Patent Description:
The present invention relates to a hydraulic composite bushing for vehicles, in particular rail vehicles. The invention also relates to a sealing method for the hydraulic composite bushing.

Hydraulic bushing is a component widely used in vehicles (such as automobiles and rail vehicles), and mainly installed on a suspension or a bogie of a vehicle for absorbing vibrations and shocks to improve the running stability and safety of vehicles. The hydraulic bushing usually includes a core shaft, a rubber member, and an outer cover arranged around the core shaft. Two hydraulic chambers filled with hydraulic fluid are provided inside the rubber member, and connected with each other through a flow channel. When the vehicle is running on a special section of a road, the wheels will drive the core shaft to move relative to the outer cover, causing the hydraulic chambers to expand and contract accordingly, so that the hydraulic fluid is able to flow between said two hydraulic chambers. In this manner, the stiffness of the hydraulic bushing can be adjusted, so that the vehicle can keep running stably.

In practical applications, when the hydraulic fluid flows through the flow channel, it is easy to flow out from a contact gap between the flow channel and other components. Accordingly, the hydraulic fluid will move laterally in the flow channel, thus seriously affecting the working performance of the hydraulic bushing. Therefore, sealing requirements for the flow channel connecting two hydraulic chambers are very high. In operation, the hydraulic bushing is subjected to load and vibration, so that the volume of the hydraulic chamber is constantly changing. In addition, the pressure of the hydraulic fluid in the hydraulic chamber is very high, which would readily lead to a surge in liquid pressure. Moreover, the space of the hydraulic chamber is limited, so that there is little room for arrangement of a sealing structure. Therefore, the sealing structure cannot withstand the liquid pressure alone, and is easily damaged, has a short service life, and cannot achieve effective sealing.

Document <CIT>, which is considered to be the closest prior art, discloses a hydraulic composite bushing according to the pre-amble of claim <NUM>.

In view of the above technical problems, the present invention aims to provide a hydraulic composite bushing, which can effectively ensure the sealing performance of a flow channel pipe, a hydraulic chamber and related connecting positions, and also effectively ensure the performance of stiffness adjustment of the hydraulic composite bushing, which is very beneficial for extending the service life of the hydraulic composite bushing.

The present invention further provides a sealing method for the hydraulic composite bushing, which has high production efficiency, and can effectively enhance the sealing performance of the hydraulic composite bushing.

According to a first aspect of the present invention, a hydraulic composite bushing is proposed, comprising: a core shaft, an outer surface of which is provided with a flow channel groove continuously extending in a spiral shape; a rubber member, arranged on the core shaft and provided with two recesses diametrically opposite to each other, the recesses being arranged radially outside of the flow channel groove; a support ring, arranged around the rubber member, and covering the recesses to form two hydraulic chambers for accommodating hydraulic fluid; a outer cover press-fitted on the support ring from a radially outer side thereof; and a sealing device mounted at an end of a flow channel pipe arranged in the flow channel groove. Two ends of the flow channel pipe pass through the rubber member along a radial direction to extend into said two hydraulic chambers, respectively, so that said two hydraulic chambers are in communication with each other through the flow channel pipe. The sealing device is arranged at each end of the flow channel pipe, wherein one end of the sealing device is arranged in the flow channel groove while the other end thereof passes through the rubber member to extend into a corresponding hydraulic chamber, thus forming a seal between the flow channel pipe and the flow channel groove.

In one embodiment, a pressing sleeve is provided between the core shaft and the rubber member, and formed into one piece with the core shaft through injection molding of plastic, rubber or polyurethane material, for press-fitting the flow channel pipe into the flow channel groove.

In one embodiment, the sealing device comprises a cylindrical sealing body, which is provided with a mounting portion axially penetrating the sealing body and a rectangular through hole extending in the radial direction. The end of the flow channel pipe passes through the rectangular through hole and is fitted in the mounting portion, so that the pressing sleeve fills the rectangular through hole to enclose the flow channel pipe during the injection molding, thereby forming the seal.

In one embodiment, a first end of the sealing body is fitted with the flow channel groove, and a second end thereof passes through the rubber member to extend into a corresponding hydraulic chamber, wherein a tip of the second end extends beyond a radially inner sidewall surface of the hydraulic chamber by at least <NUM>.

In one embodiment, the end of the flow channel pipe is fixedly connected with a filter element via the sealing device.

In one embodiment, a key slot is provided at each end of the flow channel groove, and a first end surface of the sealing body is configured to engage with a bottom surface of the key slot, so that the first end surface of the sealing body and the bottom surface of the key slot are closely fitted with each other to form the seal.

In one embodiment, a first through hole and a second through hole are respectively provided in sidewall regions of the outer cover and the support ring corresponding to the hydraulic chambers, respectively, and the first through hole communicates with the second through hole to form a liquid injection port in communication with a corresponding hydraulic chamber, for injecting hydraulic fluid into the hydraulic chamber.

In one embodiment, the liquid injection port is sealed by a high pressure ball plug.

In one embodiment, the support ring comprises a cylindrical support ring body and a cover plate fitted with the support ring body, and the support ring body is adaptively arranged on an outer peripheral surface of the rubber member, while the cover plate is fitted with the support ring body in a sealing manner, so that the support ring covers the recesses to form the hydraulic chambers.

In one embodiment, the core shaft is configured as a stepped shaft with a central projecting portion, each axial end of which is formed as a conical surface, and the flow channel groove is arranged in an axial middle region of the central projecting portion.

In one embodiment, a radial protrusion extending radially outward is provided in a middle of each recess, a maximum outer diameter of the radial protrusion being less than that of the rubber member. A radial thickness in each of a circumferential direction and an axial direction of each hydraulic chamber in its central region is less than that in each of its two side regions.

In one embodiment, the core shaft is configured as a stepped shaft with a central projecting portion, each axial end of which is provided with an annular protrusion radially outwardly extending. The flow channel groove is arranged in an axial middle region of the central projecting portion.

In one embodiment, a radial protrusion extending radially inward is provided on an inner wall region of the cover plate, an inner diameter of the radial protrusion being larger than that of each hydraulic chamber. A radial thickness in each of the circumferential direction and the axial direction of each hydraulic chamber in its central region are less than that in each of its two side regions.

In one embodiment, the hydraulic composite bushing is able to, under different operating conditions, achieve a preset ratio λn of dynamic stiffness to static stiffness, which is not less than <NUM> at a preset threshold frequency fn. Under a same ratio λ of dynamic stiffness to static stiffness, a ratio β of length to diameter of the flow channel pipe at each preset threshold frequency fn satisfies following relationships: β=L/D; β<NUM>>β<NUM>>. >βn; and β<NUM>-β<NUM>>β<NUM>-β<NUM>>. >βn-<NUM>-βn, and under a same threshold frequency f, an equivalent piston area S of each hydraulic chamber under respective λn satisfies following relationships: S<NUM><S<NUM><. <Sn, and S<NUM>-S<NUM>>S<NUM>-S<NUM>>. >Sn-Sn-<NUM>, wherein: fn is a threshold frequency of the hydraulic composite bushing; λn is the ratio of dynamic stiffness to static stiffness of the hydraulic composite bushing; n is a non-zero natural number; fn and λn are each an increasing arithmetic progression; L is a length of the flow channel pipe; D is a hydraulic diameter of the flow channel pipe; βn is the ratio of length to diameter of the flow channel pipe; and Sn is the equivalent piston area of the hydraulic chamber.

According to a second aspect of the present invention, a sealing method for a hydraulic composite bushing is proposed, comprising steps of: arranging the flow channel pipe in the flow channel groove to extend in a spiral shape; mounting the sealing device at each end of the flow channel pipe, and forming the pressing sleeve on an outer peripheral surface of the core shaft by injection molding; and forming the rubber member on the outer peripheral surface of the core shaft by vulcanization of rubber so as to form the hydraulic chambers inside the rubber member, and passing the sealing device through the rubber member to extend into a corresponding hydraulic chamber, wherein the pressing sleeve fills the rectangular through hole of the sealing device during the injection molding to form a seal between the flow channel pipe and the flow channel groove, and during the vulcanization, a tip of a second end of the sealing device extends into the hydraulic chamber by a length not less than <NUM>.

Compared with the prior arts, the present invention has the following advantages.

According to the present invention, two radially opposite hydraulic chambers of the hydraulic composite bushing are in communication with each other through the flow channel pipe arranged in a spiral shape, so that the hydraulic composite bushing <NUM> can realize stiffness adjustments in the radial hollow direction, the radial real direction and the axial direction. Therefore, the performance of stiffness adjustment of the hydraulic composite bushing is greatly enhanced, and the fatigue performance of the product is effectively improved. The flow channel pipe and the flow channel groove are sealed relative to each other by the sealing device, which significantly enhances the sealing performance between the flow channel pipe and the flow channel groove, thereby effectively preventing leakage caused by flow of the hydraulic fluid in a gap formed between the flow channel pipe and the flow channel groove. In addition, the procedure of arrangement and installation of the flow channel pipe and the sealing device is simple and convenient. Moreover, the core shaft, the rubber member, the support ring and the pressing sleeve are integrally formed by vulcanization, which significantly enhances the integrity and stiffness of the hydraulic composite bushing, improves the flexibility of the stiffness adjustment of the hydraulic composite bushing, and effectively prolongs the service life of the hydraulic composite bushing. The sealing method for the hydraulic composite bushing according to the present invention requires a simple structure only, can meet high stiffness requirements, improve the sealing performance, prolong the service life, and has high production efficiency, which is suitable for mass production.

The present invention will be explained with reference to accompanying drawings, in which:.

In this application, all drawings are schematic ones used to illustrate the principle of the present invention only, and are not drawn to actual scale.

The present invention will be described below with reference to the accompanying drawings.

It should note that the terms "axial" and "radial" in the context refer to the horizontal direction and the vertical direction in <FIG>, respectively, and the radial direction associated with a part of the hydraulic composite bushing <NUM> with the hydraulic chambers therein is defined as the hollow radial direction, while the radial direction associated with a part thereof without the hydraulic chambers is defined as the solid radial direction.

<FIG> is an axial cross-sectional view of a hydraulic composite bushing <NUM> according to one embodiment of the present invention. As shown in <FIG>, the hydraulic composite bushing <NUM> includes a core shaft <NUM>, a rubber member <NUM> disposed on an outer periphery of the core shaft <NUM>, a support ring <NUM> arranged on the rubber member <NUM> at an radially outer side thereof, and an outer cover <NUM> pressed on the support ring <NUM> through interference fit at an radially outer side thereof. The core shaft <NUM> is usually a pre-formed element, and both ends of the core shaft <NUM> can be connected to, for example, a bogie frame of a rail vehicle. The core shaft <NUM> and the support ring <NUM> are integrally formed by vulcanization, which greatly enhances the overall performance of the hydraulic composite bushing <NUM>.

According to the present invention, a flow channel groove <NUM> is formed on an outer surface of the core shaft <NUM>. As shown in <FIG>, the flow channel groove <NUM> is formed in a spiral shape around the outer surface of the core shaft <NUM>, and extends in a continuous manner along a circumferential direction and an axial direction of the core shaft <NUM>. The function of the flow channel groove <NUM> will be described below.

As shown in <FIG>, the rubber member <NUM> is arranged on the outer surface of the core shaft <NUM>. Preferably, the rubber member <NUM> is formed by vulcanization in such a way of conforming to the contour of the outer surface of the core shaft <NUM>. The rubber member <NUM> is provided with two recesses, which are arranged radially opposite to each other. Said two recesses are arranged at a radially outer side of the flow channel groove <NUM> accordingly. The two recesses are configured to extend over a part of the whole circumferential direction, and located in a middle region of the rubber member <NUM> along the axial direction. The support ring <NUM> is arranged around the outer peripheral surface of the rubber member <NUM> accordingly, and completely covers the recesses of the rubber member <NUM>, thereby forming two sealed hydraulic chambers <NUM> between the support ring <NUM> and the rubber member <NUM>, which are arranged radially opposite to each other and used to accommodate hydraulic fluid.

In one embodiment, the rubber member <NUM> and the support ring <NUM> of the hydraulic composite bushing <NUM> can be designed as a structure consisting of multiple lobes, dependent on a thickness of the support ring <NUM>. As shown in <FIG>, the number of lobes of the hydraulic composite bushing <NUM> may be determined according to the amount of interference. This can further improve the performance of stiffness adjustment of the hydraulic composite bushing <NUM>.

In this embodiment, a first through hole and a second through hole are respectively formed in a side wall of the outer cover <NUM> and that of the support ring <NUM> both corresponding to the hydraulic chambers <NUM>. As shown in <FIG>, the first through hole is in communication with the second through hole, thus forming a liquid injection port <NUM> that is in communication with a respective hydraulic chamber <NUM>. The liquid injection port <NUM> is used to inject the hydraulic fluid into the hydraulic chamber <NUM>. The liquid injection port <NUM> is sealed with a high pressure ball plug <NUM>. The liquid injection port <NUM> can be opened by the high pressure ball plug <NUM>, in order to replenish the hydraulic fluid into the hydraulic chamber <NUM>. After that, the liquid injection port <NUM> can be effectively blocked by the high pressure ball plug <NUM>, thereby closing the liquid injection port <NUM>. The high pressure ball plug <NUM> can effectively seal the liquid injection port <NUM>, which is very beneficial to improve the sealing reliability of the hydraulic chamber <NUM>.

According to the present invention, a flow channel pipe <NUM> is arranged in the flow channel groove <NUM>. The flow channel pipe <NUM> is arranged in the flow channel groove <NUM>, so as to extend around the core shaft <NUM> in a spiral manner. Two ends of the flow channel pipe <NUM> pass through the rubber member <NUM> along the radial direction thereof, respectively, to extend into the hydraulic chambers <NUM>, so that said two hydraulic chambers <NUM> are in communication with each other through the flow channel pipe <NUM>. The flow channel pipe <NUM> can be made of copper tube, stainless steel tube, plastic tube or the like, which can effectively improve the stiffness of the flow channel pipe <NUM>. Therefore, by arranging the flow channel pipe <NUM> for liquid flow in the flow channel groove <NUM>, lateral displacement of the liquid in the flow channel groove <NUM> can be effectively avoided, so that the sealing effect of the overall structure of the hydraulic composite bushing <NUM> is significantly enhanced.

In order to facilitate the installation and engagement between the flow channel pipe <NUM> and the flow channel groove <NUM> to enhance the structural strength of the tubular body of the flow channel pipe <NUM>, the bottom of the flow channel groove <NUM> is configured as a semicircle structure, which corresponds to the cross section of the tubular body of the flow channel pipe <NUM>. The top of the flow channel groove <NUM> is configured as a square groove, which has a width equal to a diameter of the tubular body of the flow channel pipe <NUM>. The overall depth of the flow channel groove <NUM> is greater than the diameter of the tubular body of the flow channel pipe <NUM>. In this manner, it can ensure that more plastic will enter into the flow channel groove <NUM> during injection, thereby effectively fixing the tubular body of the flow channel pipe <NUM>. In the meantime, when a pressing sleeve <NUM> is subjected to a larger shock load, more load can be distributed on a metal spacer of the core shaft, thereby effectively protecting the flow channel pipe <NUM>.

In this embodiment, a pressing sleeve <NUM> is provided between the core shaft <NUM> and the rubber member <NUM> in the radial direction. As shown in <FIG>, the pressing sleeve <NUM> is disposed on an area of the outer surface of the core shaft <NUM> where the flow channel groove <NUM> is provided. In one embodiment, an annular recess is provided on the outer peripheral surface of the core shaft <NUM>, and the flow channel groove <NUM> is arranged at the bottom of the annular recess. The pressing sleeve <NUM> is arranged in the annular recess, and has an outer diameter equal to the outer diameter of the core shaft <NUM>. In this manner, the outer peripheral surface of the press sleeve <NUM> is flush with that of the core shaft <NUM>. The pressing sleeve <NUM> can apply on the flow channel pipe <NUM> a mounting pressure, which is directed radially inward. The axial length of the pressing sleeve <NUM> is greater than the length of the flow channel pipe <NUM> extending in the axial direction, so as to ensure that the flow channel pipe <NUM> is totally pressed by the pressing sleeve <NUM>. In addition, both ends of the flow channel pipe <NUM> are arranged to pass through the pressing sleeve <NUM> in the radial direction thereof, and then continue to extend along the radial direction of the rubber member <NUM> to pass therethrough, until the ends of the flow channel pipe <NUM> extend into the respective hydraulic chambers <NUM>. In one embodiment, the pressing sleeve <NUM> may be made of plastic, rubber, polyurethane material or the like, and formed on the outer surface of the core shaft <NUM> by injection molding.

In order to increase the bonding area between the rubber member <NUM> and the pressing sleeve <NUM> to enhance the bonding strength therebetween, a groove can be formed on an outer surface of the pressing sleeve <NUM>. The groove may have a cross-sectional shape of ellipse, square, or the like.

In practical applications, when the rail vehicle is under some special working conditions, the movement of the wheels will drive the core shaft <NUM> and the outer cover <NUM> to move relative to each other, so that the hydraulic chamber <NUM> in the front and the hydraulic chamber <NUM> in the rear will experience expansion and contraction, respectively. In this way, the hydraulic fluid can flow between the two hydraulic chambers <NUM>, so that the stiffness of the hydraulic composite bushing <NUM> can be adjusted accordingly. As a result, the rail vehicle can keep running stably. This varying stiffness is an important property of the hydraulic composite bushing <NUM>. These features and functions of the hydraulic composite bushing <NUM> are known in the art, which can be known, for example, from <CIT> of the same applicant, which is incorporated herein by reference.

According to the present invention, the hydraulic composite bushing <NUM> also includes a sealing device <NUM>. As shown in <FIG>, the sealing device <NUM> is arranged at each end of the flow channel pipe <NUM>, in order to form a seal between the flow channel pipe <NUM> and the flow channel groove <NUM> of the core shaft <NUM>, thereby avoiding leakage of hydraulic fluid. In addition, the sealing device <NUM> can effectively prevent each end of the flow channel pipe <NUM> from being bent and deformed due to the internal pressure of a mold cavity during the injection molding and the vulcanization of the rubber member <NUM>.

As shown in <FIG>, the sealing device <NUM> includes a cylindrical sealing body <NUM>. A mounting portion <NUM>, which is a through hole penetrating the sealing body <NUM> in the axial direction, is arranged in the sealing body <NUM> for receiving the flow channel pipe <NUM>. The sealing body <NUM> is further provided with a rectangular through hole <NUM> extending in the radial direction. The end of the flow channel pipe <NUM> extends over the rectangular through hole <NUM> along the axial direction of the sealing body <NUM> to be fitted within the mounting portion <NUM>. Therefore, the sealing device <NUM> can be mounted at each end of the flow channel pipe <NUM>. A first end of the sealing body <NUM> is fitted within the flow channel groove <NUM>, and a second end thereof passes through the pressing sleeve <NUM> and the rubber member <NUM> in sequence to extend into the hydraulic chamber <NUM>. During the injection molding, the pressing sleeve <NUM> disposed between the core shaft <NUM> and the rubber member <NUM> will completely fill the rectangular through hole <NUM>, and thus entirely enclose the flow channel pipe <NUM>. Therefore, an effective seal is formed between the flow channel pipe <NUM> and the sealing body <NUM>, thus effectively preventing the liquid from entering the gap between the flow channel pipe <NUM> and the flow channel groove <NUM> to cause leakage. In this manner, the flow channel pipe <NUM> and the flow channel groove <NUM> are sealed by the sealing device <NUM>. The structure of the sealing device <NUM> effectively improves the sealing reliability of the flow channel pipe <NUM>, the hydraulic chamber <NUM> and the connecting area therebetween, which is very beneficial to enhance the sealing performance between the flow channel pipe <NUM> and the flow channel groove <NUM>. Moreover, it is also convenient to mount the sealing device <NUM>.

In one embodiment, a filter element <NUM> is provided at each end of the flow channel pipe <NUM>. The filter element <NUM> can be, for example, a filter screen, which has a lower end surface that can be positioned through an end face of the rectangular through hole <NUM>, and an upper end surface that is flush with an upper end face of the sealing body <NUM>. The filter element <NUM> can effectively prevent debris generated inside the hydraulic chambers <NUM> from clogging the flow channel pipe <NUM> in operation.

In order to prevent rubber material from penetrating into the flow channel pipe <NUM> to cause blockage during the vulcanization of the rubber member <NUM>, the end of the flow channel pipe <NUM> extending into the hydraulic chamber <NUM> is arranged to extend over a radially inner wall surface of the hydraulic chamber <NUM>. In particular, said end extends over the radially inner wall surface of the hydraulic chamber <NUM> by at least <NUM>. This stepped layer structure can enlarge the engagement area between the sealing device <NUM> and the injection mold for vulcanization, and in particular, effectively prevent the blockage caused by the penetration of the rubber material into the flow channel pipe <NUM> during the vulcanization.

In this embodiment, a key slot is provided at each end of the flow channel groove <NUM> of the core shaft <NUM>. An end face of the first end of the sealing body <NUM> is configured to be fitted with a bottom face of the key slot, so that said end face of the first end of the sealing body <NUM> can closely contact with the bottom face of the key slot. Preferably, the end face of the first end of the sealing body <NUM> and the bottom face of the key slot can be configured as arc-shaped curved surfaces engaged with each other. In this way, the sealing device <NUM> can be effectively mounted and fixed, and an effective seal can be formed between the sealing device <NUM> and the flow channel groove <NUM>. Thus, the sealing performance between the flow channel pipe <NUM> and the flow channel groove <NUM> can be further improved, and leakage caused by the hydraulic fluid flowing between the flow channel pipe <NUM> and the flow channel groove <NUM> can be effectively avoided.

According to the present invention, the rubber member <NUM> is configured to conform to the outer contour of the core shaft <NUM>. In addition, the core shaft <NUM>, the support ring <NUM> and the pressing sleeve <NUM> are formed into one piece by vulcanization, which effectively enhances the overall performance of the hydraulic composite bushing <NUM>. The core shaft <NUM> may have different structures, and the specific structures of the core shaft <NUM> and the rubber member <NUM> according to different embodiments will be described in detail below.

<FIG> show the structure of the hydraulic composite bushing <NUM> according to one embodiment of the present invention. As shown in <FIG>, the core shaft <NUM> is configured as a stepped shaft with a central projecting portion. Each axial end of the central projecting portion is form as a conical surface, so that each axial end of the central projecting portion of the core shaft <NUM> has a diameter gradually increasing from the axial end to a middle region between two conical surfaces of the central projecting portion, but the middle region has an unchanged diameter. The flow channel groove <NUM> is provided in the axial middle region of the central projecting portion, and each end of the flow channel groove <NUM> terminates axially inner of a corresponding conical surface.

In this embodiment, the rubber member <NUM> is formed by vulcanization in a manner of conforming to the outer surface contour of the core shaft <NUM>, whereby the rubber member <NUM> forms the same structure as the outer contour of the core shaft <NUM>. That is, two axial ends of the rubber member <NUM> each form a conical surface, while the middle region thereof forms a cylindrical surface, so that the rubber member <NUM> forms a substantially V-shaped structure on the end surface along the diameter direction of the core shaft <NUM> (as shown in <FIG>). In addition, two recesses extend radially inward, and are disposed diametrically opposite to each other in the axial middle region of the rubber member <NUM>, so that they are located radially outer of the flow channel groove <NUM> of the core shaft <NUM> accordingly. The V-shaped structure of the rubber member <NUM> can realize a flexible adjustment on the stiffness of three directions, i.e., the hollow radial direction, the solid radial direction and the axial direction, in the overall structure, thus effectively improving the fatigue performance of the product.

As shown in <FIG>, the support ring <NUM> includes a cylindrical support ring body <NUM>, and a cover plate <NUM> fitted to the support ring body <NUM>. The inner sidewall of the support ring <NUM> is configured to have a diameter increasing from each end toward the middle region in the axial direction, so that the surface of the inner sidewall of the support ring <NUM> is configured to be able to, at each end thereof, fit with the V-shaped conical surface of each end of the rubber member <NUM>. The support ring body <NUM> is arranged on the outer peripheral surface of the rubber member <NUM>, and the cover plate <NUM> and the support ring body <NUM> are fitted with each other in a sealing manner, so that the support ring <NUM> covers the recesses to form the hydraulic chambers <NUM>. In the sidewall region of the support ring body <NUM> corresponding to each recess is formed with a stepped hole, which penetrates the sidewall of the support ring body <NUM>, with a rubber layer <NUM> vulcanized on a stepped face of the stepped hole. The cover plate <NUM> is adaptively mounted in the stepped hole, and in particular fitted with the stepped face of the stepped hole vulcanized with the rubber layer <NUM> to completely cover the corresponding recess, so that the hydraulic chamber <NUM> is formed between the support ring <NUM> and the rubber member <NUM>. The outer cover <NUM> is arranged around the support ring <NUM> from a radially outer side thereof through an interference fit, in order to form a press-fit seal on the support ring body <NUM> and the cover plate <NUM>. Therefore, the rubber member <NUM>, the support ring body <NUM> and the cover plate <NUM> jointly form a seal for the hydraulic chambers <NUM>.

According to the present invention, the cover plate <NUM> covers the recess to form the hydraulic chamber <NUM> together with the recess. A radial protrusion <NUM> extending radially outward is provided in the middle of each recess, and has a maximum outer diameter smaller than the maximum outer diameter of the rubber member <NUM>. In addition, each hydraulic chamber <NUM> has a radial thickness in a central region along the circumferential direction which is smaller than that in each of two side regions along the circumferential direction, and has a radial thickness in a central region along the axial direction which is smaller than that in each of two side regions along the axial direction. The radial protrusion <NUM> can restrict the scope of relative movement between the outer cover <NUM> and the core shaft <NUM>, so as to achieve secondary stiffness.

<FIG> show the structure of a hydraulic composite bushing <NUM> according to another embodiment of the present invention. As shown in <FIG>, a core shaft <NUM> is configured as a stepped shaft having a central projecting portion, which has an annular protrusion <NUM> extending radially outward at each of both axial ends of the central projecting portion. A flow channel groove <NUM> is formed in an axial middle part of the central projecting portion, and located between two annular protrusions <NUM> in the axial direction. Each end of the flow channel groove <NUM> terminates axially inner of a corresponding annular protrusion <NUM>.

In this embodiment, a rubber member <NUM> is disposed between the two annular protrusions <NUM> along the axial direction. The rubber member <NUM> is formed on the outer peripheral surface of the core shaft <NUM> by vulcanization, in a manner of conforming to the outer contour of the core shaft <NUM>, so that the rubber member <NUM> has the same structure as the outer contour of the core shaft <NUM>. In addition, a pressing sleeve <NUM> is formed on the outer circumference of the core shaft <NUM> in a middle region thereof, for pressing a flow channel pipe <NUM> into a spiral flow channel groove <NUM> formed in the surface of the core shaft <NUM>. Two recesses extend radially inward, and are arranged in an axial middle region of the rubber member <NUM> in a manner of diametrically opposite to each other, so that they are located radially outside of the flow channel groove <NUM> on the core shaft <NUM>.

As shown in <FIG>, a support ring <NUM> includes a cylindrical support ring body <NUM>, and a cover plate <NUM> fitted to the support ring body <NUM>. The support ring <NUM> is bonded with the core shaft <NUM> into one piece through vulcanization. In the sidewall region of the support ring body <NUM> corresponding to each recess is formed with a stepped hole, which penetrates the sidewall of the support ring body <NUM>, with a rubber layer vulcanized on a stepped face of the stepped hole. The cover plate <NUM> is adaptively mounted in the stepped hole, and in particular fitted with the stepped face of the stepped hole vulcanized with the rubber layer to completely cover the corresponding recess, so that a hydraulic chamber <NUM> is formed between the support ring <NUM> and the rubber member <NUM>. An outer cover <NUM> is arranged around the support ring <NUM> from a radially outer side thereof through an interference fit, in order to form a press-fit seal on the support ring body <NUM> and the cover plate <NUM>. Therefore, the rubber member <NUM>, the support ring body <NUM> and the cover plate <NUM> jointly form a seal for the hydraulic chambers <NUM>. The structure of the support ring <NUM> can not only effectively ensure the sealing property of the hydraulic chamber <NUM>, but also enhance the integrity of the support ring <NUM> and the rubber member <NUM>, which further enhances the stiffness performance of the hydraulic composite bushing <NUM>, thereby ensuring stable operation of the train.

In the present embodiment, a radial protrusion <NUM> extending radially outward is provided in the sidewall region of the cover plate <NUM> corresponding to the hydraulic chamber <NUM>, and has an inner diameter larger than the inner diameter of the hydraulic chamber <NUM>. In this manner, each hydraulic chamber <NUM> has a radial thickness in a central region along the circumferential direction which is smaller than that in each of two side regions along the circumferential direction, and has a radial thickness in a central region along the axial direction which is smaller than that in each of two side regions along the axial direction. The radial protrusion <NUM> can similarly restrict the scope of relative movement between the outer cover <NUM> and the core shaft <NUM>, so as to achieve secondary stiffness.

According to the present invention, under different operating conditions of the hydraulic composite bushing <NUM>, the hydraulic composite bushing <NUM> can achieve a preset ratio λn of dynamic stiffness to static stiffness at a preset threshold frequency fn, wherein λn=Ks/Kd and is not less than <NUM>. <FIG> is a schematic diagram showing stiffness of the hydraulic composite bushing <NUM>. To this end, the flow channel pipe <NUM> or the hydraulic chamber <NUM> should meet the following conditions, that is, a ratio β of length to diameter of the flow channel pipe <NUM> at each preset threshold frequency f should satisfy the following relationship: <MAT> <MAT> and <MAT> For example, eight preset threshold frequencies are <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, respectively, and β at each frequency is: β<NUM>, β<NUM>, β<NUM>, β<NUM>, β<NUM>, β<NUM>, β<NUM> and β<NUM>. In order to achieve a predetermined λn at a preset threshold frequency fn, β at each frequency must satisfy: β<NUM>>β<NUM>>β<NUM>>β<NUM>>β<NUM>>β<NUM>>β<NUM>>β<NUM>, and β<NUM>-β<NUM>>β<NUM>-β<NUM>>. >β<NUM>-β<NUM>>β<NUM>-β<NUM>.

At the same time, an equivalent piston area S of each hydraulic chamber <NUM> under each preset λn should satisfy the following relationship: <MAT> and <MAT> wherein: fn is the threshold frequency of the hydraulic composite bushing; λn is the ratio of dynamic stiffness to static stiffness of the hydraulic composite bushing; n is a non-zero natural number; fn and λn are each an increasing arithmetic progression; L is the length of the flow channel pipe; D is the hydraulic diameter of the flow channel pipe; βn is the ratio of length to diameter of the flow channel pipe; and Sn is the equivalent piston area of the hydraulic chamber.

A sealing method for the hydraulic composite bush according to the present invention is described below. First, the flow channel pipe <NUM> is arranged in the flow channel groove <NUM>, presenting a spiral shape. The sealing device <NUM> is fixedly mounted at each end of the flow channel pipe <NUM>. Specifically, the end of the flow channel pipe <NUM> is mounted in the mounting portion <NUM> after extending over the rectangular through hole <NUM>, and aligned with the second end of the sealing body <NUM>. Subsequently, the pressing sleeve <NUM> is formed on the outer peripheral surface of the core shaft <NUM> by injection molding. During the injection molding, both ends of the flow channel tube <NUM> are exposed to pass through the pressing sleeve <NUM> in the radial direction, and the first end face of the sealing device <NUM> is formed as an arc-shaped surface, which corresponds to the key slot in the flow channel groove <NUM> and thus forms a tight fit therewith. At the same time, the pressing sleeve <NUM> fills the rectangular through hole <NUM> in the sealing device <NUM> to enclose the flow channel pipe <NUM> during the injection molding, thereby forming a seal between the flow channel pipe <NUM> and the flow channel groove <NUM>. After that, rubber is vulcanized on the outer peripheral surface of the core shaft <NUM> to form the rubber member <NUM>, so that the hydraulic chambers <NUM> are formed inside the rubber member <NUM>. During the vulcanization, the sealing device <NUM> radially passes through the rubber member <NUM> to extend into the hydraulic chambers <NUM>, with the length of the second end of the sealing device <NUM> extending into the hydraulic chambers <NUM> not less than <NUM>. This can effectively prevent both ends of the flow channel pipe <NUM> from being bent and deformed due to the internal pressure of a mold cavity during the injection molding and the vulcanization, and also effectively prevent the blockage caused by the penetration of the rubber material into the flow channel pipe <NUM> during the vulcanization of the rubber member <NUM>. Then, the support ring <NUM> and the core shaft <NUM> are bonded into one piece by vulcanization, and a rubber layer <NUM> is vulcanized on the stepped face of the stepped hole of the support ring body <NUM>, and then the cover plate <NUM> is placed to cover the recess completely, so that the hydraulic chamber <NUM> is formed between the support ring <NUM> and the rubber member <NUM>. Finally, the outer cover <NUM> is placed on the support ring <NUM> from the radially outer side thereof through interference fit, thus forming a press-fit seal on the support ring body <NUM> and the cover plate <NUM>. Therefore, the rubber member <NUM>, the support ring <NUM> and the cover plate <NUM> jointly form a seal for the hydraulic chambers <NUM>. In this manner, the hydraulic composite bushing <NUM> is completed, with sealing effect achieved for the flow channel pipe <NUM>, the hydraulic chambers <NUM> and connections thereof.

According to the present invention, two radially opposite hydraulic chambers <NUM> of the hydraulic composite bushing <NUM> are in communication with each other through the flow channel pipe <NUM> arranged in a spiral shape, so that the hydraulic composite bushing <NUM> can realize stiffness adjustments in the radial hollow direction, the radial real direction and the axial direction. Therefore, the performance of stiffness adjustment of the hydraulic composite bushing <NUM> is greatly enhanced, and the fatigue performance of the product is effectively improved. The flow channel pipe <NUM> and the flow channel groove <NUM> are sealed relative to each other by the sealing device <NUM>. The sealing device <NUM> significantly enhances the sealing performance between the flow channel pipe <NUM> and the flow channel groove <NUM>, thereby effectively preventing leakage caused by flow of the hydraulic fluid in the gap formed between the flow channel pipe <NUM> and the flow channel groove <NUM>. In addition, the procedure of arrangement and installation of the flow channel pipe <NUM> and the sealing device is simple and convenient. Moreover, the core shaft <NUM>, the support ring <NUM> and the pressing sleeve <NUM> are integrally formed by vulcanization, which significantly enhances the integrity and stiffness of the hydraulic composite bushing <NUM>, improves the flexibility of the stiffness adjustment of the hydraulic composite bushing <NUM>, and effectively prolongs the service life of the hydraulic composite bushing <NUM>. The sealing method for the hydraulic composite bushing according to the present invention requires a simple structure only, can meet high stiffness requirements, improve the sealing performance, prolong the service life, and has high production efficiency, which is suitable for mass production.

Claim 1:
A hydraulic composite bushing, comprising:
a core shaft (<NUM>), an outer surface of which is provided with a flow channel groove (<NUM>) continuously extending in a spiral shape;
a rubber member (<NUM>), arranged on the core shaft and provided with two recesses diametrically opposite to each other, the recesses being arranged radially outside of the flow channel groove;
a support ring (<NUM>), arranged around the rubber member, and covering the recesses to form two hydraulic chambers (<NUM>) for accommodating hydraulic fluid;
a outer cover (<NUM>) press-fitted on the support ring from a radially outer side thereof; characterised in that the hydraulic composite bushing is further comprising:
a sealing device (<NUM>) mounted at an end of a flow channel pipe (<NUM>) arranged in the flow channel groove,
wherein two ends of the flow channel pipe pass through the rubber member along a radial direction to extend into said two hydraulic chambers, respectively, so that said two hydraulic chambers are in communication with each other through the flow channel pipe, and
the sealing device is arranged at each end of the flow channel pipe, wherein one end of the sealing device is arranged in the flow channel groove while the other end thereof passes through the rubber member to extend into a corresponding hydraulic chamber, thus forming a seal between the flow channel pipe and the flow channel groove.