that divide the voltage generated in the piezoelectric body 23 of each shock absorber 1, and four sets of low-pass filters that extract only the low frequency components of the divided voltage of the piezoelectric body 23. 205 (L/F), 4 sets of comparators 206 that generate 1 and 0 signals by comparing the signal after filter tracking with the set level V _R , and discriminate the signals from the piezoelectric bodies 23 of the four shock absorbers 1. to operate
AND circuit 207, OR circuit 208, and this
It consists of a timer circuit 209 that closes the switch 202 for a certain period of time (approximately 2 seconds) in response to a signal from an AND/OR logic circuit.

The logic circuit determines the mounting positions of the four shock absorbers: front right side (F/R), front left side (F/L), rear right side (R/R), and front left side (R/R).
L), F・R and F・L, or R・R and R・L, or F・R and R・R, or R・
L and R・L are set voltage V _R of comparator 206 at the same time.
AND circuit 20 when a voltage exceeding
7 becomes 1, and the OR circuit 208 has a logic of 1.

Next, the operation of the system incorporating the variable damping force shock absorber according to the present invention will be explained.

In this system, similarly to a system incorporating a conventionally known variable damping force shock absorber, switching the damping force between soft and hard by manual operation is achieved by applying a high voltage to the piezoelectric body 23 of the shock absorber 1 of the present invention according to the setting. ON
Or, it goes without saying that this can be easily done by turning it off, as mentioned above. (The circuit related to manual operation is omitted.) The most important point of this system is that it can easily and easily perform the so-called auto function, which automatically switches the damping force between soft and hard depending on the vehicle's driving condition. be.

In the auto mode of this system, the running condition of the vehicle is predicted based on the voltage generated by the piezoelectric body 23 built into the four shock absorbers 1 attached to the four wheels of the vehicle, and the system quickly changes from soft to hard. Switch the damping force. In this system, the damping force in auto mode is switched from soft to hard during sudden starts, sudden braking, and slalom driving, respectively, and is applied during squats (vehicle tail-end phenomenon), dives (vehicle leaning forward), and It is possible to prevent roll and improve steering stability, as well as to improve the comfort of the ride in normal conditions.

Next, it will be explained how to predict sudden start, sudden braking, and slalom from the voltage generated by the piezoelectric bodies 23 incorporated in the four shock absorbers 1.

When the vehicle starts suddenly, the vehicle tends to perform a scouting phenomenon, in other words, the rear two wheels of the four wheels (R,
The shock absorber 1 attached to R and R/L) is retracted. Therefore, the rear two wheels (R・R and R・
Since the voltage signals from the shock absorber 1 attached to the shock absorber 1 are generated at the same time, these are detected and the damping force is switched from soft to hard to suppress the squat. That is, AND4 of the AND circuit 207 becomes 1, the timer circuit 209 closes the switch 202 for a certain period of time, and the high voltage of the high voltage power supply 201 is applied to the piezoelectric body 23 of the shock absorber 1.

During sudden braking, voltage signals are simultaneously generated from the shock absorbers attached to the front two wheels (F, R and F, L) due to a dive phenomenon, that is, the vehicle leans forward. This is detected and the damping force is switched from soft to hard to suppress the type phenomenon. At this time, AND1 of the AND circuit 207 becomes 1.

Further, during slalom running, a roll phenomenon occurs depending on the direction of cornering. At this time, either the two right wheels (F・R and R・R) or the two left wheels (F・L and R・L) of the vehicle sink, so
The voltage signal from shock absorber 1 is generated simultaneously for the two right wheels (F・R and R・R) or the two left wheels (F・L and R・L), so in response to this, the damping force is changed from soft to hard. The roll is suppressed by switching to At this time, the AND circuit 207
AND2 or AND3 becomes 1.

The control circuit 2 of this system compares the voltage generated from the piezoelectric body of each shock absorber 1 with a preset voltage (V _R ) in response to the aforementioned scout, dive, and roll phenomenon.
When the voltage is higher than the set voltage (V _R ), a signal is input to the logic circuit, and this signal is combined with AND and OR to predict the scout, dive, and roll phenomenon caused by the vehicle running condition, and is output from the high voltage power supply 201. The switch 202 is operated for a set time (approximately 2 seconds) in order to apply a high voltage of 1 to the piezoelectric body 23 of the shock absorber 1. The voltage generated by the shock absorber 1 is divided by a resistor 203, and then divided by a filter 205 having preset characteristics.
By passing the signal through a low-pass filter, it cuts out and prevents relatively high frequency components caused by vertical vibration of the tire caused by, for example, irregularities in the running road.

As described above, the shock absorber 1 with variable damping according to the present invention uses the piezoelectric body 23 as a means for switching the damping force, and expands minute displacement of the piezoelectric body 23 based on Pascal's principle to cause displacement of the spool 19. By opening and closing the side hole 18 of the piston 12, when the shock absorber 1 is compressed, a voltage signal can be generated from the piezoelectric body 23, and based on this signal, the running state of the vehicle can be predicted. This makes it possible to replace the vehicle speed sensor, steering sensor,
This has the advantage of simplifying the system, including wiring that requires many sensors such as the throttle sensor and brake pressure sensor.

(Effects of the Invention) As described above, the present invention provides a piezoelectric body on the piston in the shock absorber and a sliding member that changes the passage area of the communication passage between the first and second oil chambers. By adopting a configuration that transmits the displacement between the two, when the shock absorber contracts, the pressure in the second oil chamber is transmitted from the sliding member to the piezoelectric body, and a voltage is generated in the piezoelectric body based on this pressure. do. Therefore, it is possible to directly predict the running state of the vehicle based on the voltage of the piezoelectric body generated based on the pressure change in the oil chamber in the shock absorber. Further, since the sliding member is displaced and moved based on the voltage applied to the piezoelectric body to change the passage area, the responsiveness is much better than that of conventional rotary valves.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a variable damping force shock absorber according to an embodiment of the present invention, FIG. 2 is a schematic diagram of a vehicle control system using the shock absorber 1 shown in FIG. FIG. 2 shows a circuit diagram of the control circuit 2 shown in FIG. 1... variable damping force shock absorber, 11...
...Cylinder, 12...Piston, 12a...Casing, 14, 15...First and second oil chambers, 16...
... Aperture, 17, 18 ... Central hole and side hole serving as a communication path, 19 ... Spool (sliding member), 21 ... Spring, 23 ... Piezoelectric body, 25 ... Plunger, 27 ... Enclosure chamber.

Claims (1)

[Scope of Claims] 1. A communication passage forming first and second oil chambers in which a piston is slidably housed in a cylinder, and communicating the first and second oil chambers provided in the piston; The passage area of this communication passage is changed by sliding displacement, and one end face is disposed on the sliding member receiving pressure of the second oil chamber and the other end face side of the sliding member is disposed on the other end face side. It is characterized by comprising a piezoelectric body that receives displacement of the sliding member as stress and generates a voltage based on this stress, expands and contracts according to the applied voltage, and transmits the displacement to the sliding member. variable damping shock absorber. 2 The piezoelectric body has a piezoelectric element that has a piezoelectric effect that generates a voltage based on stress when stress is applied in the axial direction, and an inverse piezoelectric effect that expands and contracts in the axial direction based on the applied voltage. The variable damping force shock absorber according to claim 1, which is a laminated piezoelectric material laminated in multiple directions. 3. The displacement of the piezoelectric body is caused by an enclosed chamber filled with an incompressible fluid that is partitioned by a plunger that follows the piezoelectric body inside the casing, the other end surface of the sliding member, and the casing. Claim 2, wherein the pressure is transmitted to the spool through the spool, and is transmitted to the sliding member after being enlarged by the ratio of the cross-sectional area of the plunger to the area of the other end surface of the sliding member. variable damping force shock absorber.