Multi-stage fluid pressure cylinder

Abstract

A multi-stage fluid pressure cylinder (100) comprises: a cylinder tube (10); a first rod assembly (30); a second rod assembly (40); and a retaining ring (35), which is accommodated in an annular recess (30b) formed on the first rod assembly (30); a communication path (32c, 42d) is provided on at least one of the first rod assembly (30) and the second rod assembly (40); the communication path connects a gap (G1) with a chamber (5) on the opposite side of the rod; and the gap (G1) is defined by the retaining ring (35), the outer peripheral surface (42a) of the first inner piston portion (42), and the inner peripheral surface (30a) of the first rod assembly (30) when the retaining ring (35) is accommodated in the accommodation recess (42c).

Description

Technical Field

[0001] The invention relates to a multi-stage fluid pressure cylinder. Background Art

[0002] Japanese Patent Laid-Open No. JPH4-254005A discloses a multi-stage fluid pressure cylinder comprising: an outer rod member having an outer piston portion provided at its end, the outer piston portion sliding along the inner circumferential surface of the cylinder and dividing the interior of the cylinder into a rod side chamber and a rod opposite side chamber; an inner rod member having an inner piston portion provided at its end sliding along the inner circumferential surface of the outer rod member; and a retaining ring provided on the inner circumferential surface of the outer rod member to limit the movement of the inner rod member in the contraction direction. Summary of the Invention

[0003] The inner piston portion of a multi-stage fluid pressure cylinder described in Japanese Patent Application Laid-Open (JPH4-254005A) has a recessed portion that accommodates the inner diameter side of a retaining ring when the inner rod member is retracted. When this multi-stage fluid pressure cylinder is in its most retracted state, with no working fluid supplied or discharged to or from the rod-side chamber or the opposite-rod-side chamber, if an external force, forcibly extending the cylinder, acts suddenly, the pressure in the opposite-rod-side chamber decreases while the pressure in the rod-side chamber increases. This increase in rod-side chamber pressure causes the outer rod member, along with the cylinder barrel, to displace in the extension direction, causing the retaining ring attached to the outer rod member to separate from the recessed portion of the inner piston portion.

[0004] Furthermore, when the snap ring separates from the receiving recess, the volume of the gap defined by the outer circumferential surface of the inner piston portion, the inner circumferential surface of the outer rod member, and the snap ring rapidly increases. The pressure within this gap and around the receiving recess decreases relative to the pressure in the chamber on the opposite side of the rod. This decrease in pressure in the area facing the inner diameter side of the snap ring generates a fluid force acting in the radially expanding direction on the inner diameter side of the snap ring, overcoming the elastic force of the snap ring acting in this direction. This reduces the outer diameter of the snap ring, potentially causing the snap ring to separate from the outer rod member.

[0005] The object of the present invention is to prevent the snap ring from falling off.

[0006] According to a certain embodiment of the present invention, a multi-stage fluid pressure cylinder comprises: a cylinder tube; a cylindrical outer rod component, an outer piston portion is provided at the end thereof, and the outer piston portion slides along the inner circumferential surface of the cylinder tube and divides the cylinder tube into a rod side chamber and a rod opposite side chamber; an inner rod component, an inner piston portion is provided at the end thereof and slides along the inner circumferential surface of the outer rod component; a retaining ring, the outer diameter side of which is accommodated in an annular recess formed on the inner circumferential surface of the outer rod component and limits the movement of the inner rod component in the contraction direction, and a retaining ring is provided on the inner piston portion. The piston rod of the ... BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a cross-sectional view of the fluid pressure cylinder according to the embodiment of the present invention, showing the most contracted state.

[0008] Figure 2 This is a cross-sectional view showing a fluid pressure cylinder according to an embodiment of the present invention, showing a state in which the first rod assembly is in an extended position and the second rod assembly and the third rod assembly are in a retracted position.

[0009] Figure 3 This is a cross-sectional view showing a fluid pressure cylinder according to an embodiment of the present invention, showing a state in which the first rod assembly and the second rod assembly are in an extended position and the third rod assembly is in a retracted position.

[0010] Figure 4 This is a cross-sectional view showing the fluid pressure cylinder according to the embodiment of the present invention, and is a diagram showing the most extended state.

[0011] Figure 5A For the general Figure 1 The enlarged view of the A part is enlarged, which is a diagram for explaining the existing technical problems.

[0012] Figure 5B It is a diagram for explaining the existing technical problem, which is a subsequent Figure 5A A diagram of the state.

[0013] Figure 5C It is a diagram for explaining the existing technical problem, which is a subsequent Figure 5B A diagram of the state.

[0014] Figure 6 For the general Figure 1 Part B is an enlarged view showing an enlarged image.

[0015] Figure 7 FIG. 1 is a diagram showing a first modified example of the fluid pressure cylinder according to the embodiment of the present invention, which is equivalent to Figure 6 Figure of part of .

[0016] Figure 8 FIG. 2 is a diagram showing a second modified example of the fluid pressure cylinder according to the embodiment of the present invention, which is equivalent to Figure 6 Figure of part of .

[0017] Figure 9 FIG. 1 is a diagram showing a third modified example of the fluid pressure cylinder according to the embodiment of the present invention, which is equivalent to Figure 6 Figure of part of .

[0018] Figure 10 FIG. 4 is a diagram showing a fourth modified example of the fluid pressure cylinder according to the embodiment of the present invention, which is equivalent to Figure 6 Figure of part of . DETAILED DESCRIPTION

[0019] A multi-stage fluid pressure cylinder 100 according to an embodiment of the present invention will be described below with reference to the accompanying drawings. The following description will focus on a case where the multi-stage fluid pressure cylinder 100 is a multi-stage hydraulic cylinder 100 (hereinafter referred to as "hydraulic cylinder 100") driven by hydraulic oil as the working fluid.

[0020] like Figure 1 As shown, the hydraulic cylinder 100 includes: a bottomed cylindrical cylinder 10; a first rod assembly 30 as an outer rod member, which is inserted into the inner side of the cylinder 10 in a freely slidable manner; a second rod assembly 40 as an inner rod member, which is inserted into the inner side of the first rod assembly 30 in a freely slidable manner in the direction of the central axis of the cylinder 10 (hereinafter referred to as the axial direction); and a third rod assembly 50 as a second inner rod member, which is inserted into the inner side of the second rod assembly 40 in a freely slidable manner in the axial direction. In addition, Figure 1 It is a cross-sectional view showing the hydraulic cylinder 100 in the most contracted state.

[0021] The hydraulic cylinder 100 is mounted to the driven equipment via a first mounting portion 61 provided at the bottom of the cylinder tube 10 and a second mounting portion 62 provided at the end of the third rod assembly 50 protruding from the cylinder tube 10, with the cylinder tube 10 positioned vertically upward and the third rod assembly 50 positioned vertically downward. In other words, the hydraulic cylinder 100 is mounted to the driven equipment with the first mounting portion 61 displaced substantially vertically, i.e., vertically, relative to the second mounting portion 62. The mounting orientation of the hydraulic cylinder 100 is not limited to this; it may also be mounted with the cylinder tube 10 positioned vertically downward and the third cylinder assembly 50 positioned vertically upward. Furthermore, the hydraulic cylinder 100 is mounted to the driven equipment with the first mounting portion 61 displaced horizontally relative to the second mounting portion 62.

[0022] The first rod assembly 30 includes: a cylindrical outer rod portion 31; an annular outer piston portion 32, which is provided at one end of the outer rod portion 31 and slides along the inner circumferential surface 10a of the cylinder 10, thereby dividing the cylinder 10 into a rod-side chamber 2 and an opposite-rod-side chamber 5; and a cylindrical first support portion 33, which is formed so as to protrude radially inward from the other end of the outer rod portion 31 and is supported by the second rod assembly 40 so as to be free to slide.

[0023] An annular recess 30b is formed on the inner circumferential surface 30a of the first rod assembly 30, on the outer piston portion 32 side, for mounting a first snap ring 35. The first snap ring 35 is a metal wire formed into a generally annular shape with a circular cross-section and has a partially split joint (not shown). The first snap ring 35 is inserted into the first rod assembly 30 in a reduced diameter state. Due to the elastic force acting in the expanding direction, its outer diameter side is pressed against the inner circumferential surface 30a, allowing it to fit into the annular recess 30b. Thus, when the first snap ring 35 is assembled to the first rod assembly 30, its inner diameter side protrudes radially inward from the inner circumferential surface 30a of the first rod assembly 30. The first snap ring 35 is mounted after the second rod assembly 40 is inserted into the first rod assembly 30.

[0024] The second rod assembly 40 has the same shape as the first rod assembly 30 and includes: a cylindrical first inner rod portion 41, which is inserted into the outer rod portion 31; an annular first inner piston portion 42 as an inner piston portion, which is provided at one end of the first inner rod portion 41 and slides along the inner circumferential surface 30a of the first rod assembly 30; and a cylindrical second support portion 43, which is formed so as to protrude radially inward from the other end of the first inner rod portion 41 and supports the third rod assembly 50 so that it can slide freely.

[0025] A second annular recess 40b for mounting a second snap ring 45 is formed on the inner circumferential surface 40a of the second rod assembly 40 on the first inner piston portion 42 side. Like the first snap ring 35, the second snap ring 45 is a metal wire formed into a substantially annular shape with a circular cross-section and has a partially split joint (not shown). The second snap ring 45 is inserted into the second rod assembly 40 in a reduced diameter state. Due to the elastic force acting in the expanding direction, its outer diameter side is pressed against the inner circumferential surface 40a, allowing it to fit into the second annular recess 40b. Thus, when the second snap ring 45 is assembled into the second rod assembly 40, its inner diameter side protrudes radially inward from the inner circumferential surface 40a of the second rod assembly 40. The second snap ring 45 is mounted after the third rod assembly 50 is inserted into the second rod assembly 40.

[0026] The third rod assembly 50 includes a second inner rod portion 51 inserted into the first inner rod portion 41 and an annular second inner piston portion 52 coupled to one end of the second inner rod portion 51 and slidable along the inner circumferential surface 40a of the second rod assembly 40. The second inner rod portion 51 and the second inner piston portion 52 are coupled together by bolts (not shown).

[0027] In this manner, the three rod members, namely the first rod assembly 30 , the second rod assembly 40 , and the third rod assembly 50 , are inserted into the cylinder 10 .

[0028] A cylinder head 11 is provided at the opening of the cylinder tube 10 to slidably support the outer rod portion 31 of the first rod assembly 30. A recess 10b is formed at the bottom of the cylinder head 10, axially opposing the piston portions 32, 42, and 52, and is recessed toward the first mounting portion 61. The inner diameter of the recess 10b is set larger than the inner diameter of the outer piston portion 32 of the first rod assembly 30.

[0029] The first rod assembly 30, inserted into the cylinder head 10, is defined in its most retracted position by the outer piston portion 32 abutting against the bottom of the cylinder liner 10, while its most extended position is defined by the outer piston portion 32 abutting against the cylinder head 11. Furthermore, a sealing member (not shown) is provided on the inner circumference of the cylinder head 11 to seal the gap between the inner circumference of the cylinder head 11 and the outer circumference of the outer rod portion 31 to prevent leakage of hydraulic oil to the outside.

[0030] The second rod assembly 40, inserted into the first rod assembly 30, is defined in its most retracted position by the abutment of the first inner piston portion 42 with the first retaining ring 35 attached to the first rod assembly 30, while its most extended position is defined by the abutment of the first inner piston portion 42 with the first support portion 33. Furthermore, the first retaining ring 35 restricts movement of the second rod assembly 40 in the retracting direction and prevents the first rod assembly 30 from being separated from the cylinder housing 10 when the hydraulic cylinder 10 is retracted.

[0031] Furthermore, a sealing member (not shown) is provided on the inner peripheral surface of the first support portion 33 to seal the gap between the inner peripheral surface of the first support portion 33 and the outer peripheral surface of the first inner rod portion 41 in order to prevent leakage of the hydraulic oil to the outside.

[0032] The third rod assembly 50, inserted into the second rod assembly 40, is defined in its most retracted position by the abutment of the second inner piston portion 52 with the second retaining ring 45 attached to the second rod assembly 40, while its most extended position is defined by the abutment of the second inner piston portion 52 with the second support portion 43. Furthermore, the second retaining ring 45 restricts movement of the third rod assembly 50 in the retracting direction and prevents the second rod assembly 40 from being separated from the cylinder housing 10 when the hydraulic cylinder 100 is retracted.

[0033] To prevent leakage of hydraulic oil, a sealing member (not shown) is provided on the inner circumferential surface of the second support portion 43 to seal the gap between the inner circumferential surface of the second support portion 43 and the outer circumferential surface of the second inner rod portion 51. Furthermore, an annular recess 43a is formed on the inner circumferential surface of the second support portion 43. When the third rod assembly 50 is at its most extended position, the opening of a communication hole 51b (described later) formed in the second inner rod portion 51 faces the annular recess 43a. Furthermore, the annular recess 43a is formed so as to open into the second inner rod chamber 4 (described later).

[0034] In addition, in the cylinder 10 of the above-mentioned shape into which the first rod assembly 30, the second rod assembly 40 and the third rod assembly 50 are inserted, there are formed a rod side chamber 2 defined by the cylinder 10, the cylinder head 11, the outer rod portion 31 and the outer piston portion 32; a first inner rod side chamber 3 defined by the outer rod portion 31, the first support portion 33, the first inner rod portion 41 and the first inner piston portion 42; a second inner rod side chamber 4 defined by the first inner rod portion 41, the second support portion 43, the second inner rod portion 51 and the second inner piston portion 52; and an opposite-rod side chamber 5 defined by the cylinder 10, the outer piston portion 32, the first inner piston portion 42 and the second inner piston portion 52.

[0035] A first sealing member 34 is provided on the outer peripheral surface 32 a of the outer piston portion 32 of the first rod assembly 30 , and the communication between the rod side chamber 2 and the opposite rod side chamber 5 via the gap between the outer peripheral surface 32 a of the outer piston portion 32 and the inner peripheral surface 10 a of the cylinder 10 is blocked by the first sealing member 34 .

[0036] Furthermore, a plurality of supply and discharge ports 32 b for supplying and discharging hydraulic oil to and from the rod side chamber 2 are formed in the outer piston portion 32 of the first rod assembly 30 so as to penetrate in the radial direction.

[0037] A second sealing component 44 is provided on the outer peripheral surface 42a of the first inner piston portion 42 of the second rod assembly 40, and the communication between the first inner rod side chamber 3 and the rod opposite side chamber 5 through the gap between the outer peripheral surface 42a of the first inner piston portion 42 and the inner peripheral surface 30a of the first rod assembly 30 is blocked by the second sealing component 44.

[0038] Furthermore, a plurality of inner supply and discharge ports 42 b for supplying and discharging hydraulic oil to and from the first inner rod side chamber 3 are formed in the first inner piston portion 42 of the second rod assembly 40 so as to penetrate in the radial direction.

[0039] A third sealing component 54 is provided on the outer peripheral surface 52a of the second inner piston portion 52 of the third rod assembly 50, and the communication between the second inner rod side chamber 4 and the rod opposite side chamber 5 through the gap between the outer peripheral surface 52a of the second inner piston portion 52 and the inner peripheral surface 40a of the second rod assembly 40 is blocked by the third sealing component 54.

[0040] The second inner rod portion 51 of the third rod assembly 50 is formed with a supply and discharge passage 51a for supplying and discharging hydraulic oil to and from the hydraulic cylinder 100 and connected to an external device (not shown), and a communication hole 51b that connects the supply and discharge passage 51a with the second inner rod-side chamber 4. Furthermore, a connecting passage 51c is formed in the second inner rod portion 51 to connect the passage 64 formed in the second mounting portion 62 with the supply and discharge passage 51a.

[0041] The supply and exhaust passage 51a communicates with the second inner rod side chamber 4 via the communication hole 51b, communicates with the first inner rod side chamber 3 via the inner supply and exhaust port 42b and the communication hole 51b, and communicates with the rod side chamber 2 via the supply and exhaust port 32b, the inner supply and exhaust port 42b, and the communication hole 51b.

[0042] That is, the supply of hydraulic oil to the rod side chamber 2 , the first inner rod side chamber 3 , and the second inner rod side chamber 4 , and the discharge of hydraulic oil from the rod side chamber 2 , the first inner rod side chamber 3 , and the second inner rod side chamber 4 are implemented through the supply and discharge passage 51 a formed in the second inner rod portion 51 .

[0043] Furthermore, the second inner rod portion 51 is provided with a pipe-like supply / discharge pipe 55, which supplies and discharges hydraulic oil to and from the hydraulic cylinder 100 and connects to external devices. The supply / discharge pipe 55 is assembled to the second inner rod portion 51 with one end facing the opposite-rod chamber 5. Specifically, the supply / discharge pipe 55 is joined to the second inner rod portion 51 by axially penetrating the supply / discharge passage 51a. Furthermore, the second inner rod portion 51 is provided with a connecting passage 51d that connects the passage 63 formed in the second mounting portion 62 to the other end of the supply / discharge pipe 55.

[0044] Since the supply and discharge pipe 55 is provided with one end thereof opening in the opposite-rod-side chamber 5 , the hydraulic oil is supplied to and discharged from the opposite-rod-side chamber 5 via the supply and discharge pipe 55 .

[0045] Next, refer to Figures 1 to 4 The operation of the hydraulic cylinder 100 will be described. Hereinafter, a case will be described where the hydraulic cylinder 100 is mounted on a driven device with the first mounting portion 61 positioned vertically upward and the second mounting portion 62 positioned vertically downward.

[0046] When the hydraulic cylinder 100 performs extension work, working oil is supplied to the rod opposite side chamber 5 from a hydraulic source such as a pump not shown in the figure through the supply and discharge pipe 55, and the working oil in the rod side chamber 2, the first inner rod side chamber 3 and the second inner rod side chamber 4 is discharged to the fluid tank not shown in the figure through the supply and discharge passage 51a.

[0047] When the hydraulic cylinder 100 Figure 1 When the hydraulic cylinder 100 is extended from the most contracted state shown, hydraulic oil is supplied to the rod-opposite chamber 5 via the supply and discharge pipe 55. Here, the pressure-receiving area of the rod-opposite chamber 5 that receives pressure is maximized when the first rod assembly 30 is extended, and minimized when the third rod assembly 50 is extended. Therefore, when the hydraulic cylinder 100 is extended from the most contracted state, first, the cylinder tube 10 moves relative to the first rod assembly 30. Specifically, as Figure 2 As shown, the cylinder 10 is upward ( Figure 2 Furthermore, since the recessed portion 10b formed in the bottom portion of the cylinder tube 10 has an inner diameter larger than that of the outer piston portion 32 of the first rod assembly 30, the pressure of the hydraulic oil guided to the opposite-rod side chamber 5 acts on the outer piston portion 32 via the recessed portion 10b.

[0048] When the cylinder 10 moves relative to the first rod assembly 30 , the hydraulic oil in the rod side chamber 2 is guided to the supply and discharge passage 51 a through the supply and discharge port 32 b , the inner supply and discharge port 42 b , and the communication hole 51 b , and is discharged to the outside.

[0049] In addition, if Figure 2 As shown, when the cylinder 10 reaches the most extended state relative to the first rod assembly 30, that is, when the cylinder 10 moves upward until the cylinder head 11 contacts the outer piston portion 32 of the first rod assembly 30, the cylinder 10 and the first rod assembly 30 are then moved relative to the second rod assembly 40 by the pressure in the opposite-rod side chamber 5. Specifically, Figure 3 As shown, the cylinder 10 and the first rod assembly 30 are upward relative to the second rod assembly 40 ( Figure 3 upper middle side) moves.

[0050] When the first rod assembly 30 moves relative to the second rod assembly 40 , the hydraulic oil in the first inner rod side chamber 3 is guided to the supply and discharge passage 51 a through the inner supply and discharge port 42 b and the communication hole 51 b and discharged to the outside.

[0051] In addition, if Figure 3 As shown, when the first rod assembly 30 reaches the most extended state relative to the second rod assembly 40, that is, when the cylinder 10 and the first rod assembly 30 move upward until the first support portion 33 of the first rod assembly 30 abuts the first inner piston portion 42 of the second rod assembly 40, the cylinder 10, the first rod assembly 30, and the second rod assembly 40 then move relative to the third rod assembly 50 due to the pressure in the opposite-rod side chamber 5. Specifically, as Figure 4 As shown, the cylinder 10, the first rod assembly 30, and the second rod assembly 40 are upward relative to the third rod assembly 50 ( Figure 4 upper middle side) moves.

[0052] When the second rod assembly 40 moves relative to the third rod assembly 50 , the hydraulic oil in the second inner rod side chamber 4 is guided to the supply and discharge passage 51 a through the communication hole 51 b and is discharged to the outside.

[0053] In addition, if Figure 4 As shown, when the second rod assembly 40 is in the most extended state relative to the third rod assembly 50, that is, when the cylinder tube 10, the first rod assembly 30, and the second rod assembly 40 move upward until the second support portion 43 of the second rod assembly 40 abuts the second inner piston portion 52 of the third rod assembly 50, the hydraulic cylinder 100 is in the most extended state.

[0054] On the other hand, when the hydraulic cylinder 100 is contracting, hydraulic oil is supplied from the hydraulic source to the rod-side chamber 2, the first inner rod-side chamber 3, and the second inner rod-side chamber 4 via the supply and discharge passage 51a. The hydraulic oil in the counter-rod-side chamber 5 is then discharged to the fluid tank via the supply and discharge pipe 55. Alternatively, the hydraulic cylinder 100 can be contracted by the deadweight of the driven equipment connected to the first mounting portion 61. In this case, hydraulic oil does not need to be supplied to the rod-side chamber 2, the first inner rod-side chamber 3, and the second inner rod-side chamber 4. Instead, hydraulic oil is drawn from the fluid tank into the rod-side chamber 2, the first inner rod-side chamber 3, and the second inner rod-side chamber 4.

[0055] When the hydraulic cylinder 100 is retracted from its most extended state, first, the cylinder tube 10, the first rod assembly 30, and the second rod assembly 40 are retracted. Figure 4 The status shown is Figure 3 In the state shown, the third rod assembly 50 moves relative to the cylinder 10 and the first rod assembly 30. Figure 3 The status shown is Figure 2 In the state shown, relative movement is made relative to the second rod assembly 40. In addition, the cylinder 10 is further moved from Figure 2 The status shown is Figure 1 In the state shown, the hydraulic cylinder 100 is in the most contracted state due to the relative movement with respect to the first rod assembly 30 .

[0056] As shown in FIG5 , the first inner piston portion 42 of the second rod assembly 40 of the hydraulic cylinder 100 structured as described above is provided with a receiving recess 42 c that receives the inner diameter side of the first snap ring 35 when the second rod assembly 40 is in the most contracted state. The receiving recess 42 c limits the deformation of the first snap ring 35 in the radial direction inward and is configured so that when the second rod assembly 40 contracts, the first inner piston portion 42 abuts against the first snap ring 35, thereby preventing the first snap ring 35 from being detached from the first rod assembly 30. Figure 5A In the diagram, the hydraulic cylinder 100 is shown in the most retracted state. Figure 1 , a diagram showing an enlarged portion of the portion surrounded by the dotted line indicated by the arrow A.

[0057] In addition, if Figure 5A As shown, when the first retaining ring 35 is accommodated in the receiving recess 42c and the first retaining ring 35 is in contact with the first inner piston portion 42, a gap G1 defined by the outer peripheral surface 42a of the first inner piston portion 42, the inner peripheral surface 30a of the first rod assembly 30 and the first retaining ring 35 is formed on the side opposite to the rod opposite side chamber 5 separated by the first retaining ring 35.

[0058] Here, when the hydraulic cylinder 100 of the above-mentioned structure is in the most contracted state and the working oil is not supplied or discharged to the rod side chamber 2 and the opposite rod side chamber 5, if an external force suddenly acts to forcibly extend the hydraulic cylinder 100, the working oil is not supplied to the opposite rod side chamber 5 whose volume has expanded, so the pressure in the chamber decreases. On the other hand, the working oil is not discharged from the rod side chamber 2 whose volume has decreased, so the pressure in the chamber increases.

[0059] When the pressure in the rod side chamber 2 increases in this manner, the first rod assembly 30 and the cylinder tube 10 are displaced in the extension direction, and the first rod assembly 30 is displaced relative to the second rod assembly 40. Figure 5B As shown, the first snap ring 35 provided on the first rod assembly 30 is separated from the receiving recess 42 c of the first inner piston portion 42 .

[0060] like Figure 5B As shown, when the first snap ring 35 is instantly separated from the receiving recess 42c, the volume of the gap G defined by the outer peripheral surface 42a of the first inner piston portion 42, the inner peripheral surface 30a of the first rod assembly 30 and the first snap ring 35 increases rapidly. Therefore, the pressure of the gap G1 is lower than that of the opposite-rod side chamber 5, thereby generating Figure 5B The flow of the hydraulic oil from the anti-rod side chamber 5 toward the gap G1 is shown by arrow F in FIG.

[0061] Furthermore, the hydraulic oil flowing from the anti-rod side chamber 5 toward the gap G1 passes through the minute gap between the radially inner side of the first snap ring 35 and the accommodating recess 42 c . Therefore, the pressure on the inner diameter side of the first snap ring 35 is significantly reduced by the so-called Venturi effect.

[0062] Thus, when the pressure in the area facing the inner diameter side of the first snap ring 35 decreases, a fluid force that acts in the direction of reducing the diameter of the first snap ring 35 in a manner that overcomes the elastic force of the first snap ring 35 that acts in the direction of expanding the diameter is generated on the inner diameter side of the first snap ring 35, thereby reducing the outer diameter of the first snap ring 35. As a result, Figure 5C As shown, the outer diameter side of the first snap ring 35 is separated from the annular recess 30 b , and the first snap ring 35 may be detached from the first rod assembly 30 .

[0063] In contrast, in the hydraulic cylinder 100 of this embodiment, as shown in FIG. Figure 6 As shown, through holes 32 c and 42 d serving as a communication path connecting the gap G1 and the rod-opposite side chamber 5 are provided in the first rod assembly 30 and the second rod assembly 40, respectively. The gap G1 is defined by the outer peripheral surface 42 a of the first inner piston portion 42, the inner peripheral surface 30 a of the first rod assembly 30, and the first retaining ring 35.

[0064] The through hole 32 c provided as a communication passage in the first rod assembly 30 is a cut hole formed so that one end opens in the opposite-rod side chamber 5 and the other end opens in the gap G1 , and a plurality of through holes 32 c are provided in the outer piston portion 32 of the first rod assembly 30 at intervals in the circumferential direction.

[0065] The through hole 42 d provided as a communication passage in the second rod assembly 40 is a cut hole formed in a manner such that one end opens in the rod-opposite side chamber 5 and the other end opens in the gap G1, similar to the through hole 32 c. A plurality of through holes 42 d are provided in the first inner piston portion 42 of the second rod assembly 40 at intervals in the circumferential direction.

[0066] In this way, the gap G1 and the rod opposite side chamber 5 are connected through the through holes 32c and 42d. As described above, even if the volume of the gap G1 increases rapidly, the pressure difference between the gap G1 and the rod opposite side chamber 5 is suppressed from increasing. Therefore, the flow of working oil from the rod opposite side chamber 5 toward the gap G1 through the radial inner side of the first retaining ring 35 is reduced.

[0067] In addition, the working oil flows into the gap G1 from the rod opposite side chamber 5 not only through the gap between the radial inner side of the first retaining ring 35 and the receiving recess 42c, but also through the through holes 32c and 42d. Therefore, the pressure drop in the gap G1 is alleviated, and the extreme pressure drop in the area facing the inner diameter side of the first retaining ring 35 is suppressed.

[0068] This suppresses the generation of a fluid force on the inner diameter side of the first retaining ring 35 that acts in the direction of reducing the diameter of the first retaining ring 35 in a manner that overcomes the elastic force of the first retaining ring 35 that acts in the direction of expanding the diameter. As a result, it is possible to prevent the first retaining ring 35 from detaching from the first rod assembly 30.

[0069] In addition, although the through holes 32 c and 42 d are provided in the first rod assembly 30 and the second rod assembly 40 , respectively, they may be provided in only one of the first rod assembly 30 and the second rod assembly 40 .

[0070] In addition, in order to prevent not only the first snap ring 35 from being detached, but also the second snap ring 45 whose outer diameter side is accommodated in the second annular recess and whose inner diameter side is accommodated in the second accommodation recess 52b is detached from the second rod assembly 40, as shown in FIG. Figure 6 As shown, a through hole 52c serving as a communication path for communicating the second gap G2 with the rod opposite side chamber 5 can also be provided in the third rod assembly 50. The second gap G2 is defined by the outer peripheral surface 52a of the second inner piston portion 52, the inner peripheral surface 40a of the second rod assembly 40 and the second retaining ring 45.

[0071] The through-hole 52c provided in the third rod assembly 50 as a communication passage is a cut hole formed with one end opening into the opposite-rod-side chamber 5 and the other end opening into the second gap G2. A plurality of through-holes 52c are provided at intervals in the circumferential direction on the second inner piston portion 52 of the third rod assembly 50. Furthermore, through-holes serving as a communication passage that connect the second gap G2 with the opposite-rod-side chamber 5 may be formed not only in the third rod assembly 50 but also in the second rod assembly 40.

[0072] According to the above embodiment, the following effects are achieved.

[0073] In the hydraulic cylinder 100 of the above structure, through holes 32c, 42d that connect the gap G1 and the rod-opposite side chamber 5 are provided in at least one of the first rod assembly 30 and the second rod assembly 40. The gap G1 is defined by the outer peripheral surface 42a of the first inner piston portion 42, the inner peripheral surface 30a of the first rod assembly 30, and the first retaining ring 35.

[0074] In this way, by connecting the gap G1 and the opposite-rod-side chamber 5 through the through-holes 32c and 42d, when the hydraulic cylinder 100 is in the most contracted state, an external force that forcibly extends the hydraulic cylinder 100 acts rapidly, the first rod assembly 30 is displaced in the extension direction together with the cylinder tube 10, and the first retaining ring 35 is instantly separated from the accommodating recess 42c. Even if the volume of the gap G1 increases rapidly, the pressure difference between the gap G1 and the opposite-rod-side chamber 5 is suppressed from increasing.

[0075] This mitigates the pressure drop within the gap G1 and prevents an extreme pressure drop in the area facing the inner diameter side of the first snap ring 35. Consequently, the fluid force acting on the inner diameter side of the first snap ring 35 in a direction that reduces its diameter, overcoming the elastic force of the first snap ring 35 acting in the direction of expansion, is suppressed. Consequently, the first snap ring 35 is prevented from being detached from the first rod assembly 30.

[0076] Furthermore, the following modifications are also within the scope of the present invention, and it is possible to combine the configurations shown in the modifications with the configurations described in the above embodiment, or to combine the configurations described in the following different modifications with each other.

[0077] In the above embodiment, the communication path is a through hole 32c, 42d having one end opening in the opposite-rod side chamber 5 and the other end opening in the gap G1. Figure 7As shown in the first modified example, the notch groove 32d is formed by cutting the inner peripheral surface 30a of the first rod assembly 30 in the axial direction, and the notch groove 42e is formed by cutting the outer peripheral surface 42a of the first inner piston portion 42 in the axial direction. Figure 7 A diagram showing a modified example of the above embodiment shows a diagram corresponding to Figure 6 Figure of part of .

[0078] The notch groove 32d provided as a communication path in the first rod assembly 30 has a predetermined width in the circumferential direction of the outer diameter piston portion 32 and is formed along the axial direction so as to cross the annular recessed portion 30b from the end surface of the first rod assembly 30 facing the opposite rod side chamber 5. In addition, a plurality of notch grooves 32d are provided at intervals in the circumferential direction on the outer piston portion 32 of the first rod assembly 30. In addition, the depth of the notch groove 32d from the inner circumferential surface 30a of the first rod assembly 30 is formed to be deeper than the annular recessed portion 30b. In this way, Figure 7 In the cross-sectional view shown, the cutout groove 32 d is formed so as to surround the annular recess 30 b , so that the opposite-rod side chamber 5 and the gap G1 are always in communication via the cutout groove 32 d .

[0079] In addition, the notch groove 32d only needs to be formed so as to enable communication between the rod-opposite side chamber 5 and the gap G1, and does not need to be formed so as to reach the end surface of the first rod assembly 30 facing the rod-opposite side chamber 5 in the axial direction. However, in order to facilitate workability, it is preferably formed so as to open on the end surface of the first rod assembly 30 as described above.

[0080] The notch groove 42e provided as a communication passage in the second rod assembly 40 is a groove having a predetermined width in the circumferential direction of the first inner piston portion 42 and formed along the axial direction so as to cross the receiving recess 42c from the end surface of the second rod assembly 40 facing the opposite rod side chamber 5. In addition, a plurality of notch grooves 42e are provided in the first inner piston portion 42 of the second rod assembly 40 at intervals in the circumferential direction. In addition, the notch grooves 42e are opened in the radial direction on the outer circumferential surface 42a of the first inner piston portion 42 and the inner circumferential surface 40a of the second rod assembly 40. In this way, Figure 7 In the cross-sectional view shown, the notched groove 42e is formed so as to surround the accommodating recess 42c, thereby ensuring that the opposite-rod-side chamber 5 and the gap G1 are always connected via the notched groove 42e. Furthermore, the notched groove 42e only needs to be formed to allow the opposite-rod-side chamber 5 and the gap G1 to communicate, and does not need to be formed to radially reach the inner circumferential surface 40a of the second rod assembly 40.

[0081] Thus, also in the first modification, the gap G1 and the anti-rod side chamber 5 communicate via the notched grooves 32 d and 42 e . Therefore, similar to the above-described embodiment, the first snap ring 35 can be prevented from being detached from the first rod assembly 30 .

[0082] In addition, even in the first modified example, in order to prevent not only the first retaining ring 35 from being detached but also the second retaining ring 45 provided on the second rod assembly 40 from being detached, a notch groove 52d serving as a communication path for communicating the second gap G2 with the rod opposite side chamber 5 may be provided on the third rod assembly 50.

[0083] The notched groove 52d provided in the third rod assembly 50 as a communication passage has a predetermined width in the circumferential direction of the second inner piston portion 52 and is formed along the axial direction from the end surface of the third rod assembly 50 facing the opposite-rod-side chamber 5 so as to extend beyond the second accommodating recess 52b. A plurality of notched grooves 52d are provided at intervals in the circumferential direction on the second inner piston portion 52 of the third rod assembly 50. Furthermore, notched grooves for communicating the second gap G2 with the opposite-rod-side chamber 5 may be formed not only in the third rod assembly 50 but also in the second rod assembly 40.

[0084] In addition, in the above embodiment, the communication path is the through-holes 32c and 42d newly formed with respect to the first rod assembly 30. Figure 8 As shown in the second modified example, the communication path may also utilize the threaded hole 32e for the clamp to be screwed in when the first snap ring 35 is removed from the first rod assembly 30, and the threaded hole 42f for the clamp to be screwed in when the second snap ring 45 is removed from the second rod assembly 40. Figure 8 A diagram showing a modified example of the above embodiment shows a diagram corresponding to Figure 6 Figure of part of .

[0085] The threaded hole 32e, formed as a communication path in the first rod assembly 30, is a female threaded hole radially extending through the first rod assembly 30, with one end opening on the outer circumferential surface 32a of the outer piston portion 32 and the other end opening on the annular recess 30b formed on the inner circumferential surface 30a of the first rod assembly 30. Multiple threads are provided circumferentially spaced apart on the outer piston portion 32 of the first rod assembly 30. Furthermore, the inner diameter of the female threads of the threaded holes 32e is set larger than the wire diameter of the first snap ring 35, that is, the axial width of the annular recess 30b. Therefore, the open end of the threaded hole 32e, which opens on the inner circumferential surface 30a of the first rod assembly 30, is divided into two by the first snap ring 35, which is housed in the annular recess 30b. One end opens into the opposite-rod-side chamber 5, and the other end opens into the gap G1. Consequently, the opposite-rod-side chamber 5 and the gap G1 are always connected via the interior of the threaded hole 32e.

[0086] The threaded hole 42f, formed as a communication passage in the second rod assembly 40, is a female threaded hole radially extending through the second rod assembly 40, with one end opening on the outer circumferential surface 42a of the first inner piston portion 42 and the other end opening in the second annular recess 40b formed in the inner circumferential surface 40a of the second rod assembly 40. Multiple threads are provided at intervals in the circumferential direction on the first inner piston portion 42 of the second rod assembly 40. Furthermore, the inner diameter of the female threads of the threaded holes 42f is set larger than the wire diameter of the second retaining ring 45, that is, the axial width of the second annular recess 40b. Therefore, the open end of the threaded hole 42f, which opens on the inner circumferential surface 40a of the second rod assembly 40, is divided into two by the second retaining ring 45 housed in the second annular recess 40b. One end opens into the opposite-rod-side chamber 5, and the other end opens into the second gap G2. Furthermore, since the threaded hole 42f is also opened in the outer peripheral surface 42a of the first inner piston portion 42 defining the gap G1, the anti-rod side chamber 5 and the gap G1 are always in communication via the interior of the threaded hole 42f.

[0087] In this manner, even in the second modified example, the gap G1 and the opposite-rod side chamber 5 are connected via the threaded holes 32e and 42f. Therefore, similar to the above-described embodiment, the first snap ring 35 can be prevented from being detached from the first rod assembly 30. Furthermore, by utilizing the holes used when the snap rings 35 and 45 are removed, such as the threaded holes 32e and 42f, as a communication path, the manufacturing cost of the hydraulic cylinder 100 can be reduced compared to forming a separate communication path.

[0088] In the second modification, the opposite-rod chamber 5 and the second gap G2 are always connected via the inside of the threaded hole 42f. Therefore, not only the first snap ring 35 but also the second snap ring 45 provided on the second rod assembly 40 can be prevented from detaching.

[0089] In the second modification, the holes formed as the communication passages are the threaded holes 32 e and 42 f . Alternatively, the communication passages may be simple through holes having an inner diameter large enough to allow communication between the gap G1 and the anti-rod side chamber 5 .

[0090] Specifically, when a through-hole is provided in the first rod assembly 30 instead of the threaded hole 32e, the inner diameter of the through-hole is set to be larger than the wire diameter of the first snap ring 35, that is, the width of the annular recessed portion 30b in the axial direction. Furthermore, when a through-hole is provided in the second rod assembly 40 instead of the threaded hole 42f, the inner diameter of the through-hole is set to be larger than the wire diameter of the second snap ring 45, that is, the width of the second annular recessed portion 40b in the axial direction.

[0091] If one end opens on the outer peripheral surface 32a and the other end opens on the annular recess 30b, the direction in which the through hole is formed is free, but it is preferred that when the through hole is used as an insertion hole for a clamp for removing each retaining ring 35, 45, the through hole is orthogonal to the axial direction and is formed along the radial direction.

[0092] In addition, in the above embodiment, the communication path provided in the first rod assembly 30 is a single through hole 32c formed in the first rod assembly 30. Alternatively, the communication path may be formed as follows. Figure 9 As shown in the third modified example, it is composed of a plurality of communication paths (32f, 32g) formed in the first rod assembly 30. Figure 9 A diagram showing a modified example of the above embodiment shows a diagram corresponding to Figure 6 Figure of part of .

[0093] The through-hole 32f provided in the first rod assembly 30 as a communication passage is a cut hole formed with one end opening at the outer circumferential surface 32a of the outer piston portion 32 and the other end opening at the gap G1. A plurality of through-holes 32f are provided at intervals in the circumferential direction on the outer piston portion 32 of the first rod assembly 30. Furthermore, the notched groove 32g provided in the first rod assembly 30 as a communication passage is a groove in the end surface of the first rod assembly 30 facing the anti-rod chamber 5. The notched groove 32g is formed along the radial direction of the outer piston portion 32 to reach the outer circumferential surface 32a of the outer piston portion 32. A plurality of notched grooves 32g are provided at intervals in the circumferential direction on the outer piston portion 32 of the first rod assembly 30.

[0094] The through-hole 32f and the notched groove 32g thus formed form a communication path that constantly connects the opposite-rod-side chamber 5 and the gap G1 via the third gap G3 defined by the outer circumferential surface 32a of the outer piston portion 32 and the inner circumferential surface 10a of the cylinder tube 10. Thus, even in the third modified example, the gap G1 and the opposite-rod-side chamber 5 are connected via the through-hole 32f and the notched groove 32g. Therefore, similar to the above-described embodiment, the first retaining ring 35 can be prevented from being detached from the first rod assembly 30.

[0095] In the above embodiment, the communication path provided in the first rod assembly 30 always communicates with the rod opposite side chamber 5 and the gap G1. Figure 10 As shown in the fourth modified example, when the cylinder 10 slightly moves relative to the first rod assembly 30, that is, when the end surface 30c of the first rod assembly 30 abutting against the step 10c formed between the inner circumferential surface 10a of the cylinder 10 and the recess 10b slightly separates from the step 10c, the opposite-rod-side chamber 5 and the gap G1 are connected. Figure 10 A diagram showing a modified example of the above embodiment shows a diagram corresponding to Figure 6 Figure of part of .

[0096] The through hole 32h provided in the first rod assembly 30 as a communication path is a cut hole formed so that one end opens at the outer peripheral surface 32a of the outer piston portion 32 and the other end opens at the gap G1. A plurality of through holes 32h are provided in the outer piston portion 32 of the first rod assembly 30 so as to be spaced apart in the circumferential direction.

[0097] When the cylinder 10 moves relative to the first rod assembly 30 and the end face 30c of the first rod assembly 30 separates from the step 10c, the through-hole 32h thus formed connects the gap G1 with the third gap G3, a fluid chamber that communicates with the opposite-rod-side chamber 5 via the gap formed between the end face 30c and the step 10c. Specifically, the through-hole 32h connects the opposite-rod-side chamber 5 with the gap G1 via the gap formed between the end face 30c and the step 10c and the third gap G3 defined by the outer circumferential surface 32a of the outer piston portion 32 and the inner circumferential surface 10a of the cylinder 10.

[0098] Thus, also in the fourth modification, the gap G1 and the anti-rod side chamber 5 communicate via the through hole 32 h . Therefore, similar to the above-described embodiment, the first snap ring 35 can be prevented from being detached from the first rod assembly 30 .

[0099] In the above embodiment, the cross-sectional shape of each snap ring 35, 45 is circular. However, the cross-sectional shape of each snap ring 35, 45 is not limited to circular, and may be elliptical or rectangular.

[0100] In the above embodiment, the hydraulic cylinder 100 is a three-stage hydraulic cylinder 100 in which three rod members (a first rod assembly 30, a second rod assembly 40, and a third rod assembly 50) are radially overlapped within the cylinder tube 10. Alternatively, the hydraulic cylinder 100 may be a two-stage hydraulic cylinder in which two rod members are radially overlapped within the cylinder tube 10, or may be a hydraulic cylinder in which four or more rod members are radially overlapped.

[0101] Hereinafter, the configuration, function, and effects of the embodiments of the present invention will be summarized and described.

[0102] The hydraulic cylinder 100 includes: a cylinder tube 10; a cylindrical first rod assembly 30, an outer piston portion 32 provided at the end thereof, the outer piston portion 32 sliding along the inner peripheral surface 10a of the cylinder tube 10 and dividing the cylinder tube 10 into a rod side chamber 2 and an opposite rod side chamber 5; a second rod assembly 40, an inner piston portion 42 provided at the end thereof sliding along the inner peripheral surface 30a of the first rod assembly 30; a retaining ring 35, the outer diameter side of which is received in an annular recess 30b formed on the inner peripheral surface 30a of the first rod assembly 30 and restricting the movement of the second rod assembly 40 in the contraction direction, and a retaining ring 35 provided on the first inner piston portion 42 when the second rod assembly 40 contracts. The accommodating recess 42c for accommodating the first inner piston portion 42 is provided with a communication passage (32c, 32d, 32e, 32f, 32g, 32h, 42d, 42e, 42f) on at least one of the first rod assembly 30 and the second rod assembly 40. The communication passage communicates the gap G1 with the opposite-rod-side chamber 5 or the third gap G3. The gap G1 is defined by the snap ring 35, the outer peripheral surface 42a of the first inner piston portion 42, and the inner peripheral surface 30a of the first rod assembly 30 when the snap ring 35 is accommodated in the accommodating recess 42c and abuts against the first inner piston portion 42. The third gap G3 communicates with the opposite-rod-side chamber 5 when the cylinder 10 moves relative to the first rod assembly 30.

[0103] In this structure, communication paths (32c, 32d, 32e, 32f, 32g, 32h, 42d, 42e, 42f) that connect the gap G1 defined by the outer circumferential surface 42a of the first inner piston portion 42, the inner circumferential surface 30a of the first rod assembly 30, and the first retaining ring 35, and the opposite-rod-side chamber 5 or the third gap G3 that communicates with the opposite-rod-side chamber 5 are provided in at least one of the first rod assembly 30 and the second rod assembly 40.

[0104] In this way, the gap G1 is communicated with the opposite-rod-side chamber 5 via the communication passages (32c, 32d, 32e, 32f, 32g, 42d, 42e, 42f), or the third gap G3 is communicated with the gap G1 via the communication passage (32h). The third gap G3 is communicated with the opposite-rod-side chamber 5 by the relative movement of the cylinder tube 10 with respect to the first rod assembly 30. Therefore, when the hydraulic cylinder 100 is in the most contracted state, an external force that forcibly extends the hydraulic cylinder 100 acts rapidly, the first rod assembly 30 is displaced in the extension direction together with the cylinder tube 10, and the first snap ring 35 is instantly separated from the accommodating recess 42c. Therefore, even if the volume of the gap G1 increases rapidly, the pressure difference between the gap G1 and the opposite-rod-side chamber 5 is suppressed from increasing.

[0105] This mitigates the pressure drop within the gap G1 and prevents an extreme pressure drop in the area facing the inner diameter side of the first snap ring 35. Consequently, the fluid force acting on the inner diameter side of the first snap ring 35 in a direction that reduces its diameter, overcoming the elastic force of the first snap ring 35 acting in the direction of expansion, is suppressed. Consequently, the first snap ring 35 is prevented from being detached from the first rod assembly 30.

[0106] The communication passage is a through hole 32 c or 42 d formed in at least one of the first rod assembly 30 and the second rod assembly 40 . One end of the through hole 32 c or 42 d opens in the anti-rod side chamber 5 , and the other end opens in the gap G1 .

[0107] In this structure, the communication path is formed by through-holes 32c and 42d, each of which opens at one end into the opposite-rod-side chamber 5 and at the other end into the gap G1. By using through-holes 32c and 42d, which can be easily formed in the first rod assembly 30 and the second rod assembly 40, as the communication path connecting the gap G1 with the opposite-rod-side chamber 5, the first snap ring 35 can be prevented from being detached from the first rod assembly 30 with little increase in the manufacturing cost of the hydraulic cylinder 100.

[0108] The communication passage is formed as notched grooves 32 d and 42 e cut along the axial direction in at least one of the inner peripheral surface 30 a of the first rod assembly 30 and the outer peripheral surface 42 a of the first inner piston portion 42 .

[0109] In this structure, the communication path is formed by notched grooves 32d and 42e cut along the axial direction in the inner circumferential surface 30a of the first rod assembly 30 and the outer circumferential surface 42a of the first inner piston portion 42. By utilizing the through-holes 32d and 42e, which can be easily formed in the first rod assembly 30 and the second rod assembly 40, as the communication path connecting the gap G1 with the opposite-rod-side chamber 5, the first snap ring 35 can be prevented from being detached from the first rod assembly 30 with minimal increase in the manufacturing cost of the hydraulic cylinder 100.

[0110] The notched grooves 32 d and 42 e are formed along the axial direction from at least one of the end surface of the first rod assembly 30 and the end surface of the second rod assembly 40 facing the anti-rod side chamber 5 .

[0111] In this structure, the notched grooves 32d and 42e are formed along the axial direction from the end surfaces of the first rod assembly 30 and the second rod assembly 40 that face the opposite-rod-side chamber 5. By forming the notched grooves 32d and 42e along the axial direction from the end surfaces of the first rod assembly 30 and the second rod assembly 40 that face the opposite-rod-side chamber 5, a communication path that allows the gap G1 to communicate with the opposite-rod-side chamber 5 can be easily formed.

[0112] The communication passage is a threaded hole 32e having one end opened at the outer peripheral surface 32a of the outer piston portion 32 and the other end opened at the annular recess 30b. The inner diameter of the female thread of the threaded hole 32e is larger than the wire diameter of the snap ring 35.

[0113] In this structure, the communication path is a threaded hole 32e, one end of which opens into the outer peripheral surface 32a of the outer piston portion 32 and the other end of which opens into the annular recess 30b. By using the threaded hole 32e as the communication path, into which the clamp is screwed when the snap ring 35 is removed from the annular recess 30b, the first snap ring 35 can be prevented from being detached from the first rod assembly 30 without increasing the manufacturing cost of the hydraulic cylinder 100.

[0114] In addition, the hydraulic cylinder 100 further includes: a third rod assembly 50, an end of which is provided with a second inner piston portion 52 that slides along the inner circumferential surface 40a of the second rod assembly 40; a second snap ring 45, the outer diameter side of which is accommodated in the second annular recess 40b formed on the inner circumferential surface 40a of the second rod assembly 40, and restricts the movement of the third rod assembly 50 in the contraction direction, and the communication path is a threaded hole 42f with one end opening on the outer circumferential surface 42a of the first inner piston portion 42 and the other end opening in the second annular recess 40b, and the inner diameter of the female thread of the threaded hole 42f is larger than the wire diameter of the second snap ring 45.

[0115] In this structure, the communication path is a threaded hole 42f, one end of which opens into the outer peripheral surface 42a of the first inner piston portion 42 and the other end of which opens into the second annular recess 40b. By using the threaded hole 42f as the communication path, into which a jig is screwed when the second snap ring 45 is removed from the second annular recess 40b, the first snap ring 35 can be prevented from being detached from the first rod assembly 30 without increasing the manufacturing cost of the hydraulic cylinder 100.

[0116] While the embodiments of the present invention have been described above, the above embodiments merely represent a part of application examples of the present invention and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0117] This application claims priority based on Japanese Patent Application No. 2020-141111 filed with the Japan Patent Office on August 24, 2020, and all the contents of that application are incorporated into this specification by reference.

Claims

1. A multi-stage fluid pressure cylinder, wherein: have: Cylinder; a cylindrical outer rod member having an outer piston portion provided at its end portion, the outer piston portion sliding along the inner circumferential surface of the cylinder and dividing the interior of the cylinder into a rod side chamber and an opposite rod side chamber; an inner rod member having an inner piston portion provided at an end thereof for sliding along an inner peripheral surface of the outer rod member; A snap ring, the outer diameter side of which is received in an annular recess formed on the inner peripheral surface of the outer rod member, and restricts movement of the inner rod member in the contraction direction. The inner piston portion is provided with a receiving recess for receiving the inner diameter side of the retaining ring when the inner rod member contracts. A communication passage is provided on at least one of the outer rod component and the inner rod component, and the communication passage connects a gap with the rod opposite side chamber or the fluid chamber. The gap is defined by the outer peripheral surface of the retaining ring, the inner piston part and the inner peripheral surface of the outer rod component when the retaining ring is accommodated in the accommodating recess and abuts against the inner piston part. The fluid chamber is connected to the rod opposite side chamber by relative movement of the cylinder relative to the outer rod component.

2. The multi-stage fluid pressure cylinder according to claim 1, wherein: The communication passage is a through hole formed in at least one of the outer rod member and the inner rod member. One end of the through hole opens to the opposite-rod side chamber, and the other end opens to the gap.

3. The multi-stage fluid pressure cylinder according to claim 1, wherein: The communication passage is a notch groove cut along the axial direction in at least one of the inner peripheral surface of the outer rod member and the outer peripheral surface of the inner piston portion.

4. The multi-stage fluid pressure cylinder according to claim 3, wherein: The notch groove is formed along the axial direction from at least one of an end surface of the outer rod member and an end surface of the inner rod member facing the anti-rod side chamber.

5. The multi-stage fluid pressure cylinder according to claim 1, wherein: The communication passage is a threaded hole having one end opened on the outer peripheral surface of the outer piston portion and the other end opened on the annular recessed portion. The inner diameter of the female thread of the threaded hole is larger than the wire diameter of the clamping ring.

6. The multi-stage fluid pressure cylinder according to claim 1, wherein: Also features: a second inner rod member having an end portion provided with a second inner piston portion that slides along the inner circumferential surface of the inner rod member; The second snap ring has an outer diameter side received in a second annular recess formed on the inner peripheral surface of the inner rod member and restricts movement of the second inner rod member in the contraction direction. The communication passage is a threaded hole having one end opening at the outer peripheral surface of the inner piston portion and the other end opening at the second annular recessed portion. The inner diameter of the female thread of the threaded hole is larger than the wire diameter of the second clamping ring.

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