JP6113996B2 - Fluid pressure cylinder - Google Patents

Description

  The present invention relates to a hydraulic cylinder in which a piston rod is decelerated by a cushion pressure generated near the stroke end.

  For example, a fluid pressure cylinder (hydraulic cylinder) used in a hydraulic excavator or the like includes a cushion mechanism that decelerates the piston rod by a cushion pressure generated when the piston rod inserted into the cylinder tube comes near the stroke end.

  The cushion mechanism described in Patent Document 1 includes a cushion cylindrical surface provided in a cylinder tube, and a cushion bearing that is floatingly supported by a piston rod by working fluid pressure.

  In this cushion mechanism, when the piston rod comes near the stroke end, the cushion bearing enters the cushion cylindrical surface, and the flow of the working fluid is reduced between them, resulting in a cushion pressure and the piston rod decelerating. It is supposed to be.

  In this type of cushion mechanism, a planar split circle (notch) extending in an axial direction on the outer peripheral surface of the cushion bearing is formed by cutting (see FIG. 9). When the piston rod comes to the stroke end, the split portion functions as a variable restrictor that confronts the cushion cylindrical surface and restricts the flow of the working fluid. As the piston rod approaches the stroke end, the opening area of the variable throttle decreases.

  In this cushion mechanism, the cushion characteristic at which the piston rod decelerates can be changed by arbitrarily setting the angle of inclination of the split circle portion.

  The cushion mechanism described in Patent Document 2 includes a cushion cylindrical surface provided in a cylinder tube, and a cushion bearing that is supported by being fitted to a piston rod. The cushion bearing is fixed to the piston rod without being floating supported by the working fluid pressure.

  In this cushion mechanism, a tapered groove (throttle groove) having a V-shaped cross section extending in an axial direction is formed on the outer peripheral surface of the cushion bearing. Also in this case, when the piston rod comes to the stroke end, the tapered groove functions as a variable throttle that constricts the flow of the working fluid against the cylindrical surface of the cushion. As the piston rod approaches the stroke end, the opening area of the variable throttle decreases.

  In this cushion mechanism, the cushion characteristic of the piston rod decelerating can be changed by arbitrarily setting the sectional area of the tapered groove.

Japanese Patent Laid-Open No. 11-230117 JP 2008-291858 A

  However, in the cushion mechanism described in Patent Document 1, the outer peripheral surface of the cushion bearing is cut to form a split circle portion. However, the piston rod does not move due to a processing error in the cutting inclination angle of the split circle portion. There is a problem that variations in the cushion characteristics of deceleration tend to occur.

  In addition, it is conceivable to form a tapered groove having a V-shaped cross section described in Patent Document 2 on the outer peripheral surface of the cushion bearing that is floatingly supported described in Patent Document 1. However, in this case, when the cushion bearing is elastically deformed by receiving the cushion pressure, the stress concentrates on the part where the taper groove of the cushion bearing opens, and the plate thickness is increased in order to ensure the strength of the cushion bearing. There was a need.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to achieve both suppression of variation in cushion characteristics and securing of strength of a cushion bearing in a fluid pressure cylinder.

The present invention relates to a fluid pressure cylinder in which a piston rod inserted into a cylinder tube decelerates by a cushion pressure generated near the stroke end, and includes a cushion cylindrical surface provided on the cylinder tube and a cushion provided on the piston rod near the stroke end. A cylindrical cushion bearing that enters the inside of the cylindrical surface and restricts the flow of working fluid, and opens to the outer peripheral surface of the cushion bearing and tilts with respect to the central axis of the cushion bearing, so that the piston rod approaches the stroke end. Therefore, the taper groove which forms the variable aperture | diaphragm | reduced by which a flow path area reduces gradually is provided.
The taper groove is formed by only a regular arc-shaped curved surface extending along the central axis of the cushion bearing and having a continuous cross-sectional shape perpendicular to the longitudinal direction.
Further, the tapered groove is formed only by a curved surface having a circular arc shape extending along the central axis of the cushion bearing and having a continuous cross-sectional shape orthogonal to the longitudinal direction.
The taper groove has a groove inner surface extending along the central axis of the cushion bearing and recessed toward the cushion cylindrical surface, and is formed in the longitudinal direction of the taper groove of the flow path surrounded by the groove inner surface and the cushion cylindrical surface. The orthogonal cross-sectional shape was a spindle shape that swells in an arc shape from both ends to the center .

  In the present invention, when the piston rod comes near the stroke end and the cushion bearing enters the inside of the cushion cylindrical surface, the flow of the working fluid is reduced between the two, thereby causing the cushion pressure to be generated. Slow down. As the piston rod approaches the stroke end, the opening area of the variable throttle defined by the tapered groove becomes smaller. By changing the radius of curvature of the cross section of the taper groove and the inclination angle of the taper groove, the cushion characteristics can be set finely.

  Since the cross-sectional shape of the taper groove is formed in a circular arc shape, the taper groove caused by the machining error of the inclination angle is smaller than that of the split circle portion formed flat on the outer peripheral surface of the cushion bearing in the conventional device. Variations in cross-sectional area and cushion characteristics can be suppressed.

  Since the cross-sectional shape of the taper groove is curved in an arc shape, stress concentrates on the area where the taper groove of the cushion bearing opens when the cushion bearing is elastically deformed by the cushion pressure guided to the inner circumferential clearance of the bearing. Can be suppressed and the strength of the cushion bearing can be secured.

  Therefore, in the fluid pressure cylinder, it is possible to achieve both suppression of variations in cushion characteristics and securing the strength of the cushion bearing.

It is sectional drawing of the fluid pressure cylinder which concerns on 1st Embodiment of this invention. It is a perspective view of the cushion bearing which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing process of the cushion bearing which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the operation state which the piston rod of the fluid pressure cylinder which concerns on 1st Embodiment of this invention came to the stroke end. It is a characteristic view which shows the relationship between the taper groove of one Embodiment of this invention, and the cushion stroke which concerns on the split-circle part of a conventional apparatus, and the opening area of a variable aperture_diaphragm | restriction. It is a characteristic view which shows the relationship between the taper groove of one Embodiment of this invention, and the cushion stroke which concerns on the split-circle part of a conventional apparatus, and the opening area of a variable aperture_diaphragm | restriction. It is a characteristic view which shows the relationship between the taper groove of one Embodiment of this invention, and the cushion stroke which concerns on the split-circle part of a conventional apparatus, and the opening area of a variable aperture_diaphragm | restriction. It is sectional drawing which shows the manufacturing process of the cushion bearing which concerns on 2 embodiment of this invention. It is sectional drawing of the cushion bearing which concerns on a prior art example.

  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 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.

  In the hydraulic cylinder 1, the piston rod 30 moves in the direction of the central axis O by the hydraulic pressure guided to the end chamber 3 or the rod chamber 2 from a hydraulic source (working fluid pressure source) (not shown), and expands and contracts.

  The hydraulic cylinder (fluid pressure cylinder) 1 uses hydraulic oil (oil) as a working fluid supplied to and discharged from the hydraulic cylinder, but a water-soluble alternative liquid or the like may be used instead.

  A cylindrical cylinder head 40 through which the piston rod 30 is slidably inserted is provided at the open end of the cylinder tube 10. The cylinder head 40 is fastened to the cylinder tube 10 via a plurality of bolts 12.

  A bush 55, a sub seal 56, a main seal 57, and a dust seal 58 are interposed on the inner periphery of the cylinder head 40.

  When the bush 55 is in sliding contact with the outer peripheral surface 31 of the piston rod 30, the piston rod 30 is supported so as to move in the direction of the central axis O of the cylinder tube 10.

  The sub seal 56 and the main seal 57 are in sliding contact with the outer peripheral surface 31 of the piston rod 30 to seal the space between the outside and the rod chamber 2.

  The dust seal 58 is in sliding contact with the outer peripheral surface 31 of the piston rod 30 to prevent dust from entering the hydraulic cylinder 1.

  A cylindrical inner peripheral surface 44 is formed on the inner periphery of the cylinder head 40. A supply / discharge passage 5 is defined between the head inner peripheral surface 44 and the outer peripheral surface 31 of the piston rod 30. The cylinder head 40 is formed with a supply / discharge port 43 that opens to the head inner peripheral surface 44. The supply / discharge port 43 is connected to a hydraulic pipe communicating with a hydraulic source (not shown).

  During the contraction operation of the hydraulic cylinder 1 in which the piston rod 30 moves downward in FIG. 1, the pressurized hydraulic fluid supplied from the hydraulic source through the hydraulic piping flows into the rod chamber 2 through the supply / discharge passage 5. On the other hand, hydraulic fluid in the end chamber 3 is returned to the tank side of the hydraulic power source through a supply / discharge passage (not shown).

  During the extension operation of the hydraulic cylinder 1 in which the piston rod 30 moves upward in FIG. 1, the pressurized hydraulic oil supplied from the hydraulic source flows into the end chamber 3 through the supply / discharge passage. On the other hand, the hydraulic oil in the rod chamber 2 is returned to the tank side of the hydraulic power source through the supply / discharge passage 5.

  FIG. 1 shows a state where the piston rod 30 is in front of the stroke end. The hydraulic cylinder 1 includes a cushion mechanism 6 that decelerates the piston rod 30 in the vicinity of the stroke end during the extension operation.

  The cushion mechanism 6 includes a cushion cylindrical surface 45 provided on the head inner peripheral surface 44 of the cylinder head 40, and a cushion bearing 60 that enters the cushion cylindrical surface 45 when the piston rod 30 comes near the stroke end. Prepare.

  When the piston rod 30 comes near the stroke end, the cushion bearing 60 enters the inside of the cushion cylindrical surface 45, and a bearing outer peripheral gap 8 (see FIG. 4) is defined between the two. The bearing outer peripheral 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, whereby the piston rod 30 decelerates. Operation (hereinafter referred to as “cushion operation”) is performed.

  The cushion bearing 60 has an outer peripheral surface 61 on the outer periphery thereof. The outer peripheral surface 61 is formed in a cylindrical surface shape with the central axis O as the center. The outer diameter of the outer peripheral surface 61 is larger than the outer diameter of the outer peripheral surface 31 of the piston rod 30 and smaller than the inner diameter of the cushion cylindrical surface 45. When the piston rod 30 comes near the stroke end, the outer peripheral surface 61 of the cushion bearing 60 defines a bearing outer peripheral gap 8 (see FIG. 4) with the cushion cylindrical surface 45.

  On the outer periphery of the piston rod 30, an annular step 32, an outer periphery fitting surface 33, and an annular step 34 are formed side by side.

  The end surface 22 of the piston 20 is fixed in contact with the annular step 34.

  The cylindrical cushion bearing 60 is interposed with a gap between the annular step portion 32 and the piston 20 and is provided so as to be slightly movable in the direction of the central axis O.

  The cushion bearing 60 is fitted to the outer periphery of the piston rod 30 with a bearing inner peripheral gap 7 and is floatingly supported by the working fluid pressure guided to the bearing inner peripheral gap 7. The bearing inner peripheral gap 7 is defined between the inner peripheral surface 67 of the cushion bearing 60 and the outer peripheral fitting surface 33 of the piston rod 30.

  The cushion bearing 60 is formed with an annular end surface 63 orthogonal to the central axis O at one end thereof, and a tapered surface 64 extending continuously from the end surface 63 in an annular shape. The tapered surface 64 is formed in a truncated cone shape that is inclined with respect to the central axis O. At the other end of the cushion bearing 60, an annular end surface 65 orthogonal to the central axis O is formed.

  A slit (notch portion) 69 is formed on the end surface 65 (lower end surface in FIG. 1) of the cushion bearing 60 facing the piston 20. A slit 68 is also formed on the end face 63 (upper end face in FIG. 1) of the cushion bearing 60 facing the annular step 32 of the piston rod 30.

  A cushion operation is performed in which the piston rod 30 decelerates at the stroke end at which the hydraulic cylinder 1 extends. When the cushion is operated, the cushion bearing 60 moves slightly with respect to the piston rod 30 upward in FIG. 1 due to the cushion pressure, and the end face 63 abuts against the annular step portion 32 of the piston rod 30. As a result, the flow of hydraulic oil toward the upper side in FIG. 1 (supply / discharge passage 5) through the bearing inner circumferential gap 7 is narrowed by passing through the slit 68.

  On the other hand, when the hydraulic cylinder 1 is contracted from the fully extended state, pressurized hydraulic oil supplied from the hydraulic source flows into the rod chamber 2 from the supply / discharge passage 5 through the bearing outer peripheral gap 8 and the bearing inner peripheral gap 7. At this time, the cushion bearing 60 moves slightly with respect to the piston rod 30 downward in FIG. 1 due to hydraulic oil pressure guided from the hydraulic pressure source, and its end surface 65 abuts on the end surface 22 of the piston 20 and opens to the end surface 65. The slit 69 communicated with the inner circumferential clearance 7 of the bearing and the rod chamber 2. As a result, the hydraulic oil quickly flows into the rod chamber 2 from the bearing inner circumferential gap 7 through the slit 69, and the responsiveness that the hydraulic cylinder 1 is contracted from the most extended state is ensured.

  An annular groove 35 and an annular groove 36 are formed on the outer peripheral fitting surface 33 of the piston rod 30 so as to open opposite to the inner peripheral surface 67 of the cushion bearing 60.

  The annular groove 35 has a groove side surface that opens to the end portion of the outer peripheral fitting surface 33 and continues to the annular step portion 32 without a step.

  The annular groove 36 opens in the middle of the outer peripheral fitting surface 33. A cushion seal 15 that exhibits a check valve function is interposed in the annular groove 36. The cushion seal 15 is slidably brought into contact with the inner peripheral surface 67 of the cushion bearing 60 so as to be slightly movable in the direction of the central axis O.

  The annular cushion seal 15 has an abutment gap (not shown). When the cushion seal 15 is assembled to the annular groove 36, the cushion seal 15 is fitted into the annular groove 36 with the seal joint gap widened. A plurality of slits (not shown) are formed on the end face (lower end face in FIG. 1) of the cushion seal 15 facing the piston 20. On the other hand, no slit is formed on the end face (upper end face in FIG. 1) of the cushion seal 15 facing the annular step 32 of the piston rod 30.

  Thereby, when the cushion is operated, the cushion seal 15 is slightly moved upward in FIG. 1 with respect to the piston rod 30 by the cushion pressure, and the upper end surface thereof abuts against the groove side surface of the annular groove 36. As a result, the flow of the working oil directed upward in FIG. 1 through the annular groove 36 is blocked by the cushion seal 15.

  On the other hand, when the hydraulic cylinder 1 is contracted from the maximum extension state, the cushion seal 15 is slightly moved downward with respect to the piston rod 30 in FIG. A slit that contacts the groove side surface of the groove 36 and opens at the lower end surface of the cushion seal 15 communicates with the upper and lower spaces of the cushion seal 15 in the annular groove 36. As a result, the hydraulic oil flowing through the bearing inner circumferential gap 7 quickly passes through the slit opened in the lower end surface of the cushion seal 15, and the responsiveness that the hydraulic cylinder 1 is contracted from the most extended state is ensured.

  FIG. 2 is a perspective view showing the cushion bearing 60. A tapered groove 62 that opens to the outer peripheral surface 61 is formed on the outer periphery of the cushion bearing 60. The tapered groove 62 is recessed in a concave shape with respect to the outer peripheral surface 61 and functions as the variable diaphragm 9 (see FIG. 4) facing the opening end of the cushion cylindrical surface 45.

  The taper groove 62 is formed so as to be inclined with respect to the central axis O, and the depth thereof gradually decreases from one end 62A to the other end 62B. Thereby, as the piston rod 30 approaches the stroke end, the flow path cross-sectional area of the variable throttle 9 facing the opening end of the cushion cylindrical surface 45 gradually decreases.

  The tapered groove 62 has one end 62 </ b> A opened in the tapered surface 64 and the other end 62 </ b> B opened in the outer peripheral surface 61. The tapered groove 62 is not limited to the configuration described above, and one end thereof may open to the end surface 63. Further, the tapered groove 62 may have a configuration in which the other end is open to the end face 65.

  The tapered groove 62 is formed only by an arcuate curved surface (groove inner surface) 62C whose cross-sectional shape orthogonal to the longitudinal direction is curved in an arcuate shape. The cross section orthogonal to the longitudinal direction of the tapered groove 62 has a shape that continuously curves in an arc shape and does not have a linearly extending portion or a bending portion.

  FIG. 3 shows a process for processing the cushion bearing 60. By moving a cutting tool (not shown) along a positive arc S62 having a radius R and moving along a cutting center axis O62 inclined with respect to the center axis O of the cushion bearing 60, the cushion bearing 60 is cut. An arcuate curved surface (groove inner surface) 62C is formed. Thereby, the taper groove | channel 62 is formed in the cross-sectional shape which curves to the regular circular arc shape along a perfect circle.

  Hereinafter, the operation of the hydraulic cylinder 1 will be described.

  As shown in FIG. 4, when the hydraulic cylinder 1 is extended, when the cushion bearing 60 enters the cushion cylindrical surface 45, a bearing outer peripheral gap 8 is defined between the cushion bearing 60 and the cushion cylindrical surface 45. . During the extension operation, the hydraulic oil in the rod chamber 2 flows to the supply / discharge passage 5 through the bearing outer peripheral gap 8 and flows to the supply / discharge passage 5 through the bearing inner peripheral gap 7 as shown by arrows in FIG. Mainly, the bearing outer clearance 8 and the gap between the cushion seals 15 provide resistance to the flow of the hydraulic oil, and the cushion operation is performed in which the piston rod 30 decelerates as the cushion pressure in the rod chamber 2 increases.

  When the cushion is operated, the variable diaphragm 9 is defined by the tapered groove 62 facing the opening end of the cushion cylindrical surface 45. As the piston rod 30 approaches the stroke end, the opening area of the variable throttle 9 decreases. By arbitrarily setting the cross-sectional area of the taper groove and the cutting inclination angle (inclination angle), the cushion characteristic at which the piston rod 30 decelerates can be changed.

  As shown in FIG. 3, the cross section of the variable aperture 9 defined by the arc-shaped tapered groove 62 includes a regular arc S62 (a cross section of the arc-shaped curved surface 62C) serving as a cutting surface and an outer peripheral surface 61 of the cushion bearing 60. It is surrounded by an extended regular arc S61. On the other hand, as shown in FIG. 9, the cross section of the variable throttle defined by the flat split portion 169 formed on the cushion bearing 160 in the conventional apparatus is a straight line S169 that is a cutting surface (the cross section of the split portion 169). ) And a normal arc S161 obtained by extending the outer peripheral surface 161 of the cushion bearing 160. The tapered groove 62 has a cross-sectional shape extending in a narrow range in the outer peripheral direction of the cushion bearing 60 as compared with the split circle portion 169. Comparing the cross-sectional areas of the tapered groove 62 and the split-circle part 169 with the same depth (the maximum cutting width in the radial direction orthogonal to the central axis O), the cross-sectional area of the tapered groove 62 is equal to that of the split-circle part 169. It becomes smaller than the cross-sectional area. For this reason, the variation in the cross-sectional area of the tapered groove 62 caused by the machining error of the cutting inclination angle is suppressed to be smaller than the variation in the cross-sectional area of the split circle portion 169.

  5 to 7 are characteristic diagrams showing the relationship between the cushion stroke in which the cushion bearing 60 enters the cushion cylindrical surface 45 and the opening area of the variable aperture 9. 5 to 7, the characteristic indicated by the solid line is the characteristic of the variable diaphragm 9 defined by the tapered groove 62 in the present embodiment, and the characteristic indicated by the broken line is defined by the planar split circle 169 in the conventional apparatus. The characteristics of the variable aperture.

  FIG. 5 shows a characteristic A1 of the tapered groove 62 formed so that the cutting inclination angles (inclination angles) are the same, and a characteristic a1 of the split-circle portion 169. The tapered groove 62 and the split-circle portion 169 are formed to have the same depth (the cut width in the radial direction perpendicular to the central axis O) in the same cushion stroke, and the same maximum depth. In the characteristic diagram of FIG. 5, both of the characteristics A1 and a1 both decrease the opening area of the variable throttle 9 as the cushion stroke increases, but the degree of each decrease is the characteristic A1 of the present embodiment. Is smaller than the characteristic a1 of the conventional device. Comparing the opening area of the variable diaphragm 9 in the same cushion stroke, the characteristic A1 of the present embodiment is smaller than the characteristic a1 of the conventional device.

  FIG. 6 shows a taper groove having a minimum value (0 °), a median value (1 °), and a maximum value (2 °) when a machining error occurs within a range of 0 ° to 2 ° within a tolerance of the cutting inclination angle. 62 shows characteristics A2, B2, and C2 and characteristics a2, b2, and c2 of the split-circle portion 169. For the characteristic A2 and the characteristic a2 that are the minimum values, the cross-sectional area and the cutting inclination angle of the tapered groove 62 and the split circle part 169 are set so that the opening areas in the same cushion stroke overlap each other. The characteristics B2 and C2 and the characteristics b2 and c2 have the cutting inclination angles of the taper groove 62 and the split part 169 such that the machining errors (1 °, 2 °) have the same angle with respect to the characteristics A2 and the characteristics a2. Is set. From the characteristic diagram of FIG. 6, the size of the variation generated in the opening area of the variable aperture 9 due to the machining error of the cutting inclination angle is that the characteristics B2 and C2 of this embodiment are reduced compared to the characteristics b2 and c2 of the conventional apparatus. I understand. Therefore, the tapered groove 62 of the present embodiment can increase the tolerance required for the cutting inclination angle (allowable value of machining error) as compared with the conventional split-circle portion 169.

  FIG. 7 shows characteristics B3, A3, and C3 of the tapered groove 62 in which the opening area is arbitrarily set by changing the cutting radius R of the tapered groove 62. FIG. In the characteristics B3, A3, and C3, the cutting inclination angle and the depth of the tapered groove 62 are the same value, and the cutting radius R of the tapered groove 62 is set larger in the order of the characteristics B3, A3, and C3. In FIG. 7, a3 is a characteristic of the split circle portion 169 formed so that the opening area is substantially the same as the characteristic A3 of the tapered groove 62. A parameter for changing the characteristics of the split circle portion 169 is one of the cutting inclination angles. On the other hand, the taper groove 62 of the present embodiment can set the opening area of the variable aperture 9 more finely than the conventional split circle 169 by changing the cutting radius R.

  When the piston rod 30 decelerates at the stroke end where the hydraulic cylinder 1 is extended, the cushion pressure generated in the rod chamber 3 is guided to the inner periphery of the cushion bearing 60, so that the cushion bearing 60 expands in the radial direction and elastically deforms. To do. The taper groove 62 is formed only by the arcuate curved surface 62C that is continuously curved in an arcuate shape, and does not have a linearly extending portion or a bending portion. Therefore, when the cushion bearing 60 is expanded and elastically deformed by the cushion pressure. Stress concentration is suppressed. Thereby, the strength of the cushion bearing 60 can be ensured, and the occurrence of cracks or the like at the portion where the tapered groove 62 of the cushion bearing 60 is opened can be suppressed.

  According to the above 1st Embodiment, there exists an effect shown below.

  [1] The fluid pressure cylinder 1 in which the cushion bearing 60 enters the inside of the cushion cylindrical surface 45 and restricts the flow of the working fluid when the piston rod 30 comes near the stroke end. And a taper groove 62 that is inclined with respect to the central axis O of the cushion bearing 60, and the taper groove 62 is formed in an arc shape in cross section perpendicular to the longitudinal direction thereof. At the time of elastic deformation in which the cushion bearing 60 expands due to the cushion pressure to be guided, stress is prevented from concentrating on the portion where the tapered groove 62 of the cushion bearing 60 is opened, and the strength of the cushion bearing 60 can be secured.

  With the curvature radius (cutting radius R) and inclination angle of the taper groove 62 as parameters, the opening area of the variable restrictor 9 can be changed, and the cushion characteristic for the piston rod 30 to decelerate can be set finely and accurately.

  Since the tapered groove 62 is formed in the outer peripheral surface 61 of the cushion bearing 60 so as to be curved in an arc shape, compared with the split-circle portion 169 in which the outer peripheral surface of the cushion bearing in the conventional device is cut into a flat shape, the machining is performed at an inclination angle. Variations in cushion characteristics due to errors can be suppressed.

[2] The tapered groove 62 has a cross section perpendicular to the longitudinal direction formed in a regular arc shape, and does not have a portion where the curvature of the arcuate curved surface 62C changes. Therefore, the tapered groove 62 of the cushion bearing 60 is opened. It is possible to prevent the stress from concentrating on the cushion bearing 60 and to secure the strength of the cushion bearing 60.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. Below, it demonstrates centering on a different point from the said 1st Embodiment, the same code | symbol is attached | subjected to the structure same as the fluid pressure cylinder (hydraulic cylinder 1) of the said 1st Embodiment, and description is abbreviate | omitted.

  In the fluid pressure cylinder according to the first embodiment, the taper groove 62 is formed in the cushion bearing 60, and the taper groove 62 is formed in a cross-sectional shape curved in a regular arc shape. In the fluid pressure cylinder according to the second embodiment, a taper groove 72 is formed in the cushion bearing 60, and the taper groove 72 is formed in a cross-sectional shape curved in an elliptical arc shape.

  FIG. 8 shows a process for processing the cushion bearing 60. By moving a cutting tool (not shown) along an elliptical arc S72 having a radius R and moving along a cutting center axis O72 inclined with respect to the central axis O of the cushion bearing 60, the cushion bearing 60 is cut. An elliptical arc-shaped curved surface (groove inner surface) 72C is formed. Thereby, the taper groove | channel 72 is formed in the cross-sectional shape which curves in the elliptical arc shape along an ellipse.

  [3] Since the cross-sectional shape perpendicular to the longitudinal direction of the taper groove 72 is formed in an arc shape along the ellipse, the degree of freedom in setting the cross-sectional area of the taper groove 72 by changing the major axis or the minor axis of the ellipse. In addition, it is possible to prevent stress from concentrating on the portion where the tapered groove 72 of the cushion bearing 60 is opened, and to ensure the strength of the cushion bearing 60.

  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 when the fluid pressure cylinder (hydraulic cylinder 1) is contracted.

  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.

  The fluid pressure cylinder of the present invention can be used not only for construction machines such as hydraulic excavators but also for machines and equipment in other industrial fields.

1 Hydraulic cylinder (fluid pressure cylinder)
7 Bearing inner peripheral clearance 10 Cylinder tube 30 Piston rod 45 Cushion cylindrical surface 60 Cushion bearing 61 Outer peripheral surface 62, 72 Tapered groove

Claims (6)

A fluid pressure cylinder in which a piston rod inserted into a cylinder tube decelerates by a cushion pressure generated near the stroke end,
A cushion cylindrical surface provided on the cylinder tube;
A cylindrical cushion bearing that is provided on the piston rod and enters the inside of the cushion cylindrical surface near the stroke end to restrict the flow of the working fluid;
A taper groove that opens to the outer peripheral surface of the cushion bearing and is inclined with respect to the central axis of the cushion bearing, and forms a variable throttle in which the flow passage area gradually decreases as the piston rod approaches the stroke end. ,
The fluid pressure cylinder, wherein the taper groove is formed only by a regular arc-shaped curved surface extending along a central axis of the cushion bearing and having a continuous cross-sectional shape perpendicular to the longitudinal direction. A fluid pressure cylinder in which a piston rod inserted into a cylinder tube decelerates by a cushion pressure generated near the stroke end,
A cushion cylindrical surface provided on the cylinder tube;
A cylindrical cushion bearing that is provided on the piston rod and enters the inside of the cushion cylindrical surface near the stroke end to restrict the flow of the working fluid;
A taper groove that opens to the outer peripheral surface of the cushion bearing and is inclined with respect to the central axis of the cushion bearing, and forms a variable throttle in which the flow passage area gradually decreases as the piston rod approaches the stroke end. ,
The fluid pressure cylinder according to claim 1, wherein the tapered groove is formed only by a curved surface having a circular arc shape extending along a central axis of the cushion bearing and having a continuous cross-sectional shape perpendicular to the longitudinal direction. A fluid pressure cylinder in which a piston rod inserted into a cylinder tube decelerates by a cushion pressure generated near the stroke end,
A cushion cylindrical surface provided on the cylinder tube;
A cylindrical cushion bearing that is provided on the piston rod and enters the inside of the cushion cylindrical surface near the stroke end to restrict the flow of the working fluid;
A taper groove that opens to the outer peripheral surface of the cushion bearing and is inclined with respect to the central axis of the cushion bearing, and forms a variable throttle in which the flow passage area gradually decreases as the piston rod approaches the stroke end. ,
The tapered groove extends along the central axis of the cushion bearing, and has a groove inner surface that is recessed to face the cushion cylindrical surface,
A fluid pressure cylinder characterized in that a cross-sectional shape perpendicular to the longitudinal direction of the tapered groove of a flow path surrounded by the groove inner surface and the cushion cylindrical surface is a spindle shape that swells in an arc shape from both ends to the center.   The fluid pressure cylinder according to any one of claims 1 to 3, wherein the cushion bearing is floatingly supported on the outer periphery of the piston rod with a bearing inner peripheral gap. The outer peripheral surface of the front Symbol piston rod, an annular groove which is open to face the inner circumferential surface of the cushion bearing is formed,
The fluid pressure cylinder according to any one of claims 1 to 4, wherein a check valve is provided in the annular groove. A piston connected to the piston rod and partitioning the rod chamber and the end chamber in the cylinder tube;
The check valve, which has a closed gap, the fluid pressure cylinder according to claim 5, characterized in that the cushion seal the slit is formed on the end face of the piston side.

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