JP4261494B2 - Pneumatic actuator - Google Patents

Description

  The present invention relates to a pneumatic actuator that generates a fine and precise thrust.

Conventionally, various structures such as a metal cylinder, a bellows cylinder, and a ram type cylinder have been proposed as pneumatic actuators that control a workpiece with a fine and precise thrust.
In the metal cylinder, the base end of the output rod is fixed to the piston moving in the cylinder, the piston moves based on the air pressure supplied into the cylinder, and the output rod protrudes from the cylinder as the piston moves, Alternatively, it is drawn into the cylinder. By alternately supplying air pressure to both sides of the piston, a return actuator in which the output rod reciprocates is formed.

In such a metal cylinder, it is necessary to attach a packing that is in sliding contact with the inner surface of the cylinder to the piston, and to provide a packing for a bearing that supports the output rod.
The bellows cylinder uses two bellows to divide a plurality of pressure chambers in the cylinder, and alternately supply air pressure to the pressure chambers to reciprocate the piston and reciprocate the output rod.

  The ram type cylinder has a configuration in which an intermediate portion of the output rod is movably held by a sealing material, one end portion of the output rod projects into the pressure chamber, and the other end projects out of the cylinder. The output rod is moved based on the pressure difference between the air pressure supplied into the pressure chamber and the atmospheric pressure outside the cylinder.

  Thus, the ram type cylinder is usually configured as a single-acting actuator that does not have a function of returning the output rod protruding outside the cylinder into the cylinder. In addition, a configuration has been proposed in which a coil spring is built in to return the output rod into the cylinder, and a restoring force of the coil spring is applied to the output rod to form a return actuator.

Patent Document 1 discloses a magnetic spring device.
JP 2002-54671 A

  In a metal cylinder or a bellows cylinder, the piston is slidably contacted with the inner surface of the cylinder via a seal member, and the output rod is movably supported with respect to the bearing via the seal member and sealed at two locations. Dynamic resistance increases. Further, when the dimensional accuracy of the sliding portion is low, galling is likely to occur between the output rod and the bearing or between the piston and the cylinder inner surface.

Therefore, it is difficult to precisely control the thrust generated in the output rod based on the air pressure supplied into the pressure chamber.
Further, since the bellows cylinder needs to incorporate two bellows, it is difficult to reduce the size.

  Since the ram type cylinder is configured to seal the intermediate portion of the output rod with a sealing material, it is possible to prevent the occurrence of the above-described galling and generate a stable thrust. However, since it is a single-acting type, a configuration for pressing the output rod to the original position outside the cylinder is necessary to return the output rod into the cylinder.

  Further, in the configuration in which the output rod is returned into the cylinder based on the urging force of the coil spring, the urging force of the coil spring changes with respect to the movement stroke of the output rod, so that the thrust of the output rod changes. There is a point.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic actuator having a simple return function of an output rod with a simple configuration while using a single-action ram type cylinder.

  The object is to provide a pneumatic actuator composed of a ram cylinder that supports the rod in a movable manner and drives the rod by supplying air pressure to a pressure chamber provided in the case. This is accomplished by a pneumatic actuator with a magnetic spring biasing toward it.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic actuator provided with the stable return function of an output rod can be provided with a simple structure, using a single action ram type | mold cylinder.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. The pneumatic actuator shown in FIG. 1 is composed of a ram-type cylinder, and a sealing material 2 made of a metal seal is disposed in the center of a cylindrical case 1 made of a nonmagnetic material such as aluminum. The rod 3 is supported so as to be movable in the axial direction. The sealing material 2 may use a nonmagnetic material such as carbon or synthetic resin. The rod 3 is made of a non-magnetic material, and is formed, for example, by subjecting the surface of aluminum to a required hardening treatment.

  An enlarged diameter portion 4 is integrally provided at the base end portion of the rod 3 and constitutes a retainer from the sealing material 2. A pressure chamber 5 is formed between the expanded diameter portion 4 and the base end portion of the case 1, and air pressure of a predetermined pressure is supplied to the pressure chamber 5 from a pneumatic control device via a supply port (not shown). The And when the atmospheric pressure in the pressure chamber 5 rises, the rod 3 moves in the axial direction and its tip protrudes out of the case 1.

  A cylindrical outer magnet 6 is fixed to the inner peripheral surface of the tip of the case 1, and a cylindrical inner magnet 7 is fixed to the outer peripheral surface of the rod 3 inside the outer magnet 6. As shown in FIG. 2, the outer magnet 6 and the inner magnet 7 are each composed of four poles in the circumferential direction, and are magnetized so that the outer magnet 6 and the inner magnet 7 attract each other. Further, a predetermined gap is ensured between the outer magnet 6 and the inner magnet 7 and can move without contact with each other.

  A magnetic spring ms is constituted by the outer magnet 6 and the inner magnet 7 as described above, and when the rod 3 moves out of the case 1, an attractive force is exerted to return the rod 3 to its original position, that is, the case. It is like that. This suction force is constant regardless of the amount of movement of the rod 3. Further, a suction force for returning to the original position also acts on the rotation of the rod 3.

  Between the sealing material 2 and the outer magnet 6, the case 1 is provided with an exhaust port 10, and compressed air that passes through the gap between the sealing material 2 and the rod 3 can be discharged from the pressure chamber 5. ing.

  An annular position detecting magnet 8 is fitted on the outer peripheral portion of the expanded diameter portion 4 of the rod 3. A magnetic detection unit 9 that detects the magnetism of the position detection magnet 8 and outputs a detection signal to a control unit (not shown) is attached to the outer peripheral surface of the base end portion of the case 1. The control unit controls the air pressure control device based on the detection signal of the magnetic detection unit 9 to control the air pressure supplied to the pressure chamber 5.

  Next, the operation of the pneumatic actuator as described above will be described. A predetermined jig for pressing the workpiece is attached to the tip of the rod 3. In some cases, the workpiece is directly pressed by the tip of the rod 3.

  In a state where no air pressure is supplied into the pressure chamber 5, the rod 3 is held at the original position where it is almost immersed in the case 1 by the action of the magnetic spring ms. When air pressure is supplied into the pressure chamber 5 from this state, the rod 3 protrudes from the case 1 against the attractive force of the magnetic spring ms, and once the contact is made with the workpiece, the movement is temporarily stopped.

  When the movement of the rod 3 is stopped, the control unit detects that the rod 3 is in contact with the workpiece based on the detection signal of the magnetic detection unit 9 and supplies a predetermined air pressure to the pressure chamber 5. Then, the workpiece is pressed through the rod 3 with a predetermined pressure based on the air pressure in the pressure chamber 5.

  At this time, air that escapes from the pressure chamber 5 through the gap between the rod 3 and the sealing material 2 toward the distal end side of the rod 3 is discharged from the exhaust port 10, and is thus ejected from the distal end side of the case 1 toward the workpiece. It will never be done.

When the pressure in the pressure chamber 5 is lowered after the pressing operation of the workpiece is completed, the rod 3 is pulled into the case 1 by the attractive force of the magnetic spring ms and returns to the original position.
With the pneumatic actuator configured as described above, the following operational effects can be obtained.
(1) Since it is composed of a ram type cylinder, the intermediate part of the rod 3 is supported by the sealant 2 so that the rod 3 can be moved, and the rod 3 is moved with low frictional resistance. Can be made. Therefore, based on the control of the air pressure supplied to the pressure chamber 5, the pressure for pressing the workpiece can be controlled with high accuracy.
(2) If the air pressure in the pressure chamber 5 is reduced by the action of the magnetic spring ms, the rod 3 can be moved into the case 1 and automatically returned to the original position.
(3) By the action of the magnetic spring ms, an attractive force that prevents the rotation of the rod 3 acts. Although the sealing material 2 has a low resistance to the rotation of the rod 3, the magnetic spring ms prevents the rotation of the rod 3 during the pressing operation of the workpiece, and therefore prevents damage to the workpiece due to the rotation of the rod 3. Can do.
(4) Since the magnetic spring ms generates a constant restoring force regardless of the amount of movement of the rod 3, the pressing force of the rod 3 can be controlled easily and accurately.
(5) Since the magnetic spring ms does not have a sliding portion that accompanies the movement of the rod 3, it is possible to prevent the generation of dust due to the movement of the rod 3.
(6) Exhaust air from the pressure chamber 5 through the gap between the rod 3 and the sealing material 2 toward the tip of the rod 3 from the exhaust port 10 without being jetted from the tip of the case 1 toward the workpiece. be able to. At this time, since the outer magnet 6 and the inner magnet 7 constituting the magnetic spring ms are disposed on the distal end side of the case 1, air that tends to escape to the distal end side of the case 1 is obstructed by both the magnets 6 and 7. Then, it is guided to the exhaust port 10.
(7) The magnetic detector 9 can detect the moving state of the rod 3 and precisely control the pressing operation of the workpiece.
(8) The position of the position detecting magnet 8 attached to the expanded diameter part 4 can be easily detected by the magnetic detection part 9 by forming the rod 3 and its expanded diameter part 4 with a nonmagnetic material such as aluminum. Can do.
(9) By forming the rod 3 with a lightweight material such as aluminum, the inertial force of the rod 3 can be reduced. Therefore, damage to the workpiece due to the inertial force of the rod 3 can be prevented.
(10) If the sealing material 2 is formed of a lightweight material such as carbon, the weight can be reduced as compared with the case of forming it with a metal seal.
(Second embodiment)
FIG. 3 shows a second embodiment of a pneumatic actuator using a ram-type cylinder having the magnetic spring ms as described above. A rod 3 is movably supported with respect to a bearing 11 provided at the tip of the case 1, and a metal seal 12 is disposed in the case 1 adjacent to the bearing 11.

  A pressure chamber 5 is provided at the base end of the case 1, and a supply hole 13 for supplying a required air pressure is formed in the pressure chamber 5. And between the pressure chamber 5 and the metal seal 12, the magnetic spring ms comprised by the outer magnet attached to the case 1 and the inner magnet attached to the rod 3 is arrange | positioned.

Such a pneumatic actuator can be configured to have the return function and rotation prevention function of the rod 3 similar to those of the first embodiment by the action of the magnetic spring ms.
(Third embodiment)
FIG. 4 shows a third embodiment. This embodiment shows a configuration in which the pressure chamber 5 is sealed with a bellows seal 14 instead of the metal seal 12 of the second embodiment, and a bearing 11 and a magnetic spring ms are provided adjacent to each other.

In such a configuration, the same effect as that of the second embodiment can be obtained, and the bellows seal 14 is superior in sealing function to the metal seal 12, so the amount of air supplied to the pressure chamber 5 is reduced. Can be reduced. Accordingly, the air supply amount of the air pressure control device can be reduced, so that energy saving can be achieved.
(Fourth embodiment)
FIG. 5 shows a fourth embodiment. In this embodiment, an elastic seal 15 is provided instead of the metal seal 12 of the second embodiment. Even in such a configuration, a function of returning the rod 3 and a rotation preventing function similar to those of the first embodiment can be provided by the action of the magnetic spring ms.
(Fifth embodiment)
FIG. 6 shows a fifth embodiment. In this embodiment, instead of the metal seal 12 of the second embodiment, a hydrostatic bearing 16 having a sealing function is provided. The static pressure bearing 16 is a known configuration having both a bearing function and a sealing function by forming a bearing with a porous material and supplying a predetermined pressure to the supply hole 17 from a static pressure supply device (not shown). . A magnetic spring ms is disposed adjacent to the hydrostatic bearing 16.

  With such a configuration, the pneumatic actuator of the ram type cylinder provided with the hydrostatic bearing 16 has the return function and rotation prevention function of the rod 3 similar to those of the first embodiment by the action of the magnetic spring ms. Can be configured.

You may implement the said embodiment in the following aspects.
-The number of poles of the outer magnet 6 and the inner magnet 7 may be other than four. The allowable rotation angle of the rod 3 can be changed by changing the number of poles.

It is sectional drawing which shows the pneumatic actuator of 1st embodiment. It is sectional drawing which shows a magnetic spring. It is sectional drawing which shows 2nd embodiment. It is sectional drawing which shows 3rd embodiment. It is sectional drawing which shows 4th embodiment. It is sectional drawing which shows 5th embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 Sealing material 3 Rod 5 Pressure chamber 6 Outer magnet 7 Inner magnet 8 Position detection magnet 9 Magnetic detection part 10 Exhaust port ms Magnetic spring

Claims (5)

In a pneumatic actuator constituted by a ram cylinder that supports a rod movably in a case and drives the rod by supplying air pressure to a pressure chamber provided in the case,
A magnetic spring for urging the rod toward the original position ;
A sealing material for movably supporting the rod is provided in the case, the pressure chamber is provided on one end side of the sealing material, the magnetic spring is provided on the other end side of the sealing material, and the sealing material and the magnetic material are provided. A pneumatic actuator characterized in that an exhaust port is provided in the case between a spring .   The magnetic spring includes a cylindrical outer magnet attached to the inner peripheral surface of the case, and an inner magnet attached to the rod inside the outer magnet, and a magnetic force between the outer magnet and the inner magnet. The pneumatic actuator according to claim 1, wherein the rod is biased toward the original position in the axial direction and the rotational direction based on the above. The rod is made of a non-magnetic material, a position detection magnet is attached to the base end of the rod, and a magnetic detection unit for detecting the position of the position detection magnet is provided outside the case. The pneumatic actuator according to claim 1 or 2. 3. The pneumatic actuator according to claim 1, wherein the sealing material is formed of a metal seal . Claim 1 or 2 pneumatic actuator, wherein the forming the sealing member of a non-magnetic material.

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