JP2000292113A - Position detector for actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the position of a reciprocating member accurately without malfunctioning for a disturbed magnetic field while achieving a miniaturization of a position detector. SOLUTION: This position detector of an actuator is used for detecting the position of a reciprocating member sensing a magnetic force of a permanent magnet 12a provided on the reciprocating member. This position detector comprising semiconductor thin film magnetic resistors MR1-MR4 has a sensor body 20 which produces an output to a signal processing part and is formed on a sensor base 31 made of a magnetic material and the sensor base 31 is magnetized. Magnetic field focusing members 33 and 34 comprising a magnetic material are arranged in the sensor body 21 so that a biased magnetic field is applied from the sensor base 31 acting as permanent magnet. Thus, a magnetic force of the permanent magnet 12a of the reciprocating member is focused by the magnetic focusing members 33 and 34 to be applied to the sensor body 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator position detecting device for detecting the position of a reciprocating member such as a piston reciprocating by a pneumatic cylinder.

[0002]

2. Description of the Related Art As an actuator operated by air pressure, there is an actuator in which a piston is incorporated in a cylinder body so as to reciprocate in a linear direction. The actuator is driven by reciprocating a piston rod attached to the piston. The member can be moved. In such an actuator, a permanent magnet is provided on the piston, and a magnetoresistive element sensitive to a magnetic field is provided on the cylinder body, so that the reciprocating end position of the piston can be detected by the magnetoresistive element. .

[0003]

As the size of the pneumatic actuator is reduced, it is desired to reduce the size of a position detecting device including a magnetoresistive element for detecting the position of a reciprocating member such as a piston. For example, when a sensor groove is formed in a cylinder body and a position detecting device is incorporated in the sensor groove, the width of the sensor groove needs to be reduced to about several mm. However, the position detecting device has a magnetoresistive element and a signal circuit for processing an output signal from the magnetoresistive element, and conventionally, there has been a limit to miniaturization.

When an actuator is used in a factory or the like, various members that generate a magnetic field may be arranged around the actuator. For example, when a spot welder is arranged around an actuator, a large current flows through a cable for supplying power to the electrodes of the spot welder, and a magnetic field generated by the current flows through a sensor provided in the actuator. May be affected as an external magnetic field, and the external magnetic field includes a magnetic field generated by a direct current and a magnetic field generated by an alternating current. For this reason, the magnetic field from various members other than the permanent magnet provided in the actuator may affect the magnetoresistive element in the position detection device, and the position detection device may malfunction.
There is a need for a position detecting device that operates by the magnetic field of a permanent magnet by removing the influence of an external magnetic field.

SUMMARY OF THE INVENTION It is an object of the present invention to make it possible to reliably detect the position of a reciprocating member without malfunctioning with respect to a disturbance magnetic field while achieving downsizing of a position detecting device.

[0006]

A position detecting device for an actuator according to the present invention is mounted on an actuator body on which a reciprocating member is reciprocally mounted, and is responsive to a magnetic force of a permanent magnet provided on the reciprocating member. An actuator position detecting device for detecting the position of the reciprocating member,
A sensor body having a thin film formed on a sensor base made of a magnetic material and having a first pair and a second pair of semiconductor thin film magnetoresistive elements, and arranged corresponding to the first pair and the second pair of semiconductor thin film magnetoresistive elements. A first magnetic field converging member, a signal processing unit for processing an output signal from the sensor main body and outputting a detection signal to the outside, and magnetizing the sensor base to apply a bias magnetic field to the sensor main body. Is added.

The sensor main body is formed on a sensor chip obtained by cutting a wafer made of a magnetic material on which a pattern of a semiconductor thin film magnetoresistive element is formed, and the first and second magnetic field convergence arranged on the sensor chip are formed. The member is attached to the actuator body so as to face the permanent magnet of the reciprocating member.

The signal processing section is formed on a circuit chip formed by cutting a silicon wafer on which a circuit pattern is formed, and the sensor chip is directly joined to the circuit chip.

The two magnetic converging members are provided at a predetermined distance from each other in a concave portion formed on one surface of the circuit chip, and the sensor chip is joined to the other surface of the circuit chip. .

An opening is formed in the circuit chip, the magnetic field converging member is provided in the sensor chip, and the magnetic field converging member is inserted into the opening to join the sensor chip to the circuit chip. I have.

[0011]

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

FIG. 1 is a perspective view showing an example of a pneumatic actuator, and FIG. 2 is a sectional view taken along line AA in FIG.

This actuator has a cylinder body 10 constituting an actuator body. A through hole 11 is formed in the cylinder body 10, and a piston 12 is mounted in the through hole 11 so as to be able to reciprocate in a linear direction. ing.
A head cover 13 is attached to one end of the cylinder body 10, and a rod cover 14 is attached to the other end. A portion of the through hole 11 between the covers 13 and 14 is an air pressure chamber. A supply / discharge port 15 is formed in the cylinder body 10 for supplying and discharging compressed air to and from the air pressure chamber between the piston 12 and the head cover 13, and the compressed air is supplied to the air pressure chamber between the piston 12 and the rod cover 14. A supply / discharge port 16 is formed in the cylinder body 10 for supplying and discharging air.

A piston rod 17 is attached to the piston 12 so as to penetrate the rod cover 14. When compressed air is supplied through the respective supply / discharge ports 15, 16, the piston 12 is reciprocated. The piston rod 17 is reciprocated by the piston 12.

The piston 12 is provided with an annular permanent magnet 12a. In order to detect that the piston 12 has moved to the position of the reciprocating end, two sensor grooves 18 formed in the cylinder body 10 are provided. , Each with a permanent magnet 12
a position detector 19 provided with a sensor sensitive to the magnetic force
The one position detector 19 detects that the piston 12 has reached the forward limit position, and the other position detector 19 detects that the piston 12 has reached the backward limit position.

FIG. 3A shows an example of a circuit diagram of the position detector 19 shown in FIGS. 1 and 2.
A sensor body 20 formed by connecting two magneto-resistive elements MR1 to MR4 in a loop to form a bridge circuit;
In FIG. 3A, the elements MR1 and M1 having a positional relationship opposed to each other.
R4 forms a first pair of magnetoresistive elements, and the element M
R2 and MR3 form another second pair of magnetoresistive elements. A connection part is provided between the respective magnetoresistive elements of the sensor body 20.

An external power supply connected to a power supply terminal 21a is connected to the connection section via a constant current power supply circuit 22, and the connection section and the connection section are connected to a differential amplifier 23, respectively. The output from the differential amplifier 23 is sent to a comparator 25 via a delay circuit 24. The transistor 26 as a switching element is turned on and off by the output from the comparator 25. When the transistor 26 is turned on, both terminals 21b and 21c are turned on, and an output signal is output to the outside. .

This output signal is sent to the control circuit of the actuator that the piston has reached the position of the reciprocating end, and is also sent to an indicator light such as an LED. A portion from the differential amplifier 23 to the transistor 26 serves as a signal processing unit that processes a signal from the sensor main body 20 and outputs an output signal to the outside.

FIG. 3B is a diagram showing another example of a circuit diagram of the position detector 19. In this case, FIG.
In the case shown in (A), a three-wire system is used.
The positive terminal 21d is connected to the power supply circuit 22a and the transistor 26.
In FIG. 3B, members common to those in FIG. 3A are denoted by the same reference numerals.

3 (A) and 3 (B), it is possible to form a sensor body 20 having a half-bridge circuit configuration by using two magneto-resistive elements MR1 and MR2. The magnetoresistive element MR1 is a first pair of magnetoresistive elements, and the magnetoresistive element MR2 is a second pair.
It becomes a pair of magnetoresistive elements.

FIG. 4 is a view showing a sensor chip 30 having a sensor main body 20 composed of four magnetoresistive elements. By forming a resistive element pattern on a sensor base 31 composed of a magnetic material, a semiconductor thin film magnetoresistive element is formed. Element M
A sensor body 20 including R1 to MR4 is formed.

Hard magnetic materials such as hard ferrite, samarium cobalt (SmCo ₅ ), and neodymium-iron-boron composition (Nd ₂ Fe ₁₄ B) can be used as the magnetic material. To manufacture the sensor chip 30, a pattern of a plurality of sets of semiconductor thin film magnetoresistive elements constituting the sensor main body 20 is formed on a wafer made of the above-described hard magnetic material, and the wafer after the pattern formation is placed in the plane direction. Then, the wafer itself is made into a permanent magnet by being magnetized. Thereafter, a wafer made of a hard magnetic material is diced or cut for each part where one set of sensor bodies 20 is formed, that is, for each sensor chip 30. This allows
The sensor chip 30 having the semiconductor thin film magnetoresistive element is formed on the sensor base 31.

On the sensor surface of the sensor chip 30, lead wires 32a to 32d are connected corresponding to the connection terminals of the respective semiconductor thin film magnetoresistive elements, and two magnetic field converging members 33 and 34 are arranged. Each of the magnetic field converging members 33 and 34 is formed of a magnetic material such as ferrite, and one magnetic field converging member 33 corresponds to a pair of magnetoresistive elements MRa formed by two magnetoresistive elements MR1 and MR4. The other magnetic field converging member 34 corresponds to a pair of magnetoresistive elements MRb formed by the other two magnetoresistive elements MR2 and MR3, and is joined to the sensor base 31 via an insulating layer.

In this manner, the sensor switch 3 having the sensor chip 30 and the two magnetic field converging members 33 and 34
5 will be formed.

FIG. 5 is a view showing a sensor chip 30 having the sensor main body 20 having the above-described half-bridge circuit structure. The sensor chip 30 is manufactured by the same method as the sensor chip 30 shown in FIG. MR1 forms a first pair of magnetoresistive elements, and semiconductor thin film magnetoresistive element MR2 forms a second pair of magnetoresistive elements. Then, a magnetic field converging member 33 is arranged corresponding to one magnetoresistive element MR1, and a magnetic field converging member 34 is arranged corresponding to the other magnetoresistive element MR2. Sensor body 2
The output signal from 0 is output to the outside through the lead wires 32e to 32g. The sensor switch 35 of this type outputs a sine wave when the permanent magnet 12a moves to the position of the sensor body 20. Also, the magnetic field converging member 3
Since the three and 34 are provided, the output of the half bridge is symmetrical, a double output signal is output, and the S / N ratio can be increased by removing the influence of the external magnetic field.

On the other hand, in the sensor switch of the type shown in FIG. 4, when the permanent magnet 12a moves to a predetermined position, the amplitude becomes twice as large as that of the type shown in FIG. In particular, in the type having four elements as shown in FIG. 4, the output signal from the sensor body 20 is a differential input, so that the influence of the DC magnetic field of the disturbance magnetic field is removed, and the S / N ratio is increased. be able to.

FIG. 6 is a schematic view showing the operation principle of the sensor switch 35 having the structure shown in FIG. 4. The sensor main body 20 includes a sensor base 31 made of a permanent magnet and a magnetic field converging member 3.
3 and 34 so that the magnetic field converging members 33 and 34 are on the side of the piston 12 which is a reciprocating member, and the cylinder body 10 as an actuator body is
Attached to. However, in FIG. 6, the surface of the magnetoresistive element constituting the sensor main body 20 is, for convenience of drawing,
Although shown along the plane of the paper, the sensor main body 20 is attached to the cylinder main body 10 so as to face a direction perpendicular to the paper.

As described above, the sensor switch 35 is composed of the sensor chip 30 in which the sensor body 20 is formed on the sensor base 31 made of a permanent magnet and the two magnetic field converging members 3.
3 and 34, the sensor base 31 which is a permanent magnet becomes a bias magnet and the sensor body 20
Is constantly applied with the bias magnetic field Br.

The distance P between the centers of the magnetic field converging members 33 and 34 is set to be slightly larger than the width D of the permanent magnet 12a of the piston 12, and as shown in FIG. Is at a predetermined position, the magnetic field of the permanent magnet 12a is
34 and the sensor base 31 so as to pass through the sensor base 31.
0 will be affected.

If the sizes of the magnetic field converging members 33 and 34 are changed, the same sensor body 20 can be used for various actuators having different thicknesses of the permanent magnets 12a.

FIG. 7 is a characteristic diagram showing the relationship between the strength of the magnetic field applied to the sensor body 20 and the sensor output. The outputs Va and Ia are output from the output terminals of the sensor body 20 by the bias magnetic field. In this state, when the permanent magnet 12a comes to a predetermined position as shown in FIG.
The magnetic field generated by the permanent magnet 12a is applied to the sensor body 20, and outputs Vb and Ib are output from the output terminals. These outputs are respectively sent to the differential amplifier 23, and the differential output V
o and Io are output to the comparator 25 via the delay circuit 24. The comparator 25 outputs an output signal to the transistor 26 when the output is equal to or greater than the predetermined threshold value.

By adjusting the interval between the magnetic field converging members 33 and 34 to the pole pitch set by the width of the permanent magnet 12a, the magnetic field acting on the sensor body 20 can be made equal.
The respective outputs Va and Vb are symmetric.

As described above, the bias magnetic field is always applied to the sensor body 20, and the position of the piston 12 is detected when the magnetic field of the permanent magnet 12a is applied synergistically in addition to the bias magnetic field. Therefore, a member for generating an AC magnetic field or a DC magnetic field is provided in the vicinity of the actuator, and even if a disturbance magnetic field acts on the sensor body 20, the disturbance magnetic field and the magnetic field generated by the permanent magnet can be reliably distinguished. , And the S / N ratio can be increased to remove noise components and prevent the sensor switch 35 from malfunctioning.

FIG. 8 shows the sensor switch 35 shown in FIG.
FIG. 11 is a diagram showing a sensor switch 35 in which a spacer 36 made of a non-magnetic material such as resin is arranged between two magnetic field converging members 33 and 34 of FIG. Similarly, a resin spacer 36 may be provided for the sensor switch 35 of the type shown in FIG.

FIG. 9 shows the sensor switch 35 shown in FIG.
This shows that the sensor switch 35 is covered by a resin sealing portion 37 formed by resin molding. The surfaces of the two ferrite magnetic field converging members 33 and 34 are exposed on the surface of the resin sealing portion 37. The sensor switch 35 of the type shown in FIG. 4 may be entirely resin-sealed.

FIG. 10 shows the sensor switch 35 shown in FIG.
Is a view showing a position detector 19 formed by mounting a sensor on a sensor substrate 41 made of resin or the like. A sensor switch 35 and a signal for processing an output signal from the sensor switch 35 are provided on one surface 41a of the sensor substrate 41. A processing unit 42 is provided, and an LED 43 for lighting and displaying that the sensor switch 35 has been turned on is fixed to the other surface 41 b of the sensor substrate 41.

FIG. 11 is a view showing still another type of position detector 19, and the position detector 19 has a circuit pattern constituting the signal processing unit 42 formed on a silicon substrate by a semiconductor manufacturing technique. Circuit chip 40 formed in
have. The circuit chip 40 is formed by forming a circuit pattern constituting the signal processing unit 42 on the surface of a silicon wafer by a technique for manufacturing a pattern of a semiconductor integrated circuit, and cutting or dicing the silicon wafer into a predetermined size. I have.

A concave portion 44 is formed on one surface 40a of the circuit chip 40 adjacent to the signal processing portion 42 by an etching technique. In the concave portion 44, magnetic field converging members 33 and 34 made of a soft magnetic material are arranged. And the magnetic field converging member 3
The upper surfaces of the reference numerals 3 and 34 have substantially the same height as the surface of the circuit chip 40. The magnetic field converging members 33 and 34 can be formed by subjecting the surface of the concave portion 44 of the circuit chip 40 to thick film plating with a material such as Fe-Ni or Ni-Wn.

The other surface 40b of the circuit chip 40 has the structure shown in FIG.
The sensor chip 30 having the pattern of the semiconductor thin film magnetoresistive element formed thereon is connected to the sensor base 31 made of a magnetic material in the same manner as shown in FIG. , That is, bumps 45 made of the above material. Therefore, by bonding the sensor chip 30 to the other surface 40b of the circuit chip 40 and connecting the bumps 45 to the electrodes electrically connected to the signal processing unit 42 of the circuit chip 40, as shown in FIG. As shown, a circuit chip 4 on which a pattern of a signal processing unit 42 made of a semiconductor integrated circuit is formed.
0 and the sensor chip 30 are integrated to form an intelligent sensor switch 35.

FIG. 12 is a view showing another type of the position detector 19 having the sensor chip 30 and the circuit chip 40. In this case, a sensor pattern of a magnetoresistive element is provided on the surface of the sensor chip 30. At the same time, a magnetic field converging member 34 made of ferrite is joined. The circuit chip 40 has a signal processing unit 42 formed of a semiconductor integrated circuit as in the case shown in FIG. 11, and an opening 46 is formed in a part of the signal processing unit 42 by a technique such as etching. Therefore, by joining the circuit chip 40 and the sensor chip 30 with the bumps 45, the magnetic field converging member 34 is exposed on the surface of the circuit chip 40 via the opening 46.

FIG. 13 shows a state in which the entire sensor board 41 is connected to the sensor switch 35 using the position detector 19 of the type in which the sensor switch 35 and the signal processing section 42 are mounted on the sensor board 41 as shown in FIG. A position detector 19 of a type including a portion 42 and a case 38 made of resin is shown. However, in this case, the LED 43 is not provided on the sensor board 41.

If the sectional shape of the case 38 is formed into the sectional shape of the sensor groove 18 shown in FIG. 1, the position detector 19 that can be attached to the sensor groove 18 can be manufactured. This is the same for the other types of position detectors described above.

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 present invention.

For example, the illustrated position detecting device is adapted to be mounted in the sensor groove 18 of the cylinder body 10 shown in FIGS. 1 and 2, but the cross-sectional shape of the position detector 19 may be an arbitrary cross-sectional shape. In addition to the pneumatic cylinder, the position may be detected in response to a permanent magnet attached to a reciprocating member that reciprocates and oscillates, such as a rotary actuator that operates by air pressure. It can also be used as a position detecting device for a hydraulic actuator that reciprocates and a hydraulic rotary actuator. Further, the shape of the sensor switch 35 is not limited to the case shown in the figure, but may be any shape. The sensor switch 35 may be attached to the actuator as it is without being sealed with a resin or the like.

[0045]

According to the present invention, the sensor main body formed by the semiconductor thin film magnetoresistive element is arranged so as to be sandwiched between the permanent magnet and the magnetic field converging member, and the bias magnetic field is always applied to the sensor main body. Since the position of the reciprocating member is detected by synergistically applying the magnetic field of the permanent magnet provided on the reciprocating member, the position of the reciprocating member can be detected by the sensor body without being affected by an external magnetic field. It can be detected reliably.

A semiconductor thin-film magnetoresistive element constituting the sensor body is formed on a wafer made of a magnetic material, and after the wafer is magnetized at the wafer stage, the wafer is cut to form a sensor chip. Therefore, downsizing of the position detecting device having the permanent magnet for applying the bias magnetic field can be achieved.

A signal processing section for processing a signal output from the sensor body is formed on the surface of the silicon wafer, and the signal processing section is formed on a chip-shaped circuit chip by cutting the signal processing section. The size of the unit can be reduced.

By configuring the position detecting device with the sensor chip and the circuit chip, it is possible to detect the position by applying a small current to the circuit, and to achieve a reduction in power consumption.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an actuator.

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

3A is a circuit diagram showing an internal structure of a three-wire position detector, and FIG. 3B is a circuit diagram showing an internal structure of a two-wire position detector.

FIG. 4 is an exploded perspective view showing an example of a sensor switch in which a sensor body made of a semiconductor thin film magnetoresistive element is formed on a sensor base made of a magnetic material.

FIG. 5 is an exploded perspective view showing another example of the sensor switch.

FIG. 6 is a schematic diagram showing the operation principle of a position detection device having a sensor switch.

FIG. 7 is a characteristic diagram showing a relationship between the intensity of a magnetic field applied to a sensor body and a sensor output.

FIG. 8 is a perspective view showing another type of sensor switch.

FIG. 9 is a perspective view showing another type of sensor switch.

FIG. 10 is a perspective view showing another type of sensor switch.

11A is a perspective view showing another type of sensor switch, and FIG. 11B is a cross-sectional view thereof.

FIG. 12 is a perspective view showing still another type of sensor switch.

FIG. 13 is a perspective view showing a sensor switch covered by a resin case.

[Explanation of symbols]

 Reference Signs List 10 cylinder body (actuator body) 12 piston (reciprocating member) 12a permanent magnet 19 position detector 20 sensor body 23 differential amplifier 25 comparator 26 transistor 30 sensor chip 31 sensor base 32a to 32g lead wire 33, 34 magnetic field converging member Reference Signs List 35 sensor switch 36 resin spacer 37 resin sealing part 40 circuit chip 41 sensor substrate 42 signal processing part 43 LED 44 concave part 45 bump 46 opening MR1 to MR4 semiconductor thin film magnetoresistive element

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F063 AA02 BA05 BA30 CA16 CA34 DD03 EA02 GA52 GA79 LA27 3H081 AA03 BB03 CC23 CC25 GG04 GG15 GG23 5H303 AA30 BB01 BB06 BB11 CC10 DD08 EE04 FF01 GG09 HH02 HH09 MM

Claims (5)

[Claims] 1. A position of an actuator which is mounted on an actuator body in which a reciprocating member is reciprocally mounted and detects a position of the reciprocating member in response to a magnetic force of a permanent magnet provided on the reciprocating member. A detection device, comprising: a sensor body formed of a thin film on a sensor base made of a magnetic material and having a first pair and a second pair of semiconductor thin film magneto-resistive elements; First and second magnetic field converging members arranged in correspondence with each other, and a signal processing unit that processes an output signal from the sensor main body and outputs a detection signal to the outside, and magnetizes the sensor base. A position detecting device for an actuator, wherein a bias magnetic field is applied to the sensor body. 2. The position detecting device for an actuator according to claim 1, wherein the sensor body is formed on a sensor chip formed by cutting a wafer made of a magnetic material on which a pattern of a semiconductor thin-film magnetoresistive element is formed. An actuator position detecting device, wherein the first and second magnetic field converging members arranged on a chip are attached to the actuator main body so as to face the permanent magnets of the reciprocating member. 3. The position detecting device for an actuator according to claim 2, wherein the signal processing unit is formed on a circuit chip formed by cutting a silicon wafer on which a circuit pattern is formed, and the sensor chip is connected to the circuit chip. A position detecting device for an actuator, wherein the position detecting device is directly connected to the actuator. 4. The position detecting device for an actuator according to claim 3, wherein the two magnetic converging members are provided at a predetermined distance from each other in a concave portion formed on one surface of the circuit chip. A position detecting device for an actuator, wherein the sensor chip is bonded to the other surface. 5. The position detecting device for an actuator according to claim 3, wherein an opening is formed in the circuit chip, the magnetic field converging member is provided in the sensor chip, and the magnetic field converging member is inserted into the opening. An actuator position detecting device, wherein the sensor chip is bonded to the circuit chip.