JPH0361704A - Fluid bearing device and fluid pressure cylinder using fluid bearing device - Google Patents

Abstract

PURPOSE:To fit a fluid bearing device to a fluid pressure apparatus for use by providing a relief groove section on the outer periphery of a shaft member at a position apart from the small hole of a bearing member on the inside in the axial direction, and providing a communicating passage discharging the pressure fluid flowing into it to the outside. CONSTITUTION:A thin section 32 is provided on the outer periphery of a cover member 31, and a small hole 33 opened to an inner periphery 21a is provided here. A relief groove section 34 on the outer periphery of a piston rod 13 on the inside in the axial direction from the small hole 33 and a port 35 communicating the relief groove section 34 and the atmosphere are provided. The effect of a fluid on a fluid pressure apparatus can be eliminated, thus a fluid bearing device can be fitted to the apparatus for use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluid bearing device and a fluid pressure cylinder using the fluid bearing device.

[Conventional technology and its problems]

2. Description of the Related Art Hydraulic cylinders have been used in various industrial machines. In conventional hydraulic cylinders, a sealing gasket such as an O-ring is essential between the piston rod and the cylinder cover.

However, this packing wears out due to sliding due to the use of the hydraulic cylinder, that is, the movement of the piston rod, and has to be replaced after a certain period of use or after a certain total distance of movement. In other words, since conventional fluid pressure cylinders have a gasket, maintenance such as inspecting and replacing the gasket is indispensable.

In addition, the presence of the seals caused sliding resistance, resulting in a stick-slip phenomenon or the so-called pop-out phenomenon in which the piston rod popped out when the fluid pressure cylinder started operating, impairing the smoothness of the fluid pressure cylinder's operation. .

On the other hand, conventionally, in order to smoothly move the shaft member in the axial direction, hydrodynamic bearings have been designed to support the shaft member by lifting it from the bearing member using compressed air or pressure oil jetted toward the shaft member. equipment is used.

However, although the conventional fluid bearing device can be used alone, there are various problems when used by attaching it to other fluid pressure equipment.

That is, when this conventional fluid bearing device is attached to the conventional fluid pressure cylinder described above, the compressed air supplied to operate the piston of the fluid pressure cylinder goes around the fluid bearing device, and as a result, the shaft member (piston rod)
The pressure in the gap between the bearing member and the bearing member increases, and the buoyant force F decreases, causing the problem that the hydrodynamic bearing cannot perform its original function and the shaft member comes into contact with the bearing member.

Therefore, in view of the above-mentioned problem, an object of the present invention is to provide a fluid bearing device that can be used by being attached to a fluid pressure device such as a fluid pressure cylinder.

The object of the invention is to provide a fluid pressure cylinder that can eliminate packing on sliding parts, has extremely low sliding resistance, and is easy to maintain.

[Means to solve the problem]

In order to solve the above-mentioned problem, the invention of claim 1 provides an annular bearing member having a large number of small holes arranged in the circumferential direction that are opened in the inner circumferential surface and through which pressurized fluid is ejected, and the bearing member. In an apparatus, a hydrodynamic bearing consisting of a cylindrical shaft member inserted so as to have a clearance on the inner circumferential surface of the member is arranged such that the shaft member is disposed on at least one side axially distant from the position of the small hole. A circumferential relief groove facing the outer circumferential surface of the groove is provided, and a communication path is provided to communicate with the relief groove and discharge the pressurized fluid flowing into the relief groove to the outside.

The invention according to claim 2 includes a cylinder tube, a piston that moves within the cylinder tube, a piston rod connected to the piston, and a cylinder cover that closes both ends of the cylinder tube and is penetrated by the shaft member. A fluid pressure cylinder according to claim 1, wherein a fluid bearing device according to claim 1 is formed between the piston rod and the cylinder cover.

[For production]

Pressure fluid is ejected from the small hole toward the inner circumferential surface of the bearing member, thereby forming a fluid film between the shaft member and the bearing member, and the shaft member and the bearing member are brought into a non-contact state.

Pressure fluid flowing from the outside toward the small hole flows into the relief groove,
The relief groove is opened to the atmosphere through the communication path, the pressure in the small hole does not increase, and the buoyancy of the fluid bearing is maintained by the device.

In the fluid pressure cylinder, the piston rod and the fluid bearing are supported by a device, and the sliding resistance of that part is almost zero, ensuring smooth operation.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional front view of a fluid pressure cylinder 1 using a fluid bearing assembly W2 according to the present invention.

In FIG. 1, a fluid pressure cylinder 1 includes a cylinder tube 11 and a piston 1 moving B inside the cylinder tube 11.
2. Piston rod 1 connected to both sides of piston 12
3. It has cylinder covers 14 and 15 which close both ends of the cylinder tube 11 and through which the piston rod 13 passes.

The cylinder cover 14 covers a cover member 21 having an inner circumferential surface 21a with an inner diameter slightly larger than the outer diameter of the piston rod 13, and a front half of the outer circumference of the cover member 21. and a cap 22 which is attached to form an air chamber 31. Therefore, the piston rod 13 is inserted into the inner peripheral surface 21a of the cover member 21 with a clearance.

The cover member 21 is provided with thin wall portions 32 and 32 by forming circumferential grooves at two locations on the outer circumferential surface.
A large number of small holes 33, 33, . Each small hole 33 has a diameter of, for example, about 0.3 mm, and eight small holes 33 are provided at equal angular positions in the circumferential direction of each thin portion 32.

Further, the cover member 21 includes a circumferential relief groove 34 facing the outer circumferential surface of the piston rod 13 , a boat 35 communicating with the relief groove 34 , and a cylinder chamber 16 on the inside of the small hole 33 in the axial direction. A boat 36 is provided for supplying compressed air to.

The cap 22 is provided with a boat 37 for supplying compressed air to the air chamber 31.

The outer diameter of the piston 12 is slightly smaller than the inner diameter of the inner circumferential surface 11a of the cylinder tube 11, and the outer circumferential surface of the piston 12 has a large number of circumferential grooves 41 for sealing with an effect equivalent to labyrinth packing. , 41... are provided.

In addition, 51-53 are packing.

In the above-described fluid pressure cylinder 1, the piston rod 1
3 and cylinder covers on both sides 14.15! : between the piston rod 13 as a shaft member and the cylinder cover 14.1.
5 as bearing members is the device 11F2.
2 is formed.

That is, the fluid pressure cylinder 1 has a structure in which both sides of the piston rod 13 are supported by fluid bearing devices 2.2, and the piston 12 does not come into contact with the cylinder tube 11.

That is, the clearance CA between the piston rod 13 and the cover member 21 at the portion where the small hole 33 is located.

Piston rod 13 axially inner than relief groove 34
The relationship between the clearance CB1 between the cover member 21 and the clearance CC between the piston 12 and the cylinder tube 11 is as follows: Clearance CA! -i clearance CB, and clearance CA< clearance CC.

Next, the fluid pressure cylinder 1 configured as described above will be explained, focusing on the operation of the device 2, especially the fluid bearing.

When compressed air is supplied to the boat 37 through appropriate piping, the compressed air flows into the air chamber 31 and is ejected from the small hole 33 toward the piston rod 13. A thin air film is formed between the inner circumferential surface 21a and the piston rod 13 by the jet of compressed air from the small hole 33. The piston rod 13 is lifted from the inner circumferential surface 21a by the air film and is in a non-contact state. Further, the piston 12 and the cylinder tube 11 are also in a non-contact state. In this state, the piston rod 13 and cylinder cover 14.15
The frictional resistance between the piston 12 and the piston 12 is extremely low, and the sliding resistance for the piston 12 to move in the axial direction is almost zero.

Therefore, when compressed air is supplied from the boat 36, the compressed air flows into the cylinder chamber 16 and drives the piston 12 to the left in the figure.

At this time, the compressed air in the cylinder chamber 16 tries to go around to the small hole 33 through the clearance CA, but before that, it flows into the relief groove 34 and passes from the relief groove 34 through the boat 35 to the atmosphere. released, small hole 33
It doesn't reach that part.

As a result, the fluid bearing maintains the buoyancy F due to the load N2, and the fluid pressure cylinder 1 operates smoothly.

Generally, in air bearings, the buoyancy F (load) of the device F2 is the buoyancy F=KX (Ps-Pa)=-(t)Ps...
Pressure Pa of the air chamber 31...pressure K of the sliding part...constants determined according to the length of the bearing, the diameter of the shaft member, etc.

That is, the buoyant force F is proportional to (Ps-Pa).

In the case of the above-mentioned fluid bearing device 2, the pressure Pa is almost equal to atmospheric pressure, but if the relief groove 34 is not provided, the compressed air from the cylinder chamber 16 will reach the clearance CA.
The buoyant force F decreases as the pressure Pa increases and (Ps-Pa) decreases.

According to the above-described embodiment, since the relief groove 34 is provided, the compressed air from the cylinder chamber 16 does not flow into the clearance CA, and therefore, the buoyancy F of the device 2 does not decrease in the hydrodynamic bearing.

In other words, the above-mentioned fluid bearing device 2 is connected to the fluid pressure cylinder 1.
It can be used by attaching it to fluid pressure equipment such as.

Further, since the above-mentioned fluid pressure cylinder 1 does not have a gasket on the sliding portion, the sliding resistance is extremely low, the operation is smooth, and maintenance is easy since there is no need to inspect or replace the gasket.

In the above-described embodiment, the cover member 21 has two thin-walled portions 32, and each thin-walled portion 32 has a small hole 33.3.
3... are provided, but the thin wall portion 32 may be provided only at one location, or at three or more locations. The size and number of the small holes 33 can be increased or decreased, and the shapes can also be varied. Since the relief groove 34 and the boat 36 are provided at the same position in the axial direction, the length of the cylinder cover 14.15 can be reduced, but even if the relief groove 34 is provided closer to the small hole 33, for example. good.

The shape, dimensions, size, number, etc. of the escape groove portion 34 may be various other than those described above. It is also possible to mount the piston 12 with a gasket with less sliding resistance. It is also possible to form the cover member 21 and the cap 22 integrally. The clearance CB may be slightly larger than the clearance CA.

In the above-described embodiment, the hydraulic cylinder 1 is a double-rod type, but it is also possible to make the cylinder cover 14 longer and make it a single-rod type hydraulic cylinder. The fluid bearing device f2 can be used in various fluid pressure devices other than the fluid pressure cylinder l.

[Effects of the Invention] According to the invention of claim 1, it is possible to provide a fluid bearing device that can be used by being attached to a fluid pressure device such as a fluid pressure cylinder.

According to the invention of claim 2, it is possible to eliminate packing on the sliding portion, and it is possible to provide a fluid pressure cylinder that has extremely low sliding resistance and is easy to maintain.

[Brief explanation of drawings]

FIG. 1 is a sectional front view of a fluid pressure cylinder using a fluid bearing device according to the present invention. 1...Fluid pressure cylinder, 2...Fluid bearing is a device, 1
1... Cylinder tube, 12... Piston, 13
...Piston rod (shaft member), 14.15...Cylinder cover (bearing member), 21a...Inner peripheral surface, 33
...Small hole, 34...Escape groove, 35...Boat (communicating passage), CA...Clearance.

Claims (2)

[Claims] (1) It is possible to have a clearance between an annular bearing member having a large number of small holes lined up in the circumferential direction that are opened on the inner circumferential surface and through which pressurized fluid is ejected, and the inner circumferential surface of the bearing member. In a hydrodynamic bearing device comprising a cylindrical shaft member inserted into the shaft member, a circumferential relief groove facing the outer circumferential surface of the shaft member is provided on at least one side axially distant from the position of the small hole. . A hydrodynamic bearing device comprising a communication path that communicates with the relief groove and discharges the pressure fluid flowing into the relief groove to the outside. (2) A fluid pressure cylinder including a cylinder tube, a piston that moves within the cylinder tube, a piston rod connected to the piston, and a cylinder cover that closes both ends of the cylinder tube and is penetrated by the shaft member. A fluid pressure cylinder using a fluid bearing device, characterized in that the fluid bearing device of claim 1 is formed between the piston rod and the cylinder cover.