GB2115106A - Adjusting hydraulic dampers - Google Patents

Abstract

A hydraulic damper of adjustable damping force type comprises a cylinder 1, a piston 12 working in the cylinder and partitioning the interior of the cylinder into two liquid chambers, 13,14, a piston rod 7 connected to the piston and extending to the outside through one end of the cylinder, a liquid passage 38,36,46 connecting the two liquid chambers, a coaxial bore 36 formed in the piston rod and constituting a part of the liquid passage and a rotatable valve member 41 controlling the effective area of the liquid passage. A connecting rod 37 is secured to the valve member and extends through the bore in the piston rod to the outside, a pinion 52, Figure 2, is secured to the outer end of the connecting rod and engages with a rack member 59, Figure 2, and an actuator is mounted on the outer end of the piston rod to reciprocatingly move the rack member, and so adjust the valve member. <IMAGE>

Description

SPECIFICATION Hydraulic damper Background of the invention This invention relates to a hydraulic damper, and, particularly to a hydraulic damper of the type wherein the damping force is adjustable from the outside of the damper.

One prior art hydraulic damper of adjustable damping force type includes a cylinder, a piston working in the cylinder and partitioning the interior of the cylinder into two liquid chambers, a piston rod connected to the piston and extending to the outside through one end of the cylinder, a damping force generating valve mechanism for generating the damping force, a liquid passage connecting the two liquid chambers and by-passing the valve mechanism on the piston, a coaxial bore formed in the piston rod and constituting a part of the liquid passage, a connecting rod provided in the co-axial bore in the piston rod and extending to the outside, and an adjusting member secured to the inner end of the adjusting rod for adjusting the effective area of the liquid passage.

An actuating mechanism is mounted on the outer end of the piston rod for moving the adjusting rod in adjusting the damping force, however, in the conventional hydraulic dampers, there are shortcomings such that it is difficult to mount the actuating mechanism in a confined space between the upper end of the hydraulic damper and a body of a vehicle, and that the mounting of the actuating mechanism or the connection between the mechanism and the connecting rod may be affected by vibrations of the vehicle thereby deviating the adjusted condition of the damping force.

Summary ofthe invention An object of the invention is to provide a hydraulic damper which can be mounted in a confined space and the damping force of which can reliably be adjusted.

According to the invention, there is provided a hydraulic damper comprising a cylinder, a piston working in the cylinder and partitioning the interior of the cylinder into two liquid chambers, a piston rod connected to the piston and extending to the outside through one end of the cylinder, a liquid passge connecting the two liquid chambers, a coaxial bore formed in the piston rod and constitutin a part of said liquid passage, a rotatable valve member for adjusting the effective area of the liquid passage, a connecting rod provided in the coaxial bore with one end being secured to the valve member and the other end sealingly projecting to the outside, a pinion secured to the projecting end of the connecting rod, a rack member engaging with the pinion, and an actuator for reciprocally moving the rack member.

Brief description of the drawings The invention will hereinafter be explained in detail with reference to the accompanying drawings exemplifying one preferred embodiment of the invention, in which: Figure 1 is a longitudinal sectional view of a hydraulic damper according to the invention; Figure 2 is an enlarged sectional view taken along line II - II in Figure 1; Figure 3 is a sectional view taken along line Ill - Ill in Figure 1; Figure 4 is a partial enlarged front view of Figure 1; and Figure 5 is a view similar to Figure 3 but showing a condition different from Figure 3.

Description of the preferred embodiment The hydraulic damper shown in Figure 1 comprises coaxial inner and outer tubes 1 and 2, a cap 3 closing one ends of the inner and outer tubes, and a mounting ring 4 secured to the cap 3 for mounting the damper on such as a wheel axle of a vehicle. A rod guide 5 and a cap 6 are connected respectively to the upper ends of the inner tube 1 and the outer tube 2. A piston rod 7 extends through the rod guide 5 and the cap 6. There are provided between the cap 6 and the rod guide 5 a seal 8 for sealing the interior of the damper from the outside and slidably engaging with the piston rod 7, a retainer 9, a check valve 11 and a spring 10. A piston 12 is secured to the inner end of the piston rod 7 and is fitted in the inner tube 1. Thus, the inner tube 1 acts as a cylinder according to the invention.The piston 12 partitions the interior of the inner tube 1 into two liquid chambers 13 and 14.

Damping force generating valves 15 and 16 are mounted on the piston 12. In the embodiment, the valve 15 comprises two or more mutually overlapping annular discs normally covering an annular recess which is formed in the upper surface of the piston 12 and is permanently communicated with the lower liquid chamber 14 through a plurality of holes 17 (only one is shown in Figure 1), and the valve 16 comprises at least one annular disc normally covering an annular recess which is formed in the lower surface of the piston 12 and is connected permanently with the upper liquid chamber 13 through a plurality of holes 18 (only one is shown in Figure 1). One or more cut-outs are formed in the outer circumference of a disc of the valve 15 to constitute an orifice passage 19 which directly communicates the liquid chambers 13 and 14 through the holes 17.Shown at 20 are washers or retaining rings, and at 21 is a piston ring.

The valve 15 opens when the pressure in the lower liquid chamber 14 exceeds by a predetermined pressure over the upper liquid chamber 13 in the contraction stroke of the damper and the liquid flowing through the valve 15 generates a damping force. Similarly, the valve 16 generates a damping force in the extension stroke of the damper. The inner and outer tubes 1 and 2 define therebetween an annular chamber 22 which communicates with the lower end portion of the liquid chamber 14 through an opening 23 formed in the inner tube 1.

The upper portion of the chamber 22 receives gas under pressure and, the chambers 13 and 14 and the lower portion of the chamber 22 receive hydraulic liquid such as oil.

The upper end portion 26 of the piston rod 7 has external screw-threads to receive a nut 27 which clamps mounting members 28 and 29 on the piston rod 7. The mounting members 28 and 29 are mounted on another mounting member 30 through a shock absorbing member 31 such as rubber, and the mounting member 30 is secured to a body 33 of a vehicle by bolts 32. The piston rod 7 has a coaxial bore 36 which extends longitudinally from the lower end 34 to the upper end 35, and a connecting rod 37 is inserted ioosely through the bore 36. An O-ring 54 seals the gap between the rod 37 and the bore 36.

Shown at 53 is a retaining member for the O-ring 54.

A radial hole 38 is formed in the rod 7 to communicate the bore 36 with the upper liquid chamber 13. A cylindrical nut 39 is screw-threadingly connected to the lower end 34 of the piston rod 7, and the lower end of the cylindrical nut 39 is closed by an end cap 40 which also acts as a spring retainer. The cylindrical nut 39 acts to secure the piston 12 on the piston rod 7, i.e. the piston 12, the valves 15 and 16, the washers or retainers 20 are clamped against a downwardly facing shouider on the piston rod 7 by the nut 39. A valve member 41 is rotatably provided in the cylindrical nut 39, and is secured to the lower end of the connecting rod 37. The valve member 41 includes a disc shaped portion 43 having a plurality of (four in the embodiment) axial opening 42 and an arcuate wall portion 44 which slidably engages with the inner circumference of the cylindrical nut 39.At least one (three, in the embodiment) opening 46 is formed in the circumferential wall of the nut 39 to cooperate with the arcuate wall portion 44 of the valve member 41. When the valve member 41 is rotated counterclockwise direction or in arrow A direction as shown in Figure 3 to abut with a stop 45, the valve member 41 closes the openings 46 thereby intercepting the communication between the chamber 14 and a chamber 47 which is defind in the nut 39. And when the valve member 41 is rotated in arrow B direction as shown in Figure 5, the communication between the chamber 14 and the chamber 47 is established. The number of the openings 46 disclosed determines the effective area of the passage between the chambers 14 and 47.The chamber 47 permanently communicate with the chamber 13 through the openings 42, an annular space defined between the bore 36 and the connecting rod 37 and the radial hole 38. Thus, the openings 46, the chambe 47, the opening 42, the annular space between the bore 36 and the rod 37 and the hole 38 constitute a liquid passage communicating the chambers 13 and 14 and by-passing the valves 15 and 16 on the piston 12.

A coil spring 48 is provided between the valve member 41 and the end cap 40 to bias the valve member 41 in arrow C (Figure 1) direction and against a thrust washer 50. The connecting rod 37 projects to the outside through the upper end of the piston rod 7, and a pinion gear 52 is secured to the projecting end 51 of the connecting rod 37. A supporting member 55 is mounted on the upper end portion 35 of the piston rod 7 to mount thereon an electromagnetic solenoid 56 acting as an actuator.

The solenoid 56 has an actuating rod 57 which moves in the arrow D direction when the solenoid 56 is energized and moves in the arrow E direction when the solenoid 56 is deenergized. Preferably, the solenoid 56 can steppingly move the actuating rod 57 in the arrow D direction or in the arrow E direction. A generally L-shaped rack member 58 is connected to the actuting rod 57 by means of C-rings 65, and has rack teeth 59 on one arm thereof to engage with the pinion 52. A mounting plate 60 and a lock nut 61 screw-threadingly engage with and are secured to the upper end portion 35 of the piston rod 7. The supporting member 55 is mounted on the mounting plate 60 by screws 62. A cover plate 64 covers the engaging portion between the pinion 52 and rack teeth 59 and defines a space for receiving a lubricant such as grease.

When the actuating rod 57 of the solenoid 56 steppingly moves in the arrow D or E direction, the rack member 58 moves together with the actuating rod 57, and the pinion 52 engaging with the rack teeth 59 of the rack member rotates accordingly. The pinion 52, the connecting rod 37 and the valve member 41 integrally rotates in the arrow A or B direction steppingly.

In operation, the solenoid 56 is energized by operating a switch, which is preferably provided in the driver's seat of the vehicle, then, the actuating rod 56 and the rack member 58 move in the arrow D direction and, accordingly, the pinion 52 rotates in the arrow A direction as viewed from the lowerside.

The valve member 41 connected to the pinion 52 through the connecting rod 37 also rotates in the arrow A direction so that the openings 46 are closed by the valve member 41. The communication between the chamber 14 and the space 47 is intercepted. The communication between the chambers 13 and 14 in response to the reciprocation of the piston 12 solely depends on the valve 15 or 16, thus, the damping force generated at a predetermined piston speed is at the maximum.

When the driver of the vehicle wishes to reduce the damping force to accommodate the conditions of the road or the speed of the vehicle, the switch is operated to steppingly move the actuating rod 57 of the solenoid 56 in the arrow D direction. The pinion 52 rotates in the arrow B direction as viewed from the lowerside, and a predetermined number of openings 46 are disclosed by the arcuate wall 44 of the valve member 41. The chambers 13 and 14 are communicated through the hole 38, the bore 36, the holes 42, the space 47 and the openings 46, which constitute a by-pass passage by-passing the valves 15 and 16 on the piston 12. Thus, the damping force generated at the predetermined piston speed is decreased as compared with the aforesaid fully closed condition.

In the embodiment, a plurality of angularly spaced small openings 46 are formed in the cylindrical nut member 39, however, the openings 46 may be substituted by a single openings or an opening elongated in the circumferential direction.

The solenoid 56 may be substituted by a hydraulic or pneumatic cylinder or by an electric motor of the linear type.

As described heretofore, according to the inven tion, the damping force of the damper can easily be adjusted by rotating a pinion which is connected to the upper end of the connecting rod, thus, it is possible to mount the damper in a restricted space, further, the adjustment of the damping force is very easy. The pinion, the rack member and the actuator are mounted on a single supporting member and, accordingly, they can easily be mounted on a vehicle.

Claims (6)

1. A hydraulic damper comprising a cylinder, a piston working in the cylinder and partitioning the interior of the cylinder into two liquid chambers, a piston rod connected to the piston and extending to the outside through one end of the cylinder, a liquid passage connecting the two liquid chambers, a coaxial bore formed in the piston rod and constituting a part of said liquid passage, a rotatable valve member for adjusting the effective area of the liquid passage, a connecting rod provided in the coaxial bore with one end being secured to the valve member and the other end sealingly projecting to the outside, a pinion secured to the projecting end of the connecting rod, a rack member engaging with the pinion, and an actuator for reciprocally moving the rack member.

2. A hydraulic damper according to Claim 1 wherein the actuator is a solenoid being capable to reciprocate the rack member steppingly.

3. A hydraulic damper according to Claim 1 wherein the actuator is a linear motor.

4. A hydraulic damper according to Claim 1 wherein the actuator is a hydraulic or pneumatic cylinder.

5. A hydraulic damper according to Claim 1 wherein the rack member is of a generally L-shaped member with one arm having rack teeth and the other arm being connected to the actuator.

6. A hydraulic damper substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.