JPS6011285Y2 - Stroke end detection device for piston in cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting whether a piston has reached a stroke end in a double-acting hydraulic cylinder.

In a mechanical system that drives some device or mechanism (load) using an air cylinder or hydraulic cylinder, etc., each load is It may be necessary to interlock operations.

This is because if this is not applied, there is a risk that the previous operation and the subsequent operation will interfere with each other in the load.

Conventionally, the end of the operation has been detected by activating a limit switch (LS), a proximity switch, or the like by a load.

However, in this case, it is necessary to arrange a member for holding the LS etc. around the load and to attach an actuator for operating the LS.

As a result, the mechanical structure of the position detection means becomes complicated.
Also, it becomes troublesome to manage the electrical wiring.

Furthermore, if the selection and mounting method of the actuator, LS, etc. is incorrect, the LS will be damaged in a short period of time, causing a malfunction of the machine.

The purpose of the present invention is to provide a device that can detect the end of a piston's stroke in order to eliminate the above-mentioned problems by detecting the end of a load operation not on the load side but on the cylinder side. This was done as a.

A feature of the present invention is a fluid pressure cylinder that reciprocates the piston by alternately supplying pressure fluid from main ports provided at both ends of the cylinder so as to communicate with cylinder chambers on both sides of the piston. A detection port that can be closed by the piston or a member that moves integrally with the piston is attached to one end, and the detection port is connected to a conduit connected to the main port at the other end of the cylinder. In the detection pipe, there is a control valve that prevents the passage of pressure fluid below the pressure required to operate the cylinder but allows passage of pressure fluid exceeding the pressure required for operation, and a control valve that detects and detects pressure above a set value. a pressure switch that emits a signal;
A check valve for blocking the flow of pressure fluid from the detection port toward the main port is provided directly in the above order, and when the control valve allows passage of the pressure fluid, the detection port is set to the set pressure of the pressure switch. The reason for this is that the detection signal is not emitted if it is open, and the detection signal is emitted if it is closed.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

This is an example in which the present invention is applied to a gun cylinder for resistance welding.

The air cylinder 20 shown in FIG. 1 consists of a cylindrical cylinder tube 1, a head cover 2 and a rod cover 3 that cover both openings of the cylinder tube, a piston rod 4, and a piston 6 that slides inside the tube 1 fixed to the tip of the cylinder tube 1. Cylinder chambers 9 and 10 are formed on both sides of the piston.

The head cover 2 includes a recess 7 in the center, and a main port 8 and a detection port 11 at opposing positions on the periphery.

Of these, the main port 8 is open to the inner circumferential surface of the recess 7, while the detection port 11 is open to the inner end surface of the helad cover 2.

A recess 12 is similarly formed in the center of the rod cover 3, and a main port 13 opens on the inner peripheral surface thereof.

The piston rod 4 extends through the rod cover 3, and the piston 6 is fastened to the small diameter portion of the piston rod 4 by a nut 18 together with buffer members 16 and 17 on both sides.
Fixed.

A ring-shaped urethane rubber seal member 19 is attached to the rear end surface (the right end surface in FIG. 1) of the piston 6 so as to face the opening of the detection port 11.

Although a detailed explanation will be omitted, O-rings, U-rings, etc. are provided in areas where airtightness is required.

An air circuit as shown in FIG. 2 is connected to the air cylinder 20.

Pipe lines 32 and 31 connected to the main ports 8 and 13, respectively, are connected to an air supply device 34 and a tank 36 via a four-boat, two-position switching valve 3.

Further, the detection port 11 is connected to the pipeline 31 by a detection pipeline 37, and this detection pipeline 37 has an IJ
An IJ-F valve 41 (control valve), a pressure switch 42, and a check valve 43 are connected in series in this order from the branch point side.

Both the relief valve 41 and the pressure switch 42 are known.

Therefore, although a detailed explanation will be omitted, the operating pressure P2 of the relief valve 41 is made somewhat smaller than the pressure P1 generated by the air supply device 34, as shown in FIG. has also been made slightly smaller.

The check valve 43 is also of a known type, and is installed in a direction that prevents air from flowing from the detection port 11 toward the main port 13.

Although the resistance welding machine is not shown, the tip of the piston rod 4 is connected to a movable electrode, and the movable electrode is moved toward and away from the fixed electrode by reciprocating the piston 6.

Next, the operation of this embodiment will be explained.

When welding is completed, the switching valve 33 is switched to the I side, air is supplied from the pipe line 31 and the main port 13 to the left cylinder chamber 9, and the piston 6 retreats (moves to the right in FIG. 2).

At this time, the pressure in the cylinder chamber 9, conduit 31, etc. gradually increases as the piston 6 retreats, as shown by curve A in FIG.

On the other hand, the pressure in the cylinder chamber 10 is approximately zero (atmospheric pressure).

The piston 6 reaches the retraction end (return end) with
The pressure in the pipe line 31, etc., which can no longer be retreated, increases more rapidly than before and becomes equal to the pressure P1 generated by the air supply device 34.

At this time, when the pressure in the pipe line 31 etc. becomes higher than the operating pressure P2 of the relief valve 41, it opens, and the air passes through the check valve 43 and passes through the detection pipe line 37 to the detection port 11.
will be supplied.

However, at this point, the detection port 11 is closed by the seal member 19, so the pressure in the detection pipe 37 etc. is curved B.
As shown in , the pressure rises extremely rapidly and becomes equal to the pressure P2.

At this time, when the pressure becomes higher than the pressure P3, the pressure switch 42 is activated and a detection signal indicating that the piston 6 has reached the return end is issued.

When this detection signal is issued, the piston of another air cylinder (not shown) arranged in parallel with this air cylinder 20 is moved forward.

On the other hand, when the piston 6 stops at an intermediate position for some reason (for example, the movable electrode is welded to the object to be welded), the operation is as follows.

At this time, the pressure changes as shown by the two-dot chain line C in FIG. 3 from the time when the pressure piston 6 of the pipe 31 etc. stops, and the relief valve 41 opens, so that the air passes through the detection pipe 37 and reaches the detection port 11. That doesn't change.

However, since the detection port 11 is open and air is supplied from there into the cylinder chamber 10, the pressure in the detection conduit 37 does not rise much as shown by the chain double-dashed line in FIG.

Therefore, the pressure switch 42 is not activated and the detection signal is not generated, so the other air cylinder installed in parallel is not activated.

Note that if the switching valve 33 is switched to the ■ side, the air supplied from the pipe line 32 through the main port 8 into the cylinder chamber 10 will flow back from the detection port 11 into the detection pipe line 37. Since the pressure switch 42 is blocked by the check valve 43, the pressure switch 42 does not operate, and the forward movement of the piston 6 is not hindered in any way.

In this way, in this embodiment, whether or not the movable electrode of the welding machine has reached the retreating end is determined by the air cylinder 20, which is the driving source.
Since the determination is made by detecting the return end of the piston 6 on the welding machine side, it is no longer necessary to provide any position detection device on the welding machine side.

This simplifies the entire detection device, makes it easy to route the electrical wiring, and almost never causes a failure.

In particular, when many gun cylinders advance sequentially to perform multi-point welding, such as in a welding machine on an unmanned line, there is a risk of machine damage if the piston does not return completely due to welding tips welding to the workpiece, etc. There is a sex, but
According to this example, this problem is resolved.

It should be noted that the above-mentioned is only one embodiment of the present invention, and it goes without saying that the present invention can be modified and improved in other ways without departing from the spirit thereof.

For example, a pilot check valve or the like may be used as the control valve instead of the relief valve 41 described above.

In short, it is only necessary to prevent the passage of pressure fluid below the pressure required to operate the cylinder, but allow the passage of pressure fluid exceeding this pressure.

Hydraulic oil can also be used as the pressure fluid.

In addition, the operating pressures P2 and P3 of the control valves (relief valve 41 etc.) and pressure switches and the pressure generator (air supply device 3)
4, etc.), it is not essential that the generated pressure P1 be in the above-mentioned relationship.

In short, it is sufficient that the set pressure of the pressure switch is selected so that when the control valve allows pressure fluid to pass through, if the detection boat is open, it will not issue a detection signal, but if it is blocked, it will issue a detection signal. That's why.

That is, the pressures P2 and P3 may be considerably smaller than P□, or P3 may be larger than P2.

Furthermore, the cylinder can be used for various purposes other than the gun cylinder of a welding machine, and depending on its use, it may be used to detect the extrusion end (forward end) rather than the return end. You can also do that.

As detailed above, according to the stroke end detection device according to the present invention, there is no need to provide any position detection means on the load side, and the overall structure is simplified.
This makes it easier to route electrical wiring and further reduces mechanical failures.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing one embodiment of the present invention, FIG. 2 is a pneumatic circuit diagram connected to the above embodiment, and FIG. 3 is a pressure change diagram in the above embodiment. 1... Cylinder tube, 2... Head cover 3... Rod cover, 4...
・Piston rod, 6...Piston, 9.10
... Cylinder chamber, 8.13 ... Main port, 11 ... Detection port, 19 ... Seal member, 20 ... Air cylinder, 31.32
...Pipeline, 34...Air supply device, 3
7...Detection pipe line, 41...IJ IJ
-Fu valve, (control valve) 42...Pressure switch, 4
3...Check valve.

Claims (1)

[Claims for Utility Model Registration] A fluid pressure cylinder that reciprocates the piston by alternately supplying pressure fluid from main ports provided at both ends of the cylinder so as to communicate with cylinder chambers on both sides of the piston. The device is a device for detecting whether or not the cylinder has reached its stroke end, in which a detection port that can be closed by the piston or a member that moves integrally with the piston is attached to one end of the cylinder, and In a detection pipe line connecting the main port of the cylinder and the detection port, a pressure fluid having a pressure lower than the pressure required for operation of the cylinder is prevented from passing through, but a pressure fluid exceeding the pressure required for operation is prevented from passing through. A control valve that allows passage, a pressure switch that detects pressure equal to or higher than the set value and issues a detection signal, and a check valve that blocks the flow of pressure fluid from the detection port toward the main port are connected in series in the above order. and set the pressure of the pressure switch so that when the control valve allows passage of pressure fluid, the detection signal will not be emitted if the detection port is open, and the detection signal will be emitted if the detection port is closed. A piston and stroke end detection device in a cylinder characterized by the following features: