JPH0718441B2 - Pneumatic servo cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a pneumatic servo cylinder which can be arbitrarily positioned.

[Prior Art] As cylinders as actuators, there are a hydraulic cylinder using a liquid such as oil as a working medium and a pneumatic cylinder using a gas such as air as a working medium.

A hydraulic cylinder represented by a hydraulic cylinder whose working medium is incompressible can be easily adjusted in speed by a throttle valve, etc., and can be stopped at an intermediate position during the stroke, so a hydraulic cylinder is used as an actuator for operation control. It is commonly used.

However, in the hydraulic cylinder, since the hydraulic source and the piping for the hydraulic oil must be specially provided, the auxiliary equipment becomes large and the cost becomes high. Also, the use of hydraulic cylinders is not preferable for food-related and chemical-related items that dislike oil.

On the other hand, it is extremely difficult to adjust the speed and stop the intermediate position of the stroke in a pneumatic cylinder whose working medium is compressible, and when a normal pneumatic cylinder is used, a stopper is provided on the rod or non-driving body. The stop positioning is mechanically performed by this stopper. Therefore, it is not generally used as an actuator for operation control. However, as described above, a pneumatic cylinder is preferable as an actuator for food machines, chemical machines, etc. that dislike oil. Further, the compressed air source, which is the drive source of the pneumatic cylinder, can use the pneumatic line normally installed in the factory, and can be easily obtained without separately preparing.

Therefore, it is required to materialize the position control technique using the pneumatic cylinder.

As a conventional pneumatic cylinder capable of position control, there is an electric pneumatic servo cylinder shown in FIG. 5 (Japanese Patent Laid-Open No. 54-33970).

As shown in FIG. 5, a screw rod 2 is rotatably provided so as to match the axis of the cylinder body 1, and one end of the screw rod 2 is connected to an electric servomotor 3. A piston 4 slidably fitted in the cylinder body 1 is screwed into the screw rod 2, and a guide rod 5 extends from the piston 4 in parallel with the guide rod 2 through an end plate of the cylinder body. A grip piece 6 is fixed to the extended end of the guide rod 5.

Further, the inside of the cylinder body 1 is compressed by the piston 4 into a pneumatic chamber.
The air pressure chambers 7 and 8 are partitioned into 7, 8 and are connected to an air pressure source (not shown) via a solenoid valve 9.

In such an electric-pneumatic servo cylinder, when the cylinder is driven, the solenoid valve 9 is switched to supply compressed air to any of the pneumatic chambers so that it can operate in a desired driving direction. In this state, the electric servomotor 3 rotates the screw rod 2 by a required amount. The rotation of the screw rod 2 moves the piston 4. Since the force against the load with respect to the movement of the piston 4 is given by the pneumatic pressure for compression, the force required to rotate the screw rod 2 can be small.

Furthermore, the piston 4 is held in position by mechanical engagement by screwing the screw rod 2 and the piston 4.

[Problems to be Solved by the Invention] However, in the above-mentioned electric servomotor 3, the stopping accuracy (positioning accuracy) of the grip piece 6 is determined by the responsiveness of the solenoid valve 9 and the solenoid valve 9.
The responsiveness of the working medium to the opening and closing of the motor becomes a problem, and the inertial force of the load has a great influence on the stop accuracy, which is all the more remarkable when the electric servo motor 3 having a small capacity is used.

Furthermore, in order to reduce the influence of the load inertial force on the positioning due to the screw engagement of the screw rod 2 and the piston 4, the resistance between the screw rod 2 and the piston 4 is required to some extent, and the screw lead angle of the screw rod 2 is required. Is also preferably smaller. Therefore, when the electric air servo cylinder is operated at a high speed, the capacity of the electric servo motor is inevitably large.

Further, in order to reduce the influence of the load inertial force, an electromagnetic brake is attached to the output shaft of the servo motor 3, and the electromagnetic brake is operated in accordance with the switching of the electromagnetic valve 9 to restrain the screw rod 2 by the electromagnetic brake. However, even in this case, the responsiveness of the solenoid valve 9 becomes a problem, and the stop accuracy is inevitably affected by the magnitude of the load inertial force.
Further, in this case, a controller is required to match the operation of both the electromagnetic brake and the drive power source for the electromagnetic valve with the piston stop operation, which is complicated and expensive.

In view of the above situation, the present invention is to provide a pneumatic servo cylinder that can achieve high positioning accuracy with simple control.

[Means for Solving the Problems] In the present invention, a piston formed by extending a rod in a cylinder body is airtightly slidably fitted, and a valve chamber is bored from the side opposite to the rod to face the piston. A pair of seat type valves are fitted in a slidable manner in an airtight manner, both seat type valves are biased toward the adjacent side, and a nut block is sandwiched between the two seat type valves so as to leave a space around them. Both seat type valve facing surfaces and both end surfaces of the nut block can be in close contact with each other, and stoppers for restricting movement in the proximity direction at both seat type valve neutral positions are provided, and both seat type valves are provided with valve paths that open to the facing side. Install one valve passage through the piston and cylinder body to communicate with the outside, and the other valve passage through the piston to communicate with the vacant chamber that communicates with the rod side air pressure source. And the space between both seat-type valves are Driven by
A screw shaft airtightly inserted into the cylinder body is screwed into the nut block.

[Operation] Is the nut block moved by rotating the screw shaft, the nut block and one seat type valve are separated from each other, the valve path is opened, and the space on the side opposite to the rod communicates with the air pressure source? Or, it communicates with the atmosphere and the piston moves.
The movement of the piston is directly fed back to the seat type valve separated from the nut block without using a screw element or the like, and is performed until the both seat type valves and the nut block are in the neutral position.

[Examples] Examples of the present invention will be described below with reference to the drawings.

Both ends of the cylinder body 11 are airtightly closed by end plates 12 and 13 to form a cylinder body 14, and a piston 15 is provided in the cylinder body 14.
Is airtightly slidably fitted, and a rod 16 extended from a piston 15 penetrates one end plate 12. The end plate 12 is provided with an import 17 which communicates with the inside of the cylinder body 14. Inside the piston 15, a valve chamber 18 is bored from the other end plate 13 side, and a pair of donut-shaped seat type valves 19, 20 are airtightly slidably fitted in the valve chamber 18. is there. A nut block 21 is sandwiched between the seat type valves 19 and 20, a screw shaft 22 described later is screwed to the nut block 21, and a lid 23 that also serves as a rotation stopper for the nut block 21 is fixed to the piston 15. Then, the valve chamber 18 is closed. Seat type valve
Compression springs 24 and 25 are provided between the seat valve 19 and the bottom of the valve chamber 18 and between the seat valve 20 and the lid 23 to urge both seat valves 19 and 20 in the proximity direction. Stoppers 26 and 27 are provided on the inner surface of the valve chamber 18 so that both seat type valves 19 and 20 engage with the stoppers 26 and 27 at their neutral positions, and the end faces of both seat type valves 19 and 20 have a nut block 21. So that it comes into airtight contact with the end face of. Both seat type valves 19 and 20 are provided with elbow valve passages 28 and 29 that open to the outer peripheral surface and the end surface, and the inner surface of the valve chamber 18 is an elbow valve passage at the neutral position of both seat type valves 19 and 20. Grooves matching 28,29
Engrave 30,31.

One groove 30 is a gap 32 formed between the cylinder 11 and the piston 15.
Through the communication hole 33, and the cylindrical body 11 has a gap.
An outport 34 communicating with 32 is provided. The other groove 31 communicates with one empty chamber 44 partitioned by the piston 15 by the communication hole 35, and the space 36 between the seat type valves 19 and 20 has the passage 3
7 communicates with the other vacant chamber 45.

The nut block 21 is provided with a cylindrical portion 38 which is loosely fitted in the hollow portion of the seat type valve 20 on the lid 23 side, and the cylindrical portion 38 is symmetrically provided with a notch 39. An engaging piece 40 is provided on the lid 23 so as to be slidably fitted in the notch 39. A bearing 41 is fitted on the other end plate 13, and the end plate is inserted through the bearing 41.
The screw shaft 22 is airtightly supported by 13 and the projecting end from the end plate 13 is connected to an electric motor 43 via a coupling 42.

The import 17 is connected to an air pressure source (not shown), and the out port 34 is connected to a tank (not shown).

Next, the operation will be described.

First, when the rod 16 is projected, the screw shaft 22 is rotated by the electric motor 43 and the nut block 21 is moved leftward in the drawing against the compression spring 24 (see FIG. 3).
The movement of the seat type valve 20 to the left in the drawing is restricted by the stopper 27, the nut block 21 and the seat type valve 20 are separated from each other, and the communication hole 35 communicates with the space 36 via the elbow valve passage 29. The communication hole 35 communicates with a vacant chamber 44 communicating with the air pressure source, and the space 36 communicates with a vacant chamber 45 via a passage 37. Therefore, the compressed air flows from the vacant chamber 44 to the vacant chamber 45 side. Therefore, due to the difference in pressure receiving area between the rod side of the piston 15 and the motor side, the piston 15 moves to the position where the seat type valve 20 and the nut block 21 are in close contact (the neutral position between both seat type valves and the nut block). To do.

Both seat type valves 19 and 20, the nut block 21 moves to the neutral position of the piston 15 is stopped, and the piston block 15 is positioned at that position, but its position is retained by the motor 43 via the screw shaft 22 and the nut block 21. If so, the piston 15 can be stably positioned. Also, double seat type valve 1
The contact surfaces of 9,20 and nut block 21 are both flat,
Moreover, both seat type valves 19 and 20 are attached to the nut block 21 and the compression spring 24,
Since it is pressed by 25, its sealing property is good and static stability is also good.

When the rod 16 is retracted, the screw shaft 22 is rotated by the electric motor 43 and moved rightward in the figure against the compression spring 25 (see FIG. 4). The movement toward the side is restricted, the nut block 19 and the seat-type valve 19 are separated from each other, and the empty chamber 45 passes through the passage 37, the space 36, the elbow valve passage 28, the communication hole 33, the gap 32, and the outport 34. To a tank not shown. Therefore, the pressure in the vacant chamber 45 decreases and the rod 16 moves to the right.

Thus, the movement of the rod 16 to the right also stops at the point where both seat type valves and the nut block are in the neutral position, as described above. That is, by rotating the screw shaft 22 with the motor 43 and moving the nut block 21, the piston 15 (rod 16) moves.

Further, if the rotation amount of the screw shaft 22 is monitored by using a servo motor, a stepping motor, or the like for the electric motor 43, the rod 16 can be positioned at any position, and the rod 16 can be positioned with high accuracy. The inertial force of the driven body (not shown) and the piston 15 does not influence. or,
The driving force of the electric motor 43 only needs to move the nut block 21 against the force of the compression springs 24 and 25, and the inertia force does not act on the nut block 21 (small), so that the ball screw and the lead angle are large. The thing etc. can also be used.

[Effects of the Invention] As described above, according to the present invention, the structure is simple and the product can be easily commercialized, and the movement of the piston can be performed without using a screw element or the like for the seat type valve separated from the nut block. Since it is directly fed back, even if a compressive fluid is used as the working medium, it can be positioned stably and at an arbitrary position.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a partial perspective view showing an engagement relationship between a nut block and a lid, and FIG.
FIG. 4 and FIG. 4 are explanatory views of the operation before the same, and FIG. 5 is a schematic sectional view of a conventional example. 14 is a cylinder body, 15 is a piston, 16 is a rod, 18 is a valve chamber, 19 and 20 are seat type valves, 21 is a nut block, 22 is a screw shaft, 26 and 27 are stoppers, 28 and 29 are elbow valve paths. Show.

Claims (1)

[Claims] 1. A pair of seat type valves in which a piston formed by extending a rod in a cylinder body is airtightly slidably fitted, and a valve chamber is bored from the side opposite to the rod to face the piston. Both seat type valves are fitted so as to be slidable in an airtight manner and both seat type valves are biased toward the proximity side, and a nut block is sandwiched so as to leave a space between both seat type valves, and both seat type valve confronting faces and nuts. Both end surfaces of the block can be adhered to each other, a stopper for restricting movement in the proximity direction at both seat type valve neutral positions is provided, and a valve path opening to the facing surface is provided in each of both seat type valves,
One valve passage penetrates the piston and the cylinder body to communicate with the outside, and the other valve passage penetrates the piston to communicate with the vacant chamber communicating with the rod side air pressure source. A pneumatic servo cylinder in which a screw shaft, which is communicated with a space between mold valves and is driven by a motor and is hermetically inserted into a cylinder body, is screwed into the nut block.