JPH01283403A - Cylinder positioning device utilizing servo valve - Google Patents

Abstract

PURPOSE:To make it possible to uniformly maintain a piston for a long time by providing a pressure detecting means in supply/discharge pipes to drive a servo valve by a signal from the pressure detecting means and keeping the pressure of pressurized fluid in a cylinder at predetermined value. CONSTITUTION:A servo valve 10 for controlling pressure and a detecting means 32 for detecting the pressure are provided in supply/discharge pipes 9a, 9b and the servo valve 10 is controlled by a signal from the pressure detecting means 32. Accordingly, even if operating fluid leaks via a sealing portion to change pressure in a cylinder tube 1, the change is compensated so that a piston 2 can be uniformly kept for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cylinder positioning device that can maintain a constant cylinder output.

(Prior Art) A fluid pressure cylinder is one of the devices that converts the energy of pressurized fluid into mechanical motion.

As shown in FIG. 4, such a fluid pressure cylinder usually has a piston 2 slidably disposed inside a cylinder tube 1 having a cylindrical inner surface, and a piston rod 3 fixed to the piston. , and a cover 4a as a sealing member for sealing the openings at each end of the cylinder tube.
, 4b are each integrally fixed.

Then, compressed air, for example, as a working medium is supplied to each chamber 5 defined by the cylinder tube 1 and the piston 2 through supply and discharge holes 6a and 6b formed in each cover 4a and 4b. By discharging from the
The piston 2 and, by extension, the piston rod 3 fixed thereto were moved in the axial direction.

By the way, in the above-mentioned fluid pressure cylinder, the piston 2 disposed in the cylinder tube I slides on its inner surface, and also allows the working medium in the chamber 5 separated by the piston 2 to communicate with each other. A piston ring as a sealing member 7 is inserted into a groove formed in the circumferential direction on the outer surface of the
- It was customary to embed a ring or the like, or to fix a bowl-shaped packing 8 to the piston ring main body 2a with a bolt via a retainer ring, as shown in FIG.

(Problem to be Solved by the Invention) For this reason, in conventional fluid pressure cylinders, the O-ring provided on the outer periphery of the piston comes into contact with the inner surface of the cylinder tube, resulting in large frictional resistance. When the pressure is relatively low, there is a problem in that it is difficult to correctly move the piston 2 and, by extension, the piston rod 3 to a predetermined position.

To deal with this problem, it may be possible to set a larger gap between the cylinder tube and the seal member to reduce the sliding resistance, but this would make the O-ring more likely to deform, and the O-ring would fit into the gap. There were some inconveniences, such as some parts digging into it. In addition, the working fluid will flow from the high-pressure chamber to the low-pressure chamber through the gap, and will also flow out from the gap between the piston rod and the cover as a sealing member. However, there was a problem in that the behavior of the piston could not be maintained constant.

The present invention was made in view of such problems, and has a structure in which the sliding resistance between the piston and the cylinder tube is small.
It is an object of the present invention to provide a cylinder positioning device capable of holding a piston constant relative to a cylinder tube for a long period of time.

(Means for achieving the object) A fluid pressure cylinder having a piston that is slidably disposed in a cylinder tube and has a labyrinth portion formed on the outer periphery, an inflow amount of pressurized fluid flowing through the cylinder, and A servo valve that controls the pressure by adjusting the discharge amount, a sensing means that senses the pressure of the pressurized fluid applied to the cylinder, and a sensor that drives the servo valve based on a control signal and a The control means is driven based on the detection signal and maintains the pressure of the pressurized fluid in the cylinder at a predetermined value.

(Function) The pressurized fluid supplied from the operating pressure source has its inflow and discharge amounts adjusted by a servo valve driven based on a control signal, and is supplied to the chamber of the cylinder as a fluid at a desired pressure. Bring the piston into position.

In this case, the pressurized fluid moves from the high pressure chamber to the low pressure chamber over time through this labyrinth, and also through the seal placed between the piston rod and its associated cover. This causes the pressure of the pressurized fluid applied to the cylinder to fluctuate, but in order to compensate for the fluctuation, the control means detects the pressure of the pressurized fluid in the cylinder based on the detection signal from the detection means. By driving the servovalve and regulating the pressure of the pressurized fluid applied to the hydraulic cylinder, the piston, and thus the piston rod, is held substantially in place.

(Embodiments) Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing the positioning device of the present invention, and for the sake of simplicity, parts having the same functions as those shown in FIGS. 4 and 5 are denoted by the same reference numerals. The fluid pressure cylinder includes a cylinder tube 1, a piston 2 movably disposed within the cylinder tube, a piston rod 3 extending in the axial direction of the cylinder tube and integrally fixed to the piston 2, and It includes covers 4a and 4b that respectively seal the openings at both ends of the cylinder tube 1.

Feed holes 6a and 6b are formed in these covers, and the cylinder tube 1, piston 3, and cover 4a
, 4b can supply and discharge pressurized fluid as a working medium, thereby making it possible to drive the piston and the piston loft 3 fixed thereto in the axial direction.

Since the piston 2 is disposed in the axial direction of the cylinder tube 1 with a small gap therebetween, the sliding resistance against the inner surface of the cylinder is extremely low compared to conventional fluid pressure cylinders. Further, at least a part of the outer periphery thereof has a labyrinth seal 8 in which a narrow part and an enlarged part are arranged in parallel.
to prevent the pressurized fluid from flowing through the gap between the cylinder and the piston as much as possible.

A servo valve lO connected to these supply and discharge holes 6a and 6b via supply and discharge pipes 9a and 9b supplies pressurized fluid at a predetermined pressure to these chambers 5.

As shown in FIGS. 2(a) and 2(b), this servo valve controls the amount of pressurized fluid supplied from an operating pressure source (not shown) connected to the inlet 14 and the amount of pressurized fluid discharged from the outlet 16. By appropriately adjusting the amount of pressurized fluid discharged from the supply port 18, the pressure of the pressurized fluid applied to the above-mentioned fluid pressure cylinder can be changed.

As shown in FIG. 2B with only one side thereof partially cut away, the housing 12 is provided with a first flow path 20 that extends across the inlet 14 and communicates with the housing 12. , this first
The flow path 20 passes through the first valve means 22 to the second flow path 24.
is connected to. This second passage 24 communicates with a supply port 18 formed in the housing 12 for supplying pressurized fluid to the hydraulic cylinder, and also communicates with the housing 12 via a second valve means 26. It communicates with a discharge port 16 formed by opening.

The paired first and second valve means 22 and 26 are
As shown in FIG. 3, a substantially spherical valve body 32, which is displaceably disposed opposite to a concave valve seat 30 formed at one end of a hollow valve seat member 28, is made of magnetic material. By attracting the throttle adjustment plate 34 made of are changed respectively, and the opening degree is the electromagnet 3.
6 can be adjusted in accordance with the magnitude of the electrical signal applied.

Therefore, opening the valve means 22 and closing the valve means 26 increases the pressure of the pressurized fluid supplied from the supply port 18, whereas closing the valve means 22 and opening the valve means 26 increases the pressure of the pressurized fluid supplied from the supply port 18. pressure can be reduced.

In addition, a pressure detection means 38 , such as a semiconductor pressure sensor, for detecting the pressure of the pressurized fluid supplied from the supply port 18 to the fluid pressure cylinder is disposed in the middle of the second flow path 24 . The detection signal from the pressure sensing means 38 is inputted to the control means 50 via the lead wire 34 as shown in FIG. Incidentally, reference numerals 40 and 42 indicate the valve means 22 and 2.
6 indicates the receiving holes in which they are installed, and 44 indicates the lead wires for sending electrical signals to the electromagnets of these valve means.

The control means 50 controls the servo valve 10 to bring the output shaft of the hydraulic cylinder, that is, the piston rod 3, to a predetermined position.
A control signal is sent to the chambers 5 to adjust the pressure of the pressurized fluid supplied to each chamber 5, and when the piston rod 3 is brought to a predetermined position, it is determined whether the The operation of the servo valve 10 is controlled to maintain the pressure difference between the respective chambers 5 constant.

Note that in order to detect that the piston rod 3 has been brought to a predetermined position and also to detect that the piston rod 3 is in the predetermined position, a position detection means, for example a linear encoder, is arranged in relation to the piston rod 3. The control means calculates and compares the detection signals from the linear encoder and the pressure detection means 32, and controls the servo valve 10 based on the results.
It may also be configured to drive.

(Effects of the Invention) As detailed above, according to the device of the present invention, the O-ring that seals between the piston and the cylinder that accommodates it is eliminated, and the labyrinth seal is created. The piston and the cylinder are substantially prevented from mechanically contacting each other because the structure uses a labyrinth seal to seal between these members and compensates for the leakage of the working fluid that occurs due to the use of the labyrinth seal. Therefore, since the cylinder can be operated even when the operating pressure is low, the starting characteristics can be improved, and the positioning accuracy can also be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the device of the present invention in partial cross section, and Fig. 2 (a) and (b) are perspective views showing the external appearance of the servo valve of the device of the present invention, and FIG. 3 is a schematic diagram of the valve means constituting the servo valve shown in FIG. 2. FIGS. 4 and 5 are explanatory diagrams showing a conventional cylinder and a piston applied thereto. be. t-m-cylinder tube 2-piston 3--piston rod 4a, 4b-cover 5-chamber
6a, 6b - Supply/discharge hole 7 - Seal member 8 - N type packing (labyrinth seal) 9a, 9b -
Supply/discharge pipe 10-Bolt 12-Housing 14
- Inlet port 16 - Outlet port 18 - Supply port 20.24 - Channel 22.26 - Valve means 28 - Valve seat member
30-Valve seat 32-Valve body 34-Aperture adjustment plate 36-Electromagnet

Claims (1)

[Claims] 1. A fluid pressure cylinder having a piston that is slidably disposed inside a cylinder tube and has a labyrinth formed on its outer periphery, and by adjusting the inflow and discharge amounts of pressurized fluid applied to this cylinder. A servo valve that controls the pressure, a detection means that detects the pressure of the pressurized fluid applied to the cylinder, and a servo valve that is driven based on a control signal and a detection signal from the detection means. 1. A cylinder positioning device using a servo valve, comprising: a control means for maintaining the pressure of pressurized fluid in the cylinder at a predetermined value.