JP2771852B2 - Detection method of piston dropout of magnet type rodless cylinder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present application relates to a method for detecting a piston disengagement of a magnet type rodless cylinder (hereinafter, referred to as a magnet cylinder), and reliably detects a piston disengagement to prevent a trouble caused by the piston disengagement. It is something you want to do.

2. Description of the Related Art Conventional cylinders having a piston rod, which has been used for a long time, have a spatial problem that requires an installation space at least twice the stroke. Cylinders are widely used. As is well known, the rodless cylinder employs two types, a slit tube type and a magnet type in the present application, and the magnet type has major features such as preventing air leakage, It also has the following problems.

The magnet cylinder mutually attracts the inner magnet array arranged in the cylinder tube in a predetermined order and the outer magnet array arranged in the same order as the above so as to surround the cylinder tube outside the cylinder tube by magnetic force. The outer magnet row is moved by moving the inner magnet row by air pressure, and the slider performs a reciprocating motion of a predetermined stroke.The two magnet rows are physically connected but mechanically. No binding has taken place. Therefore, even if the performance of the magnet is significantly improved, the safety factor is 1.2 for the maximum value of the coupling force of both magnet rows, that is, the holding force (thrust).
It can be set only up to 2 times, and the conventional rod type cylinder is extremely low compared to the slit tube type which is 50 to 200 times 10 to 15 times. The piston may be disturbed in response.

As a countermeasure against the piston coming off, the user who uses a magnet cylinder takes measures such as reducing the applied load to less than the rated value or limiting or adjusting the air pressure and speed (especially at the start). It is difficult to completely prevent it. If the piston comes off, the holding force suddenly drops and the predetermined stroke cannot be obtained.If left unattended, various troubles will occur, especially in the case of unmanned automated lines. It is necessary to detect this as soon as possible and restore it to the old one.

Means for Solving the Problems The present application is intended to detect piston disengagement in which no countermeasure has been taken so far, and an inner moving body magnetically coupled to each other by a magnet array in which a plurality of magnets are arranged in the axial direction. In a magnet type rodless cylinder comprising a moving body and an outer moving body, when the piston is disengaged and the correspondence between the inner moving body and the outer moving body is disturbed, the leakage magnetic force from the magnet array leaking outside due to the disturbance of the correspondence. The sensor detects the magnetic force of the portion where is stronger than the normal value, and detects the piston disengagement by this detection signal. As is apparent from the above, the method of the present invention inevitably occurs in the magnet cylinder and causes loss. This is a method in which the leakage magnetic force is positively used, and detection is performed based on whether the leakage magnetic force is a normal value or stronger.

Examples Hereinafter, the present application will be described in detail with reference to the drawings showing examples. In FIG. 1, reference numeral 1 denotes a magnet cylinder 2 which is an inner magnet row and has four donut-shaped magnets 3.
Are alternately fitted to the piston shaft 5 with the yoke 4, and are fastened and fixed by the piston 6 to form an inner moving body 7, which is inserted into a cylinder tube 8 made of a non-magnetic material (such as stainless steel). The magnet poles of the respective magnets 3 are arranged as shown in FIG.
S, SN, NS and the same poles are arranged so as to correspond to each other. Next, reference numeral 9 denotes an outer magnet row, which is provided on the inner peripheral surface of a slider 10 made of an aluminum alloy and fitted to the cylinder tube 8. Similarly to the inner magnet row 2, four magnets 3 are fitted alternately with the yoke 4 so as to surround the inner magnet row 2, and the wear ring holder 11.
The outer moving body 13 is formed by being fastened and fixed by the scraper holder 12 and the magnetic poles of the magnet row 9 correspond to the same poles. NS, SN, NS,
The inner and outer moving bodies 7 and 13 are physically connected to each other by being arranged with the SN and attracting the two magnet rows 2 and 9 to each other. Therefore, when compressed air is alternately supplied into the cylinder tube 8 from the port 15 provided in the end cap 14, the inner moving body 7 reciprocates in the cylinder tube 8, and the outer moving body 13 reciprocates by this reciprocating movement.

It is conventionally known that in the magnet cylinder 1 configured as described above, a leakage magnetic force G in which the magnetic force of the magnet 3 leaks outside due to the slider 10 is generated. Since the leakage magnetic force G is lost without any involvement in the work, a test and research is conducted to reduce the loss as much as possible and to improve the performance.
And the following results were obtained.

As shown in FIG. 1, in a normal state where the inner magnet row 2 and the outer magnet row 9 face each other,
The strength of the magnetic force leaking from the magnets 3 at the right and left ends is much higher than the strength of the magnetic force leaking from the two magnets 3 in the middle part and is almost twice as large. As shown in the figure, G1 is strong at both ends and G2 is weak at the middle. Naturally, the strength (Gauss) of the magnetic force that leaks depends on the performance size of the magnet 3, etc.
Leaking with the waveform of G2 is always consistent. Further, when the number of magnets 3 is set to be more than 2, 3, or 4 and the measurement is carried out, first, in the case of 2 magnets, two waveforms of G1 are detected without detecting G2, and in the case of 3 or many magnets, G1 is detected at both left and right ends, and all middle parts are G2. From the above results, in a normal state where the inner magnet row 2 and the outer magnet row 9 face each other, the slider 10
The strength of the leakage magnetic force G leaking from the magnet indicates that both ends are strong at G1 and the middle portion is weak at G2 regardless of the number of magnets 3. In the case of two magnets 3, G2 is naturally not detected because there is no middle part. However, since each of the two magnets 3 leaks the magnetic force of G1, the arrangement of the magnets 3 in this case is such that both ends have no middle part. It is only an array.

Next, as shown in FIG. 2, when the inner moving body 7 is moved rightward without facing the inner and outer magnet rows 2 and 9, and the correspondence between the two magnet rows 7 and 9 is shifted by one step. That is, when the piston is forcibly removed and the leakage magnetic force G in this case is measured, the result is as follows. In the drawing, two magnets 3 are displaced, but when the inner moving body 7 is moved and one magnet 3 is displaced, the correspondence of the magnetic poles between the two magnet rows 2 and 9 becomes the same. Since the two act as a companion, a repulsive force acts between the two and the state is automatically changed to the state shown in the figure. Therefore, a one-step displacement in the magnet cylinder 1 is a displacement of two magnets 3. When the leakage magnetic force G when the one-step correspondence is deviated is measured and illustrated, as shown in FIG. 2, the waveform has the same tendency as that in the above-described normal state, as shown in FIG. However, the correspondence with the inner magnet row 2 was removed,
The leakage magnetic force G from the magnet 3 on the left end is much stronger than G3, which is G1, while the magnet 3 on the right end is G1. In addition, as shown in FIG. 3, when the two magnet rows 2 and 9 are disassociated and the piston is completely removed, both ends are G3. This phenomenon is the same even when the number of magnets 3 is two or more (in this case, both are G3) or more than three, and G3 is the same and is stronger than the normal value.

From the above facts, the strength of the leakage magnetic force G leaking from the slider 10 in the magnet cylinder 1 is
Regardless of whether or not the outer magnet rows 2 and 9 face each other, the magnets 3 at both ends are strong and the middle part is weak. However, if the correspondence is disturbed and the pistons come out of the state where they do not face each other, the leakage magnetic force G when facing each other
The normal values of G1, G2, G2, and G1, whereas G3, G2, and G1,
2, G1 or G3, G2, G2, G3, and the leakage magnetic force G leaking from the non-corresponding end becomes G3 higher than the normal value G1,
This phenomenon does not change regardless of external factors such as the size or shape of the magnet 3.

The present application relates to the above described leakage magnetic force G of the magnet cylinder 1.
Pays attention to the characteristics of
Only the magnetic force of G3 is detected by the sensor 16 to detect the piston disengagement.
A description will be given of the attachment. As shown in FIG. 1, the sensor 16 is fitted on a sensor rail 17 mounted so as to bridge between the end caps 14 on both sides, and the highest sensitivity level H is
When the slider 10 reaches the stroke end, the sliders 10 are positioned so as to respectively correspond to the substantially centers C of the magnets 3 at both ends of the two magnet rows 2 and 9. As described above, the sensor 16 does not detect the normal value of the leakage magnetic force G, that is, does not detect the magnetic force within the normal value range indicated by L in FIGS. Since only the magnetic force within the strong magnetic field LA that is stronger than the normal value shown in FIG.
There is a certain limit to this distance, depending on the position at which it is mounted. This distance is obtained by actual measurement as follows.

For the actual measurement, the magnet cylinder 1 having the inner diameter of the cylinder tube 8 of 16 mm and the outer diameter of the outer magnet row 9 of 25 mm is used. The actual measurement point is indicated by a point P in FIG. is there. As shown in the drawing, the slider 10 has a square upper part and a lower circular part. However, the dimensions are such that a square part is circumscribed to a circular part of 30φ. All of the arc portions have a thickness of 2.5 mm.

First, with the magnet rows 2 and 9 facing each other, the sensor 16 is directly installed at the actual measurement point P (with no gap) to detect the leakage magnetic force G, and naturally, G1, G2, G2,
When all of G1 are detected, the lamp 16a of the sensor 16 lights up four times to generate a detection signal. Next, when a detection is performed with a gap of 2 mm, the detection signal is emitted only twice, and only G1 on both sides is detected. After that, if the gear gap is increased and the detection is continued, two detection signals are issued up to 5 mm, but 5.5 times.
mm, the detection signal is not output, and from this result G1
The upper limit of the normal value range L in which is can be measured is 5 mm, but these numerical values change depending on conditions such as the performance of the magnet 3 and the sensor 16 and are not absolute.

Next, as shown in FIG. 3, when the two magnet rows 2 and 9 are disassociated and the piston is completely removed, that is, when the magnetic force of G3 which is stronger than the normal value is leaked, the actual measurement is as follows. When the gap is 0, four detection signals are naturally transmitted, and all magnetic forces of G3, G2, G2, and G3 are detected. After that, if the gap is increased and the gap becomes 2.5 mm, only two signals will be emitted, only G3 on the left and right sides higher than the normal value will be detected, and then G3 will be detected until 9 mm, but it will not be detectable with more gaps Become. From the above results, the range in which only G3 can be detected without detecting the magnetic force of G2 has a lower limit of 2.5 mm from the surface of the slider 10 and an upper limit of 9 mm. In the case of partial piston disengagement as shown in the figure, the normal value G1 that the rightmost magnet 3 leaks must not be detected.
1. The reason for satisfying the condition of detecting only G3 without detecting G2 is as follows, considering the actual measurement results in FIG.
The lower limit is 5 mm and the upper limit is 9 mm, and this range is the strong magnetic field LA that satisfies the conditions. Therefore, in this embodiment, the distance is set to 6 mm in order to prevent malfunction, the distance X from the side of the slider 10 to the sensor 16 is 6 mm, and the thickness X1 of the slider 10 is 2.5 mm as described above, as shown in FIG. Therefore, the total distance from the outer periphery of the outer magnet row 9 to the sensor 16 is set to 8.5 mm, and as described above,
When the slider 10 reaches the stroke end of each of the right and left, the center C of the magnet 3 at the side end of the outer magnet row 9 is positioned so as to correspond to the highest sensitivity position C of the sensor 16 and is fixedly fastened to the sensor rail 17. . 18 in the figure
It is an inclusion for preventing damage to the sensor 16 when tightening and fixing, and is made of rubber and a stainless steel plate.

As described above, in the present embodiment, the sensor 16 is attached to the sensor rail 17 bridged between the end caps 14 with the above-described fixed positional relationship, and the sensor 16 is mounted when the two magnet rows 2 and 9 face each other. G1, G2, G2, G1 of the normal value of the leakage magnetic force G leaked to the outer is not detected when the piston is disengaged and the correspondence of both magnet rows 2 and 9 is disturbed. Since only the G3 that is stronger than the normal value G1 at which the magnet 3 at the end of the magnet array 9 leaks is detected, if the piston comes off, the piston is surely detected at least during one reciprocation of the slider 10 and the sensor 16 is detected. The lamp 16a is turned on, and a signal is sent to a control mechanism (not shown) to stop the operation. In the drawing, the sensors 16 are mounted at the respective stroke ends on the left and right sides, but the mounting position of one sensor 16 can be freely changed as necessary, such as the intermediate position of the sensor rail 17.

Next, the embodiment shown in FIG. 5 will be described. In this embodiment, the sensor 16 is fixedly mounted on the sensor rail 17 bridged between the end caps 14 in the first embodiment, but in this embodiment, the sensor rail 17 is directly mounted on the side wall of the slider 10. The sensor is mounted on the sensor rail 17 so as to satisfy the mounting conditions of the first embodiment.
In this embodiment, the sensor 16 moves together with the slider 10, and the sensor 16 always corresponds to the magnets 3 at both ends of the outer magnet row 9, so that when the piston comes off, it is immediately detected. It has the advantages that it can.

Effect of the Invention As described in detail above, in spite of being a magnet cylinder having a low safety factor that is likely to mechanically cause piston disengagement, the present invention has been applied to detecting a piston disengagement that has not taken any measures conventionally. Focusing on the characteristics of the leakage magnetic force, which is a loss of magnetic force, without actively participating in the original operation of the magnet cylinder, and actively utilizing this characteristic, the part where the leakage magnetic force becomes stronger than the normal value due to the piston coming off Since only the magnetic force is detected to detect piston disengagement,
In carrying out the method of the present invention, it is possible to use a conventional product as it is without mounting any machining work on the magnet cylinder itself only by mounting the sensor at a position satisfying a certain mounting condition, and it is extremely simple and inexpensive. The present invention is an essential invention that reliably detects a piston disengagement, prevents malfunction, and prevents any trouble caused by the piston disengagement.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of the present invention, FIG. 1 is a front view in which main parts are cut away, FIG. 2 is a partial front view showing a state where a piston is partially removed, and FIG. 3 is a state where a piston is completely removed. FIG. 4 is a right side view of FIG. 1, and FIG. 5 is another embodiment. 1 ... Magnet rodless cylinder, 2 ... Inner magnet row, 3 ... Magnet, 7 ... Inner moving body, 9 ... Outer magnet row, 10 ... Slider,
13 ... Outside moving body, 16 ... Sensor, G ... Leakage magnetic force,
L: Normal range, LA: Strong magnetic field

Claims (1)

(57) [Claims] In a magnet type rodless cylinder including an inner moving body and an outer moving body magnetically coupled to each other by a magnet row in which a plurality of magnets are juxtaposed in the axial direction, a piston dropout occurs, When the correspondence between the moving body and the outer moving body is disturbed, the sensor detects the magnetic force of the part where the leakage magnetic force from the magnet array leaking outside due to the disturbance of the correspondence becomes stronger than the normal value, and detects the piston detachment. Detection method of piston dropout of magnet type rodless cylinder.