JP2001133288A - Position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make detectable not only distance but also origin position by processing signals from sensors for detecting moving distance. SOLUTION: This position detector detects that a moving member moving along a fixed member comes to a specific origin position. The fixed member has a magnet scale to which magnetism are put on at a specific magnetization pitch. On the moving member, two sensor circuits having a magnetic detector element assembly consisting of 4 magnetic resistor elements are placed. When synthetic A-phase and synthetic B-phase from each sensor circuit are outputted in the state that the output value of minus B-phase from one output terminal of one sensor circuit exceeds a specific reference value -Vref value, the position is judged to be the origin position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for detecting that a moving member reciprocating along a fixed member has reached a predetermined reference position.

[0002]

2. Description of the Related Art In order to reciprocate a workpiece such as a workpiece or a jig in a rectilinear direction, a moving member is reciprocated using an actuator having an electric motor or a pneumatic cylinder as a driving source. The transported object may be moved by the moving member.

When the moving member is moved by using such an actuator, it is detected how much the moving member has moved with respect to a fixed member such as the actuator body or the casing, and the moving member is moved to a predetermined reference. It is necessary to detect the position and origin position.

In order to detect the moving distance of the moving member, it is possible to detect the position of the moving member with respect to the fixed member from the moving distance using a linear encoder. However, the size of the position detecting device is increased. Therefore, a fixed member is provided with a magnet scale magnetized at a predetermined magnetized pitch, and the moving distance of the moving member is detected by detecting magnetism using a sensor including a magnetic detecting element such as an MR element. By using a semiconductor magnetoresistive element as the magnetoresistive element, the size of the position detecting device can be reduced.

[0005]

When a moving distance of a moving member is detected by using a magnetoresistive element, conventionally, a magnet scale in which magnets are magnetized at a predetermined magnetizing pitch to detect the moving distance is conventionally used. Is provided on the fixed member, and a distance detection sensor for detecting the magnet is provided on the movable member, and the movable member has a predetermined reference position, that is, an origin position. In addition to the magnet, an origin position detecting magnet is magnetized on the magnet scale, and an origin position detecting sensor is provided on the moving member in correspondence with the origin position detecting magnet.

The reason is that the distance detection sensor can detect the moving distance of the moving member, but cannot detect the origin position as a reference when the moving member starts moving. For this reason, conventionally, a magnet for distance detection and a magnet for origin position detection must be magnetized on the moving member, and a distance detection sensor and an origin detection sensor are provided on the moving member corresponding to each magnet. I had to.

An object of the present invention is to process not only a distance but also an origin position by processing a signal from a sensor for detecting a moving distance.

[0008]

According to the present invention, there is provided a position detecting device for detecting a position of a moving member moving along a fixed member, wherein the position detecting device is provided on one of the fixed member and the moving member. A magnet scale formed by magnetizing a magnet at a predetermined magnetizing pitch, and a plurality of magnetic detecting elements provided on the other of the fixed member and the moving member, the magnetic sensing elements being responsive to the magnet; A first sensor circuit that outputs an output signal of the second member, and a second sensor that is provided on the other member and has a plurality of magnetic detection elements that are sensitive to the magnet and that is out of phase with respect to the first output signal. A second sensor circuit for outputting an output signal;
Origin position detection for outputting an origin signal when the output value of the opposite polarity from the other sensor circuit exceeds a predetermined value under the condition that the output signal of one sensor circuit of the second sensor circuit is output Means.

The position detecting device according to the present invention includes the first and second position detecting devices.
Under the condition that the output value of the negative polarity from one of the sensor circuits exceeds a predetermined value, the origin signal is output when the combined output from the other sensor circuit crosses zero. I do.

In the position detecting device according to the present invention, the plurality of magnetic detecting elements constituting each of the sensor circuits may include a magnetic field extending in a direction perpendicular to the moving direction at a pitch corresponding to the magnetization pitch in the moving direction. A resistance element, wherein a temperature-correcting magnetoresistance element extending in a direction perpendicular to each of the magnetoresistance elements is connected to the sensor circuit.

A position detecting device according to the present invention is characterized in that a plurality of magnetoresistive elements constituting each of the sensor circuits and the temperature-correcting magnetoresistive elements are formed in a pattern on a single semiconductor chip.

The position detecting device according to the present invention is characterized in that the magnetized pitch at the end of the stroke of the magnet scale is set smaller than the magnetized pitch of the other portions.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing an example of an actuator having a position detecting device according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA in FIG.

This actuator has a casing 3 having a U-shaped cross section provided with end plates 1 and 2 at both ends. A screw shaft 4 is rotatably mounted on the end plates 1 and 2 and the screw shaft 4 The rotation is driven by a motor 5 fixed to the plate 2. A guide rail 6 is fixed to the bottom surface of the casing 3, and a guide member 7 that slides along the guide rail 6 is attached to a moving member 8. The moving member 8 is screwed to the screw shaft 4, and the rotation of the screw shaft 4 causes the moving member 8 to become a casing 3 which is a fixed member.
Is reciprocated in a linear direction along the axis, and the workpiece is arranged on the moving member 8. The workpiece is conveyed by the moving member 8.

When the moving member 8 is driven from one end of the casing 3 to the other end, the moving distance and direction of the moving member 8 are detected, and the origin position serving as a reference when detecting the moving distance is detected. For this purpose, the casing 3 is provided with a magnet scale 11, and the moving member 8 is provided with a detection unit 12.

FIG. 3 shows the magnet scale 11 and the detector 1.
2 is a conceptual diagram showing a basic structure of No. 2, in which a magnet scale 11 is formed by magnetizing a magnet on a band-shaped magnetic body at a constant pitch P, and an N pole and an S pole are formed at each pitch. Have been. This pitch P is set to 0.4 mm.

On the other hand, the detecting section 12 comprises a first magnetic detecting element assembly 13a composed of four magnetoresistive elements MR1 to MR4 indicated by solid lines, and four magnetic resistive elements MR5 indicated by broken lines.
And a second magnetic sensing element assembly 13b comprising: a plurality of magnetoresistive elements, each of which is parallel to each other in the width direction of the magnet scale 11, that is, in the direction perpendicular to the moving direction of the moving member 8. , And are separated from each other in the movement direction by a pitch corresponding to the magnetization pitch P. Moreover, the magnetoresistive element of the first magnetic sensing element assembly 13a and the magnetoresistive element of the second magnetic sensing element assembly 13b are shifted from each other by a half pitch.

FIG. 4 shows the first and second magnetic sensing element assemblies 1.
It is a figure which shows the circuit structure of 3a, 13b. The first magnetic sensing element assembly 13a includes four magnetoresistive elements MR1 to MR
4 to form a bridge circuit, and a positive terminal + and a ground terminal-as a power supply terminal, a first output terminal A as a positive A-phase output terminal and a negative signal having a polarity opposite to that of an output signal therefrom. It has a second output terminal -A, which is an A-phase output terminal, and constitutes a first sensor circuit 14a.

Similarly, the second magnetic sensing element assembly 13b connects the four magnetoresistive elements MR5 to MR8 to form a bridge circuit, and has a plus terminal + and a ground terminal-which are power supply terminals, and a plus B phase. And a second output terminal -B, which is a negative B-phase output terminal having a polarity opposite to that of the output signal from the first output terminal B, and a second sensor circuit 14b. Is composed.

In the bridge circuit, two magnetoresistive elements M are connected between a positive terminal + which is a power terminal and a ground terminal-.
R9 and MR10 are connected in series, and these magnetoresistance elements linearly extend in a direction perpendicular to other magnetoresistance elements. Since the two magnetoresistive elements MR9 and MR10 are connected in this direction, the two magnetoresistive elements MR9 and MR10 become insensitive sensors, and perform temperature correction to improve the temperature characteristics. All of these magnetoresistive elements are manufactured by patterning a silicon chip, that is, a semiconductor chip or a glass chip, by a diffusion method, a vapor deposition method, or the like.

FIG. 5 shows each sensor circuit when the moving member 8 provided with the detecting unit 12 shown in FIG. 4 is moved from one end (origin side) to the other end of the magnet scale 11. It is a figure which shows the output waveform from 14a, 14b. When the moving member 8 is moved from one stroke end, that is, from the origin side to the other stroke end, the magnetization pitch and the pitch of the magnetoresistive element are set to the same pitch as described above, so that the first A plus A-phase signal is output from a first output terminal A of the sensor circuit 14a, and then a plus B phase shifted from the plus A phase by 90 degrees from the first output terminal B of the second sensor circuit 14b. A phase signal is output. Further, the first sensor circuit 1
A negative A-phase signal is output from the second output terminal -A of 4a, and then a negative B-phase signal is output from the second output terminal -B of the second sensor circuit 14b.

FIG. 6 shows the plus A phase and the minus A phase shown in FIG.
FIG. 6 is a diagram showing output waveforms of a combined A phase having a phase difference, a combined B phase having a difference between a plus B phase and a minus B phase, and a minus B phase shown in FIG. 5. The moving distance of the moving member 8 can be calculated by comparing each composite waveform with a threshold value, outputting a square waveform, and counting the number. Also, by judging which composite waveform is output first, the moving direction of the moving member 8, that is, the movement from one stroke end to the other stroke end, or the movement in the opposite direction Can be determined.

When the moving member 8 starts to move from one stroke end, the plus A phase and the plus B phase are output, and then the minus A phase and the minus B phase are output. Therefore, if the minus B phase first exceeds the predetermined threshold (Vref) and the time when the combined A phase crosses the output V at zero is set as the origin position, the magnet for detecting the moving distance A magnet magnetized on the scale 11 can be used for detecting the origin position.

In FIG. 6, the data signal A is a signal that has been binarized based on whether or not the combined A phase has become equal to or higher than zero volts.
The gate signal / Z indicates a signal that is turned on when the minus B phase exceeds a predetermined threshold, and an origin position signal is output under the above-described conditions.

FIG. 7 is a block diagram showing a control circuit as origin position detecting means for detecting that the moving member 8 has reached the origin position. This control circuit has a combining circuit 21 for taking the difference between the plus A phase and the minus A phase shown in FIG.
The synthesized A phase formed by the synthesizing circuit 21 is sent to a comparator 22 where it is compared whether it is positive or more than 0 V, and a square waveform is output to a gate circuit 23.

On the other hand, the minus B-phase signal from the second sensor circuit 14b is sent to the comparator 24, where it is compared whether the minus output is larger than a predetermined threshold value (-Vref). An output signal is sent to the gate circuit 23 when it becomes larger in the negative direction. Both comparators 22, 24
When the moving member 8 is at the origin position, the origin position can be detected by this signal.

As described above, the magnetoresistive elements of the two magnetic sensing element assemblies 13a and 13b that output a voltage signal in response to the magnet magnetized on the magnet scale 11 are arranged in the order shown in FIG. When the scale 11 is relatively moved from one end to the other end, the output signal is output from the first output terminal of each of the sensor circuits 14a and 14b, and the detection signal is output from the second output terminal with a time difference. Is output. Under the condition that the combined output signal from one sensor circuit is output, when the output signal of the opposite polarity from the other sensor circuit to the one sensor circuit has a predetermined output value or more, The zero point of the output signal from the sensor circuit is used as the origin position, so that the magnet scale 11 for detecting the moving distance can be detected without using a magnet for detecting the origin and a sensor circuit for detecting the magnet. The origin position can be detected by using the unit 12.

A virtual magnetic pole exists at the end of the magnet scale 11. For example, the output voltage from the minus B phase of the second sensor circuit 14b causes an unstable factor C as shown by a two-dot chain line in FIG. May include.

FIG. 8 is a conceptual diagram showing a magnetizing method for the magnet scale 11 in which such an instability factor is prevented from being output. The magnetizing pitch at the end of the moving stroke of the moving member 8 is shown in FIG. P ₀ is set smaller than the magnetization pitch P of the other portions. The magnetization pitch P _0, is set to be about 0.05mm. As described above, when the magnetization pitch at the stroke end is reduced, it is possible to prevent the output of the instability factor C shown by the two-dot chain line in FIG.

FIG. 9 is a diagram showing a specific example of the control circuit shown in FIG. 7. The output signals of the plus A phase and the minus A phase from the first sensor circuit 14a are differentially output by the operational amplifier AMP1. The output signals of the plus B phase and the minus B phase from the second sensor circuit 14b are differentially output by the operational amplifier AMP2, and square waveforms are output to the output terminals Aout and Bout by the operational amplifiers AMP3 and AMP4 as the comparator 22, respectively. . The moving distance and direction of the moving member 8 are calculated based on the output signals from these output terminals. This control circuit can be manufactured by forming a pattern on a silicon chip including a magnetoresistive element.

The output signal from the minus B-phase output terminal -B of the second sensor 14b is amplified by the operational amplifier AMP5, compared with the comparison value Vref by the operational amplifier AMP6, inverted by the inverter 25, and inverted by the gate (D-D). FF) 23 is supplied with a gate (data input signal) / Z. The output signal of the composite A phase is also gated (clock signal) to this gate 23.
A is input as A, and the origin signal ORIGIN is output from the gate 23 by both signals, and the origin position can be detected.

In FIG. 9, a gate 26 is for detecting that the moving member 8 has passed the origin position when the moving member 8 has moved from the other end side to the one end side (origin side).
The phase output signal and the output signal from the minus B-phase output terminal -B of the second sensor 14b are input, and when passage of the origin position is detected, a pass signal END is output.

FIG. 10A is a time chart for detecting that the moving member 8 has passed the origin position when the moving member 8 has moved from the other end to the origin side, and FIG. 7 is a time chart showing a timing of detecting the origin position by moving toward the other end after passing through the origin position.

The present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the scope of the invention.

For example, the actuator which can use the position detecting device is not limited to the case where the moving member 8 is reciprocated by the motor 5 as shown in FIG.
The present invention can also be applied to a case where the moving member 8 reciprocates with a fluid such as a pneumatic cylinder. The present invention is not limited to the case where the moving member 8 reciprocates linearly, and the present invention can be applied to the case where the moving member 8 swings. Further, the magnet scale 11 and the detector 12 need only be in a relation of relative movement, and the magnet scale 11 may be provided on the moving member 8 and the detector 12 may be provided on the casing 3 as a fixed member.

[0037]

According to the present invention, in order to detect a moving distance and a direction of a moving member, a magnet magnetized on a magnet scale is used to detect a moving distance and a direction from a sensor circuit having a magnetic detecting element sensitive to magnetism. By processing the output signal, it is possible to detect that the origin position has been set with respect to the moving member. This eliminates the need to magnetize the magnet for detecting the origin on the magnet scale in order to detect the origin position, and to provide a magnetic detection element sensitive to the magnet.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an actuator having a position detection device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is a conceptual diagram illustrating a magnet scale and a detection unit.

FIG. 4 is a circuit diagram showing first and second sensor circuits respectively formed by a magnetic sensing element assembly.

FIG. 5 is a waveform diagram showing output waveforms from respective sensor circuits when the moving member is moved from one end to the other end.

FIG. 6 is a waveform diagram showing waveforms of a combined A phase and a combined B phase.

FIG. 7 is a block diagram showing a control circuit for detecting an origin position.

FIG. 8 is a conceptual diagram showing another type of magnet scale.

FIG. 9 is a circuit diagram showing a sensor signal processing circuit.

FIG. 10A is a time chart showing a state in which the moving member has returned from the origin position, and FIG. 10B is a time chart showing that the moving member has reached the origin position.

[Explanation of symbols]

 Reference Signs List 3 Casing (fixing member) 8 Moving member 11 Magnet scale 12 Detector 13a, 13b Magnetic detection element assembly 14a, 14b Sensor circuit 21 Synthesis circuit 22 Comparator 23 Gate circuit 24 Comparator 25 Inverter 26 Gate circuit MR1 to MR10 Magnetoresistive element

Claims (5)

[Claims] 1. A position detecting device for detecting a position of a moving member moving along a fixed member, wherein the position detecting device is provided on one of the fixed member and the moving member,
A magnet scale formed by magnetizing a magnet at a predetermined magnetization pitch, provided on the other of the fixed member and the moving member,
A first sensor circuit having a plurality of magnetic detection elements responsive to the magnet and outputting a first output signal; and a plurality of magnetic detection elements provided on the other member and responsive to the magnet. A second sensor circuit that outputs a second output signal that is out of phase with the first output signal; and a state in which an output signal of one of the first and second sensor circuits is output. A position detecting device comprising: origin position detecting means for outputting an origin signal when an output value of the opposite polarity from the other sensor circuit exceeds a predetermined value. 2. The position detecting device according to claim 1, wherein a negative output value from one of the first and second sensor circuits exceeds a predetermined value. A position detecting device for outputting an origin signal when a combined output from the other sensor circuit crosses zero. 3. The position detecting device according to claim 1, wherein the plurality of magnetic detecting elements constituting each of the sensor circuits are arranged in the moving direction with a pitch corresponding to the magnetization pitch. A position detecting device, comprising: magnetoresistive elements extending in a direction perpendicular to the sensor circuit, wherein a temperature-correcting magnetoresistive element extending in a direction perpendicular to each of the magnetoresistive elements is connected to the sensor circuit. 4. The position detecting device according to claim 3, wherein
A position detecting device, wherein a plurality of magneto-resistive elements constituting each of the sensor circuits and the temperature-correcting magneto-resistive elements are formed in a pattern on a single semiconductor chip. 5. The position detecting device according to claim 1, wherein the magnetized pitch at the stroke end of the magnet scale is set smaller than the magnetized pitch of the other portions. Position detecting device.