JPH0518404A - Fluid pressure cylinder - Google Patents

Abstract

PURPOSE:To decrease the sliding resistance and enhance the sealing performance by furnishing a cylinder tube in its inside with a piston having a labyrinth seal at the periphery, forming a supply and an exhaust pipe at a piston rod fixed to the piston, providing a magnetic fluid seal between cylinder and piston rod. and changing over from one seal to the other according to the piston being in motion or at a standstill. CONSTITUTION:A piston 2 is fixed to a piston rod 3 and slided within a cylinder tube 1. A labyrinth seal 7 is furnished at the periphery of this piston 2, and the piston rod 3 is provided with a supply and an exhaust pipe 6a, 6b which open to chambers 5a, 5b partitioned by the piston 2. The sliding part of the rod 3 and a cover 4 at the ends of the cylinder tube 1 is supported by a magnetic fluid seal 13 consisting of a magnetic fluid 8 attracted by magnet rings 8a, 8b. When the piston 2 is in motion, sealing is generated by the magnetic fluid 8 by feeding current to the magnetic fluid seal 13, while the sealing is borne by the labyrinth seal 7 when the piston 2 is at a standstill, and this changing-over will enhance the sliding property and sealing performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can impart a desired reciprocating motion to a piston rod connected to a piston by supplying and discharging a pressurized working medium into and from a space defined by a cylinder tube and a piston. The present invention relates to a fluid pressure cylinder.

[0002]

2. Description of the Related Art A fluid pressure cylinder is an actuator that converts the energy applied to a working fluid into a linear mechanical motion, and easily changes the output and speed by controlling the pressure and flow rate of the working fluid. Therefore, it is applied to various devices. In such a known fluid pressure cylinder, a piston 22 is usually slidably arranged in a cylinder tube 21 having a cylindrical inner surface as shown in FIG.
3 is fixed to the end of the cylinder tube 21, and covers 24a and 24b are integrally fixed to the end of the cylinder tube 21 as sealing members for sealing the opening. The covers 24a and 24b have chambers 25a and 2 defined by the cylinder tube 21 and the piston 22, respectively.
Supply / discharge pipes 26a, 26b for supplying, for example, pressurized air as a working medium to 5b are provided respectively. Here, in order to move the piston rod 23 in the direction indicated by the arrow A in the drawing, the working medium is introduced into the related chamber 25a via the supply / discharge pipe 26a, while the working medium is introduced from the related chamber 25b via the supply / discharge pipe 26b. The working medium may be discharged. On the other hand, when it is desired to move the piston rod 23 in the direction opposite to the arrow A, the working medium is guided to the related chamber 25b via the supply / discharge pipe 26b, while the working medium is discharged via the other supply / discharge pipe 26a. It may be discharged from the chamber 25a.

[0003]

Generally, in the fluid pressure cylinder having the above-mentioned conventional structure, the piston 22 disposed in the cylinder tube 21 slides on the inner surface of the tube and is separated by the piston 22. In order to shut off the mutual communication of the working medium in the chamber 25,
Further, the covers 24a and 24b as sealing members for sealing the openings of the cylinder tubes 21 block the leakage of the working medium at the sliding portions with the piston rods 23.
A piston ring, an O-ring or the like as a seal member was buried in a groove formed in the outer and inner circumferences thereof. However, in a fluid pressure cylinder having an O-ring on the outer and inner circumferences of the piston, When the piston moves, the O-ring rubs the inner surface of the cylinder tube and the outer circumference of the piston rod, so that the sliding resistance becomes large, and when the pressure of the working medium is low, the piston and the piston rod cannot be correctly moved to the desired positions. There was a problem. This problem is particularly noticeable when it is desired to hold the piston in the intermediate position. Therefore, as shown in FIG. 4, there is known a cylinder in which the sliding resistance is reduced by providing labyrinth seal portions 27 and 28a and 28b having an uneven shape on the outer peripheral portion of the piston 22 and the inner peripheral portions of the covers 24a and 24b. However, in the case of individual pieces, there is a problem that the working medium continues to leak from the labyrinth seal portions 28a and 28b even when the piston is stopped.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and FIG.
2 and 3, the fluid pressure cylinder according to the present invention includes a cylinder tube 1 and a piston 2 slidably disposed in the cylinder tube 1 and having a labyrinth seal portion 7 having an uneven shape on an outer peripheral portion. , Supply / discharge pipes 6a, 6b fixed to the piston 2 and supplying pressurized fluid to the chambers 5a, 5b
, A stator 9a, 9b, 9c, 9d, coil 11a, 11b, magnet ring 10 and magnetic fluid, which are provided at both ends of the cylinder tube 1 and support the piston rod 3 on at least one side. In a fluid pressure cylinder comprising magnetic fluid seals B and B having covers 4 and 4, the magnetic fluid seal B is labyrinth sealed by switching the energization of the coils 11a and 11b during movement and stop. , It is designed to switch to the magnetic fluid seal.

[0005]

According to the fluid pressure cylinder of the present invention, when the pressurized fluid is supplied to the associated magnetic fluid seal portions B, B via the respective supply pipes 6a, 6b, the piston is caused by the pressure difference between the chambers 5a, 5b. 2 and the inner surface of the cylinder tube 1, and the sliding resistance between the piston rod 3 and the magnetic fluid seal parts B, B associated therewith become extremely small, which facilitates starting, and residual stress acts even when stopped. It is possible to accurately perform fine positioning without having to do so. Further, when stopped, the working medium in the cylinder tube 1 can be sealed.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the fluid pressure cylinder according to the present invention with a part thereof omitted. 1 is a cylinder tube, 2 is a piston, 3 is a piston rod, and 4 is a cover. The piston 2 is fixed to a piston rod 3 which extends through a through hole provided therethrough,
A labyrinth seal portion 7 having an uneven shape is formed on the outer circumference of the piston 2. The cylinder tube 1 includes stators 9a, 9b, 9 for supporting the piston rod 3 in the inner holes.
c, 9d, coils 11a, 11b, and magnet ring 1
It is fixed with airtightness by covers 4 and 4 having magnetic fluid seals B and B composed of 0 and magnetic fluid 8. A piston 2 is slidably arranged in the cylinder tube 1, and a piston rod 3 is also slidably arranged in the covers 4a and 4b. The sliding portion between the piston 2 and the cylinder tube 1 is It is supported and sealed by the labyrinth seal portion 7. The sliding portion between the piston rod 3 and the covers 4 and 4 is supported and sealed by the magnetic fluid seal portion B made of the magnetic fluid 8 attracted by the magnetic force of the magnet rings 8a and 8b. 2 and 3 are partially enlarged views for explaining the magnetic circuit of the magnetic fluid seal portion B of the fluid pressure cylinder according to the present invention. First, when the pistons are stopped and the coils 11a and 11b are energized as shown in FIG. 2, the stators 9a and 9c have N poles and the stators 9b and 9d have S poles.
Although the magnetic circuit is formed so as to have a pole, in the magnet link 10, the stator 9b has an N pole and the stator 9c has an S pole.
Since it is magnetized so that it becomes a pole, the stators 9b, 9
In c, the magnets cancel each other out, so that a magnetic circuit indicated by an arrow O is formed by the stators 9a and 9d, the magnetic fluid 8, the piston rod 3 and the cover 4, and a magnetic fluid seal is formed. On the other hand, when the piston moves, as shown in FIG.
When the a and 11b are de-energized, the magnet ring 10 makes the stator 9b an N pole and the stator 9c an S pole, and a magnetic circuit shown by an arrow P is formed by the stators 9b and 9c, the magnetic fluid 8 and the cover 4 to form a labyrinth seal. Is formed. The piston rod 3 includes a cylinder tube 1, covers 4 and 4, and a chamber 5 defined by the piston 2.
Supply and discharge pipes 6a and 6b for supplying, for example, pressurized air as a working medium to a and 5b are respectively provided. Here, in order to move the piston rod 3 in the direction indicated by the arrow A in the figure, the coils 11a and 11b are de-energized, the magnetic fluid seal portion B is brought into a labyrinth seal state, and the working medium is associated via the supply / discharge pipe 6a. While being introduced into the chamber 5a, the working medium may be discharged from the related chamber 5b via the supply / discharge pipe 6b. Further, when stopped, the coils 11a and 11b are energized to make the magnetic fluid seal portion B in a sealed state, so that the leakage flow rate can be eliminated.

[0007]

As described in detail above, according to the present invention, the magnetic fluid seal portion is changed to the labyrinth seal or the magnetic fluid seal by switching the energization to the coil when the piston rod that performs the sliding motion is moved or stopped. Since it is configured to switch and support and seal, the sliding resistance resulting from them is extremely smaller than that of conventional cylinders.
Since the sealing property is also improved, the starting characteristics are excellent, the positioning can be performed with high accuracy, and the durability can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a fluid pressure cylinder according to the present invention.

FIG. 2 is a partially enlarged view illustrating a magnetic circuit of a fluid pressure cylinder according to the present invention.

FIG. 3 is a partially enlarged view illustrating a magnetic circuit of the fluid pressure cylinder according to the present invention.

FIG. 4 is a sectional view showing a conventional fluid pressure cylinder.

[Explanation of symbols]

 1 Cylinder Tube 2 Piston 3 Piston Rod 4 Cover 5a, 5b Chamber 6a, 6b Supply / Discharge Pipe 7 Labyrinth Seal Part 8 Magnetic Fluid 9a, 9b, 9c, 9d Stator 10 Magnet Ring 11a, 11b Coil B Magnetic Fluid Seal Part

Claims (1)

Claim: What is claimed is: 1. A piston (2) having a cylinder tube (1) and a labyrinth seal portion (7) which is slidably disposed in the cylinder tube (1) and has an irregular shape on an outer peripheral portion. ) And the chambers (5a), (5
b) a piston rod (3) having supply / discharge pipes (6a), (6b) for supplying a pressurized fluid, and a piston rod (3) provided at each end of the cylinder tube (1) at least on one side. 3) supporting the stator (9a),
(9b), (9c), (9d) and coil (11a),
A fluid pressure cylinder comprising: (11b), a magnetic ring (10), and a cover (4), (4) having a magnetic fluid seal portion (B), (B) composed of a magnetic fluid (8), Coil (11a), (1
A fluid pressure cylinder characterized in that the magnetic fluid seal portion (B) is switched between a labyrinth seal and a magnetic fluid seal by switching the energization to 1b).