JPH0781639B2 - Pneumatic cylinder with cushioning mechanism that can change stop position - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic cylinder with a cushioning mechanism capable of changing a stop position on a rod side by an external signal.

[Prior Art] It is widely practiced to attach a work piece or a working tool thereof to a piston rod of a pneumatic cylinder to convey or work the work piece. In order to cope with the recent high-mix low-volume production, it is possible to reset the piston stop position of the pneumatic cylinder with a stop position accuracy of about ± 0.1 to ± 0.05 mm in accordance with the production process each time the work is switched. It is done frequently.

For this reason, there is a strong demand for the practical application of a device capable of automatically and accurately adjusting the stop position of the pneumatic cylinder without using any human hands.

In order to change the stop position of the cylinder as described above, conventionally, a method of providing a mechanical stopper whose position can be changed outside or inside the pneumatic cylinder has been widely used (for example, JP-A-58-142072). See the bulletin). In such a method, by using a buffer mechanism together, ± 0.
A stop position accuracy of about 05 mm is relatively easy to obtain, but because the piston rod is made hollow and a complicated mechanism is provided on the rod side or head side cover of the cylinder tube, it is a commonly used buffer. The structure makes it difficult to attach a mechanism.

Then, without the buffer mechanism, the piston may collide with the mechanical stopper at a high speed, and after it rebounds, it may stop at a position apart from the mechanical stopper due to friction.
Therefore, in order to improve the accuracy of the stop position of the piston, the buffer mechanism is practically indispensable.

In addition, the current position of the piston rod is constantly detected electrically, and the drive adjuster is operated by the operation signal obtained by calculating the error from the target position by the position adjuster,
A method of controlling the position of the piston rod is also generally used, but in order to improve the stop position accuracy, not only a relatively expensive position detector and control device are required, but also the piston is operated at high speed. Since the stop position accuracy is reduced, more expensive control equipment or the like is required.

[Problem to be Solved by the Invention] The problem to be solved by the present invention is to provide a pneumatic cylinder having a shock absorbing mechanism in which the stop position of the piston on the rod side can be changed, and which has a shock absorbing mechanism to stop the piston. To do.

[Means for Solving the Problems] In order to solve the above problems, in a pneumatic cylinder with a cushioning mechanism of the present invention, a head block attached to a fixed portion, and the head block is airtightly inserted, and an axis line is attached to the fixed portion. A cylinder tube that is arranged so that its position can be adjusted in any direction, and a piston that slides inside the cylinder tube,
A piston rod that is attached to the piston and is airtightly drawn from a rod side cover that is integral with or separate from the cylinder tube, and a screw formed on the outer peripheral surface of the cylinder tube,
A moving mechanism that has a feed nut supported by a fixed portion and screwed into the screw, and a pulse motor that rotates the feed nut based on a signal from the outside, and moves the cylinder tube to a required position in the sliding direction of the piston. And a buffer mechanism that temporarily traps air discharged from the pressure chamber defined by the piston near the stroke end of the piston and buffer-stops the piston at the stroke end. .

[Operation] When the cylinder tube of the pneumatic cylinder is adjusted to the desired position by the moving mechanism and then the compressed air is supplied to and discharged from the cylinder, the piston has the same stroke start position on the head side and is set by the position of the cylinder tube. It is driven within the required stroke range, and is stopped at the end of the stroke by a shock-absorbing air pressure cushioning mechanism.

In this case, there are no members on the rod side cover and the piston side of the head block that require a particularly large space other than the supply / discharge ports, so it is possible to provide a shock absorbing mechanism for them and thereby drive the piston at high speed. The buffer mechanism can be stopped at an accurate stop position in a buffer manner.

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

The pneumatic cylinder according to the present invention makes it possible to change the piston stop position by an external signal, and particularly the rod side stop position.

FIG. 1 shows an embodiment of a pneumatic cylinder according to the present invention. In the figure, 1 is a fixed part to which a pneumatic cylinder is mounted, which is usually constituted by a part of an appropriate device to which a pneumatic cylinder is mounted, 2 is a head block mounted on the fixed part 1, 3 is the head block 2
Is a hermetically and slidably inserted cylinder tube arranged so that its position can be adjusted in the axial direction, 4 is a piston that slides in the cylinder tube 3, and 5 is a rod side cover that is integral with or separate from the tube 3. 3a shows a piston rod that hermetically penetrates 3a. The piston rod 5 can also be led out to the outside through the head block 2.
In order to simplify the drawing, the buffer mechanism for stopping the piston 4 in a buffer manner is omitted.

The cylinder tube 3 is arranged such that the head block 2 attached to the fixed portion 1 is slidably inserted therein, and a screw 6 is provided around the head block 2 and the fixed portion 1 is provided.
The guide rods 8 and 8 which are inserted in the are attached. The guide rods 8 and 8 are guided by the fixed portion 1 and prevent the cylinder tube 3 from rotating when the cylinder tube 3 moves in the axial direction.

A feed nut 10 is screwed onto the screw 6 around the cylinder tube 3. This feed nut 10 has a fixed part 1
It is supported by ball bearings 11 and 11 and cannot move in the axial direction of the cylinder tube 3 but can only rotate. Further, a gear 12 is formed on the outer circumference of the feed nut 10, and the gear 12 is meshed with a small gear 13 on a rotary shaft 15 of a pulse motor 14 mounted on the fixed portion 1, and the screw 6, The moving mechanism 9 is composed of the feed nut 10 and the pulse motor 14 for rotating the feed nut 10.

Therefore, the rotation of the pulse motor 14 causes the small gear 13 and the gear to rotate.
When the feed nut is rotated via 12, the cylinder tube 3 around which the screw 6 is provided moves forward or backward in the axial direction of the head block 2, and the rod side stop position of the piston 4 is set.

If necessary, a braking brake may be installed on the shaft of the pulse motor 14 to prevent the stop position of the cylinder tube 3 from being displaced due to a collision of the piston or a load force.

In addition, a protrusion 16 for setting the origin of the moving position of the cylinder tube 3 is provided in a part of the cylinder tube 3, and this protrusion 16 generates an electrical signal at the origin of the moving position of the cylinder tube 3. As described above, the origin position detector 17 including a switch or the like is appropriately provided on the fixed portion. The protrusion 16 may be provided on the guide rod 8 or the like.

The position detection accuracy of the origin position detector is important because it is directly related to the stop position accuracy of the piston 4 and needs to be highly accurate. Specifically, the movement amount corresponding to one step of the pulse motor (for example, 0.05 mm or less)
It is desirable to have the detection accuracy of
A signal that 16 has entered both regions near the origin (for example, a detection signal by a limit switch with a response difference of 1 to 2 mm) and a position detection signal of a specific tooth of the gear 12 on the outer periphery of the feed nut 10 screwed to the screw 6 ( It can be easily and highly accurately detected by a method such as a combination with a signal obtained by opening and closing a photoelectric switch through a small hole provided at the base of the tooth, but other appropriate configurations can be used.

Pressure air for driving the piston 4 is supplied to and discharged from the pressure chambers 18 and 19 on both sides of the piston 4 through pressure air supply and discharge ports 21 and 22. In this case, supply / discharge port on the rod side
21 is provided on the rod side cover 3a, and the head side supply / discharge port 22 is provided on the head block 2.

Therefore, since the cover 3a and the head block 2 do not have members other than the supply / discharge ports 21 and 22 which require a relatively large space, such as members for setting the stop position of the piston, The cover 3a and the head block 2 are provided with a cushioning mechanism for cushioning the piston by the containment air pressure as described below.

The buffer mechanism is generally used in a pneumatic cylinder, and an example thereof is shown in FIG. The pneumatic cylinder shown in the figure shows a case where the cushioning mechanism 24 is provided at both ends on the rod side and the head side in the cylinder tube 3, and the cover 3a and the head block 2 attached to the rod tube side end portion of the cylinder tube 3, The recessed holes 25 and 26 also functioning as the flow paths of the pressure air are provided in the axial direction, and the cushion packings 27 and 28 are attached to the inner peripheral surfaces of the recessed holes 25 and 26, and the cylinder tube 3
The cushion packing 2 is fitted into the recessed holes 25 and 26 at the stroke end of the piston 4 which is slidable inside.
Cushion rings 29, 30 that are in sliding contact with 7, 28 are attached. The pressure chambers 18 and 19 on both sides of the piston 4 and the supply and discharge ports 21 and 22 on the rod side and the head side are provided with the recessed holes 25 and 26.
Needle valve whose opening can be adjusted separately from the flow path
The bypass flow paths 31 and 32 having 33 and 34 are communicated with each other.

Therefore, when the piston 4 approaches the stroke end on the rod side, for example, the tip of the cushion ring 29 fits into the cushion packing 27, the internal pressure of the cylinder rises, and the piston is decelerated.

The drive pulse signal of the pulse motor 14 described above can be generated by an appropriate means. FIG. 3 shows an example of the signal generator.

In this signal generation unit, the signal conversion unit receives a piston stop position signal to be changed from a higher-order computer or the like, and a step of the pulse motor corresponding to the distance between the set point for stopping the cylinder tube 3 and the origin. Calculate the number and set it in the first counter. If the number of pulses corresponding to the above-mentioned number of steps is given as a signal from the host device, only the first counter need be provided.

On the other hand, the signal generator is provided with a second counter (addition / subtraction) which is reset by receiving the output signal of the origin position detector 17. This second counter counts and records the number of output pulses to the pulse motor 14 (the number of steps of the pulse motor), and the count number is compared with the count number of the first counter in the comparison control unit, The forward or backward drive pulse signal is output until the difference between the two count numbers becomes 0 corresponding to the positive or negative. In the second count, the forward pulse number is added and the backward pulse number is subtracted.

With such a configuration, the signal generator outputs the number of pulses corresponding to the position signal from the host device to the pulse motor 14.

If a drive signal is further sent to the pulse motor 14 when the cylinder tube 3 reaches the limit point for forward or reverse movement, the pulse motor may be damaged. It would be necessary to provide a limit switch for each of them, input these open / close signals to the drive signal generator, and stop the further output of the forward or reverse signals. Further, a torque limiter may be provided on the rotary shaft 15 of the pulse motor 14 to stop the output of the drive signal generator when the load on the pulse motor increases abnormally.

Further, when the above-mentioned braking brake is required for the rotating shaft 15 of the pulse motor 14, a function for controlling the braking brake in cooperation with the output of the drive signal is required.

In the pneumatic cylinder having the above structure, the cylinder tube 3 is assumed to be stopped at the origin position at the start of driving. The cylinder tube 3 may be manually moved to the origin position, but it is also easy to incorporate a sequencer in the signal generating unit to perform an automatic origin returning operation. In any case, the second signal of the signal generator is generated by the origin position signal.
The counter has been reset.

When the stop position signal is updated by a host device such as a computer and a forward signal is output from the signal generator, the pulse motor rotates in steps by a predetermined number of pulses. As a result, the feed nut 10 screwed into the screw 6 rotates corresponding to the gear ratio of the small gear 13 and the gear 12, the cylinder tube 3 starts to move forward, and the pulse motor stops when the drive signal stops. That is, the cylinder tube 3 stops at a position corresponding to the number of input pulses to the pulse motor from the origin, with an accuracy equivalent to one step of the pulse motor.

When the position of the cylinder tube 3 of the pneumatic cylinder is adjusted in this way, the piston is driven within the required range by the supply / discharge of the pressure air from the supply / discharge port to the pressure chamber of the cylinder, and the rod side cover and head of the cylinder tube are driven. By attaching the buffer mechanism 24 to the block, the piston can be stopped at an accurate stop position while being driven at high speed.

[Effect of the Invention] The pneumatic cylinder of the present invention is a moving mechanism having a screw on the outer peripheral surface of a cylinder tube, a feed nut, and a pulse motor, and drives the piston with a desired stroke by moving the cylinder tube to a set position. Therefore, it is not necessary to use an expensive device for controlling the position of the piston unlike the pneumatic servo mechanism, so that the structure can be made simple and inexpensive.

In addition, since the buffer mechanism of the piston is provided in the rod side cover and the head block having a space in the moving mechanism having the above structure, the accuracy of the stop position of the piston driven at high speed can be improved.

Furthermore, since the stroke of the piston is adjusted by the movement of the cylinder tube, the stroke can be adjusted when the stroke start position of the piston is constant.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of an embodiment of a pneumatic cylinder according to the present invention, FIG. 2 is a sectional view of a buffer mechanism for stopping a piston in a buffer manner, and FIG. 3 is a pulse motor in the pneumatic cylinder. FIG. 3 is a block configuration diagram of a signal generator that generates a drive pulse signal. 1 …… Fixed part, 2 …… Head block, 3 …… Cylinder tube, 3a …… Rod side cover, 4 …… Piston, 5 …… Piston rod, 6 …… Screw, 10 …… Feed nut, 14 …… Pulse motor, 24 ... Buffer mechanism.

Claims (1)

[Claims] 1. A head block 2 attached to a fixed portion 1, a cylinder tube 3 in which the head block 2 is airtightly inserted, and the position of which is adjustable in the axial direction with respect to the fixed portion 1, and the cylinder. A piston 4 that slides in the tube 3, a piston rod 5 that is airtightly drawn from a rod-side cover 3a that is integral with or separate from the cylinder tube 3 that is attached to the piston 4, and a piston rod 5 formed on the outer peripheral surface of the cylinder tube 3. It has a screw 6 provided, a feed nut 10 supported by the fixed portion 1 and screwed into the screw 6, and a pulse motor 14 for rotating the feed nut 10 based on a signal from the outside. Moving mechanism 9 for moving the piston 3 to a required position in the sliding direction, and the piston 3
And a buffer mechanism 24, 24 for temporarily trapping the air discharged from the pressure chambers 18, 19 partitioned by the step 3 near the stroke end of the piston 3 to stop the piston 3 at the stroke end in a buffer manner. A pneumatic cylinder with a cushioning mechanism whose stop position can be changed.