JP2010043662A - Fluid pressure cylinder device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to supply a lubricating oil for sliding between two packings provided on a piston for sealing and the piston and a cylinder tube by a simple structure. <P>SOLUTION: On the piston 12, two packings 31, 32 for sealing between the piston and the cylinder tube 11 are provided away from each other and an O-ring 33 is provided between the packings 31, 32. On the cylinder tube 11, diameter enlarged parts, whose inside diameter is expanded and on which the packings 31, 32 can move smoothly at least at one stroke end, are provided. The positions and dimensions of diameter enlarged parts 41, 42 are selected in such a way that, when the piston 12 moves to the stroke end, sealing performance between either one of the packings 31, 32 and the cylinder tube 11 is dissipated but sealing performance between the O-ring 33 and the cylinder tube 11 is not dissipated owing to the diameter enlarged parts 41, 42. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydraulic cylinder device having a piston that slides on the inner peripheral surface of a cylinder tube whose ends are closed by a cover.

  2. Description of the Related Art Conventionally, fluid pressure cylinder devices such as hydraulic cylinders, hydraulic cylinders, and pneumatic cylinders are used in automation machines, machine tools, construction machines, and other industrial machines.

  Particularly in a hydraulic cylinder, in order to obtain a sealing property between the piston and the cylinder tube, the piston is often provided with two U packings. By providing the two U-packings outwardly, reliable sealing is performed even against high pressure.

  However, in such a hydraulic cylinder, since the sealing performance by the U packing is extremely high, the hydraulic oil hardly enters between the two U packings. Therefore, the two U-packings and the cylinder tube are likely to be in a non-lubricated state, and a stable lubricating oil film is not formed. For this reason, the U packing is heavily worn.

  Similarly, the sliding surface between the piston and the cylinder tube is likely to be insufficiently lubricated, which may damage the sliding surfaces of the piston and the cylinder tube.

  A similar problem may occur when a packing other than the U packing is used.

  Conventionally, in order to solve such a problem, a mechanism has been proposed in which an oil supply hole is provided in a cylinder tube to lubricate between the piston and the cylinder tube (Patent Documents 1 and 2).

It has also been proposed to provide a lubricant holding packing for scraping the lubricant adhering to the inner peripheral surface of the cylinder tube toward the seal packing (Patent Document 3).
ACT 56-85703 2-90459 6-6709

  However, in the devices of Patent Documents 1 and 2, it is necessary to provide an oil supply device or the like on the outer peripheral surface of the cylinder tube, which increases the size of the fluid pressure cylinder device and requires troublesome maintenance.

  Further, the device of Patent Document 3 is effective when supplying a lubricant to a long piston, such as when a magnet is provided on the piston, but it is not enough to provide lubrication to the U packing itself. It is not valid.

  Further, there is a method of reducing the scraping action of the lubricating oil film by the U packing by rounding the lip of the U packing, but in this case, there is a problem that oil leakage increases.

  In addition, when grease is filled between the piston and the cylinder tube, it is effective for a certain period of time, but the effect decreases with the passage of time and is eventually lost.

  The present invention has been made in view of the above-described problems, and can provide two packings for sealing provided on the piston and lubricating oil for sliding between the piston and the cylinder tube with a simple structure. The purpose is to do so.

  A fluid pressure cylinder device according to an embodiment of the present invention is a fluid pressure cylinder device having a piston that slides on an inner peripheral surface of a cylinder tube closed at both ends by a cover, and the piston includes the cylinder tube and A first packing and a second packing are provided at a distance from each other, and a third packing is provided between the first packing and the second packing. The cylinder tube is provided with a large-diameter portion whose inner diameter is expanded and the packing can be smoothly moved at at least one stroke end, and when the piston moves to the stroke end, The large diameter portion eliminates the sealing performance between either the first packing or the second packing and the cylinder tube. And, as is not lost sealability between the said cylinder tube and said third packing, the position and dimensions of the large-diameter portion is selected.

  For example, each of the first packing and the second packing is a U-packing that is mounted so that the sealing performance is exhibited in the direction from the outside toward the inside.

  The third packing is an O-ring.

  Preferably, the large-diameter portion includes a cylindrical surface that forms a gap between the first packing and the second packing, and a tapered surface that smoothly connects the cylindrical surface and the other portion of the cylinder tube. And having.

  According to the present invention, the two packings for sealing provided on the piston and the lubricating oil for sliding between the piston and the cylinder tube can be supplied by a simple structure.

  FIG. 1 is a front sectional view of a fluid pressure cylinder device 1 according to an embodiment of the present invention, and FIG. 2 is an enlarged view showing a main part of the fluid pressure cylinder device 1 of FIG.

  As shown in FIG. 1, the fluid pressure cylinder device 1 itself is a known double-acting type. In the present embodiment, the fluid pressure cylinder device 1 is characterized by a structure for sealing the piston and a structure for supplying oil to the seal, which will be described in detail.

  The fluid pressure cylinder device 1 includes a cylindrical cylinder tube 11, a piston 12 that slides on the inner peripheral surface of the cylinder tube 11, a piston rod 13 coupled to the piston 12, a head cover 14, a rod cover 15, and a bush 16. Become.

  The head cover 14 and the rod cover 15 are provided with ports PT1 and PT2 for supplying pressure oil to the internal cylinder chambers CA and CB. The cylinder tube 11, the head cover 14, and the rod cover 15 are fastened and integrated by four tie rods 17, 17 ... and nuts 18, 18 ....

  The piston 12 is fixed to the piston rod 13 by a screw 21 and then fixed by a set screw 22. The piston rod 13 protrudes to the right of the piston 12 in FIG. 1, and a head-side cushion boss 23 is formed there. Also, a rod-side cushion boss 24 is sandwiched and fixed between the ring 25 and the left side of the piston 12 in FIG. Sealing is performed between the piston 12 and the piston rod 13 by packings 26 and 27.

  Referring also to FIG. 2, the piston 12 is provided with two packings 31, 32 spaced apart from each other for sealing between the cylinder tube 11 and between the two packings 31, 32. Is provided with an O-ring 33. In the piston 12, packing grooves 36, 37, and 38 are provided for mounting the packings 31 and 32 and the O-ring 33. The two packing grooves 36 and 37 are provided at axial positions that are inward from the respective end surfaces of the piston 12 by the same distance, and the packing groove 38 is provided at the axial center of the piston 12.

  Each of the packings 31 and 32 is a U-packing that is mounted so that the sealing performance is exhibited in the direction from the outside toward the inside.

  The piston 12 is provided with circumferential grooves 34 and 35 between the two packings 31 and 32 for holding lubricating oil on the outer circumferential surface thereof. As can be seen in FIG. 2, the circumferential grooves 34 and 35 are grooves having a V-shaped cross section.

  The cylinder tube 11 is provided with large-diameter portions 41 and 42 at both stroke ends so that the inner diameter is expanded and the packings 31 and 32 can move smoothly. When the piston 12 moves to the stroke end, the sealing performance between one of the two packings 31 and 32 and the cylinder tube 11 is eliminated by the large diameter portions 41 and 42, and the O-ring 33 and the cylinder tube are removed. The positions and dimensions of the large-diameter portions 41 and 42 are selected so that the sealing performance between the large diameter portions 11 and 11 is not lost.

  The large-diameter portions 41 and 42 include cylindrical surfaces 41a and 42a that form a gap between the two packings 31 and 32, and other portions of the cylindrical surfaces 41a and 42a and the cylinder tube 11, that is, normal cylinders. Tapered surfaces 41b and 42b that smoothly connect the inner peripheral surface 11a.

  Such large diameter portions 41 and 42 are formed, for example, by cutting both ends of the inner peripheral surface of the cylinder tube 11 with a lathe or the like. Normally, the outer lip portions of the packings 31 and 32 are in contact with the inner peripheral surface of the cylinder tube 11 (ordinary cylinder inner peripheral surface 11a) with a predetermined strength, thereby ensuring the sealing performance. However, in the large diameter portions 41 and 42, a gap is formed between the outer lip portions of the packings 31 and 32, thereby eliminating the sealing performance. However, the gaps should be as small as possible in order to prevent the packings 31 and 32 from being lifted as much as possible and prevent the packings 31 and 32 from falling off the packing grooves 36 and 37.

  In that case, considering the tension of the lip portions of the packings 31 and 32 (the dimension of the difference between the sealed state and the free state), for example, the diameter of the cylindrical surfaces 41a and 42a is changed to a normal cylinder inner peripheral surface 11a. On the other hand, it may be about 0.5 mm to 2 mm, more specifically about 1.3 mm to 1.5 mm. Further, the sealing performance may be eliminated when the piston 12 reaches, for example, about 5 mm to 10 mm before the stroke end.

  Further, the axial lengths of the large-diameter portions 41 and 42 are selected so that the large-diameter portions 41 and 42 do not reach the O-ring 33 when the piston 12 moves to the stroke end. That is, regardless of the stroke position of the piston 12, the O-ring 33 does not enter the large-diameter portions 41 and 42 and contacts the normal cylinder inner peripheral surface 11 a to maintain the sealing performance.

  As described above, the tapered surfaces 41b and 42b are portions that smoothly connect the cylindrical surfaces 41a and 42a and the normal cylinder inner peripheral surface 11a, and may be linear conical surfaces, Further, it may be a curved surface. The dimension of the taper surfaces 41b and 42b in the axial direction may be set to, for example, 2 mm to 5 mm, more specifically about 3 mm, for example.

  Note that the end surface of the cylinder tube 11 is formed with a stepped portion so as to fit into the end surface grooves 43 provided in the head cover 14 and the rod cover 15, respectively, and the tip thereof is pressed against the packing 44 attached to the end surface groove 43. The seal is done.

  Next, the operation of the fluid pressure cylinder device 1 configured as described above will be described.

  In the state shown in FIGS. 1 and 2, the pressure oil is supplied from the port PT2 to fill the cylinder chamber CB with the pressure oil, and the piston 12 has moved to the stroke end on the right side of the drawing.

  In this state, the packing 32 is in the large diameter portion 41 formed at the right end of the cylinder tube 11, whereby the sealing performance of the packing 32 is lost, and the pressure oil in the cylinder chamber CA passes through the packing 32. Thus, the O-ring 33 is reached and sealing is performed by the O-ring 33. Therefore, the pressure oil enters the circumferential groove 35 and is stored therein.

  In this state, since the pressure oil around the packing 32 is the same pressure, the packing 32 is not lifted or dropped.

  From this state, when a solenoid valve (not shown) is switched and pressure oil is supplied from the port PT1, the pressure oil flows into the cylinder chamber CA and pushes the piston 12 toward the left side in the drawing. At this time, the pressure oil is not sealed by the packing 32, but is sealed by the O-ring 33, and the pressure oil does not blow through.

  As a result, when the piston 12 moves to the left in the drawing and reaches the left stroke end, the packing 31 enters the large diameter portion 42 formed at the left end of the cylinder tube 11, thereby The sealing performance of the packing 31 is lost, and the pressure oil in the cylinder chamber CB passes through the packing 31 and reaches the O-ring 33, and sealing is performed by the O-ring 33. Therefore, the pressure oil enters the circumferential groove 34 and is stored therein.

  In this state, when pressure oil is supplied again from the port PT2, the pressure oil flows into the cylinder chamber CB and pushes the piston 12 toward the right side of the drawing. At this time, the pressure oil is not sealed by the packing 31, but is sealed by the O-ring 33, and the pressure oil does not blow through. As a result, the piston 12 moves to the right in the figure.

  Thus, the fluid pressure cylinder device 1 performs a normal reciprocating operation by supplying pressure oil from the ports PT1 and PT2. Then, the sealing performance of the packings 31 and 32 is lost due to the presence of the large diameter portions 41 and 42 at the left and right stroke ends, and the pressure oil reaches the position of the O-ring 33. Accordingly, sufficient lubricating oil is supplied to the outer circumferential surfaces of the packings 31 and 32, the O-ring 33, and the piston 12.

  Therefore, a stable lubricating oil film is formed between the two packings 31 and 32 and the O-ring 33 and the cylinder tube 11 and on other boundary surfaces, and wear of the packings 31 and 32 and the O-ring 33 is minimized. It is done.

  Further, since the sealing performance is maintained by the O-ring 33 regardless of the stroke position of the piston 12, no blow-through occurs even when the fluid pressure cylinder device 1 is used by meter-out. Although oil pressure acts on the O-ring 33, there is no problem in sealing performance because it is only a short distance at the stroke end.

  In addition, when the large diameter portions 41 and 42 are entered, the pressure oil pressure around the packings 31 and 32 is the same, so that the packings 31 and 32 do not protrude or deform.

  Moreover, the pressure accumulation between the packings 31 and 32, which has been easy to occur in the conventional art, is reduced by entering the large diameter portions 41 and 42, and the adverse effect due to this is eliminated.

  In addition, these functions can be realized by a simple structure in which the large-diameter portions 41 and 42 are provided at the end of the cylinder tube 11 and the O-ring 33 is added to the piston 12.

  Since the lifetime of the packings 31 and 32 is extended, maintenance becomes easy. It can be applied as a fluid pressure cylinder device 1 with less stick-slip.

  In the above embodiment, the sealing method between the end of the cylinder tube 11 and the head cover 14 and the rod cover 15 can be various methods or structures other than those described above.

  For example, as shown in FIG. 3, sealing may be performed with a packing 45 between the inner peripheral surface of the end portion of the cylinder tube 11. In this case, for example, a large-diameter portion 41B that does not reach the end surface may be provided at a position close to the end of the cylinder tube 11.

  In the above embodiment, U packings are used as the packings 31 and 32. However, various packings such as Y packings can be used. Further, instead of the O-ring 33, it is possible to use X packing and other various packings.

  In the above embodiment, the large-diameter portions 41 and 42 are provided at both stroke ends, but the large-diameter portion may be provided only in one of them.

  In the embodiment described above, the cylinder tube 11, piston 12, packing 31, 32, O-ring 33, large-diameter portion 41, 42, or the whole or each part of the fluid pressure cylinder device 1, the structure, shape, dimensions, number, The material and the like can be appropriately changed in accordance with the spirit of the present invention.

It is front sectional drawing of the fluid pressure cylinder apparatus of one Embodiment of this invention. It is a figure which expands and shows the principal part of the fluid pressure cylinder apparatus of FIG. It is a figure which shows the other shape of a large diameter part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid pressure cylinder apparatus 11 Cylinder tube 12 Piston 14 Head cover 15 Rod cover 31, 32 Packing (1st packing, 2nd packing)
33 O-ring (third packing)
34, 35 Circumferential grooves 41, 42 Large diameter portions 41a, 42a Cylindrical surfaces 41b, 42b Tapered surfaces

Claims (5)

A hydraulic cylinder device having a piston that slides on the inner peripheral surface of a cylinder tube closed at both ends with a cover,
The piston is provided with a first packing and a second packing, which are spaced apart from each other, for sealing between the cylinder tube, and an intermediate between the first packing and the second packing. Is provided with a third packing,
The cylinder tube is provided with a large-diameter portion whose inner diameter is expanded and the packing can move smoothly at at least one stroke end thereof,
When the piston moves to the stroke end, the large-diameter portion eliminates the sealing performance between either the first packing or the second packing and the cylinder tube, and the third The position and dimensions of the large diameter portion are selected so that the sealing performance between the packing and the cylinder tube is not lost.
A fluid pressure cylinder device. Each of the first packing and the second packing is a U-packing that is mounted so that the sealing performance is exhibited in the direction from the outer side to the inner side.
The fluid pressure cylinder device according to claim 1. The third packing is an O-ring.
The fluid pressure cylinder device according to claim 2. The large diameter portion is
A cylindrical surface forming a gap with the first packing or the second packing;
A tapered surface that smoothly connects the cylindrical surface and the other part of the cylinder tube;
The fluid pressure cylinder device according to claim 2 or 3. The piston is provided with a circumferential groove between the first packing and the second packing for holding lubricating oil on the outer circumferential surface thereof.
The fluid pressure cylinder device according to any one of claims 2 to 4.

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