JPH0245523Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a drive device for a differential cylinder used in an industrial machine using pneumatic pressure.

[Conventional technology]

Generally, a differential cylinder with a thick rod is used as a cylinder that exerts a large acting force in only one direction. This differential cylinder has the advantage of significantly reducing air consumption, but because there is a large difference in the pressure receiving area of the head chamber and rod chamber of the piston, it is difficult to control. If this is done, the risk of sudden start cannot be suppressed, and if the drive is performed using meter-in control in an attempt to suppress this, the negative effects of step slip behavior and a significant delay in securing pressurizing force at the end of the drive stroke can be avoided. Can not.

To explain this based on the drawings, Figure 1 shows:
This shows an example of a drive device that drives a differential cylinder by meter-out control. In the above drive device, if the supply/discharge switching valve 2 is switched from the illustrated position by energization in order to drive the differential cylinder 1, A high-pressure air source 3 communicates with a head chamber 7 via a pressure reducing valve 4 for setting pressurizing pressure, a supply/discharge switching valve 2, and a check valve 6. through which it communicates with the atmosphere. As a result, the piston 10 and rod 11 in the differential cylinder 1 start to be driven in the direction of the arrow, but at the start of this movement, it is impossible to avoid so-called popping out as shown in FIG. 2A. In addition, in FIG. 1, 12 is a throttle, 13 is a check valve, and 14 is a
is a pressure reducing valve that sets the supply pressure for returning the differential cylinder 1, and P _h and P _r are the pressures in the head chamber 7 and rod chamber 8.

Further, FIG. 3 shows an example of a drive device that drives a differential cylinder by meter-in control. It is constructed by replacing the stop valves 6a and 13a.

In this drive device, when the supply/discharge switching valve 2 is switched from the illustrated position by energization, the high-pressure air source 3 communicates with the head chamber 7 via the pressure reducing valve 4, the supply/discharge switching valve 2, and the throttle 12. The rod chamber 8 communicates with the atmosphere via a check valve 13a and a supply/discharge switching valve 2.
As a result, the piston 10 and the rod 11 are driven in the direction of the arrow, but as shown in FIG. When the head chamber 7 is
The problem is that it takes a long time to increase the pressure to the required pressure shown in (1).

The above-mentioned stick slip phenomenon occurs because the piston 10 and rod 11 are driven by the pressurized air flowing into the head chamber 7, shaking off the static friction force between them and the inner surface of the cylinder. decreases and the force acting on the piston 10 becomes smaller than the frictional force between the piston 10 and the inner surface of the cylinder, the piston 10 stops again,
Further, when the acting force of the head chamber 7 increases to the extent that it can shake off the static friction force, it is re-driven and this occurs because this is repeated.
Particularly near the end of the drive stroke, since the volume of the head chamber 7 increases, the pressure in the head chamber 7 due to the pressure air flowing into the head chamber 7 through the throttle 12 increases slowly, and as a result, the above-mentioned stay slip The phenomenon becomes more likely to occur.

[Problem that the invention attempts to solve]

The present invention was developed in view of the above, and when driving a differential cylinder, high pressure air from a high pressure air source is introduced into the rod chamber with a small pressure receiving area in advance, and in that state, high pressure air is introduced into the rod chamber with a small pressure receiving area. High-pressure air is supplied from a high-pressure air source to the head chamber through a restrictor to prevent sudden starts and stick slips, and when the end of the drive stroke is reached, the high-pressure air in the rod chamber is exhausted and the head is The chamber is communicated with a high-pressure air source through a pressure reducing valve in place of the above-mentioned restrictor, thereby making it possible to increase the pressure in the head chamber to the necessary pressurizing pressure in a short time.
This is a problem that needs to be solved.

[Means to solve the problem]

The present invention provides a system between a high-pressure air source and a rod chamber of a differential cylinder in which a thick rod is connected to the piston. A selector valve that selects one of the throttle and pressure reducing valves connected in parallel between the high pressure air source and the head chamber of the differential cylinder. , connect the supply/exhaust switching valve that switches the head chamber between the selector valve and the atmosphere, and when the piston reaches the end of the drive stroke, connect the supply/exhaust switching valve on the rod chamber side to the atmosphere, and connect the selector valve to the atmosphere. The above problem is solved by providing switching means on the pressure reducing valve side.

[Effect]

With the supply/discharge switching valve on the rod chamber side communicating with the high pressure air source, switch the selector valve to the throttle side and switch the supply/discharge switching valve on the head chamber side to the selector valve side to connect the high pressure air source to the head chamber. When air flows in, the piston is driven by a large driving force that overcomes the air pressure applied to the rod chamber based on the difference in pressure receiving area between the head chamber and the rod chamber. In this case, the air flowing into the head chamber is kept at a constant flow rate by the restrictor, and while the piston is driving, constant pressure air is applied to the rod chamber as a load from a high-pressure air source, so as long as the load does not change. , the piston is driven at a constant speed.

Thus, driving the piston at a high pressure level, i.e., with high pressure air on both sides of the piston, will result in a lower pressure level, where the rod chamber is open to the atmosphere and there is no back pressure on the piston. Normally, the occurrence of the stick slip phenomenon is suppressed. This compresses the high-pressure air in the rod chamber as the piston moves, which suppresses the movement of the piston and prevents the piston from being driven with sudden speed changes. This is thought to be due to the fact that the inertial force of the piston is relatively small and has no effect, and as a result, the pressure in the head chamber does not drop drastically due to the movement of the piston.

When the piston reaches the end of its drive stroke, the supply/exhaust switching valve on the rod chamber side is switched to the atmosphere side to connect the rod chamber to the atmosphere, and the selector valve is switched to the pressure reducing valve side to reduce the pressure in the head chamber. A valve supplies pressurized air set to a predetermined pressure. As a result, a large amount of pressurized air is supplied to the head chamber, so the pressure in the head chamber can be quickly raised to the set pressure in a short period of time, compared to the previous case through a restriction that limited the supply amount. It is possible to obtain a strong pressing force.

Therefore, jump starting and the above-mentioned stay slip phenomenon during and at the end of the drive stroke are prevented.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. In FIG. 5 showing the first embodiment,
20 is a high-pressure air source, 21 is a differential cylinder driven by the same, a piston 22 having a large diameter rod is inserted into the differential cylinder 21, and rod chambers 23 are provided on both sides of the piston 22. A head chamber 24 is defined and a supply/discharge switching valve 25 is connected between the rod chamber 23 and the high-pressure air source 20 to allow the rod chamber 23 to communicate with the high-pressure air source 20 and the atmosphere in a switchable manner. ing.

The high pressure air source 20 also includes the supply/discharge switching valve 2.
A head side conduit 27 is connected in parallel with the rod side conduit 26 provided with Pressure reducing valve 29 for applying the necessary pressurizing force to the head chamber 24
are connected in parallel, and the throttle 28 is connected to one input port of the selector valve 31 via an inching valve 30 that shuts off the flow path by energization for inching the differential cylinder 21. The pressure reducing valve 29 is connected to the other input port of the selector valve 31. The selector valve 31 is
This is for selecting either the throttle 28 or the pressure reducing valve 29 to communicate with the head chamber 24. A supply/discharge switching valve 32 is connected between the selector valve 31 and the head chamber 24, and the selector valve 31 is connected to the head chamber 24. The selector valve 31
It is configured so that communication can be switched between the output port and the atmosphere.

Furthermore, the supply/discharge switching valve 25 and the selector valve 3
1 is provided with appropriate means for switching them to the atmosphere side and the pressure reducing valve 29 side, respectively, when the piston reaches the end of its drive stroke. This switching means can be easily realized using known techniques, such as using a limit switch that operates at the end of the stroke.

Next, the operation of the drive device having the above configuration will be explained.

First, in order to operate the differential cylinder 21, which is waiting at the original position shown in FIG. 5, to a full stroke in the direction of the arrow, as shown in FIG. and the supply/discharge switching valve 25 are respectively switched to the OFF state. Thereby, the high pressure air source 20 is communicated with the head chamber 24 via the throttle 28, the inching valve 30, the selector valve 31, and the supply/discharge switching valve 32, and high pressure air is supplied from the high pressure air source 20 to the head chamber 24, and the piston 2
2 makes a driving stroke (advance) in the direction of the arrow together with the rod 33. Since the rod chamber 23 communicates with the high pressure air source 20 via the supply/discharge switching valve 25, high pressure air from the high pressure air source 20 flows into the rod chamber 2.
Since the urging force of the high-pressure air is always acting on the piston 22 in the counter-stroke direction, it is possible to prevent the piston 22 from jumping out and starting. Furthermore, the driving force of the piston 22 that overcomes the biasing force acting in the opposite stroke direction is sufficiently larger than the frictional force generated between the movable part and the stationary part of the differential cylinder 21, so this large driving force causes the states to Scrip behavior can also be avoided.

On the other hand, since a constant load is applied to the drive stroke speed by the high pressure air supplied to the rod chamber 23, the drive stroke speed is maintained constant by the pressure air whose flow rate is controlled by the throttle 28, and By adjusting the opening amount, the stroke speed can be changed arbitrarily. moreover,
When the piston 22 reaches the end of its driving stroke, if the supply/exhaust switching valve 25 and selector valve 31 are turned on, the rod chamber 23 is communicated with the atmosphere, and the high pressure air therein is released to the atmosphere. As the pressure decreases, the high pressure air source 20 closes the pressure reducing valve 2.
9. Communicates with the head chamber 24 via the selector valve 31 and the supply/discharge switching valve 32, and connects the pressure reducing valve 2 to the head chamber 24.
The high pressure air whose pressure was set in step 9 is immediately supplied and discharged.
The pressure in the head chamber 24 can be increased to the required pressure in a short time. This pressurizing force can be increased or decreased by adjusting the pressure reducing valve 29. After that, differential cylinder 2
In order to make the return stroke (retreat) of the motor 1, it is sufficient to switch both the supply/discharge switching valves 25 and 32 to the OFF state, as shown in FIG. As a result, high-pressure air from the high-pressure air source 20 is supplied to the rod chamber 23, and high-pressure air in the head chamber 24 is released to the atmosphere, so that the piston 22 and rod 33 perform a return stroke and return to their original positions.

Furthermore, in order to inching feed the differential cylinder, as shown in FIG. 7, the inching valve 30 may be intermittently energized during the drive stroke. That is, when the inching valve 30 is de-energized, the drive stroke continues, but when the inching valve 30 is energized, the flow path from the throttle 28 to the selector valve 31 is blocked, and the differential cylinder 21
drive stroke stops. Therefore, if the inching valve 30 is repeatedly energized and de-energized, inching feed is performed in the differential cylinder 21. In this inching feed as well, similar to the drive stroke described above, jump start is prevented, and thereby the minimum value that can be used for inching feed can be set to be extremely small. Furthermore, by applying the above-mentioned inching feed, the differential cylinder can be stopped at any intermediate position during the drive stroke.

FIG. 8 shows a second embodiment of the present invention, in which a master valve 34 is provided between the selector valve 31 and the head chamber 24, which has the functions of the supply/discharge switching valve 32 and the inching valve 30 of the first embodiment. In addition, the inching valve 30 connected in series to the throttle 28 in the first embodiment is omitted, and the other structures are the same as in the first embodiment. Therefore, when one electromagnetic operating section 34a of the master valve 34 is energized, the head chamber 24 is switched from the neutral position in the cut-off state to the first switching position where the head chamber 24 communicates with the atmosphere, and the other electromagnetic operating section 34b is energized. For example, the head chamber 24 and the selector valve 31 are switched to the second switching position where they communicate with each other.

In the differential cylinder drive device having the above configuration,
To perform a full stroke operation, as shown in FIG.
1 is turned off, and the supply/exhaust switching valve 25 is turned on, whereby the high-pressure air source 20 is switched to the throttle 28,
It communicates with the head chamber 24 via the selector valve 31 and the master valve 34, and the rod chamber 23 also communicates with the high pressure air source 20 via the supply/discharge switching valve 25.
As in the embodiment, the piston 22 makes a driving stroke in the direction of the arrow. At the end of the drive stroke, if the selector valve 31 is turned on and the supply/exhaust switching valve 25 is turned off, the rod chamber 23 is evacuated, and the head chamber 24 is supplied with the pressure reducing valve 29 via the selector valve 31 and the mask valve 34. High-pressure air with a set pressure is supplied, and the piston 22 can be urged with a required pressure. After this, the piston 2
2 to the original position, turn on the supply/discharge switching valve 25 and turn on the electromagnetic operation parts 34a, 34b of the master valve 34.
This causes the rod chamber 23 to be supplied with high pressure air from the high pressure air source 20, and the head chamber 24 to be evacuated, causing the piston 22 to make a return stroke and return to its original position. To perform inching feed, as shown in FIG. 10, during the full stroke operation, the energization to the electromagnetic operating section 34b of the master valve 34 is intermittently stopped, and the master valve 34 is moved to the second switching position. It is only necessary to alternately switch from the position to the neutral position. As a result, the differential cylinder 21 is operated by the second electromagnetic operating section 34b
Inching feed is performed in which a drive stroke is performed when energization is applied, and the stroke is stopped when energization is stopped.

FIG. 11 is a diagram showing the results of an experiment conducted under the following conditions in the first embodiment, with no load applied during the drive stroke of the piston and a pressurizing force generated at the end of the drive stroke. It is.

Differential cylinder 21: Tube diameter 94mmφ Rod diameter 80mmφ Piston pressure receiving area ratio between rod side and head side 1:3.7 Stroke 132mm Supply/discharge switching valves 25, 32, selector valve 31, inching valve 30: Effective cross-sectional area S = 3.2mm ^2Head chamber 24, rod chamber 23 and supply/discharge switching valve 2
5, 32 piping: Nylon tube φ 6/4
300 mm Supply pressure: 5 Kgf/cm ² Setting pressurizing force of pressure reducing valve 29: 4 Kgf/cm ² The throttle was set at an opening that would provide the speed represented by the piston stroke diagram shown in FIG. 11.

From the results of the above experiment, the following was confirmed.

(1) Can maintain a medium stroke speed (30 mm/s) (a).

(2) No popping out when starting (b).

(3) Despite the low speed of less than 100mm/s,
Smooth feeding is possible.

(4) The time required to establish pressure at the end of the drive stroke can be shortened (c).

[Effect of idea]

According to the differential cylinder drive device of the present invention, the rod chamber with a small pressure-receiving area in the piston is communicated with a high-pressure air source to apply an opposite biasing force to the piston, and in this state, the rod chamber with a small pressure-receiving area is made to communicate with the high-pressure air source. By supplying high-pressure air from a high-pressure air source to the large head chamber through the restrictor, it is possible to reliably prevent the piston from jumping out due to the opposite biasing force acting on the piston. The force acting on the piston that overcomes the biasing force in the opposite direction is sufficiently larger than the frictional force generated in the differential cylinder.
Furthermore, since the piston is not driven rapidly due to the high pressure air in the rod chamber, the stick slip phenomenon can also be avoided.

Furthermore, at the end of the drive stroke, pressurized air with a preset pressure is supplied to the head chamber by a pressure reducing valve, so the pressure in the head chamber can be brought to the desired pressurizing pressure in an extremely short period of time, regardless of the opening amount of the throttle. By increasing the pressure, it is possible to avoid the stick slip phenomenon at the end of the drive stroke, and most of the high pressure air in the rod chamber can be returned to the high pressure air source, that is, the rod chamber, significantly reducing air consumption. can do.

[Brief explanation of drawings]

Figures 1 and 3 are block diagrams of conventional differential cylinder drive devices, Figures 2 and 4 are diagrams showing experimental results using those devices, and Figure 5 is a first embodiment of the present invention. , FIG. 6 and FIG. 7 are diagrams explaining its operation, FIG. 8 is a diagram explaining the construction of the second embodiment of the present invention, and FIGS. 9 and 10 are diagrams explaining its operation. , FIG. 11 is a diagram showing the experimental results according to the first example. 20... High pressure air source, 21... Differential cylinder,
22... Piston, 23... Rod chamber, 24...
Head chamber, 25, 32... Supply/exhaust switching valve, 28...
Throttle, 29... pressure reducing valve, 31... selector valve.

Claims (1)

[Scope of utility model registration request] Between the high-pressure air source and the rod chamber of the differential cylinder, which has a thick rod connected to the piston, during the driving stroke of the piston, the rod chamber is used as the high-pressure air source.
At the end of the driving stroke of the piston, a supply/exhaust switching valve is connected to connect the rod chamber to the atmosphere, and a throttle and pressure reducing valve are connected in parallel between the high pressure air source and the head chamber of the differential cylinder. A selector valve that selects one of the pressure reducing valves and a supply/discharge switching valve that switches the head chamber between the selector valve and the atmosphere are connected, and when the piston reaches the end of the drive stroke, the supply/discharge switching valve on the rod chamber side is connected. A drive device for a differential cylinder, comprising means for switching the selector valve to the atmosphere side and the selector valve to the pressure reducing valve side.