Upper support for shock absorber in a suspension system

Abstract: An upper support for a suspension system, which is interposed between a body of a vehicle and a shock absorber of the vehicle, for elastically connecting the vehicle body and the shock absorber. The upper support includes an inner rigid member (10), an outer rigid member (12), at least one annular elastic body (14) interposed between the inner and outer rigid members for elastically connecting these rigid members, the above-indicated at least one elastic body at least partially defining at least one annular fluid chamber (48) which is filled with a non-compressible fluid, and at least one annular partition member (44) each of which is accommodated in the corresponding fluid chamber, such that each partition member is fixed to one of the inner and outer rigid members, and elastically connected to the other through the elastic body or bodies, so as to radially extend from the one rigid member toward the other rigid member, and such that each fluid chamber is divided by the corresponding partition member into two sections (48a, 48b) which undergo relative volumetric changes when a vibrational load is applied between the inner and outer rigid members. Each partition member has at least one orifice passage (50) which allows the non-compressible fluid to flow therethrough between the two sections of the fluid chamber upon application of the vibrational load.

Description: The present invention relates to an upper support for a suspension system which is interposed between a body of a vehicle and a shock absorber of the vehicle according to the preamble of claim 1. In a conventional suspension system of a motor vehicle, a generally cylindrical upper support is usually interposed between a body of the vehicle and a piston rod of a shock absorber which is linked with an axle or arm for supporting vehicle wheels. Such an upper support is adapted to prevent input vibrations received from the wheels through the shock absorber from being transmitted to the vehicle body, for example. The upper support generally consists of a cylindrical inner rigid member to which the piston rod of the shock absorber is fixed, a cylindrical outer rigid member which is disposed radially outwardly of the inner rigid member and fixed to the vehicle body, and an elastic body interposed between the inner and outer rigid members for elastically connecting the two members. The upper support as described above is required to be given a soft spring characteristic for improved vibration-isolating capability, for the purpose of preventing transmission of the vibrations from the shock absorber toward the vehicle body. At the same time, the upper support is required to exhibit a high degree of stiffness so as to minimize the amount of deformation thereof with respect to a static load applied thereto, for the purposes of avoiding changes in the posture of the vehicle while the vehicle is turning, braked, or rapidly accelerated or decelerated, and thus assuring high steering stability of the vehicle. To meet the above requirements, the upper support utilizes its dynamic spring or elastic characteristic to enhance the vibration-isolating capability, and its static spring or elastic characteristic to enhance the steering stability of the vehicle. However, it is extremely difficult for the known upper support to fully satisfy these requirements for the vibration-isolating capability and the steering stability, since the known upper support relies only on the elastic deformation of the elastic body for isolating the input vibrations. Namely, since there is a predetermined correlation between the dynamic and static spring constant characteristics of the elastic body, it is impossible for the upper support to be given a soft dynamic spring characteristic, without exhibiting a soft static spring characteristic. Further, since the upper support in particular is likely to receive a relatively large static load during use, the elastic body must be made of a rubber material having a relatively high static spring constant, which inevitably causes stiffening of the dynamic spring characteristic of the upper support. It is also to be noted that the dynamic spring constant of the elastic body tends to increase with an increase in the frequency of the input dynamic vibrations, while at the same time the upper support should function to insulate relatively high-frequency vibrations, such as road-oriented noises, which have frequencies of several tens or hundreds of herz. Accordingly, the known upper support suffers from an extremely high dynamic spring constant when it is subjected to the middle- to high-frequency vibrations. A generic upper support is known from the JP-A-60 139942. This upper support comprises an inner rigid member enclosed by an completely integral elastic body. This elastic body forms together with two partition members four fluid chambers, wherein two fluid chambers are situated on top of each other, respectively. The respective two fluid chamber communicate with each other through an orifice passage. The upper support according to the JP-A-60 139942 however has the disadvantage, that it is complicated to assemble. It is the object of the present invention to further develop an upper support for a suspension system according to the preamble of claim 1 such that it is easily mountable. This object is achieved by the features indicated in the characterizing portion of claim 1. Advantageous further developments are set out in the dependant claims. According to the invention the fluid chamber is divided by the corresponding partition member into two sections which undergo relative volumetric changes when a vibrational load is applied between the inner and outer rigid members. Each annular partition member has at least one orifice passage which allows the non-compressible fluid to flow therethrough between the two sections of the fluid chamber upon application of the vibrational load. In the upper support of the present invention, when the vibrations are applied between the inner and outer rigid members, relative displacements between the inner and outer rigid members in their axial directions cause the non-compressible fluid to flow between the two sections of each fluid chamber, through the orifice passage formed in the partition member. In this arrangement, the present upper support can provide an effectively reduced dynamic spring constant with respect to the input vibrations in a middle- to high-frequency range, based on resonance or flows of the fluid through the orifice passage, without lowering its static spring constant to a great extent. Thus, the upper support of the invention can exhibit excellent vibration-isolating capability while assuring a sufficient degree of steering stability of the vehicle. According to the present invention, the elastic body comprises a pair of elastic bodies which are fixed to each other in the axial direction of the upper support. The pair of elastic bodies have respective annular recesses which are open toward each other in the axial direction, and the fluid chamber comprises a fluid chamber which is at least partially defined by the annular recesses. According to an advantageous development of the present invention the partition member is fixed to the inner rigid member and elastically connected to the outer rigid member, so as to radially extend from the inner rigid member toward the outer rigid member. As an advantageous feature of the above form of the invention, the inner support member consists of a pair of inner support members while the elastic body consists of a pair of elastic bodies. Further, the partition member consists of a single partition member having a radially inner portion which is fixedly supported by and between the pair of inner support members, and a radially outer portion which is elastically supported by and between the pair of elastic bodies, so that the single partition member is fixed to the inner rigid member and elastically connected to the outer rigid member. The above and optional objects, features and advantages of the present invention will be better understood by reading the following description of a presently preferred embodiment of the invention, when considered in conjunction with the accompanying drawings, in which: Fig. 1 is an elevational view in axial cross section of one embodiment of an upper support constructed according to the present invention; Fig. 2 is a transverse cross sectional view taken along line 2-2 of Fig. 1; and Fig. 3 is an elevational view in axial cross section of an intermediate product obtained by vulcanization of a rubber material during manufacture of the upper support of Fig. 1. Referring first to Figs. 1 and 2, there is illustrated the preferred embodiment of the invention in the form of a cylindrical upper support 18 used in a suspension system of a motor vehicle. In these figures, reference numeral 10 denotes a generally cylindrical inner rigid member in the form of an inner metal member, while reference numeral 12 denotes a generally cylindrical outer rigid member in the form of an outer metal member, which is disposed substantially coaxially with and radially outwardly of the inner metal member 10, with a suitable spacing therebetween. Between the inner and outer metal members 10, 12, there are interposed a pair of elastic bodies in the form of generally annular rubber bodies 14, 14 made of a suitable rubber material, which are adapted to elastically connect the inner and outer metal members 10, 12. In the present embodiment, the inner metal member 10 is fixed to a shock absorber (not shown) of the suspension system, while the outer metal member 12 is fixed to the vehicle body. Thus, the instant upper support 18 is interposed between the shock absorber and the vehicle body, for elastically connecting these members in a vibration damping or isolating manner. More specifically described, the cylindrical inner metal member 10 is formed with an annular metal member 20 welded to its one axial end, to provide an outward flange extending radially outwardly from the one axial end of the inner metal member 10. The inner metal member 10 further includes a caulked portion 26 at the other axial end thereof. In this arrangement, the piston rod of the shock absorber is inserted through and fixedly received in a center bore 22 formed through the inner metal member 10, whereby the inner metal member 10 is attached to the shock absorber. As described above, the outer metal member 12 is disposed coaxially with and radially outwardly of the inner metal member 10, with a suitable spacing therebetween. The outer metal member 12 consists of a generally annular metal plate 24 having a relatively large outside diameter, and a cylindrical metal member 32. The annular metal plate 24 includes a radially inner portion 23 having a generally L-shaped cross section, which portion is adapted to apply suitable pressure to the rubber bodies 14 as described later. The cylindrical member 32 includes an outward flange 28 at its one axial end adjacent to the annular metal plate 24, and a caulked portion 30 at the other axial end. The annular metal plate 24 and the cylindrical member 32 are fixed together into the outer metal member 12, such that the outward flange 28 of the cylindrical member 32 and the corresponding outer portion of the metal plate 24 are superposed on and fixed to each other, as shown in Fig. 1. The superposed flange and metal plate 28, 24 have three holes 34 formed therethrough, which are substantially equally spaced apart from each other in the circumferential direction of the upper mount 18. The outer metal member 12 is secured to the vehicle body, by means of mounting bolts 36 which are threaded into the holes 34 of the member 12. The inner metal member 10 and the outer metal member 12 are integrally and elastically connected to each other, by the pair of rubber bodies 14, 14 interposed therebetween as described above. Each of the rubber bodies 14 is provided with a generally annular inner support metal member 38 and a generally cylindrical outer support metal members 40, which are respectively secured by vulcanization to the inner and outer circumferential surfaces of the rubber body 14, whereby an inner assembly 42 is obtained as an intermediate product as shown in Fig. 3. The instant upper support 18 has a pair of the thus constructed inner assemblies 42, 42, which are coaxially superposed on each other in the axial direction of the upper support 18. In this condition, the inner and outer support members 38, 40 for supporting one of the rubber bodies 14 are axially superposed on the respective inner and outer support members 38, 40 for supporting the other rubber body 14. The thus superposed inner support members 38, 38 are fitted on the outer circumference of the inner metal member 38, such that the axially opposite end faces of the superposed support to members 38, 38 are held in pressed contact with the annular metal member 20 and caulked portion 26 of the inner metal member 10, respectively, whereby the inner support members 38, 38 are supported by the inner metal member 10. On the other hand, the outer support members 40, 40 are fitted in the inner circumference of the outer metal member 12, such that the axially opposite shoulder portions of the superposed support members 40, 40 are held in pressed contact with the radially inner portion 23 of the annular metal plate 24 and the caulked portion 30 of the cylindrical member 32, respectively, whereby the superposed outer support members 40, 40 are supported by the outer metal member 12. Thus, the rubber bodies 14, 14 are interposed between the inner and outer metal members 10, 12, so as to elastically connect these members 10, 12. Between the pair of inner assemblies 42, 42 constructed as described above, there is disposed an annular partition member 44, such that its radially inner portion is gripped by and between the facing surfaces of the inner support members 38, 38, while its radially outer portion is gripped by and between the facing surfaces of the rubber bodies 14, 14. The annular partition member 44 has an inside diameter which is almost equal to the outside diameter of the inner metal member 10, and an outside diameter which is smaller by a predetermined value than the inside diameter of the outer metal member 12, as shown in Fig. 1. In this arrangement, the partition member 44 is fixed at its inner circumferential surface to the inner metal member 10, and is elastically connected at its outer peripheral portion to the outer metal member 12 through the rubber bodies 14. Each one of the rubber bodies 14, 14 of the inner assemblies 42, 42 has an annular recess 46 which is open in the axial direction of the upper support 18 toward the other rubber body 14, and which extends over the entire circumference of the rubber body 14. The annular recesses 46, 46 of the rubber bodies 14, 14 cooperate with each other to define a fluid chamber 48, which is located in the axially and radially intermediate portion of the assembly of the superposed rubber bodies 14, 14. With the partition member 44 being disposed between the inner assemblies 42, 42 as described above, the openings of the annular recesses 46, 46 of the rubber bodies 14, 14 are substantially closed by the partition member 44. Thus, the fluid chamber 48 is divided by the partition member 44 into a pair of annular sections 48a, 48b, which are formed on the opposite sides of the partition member 44 so as to extend over the entire circumference of the rubber bodies 14, 14. The partition member 44 has a communication hole 50 formed therethrough in its axial direction, such that the opposite ends of the communication hole 50 are located within the openings of the annular recesses 46, 46 of the rubber bodies 14, 14, so that the two sections 48a, 48b of the fluid chamber 48 communicate with each other through the communication hole 50. The above-described fluid chamber 48 is filled with a suitable non-compressible fluid, such as water, alkylene glycol, polyalkylene glycol and silicone oil. The filling of such a non-compressible fluid is accomplished by effecting the assembling of the pair of inner assemblies 42, 42 and the partition member 44 within a mass of the non-compressible fluid, for example. It will be understood from the above description of the present embodiment that the annular recesses 46, 46 of the rubber bodies 14, 14 constitute the fluid chamber 48, which is divided by the partition member 44 into the pair of annular sections 48a, 48b, and that the communication hole 50 formed through the partition member 44 constitutes an orifice passage 52 which allows the fluid to flow therethrough between the two sections 48a, 48b. When a vibrational load is applied from the shock absorber to the thus constructed upper support 18, the input vibrations bring about periodic relative displacements between the inner and outer metal members 10, 12 in the axial direction of the upper mount 18, to thereby cause the partition member 44 formed integrally with the inner metal member 10 to be displaced relative to the outer metal member 12 in the axial direction, due to the elastic deformation of the rubber bodies 14. As a result, relative volumetric changes occur between the two sections 48a, 48b of the fluid chamber 48, whereby the fluid is forced to flow between these sections 48a, 48b through the orifice passage 52 formed through the partition member 44. In the manner as described just above, the upper support 18 is capable of providing a sufficiently lowered dynamic spring constant, by utilizing resonance of the mass of the fluid flowing through the orifice passage 52 of the partition member 44. The orifice passage 52 is tuned to a desired frequency range of the input vibrations by suitably adjusting the cross sectional area and axial length of the orifice passage 52, so that the upper support 18 can exhibit a low dynamic spring constant with respect to the input vibrations in that frequency range. The applicant of the present invention has recognized that such an effect of providing a low dynamic spring constant can be obtained with respect to the middle- to high-frequency vibrations having frequencies of several tens or hundreds of hertz. Accordingly, the instant upper support 18 is used to effectively reduce vibrations and noises such as a road-oriented noise during running of the vehicle, thereby assuring improved driving comfort of the vehicle. The instant upper support 18 can exhibit the low dynamic spring constant as described above, based on the fluid flows which occur upon application of vibrations. Since the low dynamic spring constant contributes only to improvement of the dynamic spring characteristic of the upper support 18 with respect to the input vibrations of a relatively high frequency range, it is possible to provide the rubber bodies 14 with a sufficient degree of static spring stiffness, so as to enable the upper support 18 to cope with a static load received from the shock absorber. Thus, the instant upper support 18 also assures excellent steering stability of the vehicle. In the present embodiment, the axially opposite surfaces of the outer peripheral portion of the partition member 44 are supported by the outer metal member 12 through the rubber bodies 14 and the outer support members 40, 40. Therefore, the static spring constant of the upper support 18 can be easily tuned to a desirable value by suitably adjusting the outside diameter of the partition member 44, which determines the area of the axially opposite surfaces of the partition member 44 that is supported by the outer metal member 12 through the rubber bodies 14 as described above. The upper support 18 of the present embodiment has another advantage. That is, the inner and outer metal members 10, 12 are prevented from being excessively displaced relative to each other in radial directions of the upper support 18, by abutting contact of the partition member 44 with the outer metal member 12 through the rubber bodies 14. For example, the partition member 44 may be fixed at its outer peripheral portion to the outer metal member 12, while being elastically connected at its inner peripheral portion to the inner metal member 10 through the rubber bodies 14. Further, the specific configuration and number of the orifice passage formed in the partition member 44 are not limited to those of the illustrated embodiment, but may be suitably determined depending upon the required vibration isolating characteristics of the upper support. For example, the orifice passage may be formed so as to extend within the partition member 44 in its circumferential direction. While the upper support 18 has only one annular fluid chamber 48 in the illustrated embodiment, it is possible to divide such a fluid chamber into a plurality of fluid chambers independent of each other, by means of a suitable dividing structure. In this case, the partition member is provided for each of the fluid chambers. While the pair of rubber bodies 14, 14 are used in the illustrated embodiment, the upper support according to the present invention may employ a single rubber body which takes the form of a sleeve. In this case, the inner circumferential surface of the rubber body is secured by vulcanization to the inner metal member 10. Further, the rubber body has a pocket which is open to the outer circumferential surface thereof, so that the opening of the pocket is closed by the outer metal member 12 to define a fluid chamber between the rubber body and the outer metal member 12.

Claims: An upper support for a suspension system which is interposed between a body of a vehicle and a shock absorber of said vehicle, comprising a generally cylindrical inner rigid member (10) to which said shock absorber is fixed, at least one annular elastic body (14) disposed radially outward of said inner rigid member (10), said elastic body (14) at least partially defining at least one fluid chamber (48) which is filled with a non-compressible fluid, at least one partition member (44) accommodated in said fluid chamber (48) for dividing said fluid chamber (48) into two sections (48a, 48b), said partition member (44) having at least one orifice passage (50) which allows said non-compressible fluid to flow therethrough between said two sections (48a, 48b) and a generally cylindrical outer rigid member (12) disposed radially outward of said elastic body (14) and fixed to said body of the vehicle, characterized in that said fluid chamber (48) is carved in an annular recess (46) of said elastic body (14) comprising a pair of elastic bodies disposed in an axially contiguous manner so as to define a continuous peripheral or central elastic wall receiving the peripheral or central extremity of said partition member (44), which is formed annular. An upper support according to claim 1, characterized in that at least one outer support member (40) supporting said at least one elastic body is set in a fixed union with said outer rigid member (12), which is mountable on a vehicle body. An upper support according to one of the preceding claims, characterized in that at least one inner support member (38) is arranged between said inner rigid member (10) and said elastic body (14). An upper support according to one of the preceding claims, characterized in that said partition member (44) is fixed to said inner rigid member (10). An upper support according to claim 3, characterized in that said at least one inner support member (38) consists of a pair of inner support members (38, 38) wherein said partition member (44) has a radially inner portion which is fixedly supported by and between said pair of inner support members.

Inventors: MIYAKAWA SHINJI C O TOKAI RUBB, MIYAKAWA, SHINJI, MIYAKAWA, SHINJI, C/O TOKAI RUBBER INDUSTRIES LTD.
Applicants: TOKAI RUBBER IND LTD, TOKAI RUBBER INDUSTRIES, LTD.
Application year: 1990
Main classification: F16F13
IPC codes: B60G15, F16F13, B60G13