WO2013035540A1

WO2013035540A1 - Hydraulic pressure cylinder

Info

Publication number: WO2013035540A1
Application number: PCT/JP2012/071271
Authority: WO
Inventors: 中野　智和
Original assignee: カヤバ工業株式会社
Priority date: 2011-09-06
Filing date: 2012-08-23
Publication date: 2013-03-14
Also published as: KR20140050068A; KR101596176B1; CN103765018B; CN103765018A; JP2013053718A; JP5789456B2

Abstract

A hydraulic pressure cylinder is provided with a cushion mechanism which reduces the speed of the piston rod when the piston rod is near the end of stroke thereof relative to the cylinder tube. The cushion mechanism is provided with: a cushion bearing provided to the piston rod; a cushion cylinder surface into which the cushion bearing enters when the piston rod is near the end of stroke thereof; a cushion gap defined between the cushion cylinder surface and the cushion bearing and which throttles the flow of hydraulic fluid; a bypass path which conducts the hydraulic fluid which bypasses the cushion gap; and a resistor disposed in the bypass path. An orifice is formed in the resistor, and the orifice throttles the flow of hydraulic fluid passing through the bypass path.

Description

Fluid pressure cylinder

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

A fluid pressure cylinder (hydraulic cylinder) used for 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.

JP8-61311A and JP11-230117A disclose a cushion mechanism provided with a cushion bearing that defines a cushion gap through which a working fluid passes when the piston rod comes near the stroke end. A cushion seal (seal) having a function as a check valve is interposed inside the cushion bearing supported by floating.

¡When the piston rod comes near the stroke end, the cushion bearing enters the inside of the cylinder head and the cushion gap is defined. As a result, the working fluid flows out through the cushion gap and the cushion seal gap (orifice groove), so that the cushion pressure is generated by the resistance of the flow of the working fluid, and the piston rod is decelerated.

However, in the above conventional cushion mechanism, a dedicated cushion seal corresponding to the specifications is interposed inside the cushion bearing, which increases the cost of the product, and also due to dimensional variations such as the gap (orifice groove) of the cushion seal There may be variations in cushion performance.

Also, since the cushion seal groove for accommodating the cushion seal is formed on the outer periphery of the piston rod, the piston rod needs to be grooved.

An object of the present invention is to provide a fluid pressure cylinder capable of obtaining a predetermined cushion pressure without using a cushion seal.

According to an aspect of the present invention, there is provided a fluid pressure cylinder including a cushion mechanism that decelerates the piston rod in the vicinity of the stroke end of the piston rod with respect to the cylinder tube, the cushion mechanism including a cushion bearing provided on the piston rod, and a stroke end. A cushion cylindrical surface into which the cushion bearing enters, a cushion gap defined between the cushion cylindrical surface and the cushion bearing to restrict the flow of the working fluid, a bypass passage for guiding the working fluid bypassing the cushion gap, and a bypass A fluid pressure cylinder is provided that includes a resistor interposed in the passage and in which an orifice is formed in the resistor to restrict the flow of working fluid through the bypass passage.

Embodiments of the present invention and advantages of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of a hydraulic cylinder according to an embodiment of the present invention. FIG. 2A is a cross-sectional view of a hydraulic cylinder in which a part of FIG. 1 is enlarged. FIG. 2B is a cross-sectional view showing the AA cross section of FIG. 2A. FIG. 3 is a cross-sectional view of the hydraulic cylinder showing a state during the extension operation. FIG. 4 is a cross-sectional view of the hydraulic cylinder showing a state during the contraction operation.

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

FIG. 1 is a cross-sectional view of a hydraulic cylinder 1 according to an embodiment of the present invention. The hydraulic cylinder 1 is used, for example, as an arm cylinder of a hydraulic excavator, and the arm of the hydraulic excavator rotates when the hydraulic cylinder 1 expands and contracts.

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 coupled 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), and the piston rod 30 moves in the direction of the central axis O by the working hydraulic pressure (working fluid pressure) guided from this hydraulic power source. Telescopic operation.

For example, a water-soluble alternative liquid may be used instead of oil as the working fluid.

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 by an outer peripheral screw portion (male screw) 41 screwed into an inner peripheral screw portion (female screw) 12 of the cylinder tube 10.

The cylinder head 40 has a cylindrical head fitting portion 42 fitted to the cylinder inner peripheral surface 11. An O-ring 9 and a backup ring 19 are interposed on the outer periphery of the head fitting portion 42.

A bearing 55, a sub seal 56, a main seal 57, and a dust seal 58 are interposed in the inner peripheral portion 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 55 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.

The cylinder head 40 has a supply / discharge port 43, and the supply / discharge passage 5 is defined by the supply / discharge port 43. The supply / discharge passage 5 communicates with a hydraulic source via a hydraulic pipe (not shown) connected to the pipe port 17 of the cylinder tube 10.

A cylindrical inner peripheral surface 44 is formed on the inner periphery of the cylinder head 40. One end of the supply / discharge port 43 opens in the head inner peripheral surface 44, and the supply / discharge passage 5 is defined between the head inner peripheral surface 44 and the rod outer peripheral surface 31.

A holder 23 is interposed inside the cylinder tube 10. The holder 23 is formed in an annular shape centered on the central axis O. The holder 23 is fitted to the cylinder inner peripheral surface 11 along with the head fitting portion 42 of the cylinder head 40. An O-ring 28 and a backup ring 18 are interposed on the outer periphery of the holder 23.

The holder 23 has a cushion cylindrical surface 24 as an inner peripheral surface thereof. The cushion cylindrical surface 24 is formed in a cylindrical surface shape with the central axis O as the center.

The holder 23 has an outer peripheral tapered portion fitted into the tapered surface 13 of the cylinder inner peripheral surface 11, and an upper end surface thereof is fixed in contact with a head end surface 45 formed at the lower end of the cylinder head 40.

Note that the method for fixing the holder 23 is not limited to this. For example, the holder 23 may be fixed to the cylinder head 40 via a bolt (not shown). In this case, it is not necessary to form the tapered surface 13 on the inner surface of the cylinder tube 10. Further, the holder 23 may be integrally formed with the cylinder head 40.

1, during the contraction operation of the hydraulic cylinder 1 in which the piston rod 30 moves downward in FIG. 1, the pressurized hydraulic oil 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, 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. It flows out to the hydraulic power source.

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. FIG. 1 shows a state where the piston rod 30 is in front of the stroke end and in the vicinity of the stroke end.

The cushion mechanism 6 includes a cylindrical cushion bearing 60 attached to the piston rod 30. When the piston rod 30 comes near the stroke end, the cushion bearing 60 enters the inside of the holder 23, and the cushion gap 4 (see FIG. 3) is defined between the two. The cushion gap 4 provides 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. When the cushion pressure increases, the piston rod 30 is decelerated.

The cushion bearing 60 has a bearing outer peripheral surface 61 as its outer peripheral surface. The bearing outer peripheral surface 61 is formed in a cylindrical surface shape 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 cushion cylindrical surface 24. The cushion gap 4 is defined between the bearing outer peripheral surface 61 and the cushion cylindrical surface 24.

The split bearing part 62 (notch) which cut the bearing outer peripheral surface 61 partially is formed in the cushion bearing 60. That is, the split portion 62 is a recess provided in the bearing outer peripheral surface 61. The width of the split portion 62 is formed so as to decrease as it goes downward in FIG. Thereby, the flow path cross-sectional area defined by the split-circle portion 62 in the cushion gap 4 gradually decreases as the piston rod 30 approaches the stroke end. The clearance (gap width) of the cushion gap 4 and the shape of the split part 62 are set according to the deceleration characteristics required for the cushion mechanism 6.

The cushion mechanism 6 includes a bypass passage 50 that guides hydraulic oil that bypasses the cushion gap 4 and a resistor (set screw) 63 interposed in the bypass passage 50, and the resistor 63 passes through the bypass passage 50. An orifice 64 that restricts the flow of oil is formed.

The bypass passage 50 is defined by a bypass hole 25 penetrating the holder 23. The bypass through holes 25 extend substantially parallel to the central axis O and open to the upper and lower end surfaces of the holder 23, respectively.

FIG. 2A is an enlarged cross-sectional view of a part of FIG. 1, and FIG. 2B is a cross-sectional view showing the AA cross section of FIG. 2A.

A holder recess 26 that is recessed from the upper end surface of the holder 23 is formed on the upper end surface of the holder 23, and the upper end of the bypass through hole 25 opens in the holder recess 26. The configuration is not limited to this, and the upper end surface of the holder 23 may be open at the upper end of the bypass hole 25 without providing the holder recess 26.

A head end surface 45 orthogonal to the central axis O is formed at the lower end of the cylinder head 40, and the upper end surface of the holder 23 abuts on the head end surface 45.

The head end face 45 is formed with a bypass recess 46 that is recessed in a disc shape with the central axis O as the center. The bypass recess 46 is formed opposite to the holder recess 26 of the holder 23 and the opening end of the bypass through hole 25, and a bypass passage 50 is defined between the holder recess 26 and the opening end of the bypass through hole 25 and the bypass recess 46. Made.

When the piston rod 30 comes near the stroke end during the extension operation of the hydraulic cylinder 1, the hydraulic oil in the rod chamber 2 passes through the bypass passage 50 and the supply / discharge passage 5 to the hydraulic pressure source as shown by the arrow in FIG. 2A. And leaked.

A notch 29 is formed on the lower end surface of the holder 23. Thereby, the upper end surface 22 of the piston 20 contacts the lower end surface of the holder 23 when the hydraulic cylinder 1 is extended most. At this time, the cushion gap 4 and the bypass passage 50 communicate with the rod chamber 2 through the notch 29.

The orifice 64 gives resistance to the hydraulic fluid flowing through the bypass passage 50. Along with this, the cushion pressure in the rod chamber 2 increases, and the piston rod 30 is decelerated. The opening diameter and passage length of the orifice 64 are set according to the deceleration characteristics required for the cushion mechanism 6.

In the bypass passage 50, the hydraulic oil that has passed through the orifice 64 flows into the gap between the holder recess 26 of the holder 23 and the bypass recess 46 of the cylinder head 40, hits the inner wall surface of the bypass recess 46, and bends in the direction toward the central axis O. It is done. This prevents noise from being generated by the jet of hydraulic oil that has passed through the orifice 64.

An outer peripheral thread portion (male thread) 66 is formed on the outer periphery of the cylindrical resistor 63. On the other hand, an inner peripheral screw portion 27 is formed in the bypass through hole 25 of the holder 23. The resistor 63 is attached by screwing the outer peripheral screw portion 66 to the inner peripheral screw portion 27 of the holder 23. Since the holder 23 is provided separately from the cylinder head 40, the machining of the bypass through hole 25 can be easily performed, and the cost of the product can be reduced.

The orifice 64 and the hexagonal hole 65 are formed side by side on the inner periphery of the resistor 63. The resistor 63 is fastened and fixed to the inner peripheral screw portion 27 by a tool (not shown) engaged with the hexagonal hole 65.

Note that the present invention is not limited to this, and the resistor 63 may be configured to be press-fitted and attached to the bypass through hole 25 of the holder 23. Moreover, although the resistor 63 was interposed in the upper end part of the bypass through-hole 25 of the holder 23, you may interpose not only in this but in the lower end part of the bypass through-hole 25.

Alternatively, a through hole defining the bypass passage 50 may be formed in the holder 23 so as to extend in a direction substantially perpendicular to the central axis O, and the resistor 63 may be interposed in the through hole. In this case, the opening end of the through hole faces the cylinder inner peripheral surface 11, and the cylinder inner peripheral surface 11 stops the resistor 63 from falling off.

A length (curvature radius) R1 from the central axis O to the outer peripheral wall defining the bypass recess 46 of the cylinder head 40 is formed to be smaller than a length R2 from the central axis O to the outer peripheral end of the resistor 63. . As shown in FIG. 2B, a part of the head end surface 45 of the cylinder head 40 faces a part of the resistor 63.

As a result, even if the resistor 63 screwed into the inner peripheral screw portion 27 of the holder 23 is loosened and protrudes upward from the bypass through hole 25, a part of the resistor 63 comes into contact with the head end surface 45 of the cylinder head 40. The resistor 63 is prevented from projecting further upward. In this state, the bypass through hole 25 communicates with the bypass recess 46. Accordingly, the resistor 63 is prevented from falling off from the bypass through hole 25 of the holder 23, and the bypass passage 50 is not closed, so that the operation of the cushion mechanism 6 is maintained.

The cushion bearing 60 is fitted to the piston rod 30 so as to have a bearing inner circumferential gap 7 in the radial direction, and is supported in a floating manner so as to be movable with respect to the piston rod 30. The bearing inner circumferential gap 7 is defined between the inner circumferential surface 67 of the cushion bearing 60 and the end outer circumferential surface 33 of the piston rod 30.

The cushion bearing 60 is interposed so as to have a gap 8 in the direction of the central axis O with respect to the piston rod 30. When the lower end surface of the cushion bearing 60 is in contact with the upper end surface 22 of the piston 20, the gap 8 is defined between the upper end surface 68 of the cushion bearing 60 and the annular step portion 32 of the piston rod 30.

A notch 69 is formed on the lower end surface of the cushion bearing 60. In a state where the lower end surface of the cushion bearing 60 is in contact with the upper end surface 22 of the piston 20, the notch 69 communicates the bearing inner circumferential gap 7 and the rod chamber 2.

FIG. 3 is a cross-sectional view showing a state in which the piston rod 30 is in the vicinity of the stroke end during the extension operation of the hydraulic cylinder 1 in which the piston rod 30 moves upward as indicated by the white arrow. .

When the piston rod 30 comes near the stroke end, the cushion bearing 60 enters the inside of the holder 23, so that the cushion gap 4 is defined between them.

The cushion gap 4 gives resistance to the flow of hydraulic oil flowing out from the rod chamber 2 to the supply / discharge passage 5 and the cushion pressure in the rod chamber 2 increases. Along with this, the cushion bearing 60 is pushed upward, the upper end surface of the cushion bearing 60 comes into contact with the annular step 32 of the piston rod 30, the gap 8 is closed, and the bearing inner circumferential gap 7 and the supply / discharge passage 5 Is blocked.

Thereby, the hydraulic oil in the rod chamber 2 flows out from the supply / discharge passage 5 through the cushion gap 4 and the bypass passage 50 as indicated by arrows in FIG. The cushion gap 4 and the orifice 64 of the bypass passage 50 provide resistance to the flow of hydraulic oil flowing out from the rod chamber 2, and the cushion pressure in the rod chamber 2 increases, whereby the piston rod 30 is decelerated.

FIG. 4 is a cross-sectional view showing a state in which the piston rod 30 comes near the stroke end during the contraction operation of the hydraulic cylinder 1 in which the piston rod 30 moves downward as indicated by the white arrow. .

When pressurized hydraulic fluid is supplied to the supply / discharge passage 5 from the hydraulic source, the cushion bearing 60 is pushed downward, and the upper end surface of the cushion bearing 60 is separated from the annular step portion 32 of the piston rod 30, and between them. A gap 8 is defined to open a space between the bearing inner circumferential gap 7 and the supply / discharge passage 5.

As a result, the pressurized hydraulic oil supplied to the supply / discharge passage 5 flows into the rod chamber 2 through the gap 8, the bearing inner circumferential gap 7, and the notch 69, as indicated by arrows in FIG. It flows through the cushion gap 4 and the bypass passage 50, respectively. As described above, since the hydraulic oil flows into the rod chamber 2 through the three flow paths, the piston rod 30 quickly moves in the contraction direction.

As described above, the cushion bearing 60 functions as a check valve in the vicinity of the stroke end, which closes the bearing inner circumferential gap 7 during the extension operation and opens the bearing inner circumferential gap 7 during the contraction operation.

Hereinafter, the gist, operation, and effect of this embodiment will be described.

The hydraulic cylinder 1 of this embodiment includes a cushion mechanism 6 that decelerates the piston rod 30 in the vicinity of the stroke end of the piston rod 30 relative to the cylinder tube 10. The cushion mechanism 6 is defined and operated between a cushion bearing 60 provided on the piston rod 30, a cushion cylindrical surface 24 into which the cushion bearing 60 enters near the stroke end, and the cushion cylindrical surface 24 and the cushion bearing 60. A cushion gap 4 that restricts the flow of fluid, a bypass passage 50 that guides a working fluid that bypasses the cushion gap 4, and a resistor 63 interposed in the bypass passage 50 are provided. The resistor 63 is formed with an orifice 64 that restricts the flow of the working fluid passing through the bypass passage 50.

Thereby, by changing the shape and size of the orifice 64 formed in the resistor 63, the resistance applied to the flow of hydraulic oil passing through the bypass passage 50 can be adjusted, and a predetermined cushion pressure is obtained. be able to.

Since the orifice 64 is formed in the resistor 63 interposed in the bypass passage 50, the holder 23 that defines the bypass passage 50 can be made common among products of different specifications, and the resistor 23 can be used without increasing the part number of the holder 23. By changing 63, it is possible to cope with different specifications. Further, as compared with the case where the orifice is formed in the holder 23 that defines the bypass passage 50, the processing accuracy of the orifice 64 can be improved, and variations in cushion performance can be suppressed.

Since there is no need to interpose a cushion seal inside the cushion bearing 60 as in the conventional apparatus, it is possible to reduce the cost of the product and to eliminate the variation in cushion performance related to the cushion seal.

Since there is no need to form a cushion seal groove in which a cushion seal is interposed on the outer periphery of the piston rod 30 as in the conventional device, the strength of the piston rod 30 can be improved.

In the present embodiment, the cushion mechanism 6 includes a cylinder head 40 that slidably supports the piston rod 30 and an annular holder 23 that is interposed inside the cylinder tube 10 alongside the cylinder head 40. The holder 23 has a cushion cylindrical surface 24 and a bypass through hole 25 that defines a part of the bypass passage 50 and in which a resistor 63 is interposed. The cylinder head 40 has a head end surface 45 that faces the opening end of the bypass passage hole 25, and a bypass recess 46 that is recessed in the head end surface 45 and defines a part of the bypass passage 50. The length R1 from the central axis O of the piston rod 30 to the outer peripheral end of the resistor 63 is set to be smaller than the length R2 from the central axis O of the piston rod 30 to the outer peripheral wall defining the bypass recess 46. The removal from the hole 25 is locked.

Thereby, the resistor 63 is prevented from falling off from the bypass passage hole 25 of the holder 23 and the bypass passage 50 is not blocked, so that the operation of the cushion mechanism 6 can be maintained.

Further, since the holder 23 in which the resistor 63 is interposed is formed separately from the cylinder head 40, the cushion performance can be easily improved by replacing the holder 23 and the resistor 63 according to the required deceleration characteristics. Can be adjusted.

In this embodiment, the cylinder head 40 is formed with a head end surface 45 that faces the bypass through hole 25.

Thus, the cushion mechanism 6 can be configured by adding the holder 23 without changing the basic shape of the cylinder head 40, and the cost of the product can be suppressed.

In this embodiment, the cushion mechanism 6 includes a cylinder head 40 that slidably supports the piston rod 30, and a supply / discharge passage 5 that is defined between the piston rod 30 and the cylinder head 40 and supplies and discharges the working fluid. . The cushion bearing 60 is floatingly supported on the piston rod 30 so as to have a bearing inner circumferential gap 7. When the cushion bearing 60 enters the cushion cylindrical surface 24, the space between the bearing inner peripheral gap 7 and the supply / exhaust passage 5 is closed. On the other hand, when the cushion bearing 60 exits the cushion cylindrical surface 24, The space between the circumferential gap 7 and the supply / discharge passage 5 is opened.

Thereby, the cushion bearing 60 functions as a check valve that opens and closes between the bearing inner circumferential gap 7 and the supply / discharge passage 5, so that the piston rod 30 can be quickly moved when the fluid pressure cylinder 1 is driven.

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.

For example, a plurality of annular grooves (labyrinth grooves) may be formed in the inner peripheral surface 67 of the cushion bearing 60 that defines the bearing inner peripheral gap 7 and the end outer peripheral surface 33 of the piston rod 30. Thereby, resistance can be given to the working fluid flowing through the bearing inner circumferential gap 7, and the cushion bearing 60 can be kept coaxial with the piston rod 30.

In the above embodiment, the case where the cushion mechanism decelerates the piston rod when the hydraulic cylinder 1 is extended is illustrated. However, the piston rod may be decelerated near the stroke end of the piston rod when the hydraulic cylinder 1 is contracted. Good.

This application claims priority based on Japanese Patent Application No. 2011-193792 filed with the Japan Patent Office on September 6, 2011, the entire contents of which are incorporated herein by reference.

Claims

A fluid pressure cylinder having a cushion mechanism for decelerating the piston rod near the stroke end of the piston rod relative to the cylinder tube,
The cushion mechanism is
A cushion bearing provided on the piston rod;
A cushion cylindrical surface into which the cushion bearing enters near the stroke end; and
A cushion gap that is defined between the cushion cylindrical surface and the cushion bearing and restricts the flow of the working fluid;
A bypass passage for guiding a working fluid that bypasses the cushion gap;
A resistor interposed in the bypass passage;
With
A fluid pressure cylinder in which an orifice for restricting a flow of a working fluid passing through the bypass passage is formed in the resistor.
The fluid pressure cylinder according to claim 1,
The cushion mechanism is
A cylinder head that slidably supports the piston rod;
An annular holder interposed alongside the cylinder head inside the cylinder tube;
With
The holder includes the cushion cylindrical surface, and a bypass through hole in which the resistor is interposed and defines a part of the bypass passage,
The cylinder head has a head end surface facing the opening end of the bypass through hole, and a bypass recess formed on the head end surface and defining a part of the bypass passage,
A fluid pressure cylinder, wherein a length from a central axis of the piston rod to an outer peripheral wall portion defining the bypass recess is smaller than a length from a central axis of the piston rod to an outer peripheral end portion of the resistor.
The fluid pressure cylinder according to claim 1,
The cushion mechanism is
A cylinder head that slidably supports the piston rod;
A supply / discharge passage defined between the piston rod and the cylinder head for supplying and discharging a working fluid;
With
The cushion bearing is floating supported so as to have a bearing inner circumferential clearance with respect to the piston rod,
During the operation in which the cushion bearing enters the cushion cylindrical surface, the gap between the bearing inner peripheral gap and the supply / discharge passage is closed, and in the operation in which the cushion bearing exits the cushion cylindrical surface, the bearing inner periphery A fluid pressure cylinder in which a gap is opened between the supply / discharge passage.