JPH0716103U - Piston position detector for fluid pressure cylinder - Google Patents

Abstract

(57) [Abstract] [Purpose] The position of the piston is detected without malfunction even if either the external DC magnetic field or the external AC magnetic field acts on the piston position detecting device. The hold circuit 13 outputs an ON signal when the first sensor S1 is turned on while the second sensor S2 is turned off, and outputs an off signal as an output signal F when the second sensor S2 is turned off. When the second sensor S2 changes from off to on, the hold circuit 13 outputs an on / off output signal F corresponding to the on / off state of the first sensor S1 in the state before the change. Furthermore, when the output signal from the first sensor S1 changes while the second sensor S2 is on, the second sensor S2 outputs an off signal and then outputs corresponding to the on / off state after the change. The hold circuit 13 outputs the signal F.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a piston position detecting device for a fluid pressure cylinder for detecting the position of a piston that reciprocates in the cylinder by fluid pressure such as air pressure or hydraulic pressure.

[0002]

[Prior art]

 In order to detect the position of the piston that is reciprocally mounted in the pneumatic cylinder, a piston position detection sensor for a fluid pressure cylinder is attached to the cylinder to detect the magnetic field generated by the permanent magnet attached to the piston. The device is being used.

Since a pneumatic cylinder having such a piston position detecting device is used in a manufacturing plant for manufacturing various industrial equipment, a permanent cylinder provided in another manufacturing device around the pneumatic cylinder is used. The magnets may approach the pneumatic cylinders, or wire cables for powering other manufacturing equipment may be placed adjacent to the pneumatic cylinders.

In such a case, the magnetic field of the permanent magnet or the magnetic field generated by the current flowing through the electric wire cable may affect the sensor and cause the sensor to malfunction. Therefore, conventionally, a piston position detecting device as described in Japanese Utility Model Publication No. 5-15042 has been developed.

In order to prevent the sensor from malfunctioning due to an alternating magnetic field generated by a current flowing through an electric wire cable, that is, an external magnetic field that changes periodically, this device sets the sensitivity of an external sensor for detecting the external magnetic field to that of the piston. It is set higher than the sensitivity of a piston sensor that detects the magnetic field of a permanent magnet.

[0006]

[Problems to be Solved by the Invention] In order to provide the two sensors with a difference in sensitivity in this way, the piston sensor is arranged inside the shield, which only complicates the structure for mounting the sensor on the cylinder. However, depending on how the external magnetic field is applied, the sensitivities of the two sensors may be reversed and malfunction may occur.

Further, in the piston position detecting device described in the above publication, it is not possible to prevent malfunction of the sensor when a DC magnetic field having a constant magnetic field intensity is affected.

An object of the present invention is to use either an AC magnetic field in which a magnetic field applied from outside changes periodically as a disturbance or a DC magnetic field in which a magnetic field does not change periodically acts as a disturbance. In this case, the piston position should be detected without malfunction.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0010]

[Means for Solving the Problems]

 The following is a brief description of the outline of the typical invention disclosed in the present application.

That is, the on / off signal from the piston magnetic field detecting means for detecting the magnetic field of the magnetic field generating member provided on the piston is output via the on-delay means and the first off-delay means to detect an external magnetic field. The magnetic field detecting means is output via the second off delay means. These output signals are input to the hold circuit, and when the external magnetic field detecting means does not detect the external magnetic field, the hold circuit outputs an on / off output signal by a signal based on the piston magnetic field detecting means.

Since the ON signal of the external magnetic field detecting means and the ON signal of the piston magnetic field detecting means are not simultaneously input to the hold circuit, when the signal via the delay circuit is input to the hold circuit, the hold circuit is turned off. The signal of is output. On the other hand, if no ON signal is input at the same time, the hold circuit outputs an ON / OFF output signal corresponding to the ON / OFF state of the piston magnetic field detection unit before the ON signal from the external magnetic field detection unit is input. .

[0013]

[Action]

 According to the present invention having the above-mentioned configuration, the signal from the first off-delay means for simultaneously outputting the on-signal from the piston magnetic field detecting means and the signal from the on-delay means for delaying the output and the external magnetic field detecting means. It is possible to detect whether or not the external magnetic field has acted on the basis of the signal output from the sensor at the same time as the detection.

Further, when it is detected that the external magnetic field acts, the hold circuit outputs an on / off signal corresponding to the on / off state of the piston magnetic field detecting means, so that the piston magnetic field is not affected by the external magnetic field. The detection result of the detection means is held, and malfunction of the piston magnetic field detection means is prevented.

As the external magnetic field that can be detected, not only an AC magnetic field whose magnetic force changes periodically, but also a DC magnetic field that does not change periodically can be prevented from malfunctioning.

[0016]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a view showing a case in which the piston position detecting device of the present invention is installed to detect the position of a piston provided in a pneumatic cylinder. In a pneumatic cylinder 1, a piston 2 reciprocates by air pressure. It is mounted so that it can move freely. A permanent magnet 3 as a magnetic field generating member is mounted in the groove formed on the outer peripheral portion of the piston 2.

The detection device for detecting the position of the piston 2 has a casing 4, and a sensor substrate 5 is provided in the casing 4. A first sensor for detecting the magnetic field of the permanent magnet, that is, a piston position detection sensor S1 is mounted on the sensor substrate 5 as the piston position detection means S1 so as to be positioned on the cylinder 1 side, and the cylinder 1 is located farther from the cylinder 1 than the first sensor S1. The second sensor, that is, the external magnetic field detection sensor S2 is attached as a external magnetic field detection means at a remote position.

FIG. 2 is a block diagram showing a detection circuit provided on the sensor substrate 5. The first sensor S1 is an on-delay circuit 10 as an on-delay means and an off-delay circuit 11 as a first off-delay means. And the second sensor S2 is connected to an off-delay circuit 12 as a second off-delay means.

The output signal A1 of the on-delay circuit 10, the output signal A2 of the off-delay circuit 11, and the output signal B of the off-delay circuit 12 are respectively input to the hold circuit 13, and the output signal F of this hold circuit 13 is the output circuit. It will be output to 14. When the ON signal is output from the output circuit 14, the piston 2 is detected by the first sensor S1, and the detection signal is sent to the control circuit (not shown) via the cable 6.

The on-delay circuit 10 outputs an on signal after a delay time (first delay time) D1 when the first sensor S1 changes from off to on, and when the first sensor S1 changes from on to off. Immediately output the off signal.

The off-delay circuit 11 outputs an off signal after a delay time (second delay time) D2 when the first sensor S1 changes from on to off, and when the first sensor S1 changes from off to on. Immediately output the ON signal.

The off-delay circuit 12 outputs an off signal after a delay time (third delay time) E when the second sensor S2 changes from on to off, and the second sensor S2 changes from off to on. Sometimes, it immediately outputs an ON signal.

The hold circuit 13 outputs an ON signal when the first sensor S1 is turned on and an OFF signal when the first sensor S1 is turned off while the second sensor S2 is off. . That is, when the magnetic field of the permanent magnet 3 is detected by the first sensor S 1 under the condition that the output signal B of the off-delay circuit 12 outputs the off signal without detecting the external magnetic field, the off-delay is first performed. When the ON signal is output from the circuit 11 and then the ON signal is output from the ON delay circuit 10 after the delay time D1 has elapsed, the ON signal is output. Similarly, on condition that the output signal B 1 of the off-delay circuit 12 is outputting the off-signal, the off-delay circuit 10 first outputs the off-signal, and after the delay time D2 elapses, the off-delay circuit 11 When the off signal from is output, the off signal is output.

When the second sensor S2 changes from OFF to ON, the hold circuit 13 outputs an ON / OFF signal corresponding to ON / OFF of the first sensor S1 before the change. That is, if the first sensor S1 does not detect the magnetic field of the permanent magnet 3 and the first sensor S1 outputs the off signal, the second sensor S2 detects the external magnetic field and outputs the on signal. However, the hold circuit 13 outputs an off signal. If the first sensor S1 outputs the ON signal before the second sensor S2 changes from OFF to ON, the hold circuit 13 outputs the ON signal even after the change.

Further, the hold circuit 13 turns off the second sensor S2 when the output signal from the first sensor S1 changes from on to off or from off to on while the second sensor S2 is on. After returning to the state and the delay time E has elapsed, the ON / OFF signal corresponding to the ON / OFF state after the change of the first sensor S1 is output.

The above-mentioned delay times D1 and D2 are set to almost the same time, and the delay time E is set to a time longer than the delay times D1 and D2. Since the frequency of the commercial current is 50 or 60 Hz, E is set to a time longer than 10 msec.

Next, a change in the output signal F from the hold circuit 13 to the output circuit 14 according to ON / OFF of the first and second sensors S1 and S2 will be described with reference to FIGS. 3 to 8.

FIG. 3 is a diagram showing ON / OFF of the output signal F when the first sensor S1 is turned on / off under the condition that the external magnetic field does not affect the first sensor S1. When the magnetic field is detected, the output signal A2 from the off-delay circuit 11 changes from off to on at the same time, and after the delay time D1 elapses, the output signal A1 from the on-delay circuit 10 changes from off to on. To do. In this way, when the ON signal is input to the hold circuit 13 from the first sensor S1 with the time difference D1, the hold circuit 13 outputs the ON signal to the output circuit 14.

When the piston 2 is driven in the reverse direction and the first sensor S1 no longer detects the magnetic field of the permanent magnet 3, the output signal A1 from the on-delay circuit 10 changes from on to off, and then the delay time D2. After elapse of time, the output signal A 2 from the off-delay circuit 11 changes from on to off. In this way, when the ON signal from the first sensor S1 is input to the hold circuit 13 with the time difference D2, the hold circuit 13 outputs the OFF signal to the output circuit 14.

FIG. 4 is a diagram showing a case where the external DC magnetic field influences the cylinder under the condition that the first sensor S1 is off. In this case, the first sensor S1 also operates. It is assumed that a strong external DC magnetic field is acting.

In this case, both sensors S1 and S2 are simultaneously turned on and off by the action of the external DC magnetic field, and the output signal B from the off delay circuit 12 is immediately turned off when the second sensor S2 is turned on. At the same time when the first sensor S1 is turned on, the output signal A2 from the off-delay circuit 11 is immediately changed from off to on. However, since the output signal A1 from the on-delay circuit 10 remains off at that time, the output signal F from the hold circuit 13 remains off. The output signal B from the off-delay circuit 12 is switched from on to off after a delay time E has elapsed after the external DC magnetic field has stopped working.

As described above, when both output signals A2 and B are simultaneously switched from off to on, the output signal F from the hold circuit 13 is held off.

FIG. 5 is a diagram showing a case where the external DC magnetic field affects the cylinder under the condition that the first sensor S1 is turned on, and in this case also, as in the case of FIG. It is assumed that a strong external magnetic field is applied.

In this case, the output signals A1 and A2 from the on-delay circuit 10 and the off-delay circuit 11 are both turned on before the off-delay circuit 12 is turned on by the external magnetic field. Therefore, even if the output signal B from the off-delay circuit 12 changes from off to on due to the action of the external magnetic field, the output signal F from the hold circuit 13 retains the on state that is the state before the action of the external magnetic field. To do. That is, since the output signals A2 and B do not turn on at the same time, the output signal F holds the on state.

FIG. 6 is a diagram showing a case where the first sensor S1 detects the magnetic field of the permanent magnet 3 under the condition that the external DC magnetic field is acting. The external DC magnetic field in this case is the first sensor. It is assumed that the magnetic force is such that S1 is not affected.

In this case, the second sensor S2 changes from off to on due to the external magnetic field, but since the output signals A1 and A2 are off, the output signal F from the hold circuit 13 remains off. Hold. Under such an external magnetic field, the first sensor S1 detects the magnetic field of the permanent magnet 3 and the output signals A1 and A2 from the on-delay circuit 10 and the off-delay circuit 11 are both turned on. Even if it changes, the output signal F from the hold circuit 13 maintains the off state.

The output signal F from the hold circuit 13 changes to ON because the second sensor S2 detects that the influence of the external magnetic field has been canceled, and the output signal B of the second sensor S2 changes to OFF. In this state, the output signals A1 and A2 from the first sensor S1 are turned on.

FIG. 7 is a diagram showing a case where the external AC magnetic field affects the cylinder under the condition that the first sensor S1 is off. In this case, the external AC magnetic field is the first sensor S1. It is assumed to have such a strength that it also affects S1. It is assumed that this external AC magnetic field is generated by an electric wire cable through which a commercial current of 50 HZ flows, and that the period H of the magnetic field that affects it is 10 msec.

In this case, both sensors S1 and S2 are repeatedly turned off in response to changes in the external AC magnetic field, and the output signals A 2 and B from both off delay circuits 11 and 12 are turned off at the same time. Changes from on to on. Since the delay time E in the off-delay circuit 12 is set to be longer than the delay times D1 and D2 and longer than the cycle H, even if the output of the second sensor S2 repeatedly turns on and off, The output signal B of the ray circuit 12 remains on, and the output signal F of the hold circuit 13 remains off.

FIG. 8 is a diagram showing a case where the external AC magnetic field affects the cylinder under the condition that the first sensor S1 is turned on, and the external AC magnetic field in this case is also shown in FIG. It shall have the same strength as the case.

In this case, the first sensor S1 is turned on before the external magnetic field acts, and the output signals A1 and A2 from the on-delay circuit 10 and the off-delay circuit 11 are already turned on. There is. Due to the periodic change of the external AC magnetic field, the second sensor S2 periodically turns on and off in response to the external magnetic field, but the output signal A2 does not turn on at the same time as the output signal B. Moreover, the delay time E of the off-delay circuit 12 is set longer than the cycle H, and the second sensor S2 for detecting the external AC magnetic field is turned off before the output signal B is turned off after the delay time E. Since it changes from ON to ON, the output signal B from the OFF delay circuit 12 remains ON, as in the case of FIG.

As described above, the hold circuit 13 turns on (Lo) the output signal A1 based on the first sensor S1 on the assumption that the output signal B of the off-delay circuit 12 is off (Hi). Subsequently, when the output signal A2 is turned on (Hi), the output signal F which is on is output to the output circuit 14. When the output signal A2 based on the first sensor S1 is turned on (Lo) at the same time as the output signal B based on the second sensor S2, the hold circuit 13 turns off the output signal F to the output circuit 14. When both the output signals A1 and A2 based on the first sensor S1 are on and the output signal B 2 based on the second sensor S2 is turned on, the hold circuit 13 outputs the output signal F on. When the output signal B is turned on while both output signals A1 and A2 are turned off, the hold circuit 13 outputs the off output signal F.

The hold circuit 13 having such a function can be configured by combining known comparators so as to output the output signal F that meets the above-mentioned conditions.

FIG. 9A shows a detailed structure of the first sensor S1, and FIG. 9B shows a detailed structure of the second sensor S2.

Each of the sensors S1 and S2 is formed by combining a plurality of well-known MR elements whose resistance value changes by magnetism, and both sensors S1 and S2 are located on the same surface of the sensor substrate 5. It is installed.

The first sensor S1 has two MR elements 21 and 22 and a comparator (not shown). The two MR elements 21 and 22 are electrically connected in series to each other, and a connection point between them is provided. The output signal is sent from the to the comparator. Each of the MR elements 21 and 22 has a directivity with respect to the detectable magnetic field, and when the direction of the magnetic field to be used is 0 °, the resistance value changes to the plus side, and 90 ° The direction changes to the negative side. Moreover, the rate of change in resistance value differs depending on the direction of the magnetic field that acts, and the absolute value of the resistance value that changes when the magnetic field direction is 0 ° and 90 ° for each MR element 21 and 22 is It will be almost the same.

Since the direction of the magnetic field formed by the permanent magnet 3 is determined in advance, the two MR elements 21 and 22 forming the first sensor S1 have a directivity with respect to the magnetic field of 90 degrees relative to each other on the sensor substrate. 5 is attached. In FIG. 9, the directionality of each MR element 21 and 22 is shown by the hatching direction.

When the two MR elements 21 and 22 are arranged at a phase of 90 ° to each other in this way, when a magnetic field acts on both MR elements at a phase of 45 °, the two MR elements are equal to each other. Since the magnetic field of 2 is applied, both devices have the same amount of change even if the resistance value changes, so that the potential at the intermediate point does not change.

Therefore, for an external magnetic field whose magnetic field direction cannot be predicted, it is necessary to be able to detect the external magnetic field in a direction of 360 ° with respect to the sensor substrate 5, that is, in all directions. . Therefore, in addition to the two MR elements 23 and 24 arranged in the same manner as the two MR elements 21 and 22 in the first sensor S1, the second sensor S2 has two MR elements with a phase of 45 ° for each. 25 and 26 are arranged on the sensor substrate 5. A bridge circuit is formed by these four MR elements 23 to 26, the potential at the intermediate point is sent to the comparator, and the second sensor S2 is configured.

By configuring the second sensor S2 in this way, when an external magnetic field in a direction that affects the first sensor S1 acts on the first sensor S1, the first sensor S1 The second sensor S2 arranged on the same plane as that can reliably detect the external magnetic field. Even if the external magnetic field acts in a direction that cannot be detected by the second sensor S2, the external magnetic field in that direction is not detected by the first sensor S1 arranged on the same plane as the second sensor S2. Therefore, the first sensor, that is, the sensor S1 for detecting the piston position does not malfunction.

The invention made by the present inventor has been specifically described based on the embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, although the present invention is applied to detect the position of the piston of the pneumatic cylinder in the illustrated case, the present invention can also be applied to a hydraulic cylinder.

[0054]

[Effect of device]

 The effects obtained by the representative one of the inventions disclosed in the present application will be briefly described as follows.

(1) As described above, according to the present invention, the detection signal from the piston magnetic field detection means is output with a time difference from each other via the on-delay means and the first off-delay means, and Since the detection signal from the external magnetic field detection means and the detection signal are output with a time difference, the piston detects the magnetic field detection means by the external magnetic field via the hold circuit, It is possible to reliably prevent malfunction of the detection means.

(2) It is possible to configure the device using the same sensitivity without making the sensitivity of the piston magnetic field detecting means different from the sensitivity of the external magnetic field detecting means.

(3) Further, it is not necessary to use a magnetic shield material, and the structure of the device is simplified.

(4) As the external magnetic field, not only the AC magnetic field but also the DC magnetic field can be detected to prevent erroneous detection of the piston magnetic field detection means.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a pneumatic cylinder equipped with a piston position detecting device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a piston position detecting device of the present invention.

FIG. 3 is a time chart showing an operating state of the device when an external magnetic field does not act.

FIG. 4 is a time chart showing an operating state of the apparatus when an external DC magnetic field is applied while the first sensor is off.

FIG. 5 is a time chart showing an operating state of the device when an external DC magnetic field is applied while the first sensor is on.

FIG. 6 is a time chart showing an operating state of the device when the first sensor is turned on and off while the external CD magnetic field is acting.

FIG. 7 is a time chart showing an operating state of the device when an external AC magnetic field is applied while the first sensor is off.

FIG. 8 is a time chart showing an operating state of the apparatus when an external AC magnetic field acts while the first sensor is on.

FIG. 9A is a plan view showing a configuration of a first sensor, and FIG. 9B is a plan view showing a configuration of a second sensor.

[Explanation of symbols]

 1 Cylinder 2 Piston 3 Permanent Magnet (Magnetic Field Generating Member) 4 Casing 5 Sensor Board 6 Cable S1 1st Sensor (Piston Magnetic Field Detection Means) S2 2nd Sensor (External Magnetic Field Detection Means) 10 On Delay Circuit (On Delay Means) 11 Off Delay circuit (first off delay means) 12 Off delay circuit (second off delay means) 13 Hold circuit 14 Output circuits 21 to 26 MR element

Claims (2)

[Scope of utility model registration request] 1. A piston position detection for a fluid pressure cylinder, wherein a magnetic field generation member is attached to a piston reciprocally mounted in a fluid pressure cylinder, and the position of the piston is detected by detecting the magnetic field of the magnetic field generation member. A device, wherein the piston magnetic field detecting means for detecting the magnetic field of the magnetic field generating member, the external magnetic field detecting means for detecting an external magnetic field acting from the outside of the fluid pressure cylinder, and the piston magnetic field detecting means from OFF to ON. An on-delay unit that outputs an ON signal after a first delay time when the change occurs and an OFF signal immediately when the piston magnetic field detection unit changes from ON to OFF, and the piston magnetic field detection unit changes from ON to OFF. When the off signal is output after the second delay time and the piston magnetic field detecting means changes from off to on Outputs an ON signal immediately, and an OFF signal is output after a third delay time when the external magnetic field detecting unit changes from ON to OFF and the external magnetic field detecting unit changes from OFF to ON. The second off-delay means for immediately outputting an on-signal, the output signals from the on-delay means, the first off-delay means and the second off-delay means are input, and the external magnetic field detection means is in an off state. When the piston magnetic field detecting means is turned on, an on signal is output and when the piston magnetic field detecting means is turned off, an off signal is output, while when the external magnetic field detecting means changes from off to on, Outputs an on / off signal corresponding to on / off of the piston magnetic field detection means, and further, when the external magnetic field detection means is on. When the output signal from the piston magnetic field detection means changes, a hold circuit that outputs an output signal corresponding to the ON / OFF state of the changed piston magnetic field detection means after the external magnetic field detection means outputs OFF. A piston position detection device for a fluid pressure cylinder having the same. 2. The piston position detecting device for a fluid pressure cylinder according to claim 1, wherein the third delay time is longer than the first delay time and the second delay time.