shock absorbers

Abstract

Shock absorbers (1, 101), comprising: a cylinder (2; 102) in which a hydraulic fluid is enclosed; a piston (3; 105) which is slidably fitted into the cylinder (2; 102); a piston rod (4; 106) connected to the piston (3; 105) and extending from the cylinder (2; 102); and a damping force generation mechanism (8; 125) which generates a damping force by controlling a flow of the hydraulic fluid caused by the sliding motion of the piston (3; 105); wherein the damping force generation mechanism (8; 125) comprises: an annular disc valve (14; 147); an annular elastic sealing element (15; 148) which is integrally provided on a rear surface of the disc valve (14; 147); a cylindrical housing element (10; 134) having a base and an inner circumferential surface (10A, 134B) into which the elastic sealing element (15; 148) is slidably fitted to form a back pressure chamber (16; 155) on a rear side of the disc valve (14; 147); and a shaft section (4A; 133A) having a circular outer circumference, wherein the shaft section (4A, 133A) is arranged in a common center of the disc valve (14; 147) and the bottom of the housing element (10; 134); wherein the disc valve (14; 147) has an inner circumferential section and an outer circumferential section and is attached to the housing element (10, 134) in such a way that it can be opened at the outer circumferential section by being clamped axially to the inner circumferential section thereof; wherein a free space (C) to accommodate a misalignment between a center of the disc valve (14; 147) and a center of the shaft section (4A; 133A) at the time of clamping between the inner circumferential section of the disc valve (14; 147) and the outer circumference of the shaft section (4A; 133A) over an entire circumference of the shaft section (4A; 133A), and the free space is not connected to the counter-pressure chamber (16; 155).

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to shock absorbers that generate fluid pressure by using a damping force.

[0002] Shock absorbers, which are attached to the suspension systems of automobiles or other vehicles, generally have the following design. A piston, connected to a piston rod, slides within a cylinder containing a fluid. A stroke of the piston rod causes the piston to slide within the cylinder, which in turn results in a flow of fluid. The fluid flow is controlled by a damping force control mechanism, which includes an orifice, a disc valve, etc., thereby generating a damping force.

[0003] A hydraulic shock absorber, disclosed, for example, in the published JP 2006-10 069 A, features a backpressure chamber (control chamber) located in the rear region of a main disc valve, which forms a damping force generation mechanism. A portion of the fluid flow is introduced into the backpressure chamber, and the pressure within the chamber is applied to the main disc valve in the direction of valve closure. The pressure in the backpressure chamber is adjusted by means of a pilot valve or control valve, thereby controlling the opening of the main disc valve. This technique allows for increased degrees of freedom in adjusting the damping force characteristics or damping force curves.

[0004] In the shock absorber disclosed in published JP 2006-10 069 A, an annular oil seal (elastic sealing element) is attached to the rear surface of the main disc valve. The oil seal is slidably and gas-tightly fitted into a circular cylindrical section of a valve element in the form of a circular cylinder, one end of which is closed, thus forming a back-pressure chamber. This structure must increase the sliding and sealing properties between the cylindrical section and the valve element, and between the valve element and the oil seal, to allow the main disc valve to open and close smoothly and without difficulty, thereby maintaining a stable damping force characteristic. It should be noted that if such a structure is used, in which an inner circumferential section of the main disc valve is secured by axial clamping (see Fig. 4 and Fig. 10 of JP 2006-10 069 A), it is necessary to increase the coaxiality between the oil seal, the main disc valve and the valve element in order to increase the sliding ability and sealing ability between the cylindrical section and the valve element and the oil seal.

[0005] Further shock absorbers are shown in DE 60 2005 006 044 T2, DE 10 2011 004 740 A1 and JP 2007 - 100 726 A. SUMMARY OF THE INVENTION

[0006] However, to increase the coaxiality between the three elements—the oil seal, the main disc valve, and the valve element—it is necessary to control the dimensions of each element with high precision. This leads to reduced productivity and increased manufacturing costs. To maintain a stable damping force characteristic while generating a low damping force, the sliding resistance must be minimized, and sealing capability must be ensured while reducing the interaction between the oil seal and the cylindrical section of the valve element. Therefore, high dimensional accuracy and high coaxiality are required.

[0007] It is an object of the present invention to provide a shock absorber designed to increase the sliding and sealing capability of an elastic element formed on the rear surface of a disc valve to form a counter-pressure chamber, while reducing the coaxiality requirements for each part of a damping force generation mechanism.

[0008] To solve the problem described above, the present invention provides a shock absorber comprising a cylinder in which a fluid is enclosed, a piston slidably fitted into the cylinder, a piston rod connected to the piston and extending out of the cylinder, and a damping force generation mechanism that generates a damping force by controlling the flow of the hydraulic fluid brought about by the sliding movement of the piston.The damping force generation mechanism comprises an annular disc valve, an annular elastic sealing element integrally formed on the rear surface of the disc valve, a cylindrical housing element having a base and an inner circumferential surface into which the elastic sealing element is slidably fitted to form a back pressure chamber at the rear of the disc valve, and a shaft section having a circular outer circumference located at the common center of the disc valve and the base of the housing element. The disc valve is attached to the housing element by axial clamping it to the inner circumferential section thereof. A clearance is formed between the inner circumferential section of the disc valve and the outer circumference of the shaft section over substantially the entire circumference of the shaft section. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows an enlarged vertical sectional view showing a piston section of a shock absorber according to a first embodiment of the present invention. Fig. Figure 2 is a vertical sectional view of a shock absorber according to a second embodiment of the present invention. Fig. Figure 3 is an enlarged vertical sectional view of a damping force generation mechanism of the in Fig. 2 shock absorbers shown. Fig. 4 is an enlarged vertical sectional view of a disc valve of the in Fig. 1 shock absorber shown. Fig. Figure 5 is an enlarged vertical sectional view of a disc valve of the damping force generation mechanism, which is located in Fig. 3 is shown. DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0010] A first embodiment of the present invention is described with reference to Fig. 1 and Fig. 4 described. As in Fig. As shown in Figure 1, a shock absorber 1 according to this embodiment is a monotube hydraulic shock absorber attached to a suspension system of an automobile or other vehicle. A piston 3 is slidably fitted into a cylinder 2 (only a portion of one side wall of which is shown) in which hydraulic oil is enclosed as a hydraulic fluid. The piston 3 divides the interior of the cylinder 2 into two chambers, i.e., an upper cylinder chamber 2A and a lower cylinder chamber 2B. The piston 3 is connected to a shaft section 4A at one end of the piston rod 4 by means of a nut 5. The other end of the piston rod 4 extends outwards from the cylinder by means of a rod guide (not shown) and an oil seal (not shown) fitted into the upper end of the cylinder 2. The lower cylinder chamber 2B is connected to a reservoir (not shown) by means of a base valve (not shown) having a suitable flow resistance.The container holds hydraulic oil and a gas inside.

[0011] The piston 3 is provided with an extension line 6 and a displacement line 7 for connecting the upper and lower cylinder chambers 2A and 2B. An extension damping force generation mechanism 8 is provided at one end of the piston 3, which is closer to the lower cylinder chamber 2B, to control a damping force by controlling the flow of hydraulic oil through the extension line 6. A displacement damping force generation mechanism 9 is provided at one end of the piston 3, which is closer to the upper cylinder chamber 2A, to control a damping force by controlling the flow of hydraulic oil through the displacement line 7.

[0012] The extension damping force generation mechanism 8 is described with reference to Fig. 4 described.

[0013] The extension damping force generation mechanism 8 has a valve element 10 as a housing element in the form of a cylinder, one end of which is closed. The valve element 10 is attached to the end of the piston 3 that is closer to the lower cylinder chamber 2B. The valve element 10 is formed with an insertion hole 10B. The insertion hole 10B extends through a circular, cylindrical retaining section 11, which is located at the center of the inner surface of the valve element 10. The piston rod 4 has a small-diameter shaft section 4A at its proximal end, which has a circular outer circumference. The insertion hole 10B receives the small-diameter shaft section 4A. The valve element 10 is attached to the piston 3 by screwing a nut 5 onto the small-diameter shaft section 4A.

[0014] The piston 3 has an annular seat section 12 extending from an outer circumferential position at an end surface closer to the lower cylinder chamber 2B. The piston 3 also has an annular clamping section 13 extending from an inner circumferential position at the lower cylinder chamber side end surface. An annular space is formed between the seat section 12 and the clamping section 13. The extension pipe 6 opens into this annular space.

[0015] An inner circumferential section of an annular, flexible disc valve 14 is clamped between the retaining section 11 and the clamping section 13. An outer circumferential section of the disc valve 14 sits on the seat section 12. The disc valve 14 has an annular elastic sealing element 15, which is integrally formed on an outer circumferential section of the rear surface of the disc valve 14, thus forming a sealed disc valve. An outer circumferential section of the elastic sealing element 15 slidably and fluid-tightly abuts the inner circumferential surface 10A of the cylindrical section of the valve element 10 to form a back pressure chamber 16 in the valve element 10.

[0016] The disc valve 14 has openings 17 provided on its inner circumferential section. A separating disc element 19 and a disc element 20 are stacked on one end of the disc valve 14 that is closer to the clamping section 13. The separating disc element 19 has a plurality of cut sections 18 (openings) at positions that point towards the openings 17. The openings 17 and the cut sections 18 form a backpressure chamber inlet line 21 that connects the extension line 6 and the backpressure chamber 16 at all times. When the disc valve 14 tilts to lift off the seat section 12, it simultaneously lifts off the separating disc element 19. Consequently, the flow path area of ​​the backpressure chamber inlet line 21 increases.The separating disc element 19 and the disc element 20 are fastened by clamping them axially between the clamping section 13 of the piston 3 and the distal end of the retaining section 14 of the valve element 10, together with the disc valve 14. Hereinafter, the separating disc element 19 and the disc element are referred to together as "washer 180".

[0017] The elastic sealing element 15 is made of an elastic material, for example, rubber, and is attached to the disc valve 14 by vulcanization, bonding, or the like. The outer circumference of the elastic sealing element 15 is inclined such that its diameter increases with the distance to the disc valve 14 to which the sealing element 15 is attached. The outer circumference of the elastic sealing element 15 is in sliding contact with the inner circumferential surface 10A of the cylindrical section of the valve element 10. The outer circumference of the elastic sealing element 15 is formed from a plurality of concentrically arranged steps to create a multi-stage seal in the area of ​​sliding contact with the inner circumferential surface 10A. The outer diameter of the elastic sealing element 15 is larger than the diameter of the inner circumferential surface 10A.Consequently, an interference fit F is formed between the elastic sealing element 15 and the inner circumferential surface 10A. The inner diameter of the disc valve 14 is sufficiently larger than the outer diameter of the shaft section 4A, which is located at the common center of the disc valve 14 and the valve element 10, and also sufficiently larger than the diameter of the insertion hole 10B of the valve element 10. Therefore, a clearance C is formed between the shaft section 4A and the disc valve 14 over the entire circumference of the shaft section 4A. That is, the radial positioning of the disc valve 14 is achieved by fitting the outer circumference of the elastic sealing element 15 and the inner circumferential surface 10A of the valve element 10 together by means of the interference fit F.Any misalignment between the respective centers of the inner circumference of the disc valve 14 and the inner circumference of the valve element 10 is accommodated by the clearance C. The disc valve 14 is thus positioned radially, and the inner circumferential section of the disc valve 14 is axially clamped and secured in this state by tightening the nut 5, which serves as a fastening element.

[0018] In the preceding explanation, the clearance C between the inner circumference of the disc valve 14 and the outer circumference of the shaft section 4A was formed over the entire circumference of the shaft section 4A. However, in practice, an isolated case may occur where a region without clearance (i.e., a region with zero clearance) appears locally in the circumferential direction due to slight radial displacement of the disc valve 14 during tightening of the nut 5, or due to dimensional tolerances, etc. Nevertheless, the sliding and sealing performance of the elastic sealing element 15 can be improved compared to conventional techniques, provided that the clearance is formed over substantially the entire circumference of the shaft section 4A according to the design concept.

[0019] The minimum value Dmin of the inner diameter of the disc valve 14 can be obtained using the following equation: Dmin=dmax+(Z1+Z2) where: dmax: the maximum diameter of the shaft section 4A of the piston rod 4 is; Zl: the coaxiality between the inner circumference of the disc valve 14 and the outer circumference of the elastic sealing element 15 is; Z2: the coaxiality between the inner circumferential surface 10A of the valve element 10 and the inner circumferential surface 10B for fitting into the shaft section 4A of the piston rod 4 is.

[0020] The free space between the insertion hole 10B of the valve element 10 and the shaft section 4A of the piston rod 4 is neglected because it is small.

[0021] The base of the valve element 10 is provided with a line 22 for connecting the back pressure chamber 16 and the lower cylinder chamber 2B. The line 22 is equipped with a relief valve 23, which is a normally closed disc valve designed to release the hydraulic oil in the back pressure chamber into the lower cylinder chamber 2B when the pressure in the back pressure chamber 16 reaches a predetermined pressure. The relief valve 23 is provided with a downflow port 24 (cut-out section) that is constantly in communication with the back pressure chamber 16 and the lower cylinder chamber 2B. The relief valve 23 is further equipped with a check valve 25 that allows the flow of hydraulic oil only from the lower cylinder chamber 2B towards the back pressure chamber 16.Although the downflow opening 24 is provided by providing a cut-out section in a disc valve that forms the relief valve 23 and that abuts a seat section 10C of the valve element 10, the downflow opening 24 can also be formed by embossing the seat section 10C of the valve element 10.

[0022] Next, the displacement damping force generation mechanism 9 will be explained.

[0023] The displacement damping force generation mechanism 9 comprises a displacement line 7 and a disc valve 33. The displacement line 9 opens into an annular space formed between a seat section 30, which extends annularly from an outer circumferential position of an end surface of the piston 3 that is closer to the upper cylinder chamber 2A, and a clamp section 31, which extends annularly from an inner circumferential position of the upper cylinder chamber side end surface of the piston 3'.

[0024] The disc valve 33 has an outer circumferential section. The outer circumferential section of the disc valve 33 sits on the seat section 30. The disc valve 31 is clamped on an inner circumferential section of the outer circumferential section between the clamping section 31 and a stage section, which is formed at the proximal end of the shaft section 4A with an annular holder 32 that is clamped between the disc valve 33 and the stage section.

[0025] The disc valve 33 comprises a plurality of stacked circular, plate-shaped discs. The disc valve 33 is deflected to rise from the seat section 30 when pressure is drawn into the lower cylinder chamber 2B via the compression line 7. The disc valve 33 opens and adjusts the flow path of the displacement line 7 according to its degree of opening. The disc valve 33 is provided with an opening 33A (cut-out section) that is always connected between the upper and lower cylinder chambers 2A and 2B. The opening 33A comprises a cut-out section formed in the disc valve 33. The opening 33A can be replaced by a connecting line that is always connected between the upper and lower cylinder chambers 2A and 2B, which can be formed by embossing the seat section 30.

[0026] The following is an explanation of the operation of this embodiment, which is designed as described above.

[0027] During the extension stroke of the piston rod 4, the sliding movement of the piston 3 in the cylinder 2 causes the hydraulic oil in the upper cylinder chamber 2A to flow towards the lower cylinder chamber 2B via the extension line 6 in the piston 3, and a damping force is generated by the extension damping force generation mechanism 8. At this point, an amount of hydraulic oil equal to the amount by which the piston rod 4 leaves the cylinder 2 flows into the lower cylinder chamber 2B from the reservoir via the base valve, and the gas in the reservoir expands accordingly, thus compensating for a change in the volume of the hydraulic oil in the cylinder 2.

[0028] In the extension damping force generation mechanism 8, when the piston velocity is in a very low velocity range (i.e., in the initial stroke range of the piston rod 4), the backpressure chamber inlet line 21 and the downflow port 24 generate a damping force with opening characteristics. As the piston velocity increases, the valve 14 opens to generate a damping force with valve characteristics. At the same time as the disc valve 14 opens, the flow path area of ​​the backpressure chamber inlet line 21 increases, and the pressure in the backpressure chamber 16 increases. Consequently, as the piston velocity increases, the valve opening pressure of the disc valve 14 increases, and the damping force increases.When the pressure in the counter-pressure chamber 16 reaches a predetermined pressure, the relief valve 23 opens to release the pressure in the counter-pressure chamber 16 into the lower cylinder chamber 2B in order to prevent an excessive increase in the valve opening pressure of the disc valve 14, i.e. to prevent an excessive increase in the extension damping force.

[0029] During the displacement stroke of the piston rod 4, the sliding motion of the piston 3 in the cylinder 2 causes the hydraulic oil in the lower cylinder chamber 2b to flow towards the upper cylinder chamber 2A via the displacement line 7 in the piston 3, and a damping force is generated by means of the damping force generation mechanism 9. At this point, an amount of hydraulic oil equal to the amount by which the piston rod enters the cylinder 2 flows into the reservoir via the base valve and compresses the gas in the reservoir, thereby compensating for a change in the volume of the hydraulic oil in the cylinder 2.

[0030] In the damping force generation mechanism 9, the orifice 33A generates a damping force with opening characteristics when the piston velocity is in a low velocity range (before the disc valve 33 opens). When the piston velocity increases to reach the valve opening pressure of the disc valve 33, the disc valve 33 opens to generate a damping force with valve characteristics according to the degree of opening of the disc valve 33.

[0031] During the compression stroke in the damping force generation mechanism 8, the check valve 25 opens to introduce the pressure in the lower cylinder chamber 2B into the counter-pressure chamber 16. Consequently, the pressure in the counter-pressure chamber 16, acting on the disc valve 14 in the closing direction, becomes greater than the pressure in the lower cylinder chamber 2B, acting on the disc valve 14 in the opening direction. As a result, the extending disc valve 14 can be held securely closed, and a stable damping force can be maintained.

[0032] In the extension damping force generation mechanism 8, the outer diameter of the elastic sealing element 15 is larger than the inner diameter of the inner circumferential surface 10A of the cylindrical section of the valve element 10, creating an interference F between the elastic sealing element 15 and the cylindrical section of the valve element 10. Additionally, the inner diameter of the disc valve 14 is sufficiently larger than the outer diameter of the shaft section 4A of the piston rod 4 to create a clearance C between the disc valve 14 and the shaft section 4A. Therefore, the disc valve 14 aligns itself by fitting between the outer circumference of the elastic sealing element 15 and the inner circumferential surface 10A of the cylindrical section of the valve element 10. In this position, the disc valve 14 is axially clamped and secured by tightening the nut 5.Consequently, due to the clearance C, any misalignment between the respective centers of the outer circumference of the elastic sealing element 15, the inner circumference of the disc valve 14, the inner circumferential surface 10A of the cylindrical section of the valve element 10, and the inner circumference of the retaining section 11 is permissible. It is therefore possible to ensure sliding and sealing capability between the elastic sealing element 15 and the disc valve 14 and the inner circumferential surface 10A of the cylindrical section of the valve element 10, and thus stable damping force characteristics can be achieved. Additionally, since the requirements for dimensional tolerances and coaxiality are reduced, it is possible to increase productivity and reduce manufacturing costs.

[0033] Accordingly, when the disc valve 14 is mounted on the shaft section 4A, the inner circumferential surface 10A of the valve element 10 and the elastic sealing element 15 each form concentric circles. Furthermore, in this embodiment, the elastic sealing element 15 is attached to the disc valve 14 by means of vulcanization bonding. In this context, it is difficult to perform machining to maintain the coaxiality of the elastic sealing element 15 with respect to the disc valve 14. However, any coaxiality error due to the clearance C is permissible. Therefore, it is possible to reduce the machining time for vulcanization bonding.

[0034] Furthermore, in this embodiment, the clearance C formed between the inner circumference of the disc valve 14 and the outer circumference of the shaft section 4A of the piston rod 4 is larger than the clearance between the outer circumference of the shaft section 4A and the inner circumference of the washer 180, which comprises the separating disc element 19 and the disc element 20 stacked on the disc valve 14 when these forming elements are assembled together by means of the nut 5, which serves as a fastening or locking element. In this assembly, the washer 180 is positioned by being limited at its inner circumference by the inner circumference of the washer 180 and the outer circumference of the shaft section 4A.On the other side, the disc valve 14 is positioned by being limited at its outer circumference by the outer circumference of the elastic sealing element 15 and the inner circumferential surface 10A of the cylindrical section of the valve element 10.

[0035] Although in the aforementioned first embodiment only the extension damping force generation mechanism 8 is a counter-pressure damping force generation mechanism (control type) which has the counter-pressure chamber 16, the displacement damping force generation mechanism 9 can be a counter-pressure type damping force generation mechanism (control type) which has a counter-pressure chamber similar to that of the extension damping force generation mechanism 8.

[0036] Next, a second embodiment of the present invention will be described with reference to Fig. 2, Fig. 3 and Fig. 5 described.

[0037] As in Fig. As shown in Figure 2, a shock absorber 101 according to this embodiment has a dual-tube structure comprising a cylinder 102 and an outer tube 103 located outside the cylinder 102. A reservoir 104 is formed between the cylinder 102 and the outer tube 103. A piston 105 is slidably fitted into the cylinder 102. The piston 105 divides the interior of the cylinder 102 into two chambers, namely an upper cylinder chamber 102A and a lower cylinder chamber 102B. The piston 105 is connected to one end of the piston rod 106 by means of a nut 107. The other end section of the piston rod 106 extends through the upper cylinder chamber 102A and further through a rod guide 108 and an oil seal 109, which are fitted into the upper end section of the double tube structure comprising the cylinder 102 and the outer tube 103, and extends outwards from the cylinder 102.A base valve 110 is provided in the lower end section of the cylinder 102 to separate the lower cylinder chamber 102B and the container 104 from each other.

[0038] The piston 105 is provided with lines 111 and 112 for connecting the upper and lower cylinder chambers 102A and 102B. Line 112 is equipped with a check valve 113, which allows fluid flow only from the lower chamber 102B towards the upper cylinder chamber 102A. Line 111 is equipped with a disc valve 114, which opens when the fluid pressure in the upper cylinder chamber 102A reaches a predetermined pressure, in order to release the fluid pressure into the lower cylinder chamber 102B.

[0039] The base valve 110 is equipped with lines 115 and 116 for connecting the lower cylinder chamber 102B to the reservoir 104. Line 115 is fitted with a check valve 117, which allows fluid flow only from the reservoir 104 towards the lower cylinder chamber 102B. Line 116 is fitted with a butterfly valve 118, which opens when the fluid pressure in the lower cylinder chamber 102B reaches a predetermined pressure, releasing the fluid into the reservoir 104. A hydraulic oil is contained within the cylinder 102 as a hydraulic fluid, and the hydraulic oil and a gas are contained within the reservoir 104.

[0040] The cylinder 102 has a separating tube 120, which is fitted over it by means of sealing elements 119 arranged between the cylinder 102 at its lower and upper ends. An annular conduit 121 is formed between the cylinder 102 and the separating tube 120. The annular conduit 121 is connected to the upper cylinder chamber 102A via a conduit 122 located on a side wall of the cylinder 102 near its upper end. The separating tube 120 has a small-diameter opening section 123 extending from a lower section of its side wall. The side wall of the outer tube 103 has a large-diameter opening 124 located substantially concentrically with the opening section 123. A damping force-generating mechanism 125 is attached to the opening 124 in the side wall of the outer tube 103.

[0041] Next, the damping force generation mechanism 125 will be described primarily with reference to Fig. 3 explained.

[0042] As in Fig. As shown in Figure 3, the damping force generation mechanism 125 has a substantially circular, cylindrical housing 126, which is attached to the opening 124 of the outer tube 103. The housing 126 contains inside a control-type (back-pressure) main valve 127 and a control valve 128, which is a solenoid-operated pressure control valve that controls the valve opening pressure of the main valve 127. The damping force generation mechanism 125 also includes a fail-safe valve 129, which is located downstream of the control valve 128. The fail-safe valve 129 is operated in the event of a failure or fault.

[0043] The housing 126 comprises, extending from the opening side 124, an annular guide plate 130, a flanged cylindrical guide element 131, an annular main valve element 132, a flanged cylindrical opening guide element 133, a circular cylindrical control valve element 134 with a base in its center, an annular retaining element 135, and a circular cylindrical solenoid coil housing 136. These elements are arranged to abut one another and are fastened by connecting the coil housing 136 to the housing 126 by means of a nut 137.

[0044] The guide plate 130 is attached in close contact with an inwardly directed flange 126A formed on an end section of the housing 126. The guide plate 130 has a plurality of radially extending channels 138 (cut-out sections) that connect between the container 104 and a chamber 126B in the housing. The guide element 131 has a small-diameter section and a large-diameter section. The distal end of the small-diameter section is inserted through the guide plate 130, and the shoulder of the large-diameter section rests against the guide plate 130. In this way, the guide element 131 is secured. The proximal end section of the guide element 131 is fitted fluid-tight into the opening section 123 of the separating tube 120 with an interposed sealing element 139.The conductor element 131 has a conductor 140 which extends axially through it to connect with the annular conductor 121.

[0045] The main valve element 132 is attached, with one end section of it abutting the large-diameter section of the conduit element 131. A sealing element 143 seals between the abutting sections of the main valve element 132 and the conduit element 131. The main valve element 132 is provided with a plurality of circumferentially spaced conduits 144 extending axially through it. Conduits 144 are connected to the conduit 140 of the conduit element 131. The other end of the main valve element 132 has an annular seat section 135 extending from a position on the outer circumferential side of the openings of the conduits 144. Furthermore, the other end of the main valve element 132 has an annular clamping section 146 extending from a position on the inner circumferential side of the openings of the conduits 144.

[0046] An outer circumferential section of a disc valve 147, representing the main valve 127, sits on the seat section 145 of the main valve element 132. An inner circumferential section of the disc valve 147 is secured by clamping it axially between the clamping section 146 and the shoulder of a large-diameter section of the opening line element 133. An outer circumferential section of the rear surface of the disc valve 147 is integrally provided with an annular, elastic sealing element 148. The flanged, cylindrical opening line element 133 has a small-diameter shaft section 133A at one end. The small-diameter shaft section 133A fits into an opening in the center of the main valve element 132.The shoulder of the large-diameter section of the opening line element 133 rests against the disc valve 147, and a small-diameter shaft section 133B at the other end of the opening line element 133 is fitted into a port 152 at the center of the control valve element 134. The opening line element 133 is thus secured. The opening line element 133 has a line 149 extending axially through it. The line 149 is connected to the line 140 of the line element 131 via a fixed opening 150 formed in the distal end of the shaft section 133A.

[0047] The control valve element 134 has a cylindrical structure with a base 134A in its center. The control valve element 134 is mounted with one end of the base 134A abutting the opening line element 133. An outer circumferential section of the elastic sealing element 148 of the disc valve 147 is slidably and fluid-tightly fitted into an inner circumferential surface 134B of a circular, cylindrical section at one end of the control valve element 134, thereby forming a control chamber 151 at the rear of the disc valve 147. The disc valve 147 opens as soon as it receives pressure in the lines 134, allowing the lines 144 to communicate with the chamber 126B in the housing 126, which is located downstream of the disc valve 147. The pressure in the control chamber 151 acts on the disc valve 147 in the direction of closing the disc valve 147.Port 152 extends through the center of the base 134A of the control valve element 134. Port 152 is connected to line 149 of the opening line element 133. The control chamber 151 is connected to line 149 via lines 153, which extend axially through the large-diameter section of the opening line element 133. Lines 153, line 149, and the fixed opening 150 form an inlet line that introduces hydraulic oil into the control chamber 151.

[0048] The retaining element 135 has an annular projection 154 formed on an outer circumferential section at one end. The retaining element 135 is secured by the annular projection 154 bearing against the end of the circular, cylindrical section at the other end of the control valve element 134. Consequently, a valve chamber 155 is formed inside the cylindrical section of the control valve element 134. A circular, cylindrical section of the solenoid housing 136, which is fitted into the housing 126, is fitted into the respective outer circumferential sections of the control valve element 134 and the retaining element 135, thereby allowing the control valve element 134 and the retaining element 135 to be positioned radially.Valve chamber 155 is connected to chamber 126B in housing 126 via a line 156, which is formed between the retaining element 135 and the solenoid housing 136, and via a line 157, which is formed between the control valve element 134 and the cylindrical section of the solenoid housing 136. The port 152, valve chamber 155, and lines 156 and 157 form a control line that connects control chamber 151 and chamber 126B downstream of the disc valve 147 (main valve 127). Valve chamber 155 is fitted with a valve element 158 ​​of the control valve 128. The control valve 128 is a pressure control valve that selectively opens and closes port 152.

[0049] The solenoid housing 136 comprises a coil 159, magnetic cores 160 and 161 inserted into the coil 159, a plunger 162 guided by the cores 160 and 161, and a hollow actuating rod 163 connected to the plunger 162. These elements form the solenoid actuator S. The distal end section of the actuating rod 163 extends through the retaining element 135 and connects to the valve element 158 ​​in the valve chamber 155. When the coil 159 is supplied with an electric current via a supply cable 164, an axial thrust is generated in the plunger 162 according to the supplied current.

[0050] The valve element 158 ​​has a beveled distal end section that points towards the port 152 of the control valve element 134. An annular seat section 165 is formed on the beveled distal end section of the valve element 158. The seat section 165 selectively lifts from and engages the seat surface 166 around the port 152, thereby opening and closing the port 152. A valve spring 167 (displacement coil spring), acting as a displacement element, is arranged between the valve element 158 ​​and the base 134A of the control valve element 134. The valve element 158 ​​is displaced by the spring force of the valve spring 167 to remain normally in a retracted position in order to open the port 152. When the coil 159 is supplied with an electric current, a thrust is generated in the tappet 162, causing the valve element 158 ​​to move forward against the spring force of the valve spring 167.Consequently, the seat section 165 sits on the seat surface 166 to close the connection 152, as shown in . Fig. Figure 3 shows the pressure in the port 152, i.e., the pressure in the control chamber 151, is controlled by adjusting the valve opening pressure of the valve element 158 ​​via the thrust of the plunger 162, i.e., the electric current supplied to the coil 159.

[0051] The hollow actuating rod 163 is inserted into the valve element 158. When the valve element 158 ​​is in a valve-closed position, i.e., when the seat section 165 is seated on the seat surface 166, a line 163A in the actuating rod 163 opens into the port 152. The line 163A connects the port 152 and a chamber 161A in the core 161 at the rear of the actuating rod 163, thereby reducing the pressure-sensing area of ​​the valve element 158, through which the valve element 158 ​​receives the pressure from the port 152, and consequently increasing the variable width of the valve opening pressure of the valve element 158 ​​with respect to the thrust of the piston 162.

[0052] The fail-safe valve 129 has an annular, fail-safe disc 170. The fail-safe disc 170 is supported on an outer circumferential section of the valve between the control valve element 134 and the retaining element 135. If the coil 159 is not supplied with sufficient energy, the valve element 158 ​​is retracted by the spring force of the valve spring 167 to rest against the inner circumferential section of the fail-safe disc 170, thereby closing the flow path between the port 152 and the line 156 in the valve chamber 155. In this state, the port 152 and the line 156 are in communication with each other via an opening 170A formed in the inner circumferential edge of the fail-safe disc 170.Accordingly, when the fluid pressure at the port 152 in the valve element 155 increases to reach a predetermined pressure, the fail-safe disc 170 is deflected and the valve element 158 ​​retracts further until its return position is limited by a stop 171. Subsequently, the fail-safe disc 170 separates from the valve element 158 ​​to open the flow path between the port 152 and the line 156.

[0053] When the coil 159 is energized, the seat section 165 of the valve element 158 ​​is caused to seat on the seat surface 166 to perform pressure control by means of the control valve 128. During pressure control by means of the control valve 128, the valve element 158 ​​is separated from the fail-safe disc 170 to provide a connection between the port 152 and the line 156 in the valve chamber 155 via the opening in the center of the fail-safe disc 170.

[0054] Next, the main valve 127 will be discussed primarily with reference to Fig. 5 described.

[0055] As in the case of the aforementioned first embodiment, the elastic sealing element 158 ​​is made of an elastic material, for example, rubber, and is attached to the rear surface of the disc valve 147 by vulcanization bonding or the like. The outer circumference of the elastic sealing element 148 is formed in a plurality of steps to seal the area of ​​sliding contact with the inner circumferential surface 134B of the cylindrical section of the control valve element 134 in a multi-stage sealing manner. The outer diameter of the elastic sealing element 148 is larger than the diameter of the inner circumferential surface 134B of the cylindrical section of the control valve element 134.

[0056] Consequently, an interference F is formed between the elastic sealing element 148 and the inner circumferential surface 134B. The inner diameter of the disc valve 147 is sufficiently larger than the outer diameter of the shaft section 133A of the opening line element 133. Therefore, a clearance is formed between the disc valve 147 and the shaft section 133A of the opening line element 133 over the entire circumference of the shaft section 133A. That is, the radial positioning of the disc valve 147 is achieved by fitting the outer circumference of the elastic sealing element 148 and the inner circumferential surface 134B of the cylindrical section of the control valve element 134 together with the interference F.Any misalignment between the respective centers of the inner circumference of the disc valve 147 and the outer surroundings of the shaft section 133A of the opening line element 133 can be accommodated by the clearance C. The disc valve 147 is positioned radially in this way, and in this state, the inner circumferential section of the disc valve 147 is clamped and secured axially by tightening the nut 137.

[0057] The minimum value D'min of the inner diameter of the disc valve 147 can be obtained using the following equation as in the case of the aforementioned first embodiment: D'min=d'max+(Z1'+Z2') where: d'max: the maximum diameter of the shaft section 133A of the opening line element 133 is; Z1': the coaxiality between the inner circumference of the disc valve 147 and the outer circumference of the elastic sealing element 148 is; Z2': The coaxiality between the inner circumferential surface 134B of the cylindrical section of the control valve element 134 and the shaft section 133A of the opening line element 133 is.

[0058] The following is an explanation of the operation of this embodiment, which is arranged as described above.

[0059] The damping force control type 101 shock absorber is arranged between the sprung and unsprung elements of a vehicle's suspension system. The supply cable 164 is connected to a vehicle control unit or the like. In a normal operating condition, the coil 159 is energized to cause the seat section 165 of the valve element 158 ​​to seat on the seat surface 166 in order to carry out pressure control by means of the control valve 128.

[0060] During the extension stroke of the piston rod 106, the movement of the piston 105 in the cylinder 102 closes the check valve 113 of the piston 105. Before the disc valve 114 opens, the fluid in the upper cylinder chamber 102A is pressurized and the pressurized fluid flows through the line 122 and the annular line 121 and into the line 140 of the line element 131 of the damping force generation mechanism 125 from the opening section 123 of the separating tube 120.

[0061] At this point, an amount of fluid corresponding to the amount of movement of piston 105 flows from reservoir 104 into the lower cylinder chamber 102B by opening the check valve 117 of the base valve 110. It should be noted that when the pressure in the upper cylinder chamber 102A reaches the valve opening pressure of the disc valve 114 of piston 105, the disc valve 114 opens to release the pressure in the upper cylinder chamber 102A into the lower cylinder chamber 102B, thus preventing an excessive increase in pressure in the upper cylinder chamber 102A.

[0062] In the damping force generation mechanism 125, the fluid flows from line 140 of the line element 131 as follows. Before the disc valve 147 of the main valve 127 opens (in the low piston speed range), the fluid passes through the fixed opening 150 and line 149 of the opening line element 133 and the port 152 of the control valve element 134, forcing the valve element 158 ​​of the control valve 158 into the open position to flow into the valve chamber 155. The fluid flowing into the valve chamber 155 continues through the opening of the fail-safe disc 170 and into the reservoir 104 via lines 156 and 157, through chamber 126B in the housing 126, and further through lines 138 and the line plate 130.When the piston speed increases and the pressure in the upper cylinder chamber 102A reaches the valve opening pressure of the disc valve 147, the fluid flowing into line 140 passes through lines 144 and pushes the disc valve 147 into the open position to flow directly into chamber 126B in the housing 126.

[0063] During the displacement stroke of the piston rod 106, the movement of the piston 105 in the cylinder 102 opens the check valve 113 of the piston 105 and closes the check valve 117 of the line 115 of the base valve 110. Before the disc valve 118 opens, the fluid in the lower cylinder chamber 102B flows into the upper cylinder chamber 102A, and an amount of fluid corresponding to the amount by which the piston rod 106 enters the cylinder 102 flows from the upper cylinder chamber 102A into the reservoir 104 via a flow path similar to that during the extension stroke described above. It should be noted that when the pressure in the lower cylinder chamber 102B reaches the valve opening pressure of the disc valve 118 of the base valve 110, the disc valve 118 opens to release the pressure in the lower cylinder chamber 102B into the reservoir 104, thus preventing an excessive increase in pressure in the lower cylinder chamber 102B.

[0064] Consequently, during both the extension and retraction strokes of the piston rod 106, before the disc valve 147 of the main valve 127 opens (in the low piston speed range) at the damping force generation mechanism 125, a damping force is generated by means of the fixed opening 150 and the valve opening pressure of the valve element 158 ​​of the control valve 128. After the disc valve 147 has opened (in the high piston speed range), a damping force is generated according to the degree of opening of the valve element 158. The damping force can be controlled directly and independently of the piston speed by controlling the valve opening pressure of the control valve 128 by means of the electric current supplied to the coil 159.In this context, varying the valve opening pressure of the control valve 128 causes a change in the pressure in the back pressure chamber 155, which is connected to the line 149 on the upstream side of the control valve 128. Since the pressure in the back pressure chamber 155 acts in the direction of closing the disc valve 147, the valve opening pressure of the disc valve 157 can be controlled simultaneously by controlling the valve opening pressure of the control valve 128, and consequently the damping force characteristic control range can be broadened.

[0065] Additionally, if the electric current supplied to coil 159 is reduced to decrease the thrust of the plunger 162, the valve opening pressure of the control valve 128 decreases, and a soft damping force is generated. Conversely, if the electric current supplied to coil 159 is increased to increase the thrust of the plunger 162, the valve opening pressure of the control valve 128 increases, and a hard damping force is generated. Consequently, a soft damping force, which is generally frequently used, can be generated with a reduced electric current, and power consumption can be reduced.

[0066] In the event that the thrust of the plunger 162 is lost due to a fault such as a break in the coil 159, a fault in the vehicle control unit, etc., the valve element 158 ​​is retracted by the spring force of the valve element 167 to open the port 152. Furthermore, the valve element 158 ​​rests against the fail-safe disc 170 to close the flow path between the port 152 and the line 156 in the valve chamber 155. In this state, the fluid flow from the port 152 to the line 156 in the chamber 155 is controlled by the fail-safe valve 129 (i.e., the opening 170A and the fail-safe disc 170). Therefore, it is possible to generate a desired damping force and to control the pressure in the control chamber 151, i.e., the valve opening pressure of the fail-safe disk 170, according to the setting of the flow path area of ​​the opening 170A and the valve opening pressure of the fail-safe disk 170.Consequently, a suitable damping force can be maintained even in the event of a fault or failure.

[0067] In the main valve 127, the outer diameter of the elastic sealing element 148 is larger than the diameter of the inner circumferential surface 134B of the cylindrical section of the control valve element 134, creating an interference F between the elastic sealing element 148 and the cylindrical section 134. Additionally, the inner diameter of the disc valve 147 is sufficiently larger than the outer diameter of the shaft section 133A of the opening line element 133 to create a clearance C between the disc valve 147 and the shaft section 133A. Therefore, the disc valve 147 aligns itself automatically by being fitted between the outer circumference of the elastic sealing element 148 and the inner circumferential surface 134B of the cylindrical section of the control valve element 134. In this position, the disc valve 147 is axially clamped and secured by tightening the nut 137.Accordingly, within the free space C, any misalignment between the respective centers of the outer circumference of the elastic sealing element 148, the inner circumference of the disc valve 147, the inner circumference of the port 152, the control valve element 134, and the opening line element 133 is permissible. Therefore, it is possible to ensure sliding and sealing capability between the elastic sealing element 148 of the disc valve 147 and the inner circumferential surface 134B of the cylindrical section of the control valve element 134, and consequently, it is possible to obtain stable damping force characteristics. Additionally, since the requirements for dimensional tolerances and coaxiality are reduced, it is possible to increase productivity and lower manufacturing costs.

[0068] Accordingly, when the disc valve 147 is mounted on the shaft section 133A, the inner circumferential surface 134B of the cylindrical section at one end of the control valve element 134, which serves as the housing element, and the elastic sealing element 148 form concentric circles with each other. Furthermore, in this embodiment, the elastic sealing element 148 is attached to the main valve 127 by vulcanization bonding. In this context, it is difficult to perform the processing required to maintain the coaxiality of the elastic sealing element 148 with respect to the main valve 127. However, any coaxiality deviation within the area of ​​the clearance C can be tolerated. Therefore, it is possible to reduce the processing time for vulcanization bonding.

[0069] In the second embodiment, the clearance is also formed between the inner circumference of the main valve 127 and the outer circumference of the shaft section 133A over the entire circumference of the shaft section 133A, as in the first embodiment. However, a (single) case may occur in which a region without clearance (i.e., a region with zero clearance) may appear locally in the circumferential direction due to the main valve 127 being slightly displaced radially during tightening of the nut 137 or due to dimensional tolerances, etc. Nevertheless, the sliding and sealing performance of the elastic sealing element 148 can be improved compared to conventional techniques, provided that the clearance C is formed over substantially the entire circumference of the shaft section 133A according to the design concept.

[0070] Furthermore, in this embodiment, the clearance C formed between the inner circumference of the disc valve 147 and the outer circumference of the shaft section 133A of the opening line element 133 is larger than the clearance between the outer circumference of the shaft section 133A and the inner circumference of the washer 180', which comprises the holders 171 and 170 and a disc element 173 stacked on the disc valve 147, when these forming elements are assembled together by means of the nut 137, which serves as a fastening element. With this assembly, the washer 180' is positioned by being limited at its inner circumference by the inner circumference of the washer 180' and the outer circumference of the shaft section 133A.On the other hand, the disc valve 147 is positioned by limiting it on its outer circumference by means of the outer circumference of the elastic sealing element 147 and the inner circumferential surface 134B of the cylindrical section of the control valve element 134.

[0071] In the aforementioned second embodiment, instead of or in addition to the clearance C provided between the inner circumference of the disc valve 147 and the shaft section 133A of the opening line element 133, a clearance can be formed between the inner circumference of the connection 152 on the base of the control valve element 134 and the outer circumference of the shaft section 133B of the opening line element 133, which is fitted into the connection 152, over the entire circumference of the shaft section 133B, in order to accommodate the misalignment in the center described above. Although the control valve element 134 and the opening line element 133 are separate in the second embodiment, these elements can be integrated into a single component.

[0072] Although in the first and second embodiments a hydraulic oil and a gas were used as hydraulic fluids for reasons of operational stability and ease of handling, the present invention is not limited to these and can use other fluids alone or in combination. Although in the second embodiment the control valve 128 is a pressure control valve, it can, for example, be a flow control valve that controls the flow rate or the flow rate.

[0073] It should be noted that conventional shock absorbers also have a microscopic gap between a shaft section of a piston rod and a piston, disc, etc., that is fitted onto the shaft section. However, in this context, it should be noted that the clearance C in the aforementioned embodiments is sufficiently larger than the gap between the shaft section of the piston rod and the piston or other elements that are radially fixed to the shaft section, and the clearance C is of such a size that the disc valve can be arranged with a clearance C over the entire circumference of the shaft section according to the design concept. (From the standpoint of the design concept, it is difficult to arrange the piston or other radially fixed element with the clearance C over the entire circumference of the shaft section.)

[0074] The shock absorbers according to the aforementioned embodiments are able to increase the sliding surface and sealing capability of the elastic sealing element provided on the rear surface of the disc valve to form a counter-pressure chamber, while reducing the coaxiality requirements for each part of the damping force generation mechanism.

[0075] Although only some exemplary embodiments of this invention have been described in detail above, those skilled in the art will recognize that many modifications to these exemplary embodiments are possible without substantially departing from the new teaching and advantages of this invention. Accordingly, it is intended that all such modifications be included in the scope of protection of this invention.

[0076] The entire disclosure of JP 2010-194903, filed on August 31, 2010, comprising the description, claims, drawings and abstract, is hereby incorporated by reference in its entirety.

Claims

[1] Shock absorber (1, 101), comprising: a cylinder (2; 102) in which a hydraulic fluid is enclosed; a piston (3; 105) which is slidably fitted into the cylinder (2; 102); a piston rod (4; 106) connected to the piston (3; 105) and extending from the cylinder (2; 102); and a damping force generation mechanism (8; 125) which generates a damping force by controlling a flow of the hydraulic fluid caused by the sliding motion of the piston (3; 105); wherein the damping force generation mechanism (8; 125) comprises: an annular disc valve (14; 147); an annular elastic sealing element (15; 148) which is integrally provided on a rear surface of the disc valve (14; 147); a cylindrical housing element (10; 134) having a base and an inner circumferential surface (10A, 134B) into which the elastic sealing element (15; 148) is slidably fitted to form a back pressure chamber (16; 155) on a rear side of the disc valve (14; 147); and a shaft section (4A; 133A) having a circular outer circumference, wherein the shaft section (4A, 133A) is arranged in a common center of the disc valve (14; 147) and the bottom of the housing element (10; 134); wherein the disc valve (14; 147) has an inner circumferential section and an outer circumferential section and is attached to the housing element (10, 134) in such a way that it can be opened at the outer circumferential section by being clamped axially to the inner circumferential section thereof; wherein a free space (C) to accommodate a misalignment between a center of the disc valve (14; 147) and a center of the shaft section (4A; 133A) at the time of clamping between the inner circumferential section of the disc valve (14; 147) and the outer circumference of the shaft section (4A; 133A) over an entire circumference of the shaft section (4A; 133A), and the free space is not connected to the counter-pressure chamber (16; 155). [2] Shock absorber (1; 101), comprising: a cylinder (2; 102) in which a hydraulic fluid is enclosed; a piston (3; 105) which is slidably fitted into the cylinder (2; 102); a piston rod (4; 106) connected to the piston (3; 105) and extending from the cylinder (2; 102); and a damping force generation mechanism (8; 125) which generates a damping force by controlling a flow of the hydraulic fluid caused by the sliding motion of the piston (3; 105); wherein the damping force generation mechanism (8; 125) comprises: an annular disc valve (14; 147); an annular elastic sealing element (15; 148) which is integrally provided on a rear surface of the disc valve (14; 147); a cylindrical housing element (10; 134) having a base and an inner circumferential surface (10A; 134B) into which the elastic sealing element (15; 148) is slidably fitted to form a back pressure chamber (16; 155) on a rear side of the disc valve (14; 147); and a shaft section (4A; 133A) having a circular outer circumference, wherein the shaft section (4A, 133A) is arranged in a common center of the disc valve (14; 147) and the bottom of the housing element (10; 134); wherein the disc valve (14; 147) is attached to the housing element (10; 134) in such a way that an outer circumferential section of the disc valve (14; 147) can be opened by clamping an inner circumferential section of the disc valve axially to the housing element; wherein a free space (C) is formed between the inner circumferential section of the disc valve (14; 147) and / or an inner circumferential section of the base of the housing element (10; 134) and the outer circumference of the shaft section (4A; 133A) over an entire circumference of the shaft section (4A; 133A) to accommodate center misalignment at the time of clamping, and the free space is not connected to the counter-pressure chamber (16; 155). [3] Shock absorber (1, 101) according to claim 1 or 2, wherein the shaft section (4A; 133A) is separated from the housing element (10; 134), the shaft section (4A, 133A) being inserted into the base of the housing element (10; 134). [4] Shock absorber (1, 101) according to claim 1, wherein the shaft section (4A, 133A) is formed integrally with the housing element (10; 134). [5] Shock absorber (1, 101) according to one of claims 1 or 2, wherein, when the disc valve (14; 147) is mounted on the shaft section (4A, 133A), the inner circumferential surface of the housing element (10; 134) and the elastic sealing element (15; 148) each form concentric circles. [6] Shock absorber (1, 101) according to any one of claims 1 to 5, wherein the damping force generation mechanism further comprises: a washer (180) provided on at least one surface of the disc valve (14; 147); and a fastening element (5) that fastens the washer (180) and the disc valve (14; 147) to the shaft section (4A; 133A); wherein an inner diameter of the disc valve (14; 147) is larger than an inner diameter of the washer (180).

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