GB2154300A - Hydro-pneumatic suspension device with adjustable valve - Google Patents

Abstract

A hydro-pneumatic suspension device for a vehicle comprises an extendable and contractible suspension main body 1,5 having a variable volume liquid chamber R2, R3 therein, an accumulator 2 having a variable volume liquid chamber R1, a liquid passage 3 connecting the variable volume liquid chambers in the suspension main body and the accumulator, and a damping force generating mechanism 4, and Fig. 3, provided in the liquid passage and having a rotary shutter 28 for selectively opening a plurality of orifice passages 37, 38 thereby changing the effective area of the passage. The opposite ends 28a, 28b of a shaft rotatably supporting the rotary shutter extend respectively outside of the liquid passage and have equal areas exposed to atmospheric pressure. Virtually no axial force is therefore extend on the shutter by the liquid pressure within the device. This means that the power of the actuator 46 for rotating the shutter can be reduced. The shutter 28 is made up of two cylindrical parts 26, 27 rigidly interconnected. The flow path adjusted by the shutter bypasses the damping valves 21, 22. A check valve 36 gives a differential flow through the bypass. <IMAGE>

Description

SPECIFICATION Hydro-pneumatic suspension device This invention relates to a hydro-pneumatic suspension device for use in a vehicle such as an automobile for generating adjustable damping force by utilizing the pressure of hydraulic fluid and gas so as to restrain vibrations of the vehicle.

Recently, there is a tendency to use a damping force adjusting device in a suspension system of an automobile, since it is possible to improve the driving comfortableness of the automobile by changing the damping force characteristics in response to such as the condition of the road on which the automobile is running. For example, the damping force is decreased when the vehicle is running on a free way and the damping force is increased in running on a rough road.

One prior art suspension device is constituted such that a damping valve is provided on a piston, which is connected to a piston rod and partitions the interior of a suspension main body into two cylinder chambers, for generating a predetermined damping force by communicating the two cylinder chambers when the piston rod displaces extendingly or contractingly and, separately therefrom, there are provided in the piston rod a by-pass passage communicating the two cylinder chambers, a valve member for throttlingly adjusting the by-pass passage, and an actuating rod for operating the valve member from the outside. By operating the valve member through the actuating rod, the damping force can suitably be adjusted during the extending or contracting movement of the piston rod.

However, such prior art suspension device is provided with the adjustable damping force generating mechanism being assembled at a confined inner end portion of the piston rod, thus, the construction of the mechanism is complicated and it is not possible to manufacture cheaply.

The applicant of the present invention has proposed a hydro-pneumatic suspension device in Japanese Utility Model Application No.

118073/1983 to solve the aforesaid problems.

The hydro-pneumatic suspension device comprises an extendable and contractible suspension main body having a variable volume liquid chamber, an accumulator having a variable volume liquid chamber and connected to the suspension main body through a liquid passage, a damping force generating disc valve provided in the liquid passage and generating damping force in both of the extension and contraction strokes of the suspension main body, a check valve provided in a bypass passage by-passing the damping force generating disc valve for closing the by-pass passage during either one of the extension and contraction strokes of the suspension main body, and an adjustable shutter rotata bly provided in the by-pass passage for selectively opening a plurality of orifice passages thereby changing the effective passage area thereof and being operable from the outside of the suspension device.It is simple in the construction and unexpensive in the manufacturing cost.

The present invention relates to improve ment on aforesaid proposal and is characterized in that the opposite ends of a shaft rotatably supporting the shutter extend respectively outside of liquid passage such that any axial force due to the reaction of the liquid pressure does not act on the shutter.

Thus, the resisting force against the rotation of the shutter can be minimized, and rotating mechanism such as a rotary actuator can be minimized in the size and the power.

Further objects and advantages of the invention will become apparent from the following detailed description taken with reference to accompanying drawings which exemplify a preferred embodiment of the invention, in which: Fig. 1 is a schematic view of a basic hydropneumatic suspension device to which the present invention belongs; Fig. 2 is a longitudinal sectional view of a suspension main body and an accumulator in the hydro-pneumatic suspension device of Fig.

1 interposed therebetween a damping force generating mechanism according to the invention; Fig. 3 is an enlarged sectional view of the damping force generating mechanism of Fig.

2; Fig. 4 is a sectional view taken along line IV-IV in Fig. 3; Fig. 5 is a sectional view taken along line V V in Fig. 3; Fig. 6 is a sectional view taken along line VI-VI in Fig. 3; and Fig. 7 is a diagram showing damping force characteristics of the damping force generating mechanism of Fig. 3.

Fig. 1 shows an example of basic hydropneumatic suspension system to which the present invention belongs. The system comprises an extendable and contractible suspension main body 1 (hydraulic piston and cylinder assembly) having a piston rod 5 extending one end of the cylinder, a cylinder chamber R defined in the cylinder, an accumulator 2 connected through a pipe line 3 with the cylinder chamber R, and a damping force generating device 4 provided in the midway of the pipe line 3. The accumulator 2 has a gas chamber and a liquid chamber (not shown). When the main body 1 contracts, hydraulic liquid in the cylinder chamber R flows into the accumulator 2 with the gas therein being compressed.In response to the reciprocating movement of the piston rod 5, the hydraulic liquid reciprocally flows through the damping force generating device 4 which generates a damping force against the movement of the piston rod 5. Further, there are provided a supply circuit for increasing the amount of the liquid in the cylinder chamber R and an exhaust circuit for reducing the amount of the liquid in the cylinder chamber R. The supply circuit comprises a power source such as an electric motor 6, a hydraulic pump 7 connected to the motor 6, a normally close electromagnetic valve 8, an oil reservoir 10, a pressure relief valve 11, a check valve 1 2 and an accumulator 1 3. The exhaust system includes a normally closed electromagnetic valve 9.Such supply and exhaust circuits act to increase and decrease the height of a vehicle when the suspension system is incorporated in the vehicle such as an automobile.

Fig. 2 shows one embodicai construction of the suspension main body 1 and the accumulator 2 in Fig. 1 which are integrally connected together. Shown at B in Fig. 2 is a diaphragm or bellows which partitions the interior of the accumulator 2 with the gas chamber G and the liquid chamber R1. A piston 5a secured to the piston rod 5 partitions the interior of the cylinder into an upper cylinder chamber R2 and a lower cylinder chamber R3. The damping force generating device 4 screw-threadingly connects the suspension main body 1 and the accumulator 2.

Since the essential portion of the present invention resides in the constitution of the damping force generating device 4, the details thereof will hereinafter be explained with reference to Fig. 3 through Fig. 7.

Shown at 14 in Fig. 3 is a casing, and the interior thereof is partitioned by a central partition 14a into a first left side chamber R4 and a right side chamber which, in turn, divided by a valve body 1 5 into a second chamber R5 and a third rightmost chamber R6.

A cap 1 6 is connected to the casing 14 by such as welding to cover the open end of the first chamber R4. There are formed outer screw-threads 1 6a on the outer circumference of the cap 1 6 to secured the casing 1 4 to the suspension main body (not shown in Fig. 3).

A passage 1 6b in the cap 1 6 permanently communicates the first chamber R4 and the upper cylinder chamber R2 in the suspension main body 1. Outer screw-threads 1 4b are formed on the outer circumference of the right end portion of the casing 1 4 and are connected to the accumulator 2 (not shown in Fig. 3), whereby the third chamber R6 is permanently communicated with the liquid chamber R1 in the accumulator 2. It will be understood that the left side in Fig. 3 corresponds to the lower side in Fig. 2.

A bolt 1 7 passes through the central portion of the valve body 1 5 and has outer screw-threads on the right end portion for engaging with a nut 18 to-mount the valve body 1 5 on the bolt 1 7. A central bore 1 7a is formed in the bolt 1 7 and, a washer 19, a retainer 20, a first valve disc 21, the valve body 15, a second valve disc 22, a retainer 23 and a washer 24 are sequentially interposed between a head portion of the bolt 1 7 and the nut 1 8 and are rigidly mounted thereon. The valve discs 21 and 22 are preferably formed respectively of a plurality of mutually,overlapping thin annular discs.The bolt 1 7 and the valve body 1 5 are retained by a lock nut 25 which is screw-threaded on the inner circumference of the third chamber R6 and are clamped against the partition 14a.

The valve body 1 5 has therein first and second communicating passages 15a and 15b for communicating the second and third chambers R5 and R6. The first passage 15a (which may be constituted of two or more passages) opens when the pressure in the third chamber R6 exceeds the pressure in the second chamber R5 by a predetermined level with the first valve disc 21 being deflected and, the second passage 15b (which also may be constituted of two or more passages) opens when the pressure in the second chamber R5 exceeds the pressure in the third chamber R6 by a predetermined level with the second valve disc 22 being deflected.

A shutter 28 constituted of an outer generally cylindrical shutter 26 and an inner generally cylindrical shutter 27 is rotatably incorporated in the partition 1 4a of the casing 14.

The outer and inner shutters 26 and 27 are rigidly connected together. The outer shutter 26 has integrally a shaft 28a which is rotatably fitted in a bore 14b in the partition 14a and, the inner shutter 27 has integrally a shaft 28b which aligns with the shaft 28a and is received in a central bore 29a of a guide member 29. The guide member 29 is mounted on the casing 14 through screws 30. The shafts 28a and 28b and the guide member 29 are sealed by O-rings 31, 32 and 33. The bores 1 4b and 29a open to the outside, thus, outer ends of the shafts 28a and 28b are exposed to atmosphere. Further, the shafts 28a and 28b have the same sectional area.

The shutter 28 is rotatable in an increased diameter bore portion 1 4c in the partition 14a, and the bore portion 1 4c is coaxial with the bore 14b and the bore 29a. The interior of the shutter 28 is partitioned into fourth and fifth chambers R7 and R8 by a check valve seat 34 which is secured to the inner circumference of the shutter 28. There are provided passages 34a in the check valve seat 34 for communicating the fourth and fifth chambers R7 and R8. The passages 34a are normally closed by a check valve 36 which is disposed in the fourth chamber R7 and is biased against the check valve seat 34 by a spring 35. The check valve 36 permits the flow from the fifth chamber R8 to the fourth chamber R7 and prevents the flow in the opposite direction.

As shown in Fig. 5, there are provided three orifice passages 37a, 37b and 37c having different sectional area and three pas sages 38a, 38b and 38c in the circumferential wall of the shutter 28 defining the circum ference of the fourth chamber R7. The orifice passages 37a, 37b and 37c are spaced each other by 60 degrees and openings 38a, 38b and 38c are respectively spaced by 180 de grees relative to respective orifice openings 37a, 37b and 37c. Further, in the circumferential wall of the shutter 28 there are provided, as shown in Fig. 6, three orifice passages 41a, 41b and 41c having different sectional area.As shown in Figs. 3 and 6, in the embodiment, the orifice passages 41a, 41b and 41c are formed in the circumferential wall of the outer shutter 26 and the inner shutter 27 has in the circumferential wall thereof an annular groove 40 opening to the orifice passages 41a, 41b and 41c and four angularly spaced passages 39 permanently communicating with the annular groove 40 and opening to the fifth chamber R8.

A rotary actuator 46 is connected to the shaft 28a of the shutter 28 and is adapted to rotate the shutter 28, as viewed in Figs. 5 and 6, from the nutral position shown in the drawing in the clockwise or counterclockwise direction by 60 degrees.

The sectional area of the orifice passages 37a, 37b and 37c are decreased sequentially, i.e. the orifice passage 37a is the largest and the orifice passage 37c is the smallest. Similarly, the orifice passage 41a is the largest and the orifice passage 41c is the smallest among the orifices 41a, 41b and 41c. Further, the passage 38a is equal to or larger than the sum of the orifice passages 37a and 41a, the passage 38b is equal to or larger than the sum of orifice passages 37b and 41b, and the passage 38c is equal to or larger than the sum of orifice passages 37c and 41c.

The partition 1 4a of the casing 1 4 further has four openings 42 for communicating the first and second chambers R4 and R5, an opening 43 with one end opening to the first chamber R4 and the other end opening to the bore portion 1 4c for selectively communicating with either of orifice passages 37a, 37b and 37c, an opening 44 with one end opening to the first chamber R4 and the other end opening to the bore portion 1 4c for selectively communicating with either one of orifice passages 41a, 41b and 41c, and an opening 45 with one end opening to the passage 1 7a in the bolt 1 7 and the other end opening to the bore portion 1 4c for selectively communicating with either of the passages 38a, 38b and 38c.

When the shutter 28 is located in the neutral position as shown in Figs. 5 and 6, the largest orifice passages 37a and 41a and the passage 38a respectively open to respective openings 43, 44 and 45. When the shutter 28 is rotated by 60 degrees in the counterclockwise direction from the neutral position as viewed in the drawings, the medium size orifice passage 37b communicates first and fourth chambers R4 and R7 through the opening 43, the orifice passage 41 b com municates the first and fifth chambers R4 and R7 through the opening 44, and the passage 38b communicates the fourth and third chambers R7 and R6 through the passage 38b, the opening 45 and the passage 17a.Similarly, when the shutter 28 is rotated from the condition shown in Figs. 5 and 6 in the clockwise direction by 60 degrees, the smallest orifice passages 37c and 41c respectively communicate the first chamber R4 with fourth and fifth chambers R7 and R8, and the chamber R7 is communicated with the third chamber R6. Aforesaid three condition will hereinafter referred respectively as a first condition (neutral or the maximum passage area), a second position (medium area condition) and a third condition (the minimum area).

The operation of the damping force generating device having aforesaid constitution will now be explained.

Firstly, the shutter 28 is assumed at the first condition. In the extension stroke of the suspension main body 1, the liquid flows from the third chamber R6 on the side of the accumulator 2 to the first chamber R4 on the side of the suspension main body 1. The liquid in the third chamber R6 flows through the passage 1 7a in the bolt 17, the opening 45, the passage 38a, the fourth chamber R7, the largest orifice passage 37a and the opening 43 into the first chamber R4. The orifice passage 37a generates a relatively small resistance against the liquid flow.When the speed of the rod 5 increases, the difference in the pressure between third and second chambers R6 and R5 gradually increases, and when the pressure difference exceeds a predetermined level, the valve disc 21 deflects and the liquid in the third chamber R6 flows also into the first chamber R4 through another flow passage consisting of the first communicating passages 15a, a space formed along the deflected valve disc 21, the second chamber R5 and the openings 45. The damping force characteristic is shown by line D1 in Fig. 7. In the drawing shown at DR depicts the opening of the valve disc 21.

In the contraction stroke of the suspension main body 1, the liquid in the first chamber R4 flows into the third chamber R6. There is formed a first flow passage consisting of the opening 43, the orifice passage 37a, the fourth chamber R7, the passage 38a, the opening 45 and the passage 1 7a in the bolt 1 7 and, a second flow passage consisting of the opening 44, the orifice passage 41a, the annular groove 40, the passages 39, the fifth chamber Ra, the passages 34, a space formed between the check valve seat 35 and the check valve 36 being opened, and the fourth chamber R7. The second flow passage is merged into the first passage in the fourth chamber R7. The flow resistance is determined by orifice passages 37a and 41 a.Assuming the effective sectional area of the orifice passage 37a is a and that of the orifice passage 41 a is ss, then the effective passage area of the orifices 37a and 41 a can be determined by (a + ss) which is larger than the corresponding area a in the extension stroke.

Therefore, the inclination of the damping force characteristic curve is more gradual as compared with that in the extension stroke.

Thereafter, when the speed of the rod 5 increases sufficiently, and the difference in the pressure in the second chamber R5 being permanently communicated with the first chamber R4 through openings 42 and the third chamber R6 exceeds a predetermined level, the valve disc 22 deflects and a third passage is formed between the second and third chambers R5 and R6 through passages 15b. The damping force characteristic is shown by line D4 in Fig. 7. Shown at Dc in the drawing shows the opening of the valve disc 22.

Secondly, when the actuator 46 rotates the shutter 28 in the counterclockwise direction in Figs. 5 and 6 by 60 degrees, the shutter 28 takes the second condition. The damping force characteristics at that condition are shown by lines D2 and D5 in Fig. 7.

Thirdly, when the shutter 28 is rotated to the third condition, the smallest orifice passages 37c and 41c act to define the damping force characteristics in the range of low speed.

The damping force characteristics are shown by lines 03 and D6 in Fig. 7.

The shutter 28 according to the invention has a generally cylindrical configuration and is received in the bore portion 14c, thus, any thrust force does not act on the shutter 28.

Further, the shutter 28 is supported by the shafts 28a and 28b having the same sectional area and the outer opposite ends thereof are exposed to the atmosphere, therefore, the shutter receives the same hydraulic pressure in opposite axial directions both on the inner surfaces (the surfaces facing the chambers R7 and R7) and on the outer surfaces. Accordingly, the shutter 28 balanced pressure in axially opposite directions and can be rotated with a small resistance. Thus, the rotating force of the rotary actuator 46 can be reduced.

As described heretofore, according to the invention, the rotary shutter selectively opening a plurality of orifice openings so as to change the damping force is secured to and supported by a shaft, and the opposite ends of the shaft extend outside of liquid passage, whereby the pressure of the liquid acting on the shaft can be balanced in axially opposite directions. Thus, resisting force acting against the rotation of the shutter can be reduced, and the size and output force of the actuator for rotating the shutter can be reduced. The operation of the damping force adjusting mechanism is smooth and reliable.

Claims (6)

1. A hydro-pneumatic suspension device including an extendable and contractible suspension main body having a variable volume liquid chamber therein, an accumulator having a variable volume liquid chamber, a liquid passage connecting the variable volume liquid chambers in the suspension main body and the accumulator, and a damping force generating mechanism provided in the liquid passage and having a rotary shutter for changing the effective area of the passage, wherein opposite ends of a shaft rotatably supporting the rotary shutter extend respectively outside of the liquid passage such that the shutter has equal pressure receiving areas in axially opposite directions.

2. A hydro-pneumatic suspension device according to Claim 1, wherein a rotating mechanism for rotating the shutter is connected to one end of said shaft.

3. A hydro-pneumatic suspension device according to Claim 1, wherein said damping force generating mechanism comprises a plurality of orifice passages which are selectively opened and closed in response to the rotation of the shutter.

4. A hydro-pneumatic suspension device according to Claim 3, wherein the damping force generating mechanism further comprises a disc valve, and said shutter and the orifice passages are provided in an internal passage by-passing the disc valve.

5. A hydro-pneumatic suspension device according to Claim 4, wherein the damping force generating mechanism further comprises a check valve in said internal passage for preventing at least a portion of the liquid flow passing through said internal passage in either one of extension and contraction strokes of the suspension main body.

6. A hydro-pneumatic suspension device substantially as hereinbefore described with reference to, and as illustrated in, the accom panying drawings.