JPH0245522Y2 - - 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. In this case, the risk of sudden start cannot be prevented, and if meter-in control is used to prevent this, it is impossible to avoid the negative effects of stake slip behavior and a large delay in securing pressurizing force at the end of the stroke.

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 begin to be driven in the direction of the arrow, but at the start of this movement, so-called pop-out cannot be avoided, 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 Ph and Pr 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 this happens, there is a problem in that it takes a long time to increase the pressure in the head chamber 7 to the necessary pressure shown in FIG.

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 from a high-pressure air source is supplied to the head chamber at the required pressure via an electro-pneumatic control valve, thereby preventing jump starting and stake slip. The problem to be solved is to increase the pressure in the head chamber to the required pressure in a short time by exhausting the air and increasing the amount of current applied to the solenoid of the electro-pneumatic control valve.

[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. At the same time, a supply/exhaust switching valve is connected between the high-pressure air source and the head chamber of the differential cylinder to open the head chamber to the atmosphere when the amount of energization to the solenoid is small. When the amount of electricity increases, an electro-pneumatic control valve is connected that applies an output pressure from a high-pressure air source to the head chamber according to the amount of energization, and when the piston reaches the end of its drive stroke, the supply/exhaust switching valve is switched to the atmospheric side. Along with switching,
The above problem has been solved by providing means for increasing the amount of current applied to the solenoid of the electropneumatic control valve to an extent that can generate the required pressing force on the piston rod.

[Effect]

With the supply/discharge switching valve connected to the high pressure air source,
When a predetermined value of current is supplied to the solenoid of the electro-pneumatic control valve, high-pressure air from the high-pressure air source flows into the head chamber at a pressure corresponding to the supplied current value, so the piston is applied in the opposite direction from the rod chamber side. It is driven by a large driving force that overcomes the biasing force.

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 is switched to the atmospheric side and the amount of current applied to the solenoid of the electro-pneumatic control valve increases.
While the pressure in the rod chamber drops rapidly, the head chamber is supplied with air whose pressure has been increased due to the increase in the amount of current supplied, so that the pressure in the head chamber quickly rises to the desired air pressure. Therefore, the necessary pressing force can be obtained in a short time.

By changing the amount of current applied to the solenoid of the electro-pneumatic control valve during the drive stroke of the piston, the stroke of the piston can be adjusted to an appropriate speed.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail based on the drawings. In FIG. A piston 22 having a rod of is fitted and inserted to define a rod chamber 23 and a head chamber 24 on both sides of the piston 22,
A supply/discharge switching valve 25 is connected between the rod chamber 23 and the high-pressure air source 20 to connect the rod chamber 23 to the high-pressure air source 20 and the atmosphere, and between the head chamber 24 and the high-pressure air source 20. electro pneumatic control valve 26
are connected. The electro-pneumatic control valve 26 is attracted to the fixed iron core with a suction force proportional to the amount of current applied to the solenoid, as shown in, for example, Japanese Utility Model Application Publications No. 56-32209 and No. 56-41309. Equipped with a movable iron core, the secondary pressure is fed back to the displacement of the 3-way valve driven by the movable iron core to obtain a secondary pressure proportional to the amount of current, and the supplied current value is small. In case head chamber 2
4 is exposed to the atmosphere and the supply current value increases,
An output pressure corresponding to the current value is applied from the high-pressure air source 20 to the head chamber 24. Note that between the electropneumatic control valve 26 and the head chamber 24, as shown by broken lines in the figure, there are connected variable throttles 28 that are parallel to each other and a check valve 29 that allows outflow from the head chamber side. In that case, the flow rate to the head chamber 24 of the differential cylinder can be made constant by the variable throttle 28, so that when the load applied to the piston 22 is constant while the piston 22 is being driven, , the drive stroke speed of the piston 22 can be made more reliable. Further, by providing the check valve 29 in parallel with the variable throttle 28, the variable throttle 28 does not become an obstacle to the quick return of the piston 22 during its return stroke.

Furthermore, the supply/discharge switching valve 25 and the electro-pneumatic control valve 2
6, when the piston reaches the end of its drive stroke, the supply/exhaust switching valve 25 is switched to the atmosphere side, and the amount of current applied to the solenoid of the electro-pneumatic control valve 26 is changed to generate a required pressing force against the piston rod. Appropriate means are attached to increase the amount to a certain extent. This switching means operates the supply/discharge switching valve 2 by the operation of the limit switch at the end of the drive stroke.
5 and increasing the amount of current supplied to the solenoid of the electropneumatic control valve 26 to a set value.

In order to perform a full stroke operation with the differential cylinder drive device configured as described above, as shown in FIG. An electro-pneumatic control valve 26 supplies a constant value of current to communicate the high-pressure air source 20 with the rod chamber 23 of the differential cylinder 21 via the supply/discharge switching valve 25, and opens the high-pressure air source 20 in a limited manner. It communicates with the head chamber 24 via. As a result, high-pressure air whose pressure is set to a constant value is supplied to the head chamber 24 from the high-pressure air source 20, so that the piston 22 in the differential cylinder 21 moves forward along with the rod 27 in the direction of the arrow. Therefore, high pressure air from the high pressure air source 20 is also supplied to the rod chamber 23, which has a small pressure receiving area in the piston 22, and the piston 22
Since a biasing force acting in the counter-stroke direction is constantly acting on the piston, there is no sudden start during the drive stroke, and the driving force of the piston that overcomes the biasing force acting in the counter-stroke direction is the differential cylinder. This large driving force does not cause stick-slip behavior because it is sufficiently larger than the frictional force generated between the movable part and the stationary part.

Furthermore, even when stroking at a low speed of 100 mm/s or less, the stroke can be performed smoothly and at a constant speed. Note that the stroke speed in the drive stroke described above can be easily adjusted by changing the amount of current applied to the solenoid of the electropneumatic control valve 26, and the adjustment is also possible during the stroke.

Thereafter, when the piston 22 and the rod 27 reach the end of the drive stroke, the internal pressure of the head chamber 24 is increased to the desired pressure and the piston 22 and the rod 27 are energized by the pressure. What is necessary is to switch the exhaust switching valve 25 to the on state and increase the amount of current supplied to the solenoid of the electropneumatic control valve 26.
As a result, the high pressure air in the rod chamber 23 is released to the atmosphere, and the pressure in the head chamber 23 is increased to the desired pressurizing pressure in a short time in accordance with the increase in the amount of electricity supplied to the electropneumatic control valve 26. As a result, the piston 22 and rod 27 can be biased with the desired pressure.
This pressurizing force can be easily adjusted by changing the amount of current applied to the solenoid of the electropneumatic control valve 26. In addition, in the above drive stroke,
Most of the high-pressure air discharged from the rod chamber 23 is returned to the high-pressure air source 20, and only a very small amount of high-pressure air is released to the atmosphere at the end of the drive stroke, so air consumption can be significantly reduced.

In order to return the piston 22 and rod 27 in the differential cylinder 21 to the original position shown in FIG. 5 (retreat), as shown in FIG. The amount of current applied to the solenoid of the control valve 26 is reduced.
As a result, the head chamber 24 communicates with the atmosphere via the electro-pneumatic control valve 26 and releases high-pressure air to the atmosphere, and the rod chamber 23 communicates with the high-pressure air source 20 via the supply/discharge switching valve 25, causing the piston 22 is rod 2
7, it makes a return stroke and returns to its original position.

In addition, in order to perform inching feed in the above drive device, as shown in FIG.
At the same time, a constant value of current is supplied to the electro-pneumatic control valve 26 to perform stroke operation (feeding), and in the middle of the stroke operation, the current value applied to the electro-pneumatic control valve 26 is slightly decreased, and the electro-pneumatic control valve 26 is The output pressure of the control valve 26 may be set to a lower acting force balance pressure than before. This causes the forces acting on the piston 22 on both sides of the piston 22 to balance each other and the piston 22 to stop its drive stroke. Therefore, inching feed is possible by alternately applying a constant value for constant speed drive and a slightly lower constant value for stopping as the current supplied to the solenoid of the electropneumatic control valve 26. . Then,
Even during inching feed, the restraining force of the high-pressure air applied to the rod chamber 23 prevents jump starting, and thereby enables inching feed in extremely small amounts. In addition, as in the case of inching feed, the electro-pneumatic control valve 2 is closed during the drive stroke.
If the current value supplied to solenoid 6 is lowered,
Piston 22 and rod 27 can be stopped at any intermediate position.

[Effect of idea]

According to the drive device of the present invention, high-pressure air is introduced into the rod chamber of the piston, which has a small pressure-receiving area, to constantly apply a biasing force to the piston, and in this state, high-pressure air is supplied to the head chamber of the piston, which has a large pressure-receiving area. Since the drive stroke is made in opposition to the biasing force mentioned above, it is possible to avoid the piston from jumping out due to the biasing force in the opposite direction acting on the piston, and the piston can overcome this biasing force in the opposite direction. Since the driving force is sufficiently larger than the frictional force generated in the differential cylinder, this large driving force can also avoid stick slip behavior and enable smooth feeding even at low speeds.

In addition, high-pressure air is supplied to the head chamber through an electro-pneumatic proportional valve that can set the output pressure according to the increase or decrease in the amount of current applied to the solenoid, so the amount of current applied to the electro-pneumatic control valve can be adjusted. By doing this, not only can the speed of the drive stroke be set arbitrarily, but also the speed can be changed freely during the stroke by simply adjusting the amount of energization, and inching feed and stopping at intermediate positions are also possible. .

Furthermore, at the end of the drive stroke, the supply/exhaust switching valve is switched to the state where it communicates with the atmosphere, and the air pressure flowing into the head chamber is increased by the electro-pneumatic control valve, so that the pressure in the head chamber can be adjusted to the required level in a short period of time. The pressurizing force can be increased to obtain the desired pressurizing force, and since the high-pressure air discharged from the rod chamber during the drive stroke is returned to the high-pressure air source, air consumption can be significantly reduced. You can also do it.

[Brief explanation of the drawing]

1 and 3 are configuration diagrams of conventional differential cylinder drive devices, FIGS. 2 and 4 are diagrams showing experimental results using those devices, and FIG. 5 is a configuration of an embodiment of the present invention. 6 and 7 are diagrams explaining the operation. 20... High pressure air source, 21... Differential cylinder,
23... Rod room, 24... Head room, 25...
Supply/discharge switching valve, 26...electro-pneumatic control valve, 27...rod.

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 valve is connected between the high pressure air source and the head chamber of the differential cylinder if the amount of current to the solenoid is small. The head chamber is opened to the atmosphere, and an electro-pneumatic control valve is connected that applies output pressure to the head chamber from a high-pressure air source as the amount of current increases. A differential cylinder characterized by being provided with means for switching the supply/exhaust switching valve to the atmosphere side and increasing the amount of current applied to the solenoid of the electropneumatic control valve to an extent capable of generating a required pressing force on the piston rod. drive unit.