Damping force-adjustable shock absorber and method for manufacturing damping force-adjustable shock absorber

Abstract

The present invention provides a damping force-adjustable shock absorber capable of improving the productivity of a piston bolt. The piston bolt is formed by joining a connecting member and a piston rod member. In other words, a part (connecting member) joined to a solenoid case and a part (piston rod member) into which a sleeve is press-fitted are configured separately, and therefore, the connecting member and the piston rod member can be machined (cut) respectively by separate equipment (machining devices), making it possible to improve the productivity of the piston bolt.

Description

Damping Force Adjusting Type Shock Absorber and Method for Manufacturing Damping Force Adjusting Type Shock Absorber

[0001] The present invention relates to a damping force adjusting type shock absorber that controls the flow of working fluid with respect to the stroke of a piston rod to adjust the damping force, and a method for manufacturing the damping force adjusting type shock absorber.

[0002] Patent Document 1 discloses a damping force adjusting type shock absorber 1 (hereinafter referred to as "conventional damping force adjusting type shock absorber") having a damping force adjusting mechanism incorporated in a cylinder that controls the flow of working fluid in a common passage 11 formed in a piston bolt 5 by a pilot valve 81.

[0003] Japanese Patent No. 7223883

[0004] In the conventional piston bolt (hereinafter referred to as "conventional piston bolt") of the conventional damping force adjusting type shock absorber, since it was manufactured from a single material formed by forging, there were many processes of cutting, and the problem was low productivity.

[0005] An object of the present invention is to provide a damping force adjusting type shock absorber and a method for manufacturing the damping force adjusting type shock absorber capable of improving the productivity of the piston bolt.

[0006] The damping force adjusting type shock absorber of the present invention includes a coupling member in which a cylindrical tube portion is coupled to one axial end portion of a solenoid case, a piston rod member having an axial portion at the other axial end portion coupled to the coupling member and protruding from the coupling member toward one axial end side, a piston that partitions the inside of a cylinder into a first chamber and a second chamber through which the axial portion of the piston rod member is inserted, a passage through which working fluid flows via the piston, the coupling member, and the piston rod member, and a sleeve press-fitted into the passage formed in the piston rod member. The method for manufacturing the damping force adjusting type shock absorber of the present invention includes a step of coupling a rod and a solenoid case, a step of coupling a coupling member and a piston rod member, a step of inserting a piston into the axial portion of the piston rod member, a step of generating an axial force for fixing the piston by engaging a rotation preventing jig with a processed portion of the piston rod member and tightening a nut, and a step of coupling the coupling member and the solenoid case.

[0007] According to one embodiment of the present invention, a damping force adjustable shock absorber and a method for manufacturing a damping force adjustable shock absorber can be provided that can improve the productivity of piston bolts.

[0008] This figure shows a cross-sectional view of a part of the damping force adjustable shock absorber according to this embodiment. This figure shows an enlarged view of the main part in Figure 1. This is an explanatory diagram of this embodiment, and is a cross-sectional view of the piston bolt in the axial plane with the sleeve pressed into the spool hole of the piston rod member. This is an explanatory diagram of this embodiment, and is a plan view of the piston bolt in the spool hole of the piston rod member with the sleeve pressed into.

[0009] One embodiment of the present invention will be described with reference to the attached figures. In this embodiment, a single-tube type damping force adjustable shock absorber is described as an example, but the damping force adjustable shock absorber according to this embodiment is also applicable to a double-tube type damping force adjustable shock absorber having a reservoir. For convenience, the lower side in Figure 1 will be referred to as the "axial end side," and the upper side in Figure 1 will be referred to as the "axial other end side."

[0010] As shown in Figure 1, the damping force adjustable shock absorber 1 includes a cylinder 2 filled with working fluid and a piston 3 slidably fitted inside the cylinder 2, which divides the inside of the cylinder 2 into a first chamber 2A and a second chamber 2B. The piston 3 has a compression-side passage 4 that opens to the second chamber 2B at one axial end and an extension-side passage 5 that opens to the first chamber 2A at the other axial end. A free piston (not shown) that can move vertically inside the cylinder 2 is fitted inside the cylinder 2 at one axial end of the piston 3. The free piston divides the inside of the cylinder 2 into a second chamber 2B at the other axial end and a gas chamber (not shown) at one axial end.

[0011] The damping force adjustable shock absorber 1 has a piston rod 6, one end of which is inserted into the cylinder 2 in the axial direction and the other end of which extends out of the cylinder 2 in the axial direction, and a piston bolt 150 connected to the piston rod 6 via the solenoid case 121 of the solenoid section 120. The piston bolt 150 is fastened to the axial end of the solenoid case 121 by a screw fastening section 124.

[0012] The solenoid case 121 has a rod fastening portion 122 which is fastened to the axial end 7 of the piston rod 6 by tightening a lock nut 8, and a cylindrical portion 123 which houses the coil 125 of the solenoid portion 120 and into which the core 126 of the solenoid portion 120 is inserted. The space between the solenoid case 121 and the core 126 is sealed by an O-ring 127 provided on the outer circumference of the core 126.

[0013] The damping force adjustable shock absorber 1 has a damping force adjustment mechanism that adjusts the damping force characteristics by controlling the flow of working fluid accompanying the movement of the piston 3. The damping force adjustment mechanism has a valve mechanism 10 and a solenoid 120 (solenoid). The valve mechanism 10 has a compression-side valve mechanism 41 that controls the flow of working fluid in the compression-side passage 4 and an extension-side valve mechanism 71 that controls the flow of working fluid in the extension-side passage 5.

[0014] As shown in Figure 2, the compression valve mechanism 41 includes a bottomed cylindrical pilot case 42, a compression main valve 43 provided on the piston 3 side (the "lower side" in Figure 2) of the pilot case 42, and a compression back pressure chamber 44 formed between the pilot case 42 and the back surface of the compression main valve 43. The compression valve mechanism 41 has a seat portion 45 formed on the outer circumference of the end face on the other axial end of the piston 3, with which the compression main valve 43 abuts so as to be able to seat and dissipate. The pressure in the compression back pressure chamber 44 acts on the compression main valve 43 in the closing direction. The compression main valve 43 is a packing valve in which an annular packing 46 made of an elastic material contacts the inner circumferential surface of the pilot case 42 around its entire circumference.

[0015] The compression-side back pressure chamber 44 is connected to the first chamber 2A via a passage 47 formed in the pilot case 42 and a sub-valve 48. The sub-valve 48 opens when the pressure in the compression-side back pressure chamber 44 reaches a predetermined pressure, providing resistance to the flow of working fluid from the compression-side back pressure chamber 44 to the first chamber 2A. The compression-side back pressure chamber 44 is connected to the first pressure-receiving chamber 49 formed between the pilot case 42 and the sub-valve 48 via the passage 47 formed in the pilot case 42. The first pressure-receiving chamber 49 is defined by a first seat portion 50 formed on the outer circumference of the end face on the other axial end of the pilot case 42, and the other axial end of the passage 47 is open.

[0016] As shown in Figure 2, the extension valve mechanism 71 includes a bottomed cylindrical pilot case 72, an extension main valve 73 provided on the piston 3 side (the "upper side" in Figure 2) of the pilot case 72, and an extension back pressure chamber 74 formed between the pilot case 72 and the back surface of the extension main valve 73. The extension valve mechanism 71 has a seat portion 75 formed on the outer circumference of the end face on one axial end of the piston 3, with which the extension main valve 73 abuts so as to be able to seat and disseat. The pressure in the extension back pressure chamber 74 acts on the extension main valve 73 in the closing direction. The extension main valve 73 is a packing valve in which an annular packing 76 made of an elastic material contacts the inner circumferential surface of the pilot case 72 around its entire circumference.

[0017] The extension-side back pressure chamber 74 is connected to the second chamber 2B via a passage 77 formed in the pilot case 72 and a sub-valve 78. The sub-valve 78 opens when the pressure in the extension-side back pressure chamber 74 reaches a predetermined pressure, providing resistance to the flow of working fluid from the extension-side back pressure chamber 74 to the second chamber 2B. The extension-side back pressure chamber 74 is connected to the first pressure-receiving chamber 79 formed between the pilot case 72 and the sub-valve 78 via the passage 77 formed in the pilot case 72. The first pressure-receiving chamber 79 is defined by a first seat portion 80 formed on the outer circumference of the end face on one axial end of the pilot case 72, and the axial end of the passage 77 is open.

[0018] Furthermore, an axial force is generated in the valve components constituting the compression valve mechanism 41 and the extension valve mechanism 71 by tightening a nut 16, which is screwed onto one axial end of the piston rod member 171 of the piston bolt 150 (described later), and squeezing it between the connecting member 151 and the washer 17 of the piston bolt 150 (described later).

[0019] As shown in Figure 2, the piston bolt 150 has a spool hole 172 formed in the piston rod member 171 and a sleeve 11 that is press-fitted into the spool hole 172. A common passage 20 is formed in the piston bolt 150. The common passage 20 has an axial passage 21 formed in the sleeve 11, an axial passage 22 formed in the spool hole 172 on one axial end side of the sleeve 11, and an axial passage 23 whose other axial end opens into the axial passage 22. The inner diameter of the common passage 20 decreases in the order of axial passage 22, axial passage 21, and axial passage 23.

[0020] The common passage 20 includes a radial passage 27 that communicates with an annular passage 26 formed between the pilot case 72 and the piston rod member 171 of the piston bolt 150, a radial passage 28 that communicates with an annular passage 30 formed between one end of the piston 3 and the piston rod member 171 of the piston bolt 150, and a radial passage 29 that communicates the notch 25 formed in the piston rod member 171 of the piston bolt 150 with the axial passage 21. The sleeve 11 has communication holes 12, 12 (see Figure 3) that connect the axial passage 21 and the radial passage 29. The centerlines of the communication holes 12, 12, the radial passage 27, the radial passage 28, and the radial passage 29 are arranged on a single plane that includes the centerline (axis) of the piston rod member 171.

[0021] The compression-side back pressure chamber 44 is connected to the compression-side passage 4 via a notch (not shown) formed in the disk 54, an annular passage 24 formed between the pilot case 42 and the piston rod member 171 of the piston bolt 150, a notch 25 formed in the piston rod member 171 of the piston bolt 150, and a notch (not shown) formed in the disk 56.

[0022] The extension-side back pressure chamber 74 is connected to the extension-side passage 5 via a notch (not shown) formed in the disk 84, an annular passage 26, a radial passage 27, an axial passage 23, a radial passage 28, an annular passage 30, and a notch (not shown) formed in the disk 86.

[0023] The flow of working fluid in the common passage 20 is controlled by a pilot valve 101. The pilot valve 101 has a spool 102 made of a solid shaft and supported by a sleeve 11 so as to be movable in the axial direction. The spool 102 has a head 103 formed at the other axial end, a sliding portion 104 that is slidably fitted inside the sleeve 11, a valve body 105 formed at the one axial end, and a connecting portion 106 formed between the valve body 105 and the sliding portion 104.

[0024] The pilot valve 101 has a first valve seat 107 formed on the peripheral edge (opening) of one axial end of the axial passage 21 and a first valve portion 108 formed on the peripheral edge of the other axial end of the valve body 105. When the coil 125 of the solenoid portion 120 is not energized, the pilot valve 101 restricts the flow of working fluid in the common passage 20 by the first valve portion 108 seating (fitting) with the first valve seat 107. The pilot valve 101 has a second valve seat 109 formed on the peripheral edge (opening) of the other axial end of the axial passage 23 and a second valve portion 110 formed on the peripheral edge of the end face of one axial end of the valve body 105. When the coil 125 of the solenoid portion 120 is energized, the pilot valve 101 restricts the flow of working fluid in the common passage 20 by the second valve portion 110 seating with the second valve seat 109.

[0025] A first chamber 111 is formed between the piston bolt 150 and the end face of the core 126 of the solenoid section 120 on one axial end. An outer flange-type spring receiver 112 is formed on the head 103 of the spool 102. The inner circumference of a spring disc 113, which biases the spool 102 in the opening direction of the second valve section 110 (the "upward direction" in Figure 2), is connected to the spring receiver 112. When the coil 125 of the solenoid section 120 is not energized, the head 103 of the spool 102 is pressed against the end face of the operating rod 129 of the solenoid section 120 on one axial end by the biasing force of the spring disc 113.

[0026] When the control current for the coil 125 of the solenoid unit 120 is 0A (fail), the biasing force of the spring disc 113 moves the spool 102 in the direction of opening the pilot valve 101, and the first valve portion 108 of the valve body 105 is seated (fitted) onto the first valve seat 107. As a result, an orifice (not shown) is formed between the valve body 105 and the sleeve 11 (axial passage 21), connecting the axial passage 21 and the axial passage 22.

[0027] As shown in Figure 2, a bottomed cylindrical cap 31, with an opening at the other axial end, is fitted around the outer circumference of the coupling member 151 of the piston bolt 150. The space between the cap 31 and the coupling member 151 of the piston bolt 150 is sealed by an O-ring 39. This forms an annular second chamber 114 between the cap 31 and the piston bolt 150. The cap 31 has a through hole 32 through which the piston rod member 171 of the piston bolt 150 is inserted. The cap 31 has a notch 33 formed in the through hole 32. The notch 33 communicates with a passage 24 formed between the pilot case 42 and the piston rod member 171 of the piston bolt 150.

[0028] The second chamber 114 is provided with a check valve 35 (spool back pressure relief valve) that allows the working fluid to flow from the first chamber 111 to the second chamber 114 via the passage 34. The outer peripheral edge of the check valve 35 abuts against an annular seat portion 36 formed on the end face of the coupling member 151 of the piston bolt 150 on one axial end, so as to be able to seat and detach from it. Multiple notches 38 (only "two" are shown in Figure 2) are formed on the inner circumference of the retainer 37 that restricts the opening of the check valve 35, allowing the second chamber 114 to communicate with the compression side back pressure chamber 44 via the notch 33, the passage 24, and the notch 55 formed in the check valve 54.

[0029] As shown in Figure 1 or Figure 2, the solenoid section 120 includes a solenoid case 121, a coil 125, a core 126, a core 128, an operating rod 129, and a plunger 130 fixed to the outer circumference of the operating rod 129. The operating rod 129 is guided axially by a bush 132 mounted in a cylindrical holder 131 and a bush 133 mounted in the core 126.

[0030] An annular passage 135 is formed on the outer circumference of one end of the core 126 between it and the connecting member 151 of the piston bolt 150. The annular passage 135 is connected to the first chamber 2A by a passage 139 formed in the connecting member 151 of the piston bolt 150. A spool back pressure chamber 136 is formed in the center of the axial end of the core 126 of the solenoid section 120. The spool back pressure chamber 136 is connected to the rod back pressure chamber 138 via a notch 137 formed in the operating rod 129 and an internal rod passage 134 of the operating rod 129.

[0031] Next, the flow of the working fluid in the damping force adjustable shock absorber 1 described above will be explained. During the compression stroke, the working fluid from the second chamber 2B is introduced into the compression side back pressure chamber 44 via the compression side passage 4, the notch (notation omitted) formed in the disc 56, the notch 25 formed in the piston rod member 171 of the piston bolt 150, and the notch (notation omitted) formed in the disc 54. Also during the compression stroke, the working fluid from the second chamber 2B is introduced into the extension side back pressure chamber 74 via the compression side passage 4, the notch (notation omitted) formed in the disc 56, the notch 25 formed in the piston rod member 171 of the piston bolt 150, the annular passage 24, the radial passage 29, the axial passage 21, the axial passage 22, the axial passage 23, the radial passage 27, the annular passage 26, and the notch (notation omitted) formed in the disc 84. This prevents the extension side main valve 73 from opening due to the pressure in the second chamber 2B during the compression stroke.

[0032] Furthermore, during the compression stroke, the working fluid from the second chamber 2B is introduced into the rod back pressure chamber 138 via the compression-side passage 4, a notch (not shown) formed in the disc 56, a notch 25 formed in the shaft portion 173 of the piston rod member 171, a notch 33 formed in the cap 31, a notch 38 formed in the retainer 37, the second chamber 114, a notch (not shown) formed in the check valve 35, a chamber (not shown) formed on the inner circumference side of the seat portion 36, passage 34, the first chamber 111, the spool back pressure chamber 136, a notch 137 formed in the working rod 129, and the rod internal passage 134. In this way, in the low-speed region of the piston speed during the compression stroke, a portion of the pilot pressure applied to the compression-side back pressure chamber 44 can be applied to the rod back pressure chamber 138 as spool back pressure assist pressure.

[0033] During the compression stroke, the spool back pressure assist pressure can be adjusted by directing a portion of the working fluid introduced from the second chamber 2B to the first chamber 111 to the first chamber 2A via a notch (not shown) formed on the outer circumference of the disk 141, an annular passage 135, and a passage 139 formed in the piston rod member 171.

[0034] On the other hand, during the extension stroke, the working fluid from the first chamber 2A is introduced into the extension-side back pressure chamber 74 via the extension-side passage 5, a notch (notation omitted) formed in the disk 86, the annular passage 30, the radial passage 28, the axial passage 23, the radial passage 27, the annular passage 26, and a notch (notation omitted) formed in the disk 84. Also during the extension stroke, the working fluid from the first chamber 2A is introduced into the compression-side back pressure chamber 44 via the extension-side passage 5, a notch (notation omitted) formed in the disk 86, the annular passage 30, the radial passage 28, the axial passage 23, the axial passage 22, the axial passage 21, the radial passage 29, the annular passage 24, and a notch (notation omitted) formed in the disk 54. This prevents the compression-side main valve 43 from opening due to the pressure in the first chamber 2A during the extension stroke.

[0035] Furthermore, during the extension stroke, the working fluid from the first chamber 2A is introduced into the rod back pressure chamber 138 via the passage 139 formed in the piston rod member 171, the annular passage 135 formed on the outer circumference of the core 126, the notch (notation omitted) formed on the outer circumference of the disk 141, the spool back pressure chamber 136, the notch 137 formed in the working rod 129, and the rod internal passage 134. In this way, spool back pressure assist pressure can be applied to the rod back pressure chamber 138 in the low-speed region of the piston speed during the extension stroke. At this time, damping force of the orifice characteristic can be obtained due to the notch (notation omitted) formed on the outer circumference of the disk 141.

[0036] During the extension stroke, the spool back pressure assist pressure can be adjusted by directing a portion of the working fluid introduced from the second chamber 2B to the first chamber 111 through the passage 34, the chamber formed on the inner circumference of the seat portion 36 (reference numerals omitted), the check valve 35, the second chamber 114, the notch 38 formed in the retainer 37, the notch 33 formed in the cap 31, the notch 25 formed in the shaft portion 173 of the piston rod member 171, the notch formed in the disc 56 (reference numerals omitted), and the compression-side passage 4 to the second chamber 2B.

[0037] Next, the piston bolt 150, which is the main part of this embodiment, will be described with reference to Figure 3 or Figure 4. The piston bolt 150 is formed by joining (connecting) the aforementioned connecting member 151 and the piston rod member 171 by press-fitting. The connecting member 151 has a generally cylindrical base portion 152 and a cylindrical connecting portion 153 that extends from the outer peripheral edge of the base portion 152 toward the other axial end (upper side in Figure 3) and is connected to the cylindrical portion 123 of the solenoid case 121 by a screw fastening portion 124 (see Figure 2).

[0038] The connecting member 151 has a first recess 155 that opens on the end face 154 of the base 152 on the other axial end side, and whose cross-section is circular when measured on a plane perpendicular to the centerline (axis) of the piston bolt 150 (hereinafter referred to as the "plane perpendicular to the axis"). The connecting member 151 has a second recess 157 that opens on the bottom surface 156 of the first recess 155, and whose cross-section is circular when measured on a plane perpendicular to the axis. The connecting member 151 has a press-fit hole 159 that opens on the bottom surface 158 of the second recess 157, and whose cross-section is circular when measured on a plane perpendicular to the axis. The first recess 155, the second recess 157, and the press-fit hole 159 are arranged coaxially with respect to the centerline of the piston bolt 150. A tapered portion 160 is formed at the opening on the other axial end side of the press-fit hole 159. The other axial end side of the passage 34 opens at the annular bottom surface 156 of the first recess 155.

[0039] The piston rod member 171 has a shaft portion 173 extending from the base portion 152 of the coupling member 151 toward one axial end (the "lower side" in Figure 3), an enlarged diameter portion 174 formed by expanding the diameter of the other axial end of the piston rod member 171 radially outward to form a flange shape and housed in the second recess 157 of the coupling member 151, and a press-fit shaft portion 175 (coupling portion) formed between the shaft portion 173 and the enlarged diameter portion 174 and press-fitted into the press-fit hole portion 159 of the base portion 152 of the coupling member 151. The piston rod member 171 is formed such that the outer diameter increases in the order of shaft portion 173, press-fit shaft portion 175, and enlarged diameter portion 174.

[0040] The piston bolt 150 ensures coaxiality between the connecting member 151 and the piston rod member 171, and prevents leakage of working fluid (pilot pressure) from between the press-fit hole 159 of the connecting member 151 and the press-fit shaft portion 175 of the piston rod member 171 by adjusting the press-fit length between the press-fit hole 159 and the press-fit shaft portion 175, and by bringing the annular end face 177 on one axial end of the enlarged diameter portion 174 into contact with the annular bottom surface 158 of the second recess 157 of the connecting member 151. A tapered portion 176 is formed at one axial end of the press-fit shaft portion 175.

[0041] The piston rod member 171 has a pair of torque receiving portions 181, 181 (machined portions) for engaging with a torque receiving jig (not shown) used to prevent rotation of the piston rod member 171 when an axial force is generated in the piston 3 and valve mechanism 10 by tightening a nut 16 screwed onto one axial end of the shaft portion 173 during the assembly process. The pair of torque receiving portions 181, 181 are formed symmetrically with respect to a plane containing the center line of the piston rod member 171, which is referred to as the plane of symmetry (hereinafter referred to as the "plane of symmetry").

[0042] The torque receiving portions 181, 181 are formed on the outer peripheral edge of the enlarged diameter portion 174 and consist of a pair of grooves extending from the end face 178 on the other axial end side of the piston rod member 171 (enlarged diameter portion 174) toward the one axial end side (the "downward side" in Figure 3). The torque receiving portions 181, 181 have torque receiving surfaces 182, 182 that receive torque when tightening the nut 16, torque receiving surfaces 183, 183 that receive torque when loosening the nut 16, width surfaces 184, 184 formed between the opposing torque receiving surfaces 182, 183 and arranged parallel to the plane of symmetry, and bottom surfaces 185, 185 formed between the opposing torque receiving surfaces 182, 183 and arranged on a plane perpendicular to the plane of symmetry.

[0043] Referring to FIG. 4, when viewing the piston bolt 150 (hereinafter referred to as "piston bolt assembly") in which the sleeve 11 is press-fitted into the spool hole 172 of the piston rod member 171 from the line of sight in the center line direction of the piston rod member 171 (the "vertical direction" in FIG. 3), a straight line L1 connecting the center points in the width direction (the "vertical direction" in FIG. 4) of the pair of torque receiving portions 181, 181 coincides with the center lines of the communication holes 12, 12 formed in the sleeve 11 and the center lines of the radial passages 27, radial direction 28, and radial passage 29 formed in the shaft portion 173 of the piston rod member 171.

[0044] In other words, the phase (hereinafter referred to as "phase") of the torque receiving portions 181, 181 (machined portions) around the center line of the piston rod member 171 matches the phases of the radial passage 27, radial passage 28, and radial passage 29. In the present embodiment, the phases of the torque receiving portions 181, 181 also coincide with the phases of the passages 34, 34 that open to the annular bottom surface 156 of the first recess 155 of the coupling member 151.

[0045] In the present embodiment, different materials are used for the coupling member 151, the piston rod member 171, and the sleeve 11. For example, the material of the coupling member 151 is carbon steel such as S10C, the material of the piston rod member 171 is carbon steel such as S45C, and the material of the sleeve 11 is carbon steel such as SK95M. The materials of the coupling member 151, the piston rod member 171, and the sleeve 11 are not limited to those described above, as long as the tensile strength of the material used for the coupling member 151 is smaller than the tensile strength of the material used for the piston rod member 171, and the tensile strength of the material used for the piston rod member 171 is smaller than the tensile strength of the material used for the sleeve 11.

[0046] Next, a manufacturing method of the damping force adjusting type shock absorber 1 according to the present embodiment will be described. Here, the steps related to the assembly of the piston bolt 150 will be described. First, the sleeve 11 is press-fitted into the spool hole 172 of the piston rod member 171 to couple the piston rod member 171 and the sleeve 11. Next, the inner peripheral surface (axial passage 21) of the sleeve 11 press-fitted into the piston rod member 171 is finished to a certain accuracy by burnishing.

[0047] Here, since the phases of the torque receiving portions 181, 181 (machined portions) of the piston rod member 171 (around the center line of the piston rod member 171) coincide with the phase of the radial passage 29, when the sleeve 11 is press-fitted into the spool hole 172 of the piston rod member 171, by aligning the communication holes 12, 12 of the sleeve 11 with respect to the torque receiving portions 181, 181 of the piston rod member 171, the radial passage 29 of the piston rod member 171 and the communication holes 12, 12 of the sleeve 11 can be easily made to coincide (communicate). Further, since the piston rod member 171 and the sleeve 11 are made of materials of different materials, generation of galling and burrs during press-fitting can be suppressed. Furthermore, since the press-fitting length is longer than that of the conventional piston bolt, leakage of the working fluid (pilot pressure) from between the spool hole 172 of the piston rod member 171 and the sleeve 11 can be suppressed.

[0048] Next, the press-fitting shaft portion 175 of the piston rod member 171 is press-fitted into the press-fitting hole portion 159 of the coupling member 151 to couple the coupling member 151 and the piston rod member 171. Here, since the coupling member 151 and the piston rod member 171 are made of materials of different materials, generation of galling and burrs during press-fitting can be suppressed. Also, since the press-fitting length is ensured, coaxiality between the coupling member 151 and the piston rod member 171 can be ensured, and leakage of the working fluid (pilot pressure) from between the press-fitting hole portion 159 of the coupling member 151 and the press-fitting shaft portion 175 of the piston rod member 171 can be suppressed.

[0049] Next, the piston 3 and the valve mechanism portion 10 are assembled to the shaft portion 173 of the piston rod member 171, and further, a washer 17 and a nut 16 are attached to an end portion on one axial end side of the shaft portion 173. Next, after engaging a torque receiving jig (not shown) with the torque receiving portions 181, 181 of the piston rod member 171 to prevent rotation of the piston rod member 171, the nut 16 is tightened to generate an axial force for fixing the piston 3 and the valve mechanism portion 10.

[0050] Next, the coupling portion 153 of the coupling member 151 and the cylindrical portion 123 of the solenoid case 121 are fastened together with screws, thereby connecting the coupling member 151 and the solenoid case 121. Prior to this, the end portion 7 of the piston rod 6 (rod) is fitted into the rod fastening portion 122 of the solenoid case 121 and the lock nut 8 is tightened to connect the piston rod 6 and the solenoid case 121.

[0051] In conventional damping force adjustable shock absorbers, the piston bolt was manufactured from a single material (blank) formed by forging, resulting in a large number of machining steps and low productivity of the piston bolt, which was a problem.

[0052] In contrast, in this embodiment, the piston bolt 150 is constructed by connecting the connecting member 151 and the piston rod member 171. In other words, the part that connects to the solenoid case 121 (connecting member 151) and the part into which the sleeve 11 is press-fitted (piston rod member 171) are constructed as separate parts. This makes it possible to process (cut) the connecting member 151 and the piston rod member 171 using separate equipment (processing devices), thereby improving the productivity of the piston bolt 150. This reduces the manufacturing cost of the piston bolt 150, and consequently the manufacturing cost of the damping force adjustable shock absorber 1. In this embodiment, since the piston bolt 150 is constructed by dividing it into the connecting member 151 and the piston rod member 171, it is possible to use different materials for the connecting member 151 and the piston rod member 171. This prevents galling and burr formation when the press-fit shaft portion 175 of the piston rod member 171 is press-fitted into the press-fit hole portion 159 of the connecting member 151. Furthermore, by using different materials for the piston rod member 171 and the sleeve 11, it is possible to suppress galling and burr formation when pressing the sleeve 11 into the spool hole 172 of the piston rod member 171. Also, since the mechanical strength required for the coupling member 151 is lower than that required for the piston rod member 171, in this embodiment, by dividing the piston bolt 150 into a coupling member 151 and a piston rod member 171, it is possible to use a cheaper material with lower mechanical strength than the piston rod member 171, thereby reducing the manufacturing cost of the piston bolt 150. In this embodiment, the press-fit length of the sleeve 11 is set so that there is no leakage of working fluid (pilot pressure) from between the spool hole 172 of the piston rod member 171 and the sleeve 11, so it is possible to eliminate the brazing of the sleeve 11 that was carried out in conventional piston bolts, thereby improving the productivity of the piston bolt 150. As a result, the manufacturing cost of the piston bolt 150, and consequently the manufacturing cost of the damping force adjustable shock absorber 1, can be reduced.In this embodiment, the phase of the torque receiving portions 181, 181 (machined portions) of the piston rod member 171 is made to match the phase of the radial passage 29. Therefore, when press-fitting the sleeve 11 into the spool hole 172 of the piston rod member 171, by aligning the communication holes 12, 12 of the sleeve 11 with respect to the torque receiving portions 181, 181 of the piston rod member 171, it is possible to easily align (connect) the radial passage 29 of the piston rod member 171 and the communication holes 12, 12 of the sleeve 11, thereby streamlining the press-fitting process of the sleeve 11.

[0053] The embodiments are not limited to the forms described above, and for example, they can be configured as follows. In the embodiments described above, a pair of torque receiving portions 181, 181 (machined portions) are formed by grooves having bottom surfaces 185, 185. In other words, the torque receiving portions 181, 181 are formed on a part of the enlarged diameter portion 174 from the end face 178 on the other axial end to the end face 177 on the one axial end to constitute the piston rod member 171. However, the torque receiving portions 181, 181 may be formed by notches penetrating the outer peripheral edge of the enlarged diameter portion 174 in the axial direction. In other words, the torque receiving portions 181 may be formed on the entire length of the enlarged diameter portion 174 from the end face 178 on the other axial end to the end face 177 on the one axial end to constitute the piston rod member 171. Furthermore, the pair of torque receiving portions 181, 181 (machining portions) can be formed not only by the grooves described above, but also by, for example, holes, recesses, or two-sided width portions formed in the enlarged diameter portion 174.

[0054] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Also, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0055] This application claims priority under Japanese Patent Application No. 2024-232363, filed on 27 December 2024. The entire disclosure of Japanese Patent Application No. 2024-232363, filed on 27 December 2024, including the specification, claims, drawings, and abstract, is incorporated into this application by reference.

[0056] 1. Damping force adjustable shock absorber, 2. Cylinder, 2A. First chamber, 2B. Second chamber, 3. Piston, 6. Piston rod (rod), 11. Sleeve, 120. Solenoid section (solenoid), 121. Solenoid case, 125. Coil, 150. Piston bolt, 151. Connecting member, 171. Piston rod member, 172. Spool hole (passage)

Claims

1. A damping force adjustable shock absorber comprising: a cylinder in which a working fluid is sealed; a rod whose axial end is inserted into the cylinder and whose other axial end protrudes outward from the cylinder; a solenoid case connected to the axial end of the rod, the solenoid case housing a solenoid coil inside the solenoid case and covering a part of the core of the solenoid; a coupling member whose cylindrical portion is coupled to the axial end of the solenoid case; a piston rod member whose other axial end is coupled to the coupling member and has a shaft portion protruding axially from the coupling member to the axial end; a piston through which the shaft portion of the piston rod member is inserted and which divides the inside of the cylinder into a first chamber and a second chamber; a passage through which the working fluid flows via the piston, the coupling member, and the piston rod member; and a sleeve formed in the piston rod member and pressed into the passage.

2. A damping force adjustable shock absorber according to claim 1, wherein the coupling member and the piston rod member are made of materials of different materials.

3. A damping force adjustable shock absorber according to claim 1, wherein the coupling member, the piston rod member, and the sleeve are made of materials of different materials.

4. A damping force adjustable shock absorber according to claim 2, wherein the material used for the coupling member has a lower tensile strength than the material used for the piston rod member.

5. A damping force adjustable shock absorber according to claim 3, wherein the material used for the coupling member has a lower tensile strength than the material used for the piston rod member, and the material used for the piston rod member has a lower tensile strength than the material used for the sleeve.

6. A damping force adjustable shock absorber according to claim 1, wherein the piston rod member has an enlarged diameter portion formed at the other axial end of the piston rod member and enlarged radially outward of the piston rod member, and a processed portion formed on part or all of the area from the other axial end face of the enlarged diameter portion to the one axial end face of the enlarged diameter portion, wherein the processed portion is formed such that its phase matches that of the radial passage with respect to the center line of the piston rod member.

7. A method for manufacturing a damping force adjustable shock absorber, the damping force adjustable shock absorber comprising: a cylinder in which a working fluid is sealed; a rod in which one axial end is inserted into the cylinder and the other axial end protrudes outward from the cylinder; a solenoid case connected to one axial end of the rod, the solenoid case housing a solenoid coil inside the solenoid case and covering a part of the core of the solenoid; a coupling member whose cylindrical portion is coupled to one axial end of the solenoid case; a shaft portion protruding from the coupling member toward one axial end; an enlarged diameter portion formed at the other axial end and expanding radially outward; a coupling portion formed between the shaft portion and the enlarged diameter portion and coupled to the coupling member; and a machined portion formed on part or all of the area from the other axial end face of the enlarged diameter portion to the axial end face of the enlarged diameter portion; A damping force adjustable shock absorber comprising: a piston through which the shaft portion of the piston rod member is inserted and which divides the inside of the cylinder into a first chamber and a second chamber; a passage through which the working fluid flows via the piston and the piston rod member; and a nut provided on the shaft portion of the piston rod member for generating an axial force to fix the piston, wherein the method for manufacturing the damping force adjustable shock absorber comprises: a step of connecting the rod and the solenoid case; a step of connecting the connecting member and the piston rod member; a step of inserting the piston into the shaft portion of the piston rod member; a step of engaging a rotation-stopping jig with the machined portion of the piston rod member and tightening the nut to generate an axial force to fix the piston; and a step of connecting the connecting member and the solenoid case.

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