JP7796063B2 - Adjustable damping shock absorber and solenoid - Google Patents

Description

The present invention relates to a damping force adjustable shock absorber and solenoid that damps, for example, vehicle vibrations.

Generally, suspension systems such as semi-active suspensions mounted on vehicles are equipped with adjustable damping shock absorbers that variably adjust damping force in response to the vehicle's driving conditions, behavior, etc. Known adjustable damping shock absorbers include those that use a solenoid as an electromagnetic proportional actuator to variably adjust damping force. For example, Patent Document 1 describes this type of solenoid as comprising 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 movable in the axial direction.

Patent Document 2 also describes a solenoid in which brazing is used to join a non-magnetic member between the 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 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.

JP 2014-73018 A JP 2009-127692 A JP 2017-118124 A

In the solenoid disclosed in the above 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, if the non-magnetic member is machined after joining (for example, by cutting the inner circumferential surface), the magnetic properties change due to processing distortion, making the non-magnetic member more susceptible to magnetization. Furthermore, if a thin-walled section is provided between the first and second fixed iron cores to partially reduce the cross-sectional area of the magnetic path, the thin-walled section reduces the mechanical strength of the entire fixed iron core, resulting in reduced durability and lifespan.

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

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 as the piston rod moves; 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 that is provided between the first and second fixed iron cores and is fixed integrally to the first and second fixed iron cores by brazing; a movable iron core that is arranged on the inner circumferential side of the first and second fixed iron cores and the non-magnetic member and is provided so as to be movable in the axial direction; and a shaft portion extending in the axial direction of the movable iron core. 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 has a fitting cylindrical portion that is press-fitted with the second fixed iron core, and a thick-walled cylindrical portion that protrudes radially inward at an intermediate portion in the axial direction and is formed with a diameter larger than the outer diameter of the movable iron core, the non-magnetic member is joined to the second fixed iron core using a brazing material having a brazing temperature of 1000°C or higher between the thick-walled cylindrical portion and a conical protrusion provided at the end of the second fixed iron core , the axial end of the fitting cylindrical portion and the second fixed iron core abut against each other, the non-magnetic member is an austenitic stainless steel that has a face-centered cubic crystal structure in the brazed state, and is less likely to be magnetized than austenitic stainless steel that has been processed after brazing and has a body-centered cubic crystal structure .

A solenoid according to one embodiment of the present invention includes a coil that generates a 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 fixed cores and integrally fixed to the first and second fixed cores by brazing, and 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, the inner diameter of the non-magnetic member being larger or smaller than the inner diameters of the first and second fixed cores, and the non-magnetic member having a fitting cylindrical portion press-fitted with the second fixed core and a radially extending movable core at the axial middle. and a thick-walled cylindrical portion that protrudes inward and is formed with a diameter larger than the outer diameter of the movable core, and is joined to the second fixed core 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, and the axial end of the mating cylindrical portion abuts against the second fixed core , and is an austenitic stainless steel that is composed of a face-centered cubic crystal structure in the brazed state , and is characterized by being less susceptible to magnetization than austenitic stainless steel that has a body-centered cubic crystal structure that has been processed after brazing.

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; and a movable iron core arranged on the inner circumferential side of the first and second fixed iron cores and the non-magnetic member and provided axially movable; and a shaft portion extending in the axial direction of the movable iron core, and a valve body of the damping force adjustment valve is provided at the end of the shaft portion on the second fixed iron core side, and the non-magnetic member has a fitting cylindrical portion press-fitted into the second fixed iron core, and a thick-walled cylindrical portion protruding radially inward at the middle of the axial direction and formed with a diameter larger than the outer diameter of the movable iron core, and is joined to the second fixed iron core using a brazing material with a brazing temperature of 1000 degrees or higher between the thick-walled cylindrical portion and a conical protrusion provided at the end of the second fixed iron core, and the axial end of the fitting cylindrical portion and the second fixed iron core abut each other, and the brazed state is made of austenitic stainless steel with a face-centered cubic crystal structure , and is characterized in that it is less susceptible to magnetization than austenitic stainless steel with a body-centered cubic crystal structure that has been processed after brazing.

According to one embodiment of the present invention, it is possible to prevent the characteristics of the non-magnetic material 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.

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. FIG. 2 is an enlarged cross-sectional view showing a damping force adjusting valve and a solenoid in FIG. 1 . 3 is an enlarged cross-sectional view of a solenoid in FIG. 2 with the damping force adjusting valve removed. FIG. 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. [0023]FIG.

The damping force adjustable shock absorber and solenoid according to an embodiment of the present invention will be described in detail below with reference to Figures 1 to 4, taking as an example a case where the shock absorber and solenoid are applied to a damping force adjustable hydraulic shock absorber.

In Figure 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 composed of 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 explanation, 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.

The bottomed, cylindrical outer cylinder 2 that forms the outer shell of the hydraulic shock absorber 1 is closed at its lower end 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, concentric with the connection port 12C of the intermediate cylinder 12 (described below), and a damping force adjuster 17 (described below) is attached opposite the opening 2B. The bottom cap 3 also has a mounting eye 3A that can be attached, for example, to the wheel side of a vehicle.

The inner cylinder 4 is provided coaxially within the outer cylinder 2. The lower end of the inner cylinder 4 is fitted and attached to the bottom valve 13, and the upper end is fitted and attached to the 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 can also be, for example, water mixed with an additive.

A ring-shaped reservoir chamber A is formed between the inner cylinder 4 and the outer cylinder 2, and this reservoir chamber A is filled with gas along with the oil. This gas may be air at atmospheric pressure, or a gas such as compressed nitrogen gas may also be used. Furthermore, an oil hole 4A is drilled radially at a position midway along the length (axial direction) of the inner cylinder 4, constantly connecting the rod-side oil chamber B with the annular oil chamber D.

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 has multiple oil passages 5A, 5B formed at intervals in the circumferential direction, allowing communication between the rod-side oil chamber B and the bottom-side oil chamber C.

Here, 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 to the bottom-side oil chamber C via each oil passage 5A. This set relief pressure is set to a pressure higher than the valve-opening pressure when the damping force adjuster 17, described below, is set to hard.

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 piston rod 8's retraction stroke 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 lower than the opening pressure when the damping force adjuster 17, described below, is set to soft, so the check valve 7 does not substantially generate any damping force. This "substantially no damping force" refers to a force below the friction of the piston 5 and seal member 10, which does not affect the vehicle's movement.

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 and extends outside the outer cylinder 2 and inner cylinder 4 via a rod guide 9.

A stepped cylindrical rod guide 9 is provided at the upper end 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 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 with an elastic material such as rubber baked onto it, through whose center the piston rod 8 is inserted. The inner periphery slides against the outer periphery of the piston rod 8, creating a seal between the piston rod 8 and the rod.

The seal member 10 also has a lip seal 10A formed on its underside, which acts as a check valve and extends so as to come into contact with the rod guide 9. The lip seal 10A is positioned between the oil sump chamber 11 and the reservoir chamber A, and allows oil and other fluids in the oil sump chamber 11 to flow toward the reservoir chamber A via the return passage 9A of the rod guide 9, preventing reverse flow.

A cylindrical intermediate cylinder 12 is disposed between the outer cylinder 2 and the inner cylinder 4. This intermediate cylinder 12 is attached to the outer periphery of the inner cylinder 4 via upper and lower cylindrical seals 12A and 12B. The intermediate cylinder 12 defines an annular oil chamber D that extends around the entire outer periphery of the inner cylinder 4. The annular oil chamber D is independent of the reservoir chamber A. The annular oil chamber D is constantly connected to 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 hydraulic fluid flows as the piston rod 8 moves. The lower end of the intermediate cylinder 12 is provided with a connection port 12C to which a cylindrical holder 20 for the damping force adjustment valve 18 (described later) is attached.

The bottom valve 13 is located at the lower end of the inner cylinder 4, 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.

When the piston 5 slides downward during the retraction stroke of the piston rod 8, the compression-side disc valve 15 opens if the pressure in the bottom-side oil chamber C exceeds the relief set pressure, and the pressure at this time is relieved to the reservoir chamber A side via each oil passage 14A. This relief set pressure is set to a pressure higher than the valve-opening pressure when the damping force adjuster 17, described below, is set to hard.

The extension check valve 16 opens when the piston 5 slides upward during the extension stroke of the piston rod 8, and closes at all 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 soft, and effectively generates no damping force.

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 Figure 2 in addition to Figure 1. Note that Figure 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 Figure 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 (e.g., control to generate a hard damping force).

As shown in Figure 1, the damping force adjuster 17 has its base end (left end in Figure 1) positioned between the reservoir chamber A and the annular oil chamber D, and its tip end (right end in Figure 1) protruding radially outward from the lower side of the outer cylinder 2. The damping force adjuster 17 includes a damping force adjustment valve 18 that generates hard or soft damping forces by variably controlling the flow of oil from the annular oil chamber D to the reservoir chamber A, and a solenoid 33 (described below) that adjusts the opening and closing operation of the damping force adjustment valve 18.

In other words, the opening pressure of the damping force adjustment valve 18 is adjusted by a solenoid 33 used as a variable damping force actuator, thereby variably controlling the generated damping force to either hard or soft characteristics. The damping force adjustment valve 18 is a valve whose opening and closing operation is adjusted by the solenoid 33, and is located in a flow path (for example, between the annular oil chamber D and the reservoir chamber A) where the flow of working fluid occurs as the piston rod 8 moves.

The damping force adjustment valve 18 is composed of a substantially cylindrical valve case 19, the base end of which is fixed to the periphery of the opening 2B of the outer cylinder 2 and the tip end of which projects radially outward from the outer cylinder 2; a cylindrical holder 20, the base end of which is fixed to the connection port 12C of the intermediate cylinder 12 and the tip end of which forms an annular flange portion 20A and is disposed 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.

The base end of the valve case 19 forms an annular inner flange portion 19A extending radially inward, while the tip end of the valve case 19 forms a male thread portion 19B onto which a coupling ring 52 is threaded, connecting the valve case 19 to a cover member 51 of the solenoid 33 (described below). Between the inner surface of the valve case 19 and the outer surface of the valve member 21, and further between the inner surface of the valve case 19 and the outer surface of the pilot body 26, etc., forms an annular oil chamber 19C that is constantly in communication with reservoir chamber A.

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 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 multiple radially extending notches 22A that serve as radial oil passages connecting the oil chamber 19C and the reservoir chamber A. In this embodiment, the spacer 22 is configured to have 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, reducing the number of parts.

The valve member 21 has a central hole 21A located at its radial center and extending axially. The valve member 21 also has a plurality of oil passages 21B spaced circumferentially around the central hole 21A, with one side (left side in FIGS. 1 and 2) of each oil passage 21B constantly communicating with an oil passage 20B in the cylindrical holder 20. The other end face (right side in FIGS. 1 and 2) of the valve member 21 has 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 the main valve 23 (described later) is seated. Here, each oil passage 21B of the valve member 21 serves as a flow path through which pressurized oil flows at a flow rate corresponding to the opening of the main valve 23 between oil passage 20B of the cylindrical holder 20, which communicates with the annular oil chamber D, and oil chamber 19C of the valve case 19, which communicates with the reservoir chamber A.

The main valve 23 is composed of a disc valve whose inner circumferential side is sandwiched between the valve member 21 and the large-diameter portion 24A of the pilot pin 24. The outer circumferential side of the main valve 23 seats and lifts off from the annular valve seat 21D of the valve member 21. An elastic seal member 23A is fixed to the back side of the outer circumferential portion of the main valve 23 by baking or other means. The main valve 23 opens when it lifts off from the annular valve seat 21D upon receiving pressure from the oil passage 21B side (annular oil chamber D side) of the valve member 21. 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 degree of the main valve 23.

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

The pilot body 26 is formed as a generally bottomed cylindrical 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 around its entire circumference toward the valve member 21 (i.e., the left side in Figures 1 and 2). The elastic seal member 23A of the main valve 23 fits fluid-tightly onto the inner circumferential surface of this protruding cylindrical portion 26D, thereby forming a backpressure chamber 27 between the main valve 23 and the pilot body 26. This backpressure chamber 27 generates pressure that presses the main valve 23 in the valve closing direction, i.e., in the direction that seats the main valve 23 against the annular valve seat 21D of the valve member 21.

The bottom 26B of the pilot body 26 is provided with a valve seat 26E, located at the other end (the right end in Figures 1 and 2) of the pilot body 26, surrounding the central hole 26C and on which the pilot valve element 32 (described below) seats and disengages. Inside the cylindrical portion 26A of the pilot body 26 are a return spring 28 that urges the pilot valve element 32 away from the valve seat 26E of the pilot body 26, a disk valve 29 that forms a fail-safe valve when the solenoid 33 (described below) is de-energized (when the pilot valve element 32 is farthest from the valve seat 26E), and a retaining plate 30 with an oil passage 30A formed in its center.

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. This cap 31 has notches 31A formed in it, for example, at four circumferentially spaced positions. These notches 31A form flow paths that allow oil that flows to the solenoid 33 side through the oil passage 30A in the retaining plate 30 to flow to the oil chamber 19C (reservoir chamber A side) in the direction of arrow X shown in Figure 2.

The pilot valve element 32, together with the pilot body 26, constitutes the pilot valve. The pilot valve element 32 is formed in a stepped cylindrical shape, and its tip, which seats and disengages from the valve seat 26E of the pilot body 26, is tapered. An operating pin 49 of the solenoid 33 (described below) is fitted and fixed inside the pilot valve element 32, and the valve opening pressure of the pilot valve element 32 is adjusted in response to the supply of electricity to the solenoid 33. A flange portion 32A, which serves as a spring retainer, is formed around the entire circumference of the base end 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.

Next, the solenoid 33, which together with the damping force adjustment valve 18 constitutes the damping force adjustment device 17, will be described with reference to Figures 2, 3, and 4.

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 the 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 37, a second stator core 40, a non-magnetic ring 44, a plunger 48, an operating pin 49, and a cover member 51, etc.

The molded coil 34 is formed into a generally cylindrical shape by integrally covering (molding) the 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.

A seal groove 34C is formed around the entire circumference of the resin member 34B of the molded coil 34 on the side (axial end face) facing the cover member 51 (plate 51B) described below. A seal member (e.g., O-ring 35) is fitted within 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, including rainwater and 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.

The coil used 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 used. For example, the coil may be wound around a coil bobbin made of an electrically insulating material, and the outer periphery of the coil may be covered by an overmold (not shown) made of a resin material molded from above (the outer periphery).

The first stator core 36 constitutes a first fixed iron core located on the inner periphery of the molded coil 34 (coil 34A). The first stator core 36 is formed as a cylindrical body from a magnetic material such as low-carbon steel or mechanical structural carbon steel (S10C). A small-diameter cylindrical portion 36A for joining is formed on one axial side of the first stator core 36 (left side in Figures 3 and 4), and a non-magnetic ring 44 (described below) 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 the plunger 48 (described below), allowing the plunger 48 to move axially within the first stator core 36.

A cylindrical core cover 37 with a bottom is fitted to the other axial side (right side in Figures 3 and 4) of the first stator core 36. This core cover 37 is made of the same magnetic material as the first stator core 36 and is cylindrical with a bottom, closing the first stator core 36 from the other axial side (left side in Figures 2 and 3). A stepped hole 37A with a bottom is formed on the inside of the core cover 37, and a first bushing 38 is provided in this stepped hole 37A to slidably support an actuation pin 49 (described below). A seal groove 37B (see Figure 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 is fitted in this seal groove 37B as a sealing member, and the O-ring 39 provides a liquid-tight seal between the first stator core 36 and the core cover 37.

The core lid 37 is positioned so that its bottom end surface faces the plate 51B of the cover member 51, described below, with an axial gap between them. This axial gap prevents 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; it can also be made of a rigid metal material, ceramic material, or fiber-reinforced resin material.

The second stator core 40 constitutes a second fixed core located axially away from the first stator core 36 and on the inner circumferential 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 a single unit including a cylindrical tubular portion 40A whose inner circumferential side forms a stepped hole 40F (described below), an annular portion 40B extending radially outward from the outer periphery of one axial side of the tubular portion 40A around the entire circumference, and a cylindrical mating portion 40C protruding from the outer periphery of the annular portion 40B toward one axial side (the damping force control valve 18 side).

A circular recess 40D is recessed into the cylindrical portion 40A of the second stator core 40 on the other side axially facing the plunger 48 (described below). This recess 40D is formed as a circular groove with a diameter slightly larger than that of the plunger 48 (described below) so that the plunger 48 (described below) can be inserted inside and moved forward and backward by magnetic force. Furthermore, 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 conical surface 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 tapered conical surface with an outer diameter that gradually decreases from one axial side to the other (from the left side to the right side of the recessed portion 40D shown in Figures 3 and 4).

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

As shown in FIG. 2, the cap 31 of the damping force control valve 18 is fitted (internal fit) onto the inner periphery of the fitting portion 40C. The valve case 19 of the damping force control valve 18 is fitted (externally fit) onto the outer periphery of the fitting portion 40C. A seal groove 40H is formed around the entire periphery of the outer periphery of the fitting portion 40C. An O-ring 43 is fitted into this seal groove 40H as a sealing member, 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.

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 periphery of the molded coil 34 (coil 34A). The non-magnetic ring 44 is formed as a stepped cylinder from 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 axial middle, and first and second mating cylindrical portions 44B, 44C that protrude axially from both ends of the thick-walled cylindrical portion 44A.

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

The first cylindrical mating 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 cylindrical mating portion 44C is fitted onto the outer periphery of the cylindrical portion 40A and 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 (solidification treatment of the pure copper braze), for example, to join the non-magnetic ring 44 to the first and second stator cores 36, 40. The brazing process is followed by a rapid cooling process.

The brazed portions 45, 46 have a thickness of, for example, approximately 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., 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., 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 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).

A ring-shaped gap 47 is formed between the small-diameter cylindrical portion 36A of the first stator core 36 and the first mating cylindrical portion 44B of the non-magnetic ring 44 on its outer periphery. This gap 47 is an introduction path for pouring the brazing material (pure copper brazing) in a heated and molten state between the first stator core 36 (small-diameter cylindrical portion 36A) and the non-magnetic ring 44 (first mating cylindrical portion 44B). This gap 47 also functions as a void to absorb the difference in thermal expansion between the first and second stator cores 36, 40 and the non-magnetic ring 44.

Similar to the gap 47, an introduction passage 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 outer peripheral surface of the cylindrical portion 40A and the conical protrusion 40E) and the non-magnetic ring 44 (the second mating cylindrical portion 44C). However, when the brazing material (pure copper brazing material) is poured in a heated and molten state to join the second mating cylindrical portion 44C to the second stator core 40 (the outer peripheral side of the cylindrical portion 40A and the conical protrusion 40E), an axial external force is applied between the two to minimize the gap. However, differences in thermal expansion occur between the first and second stator cores 36, 40 and the non-magnetic ring 44 due to differences in the materials used.

As a result, an axial gap 47 is formed between the small-diameter cylindrical portion 36A of the first stator core 36 and the first mating cylindrical portion 44B of the non-magnetic ring 44, extending around the entire circumference. In this way, the non-magnetic ring 44 is joined between the first and second stator cores 36, 40 at the brazing portions 45, 46. Even if a difference in thermal expansion occurs between the two due to differences in materials during the rapid cooling process after brazing, distortion caused by this difference can be suppressed by the gap 47. The non-magnetic ring 44, as a non-magnetic member, is disposed between the first and second stator cores 36, 40 (stationary iron cores) and is integrally fixed to the first and second stator cores 36, 40 by brazing.

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 axially movable. 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 axially movable via the first and second bushings 38, 41 and the actuation pin 49 due to the magnetic force generated in the coil 34A. The plunger 48 is fixed to the actuation pin 49, which extends through its center, and moves together with the actuation pin 49. The actuation pin 49 is supported axially slidably 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.

The plunger 48 is formed in a generally 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 that attracts the plunger 48 toward the recess 40D of the second stator core 40 when magnetic force is generated by the coil 34A. The plunger 48 also has multiple communication passages 48A that are spaced apart circumferentially and extend in the axial direction (front and rear directions). These communication passages 48A allow oil within the first and second stator cores 36, 40 to flow smoothly through each communication passage 48A while the plunger 48 displaces axially together with the actuating pin 49, thereby reducing flow resistance to the plunger 48.

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, which serves as a movable iron core, is fixed integrally to the axial middle portion of the actuating pin 49 using means such as press fitting, 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 37 on the first stator core 36 side and the second stator core 40 (cylindrical portion 40A) via first and second bushings 38, 41.

One end of the actuating pin 49 (the left end in Figure 2) protrudes from the second stator core 40, and the pilot valve element 32 of the damping force control valve 18 is fixed to this protruding end. As a result, the pilot valve element 32 moves axially together with the plunger 48 and actuating pin 49. In other words, the set valve opening pressure of the pilot valve element 32 is a pressure value corresponding to the thrust of the plunger 48, which is generated when current is applied to the coil 34A. The plunger 48 moves axially 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).

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 Figure 2). This back pressure chamber 50 is connected to the central hole 24B side of the pilot pin 24 via the hollow rod (actuating pin 49). Therefore, the same pressure acts on the back pressure chamber 50 as on the pilot valve element 32, which is seated on and removed from the valve seat 26E of the pilot body 26. However, the pressure-receiving area for this pressure is smaller in the back pressure chamber 50, where the other end face of the actuating pin 49 receives pressure, than in 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.

This makes it possible to reduce the thrust to be transmitted from the plunger 48 via the actuating pin 49 to the pilot valve element 32 of the damping force control valve 18 by the difference in pressure-receiving area between them. In other words, by forming a backpressure chamber 50 between the other end of the actuating pin 49 and the core lid body 37, the thrust to be transmitted from the plunger 48 via the actuating pin 49 to the pilot valve element 32 of the damping force control valve 18 (for example, the magnetic force to be generated by the coil 34A of the molded coil 34) can be reduced, allowing for the solenoid 33 to be made smaller and lighter overall.

The cover member 51 is a magnetic cover that covers the outer periphery of the coil 34A. This 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 of the molded coil 34 (coil 34A). Here, the cover member 51 is formed as a cylindrical shape with a bottom as a whole and is roughly composed of a cylindrical casing 51A and a plate 51B that closes the other end of the casing 51A (the right end in Figures 2 and 3). The casing 51A has a notch (not shown) that exposes the cable outlet portion of the molded coil 34 mentioned above from the cover member 51.

Here, the plate 51B of the cover member 51 is provided with a fitting recess 51C into which the core lid 37 (its bottom side) of the first stator core 36 is inserted or accommodated. By fitting the bottom side of the core lid 37 into the fitting recess 51C, the first stator core 36 can exchange magnetic flux with the plate 51B of the cover member 51.

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

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

The coupling ring 52 is formed in a generally cylindrical shape, and its interior is provided with a female threaded portion 52A that screws onto the male threaded 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 threading the female threaded portion 52A into the male threaded 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.

The solenoid 33 and hydraulic shock absorber 1 in this embodiment have the configuration described above, and their operation will now be explained.

When the hydraulic shock absorber 1 is installed in a vehicle such as an automobile, the protruding end (upper end) of the piston rod 8 is attached to the vehicle body, and the mounting eye 3A on the bottom cap 3 is attached to the wheel. The solenoid 33 of the damping force adjuster 17 is then connected to a control device (controller) installed on the vehicle body via an electrical wiring cable (neither shown) or the like.

When the vehicle is traveling and vibrations occur in the up and down directions due to unevenness in the road surface, the piston rod 8 displaces by extending or retracting from the outer cylinder 2, causing the damping force adjustment device 17 to generate a damping force, thereby cushioning the vehicle vibrations. At this time, the controller changes the current value of the control signal passed through the coil 34A of the solenoid 33 and adjusts the valve opening pressure of the pilot valve element 32, thereby variably controlling the damping force generated by the hydraulic shock absorber 1.

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 from the plunger 48 through the second stator core 40 (i.e., the conical protrusion 40E, cylindrical portion 40A, annular portion 40B, and mating portion 40C), and further through the cylindrical case 51A and plate 51B of the cover member 51, before returning to the first stator core 36, forming a magnetic circuit.

In this case, the magnetic circuit can transfer magnetic flux entirely through 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 through a small gap, and between the plunger 48 and the second stator core 40. This allows the magnetic circuit of the solenoid 33 to ensure high magnetic efficiency.

A non-magnetic ring 44, a non-magnetic member, is located on the inner periphery of the molded coil 34 (coil 34A) between the first stator core 36 and second stator core 40, which constitute the main components of the solenoid 33. This non-magnetic ring 44 is joined to the first and second fixed cores (first and second stator cores 36, 40) by brazing sections 45, 46 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 after joining (for example, by cutting the inner periphery), the magnetic properties change due to the machining distortion, making the non-magnetic member more susceptible to magnetization.

In this embodiment, therefore, the non-magnetic ring 44, made of a non-magnetic material such as austenitic stainless steel, is formed as a stepped cylindrical integral body consisting of a thick-walled cylindrical portion 44A located in the middle of the axial direction and first and second mating cylindrical portions 44B, 44C that protrude axially from both ends of the thick-walled cylindrical portion 44A. The inner diameter D1 of the non-magnetic ring 44 is larger than the inner diameters of the first and second stator cores 36, 40.

In other words, 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 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 .

As a result, a plunger 48 serving as a movable core can be arranged axially movably 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). In other words, 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 it to the first and second stator cores 36, 40, and the magnetic properties of the non-magnetic ring 44 are also protected from changes due to thermal effects, distortion, etc.

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

Generally, when non-magnetic austenitic stainless steel parts are subjected to deep drawing or cutting processes, causing distortion, the material generates work-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 work-induced martensite in austenitic stainless steel can be removed by heat treatment at 1000°C or above, returning the material to the ideal face-centered cubic structure. This treatment is called solution heat treatment.

Therefore, in this embodiment, pure copper brazing is selected as the brazing material with 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-fit between the first and second stator cores 36, 40 and butted together, thermal deformation due to the high temperatures during brazing is suppressed, eliminating the need for cutting to correct the shape after brazing, and allowing the desired dimensions and shape to be maintained. Note that the brazing material may be other than pure copper brazing, as long as it can be brazed at a temperature of 1000°C or higher. For example, brass brazing, nickel brazing, gold brazing, palladium brazing, etc. may also be used.

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, etc., 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 transfer magnetic flux with all magnetic bodies in 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 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.

The first cylindrical fitting 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 cylindrical fitting portion 44C is fitted onto the outer periphery of the cylindrical portion 40A and 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. The brazing process is followed by a rapid cooling process.

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 sections 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, while also ensuring pressure resistance to the internal pressurized oil.

The solenoid 33 employed in this embodiment is a solenoid 33 used in a semi-actuator (damping force adjustable shock absorber) to adjust the opening and closing operation of the damping force adjustment valve 18. The non-magnetic portion is provided to form a magnetic path between the fixed core (first and second stator cores 36, 40) and the movable 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 provides an optimal method for enabling the damping force adjustment valve 18 to withstand high pressures.

In other words, 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, this also serves as a solution heat treatment, removing the work-induced martensite (body-centered cubic structure) created by cutting, resulting in 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, the ideal metal structure for a non-magnetic material is maintained without creating work-induced martensite, resulting in a structure that suppresses thermal deformation during the brazing process.

This allows the non-magnetic ring 44, which serves as the non-magnetic portion, to have an ideal metal structure, resulting in excellent magnetic properties, improving the thrust of the solenoid 33 and optimizing the thrust waveform. Furthermore, the number of processes required to create and manufacture the solenoid 33 is reduced, improving workability and productivity.

In the above embodiment, the second stator core 40 is described as having a cylindrical tubular portion 40A, an annular portion 40B, and a cylindrical mating portion 40C that protrudes to one axial side. 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 mating portion that protrudes to one axial side may be omitted or eliminated.

In addition, in the above embodiment, an example was described in which the cover member 51 was configured as a yoke using a magnetic material. However, the present invention is not limited to this, and for example, the cover member may be configured using a non-magnetic material, resulting in an open-coil solenoid without a yoke. Furthermore, in the above embodiment, an example was described in which the solenoid 33 was configured as a proportional solenoid. However, the present invention is not limited to this, and for example, it may be configured as an ON/OFF type solenoid.

Next, the invention included in the above-mentioned embodiment will be described. That is, in a first aspect of the present invention, there is provided a damping force control shock absorber comprising: a cylinder in which a working fluid is sealed; a piston inserted into the cylinder and dividing 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 working fluid flows as the piston rod moves; 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 poles provided on the inner periphery of the coil. The damping force adjustment valve comprises a fixed core, 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 movable core, and first and second bushings supporting the shaft portion, wherein the valve body of the damping force adjustment valve is disposed on the 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.

A damping force adjustable shock absorber according to a second aspect of the present invention is the first aspect, but the non-magnetic member is made of austenitic stainless steel. Furthermore, a damping force adjustable shock absorber according to a third aspect of the present invention is the first or second aspect, but the non-magnetic member is brazed using a brazing material with a brazing temperature of 1000°C or higher. A damping force adjustable shock absorber according to a fourth aspect of the present invention is the third aspect, but the non-magnetic member is brazed using a brazing material made of pure copper brazing.

A solenoid according to a fifth aspect of the present invention comprises a coil that generates a magnetic force when energized, 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 integrally fixed 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 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.

A solenoid according to a sixth aspect of the present invention is the fifth aspect, wherein the non-magnetic member is 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.A solenoid according to a ninth aspect of the present invention is any of the fifth to eighth aspects, wherein the inner diameter portions defining the inner diameters of the first and second fixed iron cores and the inner diameter portion defining the inner diameter of the non-magnetic member are not machined after brazing.

A tenth aspect of the present invention is a damping force adjustable shock absorber comprising: a cylinder in which a working fluid is sealed; a piston inserted into the cylinder and dividing 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 through which the working fluid flows as the piston rod moves; and a damping force adjustment 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 springs provided on the inner periphery 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 disposed on the inner periphery of the movable core; and first and second bushings that support the shaft; the valve body of the damping force control valve is disposed on the end of the shaft 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.

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 are 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, and it is also possible 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.

This application claims priority from 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.

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

Claims (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 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. The damping force adjustable shock absorber according to claim 1 ,
The non-magnetic member is brazed using a brazing material made of pure copper. 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. The solenoid of claim 3 ,
The non-magnetic member is brazed to the solenoid using a brazing material made of pure copper. 5. The solenoid according to claim 3 or 4 ,
1. A solenoid comprising: an inner diameter portion defining the inner diameter 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. 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.