JPH06300010A - Cylinder device - Google Patents

Abstract

PURPOSE:To prevent a screw part from concentration of stress thereon for preventing the generation of cracks. CONSTITUTION:A fixed nut 22 is formed into a stepped cylindrical form having a large diameter tubular part 22A and a small diameter tubular part 22B entering a large diameter bore part 21C of a piston 21. The other end face of the large diameter tubular part 22A as an abutting end face 22D is adapted to abut against the abutting end face 21E of the piston 21 and the small diameter tubular part 22B is spaced by a gap S from a step part 21B of the piston 21. Thus, a load from the piston 21 born by the abutting end face 22D of the fixed nut 22 is dispersed over the whole female screw part 22C. Also, the female screw part 22C is prevented by the gas S from the deformation caused by press.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder device suitable for operating a working device provided in, for example, a hydraulic excavator.

[0002]

2. Description of the Related Art FIGS. 5 to 8 show a hydraulic cylinder device as an example of a conventional cylinder device.

In the drawing, reference numeral 1 denotes a hydraulic cylinder device, and the hydraulic cylinder device 1 includes a cylinder body 2, a piston rod 8, a piston 10 and a fixing nut 11 which will be described later.
Etc.

First, reference numeral 2 denotes a cylinder body which constitutes an outer shell of the hydraulic cylinder device 1. The cylinder body 2 has a cylindrical tube 3, a bottom cover 4 for closing one end side of the tube 3, and It is formed in a tubular shape in which both ends are closed from a stepped tubular rod guide 5 located at the other end of the tube 3, and one end of the bottom cover 4 fixes the cylinder body 2. It is a mounting bracket 4A. Further, the rod guide 5 and the bottom cover 4 have supply / discharge ports 6, which communicate with oil chambers A and B, which will be described later.
7 are respectively drilled.

One end of 8 enters the cylinder body 2 and
The other end side shows a piston rod protruding outside the cylinder body 2 via the rod guide 5, one end side of the piston rod 8 becomes a small diameter part 8B via a shoulder part 8A, and the other end side is the piston rod 8 Mounting bracket for fixing 8C
Has become. Further, the outer circumference of the small diameter portion 8B on the tip side is
As shown in FIG. 6, a female screw portion 1 of a fixed nut 11 described later.
The screw portion 8D is screwed with the screw 1B, and a fixing groove 8E with which the tip of the set screw 12, which will be described later, abuts, is formed over the entire circumference at one end of the screw portion 8D. Further, a cylindrical one-side cushion 8F protruding toward one side is integrally formed at the tip of the small-diameter portion 8B, and the one-side cushion 8F is provided inside the bottom cover 4 when the piston rod 8 is contracted to the minimum. Flow resistance is given to the oil liquid entering and flowing out from the supply / discharge port 7, and the impact at this time is alleviated.

Reference numeral 9 denotes a cylindrical other side cushion located on the outer peripheral side of the small diameter portion 8B of the piston rod 8 and disposed between the shoulder portion 8A and the piston 10. The other side cushion 9
Is fixed to the piston rod 8 together with the piston 10 by a fixing nut 11. Then, like the one-side cushion 8F, the other-side cushion 9 imparts flow resistance to the oil liquid that enters the rod guide 5 and flows out from the supply / discharge port 6 when the piston rod 8 is fully extended. It alleviates the impact.

Reference numeral 10 denotes a piston which is slidably inserted in the cylinder body 2 in the axial direction and which defines two left and right oil chambers A and B in the cylinder body 2. A small-diameter hole portion 10A through which the small-diameter portion 8B of the piston rod 8 is inserted is formed in the center so as to penetrate in the axial direction, and the other end side of the small-diameter hole portion 10A is enlarged in diameter through an abutting end face 10B. A large diameter hole portion 10C is formed. Then, the other end side of the fixed nut 11 enters the large diameter hole portion 10C, and the abutting end surface 11D of the fixed nut 11 abuts on the abutting end surface 10B.

Reference numeral 11 denotes a fixing nut provided on one end side of the piston rod 8, and the fixing nut 11 includes a nut body 11A formed in a stepped cylindrical shape and the nut body 11
A female screw portion 11B formed on the inner peripheral side of A and a fixing screw hole 11C which is located on one end side of the nut body 11A and which is formed in the radial direction so as to correspond to the fixing groove 8E of the piston rod 8. The set screw 1 is generally configured and holds the fixing screw 11 in the fixing screw hole 11C.
2 is screwed on. The other end surface of the nut body 11A is an abutting end surface 11D that abuts the abutting end surface 10B of the piston 10.

Thus, the fixing nut 11 is internally threaded to the thread portion 8D of the piston rod 8 while the piston 10 is attached to the small diameter portion 8B through the cushion 9 on the other side until it abuts on the shoulder portion 8A of the piston rod 8. The abutting end face 1 while screwing the portion 11B and inserting the other end into the large diameter hole portion 10C.
1D and the abutting end surface 10B of the piston 10 are abutted against each other to press the piston 10 to the other side, and the piston 10 and the other side cushion 9 are sandwiched and fixed between the shoulder portion 8A. Then, in this state, the set screw 12 is screwed into the fixed screw hole 11C of the fixed nut 11 to prevent rotation thereof.

The hydraulic cylinder device 1 according to the prior art has the above-described structure, and supplies the pressure oil from the hydraulic pump to the oil chamber A from the supply / discharge port 6 via a hose or the like (neither is shown). By doing so, the piston rod 8 is contracted through the piston 10 and the fixing nut 11, and pressure oil is supplied from the supply / discharge port 7 into the oil chamber B. , Shoulder 8
The piston rod 8 is extended via A. Further, when the piston rod 8 is at the minimum contraction and at the maximum expansion, the one-side cushion 8F and the other-side cushion 9 of the piston rod 8 buffer the shock at this time.

[0011]

By the way, in the above-mentioned conventional hydraulic cylinder device 1, the fixing nut 11 is screwed to the threaded portion 8D to fix the piston 10 and the like to the piston rod 8, and the piston rod 8 is fixed. Since the load during the contracting operation is received by the fixed nut 11, all the load during the contracting operation acts on the threaded portion 8D via the fixed nut 11, and the threaded portion 8D is easily cracked. There is a problem.

Further, in the hydraulic cylinder device 1 used for the working device of the construction machine, when the excavation work or the like is performed, the load at the time of excavation is the screw portion 8D of the piston rod 8.
However, there is a problem that a so-called one-shot fracture occurs in which the thread of the screw portion 8D is sheared and collapses so as to be peeled off due to shear failure.

Therefore, in order to solve the above-mentioned problem, pressure oil is supplied from the respective supply / discharge ports 6 and 7 in a state where the mounting bracket 4A of the bottom cover 4 and the mounting bracket 8C of the piston rod 8 are fixed with an arbitrary width dimension. The state of the load (stress) applied to the screw portion 8D after being supplied and discharged was measured. As a result, as shown in FIGS. 7 and 8, the female screw portion 11B of the fixing nut 11 is
In addition to the large stress being applied to the first and second crests on the other end side of the threaded portion 8D of the piston rod 8 with which is screwed, the ratio of the load received at the first and second crests is different. It was much larger than the thread.

The causes of these are the abutting end face 10B of the piston 10 and the abutting end face 11 of the fixed nut 11.
Due to the abutment with D, the female screw portion 11B of the fixing nut 11
Since the other end side is pressed and deformed, it is considered that a large stress acts on the first and second crests of the screw portion 8D located at this portion. C
Not only the tensile stress concentrates in the vicinity of the portion and a crack is generated in the C portion, but the growth of the crack causes the screw portion 8D to grow.
It was clarified that it would break.

Therefore, the piston rod 8 as described above is used.
It is conceivable to increase the diameter of the threaded portion 8D in order to prevent damage to the threaded portion 8D.
When the diameter of is increased, the shoulder portion 8A and the other side cushion 9
The area of abutment with and the surface pressure of the abutting surface becomes excessive, and the other side cushion 9 is damaged. As a countermeasure against this, it is conceivable to increase the diameter dimension of the piston rod 8 to increase the abutting area of the shoulder portion 8A and the cushion 9 on the other side. There is a problem that the diameter of the main body 2 must be increased, and as a result, the entire hydraulic cylinder device 1 is increased in size.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a cylinder device capable of preventing stress concentration from occurring in a screw portion and preventing occurrence of cracks and the like. And

[0017]

In order to solve the above-mentioned problems, the cylinder device adopted by the present invention has a cylinder body with both ends closed, and one end enters the cylinder body to form a threaded portion. The piston rod has the other end protruding outside the cylinder body, and a small diameter hole portion that is provided slidably in the cylinder body in the axial direction and into which the piston rod is inserted and has one end side of the small diameter hole portion. A piston having a large diameter hole through a step portion and a fixing nut fastened to a threaded portion of the piston rod to fix the piston to the piston rod are provided, and the fixing nut is provided on one end side. A large-diameter tubular portion and a small-diameter tubular portion located on the other end side and entering the large-diameter hole portion of the piston are formed into a stepped tubular shape, and the inner peripheral side thereof is screwed into the threaded portion of the piston rod. When the internal thread is formed To, in that a configuration for abutting the one end face and the other end surface of the large diameter cylindrical portion of the large-diameter hole portion of the piston from each other.

The other end surface of the large diameter cylindrical portion of the fixing nut is 1/4 of the axial length of the female screw portion from the other end of the small diameter cylindrical portion.
It is preferable to arrange them at positions separated from each other.

Further, it is preferable to form a gap between the step portion of the piston and the other end surface of the small diameter cylindrical portion of the fixing nut when the piston is fixed to the piston rod by the fixing nut.

[0020]

With the above construction, the load applied to the fixed nut during the contraction operation of the piston is received by the other end surface of the large diameter tubular portion of the fixed nut, and is distributed from the other end surface of the large diameter tubular portion to the entire female thread portion. It Further, at this time, since the other end surface of the female screw portion is separated from the step portion of the piston, it is possible to prevent the other end side of the female screw portion from being deformed by the load received by the piston. As a result, it is possible to prevent the load from being concentrated on a part of the threaded portion of the piston rod.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. In the embodiments, the same components as those of the prior art shown in FIGS. 5 to 8 described above are designated by the same reference numerals, and the description thereof will be omitted.

First, FIGS. 1 to 3 show a first embodiment of the present invention.

In the figure, reference numeral 21 denotes a piston according to the present embodiment which replaces the piston 10 according to the prior art, and the small diameter portion 8B of the piston rod 8 is located at the axial center of the piston 21.
The small diameter hole portion 21A is formed so as to penetrate therethrough in the axial direction, and a large diameter hole portion 21C is formed on the other end side of the small diameter hole portion 21A, the diameter of which is increased via the step portion 21B. Further, on one end side of the piston 21, an annular projection portion 21 located on the outer peripheral side of the large diameter hole portion 21C and protruding annularly toward one side is formed.
D is formed, and one end surface of the annular protrusion 21D abuts on an abutting end surface 22D of a fixed nut 22 described later.
It is 1E. Further, the axial dimension of the large diameter hole portion 21C is between the other end surface of the small diameter cylindrical portion 22B and the step portion 21B in a state where the abutting end surface 22D of the fixed nut 22 abuts against the abutting end surface 21E. The size is set so that the gap S can be formed.

Reference numeral 22 denotes a fixing nut according to the present embodiment, which is provided on one end side of the piston rod 8 instead of the fixing nut 11 according to the prior art, and the fixing nut 22 is located on the one end side and has a large diameter. A cylindrical large-diameter cylindrical portion 22A,
It is formed in a stepped cylindrical shape from a small diameter cylindrical portion 22B formed on the other end side of the large diameter cylindrical portion 22A and having a small diameter.
The inner peripheral side of 2A, 22B is the threaded portion 8D of the piston rod 8.
It is a female screw portion 22C that is screwed into. The other end surface of the large-diameter cylindrical portion 22A has an abutting end surface 21E of the piston 21.
Abutting end face 22D that abuts against the other end of the small-diameter cylindrical portion 22B with a dimension L1.
Is set to 1/4 to 1/2 of the axial length dimension L2 of. Further, a fixing screw hole 22E into which the set screw 12 for locking the fixing nut 22 is screwed is formed in a radial direction on one end side of the large diameter cylindrical portion 22A.

The fixing nut 22 is used for the piston 2
1 is attached to the small diameter portion 8B through the other side cushion 9 until it comes into contact with the shoulder portion 8A of the piston rod 8, and the small diameter cylindrical portion 22B is inserted into the large diameter hole portion 21C in the threaded portion 8D of the piston rod 8. While engaging the internal threaded portion 22C with each other, the abutting end surface 22D and the abutting end surface 21E of the piston 21 abut against each other, so that the piston 21 is pressed to the other side and the shoulder portion together with the cushion 9 on the other side. It is designed to be clamped between 8A and 8A. Then, in this state, the set screw 12 is screwed into the fixed screw hole 22E of the fixed nut 22 to prevent rotation.

The hydraulic cylinder device 1 according to the present embodiment has the above-mentioned structure, and its basic operation is not particularly different from that of the prior art.

However, in this embodiment, the fixing nut 22 is located at the large diameter cylindrical portion 22A on one end side and the piston 2 at the other end side.
1 is formed into a stepped cylindrical shape from a small-diameter cylindrical portion 22B that enters the large-diameter hole portion 21C, and the other end surface of the large-diameter cylindrical portion 22A is abutted against the abutting end surface 21E of the piston 21 as an abutting end surface 22D. Then, the small diameter cylindrical portion 22B and the stepped portion 21B of the piston 21 are
A space S is provided between and. Therefore, the fixing nut 22 can distribute the load from the piston 21 received by the abutting end surface 22D to the entire female screw portion 22C, and also the female screw portion 22C of the fixing nut 22.
Can be prevented from being pressed and deformed. As a result, it is possible to prevent stress concentration from occurring in a part of the threaded portion 8D of the piston rod 8 as shown by the solid line in FIGS.
This load can be dispersed and distributed to the entire screw portion 8D (note that the chain double-dashed line in FIGS. 2 and 3 is based on the conventional technique).

Thus, according to the present embodiment, the load received by the abutting end surface 22D of the fixing nut 22 is the internal thread portion 22C.
Since it can be dispersed over the whole, the load (stress) can be evenly distributed to the threaded portion 8D of the piston rod 8, the stress can be prevented from concentrating on a part of the threaded portion 8D, and the threaded portion can be prevented. It is possible to prevent cracks and fractures in 8D, and to prevent the screw threads from collapsing due to one-time breakage, thereby extending the life and greatly improving the reliability.

Further, the abutting end surface 22D of the fixed nut 22 is separated from the other end of the small-diameter cylindrical portion 22B to one side with a separation dimension L1 which is ¼ to 1/2 of the axial length dimension L2 of the female screw portion 22C. Since the abutting end surface 22D is disposed at a position so that the abutting end surface 22D is sufficiently separated from the other end of the female screw portion 22C, the load received by the abutting end surface 22D can be more effectively dispersed over the entire female screw portion 22C. Therefore, the threaded portion 8D of the piston rod 8 can be more reliably prevented from being damaged due to stress concentration.

Further, since stress concentration can be prevented from occurring in the threaded portion 8D of the piston rod 8, for example, by increasing the pressure of the pressure oil supplied to the oil chambers A and B for use, the cylinder body can be enlarged. The output when the piston rod 8 is expanded or contracted can be increased without reducing the diameter. In addition, on the other hand, the diameter of the screw portion 8D can be reduced, the diameter of the hydraulic cylinder device 1 can be reduced, and the piston rod 8 can be formed from an inexpensive material, which reduces the cost. Can be achieved.

Next, FIG. 4 shows a second embodiment of the present invention. The feature of this embodiment is that the abutting end face of the fixing nut is separated from the other end of the small diameter cylindrical portion by at least the axial length dimension of the female screw portion. It has been placed in the specified position.

In the figure, 31 indicates a piston according to the present embodiment which replaces the piston 10 according to the prior art, and the small diameter portion 8B of the piston rod 8 is located at the axial center of the piston 31.
The small diameter hole portion 31A is formed so as to penetrate therethrough in the axial direction, and the large diameter hole portion 31C is formed on the other end side of the small diameter hole portion 31A, the diameter of which is increased via the step portion 31B. Further, at one end side of the piston 31, a tubular annular protrusion located on the outer peripheral side of the large diameter hole portion 31C and largely protruding toward one side so as to cover the outer periphery of the screw portion 8D of the piston rod 8. 31
D is formed, and one end surface of the annular projection 31D abuts on an abutting end surface 32D of a fixed nut 32 described later.
It is 1E. Further, the axial dimension of the large diameter hole portion 31C is between the other end surface of the small diameter cylindrical portion 32B and the step portion 31B in a state where the abutting end surface 32D of the fixing nut 32 abuts against the abutting end surface 31E. The size is set so that the gap S can be formed. Further, the annular projection 31D is provided with a through hole 31F located at one end side for radially attaching the set screw 12 to the fixed nut 32 in the radial direction.

Reference numeral 32 denotes a fixing nut according to the present embodiment, which is provided on one end side of the piston rod 8 in place of the fixing nut 11 according to the prior art. The fixing nut 32 is located on the one end side and has a large diameter. A cylindrical large-diameter cylindrical portion 32A,
The large-diameter cylindrical portion 32A is formed in a stepped cylindrical shape from the inner peripheral side of the small-diameter cylindrical portion 32B extending toward the other side, and the inner peripheral side of the small-diameter cylindrical portion 32B has a screw portion 8D of the piston rod 8. It is a female screw portion 32C that is screwed into. The other end surface of the large-diameter cylindrical portion 32A becomes an abutting end surface 32D that abuts the abutting end surface 31E of the piston 31, and the abutting end surface 32D is separated from the other end of the small-diameter tubular portion 32B by a dimension L3. The separation dimension L3 is set at a position larger than the axial length dimension L4 of the female screw portion 32C. Further, a fixing screw hole 32E into which the set screw 12 for stopping the rotation of the fixing nut 32 is screwed is formed in the one end side of the small diameter cylindrical portion 32B in the radial direction.

Thus, even in this embodiment having such a structure, the same effect as that of the first embodiment can be obtained, but particularly in this embodiment, the abutting end face 32D of the fixing nut 32 is obtained. Is located at one side from the other end of the small-diameter cylindrical portion 32B by a separation dimension L3 which is larger than the axial length dimension L4 of the female threaded portion 32C, so that the load received by the abutting end surface 32D is Total length L of female thread 32C
4 can be more effectively dispersed, and stress concentration can be reliably prevented from occurring in the threaded portion 8D of the piston rod 8.

In each of the above-mentioned embodiments, the hydraulic cylinder device 1 is described as an example of the cylinder device, but the pistons 21 and 31 are fixed to the piston rod 8 via the fixing nuts 22 and 32. If so, it may be applied to other cylinder devices such as a pneumatic cylinder device.

[0036]

As described above in detail, according to the present invention, a large diameter hole portion is provided on one end side of the small diameter hole portion of the piston through a step portion, and a fixing nut is provided on one end side of the large diameter cylinder portion and the other end. By forming a stepped tubular shape from a small-diameter tubular portion that is located on the side and enters the large-diameter hole portion of the piston, and by screwing an internal thread portion formed on the inner peripheral side thereof into the threaded portion of the piston rod. Since the one end surface of the large-diameter hole portion of the piston and the other end surface of the large-diameter cylindrical portion are made to abut against each other, the load received by the other end surface of the large-diameter cylindrical portion of the fixing nut is applied to the large-diameter cylinder. It is possible to disperse from the other end surface of the portion to the entire female thread portion, prevent cracks and fractures due to stress concentration from occurring in the thread portion of the piston rod, extend the life, and improve the reliability.

The other end surface of the large-diameter cylindrical portion of the fixing nut is ¼ of the axial length of the female screw portion from the other end of the small-diameter cylindrical portion.
Since they are arranged at the positions separated from each other as described above, the other end of the small-diameter cylinder portion and the other end surface of the large-diameter cylinder portion can be sufficiently separated, and the load received by the piston can be effectively distributed over the entire female screw portion. Can be made.

Further, since the gap is formed between the step portion of the piston and the other end surface of the small diameter cylindrical portion of the fixing nut, the other end side of the female screw portion is prevented from being deformed by the load received. Therefore, it is possible to reliably prevent the load from being concentrated on a part of the threaded portion of the piston rod.

[Brief description of drawings]

FIG. 1 is a piston rod according to a first embodiment of the present invention,
FIG. 7 is an enlarged vertical sectional view showing the piston and the fixing nut at the same position as in FIG. 6.

FIG. 2 is a characteristic diagram showing stress applied to a thread of the piston rod in FIG.

FIG. 3 is a characteristic diagram showing a state in which a load received by a screw thread of the piston rod in FIG. 1 is shared.

FIG. 4 is an enlarged vertical sectional view showing a piston rod, a piston and a fixing nut according to a second embodiment of the same position as FIG.

FIG. 5 is a vertical sectional view showing a hydraulic cylinder device according to a conventional technique.

6 is an enlarged vertical sectional view showing a piston rod, a piston and a fixing nut in FIG.

FIG. 7 is a characteristic diagram showing stress applied to a thread of the piston rod in FIG.

8 is a characteristic diagram showing a state in which a load received by a screw thread of the piston rod in FIG. 5 is shared.

[Explanation of symbols]

1 Hydraulic Cylinder Device 2 Cylinder Body 8 Piston Rod 8D Threaded Part 21, 31 Piston 21A, 31A Small Diameter Hole 21B, 31B Step 21C, 31C Large Diameter 21E, 31E Abutting End Face (One End of Large Diameter Hole) 22, 32 Fixing nuts 22A, 32A Large diameter cylindrical portion 22B, 32B Small diameter cylindrical portion 22C, 32C Female threaded portion 22D, 32D Abutting end surface (other end surface of large diameter tubular portion) L1, L3 Fixed nut abutting end surface and small diameter tube Distance from the other end of the part L2, L4 Axial length of female thread of fixed nut S Gap

Claims (3)

[Claims] 1. A cylinder body having both ends closed, one end of the cylinder body entering into the cylinder body to form a threaded portion, and the other end of the piston rod projecting outside the cylinder body. A piston that is slidably provided and has a small diameter hole into which the piston rod is inserted and one end side of the small diameter hole is a large diameter hole through a step, and the piston is attached to the piston rod. A fixing nut fastened to the threaded portion of the piston rod for fixing, and the fixing nut is located at one end side of the large diameter cylindrical portion and the other end side and enters the large diameter hole portion of the piston. It is formed in a stepped tubular shape from a small-diameter tubular portion, and an internal thread portion that is screwed into the threaded portion of the piston rod is formed on the inner peripheral side thereof, and one end face of the large-diameter hole portion of the piston and the large-diameter tubular portion. A structure for abutting the other end surface of the part with each other Cylinder device made up of components. 2. The other end surface of the large diameter cylindrical portion of the fixing nut is arranged at a position separated from the other end of the small diameter cylindrical portion by ¼ or more of the axial length dimension of the female screw portion. The cylinder device described. 3. A structure in which a gap is formed between the step portion of the piston and the other end surface of the small diameter cylindrical portion of the fixed nut when the piston is fixed to the piston rod by the fixed nut. Cylinder device described in.