JPH0792095B2 - Air actuator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air actuator that outputs a reciprocating movement force by introducing and discharging compressed air, and particularly to control of a reciprocating movement force that is output.

[Prior Art] Conventionally, air actuators have been used to drive various members such as opening and closing valves. This air actuator moves a piston in a cylinder and outputs a reciprocating force by introducing and discharging compressed air into the cylinder. Further, since this air actuator uses air as its drive source, it has advantages that handling such as supply and discharge is very simple and that the operation is reliable.

Further, with the recent progress of control equipment, electronic control has been adopted in various fields, the range of use of various actuators has expanded, and the importance of air actuators has also increased.

Here, a conventional air actuator will be described with reference to FIG. In the figure, a cylinder 10 is an airtight pressure-resistant container, and is formed in a cylindrical shape. A piston 12 having a cylindrical shape substantially the same as that of the cylinder 10 and having a diameter slightly smaller than that of the cylinder is slidably accommodated in the inside thereof, and the piston 12 allows the piston 12 to move to the inside of the cylinder 10. The first air introducing chamber 10a and the second air introducing chamber 10b are formed as partitions. On the other hand, the piston 12 has an output shaft 14
Is fixed, and by connecting the output shaft 14 to each member, the member can be reciprocated.

Then, the first and second air introduction chambers 10 at both ends of the cylinder 10
Pipes 16a and 16b are connected to a and 10b, respectively, and these pipes 16a and 16b are connected to a compressed air source or the atmosphere via a switching valve 18.

Therefore, if the switching valve 18 is operated to introduce the compressed air into the first air introducing chamber 10a through the pipe 16a, the piston 12 moves leftward in the drawing due to the pressure of the compressed air. on the other hand,
When the switching valve 18 is operated to introduce compressed air into the second air introducing chamber 10b from the pipe 16b, the piston 12 moves to the right.

Then, by controlling the introduction amount of the compressed air, the movement amount or movement force of the piston 12 can be controlled, and the reciprocating movement force to be output can be controlled.

[Problems to be Solved by the Invention] In such a conventional air cylinder, when controlling the output reciprocating movement amount, etc., a flow rate adjusting valve is provided in the air circulation path on the discharge side, and the air flow is controlled by controlling the discharge flow rate. It controls speed and so on. In particular, when operating the air actuator, it is often the case that the moving speed of the air actuator is controlled to be constant such as opening and closing of the valve, and suitable control can be performed by adjusting the amount of discharged air.

That is, for example, a valve as shown in FIG. 4 is used for adjusting the flow rate of air. With this valve, the needle 20
The one that adjusts the flow area by adjusting the flow area of the air flow passage by the relative movement of the air flow path with respect to the opening 22 is adopted. Then, according to such a flow rate adjusting method, the air circulates through a considerably small distribution path, and here, the air circulates at a substantially sonic speed. In this way, within the range where the air flows at the sonic velocity, the velocity of the air does not change due to the change in the opening area. Therefore, the discharge amount can be adjusted appropriately by adjusting the opening area, and the movement amount of the actuator can be effectively controlled. In particular, even if the force required to move the driven member changes to some extent, the moving speed can be kept constant.

On the other hand, the air actuator may be used to make changes at a predetermined cycle. This is, for example, when applying a sinusoidal load to a soil sample in a soil test apparatus and detecting a strain change or the like against the load to inspect the physical properties of the soil sample.

In such a case, the reciprocating force is controlled by providing a flow rate adjusting valve in the compressed air introduction path, sequentially changing the cross-sectional area of the air circulation path, and controlling the amount of compressed air introduced into the cylinder.

However, as described above, when the compressed air flows through the small gap, the velocity thereof reaches the sonic velocity. this is,
It means that the flow velocity does not change even if there is some fluctuation in the pressure on both sides of the small opening. Therefore, even if the pressure in the cylinder fluctuates, the velocity of the air flowing through the servo valve does not change at all.

If a moving force that gradually changes under such a condition is output, the output shaft of the actuator may vibrate due to a change in stress with respect to the output. Then, as described above, unnecessary vibration is generated in the output shaft.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide an air actuator having a damper function of absorbing vibration and the like.

[Means for Solving the Problems] An air actuator according to the present invention includes a hollow cylinder, and a first piston that is slidably accommodated in the cylinder and that forms a first air introduction chamber as a partition on one end side of the cylinder. Portion, a second piston portion slidably accommodated in the cylinder and partitioning and forming a second air introduction chamber on the other end side of the cylinder, and a connecting shaft for connecting and fixing the first piston portion and the second piston portion. And a damper chamber which is formed in the middle part of the cylinder by the first and second piston parts and is filled with air, and a damper chamber which is fixed to the cylinder and divides the damper chamber into two spaces, and the connecting shaft penetrates through the central part. And a partition wall having a through hole formed therein and a damper chamber formed around the connecting shaft by making the diameter of the through hole of the partition wall larger than the diameter of the connecting shaft and formed by the partition wall. And a gap that provides resistance to the air in the damper chamber that flows through the space and that provides a buffering force to the movement of the piston by the resistance of the air that flows through the gap. .

[Operation] The air actuator according to the present invention has the above-described configuration, and the first and second pistons move by introducing compressed air into the first air introducing chamber or the second air introducing chamber. .

Here, a damper chamber is formed in the middle of the first and second piston portions, and the damper chamber is divided into two chambers by the partition wall, and the communication portion is formed in the partition wall. When the piston moves, the air in the damper chamber moves through the communication section.

Therefore, the resistance against the movement of the piston can be imparted to the piston by the resistance of the fluid passing through the fluid communication portion in the damper chamber, whereby a desired buffer force (damper action) can be obtained.
Can be obtained.

[Embodiment] An embodiment of the air actuator according to the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 is a cross-sectional view showing the structure of the first embodiment, in which both ends of a cylindrical cylinder 30 are closed by end plates 32a and 32b, and the inside thereof is a closed space. Then, the first piston portion 34a and the second piston portion 34b are housed inside this.

On the other hand, an output shaft 36 is fixed to the first and second piston portions 34a and 34b, which are connected to each other and penetrate the end plates 32a and 32b of the cylinder 30. Therefore, the viston section 34a,
34b integrally moves as a piston 34, and this moving force is output from the output shaft 36.

A first air introduction chamber 38a is formed on the right side of the piston 34a in the cylinder 30, and a second air introduction chamber 38b is formed on the left side of the piston 34b.

The pipes 42a, 4 are provided in the first air introduction chamber 38a and the second air introduction chamber 38b.
It is connected to the servo valve 44 via 2b. This servo valve 44 is supplied with a predetermined electric signal, so that the piping 42a, 42a
Change the area of the air flow path for b and pipe at the specified flow rate.
Compressed air is introduced into 2a and 42b.

Here, a characteristic of the present invention is that the piston 34
Is formed by the first piston 34a and the second piston 34b, and the damper chamber 50 is formed between the two pistons 34a, 34b. The damper chamber 50 is divided into a first damper chamber 50a and a second damper chamber 50b by a partition wall 52 extending from the outer wall of the cylinder. Further, the damper chamber 50 hermetically accommodates fluid (air), and the air in the damper chamber 50 moves as the piston portion 34 moves.

A donut-shaped gap 54 having a predetermined area is formed as a communicating portion around the partition wall 52 and the shaft 36. Therefore, when the piston 34 moves, the fluid moves between the first damper chamber 50a and the second damper chamber 50b through the gap 54 in the damper chamber 50.

The bellows 60 is for achieving a seal between the piston 34 and the cylinder 30, and even if the piston 34 moves, it reliably forms a partition between the air introduction chamber 38 and the damper chamber 50.

In such an apparatus, if compressed air is alternately introduced into the air introduction chambers 38a, 38b via the servo valve 44, the output shaft 36
A predetermined reciprocating movement is achieved at. In the device of this embodiment, when the piston portion 34 moves, the fluid contained in the damper chamber 50 inside the piston portion 34 moves through the gap 54. Therefore, by adjusting the area of the gap 54, it is possible to impart a desired resistance to the movement of the piston 34 here. If resistance to the movement of the piston 34 can be imparted, the vibration generated in the output shaft 36 is absorbed here, and a damper (buffer) action for the movement of the piston can be achieved.

Second Embodiment FIG. 2 is a sectional view showing the structure of the second embodiment.
The same members as those in the embodiment are designated by the same reference numerals and the description thereof will be omitted.

A characteristic of the second embodiment is that a bellows 70 is adopted in place of the belofram 60 of the first embodiment,
The bellows 70 having such a bellows can also partition the air introducing chamber 38 and the damper chamber 50 along with the movement of the piston 34. Further, in this example, the bellows 70 includes a partition wall 54 for partitioning the damper chamber 50 and pistons 38a, 38b.
The partition wall 54 also serves as a partition between the first air introduction chamber 38a and the second air introduction chamber 38b, since they are connected to each other.

Therefore, also in the second embodiment, a suitable damper action can be achieved as in the above-described first embodiment.

As described above, in the present embodiment, since air is used as the fluid sealed in the damper chamber, the piston 34 and the cylinder 30 need not be completely sealed. In addition, it is necessary to adjust the resistance force so that the speed at which the air enclosed in the damper chamber flows through the gap 54 is equal to or lower than the speed of sound.

Further, in the above embodiment, the piston 34 and the cylinder 30 are sealed by the bellows 60, but other means such as packing may be used.

[Effects of the Invention] As described above, according to the air actuator of the present invention, the actuator itself has a built-in damper, so that vibration or the like in the output can be effectively prevented.

[Brief description of drawings]

1 is a front sectional view of an air actuator according to a first embodiment of the present invention, FIG. 2 is a front sectional view of a second embodiment, FIG. 3 is a schematic configuration diagram of a conventional air actuator, and FIG. It is a schematic block diagram which shows an example of a flow controller. 30 …… Cylinder 34a …… First piston 34b …… Second piston 38a …… First air introduction chamber 38b …… Second air introduction chamber 50 …… Damper chamber 52 …… Partition wall 54 …… Gap

Claims (1)

[Claims] 1. A hollow cylinder, a first piston portion which is slidably accommodated in the cylinder and which forms a first air introduction chamber at one end of the cylinder, and a slidably accommodated in the cylinder. , A second piston portion for partitioning and forming a second air introduction chamber on the other end side in the cylinder, a connecting shaft for connecting and fixing the first piston portion and the second piston portion, and a cylinder of the cylinder by the first and second piston portions. A damper chamber that is formed in the middle part and is filled with air, and a partition wall that is fixed to the cylinder and divides the damper chamber into two spaces, and that has a through hole through which the connecting shaft penetrates in the center part, By making the diameter of the through hole of the partition wall larger than the diameter of the connecting shaft, it is formed around the connecting shaft and connects the two spaces of the damper chamber formed by the partition wall,
An air actuator, comprising: a gap that gives resistance to the air in the damper chamber flowing therethrough; and a buffering force for the movement of the piston due to the resistance of the air flowing through the gap.