JPH0147323B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a damping force control device for a hydraulic shock absorber that controls the damping force so as to obtain an optimum damping characteristic while detecting the operating state.

The damping characteristics required of a hydraulic shock absorber for a vehicle vary depending on driving conditions in terms of ride comfort and handling.

For example, when driving at a high speed on a flat road, the suspension characteristics are relatively stiff, when driving on a rough road, the same suspension characteristics are soft, and when the load at that time is large, the suspension characteristics are relatively stiff. Even with weight, the required damping characteristics change depending on the stroke position of the shock absorber, such as being hard near the maximum compression and soft at the neutral position.

In response to these problems, hydraulic shock absorbers have been proposed that change the damping characteristics under specific conditions, for example, increase the damping force on the front wheel side during sudden braking to prevent sinking. There has never been a hydraulic shock absorber that can always provide optimal damping characteristics depending on the operating conditions.

The present invention aims to solve these conventional problems.

In order to achieve this object, the present invention includes a vehicle speed sensor that outputs a signal according to the vehicle speed, a displacement sensor that outputs a signal according to the stroke displacement of the shock absorber, and the output of this displacement sensor is differentiated to obtain the displacement speed. an operating state detection means consisting of a differential circuit or the like that outputs a corresponding signal; a microcomputer that calculates a predetermined damping force arbitrarily determined in advance to correspond to the detected value based on the detected value; and a shock absorber. It is equipped with an electromagnetic solenoid that attracts a damping valve made of a magnetic material that opens and closes a passage through which hydraulic oil flows during expansion side and compression side operation to a valve seat portion and continuously increases and decreases the opening and closing pressure according to the output of the microcomputer. Ta. As a result, various driving conditions of the vehicle are accurately detected, and the control system including a microcomputer calculates the optimal damping force characteristics at each time, and based on the results, the damping force can be quickly and continuously increased or decreased. This improves vehicle ride comfort and handling stability.

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

First, FIG. 1 shows the control circuit of the present invention. In the figure, 61 is a vehicle speed sensor that outputs a signal according to the vehicle speed, and 62 is a displacement sensor that outputs a signal according to the displacement of the hydraulic shock absorber (piston displacement). , 63 is an acceleration sensor that outputs a signal corresponding to the acceleration in the longitudinal direction of the vehicle, and 64 is a signal setting device that includes a potentiometer that can manually output an arbitrary signal.

The output of the displacement sensor 62 passes through a low-pass filter 65 that removes high-frequency components of the output wave as a displacement signal X, and passes through a differentiation circuit 66 that differentiates the output as a piston speed signal V. )70.

The control circuit 70 also includes the vehicle speed sensor 6.
A vehicle speed signal Vw from 1 and a manual signal E ₀ from a signal setter 64 are respectively input, and an acceleration signal α from an acceleration sensor 63 is directly input to a control circuit 70 or an adder to be described later.

Specifically, in the control circuit 70, the second
As shown in the figure, the optimum damping characteristics are calculated according to the operating conditions.

First, based on the vehicle speed signal Vw, a voltage E ₁ (however, E ₁ = f
(Vw)) is generated by a table pickup or a function generator, which provides a soft ride in the low speed range, while providing stiffer damping characteristics as the vehicle speed increases, improving handling.

In addition _, based on _the displacement signal ), and on the compression side, the displacement is zero from the maximum extension to near neutral, and as it contracts, the voltage changes so that the damping force sharply increases.
E ₃ (E ₃ = f(X)) is created in the same way, and this increases the damping force on the rebound side near the maximum extension to prevent extension, and increases the damping force on the compression side near the maximum pressure to prevent bottoming out. .

Furthermore, based on the piston speed signal V, a voltage E ₄ t is applied that increases the damping force on the rebound and compression sides as the speed increases from the low speed range to the compression and compression sides, respectively.
and E ₄ c, which increases the damping force as the piston speed increases to improve maneuverability.

Then, the control voltage E ₁ described above is applied to the adder 71
is input together with the signal E ₀ based on the manual operation described above.

The adder 72 receives the output of the adder 71 along with the control voltage E ₂ , and also has a relay 74 which is switched on by the output of the comparator 73 which is turned on when the displacement signal X exceeds a certain set value on the expansion side. The control voltage E 4 t is inputted through the control voltage E ₄ t.

Similarly, the adder 75 receives the output from the adder 71 along with the control voltage E ₃ , and further includes a relay 77 that is switched on by the output of the comparator 76, which is turned on when the displacement signal X exceeds a certain set value on the pressure side. The control voltage E ₄ c is inputted via.

The output of the adder 72 is inputted to an electromagnetic solenoid coil that increases the damping force of the expansion-side damping valve of the shock absorber, which will be described later, via the adder 80 shown in FIG. Similarly, it passes through an adder 81 and is input to an electromagnetic solenoid coil that increases the damping force of the compression side damping valve.

The adder 80 is simultaneously input with a deceleration signal from the acceleration sensor 63 to increase the rebound damping force during deceleration, and the adder 81 is input with an acceleration signal to increase the compression damping force during acceleration to increase steering stability. (However, this explanation is based on the case where it is used as a shock absorber for the rear wheels of a vehicle, and prevents the rear wheels from lifting up during deceleration and sinking during acceleration.) In this way, the control circuit (microcomputer) 70 outputs a damping force control signal that satisfies both riding comfort and handling according to the driving conditions in a responsive manner. These signals can be freely set according to the individual's preference, and the hydraulic shock absorbers shown in FIGS. 3 and 4 are controlled based on these signals. Next, to explain this, first, a piston 2 is housed in the cylinder 1 so as to be freely slidable and defines oil chambers C ₁ and C ₂ , while a bracket 3 at the lower end of the cylinder and a piston rod 4 connected to the piston 2 are installed in the cylinder 1 . are connected to the axle and the vehicle body, respectively, via a bracket 5 at the tip.

A spring holder 6 is screwed onto the lower part of the outer circumference of the cylinder 1, and a suspension spring 8 is interposed between the spring holder 7 and the spring holder 7, which is connected to the tip of the piston rod 4. This supports the load and absorbs shock. do.

The piston rod 4 is slidably supported by a bearing part 10 fitted into the upper part of the cylinder 1, and a stop rubber 11 which receives the full extension load of the piston 2 is attached to the bearing part 10 via a retainer 12.

A stopper 14 is engaged with a stepped portion 13 at the distal end of the piston rod 4 facing the stop rubber 11, and the piston 2 is fixed by a piston nut 15 when inserted into the stepped portion 13.

The inside of the piston 2 made of this magnetic material is hollowed out into a cylindrical shape to form a valve body, and the solenoid coil 17 wound around the bobbin 16 is inserted into the stepped part 13a in the hollow part 2B. They are housed to form an electromagnetic solenoid 18.

As is clear from FIG. 4, a hollow disc-shaped extension damping valve 20 made of a magnetic material is attached to the end of the electromagnetic solenoid 18, with its center part tightened together by the piston nut 15, and the piston 2
A valve hole 21 passing through the valve hole 21 and communicating the upper and lower oil chambers C ₁ and C ₂ is closed.

The seat portion 22 formed at the opening of the valve hole 21 is formed on the collar portion 16A of the bobbin 16 made of the non-magnetic material.
When the electromagnetic solenoid 18 is excited, the expansion-side damping valve 20 that closes the valve seat 2 is attracted to an attraction part 24 at the outer peripheral end of the piston 2, and the pressing force against the valve seat part 22 increases.

A compression side valve hole 2 is provided on the outside of the expansion side valve hole 21.
5 is formed passing through the piston 2, and the piston 2
A pressure side check valve 26 that closes the valve hole 25 at the upper end of the valve is interposed between the valve hole 25 and the stopper 14.

By the way, the lead wire 29 of the solenoid coil 17 passes through a wiring passage 27 provided at the center of the piston rod 4 and is taken out to the outside from a guide hole 30 cut out in the upper bracket 5 of the piston rod 4. By inputting a control signal, the excitation force of the electromagnetic solenoid 18, in other words, the set load (valve opening pressure) of the expansion side damping valve 20 can be continuously adjusted.

Note that a sealing material 32 such as synthetic resin is sealed in the lead wire 29 to the guide hole 30, so that the hydraulic oil in the oil chambers C ₁ and C ₂ leaks from the wiring passage 27 to the outside. It prevents

On the other hand, a separate tank 33 is installed at the bottom of the cylinder 1.
A through hole 34 is formed to communicate with the tank 33, and a communication pipe 35 is connected to the through hole 34.

A free piston 36 is slidably housed inside the tank 33, and defines an oil reservoir chamber _C3 and a gas chamber _C4 .

Gas chamber C ₄ is filled with inert gas (air) at a specified pressure.
is enclosed, and pressurizes the hydraulic oil in the oil reservoir chamber _C3 via the free piston 36.

An electromagnetic solenoid 39 configured in the same manner as described above is housed inside the valve body 38 at the inlet portion of the tank 33 in order to adjust the compression side damping force.

That is, this electromagnetic solenoid 39 is connected to a cylindrical cap 40 screwed onto the open end of the tank 33.
A solenoid coil 41 housed in the cavity of this valve body 38 is also fitted with a concentric valve body 38 made of magnetic material.
A fixed shaft 4 passes through the center of the bobbin 42 wound with
3, tighten the fastening nut 45 to fix it. In addition,
A fixed shaft 43 passes through the cap 40 and is locked therein.

A compression side valve hole 46 and an expansion side valve hole 47 are provided to penetrate through the valve body 38, and a disk-shaped compression side damping valve is pressed against the end surface of the bobbin 42 when the compression side valve hole 46 and the electromagnetic solenoid 39 are tightened together. 48 is closed.

As described above, when the electromagnetic solenoid 39 is excited, this compression side damping valve 48 is pressed against the seat portion according to the exciting force, thereby increasing the valve setting load.

The other extension side valve hole 47 is opened and closed by an extension side check valve 50 provided on the opposite end surface of the valve body 38.

The lead wire 51 of the solenoid coil 41 of the electromagnetic solenoid 39 is taken out to the outside through a wiring passage 52 that passes through the inside of the fixed shaft 43, and this extraction part is filled with a sealing material 53 to prevent leakage of hydraulic oil. .

Therefore, during pressure side operation when the piston rod 4 enters the inside of the cylinder 1, the hydraulic oil from the lower oil chamber _C2 , which contracts, flows into the upper oil chamber C1, which expands as the piston ₂ descends, and the piston The compression side check valve 26 is expanded from the compression side valve hole 25 of No. 2 and flows in with almost no resistance, and at this time, the compression side damping valve 2
0 is pressed against the seat portion 22 by hydraulic pressure and sealed.

On the other hand, the hydraulic oil corresponding to the volume entered by the piston rod 4 flows from the lower oil chamber C ₂ to the oil reservoir chamber C ₃ of the tank 33.
It flows through the tank pressure side damping valve 48.
(The expansion side check valve 50 is closed by hydraulic pressure.) At this time, the valve opening pressure of the compression side damping valve 48 is a combination of the elastic force of the valve and the adsorption force of the electromagnetic solenoid 39. Therefore, resistance based on this combined load is imparted to the hydraulic oil flowing through the compression side damping valve 48, and this becomes a so-called compression side damping force.

The attraction force of the compression side damping valve 48 changes according to the excitation current applied to the solenoid coil 41 of the electromagnetic solenoid 39, and the damping force can be increased or decreased steplessly according to the control current value.

Therefore, for the electromagnetic solenoid 39,
By supplying a control current through the control circuit 70, an optimum compression damping force can be obtained depending on the operating condition.

Next, during the extension side operation where the piston rod 4 extends, the upper oil chamber contracts as the piston 2 rises.
Hydraulic oil flows into the expanding lower oil chamber C ₂ from C ₁ and is replenished from the oil reservoir chamber C ₃ of the tank 33 with hydraulic oil corresponding to the volume of the piston rod 4 that has slipped out.

At this time, the hydraulic oil from the tank 33 expands the tank extension check valve 50 and flows into the lower oil chamber _C2 with almost no resistance, but the hydraulic oil from the upper oil chamber _C1 Side damping valve 20
Outflow resistance is applied according to the set load, and this acts as a damping force on the rebound side similarly to the above, and damps the vibration on the rebound side of the piston rod 4.

The set load of the expansion damping valve 20 changes continuously in accordance with the attraction force of the electromagnetic solenoid 18, as described above, and the excitation force is changed in accordance with the current from the control circuit 70. This allows the rebound damping force to be controlled to the optimum level depending on the driving conditions.

The expansion damping valve 20 is fixed in a state where its central portion is tightened together with the bobbin 16, and in addition to its own elastic force, an electromagnetic attraction force is applied to change the valve load. Because it is a thing,
There are no so-called mechanical moving parts, so even if the piston 2 repeatedly moves up and down violently,
There is almost no possibility that the damping force of the rebound damping valve 20 fluctuates due to the inertial force.

As described above, according to the present invention, it is possible to always apply an optimal damping force according to all driving conditions, and the effect is that it is possible to simultaneously improve the ride comfort and the handling stability of the vehicle. There is.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of the present invention, FIG. 2 is a detailed block diagram of the control circuit, FIG. 3 is a sectional view of the hydraulic shock absorber, and FIG. 4 is an enlarged view of the main parts thereof. 1... Cylinder, 2... Piston, 4... Piston rod, 18... Electromagnetic solenoid, 20...
Extension side damping valve, 39...Electromagnetic solenoid, 48
...Compression side damping valve, 61...Vehicle speed sensor, 62
...Displacement sensor, 63... Acceleration sensor, 70...
...Control circuit (microcomputer).

Claims (1)

[Claims] 1 From a vehicle speed sensor that outputs a signal according to the vehicle speed, a displacement sensor that outputs a signal according to the stroke displacement of the shock absorber, and a differentiation circuit that differentiates the output of this displacement sensor and outputs a signal according to the displacement speed. a microcomputer that calculates and outputs a predetermined damping force arbitrarily determined in advance to correspond to the detected value based on the detected value; A hydraulic system characterized by comprising: a damping valve made of a magnetic material that opens and closes a flow path through which oil flows; and an electromagnetic solenoid that attracts a damping valve made of a magnetic material to a valve seat portion and continuously increases and decreases the opening and closing pressure according to the output of the microcomputer. Shock absorber damping force control device.