Fluid pressure shock absorber

Abstract

To secure an installation space for a damping valve in a fluid pressure buffer.SOLUTION: A shock absorber 100 comprises: a cylinder tube 10; a piston rod 20 inserted into the cylinder tube 10 so as to freely advance and retreat; a piston 30 connected to the piston rod 20, and for partitioning the inside of the cylinder tube 10 into a rod side chamber 2 and a bottom side chamber 1; and a damping part 50 for generating damping force by applying resistance to a flow of working fluid between the rod side chamber 2 and the bottom side chamber 1. The piston rod 20 comprises: a rod part 21 connected to the piston 30, and slidably supported by the cylinder tube 10; and a head part 23 exposed to the outside of the cylinder tube 10. The damping part 50 is provided in the head part 23 of the piston rod 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hydraulic shock absorber. [Background technology]

[0002] In the hydraulic shock absorber described in Patent Document 1, the piston rod has a rod portion extending to the outside of the cylinder, and a piston connected to an end of the rod portion and slidably moving inside the cylinder to divide the inside of the cylinder into a bottom side chamber and a rod side chamber. The rod portion has an inner-rod space formed inside the rod portion and communicating with the bottom side chamber of the cylinder, a first communication passage connecting the inner-rod space and the rod side chamber of the cylinder, and an orifice plug replaceably provided in the first communication passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-206374 A Summary of the Invention [Problem to be solved by the invention]

[0004] The fluid pressure shock absorber described in Patent Document 1 is configured to generate a damping force with a compact structure by providing an orifice plug in a first communication passage formed in a rod portion.

[0005] On the other hand, when it is desired to realize a variety of damping characteristics in a fluid pressure shock absorber, the structure of the damping section that generates the damping force may become large and complicated. In such a case, it is necessary to secure the installation space for the damping section.

[0006] The present invention has been made in consideration of the above problems, and has an object to provide a fluid pressure shock absorber that can ensure an installation space for a damping portion. [Means for solving the problem]

[0007] The present invention is a fluid pressure shock absorber comprising: a cylinder tube; a piston rod inserted into the cylinder tube so as to be capable of moving back and forth; a piston connected to the piston rod and dividing the inside of the cylinder tube into a rod side chamber and a bottom side chamber; and a damping section that generates a damping force by applying resistance to the flow of a working fluid between the rod side chamber and the bottom side chamber, the piston rod having a rod section connected to the piston and slidably supported by the cylinder tube, and a head section connected to the rod section and exposed to the outside of the cylinder tube, and the damping section is provided in the head section of the piston rod. The piston rod is provided with a rod internal space formed inside the rod portion, a first communication passage for guiding the working fluid between the rod side chamber and the rod internal space, and a second communication passage for guiding the working fluid between the rod internal space and the damping portion, and the piston rod further has a flow passage portion accommodated in the rod internal space and guiding the working fluid between the bottom side chamber and the damping portion. It is characterized by:

[0008] In this invention, since the damping portion is provided on the head portion of the piston rod, it is easy to ensure installation space for the damping portion. Furthermore, in the present invention, even if the fluid pressure shock absorber is of a so-called internal piping type in which the flow path connecting the bottom side chamber and the rod side chamber is provided inside the fluid pressure shock absorber, it is possible to ensure the installation space for the damping section.

[0009] The present invention also provides a fluid pressure shock absorber comprising: a cylinder tube; a piston rod inserted into the cylinder tube so as to be able to move back and forth; a piston connected to the piston rod and dividing the inside of the cylinder tube into a rod side chamber and a bottom side chamber; and a damping section that generates a damping force by applying resistance to a flow of working fluid in either direction between the rod side chamber and the bottom side chamber, wherein the piston rod has a rod section connected to the piston and supported slidably by the cylinder tube, and a head section exposed to the outside of the cylinder tube, and the damping section is provided at the head section of the piston rod. The present invention also provides a fluid pressure shock absorber comprising: a cylinder tube; a piston rod inserted into the cylinder tube so as to be able to move back and forth and disposed below the cylinder tube; a piston connected to the piston rod and dividing the inside of the cylinder tube into a rod side chamber and a bottom side chamber; and a damping section that generates a damping force by applying resistance to the flow of working fluid between the rod side chamber and the bottom side chamber, wherein the piston rod has a rod section connected to the piston and supported slidably by the cylinder tube, and a head section exposed to the outside of the cylinder tube, and the damping section is disposed at the head section of the piston rod.

[0010] In these inventions, the damping portion is provided on the head portion of the piston rod, which makes it easy to ensure installation space for the damping portion.

[0011] The present invention also provides a fluid pressure shock absorber comprising: a cylinder tube; a piston rod inserted into the cylinder tube so as to be able to move back and forth; a piston connected to the piston rod and dividing the inside of the cylinder tube into a rod side chamber and a bottom side chamber; and a damping section that generates a damping force by applying resistance to a flow of working fluid between the rod side chamber and the bottom side chamber, wherein the piston rod has a rod section connected to the piston and supported slidably by the cylinder tube, and a head section exposed to the outside of the cylinder tube, and the damping section is provided in the head section of the piston rod, and comprises a damping valve whose resistance to the working fluid changes depending on its position, and a switching section that is pressed by the cylinder tube as the piston rod enters the cylinder tube to switch the position of the damping valve.

[0012] In this invention, the damping portion is provided on the head portion of the piston rod, which makes it easy to secure the installation space for the damping portion. Furthermore, in this invention, the damping characteristics of the damping force generated by the damping portion can be changed according to the stroke of the piston rod of the fluid pressure shock absorber. Therefore, the fluid pressure shock absorber can generate an appropriate damping force according to the stroke.

[0013] The present invention is also characterized in that the damping section has a first resistance section and a second resistance section, each of which provides resistance to the flow of working fluid, and the first resistance section provides resistance only to the flow of working fluid from one of the rod side chamber and the bottom side chamber to the other.

[0014] In this invention, since an installation space for the damping portion can be secured, two resistance portions, a first resistance portion and a second resistance portion, can be provided, and the damping force can be made to differ between contraction and expansion of the fluid pressure buffer.

[0015] Also, in the present invention, the damping portion has a variable throttle portion that is variable in the resistance it imparts to the flow of the working fluid passing therethrough.

[0016] In this invention, since the damping force generated by the damping section can be adjusted, it is possible to generate a damping force suited to the product in which the fluid pressure shock absorber is used, the conditions of use, and the like.

[0017] Furthermore, the present invention is characterized in that the damping portion has a damping valve that changes the resistance applied to the working fluid depending on the position, and a solenoid portion that is driven by energization to switch the position of the damping valve.

[0018] In this invention, the damping force generated by the damping valve can be adjusted at any desired timing by energizing the solenoid portion, thereby improving convenience. Effect of the Invention

[0019] According to the present invention, it is possible to ensure a space for installing the damping portion of the fluid pressure shock absorber. [Brief description of the drawings]

[0020] [Figure 1] 1 is a cross-sectional view of a shock absorber according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view showing the structure around the head portion of the shock absorber according to the first embodiment. [Diagram 3] FIG. 11 is a schematic diagram showing a configuration of an attenuation section according to a modified example of the first embodiment. [Figure 4] FIG. 6 is a cross-sectional view of a shock absorber according to a second embodiment. [Diagram 5] FIG. 11 is a schematic diagram showing the configuration of an attenuation section according to a second embodiment. [Figure 6] FIG. 11 is a schematic diagram showing a configuration of an attenuation section according to a modified example of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, a fluid pressure shock absorber according to each embodiment of the present invention will be described with reference to the drawings.

[0022] (First embodiment) A fluid pressure shock absorber according to a first embodiment will be described with reference to Figures 1 and 2. In the following, a case will be described in which the fluid pressure shock absorber is a shock absorber 100 mounted on a vehicle.

[0023] Shock absorber 100 is a device that is interposed, for example, between the body and an axle of a vehicle, and generates a damping force to suppress vibration of the vehicle body.

[0024] 1, the shock absorber 100 includes a cylindrical cylinder tube 10, a piston rod 20 inserted into the cylinder tube 10 so as to be freely movable back and forth and extending out of the cylinder tube 10, and a piston 30 connected to the tip of the piston rod 20 and slidably moving along the inner circumferential surface of the cylinder tube 10. In this embodiment, the shock absorber 100 is mounted on the vehicle with the cylinder tube 10 on the upper side and the piston rod 20 on the lower side.

[0025] The inside of the cylinder tube 10 is divided into a bottom side chamber 1 and a rod side chamber 2 by the piston 30. Hydraulic oil is sealed in the bottom side chamber 1 and the rod side chamber 2 as a working fluid. Although not shown, gas is sealed in the bottom side chamber 1 together with the hydraulic oil to obtain a spring action by utilizing the volume change in the cylinder tube 10 caused by the piston rod 20 moving in and out of the cylinder tube 10. In this way, the shock absorber 100 is a fluid pressure buffer equipped with the function of an air suspension that can support the vehicle body by the spring action of the gas. In this case, the shock absorber 100 can generate a damping force and support the vehicle body without providing a separate spring to support the vehicle body.

[0026] However, this is not limiting, and gas does not have to be sealed in the cylinder tube 10. Also, a free piston may be provided movably inside the bottom side chamber 1 to separate the bottom side chamber 1 into a liquid chamber filled with hydraulic oil and an air chamber filled with gas. In this case, the piston 30 is configured to face the liquid chamber. By providing the free piston, the gas in the air chamber is not guided to the damping section 50 described later, so the shock absorber 100 can be used with the cylinder tube 10 on the lower side and the piston rod 20 on the upper side. In other words, the posture of the shock absorber 100 in the vertical direction is not limited.

[0027] The cylinder tube 10 is a cylindrical member with a bottom, and its open end is closed by a cylinder head 11, through which the piston rod 20 is slidably inserted. The cylinder head 11 is fixed to the cylinder tube 10 by fastening it to an end of the cylinder tube 10 with bolts (not shown). A seal member (not shown) and a dust seal (not shown) that come into sliding contact with the outer circumferential surface of the piston rod 20 are provided on the inner circumferential surface of the cylinder head 11.

[0028] A mounting portion 10a for mounting the shock absorber 100 to a vehicle is provided at a closed end of the cylinder tube 10 (the end opposite to the cylinder head 11).

[0029] The piston rod 20 has a rod portion 21 connected to the piston 30 and supported so as to be able to slide freely in the cylinder head 11 of the cylinder tube 10, a head portion 23 exposed to the outside of the cylinder tube 10, and a pipe portion 27 serving as a flow path portion provided inside the rod portion 21.

[0030] The rod portion 21 is formed with a recess 21a that opens to the end face on the piston 30 side. A rod inner chamber 2a is formed as a rod internal space by the recess 21a inside the rod portion 21. An end of the rod portion 21 is connected to the piston 30 by a bolt (not shown).

[0031] The head portion 23 is formed with a larger diameter than the rod portion 21, and is always exposed to the outside of the cylinder tube 10 regardless of the expansion / contraction state of the shock absorber 100 (in other words, the stroke position of the piston rod 20 relative to the cylinder tube 10). From another perspective, the head portion 23 is a portion of the piston rod 20 that does not slide relative to the cylinder head 11. The head portion 23 is formed, for example, as a separate body from the rod portion 21, and is connected to the end of the rod portion 21 by a method such as welding. Note that the rod portion 21 and the head portion 23 are not limited to a configuration in which they are formed separately and then connected, and may be formed integrally.

[0032] The head portion 23 is provided with a stopper portion 24 that determines the stroke end of the shock absorber 100 during contraction, and a mounting portion 20a for mounting the shock absorber 100 to a vehicle. The stopper portion 24 is provided with an annular cushion ring 15 that prevents a collision between the cylinder head 11 and the piston rod 20 at the stroke end during contraction of the shock absorber 100.

[0033] The pipe portion 27 is a cylindrical tubular member having a through hole 27a formed along the axial direction. The through hole 27a of the pipe portion 27 communicates with the bottom side chamber 1 through a piston passage 31 formed in the piston 30.

[0034] One end of the pipe portion 27 is inserted into an insertion hole 23a formed in the head portion 23, and the other end is inserted into an insertion hole 30a formed in the piston 30. In this manner, the pipe portion 27 is provided so as to be sandwiched between the head portion 23 and the piston 30. Between the pipe portion 27 and the insertion hole 23a of the head portion 23 and between the pipe portion 27 and the insertion hole 30a of the piston 30, O-rings (not shown) are provided to seal the gaps.

[0035] The rod inner chamber 2a is formed as an annular space by the outer peripheral surface of the pipe portion 27, the inner peripheral surface of the rod portion 21, the head portion 23, and the piston 30. The rod inner chamber 2a communicates with the rod side chamber 2 through a plurality of first communication passages 22 formed in the rod portion 21 of the piston rod 20. The plurality of first communication passages 22 are arranged in the circumferential direction of the rod portion 21 and formed penetrating in the radial direction so as to open to the inner and outer peripheral surfaces of the rod portion 21. By providing the rod inner chamber 2a, when the shock absorber 100 contracts at high speed or when it contracts from the maximum extension state, the hydraulic oil in the rod inner chamber 2a is quickly guided to the rod side chamber 2. This suppresses a sudden pressure drop in the rod side chamber 2.

[0036] The shock absorber 100 further includes a damping section 50 that generates a damping force by applying resistance to the flow of hydraulic oil between the rod side chamber 2 and the bottom side chamber 1. The damping section 50 is provided inside the head section 23 of the piston rod 20.

[0037] As shown in FIG. 2, the head portion 23 is formed with an accommodating hole 40 that accommodates the damping portion 50, a connecting hole 45 that connects the accommodating hole 40 to the through hole 27a of the pipe portion 27, and second connecting passages 46a, 46b that connect the accommodating hole 40 to the rod inner chamber 2a.

[0038] The bottom side chamber 1 and the rod side chamber 2 communicate with each other through a flow passage formed by the piston passage 31 (see FIG. 1), the through hole 27a of the pipe portion 27, the connection hole 45, the accommodation hole 40, the second communication passages 46a and 46b, the rod inner chamber 2a, and the first communication passage 22 (see FIG. 1). In this manner, the shock absorber 100 is of a so-called internal piping type in which a flow passage communicating between the bottom side chamber 1 and the rod side chamber 2 is provided inside the shock absorber 100. Note that the shock absorber 100 may be of a so-called external piping type in which a part of the flow passage communicating between the bottom side chamber 1 and the rod side chamber 2 is provided outside the shock absorber 100.

[0039] As shown in Figs. 1 and 2, the damping portion 50 has a first resistance portion 51 and a second resistance portion 60 that each provide resistance to the flow of hydraulic oil.

[0040] The first resistance portion 51 applies resistance only to the flow of hydraulic oil from the bottom side chamber 1 to the rod side chamber 2. The first resistance portion 51 has a first orifice 52 as a first throttle portion that applies resistance to the hydraulic oil passing therethrough to generate a damping force, and a check valve 55 that allows the hydraulic oil to flow only from the bottom side chamber 1 to the rod inner chamber 2a.

[0041] The second resistance portion 60 applies resistance to the flow of hydraulic oil in both directions between the bottom side chamber 1 and the rod side chamber 2. The second resistance portion 60 has a second orifice 61 as a second throttle portion that applies resistance to the hydraulic oil passing therethrough and generates a damping force.

[0042] The first resistance portion 51 and the second resistance portion 60 are provided in parallel to each other, as shown in Fig. 1. In the first resistance portion 51, a check valve 55 is provided at a position closer to the bottom-side chamber 1 than the first orifice 52 in the flow of hydraulic oil.

[0043] A specific configuration of the attenuation section 50 will be described below mainly with reference to FIG.

[0044] As shown in FIG. 2, the damping portion 50 is accommodated in an accommodating hole 40 formed in the head portion 23 of the piston rod 20 and is provided inside the head portion 23 .

[0045] The damping portion 50 has a first orifice plug 53 in which the first orifice 52 is provided, and a second orifice plug 62 in which the second orifice 61 is provided.

[0046] The accommodating hole 40 of the head portion 23 is composed of a first accommodating portion 41 that accommodates the first orifice plug 53 and the check valve 55, a second accommodating portion 42 that accommodates the second orifice plug 62, and a communication portion 43 that communicates between the first accommodating portion 41 and the second accommodating portion 42. The first accommodating portion 41 and the second accommodating portion 42 each open to the outer surface of the head portion 23, and the respective openings are sealed by plugs 80, 81.

[0047] The check valve 55 has a ball body 56 as a valve body, and a seating portion 57 on which the ball body 56 is seated. The seating portion 57 is formed in a step portion formed between the first storage portion 41 and the communication portion 43. When the ball body 56 is seated on the seating portion 57, the flow of hydraulic oil from the first storage portion 41 to the communication portion 43 is blocked.

[0048] Further, in the head portion 23, second communication passages 46a, 46b are formed which communicate between the rod inner chamber 2a and the first accommodation portion 41 and the second accommodation portion 42.

[0049] One of the second communication passages 46a is formed between the first orifice plug 53 and a plug 80 that seals the opening of the first accommodating portion 41 so as to open into the first accommodating portion 41. The other of the second communication passages 46b is formed between the second orifice plug 62 and a plug 81 that seals the opening of the second accommodating portion 42 so as to open into the second accommodating portion 42. In other words, when viewed from the perspective of the flow of hydraulic oil between the bottom side chamber 1 and the rod side chamber 2, the first orifice plug 53 is provided between one of the second communication passages 46a and the communication portion 43, and the second orifice plug 62 is provided between the other of the second communication passages 46b and the communication portion 43.

[0050] When the shock absorber 100 contracts, the pressure in the bottom side chamber 1 rises, and the hydraulic oil in the bottom side chamber 1 is guided to the communication part 43 of the accommodation hole 40 through the pipe part 27. A part of the hydraulic oil guided to the communication part 43 opens the check valve 55 and passes through the first orifice 52 to be guided from the second communication passage 46a to the rod inner chamber 2a, and the remaining part passes through the second orifice 61 to be guided from the second communication passage 46b to the rod inner chamber 2a. The hydraulic oil guided to the rod inner chamber 2a is guided to the rod side chamber 2 through the first communication passage 22. In this way, when the shock absorber 100 contracts, the hydraulic oil in the bottom side chamber 1 passes through both the first orifice 52 and the second orifice 61 and is guided to the rod side chamber 2. Therefore, in the shock absorber 100, a damping force is generated according to the flow resistance exerted by the first orifice 52 and the second orifice 61 as a whole.

[0051] When the shock absorber 100 is extended, the pressure in the rod side chamber 2 increases, and the hydraulic oil in the rod side chamber 2 is guided to the second housing portion 42 through the rod inner chamber 2a and the second communication passage 46b. The hydraulic oil guided to the second housing portion 42 passes through the second orifice 61 and is guided to the bottom side chamber 1 through the pipe portion 27.

[0052] On the other hand, the check valve 55 is closed by the pressure rise in the rod side chamber 2, so that the hydraulic oil in the rod side chamber 2 is not led to the bottom side chamber 1 through the second orifice 61. Therefore, when the shock absorber 100 is extended, a damping force is generated according to the flow resistance of the second orifice 61. Therefore, when the shock absorber 100 is extended, the hydraulic oil is allowed to flow from the bottom side chamber 1 to the rod side chamber 2 through the first orifice 52, so that the shock absorber 100 is likely to generate a larger damping force during the extension operation than during the contraction operation. As a result, when the vehicle runs over a protrusion on the road surface, the shock absorber 100 contracts relatively smoothly, and then generates a large damping force during the extension operation, effectively damping the vibration input from the road surface to the vehicle body.

[0053] According to the above-described first embodiment, the following effects are achieved.

[0054] In the shock absorber 100, the damping section 50 is provided inside the head section 23 of the piston rod 20. The head section 23 is easier to secure a volume than the rod section 21, and accordingly, it is easier to secure an installation space for the damping section 50. Therefore, even if the damping section 50 has a relatively complicated or large configuration, it can be easily incorporated into the shock absorber 100. This makes it possible to realize a variety of damping characteristics in the shock absorber 100.

[0055] Furthermore, in the shock absorber 100, the damping section 50 is provided on the head section 23 of the piston rod 20, which is always exposed to the outside of the cylinder tube 10, and therefore adjustment can be made without disassembling the shock absorber 100, as compared to when the damping section 50 is provided on the rod section 21 or the piston 30. Specifically, the damping characteristics of the shock absorber 100 can be easily changed by removing the plugs 80, 81 exposed to the outside and replacing the first orifice plug 53 and the second orifice plug 62.

[0056] Next, modified examples of the present embodiment will be described. The following modified examples are also within the scope of the present invention, and it is possible to combine the following modified examples with the configurations of the above-described embodiment, to combine the following modified examples with the configurations of the embodiments described below, or to combine the following modified examples with each other.

[0057] In the above embodiment, the first orifice 52 and the second orifice 61 are fixed orifices with a constant flow resistance. In contrast, the first orifice 52 and / or the second orifice 61 may be variable orifices (variable throttle sections) with a variable flow resistance. For example, as shown in FIG. 3, the shock absorber 100 has the second orifice 61a which is a variable orifice, so that the damping force of the shock absorber 100 can be adjusted more easily. The variable orifice and its adjustment mechanism can be configured in a known manner, so that a specific description and illustration are omitted, but for example, the opening area (flow area) of the second orifice 61a can be adjusted by hand tools.

[0058] In the above embodiment, the first resistance portion 51 applies resistance only to the flow of hydraulic oil from the bottom side chamber 1 to the rod side chamber 2. As a result, the shock absorber 100 has different damping characteristics during extension and contraction. In contrast, the first resistance portion 51 may apply resistance only to the flow of hydraulic oil from the rod side chamber 2 to the bottom side chamber 1. The first resistance portion 51 may apply resistance only to the flow of hydraulic oil from the bottom side chamber 1 to the rod side chamber 2, and the second resistance portion 60 may apply resistance only to the flow of hydraulic oil from the rod side chamber 2 to the bottom side chamber 1. In this case, it is desirable that the first orifice 52 and the second orifice 61 have different damping characteristics. Furthermore, it is not essential that the damping portion 50 has the first resistance portion 51 and the second resistance portion 60 arranged in parallel with each other, and the damping portion 50 may have any configuration depending on the desired damping force to be generated in the shock absorber 100. For example, the damping section 50 may generate a damping force with the same damping characteristics when the shock absorber 100 expands and contracts.

[0059] Second embodiment Next, a shock absorber 200 according to a second embodiment will be described with reference to Figures 4 and 5. The following description will focus on the differences from the first embodiment, and the same components as those in the first embodiment will be given the same reference numerals and will not be described as necessary. Specifically, the shock absorber 200 according to the second embodiment differs from the shock absorber 100 according to the first embodiment in the configuration of the damping section 150.

[0060] As shown in Figs. 4 and 5, the damping section 150 of the shock absorber 200 according to the second embodiment has a first resistance section 51 and a second resistance section 160 provided in parallel with each other, similar to the first embodiment.

[0061] The configuration of the first resistance portion 51 is similar to that of the first embodiment, and therefore a description thereof will be omitted.

[0062] As shown in FIG. 5, the second resistance portion 160 has a damping valve 161 whose resistance to the flow of hydraulic oil passing therethrough changes depending on the position.

[0063] The damping valve 161 has a first throttling position 161A which applies a predetermined resistance to the flow of hydraulic oil passing therethrough, and a second throttling position 161B which applies a resistance to the flow of hydraulic oil passing therethrough that is different in magnitude from the resistance applied by the first throttling position 161A. In other words, the first throttling position 161A and the second throttling position 161B have different pressure loss characteristics with respect to the flow of hydraulic oil passing therethrough. The damping valve 161 has a valve body (not shown) which switches positions, and a spring 162 which serves as a biasing member for biasing the valve body. In the damping valve 161, the valve body is biased by the spring 162 so as to be in the first throttling position 161A.

[0064] As shown in FIG. 4, the damping portion 150 has a switching portion 165 that is pressed by the cylinder tube 10 as the piston rod 20 enters the cylinder tube 10 to switch the position of the damping valve 161.

[0065] The switching portion 165 has a lever portion 166 that protrudes to the outside of the piston rod 20, and a pressing rod portion 167 that presses the valve body in response to switching of the lever portion 166. At least a portion of the pressing rod portion 167 is inserted into the head portion 23 of the piston rod 20.

[0066] In the second embodiment, the cylinder head 11 of the cylinder tube 10 is provided with a protrusion 120 for switching the lever portion 166, as shown in FIG.

[0067] Generally, in a shock absorber, the stroke range of the piston rod used may vary depending on the condition of the object, such as a vehicle or equipment, to which the shock absorber is attached. In other words, both a situation in which the shock absorber expands and contracts in a relatively extended state and a situation in which the shock absorber expands and contracts in a relatively contracted state may occur. For example, the stroke range of the shock absorber differs between a state in which the vehicle is loaded with cargo such as people or luggage and a state in which the vehicle is not loaded. In such a case in which the stroke range varies depending on the situation, it is desirable to configure the damping characteristics of the shock absorber to differ according to the stroke range.

[0068] 4 and 5, in the shock absorber 200, in a relatively extended state, the damping valve 161 of the damping section 50 takes the first throttling position 161A due to the biasing force of the spring 162. Therefore, when the shock absorber 100 expands and contracts in the extended state, a damping force is generated based on the damping characteristics according to the pressure loss characteristics of the first throttling position 161A.

[0069] When the shock absorber 200 is in a relatively contracted state, the lever portion 166 is pressed by the protruding portion 120 of the cylinder tube 10, and the damping valve 161 is switched to the second throttling position 161B. Therefore, when the shock absorber 200 expands or contracts in the contracted state, a damping force is generated based on the damping characteristics according to the pressure loss characteristics of the second throttling position 161B.

[0070] In this way, in the shock absorber 200, since the damping section 150 is provided in the head section 23, the damping section 150 can be easily incorporated into the shock absorber 100 even if the shock absorber 100 has a complicated configuration including the damping valve 161 and the switching section 165. In this embodiment, when the stroke region of the piston rod 20 changes, the position of the damping valve 161 is switched, and the damping characteristics of the damping force generated by the shock absorber 200 change. Therefore, the pressure loss characteristics of the first throttling position 161A of the damping valve 161 can be configured to generate damping characteristics suitable for when the shock absorber 100 is in an extended state, and the pressure loss characteristics of the second throttling position 161B can be configured to generate damping characteristics suitable for when the shock absorber 100 is in a contracted state. This allows the shock absorber 100 to generate an appropriate damping force according to the situation of the object to which it is attached.

[0071] In this embodiment, the lever portion 166 is configured to be pressed against the protruding portion 120 of the cylinder tube 10 by direct contact therewith, but the present invention is not limited thereto, and may be configured, for example, such that the lever portion 166 is pressed by the magnetic force (repulsive force) of a magnet provided on the cylinder tube 10. In other words, the switching portion may be configured to be switched by being pressed by the cylinder tube 10 in a non-contact manner.

[0072] Next, a modified example of the second embodiment will be described with reference to FIG.

[0073] In the second embodiment, the damping unit 150 has a switching unit 165 that is pressed by the cylinder tube 10 as the piston rod 20 enters the cylinder tube 10 to switch the position of the damping valve 161. As a result, the shock absorber 200 generates a damping force with different damping characteristics in a relatively extended state and a relatively contracted state.

[0074] In contrast, a damping section 250 according to a modified example shown in FIG. 6 has, instead of the switching section 165, a solenoid section 265 that is driven by energization to switch the position of the damping valve 161.

[0075] When an electric signal is input from the controller 90, the solenoid unit 265 moves the valve element of the damping valve 161 against the biasing force of the spring 162. This switches the position of the damping valve 161 from the first throttle position 161A to the second throttle position 161B. In a state in which the power supply to the solenoid unit 265 is cut off, the damping valve 161 is switched to the first throttle position 161A by the biasing force of the spring 162.

[0076] According to this modification, in addition to the same effects as those of the second embodiment, the following effects are achieved.

[0077] 6, the position of the damping valve 161 is switched by the solenoid unit 265, so that the damping characteristics of the damping valve 161 can be changed not only in the stroke region of the piston rod 20 but also in various other situations. For example, the damping characteristics can be changed according to the vehicle's running state, such as the vehicle's steering operation and road surface conditions. In this way, the damping characteristics of the shock absorber 200 can be changed at any time, improving convenience.

[0078] The configuration, operation, and effects of each embodiment of the present invention will be described below.

[0079] The shock absorber 100, 200 comprises a cylinder tube 10, a piston rod 20 inserted into the cylinder tube 10 so as to be able to move back and forth, a piston 30 connected to the piston rod 20 and dividing the inside of the cylinder tube 10 into a rod side chamber 2 and a bottom side chamber 1, and a damping section 50, 150, 250 that generates a damping force by applying resistance to the flow of working fluid between the rod side chamber 2 and the bottom side chamber 1, the piston rod 20 having a rod section 21 connected to the piston 30 and supported slidably on the cylinder tube 10, and a head section 23 exposed to the outside of the cylinder tube 10, and the damping section 50, 150, 250 is provided on the head section 23 of the piston rod 20.

[0080] In this configuration, by providing the damping portions 50, 150, 250 on the head portion 23 of the piston rod 20, the installation space for the damping portions 50, 150, 250 can be easily secured.

[0081] In addition, in the shock absorbers 100, 200, the piston rod 20 is formed with a rod inner chamber 2a formed inside the rod portion 21, a first communication passage 22 that guides hydraulic oil between the rod side chamber 2 and the rod inner chamber 2a, and second communication passages 46a, 46b that guide hydraulic oil between the rod inner chamber 2a and the damping portion 50, 150, 250, and the piston rod 20 further has a pipe portion 27 that is housed in the rod inner chamber 2a and guides hydraulic oil between the bottom side chamber 1 and the damping portion 50, 150, 250.

[0082] In this configuration, even if the flow path connecting the bottom side chamber 1 and the rod side chamber 2 is provided inside the shock absorber 100, 200, that is, a so-called internal piping type, the installation space for the damping section 50, 150, 250 can be secured.

[0083] In addition, in the shock absorbers 100, 200, the damping sections 50, 150, 250 each have a first resistance section 51 and a second resistance section 60, 160, 260 that provide resistance to the flow of working fluid, and the first resistance section 51 provides resistance only to the flow of working oil from one of the rod side chamber 2 and the bottom side chamber 1 to the other.

[0084] In this configuration, since installation space for the damping sections 50, 150, 250 can be secured, two resistance sections, the first resistance section 51 and the second resistance section 60, 160, 260, can be provided, and the damping force can be made to differ between contraction and expansion of the shock absorbers 100, 200.

[0085] In addition, in the modified example of the shock absorber 100 according to the first embodiment, the damping section 50 has a second orifice 61a that is variable in resistance applied to the flow of hydraulic oil passing therethrough.

[0086] In this configuration, the damping force generated by the damping section 50 can be adjusted, so that a damping force can be generated that is suited to the product in which the shock absorber is used, the usage conditions, and the like.

[0087] In addition, in the shock absorber 200 of the second embodiment, the damping section 150 has a damping valve 161 that changes the resistance applied to the working fluid depending on the position, and a switching section 165 that is pressed by the cylinder tube 10 as the piston rod 20 enters the cylinder tube 10 to switch the position of the damping valve 161.

[0088] In this configuration, the damping characteristics of the damping force generated by the damping section 150 can be changed according to the stroke of the piston rod 20 of the shock absorber 100. Therefore, the shock absorber 200 can generate an appropriate damping force according to the stroke.

[0089] In addition, in the shock absorber 200 according to the second embodiment, the damping section 250 has a damping valve 161 that changes the resistance applied to the working fluid depending on the position, and a solenoid section 265 that is driven by energization to switch the position of the damping valve 161.

[0090] In this invention, the damping force generated by the damping valve 161 can be adjusted at any desired timing by energizing the solenoid portion 265, thereby improving convenience.

[0091] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments. [Explanation of symbols]

[0092] 100, 200...shock absorber, 1...bottom side chamber, 2...rod side chamber, 2a...rod inner chamber (rod inner space), 10...cylinder tube, 20...piston rod, 21...rod portion, 22...first communication passage, 23...head portion, 27...pipe portion (flow passage portion), 30...piston, 46a, 46b...second communication passage, 50, 150, 250...damping portion, 51...first resistance portion, 60, 160, 260...second resistance portion, 61a...second orifice (variable throttle portion), 161...damping valve, 165...switching portion, 265...solenoid portion

Claims

1. A cylinder tube; a piston rod inserted into the cylinder tube so as to be capable of moving forward and backward; a piston connected to the piston rod and dividing the inside of the cylinder tube into a rod side chamber and a bottom side chamber; a damping unit that generates a damping force by applying resistance to a flow of a working fluid between the rod side chamber and the bottom side chamber, The piston rod is a rod portion connected to the piston and slidably supported by the cylinder tube; a head portion exposed to the outside of the cylinder tube, The damping portion is provided in the head portion of the piston rod, The piston rod is provided with a rod internal space formed inside the rod portion, a first communication passage for guiding a working fluid between the rod side chamber and the rod internal space, and a second communication passage for guiding a working fluid between the rod internal space and the damping portion, The fluid pressure shock absorber according to claim 1, wherein the piston rod further includes a flow passage portion that is accommodated in the rod internal space and guides a working fluid between the bottom side chamber and the damping portion.

2. A cylinder tube, a piston rod inserted into the cylinder tube so as to be capable of moving forward and backward; a piston connected to the piston rod and dividing the inside of the cylinder tube into a rod side chamber and a bottom side chamber; a damping unit that generates a damping force by applying resistance to a flow of the working fluid in either direction between the rod side chamber and the bottom side chamber, The piston rod is a rod portion connected to the piston and slidably supported by the cylinder tube; a head portion exposed to the outside of the cylinder tube, 13. A hydraulic shock absorber, comprising: a damping portion provided at the head portion of the piston rod.

3. A cylinder tube, a piston rod that is inserted into the cylinder tube so as to be capable of moving forward and backward and is disposed below the cylinder tube; a piston connected to the piston rod and dividing the inside of the cylinder tube into a rod side chamber and a bottom side chamber; a damping unit that generates a damping force by applying resistance to a flow of a working fluid between the rod side chamber and the bottom side chamber, The piston rod is a rod portion connected to the piston and slidably supported by the cylinder tube; a head portion exposed to the outside of the cylinder tube, 13. A hydraulic shock absorber, comprising: a damping portion provided at the head portion of the piston rod.

4. A cylinder tube, a piston rod inserted into the cylinder tube so as to be capable of moving forward and backward; a piston connected to the piston rod and dividing the inside of the cylinder tube into a rod side chamber and a bottom side chamber; a damping unit that generates a damping force by applying resistance to a flow of a working fluid between the rod side chamber and the bottom side chamber, The piston rod is a rod portion connected to the piston and slidably supported by the cylinder tube; a head portion exposed to the outside of the cylinder tube, The damping portion is provided in the head portion of the piston rod, The attenuation portion is a damping valve that changes the resistance applied to the working fluid depending on the position; a switching portion that is pressed by the cylinder tube as the piston rod enters the cylinder tube, thereby switching a position of the damping valve.

5. A fluid pressure shock absorber according to any one of claims 1 to 3, The damping portion includes a first resistance portion and a second resistance portion each of which provides resistance to a flow of the working fluid, The fluid pressure shock absorber, wherein the first resistance portion applies resistance only to a flow of working fluid from one of the rod side chamber and the bottom side chamber to the other.

6. A fluid pressure shock absorber according to any one of claims 1 to 3, A fluid pressure shock absorber, wherein the damping portion has a variable throttle portion that varies the resistance applied to the flow of the working fluid passing therethrough.

7. A fluid pressure shock absorber according to any one of claims 1 to 3, The attenuation portion is a damping valve that changes the resistance applied to the working fluid depending on the position; a solenoid portion that is driven by energization to switch the position of the damping valve.

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