Bonded body, method for manufacturing bonded body, and shock absorber

Abstract

The present invention provides a bonded body having good coaxiality in which distortion is reduced by homogenizing residual stress in the circumferential direction of a bonded portion between a rod-shaped member and a mating member in plastic flow bonding, a method for manufacturing the bonded body, and a shock absorber using the bonded body and method. This method for manufacturing the bonded body comprises: first and second plastic flow steps for bonding a piston rod (rod-shaped member) and a solenoid case (mating member); first and second centering steps for correcting the misalignment between the axial center of the piston rod and the axial center of the solenoid case; and first and second stress homogenization steps for homogenizing the residual stress in the bonded portion over the entire circumference, and therefore the coaxiality and bonding strength of the bonded body can be simultaneously satisfied.

Description

Combined body, combined body manufacturing method, and shock absorber

[0001] The present invention relates to a joined body joined by plastic flow bonding, a method for manufacturing the joined body, and a shock absorber manufactured by the manufacturing method.

[0002] Patent Document 1 discloses a method of joining two members (hereinafter referred to as the "conventional joining method") in which one end of a piston rod and a solenoid case are joined by a plastic flow joining method (metal flow).

[0003] In Patent Document 2, one end of the piston rod and the solenoid case are joined by screw fastening, and this is cited for comparison with the plastic flow joining method of the present invention.

[0004] International Publication No. 2023 / 017722 Japanese Patent Application Laid-Open No. 2021-121756

[0005] Conventional joining methods have had the problem of variations in the coaxiality of the piston rod (rod-shaped component) and solenoid case (mating component) after joining. High coaxiality increases the sliding resistance of the piston inside the shock absorber, which can lead to poor shock absorber response and a shortened service life. The causes of this increased coaxiality after joining are misalignment of the axial centers of the joining components and distortion caused by uneven circumferential residual stress at the joining point due to plastic flow joining.

[0006] The present invention aims to provide a combined body with good coaxiality in which distortion is suppressed by equalizing the circumferential residual stress at the joint between a rod-shaped member and a mating member in a plastic flow joining method, a method for manufacturing the combined body, and a shock absorber using the combined body.

[0007] The combined body of the present invention is a combined body of two members, comprising a rod-shaped member and a mating member, and is characterized in that one end of the rod-shaped member is fitted into a fitting hole in the mating member, and the rod-shaped member and the mating member are joined together by applying pressure to the material of the mating member and causing it to plastically flow into a groove provided on the circumferential surface of the rod-shaped member, the mating member having a pressurized portion formed by the pressure and a straight portion formed in the gap between the pressurized portion and the rod-shaped member during plastic flow, the pressurized portion being located closer to one end of the rod-shaped member than the groove, and the rod-shaped member having a fragile portion on its one end that is pressed and deformed by the excess material after the plastic flow of the material into the groove due to the pressure is completed. The method for manufacturing a combined body of the present invention is a method for manufacturing a combined body of two members, the combined body comprising a rod-shaped member and a mating member, one end of the rod-shaped member being fitted into a fitting hole of the mating member, and the rod-shaped member and the mating member being joined by applying pressure to the material of the mating member to cause plastic flow into a groove provided on the circumferential surface of the rod-shaped member, the mating member having a pressurized portion formed by the pressure and a straight portion formed in a gap between the pressurized portion and the rod-shaped member during plastic flow, the pressurized portion being located closer to one end of the rod-shaped member than the groove, and the rod-shaped member having a fragile portion at its one end that is pressed and deformed by the excess material after the plastic flow of the material into the groove due to the pressure is completed, The manufacturing apparatus for the combined body includes an upper mold having a pressure mechanism that applies pressure to one end face of the mating member, and a lower mold that holds the rod-shaped member and the mating member with the one end of the rod-shaped member mated with the mating hole of the mating member, the upper mold being arranged coaxially with the lower mold and able to be raised and lowered freely, and the manufacturing method for the combined body includes a centering process in which the pressure mechanism causes the material of the mating member to plastically flow, correcting any misalignment of the axis that occurs between the mating member and the rod-shaped member while the mating member forms the straight portion, a plastic flow process in which the material of the mating member plastically flows into the groove, and a stress equalization process in which the fragile portion of the rod-shaped member is pressed against the excess material of the mating member and deformed.The shock absorber of the present invention is a shock absorber comprising: a cylinder in which a working fluid is sealed; a piston mechanism that divides the interior of the cylinder into two chambers; a piston rod having one end coupled to the piston mechanism and the other end extending to the outside of the cylinder; and a coupling portion formed by fitting one end of the piston rod into a fitting hole of the piston mechanism and pressurizing a material of the piston mechanism to cause plastic flow within a groove provided on a circumferential surface of the piston rod, the groove having a first groove provided on one end side of the piston rod and a second groove provided axially away from the first groove towards the other end side of the piston rod; the piston mechanism having a pressurizing portion formed by pressurization, the pressurizing portion comprising: The piston mechanism has a first pressurizing portion provided on the first groove side and a second pressurizing portion provided on the second groove side, and the piston mechanism has a straight portion formed in the gap between the pressurizing portion and the piston rod during plastic flow, and the straight portion has a first straight portion provided on the first groove side and a second straight portion provided on the second groove side, and on the first straight portion side, the first pressurizing portion is located closer to one end of the piston rod than the first groove, and on the second straight portion side, the second pressurizing portion is located closer to the other end of the piston rod than the second groove, and the piston rod has a fragile portion on its one end side that is pressed and deformed by excess material after plastic flow of material into the grooves due to the pressurization is completed.

[0008] According to one embodiment of the present invention, it is possible to provide a combined body with good coaxiality in which distortion is suppressed by equalizing the circumferential residual stress at the joint between a rod-shaped member and a mating member in a plastic flow joining method, a method for manufacturing the combined body, and a shock absorber using the combined body.

[0009] 1 is a diagram showing a cross section of a portion of a shock absorber according to a first embodiment, taken along an axial plane; FIG. 2 is an enlarged view of a portion of FIG. 1; FIG. 3 is a cross section of a combined body according to a first embodiment, taken along an axial plane; FIG. 4 is an enlarged view of a portion of FIG. 3; FIG. 5 is an explanatory view of a manufacturing apparatus used in a method for manufacturing a combined body according to a first embodiment; FIG. 6 is an explanatory view of the first embodiment, showing a state before local pressurization is started; FIG. 7 is an explanatory view of a first plastic flow process; FIG. 8 is an explanatory view of a second plastic flow process; FIG. 9 is an explanatory view of a restraining ring removal process; FIG. 10 is a diagram showing experimental results regarding the depth D5 of a weakened portion of a piston rod (rod-shaped member); FIG. 11 is a diagram for explaining the process flow of a method for manufacturing a combined body according to a first embodiment, showing a state in which a piston rod and a solenoid case (mating member) are set in a press device; FIG. 12 is a diagram for explaining the process flow of a method for manufacturing a combined body according to a first embodiment, showing a state in which a restraining ring is clamped by a clamper; FIG. 13 is a diagram for explaining the process flow of a method for manufacturing a combined body according to a first embodiment, showing a state in which a restraining ring is set in a solenoid case; FIG. 14 is a diagram for explaining the process flow of a method for manufacturing a combined body according to a first embodiment, showing a state in which a restraining ring is set in a solenoid case and a transport unit is retracted. FIG. 1 is a diagram for explaining the process flow of the method for producing a combined body according to the first embodiment, showing a state in which the piston rod and the solenoid case are plastic flow bonded; FIG. 2 is a diagram for explaining the process flow of the method for producing a combined body according to the first embodiment, showing a state in which the upper die is raised after completion of plastic flow bonding; FIG. 3 is a diagram for explaining the process flow of the method for producing a combined body according to the first embodiment, showing a state in which a block is inserted between the constraint ring and the punch holder; FIG. 4 is a diagram for explaining the process flow of the method for producing a combined body according to the first embodiment, showing a state in which the constraint ring is abutted against the block; FIG. 5 is a diagram for explaining the process flow of the method for producing a combined body according to the first embodiment, showing a process in which the constraint ring is removed; FIG. 6 is a diagram for explaining the process flow of the method for producing a combined body according to the first embodiment, showing a state in which the upper die is raised after the constraint ring has been removed.23 is a diagram for explaining the process flow of the method for manufacturing a combined body according to the first embodiment, showing a state in which the restraint ring has been transported to a restraint ring placement position by a transport unit. 24 is a diagram for explaining the process flow of the method for manufacturing a combined body according to the first embodiment, showing a state in which the block has been retracted from the state of FIG. 21. 25 is an explanatory diagram of a rotary mechanism of a manufacturing apparatus used in a method for manufacturing a combined body according to the second embodiment, showing a state in which the rotating part is located at a lower limit position relative to the fixed part. 26 is an explanatory diagram of a rotary mechanism of a manufacturing apparatus used in a method for manufacturing a combined body according to the second embodiment, showing a state in which the rotating part has been raised relative to the fixed part from the state of FIG. 23. 27 is an explanatory diagram of a rotary mechanism of a manufacturing apparatus used in a method for manufacturing a combined body according to the second embodiment, showing a state in which the rotating part is located at an upper limit position relative to the fixed part. 28 is an explanatory diagram of a rotary mechanism of a manufacturing apparatus used in a method for manufacturing a combined body according to the second embodiment, showing a state in which the rotating part has been lowered relative to the fixed part from the state of FIG. 25. 29 is an explanatory diagram of a rotary mechanism of a manufacturing apparatus used in a method for manufacturing a combined body according to the second embodiment, showing a state in which the rotating part is located at a lower limit position relative to the fixed part. 29 is an explanatory diagram of a rotary mechanism of a manufacturing apparatus used in a method for manufacturing a combined body according to the second embodiment, showing a state in which the rotating part has reached a lock position relative to the fixed part. 31 is an explanatory diagram of a rotary mechanism of a manufacturing apparatus used in a method for manufacturing a combined body according to a second embodiment, showing a state in which the lower end corners of each inner cam of the rotating part abut against the second cam surface of the corresponding outer cam of the fixed part 81. FIG. 32 is an explanatory diagram of a manufacturing apparatus used in a method for manufacturing a combined body according to a second embodiment, showing a state in which a piston rod and a solenoid case (a mating member) are set in a press device. FIG. 33 is an explanatory diagram of a manufacturing apparatus used in a method for manufacturing a combined body according to a second embodiment, showing a state in which plastic flow bonding between the lower end of the piston rod and the bottom of the solenoid case is completed. FIG. 34 is an explanatory diagram of a manufacturing apparatus used in a method for manufacturing a combined body according to a second embodiment, showing a state in which the combined body is lifted up together with the constraint ring as the fixed part holding the constraint ring rises from the state of FIG.FIG. 10 is an explanatory diagram of a manufacturing apparatus used in a method for manufacturing a combined body according to a second embodiment, showing a state in which the restraining ring has been removed (pulled out) from the bottom of the solenoid case (mating member).

[0010] (First embodiment) A first embodiment of the present invention will be described with reference to the accompanying drawings. For convenience, the up-down direction in Fig. 1 will be referred to as the "up-down direction." Fig. 1 shows a so-called built-in-piston type damping force adjustable shock absorber 1 in which a damping force adjustment mechanism 17 is built into a cylinder 2.

[0011] As shown in Figure 1, shock absorber 1 has a twin-cylinder structure in which an outer cylinder 10 is provided on the outer periphery of cylinder 2. Shock absorber 1 has a piston mechanism 140 including a piston 3 and a damping force adjustment mechanism 17. Piston 3 is slidably fitted into cylinder 2, dividing the interior of cylinder 2 into two chambers: an upper cylinder chamber 2A and a lower cylinder chamber 2B. A lower end 143 (one end) of a piston rod 141 (rod-shaped member) is coupled to piston mechanism 140. The other end side (upper side in Figure 1) of piston rod 141 extends outside of cylinder 2.

[0012] A reservoir 18 is formed between the cylinder 2 and the outer cylinder 10, and a base valve 35 is provided at the lower end of the cylinder 2 to separate the cylinder lower chamber 2B from the reservoir 18. Oil is sealed in the cylinder 2 as a working fluid, and oil and gas are sealed in the reservoir 18. A bottom cap 40 is joined to the lower end of the outer cylinder 10.

[0013] The damping force adjustment mechanism 17 includes a valve mechanism 21 and a solenoid 25. The solenoid 25 includes a solenoid case 191 (a mating member). The solenoid case 191 houses a solenoid mechanism (not shown) and an armature coil (not shown) that operates the solenoid mechanism. A lower end 143 (one end) of a piston rod 141 (a rod-shaped member) is joined to a bottom 192 of the solenoid case 191 by plastic flow. That is, the lower end 143 of the piston rod 141 is connected to the piston 3 via the solenoid case 191 and the valve mechanism 21. A bump stopper 28 attached to the piston rod 141 abuts against the bottom 192 of the solenoid case 191.

[0014] The piston rod 141 (rod-shaped member) is inserted through a rod guide 31 and an oil seal 32 attached to the cylinder 2 and the upper end opening of the outer cylinder 10. The piston rod 141 is a hollow shaft having a hollow portion 142 extending along the axial direction (vertical direction). As shown in FIG. 2 , a cable 26 is inserted through the hollow portion 142 of the piston rod 141. The cable 26 passes through a lower end portion 143 of the piston rod 141 and is connected to the solenoid 25. A collar 27 for fixing the cable 26 is provided at the connection between the cable 26 and the solenoid 25. The collar 27 is inserted into a fragile portion 130 (described later) formed in the lower end portion 143 of the piston rod 141.

[0015] The shock absorber 1 (see FIG. 1) has a combination 190 of a piston rod 141 (rod-shaped member) and a solenoid case 191 (mating member). As shown in FIG. 3, the combination 190 is manufactured by fitting the lower end 143 (one end) of the piston rod 141 into a fitting hole 195 formed in a bottom 192 of the solenoid case 191, and then locally pressurizing the bottom 192 of the solenoid case 191, thereby causing the material of the solenoid case 191 to plastically flow into first annular grooves 146, 147 (first groove) and a second annular groove 148 (second groove) (hereinafter referred to as "annular grooves 146, 147, 148" as necessary) formed in an outer circumferential surface 145 of the lower end 143 of the piston rod 141.

[0016] As shown in Fig. 4, two first annular grooves 146, 147 (first grooves) having a V-shaped cross section are formed on the lower end side (one end side of the rod-shaped member) of the outer peripheral surface 145 of the lower end portion 143 (one end) of the piston rod 141 (rod-shaped member). The first annular groove 147 is located directly above the first annular groove 146 in the axial direction (the other end side of the rod-shaped member) in Fig. 4, and has the same axial width W1 and radial depth D1 as the first annular groove 146.

[0017] A second annular groove 148 having a width W2 and a depth D2 smaller than the width W1 of the first annular grooves 146, 147 is provided on the outer peripheral surface 145 of the lower end 143 (one end) of the piston rod 141 (rod-shaped member) at a position spaced a distance Y axially upward (towards the other end of the rod-shaped member) from the first annular groove 147. After plastic flow of material into the first annular grooves 146, 147 (first groove) due to localized pressure is completed, a fragile portion 130 is formed radially inside the lower end 143 of the piston rod 141, which is pressed and deformed by the remaining material of the solenoid case 191 (mating member).

[0018] 4, the fragile portion 130 has a hole (counterbore) shape with an inner diameter W5 and a depth D5. In the first embodiment, the inner diameter W5 of the fragile portion 130 and the inner diameter of the hollow portion 142 are set to be different, but they may be the same. In addition, the lower end side (one end side) of the outer circumferential surface 145 of the lower end portion 143 (one end) of the piston rod 141 (rod-shaped member) has an outer diameter W6.

[0019] A first annular recess 196 (first pressurizing portion) is formed by localized pressurization in the lower end surface 194 of the bottom 192 of the solenoid case 191 (mating member) near the first annular groove 146 (first groove) of the piston rod 141 (rod-shaped member). The first annular recess 196 is located axially lower than the first annular groove 146 (toward one end of the rod-shaped member) and has a radial width W3 and an axial depth D3. Furthermore, a cylindrical first straight portion 131 having a radial width R and extending axially is formed in the bottom 192 of the solenoid case 191 radially inward of the first annular recess 196, i.e., between the first annular recess 196 and the piston rod 141.

[0020] Meanwhile, a second annular recess 198 (second pressurizing portion) is formed by localized pressurization near the second annular groove 148 (second groove) of the piston rod 141 (rod-shaped member) on the inner peripheral side of the upper end surface 193 of the bottom portion 192 of the solenoid case 191 (mating member). The second annular recess 198 is located axially above the second annular groove 148 (toward the other end of the rod-shaped member) and has a radial width W4 and an axial depth D4. Furthermore, a cylindrical second straight portion 132 having a radial width T and extending axially is formed on the bottom portion 192 of the solenoid case 191 radially inward of the second annular recess 198, i.e., between the second annular recess 198 and the piston rod 141.

[0021] The upper end surface 193 of the bottom portion 192 of the solenoid case 191 (the mating member) has a radial width W7 and serves as a pressure-receiving surface when pressure is applied by a first punch 221, which will be described later. The solenoid case 191 also has a material relief portion 133, which is formed by the flow of excess material after plastic flow of the material into the first annular grooves 146, 147 due to localized pressure is completed, radially outward and axially upward (toward the other end of the rod-shaped member) from the upper end surface 193 of the bottom portion 192. The material relief portion 133 has, on its radially inner side, an annular slope 134 whose diameter narrows downward in the axial direction (toward one end of the rod-shaped member).

[0022] Here, the relationship between the width W1 of the first annular grooves 146, 147 (first groove) and the width W2 of the second annular groove 148 (second groove) is preferably W2≦0.7×W1. Furthermore, the relationship between the axial distance Y between the first annular groove 147 and the second annular groove 148 and the width W1 of the first annular grooves 146, 147 is preferably Y≧2×W1. Furthermore, the material of the solenoid case 191 (mating member) is preferably a metal softer than the material of the piston rod 141 (rod-shaped member). For example, the material of the piston rod 141 is carbon steel S45C for mechanical structures, and the material of the solenoid case 191 is carbon steel S10C for mechanical structures (free-cutting steel).

[0023] 5 shows a manufacturing apparatus 210 used in the manufacturing method of the combined body 190 according to the first embodiment. The manufacturing apparatus 210 has an upper mold 203 attached to the slider 52 of the press device 50 shown in FIG. 11 and a lower mold 204 attached to the bolster 53 of the press device. The upper mold 203 is arranged coaxially with the lower mold 204 and can be raised and lowered. The lower mold 204 has a base block 211 fixed to the bolster 53 of the press device.

[0024] A rod insertion hole 212 is formed in the center of the base block 211, through which the upper end 150 (other end) of the piston rod 141 (rod-shaped member) is inserted. A support jig 213 is inserted into the lower end of the rod insertion hole 212. The support jig 213 receives the upper end surface 151 of the piston rod 141, i.e., receives the axial component of the pressing force applied by the plastic flow bonding method. The up and down directions of the piston rod 141 and the solenoid case 191 (mating member) are based on the state in which the combined body 190 is assembled to the shock absorber 1 (see FIG. 1). That is, in FIG. 5, the lower end surface 194 of the solenoid case 191 is positioned facing upward.

[0025] A pair of rings 214, 215 are arranged on the support jig 213 with a gap between them in the axial direction (vertical direction). The rings 214, 215 are made of a material that is softer than the material of the piston rod 141 (rod-shaped member). The rings 214, 215 have centering holes 216, 216 for centering the piston rod 141. A spacer 217 is arranged between the pair of rings 214, 215 to adjust the gap between the rings 214, 215. Note that a plurality of spacers 217 may be stacked. Furthermore, three or more rings 214, 215 may be provided as needed.

[0026] The lower die 204 has a second punch 231 arranged on the ring 215 and a punch holder 232 formed with a punch mounting hole 233 into which the second punch 231 is inserted. The second punch 231 has a rod insertion hole 234 through which the lower end 143 (one end) of the piston rod 141 (rod-shaped member) is inserted. A certain clearance C2 (see FIG. 8) is formed between the rod insertion hole 234 and the piston rod 141.

[0027] As shown in Figures 5 and 6, the second punch 231 has a second annular protrusion 236 formed on its upper end surface 235. The second annular protrusion 236 is formed on the periphery of the opening of the rod insertion hole 234 of the second punch 231 and applies local pressure to the periphery of the opening of the mating hole 195 in the upper end surface 193 of the bottom portion 192 of the solenoid case 191 (the mating member). The second punch 231 has an annular step 239 formed radially outward of the upper end surface 235 and recessed relative to the upper end surface 235. During local pressure application as shown in Figure 8, a gap is formed between the annular step 239 and the recess 133 formed on the upper end surface 193 of the bottom portion 192 of the solenoid case 191.

[0028] As shown in FIG. 5 , the manufacturing apparatus 210 has a restraint ring 205 that prevents the bottom 192 (annular outer periphery) of the solenoid case 191 from deforming radially outward when pressure is applied, i.e., when the piston rod 141 (rod-shaped member) and the solenoid case 191 (mating member) are coupled. The restraint ring 205 is disposed on a punch holder 232 of a lower mold 204. The restraint ring 205 has a restraint hole 206 into which the bottom 192 of the solenoid case 191 is inserted. The restraint ring 205 is configured independently of the upper mold 203 and the lower mold 204 of the manufacturing apparatus 210. Note that in a restraint ring attachment process described below, a certain clearance (reference numeral omitted) larger than clearance C2 (see FIG. 8 ) is set between the restraint hole 206 of the restraint ring 205 and the outer periphery 238 of the second punch 231.

[0029] The upper die 203 is arranged above the lower die 204 and coaxially therewith so as to be able to move up and down freely. The upper die 203 has a first punch 221 having a recess 223 formed in the center of a lower end surface 222 and a first annular protrusion 225 formed on the periphery of the opening of the recess 223 in the lower end surface 222. The lower end portion 143 (one end) of the piston rod 141 (rod-shaped member) is inserted into the recess 223 of the first punch 221. The first annular protrusion 225 of the first punch 221 applies local pressure to the periphery of the opening of the fitting hole 195 in the lower end surface 194 of the bottom 192 of the solenoid case 191 (mating member).

[0030] A certain clearance C1 (see FIG. 8 ) is provided between the inner peripheral surfaces of the first annular convex portion 225 and concave portion 223 of the first punch 221 and the outer peripheral surface 145 of the lower end portion 143 (one end) of the piston rod 141 (rod-shaped member). Note that a certain clearance (reference numeral omitted) larger than the clearance C1 is set between the outer peripheral surface 224 of the first punch 221 and the inner peripheral surface 201 of the reduced diameter portion 200 of the cylindrical portion 199 of the solenoid case 191 (mating member).

[0031] Next, a process flow of the manufacturing method (plastic flow bonding) of the combined body 190 according to the first embodiment using the above-described manufacturing apparatus 210 will be described. Here, the manufacturing apparatus 210 is combined with a press apparatus 50 shown in FIGS. 11 to 22 . The press machine 51 used in the press apparatus 50 may be, for example, an existing servo press. As shown in FIGS. 5 and 11 , the press apparatus 50 has a transport unit 55 equipped with a clamper 56 capable of clamping / unclamping the solenoid case 191 (the mating member) and the restraint ring 205.

[0032] The transport unit 55 has rails 57 extending horizontally, a slide section 58 that moves the clamper 56 along the rails 57, and an elevator section (not shown) that is provided on the slide section 58 and raises and lowers the clamper 56. The press device 50 also has a block 60 that is inserted between the restraint ring 205 and the punch holder 232 at a timing that will be described later, and a block drive section (not shown) that moves the block 60 forward (insertion) and backward (retraction).

[0033] First, the transport unit 55 clamps the solenoid case 191 (mating member) supplied by the member supply unit (not shown) with the clamper 56. Next, as shown in Fig. 11 , the transport unit 55 operates the clamped solenoid case 191 to fit the lower end (one end) of the piston rod 141 (rod-shaped member) set in the manufacturing apparatus 210 into the fitting hole 195 (see Fig. 5 ) in the bottom 192 of the solenoid case 191.

[0034] Next, as shown in Fig. 12, the transport unit 55 clamps the restraint ring 205 placed on the restraint ring mounting portion 59 with the clamper 56. Next, as shown in Fig. 13, the transport unit 55 operates the clamped restraint ring 205 and positions the restraint ring 205 coaxially with the solenoid case 191. Next, the transport unit 55 fits the bottom 192 (see Fig. 5) of the solenoid case 191 into the restraint hole 206 (see Fig. 5) of the restraint ring 205, and then unclamps the restraint ring 205 and retracts the clamper 56 to the retracted position as shown in Fig. 14.

[0035] Next, as shown in Fig. 15, the slider 52 of the press 51 is lowered to lower the upper die 203, thereby plastically flow bonding the piston rod 141 (rod-shaped member) and the solenoid case 191 (mating member). Next, as shown in Fig. 16, the slider 52 of the press 51 is raised to raise the upper die 203. At this time, the solenoid case 191 is pressed into the first punch 221 and the restraint ring 205 of the upper die 203 due to deformation after the pressurization is completed, so the restraint ring 205 is raised integrally with the combined body 190 as the upper die 203 is raised.

[0036] 17, the ascent of the upper die 203 is stopped at a predetermined position (block insertion position) where the axial gap generated between the constraint ring 205 and the punch holder 232 is equal to or greater than the height (axial length) of the constraint ring 205, and then a block 60 that restricts the descent of the constraint ring 205 is inserted between the constraint ring 205 and the punch holder 232. Next, when the upper die 203 is lowered again, the constraint ring 205 and the block 60 come into contact with each other, as shown in FIG.

[0037] When the upper mold 203 is further lowered after the restraint ring 205 comes into contact with the block 60, the block 60 prevents the restraint ring 205 from descending, and only the upper mold 203 and the combined body 190 descend, as shown in Fig. 19, so that the restraint ring 205 can be removed (pulled out) from the bottom 192 (see Fig. 5) of the solenoid case 191 (the mating member). Next, the descent of the upper mold 203 is stopped at a position where separation of the restraint ring 205 and the solenoid case 191 is completed (the restraint ring separation position), and then the upper mold 203 is raised to the product discharge position as shown in Fig. 20.

[0038] Next, transport unit 55 clamps restraint ring 205 remaining on block 60 with clamper 56, and places clamped restraint ring 205 on restraint ring placement section 59, as shown in Fig. 21. Next, as shown in Fig. 22, block 60 is retracted, and then combined body 190 is ejected from manufacturing apparatus 210. This completes the series of steps in the method for manufacturing combined body 190.

[0039] Next, the operation of the manufacturing apparatus 210 will be described. Here, Fig. 6 shows the state before the upper mold 203 of the manufacturing apparatus 210 is lowered and local pressure application begins. In this state, the lower end 143 (one end) of the piston rod 141 (rod-shaped member) is fitted into the fitting hole 195 of the bottom 192 of the solenoid case 191 (mating member), and the restraining hole 206 of the restraining ring 205 is fitted into the outer peripheral surface 197 of the bottom 192 of the solenoid case 191. Furthermore, the tip end surface 226 of the first annular protrusion 225 of the first punch 221 abuts against the lower end surface 194 of the bottom 192 of the solenoid case 191, near the first annular groove 146 of the piston rod 141. Furthermore, the tip surface 237 of the second annular protrusion 236 of the second punch 231 abuts against the upper end surface 193 of the bottom portion 192 of the solenoid case 191 in the vicinity of the second annular groove 148 of the piston rod 14 .

[0040] 6, there is actually a gap (not shown) between the fitting hole 195 in the bottom 192 of the solenoid case 191 (mating member) and the outer circumferential surface 145 of the lower end 143 (one end) of the piston rod 141 (rod-shaped member), and a positional deviation equivalent to the gap may occur between the axis of the solenoid case 191 and the axis of the piston rod 141 before local pressure is applied. Also, in FIG. 6, of the gaps between the fitting hole 195 in the bottom 192 of the solenoid case 191 and the outer circumferential surface 145 of the lower end 143 of the piston rod 141, the gap on the side of the first annular grooves 146, 147 is indicated as clearance C3, and the gap on the side of the second annular groove 148 is indicated as clearance C4. Here, before local pressure application, the clearance C3 at any position in the circumferential direction is equal to C4, but for convenience, they are shown separately because this is necessary to explain the action of the centering process that corrects the misalignment between the axis of the solenoid case 191 and the axis of the piston rod 141.

[0041] 6, when the upper die 203 is lowered, the inner periphery 202 of the bottom 192 of the solenoid case 191 (the mating member) is locally pressurized by the first annular convex portion 225 of the first punch 221 and the second annular convex portion 236 of the second punch 231. Here, based on the Tresca deformation condition, first, the material of the solenoid case 191 near the second annular groove 148 undergoes deformation (plastic flow) such that it flows into the gap of the clearance C4 and into the second annular groove 148.

[0042] If there is any misalignment between the axial centers of the solenoid case 191 (mating member) and the piston rod 141 (rod-shaped member), when the second straight portion 132 (see FIG. 8) is formed by deformation due to pressure, the solenoid case 191 moves radially relative to the piston rod 141, and the clearance C4 becomes uniform over the entire circumference, thereby correcting the misalignment between the axial centers of the solenoid case 191 and the piston rod 141 (first centering step). Then, as shown in FIG. 7, the material of the solenoid case 191 is filled into the second annular groove 148, and the upper end surface 235 of the second punch 231 comes into contact with the upper end surface 193 of the bottom portion 192 of the solenoid case 191, forming the annular second joint portion 243 (first plastic flow step).

[0043] Next, when the upper end surface 235 of the second punch 231 comes into contact with the upper end surface 193 of the bottom portion 192 of the solenoid case 191 (the mating member), the material of the solenoid case 191 facing the first annular protrusion 225 of the first punch 221 begins to deform and flows into the gap of the clearance C3. As the upper die 203 further descends, the material of the solenoid case 191 near the first annular grooves 146, 147 undergoes deformation (plastic flow) such that it flows into the first annular grooves 146, 147 of the piston rod 141 (the rod-shaped member).

[0044] At this time, if there is a misalignment between the axial center of the solenoid case 191 (mating member) and the axial center of the piston rod 141 (rod-shaped member), when the first straight section 131 (see Figure 8) is formed by deformation due to pressure, the solenoid case 191 moves radially relative to the piston rod 141, and the clearance C3 becomes uniform around the entire circumference, thereby correcting the misalignment between the axial center of the solenoid case 191 and the axial center of the piston rod 141 (second centering process).

[0045] 8 , the material of the solenoid case 191 (the mating member) is filled into the first annular grooves 146, 147 of the piston rod 141 (the rod-shaped member), thereby forming the first annular joints 241, 242 (second plastic flow process). Note that if the misalignment between the axis of the solenoid case 191 and the axis of the piston rod 141 is not completely resolved in the second plastic flow process, the material of the solenoid case 191 will not fill the first annular grooves 146, 147 uniformly around the entire circumference. However, the remaining material after filling presses the weakened portion 130 formed in the piston rod 141, deforming the lower end 143 of the piston rod 141 radially inward nonuniformly along the circumferential direction, thereby equalizing the residual stress in the joints 241, 242, 243 around the entire circumference (first stress equalization process).

[0046] Furthermore, when the material of the solenoid case 191 (mating member) has completely filled into the first annular grooves 146, 147 of the piston rod 141 (rod-shaped member), it flows into the gap between the bottom 192 of the solenoid case 191 and the annular step 239 of the second punch 231 to form a material relief portion 133, and by allowing the excess material that does not fill the annular grooves 146, 147, 148 to escape, the residual stress in the joints 241, 242, 243 is equalized over the entire circumference (second stress equalization step). Then, as shown in Figure 8, when the material relief portion 133 has been formed over the entire circumference of the upper end surface 193 of the bottom 192 of the solenoid case 191, the application of pressure by the manufacturing apparatus 210 is completed.

[0047] Here, after pressure application is complete, the solenoid case 191 (the mating member) is deformed and press-fitted into the first punch 221 and the restraint ring 205 of the upper die 203. When the upper die 203 is raised in this state, the combined body 190 (solenoid case 191) and the restraint ring 205 are pulled up together. Then, when the axial gap created between the restraint ring 205 and the punch holder 232 (see FIG. 5 ) becomes equal to or greater than the height (axial length) of the restraint ring 205, a block 60 is inserted between the restraint ring 205 and the punch holder 232 to limit the descent of the restraint ring 205.

[0048] 9 shows a state in which, after the block 60 has been inserted between the restraint ring 205 and the punch holder 232, the upper die 203 is lowered again, bringing the restraint ring 205 into contact with the block 60. When the upper die 203 is further lowered from the state shown in FIG. 9, only the upper die 203 and the combined body 190 descend, and the restraint ring 205 does not descend, so that the bottom 192 of the solenoid case 191 (the mating member) can be removed (pulled out) from the restraint hole 206 of the restraint ring 205 (restriction ring removal process).

[0049] Thus, the manufacturing method (plastic flow joining method) for the combined body 190 according to the first embodiment includes first and second plastic flow processes for joining the piston rod 141 (rod-shaped member) and the solenoid case 191 (mating member), first and second centering processes for correcting the misalignment between the axial center of the piston rod 141 and the axial center of the solenoid case 191, and first and second stress equalization processes for equalizing the residual stresses in the combined portions 241, 242, and 243 after joining over the entire circumference.

[0050] In the first embodiment, even if the piston rod 141 and the solenoid case 191 are set in the manufacturing apparatus 210 in a state where the axial center of the piston rod 141 (rod-shaped member) and the axial center of the solenoid case 191 (mating member) are misaligned before joining, i.e., there is a gap between the outer surface 145 of the lower end 143 (one end) of the piston rod 141 and the fitting hole 195 of the bottom 192 of the solenoid case 191, and the gap is uneven, the piston rod 141 and the solenoid case 191 can be quickly joined with high coaxiality by applying local pressure to the solenoid case 191 with the first punch 221 and the second punch 231.

[0051] In addition, in the first embodiment, the restraint ring 205 is configured to be independent from the manufacturing apparatus 210, and includes a restraint ring attachment process in which the restraint ring 205 is pre-set on the solenoid case 191 (counterpart) before pressurization, and a restraint ring removal process in which the restraint ring 205 is removed (pulled out) from the solenoid case 191 after pressurization is complete, resulting in a manufacturing method in which the piston rod 141 (rod-shaped member) is not directly pressurized throughout the entire manufacturing process.

[0052] As a result, in the first embodiment, it is possible to reduce the pressurizing force received by the piston rod 141 and suppress deformation of the opening periphery and upper end surface 151 (pressure-receiving surface) of the upper end portion 150 (other end) of the piston rod 141. Furthermore, in the first embodiment, the deformation of the fragile portion 130 of the piston rod 141 in the first stress equalization step is not hindered, and the piston rod 141 itself is not deformed in the restraining ring removal step, so the coaxiality of the combined body 190 can be improved.

[0053] The inventors of the present application then conducted their own experiments to determine the dimensions shown in FIG. 4 in order to more effectively reduce the coaxiality between the piston rod 141 (rod-shaped member) and the solenoid case 191 (mating member) after they are joined together.

[0054] Fig. 10 shows the results of an experiment regarding the depth D5 of the fragile portion 130 of the piston rod 141 (rod-shaped member). In Fig. 10, the horizontal axis represents the ratio (hereinafter referred to as "D5 / K") of the depth D5 of the fragile portion 130 to the distance K from the lower end surface 194 of the bottom portion 192 of the solenoid case 191 (mating member) to the first annular groove 146 of the piston rod 141 (rod-shaped member), and the vertical axis represents the concentricity of the piston rod 141 and the solenoid case 191 after they are coupled.

[0055] The results shown in Figure 10 confirmed that the larger the D5 / K, the better the coaxiality of the combined body 190. However, considering that too large a D5 / K would cause excessive deformation of the fragile portion 130 and reduce the bonding strength, D5 / K was set to 1.6. When the inner diameter W5 of the fragile portion 130 was varied at D5 / K = 1.6, it was found that if the inner diameter W5 was too small, the fragile portion 130 would be less likely to deform, resulting in insufficient first stress equalization and reduced coaxiality of the combined body 190. On the other hand, it was found that if the inner diameter W5 was too large, the fragile portion 130 would be excessively deformed and reduce the bonding strength. Therefore, it is desirable that the inner diameter W5 of the fragile portion 130 satisfy the relationship 0.35 x W6 ≤ W5 ≤ 0.7 x W6, relative to the outer diameter W6 of the lower end (one end) of the outer peripheral surface 145 at the lower end 143 (one end) of the piston rod 141 (rod-shaped member).

[0056] Furthermore, the width R of the first straight portion 131 and the width T of the second straight portion 132 are preferably set to approximately 0.05 to 0.5 mm to prevent breakage of the punches 221 and 231 during pressure application. The first annular recess 196 (first pressure applying portion) formed in the solenoid case 191 (the mating member) is preferably positioned below (on one end of) the piston rod 141 relative to the first annular groove 146 formed in the piston rod 141 (the rod-shaped member) (D3<K), and the second annular recess 198 (second pressure applying portion) formed in the solenoid case 191 is preferably positioned above (on the other end of) the piston rod 141 relative to the second annular groove 148 formed in the piston rod 141 (D4<J). Note that J in FIG. 4 is the distance from the upper end surface 193 of the bottom 192 of the solenoid case 191 to the second annular groove 148 of the piston rod 141.

[0057] In the first embodiment, the inner diameter W7 of the upper end surface 193 of the bottom portion 192 of the solenoid case 191 (the counterpart member) is set so that the upper end surface 193, which comes into contact with the upper end surface 235 (see FIG. 8 ) of the second punch 231, exceeds the yield stress of the material of the solenoid case 191 after the second plastic flow process. Note that if the inner diameter W7 is too large, the upper end surface 193 of the bottom portion 192 of the solenoid case 191 will not yield, and the material relief portion 133 will not be formed.

[0058] However, with conventional manufacturing methods, there is a large variation in the coaxiality between the piston rod and the solenoid case, which increases the sliding resistance between the piston and cylinder when the piston rod strokes, which may result in a deterioration in the responsiveness of the shock absorber and a reduction in the shock absorber's lifespan.

[0059] In contrast, the manufacturing method (plastic flow joining method) for the combined body 190 according to the first embodiment includes first and second plastic flow processes for joining the piston rod 141 (rod-shaped member) and the solenoid case 191 (mating member), first and second centering processes for correcting the misalignment between the axial center of the piston rod 141 and the axial center of the solenoid case 191, and first and second stress equalization processes for equalizing the residual stress of the combined portions 241, 242, and 243 after pressurization over the entire circumference.

[0060] In the first embodiment, a weakened portion 130 is provided at a lower end portion 143 (one end portion) of a piston rod 141 (rod-shaped member) of a combined body 190, and a depth D5 of the weakened portion 130 is set so that D5 / K≧1.6, where K is a distance from the lower end surface of the piston rod 141 to the first annular groove 146 (first groove). Furthermore, in the first embodiment, an inner diameter W5 of the weakened portion 130 is set so that a relationship of 0.35×W6≦W5≦0.7×W6 is satisfied, relative to an outer diameter W6 of the piston rod 141. Furthermore, in the first embodiment, an inner diameter W7 of an upper end surface 193 of a bottom portion 192 of a solenoid case 191 (counterpart) is set so that the material of a portion of the upper end surface 193 that comes into contact with an upper end surface 235 (see FIG. 8 ) of a second punch 231 exceeds the yield stress after the second plastic flow process.

[0061] According to the first embodiment, even when the piston rod 141 and the solenoid case 191 are set in the manufacturing apparatus 210 in a state in which the axial center of the piston rod 141 (rod-shaped member) and the axial center of the solenoid case 191 (mating member) are misaligned before connection, that is, in a state in which there is a gap between the outer surface 145 of the lower end portion 143 (one end portion) of the piston rod 141 and the mating hole 195 of the bottom portion 192 of the solenoid case 191 before connection and the gap is uneven, the piston rod 141 and the solenoid case 191 can be quickly connected with high coaxiality by applying local pressure to the solenoid case 191 with the first punch 221 and the second punch 231.

[0062] Furthermore, in the first embodiment, the connecting portions 241, 242, 243 have sufficient strength required for the shock absorber 1, and in addition, since they are formed by adhesion between newly formed surfaces of the piston rod 141 (rod-shaped member) and the solenoid case 191 (mating member), they are impermeable to air and oil, eliminating the need for a liquid-tight seal member when applied to the shock absorber 1. This makes it possible to make the connecting body 190 smaller (shorten the axial length) and reduce the number of parts compared to connecting portions that are conventionally fastened by screws.

[0063] For example, in the shock absorber shown in Figure 1 of Patent Document 2, the piston rod 9 and the case member 8 are fastened together by a threaded joint 11, but if this threaded joint is replaced with the plastic flow joining method according to the first embodiment, the nut 12 for preventing loosening and the small diameter portion 13 against which the end face of the threaded portion of the piston rod 9 abuts, shown in Figure 1 of Patent Document 2, become unnecessary, and the axial length of the shock absorber can be shortened by the height (axial length) of the nut 12 and the small diameter portion 13. Furthermore, in the first embodiment, the joint portion becomes a metal seal, so the O-ring 14 shown in Figure 1 of Patent Document 2 becomes unnecessary, and two parts can be eliminated, including the nut 12.

[0064] In addition, in conventional manufacturing methods, when a rod-shaped member and a mating member must be joined with high coaxiality, for example, the mating portion between the rod-shaped member and the mating member is machined with high precision before joining and then press-fitted. However, press-fitting can result in galling, seizure, or the generation of foreign matter at the mating portion. To address this issue, the use of processing oil or the provision of a guide groove at the mating portion are common solutions. However, the former method can cause oil to enter the mating groove (annular groove) during plastic flow, reducing the strength and liquid-tightness of the joint. The latter method increases the axial length of the combined body by the height (axial length) of the guide groove, resulting in a larger part. Furthermore, when a small-diameter, hollow rod-shaped member is press-fitted into a mating member as in the first embodiment, the press-fit load cannot be set high due to the risk of deformation of the pressurized rod-shaped member, making it difficult to ensure sufficient joint strength through press-fitting alone when used in a shock absorber.

[0065] In contrast, the manufacturing method (plastic flow joining method) for the combined body 190 according to the first embodiment includes first and second plastic flow processes for joining the piston rod 141 (rod-shaped member) and the solenoid case 191 (mating member), first and second centering processes for correcting the misalignment between the axis of the piston rod 141 and the axis of the solenoid case 191, and first and second stress equalization processes for equalizing the residual stresses of the combined portions 241, 242, and 243 over the entire circumference. Therefore, it is possible to simultaneously satisfy the coaxiality and joining strength of the combined body 190, and there is no need for a preliminary process for ensuring coaxiality in advance, as in the press-fit method described above.

[0066] In addition, in the first embodiment, since it is possible to ensure coaxiality between the piston rod 141 (rod-shaped member) and the solenoid case 191 (mating member) while allowing for a gap at the mating portion between the piston rod 141 (rod-shaped member) and the solenoid case 191, there is no risk of galling or seizure during coupling, or the generation of foreign matter, which were necessary measures in the conventional press-fit method. Furthermore, in the first embodiment, coupling is completed simply by applying pressure to the solenoid case 191, i.e., the piston rod 141 is not directly pressurized, so deformation of the piston rod 141 itself can be prevented.

[0067] Furthermore, the manufacturing method (plastic flow bonding method) for the combined body 190 according to the first embodiment separates the restraint ring 205 from the manufacturing apparatus 210 and includes a restraint ring attachment process in which the restraint ring 205 is set in advance before pressurizing the solenoid case 191 (the mating member), and a restraint ring removal process in which the restraint ring 205 is removed (pulled out) after pressurization is complete. This eliminates the need to directly pressurize the piston rod 141 throughout the entire process, thereby reducing the pressurizing force applied to the piston rod 141 and preventing deformation of the opening periphery of the upper end 150 (the other end) of the piston rod 141 and the upper end surface 151 (the pressure-receiving surface). Furthermore, in the first embodiment, the deformation of the fragile portion 130 of the piston rod 141 during the first stress equalization process is not hindered, and the piston rod 141 itself is not deformed during the restraint ring removal process, ensuring the coaxiality of the combined body 190.

[0068] In the first stress equalization step in the first embodiment, the weakened portion 130 formed in the piston rod 141 (rod-shaped member) in order to equalize the residual stress of the joints 241, 242, 243 over the entire circumference has a collar 27 inserted inside it that secures the cable 26 connected to the upper end (upper part in Figures 1 and 2) of the solenoid 25, so that the axial length of the piston mechanism 140 can be shortened by the height (axial length) of the collar 27.

[0069] Furthermore, in order to equalize the circumferential residual stresses of the joints 241, 242, 243 formed in the second stress equalization step in the first embodiment, the material relief portion 133 formed in the solenoid case 191 (mating member) has a radially inner annular inclined surface 134 formed in a guide shape that receives the tapered portion on the outer periphery of the bump stopper 28 (see FIG. 1 ). By inducing the plastic flow of the material to extend along the inclined surface 134, it is possible to reduce the load on the bump stopper 28 when the shock absorber 1 elongates and the tapered portion of the bump stopper 28 collides with the solenoid case 191, and to prevent localized wear of the bump stopper 28. Furthermore, the guide shape formed by the material relief portion 133 of the solenoid case 191 is formed to follow the shape of the tapered portion of the bump stopper 28, so it is possible to avoid disadvantages such as an increase in axial length and a decrease in stroke amount of the shock absorber 1.

[0070] As described above, in the first embodiment, not only is high coaxiality achieved in the connection between the piston rod 141 (rod-shaped member) and the solenoid case 191 (mating member), but the required connection strength and oil-tightness of the shock absorber 1 can also be satisfied. Furthermore, compared to conventional screw fastening, it is possible to shorten the axial length and reduce the number of parts. Furthermore, compared to the press-fit method, there is no risk of galling, seizure, or the generation of foreign matter during connection, ensuring high coaxiality. Furthermore, the connection can be completed by applying local pressure only to the solenoid case 191 (mating member). Since the piston rod 141 (rod-shaped member) is not directly pressurized throughout the entire connection process, deformation of the piston rod 141 itself can be suppressed. Therefore, the method for joining two members (plastic flow joining method) according to the first embodiment is suitable as a method for joining the piston rod 141 (rod-shaped member) and the solenoid case 191 (mating member) in the shock absorber 1. In the first embodiment, when the solenoid case 191 (mating member) is set in the lower mold 204, that is, when the mating hole 195 in the bottom 192 of the solenoid case 191 is fitted into the lower end (one end) of the piston rod 141 (rod-shaped member) set in the lower mold 204 (manufacturing apparatus 210), the bottom 192 of the solenoid case 191 is restrained by the restraining ring 205 and the upper mold 203 is lowered, the piston rod 141 and the solenoid case 191 are plastic flow bonded together. However, for example, after the solenoid case 191 (mating member) is set in the upper mold 203, the bottom 192 of the solenoid case 191 may be restrained by the restraining ring 205 during the process of lowering the upper mold 203, and the piston rod 141 and the solenoid case 191 may be plastic flow bonded together.

[0071] Second Embodiment Next, a second embodiment will be described with reference to Figures 23 to 33. Note that the same names and symbols are used for parts common to the first embodiment, and duplicated descriptions will be omitted.

[0072] In the first embodiment described above, in the restraining ring removal process, the upper die 203 is raised to raise the first punch 221, the connecting body 190, and the restraining ring 205 as a unit, and when the axial gap between the restraining ring 205 and the punch holder 232 becomes equal to or greater than the height (axial length) of the restraining ring 205, a block 60 is inserted between the restraining ring 205 and the punch holder 232 to restrict the descent of the restraining ring 205. Next, the upper die 203 is lowered again to bring the restraining ring 205 into contact with the block 60, and the upper die 203 is further lowered to move the restraining ring 205 and the connecting body 190 relative to each other in the axial direction, thereby removing (pulling out) the restraining ring 205 from the restraining hole 206 of the solenoid case 191 (the mating member).

[0073] In contrast to this, in the second embodiment, the upper mold 203 is provided with a holding unit 70 that holds the restraint ring 205 coaxially with the piston rod 141 (rod-shaped member) and solenoid case 191 (counterpart) set in the manufacturing apparatus 210, and the manufacturing apparatus 210 is configured by further providing the holding unit 70 with a rotary mechanism 71 having a fixed portion 81 and a rotating portion 101.

[0074] As shown in Figure 23 or 30, the holding unit 70 has a cylindrical fixed part 81 suspended from the upper die 203 via multiple shafts 72 (only two are shown in Figure 23), and a cylindrical rotating part 101 attached to the outer periphery of the fixed part 81 so as to be movable axially and rotationally relative to the fixed part 81. The fixed part 81 has an axial hole 82 through which the first punch 221 is inserted. A restraining ring 205 is slidably inserted into the axial hole 82. That is, the restraining ring 205 is movable axially and rotationally within the axial hole 82. A step 83 is formed at the lower end of the axial hole 82 to restrict downward movement of the restraining ring 205 relative to the axial hole 82.

[0075] As shown in FIG. 23 , the rotary mechanism 71 has a plurality of outer cams 85 formed on the upper end (other end side) of the outer peripheral surface 84 of the fixed portion 81 and a plurality of outer cams 93 formed on the lower end (one end side) of the outer peripheral surface 84. The plurality of outer cams 85 are arranged at regular intervals in the circumferential direction. Between adjacent outer cams 85, inner cam restricting portions 86 extending between the upper ends of the adjacent outer cams 85 and inner cam insertion portions 87 into which inner cams 111 formed on the rotating portion 101 can be inserted are alternately provided in the circumferential direction. The outer cams 85 have a first cam surface 88 extending downward from the upper end of the fixed portion 81 and parallel to the axis of the fixed portion 81, and a second cam surface 89 extending from the lower end of the first cam surface 88 to the upper left in FIG. 23 at an arbitrary inclination angle.

[0076] On the other hand, the multiple outer cams 93 are arranged in the circumferential direction. As a result, the multiple outer cams 93 form peaks 94 and valleys 95. The outer cam 93 has a first cam surface 96 that extends upward from the lower end of the fixed portion 81 and is parallel to the axis of the fixed portion 81, and a second cam surface 97 that extends from the upper end of the first cam surface 96 downward and to the left in FIG. 23 at an arbitrary inclination angle. The circumferential length of the lower (one end) outer cam 93 is set longer than the circumferential length of the upper (other end) outer cam 85, and therefore longer than the circumferential length of the inner cam insertion portion 87.

[0077] As shown in FIG. 23 , the rotary mechanism 71 has a plurality of (four in the second embodiment) inner cams 111 formed on the upper end (other end) of the inner circumferential surface 102 (see FIG. 30 ) of the rotating part 101. The inner cams 111 are arranged at regular intervals in the circumferential direction so that they can face each other in the axial direction with the plurality of inner cam restricting portions 86 of the fixed part 81 and so that they can face each other in the axial direction with the plurality of inner cam insertion portions 87 of the fixed part 81. Each inner cam 111 has a first cam surface 112 that extends downward from the upper end of the rotating part 101 and is parallel to the axis of the rotating part 101, and a second cam surface 113 that extends from the lower end of the first cam surface 112 at an inclination angle of 45 degrees upward and to the right in FIG. 23 . The circumferential length of the inner cam 111 is set shorter than the circumferential lengths of the inner cam restricting portions 86 of the fixed part 81 and the inner cam insertion portions 87.

[0078] Next, the operation of the rotary mechanism 71 will be described. First, with the upper mold 203 in the material setting position shown in FIG. 30 , the lower end (one end) of the piston rod 141 (rod-shaped member) is fitted into the fitting hole 195 (see FIG. 5 ) in the bottom 192 of the solenoid case 191 (mating member) set in the lower mold 204. At this time, each inner cam 111 of the rotating unit 101 is fitted into each valley 95 between adjacent outer cams 93 of the fixed unit 81. As a result, as shown in FIG. 23 , the first cam surface 112 of each inner cam 111 abuts against the first cam surface 96 of the corresponding outer cam 93, and the second cam surface 113 of the inner cam 111 abuts against the second cam surface 97 of the corresponding outer cam 93. In the state shown in FIG. 23 , the rotating unit 101 is located at its lowest position relative to the fixed unit 81.

[0079] Next, when the upper die 203 and the fixed part 81 are lowered from the lowest position of the rotating part 101 shown in Fig. 23 , the rotating part 101 rises relative to the fixed part 81 at the point when the lower end of the rotating part 101 abuts against the punch holder 232 (see Fig. 30 ). During the process of the rotating part 101 rising relative to the fixed part 81, the upper end corners 114 of each inner cam 111 of the rotating part 101 abut against the second cam surfaces 89 of the corresponding outer cams 85 of the fixed part 81, as shown in Fig. 24 . When the fixed part 81 is further lowered to raise the rotating part 101 relative to the fixed part 81, as the rotating part 101 rises, the upper end corners 114 of each inner cam 111 move (slide) along the second cam surfaces 89 of the corresponding outer cams 85 toward the inner cam insertion parts 87, and the rotating part 101 rotates clockwise on the punch holder 232 (see Fig. 30 ) relative to the fixed part 81.

[0080] Then, in the process of the rotating part 101 reaching its upper limit position (see FIG. 25) relative to the fixed part 81, in other words, in the process of the bottom part 192 (see FIG. 5) of the solenoid case 191 (the mating member) being plastically flow bonded to the lower end part 143 (see FIG. 5) of the piston rod 141 (the rod-shaped member), each inner cam 111 of the rotating part 101 is inserted into the corresponding inner cam insertion part 87 of the fixed part 81. Here, when the rotating part 101 reaches its upper limit position relative to the fixed part 81, the lower end of the fixed part 81 abuts against the punch holder 232 (see FIG. 30), and the upper end of the rotating part 101 is positioned higher than the upper end of the fixed part 81.

[0081] Furthermore, when the rotating part 101 reaches its upper limit position relative to the fixed part 81 (see Figure 25), the bottom 192 (see Figure 5) of the solenoid case 191 (mate member) is fitted into the restraint hole 206 (see Figure 5) of the restraint ring 205 held by the fixed part 81, and when the upper mold 203 and the first punch 221 are further lowered, the bottom 192 of the solenoid case 191 is pressurized by the first punch 221 and the second punch 231 (see Figure 5), and when the upper mold 203 reaches the completion of bonding position (see Figure 31), the plastic flow bonding between the lower end part 143 (see Figure 5) of the piston rod 141 and the bottom 192 of the solenoid case 191 is completed.

[0082] Next, when the upper die 203 and the fixed part 81 are raised from the upper limit position of the rotating part 101 shown in Fig. 25 , as the rotating part 101 descends relative to the fixed part 81, the lower end corners 115 of each inner cam 111 of the rotating part 101 come into contact with the upper part of the second cam surface 97 of the corresponding outer cam 93 (located directly below the inner cam 111) of the fixed part 81, as shown in Fig. 26 . When the fixed part 81 is further raised to lower the rotating part 101 relative to the fixed part 81, the lower end corners 115 of each inner cam 111 move (slide) along the second cam surface 97 of the corresponding outer cam 93 toward the valley portions 95 of the outer cam 93 as the rotating part 101 descends, and the rotating part 101 further rotates clockwise on the punch holder 232 (see Fig. 30 ) relative to the fixed part 81.

[0083] 27, the inner cams 111 of the rotating part 101 fit into the valleys 95 between the adjacent outer cams 93 of the fixed part 81, and when the rotating part 101 reaches its lowest position relative to the fixed part 81, the rising of the fixed part 81, i.e., the descent of the rotating part 101, stops. Note that because the solenoid case 191 (see FIG. 5) is pressed into the first punch 221 and the restraining ring 205 (see FIG. 32) due to deformation after the pressurization is complete, as the fixed part 81 holding the restraining ring 205 rises, the combined body 190 is pulled up integrally with the restraining ring 205, as shown in FIG.

[0084] 27, when the upper die 203 and the fixed part 81 are lowered from the lowest limit position of the rotating part 101, as the rotating part 101 rises relative to the fixed part 81, the upper corners 114 of the inner cams 111 of the rotating part 101 come into contact with the lower part of the second cam surface 89 of the corresponding outer cam 85 (positioned directly above the inner cam 111) of the fixed part 81. When the fixed part 81 is further lowered to raise the rotating part 101 relative to the fixed part 81, as the rotating part 101 rises, the upper corners 114 of the inner cams 111 move (slide) along the second cam surface 89 of the corresponding outer cam 85 toward the inner cam restricting part 86, and the rotating part 101 further rotates clockwise on the punch holder 232 (see FIG. 30) relative to the fixed part 81.

[0085] Then, as shown in Figure 28, the third cam surface 116 of each inner cam 111 of the rotating part 101 abuts against the inner cam regulating part 86 of the fixed part 81, and when the rotating part 101 reaches a locked position relative to the fixed part 81, the descent of the fixed part 81 is prevented. Thereafter, only the first punch 221 and the connecting body 190 descend, and as shown in Figure 33, the restraining ring 205 can be removed (pulled out) from the bottom 192 of the solenoid case 191 (counterpart).

[0086] Next, the descent of the upper mold 203 is stopped at the position where separation of the restraint ring 205 (see Figure 30) and the solenoid case 191 (see Figure 5) is completed (restraint ring separation position), and then the upper mold 203, the first punch 221, and the fixed part 81 are raised, and the rotating part 101 is lowered relative to the fixed part 81.As the rotating part 101 descends relative to the fixed part 81, as shown in Figure 29, the lower end corner 115 of each inner cam 111 of the rotating part 101 abuts against the upper part of the second cam surface 97 of the corresponding outer cam 93 of the fixed part 81 (located directly below the inner cam 111). When the fixed portion 81 is further raised and the rotating portion 101 is lowered relative to the fixed portion 81, as the rotating portion 101 descends, the lower end corner portion 115 of each inner cam 111 moves (slides) along the second cam surface 97 of the corresponding outer cam 93 toward the valley portion 95 of the outer cam 93, and the rotating portion 101 further rotates clockwise relative to the fixed portion 81 on the punch holder 232 (see Figure 30).

[0087] Then, each inner cam 111 of the rotating part 101 is fitted into each valley 95 between adjacent outer cams 93 of the fixed part 81, and the rotating part 101 returns to the lower limit position relative to the fixed part 81 shown in Figure 23.

[0088] According to the second embodiment, it is possible to obtain the same effects as those of the first embodiment. Furthermore, a manufacturing apparatus 210 for a combined body 190 according to the second embodiment includes a holding unit 70 that is provided on an upper mold 203 and that holds a restraint ring 205 coaxially with respect to a piston rod 141 (a rod-shaped member) and a solenoid case 191 (a mating member). The holding unit 70 has a cylindrical fixed portion 81 that rises and falls integrally with the upper mold 203, and a rotating portion 101 that is provided on the outer periphery of the fixed portion 81. The holding unit 70 includes a rotary mechanism 71 that has an outer cam 85 that is provided circumferentially at the upper end of the fixed portion 81, an outer cam 93 that is provided circumferentially at the lower end of the fixed portion 81, and an inner cam 111 that is provided at the upper end of the rotating portion 101 and cooperates with the outer cam 85 and the outer cam 93.

[0089] In addition, in the manufacturing method of the combined body 190 according to the second embodiment, the rotating part 101 is rotated in the circumferential direction on the punch holder 232 relative to the fixed part 81 from a state in which the rotating part 101 is located at a lower limit position relative to the fixed part 81, and raised to an upper limit position, the restraining ring 205 held by the fixed part 81 is fitted onto the outer periphery of the bottom part 192 of the solenoid case 191 (counterpart) set in the lower die 204, and then the bottom part 192 of the solenoid case 191 (counterpart) is pressurized to pressurize the piston rod 141 (rod-shaped member) and the solenoid case 19 1 by plastic flow bonding; next, a step of lowering the rotating part 101 to a lower limit position relative to the fixed part 81 while rotating the rotating part 101 in a circumferential direction on the punch holder 232; next, a step of raising the rotating part 101 relative to the fixed part 81, during which the raising of the rotating part 101 relative to the fixed part 81 is restricted at a locked position (a restraining ring removal step); and next, a step of raising the rotating part 101 from the locked position relative to the fixed part 81 to a lower limit position while rotating the rotating part 101 in a circumferential direction on the punch holder 232.

[0090] In the second embodiment, compared to the first embodiment, the process of transporting / carrying out the restraining ring 205 using the transport unit 55 is not necessary, so the manufacturing process of the combined body 190 can be streamlined and manufacturing costs can be reduced.

[0091] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0092] This application claims priority to Japanese Patent Application No. 2024-18110, filed February 8, 2024. The entire disclosure of Japanese Patent Application No. 2024-18110, filed February 8, 2024, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

[0093] 130: Weakened portion, 131: First straight portion, 132: Second straight portion, 141: Piston rod (rod-shaped member), 143: Lower end portion (one end portion), 145: Outer circumferential surface (circumferential surface), 146, 147: First annular groove, 148: Second annular groove, 191: Solenoid case (mating member), 195: Fitting hole, 196: First annular recess (first pressure applying portion), 198: Second annular recess (second pressure applying portion)

Claims

1. A combination of two members, the combination comprising a rod-shaped member and a mating member, wherein one end of the rod-shaped member is fitted into a fitting hole in the mating member, and the rod-shaped member and the mating member are joined by applying pressure to the material of the mating member and causing it to plastically flow into a groove provided on the circumferential surface of the rod-shaped member, the mating member having a pressurized portion formed by the application of pressure and a straight portion formed in the gap between the pressurized portion and the rod-shaped member during plastic flow, the pressurized portion being located closer to one end of the rod-shaped member than the groove, and the rod-shaped member having a fragile portion at its one end that is pushed and deformed by the excess material after the plastic flow of the material into the groove due to the application of pressure is completed.

2. A combination of two members, the combination comprising a rod-shaped member and a mating member, wherein one end of the rod-shaped member is fitted into a fitting hole in the mating member, and the material of the mating member is pressurized to cause plastic flow within a groove provided on the circumferential surface of the rod-shaped member, thereby joining the rod-shaped member and the mating member; the groove has a first groove provided on one end side of the rod-shaped member and a second groove provided axially away from the first groove towards the other end side of the rod-shaped member; the mating member has a pressurizing portion formed by pressurization, the pressurizing portion having a first pressurizing portion provided on the first groove side and a second pressurizing portion provided on the second groove side; the mating member has a straight portion formed in the gap between the pressurizing portion and the rod-shaped member during plastic flow, the straight portion having a first straight portion provided on the first groove side and a second straight portion provided on the second groove side; a combined body characterized in that, on the side of the first straight section, the first pressure applying section is located closer to one end of the rod-shaped member than the first groove, and on the side of the second straight section, the second pressure applying section is located closer to the other end of the rod-shaped member than the second groove, and the rod-shaped member has a fragile section on its one end that is pushed and deformed by excess material after plastic flow of material into the groove due to the pressure is completed.

3. A combination of two members, the combination comprising a rod-shaped member and a mating member, wherein one end of the rod-shaped member is fitted into a fitting hole in the mating member, and the material of the mating member is pressurized to cause plastic flow within a groove provided on the circumferential surface of the rod-shaped member, thereby joining the rod-shaped member and the mating member; the groove has a first groove provided on one end side of the rod-shaped member and a second groove provided axially away from the first groove towards the other end side of the rod-shaped member; the mating member has a pressure section formed by pressure, the pressure section having a first pressure section provided on the first groove side and a second pressure section provided on the second groove side; the mating member has a straight section formed in the gap between the pressure section and the rod-shaped member during plastic flow, the straight section having a first straight section provided on the first groove side and a second straight section provided on the second groove side; a combined body, characterized in that, on the side of the first straight section, the first pressure applying section is located closer to one end of the rod-shaped member than the first groove, and on the side of the second straight section, the second pressure applying section is located closer to the other end of the rod-shaped member than the second groove, and the mating member has a material escape section formed by allowing excess material to flow after plastic flow of material into the groove due to the pressure is completed.

4. A combination of two members, the combination comprising a rod-shaped member and a mating member, wherein one end of the rod-shaped member is fitted into a fitting hole in the mating member, and the material of the mating member is pressurized to cause plastic flow within a groove provided on the circumferential surface of the rod-shaped member, thereby joining the rod-shaped member and the mating member; the groove has a first groove provided on one end side of the rod-shaped member and a second groove provided axially away from the first groove towards the other end side of the rod-shaped member; the mating member has a pressurizing portion formed by pressurization, the pressurizing portion having a first pressurizing portion provided on the first groove side and a second pressurizing portion provided on the second groove side; the mating member has a straight portion formed in the gap between the pressurizing portion and the rod-shaped member during plastic flow, the straight portion having a first straight portion provided on the first groove side and a second straight portion provided on the second groove side; a combined body, characterized in that, on the first straight section side, the first pressure applying section is located closer to one end of the rod-shaped member than the first groove, and on the second straight section side, the second pressure applying section is located closer to the other end of the rod-shaped member than the second groove; the rod-shaped member has a fragile section at one end thereof that is pressed and deformed by excess material after plastic flow of material into the groove due to the pressure is completed; and the mating member has a material escape section that is formed by causing excess material to flow after plastic flow of material into the groove due to the pressure is completed.

5. A combination according to claim 4, characterized in that the depth of said first groove is greater than the depth of said second groove.

6. A method for manufacturing a combined body of two members, the combined body comprising a rod-shaped member and a mating member, one end of the rod-shaped member being fitted into a fitting hole of the mating member, and the rod-shaped member and the mating member being joined by applying pressure to the material of the mating member to cause plastic flow into a groove provided on the circumferential surface of the rod-shaped member, the mating member having a pressurized portion formed by the pressure and a straight portion formed in the gap between the pressurized portion and the rod-shaped member during plastic flow, the pressurized portion being located closer to one end of the rod-shaped member than the groove, the rod-shaped member having a weakened portion at one end that is deformed by being pressed by the excess material after the plastic flow of the material into the groove due to the pressure is completed, the manufacturing apparatus for the combined body having an upper mold having a pressurizing mechanism that pressurizes one end face of the mating member, and a lower mold that holds the rod-shaped member and the mating member in a state in which the one end of the rod-shaped member is fitted into the fitting hole of the mating member, The upper mold is arranged coaxially with the lower mold and can be raised and lowered freely, and the method for manufacturing the combined body comprises: a centering process in which the pressure mechanism causes the material of the mating member to plastically flow, and the mating member forms the straight portion while correcting any misalignment of the axis that occurs between the mating member and the rod-shaped member; a plastic flow process in which the material of the mating member plastically flows into the groove; and a stress equalization process in which the fragile portion of the rod-shaped member is pressed and deformed by the excess material of the mating member.

7. A method for manufacturing a combined body of two members, the combined body comprising a rod-shaped member and a mating member, wherein one end of the rod-shaped member is fitted into a fitting hole in the mating member, and the material of the mating member is pressurized to cause plastic flow within a groove provided on the circumferential surface of the rod-shaped member, thereby combining the rod-shaped member and the mating member, the groove having a first groove provided on one end side of the rod-shaped member and a second groove provided axially away from the first groove towards the other end side of the rod-shaped member, the mating member having a pressurizing portion formed by pressurization, the pressurizing portion having a first pressurizing portion provided on the first groove side and a second pressurizing portion provided on the second groove side, the mating member having a straight portion formed in the gap between the pressurizing portion and the rod-shaped member during plastic flow, the straight portion having a first straight portion provided on the first groove side and a second straight portion provided on the second groove side, On the first straight section side, the first pressurizing section is located closer to one end of the rod-shaped member than the first groove, and on the second straight section side, the second pressurizing section is located closer to the other end of the rod-shaped member than the second groove, and the rod-shaped member has a weak section at one end that is pressed and deformed by excess material after plastic flow of the material into the groove due to the pressurizing is completed, the manufacturing device for the combined body has an upper mold having a pressurizing mechanism that pressurizes one end face of the mating member, and a lower mold that holds the rod-shaped member and the mating member in a state where the one end of the rod-shaped member is mated with the mating hole of the mating member, the upper mold is arranged coaxially with the lower mold and can be raised and lowered, and the manufacturing method for the combined body includes: a first centering step in which the pressurizing mechanism causes the material of the mating member to plastically flow, and the mating member forms the second straight section while correcting misalignment of the axis occurring between the rod-shaped member and the mating member, and a first plastic flow step in which the material of the mating member is plastically flowed into the second groove, A method for manufacturing a combined body, comprising: a second centering step in which the mating member corrects an axial misalignment that occurs between the mating member and the rod-shaped member while forming the first straight portion; a second plastic flow step in which material of the mating member is plastically flowed into the first groove; and a stress equalization step in which the fragile portion of the rod-shaped member is pressed and deformed by excess material of the mating member.

8. A method for manufacturing a combined body of two members, the combined body comprising a rod-shaped member and a mating member, wherein one end of the rod-shaped member is fitted into a fitting hole in the mating member, and the material of the mating member is pressurized to cause plastic flow within a groove provided on the circumferential surface of the rod-shaped member, thereby combining the rod-shaped member and the mating member, the groove having a first groove provided on one end side of the rod-shaped member and a second groove provided axially away from the first groove towards the other end side of the rod-shaped member, the mating member having a pressurizing portion formed by pressurization, the pressurizing portion having a first pressurizing portion provided on the first groove side and a second pressurizing portion provided on the second groove side, the mating member having a straight portion formed in the gap between the pressurizing portion and the rod-shaped member during plastic flow, the straight portion having a first straight portion provided on the first groove side and a second straight portion provided on the second groove side, On the first straight section side, the first pressurizing section is located closer to one end of the rod-shaped member than the first groove, and on the second straight section side, the second pressurizing section is located closer to the other end of the rod-shaped member than the second groove; the mating member has a material relief section formed by flowing excess material after plastic flow of the material into the groove due to the pressurizing is completed; the manufacturing device for the combined body has an upper mold having a pressurizing mechanism that pressurizes one end face of the mating member, and a lower mold that holds the rod-shaped member and the mating member in a state where the one end of the rod-shaped member is mated with the mating hole of the mating member; the upper mold is arranged coaxially with the lower mold and can be raised and lowered; and the manufacturing method for the combined body includes: a first centering step in which the pressurizing mechanism causes the material of the mating member to plastically flow, and the mating member forms the second straight section while correcting misalignment of the axis occurring between the mating member and the rod-shaped member; and a first plastic flow step in which the material of the mating member is plastically flowed into the second groove. A method for manufacturing a combined body, comprising: a second centering step in which the mating member corrects an axial misalignment that occurs between the mating member and the rod-shaped member while forming the first straight portion; a second plastic flow step in which material of the mating member is plastically flowed into the first groove; and a stress equalizing step in which excess material of the mating member is flowed to form the material relief portion.

9. A method for manufacturing a combined body of two members, the combined body comprising a rod-shaped member and a mating member, wherein one end of the rod-shaped member is fitted into a fitting hole in the mating member, and the material of the mating member is pressurized to cause plastic flow within a groove provided on the circumferential surface of the rod-shaped member, thereby combining the rod-shaped member and the mating member, the groove having a first groove provided on one end side of the rod-shaped member and a second groove provided axially away from the first groove towards the other end side of the rod-shaped member, the mating member having a pressurizing portion formed by pressurization, the pressurizing portion having a first pressurizing portion provided on the first groove side and a second pressurizing portion provided on the second groove side, the mating member having a straight portion formed in the gap between the pressurizing portion and the rod-shaped member during plastic flow, the straight portion having a first straight portion provided on the first groove side and a second straight portion provided on the second groove side, On the first straight section side, the first pressure section is located closer to one end of the rod-shaped member than the first groove, and on the second straight section side, the second pressure section is located closer to the other end of the rod-shaped member than the second groove, the rod-shaped member has a weakened portion at one end thereof that is pressed and deformed by excess material after plastic flow of material into the groove due to the pressure is completed, the mating member has a material relief portion that is formed by allowing excess material to flow after plastic flow of material into the groove due to the pressure is completed, the manufacturing device for the combined body has an upper mold having a pressure mechanism that presses one end face of the mating member, and a lower mold that holds the rod-shaped member and the mating member in a state in which the one end of the rod-shaped member and the mating hole of the mating member are mated, the upper mold is arranged coaxially with the lower mold and can be raised and lowered, the manufacturing method for the combined body comprises: a first centering step in which the pressure mechanism causes the material of the counter member to plastically flow, and the counter member corrects any misalignment between the counter member and the rod-shaped member while forming the second straight portion; a first plastic flow step in which the material of the counter member plastically flows into the second groove; a second centering step in which the counter member corrects any misalignment between the counter member and the rod-shaped member while forming the first straight portion; and a second plastic flow step in which the material of the counter member plastically flows into the first groove.A method for manufacturing a combined body, comprising: a first stress equalizing step in which the fragile portion of the rod-shaped member is pressed and deformed by excess material of the mating member; and a second stress equalizing step in which the excess material of the mating member is caused to flow, thereby forming a material relief portion.

10. A method for manufacturing a combined body of two members, the combined body comprising a rod-shaped member and a mating member, wherein one end of the rod-shaped member is fitted into a fitting hole in the mating member, and the material of the mating member is pressurized to cause plastic flow within a groove provided on the circumferential surface of the rod-shaped member, thereby combining the rod-shaped member and the mating member, the groove having a first groove provided on one end side of the rod-shaped member and a second groove provided axially away from the first groove towards the other end side of the rod-shaped member, the mating member having a pressurizing portion formed by pressurization, the pressurizing portion having a first pressurizing portion provided on the first groove side and a second pressurizing portion provided on the second groove side, the mating member having a straight portion formed in the gap between the pressurizing portion and the rod-shaped member during plastic flow, the straight portion having a first straight portion provided on the first groove side and a second straight portion provided on the second groove side, On the first straight section side, the first pressure section is located closer to one end of the rod-shaped member than the first groove, and on the second straight section side, the second pressure section is located closer to the other end of the rod-shaped member than the second groove, the rod-shaped member has a weakened portion at one end thereof that is pressed and deformed by excess material after plastic flow of material into the groove due to the pressure is completed, and the mating member has a material relief portion that is formed by allowing excess material to flow after plastic flow of material into the groove due to the pressure is completed, and the manufacturing device for the combined body comprises an upper mold having a pressure mechanism that applies pressure to one end face of the mating member, a lower mold that holds the rod-shaped member and the mating member in a state in which the one end of the rod-shaped member and the mating hole of the mating member are mated, and a restraining ring that restrains the annular outer periphery of the mating member from deforming radially outward during joining, the upper mold is arranged coaxially with the lower mold and can be freely raised and lowered, and the manufacturing method for the combined body comprises: a restraint ring mounting step of mounting the restraint ring to the outer circumferential annular portion of the mating member; a first centering step of plastically flowing the material of the mating member by the pressure mechanism, and correcting the misalignment of the axial center occurring between the mating member and the rod-shaped member while the mating member forms the second straight portion; and a first plastic flow step of plastically flowing the material of the mating member into the second groove.a second centering step of correcting an axial misalignment that occurs between the mating member and the rod-shaped member while the mating member forms the first straight portion; a second plastic flow step of causing material of the mating member to plastically flow into the first groove; a first stress equalizing step of deforming the weak portion of the rod-shaped member by being pressed by excess material of the mating member; a second stress equalizing step of causing the excess material of the mating member to flow and form a material relief portion; and a restraining ring removal step of removing the restraining ring from the outer peripheral annular portion of the mating member.

11. A shock absorber comprising: a cylinder in which a working fluid is sealed; a piston mechanism that divides the interior of the cylinder into two chambers; a piston rod having one end connected to the piston mechanism and the other end extending outside the cylinder; and a coupling portion formed by fitting one end of the piston rod into a fitting hole in the piston mechanism and pressurizing the material of the piston mechanism to cause plastic flow within a groove provided on the circumferential surface of the piston rod; the groove having a first groove provided on one end side of the piston rod and a second groove provided axially away from the first groove towards the other end side of the piston rod; the piston mechanism having a pressurizing portion formed by pressurization, the pressurizing portion having a first pressurizing portion provided on the first groove side and a second pressurizing portion provided on the second groove side; the piston mechanism having a straight portion formed in the gap between the pressurizing portion and the piston rod during plastic flow, the straight portion having a first straight portion provided on the first groove side and a second straight portion provided on the second groove side; a shock absorber characterized in that, on the side of the first straight section, the first pressure applying portion is located closer to one end of the piston rod than the first groove, and on the side of the second straight section, the second pressure applying portion is located closer to the other end of the piston rod than the second groove, and the piston rod has, on its one end side, a fragile portion that is pushed and deformed by excess material after plastic flow of material into the groove due to the pressure is completed.

12. A shock absorber comprising: a cylinder in which a working fluid is sealed; a piston mechanism that divides the interior of the cylinder into two chambers; a piston rod having one end connected to the piston mechanism and the other end extending outside the cylinder; and a coupling portion formed by fitting one end of the piston rod into a fitting hole in the piston mechanism and pressurizing the material of the piston mechanism to cause plastic flow within a groove provided on the circumferential surface of the piston rod; the groove having a first groove provided on one end side of the piston rod and a second groove provided axially away from the first groove towards the other end side of the piston rod; the piston mechanism having a pressurizing portion formed by pressurization, the pressurizing portion having a first pressurizing portion provided on the first groove side and a second pressurizing portion provided on the second groove side; the piston mechanism having a straight portion formed in the gap between the pressurizing portion and the piston rod during plastic flow, the straight portion having a first straight portion provided on the first groove side and a second straight portion provided on the second groove side; a shock absorber, characterized in that, on the side of the first straight section, the first pressure applying section is located closer to one end of the piston rod than the first groove, and on the side of the second straight section, the second pressure applying section is located closer to the other end of the piston rod than the second groove; the piston rod has a fragile section at one end thereof that is pushed and deformed by excess material after plastic flow of the material into the groove due to the pressure is completed; and the piston mechanism has a material relief section that is formed by flowing excess material after plastic flow of the material into the groove due to the pressure is completed.

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