JP7510367B2 - Shock absorber - Google Patents

Description

This invention relates to a shock absorber.

Some shock absorbers used in vehicle suspensions are equipped with a damping valve that can vary the damping force. Such shock absorbers are comprised of a cylinder, a piston that divides the inside of the cylinder into an extension side chamber and a compression side chamber, a piston rod that is connected at one end to the piston and is inserted movably into the cylinder, and a damping valve.

The damping valve is provided with an extension side passage and a compression side passage that communicate with an extension side chamber and a compression side chamber provided in the piston, an extension side leaf valve and a compression side leaf valve that open and close the extension side passage and the compression side passage, respectively, an extension side spool and a compression side spool that press the extension side leaf valve and the compression side leaf valve, respectively, and an electromagnetic pressure control valve equipped with a solenoid that adjusts the pressure in the extension side back pressure chamber and the compression side back pressure chamber that presses the extension side spool and the compression side spool with internal pressure (see, for example, Patent Document 1).

In a shock absorber configured in this manner, the pressure in the expansion side back pressure chamber and the compression side back pressure chamber can be controlled by a single electromagnetic pressure control valve, thereby controlling the damping force during expansion and contraction.

Patent Publication No. 2019-138401

In a conventional shock absorber, the piston rod comprises a cylindrical rod body and a cylindrical housing connected to the lower end of the rod body and accommodating an electromagnetic pressure control valve. More specifically, the housing comprises a large-diameter cylindrical section that accommodates the solenoid, a flange section provided on the inner circumference of the upper end of the cylindrical section, and a shaft section that rises cylindrically from the flange section and has a male screw at its tip that screws into a female screw provided on the inner circumference of the lower end of the rod body. In addition, an annular groove is formed on the shaft section closer to the cylindrical section than the male screw, in which a seal ring is fitted to seal between the rod body and the housing.

The housing constructed in this manner is fastened to the lower end of the rod body with a screw, and functions as a magnetic circuit for the solenoid housed inside. Therefore, from the viewpoint of functioning as a magnetic circuit for the solenoid, the housing is preferably formed from a soft magnetic material with magnetic properties of low coercive force and high permeability. Housings are often formed from carbon steel, which is a soft magnetic material; the less carbon content carbon steel contains, the smaller the coercive force and the higher the permeability, making it ideal for forming a magnetic circuit.

For this reason, in conventional shock absorbers, the housing is made of low-carbon steel with a low carbon content, allowing the housing to exhibit good magnetic properties as a magnetic circuit. However, as the carbon content of carbon steel decreases, the coercive force tends to decrease and the magnetic permeability tends to increase, but the strength also decreases.

Therefore, in conventional shock absorbers, if an attempt was made to realize good magnetic properties for the solenoid's magnetic circuit by using low carbon steel for the housing, the housing may end up lacking in strength.

Therefore, the present invention aims to provide a shock absorber that can overcome the lack of strength of the housing while achieving good magnetic characteristics for forming a magnetic circuit of a solenoid.

The shock absorber of the present invention comprises a cylinder, a piston rod slidably inserted into the cylinder and in sliding contact with the inner circumference of an annular rod guide provided at the end of the cylinder, a piston connected to the piston rod and dividing the inside of the cylinder into an extension side chamber and a compression side chamber, a damping passage provided in the piston and communicating the extension side chamber and the compression side chamber, and a solenoid valve provided in the damping passage and having a solenoid and capable of adjusting the resistance to the flow of fluid passing through the damping passage by adjusting the thrust of the solenoid. The shock absorber comprises a rod body in which the piston rod slides against the inner circumference of the rod guide, and a housing screwed to the rod body and accommodating a coil in the solenoid, the housing having a cylindrical accommodating section formed of carbon steel and accommodating the coil to form a magnetic circuit of the solenoid, and a rod connection section formed of carbon steel or alloy steel and screwed to the rod body and frictionally welded to the accommodating section, the carbon content of the carbon steel forming the accommodating section being less than the carbon content of the carbon steel or alloy steel forming the rod connection section.

A shock absorber constructed in this way not only ensures strength at the part of the housing where it is fastened to the rod body, but also because the housing part that houses the coil is made of carbon steel with a lower carbon content than the rod connection part, it can exhibit good magnetic properties to form part of the magnetic circuit of the solenoid.

The housing portion and the rod connection portion of the shock absorber may be frictionally welded at a position that does not straddle the magnetic path of the solenoid. A shock absorber configured in this way can effectively improve the suction force of the solenoid, thereby improving the damping force adjustment capability of the solenoid valve and contributing to the miniaturization of the solenoid.

Furthermore, the piston in the shock absorber may be connected to a housing portion. With a shock absorber configured in this way, the housing portion, which is a large-diameter cylinder in order to house the solenoid coil inside, has a large moment of area even if it is made of low-carbon steel, so there is no need to worry about strength when holding the piston.

The shock absorber may also be configured so that the rod body is cylindrical and has a female thread on its inner circumference, and the rod connection part has a male thread that is inserted into the rod body and screwed into the female thread. With a shock absorber configured in this way, the part where the rod connection part is screwed into the rod body is inserted into the rod body that is in sliding contact with the inner circumference of the rod guide, resulting in a structure that does not impede axial movement of the rod body relative to the rod guide, which is advantageous in terms of ensuring the stroke length of the shock absorber.

The shock absorber of the present invention can eliminate the lack of strength of the housing while achieving good magnetic properties for forming the magnetic circuit of the solenoid.

FIG. 2 is a cross-sectional view of a shock absorber according to one embodiment. FIG. 11 is a cross-sectional view of a shock absorber according to a modified example of the embodiment.

The present invention will be described below based on the illustrated embodiment. As shown in FIG. 1, the shock absorber D in one embodiment is configured with a cylinder 1, a piston rod 2 slidably inserted into the cylinder 1 and in sliding contact with the inner circumference of an annular rod guide 10 provided at the end of the cylinder 1, a piston 3 connected to the piston rod 2 and dividing the inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2, a damping passage 4 provided in the piston 3 and communicating between the extension side chamber R1 and the compression side chamber R2, and a solenoid valve V provided in the damping passage 4 and having a solenoid Sol that can adjust the resistance applied to the flow of fluid passing through the damping passage 4 by adjusting the thrust of the solenoid Sol.

The following is a detailed explanation of each part of the shock absorber D. The cylinder 1 has a closed lower end (not shown), and an annular rod guide 10 is attached to the upper end. The rod guide 10 is annular, and is equipped with a cylindrical bush 10a on its inner periphery that slides against the outer periphery of the piston rod 2, and an annular seal member 10b. It closes the upper end of the cylinder 1 in FIG. 1 and guides the axial movement of the piston rod 2.

The piston rod 2 has a rod body 21 that slides against the inner circumference of the bush 10a of the rod guide 10, and a housing 22 that is screwed to the rod body 21 and contains the coil 30 in the solenoid Sol.

The rod body 21 is cylindrical and has an expanded inner diameter portion 21a, the inner diameter of which is larger at the lower end in FIG. 1 than at the upper end, and a female screw portion 21b on the inner circumference of the expanded inner diameter portion 21a near the lower end in FIG. 1.

On the other hand, the housing 22 is configured with a topped cylindrical storage portion 23 that stores the solenoid Sol, and a rod connection portion 24 that is screwed into the rod main body 21 and joined to the storage portion 23 by friction welding.

The housing 23 comprises a cylindrical section 23a disposed on the outer periphery of the coil 30 of the solenoid Sol, a cylindrical shaft section 23b whose upper end in FIG. 1 is joined by friction welding to the lower end of the rod connection section 24, and an annular shoulder section 23c connecting the outer periphery of the cylindrical section 23a and the outer periphery of the shaft section 23b. The shaft section 23b comprises a fitting section 23b1 whose tip side, which is the upper end in FIG. 1, is formed with a small diameter and is inserted into the inner diameter expansion section 21a of the rod main body 21, and a step section 23b2 on the outer periphery.

The rod connection part 24 is axially shaped and has an outer diameter smaller than the cylindrical part 23a of the accommodation part 23, and is inserted into the inner diameter expansion part 21a. The rod connection part 24 has a male screw part 24a at a position corresponding to the female screw part 21b provided on the inner diameter expansion part 21a of the rod main body 21 on the outer periphery, and is screwed to the rod main body 21 by screwing the male screw part 24a into the female screw part 21b. The rod connection part 24 also has an annular groove 24b on the outer periphery below the male screw part 24a, in which a seal ring 25 is attached. The seal ring 25 is in close contact with the inner periphery of the rod main body 21 and the rod connection part 24, sealing the inside of the rod main body 21 liquid-tight. When the rod connection part 24 is screwed to the rod main body 21 in this way, the shaft part 23b of the accommodation part 23 is inserted into the rod main body 21 until the lower end of the rod main body 21 abuts against the step part 23b2 of the shaft part 23b.

The accommodation section 23 in the housing 22 is manufactured from carbon steel as a base material, and the rod connection section 24 is manufactured from carbon steel or alloy steel as a base material, but the carbon content of the accommodation section 23 is less than that of the rod connection section 24. Specifically, the accommodation section 23 is made of carbon steel with a carbon content of 0.28% or less of the total weight, or low-carbon steel with a low carbon content of S25C or less, and the rod connection section 24 is made of carbon steel with a carbon content of 0.42% or more of the total weight, high-carbon steel with a carbon content of S45C or more, or SCM (chromium molybdenum steel). In this way, the accommodation section 23 and the rod connection section 24 are made of carbon steels with different carbon contents. To join the housing part 23 and the rod connection part 24 by friction welding, the upper end of the shaft part 23b of the housing part 23 in FIG. 1 and the lower end of the rod connection part 24 in FIG. 1 are butted together and brought into rotating contact to generate high heat, and then an axial force is applied to both parts to apply high pressure to their joining surfaces. In this way, the housing part 23 and the rod connection part 24 are solid-phase welded together under high temperature and pressure to form an integrated unit.

The solenoid Sol comprises a resin-molded cylindrical coil 30 housed in the housing 22, a perforated disk-shaped iron plate 31 fitted to the upper end of the coil 30 in FIG. 1, a topped cylindrical first fixed iron core 32 fitted to the inner circumference of the coil 30, a ring-shaped second fixed iron core 33 abutting the lower end of the coil 30 in FIG. 1 and having a socket 33 a fitted to the inner circumference of the coil 30, and a coil 30 . The plate 31 includes a filler ring 35 made of a non-magnetic material that is fitted around the inner circumference of the first stationary core 32 and the inner circumference of the socket 33a of the second stationary core 33, a movable core 34 that is slidably inserted around the inner circumference of the first stationary core 32 and the inner circumference of the socket 33a of the second stationary core 33, and a spring 36 that biases the movable core 34 downward in Fig. 1 between the movable core 34 and the first stationary core 32 to project the movable core 34 from inside the coil 30. The outer circumference of the plate 31 abuts against the inner circumference of the tube portion 23a of the accommodation portion 23, and the coil side end of the plate 31, which is the lower end in Fig. 1, abuts against the first stationary core 32. The outer circumference of the second stationary core 33 abuts against the inner circumference of the tube portion 23a of the accommodation portion 23. The accommodation portion 23 of the housing 22 forms a magnetic circuit in the solenoid Sol together with the first stationary iron core 32, the movable iron core 34, and the second stationary iron core 33, as shown by the dashed line B in FIG. 1. Therefore, when the coil 30 is energized, the magnetic flux passes through the first stationary iron core 32, the movable iron core 34, the second stationary iron core 33, and the cylindrical portion 23a of the accommodation portion 23, and attracts the movable iron core 34 against the biasing force of the spring 36. As described above, the accommodation portion 23 forms a part of the magnetic circuit of the solenoid Sol, and the joint portion A, which is the portion where the accommodation portion 23 and the rod connection portion 24 are frictionally welded, is located at a position that does not straddle the magnetic path of the solenoid Sol. In other words, the accommodation portion 23 and the rod connection portion 24 are frictionally welded at a position that does not straddle the magnetic path of the solenoid Sol.

The force with which the solenoid Sol attracts the movable iron core 34 changes depending on the amount of electricity passing through the coil 30, so the thrust of the spring 36 that protrudes the movable iron core 34 from the coil 30 can be adjusted by adjusting the amount of electricity passing through the coil 30. Electricity is passed through the coil 30 via a harness 37 that is connected to the coil 30 and is also connected to an external power source through the piston rod 2.

The piston 3 is connected to the lower end of the tubular portion 23a in the storage portion 23 of the housing 22. The piston 3 and the housing 22 may be connected by screw fastening, or, if the piston 3 is annular (not shown), a shaft portion that is inserted into the piston 3 may be provided at the lower end of the storage portion 23, and the piston 3 may be fixed to the outer periphery of the shaft portion using a piston nut that is screwed onto the tip of the shaft portion.

The piston 3 is in sliding contact with the inner circumference of the cylinder 1, dividing the inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2. A free piston (not shown) that slides inside the cylinder 1 is provided below the cylinder 1 in FIG. 1, and this free piston forms an air chamber below the compression side chamber R2 inside the cylinder 1. The extension side chamber R1 and the compression side chamber R2 are filled with hydraulic oil as a fluid. The fluid filled in the extension side chamber R1 and the compression side chamber R2 can be any liquid that can exert a damping force other than hydraulic oil, and in the case of an air shock absorber, it may be a gas, in which case it is not necessary to install an air chamber. In this embodiment, the shock absorber D is configured as a so-called single-cylinder shock absorber with an air chamber inside the cylinder 1, but it may also be configured as a so-called double-cylinder shock absorber with an outer cylinder that forms a reservoir between the cylinder 1 and the outer circumference of the cylinder 1.

The piston 3 is provided with a damping passage 4 that communicates the extension side chamber R1 and the compression side chamber R2. An electromagnetic valve V including a solenoid Sol is provided in the middle of the damping passage 4. In this embodiment, the damping passage 4 includes a first passage 4a and a second passage 4b that connect the extension side chamber R1 and the compression side chamber R2, and a connecting passage 4c that connects the middle of the first passage 4a and the second passage 4b. The first passage 4a is provided with check valves 4d and 4e that are arranged in opposite directions across the connection point of the connecting passage 4c, and the second passage 4b is also provided with check valves 4f and 4g that are arranged in opposite directions across the connection point of the connecting passage 4c. The check valve 4d only allows the hydraulic oil to flow from the extension side chamber R1 to the connecting passage 4c through the first passage 4a, and the check valve 4e only allows the hydraulic oil to flow from the compression side chamber R2 to the connecting passage 4c through the first passage 4a. In addition, the check valve 4f allows hydraulic oil to flow only from the second passage 4b to the connecting passage 4c toward the expansion side chamber R1, and the check valve 4g allows hydraulic oil to flow only from the second passage 4b to the connecting passage 4c toward the compression side chamber R2. Furthermore, the valve body 6 of the solenoid valve V is provided midway through the connecting passage 4c.

When the shock absorber D expands, the hydraulic oil in the compressed expansion-side chamber R1 pushes open the check valve 4d in the first passage 4a, passes through the valve body 6 of the connecting passage 4c, and pushes open the check valve 4g in the second passage 4b, moving to the expanding expansion-side chamber R2. On the other hand, when the shock absorber D contracts, the hydraulic oil in the compressed expansion-side chamber R2 pushes open the check valve 4e in the first passage 4a, passes through the valve body 6 of the connecting passage 4c, and pushes open the check valve 4f in the second passage 4b, moving to the expanding expansion-side chamber R1. In this way, the damping passage 4 is rectified by the check valves 4d, 4e, 4f, and 4g to set the connecting passage 4c as a one-way passage, and the hydraulic oil passes through the solenoid valve V provided in the connecting passage 4c from upstream to downstream, regardless of whether the shock absorber D expands or contracts.

Specifically, the solenoid valve V includes a valve body 6 provided in the connecting passage 4c in the damping passage 4, a pilot passage 7 that applies pressure from the upstream side of the connecting passage 4c to the valve body 6 in the valve opening direction, and a solenoid Sol that applies a thrust to the valve body 6 in the valve closing direction through the movable iron core 34. In the solenoid valve V configured in this manner, when the amount of current applied to the coil 30 is increased, the suction force resisting the biasing force of the spring 36 increases, so the thrust of the solenoid Sol that presses the valve body 6 in the valve closing direction decreases, and when the amount of current applied to the coil 30 is decreased, the suction force resisting the biasing force of the spring 36 decreases, so the thrust of the solenoid Sol that presses the valve body 6 in the valve closing direction increases.

Therefore, when the amount of current applied to the solenoid Sol increases, the thrust force pressing the valve body 6 in the valve closing direction decreases, and the pressure that the pilot passage 7 must apply to open the valve body 6 also decreases. Also, when the amount of current applied to the solenoid Sol decreases, the thrust force pressing the valve body 6 in the valve closing direction increases, and the pressure that the pilot passage 7 must apply to open the valve body 6 also increases. In this way, the solenoid valve V in the shock absorber D of this embodiment can adjust the valve opening pressure by adjusting the amount of current applied to the solenoid Sol.

When the shock absorber D configured in this way is extended, as described above, hydraulic oil moves from the extension side chamber R1 to the compression side chamber R2 through the connecting passage 4c of the damping passage 4. When the hydraulic oil passes through the solenoid valve V, the solenoid valve V provides resistance to the flow of the hydraulic oil, so that the shock absorber D generates an extension side damping force that impedes the extension operation. The valve opening pressure of the solenoid valve V can be changed by adjusting the thrust applied to the valve body 6 according to the amount of electricity supplied to the coil 30 in the solenoid Sol, thereby adjusting the resistance when the hydraulic oil passes through the solenoid valve V. Therefore, the extension side damping force of the shock absorber D is adjusted by adjusting the thrust of the solenoid Sol. Note that when the shock absorber D is extended, the piston rod 2 retracts from the cylinder 1, but the volume fluctuation in the cylinder 1 caused by the piston rod 2 retracting from the cylinder 1 is compensated for by the expansion of the air chamber.

When the shock absorber D is contracting, as described above, hydraulic oil moves from the compression side chamber R2 to the extension side chamber R1 via the connecting passage 4c of the damping passage 4. When the hydraulic oil passes through the solenoid valve V, the solenoid valve V applies resistance to the flow of hydraulic oil, so the shock absorber D generates a compression side damping force that impedes the contraction. Therefore, just as when the shock absorber D is expanding, the compression side damping force of the shock absorber D is adjusted by adjusting the thrust of the solenoid Sol.

The housing 22 that accommodates the solenoid Sol in the piston rod 2 of the shock absorber D has an accommodation section 23 that is made of carbon steel and accommodates the coil 30 of the solenoid Sol to form a part of the magnetic circuit of the solenoid Sol, and a rod connection section 24 that is made of carbon steel or alloy steel and is screwed to the rod body 21 and frictionally welded to the accommodation section 23. Furthermore, the carbon content of the carbon steel that forms the accommodation section 23 is less than the carbon content of the carbon steel or alloy steel that forms the rod connection section 24. Therefore, the magnetic properties of the accommodation section 23 have a lower coercive force and a higher magnetic permeability than the magnetic properties of the rod connection section 24, and therefore exhibit excellent magnetic properties for forming a part of the magnetic circuit of the solenoid Sol. On the other hand, the rod connection section 24 is made of carbon steel or alloy steel that has a higher carbon content than the accommodation section 23, and therefore has a higher strength than the accommodation section 23. Therefore, the rod connection part 24 that is screwed to the rod body 21 is made of carbon steel or alloy steel with high strength, so the strength of the male screw part 24a, which is the screw-fastening part with the rod body 21, and the part with a narrow diameter where the annular groove 24b in which the seal ring 25 is attached is formed is also sufficiently ensured. In this way, not only is the strength of the part of the housing 22 that is fastened to the rod body 21 ensured, but the accommodation part 23 that accommodates the coil 30 is made of carbon steel with a lower carbon content than the rod connection part 24, so it can exhibit good magnetic properties to form part of the magnetic circuit of the solenoid Sol.

As described above, the shock absorber D of this embodiment includes a cylinder 1, a piston rod 2 slidably inserted into the cylinder 1 and in sliding contact with the inner circumference of an annular rod guide 10 provided at the end of the cylinder 1, a piston 3 connected to the piston rod 2 and dividing the inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2, a damping passage 4 provided in the piston 3 and communicating between the extension side chamber R1 and the compression side chamber R2, and an electromagnetic valve V provided in the damping passage 4, having a solenoid Sol, and capable of adjusting the resistance applied to the flow of fluid passing through the damping passage 4 by adjusting the thrust of the solenoid Sol. The piston rod 2 It has a rod body 21 that slides against the inner circumference of the rod guide 10, and a housing 22 that is screwed to the rod body 21 and accommodates the coil 30 in the solenoid Sol. The housing 22 is made of carbon steel and has a cylindrical accommodation section 23 that accommodates the coil 30 and forms the magnetic circuit of the solenoid Sol, and a rod connection section 24 that is made of carbon steel or alloy steel and is screwed to the rod body 21 and joined to the accommodation section 23 by friction welding. The carbon content of the carbon steel that forms the accommodation section 23 is less than the carbon content of the carbon steel or alloy steel that forms the rod connection section 24.

As described above, the shock absorber D configured in this manner not only ensures the strength of the portion of the housing 22 where it is fastened to the rod body 21, but also exhibits good magnetic properties for forming part of the magnetic circuit of the solenoid Sol, since the housing portion 23 that houses the coil 30 is made of carbon steel with a lower carbon content than the rod connection portion 24. Therefore, the shock absorber D of this embodiment can eliminate the lack of strength of the housing 22 while achieving good magnetic properties for forming the magnetic circuit of the solenoid Sol. In addition, since the suction force of the solenoid Sol can be increased, the range of damping force adjustment by the solenoid valve V can also be increased.

When the housing portion 23 is made of low carbon steel with the same or less carbon content than S25C, it can exhibit excellent magnetic properties as a magnetic circuit for the solenoid Sol. The rod connection portion 24 can be made of high carbon steel or alloy steel that can be screwed to the rod body 21 and ensure the strength of the small diameter portion, and is preferably made of carbon steel with a carbon content of about S45C.

In addition, in the shock absorber D of this embodiment, the housing portion 23 and the rod connection portion 24 are frictionally welded at a position that does not cross the magnetic path of the coil 30, so the magnetic path of the solenoid Sol passes only through the housing portion 23, which has excellent magnetic properties, without crossing the rod connection portion 24, which has a high carbon content. Therefore, with the shock absorber D configured in this way, the suction force of the solenoid Sol can be effectively improved, which can improve the damping force adjustment ability of the solenoid valve V and also contribute to the miniaturization of the solenoid Sol.

In the case of the shock absorber D of this embodiment, the rod body 21 is cylindrical and has a female screw portion 21b on the inner circumference, and the rod connection portion 24 is inserted into the rod body 21 and has a male screw portion 24a that is screwed into the female screw portion 21b. In this way, the part where the rod connection portion 24 is screwed into the rod body 21 is inserted into the rod body 21 that slides against the inner circumference of the rod guide 10, so that the structure does not hinder the axial movement of the rod body 21 relative to the rod guide 10, which is advantageous in terms of ensuring the stroke length of the shock absorber D. However, if the stroke length of the shock absorber D can be sufficiently ensured, instead of the structure in which all or a part of the rod connection portion 24 is inserted into the inner circumference of the rod body 21, a structure in which the part of the rod connection portion 24 that is fastened to the rod body 21 is cylindrical, a female screw portion is provided on the inner circumference, and the structure is screwed to the outer circumference of the rod body 21 may be adopted. In addition, in the case of shock absorber D of this embodiment, the entire rod connection portion 24 is housed within the rod body 21, and the joint portion A formed by friction welding between the housing portion 23 and the rod connection portion 24 is housed within the rod body 21, so there is an advantage that the joint portion A does not come into sliding contact with the inner circumference of the rod guide 10, and buffing the surface of the housing portion 23 is not required.

Furthermore, since the housing 22 is screwed to the rod body 21, it is possible to separate the piston rod 2 into the rod body 21 and the housing 22. Therefore, after performing an assembly process in which the solenoid valve V and piston 3 are attached to the housing 22, the assembled housing 22 can be screwed to the rod body 21. In this way, since the housing 22 can be separated from the rod body 21, it is no longer necessary to assemble the solenoid valve V and piston 3 while paying attention to the outer periphery of the rod body 21 that slides against the inner periphery of the rod guide 10, which requires buffing, and this reduces the burden on the worker during assembly.

In the case of shock absorber D of this embodiment, piston 3 is connected to storage section 23 of housing 22. Storage section 23 is a large-diameter cylinder that houses coil 30 of solenoid Sol inside, and even if it is made of low carbon steel, the moment of inertia is large, so there is no need to worry about strength when holding piston 3.

In the above description, the accommodation portion 23 is formed of the tube portion 23a, the shoulder portion 23c, and the shaft portion 23b joined to the rod connection portion 24 by friction welding, but the housing 40 may be configured as in the shock absorber D1 of a modified embodiment of the embodiment shown in FIG. 2. In the shock absorber D1 of the modified embodiment, the accommodation portion 41 in the housing 40 is a tube up to a portion horizontally facing the end plate 31 that forms the magnetic circuit of the solenoid Sol, and the rod connection portion 42 includes a shaft portion 42a that is screwed into the rod main body 21 and a flange portion 42b provided on the outer periphery of the shaft portion 42a at the lower end in FIG. 2. The shaft portion 42a includes a male screw portion 42c provided on the outer periphery at the upper end in FIG. 2, and an annular groove 42d provided on the outer periphery of the male screw portion 42c at the lower end in FIG. 2, in which the seal ring 25 is attached. Additionally, the housing portion 41 is made of carbon steel, and the rod connection portion 42 is made of carbon steel or alloy steel, but the carbon content of the carbon steel that forms the housing portion 41 is less than the carbon content of the carbon steel or alloy steel that forms the rod connection portion 42. Specifically, the housing portion 41 is made of carbon steel with a carbon content equal to or less than S25C, and the rod connection portion 42 is made of carbon steel or alloy steel with a carbon content equal to or more than S45C.

The upper end of the accommodation portion 41 and the outer periphery of the flange portion 42b of the rod connection portion 42 facing the upper end of the accommodation portion 41 are joined by friction welding, and the accommodation portion 41 and the rod connection portion 42 are joined. Even in this way, a part of the magnetic circuit of the solenoid Sol can be formed by the accommodation portion 41 arranged on the outer periphery of the coil 30, and the plate 31 and the accommodation portion 41 face each other in the horizontal direction, and as shown by the line B1 in FIG. 2, the magnetic path does not cross the joint portion A1 between the accommodation portion 41 and the rod connection portion 42. Therefore, the accommodation portion 41 in the housing 40 has good magnetic characteristics for forming the magnetic circuit of the solenoid Sol, and the joint portion A1 does not cross the magnetic path. Therefore, according to the shock absorber D1 configured in this way, the suction force of the solenoid Sol can be effectively improved, so that the damping force adjustment ability of the solenoid valve V can be improved and the solenoid Sol can be made smaller.

To summarize the above, when forming the housing 40 with the accommodation portion 41 and the rod connection portion 42, if the joint between the two is provided in a range where the magnetic path of the solenoid Sol does not cross and the strength of the rod connection portion 42 is not reduced, the output of the solenoid Sol can be effectively improved while resolving the lack of strength of the housing 40. In the case of this embodiment, since the plate 31 forming part of the magnetic circuit is disposed at the upper end of the coil 30 in FIG. 2, the accommodation portion 41 and the rod connection portion 42 may be joined by friction welding in the range M below the annular groove 42d, which is the portion from the joint A1 where the strength of the rod connection portion 42 is reduced. In terms of the overall shape of the housing 40, the shapes of the accommodation portion 41 and the rod connection portion 42 may be appropriately changed depending on the position of the joint A1. If the plate 31 is not provided, a magnetic circuit is formed at the upper end of the coil 30 in FIG. 2, so it is preferable to abut the portion of the coil 30 that contacts the upper end in FIG. 2 with the housing portion 41 made of carbon steel with a low carbon content, and therefore a structure in which the housing portion 23 extends at least to the shoulder portion 23c, as in the housing portion 23 shown in FIG. 1, is desirable. In addition, since the housing portions 23, 41 and the rod connection portions 24, 42 are joined by friction welding, the axial force acting on the housing portions 23, 41 can be smaller if they are joined at a portion where the area of the joint is smaller in order to apply high pressure to the joint, so joining at the joint A shown in FIG. 1 is advantageous in terms of processing.

The structure of the solenoid Sol described above is merely an example, and the design may be modified as long as the housing portions 23 and 41 house the coil 30 and form part of the magnetic circuit of the solenoid Sol.

In addition, in the shock absorbers D and D1 described above, the solenoid valve V is configured as an electromagnetic relief valve that adjusts the valve opening pressure of the valve body 6 by the solenoid Sol, but the configuration of the solenoid valve V is not limited to this. Therefore, for example, the solenoid valve V may be a solenoid valve that adjusts the opening degree of the valve body 6 by the thrust applied by the solenoid Sol, in addition to adjusting the valve opening pressure by applying thrust to the valve body 6 installed in the damping passage 4 by the solenoid Sol. Furthermore, instead of a structure in which the solenoid Sol directly applies thrust to the valve body 6 installed in the damping passage 4 to adjust the damping force, when a structure is adopted in which back pressure acts in the valve closing direction on the valve body installed in the middle of the damping passage 4, the solenoid Sol may apply thrust to a control valve that adjusts the back pressure, and the back pressure may be adjusted by adjusting the control valve to adjust the valve opening pressure and the opening degree of the valve body installed in the damping passage 4.

The structure of the damping passage 4 can also be modified as appropriate, and part or all of the damping passage 4 may be provided within the accommodation portion 23, 41. The solenoid valve V may also be installed in the damping passage 4 so as to adjust the damping force of only the extension side or only the compression side of the shock absorber D, D1.

Although the preferred embodiment of the present invention has been described in detail above, modifications, variations, and changes are possible without departing from the scope of the claims.

1: Cylinder, 2: Piston rod, 3: Piston, 4: Damping passage, 10: Rod guide, 21: Rod body, 21b: Female thread, 22, 40: Housing, 23, 41: Storage section, 24, 42: Rod connection section, 24a, 42c: Male thread, 30: Coil, D, D1: Shock absorber, R1: Expansion side chamber, R2: Compression side chamber, Sol: Solenoid, V: Solenoid valve

Claims (4)

A cylinder;
a piston rod that is slidably inserted into a cylinder and is in sliding contact with an inner periphery of an annular rod guide provided at an end of the cylinder;
a piston connected to the piston rod to divide the inside of the cylinder into an expansion-side chamber and a compression-side chamber;
a damping passage communicating the expansion-side chamber and the compression-side chamber;
a solenoid valve provided in the damping passage, the solenoid having a solenoid and capable of adjusting resistance to a flow of fluid passing through the damping passage by adjusting a thrust of the solenoid,
The piston rod has a rod body that is in sliding contact with an inner periphery of the rod guide, and a housing that is screwed to the rod body and accommodates a coil in the solenoid,
the housing has a cylindrical receiving portion made of carbon steel, receiving the coil and forming a part of the magnetic circuit of the solenoid, and a rod connection portion made of carbon steel or alloy steel, screwed to the rod main body and joined to the receiving portion by friction welding;
a carbon content in the carbon steel forming the housing portion is lower than a carbon content in the carbon steel or alloy steel forming the rod connection portion, The shock absorber according to claim 1, wherein the housing portion and the rod connection portion are frictionally welded to each other at a position that does not straddle a magnetic path of the solenoid. The shock absorber according to claim 1 or 2, wherein the piston is connected to the housing portion. The rod body is cylindrical and has a female screw portion on an inner periphery.
The shock absorber according to any one of claims 1 to 3, wherein the rod connection portion has a male screw portion that is inserted into the rod body and screwed into the female screw portion.

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