JP7609650B2 - Fluid Pressure Cylinder - Google Patents

Description

The present invention relates to a fluid pressure cylinder.

Patent document 1 discloses a fluid pressure cylinder in which a piston rod with a piston fastened thereto is reciprocally disposed within a cylinder tube, the fluid pressure cylinder includes a cylinder head that closes the end opening of the cylinder tube, and a bearing is attached to the inner peripheral surface of the cylinder head by a snap ring.

JP 2013-199950 A

In the fluid pressure cylinder described in Patent Document 1, a snap ring must be used to prevent the bearing from coming loose when the bearing is mounted on the inner peripheral surface of the cylinder head. This requires a large number of parts to make up the fluid pressure cylinder. Also, a groove must be formed separately to accommodate the snap ring. Thus, the structure to prevent the bearing from coming loose in the fluid pressure cylinder described in Patent Document 1 is complex.

The present invention was made in consideration of the above problems, and aims to prevent the bearing from coming loose with a simple structure.

The present invention is a fluid pressure cylinder in which a piston rod provided with a piston is reciprocally disposed within a cylinder tube, the fluid pressure cylinder comprising: a closure member that closes an end opening of the cylinder tube and has an insertion hole through which the piston rod is inserted; a bearing that is provided in the closure member and slidably supports the piston rod; and a pressure chamber defined between the closure member and the piston, the closure member having a bearing accommodating groove formed on the inner peripheral surface of the insertion hole and in which the bearing is accommodated, the bearing accommodating groove having a groove bottom against which the outer peripheral surface of the bearing abuts, and a slip-out prevention wall that prevents the bearing from slipping out towards the pressure chamber, the slip-out prevention wall having a height greater than the clearance between the bearing and the piston rod, the bearing is press-fitted to overcome the slip-out prevention wall and is accommodated in the bearing accommodating groove, and the slip-out prevention wall is formed with a first tapered portion that guides the bearing to the groove bottom .

According to this invention, the height of the retaining wall that prevents the bearing from coming out toward the pressure chamber is greater than the clearance between the bearing and the piston rod, so the bearing is prevented from climbing over the retaining wall and coming out of the bearing groove. Therefore, the bearing can be prevented from coming out with a simple structure without using a snap ring. In addition, the bearing is smoothly pressed into the bearing groove while being guided by the first tapered portion, improving the ease of installation of the bearing.

The present invention is also characterized in that the retaining wall is formed with a second tapered portion that faces the end face of the bearing, and the inclination angle of the second tapered portion is greater than the inclination angle of the first tapered portion.

According to this invention, the workability of the blocking member is improved compared to a bearing housing groove in which the second tapered portion is not formed. In addition, by making the inclination angle of the second tapered portion larger than the inclination angle of the first tapered portion, the bearing is less likely to come out.

The present invention also provides a fluid pressure cylinder in which a piston rod provided with a piston is reciprocally disposed within a cylinder tube, the fluid pressure cylinder comprising: a closure member that closes an end opening of the cylinder tube and has an insertion hole through which the piston rod passes; a bearing provided in the closure member and supporting the piston rod so that it can slide; and a pressure chamber defined between the closure member and the piston, the closure member having a bearing accommodating groove formed on the inner surface of the insertion hole and accommodating the bearing, the bearing accommodating groove having a groove bottom against which the outer circumferential surface of the bearing abuts, a stop wall that prevents the bearing from coming out towards the pressure chamber, and a restriction wall that faces the stop wall and restricts axial movement of the bearing, the stop wall having a height greater than a clearance between the bearing and the piston rod, and the restriction wall having a height greater than that of the stop wall.

According to this invention, the height of the retaining wall that prevents the bearing from falling out toward the pressure chamber is greater than the clearance between the bearing and the piston rod, so the bearing is prevented from climbing over the retaining wall and falling out of the bearing groove. Therefore, the bearing can be prevented from falling out with a simple configuration without using a snap ring. Also, by making the height of the restricting wall that restricts the axial position of the bearing greater than the height of the retaining wall, the height of the retaining wall can be reduced, so that the amount of deformation of the bearing when the bearing is press-fitted into the bearing groove can be kept small.

The present invention makes it possible to prevent bearings from coming loose with a simple structure.

1 is a cross-sectional view of a fluid pressure cylinder according to an embodiment of the present invention. FIG. 2 is an enlarged view of a portion A surrounded by a dashed line in FIG.

The following describes an embodiment of the present invention with reference to the drawings.

A fluid pressure cylinder according to an embodiment of the present invention will be described with reference to FIG. 1. Below, a case will be described in which the fluid pressure cylinder is a hydraulic cylinder 100 that is driven by hydraulic oil as the working fluid. FIG. 1 is a cross-sectional view of the cylinder head 40 and its surroundings of the hydraulic cylinder 100.

The hydraulic cylinder 100 is used as an actuator mounted on construction machinery or industrial machinery. For example, the hydraulic cylinder 100 is used as an arm cylinder mounted on a hydraulic excavator, and the arm of the hydraulic excavator rotates when the hydraulic cylinder 100 extends or retracts.

As shown in FIG. 1, the hydraulic cylinder 100 includes a cylindrical cylinder tube 10, a piston 20 that is slidably inserted into the cylinder tube 10 and divides the cylinder tube 10 into a rod side chamber 11 and a non-rod side chamber 12 as pressure chambers, a piston rod 30 that has one end connected to the piston 20 and the other end extending outside the cylinder tube 10 and reciprocates within the cylinder tube 10, and a cylinder head 40 that serves as a blocking member that blocks the end opening of the cylinder tube 10.

The inside of the cylinder tube 10 is divided by the piston 20 into two fluid pressure chambers, a rod side chamber 11 and an anti-rod side chamber 12, which serve as pressure chambers. The hydraulic cylinder 100 expands and contracts along the axial direction due to hydraulic pressure guided from a hydraulic source to the rod side chamber 11 or the anti-rod side chamber 12. Note that a hydraulic fluid such as a water-soluble substitute liquid may be used instead of oil as the hydraulic oil.

The cylinder head 40 is a generally cylindrical member with a through hole 41 through which the piston rod 30 passes. The cylinder head 40 is connected to a flange portion 10a formed at the end of the cylinder tube 10 via a bolt 39.

On the inner circumferential surface of the insertion hole 41, a bearing 55, a sub seal 56, a main seal 57, and a dust seal 58 are arranged in this order toward the outside. These make sliding contact with the outer circumferential surface of the piston rod 30, and the bearing 55 in particular supports the piston rod 30 so that it can slide freely in the axial direction of the cylinder tube 10. In addition, the bearing 55 is a cylindrical bearing made of a mixed material in which resin is dispersed in a metal such as an alloy, and therefore has a certain degree of flexibility.

The cylinder head 40 is also provided with a supply/discharge port 42 that supplies/discharges hydraulic oil to/from the rod side chamber 11. One end of the supply/discharge port 42 opens to the inner peripheral surface of the insertion hole 41, and the other end of the supply/discharge port 42 opens to the outer surface of the cylinder head 40. The other end of the supply/discharge port 42 is connected to a hydraulic pipe (not shown), which is connected to a hydraulic source or a tank via a switching valve.

The cylinder head 40 is provided with a cylindrical portion 45 that fits into the inner peripheral surface of the flange portion 10a of the cylinder tube 10. An O-ring 59 that seals between the cylinder tube 10 and the cylinder head 40 is provided on the outer peripheral surface of the cylindrical portion 45. The tip surface of the cylindrical portion 45 functions as a restricting surface against which the piston 20 abuts when the hydraulic cylinder 100 is fully extended, restricting the movement of the piston 20 and the piston rod 30.

The insertion hole 41 has a first insertion hole 41a through which the cushion ring 34 described below can enter, and a second insertion hole 41b having an inner diameter smaller than that of the first insertion hole 41a. The first insertion hole 41a is provided on the cylindrical portion 45 side, and the second insertion hole 41b is provided on the opposite side of the supply/discharge port 42 from the first insertion hole 41a.

The piston rod 30 has a small diameter section 31 formed at the tip to which the piston 20 is fastened, a large diameter section 32 having an outer diameter larger than that of the small diameter section 31 and slidably supported by the cylinder head 40, and a medium diameter section 33 formed between the small diameter section 31 and the large diameter section 32 and having a cushion ring 34 disposed radially outward. The outer diameter of the medium diameter section 33 and the inner diameter of the cushion ring 34 are set smaller than the outer diameters of the large diameter section 32 and the piston 20, so that the cushion ring 34 does not come out of the piston rod 30.

The cushion ring 34 is a cylindrical member having an outer diameter that can enter the first insertion hole 41a of the cylinder head 40, and is provided to slow down the movement speed of the piston rod 30 when the hydraulic cylinder 100 reaches its most extended state.

Next, the operation of the hydraulic cylinder 100 configured as described above will be explained.

When the hydraulic source is connected to the anti-rod side chamber 12 and the tank is connected to the rod side chamber 11, hydraulic oil is supplied to the anti-rod side chamber 12 and the hydraulic oil in the rod side chamber 11 is discharged to the tank through the supply/discharge port 42. This causes the piston rod 30 to move leftward in FIG. 1, and the hydraulic cylinder 100 extends.

When the hydraulic cylinder 100 extends, the hydraulic oil in the rod side chamber 11 is guided to the supply/discharge port 42 through a passage with a relatively large cross-sectional area formed between the outer circumferential surface of the large diameter portion 32 and the inner circumferential surface of the first insertion hole 41a until the cushion ring 34 enters the first insertion hole 41a. Therefore, the piston rod 30 can move at a relatively high speed.

When the hydraulic cylinder 100 is further extended and the cushion ring 34 enters the first insertion hole 41a, the hydraulic oil in the rod side chamber 11 is guided to the supply and discharge port 42 through a passage with a relatively small cross-sectional area formed between the inner surface of the cushion ring 34 and the outer surface of the medium diameter section 33, and between the outer surface of the cushion ring 34 and the inner surface of the first insertion hole 41a.

In this way, if the cross-sectional area of the passage connecting the supply/discharge port 42 and the rod side chamber 11 is small, resistance is applied to the flow of hydraulic oil toward the supply/discharge port 42, resulting in an increase in pressure in the rod side chamber 11 and a slower movement speed of the piston rod 30.

In addition, as the cushion ring 34 enters the first insertion hole 41a, the cross-sectional area of the passage connecting the supply/discharge port 42 and the rod side chamber 11 gradually decreases, further slowing down the movement speed of the piston rod 30. In this way, the cushioning effect of the cushion ring 34 is exerted, preventing the piston 20 from colliding forcefully with the cylinder head 40.

On the other hand, when the hydraulic source is connected to the rod side chamber 11 and the tank is connected to the anti-rod side chamber 12, hydraulic oil is supplied to the rod side chamber 11 through the supply/discharge port 42, and hydraulic oil in the anti-rod side chamber 12 is discharged to the tank. This causes the piston rod 30 to move to the right in FIG. 1, causing the hydraulic cylinder 100 to contract.

Next, the second insertion hole 41b will be described with reference to Figures 1 and 2.

As shown in Figures 1 and 2, a bearing housing groove 51, a sub-seal housing groove 52, a main seal housing groove 53, and a dust seal housing groove 54 are formed in the inner peripheral surface of the second insertion hole 41b in this order toward the outside. The bearing 55, the sub-seal 56, the main seal 57, and the dust seal 58 are housed (attached) in the bearing housing groove 51, the sub-seal housing groove 52, the main seal housing groove 53, and the dust seal housing groove 54, respectively. The sub-seal 56, the main seal 57, and the dust seal 58 are in sliding contact with the outer peripheral surface of the piston rod 30.

As shown in FIG. 2, the bearing housing groove 51 has a groove bottom 511 extending along the axial direction, a retaining wall 512 provided on one axial side of the groove bottom 511 to define the bearing housing groove 51, and a restricting wall 513 provided on the other axial side of the groove bottom 511 to define the bearing housing groove 51.

The groove bottom 511 is formed so that its diameter is approximately equal to the outer diameter of the bearing 55. As a result, when the bearing 55 is accommodated in the bearing accommodation groove 51, the outer circumferential surface of the bearing 55 abuts against the groove bottom 511. The groove bottom 511 is also formed so that its diameter is smaller than the inner diameter of the first insertion hole 41a. In other words, the first insertion hole 41a is formed so that its inner diameter is larger than the outer diameter of the bearing 55. As a result, the bearing 55 can smoothly pass through the first insertion hole 41a and enter the second insertion hole 41b without being pressed in.

The retaining wall 512 is an annular wall portion for preventing the bearing 55 from coming out toward the rod side chamber 11. The retaining wall 512 is formed to protrude radially from the groove bottom 511 toward the axis O. When the large diameter portion 32 of the piston rod 30 is not inserted into the cylinder head 40, the bearing 55 is pressed into the bearing accommodation groove 51, overcoming the retaining wall 512.

When the large diameter portion 32 of the piston rod 30 is inserted into the cylinder head 40, the height h1 of the retaining wall 512 is greater than the clearance c1 between the bearing 55 housed in the bearing housing groove 51 and the large diameter portion 32 of the piston rod 30 (see FIG. 2). Specifically, the clearance c1 is the radial dimension between the inner circumferential surface of the bearing 55 and the outer circumferential surface of the large diameter portion 32.

That is, when the large diameter portion 32 of the piston rod 30 is inserted into the cylinder head 40, the clearance c3 between the apex 512c of the retaining wall 512 and the large diameter portion 32 of the piston rod 30 is smaller than the thickness d of the bearing 55 (i.e., the dimension between the inner peripheral surface of the bearing 55 and the outer peripheral surface of the bearing 55) (see FIG. 2). As a result, the bearing 55 does not pass through the clearance c3 between the apex 512c of the retaining wall 512 and the large diameter portion 32 of the piston rod 30, so the bearing 55 does not climb over the retaining wall 512 and fall out of the bearing housing groove 51.

The height h1 of the retaining wall 512 (i.e., the amount by which the retaining wall 512 protrudes from the groove bottom 511) is smaller than the thickness d of the bearing 55. This allows the height of the retaining wall 512 to be reduced, thereby minimizing the amount of deformation of the bearing 55 during press-fitting.

The retaining wall 512 has a first tapered portion 512a that guides the bearing 55 to the groove bottom 511, and a second tapered portion 512b that faces the end face 55a of the bearing 55. In this embodiment, the first tapered portion 512a is directly connected to the second tapered portion 512b in the axial direction, but is not limited to this. For example, the first tapered portion 512a may be indirectly connected to the second tapered portion 512b via a flat portion extending along the axial direction.

The first tapered portion 512a is formed so that the clearance between the large diameter portion 32 of the piston rod 30 gradually decreases toward the outside (opposite the piston side). As a result, the bearing 55 is smoothly pressed into the bearing housing groove 51 while being guided by the first tapered portion 512a. From the viewpoint of improving the ease of pressing in the bearing 55, it is preferable that the inclination angle α of the first tapered portion 512a is 60° or less, more preferably 45° or less, and even more preferably 30° or less. In this embodiment, the inclination angle α of the first tapered portion 512a is 20°. The inner diameter at the end 512d of the first tapered portion 512a is larger than the inner diameter of the groove bottom 511. This makes it easier to insert the bearing 55 into the bearing housing groove 51.

On the other hand, the second tapered portion 512b is formed so that the clearance between it and the large diameter portion 32 of the piston rod 30 gradually increases outward. This makes it easier to machine the cylinder head 40 compared to a bearing housing groove 51 in which the second tapered portion 512b is not formed. From the viewpoint of making it difficult for the bearing 55 to come out, it is preferable to make the inclination angle β of the second tapered portion 512b larger than the inclination angle α of the first tapered portion 512a. In this embodiment, the inclination angle β of the second tapered portion 512b is 30°.

The restricting wall 513 is an annular wall portion that faces the retaining wall 512 and restricts the axial movement of the bearing 55. The restricting wall 513 is formed to protrude radially from the groove bottom 511 toward the axis O. The restricting wall 513 has a height h2 (i.e., the amount of protrusion of the restricting wall 513 from the groove bottom 511) that is greater than the height h1 of the retaining wall 512 (see FIG. 2). This allows the height of the retaining wall 512 to be lowered, thereby minimizing the amount of deformation of the bearing 55 during press-fitting.

When the large diameter portion 32 of the piston rod 30 is inserted into the cylinder head 40, the restricting wall 513 does not come into contact with the large diameter portion 32 of the piston rod 30. The clearance c2 between the restricting wall 513 and the large diameter portion 32 of the piston rod 30 is equal to the clearance c1 between the bearing 55 and the large diameter portion 32 of the piston rod 30 (see FIG. 2).

In other words, when the large diameter portion 32 of the piston rod 30 is inserted into the cylinder head 40, the clearance c2 between the restricting wall 513 and the large diameter portion 32 of the piston rod 30 is smaller than the thickness d of the bearing 55 (see FIG. 2). As a result, the bearing 55 cannot pass through the clearance c2 between the restricting wall 513 and the large diameter portion 32 of the piston rod 30, so the bearing 55 does not climb over the restricting wall 513 and come out of the bearing housing groove 51.

The configuration, operation, and effects of the embodiment of the present invention are summarized below.

The hydraulic cylinder 100 according to this embodiment is a hydraulic cylinder 100 in which a piston rod 30 provided with a piston 20 is reciprocally provided in a cylinder tube 10, and includes a cylinder head 40 that closes the end opening of the cylinder tube 10 and has an insertion hole 41 through which the piston rod 30 is inserted, a bearing 55 provided in the cylinder head 40 to slidably support the piston rod 30, and a rod side chamber 11 partitioned between the cylinder head 40 and the piston 20. The cylinder head 40 has a bearing accommodation groove 51 formed on the inner peripheral surface of the insertion hole 41 and in which the bearing 55 is accommodated. The bearing accommodation groove 51 has a groove bottom 511 against which the outer peripheral surface of the bearing 55 abuts, and a slip-out prevention wall 512 that prevents the bearing 55 from slipping out toward the rod side chamber 11, and the slip-out prevention wall 512 has a height greater than the clearance between the bearing 55 and the piston rod 30.

According to this configuration, the bearing housing groove 51 is formed on the inner peripheral surface of the insertion hole 41 of the cylinder head 40, so that when the piston rod 30 is not inserted into the insertion hole 41 of the cylinder head 40, the bearing 55 is housed in the bearing housing groove 51 by press-fitting. In addition, the height h1 of the retaining wall 512 that prevents the bearing 55 from coming out toward the rod side chamber 11 is greater than the clearance c1 between the bearing 55 and the piston rod 30, so that when the piston rod 30 is inserted into the insertion hole 41 of the cylinder head 40, the bearing 55 does not climb over the retaining wall 512 and come out of the bearing housing groove 51. Therefore, it is possible to prevent the bearing 55 from coming out with a simple configuration without using a snap ring.

In addition, in this embodiment, the bearing 55 is accommodated in the bearing accommodation groove 51 by press-fitting via the retaining wall 512, and the retaining wall 512 is formed with a first tapered portion 512a that guides the bearing 55 to the groove bottom 511.

With this configuration, the bearing 55 is smoothly pressed into the bearing housing groove 51 while being guided by the first tapered portion 512a, improving the installation of the bearing 55.

In addition, in this embodiment, the retaining wall 512 is formed with a second tapered portion 512b that faces the end face of the bearing 55, and the inclination angle β of the second tapered portion 512b is greater than the inclination angle α of the first tapered portion 512a.

This configuration improves the workability of the cylinder head 40 compared to a bearing housing groove 51 in which the second tapered portion 512b is not formed. In addition, by making the inclination angle β of the second tapered portion 512b larger than the inclination angle α of the first tapered portion 512a, the bearing 55 is less likely to come loose.

In addition, in this embodiment, the bearing housing groove 51 further has a restricting wall 513 that faces the retaining wall 512 and restricts the axial movement of the bearing 55, and the height h2 of the restricting wall 513 is greater than the height h1 of the retaining wall 512. This allows the height of the retaining wall 512 to be reduced, thereby minimizing the amount of deformation of the bearing 55 during press-fitting.

Although the present embodiment has been described above, the above embodiment merely illustrates some of the application examples of the present invention, and is not intended to limit the technical scope of the present invention to the specific configuration of the above embodiment.

(Modification)
In the above embodiment, the anti-pullout wall 512 is formed around the entire circumference of the ring, but this is not limited to this. For example, the anti-pullout wall 512 may be formed around a part of the ring, or may be formed as multiple walls around the ring at a predetermined interval.

In the above embodiment, the retaining wall 512 is formed with the first tapered portion 512a and the second tapered portion 512b that is continuous with the first tapered portion 512a, but this is not limited thereto. For example, the second tapered portion 512b may not be formed, and only the first tapered portion 512a may be formed. In this case, compared to the retaining wall 512 in which the first tapered portion 512a and the second tapered portion 512b are formed, the space required to form the second tapered portion 512b can be saved, and the bearing accommodation groove 51 can be made smaller in the axial direction.

In the above embodiment, the restricting wall 513 is provided so that the clearance c2 between the restricting wall 513 and the large diameter portion 32 of the piston rod 30 is equal to the clearance c1 between the bearing 55 and the large diameter portion 32 of the piston rod 30, but this is not limited thereto. For example, the restricting wall 513 may be provided so that the clearance c2 between the restricting wall 513 and the large diameter portion 32 of the piston rod 30 is larger than the clearance c1 between the bearing 55 and the large diameter portion 32 of the piston rod 30. In this case, it is possible to prevent the restricting wall 513 and the large diameter portion 32 of the piston rod 30 from coming into contact with each other.

10: Cylinder tube, 20: Piston, 30: Piston rod, 40: Cylinder head (blocking member), 51: Bearing accommodation groove, 55: Bearing, 511: Groove bottom, 512: Anti-pullout wall, 513: Restriction wall, 512a: First taper portion, 512b: Second taper portion, 100: Hydraulic cylinder (fluid pressure cylinder)

Claims (3)

A fluid pressure cylinder in which a piston rod having a piston is reciprocally disposed within a cylinder tube,
a closing member that closes an end opening of the cylinder tube and has an insertion hole through which the piston rod is inserted;
a bearing provided in the blocking member and configured to slidably support the piston rod;
a pressure chamber defined between the closing member and the piston,
the blocking member has a bearing accommodating groove formed on an inner circumferential surface of the insertion hole and configured to accommodate the bearing,
The bearing accommodating groove is
a groove bottom portion against which an outer peripheral surface of the bearing abuts;
a retaining wall that prevents the bearing from coming out toward the pressure chamber,
The height of the retaining wall is greater than the clearance between the bearing and the piston rod,
The bearing is press-fitted into the bearing accommodating groove, overcoming the retaining wall.
a first tapered portion formed on the retaining wall for guiding the bearing to the bottom of the groove , The retaining wall is formed with a second tapered portion facing an end surface of the bearing,
2. The fluid pressure cylinder according to claim 1 , wherein an inclination angle of the second tapered portion is larger than an inclination angle of the first tapered portion. A fluid pressure cylinder in which a piston rod having a piston is reciprocally disposed within a cylinder tube,
a closing member that closes an end opening of the cylinder tube and has an insertion hole through which the piston rod is inserted;
a bearing provided in the blocking member and configured to slidably support the piston rod;
a pressure chamber defined between the closing member and the piston,
the blocking member has a bearing accommodating groove formed on an inner circumferential surface of the insertion hole and configured to accommodate the bearing,
The bearing accommodating groove is
a groove bottom portion against which an outer peripheral surface of the bearing abuts;
a retaining wall that prevents the bearing from coming out toward the pressure chamber;
a restriction wall that faces the fall-out prevention wall and restricts axial movement of the bearing,
The height of the retaining wall is greater than the clearance between the bearing and the piston rod,
A fluid pressure cylinder, wherein the regulating wall has a height greater than a height of the retaining wall.

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