JPH08152301A - Piston position detector - Google Patents

Abstract

PURPOSE: To provide piston position detector which can detect the optimal fixing range and the dangerous fixing range stably regardless of the field distribution range of a piston to be detected while suppressing the effect of external field or the like. CONSTITUTION: A magnetic resistance element 2 comprises a magneto-sensitive pattern part 6 having a magnetic detecting direction matching the positional detecting direction, and a pair of magneto-sensitive pattern parts 11, 12 having magnetic detecting directions inclining by 45 deg. upper rightward and upper leftward, respectively, from the positional detecting direction. A detection range formed by the magneto-sensitive pattern part 6 and a pair of detection ranges of the magneto-sensitive pattern parts 11, 12 formed on the opposite sides of the detection range define a dangerous fixing range and an optimal fixing range.

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 magnetically detecting the piston position of a fluid pressure cylinder.

[0002]

2. Description of the Related Art Conventionally, as such a piston position detecting device, there is one disclosed, for example, in Japanese Utility Model Publication No. 6-12484. As shown in FIG. 8, the piston position detecting device is composed of two magnetic sensors 51, 52 provided at a predetermined distance d in the axial direction of the cylinder tube T of the pneumatic cylinder S or the like. ing. This distance corresponds to the width of the magnet M provided on the piston P. When the piston P approaches the pair of magnetic sensors 51, 52 from the first magnetic sensor 51 side, the first magnetic sensor 51 first detects the magnet M and outputs an output voltage corresponding to the strength of the magnetic field. Then, when the output voltage V1 exceeds the threshold voltage VTH, the first indicator lamp corresponding to the first magnetic sensor 51 is turned on.

When the piston P moves further in the same direction,
The second magnetic sensor 52 also detects the magnet M and outputs an output voltage corresponding to the strength of the magnetic field. When the output voltage V2 exceeds the threshold voltage VTH, the second indicator lamp corresponding to the second magnetic sensor 52 is turned on in addition to the first indicator lamp. Further, the piston P moves in the same direction so that the output voltage V1 of the first magnetic sensor 51 becomes equal to the threshold voltage V1.
When the output voltage V2 of the second magnetic sensor 52 exceeds the threshold value while falling below TH, only the second indicator light is turned on.

The range in which both the first and second indicators are lit is the optimum mounting range, and the range in which only one of the two indicators is lit is the dangerous mounting range.

[0005] In addition to the above piston position detecting device,
There is a magnetic proximity switch disclosed in Japanese Utility Model Publication No. 6-24722. As shown in FIG. 10, reed switches 53 and 54 having different sensitivities are arranged in parallel with each other in the axial direction of the cylinder tube T. When the piston P approaches from one side, the first reed switch 53 with high sensitivity
Since the strength of the magnetic field acting on the magnetic field exceeds the operating magnetic field MJTH1, the first reed switch 53 is turned on and only the first indicator lamp is turned on.

When the piston P moves further in the same direction,
Since the strength of the magnetic field acting on the second reed switch 54, which has lower sensitivity, exceeds the operating magnetic field MJTH2,
When the reed switch 54 is turned on, only the second indicator light is turned on. Further, the strength of the magnetic field acting on the second reed switch 54 when the piston P moves in the same direction is lower than the operating magnetic field MJTH2, and the first reed switch 53
When the strength of the magnetic field acting on the magnetic field exceeds the operating magnetic field MJTH1, only the first reed switch 53 is turned on again so that only the first indicator lamp is turned on.

The range in which only the second indicator light is illuminated is the optimum mounting range for the piston position, and the range in which only the first indicator lamp is illuminated is the dangerous mounting range.

[0008]

However, in the case of the former piston position detecting device, as shown in FIG. 9, the output voltage V1 of both magnetic sensors 51 and 52 in the optimum mounting range,
V2 is in the range below its maximum output voltage. Therefore, since the voltage difference between the output voltage and the threshold voltage VTH in the optimum mounting range is small, when the output voltage fluctuates due to an external magnetic field or the like, the output voltage does not exceed the threshold voltage VTH despite being in the optimum mounting range. There was a high possibility that malfunctions could occur below that. Further, both magnetic sensors 51 and 52 must correspond to the width of the magnet M, and it is necessary to prepare a magnetic sensor according to the width of each magnet. Therefore, it is necessary to prepare various types of piston position detecting devices so as to correspond to various pneumatic cylinders S.

In the case of the latter magnetic detection switch, as shown in FIG. 11, if the operating magnetic field MJTH2 is set high and the optimum mounting range is set narrow in order to increase the detection accuracy of the piston position, the second mounting The difference between the maximum value of the magnetic field acting on the reed switch 54 and the operating magnetic field MJTH2 becomes small. As a result, if the fluctuation of the magnetic field due to the external magnetic field or the like becomes large, there is a high possibility that a malfunction will occur, as in the case described above.

The present invention has been made to solve the above problems, and its purpose is to stabilize the optimum mounting range and the dangerous mounting range regardless of the size of the distribution range of the magnetic field from the piston for position detection. Therefore, it is an object of the present invention to provide a piston position detection device that can be reliably detected and is not easily affected by an external magnetic field or the like.

[0011]

In order to solve the above problems, a first aspect of the present invention is directed to a first magnetoresistive detecting section arranged so that the magnetic field detecting direction is the position detecting direction, and each magnetic field detecting direction. And a second magnetoresistive detection section composed of a pair of magnetically sensitive pattern sections connected in series with each other, which are inclined by equal offset angles in the clockwise direction and the counterclockwise direction from the position detection direction. And a position at which the output of the first magnetoresistive detection unit reaches a peak and a position at which the output of each magnetically sensitive pattern unit of the second magnetoresistive detection unit is inverted, are substantially aligned with each other. The output voltage output by the first magnetic resistance detection unit and the output voltage output by the second magnetic resistance detection unit are set to be an appropriate range based on the threshold voltage set for the output voltage.
The range determined by the threshold voltage set for this output voltage and the range determined by the proper range are set as the dangerous mounting range, and the range excluding the dangerous mounting range from the proper range is set as the optimum mounting range. did.

According to a second aspect of the present invention, in the first aspect of the invention, the offset angle of each magnetic sensitive pattern portion of the second magnetoresistive detection portion is set to approximately 45 ° from the position detection direction. .

According to a third aspect of the present invention, in the piston position detecting device according to any of the first to third aspects, there is provided display means for distinguishably displaying the optimum mounting range and the dangerous mounting range. Provided.

[0014]

Therefore, according to the invention described in claim 1, the first
The magnetoresistive detector has the highest sensitivity to a magnetic field in the direction of position detection and outputs an output voltage corresponding to the magnetic field. The range determined based on this output voltage and the threshold voltage is the proper range. The second magnetoresistive detector has the highest sensitivity to the magnetic field in the directions inclined by the same offset angle in the clockwise direction and the counterclockwise direction from the position detection direction, and outputs the output voltage corresponding to the magnetic field. . The range determined based on the output voltage and the threshold voltage and the range determined based on the appropriate range are the dangerous mounting range.
Further, the optimum mounting range is the range that excludes the dangerous mounting range from the appropriate range. As a result, the dangerous mounting range and the optimum mounting range are detected with high sensitivity by the different magnetic resistance detection units.

According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, since the magnetoresistive detection directions of both the magnetically sensitive pattern portions are orthogonal to each other, the movement of the piston causes both of them to move. The output voltage is reliably output from.

According to the invention described in claim 3, in addition to the operation of the invention described in claim 1 or 2, the dangerous mounting range and the optimum mounting range are displayed in a distinguishable manner.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment embodying the present invention will now be described with reference to FIGS.
It will be described with reference to FIG. The piston position detection device of this embodiment is composed of a magnetoresistive element and an output voltage determination circuit. It should be noted that the description of the external configuration such as the case portion of the piston position detection device is omitted.

As shown in FIGS. 2A and 2B, a circuit board 1 is provided inside a case (not shown), and a magnetoresistive element 2 is mounted on the circuit board 1. or,
An output voltage determination circuit is formed on the circuit board 1.

The magnetoresistive element 2 has a first magnetic resistance detecting section 4 formed on the lower side of one surface of a substrate 3 formed of glass or the like, and a second magnetic resistance detecting section 4 is formed on the upper side of the first magnetic resistance detecting section 4. The resistance detector 5 is formed. First magnetic resistance detection unit 4
Is a substantially square-shaped magnetic sensitive pattern portion 6 formed substantially at the center of the magnetoresistive element 2 in the position detecting direction, and a temperature compensating pattern portion 7 formed on the right side of the magnetic sensitive pattern portion 6. It is configured. In the present specification,
The "position detection direction" means a direction parallel to the moving direction of the piston in a state where the piston position detection device is fixed to the fluid pressure cylinder that is to detect the position of the piston. The magnetic sensitive pattern portion 6 is formed of a ferromagnetic thin film formed in a zigzag pattern having an equal width in the vertical direction. The width of the pattern lines 6a and the pitch between the pattern lines 6a are formed to be constant. The temperature compensating pattern portion 7 is formed of a ferromagnetic thin film formed in a zigzag pattern having the same width in the left-right direction. The width of the pattern lines 7a and the pitch between the pattern lines are formed to be the same as in the magnetic sensitive pattern portion 6. Therefore, the magnetic detection direction of the first magnetic resistance detection unit 4 matches the position detection direction. The central portions of the magnetic sensitive pattern portion 6 and the temperature compensating pattern portion 7 are connected to each other and also to the land 8 on the lower left side of the substrate 3. The left side of the magnetic sensitive pattern portion 6 is connected to the upper left land 9 of the substrate 3, and the right side of the temperature compensating pattern portion 7 is also connected to the lower right land 10.

The second magnetoresistive detector 5 includes the magnetoresistive element 2
First magnetic sensitive pattern portion 11 formed on the left side with respect to the center of the substrate 3 in the position detection direction, and a second substantially rectangular shape formed on the right side with respect to the center. It is composed of a magnetic pattern portion 12. The first magnetic sensitive pattern portion 11 and the second magnetic sensitive pattern portion 12 are arranged at a position facing the center of the magnetic sensitive pattern portion 6 of the first magnetic resistance detection portion 4 in the position detection direction. The first magnetic sensitive pattern portion 11 is rotated counterclockwise from the position detection direction by 45.
It is formed of a ferromagnetic thin film formed in a zigzag, serpentine pattern of equal width. Pattern line 11
The width of a and the pitch between the pattern lines 11a are formed to be constant. The second magnetic sensitive pattern portion 12 is formed of a ferromagnetic thin film formed in a zigzag pattern having an equal width and inclined 45 ° clockwise from the position detection direction. The width of the pattern lines 12a and the pitch between the pattern lines 12a are formed to be the same as in the first magnetic sensitive pattern portion 11. That is, the magnetic resistance detection direction of the first magnetic sensitive pattern portion 11 and the magnetic resistance detection direction of the second magnetic sensitive pattern portion 12 are inclined from the position detection direction at an offset angle of 45 ° in the clockwise direction and the counterclockwise direction, respectively. It is arranged. Therefore, the magnetic field detection directions of the magnetically sensitive pattern portions 11 and 12 are orthogonal to each other. First magnetic sensitive pattern portion 11
And the left side of the second magnetically sensitive pattern portion 12 are connected to each other and to the land 13 on the upper right side of the substrate 3. The left side of the first magnetic sensitive pattern portion 11 is connected to the land 9, and the right side of the second magnetic sensitive pattern portion 12 is connected to the land 10. Therefore, the left side of the magnetic sensitive pattern portion 6 and the left side of the first magnetic sensitive pattern portion 11 are connected to each other, and the right side of the temperature compensating pattern portion 7 and the right side of the second magnetic sensitive pattern portion 12 are connected to each other. ing. That is, the magnetic sensitive pattern portion 6, the temperature compensation pattern portion 7, the first
Magnetic sensitive pattern portion 11 and second magnetic sensitive pattern portion 12
Are bridge-connected with the magnetic sensitive pattern portion 6 and the second magnetic sensitive pattern portion 12, and the temperature compensating pattern portion 7 and the first magnetic sensitive pattern portion 11 arranged at positions facing each other.

In the magnetoresistive element 2, a magnetic field from a magnet provided in the piston is applied to each of the magnetoresistive detectors 4 and 5 in a state where the piston position detector is attached to a pneumatic cylinder or the like for detecting the piston position. Are formed in such a size that they act in almost the same direction.

Next, the electrical construction of the piston position detecting device will be described. FIG. 3 shows an output voltage determination circuit 41 as a detection range determination unit to which the magnetoresistive element 2 is connected. The magnetoresistive element 2 is connected to the power supply line 14 to which the power supply voltage VC of the output voltage determination circuit 41 is applied via the land 9, and the ground line 15 is also connected to the ground line 15 via the land 10. Therefore, the magnetic sensitive pattern portion 6 and the temperature compensation pattern portion 7 of the first magnetic resistance detection unit 4, and the first magnetic sensitive pattern portion 11 and the second magnetic sensitive pattern of the second magnetic resistance detection unit 5. The parts 12 are connected in parallel with each other. Then, the first magnetic resistance detecting section 4 outputs the output voltage V1 to the non-inverting input terminal of the comparator 16 from between the magnetic sensitive pattern section 6 and the temperature compensating pattern section 7 (that is, the land 8). Further, the second magnetic resistance detecting section 5 outputs the output voltage V2 from the first magnetic sensitive pattern section 11 and the second magnetic sensitive pattern section 12 to the non-inverting input terminal of the comparator 17 and the inverting input terminal of the comparator 18. Are output respectively. When the magnetic field is not acting on the magnetic sensing pattern section 6, the magnetic resistance detecting section 4 uses the power supply voltage VC as the output voltage V1 with the respective resistance values of the magnetic sensing pattern section 6 and the temperature compensating pattern section 7. The divided reference voltage VREF is output. Similarly, the magnetic resistance detecting section 5 divides the power supply voltage VC as the output voltage V2 by the resistance value of each of the magnetic sensitive pattern portions 11 and 12 in a state where no magnetic field is applied to the magnetic sensitive pattern portions 11 and 12. The compressed reference voltage VREF is output. The magnetic sensitive pattern portion 6, the temperature compensating pattern portion 7 and each magnetic sensitive pattern portion 1
In the state where the magnetic field does not act on 1 and 12, the resistance values of the pattern portions 6, 7, 11, and 12 are set to be the same. Therefore, the reference voltage VREF is one half of the power supply voltage VC.

Threshold voltage setting circuits 19, 20, and 21 are connected between the power supply line 14 and the ground line 15, respectively. The threshold voltage setting circuit 19 is composed of two resistors 22 and 23 connected in series. The threshold voltage setting circuit 19 outputs the threshold voltage VTH from between the resistor 22 and the resistor 23 to the inverting input terminal of the comparator 16.
The threshold voltage setting circuit 20 is composed of two resistors 24 and 25 connected in series. The threshold voltage setting circuit 20 outputs the threshold voltage VTHL from between the resistor 24 and the resistor 25 to the inverting input terminal of the comparator 17.
Further, the threshold voltage setting circuit 21 is connected in series with 2
It is composed of individual resistors 26 and 27. The threshold voltage setting circuit 21 outputs the threshold voltage VTHU from between the resistors 26 and 27 to the non-inverting input terminal of the comparator 18. The reference voltage VRE of the threshold voltages VTHL and VTHU
The absolute value of the voltage difference from F is set equal.

The comparator 16 outputs a signal SG1 based on the threshold voltage VTH and the output voltage V1 to the NAND circuit 28. Further, the comparator 16 outputs the signal SG1 to the NAND circuit 29. The comparator 17 has a threshold voltage V
AND circuit 3 for the signal SG2 based on THL and output voltage V2
Output to 0. Further, the comparator 18 has a threshold voltage V
The AND circuit 3 outputs the signal SG3 based on the THU and the output voltage V2.
Output to 0. The AND circuit 30 outputs the signals SG2 and SG3.
Based on the signal SG4 via the inverting circuit 31 NAND circuit 2
Output to 8. Further, the AND circuit 30 outputs the signal SG4 to the NAND circuit 29.

The range in which the signal SG1 is at the H level is set as a proper range, and this proper range is divided into a dangerous mounting range and an optimum mounting range. The range in which the signal SG4 is at the L level is set so as to overlap both sides of the proper range. The range that overlaps both sides of this proper range is the dangerous mounting range, and the range excluding the dangerous mounting range from the proper range is the optimum mounting range.

The anode of a light emitting diode (hereinafter, referred to as LED) 32 that lights up in red is connected to the power supply line 14, and the cathode of the LED 32 is connected to the output side of the NAND circuit 28 via a resistor 33. . Also, the power line 14
The anode of LED34 that lights up in green is connected to
The cathode of the LED 34 is connected to the NAND circuit 2 via the resistor 35.
9 is connected to the output side. In this embodiment, LED3
2, 34 constitute a display means.

Further, the comparator 16 sends the signal SG1 to the resistor 3
It outputs to the base of the NPN transistor 37 via 6. The emitter of the transistor 37 is connected to the ground line 15, and the collector is connected to the output terminal 38. The base and emitter of the transistor 37 are connected via a resistor 39. The cathode of the Zener diode 40 is connected to the collector of the transistor 37, and the anode of the Zener diode 40 is connected to the emitter thereof. In this embodiment, the output circuit 42 is composed of the transistor 37, the Zener diode 40, and the resistors 36 and 39.
Then, the output circuit 42 outputs the output signal SG based on the signal SG1.
5 is output to the output terminal 38.

Next, the operation of the piston position detecting device constructed as described above will be described. 2 (a),
As shown in (b), the piston position detecting device of this embodiment is used by being fixed to the outer peripheral surface of the cylinder tube T of the pneumatic cylinder S in which the ring-shaped magnet M is attached to the outer peripheral side of the piston P, for example. To be done. FIG. 2 is a schematic view showing a mounted state of the piston position detecting device, and its dimensional relationship is greatly different from the actual one. The piston position detecting device is mounted so that the magnetic resistance detecting portions 4 and 5 of the magnetic resistance element 2 are arranged in a plane substantially including the axis of the cylinder tube T.

In the pneumatic cylinder S to which the piston position detecting device is attached in this manner, as shown in FIGS. 5 to 7, the case where the piston approaches the piston position detecting device and then moves away in the opposite direction will be described. . The strength of the magnetic field G acting on the first magnetic resistance detection unit 4 gradually increases until it reaches a position where the magnet M faces the center of the magnetic sensitive pattern unit 6, and then reaches the maximum. It gradually decreases as you move away from it. Therefore, the magnetic resistance detector 4
As shown in FIG. 4, the output voltage V1 is output from the reference voltage VREF with respect to the piston position and has a bilaterally symmetrical output characteristic that is convex upward.

On the other hand, the magnetic fields acting on the magnetic sensitive pattern portions 11 and 12 of the second magnetoresistive detecting portion 5 are as follows. As shown in FIG. 5, when the magnet M approaches the magnetoresistive element 2 from the left side, a magnetic field in a direction substantially orthogonal to the pattern line 11a is applied to the first magnetic sensitive pattern section 11 of the second magnetoresistive detection section 5. To work. On the other hand, the second magnetic sensitive pattern portion 1
2 is a magnetic field G in a direction substantially parallel to the pattern line 12a.
Works. As a result, the resistance value of the first magnetically sensitive pattern portion 11 decreases, so that the output voltage V2 becomes higher than the reference voltage VREF and becomes the output peak value. At this time,
Since the magnetic field G having a direction of approximately 45 ° with respect to each magnetic sensitive direction acts on the magnetic sensitive pattern portion 6 and the temperature compensating pattern portion 7, the output voltage V1 of the magnetic resistance detecting portion 5 is almost the reference. The voltage becomes VREF.

Next, the magnet M moves in the same direction, and the centers thereof are the first magnetic sensitive pattern portion 11 and the second magnetic sensitive pattern portion 1.
When they are arranged at positions opposite to each other, as shown in FIG. 6, a magnetic field G having a direction of approximately 45 ° with respect to each magnetic sensitive direction of both magnetic sensitive pattern portions 11 and 12 acts. As a result, the decrease in the resistance value of each of the first magnetic sensitive pattern portion 11 and the second magnetic sensitive pattern portion 12 becomes substantially the same, so that the output voltage V2 becomes approximately the reference voltage VREF. At this time, since the magnetic field G in the position detection direction acts on the magnetoresistive detection unit 5, the output voltage V1 of the magnetoresistive detection unit 5 is
Is the maximum output voltage value.

When the magnet M is further moved and is arranged at a position away from the right side of the magnetoresistive element 2, as shown in FIG. 7, the pattern line 12a is formed on the second magnetic sensitive pattern portion 12.
A magnetic field is applied in a direction substantially orthogonal to. On the other hand, the magnetic field G in the direction substantially parallel to the pattern line 11a acts on the first magnetic sensitive pattern portion 11. As a result, the resistance value of the second magnetically sensitive pattern portion 12 decreases, so that the output voltage V
2 becomes lower than the reference voltage VREF and becomes an output peak value. At this time, since the magnetic field G having a direction of approximately 45 ° with respect to each magnetic sensitive direction acts on the magnetic sensitive pattern portion 6 and the temperature compensating pattern portion 7, the output voltage V1 of the magnetic resistance detecting portion 5 is increased. Becomes almost the reference voltage VREF.

As a result of the above, the output voltage V2 output from the second magnetic resistance detecting section 5 is, as shown in FIG. 4, on the left side with respect to the position opposed between the magnetic resistance detecting sections 11 and 12. It becomes higher than the reference voltage VREF, and the reference voltage V
The characteristic is lower than REF. Further, the output characteristic is substantially point-symmetrical with respect to the position where the reference voltage VREF is obtained.
The piston position when the output voltage V1 of the magnetic resistance detection unit 4 reaches the maximum output voltage value and the piston position when the output voltage V2 of the magnetic resistance detection unit 5 reaches the reference voltage VREF are substantially the same. .

The output voltage V1 output from the first magnetic resistance detecting section 4 is compared with the threshold voltage VTH by the comparator 16. The output voltage V1 from the comparator 16 is
A signal SG1 that is at the H level is output in the range where the threshold voltage is equal to or higher than the threshold voltage VTH.

Further, the output voltage V2 output from the second magnetoresistive detector 5 is compared with the threshold voltage VTHL by the comparator 17.
Is compared with the output voltage V2, and a signal SG2 of L level is output in the range where the output voltage V2 is lower than the threshold voltage VTHL.
Further, the output voltage V2 is compared with the threshold voltage VTHU by the comparator 18, and the signal SG3 which is at L level is output in the range where the output voltage V2 is equal to or higher than the threshold voltage V2. Therefore, the AND circuit 30 outputs the signal SG4 which becomes L level in the range where the signal SG2 is L level or the signal SG3 is L level.

As a result, when the piston position is out of the detection range, the signal SG1 becomes L level and the signal SG4 becomes H level or L level. As a result, the NAND circuit 28,
Since the output side of 29 both becomes H level, LED32,
Neither 34 lights up. Further, when the piston position is in the dangerous mounting range, the signal SG1 becomes H level and the signal SG4 becomes L level. As a result, the potential on the output side of the NAND circuit 28 becomes L level and the potential on the output side of the NAND circuit 29 remains at H level, so that only the LED 32 lights up in red. Further, when the piston position is within the optimum mounting range, the signal SG1 becomes H level and the signal SG4 becomes H level. As a result, the output side of the NAND circuit 28 becomes H level and the output side of the NAND circuit 29 becomes L level, so that only the LED 34 lights up in green. Therefore, the operator can easily visually recognize that the piston position is in each range.

When the piston position is within the detection range, the output circuit outputs the H-level output signal SG5.
Therefore, this output signal SG5 can be used as a control signal for sequence control.

As described in detail above, according to the piston position detecting apparatus of the present embodiment, the optimum mounting range is formed in the region where the output voltage V1 has a high value within the proper range of the first magnetic resistance detecting section 4. . Therefore, the piston position can be detected with a high voltage margin value, so that the piston position can be detected stably and reliably even when the output voltage V1 of the magnetoresistive detector 4 varies due to an external magnetic field or the like. You can

Further, according to this embodiment, the directions of the magnetic fields G acting on the magnetic sensitive pattern portions 6, 11, 12 and the temperature compensating pattern portions 7 of the respective magnetic resistance detecting portions 4, 5 are made substantially the same. Then, the magnetoresistive element 2 was formed. The optimum mounting range and the dangerous mounting range are set under the condition that the same magnetic field G acts, and the piston position can be determined. Therefore, the piston position can be detected regardless of the width of the magnet such as the pneumatic cylinder to which the present piston position detecting device is attached.

Further, according to the present embodiment, the second magnetoresistive detecting portion 5 is constituted by connecting the magnetic sensitive pattern portions 11 and 12 formed in the same pattern shape in series, so that the magnetic sensitive pattern portions 11 and 12 are formed. One performs temperature compensation for the other. As a result, each magnetic sensing pattern portion 1 due to temperature fluctuation
Since the fluctuations of the output voltages V and V2 of 1 and 12 are suppressed,
Changes in the dangerous mounting range due to temperature changes are suppressed. Therefore, it is possible to improve the stability of the detection accuracy with respect to temperature fluctuations.

Further, according to the present embodiment, the temperature compensating pattern portion 7 with respect to the change of the resistance value of the first magnetic resistance detecting portion 4 is used.
Since the temperature compensation is performed by, the fluctuation of the output voltage due to the temperature fluctuation is suppressed. Therefore, it is possible to suppress the fluctuation of the optimum mounting range due to the temperature fluctuation, and it is possible to improve the stability of the detection accuracy with respect to the temperature fluctuation.

In addition, according to this embodiment, the two LEDs 32 whose emission color differs between the dangerous mounting range and the optimum mounting range,
Since it is displayed so as to be discriminable at 34, it is possible to easily visually recognize in which range the piston position is.

The present invention can be configured as follows in addition to the above embodiment. (1) Each magnetic resistance detection unit 1 of the second magnetic resistance detection unit 5
Offset angle of 1 and 12 from the position detection direction is 45 °
Other angles may be used.

(2) The positions of the magnetic resistance detecting portions 4 and 5 may be appropriately changed within a range in which the magnetic fields G in substantially the same direction act on the magnetic sensitive pattern portions 6, 7, 11, and 12. For example, the center between the magnetic sensitive pattern portions 6 and 7 is set to the magnetic sensitive pattern portion 1
It may be configured so as to coincide with the center between 1 and 12.

Further, the second magnetoresistive detecting section 4 is used.
The position of the magnetic resistance detection unit 5 may be changed in the vertical direction. In this case, the size of the magnetic sensitive pattern portions 11 and 12 and the distance between the magnetic sensitive pattern portions 11 and 12 are appropriately adjusted so that a dangerous mounting area having an appropriate size is formed.
The sensitivity of the magnetic resistance detection unit 5 is optimized.

(3) The temperature compensating pattern portion 7 of the first magnetoresistive detecting portion 4 has a magnetic sensitive direction 90 with the magnetic sensitive pattern portion 6.
The magnetic sensitive pattern portion 6 may be the same as the magnetic sensitive pattern portion 6 that is different (that is, the same as the temperature compensating pattern portion 7). Even in this case, the temperature compensation for the magnetic sensitive pattern portion 6 can be performed.

(4) The first magnetoresistive detecting section 4 may be composed of only the magnetic sensitive pattern section 6 without providing the temperature compensating pattern section 7. (5) The first magnetoresistive detector 4 and the second magnetoresistive detector 5 may be formed in multiple layers at the same position on the substrate 3 with an insulating layer interposed.

Alternatively, the same substrate 3 may be formed separately on the front and back sides. Further, the magnetoresistive detectors 4 and 5 formed on different substrates 3 may be integrated by pasting both substrates 3 together.

(6) The piston position is set to the LEDs 32, 34.
May be output to a programmable controller or the like as an output signal corresponding to the optimum mounting range and the dangerous mounting range.

(7) A positive feedback may be applied to the comparator 16 of the output voltage determination circuit. That is, as shown by the chain double-dashed line in FIG. 3, the non-inverting input terminal and the output terminal of the comparator 16 are connected via the resistor 43. In this case, it is possible to stably switch from the dangerous mounting range to the optimal mounting range or from the optimal mounting range to the dangerous mounting range.

(8) The magnet M attached to the piston P is not limited to the ring shape, and may be, for example, a cylindrical shape, a semi-cylindrical shape, a quadrangular shape, or the like. (9) Each magnetic resistance detection unit 4 of the piston position detection device 4,
Although 5 is used in a state of being arranged in a plane including the axis of the cylinder tube T, it may be configured to be used in a state of being slightly displaced from that plane.

In the following, besides the technical idea described in the claims, the technical idea grasped in each of the above-mentioned embodiments will be described together with its effect. (1) In the piston position detecting device according to any one of claims 1 to 3, fluid pressure for detecting the piston position by the pattern surface of each of the magnetically sensitive pattern portions 11 and 12 of the second magnetic resistance detecting portion 5. A piston position detection device that can be mounted so as to be perpendicular to the isomagnetic field surface of the magnetic field from the cylinder piston.

With this structure, since the strength of the magnetic field in the magnetically sensitive direction of each magnetically sensitive pattern portion becomes large, the dangerous mounting range can be stably and reliably detected.

[0054]

As described in detail above, according to the first aspect of the present invention, on the both sides of the range which is detected with high sensitivity by one magnetoresistive detecting section, the other magnetoresistive detecting section has a high value. A range that can be detected with sensitivity is formed, and a dangerous mounting range and an optimum mounting range are formed in both of these ranges, so the piston position is stable and secure in the optimum mounting range even when disturbances such as external magnetic fields act. Can be detected. Further, since the piston position is determined in the state where the magnetic field in the same direction acts on the magnetoresistive element, the piston position can be detected regardless of the size of the magnetic field distribution range from the piston for position detection. You can Therefore, the piston position can be reliably detected regardless of the width of the magnet attached to the piston.

According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, since the output voltage can be reliably taken out from each magnetic sensitive pattern portion, the dangerous mounting range can be reduced. It can be reliably formed.

Further, according to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, it is possible to visually recognize the state where the piston position is in the optimum mounting range or the dangerous mounting range. Can be displayed.

[Brief description of drawings]

FIG. 1 is a schematic front view of a magnetoresistive element.

2A is a schematic front view showing a piston position detection device mounted on a cylinder, and FIG. 2B is a schematic side view of the same.

FIG. 3 is an electric circuit diagram of a piston position detection device.

FIG. 4 is an operation chart of an output voltage of each magnetic resistance detection unit and each processing signal.

FIG. 5 is a schematic diagram showing how magnetic fields act on both magnetoresistive detectors.

FIG. 6 is a schematic diagram showing how magnetic fields act on both magnetoresistive detectors.

FIG. 7 is a schematic diagram showing how magnetic fields act on both magnetoresistive detectors.

FIG. 8 is a schematic front view showing a conventional piston position detecting device.

FIG. 9 is a graph showing the relationship between piston position and output voltage.

FIG. 10 is a schematic plan view showing another conventional magnetic proximity switch.

FIG. 11 is a graph showing the relationship between piston position and sensitivity.

[Explanation of symbols]

4 ... 1st magnetic resistance detection part, 5 ... 2nd magnetic resistance detection part, 6 ... Magnetic sensitive pattern part, 7 ... Temperature compensation pattern part,
11 ... Magnetosensitive pattern portion, 12 ... Magnetosensitive pattern portion, 32,
34 ... LED as display means, 41 ... Output voltage judging circuit as detection range judging section, V1 ... Output voltage, V2 ... Output voltage, VTH ... Threshold voltage, VTHL, VTHU ... Threshold voltage.

Claims (3)

[Claims] 1. A first magnetoresistive detector (4) having a magnetic field detection direction arranged in a position detection direction, and each magnetic field detection direction inclined from the position detection direction by an offset angle equal to clockwise and counterclockwise directions, respectively. And a second magnetoresistive detector (5) composed of a pair of magnetically sensitive pattern portions (11, 12) arranged in series and connected to each other in series. The position where the output of the first magnetic resistance detection unit (4) reaches a peak and the position where the outputs of the magnetic sensitive pattern units (11, 12) of the second magnetic resistance detection unit (5) are inverted are substantially matched. So that the output voltage (V1
) And the threshold voltage (VTH) set with respect to this output voltage (V1) is set as an appropriate range, and the output voltage (V2) output from the second magnetic resistance detection section (5) is set.
And the range determined by the threshold voltage (VTHL, VTHU) set for this output voltage (V2) and the range determined by the proper range are the dangerous mounting range. A piston position detecting device provided with a detection range discriminating section (41) whose optimum mounting range is the excluded range. 2. The piston position detecting device according to claim 1, wherein the offset angle of each magnetic sensitive pattern portion (11, 12) of the second magnetic resistance detecting portion (5) is approximately 45 ° from the position detecting direction. . 3. The piston position detecting device according to claim 1 or 2, further comprising display means (32, 34) for distinguishably displaying an optimum mounting range and a dangerous mounting range.