Adjustable damping shock absorber and solenoid

Abstract

The characteristics of the non-magnetic material can be maintained, and the magnetic flux density for the movable iron core can be kept high between the first and second fixed iron cores. [Solution] A non-magnetic ring is provided between the first and second stator cores, which constitute the main part of the solenoid, and is positioned on the inner periphery of the coil. The non-magnetic ring is brazed to the first and second fixed cores (first and second stator cores) to increase the magnetic flux density of the magnetic circuit for the movable core (plunger). The non-magnetic ring is made of a non-magnetic material such as austenitic stainless steel, and its inner diameter is larger or smaller than the inner diameters of the first and second stator cores, forming a radial gap between the non-magnetic ring and the plunger.

Description

[Technical Field]

[0001] The present invention relates to a damping force adjustable shock absorber and a solenoid for damping vibrations of a vehicle, for example. [Background technology]

[0002] Generally, suspension systems such as semi-active suspensions mounted on vehicles are equipped with adjustable damping shock absorbers that variably adjust damping force in accordance with the vehicle's driving conditions, behavior, etc. Among adjustable damping shock absorbers, those that use a solenoid as an electromagnetic proportional actuator that variably adjusts damping force are known. For example, Patent Document 1 describes this type of solenoid that includes a coil that generates magnetic force when energized, first and second fixed iron cores (stator cores) made of a magnetic material and arranged on the inner periphery of the coil, a non-magnetic member that axially connects the first and second fixed iron cores, and a movable iron core (plunger) that is arranged on the inner periphery of the first and second fixed iron cores and the non-magnetic member and is axially movable.

[0003] Patent Document 2 also describes a solenoid in which a brazing method is used to join a non-magnetic member between first and second fixed cores. In this case, for example, after the second fixed core and the non-magnetic member are joined by brazing, the inner peripheral surface is machined to form a flush surface without any steps. This improves the sliding properties of the movable core. Furthermore, Patent Document 3 describes a solenoid in which a thin-walled portion is provided between the first and second fixed cores to partially reduce the cross-sectional area of ​​the magnetic path. This increases the magnetic flux density passing through the movable core between the first and second fixed cores, improving performance as a solenoid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-73018 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-127692 [Patent Document 3] Japanese Patent Application Publication No. 2017-118124 Summary of the Invention [Problem to be solved by the invention]

[0005] In the solenoid disclosed in the above-mentioned patent document, a non-magnetic member is joined between the first and second fixed iron cores, and the non-magnetic member increases the magnetic flux density of the magnetic circuit relative to the movable iron core. However, when the non-magnetic member is machined after joining (for example, by cutting the inner peripheral surface), the magnetic properties change due to processing distortion, making the non-magnetic member more susceptible to magnetization. Furthermore, if a thin-walled portion is provided between the first and second fixed iron cores to partially reduce the cross-sectional area of ​​the magnetic path, the thin-walled portion reduces the mechanical strength of the entire fixed iron core, resulting in reduced durability and lifespan. [Means for solving the problem]

[0006] The present invention has been made in consideration of the problems of the prior art described above, and an object of the present invention is to provide a damping force adjustable shock absorber and solenoid that can maintain the characteristics of non-magnetic materials and can maintain a high magnetic flux density for the movable iron core between the first and second fixed iron cores.

[0007] In order to solve the above-mentioned problems, one embodiment of the present invention is a damping force control shock absorber comprising: a cylinder in which a working fluid is sealed; a piston inserted into the cylinder to divide the interior of the cylinder into a rod-side chamber and a bottom-side chamber; a piston rod connected to the piston and extending to the outside of the cylinder; a flow path in which a flow of the working fluid occurs due to movement of the piston rod; and a damping force control valve provided in the flow path and whose opening and closing operation is adjusted by a solenoid, wherein the solenoid comprises a coil that generates a magnetic force when energized, and a damping force control valve having a magnetic field generated by a current passing through the solenoid and a magnetic field generated by a current passing through the solenoid. a first and second fixed cores provided on the circumferential side of the damping force control valve, a non-magnetic member provided between the first and second fixed cores and integrally fixed to the first and second fixed cores by brazing, a movable core disposed on the inner circumferential side of the first and second fixed cores and the non-magnetic member and provided so as to be movable in the axial direction, and a shaft portion extending in the axial direction of the movable core, wherein a valve body of the damping force control valve is provided at an end of the shaft portion on the second fixed core side, and the inner diameter of the non-magnetic member is larger or smaller than the inner diameter of the first and second fixed cores, and the non-magnetic member is The rotor includes a fitting cylindrical portion into which the second fixed core is press-fitted, and a thick-walled cylindrical portion that protrudes radially inward at an axial middle and has a diameter larger than the outer diameter of the movable core, and the thick-walled cylindrical portion and The second fixed core is joined to the conical protrusion provided at the end of the second fixed core using a brazing material having a brazing temperature of 1000°C or higher, the fitting cylindrical portion The axial end of the second fixed core abuts against the second fixed core. and an austenitic stainless steel having a face-centered cubic crystal structure in the brazed state. , which has been processed after the brazing Austenitic stainless steel with a body-centered cubic crystal structure It is characterized by being relatively difficult to magnetize.

[0008] Furthermore, a solenoid according to one embodiment of the present invention comprises a coil that generates a magnetic force when energized, first and second fixed iron cores provided on the inner circumferential side of the coil, a non-magnetic member provided between the first and second fixed iron cores and integrally fixed to the first and second fixed iron cores by brazing, and a movable iron core disposed on the inner circumferential side of the first and second fixed iron cores and the non-magnetic member and provided so as to be movable in the axial direction, wherein the inner diameter of the non-magnetic member is larger or smaller than the inner diameter of the first and second fixed iron cores, and the non-magnetic member is The rotor includes a fitting cylindrical portion into which the second fixed core is press-fitted, and a thick-walled cylindrical portion that protrudes radially inward at an axial middle and has a diameter larger than the outer diameter of the movable core, and the thick-walled cylindrical portion andThe second fixed core is joined to the conical protrusion provided at the end of the second fixed core using a brazing material having a brazing temperature of 1000°C or higher, the fitting cylindrical portion The axial end of the second fixed core abuts against the second fixed core. and an austenitic stainless steel having a face-centered cubic crystal structure in the brazed state. , which has been processed after the brazing Austenitic stainless steel with a body-centered cubic crystal structure It is characterized by being relatively difficult to magnetize.

[0009] Furthermore, one embodiment of the present invention is a damping force control shock absorber comprising: a cylinder in which a working fluid is sealed; a piston inserted into the cylinder to divide the interior of the cylinder into a rod-side chamber and a bottom-side chamber; a piston rod connected to the piston and extending to the outside of the cylinder; a flow path in which a flow of the working fluid is generated by movement of the piston rod; and a damping force control valve provided in the flow path and whose opening and closing operation is adjusted by a solenoid, wherein the solenoid comprises: a coil that generates a magnetic force when energized; first and second fixed iron cores provided on the inner circumferential side of the coil; a non-magnetic member provided between the first and second fixed iron cores and fixed integrally to the first and second fixed iron cores by brazing; a movable iron core disposed on the inner circumferential side of the first and second fixed iron cores and the non-magnetic member and provided so as to be movable in the axial direction; and a shaft portion extending in the axial direction of the movable iron core, wherein a valve body of the damping force control valve is provided at an end of the shaft portion on the second fixed iron core side, and the non-magnetic member is The rotor includes a fitting cylindrical portion into which the second fixed core is press-fitted, and a thick-walled cylindrical portion that protrudes radially inward at an axial middle and has a diameter larger than the outer diameter of the movable core, and the thick-walled cylindrical portion and The second fixed core is joined to the conical protrusion provided at the end of the second fixed core using a brazing material having a brazing temperature of 1000°C or higher, the fitting cylindrical portion The axial end of the second fixed core abuts against the second fixed core. and an austenitic stainless steel having a face-centered cubic crystal structure in the brazed state. , which has been processed after the brazing Austenitic stainless steel with a body-centered cubic crystal structure It is characterized by being relatively difficult to magnetize.

[0010] According to one embodiment of the present invention, it is possible to prevent the characteristics of the non-magnetic member from changing due to thermal effects, etc., and to maintain a high magnetic flux density passing through the movable iron core between the first and second fixed iron cores. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a longitudinal sectional view showing a damping force adjustable hydraulic shock absorber provided with a solenoid according to an embodiment of the present invention. [Figure 2] 2 is an enlarged cross-sectional view showing a damping force control valve and a solenoid in FIG. 1. FIG. [Figure 3] 3 is an enlarged cross-sectional view of a solenoid in FIG. 2 with the damping force control valve removed. [Figure 4] 4 is a cross-sectional view showing a pre-assembled state of first and second stator cores and a non-magnetic ring of the solenoid in FIG. 3. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A damping force adjustable shock absorber and a solenoid according to an embodiment of the present invention will be described in detail below with reference to FIGS. 1 to 4, taking as an example a case where the damping force adjustable hydraulic shock absorber is used.

[0013] 1, a damping force adjustable hydraulic shock absorber 1 (hereinafter referred to as hydraulic shock absorber 1) is provided with a solenoid 33, which will be described later. This hydraulic shock absorber 1 is configured to include an outer cylinder 2, an inner cylinder 4, a piston 5, a piston rod 8, a rod guide 9, and a damping force adjusting device 17. In the following description, for example, one axial side of the outer cylinder 2 or inner cylinder 4 will be referred to as the lower side, lower portion side, or lower end side, and the other axial side will be referred to as the upper side, upper portion side, or upper end side.

[0014] The bottomed cylindrical outer cylinder 2 that forms the outer shell of the hydraulic shock absorber 1 has its lower end closed by a bottom cap 3, and the upper end of the outer cylinder 2 forms a crimped portion 2A that is bent radially inward. A rod guide 9 and a seal member 10 are provided between the crimped portion 2A and the inner cylinder 4. Meanwhile, an opening 2B is formed at the bottom of the outer cylinder 2 concentrically with a connection port 12C of an intermediate cylinder 12 (described later), and a damping force adjuster 17 (described later) is attached opposite the opening 2B. The bottom cap 3 also has a mounting eye 3A that is attached to, for example, the wheel side of a vehicle.

[0015] An inner cylinder 4 is provided coaxially within the outer cylinder 2. The lower end of the inner cylinder 4 is fitted and attached to a bottom valve 13, and the upper end is fitted and attached to a rod guide 9. A working liquid is sealed within the inner cylinder 4 as a working fluid. The working liquid is not limited to oil, but may be, for example, water mixed with an additive.

[0016] An annular reservoir chamber A is formed between the inner cylinder 4 and the outer cylinder 2, and gas is sealed in this reservoir chamber A together with the oil. This gas may be air at atmospheric pressure, or a gas such as compressed nitrogen gas may also be used. In addition, an oil hole 4A is drilled radially at a position midway along the length (axial direction) of the inner cylinder 4, which constantly connects the rod-side oil chamber B to the annular oil chamber D.

[0017] The piston 5 is slidably inserted into the inner cylinder 4. The piston 5 divides the interior of the inner cylinder 4 into a rod-side chamber (rod-side oil chamber B) and a bottom-side chamber (bottom-side oil chamber C). The piston 5 is formed with a plurality of oil passages 5A, 5B spaced apart in the circumferential direction, allowing communication between the rod-side oil chamber B and the bottom-side oil chamber C.

[0018] An extension-side disc valve 6 is provided on the lower end surface of the piston 5. This extension-side disc valve 6 opens when the pressure in the rod-side oil chamber B exceeds a set relief pressure as the piston 5 slides upward during the extension stroke of the piston rod 8, and relieves the pressure at this time through each oil passage 5A into the bottom-side oil chamber C. This set relief pressure is set to a pressure higher than the valve-opening pressure when the damping force adjusting device 17, described below, is set to hard.

[0019] A compression-side check valve 7 is provided on the upper end surface of the piston 5. The check valve 7 opens when the piston 5 slides downward during the compression stroke of the piston rod 8 and closes at other times. This check valve 7 allows oil in the bottom-side oil chamber C to flow through each oil passage 5B toward the rod-side oil chamber B and prevents oil from flowing in the opposite direction. The opening pressure of this check valve 7 is set to a pressure lower than the opening pressure when the damping force adjusting device 17, described below, is set to soft, so that the check valve 7 does not substantially generate a damping force. This "not substantially generating a damping force" means that the force is below the friction of the piston 5 and the seal member 10 and does not affect the movement of the vehicle.

[0020] The piston rod 8 extends axially (up and down) within the inner cylinder 4. The lower end of the piston rod 8 is inserted into the inner cylinder 4 and fixed to the piston 5 by a nut 8A or the like. The upper end of the piston rod 8 protrudes so as to extend outside the outer cylinder 2 and the inner cylinder 4 via a rod guide 9.

[0021] A stepped cylindrical rod guide 9 is provided on the upper end side of the inner cylinder 4. The rod guide 9 positions the upper part of the inner cylinder 4 in the center of the outer cylinder 2, and guides the piston rod 8 axially slidably on its inner periphery. An annular seal member 10 is provided between the rod guide 9 and the crimped portion 2A of the outer cylinder 2. The seal member 10 is made of an annular metal plate, through the center of which the piston rod 8 is inserted, with an elastic material such as rubber baked onto it. The inner periphery of the seal member 10 slides against the outer periphery of the piston rod 8, providing a seal between the piston rod 8 and the rod guide 9.

[0022] Additionally, a lip seal 10A acting as a check valve is formed on the underside of the seal member 10, extending so as to come into contact with the rod guide 9. The lip seal 10A is disposed between the oil sump chamber 11 and the reservoir chamber A, and allows oil and liquid in the oil sump chamber 11 to flow toward the reservoir chamber A via the return passage 9A of the rod guide 9, while preventing reverse flow.

[0023] An intermediate cylinder 12 made of a cylindrical body is disposed between the outer cylinder 2 and the inner cylinder 4. This intermediate cylinder 12 is attached, for example, to the outer periphery of the inner cylinder 4 via upper and lower cylindrical seals 12A and 12B. The intermediate cylinder 12 forms an annular oil chamber D inside, extending to surround the entire outer periphery of the inner cylinder 4, and the annular oil chamber D is an oil chamber independent of the reservoir chamber A. The annular oil chamber D is constantly in communication with the rod-side oil chamber B via a radial oil hole 4A formed in the inner cylinder 4. The annular oil chamber D serves as a flow path through which a flow of hydraulic fluid occurs as the piston rod 8 moves. In addition, a connection port 12C is provided at the lower end of the intermediate cylinder 12 to which a cylindrical holder 20 of a damping force control valve 18 (described later) is attached.

[0024] The bottom valve 13 is located at the lower end of the inner cylinder 4 and is provided between the bottom cap 3 and the inner cylinder 4. The bottom valve 13 is composed of a valve body 14 that defines a reservoir chamber A and a bottom-side oil chamber C between the bottom cap 3 and the inner cylinder 4, a contraction-side disc valve 15 provided on the underside of the valve body 14, and an extension-side check valve 16 provided on the upper side of the valve body 14. The valve body 14 has oil passages 14A and 14B formed at intervals in the circumferential direction, which allow communication between the reservoir chamber A and the bottom-side oil chamber C.

[0025] The compression-side disc valve 15 opens when the pressure in the bottom-side oil chamber C exceeds a set relief pressure during the downward sliding displacement of the piston 5 during the compression stroke of the piston rod 8, and relieves the pressure at this time via each oil passage 14A to the reservoir chamber A. This set relief pressure is set to a pressure higher than the valve-opening pressure when the damping force adjusting device 17, which will be described later, is set to hard.

[0026] The extension check valve 16 opens when the piston 5 slides upward during the extension stroke of the piston rod 8, and closes at other times. This extension check valve 16 allows oil in the reservoir chamber A to flow through each oil passage 14B toward the bottom-side oil chamber C, and prevents oil from flowing in the opposite direction. The opening pressure of the extension check valve 16 is set to a pressure lower than the opening pressure when the damping force adjuster 17, described below, is set to the soft setting, and therefore generates virtually no damping force.

[0027] Next, the damping force adjusting device 17 for variably adjusting the damping force generated by the hydraulic shock absorber 1 will be described with reference to Fig. 2 in addition to Fig. 1. Note that Fig. 2 shows the damping force adjusting device 17 in a state in which the plunger 48 (operating pin 49) has moved to the left side of Fig. 2 (i.e., in the valve closing direction in which the pilot valve element 32 seats on the valve seat portion 26E of the pilot body 26) by externally energizing the coil 34A of the solenoid 33 (for example, control to generate a hard damping force).

[0028] 1, the damping force adjusting device 17 is disposed with its base end (left end in FIG. 1) interposed between the reservoir chamber A and the annular oil chamber D, and its tip end (right end in FIG. 1) protruding radially outward from the lower part of the outer cylinder 2. The damping force adjusting device 17 is configured to include a damping force adjusting valve 18 that generates a damping force with hard or soft characteristics by variably controlling the flow of oil from the annular oil chamber D to the reservoir chamber A, and a solenoid 33 (described later) that adjusts the opening and closing operation of the damping force adjusting valve 18.

[0029] That is, the valve opening pressure of the damping force control valve 18 is adjusted by a solenoid 33 used as a damping force variable actuator, thereby variably controlling the generated damping force to have hard or soft characteristics. The damping force control valve 18 is a valve whose opening and closing operation is adjusted by the solenoid 33, and is provided in a flow path (for example, between the annular oil chamber D and the reservoir chamber A) where the flow of working fluid occurs due to the movement of the piston rod 8.

[0030] Here, the damping force adjustment valve 18 is composed of an approximately cylindrical valve case 19 whose base end side is fixed around the opening 2B of the outer tube 2 and whose tip end side protrudes radially outward from the outer tube 2, a cylindrical holder 20 whose base end side is fixed to the connection port 12C of the intermediate tube 12 and whose tip end side forms an annular flange portion 20A and is arranged with a gap inside the valve case 19, and a valve member 21 that abuts against the flange portion 20A of the cylindrical holder 20, etc.

[0031] The base end side of the valve case 19 forms an annular inner flange portion 19A extending radially inward, and the tip end side of the valve case 19 forms an externally threaded portion 19B onto which a coupling ring 52 is threadedly attached, which couples the valve case 19 to a cover member 51 of a solenoid 33, which will be described later. An annular oil chamber 19C that is constantly in communication with the reservoir chamber A is formed between the inner circumferential surface of the valve case 19 and the outer circumferential surface of the valve member 21, and further between the inner circumferential surface of the valve case 19 and the outer circumferential surfaces of the pilot body 26, etc.

[0032] The inside of the cylindrical holder 20 has an oil passage 20B that is connected to the annular oil chamber D on one side and extends to the position of the valve member 21 on the other side. An annular spacer 22 is sandwiched between the flange portion 20A of the cylindrical holder 20 and the inner flange portion 19A of the valve case 19. This spacer 22 has a plurality of radially extending notches 22A that serve as radial oil passages for connecting the oil chamber 19C and the reservoir chamber A. In this embodiment, the spacer 22 is configured to have the notches 22A for forming the oil passages. However, the inner flange portion 19A of the valve case 19 may also have radial notches for forming the oil passages. In this configuration, the spacer 22 can be omitted, thereby reducing the number of parts.

[0033] The valve member 21 is provided with a central hole 21A located at the radial center and extending in the axial direction. The valve member 21 is also provided with a plurality of oil passages 21B spaced apart circumferentially around the central hole 21A, and one side (the left side in FIGS. 1 and 2) of each of these oil passages 21B is constantly in communication with an oil passage 20B in the cylindrical holder 20. The other end face (the right side in FIGS. 1 and 2) of the valve member 21 is provided with an annular recess 21C formed to surround the other opening of each oil passage 21B, and an annular valve seat 21D located radially outward of the annular recess 21C and on which a main valve 23 (described later) is seated and released. Each oil passage 21B in the valve member 21 serves as a flow path through which pressurized oil flows at a flow rate corresponding to the aperture of the main valve 23 between the oil passage 20B in the cylindrical holder 20, which is in communication with the annular oil chamber D, and an oil chamber 19C in the valve case 19, which is in communication with the reservoir chamber A.

[0034] The main valve 23 is configured as a disc valve whose inner peripheral side is sandwiched between the valve member 21 and the large diameter portion 24A of the pilot pin 24. The outer peripheral side of the main valve 23 is seated and released from annular valve seat 21D of the valve member 21. An elastic seal member 23A is fixed to the back side of the outer peripheral portion of the main valve 23 by means of baking or the like. The main valve 23 opens when it receives pressure from the oil passage 21B side (annular oil chamber D side) of the valve member 21 and releases itself from the annular valve seat 21D. As a result, the oil passage 21B (annular oil chamber D side) of the valve member 21 is connected to the oil chamber 19C (reservoir chamber A side) via the main valve 23, and the flow rate of pressurized oil at this time is variably adjusted according to the opening of the main valve 23.

[0035] The pilot pin 24 is formed in a stepped cylindrical shape and has an annular large-diameter portion 24A at its axially intermediate portion. The pilot pin 24 has a central hole 24B extending axially on its inner circumferential side, and a small-diameter hole (orifice 24C) is formed at one end (the end on the cylindrical holder 20 side) of the central hole 24B. One end (the left end in FIGS. 1 and 2 ) of the pilot pin 24 is press-fitted into the central hole 21A of the valve member 21, and the main valve 23 is sandwiched between the large-diameter portion 24A and the valve member 21. The other end (the right end in FIGS. 1 and 2 ) of the pilot pin 24 is fitted into the central hole 26C of the pilot body 26. In this state, an oil passage 25 extending axially is formed between the central hole 26C of the pilot body 26 and the other end of the pilot pin 24. This oil passage 25 is in communication with a backpressure chamber 27 formed between the main valve 23 and the pilot body 26. In other words, a plurality of axially extending oil passages 25 are provided in the circumferential direction on the side surface on the other end side of the pilot pin 24, and other circumferential positions are press-fitted into the central hole 26C of the pilot body 26.

[0036] The pilot body 26 is formed as a generally bottomed tubular body having a cylindrical portion 26A with a stepped hole formed on the inside and a bottom portion 26B that closes the cylindrical portion 26A. The bottom portion 26B of the pilot body 26 has a central hole 26C into which the other end of the pilot pin 24 fits. A protruding cylindrical portion 26D is integrally formed on the outer periphery of the bottom portion 26B of the pilot body 26, extending along its entire circumference toward the valve member 21 (i.e., the left side in FIGS. 1 and 2). The elastic seal member 23A of the main valve 23 is fitted liquid-tightly to the inner circumferential surface of the protruding cylindrical portion 26D, thereby forming a backpressure chamber 27 between the main valve 23 and the pilot body 26. The backpressure chamber 27 generates pressure that presses the main valve 23 in a valve-closing direction, i.e., in a direction that seats the main valve 23 against the annular valve seat 21D of the valve member 21.

[0037] A valve seat 26E, on which a pilot valve element 32 (described later) is seated and released, is located on the other end side (the right end side in FIGS. 1 and 2) of the bottom 26B of the pilot body 26 and is provided so as to surround the central hole 26C. Also, inside the cylindrical portion 26A of the pilot body 26, there are disposed a return spring 28 that urges the pilot valve element 32 in a direction away from the valve seat 26E of the pilot body 26, a disk valve 29 that constitutes a fail-safe valve when a solenoid 33 (described later) is in a de-energized state (when the pilot valve element 32 is farthest from the valve seat 26E), a retaining plate 30 in which an oil passage 30A is formed on the central side, and the like.

[0038] A cap 31 is fitted and fixed to the open end of the cylindrical portion 26A of the pilot body 26, with the return spring 28, disc valve 29, retaining plate 30, etc., arranged inside the cylindrical portion 26A. Notches 31A are formed in the cap 31 at, for example, four positions spaced apart in the circumferential direction. These notches 31A serve as flow paths that allow oil that has flowed to the solenoid 33 side through the oil passage 30A of the retaining plate 30 to flow to the oil chamber 19C (reservoir chamber A side) in the direction of arrow X shown in FIG. 2.

[0039] The pilot valve element 32 and the pilot body 26 constitute a pilot valve. The pilot valve element 32 is formed in a stepped cylindrical shape, and its tip, which seats on and off the valve seat 26E of the pilot body 26, is tapered. An operating pin 49 of a solenoid 33 (described later) is fitted and fixed inside the pilot valve element 32, and the valve opening pressure of the pilot valve element 32 is adjusted in accordance with the supply of electricity to the solenoid 33. A flange portion 32A, which serves as a spring support, is formed around the entire circumference on the base end side of the pilot valve element 32. This flange portion 32A abuts against the disc valve 29 when the solenoid 33 is not energized (i.e., when the pilot valve element 32 has displaced to the fully open position where it is farthest from the valve seat 26E), preventing the pilot valve element 32 from opening further.

[0040] Next, the solenoid 33, which constitutes the damping force adjusting device 17 together with the damping force adjusting valve 18, will be described with reference to FIGS. 2, 3 and 4. FIG.

[0041] The solenoid 33 is used in a damping force adjustable shock absorber to adjust the opening and closing operation of the damping force adjustment valve 18. That is, the solenoid 33 used as a variable damping force actuator of the damping force adjuster 17 is composed of a molded coil 34, a first stator core 36, a core cover body 37, a second stator core 40, a non-magnetic ring 44, a plunger 48, an operating pin 49, a cover member 51, etc.

[0042] The molded coil 34 is formed into a substantially cylindrical shape by integrally covering (molding) a coil 34A wound around a coil bobbin with a resin member 34B such as a thermosetting resin. A portion of the circumference of the molded coil 34 forms a cable outlet (not shown) that protrudes axially or radially outward, and an electric cable (not shown) is connected to this cable outlet. When power is supplied (energized) from an external cable, the coil 34A becomes an electromagnet and generates magnetic force.

[0043] A seal groove 34C is formed around the entire circumference of the resin member 34B of the molded coil 34 on the side surface (axial end surface) facing the cover member 51 (plate 51B) described below. A seal member (e.g., O-ring 35) is fitted in this seal groove 34C. This O-ring 35 provides a liquid-tight seal between the molded coil 34 and the cover member 51 (plate 51B). This prevents dust containing rainwater or muddy water from entering the first and second stator cores 36, 40 through the gap between the cover member 51 and the molded coil 34.

[0044] The coil employed in the present invention is not limited to the molded coil 34 consisting of the coil 34A and the resin member 34B, and other coils may also be employed. For example, a configuration may be adopted in which the coil is wound around a coil bobbin made of an electrically insulating material, and the outer periphery of the coil is covered with an overmold (not shown) made of a resin material molded from above (the outer periphery side).

[0045] The first stator core 36 constitutes a first fixed core provided on the inner periphery of the molded coil 34 (coil 34A). The first stator core 36 is formed as a cylindrical body using a magnetic material such as low-carbon steel or carbon steel for mechanical structures (S10C). A small-diameter cylindrical portion 36A for joining is formed on one axial side (the left side in FIGS. 3 and 4) of the first stator core 36, and a non-magnetic ring 44 (described later) is joined to this small-diameter cylindrical portion 36A by a brazing portion 45. The inner diameter of the first stator core 36 is formed slightly larger than the outer diameter of a plunger 48 (described later), allowing the plunger 48 to move axially within the first stator core 36.

[0046] A cylindrical core cover 37 with a bottom is fitted to the other axial side of the first stator core 36 (the right side in FIGS. 3 and 4). The core cover 37 is made of the same magnetic material as the first stator core 36 and is cylindrical with a bottom, and closes the first stator core 36 from the other axial side (the left side in FIGS. 2 and 3). A stepped hole 37A with a bottom is formed inside the core cover 37, and a first bushing 38 is provided in the stepped hole 37A to slidably support an actuation pin 49 (described later). A seal groove 37B (see FIG. 3) is formed around the entire periphery of the outer periphery of the core cover 37 between the inner periphery of the first stator core 36 and the core cover 37. An O-ring 39 serving as a seal member is fitted in the seal groove 37B, and the O-ring 39 provides a liquid-tight seal between the first stator core 36 and the core cover 37.

[0047] The core lid 37 is disposed so that its bottom end face faces a plate 51B of the cover member 51, which will be described later, with an axial gap therebetween. This axial gap serves to prevent axial force from being directly applied to the first stator core 36 from the plate 51B side of the cover member 51 via the core lid 37. The core lid 37 does not necessarily have to be made of a magnetic material, and can also be made of a rigid metal material, ceramic material, or fiber-reinforced resin material.

[0048] The second stator core 40 constitutes a second fixed core that is spaced apart from the first stator core 36 in the axial direction and is provided on the inner peripheral side of the molded coil 34 (coil 34A). Like the first stator core 36 (first fixed core), the second stator core 40 is formed in a stepped cylindrical shape from a magnetic material such as low-carbon steel or carbon steel for mechanical structures (S10C). The second stator core 40 is formed as an integral unit that includes a cylindrical tubular portion 40A whose inner peripheral side forms a stepped hole 40F (described later), an annular portion 40B that extends radially outward from the outer periphery on one axial side of the tubular portion 40A over the entire circumference, and a cylindrical fitting portion 40C that protrudes from the outer periphery of the annular portion 40B toward one axial side (the damping force control valve 18 side).

[0049] A circular recess 40D is recessed into the cylindrical portion 40A of the second stator core 40 on the other side axially facing a plunger 48 (described later). This recess 40D is formed as a circular groove with a diameter slightly larger than that of the plunger 48 (described later) so that the plunger 48 (described later) can be inserted therein and moved forward and backward by magnetic force. In addition, a conical protrusion 40E is provided on the other side of the cylindrical portion 40A so as to surround the periphery (outer periphery) of the recess 40D. The outer circumferential surface of this conical protrusion 40E is formed as a cone so that the magnetic characteristics between the cylindrical portion 40A of the second stator core 40 and the plunger 48 are linear. That is, the conical protrusion 40E protrudes cylindrically from the outer periphery of the cylindrical portion 40A of the second stator core 40 toward the other axial side, and its outer periphery forms a conical surface that is tapered so that the outer diameter dimension gradually decreases from one axial side to the other axial side (from the left side to the right side of the recessed portion 40D shown in Figures 3 and 4).

[0050] 3 and 4, a stepped hole 40F is formed on the inner peripheral side of the cylindrical portion 40A, and a second bushing 41 is fitted into this stepped hole 40F to slidably support an operating pin 49 (described later). Meanwhile, a seal groove 40G in which a seal member (e.g., an O-ring 42) is fitted is formed in the annular portion 40B of the second stator core 40 on the other side facing the molded coil 34, and this O-ring 42 provides a liquid-tight seal between the molded coil 34 and the annular portion 40B.

[0051] 2, the cap 31 of the damping force control valve 18 is fitted (internal fit) onto the inner circumferential side of the fitting portion 40C. Furthermore, the valve case 19 of the damping force control valve 18 is fitted (externally fit) onto the outer circumferential side of the fitting portion 40C. Furthermore, a seal groove 40H is provided around the entire periphery on the outer circumferential surface of the fitting portion 40C. An O-ring 43 serving as a seal member is fitted into this seal groove 40H, and the O-ring 43 provides a liquid-tight seal between the second stator core 40 (fitting portion 40C) and the valve case 19 of the damping force control valve 18.

[0052] The non-magnetic ring 44 is a non-magnetic member located between the first and second stator cores 36, 40 and provided on the inner circumferential side of the molded coil 34 (coil 34A). The non-magnetic ring 44 is formed as a stepped cylinder made of a non-magnetic material such as austenitic stainless steel. The non-magnetic ring 44 is composed of a thick-walled cylindrical portion 44A located in the middle in the axial direction and first and second mating cylindrical portions 44B, 44C protruding axially from both ends of the thick-walled cylindrical portion 44A.

[0053] Here, the non-magnetic ring 44 has the thick-walled cylindrical portion 44A and the fitting cylindrical portions 44B, 44C with the same outer diameter. However, as shown in Fig. 4, the thick-walled cylindrical portion 44A is formed with the smallest inner diameter D1, and the first and second fitting cylindrical portions 44B, 44C are formed with inner diameters larger than that of the thick-walled cylindrical portion 44A (dimension D1). The first and second fitting cylindrical portions 44B, 44C are molded from a non-magnetic material with the required thickness (radial thickness) so as to ensure the desired coaxiality with the thick-walled cylindrical portion 44A.

[0054] The first fitting cylindrical portion 44B of the non-magnetic ring 44 is fitted from the outside into the small-diameter cylindrical portion 36A of the first stator core 36, and the two are joined by a brazing portion 45. The second fitting cylindrical portion 44C is fitted onto the outer periphery of the cylindrical portion 40A and the conical protrusion 40E of the second stator core 40, and the two are joined by a brazing portion 46. The brazing portions 45, 46 each use a brazing material made of pure copper brazing, and are formed by brazing at 1000°C or higher (solidification treatment of the pure copper brazing), for example, to join the non-magnetic ring 44 to the first and second stator cores 36, 40. A rapid cooling process is performed after the brazing process.

[0055] The brazing portions 45, 46 have a thickness of, for example, about 25 to 51 μm and join the non-magnetic ring 44 to the first and second stator cores 36, 40. In this state, the inner diameter of the non-magnetic ring 44 (i.e., the dimension D1 of the thick-walled cylindrical portion 44A) is formed so as to be larger than the inner diameter of the first stator core 36 and larger than the inner diameter of the second stator core 40 (i.e., the radial dimension of the recessed portion 40D), as shown in FIG. 4 . The inner diameter of the non-magnetic ring 44 (i.e., the dimension D1 of the thick-walled cylindrical portion 44A) is larger than the inner diameters of the first and second fixed iron cores (first and second stator cores 36, 40). In this embodiment, the inner diameter of the non-magnetic ring 44 is larger than the inner diameters of the first and second stator cores, but the inner diameter of the non-magnetic ring 44 may also be smaller than the inner diameters of the first and second stator cores. Making the inner diameter of the non-magnetic ring 44 smaller or larger than the inner diameters of the first and second stator cores means, in other words, that the inside of the non-magnetic ring 44 is not machined after being brazed to the first and second stator cores (without machining, there would be tolerances in the inner diameters of the non-magnetic ring 44 and the first and second stator cores, and it would be impossible for mass-produced products to all have the same inner diameter).

[0056] An annular gap 47 is formed between the small diameter cylindrical portion 36A of the first stator core 36 and the first fitting cylindrical portion 44B of the non-magnetic ring 44 on the outer circumferential side thereof. This gap 47 is an introduction path for pouring the brazing material (pure copper brazing material) in a heated and molten state between the first stator core 36 (small diameter cylindrical portion 36A) and the non-magnetic ring 44 (first fitting cylindrical portion 44B). This gap 47 functions as an air gap for absorbing the difference in thermal expansion between the first and second stator cores 36, 40 and the non-magnetic ring 44.

[0057] Similar to the gap 47, an introduction path for pouring the brazing material (pure copper brazing material) of the brazing portion 46 in a heated and molten state is also formed between the second stator core 40 (the cylindrical portion 40A and the outer peripheral surface of the conical protrusion 40E) and the non-magnetic ring 44 (the second fitting cylindrical portion 44C). However, when the brazing material (pure copper brazing material) in a heated and molten state is poured into the non-magnetic ring 44 to join the second fitting cylindrical portion 44C to the second stator core 40 (the cylindrical portion 40A and the outer peripheral side of the conical protrusion 40E), an axial external force is applied between them to minimize the gap. However, a difference in thermal expansion occurs between the first and second stator cores 36, 40 and the non-magnetic ring 44 due to the difference in materials.

[0058] For this reason, an axial gap 47 is formed between the small-diameter cylindrical portion 36A of the first stator core 36 and the first fitting cylindrical portion 44B of the non-magnetic ring 44, extending over the entire circumference. In this way, the non-magnetic ring 44 is joined between the first and second stator cores 36, 40 at the brazed portions 45, 46, and even if a difference in thermal expansion occurs between the two due to differences in materials (components) during rapid cooling after brazing, the occurrence of distortion due to this difference can be suppressed by the gap 47. The non-magnetic ring 44, as a non-magnetic member, is provided between the first and second stator cores 36, 40 (stationary iron cores) and is fixed integrally to the first and second stator cores 36, 40 by brazing.

[0059] The plunger 48, which serves as a movable core, is disposed on the inner periphery of the first and second stator cores 36, 40 (first and second fixed cores) and the non-magnetic ring 44 (non-magnetic member), and is provided so as to be movable in the axial direction. That is, the plunger 48 is disposed on the inner periphery of the first and second stator cores 36, 40 and the non-magnetic ring 44, and is provided so as to be movable in the axial direction via the first and second bushings 38, 41 and the actuation pin 49 by the magnetic force generated in the coil 34A. The plunger 48 is fixed to the actuation pin 49, which extends through the center of the plunger 48, and moves together with the actuation pin 49. The actuation pin 49 is supported by the core cover 37 on the first stator core 36 side and the second stator core 40, via the first and second bushings 38, 41, so as to be slidable in the axial direction.

[0060] Here, the plunger 48 is formed in a substantially cylindrical shape from an iron-based magnetic material, similar to the first and second stator cores 36, 40, and generates a thrust in a direction in which the plunger 48 is attracted toward the recessed portion 40D of the second stator core 40 when a magnetic force is generated by the coil 34A. The plunger 48 also has a plurality of communication passages 48A formed therein, spaced apart in the circumferential direction and extending in the axial direction (front-rear direction). These communication passages 48A are flow passages that allow the oil in the first and second stator cores 36, 40 to flow smoothly through each communication passage 48A while the plunger 48 is displaced in the axial direction together with the actuation pin 49, thereby suppressing the generation of flow resistance to the plunger 48.

[0061] The actuating pin 49 is a shaft portion that transmits the thrust of the plunger 48 to the pilot valve element 32 of the damping force control valve 18, and is formed from a hollow rod. The plunger 48 as a movable iron core is fixed integrally to the axial middle portion of the actuating pin 49 by means of press fitting or the like, thereby forming the plunger 48 and actuating pin 49 into a sub-assembly. Both axial ends of the actuating pin 49 are slidably supported by the core cover body 37 on the first stator core 36 side and the second stator core 40 (cylindrical portion 40A) via first and second bushings 38, 41.

[0062] One end of the actuating pin 49 (the left end in FIG. 2) protrudes from the second stator core 40, and the pilot valve element 32 of the damping force control valve 18 is fixed to the protruding end. Therefore, the pilot valve element 32 moves integrally in the axial direction together with the plunger 48 and the actuating pin 49. In other words, the set valve-opening pressure of the pilot valve element 32 becomes a pressure value corresponding to the thrust of the plunger 48 based on the energization of the coil 34A. The plunger 48 moves in the axial direction due to the magnetic force from the coil 34A, thereby opening and closing the pilot valve of the hydraulic shock absorber 1 (i.e., the pilot valve element 32 relative to the pilot body 26).

[0063] The back pressure chamber 50 is an oil chamber formed between the core cover body 37 and the other end of the actuating pin 49 (the right end in FIG. 2). This back pressure chamber 50 is in communication with the center hole 24B side of the pilot pin 24 via the hollow rod (actuating pin 49). Therefore, the same pressure as that acting on the pilot valve element 32 seated on and separated from the valve seat 26E of the pilot body 26 acts on the back pressure chamber 50. However, with regard to the pressure-receiving area for this pressure, the area where the other end face of the actuating pin 49 receives pressure within the back pressure chamber 50 is smaller than the area where the pilot valve element 32 (one end side of the actuating pin 49) receives pressure between itself and the valve seat 26E.

[0064] As a result, the thrust to be transmitted from the plunger 48 to the pilot valve element 32 of the damping force control valve 18 via the actuating pin 49 can be reduced by the difference in pressure-receiving area between them. In other words, by forming a back pressure chamber 50 between the other end side of the actuating pin 49 and the core cover body 37, the thrust to be transmitted from the plunger 48 to the pilot valve element 32 of the damping force control valve 18 via the actuating pin 49 (for example, the magnetic force to be generated by the coil 34A of the molded coil 34) can be reduced, and the solenoid 33 as a whole can be made smaller and lighter.

[0065] The cover member 51 is a magnetic cover that covers the outer periphery of the coil 34A. The cover member 51 is formed as a yoke using a magnetic material (magnetic substance) and forms a magnetic circuit (magnetic path) on the outer periphery side of the molded coil 34 (coil 34A). The cover member 51 is formed in a cylindrical shape with a bottom as a whole and is generally composed of a cylindrical casing 51A and a plate 51B that closes the other end side of the cylindrical casing 51A (the right end in FIGS. 2 and 3). The casing 51A has a notch (not shown) for exposing the cable outlet portion of the molded coil 34 described above from the cover member 51.

[0066] Here, a fitting recess 51C is provided in the plate 51B of the cover member 51, into which the core lid 37 (its bottom side) of the first stator core 36 is inserted or housed. The bottom side of the core lid 37 is fitted into the fitting recess 51C, so that the first stator core 36 can exchange magnetic flux with the plate 51B of the cover member 51.

[0067] Meanwhile, the inner peripheral surface of cylindrical case 51A of cover member 51 faces the outer peripheral surface of molded coil 34 with a gap therebetween. This gap is configured to prevent radial force acting on cover member 51 from being directly applied to molded coil 34. In addition, the outer peripheral surface of annular portion 40B of second stator core 40 abuts against the inner peripheral surface of cylindrical case 51A by, for example, light press fitting, allowing magnetic flux to be transferred between cover member 51 and second stator core 40 (annular portion 40B).

[0068] Engagement protrusions 51D that protrude radially outward beyond other portions are provided (along the entire circumference or at multiple locations spaced apart circumferentially) on the opening end of the cover member 51 (i.e., one axial end of the cylindrical case 51A located on the left side in FIG. 2). The engagement protrusions 51D are adapted to engage with a coupling ring 52 that is screwed onto the valve case 19 of the damping force control valve 18.

[0069] The coupling ring 52 is formed in a substantially cylindrical shape, and is provided on its inside with a female thread portion 52A that screws onto the male thread portion 19B of the valve case 19, and a flange-shaped engaging portion 52B that extends radially inward so that its inner diameter is smaller than the outer diameter of the engaging protrusion 51D of the cylindrical case 51A. The coupling ring 52 is a coupling member that integrally connects the damping force control valve 18 and the solenoid 33 by screwing the female thread portion 52A into the male thread portion 19B of the valve case 19 with the flange-shaped engaging portion 52B abutting against the engaging protrusion 51D of the cylindrical case 51A.

[0070] The solenoid 33 and the hydraulic shock absorber 1 according to this embodiment have the above-described configuration, and their operation will now be described.

[0071] First, when mounting the hydraulic shock absorber 1 on a vehicle such as an automobile, for example, the protruding end (upper end) of the piston rod 8 is attached to the vehicle body, and the mounting eye 3A provided on the bottom cap 3 is attached to the wheel. Then, the solenoid 33 of the damping force adjuster 17 is connected to a control device (controller) provided on the vehicle body via an electrical wiring cable (neither is shown) or the like.

[0072] When the vehicle is traveling and vibrations in the up and down directions occur due to unevenness of the road surface or the like, the piston rod 8 is displaced so as to extend or contract from the outer cylinder 2, and a damping force can be generated by the damping force adjusting device 17 or the like, thereby cushioning the vibrations of the vehicle. At this time, the controller changes the current value of the control signal that is energized to the coil 34A of the solenoid 33, and adjusts the valve opening pressure of the pilot valve body 32, thereby variably controlling the damping force generated by the hydraulic shock absorber 1.

[0073] Here, the magnetic force (magnetic flux) generated by the coil 34A of the solenoid 33 passes from the first stator core 36 through the movable iron core (plunger 48) side, avoiding the non-magnetic ring 44, which is a non-magnetic member, and then passes from the plunger 48 through the second stator core 40 (i.e., the conical protrusion 40E, the cylindrical portion 40A, the annular portion 40B and the mating portion 40C), and further through the cylindrical case 51A and plate 51B of the cover member 51, forming a magnetic circuit that returns to the first stator core 36.

[0074] In this case, the magnetic circuit can transfer magnetic flux through all contact portions (i.e., areas where magnetic bodies come into surface contact with each other) except for the transfer of magnetic flux between the plunger 48 and the first stator core 36, which face each other with a small gap therebetween, and between the plunger 48 and the second stator core 40. Therefore, the magnetic circuit of the solenoid 33 can ensure high magnetic efficiency.

[0075] Meanwhile, a non-magnetic ring 44, which is a non-magnetic member, is provided between the first stator core 36 and the second stator core 40, which constitute the main part of the solenoid 33, on the inner circumferential side of the molded coil 34 (coil 34A). This non-magnetic ring 44 is joined to the first and second fixed cores (first and second stator cores 36, 40) by brazing portions 45, 46 so as to increase the magnetic flux density of the magnetic circuit for the movable core (plunger 48). However, if the non-magnetic member (non-magnetic ring 44) is machined (for example, by cutting the inner circumferential surface) after joining, the magnetic properties of the non-magnetic member change due to processing distortion, which causes a problem in that the non-magnetic member becomes easily magnetized.

[0076] Therefore, in this embodiment, a non-magnetic ring 44 made of a non-magnetic material such as austenitic stainless steel is formed as a stepped cylindrical integral body with a thick-walled cylindrical portion 44A at the axial middle and first and second fitting cylindrical portions 44B, 44C that protrude axially from both ends of the thick-walled cylindrical portion 44A. The non-magnetic ring 44 has an inner diameter D1 that is larger than the inner diameters of the first and second stator cores 36, 40.

[0077] That is, when the non-magnetic ring 44 is joined between the first stator core 36 and the second stator core 40 by the brazing portions 45, 46, the inner diameter of the non-magnetic ring 44 (i.e., the dimension D1 of the thick-walled cylindrical portion 44A) is formed to be larger than the inner diameter of the first stator core 36 and larger than the inner diameter of the second stator core 40 (i.e., the radial dimension of the recessed portion 40D), as shown in FIG.

[0078] Therefore, a plunger 48 as a movable core can be arranged axially movably on the inner periphery side of the first and second stator cores 36, 40 (first and second fixed cores) and the non-magnetic ring 44 (non-magnetic member). That is, because the plunger 48 can be arranged with a gap inside the non-magnetic ring 44, there is no need to machine the non-magnetic ring 44 (for example, by cutting the inner periphery) after joining the first and second stator cores 36, 40, and the magnetic properties of the non-magnetic ring 44 will not change due to thermal effects, distortion, or the like.

[0079] In this case, non-magnetic ring 44 is a non-magnetic member made of austenitic stainless steel, and when this non-magnetic ring 44 is joined between first stator core 36 and second stator core 40 by brazing portions 45, 46, brazing is performed using pure copper brazing filler metal (brazing material) or the like. That is, when austenitic stainless steel is subjected to solution heat treatment at a temperature of 1000°C or higher, for example, deformation-induced martensite is removed and the crystal structure can be restored to a face-centered cubic structure that is ideal for non-magnetic materials.

[0080] Generally, when non-magnetic austenitic stainless steel parts are subjected to deep drawing or cutting, distortion occurs in the material, causing the material to produce strain-induced martensite, and some of the crystal structure transforms into a body-centered cubic structure rather than the face-centered cubic structure that is ideal for non-magnetic materials, making the non-magnetic material more susceptible to magnetization. However, the strain-induced martensite in austenitic stainless steel can be removed by heat treatment at 1000°C or higher, returning it to the ideal face-centered cubic structure. This treatment is called solution heat treatment.

[0081] Therefore, in this embodiment, pure copper brazing filler metal is selected as the brazing material having a brazing temperature of 1000°C or higher, and a process that combines brazing and solution heat treatment is performed at the brazing portions 45, 46. This allows the crystal structure of the non-magnetic ring 44 joined between the first and second stator cores 36, 40 to be restored to the face-centered cubic structure that is ideal for non-magnetic materials. Furthermore, because the non-magnetic ring 44 is press-fitted between the first and second stator cores 36, 40 and butted together, thermal deformation due to high temperatures during brazing is suppressed. This eliminates the need for cutting for shape correction after brazing, allowing the ring to maintain its desired dimensions and shape. Note that the brazing filler metal may be other than pure copper brazing filler metal as long as it has a brazing temperature of 1000°C or higher. For example, brass brazing filler metal, nickel brazing filler metal, gold brazing filler metal, palladium brazing filler metal, etc. may also be used.

[0082] Thus, according to this embodiment, it is possible to prevent the characteristics of the non-magnetic ring 44 (non-magnetic member) from changing due to thermal effects, distortion, and the like, and to maintain a high magnetic flux density passing through the non-magnetic ring 44 (non-magnetic member) between the first and second stator cores 36, 40. Furthermore, the magnetic circuit of the solenoid 33 can exchange magnetic flux with all magnetic bodies in surface contact with each other, except for the exchange of magnetic flux between the plunger 48 and the first stator core 36, which face each other via a small gap, and between the plunger 48 and the second stator core 40, so the magnetic circuit of the solenoid 33 can ensure high magnetic efficiency.

[0083] Moreover, the first fitting cylindrical portion 44B of the non-magnetic ring 44 is fitted from the outside into the small-diameter cylindrical portion 36A of the first stator core 36, and the two are joined by a brazing portion 45. The second fitting cylindrical portion 44C is fitted onto the outer periphery of the cylindrical portion 40A and the conical protrusion 40E of the second stator core 40, and the two are joined by a brazing portion 46. The brazing portions 45, 46 are each made of a brazing material made of pure copper, and are brazed at a temperature of 1000°C or higher, for example, to join the non-magnetic ring 44 to the first and second stator cores 36, 40, and a rapid cooling process is performed after the brazing process.

[0084] In this embodiment, the first and second stator cores 36, 40 and the non-magnetic ring 44 are configured as described above, and the brazing portions 45, 46 are brazed using pure copper brazing filler metal at a temperature of, for example, 1000°C or higher. This allows the three components, the first and second stator cores 36, 40 and the non-magnetic ring 44, to be joined together in a shape that satisfies coaxiality, and also ensures pressure resistance to the internal pressure oil.

[0085] Therefore, the solenoid 33 employed in this embodiment is a solenoid 33 used in a semi-actuator (damping force adjustable shock absorber) for adjusting the opening and closing operation of the damping force adjustment valve 18. As a means for providing a non-magnetic portion for the purpose of forming a magnetic path between the fixed iron core (first and second stator cores 36, 40) and the movable iron core (plunger 48), joining a non-magnetic member (non-magnetic ring 44) between the magnetic members (first and second stator cores 36, 40) with brazing portions 45, 46 can provide an optimal method for enabling the damping force adjustment valve 18 to withstand high pressures.

[0086] That is, by setting the brazing temperature when joining the non-magnetic ring 44 between the first and second stator cores 36, 40 to 1000°C or higher as described above, it is possible to perform solution heat treatment and remove the work-induced martensite (body-centered cubic structure) created by cutting, thereby obtaining a metal structure with a face-centered cubic structure that is ideal for magnetic properties. Furthermore, because no cutting is performed for the purpose of correcting the shape after brazing, work-induced martensite is not created, the metal structure is maintained as an ideal non-magnetic material, and a structure can be achieved that suppresses thermal deformation during the brazing process.

[0087] This allows the non-magnetic ring 44 as the non-magnetic portion to have an ideal metal structure, making it possible to obtain excellent magnetic properties, thereby improving the thrust and optimizing the thrust waveform of the solenoid 33. Furthermore, the number of processes required to manufacture and produce the solenoid 33 is reduced, making it possible to improve workability and productivity.

[0088] In the above embodiment, the second stator core 40 is described as including a cylindrical tubular portion 40A, an annular portion 40B, and a cylindrical fitting portion 40C that protrudes to one side in the axial direction. However, the present invention is not limited to this. For example, the second fixed core (i.e., the second stator core) may be formed by the cylindrical tubular portion 40A and the annular portion 40B, and the cylindrical fitting portion that protrudes to one side in the axial direction may be omitted or eliminated.

[0089] In the above embodiment, the cover member 51 is configured as a yoke using a magnetic material. However, the present invention is not limited to this. For example, the cover member may be configured as a non-magnetic material, and the solenoid may be an open coil type solenoid without a yoke. Furthermore, in the above embodiment, the solenoid 33 is configured as a proportional solenoid. However, the present invention is not limited to this. For example, the solenoid may be configured as an ON / OFF type solenoid.

[0090] Next, the invention included in the above-mentioned embodiments will be described. That is, a first aspect of the present invention is a damping force control shock absorber comprising: a cylinder in which a working fluid is sealed, a piston inserted into the cylinder to divide the interior of the cylinder into a rod-side chamber and a bottom-side chamber, a piston rod connected to the piston and extending to the outside of the cylinder, a flow path in which a flow of the working fluid occurs due to movement of the piston rod, and a damping force control valve provided in the flow path and whose opening and closing operation is adjusted by a solenoid, wherein the solenoid comprises a coil that generates a magnetic force when energized, and first and second magnetic bearings provided on the inner circumferential side of the coil. The damping force control valve comprises a fixed iron core, a non-magnetic member disposed between the first and second fixed iron cores and integrally fixed to the first and second fixed iron cores by brazing, a movable iron core disposed on the inner periphery of the first and second fixed iron cores and the non-magnetic member and movable in the axial direction, a shaft portion disposed on the movable iron core, and first and second bushings supporting the shaft portion, wherein the valve body of the damping force control valve is disposed on the end of the shaft portion on the second fixed iron core side, and the inner diameter of the non-magnetic member is larger or smaller than the inner diameter of the first and second fixed iron cores.

[0091] A second aspect of the present invention is a damping force control shock absorber in the first aspect, wherein the non-magnetic member is made of austenitic stainless steel.A third aspect of the present invention is a damping force control shock absorber in the first or second aspect, wherein the non-magnetic member is brazed using a brazing material with a brazing temperature of 1000°C or higher.A fourth aspect of the present invention is a damping force control shock absorber in the third aspect, wherein the non-magnetic member is brazed using a brazing material made of pure copper brazing.

[0092] A solenoid according to a fifth aspect of the present invention comprises a coil that generates a magnetic force when current is passed through it, first and second fixed iron cores arranged on the inner periphery of the coil, a non-magnetic member arranged between the first and second fixed iron cores and fixed integrally to the first and second fixed iron cores by brazing, a movable iron core arranged on the inner periphery of the first and second fixed iron cores and the non-magnetic member and arranged so as to be movable in the axial direction, a shaft portion arranged on the movable iron core, and first and second bushings that support the shaft portion, and is characterized in that the inner diameter of the non-magnetic member is larger or smaller than the inner diameter of the first and second fixed iron cores.

[0093] A solenoid according to a sixth aspect of the present invention is the fifth aspect, wherein the non-magnetic member is a member made of austenitic stainless steel.A solenoid according to a seventh aspect of the present invention is the fifth or sixth aspect, wherein the non-magnetic member is brazed using a brazing material having a brazing temperature of 1000°C or higher.A solenoid according to an eighth aspect of the present invention is the seventh aspect, wherein the non-magnetic member is brazed using a brazing material made of pure copper brazing.A solenoid according to a ninth aspect of the present invention is the fifth to eighth aspects, wherein inner diameter portions that define the inner diameters of the first and second stationary iron cores and the inner diameter portion that defines the inner diameter of the non-magnetic member are not machined after brazing.

[0094] A tenth aspect of the present invention is a damping force control shock absorber comprising: a cylinder in which a working fluid is sealed; a piston inserted into the cylinder to divide the interior of the cylinder into a rod side chamber and a bottom side chamber; a piston rod connected to the piston and extending to the outside of the cylinder; a flow path in which a flow of the working fluid is generated by movement of the piston rod; and a damping force control valve provided in the flow path and whose opening and closing operation is adjusted by a solenoid, wherein the solenoid comprises a coil that generates a magnetic force when energized, and first and second fixed coils provided on the inner circumferential side of the coil. The damping force control valve comprises a fixed core and a non-magnetic member disposed between the first and second fixed cores and integrally fixed to the first and second fixed cores by brazing; a movable core disposed on the inner periphery of the first and second fixed cores and the non-magnetic member and movable in the axial direction; a shaft portion disposed on the inner periphery of the movable core; and first and second bushings that support the shaft portion, wherein the valve body of the damping force control valve is disposed on the end of the shaft portion on the second fixed core side, and the inner diameter portion that defines the inner diameter of the non-magnetic member is not machined after brazing.

[0095] The present invention is not limited to the above-described embodiments and 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.

[0096] This application claims priority to Japanese Patent Application No. 2018-241220, filed December 25, 2018. The entire disclosure of Japanese Patent Application No. 2018-241220, filed December 25, 2018, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety. [Explanation of symbols]

[0097] DESCRIPTION OF SYMBOLS 1 Hydraulic shock absorber (damping force adjustable shock absorber) 4 Inner cylinder (cylinder) 5 Piston 8 Piston rod 17 Damping force adjustment device 18 Damping force adjustment valve 32 Pilot valve body (valve body) 33 Solenoid 34 Molded coil 34A Coil 36 First stator core (first fixed iron core) 37 Core cover body 38 First bush 40 Second stator core (second fixed iron core) 40A Cylinder portion 41 Second bush 44 Non-magnetic ring (non-magnetic member) 45, 46 Brazed portion 48 Plunger (movable iron core) 49 Operating pin (shaft portion) A Reservoir chamber B Rod side oil chamber (rod side chamber) C Bottom side oil chamber (bottom side chamber) D Annular oil chamber (flow path) D1 Dimension (inner diameter of non-magnetic member)

Claims

1. A damping force adjustable shock absorber, comprising: a cylinder in which a working fluid is sealed; a piston inserted into the cylinder to divide the interior of the cylinder into a rod-side chamber and a bottom-side chamber; a piston rod connected to the piston and extending to the outside of the cylinder; a flow path in which the flow of the working fluid occurs due to the movement of the piston rod; a damping force adjusting valve provided in the flow path and having an opening / closing operation adjusted by a solenoid; Equipped with The solenoid is A coil that generates magnetic force when energized; first and second fixed cores provided on the inner circumferential side of the coil; a non-magnetic member provided between the first and second stationary iron cores and integrally fixed to the first and second stationary iron cores by brazing; a movable core disposed on the inner circumferential side of the first and second fixed cores and the non-magnetic member, and movable in the axial direction; a shaft portion extending in the axial direction of the movable iron core; Equipped with a valve body of the damping force control valve is provided at an end of the shaft portion on the second fixed iron core side, the inner diameter of the non-magnetic member is larger or smaller than the inner diameters of the first and second fixed iron cores, The non-magnetic member is a fitting cylindrical portion into which the second fixed core is press-fitted; a thick-walled cylindrical portion that protrudes radially inward from an axially intermediate position and has a diameter larger than the outer diameter of the movable core; A damping force adjustable shock absorber characterized in that the thick-walled cylindrical portion and the conical protrusion provided on the end of the second fixed iron core are joined to the second fixed iron core using a brazing material with a brazing temperature of 1000 degrees or higher, the axial end of the mating cylindrical portion abuts against the second fixed iron core, and the brazed state is made of austenitic stainless steel having a face-centered cubic crystal structure, and is less susceptible to magnetization than austenitic stainless steel having a body-centered cubic crystal structure that has been processed after brazing.

2. 2. The damping force adjustable shock absorber according to claim 1, The non-magnetic member is brazed using a brazing material made of pure copper.

3. A coil that generates magnetic force when energized; first and second fixed cores provided on the inner circumferential side of the coil; a non-magnetic member provided between the first and second stationary iron cores and integrally fixed to the first and second stationary iron cores by brazing; a movable core disposed on the inner circumferential side of the first and second fixed cores and the non-magnetic member, and movable in the axial direction; Equipped with the inner diameter of the non-magnetic member is larger or smaller than the inner diameters of the first and second fixed iron cores, The non-magnetic member is a fitting cylindrical portion into which the second fixed core is press-fitted; a thick-walled cylindrical portion that protrudes radially inward from an axially intermediate position and has a diameter larger than the outer diameter of the movable core; A solenoid characterized in that the thick-walled cylindrical portion and the second fixed core are joined to each other using a brazing material with a brazing temperature of 1000 degrees or higher between the thick-walled cylindrical portion and a conical protrusion provided on the end of the second fixed core, the axial end of the mating cylindrical portion abutting against the second fixed core, the brazed state being made of austenitic stainless steel having a face-centered cubic crystal structure, and the solenoid is less susceptible to magnetization than austenitic stainless steel having a body-centered cubic crystal structure that has been processed after brazing.

4. 4. The solenoid of claim 3, The non-magnetic member is brazed to the solenoid using a brazing material made of pure copper.

5. 5. The solenoid according to claim 3 or 4, 1. A solenoid comprising: an inner diameter portion defining the inner diameter of each of the first and second fixed iron cores; and an inner diameter portion defining the inner diameter of the non-magnetic member, the inner diameter portion being not machined after brazing.

6. A damping force adjustable shock absorber, comprising: a cylinder in which a working fluid is sealed; a piston inserted into the cylinder to divide the interior of the cylinder into a rod-side chamber and a bottom-side chamber; a piston rod connected to the piston and extending to the outside of the cylinder; a flow path in which the flow of the working fluid occurs due to the movement of the piston rod; a damping force adjusting valve provided in the flow path and having an opening / closing operation adjusted by a solenoid; Equipped with The solenoid is A coil that generates magnetic force when energized; first and second fixed cores provided on the inner circumferential side of the coil; a non-magnetic member provided between the first and second stationary iron cores and integrally fixed to the first and second stationary iron cores by brazing; a movable core disposed on the inner circumferential side of the first and second fixed cores and the non-magnetic member, and movable in the axial direction; a shaft portion extending in the axial direction of the movable iron core; Equipped with a valve body of the damping force control valve is provided at an end of the shaft portion on the second fixed iron core side, The non-magnetic member is a fitting cylindrical portion into which the second fixed core is press-fitted; a thick-walled cylindrical portion that protrudes radially inward from an axially intermediate position and has a diameter larger than the outer diameter of the movable core; A damping force adjustable shock absorber characterized in that the thick-walled cylindrical portion and the conical protrusion provided on the end of the second fixed iron core are joined to the second fixed iron core using a brazing material with a brazing temperature of 1000 degrees or higher, the axial end of the mating cylindrical portion abuts against the second fixed iron core, and the brazed state is made of austenitic stainless steel having a face-centered cubic crystal structure, and is less susceptible to magnetization than austenitic stainless steel having a body-centered cubic crystal structure that has been processed after brazing.

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