GB2113355A

GB2113355A - Hydraulic damper

Info

Publication number: GB2113355A
Application number: GB08235946A
Authority: GB
Inventors: Ieaki Miura; Teiji Katsumori; Kunio Ishida
Original assignee: Tokico Ltd
Current assignee: Tokico Ltd
Priority date: 1981-12-18
Filing date: 1982-12-17
Publication date: 1983-08-03
Also published as: BR8207357A; KR870003413Y1; KR840002697A; KR870003414Y1; DE3246866A1; GB2113355B; DE3246866C2

Abstract

A hydraulic damper including a cylinder containing hydraulic liquid therein, a piston 6 working in the cylinder and partitioning the interior of the cylinder into first and second liquid chambers, a piston rod 7 secured to the piston and extending to the outside, and a disc valve 14 mounted on each side of the piston for generating the damping force. The disc valve 14 exposed to the first liquid chamber comprises at least three mutually overlapping annular discs, with a first disc 24 which is located contiguous to the piston being easily deflectable, with a second disc 25 which is located contiguous to the first disc having at least one opening 25b with one end of which being communicated permanently with the first liquid chamber 5. The opening in the second disc is closed by the first disc when the piston moves toward the second liquid chamber, and the opening is opened due to the deflection of the first disc when the piston moves toward the first liquid chamber. <IMAGE>

Description

SPECIFICATION Hydraulic damper This invention relates to a hydraulic damper and, particularly to a hydraulic damper of the kind including a cylinder containing hydraulic liquid therein, a piston working in the cylinder and partitioning the interior thereof into first and second liquid chambers, a piston rod secured to the piston and extending to the outside, a disc valve mounted on each side of the piston for generating the damping force.

Usually, the disc valve exposed to the first liquid chamber opens when the piston moves toward the second liquid chamber and generates the damping force at that condition, and when the piston moves toward the first liquid chamber, the disc valve provided in the second liquid chamber acts to generate the damping force.

When the hydraulic damper of the kind aforementioned is used in a suspension system of a vehicle such as an automobile wherein the damper is installed between the sprung mass and the unsprung mass of the vehicle, it is sometimes required that the damping force in the contraction stroke of the damper should drastically be decreased as compared with the damping force in the extension stroke of the damper, so as to improve the driving comfortability of the vehicle.

The damping force of the disc valve is usually determined by the rigidity of the valve disc, thus, it is usually possible to determine the damping force as desired by changing the thickness and the material of the valve disc, however, when the desired damping force is not so large, the dimensional tolerance in the thickness of the valve disc affects largely on the damping force.

The invention has been made in view of the aforesaid circumstances and the object of the invention is to provide a hydraulic damper of the kind aforementioned with the damping force in one direction of the movement of the piston being reduced sufficiently as compared with the damping force in the other direction of the piston movement, with the construction thereof being simple and the assembling operation thereof being easy.

According to the invention, there is provided a disc valve of the kind aforementioned and is characterized in that the disc valve exposed to the first liquid chamber comprises at least three mutually overlapping annular discs, that a first disc which is located contiguous to the piston is easily deflectable, that a second disc which is located contiguous to the first disc has at least one opening with one end of which being communicated permanently with the first liquid chamber, and that said opening is closed by the first disc when the piston moves toward the second liquid chamber and that said opening is opened due to the deflection of the first disc when the piston moves toward the first liquid chamber.

In utilizing the hydraulic damper according to the invention in a suspension system of a vehicle, it is preferable to reduce the damping force in the contraction stroke of the damper as compared with that in the extension stroke, whereby the driving comfortability of the vehicle can be improved.

Further objects and advantages of the invention will become apparent from the following detailed descriptions taken with reference to accompanying drawings exemplifying some preferred embodiments of the invention, in which: Figure 1 is a partially sectional explanatory view of a hydraulic damper according to the invention; Figure 2 is an enlarged view of a part of Fig. 1; Figures 3 and 4 are front views of discs incorporated respectively in the hydraulic damper of Fig. 2; Figure 5 is a diagram showing the relationship between the damping force and the piston speed; Figure 6 is a partial sectional view of a hydraulic damper according to a second em embodiment of the invention; Figure 7 is an enlarged view showing the essential portion of Fig. 6;; Figures 8-1 1 are front views of discs incorporated respectively in the hydraulic damper of Fig. 7; Figure 12 is an enlarged partial view similar to Fig. 7 but showing a third embodiment of the invention; Figure 13 is a view similar to Fig. 12 but showing a fourth embodiment of the invention; Figures 14 and 15 are front views of discs respectively incorporated in the damper of Fig. 1 3; and Figure 16 is a view similar to Fig. 13 but showing a fifth embodiment of the invention.

Figs. 1-4 show a hydraulic damper according to a first preferred embodiment of the invention which comprises a cylinder 2, a piston 6 slidably fitted in the cylinder 2 and defining two liquid chambers 3 and 4 within the cylinder 2, and a piston rod 7 secured to the piston 6 and extending through the liquid chamber 4 and sealingly and slidingly through one end 2a of the cylinder 2 to the outside. A mounting member 9 is secured to the projecting end 8 of the piston rod 7 for mounting the damper to such as a body of a vehicle.

Another mounting member 10 is secured to the other end 2b of the cylinder 2 for mounting the damper to such as a wheel axle of the vehicle. There are provided on opposite sides of the piston 2 annular recesses, and the annular recess on the side of the liquid chamber 4 is communicated permanently with the liquid chamber 3 through a plurality of pas sages 11, but only one of which is shown in Fig. 1. Similarly an annular recess 1 2a provided on the side of the liquid chamber 3 is communicated permanently with a plurality of passages 12 with the liquid chamber 4. The passages 11 and 1 2 are independently formed through the piston 6. The annular recesses constitute respectively valve seats for disc valves 1 3 and 14 for generating the damping force of the damper.The disc valve 1 3 comprises three mutually overlapping annular discs 13a, 1 3b and 1 3c which are located by a retainer 1 5 and a washer 1 7.

The annular disc 1 3c has one or more cutouts in the outer circumference thereof to constitute a permanent orifice 20 through which the liquid chambers 3 and 4 are permanently communicated. The disc valve 1 3 generates the damping force in the contraction stroke of the damper.

Similarly, the disc valve 14 comprises a plurality of mutually overlapping annular discs (the detailes of which will hereinafter be described) and an annular retainer 1 6 and a washer 1 8. The disc valves 1 3 and 14 and the piston 6 are secured to a reduced diameter and portion 7a of the piston rod 7 by a nut 1 9 which engages serew-threading with the external screw threads 7c on the tip end of the reduced diameter portion 7a.It will be understood that the assembling operation is very simple since the nut 1 9 acts to clamp the washer 17, the retainer 15, the valve discs 13a, 1 3b and 1 3c, the piston 6, the valve discs constituting the disc valve 14, the retainer 1 6 and the washer 1 8 against a shoulder 7b which is defined on the piston rod 7.

The disc valve 1 3 essentially has a damping force characteristics as depicted in broken line 21 in Fig. 5 in the contraction stroke of the damper. When the piston speed in arrow A direction (Fig. 1) is small, the liquid in the chamber 3 flows through the passages 11 and the orifice 20 to the chamber 4, and generates the damping force as depicted in the portion 21a in the broken line 21 in Fig.

5. When the piston speed exceeds V0 the outer circumferences of valve discs 13a, 1 3b and 13c are deflected in the direction separating from the piston 6, and the damping force characteristics in this condition are depicted by the portion 21 b in the broken line 21.

The disc valve 14 comprises, according to the invention, three mutually overlapping annular discs 24, 25 and 26 and an annular disc 27 which is thicker than the annular disc 24. The disc 24 which is contiguous to the piston 6 has an inner circumferential portion 24b, an outer circumferential portion 24a and a bridge portion 24c as shown in Fig. 4. The inner circumferential portion 24b is clamped between the piston 6 and the inner circumferential portion of the disc 25, and the outer circumferential portion 24a slidably engages with the inner circumference of the annular disc 27. Further, the diameter of the disc 24 is smaller than that of the disc 25. The disc 24 constitutes a first disc according to the invention, and the outer circumferential portion 24a is easily deflectable in the directions of arrows D and E with respect to the inner circumferential portion 24b.

The disc 25 constituting a second disc according to the invention has a predetermined number (four in Fig. 4) of cut-outs 25a in the outer circumferential portion 25b which permanently communicates with the liquid chamber 3, and the outer circumferential portion 25b normally abuts with the disc 27 to press the same against an annular rim 33 of the recess 12b in the piston 6. The rim 33 acts as a valve seat of the disc valve 14. The disc 27 may be supported on the outer circumference of the disc 24 but, alternately, the disc 27 may integrally be connected to the disc 25 by such as bonding. The thickness of the disc 27 is larger than that of the disc 24, thus, a generally wedge shaped small clearance 34 is formed between the outer circumferential portion 24a of the disc 24 and adjacent surface of the disc 25.

In a modified form, the thickness of the disc 27 is equal to that of the disc 24 and, in such case, the small clearance 34 is diminished.

The cut-out portions 25a of the disc 25 are normally covered by the outer circumferential portion 24a of the disc 24. The number, the location and the configuration of the cut-outs 25a may be determined as desired.

The disc 26 constituting a third disc according to the invention backs up the disc 25 with the diameter of which being equal to that of the disc 25.

The discs 24, 25, 26 and 27 are preferably formed of a resilient material such as a spring steel and may be formed of such as a punching process.

The disc valve 14 having the constitution as described heretofore cooperates with the disc valve 1 3 to generate the damping force as depicted in solid lines 36 and 37 in Fig. 5.

In the extension stroke of the damper wherein the piston 6 moves in the arrow B direction or toward the liquid chamber 4, and when the piston speed is small, the liquid in the chamber 4 flows into the chamber 3 through the orifice 20 and the passage 11, and the damping force is depicted by a portion 36a. The outer circumferential portion 24a of the disc 24 deflects in the arrow E direction and intercepts the communication between the liquid chamber 3 and the passage 1 2. When the piston speed exceeds a predetermined speed V1, the disc valve 14 opens to make an annular passage between the valve seat 33 and the disc 27. The damping force at that condition is shown by a portion 36b.

While, in the contraction stroke and when the piston speed is low, the small clearance 34 serves also as an orifice in addition to the orifice 20 thereby generating a damping force as depicted by a portion 37a. When the piston speed is increased by a small amount, the outer circumferential portion 24a of the disc 24 deflects in the arrow D direction and the liquid flow passing through the cut-out portions 25a and the passage 1 2 increases which cooperates with the flow passing through the orifice 20 to generate the damping force as depicted by a portion 37b in Fig.

5. When the piston speed further increases to exceed a predetermined speed V3, the disc valve 1 3 opens thereby generating the damping force as defined in a portion 37c in Fig.

5.

It will be understood that the flow passing through the cut-outs 25a in the disc 25 is limited by the effective minimum passage area which is usually defined by the total opening 38 in the outer circumference of the disc 25 and, thus, the amount of the deflection of the disc 24 does not increase excessively. Further, the portion 37c in Fig. 5 is generally parallel to the portion 21 b.

As described heretofore, the damping force in the contraction stroke of the damper can substantially be reduced by providing the flexible disc 24 on the disc valve 1 4 which normally provides the damping force in the extension stroke of the damper. Therefore, when the damper is incorporated in the suspension system of the vehicle, the driving comfortability of the vehicle is improved.

When the small clearance 34 is not provided, the damping force in the contraction stroke of the damper is defined by chain lines 37c and 37b with the lines 37b merging with the broken line portion 21a at a piston speed v2m Figs. 6 and 7 show a second embodiment of the invention wherein the disc valve 14 in the first embodiment is substituted by a disc valve 54. The disc valve 54 comprises four mutually overlapping annular discs 40, 41, 25 and 26 which are shown respectively in Figs. 8, 9, 10 and 11. The disc 40 is formed of an annular solid plate of relatively thin thickness such that the outer circumferential portion 40a thereof is easily deformable with respect to the inner circumferential portion which is clamped between the piston 6 and the disc 41. The disc 40 constitutes the first disc according to the invention.

The disc 41 has at least one arcuate opening 41d similarly to the disc 24 in the first embodiment, but the opening 41 does not aim to reduce the rigidity or to increase the flexibility of the disc 41 and serves as a simple opening which is normally covered by the outer circumferential portion 40a of the disc 40. The opening 41d in the disc 41 is permanently communicated with cutout portions 25a in the disc 25. Thus, the disc 41 and the disc 25 in the second embodiment cooperate to constitute the second disc according to the invention. The disc 26 shown in Fig. 11 is similar to the disc 26 in Fig. 2.

The damping force in the second embodiment is generally depicted by lines 36 and 39 in Fig. 5.

Fig. 1 2 shows a third embodiment of the invention wherein the disc valve 54 in the embodiment of Fig. 7 is substituted by a disc valve 64. The disc valve 64 comprises four mutually overlapping annular discs 55, 56, 57 and 58. The discs 56, 57 and 58 are respectively similar to the discs 41, 25 and 26 in Figs. 9, 10 and 11. The outer diameter of the disc 55 is nearly equal to that of the disc 56 and the inner circumferential portion of the disc 55 normally covers one or more axial openings 56a in the disc 56 which are similar to openings 41 d in the disc 41. The outer circumferential portion of the disc 55 is preferably attached to the outer circumferential portion of the disc 56 by such as bonding.

The inner circumferential portion of the disc 55 is easily deflectable relative to the outer circumferential portion thereof.

The damping force characteristics of the damper of the third embodiment are generally similar to that of the damper of Figs. 6 and 7.

Fig. 1 3 shows a disc valve 74 as a fourth embodiment of the invention which is modified slightly from the third embodiment of Fig.

1 2. The disc valve 74 comprises mutually overlapping annular discs 65, 66, 67 and 68 which may respectively substantially be similar to discs 55, 56, 57 and 58. Further, there is provided a disc 69 for locating and guiding the inner circumference of the flexible disc 65. The disc 69 has, as shown in Fig. 14 at least three angularly spaced projections 69a on the outer circumference thereof for locating and guiding the inner circumference of the disc 65. The projections 69a define therebetween cut-outs 69b for providing sufficient passage area for the liquid flowing in arrow G direction when the inner circumference of the disc 65 is deflected. The embodiment of Fig.

1 3 is advantageous over the embodiment of Fig. 1 2 in that the disc 65 is located coaxially by the disc 69 which enables to omit the bonding operation between the discs 65 and 66. It will be understood that the configuration of the disc 66 shown in Fig. 1 5 is somewhat different from that of the disc 41 shown in Fig. 9, but the difference therebetween belongs to the matter of design.

Fig. 1 6 shows a disc valve 84 as a fifth embodiment of the invention which is a combination of Fig. 2 and Fig. 1 3. Namely, the disc valve 84 essentially comprises three mutually overlapping discs 75, 76 and 77. The inner circumferential portion of the disc 75 is easily flexible, and the disc 76 has at least one cut-out 76a in the outer circumference thereof for defining an orifice opening 38 communicating permanently with the liquid chamber 3 and for providing a sufficient axial cross-sectional area in deflecting the inner circumference of the disc 75. The disc 77 is a backing up disc for the disc 76. Further, the disc valve 84 has an additional backing up disc 78 and a locating and guiding disc 79.

The operation or the function of the embodiments of Figs. 12, 1 3 and 1 6 are similar to that of the first embodiment. It will be understood that, in Figs. 12, 1 3 and 16, the inner circumference of discs 55, 65 and 75 are shown as being deflected excessively in phantom lines, but the deflection of the flexible disc is usually very small since when the disc is deflected a large passage area is formed along the entire circumference of the disc and the liquid flow flowing therethrough is limited by the orifice opening 38.

In the embodiments, the hydraulic damper are shown as a single tube type, but the invention can equally be applied to a dual tube type hydraulic damper.

As described heretofore, according to the invention, a disc valve which is located on one side of the piston for normally generating the damping force when the piston moves toward the other side comprises at least three mutually overlapping annular discs. Further, a first disc located contiguous to the piston has easily deformable inner or outer circumferential portion, and a second disc located contiguous to the first disc has at least one opening with one end of which being permanently communicated with liquid chamber on the one side of the piston and the other end of the opening being normally closed by the first disc. When the piston moves toward the other side of the piston, the opening in the second disc opens by deflecting the first disc.

Whereby the damping force generated by the other disc valve can substantially be decreased. Particularly, the gradient in the rising up portions such as 37a, 37b and 39b shown in Fig. 5 is very gentle. The construction is simple, the assembling operation is easy, further, it is possible to effectively prevent the generation of noisey sounds which would be caused of the liquid flow through a restricted passage and to prevent the generation of the cavitation in the liquid flow. Further, the ratio between the damping force in the extension and contraction strokes of the damper particularly in the range of low piston speed can be determined as desired.

The embodiments wherein the damping force in the contraction stroke is reduced as compared with that in the extension stroke of the damper is particularly advantageous in applying the damper in the vehicle suspension system, whereby the driving comfortability can be improved.

Claims

1. A hydraulic damper including a cylinder containing hydraulic liquid therein, a piston working in the cylinder and partitioning the interior of the cylinder into first and second liquid chambers, a piston rod secured to the piston and extending to the outside, and a disc valve mounted on each side of the piston for generating the damping force, characterized in that the disc valve exposed to the first liquid chamber comprises at least three mutually overlapping annular discs, that a first disc which is located contiguous to the piston is easily deflectable, that a second disc which is located contiguous to the first disc has at least one opening with one end of which being communicated permanently with the first liquid chamber, and that said opening is closed by the first disc when the piston moves toward the second liquid chamber and that said opening is opened due to the deflection of the first disc when the piston moves toward the first liquid chamber.

2. A hydraulic damper according to Claim 1 wherein said disc valve further comprises a third disc for backing up the second disc.

3. A hydraulic damper according to Claim 2 wherein said one end of the opening in the second disc is defined by a cut-out formed in the outer circumference of the second disc.

4. A hydraulic damper according to Claim 1 wherein the first disc has large and small diameter coaxial annular portions which are integrally connected by a radial bridge portion whereby the large diameter annular portion can easily deflect with respect to the remaining portions.

5. A hydraulic damper according to Claim 4 wherein the outer circumference of the first disc being guided by a fourth annular disc which is also interposed between the piston and the second disc and moves together with the second disc when the piston moves toward the second liquid chamber with the second disc being deflected in the direction separating from the piston.

6. A hydraulic damper according to Claim 1 wherein the first disc is a thin annular plate with the inner circumferential portion thereof normally covering the other end of said opening in the second disc and being easily deflectable in the direction separating from the second disc when the piston moves in the direction toward the first liquid chamber.

7. A hydraulic damper substantially as hereinbefore described with reference to, and as illustrated in, Figs. 1 to 5, or Figs. 6 to 11, or Fig. 12, or Figs. 13 to 15, or Fig. 16 of the accompanying drawings.