JP2012202446A - Cushion mechanism of fluid pressure cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cushion mechanism of a fluid pressure cylinder capable of adjusting a cushion pressure.SOLUTION: The cushion mechanism includes a cushion gap 8 for throttling the flow of a working fluid, a bypass route 50 which introduces a working oil that detours the cushion gap 8, a valve housing hole 53 to which the bypass route 50 opens, a spool 64 which is stored in the valve housing hole 53 to increase/decrease a route opening area of the bypass route 50, a set screw 63 for supporting the spool 64, and a threaded hole 54 to which the set screw 63 is screwed.

Description

  The present invention relates to a fluid pressure cylinder cushion mechanism that decelerates a piston rod near the stroke end of the piston rod in a cylinder tube.

  For example, a fluid pressure cylinder (hydraulic cylinder) used in a hydraulic excavator or the like includes a cushion mechanism that generates a cushion pressure near the stroke end of the piston rod to decelerate the piston rod.

  Conventionally, as this kind of cushion mechanism, when the piston rod comes near the stroke end, a cushion bearing that defines a cushion gap through which the working fluid passes, and a spacer member that is interposed so as to face the cushion bearing (See Patent Document 1).

  In this cushion mechanism, when the piston rod comes close to the stroke end, the cushion bearing enters the inside of the spacer member to define a cushion gap, and this cushion gap provides resistance to the flow of the working fluid. Pressure is generated.

JP 2004-11781 A

  However, in such a conventional cushion mechanism, there is a possibility that the cushion pressure deviates from the set value due to dimensional variations of a cushion bearing or the like that defines the cushion gap.

  The present invention has been made in view of the above problems, and an object thereof is to provide a cushion mechanism for a fluid pressure cylinder capable of adjusting the cushion pressure.

  The present invention is a fluid pressure cylinder cushion mechanism that decelerates a piston rod in the vicinity of the stroke end of the piston rod relative to the cylinder tube, and includes a cushion gap that restricts the flow of the working fluid, and a bypass that guides hydraulic oil that bypasses the cushion gap A passage, a valve housing hole in which the bypass passage is opened, a spool that is housed in the valve housing hole to increase or decrease the passage opening area of the bypass passage, a set screw that supports the spool, and a screw that is screwed into the set screw It was set as the structure provided with a hole.

  According to the present invention, by adjusting the screwing position of the set screw with respect to the screw hole, the spool is displaced in the valve housing hole, and the passage opening area of the bypass passage can be changed. By adjusting the cushion pressure in this way, the excess or deficiency of the cushion pressure due to the dimensional variation of the members that define the cushion gap is eliminated.

1 is a cross-sectional view of a hydraulic cylinder showing an embodiment of the present invention. Similarly, sectional drawing of the hydraulic cylinder which expanded a part of FIG. The figure which similarly shows operation | movement of a bypass aperture adjustment mechanism. Sectional drawing of the pressure cylinder which shows other embodiment. Similarly, sectional drawing of the hydraulic cylinder which expanded a part of FIG. The figure which similarly shows operation | movement of a bypass aperture adjustment mechanism.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
A hydraulic cylinder 1 shown in FIG. 1 is used as an arm cylinder of a hydraulic excavator, for example. As the hydraulic cylinder 1 expands and contracts, the arm of the hydraulic excavator rotates.

  The hydraulic cylinder (fluid pressure cylinder) 1 includes a cylindrical cylinder tube 10, a piston 20 that partitions the rod chamber 2 and the end chamber 3 in the cylinder tube 10, and a piston rod 30 that is connected to the piston 20. Prepare. The rod chamber 2 and the end chamber 3 communicate with a hydraulic source (working fluid pressure source) (not shown), respectively, and the piston rod 30 moves in the direction of the central axis O by the working oil pressure (working fluid pressure) guided from the hydraulic source. Telescopic operation. FIG. 1 shows a state in which the piston rod 30 has come close to the stroke end.

  Note that a working fluid such as a water-soluble alternative liquid may be used instead of the oil as the working oil.

  A cylinder head 40 is fastened to the end of the cylindrical cylinder tube 10 via a plurality of bolts 41.

  A cylinder head 40 through which the piston rod 30 is slidably inserted is provided at the opening end of the cylinder tube 10.

  The cylinder head 40 has a cylindrical head fitting portion 42 that is fitted to the cylinder inner peripheral surface 11. A seal ring 9 is interposed between the head fitting portion 42 and the cylinder inner peripheral surface 11 to seal the rod chamber 2.

  A bearing 59, a sub seal 56, a main seal 57, and a dust seal 58 are interposed on the inner periphery of the cylinder head 40, and these are in sliding contact with the rod outer peripheral surface 31 of the piston rod 30. When the bearing 59 is in sliding contact with the rod outer peripheral surface 31, the piston rod 30 is supported so as to translate in the direction of the central axis O of the cylinder tube 10.

  A supply / exhaust port 43 is opened on the flange surface 46 of the cylinder head 40, and a hydraulic pipe (not shown) communicating with a hydraulic power source is connected to the supply / exhaust port 43.

  A head annular groove 45 and a head inner peripheral surface 44 are formed on the inner periphery of the cylinder head 40, and the supply / discharge passage 5 is defined between these and the piston rod 30. One end of the supply / discharge port 43 is opened in the head annular groove 45. The head inner peripheral surface 44 is formed in a cylindrical surface shape centered on the central axis O.

  In the contraction operation of the hydraulic cylinder 1 in which the piston rod 30 moves downward in FIG. 1, the pressurized hydraulic fluid supplied through the hydraulic piping from the hydraulic source passes through the supply / discharge port 43 and the supply / discharge passage 5 to the rod. It flows into the chamber 2 (see the white arrow in the figure).

  On the other hand, when the hydraulic cylinder 1 in which the piston rod 30 moves upward in FIG. 1 is extended, the hydraulic oil in the rod chamber 2 passes through the supply / discharge passage 5, the supply / discharge port 43, and the hydraulic piping in the middle of the stroke. To the hydraulic pressure source (see the white arrow in the figure).

  The hydraulic cylinder 1 is provided with a cushion mechanism 6 that decelerates the piston rod 30 when the piston rod 30 comes near the stroke end.

  The cushion mechanism 6 includes a cushion gap 8 defined when the piston rod 30 comes near the stroke end.

  A cylindrical cushion bearing 60 is attached to the piston rod 30. The cushion bearing 60 is fitted to the outer peripheral surface of the end portion of the piston rod 30 and is sandwiched between the annular step portion 32 of the piston rod 30 and the upper end surface 22 of the piston 20.

  The configuration is not limited to this, and the cushion bearing may be formed integrally with the piston rod 30.

  The cushion bearing 60 may be fitted to the piston rod 30 with a gap, and the cushion bearing 60 may be floatingly supported so as to be movable in the radial direction of the piston rod 30.

  When the piston rod 30 comes close to the stroke end during the extension operation of the hydraulic cylinder 1, the cushion bearing 60 enters the inside of the head inner peripheral surface 44, thereby defining the cushion gap 8 therebetween. When the cushion bearing 60 enters the inside of the head inner peripheral surface 44, the hydraulic oil in the rod chamber 2 flows out to the hydraulic source through the cushion gap 8, the supply / discharge passage 5, and the hydraulic piping. The cushion gap 8 gives resistance to the flow of hydraulic oil flowing out from the rod chamber 2 through the supply / discharge passage 5, and the pressure in the rod chamber 2 (hereinafter referred to as cushion pressure) increases, thereby causing the piston rod 30 to move. Slow down.

  The cushion bearing 60 has a bearing outer peripheral surface 61 as its outer peripheral surface. The outer peripheral surface 61 of the bearing is formed in a cylindrical surface centered on the central axis O.

  The outer diameter of the bearing outer peripheral surface 61 is formed larger than the outer diameter of the rod outer peripheral surface 31 and smaller than the inner diameter of the head inner peripheral surface 44. When the cushion bearing 60 enters the head inner peripheral surface 44 in the vicinity of the stroke end, a cushion gap 8 is defined between them.

  The cushion bearing 60 is formed with a not-shown split circle (notch) in which the bearing outer peripheral surface 61 is partially removed. As the piston rod 30 approaches the stroke end, the flow passage cross-sectional area of the cushion gap 8 defined by the split circle portion gradually decreases. According to the deceleration characteristics required for the cushion mechanism 6, the clearance (gap width) of the cushion gap 8 and the shape of the split circle portion are set.

  However, the slight clearance of the cushion gap 8 may deviate from the set value due to dimensional variations of the bearing outer peripheral surface 61 and the head inner peripheral surface 44 that define the cushion gap 8.

  In response to this, the cushion mechanism 6 is provided with a bypass passage 50 that guides hydraulic oil that bypasses the cushion gap 8 and a bypass throttle adjustment mechanism 65 that adjusts the passage opening area of the bypass passage 50. .

  The bypass passage 50 is defined by through holes 51 and 52 and a notch 48 formed in the cylinder head 40. The through holes 51 and 52 are formed to extend on a straight line parallel to the central axis O. One end of the through hole 51 opens to the supply / discharge port 43, and one end of the through hole 52 opens to the rod chamber 2 through the notch 48. Thereby, the bypass passage 50 communicates the supply / exhaust port 43 and the rod chamber 2.

  In the state in which the hydraulic cylinder 1 is most extended, the upper end surface 22 of the piston 20 contacts the lower end surface 49 of the cylinder head 40, but the cushion gap 8 and the bypass passage 50 are communicated with the rod chamber 2 by the notch 48.

  FIG. 2 is an enlarged cross-sectional view of a part of FIG. During the extension operation of the hydraulic cylinder 1, the hydraulic oil in the rod chamber 2 flows through the cushion gap 8 and through the bypass passage 50 to the supply / exhaust port 43 as indicated by arrows in the drawing.

  The bypass throttle adjusting mechanism 65 includes a valve accommodating hole 53 that intersects with the through hole 51 of the bypass passage 50, a spool 64 that is accommodated in the valve accommodating hole 53 and has a variable passage opening area of the bypass passage 50, and the cylinder head 40. A set screw 63 for supporting the spool 64 and a screw hole 54 for screwing the set screw 63 are provided. The set screw 63 is configured such that the screwing position with respect to the screw hole 54 is adjusted by an operator.

  The valve housing hole 53 is formed so as to extend on a straight line substantially orthogonal to the central axis O, and is also substantially orthogonal to the through hole 51 of the bypass passage 50. The screw hole 54 is formed coaxially with the valve housing hole 53.

  A working hole (screw hole) 55 is formed in the cylinder head 40 coaxially with the screw hole 54. This working hole 55 opens in the outer wall surface of the cylinder head 40, and the stopper 74 is attached. The plug 74 is screwed into the work hole 55 and is attached to the valve hole 53 so that the hydraulic oil does not leak out through the valve hole 53.

  The spool 64 includes a pair of land portions 67 and 69 and a valve shaft portion 68 that connects the land portions 67 and 69. The land portions 67 and 69 are fitted into the valve housing hole 53 with the bypass passage 50 (through hole 51) interposed therebetween, and the opening area of the bypass passage 50 is variable according to the axial position of the land portions 67 and 69. Configure the aperture.

  The set screw 63 includes a head portion 72 that is screwed into the screw hole 54, and a shaft portion 70 that is in contact with the end surface 64 a of the spool 64. A male screw that is screwed into the screw hole 54 is formed on the outer periphery of the head portion 72, and a tool engaging portion 71 that engages with a tool is opened on the end surface of the head portion 72. For example, the tool engaging portion 71 is a hexagonal hole, and a hexagon wrench is used as a tool that engages with the tool engaging portion 71.

  A coiled spring 66 is interposed between the end face 64 b of the spool 64 and the bottom 53 a of the valve accommodating hole 53 by being compressed. The spool 64 is pressed against the set screw 63 by the spring force of the spring 66.

  When the operator changes the screwing position of the head portion 72 and moves the set screw 63 in the axial direction, the spool 64 pressed against the spring 66 moves together. Thereby, one of the land portions 67 and 69 faces the bypass passage 50, and the opening area of the bypass passage 50 is reduced.

  FIGS. 3A and 3B are views seen from the direction of arrow A in FIG. 1, showing the operation of the spool 64, and the hatched portion shows the opening (flow path portion) of the bypass passage 50. ing.

  FIG. 3A shows a state in which the spool 64 is in the fully open position. In this state, the land portions 67 and 69 are located on both sides of the bypass passage 50, and the opening area of the bypass passage 50 is not reduced by the land portions 67 and 69.

  FIG. 3B shows a state where the spool 64 is in the half-open position. In this state, the land portion 69 faces the bypass passage 50, and the opening area of the bypass passage 50 is reduced by about half by the land portion 69. From this state, the opening area of the bypass passage 50 is increased by moving the spool 64 in the right direction in the figure, while the opening area of the bypass passage 50 is decreased by moving in the left direction.

  When the hydraulic cylinder 1 is manufactured, after the assembly process of the hydraulic cylinder 1 is completed, a test process for measuring the operating characteristics of the hydraulic cylinder 1 is performed, and the operator adjusts the bypass throttle adjusting mechanism 65 based on the measurement result. An adjusting step is performed.

  In the test process, the hydraulic cylinder 1 is expanded and contracted under a predetermined condition by an actuator (not shown), and the expansion and contraction operation speed corresponding to the stroke of the piston rod 30 is measured.

  In the adjustment step, the opening degree of the spool 64 is adjusted according to the difference between the measured value of the deceleration near the stroke end and the set value. This adjustment is performed by the operator inserting a tool through the work hole 55 and engaging the tool engaging portion 71 of the set screw 63 to rotate the set screw 63 and changing the screwing position of the set screw 63.

  When the measured value of the deceleration is lower than the set value, the opening area of the bypass passage 50 is adjusted to be smaller than a predetermined reference opening, and the cushion pressure is increased. On the other hand, when the measured value of the deceleration is higher than the set value, the opening area of the bypass passage 50 is adjusted to be larger than a predetermined reference opening, and the excessive cushion pressure is lowered.

  Thus, the hydraulic cylinder 1 adjusts the opening area of the bypass passage 50 for each product, so that the cushion pressure caused by the dimensional variation of the bearing outer peripheral surface 61 and the head inner peripheral surface 44 that define the cushion gap 8 and the like. This eliminates the excess and deficiency, and allows the deceleration near the stroke end to approach the set value.

  As described above, in the present embodiment, the cushion mechanism 6 of the fluid pressure cylinder 1 that decelerates the piston rod 30 in the vicinity of the stroke end of the piston rod 30 with respect to the cylinder tube 10, and the cushion gap 8 that restricts the flow of the working fluid; A bypass passage 50 that guides hydraulic oil that bypasses the cushion gap 8, a valve accommodation hole 53 that opens the bypass passage 50, and a spool 64 that is accommodated in the valve accommodation hole 53 and increases or decreases the passage opening area of the bypass passage 50. And a set screw 63 that supports the spool 64 and a screw hole 54 into which the set screw 63 is screwed.

  Based on the above configuration, by adjusting the screwing position of the set screw 63 with respect to the screw hole 54, the spool 64 is displaced in the valve housing hole 53, and the passage opening area of the bypass passage 50 is changed. As a result, the cushion pressure is adjusted by changing the resistance applied to the working fluid flowing through the bypass passage 50, so that the excess or deficiency of the cushion pressure due to the dimensional variation of the members defining the cushion gap 8 is eliminated. The As a result, the variation in cushioning performance can be suppressed without increasing the dimensional accuracy of the members that define the cushion gap 8, thereby reducing the cost of the product.

(Second Embodiment)
Next, another embodiment shown in FIGS. 4 to 6 will be described. This has basically the same configuration as the embodiment of FIGS. 1 to 3, and only the differences will be described. In addition, the same code | symbol is attached | subjected to the same structure part as the said embodiment.

  As shown in FIG. 4, a holder 23 is interposed inside the cylinder tube 10. The holder 23 is formed in an annular shape centering on the central axis O, and is fitted to the cylinder inner peripheral surface 11 along with the head fitting portion 42 of the cylinder head 40. The holder 23 has a lower end outer peripheral portion seated on the tapered surface 12 of the cylinder inner peripheral surface 11, and a lower end surface 47 of the cylinder head 40 abuts on the upper end surface and is sandwiched between the two.

  In addition, about the fixing method of the holder 23, you may fix the cylinder head 40 and the holder 23 with the volt | bolt which is not illustrated in addition to this, for example. In this case, it is not necessary to form the tapered surface 12 on the inner surface of the cylinder tube 10.

  FIG. 5 is an enlarged cross-sectional view of a part of FIG. The inner peripheral surface 24 of the holder 23 is formed in a cylindrical surface shape with the central axis O as the center. When the piston rod 30 comes near the stroke end during the extension operation of the hydraulic cylinder 1, the cushion bearing 60 enters the inside of the holder 23, thereby defining the cushion gap 8 therebetween.

  A bypass passage 28 is provided in the holder 23. The bypass passage 28 is defined by a notch 25 formed in the cylinder head 40, through holes 26 and 27, and a notch 29. The through holes 26 and 27 are formed to extend on a straight line parallel to the central axis O. One end of the through hole 26 opens into the supply / discharge passage 5 through the notch 25, and one end of the through hole 27 opens into the rod chamber 2 through the notch 29. As a result, the bypass passage 28 communicates the supply / exhaust port 43 and the rod chamber 2 via the supply / discharge passage 5.

  In the state in which the hydraulic cylinder 1 is most contracted, the upper end surface 22 of the piston 20 contacts the lower end surface 39 of the holder 23, but the cushion gap 8 and the bypass passage 50 are communicated with the rod chamber 2 by the notch 29.

  During the contraction operation of the hydraulic cylinder 1, the hydraulic oil in the rod chamber 2 flows through the cushion gap 8 and through the bypass passage 28 to the supply / discharge passage 5 as indicated by arrows in FIG. 2.

  As shown in FIG. 5, the bypass throttle adjusting mechanism 65 has a valve housing hole 33 that intersects the through hole 51 of the bypass passage 50, and is accommodated in the valve housing hole 33 so that the passage opening area of the bypass passage 28 is variable. A spool 64, a set screw 63 that supports the spool 64 with respect to the holder 23, and a screw hole 34 into which the set screw 63 is screwed are provided. The set screw 63 is configured such that the screwing position with respect to the screw hole 34 is adjusted by an operator.

  In the holder 23, the valve accommodation hole 33 is formed so as to extend on a straight line substantially orthogonal to the central axis O, and a screw hole 34 is formed coaxially with the valve accommodation hole 33.

  The spool 64 and the set screw 63 have the same configuration as in the above embodiment. When the operator changes the screwing position of the head portion 72 and moves the set screw 63 in the axial direction, one of the land portions 67 and 69 faces the bypass passage 28 so that the opening area of the bypass passage 28 increases or decreases. It has become.

  A working hole (screw hole) 55 is formed in the cylinder tube 10 coaxially with the screw hole 34. One end of the working hole 55 is opposed to the screw hole 34 of the holder 23, the other end is opened on the outer wall surface of the cylinder tube 10, and the plug 74 is attached.

  6A and 6B are views seen from the direction of arrow A in FIG. 4, showing the operation of the spool 64, and the hatched portion shows the opening (flow path portion) of the bypass passage 28. ing.

  FIG. 6A shows a state where the spool 64 is in the fully open position. In this state, the land portions 67 and 69 are located on both sides of the bypass passage 28, and the opening area of the bypass passage 28 is not reduced by the land portions 67 and 69.

  FIG. 6B shows a state where the spool 64 is in the half-open position. In this state, the land portion 69 faces the bypass passage 28, and the opening area of the bypass passage 28 is reduced by about half by the land portion 69. From this state, the opening area of the bypass passage 28 increases when the spool 64 moves to the right in the figure, and the opening area of the bypass passage 28 decreases by moving to the left.

  As described above, in the present embodiment, the holder 23 interposed inside the cylinder tube 10 is provided, and the bypass throttle adjusting mechanism 65 is interposed in the holder 23.

  Based on the above configuration, since the holder 23 is formed separately from the cylinder head 40, the holder 23 corresponding to the required deceleration characteristics can be interposed inside the cylinder tube 10, and the bypass throttle adjusting mechanism 65 can be provided. Are easily exchanged. Moreover, by adding the holder 23, it becomes possible to carry out without changing the basic shape of the cylinder head 40, and the cost of the product can be suppressed.

  In the present embodiment, the cushion gap 8 is defined by the inner peripheral surface 24 of the holder 23.

  Based on the above configuration, when the fluid pressure cylinder 1 does not need to include the cushion mechanism 6, it can be easily handled by removing the holder 23. Moreover, the clearance of the cushion gap 8 can be easily changed by exchanging the holder 23.

  The present invention can also be applied to a cushion mechanism (not shown) that decelerates the piston rod in the vicinity of the stroke end of the piston rod during the contraction operation of the fluid pressure cylinder.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

1 Hydraulic cylinder (fluid pressure cylinder)
5 Supply / exhaust passage 6 Cushion mechanism 8 Cushion gap 10 Cylinder tube 23 Holder 28, 50 Bypass passage 33, 53 Valve accommodation hole 34, 54 Screw hole 55 Work hole 30 Piston rod 40 Cylinder head 43 Supply / exhaust port 60 Cushion bearing 61 Bearing outer circumference Surface 63 Set screw 64 Spool 65 Bypass iris adjustment mechanism 66 Spring

Claims (3)

A fluid pressure cylinder cushion mechanism that decelerates the piston rod near the stroke end of the piston rod relative to the cylinder tube,
A cushion gap that restricts the flow of the working fluid;
A bypass passage for guiding hydraulic oil that bypasses the cushion gap;
A valve housing hole in which the bypass passage opens;
A spool that is housed in the valve housing hole and increases or decreases the passage opening area of the bypass passage;
A set screw that supports the spool;
A cushion mechanism for a fluid pressure cylinder, comprising: a screw hole into which the set screw is screwed. A holder interposed inside the cylinder tube;
2. The hydraulic cylinder cushion mechanism according to claim 1, wherein the bypass passage is formed in the holder and the bypass throttle adjusting mechanism is interposed.   The cushion mechanism for a hydraulic cylinder according to claim 2, wherein the cushion gap is defined by an inner peripheral surface of the holder.

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