JPS6326403A - Static pressure non-contact type cylinder device - Google Patents

Abstract

PURPOSE:To prevent stick-slip in low-speed operation by providing static pressure pockets and restriction parts between a piston head and the inner wall of a cylinder and between a piston rod and the rod insertion hole of a cylinder end in order to support a piston in non-contact manner. CONSTITUTION:In case of a cylinder device 1 which is fixed on the back side of a working table making reciprocating motion on the body 2 of a surface grinder, fluid passages 17 and 17' and a plurality of restriction passages 12 and 12' which extend radially from these fluid passages 17 and 17' to the outer peripheral part of a head are formed in piston heads 5 and 5' fixed to the tip end of a hollow piston rod 6 into which static pressure oil supply pipes 7 and 7' are inserted. Also, a plurality of static pressure pockets 11 and 11' where restriction passages 12 and 12' open are formed on the outer peripheral part of the head. Furthermore, a plurality of static pressure pockets 14 are formed approximately in the middle of the inner peripheral part of an end bush 8 fixed to each end of a cylinder 3, and a restriction passage 15 connecting each static pressure pocket 14 to a cylinder house 16 are formed.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a cylinder device used in a hydraulic drive device for low-speed table feeding such as a surface grinder, in which a piston and a cylinder are connected by a 49'/C static pressure fluid film. The present invention relates to a static pressure non-contact type cylinder device that is operated in a non-contact state.

(Prior art) A cylinder device for feeding a table in a machine tool usually has a cylinder fixed to the back side of the table, a piston rod fixed on a bed, and hydraulic oil introduced into the cylinder to move the cylinder back and forth with the table against the piston. It is configured like this. In this type of conventional hydraulic cylinder device, in order to seal the hydraulic oil in the cylinder chamber, there are gaps between the outer peripheral surface of the piston head and the inner wall of the cylinder, and between the piston rod and the piston rod insertion hole at the end of the cylinder. 0
1J ring, packing and other sealing devices are provided.

In this case, the piston head and the cylinder inner wall are in close contact with each other and slide relative to each other.

(Problems to be Solved by the Invention) In the above-mentioned conventional cylinder device, the cylinder and the piston come into sliding contact directly or through a seal Rf such as a packing, so the feeding operation may not be smooth. In the case of low-speed feed, a jammed feed phenomenon called stick-slip occurs. In the case of high-speed feeding, heat generation occurs due to sliding frictional resistance between the sliding part and the sealing device, which deteriorates the sealing device and impairs accuracy due to thermal displacement of the main body. There were drawbacks such as the need for repairs due to wear of the sliding parts. There are also sealless cylinders that do not require a seal f, but in this case, in order to prevent the piston and cylinder from colliding due to positive surge when the feed direction is reversed at high speed, cylinders that perform high-speed reversal operations (VC)
It also had drawbacks such as being unsuitable for long strokes.

(Means for Solving the Problems) The static pressure non-contact cylinder device according to the present invention has extremely small gaps and constrictions between the piston head and the cylinder inner wall and between the piston rod and the piston rod insertion hole at the end of the cylinder. A static pressure pocket is formed with a static pressure pocket, a static pressure oil supply pipe is provided in the piston head and communicates with the static pressure pocket, and the static pressure oil introduced into the static pressure pocket is supplied to cylinder device hydraulic oil. The pressure is increased to a pressure higher than 1 to cause the oil to flow out of the gap, thereby forming a hydrostatic oil film in the gap.

(Example 5) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a partial vertical sectional view of a static pressure non-contact type cylinder device according to an embodiment of the present invention, and FIG.
FIG. 3 is a cross-sectional view taken along line I--■ in FIG. 1 as well. Moreover, FIG. 4 is an overall side view when the cylinder device according to the present invention is used in a table feed drive section of a surface grinder. Referring to FIG. 4, a processing table 1 that reciprocates on a main body (bed) 2 of a surface grinder.
Cylinder 3 according to the invention via bracket 4 on the back side of
is fixed at three locations: one at both ends and the center. A pair of piston rods 6.6 with piston heads at their tips
' are inserted from both ends of the cylinder, and the rear end of each piston rod 6.6' is fixed to a foot member 9.9' having a hydraulic oil supply passage 9a (FIG. 1). Foot members 9, 9
' is fixed to the bed 2YC and connected to a hydraulic oil supply source (not shown). As described later, the piston rod 6.6
' is formed hollow, and a static pressure oil supply pipe 7 is installed in this hollow part.
．． 7' is inserted. In Fig. 4, when hydraulic oil is introduced into the cylinder chamber from the foot member 9 on one side (inlet side) through the hollow piston rod 6, it is introduced into the cylinder chamber from the foot member 9 on the other side (on the B side).
Back-pressure hydraulic oil is discharged from the foot member 9', and the cylinder 3, and therefore the table 1, are sent in the direction of the arrow in the figure. If the flow directions of the hydraulic oil and the back pressure oil are reversed, the direction of movement of the cylinder 3 will be reversed.

The internal structure of the cylinder will be described in detail with reference to FIGS. 1, 2, and 3. The piston head 5 fixed to the tip of the hollow piston rod 6 is formed with a fluid passage 17 and a plurality of Vi4X throttle passages 12 in the illustrated embodiment extending radially from the passage 17 to the outer circumference of the head. Furthermore, four static pressure pockets 11 are formed in the circumferential direction on the outer periphery of the head, into which the throttle passages 12 are opened. The outer peripheral portion of the piston head other than the static pressure pocket 11 has a slight gap (piston head gap) 18 with respect to the inner wall of the cylinder.

-y-t One member 9yc is held and the static pressure oil supply vibe 7 extending into the hollow part of the piston rod 6 is connected to the piston head 5.
is connected to the fluid passage 17 of. A plurality of communication holes 10 are provided in the circumferential direction on the outer periphery near the tip of the piston rod 6, which communicate with the hollow portion of the rod and the cylinder chamber 16.

Each end '/c of the cylinder 3 has a cylinder end bushing 8
is fixed, and the bush defines a piston rod insertion hole. The inner circumference of the cylinder end bushing 8 has a slight gap (bushing gap) 2 with respect to the piston rod 6.
1, and a plurality of static pressure pockets 14 (in the illustrated embodiment, four in the circumferential direction as shown in FIG. 3) are formed approximately in the middle of the inner periphery.

Furthermore, the bushing 8YC has a throttle passage 15 extending in the radial direction that communicates each static pressure pocket 14 with the cylinder chamber 16.
is formed. A discharge port 13 for the hydrostatic oil discharged from the static pressure pocket 11 of the piston head 5 through the piston head gap 18 is provided at the axial center of the cylinder 3 .

Although the structure of one side of the cylinder 3 from the center has been described above, the same applies to the other side.

With this configuration, pressure oil is supplied from the hydraulic oil supply path 9a of one foot member 9 to the hollow part of the piston rod 6, and further from the communication hole 10 into the 10,000 cylinder chambers 16 as shown by arrow A. The back pressure oil in the other cylinder chamber 16' is sent out from the communication hole 10' of the other piston rod 6' through the hollow part of the piston rod as shown by arrow B, and from the other 7-piece member (not shown in FIG. 1). When discharged, cylinder 3 ij ? nl One foot member 9
Move to the side. At this time, static pressure oil having a pressure higher than the hydraulic pressure of the hydraulic oil is simultaneously supplied from the static pressure oil supply pipes 7° 7' on both sides as shown by arrow C. Static pressure oil is piston head 5°5'
The static pressure pockets 11.11'lC are press-fitted with load capacity in the throttle passages 12 and 12', and the rigidity of the oil film is provided in the extremely small gaps 18 and 18' on the outer periphery of the piston head, and furthermore, the cylinder chambers 16 and 16' on both sides are flows into.

At the cylinder end, the hydraulic oil and the static pressure oil flowing from the gap in the piston head flow into the throttle passage 15f of the cylinder end bushing 8! : Passed through and press-fitted into the static pressure pocket 14 on the bushing side, providing oil film rigidity in the extremely small gap 21 between the piston rod 6 and the bushing 8. The same applies to the bushing on the back pressure oil side of the cylinder. The static pressure oil, hydraulic oil (pressure oil), and back pressure oil in the cylinder eventually leak out from the gap in the cylinder end bushing, but if the gap is uneven in any radial direction, the side with the larger gap The pocket pressure decreases and the pocket pressure on the side with the smaller clearance increases, which exerts a self-correcting action to bring the piston head and piston rod into a concentric position with the cylinder and cylinder end bushings, causing the piston head and rod to become concentric. Non-contact support is provided without metal contact with the cylinder and bushing. Incidentally, the oil flowing out from the discharge port 13 and both ends of the cylinder is collected by an oil receiver on the lower side of the cylinder.

In the above-described embodiment, the piston is fixed and the cylinder side is moved, but this can be reversed and the cylinder is fixed with a pedestal and the piston is connected to the moving table.

(Effects of the Invention) As explained above, according to the present invention, a static pressure pocket and a constriction portion are provided between the piston head and the inner wall of the cylinder, and between the piston rod and the rod insertion hole at the end of the cylinder, so that the piston can be moved without contact. Because it is supported, stick-slip phenomenon does not occur even in low-speed operation, expanding the possible low-speed range, and even in high-speed operation, there is no problem of heat generation or wear due to frictional contact, which is advantageous in terms of maintenance, and maintains high accuracy. There are effects such as being able to do it.

[Brief explanation of the drawing]

FIG. 1 is a partial longitudinal cross-sectional view of a static pressure non-contact type cylinder device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the [[-11 line] of FIG. 1, and FIG. FIG. 1 is a cross-sectional view taken along line I-1'F--, and FIG. 4 is an overall side view of an embodiment in which the present invention is applied to a table drive mechanism of a surface grinder. 3... Cylinder % 5,5'...-Piston head, 6.6'... Piston rod, 7.7'... Hydrostatic oil supply pipe, 8... Cylinder end bushing, 9. 9'... 7 parts, 10, 10'... Communication hole, 11, 11'... Piston head side static pressure pocket, 12.12', 15... Restriction passage, 13... drain hole. 14... Cylinder end side static pressure pocket. 16, l6'... cylinder chamber, 18, 18'
, 21...Gap. Sub-Agent Patent Attorney Rikichi Somekawa Diagram 2

Claims (1)

[Claims] A static pressure pocket having an extremely small gap and a constriction is formed between the piston head and the inner wall of the cylinder and between the piston rod and the piston rod insertion hole at the end of the cylinder, and communicates with the static pressure pocket in the piston rod. Further, the static pressure oil introduced into the static pressure pocket is made higher than the pressure of the hydraulic oil of the cylinder device and flows out from the gap, thereby forming a hydrostatic oil film in the gap. A static pressure non-contact type cylinder device characterized by forming.