JP2598754Y2 - Piston position detector - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston position detecting device, and more particularly, to a piston position detecting device for detecting a position of a piston sliding in a pneumatic cylinder.

[0002]

2. Description of the Related Art Conventionally, in an assembling robot for assembling a work to a device, the work is transferred to a mounting position of the device by a pneumatic cylinder.

In the assembly robot, a position of a piston sliding inside the pneumatic cylinder is detected by a magnetic detection sensor attached to an outer peripheral portion of the pneumatic cylinder, and this piston position detection signal is output to a sequencer. The sequencer determines whether or not the work is positioned at the mounting position based on the position detection signal, and outputs the next operation signal to the assembly robot based on the determination result.

In this case, the magnetic detection sensor for detecting the piston position usually detects the strength of the magnetic field generated by the magnet in a direction parallel to the sliding direction of the piston (hereinafter referred to as the strength of the magnetic field in the parallel direction). The piston position detection signal provided by the single magnetic detection sensor is arranged as shown in FIG.
Becomes

In a pneumatic cylinder to which such a magnetic detection sensor is attached, for example, when a tire is transferred to a hub of a vehicle and positioned, a stop position of a piston is determined by a piston because the work is an elastic body. (See period T in FIG. 8), the piston position detection signal, which once became low, becomes a high voltage (see FIG. 8 (a)), which may cause a malfunction of the sequencer. Become.

Therefore, another magnetic detection sensor is disposed so as to partially overlap the piston detection range of the above-described magnetic detection sensor (see FIG. 8B), and the logical sum of the output signals of the respective magnetic detection sensors is provided. By using the output as a piston position detection signal (see FIG. 8 (C)), a method is used in which the piston position detection range is extended and the piston position detection signal is not turned off even if the stop position of the piston is unstable. ing.

On the other hand, a method of preventing a malfunction of a sequencer by electrically holding a rise of a piston position detection signal output from a magnetic detection sensor for a predetermined time has been used.

[0008]

However, in the above-described method of holding the piston position detection signal output from the switch in the prior art electrically for a predetermined time, the transferred signal is not the actual piston position detection signal. When the piston slides beyond the set range due to troubles such as dropping of the work inside, there is a disadvantage that the position of the piston cannot be correctly detected.

On the other hand, in the method of disposing a plurality of magnetic detection sensors, a large number of magnetic detection sensors must be attached in order to secure a desired detection range, resulting in an increase in product manufacturing cost. There is.

The present invention has been made to solve such a problem, and provides a piston position detecting device capable of reliably and widely detecting the position of a piston sliding in a pneumatic cylinder. The purpose is to:

[0011]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a piston which slides in a pneumatic cylinder by compressed air, and a straight line connecting magnetic poles to a sliding direction of the piston. A piston position detection device that detects a position of the piston based on the strength of a magnetic field generated by the magnet, the piston position detection device being attached to an outer periphery of a cylindrical portion of the pneumatic cylinder, and a sliding direction of the piston. A first magnetic detection sensor for detecting the strength of the magnetic field generated by the magnet, and an outer periphery of a cylindrical portion of the pneumatic cylinder and mounted on the same circumference as the first magnetic detection sensor. A second magnetic detection sensor for detecting the strength of a magnetic field generated by the magnet in a direction perpendicular to the sliding direction of the piston, and a detection magnetic field output from the first magnetic detection sensor. corresponding to First comparing means for comparing the signal with a preset set value, and comparing a signal corresponding to the strength of the detected magnetic field output from the second magnetic detection sensor with a preset set value. A second comparing means, a signal indicating a comparison result output from the first comparing means, and the second comparing means;
Output means for outputting a detection signal of the piston position based on a logical sum signal of a signal indicating a comparison result output from the comparison means.

In a second aspect of the present invention, a magnet is mounted on a piston which slides in a pneumatic cylinder by compressed air so that a straight line connecting the magnetic poles is in the sliding direction of the piston. A piston position detecting device that detects the position of the piston based on the outer periphery of a cylinder portion of the pneumatic cylinder, and is disposed at a predetermined distance in a sliding direction of the piston, A plurality of magnetic detection sensors for detecting the strength of the magnetic field generated by the magnet in a direction perpendicular to the sliding direction; and a signal corresponding to the strength of the detection magnetic field output from each of the magnetic detection sensors and preset. A plurality of comparing means for comparing the respective set values with each other, and a detection signal of the piston position based on a logical sum signal of the signals indicating the comparison results output from the respective comparing means. Characterized in that it comprises a power means.

[0013]

According to a first aspect of the present invention, the strength of a magnetic field generated in a sliding direction of a piston mounted on a magnet by a magnet mounted on the piston is detected by a first magnetic detection mounted on an outer periphery of a cylindrical portion of a pneumatic cylinder. A signal corresponding to the strength of the detected magnetic field and a set value are compared by a first comparing means. On the other hand, the intensity of the magnetic field generated by the magnet in a direction perpendicular to the sliding direction of the piston is determined by a second magnetic detection sensor attached on the same circumference as the first magnetic detection sensor. A signal corresponding to the strength of the detected magnetic field is compared with a set value by a second comparing means.
The output means outputs a piston position detection signal based on the logical sum signal of the comparison result signal output from the comparison means and the comparison result signal output from the first comparison means.

At this time, the signal corresponding to the strength of the magnetic field output from the first magnetic detection sensor has a peak value when the piston reaches directly below the first magnetic detection sensor, while the second signal has a peak value. The signal output from the magnetic detection sensor has a peak value at two positions where the piston is separated by a predetermined distance from immediately below the second magnetic detection sensor, and when the piston reaches the vicinity immediately below the second magnetic detection sensor. By obtaining the logical sum signal of these signals, the piston position is determined by the second magnetic detection sensor when the piston is separated by a predetermined distance from immediately below the first and second magnetic detection sensors. When the detection is performed, the piston position can be detected by the first magnetic detection sensor when the piston is located immediately below each magnetic detection sensor.

Further, in the second invention, the strength of a magnetic field generated by the magnet mounted on a piston sliding in the pneumatic cylinder in a direction perpendicular to the sliding direction of the piston is determined by the pneumatic The outer periphery of the cylinder portion of the cylinder, and is detected by a plurality of magnetic detection sensors arranged at a predetermined distance in the sliding direction of the piston, the magnetic field generated by the magnets output from the respective magnetic detection sensors A signal corresponding to the strength is compared with respective preset values by respective comparing means, and a piston position detection signal is generated based on a logical sum signal of a comparison result signal output from the respective comparing means. Is output by the output means.

In this case, when the piston is separated by a predetermined distance from immediately below the magnetic detection sensor, the piston position is detected by the predetermined magnetic detection sensor. When the piston is located immediately below the predetermined magnetic detection sensor, another piston is detected. The piston position can be detected by the magnetic detection sensor.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the piston position detecting device according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the structure of a piston position detecting device 10 used in the first embodiment of the present invention.

The piston position detecting device 10 is mounted on the same circumference on the outer peripheral portion of the cylinder of the pneumatic cylinder 12 and detects the strength of the magnetic field by the magnet 16 fixed to the piston 14 in an annular shape. Magnetic detection sensors 18 and 20 that output a voltage based on the strength of the magnetic field, and a detection circuit 22 that detects a piston position based on the voltage output from the magnetic detection sensors 18 and 20 include: The detected piston position signal is output to the sequencer 24.

Since the magnetic detection surface of the magnetic detection sensor 18 is provided so as to be perpendicular to the sliding direction of the piston 14, the magnetic detection sensor 18 moves in a direction parallel to the sliding direction of the piston 14. The strength of the magnetic field generated by the magnet 16, that is, the strength of the parallel magnetic field is detected (FIG. 2).
(See FIG. 2A), the voltage V ₁ output from the magnetic detection sensor 18 becomes maximum when the piston 14 reaches just below the magnetic detection sensor 18 (see FIG. 2B).

On the other hand, since the magnetic detection surface of the magnetic detection sensor 20 is disposed so as to be parallel to the sliding direction of the piston 14, the magnetic detection sensor 20
4 (hereinafter, referred to as a vertical magnetic field strength) generated by the magnet 16 in a direction perpendicular to the sliding direction (see FIG. 3A), and is output from the magnetic detection sensor 20. The voltage V ₂ is determined by the piston 14 when the magnetic detection sensor 2
When it reaches just below 0, it becomes smaller, and when the magnet 16 reaches a predetermined position immediately before and after the magnetic detection sensor 20, it becomes a peak value (see FIG. 3B).

The piston 14 has a piston rod 26
A fluid passage 28 (the other is not shown) is connected to two chambers separated by the piston 14.

FIG. 4 shows an electric circuit of the detection circuit 22.

The detection circuit 22 compares a voltage V ₁ corresponding to the position of the piston 14 output from the magnetic detection sensor 18 with a preset voltage V _R1.
And a diode 32 for blocking a current flowing into the output terminal of the comparison circuit 30, a voltage V ₂ corresponding to the position of the piston 14 output from the magnetic detection sensor 20, and a preset voltage V _R2. A comparison circuit 34, a diode 36 for blocking a current flowing into an output terminal of the comparison circuit 34, and the comparison circuit 30 or the comparison circuit 34.
And an indicator 38 which is turned on by a position detection signal of the piston 14 output from the control circuit. The diodes 32 and 36 constitute a logical sum circuit of the output voltage V _O1 of the comparison circuit 30 and the output voltage V _O2 of the comparison circuit 34. I do.

Further, the detecting circuit 22 includes the comparing circuit 3
0 or when a position detection signal of the piston 14 is output from the comparison circuit 34, the position detection signal is
4. A transistor 40 as an output means for outputting to the
And the collector terminal of the open-collector transistor 40 is connected to the input terminal of the sequencer 24.
The transistor 40 has a base resistor 42 and a bias resistor 4
4 are connected.

The operation of detecting the position of the piston 14 in the piston position detection circuit 10 configured as described above will be described.

The piston 14 starts moving in the direction of arrow G in FIG. 1 under the action of compressed air supplied from a compressed air supply source (not shown) to the cylinder chamber 46 via the pipe 28, and the piston 14 is moved to the position L1 in FIG. When reached, larger becomes the voltage V ₂ is set voltage V _R2 corresponding to the intensity of the vertical magnetic field by the magnet 16 which is output from the magnetic sensor 20, the output voltage V _O2 of the comparator circuit 34 and the voltage "H" (Fig. 5
(See (1)). This voltage “H” causes the transistor 4
0 is conducted between the collector and the emitter, and the collector voltage V
_S becomes the voltage “L”, and a signal indicating that the piston 14 has reached the predetermined position is output to the sequencer 24.

At this time, the display 38 is turned on by the voltage "H" output from the comparison circuit 34, and the piston 14
Indicates that has reached the predetermined position.

Next, when the piston 14 reaches the position L2 in FIG. 2, the voltage V ₁ corresponding to the strength of the horizontal magnetic field of the magnet 16 output from the magnetic detection sensor 18 becomes the set voltage V _R1.
The output voltage V _O1 of the comparison circuit 30 becomes the voltage “H” (see FIG. 5B).
Between the collector and the emitter is continuously conducted by the voltage “H” output from the comparison circuit 34, and thus the collector-emitter is controlled by the voltage “H” output from the comparison circuit 30.
The state of conduction between the emitters does not change.

Further, when the piston 14 reaches the position L3 in FIG. 3, the output voltage V _O2 of the comparison circuit 34 becomes “L” (see FIG. 5 (3)). _{Since O1} is at the voltage “H”, the transistor 40
Continuity between the collector and the emitter is continued.

Next, the piston 14 is
8 and 20 and reaches the position L4 in FIG. 3, the output voltage V _O2 of the comparison circuit 34 becomes the voltage “H” again (see FIG. 5 (4)), and the piston 14 is moved to the position L4 in FIG.
Even when the output voltage V _O1 of the comparison circuit 30 reaches the voltage “L” after reaching the position 5 (see FIG. 5 (5)), the output voltage V _O2 of the comparison circuit 34 is the voltage “H”.
The conduction state between the collector and the emitter of 0 is maintained.

Further, when the piston 14 reaches the position L6 in FIG. 3 and the output voltage V _O2 of the comparison circuit 34 becomes “L” (see FIG. 5 (6)), the collector and the emitter of the transistor 40 are cut off. You.

As described above, in the first embodiment, the magnetic detection sensor 18 detects the strength of the horizontal magnetic field of the magnet 16 and the magnetic detection sensor 20 detects the strength of the vertical magnetic field of the magnet 16. Te, by obtaining a logical sum of the strength of these magnetic fields, FIG period T ₁ can detect the piston 14 in the range of positions of L1 to L6, magnetic detection for detecting the intensity of the horizontal magnetic field As compared with the conventional method using two sensors, the position detection range of the piston 14 can be extended.

Next, a second step for detecting the position of the piston 14 is described.
An example will be described.

FIG. 6 shows the structure of the piston position detecting device 50 used in the second embodiment of the present invention.

In the following description, the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

The detection circuit 50 includes the magnetic detection sensors 20 and 52 mounted on the pneumatic cylinder 12 and the detection circuit 2.
2 and a sequencer 24, and the magnetic detection sensors 20 and 52 detect the strength of the vertical magnetic field generated by the magnet 16 (see FIG. 3). Further, the magnetic detection sensors 20 and 5
Reference numeral 2 is provided on the outer peripheral portion of the pneumatic cylinder 12 at a predetermined distance.

In this case, the magnetic detection sensors 20 and 52
The magnetic detection sensor 52 detects the piston 14 when the piston 14 is at the position shown in FIGS. 3L3 to L4 with respect to the arrangement position of the magnetic detection sensor 20, while the piston 14 is at the arrangement position of the magnetic detection sensor 52. 3L3 to L4, the magnetic detection sensor 20 is disposed so as to detect the piston 14.

The voltage V output from the magnetic detection sensor 52
₁ is output to the comparison circuit 30 constituting the detection circuit 22, while the voltage V ₂ output from the magnetic detection sensor 20 is output to the comparison circuit 34.

The operation of detecting the position of the piston 14 sliding inside the pneumatic cylinder 12 by the piston position detecting device 50 configured as described above will be described with reference to the timing chart of FIG.

The piston 14 moves in the direction of arrow G in FIG. 1 under the action of the compressed air supplied to the cylinder chamber 46 via the pipe 28, and reaches a predetermined position and is output from the magnetic detection sensor 52. When voltages V ₁ becomes larger than the set voltage V _R1 that is output voltage "H" from the comparator circuit 30 (see FIG. 7 (7)), between the collector and emitter of the transistor 40 becomes conductive by the voltage "H" (Fig. 7
(8)).

Further, when the piston 14 reaches the next predetermined position and the voltage V ₂ output from the magnetic detection sensor 20 becomes larger than the set voltage V _R2 , the output voltage V
_O2 becomes the voltage “H” (see FIG. 7 (9)). At this time,
Since the collector-emitter of the transistor 40 is already conducting by the output voltage V _O1 of the comparison circuit 30, the conduction state between the collector and the emitter does not change by the output voltage V _O2 of the comparison circuit.

Next, as the piston 14 moves, the output voltage V _O1 of the comparison circuit 30 becomes “L”, the output voltage V _O1 of the comparison circuit 30 becomes “H”, and the output voltage V _O2 is the voltage “L”, and the output voltage V _{O2 of the} comparison circuit 34 is
Is the voltage “H”, the output voltage V _O1 of the comparison circuit 30 becomes the voltage “L”, and further, the output voltage V _O2 of the comparison circuit 34 becomes the voltage “L” (FIGS. 7 (10) to (15)). )), The conduction state between the collector and the emitter of the transistor 40 continues.

As described above, in the second embodiment, the magnetic detection sensors 20 and 52 for detecting the strength of the magnetic field in the vertical direction are arranged at a predetermined distance from each other, so that the period T _{2 in} FIG.
The position of the piston 14 can be detected, and the position detection range of the piston 14 can be extended as compared with the conventional method using two magnetic detection sensors for detecting the strength of the horizontal magnetic field.

As described above, according to the present embodiment,
A magnetic detection sensor 18 for detecting the strength of a parallel magnetic field and a magnetic detection sensor 20 for detecting the strength of a vertical magnetic field, or a magnetic detection sensor 20 for detecting the strength of a vertical magnetic field
And 52, the position of the piston 14 is detected over a wider range than in the case where the position of the piston 14 is detected by combining a conventional magnetic detection sensor that detects the strength of a parallel magnetic field. The position can be detected.

In this embodiment, the case where two magnetic detection sensors are combined has been described as an example. However, by providing a plurality of magnetic detection sensors for detecting the strength of the vertical magnetic field, the piston 14 It is possible to further extend the position detection range.

[0047]

In the piston position detecting device according to the present invention, the output signal has a peak value at two positions where the piston is separated by a predetermined distance from immediately below the magnetic detection sensor, and the piston reaches the vicinity immediately below the magnetic detection sensor. Then, the piston position is detected by a magnetic detection sensor that becomes an output signal of a small value, and the piston that has reached the vicinity immediately below the magnetic detection sensor is detected by another magnetic detection sensor, and the OR signal of these detection signals is detected. By expanding the position detection range of the piston compared with the conventional case where the detection range is overlapped with a magnetic detection sensor that can output a peak value when the piston reaches directly below Is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a piston position detecting device used in a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an operation of a magnetic detection sensor for detecting the strength of a magnetic field generated by the magnet in a direction parallel to a straight line connecting the magnetic poles of the magnet.

FIG. 3 is a diagram for explaining an operation of a magnetic detection sensor that detects the strength of a magnetic field generated by the magnet in a direction perpendicular to a straight line connecting the magnetic poles of the magnet.

FIG. 4 is a diagram showing a configuration of a detection circuit in the first embodiment shown in FIG.

FIG. 5 is a timing chart for explaining a relationship between each magnetic detection sensor and a conduction state between a collector and an emitter of a transistor in the first embodiment shown in FIG. 1;

FIG. 6 is a diagram showing a configuration of a piston position detecting device used in a second embodiment of the present invention.

FIG. 7 is a timing chart for explaining a relationship between each magnetic detection sensor and a conduction state between a collector and an emitter of a transistor in the second embodiment shown in FIG. 6;

FIG. 8 is a timing chart illustrating a piston position detection method in a conventional example.

[Explanation of symbols]

10, 50: Piston position detecting device 12: Pneumatic cylinder 14: Piston 16: Magnet 18, 20, 52: Magnetic detection sensor 22: Detection circuit 24: Sequencer 30, 34: Comparison circuit 32, 36: Diode 40: Transistor

Claims (2)

(57) [Scope of request for utility model registration] A piston which slides in a pneumatic cylinder with compressed air is provided with a magnet whose straight line connecting the magnetic poles is in the sliding direction of the piston, and the piston is moved based on the strength of the magnetic field by the magnet. A piston position detection device for detecting a position, wherein the first magnetic detection sensor is attached to an outer periphery of a cylindrical portion of the pneumatic cylinder, and detects a strength of a magnetic field generated by the magnet in a sliding direction of the piston. A magnetic field generated by the magnet, which is attached to the outer circumference of the cylindrical portion of the pneumatic cylinder and on the same circumference as the first magnetic detection sensor, and is generated in a direction perpendicular to the sliding direction of the piston. A second magnetic detection sensor for detecting the strength of the first magnetic detection sensor, and a first comparing means for comparing a signal corresponding to the strength of the detection magnetic field output from the first magnetic detection sensor with a preset set value When, A second comparison unit that compares a signal corresponding to the strength of the detection magnetic field output from the second magnetic detection sensor with a preset value, and a comparison result output from the first comparison unit Output means for outputting a detection signal of the piston position based on a logical sum signal of a signal indicating the comparison result and a signal indicating the comparison result output from the second comparison means. . 2. A piston which slides in a pneumatic cylinder by compressed air and has a magnet whose straight line connecting the magnetic poles is in the sliding direction of the piston, and the piston is moved based on the strength of the magnetic field by the magnet. A piston position detection device for detecting a position, which is disposed on an outer periphery of a cylindrical portion of the pneumatic cylinder and is separated from the piston by a predetermined distance in a sliding direction of the piston, and is disposed with respect to a sliding direction of the piston. A plurality of magnetic detection sensors for detecting the strength of the magnetic field generated by the magnet in a vertical direction; signals corresponding to the strengths of the detection magnetic fields output from the respective magnetic detection sensors and respective preset values And a plurality of comparing means for comparing the two, and an output means for outputting a detection signal of the piston position based on a logical sum signal of signals indicating the comparison results output from the respective comparing means. A piston position detecting device characterized by the above-mentioned.