JP2709032B2 - Piston position detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as such a piston position detecting device, there is, for example, a position detecting device disclosed in Japanese Utility Model Publication No. 57-6962. This position detecting device is shown in FIG.
As shown in FIG. 3, a pair of magneto-sensitive pattern portions 8 formed of a ferromagnetic thin film and arranged so that the respective magneto-sensitive directions are orthogonal to each other.
1 and 82 are provided. The magnetoresistive detecting section 83 senses a magnetic field in the magnetosensitive pattern section 81 whose magnetic sensing direction coincides with the position detecting direction, and senses the magnetic field in the magnetic sensing pattern section 82 whose magnetic sensing direction is orthogonal to the position detecting direction. Temperature compensation is performed on the magnetic pattern portion 81. As shown in FIG.
The output voltage VO output corresponding to the piston position is symmetrical with respect to the output voltage VREF in a state where no magnetic field is applied to the magneto-sensitive pattern portion 81, in which a convex curve is formed on the output voltage VREF and the whole curve is gentle. Output characteristics. For the determination of the piston position, first, threshold voltages VTHL and VTHU of two output levels appropriate for the output voltage VO are set. The two threshold voltages VTHL, VTHL
The optimum mounting range and the dangerous mounting range are set based on the above, and the piston position is determined in each of these ranges.

That is, for example, when the output voltage value for a certain piston position is equal to or higher than the high threshold voltage VTHU, it is determined that the piston position is within the optimum mounting range. or,
When the output voltage value is lower than the high threshold voltage TTFU and higher than the low threshold voltage VTHL, it is determined that the piston position is in the dangerous mounting range. Further, when the output voltage value is lower than the low threshold voltage VTHL,
It is determined that the piston position is out of the range including the dangerous mounting range and the optimum mounting range.

[0004]

By the way, in a piston position detecting device, an output voltage VO due to an external magnetic field or the like is used.
In order to prevent malfunction due to fluctuations in the output voltage VO, the voltage difference ΔVU between the maximum output voltage value VMAX of the output voltage VO and the high threshold voltage VTHU and the voltage difference ΔVL between the output voltage VREF and the low threshold voltage VTHL are Each must secure a certain amount of time. That is, the respective voltage differences ΔVU, ΔVL maintain the optimum mounting range and the dangerous mounting range at the respective threshold voltages VTHL, VTHU even when the output voltage VO or the output voltage VREF fluctuates due to an external magnetic field or the like, and malfunction. And a margin for determining the piston position. In the piston position detecting device, it is desirable to set the optimum mounting range to about 3 mm in order to secure the mounting accuracy of the piston position. At the same time, the dangerous mounting range is desirably set to the same size as the optimal mounting range so that a deviation of the piston position from the optimum mounting range can be detected.

However, in the case of the position detecting device described above, the magnetic field of a magnet provided on a piston such as a pneumatic cylinder is detected by only one magnetic sensing pattern portion.
Each of its output voltage levels is relatively low. That is, since the sensitivity to the magnetic field is low, when the magnetic field of the magnet to be detected is relatively weak, sufficient voltage differences .DELTA.VU and .DELTA.V with respect to the maximum output voltage value VMAX and the output voltage VREF of the output voltage VO, respectively.
In some cases, it is difficult to set each of the threshold voltages VTHL and VTHU with VL. In this case, if the output voltage VO fluctuates due to an external magnetic field or the like, the optimum mounting range and the dangerous mounting range cannot be determined normally. As a result, the piston position is not correctly determined and malfunctions, and the detection of the piston position is hindered.

Further, a voltage difference ΔVU,
Even if the threshold voltages VTHL and VTHL can be set while securing ΔVL, the voltage difference between the two threshold voltages (= ΔVU−ΔVL) is narrowed, and the optimum mounting range to be set is limited. It becomes large and the dangerous mounting area becomes small. Therefore, it has not been possible to obtain an optimum mounting range and a dangerous mounting range of an appropriate size necessary for detecting the piston position.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object of the present invention is to prevent a malfunction caused by an external magnetic field or the like even when a magnetic field from a piston for position detection is weak. It is an object of the present invention to provide a piston position detecting device which can be used.

[0008] The second object is, in addition to the first object,
An object of the present invention is to provide a piston position detecting device that can set an appropriate dangerous mounting range and an optimum mounting range.
A third object is to provide a piston position detecting device having a sub-optimal mounting range between the optimum mounting range and the dangerous mounting range in addition to the second object.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 provides a plurality of magnetic heads having a plurality of output levels different from each other with respect to an output voltage output in accordance with a piston position. A piston position detecting device that sets a threshold voltage and determines a piston position in a plurality of ranges set based on each threshold voltage. The piston position detecting device includes a plurality of magnetoresistive detectors and detects positions of the respective magnetoresistive detectors. A difference output generation unit that arranges the same direction and arranges the position where each output peak coincides, and generates a difference output voltage having a higher output level than the individual output voltage from the output voltage of each magnetoresistance detection unit. And a plurality of threshold voltages are set for the differential output voltage output by the differential output generation unit to determine the piston position.

According to a second aspect of the present invention, in the first aspect of the present invention, each of the magnetoresistive detecting sections determines a pitch of a pattern line in a position detecting direction of the magnetosensitive pattern section. Are formed so that the center in the position detection direction is the smallest and becomes larger from the center toward both ends.

According to a third aspect of the present invention, in the first or the second aspect of the present invention, the plurality of magnetoresistive detectors are arranged substantially in a direction perpendicular to the pattern surface of each magneto-sensitive pattern. In addition, they were arranged at such a distance that the magnetic fields acting on each magneto-sensitive pattern portion were substantially equal.

According to a fourth aspect of the present invention, in the first aspect of the present invention, three threshold voltages having different levels from each other are set with respect to the output voltage. The optimum mounting range, the sub-optimal mounting range, and the dangerous mounting range are set based on the threshold voltage.

[0013]

Therefore, according to the first aspect of the present invention, the positions detected in the same direction and the respective output peaks are output from a plurality of magnetoresistive detectors arranged so as to coincide with each other. A differential output voltage having an output level higher than each individual output voltage is generated from the output voltage. This differential output voltage has an output characteristic that increases more gradually as the position approaches the highest sensitivity position than the individual output voltages.
Then, a plurality of attachment ranges are set for the difference output voltage with a plurality of threshold voltages, and the piston position is determined in each attachment range. As a result, since each threshold voltage can be set with a large voltage difference with respect to the upper limit value and the lower limit value of the differential output voltage, a malfunction does not easily occur even if the output voltage fluctuates due to an external magnetic field or the like. . Further, even if the difference output voltage fluctuates, the fluctuation of the piston position corresponding to the voltage value determined by each threshold voltage is reduced.

According to the second aspect of the present invention, in addition to the operation of the first aspect, the output characteristic of the differential output voltage is such that the rate of increase increases as the position approaches the highest sensitivity position. Resulting in increasing characteristics. As a result, the difference between the sizes of the respective mounting ranges set by the respective threshold voltages increases.

According to the third aspect of the present invention, in addition to the function of the first or second aspect of the present invention, each magneto-sensitive pattern of each magneto-resistive detector has substantially the same strength. Due to the action of the magnetic field, the output level of the differential output voltage becomes higher than the level of each output voltage. As a result, each threshold voltage can be set while securing a larger voltage difference, so that even if the output voltage fluctuates due to an external magnetic field or the like, a malfunction hardly occurs.

According to a fourth aspect of the present invention, in addition to the operation of the first aspect of the present invention, the piston position is set between the optimum mounting range and the dangerous mounting range. The determination is made based on the three sub-optimal mounting ranges that are set.

[0017]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. The piston position detecting device according to the present embodiment includes a magnetoresistive element and an output voltage determining circuit. The description of the external configuration such as the case portion of the piston position detecting device will be omitted, and only the internal configuration will be described.

As shown in FIG. 4, a circuit board 1 is provided inside a case (not shown), and a magnetoresistive element 2 is mounted on the circuit board 1. Further, an output voltage determination circuit is formed on the circuit board 1.

As shown in FIG. 1, a first magnetoresistive detecting section 4 is provided at a substantially lower half position on one surface of a substrate 3 formed of glass or the like of a magnetoresistive element 2, and a second magnetic resistance detecting section 4 is provided at an upper half position. Each of the resistance detectors 5 is formed. The first magnetic resistance detecting section 4 includes a magneto-sensitive pattern section 6 provided on a lower side and a temperature compensation pattern section 7 provided on an upper side.
The magneto-sensitive pattern section 6 is formed of a ferromagnetic thin film formed in a zigzag pattern having the same width in the vertical direction. The line width of the pattern line 6a forming this pattern is 2
The pitch between the pattern lines 6a is constant at 0 μm. The left end of the magneto-sensitive pattern portion 6 is connected to a land 8 formed on the lower left side of the substrate 3, and the right end is connected to a land 9 formed on the lower right side of the substrate 3. Further, the temperature compensating pattern section 7 is formed of a ferromagnetic thin film formed in a serpentine pattern having the same width in the position detection direction. The pattern line forming this pattern has a constant line width of 4 μm, and the pitch between the pattern lines is also constant. The lower left end of the temperature compensation pattern section 7 is connected to a land 8, and the upper left end is connected to a land 13 formed on the upper left side of the substrate 3. The length of the temperature compensating pattern 7 in the position detection direction is shorter than the length of the magneto-sensitive pattern 6 in the position detection direction (substantially half in this embodiment). The resistance values of the magneto-sensitive pattern portions 6, 11 and the resistance values of the temperature compensating pattern portions 7, 12 when no magnetic field is applied are set to be equal. In the present specification, the "position detection direction" means a direction parallel to the movement direction of the piston in a state where the piston position detection device is fixed to the fluid pressure cylinder whose piston position is to be detected.

The second magnetoresistive detecting section 5 is also composed of a magneto-sensitive pattern section 11 and a temperature compensating pattern section 12, like the first magnetoresistive detecting section 4. Magnetic sensing pattern section 11
Are formed in the same manner as the magneto-sensitive pattern section 6, and the temperature compensation pattern section 12 is formed in the same manner as the temperature compensation pattern section 7. However, the magneto-sensitive pattern section 11 is disposed above the temperature compensation pattern section 12, and the temperature compensation pattern section 12
Are disposed at positions facing the upper side of the temperature compensation pattern section 7. The left end of the magneto-sensitive pattern portion 11 is a land 13 formed on the upper left side of the substrate 3, and the right end is a land 10
Connected to each other. The lower right end of the temperature compensation pattern section 12 is connected to the land 9, and the upper right end is connected to the land 10. Therefore, both magneto-sensitive pattern portions 6, 1
1 and both temperature compensating patterns 7, 12 are lands 9, 1
3 are bridge-connected. The magneto-sensitive pattern portions 6, 11 and the temperature compensating pattern portions 7, 12 are respectively arranged at positions facing the bridge.

Next, the electrical configuration of the output voltage determining circuit connected to the magnetoresistive element 2 will be described. FIG. 2 shows an output voltage determination circuit 21 to which the magnetoresistive element 2 is connected.
Is shown. The magnetoresistive element 2 is connected via a land 9 to a power supply line 22 to which a power supply voltage VC is applied.
3 is connected via a land 13. Therefore, the magneto-sensitive pattern section 6 and the temperature-compensating pattern section 7 and the temperature-compensating pattern section 12 and the magneto-sensitive pattern section 11 are connected in parallel with each other. The non-inverting input terminal of an operational amplifier 24 as a differential output voltage generating section is connected between the magnetic sensing pattern section 6 of the first magnetic resistance detecting section 4 and the temperature compensating pattern section 7 (that is, the land 8). I have. The operational amplifier 2 is located between the second magnetic resistance detecting section 5 and the magnetic sensing pattern section 11 of the temperature compensating pattern section 12 (that is, the land 10).
4 inverting input terminals. The output side of the operational amplifier 24 is connected to the non-inverting input terminals of the comparators 25 and 26.

A threshold voltage setting circuit 27 is connected between the power supply line 22 and the ground line 23. The threshold voltage setting circuit 27 includes three resistors 28, 29, 3 connected in series.
0. The connection between the resistors 28 and 29 is connected to the inverting input terminal of the comparator 25, and the connection between the resistors 29 and 30 is connected to the inverting input terminal of the comparator 26.

The output side of the comparator 25 is an exclusive OR circuit (hereinafter, referred to as an Ex-OR circuit).
31 and an AND circuit 32.
The output side of the comparator 26 is connected to the Ex-OR circuit 31 and the AND circuit 32, respectively.

The output side of the Ex-OR circuit 31 is connected to the anode of a red light emitting diode (hereinafter referred to as LED) 34 via a resistor 33, and the output side of the AND circuit 32 is connected via a resistor 35. It is connected to the anode of the green LED 36. Each cathode of the LEDs 34 and 36 is connected to the output circuit 37. The output side of the output circuit 37 is connected to the output terminal 38. In this embodiment, LE
The display means is constituted by D34 and D36.

Next, the operation of the piston position detecting device configured as described above will be described. FIG. 4 (a),
As shown in (b), the piston position detecting device of the present embodiment is used, for example, by being fixed to the outer peripheral surface of a cylinder tube T of a pneumatic cylinder S in which a ring-shaped magnet M is attached to the outer peripheral portion of a piston P. Is done. FIG. 4 is a schematic diagram showing the state of attachment of the piston position detecting device, and its dimensional relationship is significantly different from the actual one. The piston position detecting device is mounted such that both magnetoresistive detecting portions of the magnetoresistive element 2 are arranged in a plane including the axis of the cylinder tube T.

In the pneumatic cylinder S to which the piston position detecting device is attached, the piston P approaches the piston position detecting device and then moves away in the opposite direction. Since the magnetic field does not act on the magnetoresistive element 2 when the position of the piston P is far from the magnetoresistive element 2, the first magnetoresistive detecting section 4 sets the power supply voltage VC as the output voltage V1 to the resistance value of the magnetosensitive pattern section 6. And a reference voltage VREF which is a voltage divided by the resistance value of the temperature compensation pattern unit 7
Is output. Similarly, the second magnetoresistive detector 5 uses the reference voltage VREF, which is a voltage obtained by dividing the power supply voltage VC as the output voltage V2 by the resistance value of the magneto-sensitive pattern section 11 and the resistance value of the temperature compensation pattern section 12. Output. The resistance values of the magneto-sensitive pattern section 6 and the temperature compensation pattern section 7 when no magnetic field is applied, and the resistance values of the magneto-sensitive pattern section 11 and the temperature compensation pattern section 12 are set to be equal. For,
The voltage value of the reference voltage VREF is one half of the power supply voltage VC.

The strength of the magnetic field acting on each of the magnetoresistive detectors 4 and 5 is determined by the position where the magnet M is opposed to the center of the magnetosensitive pattern sections 6 and 11 of each of the magnetoresistive detectors 4 and 5 in the position detection direction. Until the magnet M moves away from the center, it gradually decreases until it reaches a maximum. Accordingly, as shown in FIG. 3, the first magnetoresistive detector 4 outputs an output voltage V1 having a symmetrical output characteristic of a convex upward and downward from the reference voltage VREF corresponding to the piston position. On the other hand, the second magnetoresistive detector 5 outputs an output voltage V2 having a left-right symmetrical output characteristic which is convex downward from the reference voltage VREF in accordance with the piston position. That is, the output voltages V1 and V2 have the highest sensitivity from both ends to the center of each of the detection ranges in which the output voltage value starts to become higher (or lower) than the reference voltage VREF due to the magnetic field acting on each of the magnetoresistance detectors 4 and 5. The output characteristic is such that the voltage value gradually increases to the position. Since the magneto-sensitive pattern portion 11 is arranged at a position farther from the magnet M than the magneto-sensitive pattern portion 6, the output level of the output voltage V2 is slightly lower than the output voltage V1. In this embodiment, since the line width of the pattern lines of the temperature compensating patterns 7 and 12 is formed to be 4 μm, the change in the resistance value due to the magnetic field in the position detection direction is extremely small. Therefore, the output characteristics of the output voltages V1 and V2 are substantially determined by the change in the resistance value of the magnetosensitive pattern portions 6 and 11 due to the magnetic field.

From the operational amplifier 24, the two output voltages V1, V
The output voltage VDEF as the difference output voltage which is the difference between 2
(= V1 -V2) is output. Therefore, the maximum output voltage value of the output voltage VDEF is a voltage value obtained by adding the absolute value of the voltage difference between the output peaks of the two output voltages V1 and V2 with respect to the reference voltage VREF. The output characteristics of each output voltage V
1. As compared with V2, the characteristic becomes gradually larger as the position approaches the highest sensitivity position. As a result, the output voltage V
For DEF, the first threshold voltage VTHL and the second threshold voltage VTHU can be set with a larger voltage difference than when set for the individual output voltages V1 and V2.

On the other hand, the resistance 2 of the threshold voltage setting circuit 27
From between the resistor 8 and the resistor 29, a first threshold voltage VTHL based on the power supply voltage VC is output to the inverting input terminal of the comparator 25. Similarly, a second threshold voltage VTHU based on the power supply voltage VC is output to the inverting input terminal of the comparator 26 from between the resistors 29 and 30.

The output voltage VDEF output from the operational amplifier 24
Is compared with the first threshold voltage VTHL by the comparator 25, and the comparator 25 outputs the signal SG1 which becomes H level within the dangerous mounting range and the optimum mounting range where the output voltage VDEF is equal to or higher than the first threshold voltage VTHL. Is done. Similarly, the output voltage VDEF is compared with the second threshold voltage VTHU by the comparator 26, and when the output voltage VDEF is within the optimum mounting range in which the output voltage VDEF is equal to or higher than the second threshold voltage VTHU, the signal from the comparator 26 becomes H level. SG2 is output. In this embodiment, the range where the signal SG2 is at the H level is the optimum mounting range, and the range where the signal SG2 is at the L level and the signal SG1 is at the H level is the dangerous mounting range.

From the Ex-OR circuit 31, a signal SG3 based on the signal SG1 and the signal SG2 is output to the anode of a red light emitting diode (hereinafter, referred to as LED) 34 via a resistor 33. The AND circuit 32 outputs a signal S
A signal SG3 based on G1 and the signal SG2 is output to the anode of the green LED 36 via the resistor 35. further,
The output circuit 37 outputs a signal SG5 based on the signals SG3 and SG4 to an output terminal 38.

Therefore, when the piston position is out of both the dangerous mounting range and the optimum mounting range, the signals SG1 and SG2 are both at the L level, and both the signals SG3 and SG4 are also at the L level. As a result, the LEDs 34 and 36 do not light up outside the dangerous mounting range and the optimum mounting range. When the piston position is within the dangerous mounting range,
Since the signal SG1 goes high and the signal SG2 goes low,
The signal SG3 goes high and the signal SG4 goes low. As a result, when the piston position is within the dangerous
The LED 34 lights up in red, and the LED 36 does not light up. Further, when the piston position is within the optimal mounting range, the signal SG1
Becomes H level and the signal SG2 becomes L level.
Is at the L level and the signal SG4 is at the H level. As a result, when the piston position is within the optimum mounting range, the LED 34 does not light up and the LED 36 lights up green. Therefore, the operator can easily visually recognize the range of the piston position.

When the piston position is in one of the optimum mounting range and the dangerous mounting range, the output circuit 37 outputs a signal SG5 at H level. Therefore, this signal SG5
Can be used for sequence control.

As described in detail above, according to the piston position detecting device of the present embodiment, the first threshold value is provided with a sufficient voltage difference from the reference voltage VREF and the maximum output voltage value with respect to the output voltage VDEF. The voltage VTHL and the second threshold voltage VTH
U can be set individually. As a result, when the magnetic field to be detected is weak, the output voltage VDEF
Erroneous operation is less likely to occur even if the value fluctuates.

Since the gradient of the characteristic of the output voltage VDEF is steeper than the gradient of the output voltages V1 and V2, even if the output voltage VDEF fluctuates due to an external magnetic field or the like, the threshold voltages VTHL and VTHU change. The fluctuation of the piston position corresponding to the voltage value determined by the above operation is reduced. Therefore, each threshold voltage V
Since the optimum mounting range and the dangerous mounting range set by THL and VTHU are less likely to fluctuate, it is possible to detect a piston position that is less affected by an external magnetic field. Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. It should be noted that the piston position detecting device of the present embodiment is different from the piston position detecting device of the first embodiment in that the patterns of the magneto-sensitive patterns 6, 11 of the first magnetoresistive detectors 4, 5 of the magnetoresistive element 2, Pattern line 6a, 1
Since only the pitch configuration of 1a is different and the other configurations are the same, the same reference numerals are used and the description is omitted.

As shown in FIG. 5, each magneto-sensitive pattern section 6, 11 of each first magnetoresistive detecting section 4, 5 of the present embodiment has a
As in the embodiment, the ferromagnetic thin film is formed of a serpentine pattern having the same width in the vertical direction.
The line width of the pattern lines 6a and 11a is formed to be constant. The pitch W between the pattern lines 6a and 11a is the smallest W at the center of the magneto-sensitive pattern portions 6 and 11 in the position detection direction.
It is formed so as to increase from the center toward both ends, and to increase by a constant amount. Therefore, the pitch at both ends is maximum at W2. In addition, the magneto-sensitive pattern portion 11 of the second magnetic resistance detecting section 5 is formed in the same manner.

Next, the operation of the piston position detecting device configured as described above will be described. The piston position detecting device of the present embodiment is used similarly to the piston position detecting device of the first embodiment.

When a magnetic field acts on the magneto-sensitive pattern portions 6, 11, the internal resistance of the magneto-sensitive pattern portions 6, 11 decreases according to the magnitude of the pitch W between the pattern lines 6a, 11a in the region where the magnetic field acts. I do. That is, when a magnetic field acts on a region where the pitch W is wide, the decrease in the internal resistance is small and the pitch W
When a magnetic field acts on a narrow region, the internal resistance is greatly reduced. In the present embodiment, the pitch W of each of the magneto-sensitive pattern portions 6 and 11 is formed so as to be smallest at the center in the position detection direction and to increase by a certain amount from the center to both ends, so that the output voltages V1 and V2 Is an output characteristic that is larger than the output voltages V1 and V2 of the first embodiment and gradually increases with respect to the piston position. The output level of the output voltage V2 is slightly lower than that of the output voltage V1, as in the first embodiment. As a result, in the same manner as in the first embodiment, the maximum output voltage value of the output voltage VDEF as the obtained differential output voltage is obtained by adjusting the absolute value of the voltage difference between the output peak values of the two output voltages V1 and V2 with respect to the reference voltage VREF. Voltage value. Therefore, for the output voltage VDEF, the first threshold voltage VTHL and the second threshold voltage VTHU having a large voltage difference are set as compared with the setting for the individual output voltages V1 and V2. Can be. Also, the output voltage V
The output characteristic of REF becomes steeper than the slope of the output voltage VDEF of the first embodiment.

Therefore, according to the piston position detecting device of this embodiment, in addition to the effects of the first embodiment, the output voltage VDE
Since the gradient of the characteristic of F can be steeper than the output voltage VDEF of the first embodiment, the fluctuation of the piston position corresponding to the voltage value determined by each threshold voltage can be further reduced. it can. Therefore, each threshold voltage VTH
Since the optimum mounting range and the dangerous mounting range set by L and VTHU can be made harder to fluctuate, it is possible to detect the piston position with less influence of the external magnetic field. Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. The piston position detection device of the present embodiment also includes a magnetoresistive element and an output voltage determination circuit. Note that the same components as those of the piston position detecting devices of the first and second embodiments have the same reference numerals and description thereof will be omitted.

As shown in FIGS. 7 to 10, a magneto-sensitive pattern portion 43 and temperature compensating pattern portions 44 and 45 are formed on one surface of the substrate 42 of the magnetoresistive element 41. The magneto-sensitive pattern portion 43 is formed at the lower center (in FIGS. 7 and 8) of the substrate 42, and the temperature compensation pattern portions 44 and 45 are formed on both upper sides of the magneto-sensitive pattern portion 43, respectively. The magneto-sensitive pattern portion 43 is formed of a ferromagnetic thin film formed in a zigzag pattern having the same width in the vertical direction. The pattern line 43a forming this pattern has a constant line width of 20 μm. The pitch between the pattern lines 43a is formed to be the smallest at the center of the magneto-sensitive pattern portion 43 in the position detection direction, and to be larger from the center to both ends. Each of the temperature compensating pattern portions 44 and 45 is formed of a ferromagnetic thin film formed in a serpentine pattern having the same width in the left-right direction. The pattern line forming this pattern has a constant line width of 4 μm, and the pitch between the pattern lines is constant. The right side of the magneto-sensitive pattern portion 43 is the substrate 4
2 is connected to a land 46 formed between the lower right side and the upper center, and similarly the left side is connected to a land 47 formed between the lower left side and the upper center of the substrate 42. The upper left end of the temperature compensation pattern portion 44 is connected to a land 48 formed on the upper left side of the substrate 42, and the lower left end is
7 is connected. Similarly, the upper right end of the temperature compensation pattern section 45 is connected to a land 49 formed on the upper right side of the substrate 42, and the lower right end is connected to the land 46.

An insulating layer 50 is formed on the magneto-sensitive pattern section 43 and the temperature compensation pattern sections 44 and 45.
As shown in FIG. 7, a magneto-sensitive pattern portion 51 is formed on the upper surface of the insulating layer 50 at a position facing the magneto-sensitive pattern portion 43. The magneto-sensitive pattern section 51 is a magnetic-sensitive pattern section 43.
It is formed with the same configuration as that described above. The right end of the magneto-sensitive pattern portion 51 is connected to a land 52 formed vertically on the right side of the upper surface of the insulating layer 50, and the left side is connected to a land 53 formed vertically on the left side of the upper surface of the insulating layer 50. ing. The land 5 is located at the upper center of the upper surface of the insulating layer 50.
4, 55 are formed side by side. The lands 49 and lands 52 are connected through contact holes 50a formed in the insulating layer 50, and similarly the lands 48 and lands 53 are connected through contact holes 50a. Further, the lands 54 and the lands 46 and the lands 55 and the lands 47 are formed in the contact holes 5 respectively.
0a. Therefore, between the land 54 and the land 53, the magnetic sensing pattern 43 and the temperature compensating pattern 44, and the temperature compensating pattern 45 and the magnetic sensing pattern 51 are connected in series. An insulating layer 56 is formed on the magneto-sensitive pattern 51. Each land 52, 53, 54, 55 is formed from the insulating layer 56 to the opening 5.
It is exposed to the outside at 6a. In addition, the magnetic sensing pattern part 4
3 and the temperature compensating pattern section 44 constitute a first magnetic resistance detecting section 57, and the magneto-sensitive pattern section 51 and the temperature compensating pattern section 45 constitute a second magnetic resistance detecting section 58. The resistance values of the magneto-sensitive pattern portions 43 and 51 and the temperature compensation pattern portions 44 and 45 in a state where no magnetic field is applied are set to be equal.

Next, the electrical configuration of the output voltage determination circuit connected to the magnetoresistive element will be described. FIG. 11 shows an output voltage judging circuit 6 to which the magnetoresistive element 41 is connected.
1 is shown. The magnetoresistive element 41 is connected via a land 54 to a power supply line 62 to which a power supply voltage VC is applied, and is also connected via a land 53 to a ground line 63. Therefore, the magneto-sensitive pattern section 43 and the temperature compensation pattern section 44,
In addition, the temperature compensation pattern section 45 and the magneto-sensitive pattern section 51
Are connected in parallel. The non-inverting input terminal of the operational amplifier 64 is connected between the magnetic sensing pattern portion 43 of the first magnetic resistance detecting portion 57 and the temperature compensating pattern portion 44 (that is, the land 55). Pattern part 5
1 and the temperature compensation pattern portion 45 (that is, the land 5
2) is connected to the inverting input terminal of the operational amplifier 64. The output side of the operational amplifier 64 is a comparator 65, 6
6, 67 non-inverting input terminals.

A threshold voltage setting circuit 68 is connected between the power supply line 62 and the ground line 63. The threshold voltage setting circuit 68 includes four resistors 69, 70, 7 connected in series.
1, 72. Threshold voltage setting circuit 6
8 between the resistors 69 and 70 is connected to the inverting input terminal of the comparator 65, and between the resistors 70 and 71 is connected to the inverting input terminal of the comparator 66. Further, a portion between the resistors 71 and 72 is connected to an inverting input terminal of the comparator 67.

The output side of the comparator 65 is connected to the base of the NPN transistor 72, and the output side of the comparator 66 is connected to the base of the NPN transistor 73. The output side of the comparator 67 is connected to the base of the PNP transistor 74.

The emitter of the transistor 74 is connected to the power line 62
, And the collector of the transistor 74 is connected to the anode of a red light emitting diode (hereinafter, referred to as LED) 75. The collector of the transistor 72 is connected to the cathode of the LED 75, and the emitter of the transistor 72 is grounded. The collector of the transistor 73 is connected to the power supply line 62, and the emitter of the transistor 73 is connected to the anode of the green LED 76. The cathode of the LED 76 is grounded. Note that L
The EDs 75 and 76 are one-piece LEDs, and when one of them is lit, the ED 75 or 76 is illuminated by the color of the LED 75 or 76. When both the LEDs 75 and 76 are lit, the LED illuminates yellow, which is a combination of red and green.

Next, the operation of the piston position detecting device configured as described above will be described. The piston position detecting device of the present embodiment is used similarly to the piston position detecting device of the second embodiment.

The first magnetoresistive detecting section 57 outputs an output voltage V1 from between the magnetic sensing pattern section 43 and the temperature compensating pattern section 44 (that is, the land 55) to the non-inverting input terminal of the operational amplifier 64. Further, the second magnetic resistance detecting section 58 is provided between the temperature compensating pattern section 45 and the magneto-sensitive pattern section 51 (that is, the magnetic sensing pattern section 51).
The output voltage V2 is output from the land 52) to the inverting input terminal of the operational amplifier 64. As shown in FIG.
The output voltage V1 output from the magnetoresistive detector 57 has a characteristic that gradually increases to the maximum sensitivity position with respect to the piston position, similarly to the output voltage V1 of the second embodiment. The output voltage V2 output from the second magnetoresistive detector 58 has such a characteristic that it gradually decreases to the highest sensitivity position. In the present embodiment, since the magneto-sensitive pattern portion 43 of the second magneto-resistance detecting portion 57 and the magneto-sensitive pattern portion 51 of the second magneto-resistance detecting portion 58 are provided at positions overlapping the substrate 42, each magneto-sensitive pattern portion 43 is provided. , 51
Are almost equal. As a result, the absolute values of the output levels of the output voltages V1 and V2 become substantially equal.

The operational amplifier 64 subtracts the output voltage V2 from the output voltage V1 and outputs the output voltage VDEF to the comparator 6
5, 66 and 67 are output to the non-inverting input terminals. Therefore, the output level of the output voltage VDEF obtained from the difference between the two output voltages V1 and V2 is higher than the output level of the output voltage VDEF of the second embodiment. Further, the output characteristic has a steeper gradient than the output voltage VDEF of the second embodiment.

The threshold voltage setting circuit 68 provides a first threshold voltage V based on the voltage VC between the resistor 69 and the resistor 70.
THL is output to the inverting input terminal of the comparator 65.
Also, the third threshold voltage VTHM is output to the inverting input terminal of the comparator 66 from between the resistors 70 and 71. Further, the threshold voltage setting circuit 68 outputs the second threshold voltage VTHU from between the resistors 71 and 72 to the inverting input terminal of the comparator 67. For this output voltage VDEF, a first threshold voltage VTH having a larger voltage difference than that set for each output voltage V1, V2.
L and the second threshold voltage VTHU can be set.

Output voltage VDEF output from operational amplifier 64
Is compared with the first threshold voltage VTHL by the comparator 65, and becomes H level in a dangerous mounting range where the output voltage VDEF is equal to or higher than the first threshold voltage VTHL, a sub-optimal mounting range, and an optimum mounting range. The signal SG11 is output. The output voltage VDEF is compared with the third threshold voltage VTHM by the comparator 66. When the output voltage VDEF is equal to or higher than the third threshold voltage VTHM, the output voltage VDEF is set to the H level in a range including the sub-optimal mounting range and the optimal mounting range. The signal SG12 is output. Further, the output voltage VDEF is determined by the comparator 67.
Is compared with the second threshold voltage VTHU, and the output voltage VDE
In the optimum mounting range where F is equal to or higher than the second threshold voltage VTHU, a signal SG13 which is at H level is output.

The comparator 65 outputs a signal SG11 based on the output voltage VDEF and the first threshold voltage VTHL to the base of the NPN transistor 72. Comparator 6
6 outputs a signal SG12 based on the output voltage VDEF and the third threshold voltage VTHM to the base of the NPN transistor 73. Further, the comparator 67 outputs a signal SG13 based on the output voltage VDEF and the second threshold voltage VTHU to the base of the PNP transistor 74. And the signal SG1
3 is at the H level, and the range of the signal S
The range where G13 is at the L level and signal SG12 is at the H level is the sub-optimal mounting range. Further, a range in which the signal SG12 is at the L level and the signal SG11 is at the H level is defined as a dangerous mounting range. Therefore, when the piston position is out of the range consisting of the dangerous mounting range, the sub-optimal mounting range, and the optimal mounting range,
Since the signals SG11, SG12 and SG13 are all at L level, the transistors 72 and 73 are turned off and the transistor 74 is turned on. As a result, when it is out of the range including the dangerous mounting range, the sub-optimal mounting range, and the optimum mounting range, L
The EDs 75 and 76 do not light up. When the piston position is in the dangerous mounting range, the signal SG11 is at the H level and the signals SG12 and SG13 are at the L level, so that the transistors 72 and 74 are turned on and the transistor 73 is turned off. As a result, when it is within the dangerous mounting range, the LED 75 lights up in red. When the piston position is within the sub-optimal mounting range, the signals SG11 and SG12 go high and the signal SG13 goes low, so that the transistors 72 and
3, 74 are all turned on. As a result, LEDs 75, 7
Since 6 lights up together, yellow is visually recognized. Further, when the piston position is within the optimum mounting range, the signals SG11, SG11,
Since SG12 and SG13 are all at H level, the transistors 72 and 73 are turned on and the transistor 74 is turned off. As a result, the LED 76 turns green. Therefore,
The operator can easily visually recognize the range of the piston position. As described in detail above, according to the piston position detecting device of the present embodiment, in addition to the effects of the second embodiment, the output voltage VDE of the piston position detecting device of the second embodiment is also increased.
Since an output voltage VDEF having a higher output level than that of F can be obtained, each of the threshold voltages VTHL and VTHU can be set with a larger voltage difference. Therefore, even when the magnetic field to be detected is weak, malfunction due to an external magnetic field or the like can be further reduced.

Further, according to the present embodiment, by setting three threshold voltages VTHL, VTHM, and VThu with respect to the output voltage VDEF, a sub-optimal mounting range can be set between the optimum mounting range and the dangerous mounting range. Set. Therefore, since the piston position deviating from the optimum mounting range can be detected twice in the sub-optimal mounting range and the dangerous mounting range, for example, the detection in the sub-optimal mounting range deviates from the optimum mounting range. As a notice range for notifying that, the detection of the dangerous mounting range can be immediately used as a limit range in which the piston position should be corrected to the optimum mounting range.

The present invention can be configured as follows in addition to the above embodiment. (1) In the first to third embodiments, the first magnetoresistive detector 4,
5, 57, and 58 of the magneto-sensitive pattern portions 6, 11, 43, and 5
The first pattern surface need not be arranged in a plane including the axis of the cylinder tube T. For example, the pattern surface may be arranged in parallel with a surface including a tangent to the outer peripheral surface of the cylinder tube T.

(2) In the second and third embodiments, the pattern lines 6a, 11a,
The pitches of 43a and 51a are set to the magneto-sensitive pattern portions 6, 11, and 4.
It may be formed so as to increase by the same size on both sides from the center of 3, 51 (ie, in an arithmetic progression).

(3) In the third embodiment, the magneto-sensitive pattern 4
The pitch between the 3, 51 pattern lines 43a, 51a may be formed to be constant. Even in this case, the individual output voltages V1
, V2 can be obtained at an output level higher than V2.

(4) In the piston position detecting device of the first or second embodiment, three threshold voltages are set, and a sub-optimal mounting range is set in addition to the optimum mounting range and the dangerous mounting range. May be.

(5) In the third embodiment, the two magneto-sensitive pattern portions 43 and 51 may be formed separately on the front and back of the substrate 42. Further, a configuration in which three or more magneto-sensitive pattern portions are provided may be adopted.

Also, one magneto-sensitive pattern portion 4 is provided for each.
The magnetoresistive element 41 may be formed by laminating the substrates 42 on which the layers 3 and 51 are formed. (6) In the first and second embodiments, the temperature compensation pattern portions 7 and 12 may be arranged above and below the substrate 3 with the both magneto-sensitive pattern portions 6 and 11 interposed therebetween. Further, the temperature compensating patterns 7, 12 may not be provided at the center of the substrate 3 in the left-right direction, but may be arranged at a position deviated leftward or rightward.

(7) In the first and second embodiments, the LED 3
The 4,36 colors may be a combination of colors other than the combination of green and red. Alternatively, the colors of the LEDs 34 and 36 may be the same, and only one of the LEDs 34 and 36 may be turned on in the dangerous mounting range, and both may be turned on in the optimum mounting range.

Further, a configuration may be adopted in which one LED blinks in the dangerous mounting range and is continuously lit in the optimum mounting range. (8) In the third embodiment, LEs of different colors or of the same color
Three Ds may be provided, and different LEDs may be turned on for each detection range.

(9) Instead of the LED, for example, a light emitting element such as an electroluminescent element (EL element), a liquid crystal element, or a display element may be used to display the optimum mounting range and the dangerous mounting range. .

(10) The piston position is indicated by LEDs 34, 3
6 (75, 76), the signal may be output to a programmable controller or the like as an output signal corresponding to each mounting range.

(11) In the first and second embodiments, the comparators 25 and 26 may be configured to apply positive feedback. That is, as shown by a two-dot chain line in FIG. 3, the non-inverting input terminal and the output terminal of each of the comparators 25 and 26 are connected via the resistor 39, respectively. In this case, stable switching from the dangerous mounting range (sub-optimal mounting range) to the optimal mounting range (sub-optimal mounting range) or the optimal mounting range (sub-optimal mounting range) to the dangerous mounting range (sub-optimal mounting range) is stabilized. Can be done.

Similarly, in the third embodiment, the comparators 65, 66, 67 of the output voltage determination circuit 61 may be configured to apply a positive feedback. (12) The shape of the magnet M attached to the piston P is not limited to a ring shape, and may be, for example, a columnar shape, a semi-cylindrical shape, a quadrangular prism shape, or the like.

Hereinafter, in addition to the technical ideas described in the claims, the technical ideas grasped in each of the above-described embodiments will be described together with their effects. (1) In the piston position detecting device according to the third aspect, each of the first magnetoresistive detecting portions 43 and 51 is formed by laminating the insulating layer 50 on one surface side of the substrate 42. According to such a configuration, three or more magnetic detection units can be easily formed. Also, each magnetic pattern portion 4
The positioning accuracy of 3, 51 can be increased. Further, when three or more magnetoresistive detectors are provided, the whole can be made compact.

(2) In the piston position detecting device according to any one of claims 1 to 4, the display means 34, 36 (75) for distinguishably displaying each detection range set by the threshold voltage. , 76). According to such a configuration, the piston position can be displayed visually.

[0067]

As described above in detail, according to the first aspect of the present invention, since each threshold voltage can be set by taking a large voltage difference from the output peak value, the magnetic field to be detected is reduced. Even in a weak case, malfunction due to an external magnetic field or the like can be suppressed.

According to the second aspect of the present invention, in addition to the effect of the first aspect, the output characteristic of the differential output voltage is increased such that the rate of increase increases as the position approaches the highest sensitivity position. Therefore, it is possible to set an appropriate mounting range while setting each threshold voltage while securing a large voltage difference from the output peak value or the reference voltage.

According to the third aspect of the present invention, in addition to the effects of the first or second aspect of the present invention, a further effect is obtained between each threshold voltage and the output peak value or the reference voltage. Since an appropriate mounting range can be set while securing a large voltage difference, even when the magnetic field to be detected is weak, malfunction due to an external magnetic field or the like can be further reduced.

According to the fourth aspect of the present invention, in addition to the effects of the first to third aspects, a sub-optimal mounting range between the optimum mounting range and the dangerous mounting range is provided. Therefore, for example, the detection in the sub-optimal mounting range is set as a notice range for notifying that the piston position has deviated from the optimal mounting range, and the detection in the dangerous mounting range is immediately corrected to the optimal mounting range. It can be used as a power limit range.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a magnetoresistive element according to a first embodiment.

FIG. 2 is an electric circuit diagram of a piston position detecting device.

FIG. 3 is a chart showing a relationship between an output voltage and an output signal.

4A is a schematic front view of a piston position detecting device mounted on a cylinder, and FIG.

FIG. 5 is a schematic front view showing a magnetoresistive element according to a second embodiment.

FIG. 6 is a chart showing a relationship between an output voltage and an output signal.

FIG. 7 is a schematic front view showing the upper layer of the magnetoresistive element according to the third embodiment.

FIG. 8 is a schematic front view showing a lower layer of the magnetoresistive element.

FIG. 9 is a schematic sectional view corresponding to line AA in FIG. 7;

FIG. 10 is a schematic sectional view corresponding to line BB in FIG. 7;

FIG. 11 is an electric circuit diagram of a piston position detecting device.

FIG. 12 is a chart showing a relationship between an output voltage and each signal.

FIG. 13 is an electric circuit diagram of a conventional position detecting device.

FIG. 14 is a graph showing a relationship between an output voltage and each range.

[Explanation of symbols]

4, 5 ... Magnetic resistance detecting section, 6 ... Magnetic sensing pattern section, 6a ...
Pattern line, 11: magneto-sensitive pattern section, 11a: pattern line, 24: difference circuit as difference output generation section, 43, 5
Reference numeral 1: magnetic sensing pattern part, 57, 58 ... magnetic resistance detecting part, 6
4: Difference circuit as difference output generation unit, V1, V2 ... output voltage, VDEF ... output voltage as difference output voltage, VTH
L, VTHM, VTHU ... threshold voltage.

Claims (4)

(57) [Claims] 1. A magnetoresistive detector (4, 5, 57, 58)
Output voltage (V1, V1) corresponding to the piston position
2) In a piston position detecting device that sets a plurality of threshold voltages having different output levels to each other and determines a piston position in a plurality of ranges set based on each of the threshold voltages, a magnetic resistance detecting unit ( 4,5,57,58) and the same direction of position detection of each of the magnetoresistive detectors (4,5,57,58), and they are arranged such that their output peak positions coincide. Difference output generation for generating a difference output voltage (VDEF) having an output level larger than each output voltage (V1, V2) from the output voltages (V1, V2) of the respective magnetoresistive detectors (4, 5, 57, 58). (24, 64), wherein a plurality of threshold voltages are set for the differential output voltage (VDEF) output from the differential output generator (24, 64) to determine the piston position. Detector . 2. Each of the magnetoresistive detectors (4, 5) sets the pitch of the pattern lines (6a, 11a) in the position detection direction of the magnetosensitive pattern (6, 11) to the magnetosensitive pattern (6, 11). 1
2. The piston position detecting device according to claim 1, wherein the center in the position detecting direction of 1) is formed to be the smallest, and to increase from the center to both ends. 3. A plurality of magnetoresistive detectors (57, 58).
Are substantially opposed to each other in a direction perpendicular to the pattern surface of each magneto-sensitive pattern portion (43, 51), and are arranged at a distance at which the magnetic fields acting on each magneto-sensitive pattern portion (43, 51) are substantially equal. The piston position detecting device according to claim 1 or 2. 4. Three threshold voltages (VTHL, VTHM, VTH) having different levels with respect to the output voltage (VDEF).
U) is set, and each threshold voltage (VTHL, VTHM, VTH
The piston position detecting device according to any one of claims 1 to 3, wherein an optimum mounting range, a sub-optimal mounting range, and a dangerous mounting range are set based on U).