JP7360253B2 - fluid pressure cylinder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fluid pressure cylinder.

Patent Document 1 discloses an in-rod passage formed along the axial direction of a piston rod and communicating between a fluid pressure source and the inside of a cylinder tube, and a plug inserted from an open end of the in-rod passage that opens into the cylinder tube. discloses a hydraulic cylinder that includes a lateral hole formed in a piston rod in a radial direction and that crosses an internal passageway in the rod, and a pin inserted into the lateral hole. The piston rod has an inner threaded part formed on the inner periphery of the rod internal passage, and the plug has an outer threaded part that screws into the inner threaded part, and an engaging part that engages with the pin to prevent the plug from rotating. is formed.

Further, in this hydraulic cylinder, the piston rod and the piston are prevented from rotating by a screw that is screwed into a screw hole formed in the piston and a ball that is pressed against the outer periphery of the piston rod by the screw.

Unexamined Japanese Patent Publication No. 2015-25506

In the fluid pressure cylinder of Patent Document 1, the plug is provided with an engaging portion, and a pin is engaged with the engaging portion of the plug through a horizontal hole formed in the piston rod, thereby preventing the plug from rotating. Therefore, it is necessary to process the piston rod and plug to prevent them from rotating.

In addition, in this fluid pressure cylinder, it is necessary to provide a mechanism for preventing rotation between the piston and the piston rod, and a mechanism for preventing rotation between the plug and the passageway in the rod of the piston rod. In a pressure cylinder, the structure around the piston becomes complicated.

The present invention has been made in view of the above problems, and an object of the present invention is to simplify the structure around the piston in a fluid pressure cylinder.

The present invention relates to a fluid pressure cylinder, which includes a cylinder tube, a piston rod inserted into the cylinder tube, and a piston that is attached to the end of the piston rod by screw fastening and partitions the inside of the cylinder tube into a rod side chamber and a bottom side chamber. a locking part that is inserted into the piston and presses the end of the piston rod from the outside in the radial direction to the inside to prevent loosening of the screw fastening; and an internal passage formed in the piston rod along the axial direction. , a communication passage formed in the piston rod and communicating the internal passage and the rod side chamber, and a plug inserted into the internal passage to close the opening of the internal passage to the end surface at the end of the piston rod, the plug having a locking part. It is characterized in that it is prevented from coming off from the internal passage only by the piston rod that is deformed by the pressure of the piston rod.

Further, in the present invention, a female threaded portion into which the plug is screwed is formed on the inner periphery of the internal passage, and the female threaded portion is deformed by the pressure of the locking portion, thereby preventing the plug from coming off from the internal passage. Features.

In these inventions, the piston rod is deformed by the pressing force of the locking part for preventing loosening of the screw connection between the piston and the piston rod, and such deformation of the piston rod prevents the plug from coming out from the internal passage. be done. Therefore, there is no need to process the piston rod or the plug to prevent the plug from coming off, and there is no need to provide a structure to prevent the plug from coming off in addition to preventing loosening of the screw connection between the piston and the piston rod.

Further, in the present invention, the locking part presses the piston rod radially inward so as to narrow the opening of the internal passage, and the plug is prevented from coming off from the internal passage by narrowing the opening of the internal passage. It is characterized by

In this invention, the plug only needs to be inserted into the internal passage, and there is no need to attach the plug to the internal passage with screws, etc., so there is no need to process the plug or the internal passage with screws, etc., and the manufacturing cost is reduced. reduced.

According to the present invention, the structure around the piston in the fluid pressure cylinder is simplified.

FIG. 1 is a sectional view of a hydraulic cylinder according to an embodiment of the present invention. 1 is a sectional view showing the vicinity of a piston in a hydraulic cylinder according to an embodiment of the present invention. It is a view taken along arrow A in FIG. 2. It is a sectional view showing a piston periphery concerning a first modification of a hydraulic cylinder concerning an embodiment of the present invention. It is a sectional view showing the piston periphery concerning the 2nd modification of the hydraulic cylinder concerning the embodiment of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to drawings, the hydraulic cylinder 100 which drives hydraulic oil as a hydraulic fluid is demonstrated as a hydraulic cylinder based on embodiment of this invention.

As shown in FIG. 1, the hydraulic cylinder 100 includes a cylindrical cylinder tube 10, a piston rod 20 inserted into the cylinder tube 10, and a proximal end (base end) of the piston rod 20. A piston 30 is provided.

The piston 30 is provided slidably along the inner peripheral surface of the cylinder tube 10. The interior of the cylinder tube 10 is divided into two fluid pressure chambers, a rod side chamber 1 and a bottom side chamber 2, by the piston 30.

As shown in FIG. 2, the piston rod 20 includes a base end (end) 21 having a male threaded portion 21a formed on the outer periphery, a main body 22 having an outer diameter larger than the base end 21, and a main body 22. It has a step surface 23 formed by the difference in outer diameter of the base end portion 21 and on which the piston 30 is seated. The piston rod 20 has a male threaded portion 21a screwed into a female threaded portion 30a formed on the inner circumference of the piston 30, and applies a predetermined tightening force (hereinafter referred to as "piston tightening force") with the piston 30 seated on the stepped surface 23. ) is connected to the piston 30 by tightening. Note that the piston tightening force does not refer to a single value, but has a predetermined numerical range.

The outer periphery of the proximal end portion 21 includes a male threaded portion 21a and a cylindrical portion 21b that is a cylindrical surface connected to a proximal end surface 20a (see FIG. 2) that is an end surface on the proximal side of the piston rod 20. That is, the male threaded portion 21a is not formed over the entire length of the base end portion 21 in the axial direction, but is formed in a portion of the base end portion 21 in the axial direction. The cylindrical portion 21b is formed to have a smaller outer diameter than the male threaded portion 21a.

As shown in FIG. 1, the tip of the piston rod 20 is formed with a mounting portion 20b for attachment to other equipment, and extends from the open end of the cylinder tube 10.

A cylinder head 11 through which a piston rod 20 is inserted is provided at the open end of the cylinder tube 10 . The cylinder head 11 is fastened to the open end of the cylinder tube 10 using a plurality of bolts (not shown). Furthermore, an attachment portion 10a for attachment to other equipment is formed at the end of the cylinder tube 10.

As shown in FIGS. 1 and 2, the piston rod 20 is formed with a rod side passage 5 that leads hydraulic oil to the rod side chamber 1 and a bottom side passage 8 that leads hydraulic oil to the bottom side chamber 2.

The rod-side passage 5 is open to the proximal end surface 20a of the piston rod 20, and has an internal passage 6 formed along the axial direction of the piston rod 20, and an internal passage 6 formed to extend in the radial direction of the piston rod 20. It has a communication path 7 that communicates with the side chamber 1. The communication passage 7 is provided perpendicularly to the internal passage 6 and opens to the outer circumferential surface of the main body portion 22 of the piston rod 20.

A rod-side port 9a is formed at the tip of the piston rod 20 extending from the cylinder tube 10 to introduce hydraulic oil into the internal passage 6. A pipe (not shown) is connected to the rod side port 9a, and the rod side port 9a is selectively connected to a hydraulic source (fluid pressure source) or a tank (not shown) through the pipe.

A plug 40 is inserted into the internal passage 6 to close the opening to the proximal end surface 20a of the piston rod 20. As shown in FIG. 2, the plug 40 is formed coaxially with a plug threaded portion 41 having a male threaded portion 41a formed on its outer periphery, and is located closer to the distal end of the piston rod 20 than the plug threaded portion 41 (see FIG. A sealing member 43 is provided on the outer periphery of the axial portion 42 and seals between the outer periphery of the axial portion 42 and the inner periphery of the internal passage 6.

The internal passageway 6 is formed with a female threaded part 6a into which the plug threaded part 41 of the plug 40 is screwed, and a seating surface 6b that serves as a seating surface for screwing the plug 40 and the internal passageway 6 together.

The plug 40 is attached to the internal passageway 6 by screwing the plug threaded part 41 into the female threaded part 6a of the internal passageway 6 and tightening it with a predetermined tightening force from a state in which it contacts the seating surface 6b. Further, by sealing between the shaft portion 42 and the internal passage 6 by the sealing member 43, communication between the internal passage 6 and the bottom side chamber 2 is cut off.

The bottom passage 8 opens to the base end surface 20a of the piston rod 20 and is formed along the axial direction of the piston rod 20. Further, as shown in FIG. 1, a bottom port 9b is formed at the tip of the piston rod 20 extending from the cylinder tube 10 to introduce hydraulic oil to the bottom passage 8. A pipe (not shown) is connected to the bottom port 9b, and the bottom port 9b is selectively connected to a hydraulic power source or a tank through the pipe.

When hydraulic oil (working fluid) is selectively guided from the hydraulic source to the rod side chamber 1 or the bottom side chamber 2 through the rod side passage 5 or the bottom side passage 8, the piston rod 20 moves relative to the cylinder tube 10. This causes the hydraulic cylinder 100 to expand and contract.

As shown in FIGS. 2 and 3, the hydraulic cylinder 100 presses the base end 21 of the piston rod 20 from the outside in the radial direction inward (toward the central axis O1 of the piston rod 20), and the piston The piston rod 30 and the piston rod 20 are further provided with a locking portion 50 that prevents the screw connection from loosening.

The locking portion 50 is inserted into an insertion hole 55 formed in the piston 30 along the radial direction. The insertion hole 55 is a through hole that opens into the outer peripheral surface of the piston 30 and the inner peripheral surface where the female threaded portion 30a is formed. The insertion hole 55 is provided at a position facing the outer periphery of the cylindrical portion 21b of the piston rod 20 when the piston 30 and the piston rod 20 are connected. In addition, as shown in FIGS. 2 and 3, the insertion hole 55 is located on the outside in the radial direction of the plug threaded portion 41 of the plug 40 when the piston 30 and the piston rod 20 are connected, and the center axis O3 thereof is located outside the plug threaded portion 41 of the plug 40. It is provided at a position perpendicular to the central axis O2 of the plug 40 (the central axis of the internal passage 6). As a result, the positions (angles) in the circumferential direction of the locking part 50 and the plug 40 with respect to the central axis O1 of the piston 30 (piston rod 20) are aligned, and the locking part 50 and the plug 40 are aligned with each other relative to the central axis O1 of the piston 30. (see Figure 3).

The locking part 50 is provided between a set screw 51 serving as a threaded member that is screwed into a female threaded part 55a formed in an insertion hole 55, and the outer peripheral surface of the piston rod 20, and is provided between the set screw 51 and the outer peripheral surface of the piston rod 20. It has a steel ball 52 as a spherical pressing member that presses inward in the radial direction.

In the locking portion 50, the set screw 51 is tightened with a predetermined tightening force, so that the steel ball 52 presses the cylindrical portion 21b of the piston rod 20 with a predetermined pressing force. As a result, the cylindrical portion 21b of the piston rod 20 is locked to the steel ball 52 in the axial direction, and the piston 30 and the piston rod 20 are prevented from loosening.

Further, when the piston rod 20 is pressed by the locking part 50, the part of the piston rod 20 is arranged so that the female thread part 6a formed in the internal passage 6 comes into close contact with the male thread part 41a of the plug thread part 41 of the plug 40. (the portion between the internal passage 6 and the steel ball 52) is deformed. As a result, the female threaded portion 6a of the internal passage 6 and the male threaded portion 41a of the plug 40 are prevented from loosening, and the plug 40 is prevented from coming off from the internal passage 6.

It is desirable that the cylindrical portion 21b of the piston rod 20 and the female threaded portion 6a of the internal passage 6 be deformed within their respective elastic ranges by the pressure of the locking portion 50. That is, the tightening force of the set screw 51 of the locking part 50 is desirably set to such an extent that the cylindrical part 21b of the piston rod 20 and the female threaded part 6a of the internal passage 6 are not plastically deformed but are elastically deformed. According to this, even after an overhaul in which the piston 30 and the piston rod 20 are disassembled, the piston 30 and the piston rod 20 can be reused without being repaired. Note that the present invention is not limited to this, and the cylindrical portion 21b of the piston rod 20 and the female threaded portion 6a of the internal passage 6 may be plastically deformed by the pressure of the locking portion 50. Further, the locking portion 50 is configured to press the cylindrical portion 21b, not the male threaded portion 21a, against the piston rod 20. When the male threaded portion 21a is pressed by the locking portion 50, the threads of the male threaded portion 21a are pressed, so plastic deformation is more likely to occur than when the cylindrical portion 21b is pressed. In other words, by configuring the cylindrical portion 21b to be pressed by the locking portion 50, the deformation of the piston rod 20 can be easily made into elastic deformation, and the piston rod 20 can be easily reused after being disassembled. Note that the configuration in which the locking part 50 presses the cylindrical part 21b is not essential, and a configuration in which the male threaded part 21a is pressed as described later may be used.

As described above, the locking portion 50 prevents the piston 30 and the piston rod 20 from loosening by pressing the cylindrical portion 21b of the base end portion 21 of the piston rod 20 from the outside in the radial direction toward the inside. The internal threaded portion 6a of the internal passage 6 is deformed radially inward to prevent the plug 40 from coming off. In other words, the locking portion 50 serves as a locking mechanism for the piston 30 and the piston rod 20, and also functions as a locking mechanism for the plug 40. Therefore, there is no need to provide a structure for preventing the plug 40 from coming off in addition to preventing the piston 30 and the piston rod 20 from loosening, and there is no need to process the piston rod 20 or the plug 40 to prevent the plug 40 from coming off. Therefore, the plug 40 can be prevented from coming off from the internal passage 6 of the piston rod 20 with a simple structure.

Generally, as a method for preventing two screwed members from loosening, a method of plastically deforming at least one of the two members by caulking with a punch or the like is also known. However, loosening prevention by caulking is often performed manually by an operator, and requires skilled work.

In contrast, in this embodiment, by screwing the set screw 51 with a predetermined tightening force, the piston 30 and the piston rod 20 are prevented from loosening, and the plug 40 is prevented from coming off (the plug 40 and the internal passage 6 are prevented from loosening). It will be done. Therefore, since it is only necessary to manage the tightening force, it is possible to easily prevent the piston 30 and the piston rod 20 from loosening, and the plug 40 and the internal passage 6 from loosening.

Next, a method for manufacturing the hydraulic cylinder 100 will be described. Specifically, a method for assembling the piston 30 and the piston rod 20 will be described.

As a method for assembling the piston 30 and the piston rod 20, the piston 30 and the piston rod 20 are fastened together with a predetermined tightening force (piston tightening force), and then the piston rod 20 is pressed by the locking part 50 (hereinafter referred to as the "first method"). A method of fastening the piston 30 and the piston rod 20 with a piston tightening force while the piston rod 20 is pressed by the locking part 50 (hereinafter referred to as the "second assembly method"). ) and.

First, the first assembly method will be explained.

In the first assembly method, first, the male threaded portion 21a of the piston rod 20 is screwed into the female threaded portion 30a of the piston 30, and both are tightened with a predetermined piston tightening force to connect the piston 30 and the piston rod 20. At this time, the circumferential positions of the insertion hole 55 of the piston 30 and the internal passage 6 of the piston rod 20 are aligned. Furthermore, the male threaded part 41a of the plug threaded part 41 of the plug 40 is screwed into the female threaded part 6a of the internal passage 6 of the piston rod 20, and the plug 40 is tightened with a predetermined tightening force. As a result, the opening of the internal passage 6 is closed, and communication between the rod side chamber 1 and the bottom side chamber 2 through the internal passage 6 and the communication passage 7 is cut off.

Next, the steel ball 52 is inserted into the insertion hole 55 of the piston 30, and the set screw 51 is screwed into the female threaded portion 55a of the insertion hole 55. Then, the set screw 51 is tightened with a predetermined tightening force to press the steel ball 52 against the outer periphery of the cylindrical portion 21b of the piston rod 20. As a result, the steel ball 52 and the cylindrical portion 21b of the piston rod 20 are locked in the axial direction, and the cylindrical portion 21b of the piston rod 20 is pressed from the outside in the radial direction to the inside, thereby causing the internal passage The female threaded portion 6a of No. 6 is deformed. Therefore, the piston 30 and piston rod 20 are prevented from loosening, and the plug 40 is prevented from coming off. In this way, the piston 30 and piston rod 20 are assembled.

Next, a second assembly method will be explained.

In the second assembly method, first, the male threaded portion 21a of the piston rod 20 is screwed into the female threaded portion 30a of the piston 30, and the end surface of the piston 30 is brought into contact with the stepped surface 23 of the piston rod 20. Then, the piston 30 and the piston rod 20 are tightened with a tightening force smaller than the piston tightening force (hereinafter referred to as "temporary assembly tightening force"). Thereby, the piston 30 and the piston rod 20 are temporarily assembled. Furthermore, the plug 40 is tightened and attached to the internal passage 6 with a predetermined tightening force.

Next, the steel ball 52 is inserted into the insertion hole 55, and the set screw 51 is screwed into the female threaded portion 55a of the insertion hole 55 and tightened.

In this state, the piston 30 and the piston rod 20 are further tightened (retightened) until the circumferential positions of the locking portion 50 and the plug 40 match and the tightening force reaches the piston tightening force. As a result, the piston 30 and the piston rod 20 are fastened together by the piston tightening force, and the pressing force of the locking portion 50 prevents the piston 30 and the piston rod 20 from loosening and prevents the plug 40 from coming off.

The piston 30 and the piston rod 20 can also be assembled by this second assembly method.

In addition, when the piston rod 20 is plastically deformed by the locking part 50, the temporary assembly tightening force is such that when the piston 30 and the piston rod 20 are tightened one rotation or more from the state where the piston 30 and the piston rod 20 are temporarily assembled, It is desirable that the tightening force is set to reach the piston tightening force. According to this, a state in which the circumferential positions of the locking part 50 and the plug 40 are coincident always occurs before the tightening force reaches the piston clamping force, so that the locking part 50 is able to prevent the locking part 50 from internally threaded part 6a of the internal passage 6. can be reliably pressed and plastically deformed. Therefore, the plug 40 can be prevented from coming off more reliably.

Next, a modification of this embodiment will be described.

First, the modification shown in FIGS. 4 and 5 will be described.

In the embodiment described above, the plug 40 is prevented from coming off by deforming the female screw portion 6a of the internal passage 6 by pressing the locking portion 50. On the other hand, as in the modification shown in FIGS. 4 and 5, the piston rod 20 may be deformed so as to narrow the opening of the internal passage 6 by the pressure of the locking part 50.

In the modification shown in FIG. 4, the inner periphery of a part of the internal passage 6 on the opening side to the proximal end surface 20a of the piston rod 20 is formed as a cylindrical surface 106a instead of the female threaded portion 6a as in the above embodiment. The plug 140 has a base portion 141 whose outer periphery is formed into a cylindrical surface in place of the plug screw portion 41 in the above embodiment, and is inserted into the internal passage 6. The end face of the plug 140 does not protrude from the end face of the piston rod 20 and is located within the internal passage 6. Therefore, an inner space S is defined inside the internal passage 6 and between the end surface of the plug 140 and the end surface 20a of the piston rod 20.

The locking portion 50 presses the outer periphery (cylindrical portion 21b) of the piston rod 20 located on the radially outer side of the inner space S radially inward. That is, the insertion hole 55 of the piston 30 is provided so as to be located within an axial range in which the inner space S is defined in a state where the piston 30 and the piston rod 20 are fastened together. As a result, the cylindrical portion 21b of the piston rod 20 is engaged with the steel ball 52 of the locking portion 50, and the piston 30 and the piston rod 20 are prevented from loosening.

Furthermore, since the outer periphery of the piston rod 20 on the radially outer side of the inner space S is pressed by the locking portion 50, the portion of the piston rod 20 that is pressed is deformed radially inward. Thereby, the opening of the internal passage 6 is narrowed so that the internal diameter is reduced. Therefore, the plug 140 is axially locked to a portion of the piston rod 20 that has been deformed so as to narrow the internal passage 6, and the plug 140 is prevented from coming off.

According to this modification, the plug 140 is prevented from coming off by deforming the piston rod 20 so as to narrow the opening of the internal passage 6. Therefore, the plug 40 does not need to be attached to the internal passage 6 by screwing, and there is no need to thread the outer periphery of the plug 140 or the inner periphery of the internal passage 6. Therefore, the number of man-hours for machining the plug 140 and the piston rod 20 can be reduced, and costs can be reduced.

Note that the plug 140 may be attached to the internal passage 6 by screw fastening, similarly to the above embodiment. Even in this case, the plug 140 is prevented from coming off by deforming the piston rod 20 so as to narrow the opening of the internal passage 6 by the locking part 50.

In addition, as shown in FIG. 5, when the plug 140 is prevented from coming off by narrowing the opening of the internal passage 6, the plug 140 has a base part 141 facing the internal passage 6 and a base part 141 facing the internal passage 6, and a base part 141 facing the internal passage 6. A small diameter portion 44 extending in the axial direction from the base portion 141 and having a smaller outer diameter than the base portion 141 may be included. In this case, an annular inner space S is formed between the outer peripheral surface of the small diameter portion 44 and the cylindrical surface 106a of the internal passage 6. The locking portion 50 presses the axial range in the piston rod 20 in which the inner space S is defined inward in the radial direction, thereby narrowing the opening of the internal passage 6 and preventing the plug 140 from coming off. In this case, as shown in FIG. 5, the small diameter portion 44 is desirably formed so as not to protrude from the internal passage 6 beyond the end surface of the piston rod 20 toward the proximal end.

Next, other modified examples will be explained.

In the above embodiment, the female threaded portion 30a is formed on the inner circumference of the piston 30, and the male threaded portion 21a of the piston rod 20 and the female threaded portion 30a of the piston 30 are screwed together, and the piston rod 20 and the piston 30 are screwed together. . That is, the piston rod 20 and the piston 30 are directly screwed together. On the other hand, although not shown in the drawings, a nut is separately provided to hold the piston 30 between the stepped surface 23 of the piston rod 20, and the nut is screwed onto the piston rod 20, so that the piston 30 is attached to the piston rod 20. It may also be configured so that it can be attached. That is, the piston 30 may be attached to the piston rod 20 with a nut having a female thread that is screwed into the male thread 21a of the piston rod 20. In this case, the locking portion 50 may be provided on the nut. Even in this case, the same effects as in the above embodiment can be achieved. In this way, "the piston is attached to the piston rod by screw fastening" means that the piston 30 is attached by being directly screwed to the piston rod 20 and the nut is screwed to the piston rod 20. This includes both a configuration that is attached to the piston rod 20 and a configuration that is attached to the piston rod 20.

In the above embodiment, the locking part 50 includes a set screw 51 and a steel ball 52. On the other hand, the locking part 50 is not limited to the above configuration, and can have any configuration as long as it presses the piston rod 20 to prevent loosening. For example, the locking part 50 may not include the steel ball 52 and may be configured only by the set screw 51.

Further, in the embodiment described above, the locking portion 50 is provided so as to press the cylindrical portion 21b of the piston rod 20 toward the central axis O1 of the piston rod 20. More specifically, the positions (angles) of the locking part 50 and the plug 40 in the circumferential direction with respect to the central axis O1 of the piston 30 match, and the locking part 50 and the plug 40 are aligned with each other with respect to the central axis O1 of the piston 30. lined up in the radial direction. On the other hand, as long as the locking part 50 is configured to prevent the plug 40 from coming off (preventing the plug 40 from loosening between the plug 40 and the internal passage 6), the locking part 50 is not limited to the above configuration. For example, the locking portion 50 may be provided at a position shifted from the plug 40 in the circumferential direction. Further, in the locking portion 50, the central axis O3 of the set screw 51 (the central axis of the insertion hole 55) does not need to be orthogonal to the central axis O1 of the piston 30 or the central axis O2 of the plug 40.

Further, in the above embodiment, the base end portion 21 of the piston rod 20 has a male thread portion 21a and a cylindrical portion 21b, and the cylindrical portion 21b is pressed radially inward by the locking portion 50. On the other hand, the male threaded portion 21a may be pressed radially inward by the locking portion 50. In this case, the outer periphery of the base end portion 21 may be formed as a male threaded portion 21a over the entire axial length without the cylindrical portion 21b. The piston rod 20 and the piston 30 are prevented from loosening by elastically or plastically deforming the threads of the male threaded portion 21a by the set screw 51 of the locking portion 50.

In addition, when the male threaded portion 21a of the piston rod 20 and the female threaded portion 6a of the internal passage 6 are plastically deformed to prevent the piston 30 and the piston rod 20 from loosening and to prevent the plug 40 from coming off, the second assembly method may be used to prevent loosening. The circumferential positions of the stop portion 50 and the plug 40 do not have to match.

Specifically, in this case, the piston 30 and the piston rod 20 are temporarily assembled, and the set is performed using a tightening force to the extent that the male threaded portion 21a of the piston rod 20 and the female threaded portion 6a of the internal passage 6 are plastically deformed. The screw 51 is tightened to press the steel ball 52 against the male threaded portion 21a. Next, the piston 30 and the piston rod 20 are further tightened until the tightening force reaches the piston tightening force. The tightening force of the set screw 51 is large enough to plastically deform the male threaded portion 21a of the piston rod 20 and the female threaded portion 6a of the internal passage 6. Therefore, in the process of retightening, the piston 30 facing the locking portion 50 The male threaded portion 21a of is plastically deformed. Furthermore, when the circumferential positions of the locking part 50 and the plug 40 coincide, the internal thread part 30a of the internal passage 6 is pressed by the locking part 50 and plastically deformed.

According to this method, when the circumferential positions of the locking part 50 and the plug 40 coincide in the process of retightening, the internal thread part 30a of the internal passage 6 is plastically deformed and the plug 40 can be prevented from coming off. Therefore, it is not necessary to finally match the circumferential positions of the locking part 50 and the plug 40, and there is no need to align the locking part 50 and the plug 40. It can be done easily.

According to the above embodiment, the following effects are achieved.

In the hydraulic cylinder 100, the locking portion 50 presses the cylindrical portion 21b on the outer periphery of the piston rod 20 from the outside in the radial direction toward the inside, thereby preventing the piston 30 and the piston rod 20 from loosening, and also preventing the plug 40 from coming off. We also do Therefore, there is no need to provide a structure for preventing the plug 40 from coming off in addition to preventing the piston 30 and the piston rod 20 from loosening, and there is no need to process the piston rod 20 or the plug 40 to prevent the plug 40 from coming off. Therefore, the plug 40 can be prevented from coming off from the internal passage 6 of the piston rod 20 with a simple structure.

Further, since the cylindrical portion 21b at the base end portion 21 of the piston rod 20 is pressed by the locking portion 50, the deformation of the piston rod 20 is likely to be elastic deformation, and the piston rod 20 can be easily reused after an overhaul.

Furthermore, in the hydraulic cylinder 100, by tightening the set screw 51 with a predetermined tightening force, the piston 30 and the piston rod 20 are prevented from loosening, and the plug 40 is prevented from coming off (the plug 40 and the internal passage 6 are prevented from loosening). . Therefore, since it is only necessary to manage the tightening force, it is possible to easily prevent the piston 30 and the piston rod 20 from loosening, and the plug 40 and the internal passage 6 from loosening.

Further, in the hydraulic cylinder 100 according to the modified example, the locking portion 50 presses the piston rod 20 inward in the radial direction and deforms the piston rod 20 so as to narrow the opening of the internal passage 6, thereby preventing the plug 140 from coming off. Therefore, the plug 140 does not need to be attached to the internal passage 6 by screwing, and there is no need to thread the outer periphery of the plug 140 or the inner periphery of the internal passage 6. Therefore, the number of man-hours for machining the plug 40 and the piston rod 20 can be reduced, and costs can be reduced.

Hereinafter, the configuration, operation, and effects of the embodiments of the present invention will be collectively described.

The hydraulic cylinder 100 includes a cylinder tube 10, a piston rod 20 having a male threaded portion 21a formed at the base end portion 21 and inserted into the cylinder tube 10, and a piston rod 20 that is connected to the piston rod 20 by screwing into the male threaded portion 21a. A piston 30 is inserted into the piston 30 and partitions the inside into a rod side chamber 1 and a bottom side chamber 2. A locking part 50 that prevents loosening, an internal passage 6 formed in the piston rod 20 along the axial direction, a communication passage 7 formed in the piston rod 20 that communicates the internal passage 6 and the rod side chamber 1, A plug 40 is inserted into the passage 6 and closes the opening of the internal passage 6 to the proximal end surface 20 a of the proximal end 21 of the piston rod 20 . It is prevented from coming off from the passage 6.

Further, in the hydraulic cylinder 100, a female threaded portion 6a into which the plug 40 is screwed is formed on the inner periphery of the internal passage 6, and when the female threaded portion 6a is deformed by the pressure of the locking portion 50, the plug 40 is inserted into the internal passageway. It is stopped from falling out from 6.

In these configurations, the piston rod 20 is deformed by the pressing force of the locking part 50 for preventing the piston 30 and the piston rod 20 from loosening, and this deformation of the piston rod 20 causes the plug 40 to flow from the internal passage 6. is prevented from falling out. Therefore, there is no need to process the piston rod 20 or the plug 40 to prevent the plug 40 from coming off, and there is no need to provide a structure to prevent the plug 40 from coming off in addition to preventing the piston 30 and the piston rod 20 from loosening. Therefore, the structure around the piston 30 in the hydraulic cylinder 100 is simplified.

Furthermore, in the hydraulic cylinder 100 according to the modified example, the locking part 50 presses the piston rod 20 inward in the radial direction so as to narrow the opening of the internal passage 6, and the plug 140 presses the piston rod 20 inward in the radial direction so as to narrow the opening of the internal passage 6. This prevents it from coming off from the internal passage 6.

In this configuration, the plug 140 only needs to be inserted into the internal passage 6, and there is no need to attach the plug 140 to the internal passage 6 with screws, so there is no need to thread the plug 140 or the internal passage 6, Manufacturing costs are reduced.

Further, in the hydraulic cylinder 100, the locking part 50 is provided between the set screw 51 that is screwed into the insertion hole 55 formed in the piston 30 along the radial direction, and the outer peripheral surface of the set screw 51 and the piston rod 20. A spherical steel ball 52 is provided and presses the piston rod 20 radially inward.

Although the embodiments of the present invention have been described above, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. do not have.

DESCRIPTION OF SYMBOLS 1...Rod side chamber, 2...Bottom side chamber, 6...Internal passage, 6a...Female threaded part, 7...Communication passage, 10...Cylinder tube, 20...Piston rod, 20a...Proximal end surface (end surface), 21...Proximal end (end surface) part), 30...Piston, 40, 140...Plug, 50...Loosening part), 100...Hydraulic cylinder

Claims (3)

cylinder tube,
a piston rod inserted into the cylinder tube;
a piston that is attached to the end of the piston rod by screw fastening and partitions the inside of the cylinder tube into a rod side chamber and a bottom side chamber;
a locking part that presses the end of the piston rod from the outside in the radial direction toward the inside to prevent the screw fastening from loosening;
an internal passage formed in the piston rod along the axial direction;
a communication passage formed in the piston rod and communicating the internal passage and the rod side chamber;
a plug that is inserted into the internal passage and closes an opening of the internal passage to an end surface at the end of the piston rod;
A fluid pressure cylinder, wherein the plug is prevented from coming off from the internal passage only by the piston rod that is deformed by the pressure of the locking part. A female screw portion into which the plug is screwed is formed on the inner periphery of the internal passage,
2. The fluid pressure cylinder according to claim 1, wherein the plug is prevented from coming off from the internal passage by deforming the female threaded portion under pressure of the locking portion. The locking portion presses the piston rod radially inward so as to narrow the opening of the internal passage,
The fluid pressure cylinder according to claim 1, wherein the plug is prevented from coming off from the internal passage by narrowing the opening of the internal passage.

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