Fluid pressure cylinder

Abstract

To decrease a pressure loss without enlarging a fluid pressure cylinder.SOLUTION: A hydraulic cylinder 100 is equipped with a rod member 60 and a rod head 75. The rod member 60 has a first rod inner passage 63 that is provided in the rod member 60 and leads a working fluid to one of a rod side chamber 1 and an opposite rod side chamber 5, and an annular second rod inner passage 64 that is provided in the rod member 60 so as to surround the first rod inner passage 63 and leads the working fluid to the other of the rod side chamber 1 and the opposite rod side chamber 5. The rod head 75 has a first passage 80 that communicates the outside of the rod head 75 and the first rod inner passage 63, and a second passage 81 that communicates the outside of the rod head 75 and the second rod inner passage 64. The second passage 81 has a main passage 81a opening to an outer surface of the rod head 75, and a plurality of branch passages 81b branching off from the main passage 81a and respectively communicating to the second rod inner passage 64.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a fluid pressure cylinder.

Background Art

[0002] Patent Document 1 discloses a fluid pressure cylinder including a cylinder tube, a piston portion slidably inserted into the cylinder tube and partitioning a rod side chamber and a rodless side chamber in the cylinder tube, a rod member inserted into the cylinder tube, and a pipe member provided in the rod member for guiding a working fluid to the rodless side chamber. A hollow portion is formed in the rod member, and the hollow portion communicates with the rod side chamber. Further, the rod member has a mounting portion for attaching the fluid pressure cylinder to a driving target, and two flow paths provided in the mounting portion communicate with the pipe member and the hollow portion, respectively.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the fluid pressure cylinder as described in Patent Document 1, since two flow paths are provided in the mounting portion, it is difficult to secure the cross-sectional area of the flow paths, and there is a problem that the pressure loss generated in the two flow paths is large. If the mounting portion is enlarged to increase the cross-sectional area of the two flow paths, the fluid pressure cylinder will be enlarged.

[0005] The present invention has been made in view of the above problems, and an object thereof is to reduce the pressure loss without enlarging the fluid pressure cylinder.

Means for Solving the Problems

[0006] The present invention relates to a fluid pressure cylinder comprising: a cylinder tube; a piston portion slidably inserted into the cylinder tube and dividing the cylinder tube into a rod side chamber and a non-rod side chamber; a rod member inserted into the cylinder tube and having one end connected to the piston portion; and a rod head provided at the other end of the rod member, wherein the rod member has a first rod internal passage provided within the rod member for guiding working fluid to one of the rod side chamber and the non-rod side chamber; and an annular second rod internal passage provided within the rod member so as to surround the first rod internal passage for guiding working fluid to the other of the rod side chamber and the non-rod side chamber; and the rod head has a first passage connecting the outside of the rod head to the first rod internal passage and a second passage connecting the outside of the rod head to the second rod internal passage. A cylindrical mounting portion that is attached to the object to be mounted, and a protruding portion that extends from the outer surface of the mounting portion, The second passage has a main passage that opens to the outer surface of the rod head, and a plurality of branch passages that branch off from the main passage and communicate with the second rod internal passage. The first and second passages are provided opening to the tip surface of the protruding portion in the direction of protrusion, the opening of the second passage is provided closer to the mounting portion than the opening of the first passage, and the first passage is provided so as to cross between the multiple branch passages. It is characterized by the following:

[0007] In this invention, an annular second rod internal passage is provided within the rod member so as to surround the first rod internal passage, and multiple branch passages of the second rod internal passage each guide working fluid into the second rod internal passage. By configuring a part of the second rod internal passage with multiple branch passages in this way, the flow path cross-sectional area of ​​the second rod internal passage can be increased without increasing the diameter of the second rod internal passage. Therefore, the pressure loss occurring in the second passage can be reduced. Furthermore, since the second passage opens closer to the mounting section than the first passage, and the first passage is provided to cross between multiple branch passages of the second passage, the first passage can be shortened. Therefore, the rod head can be made more compact.

[0008] Furthermore, the present invention is A fluid pressure cylinder comprising: a cylinder tube; a piston portion slidably inserted into the cylinder tube and dividing the cylinder tube into a rod-side chamber and a non-rod-side chamber; a rod member inserted into the cylinder tube and having one end connected to the piston portion; and a rod head provided at the other end of the rod member, wherein the rod member has a first rod internal passage provided within the rod member for guiding working fluid to one of the rod-side chamber and the non-rod-side chamber; and an annular second rod internal passage provided within the rod member so as to surround the first rod internal passage and for guiding working fluid to the other of the rod-side chamber and the non-rod-side chamber, wherein the rod head has a first passage connecting the outside of the rod head to the first rod internal passage; a second passage connecting the outside of the rod head to the second rod internal passage; and a relief valve that allows the flow of working fluid from the second passage to the first passage, wherein the second passage has a main passage opening to the outer surface of the rod head; and a plurality of branch passages branching off from the main passage and each communicating with the second rod internal passage.

[0009] In this invention, An annular second rod internal passage is provided within the rod member so as to surround the first rod internal passage, and multiple branch passages of the second rod internal passage each guide the working fluid into the second rod internal passage. In this way, by configuring a part of the second rod internal passage with multiple branch passages, the flow path cross-sectional area of ​​the second rod internal passage can be increased without increasing the diameter of the second rod internal passage. Therefore, the pressure loss occurring in the second passage can be reduced.

[0010] Furthermore, the present invention is A fluid pressure cylinder comprising: a cylinder tube; a piston portion slidably inserted into the cylinder tube and dividing the cylinder tube into a rod side chamber and a non-rod side chamber; a rod member inserted into the cylinder tube and having one end connected to the piston portion; and a rod head provided at the other end of the rod member, wherein the rod member has a first rod internal passage provided within the rod member for guiding working fluid to one of the rod side chamber and the non-rod side chamber; and an annular second rod internal passage provided within the rod member so as to surround the first rod internal passage for guiding working fluid to the other of the rod side chamber and the non-rod side chamber; and the rod head is a rod head The rod head has a first passage connecting the outside of the rod head to the first rod internal passage, and a second passage connecting the outside of the rod head to the second rod internal passage. The second passage has a main passage that opens to the outer surface of the rod head, and a plurality of branch passages that branch off from the main passage and each connect to the second rod internal passage. The first rod internal passage has a connection point with the first passage offset from the center of the rod member, and when the end face of the rod head is divided into two virtual regions by a virtual line passing through the central axis of the rod member, the center of the opening of the first passage is located only within one virtual region, and the centers of the openings of each of the plurality of branch passages are located only within the other virtual region.

[0011] In this invention, An annular second rod internal passage is provided within the rod member so as to surround the first rod internal passage, and multiple branch passages of the second rod internal passage each guide the working fluid into the second rod internal passage. In this way, by configuring a part of the second rod internal passage with multiple branch passages, the flow path cross-sectional area of ​​the second rod internal passage can be increased without increasing the diameter of the second rod internal passage. Therefore, the pressure loss occurring in the second passage can be reduced. Since the first rod's internal passage is positioned offset from the central axis of the rod member, the area in which the branch passage of the second passage communicates with the second rod's internal passage can be maximized.

[0012] In addition, the present invention The first passage is characterized by being provided so as not to be located between multiple branch passages. In this invention, the first passage is not located between multiple branch passages. Therefore, the diameter of the branch passages can be increased without increasing the diameter of the passage inside the second rod, and the total cross-sectional area of ​​the branch passages can be increased.

[0013] Furthermore, the present invention is characterized in that the internal passage of the first rod is provided such that the portion communicating with the first passage is offset from the center of the rod member. In this invention Since the first rod's internal passage is positioned offset from the central axis of the rod member, the area in which the branch passage of the second passage communicates with the second rod's internal passage can be maximized.

Advantages of the Invention

[0014] According to the present invention, it is possible to reduce the pressure loss without making the fluid pressure cylinder large-sized.

Brief Description of the Drawings

[0015] [Figure 1] It is a schematic cross-sectional view of a hydraulic cylinder according to an embodiment of the present invention, showing the most contracted state. [Figure 2] It is a plan view showing an enlarged rod head. [Figure 3] It is a perspective view showing an enlarged rod head. [Figure 4] It is an enlarged view of the rod head as seen from the A direction in FIG. 3. [Figure 5] It is a schematic cross-sectional view of a hydraulic cylinder according to an embodiment of the present invention, showing a state where the first piston is in the extended position and the second piston and the third piston are in the contracted positions. [Figure 6] It is a schematic cross-sectional view of a hydraulic cylinder according to an embodiment of the present invention, showing a state where the first piston and the second piston are in the extended positions and the third piston is in the contracted position. [Figure 7] It is a schematic cross-sectional view of a hydraulic cylinder according to an embodiment of the present invention, showing the most extended state. [Figure 8] It is a schematic cross-sectional view of a rod head according to Modification 2 of an embodiment of the present invention. [Figure 9] It is a schematic cross-sectional view of a rod head according to Modification 3 of an embodiment of the present invention. [Figure 10] It is an enlarged cross-sectional view of a protruding portion of a rod head according to Modification 4 of an embodiment of the present invention.

Modes for Carrying Out the Invention

[0016] Embodiments of the present invention will be described below with reference to the drawings.

[0017] Referring to Figures 1 to 4, a multi-stage fluid pressure cylinder 100 according to an embodiment of the present invention will be described. In the following, the case in which the multi-stage fluid pressure cylinder 100 is a multi-stage hydraulic cylinder 100 that drives a hydraulic fluid as the working fluid (hereinafter simply referred to as "hydraulic cylinder 100") will be described.

[0018] The hydraulic cylinder 100 is attached to an object and drives the object by extending and retracting. For example, the hydraulic cylinder 100 is a hoist cylinder attached between the cargo bed and the body of a dump truck to raise and lower the cargo bed. When the hydraulic cylinder 100 extends, the cargo bed tilts and the cargo on the cargo bed is discharged.

[0019] As shown in Figure 1, the hydraulic cylinder 100 comprises a bottomed cylindrical cylinder tube 10, a piston portion 20 slidably inserted into the cylinder tube 10 and dividing the cylinder tube 10 into a rod-side chamber 1 and an anti-rod-side chamber 5, a rod member 60 inserted into the cylinder tube 10 with one end connected to the piston portion 20, a cylinder-side mounting portion 70 provided at the bottom of the cylinder tube 10, and a rod head 75 as a rod-side mounting portion provided at the other end of the rod member 60. Figure 1 is a schematic cross-sectional view showing the hydraulic cylinder 100 in its most contracted state.

[0020] The hydraulic cylinder 100 is mounted to the object via the cylinder-side mounting portion 70 and the rod head 75 such that the cylinder tube 10 is positioned vertically upward and the rod member 60 is positioned vertically downward. The hydraulic cylinder 100 is mounted to the object such that the cylinder-side mounting portion 70 is displaced approximately vertically, i.e., vertically, relative to the rod head 75. However, the direction in which the hydraulic cylinder 100 is mounted is not limited to this; it may also be mounted so that the cylinder tube 10 is positioned vertically downward and the rod member 60 is positioned vertically upward. Furthermore, the hydraulic cylinder 100 may be mounted to the object so that it extends and retracts horizontally.

[0021] The piston section 20 includes a first piston 30 that slides along the inner circumferential surface of the cylinder tube 10, a second piston 40 that slides along the inner circumferential surface of the first piston 30, and a third piston 50 that slides along the inner circumferential surface of the second piston 40 and to which a rod member 60 is connected. A cylinder head 11 is provided at the opening of the cylinder tube 10 to slidably support the first piston 30 of the piston section 20.

[0022] The rod side chamber 1 has a first rod side chamber 2, a second rod side chamber 3, and a third rod side chamber 4. The first rod side chamber 2 is partitioned by the cylinder tube 10, the cylinder head 11, and the first piston 30. The second rod side chamber 3 is partitioned by the first piston 30 and the second piston 40. The third rod side chamber 4 is partitioned by the second piston 40, the third piston 50, and the rod member 60.

[0023] The anti-rod side chamber 5 is partitioned by the cylinder tube 10, the piston portion 20, and the rod member 60. In this way, the rod side chamber 1 and the anti-rod side chamber 5 are partitioned within the cylinder tube 10.

[0024] A sealing member (not shown) is provided on the inner circumferential surface of the cylinder head 11 to seal the gap between it and the outer circumferential surface of the first piston 30.

[0025] A recess 10a is formed at the bottom of the cylinder tube 10, opening to the anti-rod side chamber 5. The recess 10a is formed with an inner diameter larger than the inner diameter of the first piston 30. As a result, the pressure of the hydraulic fluid guided into the recess 10a acts on the first piston 30.

[0026] The first piston 30 includes a cylindrical first body portion 31, a cylindrical first sliding contact portion 32 formed projecting radially outward from one end of the first body portion 31 and sliding against the inner circumferential surface of the cylinder tube 10, a cylindrical first support portion 33 formed projecting radially inward from the other end of the first body portion 31 and slidably supporting the second piston 40, and a first piston ring 34 provided on the outer circumferential surface of the first sliding contact portion 32.

[0027] A first communication port 30A, which penetrates radially, is formed in the first main body portion 31 at a position adjacent to the first sliding contact portion 32. The first rod side chamber 2 communicates with the second rod side chamber 3 through the first communication port 30A when the second piston 40 is in its most retracted position.

[0028] The first sliding contact portion 32 slides between the bottom of the cylinder tube 10 and the cylinder head 11. The first piston 30 is defined as having its most retracted position when the first sliding contact portion 32 abuts against the bottom of the cylinder tube 10, and its most extended position when it abuts against the cylinder head 11.

[0029] A sealing member (not shown) is provided on the inner circumferential surface of the first support portion 33 to close the gap between it and the outer circumferential surface of the second piston 40.

[0030] The first piston ring 34 is an annular member. The first piston ring 34 blocks communication between the first rod-side chamber 2 and the anti-rod-side chamber 5 through the gap between the outer circumferential surface of the first sliding contact portion 32 and the inner circumferential surface of the cylinder tube 10.

[0031] Furthermore, a bush (not shown) is provided on the outer circumferential surface of the first sliding contact portion 32, which slides against the inner circumferential surface of the cylinder tube 10. The first piston 30 is slidably supported by the cylinder tube 10 as the bush slides against the inner circumferential surface of the cylinder tube 10.

[0032] A first snap ring 25, which can engage with the second piston 40, is fitted into the annular groove on the inner circumferential surface of the first main body 31. The first snap ring 25 prevents the first piston 30 from falling out of the second piston 40.

[0033] The second piston 40 has the same configuration as the first piston 30. Specifically, as shown in Figure 1, the second piston 40 includes a cylindrical second body portion 41, a cylindrical second sliding contact portion 42 formed projecting radially outward from one end of the second body portion 41 and sliding against the inner circumferential surface of the first piston 30, a cylindrical second support portion 43 formed projecting radially inward from the other end of the second body portion 41 and slidably supporting the rod member 60, and a second piston ring 44 provided on the outer circumferential surface of the second sliding contact portion 42.

[0034] A second communication port 40A, which penetrates radially, is formed in the second main body portion 41 at a position adjacent to the second sliding contact portion 42. The second rod side chamber 3 communicates with the third rod side chamber 4 through the second communication port 40A when the third piston 50 is in its most retracted position.

[0035] The second sliding contact portion 42 slides between the first snap ring 25 and the first support portion 33 of the first piston 30. The second piston 40 is defined as having its most retracted position when the second sliding contact portion 42 abuts against the first snap ring 25, and its most extended position when it abuts against the first support portion 33.

[0036] A sealing member (not shown) is provided on the inner circumferential surface of the second support portion 43 to close the gap between it and the outer circumferential surface of the rod member 60.

[0037] The second piston ring 44 is an annular member similar to the first piston ring 34. The second piston ring 44 blocks communication between the second rod-side chamber 3 and the anti-rod-side chamber 5 through the gap between the outer circumferential surface of the second sliding contact portion 42 of the second piston 40 and the inner circumferential surface of the first body portion 31 of the first piston 30.

[0038] A bush (not shown) is provided on the outer circumferential surface of the second sliding contact portion 42, which slides against the inner circumferential surface of the first piston 30. The second piston 40 is slidably supported by the first piston 30 by the sliding contact of the bush with the inner circumferential surface of the first piston 30.

[0039] A second snap ring 26, which can engage with the third piston 50, is fitted into the annular groove on the inner circumferential surface of the second main body 41. The second snap ring 26 prevents the second piston 40 from falling out of the third piston 50.

[0040] The third piston 50 has an annular third sliding contact portion 52 that slides against the inner circumferential surface of the second piston 40, and a third piston ring 54 provided on the outer circumferential surface of the third sliding contact portion 52. An annular flange portion 53 is formed on the inner circumferential surface of the third sliding contact portion 52, and the flange portion 53 is connected to the tip of the rod member 60 via a plurality of bolts.

[0041] The third sliding contact portion 52 slides between the second snap ring 26 and the second support portion 43 of the second piston 40. The most retracted position of the third piston 50 is defined when the third sliding contact portion 52 abuts against the second snap ring 26, and the most extended position is defined when it abuts against the second support portion 43.

[0042] The third piston ring 54 is an annular member similar to the first and second piston rings 34 and 44. The third piston ring 54 blocks communication between the third rod-side chamber 4 and the anti-rod-side chamber 5 through the gap between the outer circumferential surface of the third sliding contact portion 52 of the third piston 50 and the inner circumferential surface of the second body portion 41 of the second piston 40.

[0043] Furthermore, a bush (not shown) is provided on the outer circumferential surface of the third sliding contact portion 52, which slides against the inner circumferential surface of the second piston 40. The third piston 50 is slidably supported by the second piston 40 by the sliding contact of the bush with the inner circumferential surface of the second piston 40.

[0044] As shown in Figure 1, the rod member 60 is formed in a bottomed cylindrical shape, with the third sliding contact portion 52 of the third piston 50 connected to the bottom portion 61, and the rod head 75 connected to the opening 62. The rod member 60 moves axially within the cylinder tube 10 together with the third piston 50.

[0045] A pipe-shaped piping 65 is provided within the hollow portion of the rod member 60, extending in the axial direction of the rod member 60. One end of the piping 65 opens to the anti-rod side chamber 5, and the other end opens to the rod head 75. Specifically, one end of the piping 65 is inserted into a first through-hole 61a that penetrates the center of the bottom 61 of the rod member 60 in the axial direction, and is fixed to the first through-hole 61a by press-fitting or welding. In other words, one end of the piping 65 is provided so that its center coincides with the central axis O of the rod member 60. The other end of the piping 65 is inserted into the rod head 75 (piping mounting hole 77d, described later) and is fixed to the rod head 75 by press-fitting or welding. A first rod internal passage 63 is formed inside the piping 65. Hydraulic fluid is supplied to and discharged from the anti-rod side chamber 5 through the first rod internal passage 63.

[0046] A second rod internal passage 64 is formed inside the rod member 60, outside the piping 65. Specifically, the second rod internal passage 64 is formed in an annular shape between the inner circumferential surface of the rod member 60 and the outer circumferential surface of the piping 65. The second rod internal passage 64 communicates with the third rod side chamber 4 through a second through hole 61b formed in the bottom 61 of the rod member 60. Hydraulic fluid is supplied to and discharged from the rod side chamber 1 through the second rod internal passage 64.

[0047] Thus, the rod member 60 has a first rod internal passage 63 provided within the rod member 60 for guiding hydraulic fluid to the non-rod side chamber 5, and an annular second rod internal passage 64 provided within the rod member 60 so as to surround the first rod internal passage 63 for guiding hydraulic fluid to the rod side chamber 1.

[0048] As shown in Figures 2 and 3, the rod head 75 has a cylindrical mounting portion 76 that is attached to the object to be mounted, a connecting portion 77 that is connected to the rod member 60, and a protruding portion 78 that protrudes from the outer surface of the mounting portion 76.

[0049] The mounting portion 76 constitutes the main body of the rod head 75. The connecting portion 77 is provided continuously with the mounting portion 76. The connecting portion 77 has a pipe mounting hole 77d that opens at the end face 77c and into which the end of the pipe 65 is inserted and attached. The end face 77c is abutted against the end face of the opening 62 of the rod member 60 and connected by welding or the like. The inner diameter of the pipe mounting hole 77d is formed to be approximately the same as the outer diameter of the pipe 65. The end of the pipe 65 is inserted into the pipe mounting hole 77d and attached by press-fitting, welding or the like.

[0050] The protruding portion 78 is provided such that one side is continuous with the outer circumferential surface of the rod member 60 and the other side is continuous with the outer circumferential surface of the mounting portion 76. Specifically, the protruding portion 78 has a rod-side inclined side surface 78a that is continuous with the outer circumferential surface of the rod member 60 via the connecting portion 77 and is formed at an angle with respect to the mounting portion 76, and a rod head-side inclined side surface 78b that is continuous with the outer circumferential surface of the mounting portion 76 and is formed at an angle with respect to the mounting portion 76. The rod-side inclined side surface 78a and the rod head-side inclined side surface 78b are formed parallel to each other. In a cross section (shown in Figure 1) that includes the central axis O of the rod member 60 and is parallel to the mounting portion 76, the protruding portion 78 is inclined such that the angle between the rod-side inclined side surface 78a and the outer circumferential surface of the rod member 60 is obtuse.

[0051] The rod head 75 has a first passage 80 that connects the outside of the rod head 75 to the first rod internal passage 63, and a second passage 81 that connects the outside of the rod head 75 to the second rod internal passage 64. A pump (not shown) or a tank (not shown) provided externally is selectively connected to the anti-rod side chamber 5 through the first passage 80 and the first rod internal passage 63 to supply and discharge hydraulic fluid. A pump or a tank provided externally is selectively connected to the rod side chamber 1 through the second passage 81 and the second rod internal passage 64 to supply and discharge hydraulic fluid.

[0052] The first passage 80 opens to the tip surface 78c of the projection 78 in the projection direction and to the pipe mounting hole 77d of the connecting portion 77. The first passage 80 has a passage 80a that extends linearly from the tip surface 78c of the projection 78, and a passage 80b that extends axially from the pipe mounting hole 77d and communicates with passage 80a. Passage 80b is provided concentrically with the pipe mounting hole 77d. The first passage 80 is provided so that the flow path cross-sectional area is uniform.

[0053] As shown in Figure 4, in this embodiment, the openings of the pipe mounting hole 77d and the passage 80b of the first passage 80 are offset from the central axis O of the rod member 60. In other words, the ends of the pipe 65 attached to the pipe mounting hole 77d and the passage 80b are positioned so that their centers are offset from the central axis O of the rod member 60. Thus, the first rod internal passage 63 and the pipe 65 are provided with a gentle incline within the rod member 60 such that one end coincides with the central axis O of the rod member 60 and the other end is offset from the central axis O of the rod member 60. In Figure 4, the offset of the openings of the pipe mounting hole 77d and the passage 80b from the central axis O is exaggerated. Note that the openings of the pipe mounting hole 77d and the passage 80b of the first passage 80 may also coincide with the central axis O of the rod member 60.

[0054] As shown in Figures 3 and 4, the second passage 81 opens to the tip surface 78c of the protruding portion 78 and the end surface 77c of the connecting portion 77. The second passage 81 opens to the mounting portion 76 side of the tip surface 78c of the protruding portion 78 than the first passage 80. The second passage 81 has a main passage 81a that opens to the outer surface of the rod head 75, and a plurality of branch passages 81b that branch off from the end of the main passage 81a and communicate with the second rod internal passage 64. In this embodiment, two branch passages 81b are provided. Specifically, the main passage 81a is provided extending in a straight line from the tip surface 78c of the protruding portion 78. The branch passages 81b branch off from the main passage 81a in the direction perpendicular to the rod head 75 (perpendicular to the plane of the paper in Figure 2) and extend in a straight line parallel to each other to the end surface 77c of the connecting portion 77. The branch passage 81b does not connect to the passage 80a of the first passage 80, but is provided intersecting with passage 80a in the plan view shown in Figures 1 and 2. In other words, the passage 80a of the first passage 80 is provided so as to cross between the two branch passages 81b, and the passage 80a of the first passage 80 is located between the two branch passages 81b. The main passage 81a and the branch passages 81b are provided so that their flow cross-sectional areas are uniform. Furthermore, the flow cross-sectional area of ​​the main passage 81a is provided to be greater than or equal to the sum of the flow cross-sectional areas of the two branch passages 81b. Note that there may be two or more branch passages 81b.

[0055] As shown in Figure 4, the opening of passage 80b for the first rod internal passage 63 and the two openings of branch passage 81b for the second rod internal passage 64 are arranged such that the shape formed by connecting their respective centers is triangular. Specifically, when the end face 77c of the rod member 60 is divided into two semicircles by a virtual line B passing through the central axis O, the center of the opening of passage 80b is located within one semicircle (the right semicircle in Figure 4), and the centers of the two openings of branch passage 81b are located within the other semicircle (the left semicircle in Figure 4).

[0056] In a hydraulic cylinder, if the cross-sectional area of ​​the fluid passage is small, the pressure loss in that passage will be large. In a hydraulic cylinder like the one in this embodiment, if the second passage is a single passage without branches and does not have multiple branched passages, one might consider increasing the diameter of the second passage in order to increase its cross-sectional area. However, the diameter of the second passage cannot be made larger than the passage inside the second rod that it communicates with. In particular, since the passage inside the second rod is annular, it is difficult to increase the diameter of the second passage. If the diameter of the second passage is increased by increasing the size of the passage inside the second rod, the diameter of the rod member will also increase, resulting in a larger hydraulic cylinder.

[0057] In contrast, in the hydraulic cylinder 100 of this embodiment, by configuring a portion of the second passage 81 with multiple branch passages 81b, the total flow path cross-sectional area of ​​a portion of the second passage 81 can be increased. In other words, the total flow path cross-sectional area of ​​the multiple branch passages 81b can be increased without increasing the diameter of the second rod internal passage 64. Furthermore, the main passage 81a of the second passage 81 does not directly communicate with the second rod internal passage 64. Therefore, the diameter of the main passage 81a can be increased without increasing the diameter of the second rod internal passage 64, thereby increasing the flow path cross-sectional area of ​​the main passage 81a. Thus, the pressure loss occurring in the second passage 81 can be reduced without increasing the size of the hydraulic cylinder 100.

[0058] Furthermore, in the hydraulic cylinder 100 of this embodiment, at the tip surface 78c of the protruding portion 78, the second passage 81 opens to the mounting portion 76 more than the first passage 80, and the first passage 80 is provided to cross between the multiple branch passages 81b of the second passage 81. Therefore, compared to a configuration in which the first passage 80 is not provided to cross between the multiple branch passages 81b of the second passage 81, as shown in the modified example 2 described later in Figure 8, the first passage 80 (specifically, the passage 80b of the first passage 80) can be shortened. Thus, the rod head 75 can be made more compact.

[0059] Next, the operation of the hydraulic cylinder 100 will be explained with reference to Figures 1, 5 to 7. In the following explanation, the hydraulic cylinder 100 will be described as being mounted to the object such that the cylinder-side mounting portion 70 is positioned vertically upward and the rod head 75 is positioned vertically downward.

[0060] When the hydraulic cylinder 100 extends, hydraulic fluid is supplied to the anti-rod side chamber 5 from a hydraulic source (not shown) such as a pump through the first passage 80, and the hydraulic fluid from the first, second, and third rod side chambers 2, 3, and 4 is discharged to a tank (not shown) through the second passage 81. During the extension operation of the hydraulic cylinder 100, the first piston 30, the second piston 40, and the third piston 50 move relative to the cylinder tube 10 in that order.

[0061] When the hydraulic cylinder 100 extends from the fully retracted state shown in Figure 1, hydraulic fluid is supplied to the anti-rod side chamber 5 through the first passage 80. Here, the pressure-receiving area of ​​the anti-rod side chamber 5 is largest for the first piston 30 and smallest for the third piston 50. In other words, the inner pistons have smaller pressure-receiving areas. Therefore, when the hydraulic cylinder 100 extends from the fully retracted state, the cylinder tube 10 first moves relative to the first piston 30. Specifically, as shown in Figure 5, the cylinder tube 10 moves upward (upper side in Figure 5) relative to the first piston 30.

[0062] As the first piston 30 and the cylinder tube 10 move relative to each other, the hydraulic fluid in the first rod side chamber 2 is guided to the second passage 81 through the first communication port 30A, the second rod side chamber 3, the second communication port 40A, the third rod side chamber 4, the second through hole 61b, and the second rod internal passage 64, and discharged.

[0063] As shown in Figure 5, when the cylinder tube 10 moves to the end of the extended stroke of the first piston 30, where the cylinder head 11 contacts the first piston 30, the cylinder tube 10 and the first piston 30 move relative to the second piston 40, which has a larger pressure-receiving area than the third piston 50, due to the pressure in the anti-rod side chamber 5. Specifically, as shown in Figure 6, the cylinder tube 10 and the first piston 30 move upward (upper side in Figure 6) relative to the second piston 40.

[0064] As the first piston 30 and the second piston 40 move relative to each other, the hydraulic fluid in the second rod side chamber 3 is guided to the second passage 81 through the second communication port 40A, the third rod side chamber 4, the second through hole 61b, and the second rod internal passage 64, and discharged.

[0065] As shown in Figure 6, when the cylinder tube 10 and the first piston 30 move to the end of the extension stroke of the second piston 40, where the first support portion 33 of the first piston 30 contacts the second piston 40, the cylinder tube 10, the first piston 30, and the second piston 40 move relative to the third piston 50 due to the pressure from the anti-rod side chamber 5. Specifically, as shown in Figure 7, the cylinder tube 10, the first piston 30, and the second piston 40 move upward (upper side in Figure 7) relative to the third piston 50.

[0066] As the third piston 50 and the second piston 40 move relative to each other, the hydraulic fluid in the third rod side chamber 4 is guided through the second through-hole 61b and the second rod internal passage 64 to the second passage 81 and discharged. The cylinder tube 10, the first piston 30, and the second piston 40 move until the second support portion 43 of the second piston 40 comes into contact with the third piston 50. In this way, as shown in Figure 7, the hydraulic cylinder 100 is in its fully extended state.

[0067] When the hydraulic cylinder 100 retracts, hydraulic fluid is supplied from the hydraulic source to the first, second, and third rod side chambers 2, 3, and 4 through the second passage 81, the second rod internal passage 64, and the second through hole 61b, and the hydraulic fluid in the non-rod side chamber 5 is discharged to the tank through the first rod internal passage 63 and the first passage 80. During the retraction of the hydraulic cylinder 100, the third piston 50, the second piston 40, and the first piston 30 move relative to the cylinder tube 10 in this order. Alternatively, the hydraulic cylinder 100 retracts due to the weight of the driven equipment connected to the cylinder tube 10 and the cylinder side mounting portion 70. In that case, it is not necessary to supply hydraulic fluid to the first, second, and third rod side chambers 2, 3, and 4.

[0068] According to the above embodiment, the following effects are achieved.

[0069] In the hydraulic cylinder 100, multiple branch passages 81b of the second passage 81 each lead hydraulic fluid to the second rod internal passage 64. By configuring a portion of the second passage 81 with multiple branch passages 81b, the flow path cross-sectional area of ​​the second passage 81 can be increased without increasing the diameter of the second rod internal passage 64. Therefore, the pressure loss occurring in the second passage 81 can be reduced without increasing the size of the hydraulic cylinder 100.

[0070] In the hydraulic cylinder 100, the second passage 81 opens to the mounting portion 76 more than the first passage 80, and the first passage 80 is provided to cross between the multiple branch passages 81b of the second passage 81, so the first passage 80 can be shortened. Therefore, the rod head 75 can be made more compact.

[0071] Next, a modified example of this embodiment will be described.

[0072] <Example 1> In the above embodiment, the first rod internal passage 63 communicates with the anti-rod side chamber 5, and the second rod internal passage 64 communicates with the rod side chamber 1. However, the hydraulic cylinder 100 may also be configured such that the first rod internal passage 63 communicates with the rod side chamber 1, and the second rod internal passage 64 communicates with the anti-rod side chamber 5. Specifically, the first rod internal passage 63 is formed by curving radially within the rod member 60 and communicates with the third rod side chamber 4, and the second rod internal passage 64 is formed so as to penetrate the bottom 61 of the rod member 60 in the axial direction and communicates with the anti-rod side chamber 5. This configuration also provides the same effects as the above embodiment.

[0073] <Modification 2> In the above embodiment, the branch passage 81b of the second passage 81 is provided intersecting with the passage 80a of the first passage 80 in the plan view shown in Figures 1 and 2. However, the hydraulic cylinder 100 is not limited to this, and the second passage 81 may be provided without intersecting with the first passage 80 in the plan view shown in Figures 1 and 2. Specifically, as shown in Figure 8, the second passage 81 opens at the tip surface 78c of the protrusion 78 toward the rod-side inclined side surface 78a of the first passage 80, and the branch passage 81b is provided without intersecting with the passage 80a of the first passage 80 in the plan view shown in Figure 8.

[0074] In the above embodiment, the branch passage 81b intersects with passage 80a in the plan view shown in Figures 1 and 2, and passage 80a is located between the two branch passages 81b. Therefore, even if one tries to increase the diameter of the branch passage 81b without increasing the diameter of the second rod's internal passage 64, the distance between the two branch passages 81b must be greater than that of passage 80b, thus limiting the increase in the diameter of the branch passage 81b. In contrast, in this modified example, passage 80a of the first passage 80 is not located between the two branch passages 81b. In other words, passage 80a is provided so as to extend so as not to be located between multiple branch passages 81b. Therefore, the diameter of the branch passage 81b can be increased without increasing the diameter of the second rod's internal passage 64, and the total flow path cross-sectional area of ​​the branch passage 81b can be increased.

[0075] Furthermore, as shown in Figure 4, in the above embodiment, the end of the pipe 65 and the center of the passage 80b of the first passage 80 are offset from the central axis O of the rod member 60. This makes it possible to maximize the opening area of ​​the two branch passages 81b relative to the second rod internal passage 64 within a limited space. Therefore, by configuring the passage 80a of the first passage 80 not to be located between the two branch passages 81b, as in this modified example, the diameter of the branch passages 81b can be increased, and the total flow path cross-sectional area of ​​the branch passages 81b can be increased.

[0076] <Variation 3> In the above embodiment, the rod head 75 has a protrusion 78, and the first passage 80 and the second passage 81 open at the tip surface 78c of the protrusion 78. However, as shown in Figure 9, the rod head 75 may not have a protrusion 78, and the first passage 80 and the second passage 81 may be provided opening on the side surface of the connecting portion 77. The passage 80a of the first passage 80 and the main passage 81a of the second passage 81 open 180 degrees apart from each other. Even with such a configuration, similar to the above modified example 2, the diameter of the branch passage 81b can be increased without increasing the diameter of the second rod internal passage 64. Furthermore, as shown in Figure 4, by offsetting the center of the passage 80b of the first passage 80 from the central axis O of the rod member 60, the opening area of ​​the two branch passages 81b relative to the second rod internal passage 64 can be maximized within a limited space.

[0077] <Modification 4> In the above embodiment, the rod head 75 has a first passage 80 that connects the outside of the rod head 75 to the first rod internal passage 63, and a second passage 81 that connects the outside of the rod head 75 to the second rod internal passage 64. In addition, as shown in Figure 10, the rod head 75 may also have a third passage 82 that can connect the first passage 80 and the second passage 81, and a relief valve 90 provided in the third passage 82. The third passage 82 opens on the rod-side inclined surface 78a of the protrusion 78, and the relief valve 90 is inserted through this opening and provided in the third passage 82. The relief valve 90 opens when the pressure in the second passage 81 becomes greater than the pressure in the first passage 80 by a predetermined value or more, allowing the flow of hydraulic fluid from the second passage 81 to the first passage 80. Thus, in this modified example, the third passage 82 and the relief valve 90 are provided in the protrusion 78.

[0078] Hydraulic cylinders may be subjected to external forces that force them to extend beyond their extension speed during extension operation. For example, in a hydraulic cylinder installed between the bed and body of a dump truck, which extends to tilt the bed and discharge the load, when the load is discharged all at once, the weight of the load just before discharge at the end of the bed causes a force that momentarily rotates the bed around the connection point with the vehicle body. As a result, an external force acts on the hydraulic cylinder that forces it to extend beyond its extension speed during extension operation. In this case, the supply of hydraulic fluid in the non-rod side chamber cannot keep up, resulting in negative pressure, while the discharge of hydraulic fluid in the rod side chamber cannot keep up, causing the pressure to rise. In this state, when the external force acting on the hydraulic cylinder is removed, the hydraulic cylinder will momentarily contract because the non-rod side chamber is under negative pressure. This may cause an impact to occur inside the hydraulic cylinder.

[0079] In contrast, in the hydraulic cylinder 100 of this modified example, a third passage 82 and a relief valve 90 are provided in the rod head 75. The relief valve 90 allows the flow of hydraulic fluid from the second passage 81 to the first passage 80 when the pressure in the second passage 81 becomes greater than or equal to a predetermined value than the pressure in the first passage 80. Therefore, by adjusting the relief pressure of the relief valve 90, when an external force acts on the hydraulic cylinder 100 during its extension operation that exceeds the extension speed, hydraulic fluid can be guided from the rod side chamber 1 to the anti-rod side chamber 5 through the third passage 82. Thus, it is prevented that the hydraulic cylinder 100 will contract instantaneously and generate an impact. Furthermore, in the hydraulic cylinder 100, since the third passage 82 and the relief valve 90 are provided in the rod head 75, which is close to the rod side chamber 1 and the anti-rod side chamber 5, it is possible to effectively prevent the anti-rod side chamber 5 from becoming negative pressure.

[0080] Furthermore, in this modified hydraulic cylinder 100, the third passage 82 opens to the rod-side inclined side surface 78a of the projection 78, and the relief valve 90 is inserted through this opening, making it easy to install, adjust, and replace the relief valve 90. Moreover, the relief valve 90 is provided on the rod-side inclined side surface 78a of the projection 78, which is continuous with the outer circumferential surface of the rod member 60. In the projection 78, the rod-side inclined side surface 78a is formed to be longer in the projection direction than the rod head-side inclined side surface 78b. Therefore, by providing the relief valve 90 on the rod-side inclined side surface 78a, space for the relief valve 90 can be secured even if the amount of projection 78 protruding from the mounting portion 76 is small, thus making the hydraulic cylinder 100 more compact.

[0081] The configuration, operation, and effects of the embodiments of the present invention will be described below.

[0082] The hydraulic cylinder 100 comprises a cylinder tube 10, a piston portion 20 slidably inserted into the cylinder tube 10 and dividing the cylinder tube 10 into a rod side chamber 1 and a non-rod side chamber 5, a rod member 60 inserted into the cylinder tube 10 with one end connected to the piston portion 20, and a rod head 75 provided at the other end of the rod member 60, wherein the rod member 60 includes a first rod internal passage 63 provided within the rod member 60 that guides the working fluid to one of the rod side chamber 1 and the non-rod side chamber 5, and the first rod internal passage 63 The rod head 75 has an annular second rod internal passage 64 provided within the rod member 60 so as to surround it, which guides the working fluid to the other side of the rod side chamber 1 and the anti-rod side chamber 5. The rod head 75 has a first passage 80 that connects the outside of the rod head 75 to the first rod internal passage 63, and a second passage 81 that connects the outside of the rod head 75 to the second rod internal passage 64. The second passage 81 has a main passage 81a that opens to the outer surface of the rod head 75, and a plurality of branch passages 81b that branch off from the main passage 81a and each connect to the second rod internal passage 64.

[0083] In this configuration, an annular second rod internal passage 64 is provided within the rod member 60 so as to surround the first rod internal passage 63, and multiple branch passages 81b of the second passage 81 each guide the working fluid into the second rod internal passage 64. By configuring a part of the second passage 81 with multiple branch passages 81b in this way, the flow path cross-sectional area of ​​the second passage 81 can be increased without increasing the diameter of the second rod internal passage 64. Therefore, the pressure loss occurring in the second passage 81 can be reduced.

[0084] Furthermore, in the hydraulic cylinder 100, the first passage 80 is provided so as not to be located between the multiple branch passages 81b.

[0085] In this configuration, the first passage 80 is not located between multiple branch passages 81b. Therefore, the diameter of the branch passages 81b can be increased without increasing the diameter of the second rod internal passage 64, thereby increasing the total flow path cross-sectional area of ​​the branch passages 81b.

[0086] Furthermore, in the hydraulic cylinder 100, the first rod internal passage 63 is provided such that the portion communicating with the first passage 80 is offset from the center of the rod member 60.

[0087] In this configuration, the first rod internal passage 63 is provided offset from the central axis of the rod member 60, thereby maximizing the area in which the multiple branch passages 81b of the second passage 81 communicate with the second rod internal passage 64.

[0088] Furthermore, in the hydraulic cylinder 100, the rod head 75 further has a cylindrical mounting portion 76 that is attached to the object to be mounted, and a projection portion 78 that protrudes from the outer surface of the mounting portion 76. The first passage 80 and the second passage 81 are provided opening at the tip surface 78c of the projection portion 78 in the projection direction, the opening of the second passage 81 is provided closer to the mounting portion 76 than the opening of the first passage 80, and the first passage 80 is provided so as to cross between a plurality of branch passages 81b.

[0089] In this configuration, the second passage 81 opens to the mounting portion 76 more than the first passage 80, and the first passage 80 is provided so as to cross between the multiple branch passages 81b of the second passage 81, thus the first passage 80 can be shortened. Therefore, the rod head 75 can be made more compact.

[0090] Although embodiments of the present invention have been described above, these embodiments only represent a part of the 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.

[0091] In this embodiment, a multi-stage fluid pressure cylinder was used as an example, but this can also be applied to fluid pressure cylinders that are not multi-stage, as long as they have a rod passage within the rod member that guides the working fluid to the rod-side chamber and the non-rod-side chamber. [Explanation of Symbols]

[0092] 1…Rod side chamber, 5…Non-rod side chamber, 10…Cylinder tube, 20…Piston section, 60…Rod member, 63…First rod inner passage, 64…Second rod inner passage, 75…Rod head, 76…Mounting section, 78…Protruding section, Tip surface…78c, 80…First passage, 81…Second passage, 81a…Main passage, 81b…Branch passage, 100…Hydraulic cylinder (fluid pressure cylinder)

Claims

1. Cylinder tube and A piston portion is slidably inserted into the cylinder tube and divides the cylinder tube into a rod-side chamber and a non-rod-side chamber. A rod member inserted into the cylinder tube and having one end connected to the piston portion, The rod member comprises a rod head provided at the other end of the rod member, The aforementioned rod member is A first rod internal passage is provided within the rod member and guides the working fluid to one of the rod side chamber and the anti-rod side chamber, It has an annular second rod internal passage provided within the rod member so as to surround the first rod internal passage and for guiding the working fluid to the other side of the rod side chamber and the anti-rod side chamber, The aforementioned rod head is A first passage connecting the outside of the rod head and the first internal passage of the rod, A second passage connecting the outside of the rod head and the internal passage of the second rod, A cylindrical mounting part that is attached to the object to be mounted, It has a protruding portion that extends from the outer surface of the mounting portion, The aforementioned second passage is, The main passage opening on the outer surface of the rod head, It has a plurality of branch passages that branch off from the main passage and each communicate with the second rod internal passage, The first passage and the second passage are provided opening to the tip surface of the protruding portion in the direction of protrusion, The opening of the second passage is provided on the mounting side of the opening of the first passage. The fluid pressure cylinder is characterized in that the first passage is provided so as to cross between the plurality of branch passages.

2. Cylinder tube and A piston portion is slidably inserted into the cylinder tube and divides the cylinder tube into a rod-side chamber and a non-rod-side chamber. A rod member inserted into the cylinder tube and having one end connected to the piston portion, The rod member comprises a rod head provided at the other end of the rod member, The aforementioned rod member is A first rod internal passage is provided within the rod member and guides the working fluid to one of the rod side chamber and the anti-rod side chamber, It has an annular second rod internal passage provided within the rod member so as to surround the first rod internal passage and for guiding the working fluid to the other side of the rod side chamber and the anti-rod side chamber, The aforementioned rod head is A first passage connecting the outside of the rod head and the first internal passage of the rod, A second passage connecting the outside of the rod head and the internal passage of the second rod, It has a relief valve that allows the flow of hydraulic fluid from the second passage to the first passage, The aforementioned second passage is, The main passage opening on the outer surface of the rod head, A fluid pressure cylinder characterized by having a plurality of branch passages that branch off from the main passage and each communicate with the second rod internal passage.

3. Cylinder tube and A piston portion is slidably inserted into the cylinder tube and divides the cylinder tube into a rod-side chamber and a non-rod-side chamber. A rod member inserted into the cylinder tube and having one end connected to the piston portion, The rod member comprises a rod head provided at the other end of the rod member, The aforementioned rod member is A first rod internal passage is provided within the rod member and guides the working fluid to one of the rod side chamber and the anti-rod side chamber, It has an annular second rod internal passage provided within the rod member so as to surround the first rod internal passage and for guiding the working fluid to the other side of the rod side chamber and the anti-rod side chamber, The aforementioned rod head is A first passage connecting the outside of the rod head and the first internal passage of the rod, It has a second passage that connects the outside of the rod head and the internal passage of the second rod, The aforementioned second passage is, The main passage opening on the outer surface of the rod head, It has a plurality of branch passages that branch off from the main passage and each communicate with the second rod internal passage, The first rod internal passage is provided such that the portion communicating with the first passage is offset from the center of the rod member. A fluid pressure cylinder characterized in that, when the end face of the rod head is divided into two virtual regions by a virtual line passing through the central axis of the rod member, the center of the opening of the first passage is located only within one of the virtual regions, and the centers of the openings of each of the plurality of branch passages are located only within the other virtual region.

4. The fluid pressure cylinder according to any one of claims 1 to 3, characterized in that the first passage extends so as not to be located between the plurality of branch passages.

5. The fluid pressure cylinder according to claim 1 or 2, characterized in that the first rod internal passage has a communication portion with the first passage offset from the center of the rod member.

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