JP2017172768A - Fluid pressure cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more surely soften a shock caused when a hydraulic cylinder completely expands or contracts.SOLUTION: A hydraulic cylinder 100 has a cushion mechanism 60. The cushion mechanism 60 comprises a main passage 5, a cushion ring 61 entering the main passage 5 near a stroke end, a bypass passage 63 bypassing the main passage 5, a relief valve 64 provided in the bypass passage 63, a first back-pressure passage 65 introducing the pressure in a rod side chamber 1 into a back-pressure chamber 64g of the relief valve 64, and an orifice plug 66 provided in the first back-pressure passage 65. The relief valve 64 has a relief set pressure change part 64d raising a relief set pressure in association with a rise of the pressure in the back-pressure chamber 64g.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fluid pressure cylinder.

  In general, a fluid pressure cylinder used in a hydraulic excavator or the like includes a cushion mechanism that reduces an impact generated when a piston rod reaches a stroke end (Patent Document 1).

  The cushion mechanism disclosed in Patent Document 1 is configured to restrict the flow of the working fluid flowing out from the fluid pressure chamber to the supply / discharge port in the vicinity of the stroke end. When the flow of the working fluid is throttled, the piston rod is decelerated, and the impact generated when the fluid pressure cylinder is fully expanded and contracted is reduced.

  Further, the cushion mechanism of Patent Document 1 includes a bypass passage that guides the working fluid in the fluid chamber to the supply / discharge port while bypassing the throttle passage, and a relief valve provided in the bypass passage. The relief valve opens the bypass passage when the pressure in the fluid pressure chamber reaches a predetermined value, and allows the working fluid in the fluid chamber to flow out to the supply / discharge port through the bypass passage.

JP 2009-287714 A

  In the fluid pressure cylinder disclosed in Patent Document 1, the flow of the working fluid flowing out from the fluid pressure chamber to the supply / discharge port through the bypass passage is restricted to some extent even by the relief valve. When the relief valve restricts the flow of the working fluid, the impact is alleviated even when the relief valve is opened.

  However, when the piston rod moves at high speed near the stroke end and the pressure in the fluid pressure chamber increases, the flow of the working fluid in the bypass passage may not be sufficiently throttled by the relief valve. In this case, the piston rod does not decelerate and the impact may not be mitigated.

  An object of the present invention is to more reliably mitigate an impact that occurs when a fluid pressure cylinder is fully expanded and contracted.

  A first invention includes a cylinder tube, a piston rod, a piston, a closing member, a supply / discharge port, and a cushion mechanism, and the cushion mechanism includes a main passage communicating the pressure chamber and the supply / discharge port. An entrance portion that enters the main passage near the stroke end and restricts the flow of the working fluid in the main passage, a bypass passage that bypasses the main passage and connects the pressure chamber and the supply / discharge port, and a bypass passage. A relief valve that allows the flow of the working fluid when the pressure in the pressure chamber reaches the relief set pressure, a first back pressure passage that guides the pressure in the pressure chamber to the back pressure chamber of the relief valve, and a first back pressure passage And a first throttle portion that provides resistance to the flow of the working fluid, and the relief valve has a relief set pressure changing portion that increases the relief set pressure as the pressure in the back pressure chamber increases. Feature To.

  In the first invention, when the piston rod moves at high speed near the stroke end and the entry portion enters the main passage, the pressure in the pressure chamber rises. When the pressure in the pressure chamber reaches the initial relief setting pressure, the relief valve opens. If the pressure in the pressure chamber rises even after the relief valve is opened, the pressure in the pressure chamber is guided to the back pressure chamber through the first back pressure passage having the first throttle portion, and the pressure in the back pressure chamber is reduced. Rise gradually. As the pressure in the back pressure chamber rises, the relief setting pressure rises by the relief setting pressure changing portion. When the relief set pressure reaches the pressure in the pressure chamber, the relief valve is closed, and the working fluid in the pressure chamber is not guided to the supply / discharge port through the bypass passage. As a result, the flow rate of the working fluid discharged from the supply / discharge port decreases, and the piston rod decelerates before reaching the stroke end.

  The second invention is characterized in that the first throttle portion is detachable from the closing member.

  In the second invention, since the first throttle portion is detachably provided on the closing member, the first throttle portion can be replaced when the resistance applied to the flow of the working fluid in the first back pressure passage is changed. That's fine. Therefore, the rate of increase in pressure in the back pressure chamber can be easily changed, and the cushion characteristics can be easily adjusted.

  According to a third aspect of the present invention, the cushion mechanism is provided in the second back pressure passage for guiding the pressure in the back pressure chamber to the supply / exhaust port, and the resistance greater than the resistance provided by the first throttle portion. And a second throttle part for imparting to the flow of the working fluid.

  In the third invention, since the second back pressure passage guides the pressure in the back pressure chamber to the supply / discharge port, when the piston rod stops and the pressure chamber stops increasing, the pressure in the back pressure chamber is It is guided to the supply / discharge port through the back pressure passage and decreases. Therefore, the relief set pressure can be returned to the initial value. Further, the second restricting portion imparts a larger resistance to the working fluid flow than the resistance imparted to the working fluid flow by the first restricting portion. Therefore, the flow rate of the working fluid led from the back pressure chamber to the supply / discharge port through the second back pressure passage is smaller than the flow rate of the working oil led from the pressure chamber to the back pressure chamber through the first back pressure passage. Therefore, when the piston rod moves at high speed near the stroke end and the pressure in the pressure chamber continues to rise above the relief setting pressure, the pressure in the back pressure chamber can be reliably increased, and the impact can be more reliably mitigated. can do.

  The fourth invention is characterized in that the second throttle portion is detachable from the closing member.

  In the fourth invention, since the second throttle portion is detachable from the closing member, the second throttle portion may be replaced when the resistance given to the flow of the working fluid in the second back pressure passage is changed. . Therefore, the rate of increase in pressure in the back pressure chamber can be easily changed, and the cushion characteristics can be easily adjusted.

  According to a fifth aspect of the present invention, the relief valve is urged in a direction in which the relief valve is opened and closed with respect to the valve seat provided in the bypass passage so as to open and close the bypass passage, and the valve body is seated on the valve seat. An urging member that determines a relief setting pressure according to the pressure, and the relief setting pressure changing portion supports the urging member and moves in response to the pressure in the back pressure chamber to generate the urging force of the urging member. A support member to be changed is provided, and the pressure receiving area of the support member is larger than the pressure receiving area of the valve body.

  In the fifth invention, since the pressure receiving area of the support member is larger than the pressure receiving area of the valve body, even when the pressure in the back pressure chamber is lower than the pressure in the pressure chamber, the force acting on the valve body by the pressure in the pressure chamber A greater force acts on the support member. Even before the pressure in the back pressure chamber reaches the pressure in the pressure chamber, the support member moves to increase the urging force of the urging member and raise the relief set pressure. Therefore, the relief valve can be closed to reduce the flow rate of the working fluid discharged from the supply / discharge port, and the impact can be more reliably mitigated.

  According to a sixth aspect of the present invention, the relief valve further includes a regulating member that regulates a moving range of the support member according to a position with respect to the closing member, and the regulating member is movable with respect to the closing member.

  In the sixth invention, since the regulating member regulates the movement range of the supporting member according to the position with respect to the closing member, the position of the supporting member is determined by the regulating member when the pressure in the back pressure chamber is not increased. As a result, the initial urging force of the urging member is determined, and the initial relief setting pressure is determined. Further, since the regulating member is movably provided on the closing member, the regulating member may be moved relative to the closing member when changing the initial relief setting pressure. Therefore, the initial relief setting pressure can be easily changed, and the cushion characteristics can be easily adjusted.

  According to the present invention, it is possible to more reliably alleviate the impact that occurs when the fluid pressure cylinder is fully expanded and contracted.

It is a fragmentary sectional view of the fluid pressure cylinder concerning the embodiment of the present invention. It is sectional drawing of a head and shows the state which has a piston rod in a normal stroke area | region. It is sectional drawing of a head and shows the state which a piston rod moves at low speed near stroke end. It is sectional drawing of a head and shows the state which a piston rod moves at a somewhat high speed near the stroke end. It is sectional drawing of a head and shows the state which a piston rod moves at high speed near stroke end. It is an expanded sectional view of a fluid pressure cylinder concerning a modification of an embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. Here, the hydraulic cylinders 100 and 200 in which hydraulic oil is used as the working fluid will be described, but this embodiment is applicable to a fluid pressure cylinder in which other fluid such as hydraulic water is used. Although an example applied to the double-acting hydraulic cylinders 100 and 200 will be described, the present embodiment is also applicable to a single-acting hydraulic cylinder.

  The hydraulic cylinders 100 and 200 are used as actuators mounted on construction machines and industrial machines. For example, the hydraulic cylinders 100 and 200 are used as arm cylinders mounted on a hydraulic excavator. As the hydraulic cylinders 100 and 200 expand and contract, the arm of the hydraulic excavator rotates.

  As shown in FIG. 1, the hydraulic cylinder 100 includes a hollow cylinder 10, a piston rod 20 provided in the cylinder 10 so as to be able to reciprocate, and a piston 30 connected to the piston rod 20. The piston 30 is slidably accommodated in the cylinder 10.

  The cylinder 10 includes a cylindrical cylinder tube 11, a head side flange portion 12 provided at one end of the cylinder tube 11, and a cylinder bottom 13 provided at the other end of the cylinder tube 11. The head side flange portion 12 and the cylinder bottom 13 are joined to the cylinder tube 11 by welding.

  The piston rod 20 extends outside the cylinder 10 through the inside of the head side flange portion 12. A cylinder head 40 as a closing member is fastened to the head side flange portion 12 using a plurality of bolts 14.

  The cylinder head 40 is formed in an annular shape and slidably supports the piston rod 20. One open end of the cylinder tube 11 is closed by the cylinder head 40. The cylinder 10, the piston 30 and the cylinder head 40 form a rod side chamber 1 as a pressure chamber. The cylinder head 40 is formed with a head side port 3 as a supply / discharge port communicating with the rod side chamber 1.

  The cylinder bottom 13 closes the other open end of the cylinder tube 11. The cylinder 10, the piston 30 and the cylinder bottom 13 form an anti-rod side chamber 2 as a pressure chamber. The cylinder bottom 13 is formed with a bottom port (not shown) as a supply / discharge port communicating with the non-rod side chamber 2.

  The head side port 3 and the bottom side port are selectively connected to a hydraulic pump (not shown) as a hydraulic supply source or a tank (not shown) as a hydraulic oil reservoir through a switching valve (not shown). When one of the head side port 3 and the bottom side port communicates with the hydraulic pump by the switching valve, the other communicates with the tank.

  When hydraulic oil from the hydraulic pump is supplied to the rod side chamber 1 through the head side port 3, the piston rod 20 and the piston 30 move in a direction to reduce the anti-rod side chamber 2, and the hydraulic cylinder 100 contracts. At this time, the hydraulic oil in the non-rod side chamber 2 is discharged through the bottom port.

  When hydraulic oil from the hydraulic pump is supplied to the non-rod side chamber 2 through the bottom side port, the piston rod 20 and the piston 30 move in a direction to reduce the rod side chamber 1, and the hydraulic cylinder 100 extends. At this time, the hydraulic oil in the rod side chamber 1 is discharged through the head side port 3.

  The cylinder bottom 13 is provided with a connecting portion 13a that is connected to a construction machine or an industrial machine. A hole 13b is formed in the connecting portion 13a, and the connecting portion 13a is connected to a construction machine or an industrial machine via a pin (not shown) that passes through the hole 13b.

  A connecting portion 21 connected to a construction machine or an industrial machine is provided at the end of the piston rod 20 located outside the cylinder 10. Similar to the connecting portion 13a, a hole 22 is formed in the connecting portion 21, and the connecting portion 21 is connected to a construction machine or an industrial machine via a pin (not shown) inserted through the hole 22.

  FIG. 2 is an enlarged cross-sectional view of the periphery of the cylinder head 40, showing a state where the piston rod 20 is in the normal stroke region. As shown in FIG. 2, the cylinder head 40 includes a contact portion 41 that contacts the end surface of the head-side flange portion 12, a fitting portion 42 that fits the inner peripheral surface of the head-side flange portion 12, and the piston rod 20. And a support portion 43 for supporting the.

  The fitting portion 42 extends in an annular shape from the contact portion 41 toward the cylinder bottom 13 (see FIG. 1). An O-ring 44 is disposed between the outer peripheral surface of the fitting portion 42 and the inner peripheral surface of the head side flange portion 12. The O-ring 44 can prevent the hydraulic oil in the rod side chamber 1 from leaking from between the outer peripheral surface of the fitting portion 42 and the inner peripheral surface of the head side flange portion 12.

  The support portion 43 extends annularly from the contact portion 41 on the side opposite to the fitting portion 42. A bearing 45, a sub seal 46, a main seal 47, and a dust seal 48 are disposed on the inner peripheral surface of the support portion 43.

  The contact part 41, the fitting part 42, and the support part 43 may be integrally formed, or the fitting part 42 and the support part 43 may be formed separately from the contact part 41.

  The piston rod 20 includes a rod main body 23 that is slidably supported by the support portion 43, and a small diameter portion 24 having an outer diameter smaller than the outer diameter of the rod main body 23. The small diameter portion 24 is formed continuously from the rod body 23 in the axial direction, and a step portion 25 is formed between the rod body 23 and the small diameter portion 24. A male screw 24 a is formed on the outer peripheral surface of the small diameter portion 24.

  The piston 30 is formed in an annular shape, and an internal thread 30 a is formed on the inner peripheral surface of the piston 30. The piston 30 is connected to the piston rod 20 by screwing the female screw 30a of the piston 30 and the male screw 24a of the piston rod 20 together.

  The inner diameter of the fitting portion 42 of the cylinder head 40 is larger than the outer diameter of the rod main body 23, and the annular main passage 5 is formed by the inner peripheral surface of the fitting portion 42 and the outer peripheral surface of the rod main body 23. The main passage 5 communicates the rod side chamber 1 and the head side port 3 through an annular groove 41 a formed on the inner peripheral surface of the annular contact portion 41.

  During the contracting operation of the hydraulic cylinder 100, the hydraulic oil supplied from the head side port 3 is supplied to the rod side chamber 1 through the annular groove 41 a and the main passage 5. When the hydraulic cylinder 100 is extended, the hydraulic oil in the rod side chamber 1 is discharged from the head side port 3 through the main passage 5 and the annular groove 41a.

  The hydraulic cylinder 100 further includes a cushion mechanism 60 that decelerates the piston rod 20 near the stroke end during the extension operation. Hereinafter, the cushion mechanism 60 will be described in detail.

  The cushion mechanism 60 includes the main passage 5 and an annular cushion ring 61 as an entry portion that enters the main passage 5 near the stroke end. The cushion ring 61 is provided on the outer periphery of the small diameter portion 24 of the piston rod 20.

  The inner diameter of the cushion ring 61 is substantially equal to the outer diameter of the small diameter portion 24, and the cushion ring 61 is sandwiched between the step portion 25 of the piston rod 20 and the piston 30. That is, the cushion ring 61 is fixed to the piston rod 20 by the step portion 25 and the piston 30.

  The outer diameter of the cushion ring 61 is larger than the outer diameter of the rod body 23 and smaller than the inner diameter of the fitting portion 42 of the cylinder head 40. In a state where the cushion ring 61 has entered the main passage 5, the flow passage cross section of the main passage 5 is narrowed by the cushion ring 61, and the flow of hydraulic oil in the main passage 5 is narrowed. A passage formed by the inner peripheral surface of the fitting portion 42 and the outer peripheral surface of the cushion ring 61 when the cushion ring 61 enters the main passage 5 is also referred to as a “throttle passage 62” (FIGS. 3 to 5). reference).

  When the cushion ring 61 enters the main passage 5 during the extension operation of the hydraulic cylinder 100 and the flow of hydraulic oil is throttled (see FIG. 3), the flow rate of the hydraulic oil flowing from the rod side chamber 1 to the main passage 5 decreases, and the rod side chamber 1 pressure increases. As a result, the piston rod 20 is decelerated.

  Thus, the cushion mechanism 60 exhibits a cushioning action when the cushion ring 61 enters the main passage 5. Hereinafter, the pressure in the rod side chamber 1 in a state where the cushion mechanism 60 exhibits a cushioning action is also referred to as “cushion pressure”.

  The cushion mechanism 60 includes a bypass passage 63 that bypasses the main passage 5 and communicates the rod-side chamber 1 and the head-side port 3, and a relief valve 64 provided in the bypass passage 63. The bypass passage 63 is formed in the cylinder head 40 so as to open to the end surface of the fitting portion 42 and to open to the bottom surface of the annular groove 41a.

  The relief valve 64 opens when the pressure in the rod side chamber 1 reaches the relief set pressure, and allows the hydraulic oil to flow in the bypass passage 63. The relief valve 64 is closed when the pressure in the rod side chamber 1 is less than the relief set pressure, and shuts off the flow of hydraulic oil in the bypass passage 63.

  The structure of the relief valve 64 will be described in more detail. The relief valve 64 serves as a valve seat 64a provided in the bypass passage 63, a valve body 64b provided so as to be separable from the valve seat 64a, and a biasing member that urges the valve body 64b in a direction to seat the valve seat 64a. Spring 64c. The urging force of the spring 64c varies depending on the compression amount of the spring 64c, and the spring 64c exhibits a larger urging force as the compression amount is larger.

  When the force acting on the valve body 64b due to the pressure in the rod side chamber 1 is larger than the urging force of the spring 64c, the valve body 64b moves away from the valve seat 64a and allows the hydraulic oil to flow in the bypass passage 63. When the force acting on the valve body 64b due to the pressure in the rod side chamber 1 is smaller than the urging force of the spring 64c, the valve body 64b sits on the valve seat 64a and blocks the flow of hydraulic oil in the bypass passage 63. Thus, the relief setting pressure of the relief valve 64 is determined according to the magnitude of the urging force of the spring 64c.

  The relief valve 64 further includes a support member 64d that supports the spring 64c. The support member 64d is slidably accommodated in the housing 64e of the relief valve 64. The opening of the housing 64e is closed by a plug 64f. A back pressure chamber 64g of the relief valve 64 is formed in the housing 64e by the plug 64f and the support member 54d.

  When the pressure in the back pressure chamber 64g increases, the support member 64d moves in a direction to compress the spring 64c. The urging force of the spring 64c increases, and the relief setting pressure of the relief valve 64 increases. When the pressure in the back pressure chamber 64g decreases, the support member 64d moves in the direction in which the spring 64c extends. The biasing force of the spring 64c decreases, and the relief setting pressure of the relief valve 64 decreases.

  As described above, the support member 64d receives the pressure in the back pressure chamber 64g and moves in the housing 64e, thereby changing the compression amount of the spring 64c. As the compression amount of the spring 64c changes, the urging force of the spring 64c changes, and the relief set pressure of the relief valve 64 changes. That is, the support member 64d operates as a relief set pressure changing portion that increases the relief set pressure as the pressure in the back pressure chamber 64g increases.

  When the cushion mechanism 60 exerts a cushioning action during the extension operation of the hydraulic cylinder 100 and the cushion pressure reaches the relief set pressure, the relief valve 64 is opened and the flow of hydraulic oil in the bypass passage 63 is allowed (see FIG. 4). ). The hydraulic oil in the rod side chamber 1 flows to the head side port 3 through the main passage 5 and also flows to the head side port 3 through the bypass passage 63. Since the flow rate of the hydraulic fluid flowing from the rod side chamber 1 to the head side port 3 increases, the increase of the cushion pressure is stopped or moderated. As a result, the deceleration of the piston rod 20 becomes gentle, and a sudden change in the speed of the piston rod 20 can be prevented.

  The cushion mechanism 60 includes a first back pressure passage 65 that guides the pressure in the rod side chamber 1 to the back pressure chamber 64g, and an orifice plug as a first throttle portion that imparts resistance to the flow of hydraulic oil in the first back pressure passage 65. 66. The first back pressure passage 65 is provided in the cylinder head 40 so as to branch from the upstream side of the relief valve 64 in the bypass passage 63. The orifice plug 66 is detachably provided on the cylinder head 40.

  If the piston rod 20 moves at a high speed even when the cushion mechanism 60 exerts a cushioning action during the extension operation of the hydraulic cylinder 100, the opening degree of the relief valve 64 may be insufficient and the cushion pressure may continue to rise. In this case, the cushion pressure is guided to the back pressure chamber 64g through the first back pressure passage 65. Since resistance is applied to the flow of hydraulic oil in the first back pressure passage 65 by the orifice plug 66, the pressure in the back pressure chamber 64g gradually increases.

  As the pressure in the back pressure chamber 64g increases, the support member 64d of the relief valve 64 moves in the housing 64e and increases the amount of compression of the spring 64c. As a result, the urging force of the spring 64c increases, and the relief setting pressure of the relief valve 64 increases.

  When the relief setting pressure reaches the cushion pressure, the relief valve 64 is closed, and the flow of hydraulic oil in the bypass passage 63 is shut off (see FIG. 5). As a result, the hydraulic oil in the rod side chamber 1 does not flow to the head side port 3 through the bypass passage 63, and the flow rate of the hydraulic oil flowing from the rod side chamber 1 to the head side port 3 decreases. The flow rate of the hydraulic oil discharged from the head side port 3 decreases, and the piston rod 20 decelerates before reaching the stroke end. Therefore, the impact generated when the hydraulic cylinder 100 is fully extended and the piston rod 20 stops can be mitigated.

  The rate of pressure increase in the back pressure chamber 64g can be varied by changing the resistance that the orifice plug 66 imparts to the hydraulic fluid flow. Specifically, the orifice diameter of the orifice plug 66 may be changed.

  In the hydraulic cylinder 100, since the orifice plug 66 is detachably provided on the cylinder head 40, the orifice plug 66 can be easily replaced. Therefore, the rate of increase of the pressure in the back pressure chamber 64g can be easily changed, and the cushion characteristics can be easily adjusted.

  If the cushion pressure does not increase after the cushion mechanism 60 exhibits a cushioning action and the relief valve 64 is opened, the pressure difference between the front and rear of the orifice plug 66 is small. Therefore, the hydraulic oil in the rod side chamber 1 hardly flows into the back pressure chamber 64g through the first back pressure passage 65. The pressure in the back pressure chamber 64g hardly increases and the relief setting pressure does not increase. Accordingly, the relief valve 64 remains open, and the hydraulic oil in the rod side chamber 1 flows to the head side port 3 through the main passage 5 (throttle passage 62) and to the head side port 3 through the bypass passage 63 (see FIG. 4). At this time, since the flow of the working fluid in the bypass passage 63 is also restricted by the relief valve 64, the impact generated when the hydraulic cylinder 100 is fully extended can be reduced.

  The cushion mechanism 60 includes a second back pressure passage 67 that guides the pressure in the back pressure chamber 64g to the head-side port 3, and an orifice plug 68 as a second throttle portion provided in the second back pressure passage 67. In addition. The second back pressure passage 67 is provided in the cylinder head 40 by branching from the downstream side of the relief valve 64 in the bypass passage 63. The orifice plug 68 is detachably attached to the cylinder head 40.

  When the piston rod 20 stops and the pressure in the rod side chamber 1 stops increasing, the pressure in the back pressure chamber 64g is guided to the head side port 3 through the second back pressure passage 67. Therefore, the pressure in the back pressure chamber 64g can be easily reduced, and the relief setting pressure can be returned to the initial value.

  The orifice plug 68 imparts a greater resistance to the hydraulic oil flow than the orifice plug 66 imparts to the hydraulic oil flow. Therefore, the flow rate of the hydraulic fluid guided from the back pressure chamber 64g to the head side port 3 through the second back pressure passage 67 is based on the flow rate of the hydraulic fluid guided from the rod side chamber 1 to the back pressure chamber 64g through the first back pressure passage 65. There are few. Therefore, when the cushion pressure exceeds the relief set pressure and continues to rise, the pressure in the back pressure chamber 64g can be reliably increased, and the impact can be more reliably mitigated.

  The flow rate of the hydraulic oil in the second back pressure passage 67 can be changed by changing the resistance applied by the orifice plug 68 to the flow of the hydraulic oil. Specifically, the orifice diameter of the orifice plug 68 may be changed. In the hydraulic cylinder 100, since the orifice plug 68 is detachably provided on the cylinder head 40, the orifice plug 68 can be easily replaced. Therefore, the rising speed and the falling speed of the pressure in the back pressure chamber 64g can be easily changed, and the cushion characteristic can be easily adjusted.

  When the hydraulic cylinder 100 contracts, the hydraulic oil supplied from the head side port 3 is guided to the rod side chamber 1 through the main passage 5 (throttle passage 62), and the first back pressure passage 65 and the second back pressure passage 65 are also supplied. It is guided to the rod side chamber 1 through the pressure passage 67. Therefore, hydraulic oil can be easily supplied to the rod side chamber 1, and the responsiveness of the hydraulic cylinder 100 can be improved.

  In the hydraulic cylinder 100, the pressure receiving area of the support member 64d is larger than the pressure receiving area of the valve body 64b. Therefore, even when the pressure in the back pressure chamber 64g is lower than the pressure in the rod side chamber 1, a force larger than the force acting on the valve body 64b due to the pressure in the rod side chamber 1 acts on the support member 64d. Even before the pressure in the back pressure chamber 64g reaches the cushion pressure, the support member 64d moves to compress the spring 64c and increase the relief set pressure. Therefore, the relief valve 64 can be closed to reduce the flow rate of the hydraulic oil discharged from the head side port 3, and the impact can be more reliably mitigated.

  The relief valve 64 further includes a regulating rod 64h as a regulating member that regulates the movement range of the support member 64d. The restriction rod 64h is provided movably on the cylinder head 40 via the plug 64f.

  In a state where the pressure in the back pressure chamber 64g is not increased, the support member 64d is pressed against the regulation rod 64h by the spring 64c (see FIG. 2). That is, the movement range of the support member 64d in the extending direction of the spring 64c is restricted. As a result, the initial compression amount of the spring 64c is determined, and the initial relief setting pressure of the relief valve 64 is determined.

  The restriction rod 64h is inserted through a hole formed in the plug 64f. The outer peripheral surface of the restriction rod 64h and the inner peripheral surface of the plug 64f are screwed together. By rotating the restriction rod 64h with respect to the plug 64f, the restriction rod 64h moves in the extending and contracting direction of the spring 64c. As described above, the restriction rod 64h is provided in the cylinder head 40 so as to be movable in the extending and contracting direction of the spring 64c.

  When changing the initial relief setting pressure of the relief valve 64, the restriction rod 64h may be rotated relative to the plug 64f to change the position of the restriction rod 64h relative to the cylinder head 40. Therefore, the initial relief setting pressure can be easily changed, and the cushion characteristics can be easily adjusted.

  Next, the operation of the hydraulic cylinder 100 will be described with reference to FIGS.

  First, the case where the piston rod 20 moves at a low speed near the stroke end will be described with reference to FIG. Here, “low speed” is a speed at which the cushion pressure does not reach the relief set pressure of the relief valve 64 even when the cushion ring 61 enters the main passage 5 and the flow of hydraulic oil in the main passage 5 is throttled.

  Since the cushion pressure does not reach the initial relief setting pressure of the relief valve 64, the relief valve 64 does not open and the flow of hydraulic oil in the bypass passage 63 is blocked. The hydraulic oil in the rod side chamber 1 mainly flows to the head side port 3 through the main passage 5 (throttle passage 62).

  Since the flow of the hydraulic oil in the main passage 5 is throttled by the cushion ring 61, the flow rate of the hydraulic oil flowing from the rod side chamber 1 to the head side port 3 is reduced, and the piston rod 20 is decelerated. As a result, the impact generated when the hydraulic cylinder 100 is fully extended and the piston rod 20 stops can be mitigated.

  Next, the case where the piston rod 20 moves slightly faster near the stroke end will be described with reference to FIG. Here, “slightly faster” means that when the cushion ring 61 enters the main passage 5, the cushion pressure reaches the initial relief setting pressure of the relief valve 64, the relief valve 64 is opened, and then the cushion pressure Is the speed maintained at the initial relief setting pressure.

  Since the cushion pressure reaches the initial relief setting pressure of the relief valve 64, the relief valve 64 is opened, and the flow of hydraulic oil in the bypass passage 63 is allowed. The hydraulic oil in the rod side chamber 1 flows to the head side port 3 through the main passage 5 (throttle passage 62) and flows to the head side port 3 through the bypass passage 63.

  Since the cushion pressure does not increase after reaching the initial relief setting pressure of the relief valve 64, the pressure difference before and after the orifice plug 66 is small. Therefore, the hydraulic oil in the rod side chamber 1 hardly flows into the back pressure chamber 64g through the first back pressure passage 65.

  The pressure in the back pressure chamber 64g hardly increases, and the relief setting pressure of the relief valve 64 does not increase. Therefore, the relief valve 64 remains open. At this time, since the flow of the working fluid in the bypass passage 63 is also restricted by the relief valve 64, the impact generated when the hydraulic cylinder 100 is fully extended can be reduced.

  Next, the case where the piston rod 20 moves at high speed near the stroke end will be described with reference to FIGS. Here, “high speed” means a speed at which the cushion pressure continues to increase even after the cushion ring 61 enters the main passage 5 and the cushion pressure reaches the initial relief setting pressure of the relief valve 64 and the relief valve 64 is opened. It is.

  When the cushion ring 61 enters the main passage 5, the cushion pressure reaches the initial relief setting pressure of the relief valve 64. The relief valve 64 is opened, and the flow of hydraulic oil in the bypass passage 63 is allowed (see FIG. 4). The hydraulic oil in the rod side chamber 1 flows to the head side port 3 through the main passage 5 and also flows to the head side port 3 through the bypass passage 63.

  Since the flow rate of the hydraulic fluid flowing from the rod side chamber 1 to the head side port 3 increases, the increase of the cushion pressure is stopped or moderated. As a result, the deceleration of the piston rod 20 becomes gentle, and a sudden change in the speed of the piston rod 20 can be prevented.

  Since the cushion pressure also increases after the relief valve 64 is opened, the cushion pressure is guided to the back pressure chamber 64g through the first back pressure passage 65. Since resistance is given to the flow of hydraulic oil in the first back pressure passage 65 by the first back pressure passage 65, the pressure in the back pressure chamber 64g gradually increases.

  As the pressure in the back pressure chamber 64g increases, the relief setting pressure of the relief valve 64 increases. When the relief setting pressure reaches the cushion pressure, the relief valve 64 is closed, and the flow of hydraulic oil in the bypass passage 63 is shut off (see FIG. 5).

  The hydraulic oil in the rod side chamber 1 does not flow to the head side port 3 through the bypass passage 63, and the flow rate of the hydraulic oil flowing from the rod side chamber 1 to the head side port 3 decreases. The flow rate of the hydraulic oil discharged from the head side port 3 decreases, and the piston rod 20 decelerates before reaching the stroke end. Therefore, the impact generated when the hydraulic cylinder 100 is fully extended and the piston rod 20 stops can be mitigated.

  In the above description, the cushion mechanism 60 that decelerates the piston rod 20 near the stroke end during the extension operation has been described. The present embodiment can also be applied to a cushion mechanism that decelerates the piston rod 20 in the vicinity of the stroke end during a contraction operation. Hereinafter, the cushion mechanism that reduces the impact during the contraction operation will be described.

  FIG. 6 is an enlarged cross-sectional view of a hydraulic cylinder 200 according to a modification of the present embodiment, and mainly shows a cushion mechanism 260 that decelerates the piston rod near the stroke end during a contraction operation.

  As shown in FIG. 6, the bottom side port 4 is provided in the cylinder bottom 213. The cylinder bottom 213 includes an annular portion 252 that fits on the inner peripheral surface of the cylinder tube 11 and a protruding portion 251 that protrudes radially outward from the annular portion 252.

  A main passage 205 is formed by the inner peripheral surface of the annular portion 252. The main passage 205 communicates the anti-rod side chamber 2 and the bottom side port 4 through an annular groove 252 a formed on the inner peripheral surface of the annular portion 252.

  The cushion mechanism 260 includes a main passage 205 and a cushion ring 261 that enters the main passage 205 near the stroke end. The cushion ring 261 is provided on the outer periphery of the small diameter portion 24 of the piston rod 20 and is fixed to the small diameter portion 24 by screwing.

  In a state where the cushion ring 261 has entered the main passage 205, the flow passage cross section of the main passage 205 is narrowed by the cushion ring 261, and the flow of hydraulic oil in the main passage 205 is reduced.

  The cushion mechanism 260 includes a bypass passage 263 that bypasses the main passage 205 and communicates the anti-rod side chamber 2 and the bottom port 4, and a relief valve 264 provided in the bypass passage 263.

  The relief valve 264 opens when the pressure in the non-rod side chamber 2 reaches the relief set pressure, and allows the hydraulic oil to flow in the bypass passage 263. The relief valve 264 closes when the pressure in the non-rod-side chamber 2 is lower than the relief set pressure, and blocks the flow of hydraulic oil in the bypass passage 263.

  Since the structure of the relief valve 264 is the same as that of the relief valve 64 (see FIGS. 2 to 5), the description thereof is omitted here.

  The cushion mechanism 260 further includes a first back pressure passage 265, an orifice plug 266, a second back pressure passage 267, and an orifice plug 268. The first back pressure passage 265 guides the pressure in the non-rod side chamber 2 to the back pressure chamber 264 g of the relief valve 264. The orifice plug 266 provides resistance to the flow of hydraulic oil in the first back pressure passage 265. The second back pressure passage 267 guides the pressure in the back pressure chamber 264 g to the bottom side port 4. The orifice plug 268 imparts resistance to the flow of hydraulic oil in the second back pressure passage 267.

  Also in the hydraulic cylinder 200, as in the hydraulic cylinder 100, it is possible to mitigate the impact that occurs when the hydraulic cylinder 200 contracts completely and the piston rod 20 stops.

  Hereinafter, the configuration, operation, and effect of the embodiment of the present invention will be described together.

  In the present embodiment, the hydraulic cylinders 100 and 200 are accommodated in the cylinder tube 11, the piston rod 20 provided in the cylinder tube 11 so as to be able to reciprocate, and the piston rod 20 slidably accommodated in the cylinder tube 11. Formed on the cylinder head 40 and the cylinder bottom 213, and the cylinder head 40 and the cylinder bottom 213 forming the rod side chamber 1 and the anti-rod side chamber 2 between the piston 30 and the piston 30. The head-side port 3 and the bottom-side port 4 communicating with the rod-side chamber 1 and the anti-rod-side chamber 2 and the hydraulic oil in the rod-side chamber 1 and the anti-rod-side chamber 2 are discharged from the head-side port 3 and the bottom-side port 4. When 20 moves, the piston rod 20 is decelerated near the stroke end. The cushion mechanisms 60 and 260 are formed by the cylinder head 40 and the cylinder bottom 213, and communicate the rod side chamber 1 and the non-rod side chamber 2 with the head side port 3 and the bottom side port 4. Main passages 5, 205 that are provided in the piston rod 20, cushion rings 61, 261 that enter the main passages 5, 205 near the stroke end and restrict the flow of hydraulic oil in the main passages 5, 205, and a cylinder head 40 and the cylinder bottom 213, bypass passages 63 and 263 that bypass the main passages 5 and 205 and communicate the rod side chamber 1 and the anti-rod side chamber 2 with the head side port 3 and the bottom side port 4, and the bypass passage 63. , 263, the pressure in the rod side chamber 1 and the anti-rod side chamber 2 is relief set Relief valves 64 and 264 that allow the flow of hydraulic oil when the pressure reaches the pressure, and the pressure in the rod side chamber 1 and the anti-rod side chamber 2 provided in the cylinder head 40 and the cylinder bottom 213 are adjusted to the back pressure chambers of the relief valves 64 and 264. Relief valves 64, 264, and first back pressure passages 65, 265 leading to 64g, 264g, and orifice plugs 66, 266 provided in the first back pressure passages 65, 265 to provide resistance to the flow of hydraulic oil. Has a relief setting pressure changing portion 64d that increases the relief setting pressure as the pressure in the back pressure chambers 64g and 264g increases.

  In this configuration, when the piston rod 20 moves at high speed near the stroke end and the cushion rings 61 and 261 enter the main passages 5 and 205, the pressures in the rod side chamber 1 and the anti-rod side chamber 2 rise. When the pressure in the rod side chamber 1 and the non-rod side chamber 2 reaches the initial relief setting pressure, the relief valves 64 and 264 are opened. If the pressure in the rod side chamber 1 and the anti-rod side chamber 2 rises even when the relief valves 64 and 264 are opened, the pressure in the rod side chamber 1 and the anti-rod side chamber 2 has the orifice plugs 66 and 266. The pressure is led to the back pressure chambers 64g and 264g through the one back pressure passages 65 and 265, and the pressure in the back pressure chambers 64g and 264g gradually increases. As the pressure in the back pressure chambers 64g and 264g increases, the relief set pressure rises by the relief set pressure changing portion 64d. When the relief set pressure reaches the pressure in the rod side chamber 1 and the anti-rod side chamber 2, the relief valves 64 and 264 are closed, and the hydraulic oil in the rod side chamber 1 and the anti-rod side chamber 2 passes through the bypass passages 63 and 263 to the head side. It is not guided to the port 3 and the bottom side port 4. As a result, the flow rate of the hydraulic oil discharged from the head side port 3 and the bottom side port 4 decreases, and the piston rod 20 decelerates before reaching the stroke end. Therefore, the impact generated when the hydraulic cylinders 100 and 200 are fully expanded and contracted can be more reliably mitigated.

  In the present embodiment, the orifice plugs 66 and 266 are detachable from the cylinder head 40 and the cylinder bottom 213.

  In this configuration, since the orifice plugs 66 and 266 are detachably provided on the cylinder head 40 and the cylinder bottom 213, when the resistance applied to the flow of hydraulic oil in the first back pressure passages 65 and 265 is changed, The orifice plugs 66 and 266 may be replaced. Therefore, the rising speed of the pressure in the back pressure chambers 64g and 264g can be easily changed, and the cushion characteristic can be easily adjusted.

  Further, in the present embodiment, the cushion mechanisms 60 and 260 are provided in the cylinder head 40 and the cylinder bottom 213, and are second back pressure passages that guide the pressure in the back pressure chambers 64g and 264g to the head side port 3 and the bottom side port 4. 67, 267, and orifice plugs 68, 268, which are provided in the second back pressure passages 67, 267, and which impart a greater resistance to the flow of hydraulic oil than the resistance provided by the orifice plugs 66, 266. It is characterized by.

  In this configuration, the second back pressure passages 67 and 267 guide the pressure in the back pressure chambers 64g and 264g to the head side port 3 and the bottom side port 4, so that the piston rod 20 stops and the rod side chamber 1 and the anti-rod side chamber are stopped. When the increase in the pressure in 2 stops, the pressure in the back pressure chambers 64g and 264g is guided to the head side port 3 and the bottom side port 4 through the second back pressure passages 67 and 267, and decreases. Therefore, the relief set pressure can be returned to the initial value. In addition, the orifice plugs 68 and 268 impart resistance to the hydraulic oil flow that is greater than the resistance imparted to the hydraulic oil flow by the orifice plugs 66 and 266. Therefore, the flow rate of the hydraulic fluid guided from the back pressure chambers 64g and 264g to the head side port 3 and the bottom side port 4 through the second back pressure passages 67 and 267 is changed from the rod side chamber 1 and the anti-rod side chamber 2 to the first back pressure passage. The flow rate of hydraulic fluid guided to the back pressure chambers 64g and 264g through 65 and 265 is smaller. Therefore, when the piston rod 20 moves at high speed near the stroke end and the pressure in the rod side chamber 1 and the anti-rod side chamber 2 continues to rise above the relief set pressure, the pressure in the back pressure chambers 64g and 264g is surely increased. It can be raised and the impact can be mitigated more reliably.

  In the present embodiment, the orifice plugs 68 and 268 are detachable from the cylinder head 40 and the cylinder bottom 213.

  In this configuration, the orifice plugs 68 and 268 are detachable from the cylinder head 40 and the cylinder bottom 213. Therefore, when the resistance given to the flow of hydraulic oil in the second back pressure passages 67 and 267 is changed, the orifice plug 68 and 268 may be replaced. Therefore, the rising speed of the pressure in the back pressure chambers 64g and 264g can be easily changed, and the cushion characteristic can be easily adjusted.

  Further, in the present embodiment, the relief valves 64 and 264 are provided with a valve body 64b that opens and closes the bypass passages 63 and 263 by opening and closing the valve seat 64a provided in the bypass passages 63 and 263, and the valve body 64b. A spring 64c that urges the seat 64a in a direction to be seated and determines a relief setting pressure according to the magnitude of the urging force, and the relief setting pressure changing portion 64d supports the spring 64c and includes a back pressure chamber 64g, A support member 64d that receives the pressure in H.264g and moves to change the biasing force of the spring 64c is provided, and the pressure receiving area of the support member 64d is larger than the pressure receiving area of the valve body 64b.

  In this configuration, since the pressure receiving area of the support member 64d is larger than the pressure receiving area of the valve body 64b, even when the pressure in the back pressure chambers 64g and 264g is lower than the pressure in the rod side chamber 1 and the anti-rod side chamber 2, A force larger than the force acting on the valve body 64b due to the pressure in the rod side chamber 1 and the non-rod side chamber 2 acts on the support member 64d. Even before the pressure in the back pressure chambers 64g and 264g reaches the pressure in the rod side chamber 1 and the anti-rod side chamber 2, the support member 64d moves to increase the urging force of the spring 64c and raise the relief set pressure. Therefore, the relief valves 64 and 264 are closed to reduce the flow rate of the hydraulic oil discharged from the head side port 3 and the bottom side port 4, and the impact can be more reliably mitigated.

  In the present embodiment, the relief valves 64 and 264 further include a restriction rod 64 h that restricts the movement range of the support member 64 d according to the positions with respect to the cylinder head 40 and the cylinder bottom 213, and the restriction rod 64 h is the cylinder head 40. And the cylinder bottom 213 is movable.

  In this configuration, since the restriction rod 64h restricts the movement range of the support member 64d according to the position with respect to the cylinder head 40 and the cylinder bottom 213, the support member 64d is in a state where the pressure in the back pressure chambers 64g and 264g is not increased. Is determined by the restriction rod 64h. As a result, the initial biasing force of the spring 64c is determined, and the initial relief setting pressure is determined. Further, since the restriction rod 64h is movable with respect to the cylinder head 40 and the cylinder bottom 213, when changing the initial relief setting pressure, the restriction rod 64h is moved with respect to the cylinder head 40 and the cylinder bottom 213. Just do it. Therefore, the initial relief setting pressure can be easily changed, and the cushion characteristics can be easily adjusted.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  DESCRIPTION OF SYMBOLS 1 ... Rod side chamber (pressure chamber), 2 ... Anti-rod side chamber (pressure chamber), 3 ... Head side port (supply / discharge port), 4 ... Bottom side port (supply / discharge port), 5 ... Main passage, 11 ... Cylinder tube, 20 ... Piston rod, 30 ... Piston, 40 ... Cylinder head (blocking member), 60 ... Cushion mechanism, 61 ... Cushion ring (Entrance), 63 ... detour passage, 64 ... relief valve, 64a ... valve seat, 64b ... valve body, 64c ... spring (biasing member), 64d ... support member (Relief set pressure changing portion), 64 g... Back pressure chamber, 64 h... Regulating rod (regulating member), 65... First back pressure passage, 66. 67 ... Second back pressure passage, 68 ... Orifice plug Second throttle part), 100 ... hydraulic cylinder (fluid pressure cylinder), 200 ... hydraulic cylinder (fluid pressure cylinder), 205 ... main passage, 250 ... cylinder bottom (blocking member), 260 · · · Cushion mechanism, 261 · · · cushion ring (entrance), 263 · · · detour passage, 264 · · · relief valve, 264g · · · back pressure chamber, 265 · · · first back pressure passage, 266 · ..Orifice plug (first throttle part), 267 ... second back pressure passage, 268 ... orifice plug (second throttle part)

Claims (6)

A cylinder tube;
A piston rod provided in the cylinder tube so as to be capable of reciprocating;
A piston connected to the piston rod and slidably received in the cylinder tube;
A closing member that closes the open end of the cylinder tube and forms a pressure chamber with the piston;
A supply / discharge port formed in the closing member and communicating with the pressure chamber;
A cushion mechanism that decelerates the piston rod near the stroke end when the working fluid in the pressure chamber is discharged from the supply / discharge port and the piston rod moves, and
The cushion mechanism is
A main passage formed by the closing member and communicating the pressure chamber and the supply / exhaust port;
An entry portion provided in the piston rod, for entering the main passage near the stroke end and restricting a flow of the working fluid in the main passage;
A bypass passage provided in the closing member, bypassing the main passage and communicating the pressure chamber and the supply / discharge port;
A relief valve provided in the bypass passage and allowing the flow of working fluid when the pressure in the pressure chamber reaches a relief setting pressure;
A first back pressure passage provided in the closing member and guiding a pressure in the pressure chamber to a back pressure chamber of the relief valve;
A first throttle portion provided in the first back pressure passage for imparting resistance to the flow of the working fluid;
With
The fluid pressure cylinder, wherein the relief valve includes a relief setting pressure changing portion that increases the relief setting pressure as the pressure in the back pressure chamber increases.   The fluid pressure cylinder according to claim 1, wherein the first throttle portion is detachable from the closing member.   The cushion mechanism is provided in the closing member, provided in the second back pressure passage for guiding the pressure in the back pressure chamber to the supply / exhaust port, and in the second back pressure passage, and is provided by the first throttle portion. The fluid pressure cylinder according to claim 1, further comprising a second throttle portion that imparts a resistance larger than the resistance to the flow of the working fluid.   The fluid pressure cylinder according to claim 3, wherein the second throttle portion is detachable from the closing member. The relief valve is detachably seated on a valve seat provided in the bypass passage and opens and closes the bypass passage, and a biasing force is applied in a direction in which the valve body is seated on the valve seat. And an urging member that determines the relief setting pressure according to
The relief set pressure changing unit includes a support member that supports the urging member and moves under the pressure in the back pressure chamber to change the urging force of the urging member,
The fluid pressure cylinder according to any one of claims 1 to 4, wherein a pressure receiving area of the support member is larger than a pressure receiving area of the valve body. The relief valve further includes a regulating member that regulates a moving range of the support member according to a position with respect to the closing member,
The fluid pressure cylinder according to claim 5, wherein the regulating member is movable with respect to the closing member.

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