JPH09297003A - Displacement detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a displacement detection apparatus whose offset adjusting accuracy and output characteristic accuracy are enhanced and which is adjusted easily by a method wherein an offset adjusting means which is composed of a plurality of resistors is installed at least at one out of components for a Whetstone bridge circuit. SOLUTION: One end of a magnetism detection element 1 and one end of a thick-film resistance 10a are connected to a power-supply terminal (+B). One end of a magnetism detection element 2 and one end of a thick-film resistance 11a are grounded. Ends, on the other side, of the magnetism detection elements 1, 2 are connected to a connection point 5. The other end of the thick-film resistance 10a and one end of a thick-film resistance 10b are connected in common. The other end of the thick-film resistance 11a and one end of the thick-film resistance 11b are connected in common. Respective end, on the other side, of the thick-film resistances 10b, 11b are connected to a connection point 6. The resistances 10a, 10b, 11a, 11b form an offset adjusting means. Then, the output of the connection point 5 by the elements 1, 2 whose resistance is changed by an applied magnetic field and the output of the connection point 6 by the resistances 10b, 11b which are arranged so as to be faced together with the resistances 10a, 11a are amplified by a differential amplifier 7, and an output which corresponds to a rotating displacement or a linear displacement is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement detecting device, and more particularly to a displacement detecting device which detects a rotational displacement or a linear displacement by a magnetic detecting element.

[0002]

2. Description of the Related Art FIG. 5 is a schematic diagram showing a conventional displacement detecting device using a magnetic detecting element. In the figure,
1 and 2 are magnetic detection elements as constituent elements, and 3 and 4 are thick film resistors printed on, for example, a ceramic substrate, and one end of each of the magnetic detection element 1 and the thick film resistor 3 is commonly connected to a power supply terminal. + B, one ends of the magnetic detection element 2 and the thick film resistor 4 are commonly connected and grounded, and the other ends of the magnetic detection elements 1 and 2 are connected to the connection point 5, and the thick film resistors 3 and 4 are connected. The other end is connected to the connection point 6 to form a Wheatstone bridge circuit. Reference numeral 7 denotes a differential amplifier circuit whose input terminals are connected to the connection points 5 and 6, respectively.

Next, the operation will be described. The output of the connection point 5 of the magnetic detection elements 1 and 2 which causes a resistance change due to the applied magnetic field and the output of the connection point 6 of the thick film resistors 3 and 4 which are arranged so as to face the magnetic detection elements 1 and 2 respectively differ. It is amplified by the dynamic amplification circuit 7 and an output corresponding to the rotational displacement or the linear displacement is obtained.

By the way, in such a displacement detecting device, the offset adjustment of the Wheatstone bridge circuit is generally performed by trimming the thick film resistors 3 or 4. The problem here is the accuracy of offset adjustment. The magnetic detection elements 1 and 2 usually have a magnetic sensitive surface formed in a predetermined pattern, and apply a magnetic field in a direction perpendicular to the pattern of the magnetic sensitive surface or at a predetermined angle equal to or higher than the saturation magnetic field. By doing so, the resistance value of the predetermined pattern forming the magnetoresistive element is, as shown in FIG. 6, the minimum value (Rmin) according to the magnetic flux density of the applied magnetic field with the maximum value (Rmax) when not applied. ). As an example, when the magnetoresistive elements 1 and 2 are ferromagnetic magnetoresistive elements, if the difference between the maximum value and the minimum value of the resistance value is ΔR, the resistance change rate (ΔR / Rmax) when a magnetic field is applied is, for example, Ni-Fe is as small as about 3%. Therefore, it is necessary to provide the differential amplifier circuit 7 in the subsequent stage to perform amplification.
The output characteristics depend on the offset adjustment accuracy.

[0005]

However, in the conventional displacement detecting device, this offset adjustment is performed by directly trimming the single thick film resistor 3 or 4 having a large resistance value inserted in the arm of the Wheatstone bridge circuit. And
Since the resistance value greatly changes with respect to the trimmed amount, there is a problem that good offset adjustment accuracy cannot be ensured. That is, for example, assuming that the voltage of the power supply terminal + B is V, the voltage V / 2 of the same potential appears at the connection points 5 and 6 if the offset adjustment is complete, and both inputs of the differential amplifier circuit 7 are input. The potential difference between the terminals is zero. Therefore, the output side of the differential amplifier circuit 7 is provided with the corresponding FIG.
The output voltage (V ₁ + V ₂ ) / 2 amplified by the amplification degree of the differential amplifier circuit 7 as shown by the solid line is output as the midpoint voltage.

In this state, when the displacement of the object is detected by the magnetic detection elements 1 and 2, the offset voltage of the Wheatstone bridge circuit is 0V in this case,
The potential difference between the connection points 5 and 6 of the Wheatstone bridge circuit changes up and down substantially with 0V as a reference.
As a result, this change is detected as a detection output by the differential amplifier circuit 7.
And the output voltage changes vertically between the voltages V ₁ and V ₂ around the midpoint voltage (V ₁ + V ₂ ) / 2 as shown in FIG. Here, the voltages V ₁ and V ₂ are substantially the maximum values on the respective sides of the output voltage of the differential amplifier circuit 7 when the detected body is displaced to the left and right (−X side and X side) with reference to 0. It represents.

However, if the offset adjustment of the Wheatstone bridge circuit is poor, the Wheatstone bridge circuit and the differential amplifier circuit 7 perform the above-mentioned operation in a state where the offset voltage is shifted from the reference value due to the adjustment deviation. Displacement detection becomes inaccurate.
In FIG. 4, the characteristic indicated by the broken line shows the actual output voltage of the differential amplifier circuit 7 in the conventional displacement detection device after the offset adjustment, and the offset adjustment is compared with the ideal characteristic indicated by the solid line. As a result of the offset adjustment by trimming the thick film resistors 3 or 4, a vertical shift amount D ₁ is generated.

By the way, the offset voltage in the Wheatstone bridge circuit of the conventional displacement detecting device is about 10 mV, although it depends on the trimming method.
The amplification degree of the differential amplifier circuit 7 is about 67 times (for example, the amount of change of the potential difference between the connection points 5 and 6 of the Wheatstone bridge circuit with respect to the reference value (medium voltage) is ± 30 mV, V ₁ is 0.5 V,
Assuming that V ₂ is 4.5 V and the output voltage V _FS (= V ₂ −V ₁ ) of the differential amplifier circuit 7 at full scale is 4 V), the above-mentioned deviation D ₁ becomes 670 mV.

As described above, in the conventional displacement detection device, this offset adjustment is performed by trimming the thick film resistors 3 or 4 of the Wheatstone bridge circuit, so that good offset adjustment accuracy cannot be ensured and the output characteristics are improved. There was a problem of deterioration. Further, in order to improve the offset adjustment accuracy by trimming only the single thick film resistor 3 or 4 having a large resistance value inserted in the side of the Wheatstone bridge circuit, the value of the resistance value with respect to the trimmed amount as described above is set. Since there is a large change, it is difficult to make adjustments to reach the desired value, and it is troublesome and the workability is poor.

The present invention has been made to solve the above problems, and can improve the offset adjustment accuracy of the Wheatstone bridge circuit and the output characteristic accuracy, and can easily perform the offset adjustment. An object of the present invention is to provide a displacement detection device with excellent workability.

[0011]

According to a first aspect of the present invention, there is provided a displacement detecting device comprising a bridge circuit using a detecting element as at least one of the four side components, the displacement detecting device comprising: At least one of them uses an offset adjusting means composed of a plurality of resistors.

A displacement detecting device according to a second aspect of the present invention is the displacement detecting device according to the first aspect of the invention, wherein a plurality of resistors are connected in series, and offset adjustment is performed using at least one of the plurality of resistors. is there.

A displacement detecting device according to a third aspect of the present invention is the displacement detecting device according to the first aspect of the invention, wherein a plurality of resistors are connected in parallel, and offset adjustment is performed using at least one of the plurality of resistors. is there.

A displacement detecting device according to a fourth aspect of the present invention is the displacement detecting device according to any one of the first to third aspects, in which the resistance value ratios of the plurality of resistors are different.

A displacement detecting device according to a fifth aspect of the present invention is the displacement detecting device according to any one of the first to fourth aspects, wherein the plurality of resistors are thick film resistors.

According to a sixth aspect of the invention, there is provided a displacement detecting device according to any one of the first to fifth aspects, wherein a magnetic detecting element is used as the detecting element.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings, taking a case where a magnetic detection element is used as a detection element. Embodiment 1. 1 is a configuration diagram showing a first embodiment of the present invention, in which parts corresponding to those in FIG.
The detailed description is omitted. In the figure, 10a and 1
0b is a thick film resistor as a resistor which is an offset adjusting means having different resistance values printed in series on a ceramic substrate, and 11a and 11b are different resistance values which are also printed in series on a ceramic substrate. It is a thick film resistor as a resistor which is an offset adjusting means. These thick film resistors 10a and 10b and 11a and 1
The resistance value ratio of 1b is, for example, about 1: 2 to 1: 100.

Each end of the magnetic detecting element 1 and the thick film resistor 10a is commonly connected and connected to the power supply terminal + B, and each end of the magnetic detecting element 2 and the thick film resistor 11a is commonly connected and grounded. The other ends of 1 and 2 are connected to a connection point 5, the other end of the thick film resistor 10a and one end of the thick film resistor 10b are commonly connected, and the other end of the thick film resistor 11a and the thick film resistor 11b are connected.
Has one end connected in common, and the other ends of the thick film resistors 10b and 11b are connected to the connection point 6 to form a Wheatstone bridge circuit.

Next, the operation will be described. The output of the connection point 5 of the magnetic detection elements 1 and 2 that causes a resistance change due to the applied magnetic field, and the thick film resistance 10b and the thick film resistance 10b that are arranged to face the magnetic detection elements 1 and 2 together with the thick film resistances 10a and 11a, respectively. The output of the connection point 6 of 11b is amplified by the differential amplifier circuit 7, and the output corresponding to the rotational displacement or the linear displacement is obtained.

Here, the offset adjustment of the Wheatstone bridge circuit will be considered. There are several possible ways to do this. As a first method, for example, by fixing the thick film resistors 10a and 11a having a large resistance value to a certain value,
The thick film resistors 10b and 11b having a small resistance value are configured as thick film resistors in consideration of only the variation in the resistance value necessary for adjustment. When adjusting, these thick film resistors 10b
Adjustment is performed by trimming at least one of and 11b.

As a second method, thick film resistors 10a and 10
Since b and the thick film resistors 11a and 11b have different resistance values from each other, first, on at least one side, the thick film resistor 10a or 11a having the larger resistance value is trimmed for rough adjustment, and then, The trimming is performed on the thick film resistor 10b or 11b having the smaller resistance value for fine adjustment.

In FIG. 4, the alternate long and short dash line shows the actual output voltage of the differential amplifier circuit 7 after the offset adjustment in the present embodiment, and the ideal offset adjustment is shown by the complete solid line. With respect to the characteristics, as described above, the thick film resistors 10a and 10b or the thick film resistors 11a and 11b are trimmed and adjusted, respectively, and as a result, a vertical shift amount D ₂ (<< D ₁ ) occurs. In the present embodiment, as described above, when performing the offset adjustment, the thick film resistance of the smaller resistance value is finally adjusted to the desired value, so the value of the resistance value with respect to the trimmed amount is set. There change is small, it is possible to offset adjustment precision, it is possible to suppress the shift amount D ₂ mentioned above considerably smaller value of about several tenths of a degree for example 50mV conventional shift amount D _1, trimming Depending manner of the deviation amount D ₂ 0 or offset voltage can be set to 0.

As described above, in the present embodiment, the thick film resistor for offset adjustment is substantially divided into two, and the thick film resistor is trimmed in consideration of only the resistance value variation necessary for the adjustment. Adjustment, or first, the thick film resistance with the larger resistance value is roughly adjusted, and then the thick film resistance with the smaller resistance value is finely adjusted. Since the smaller thick film resistance adjusts to the desired value, the resistance value changes little with respect to the trimmed amount, enabling highly accurate offset adjustment and improving the offset adjustment accuracy of the Wheatstone bridge circuit. In addition, the adjustment of the thick film resistance can be facilitated, and the workability can be improved.

Embodiment 2 FIG. 2 is a configuration diagram showing a second embodiment of the present invention. The portions corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In the first embodiment described above, the two thick film resistors 10a, 10b and 11a, 11b, which are respectively in series with the magnetic detection elements 1 and 2 forming the Wheatstone bridge circuit, are arranged so as to face each other. In the present embodiment,
N in series with each of the magnetic detection elements 1 and 2
This is a case where the thick film resistors 10a to 10n and 11a to 11n are arranged to face each other. Reference numerals 10a to 10c are thick film resistors as resistors, which are offset adjusting means having different resistance values printed on a ceramic substrate, for example, 11a.
11c are thick film resistors as resistors, which are offset adjusting means having different resistance values printed on a ceramic substrate, for example.

Next, the operation will be described. The outputs of the connection points 5 of the magnetic detection elements 1 and 2 that cause a resistance change due to the applied magnetic field, and 10a to 10n and 11a, which are arranged to face the magnetic detection elements 1 and 2, respectively.
The output of the connection point 6 of the thick film resistors 10n and 11n of 11n is amplified by the differential amplifier circuit 7, and the output corresponding to the rotational displacement or the linear displacement is obtained.

Here, the offset adjustment of the Wheatstone bridge circuit will be considered. Also in this case, several methods are possible. As a first method, for example, the thick film resistors 10a and 11a having a larger resistance value are fixed to a certain value, and the thick film resistors 10b to 10n and 11b to 11n having a smaller resistance value are required to be adjusted. It is configured as a thick film resistor that allows for only fluctuations. When adjusting, the thick film resistors 10b to 10n and 11b to 11 are to be adjusted.
Adjustment is performed by trimming at least one of n. In this case, the number of thick film resistors for fixing the resistance value can be set to any value as long as at least one thick film resistor having a small adjustable resistance value is finally present.

As a second method, thick film resistors 10a-10
n and the thick film resistors 11a to 11n have different resistance values from each other. Therefore, at least on one side, the thick film resistor 10a or 11a having the larger resistance value is first trimmed to perform rough adjustment, and The trimming is performed on the thick film resistor 10b to 10n or 11b to 11n having the smaller resistance value to perform fine adjustment. In this case, the number of thick film resistors to be subjected to rough adjustment and fine adjustment can be set to any value.

Also in this case, as described above, when the offset adjustment is performed, it is possible to finally reach the desired value by adjusting the thick-film resistance of the smaller resistance value, so that the resistance with respect to the trimmed amount is reduced. The change in the value is small, the offset adjustment can be performed with high accuracy, and the above-mentioned deviation D ₂ can be suppressed to about several tenths of the conventional deviation D _{1. In} some cases, the deviation D ₂ can be reduced. 0, that is, the offset voltage is 0
It can be.

As described above, in the present embodiment, the thick film resistors for performing the offset adjustment are substantially divided into n pieces and arranged in series, and the thick film resistors in consideration of only the resistance value variation necessary for the adjustment are provided. Adjust by trimming, or first, roughly adjust the thick film resistance of the larger resistance value, and then finely adjust the thick film resistance of the smaller resistance value. By adjusting the thick film resistance of the smaller resistance value to the desired value, the resistance value changes little with respect to the trimmed amount, enabling highly accurate offset adjustment and improving the offset adjustment accuracy of the Wheatstone bridge circuit. In addition, the adjustment of the thick film resistance can be facilitated, and the workability can be improved.

Embodiment 3 FIG. 3 is a configuration diagram showing a third embodiment of the present invention. The portions corresponding to those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted. In the above-described second embodiment, n thick film resistors 10a to 10n and 11a to 11n, which are in series with the magnetic detection elements 1 and 2 forming the Wheatstone bridge circuit, are arranged to face each other. However, in the present embodiment,
N in parallel with the magnetic detection elements 1 and 2
This is a case where the thick film resistors 10a to 10n and 11a to 11n are arranged to face each other. The thick film resistors 10a to 10n and the thick film resistors 11a to 11n of this parallel configuration can be set to arbitrary numbers.

Next, the operation will be described. The outputs of the connection points 5 of the magnetic detection elements 1 and 2 that cause a resistance change due to the applied magnetic field, and 10a to 10n and 1 that are arranged in parallel facing the magnetic detection elements 1 and 2, respectively.
The output of the connection point 6 of 1a to 11n is amplified by the differential amplifier circuit 7, and the output corresponding to the rotational displacement or the linear displacement is obtained.

Here, the offset adjustment of the Wheatstone bridge circuit will be considered. Also in this case, several methods are possible. As a first method, for example, the thick film resistors 10n and 11n having a smaller resistance value are fixed to a certain value, and the thick film resistors 10a to 10n-1 and 11a to 11n-1 having a larger resistance value are adjusted. It is configured as a thick film resistor that allows for only the necessary resistance value fluctuations. When adjusting, the thick film resistors 10a to 10n-1 and 11a are to be adjusted.
Adjustment is performed by trimming at least one of 11n-1. In this case, the number of the thick film resistors that fix the resistance value is at least one thick film resistor with a large adjustable resistance value.
If they exist, they can be set to arbitrary values.

As a second method, thick film resistors 10a to 10 are used.
Since n and the thick film resistors 11a to 11n have different resistance values from each other, on at least one side, first, the thick film resistor 10n or 11n having a smaller resistance value is trimmed to perform rough adjustment, and , Thick film resistors 10a to 10n-1 and 11a to 11n-1 having a larger resistance value
Trimming is performed on and fine adjustment is performed. in this case,
The number of thick film resistors that are the targets of rough adjustment and fine adjustment can be set to any value.

Also in this case, as described above, when the offset adjustment is performed, it is possible to finally reach the desired value by adjusting the thick film resistance having the larger resistance value. The change in the value is small, the offset adjustment can be performed with high accuracy, and the above-mentioned deviation D ₂ can be suppressed to about several tenths of the conventional deviation D _{1. In} some cases, the deviation D ₂ can be reduced. 0, that is, the offset voltage is 0
It can be.

As described above, in the present embodiment, the thick film resistors for performing the offset adjustment are substantially divided into n pieces and arranged in parallel, and the thick film resistors that allow only the variation in the resistance value necessary for the adjustment are provided. Trimming and adjustment, or first, roughly adjusting the thick film resistance of the smaller resistance value, and then finely adjusting the thick film resistance of the larger resistance value. By adjusting the thick film resistance of the larger resistance value to the desired value, the resistance value changes little with respect to the trimmed amount, enabling highly accurate offset adjustment and improving the offset adjustment accuracy of the Wheatstone bridge circuit. In addition, the adjustment of the thick film resistance can be facilitated, and the workability can be improved.

Embodiment 4 FIG. In each of the above-described embodiments, the thick film resistors arranged on each side facing the magnetic detection element forming the Wheatstone bridge circuit have been described for a plurality of cases, but only at least one side is described. A plurality of thick film resistors including at least one adjusting thick film resistor may be used, and the thick film resistor inserted on the other side may be a single thick film resistor. In the third embodiment, the thick film resistors having the parallel configuration are trimmed. However, the thick film resistors having the large resistance values are sequentially added to the thick film resistors having the small resistance values to perform fine adjustment. Alternatively, the thick film resistors configured in parallel in advance may be sequentially cut and finely adjusted, or the thick film resistor having a small resistance value may be cut by coarse adjustment and the resistance value may be finely adjusted. The thick film resistor having a large value may be trimmed and finely adjusted. In the case of the adjustment by this cutting, the influence of heat by the laser light at the time of trimming is not applied, so that the adjustment can be performed more accurately. In each of the above-described embodiments, the case where the magnetic detection element is used as the detection element has been described, but the present invention is not limited to this, and other elements such as a piezoelectric element that detects pressure and a strain gauge that detects strain are used. However, the same effect can be obtained. The offset adjustment may be performed using the magnetic detection element 1 or 2 side.

[0037]

As described above, according to the first aspect of the present invention, there is provided a displacement detecting device provided with a bridge circuit using a detecting element as at least one of the four side components, and at least one of the components. Since the offset adjusting means composed of a plurality of resistors is used, it is possible to perform highly accurate offset adjustment, improve the offset adjustment accuracy of the bridge circuit, and make the offset adjustment easy and improve work efficiency. The effect is that it can be realized.

According to the invention of claim 2, in the invention of claim 1, the plurality of resistors are connected in series, and the offset adjustment is performed using at least one of the plurality of resistors. Offset adjustment is possible, the offset adjustment accuracy of the bridge circuit can be improved,
Further, there is an effect that the offset adjustment becomes easy and the workability can be improved. Also, when offset adjustment is performed using both of a plurality of resistors, one can be roughly adjusted and then the other can be finely adjusted to drive it to a desired value, enabling more accurate offset adjustment. There is an effect.

According to the invention of claim 3, in the invention of claim 1, a plurality of resistors are connected in parallel, and the offset adjustment is performed using at least one of the plurality of resistors, so that a high precision is achieved. Offset adjustment is possible, the offset adjustment accuracy of the bridge circuit can be improved,
Further, there is an effect that the offset adjustment becomes easy and the workability can be improved. Further, when offset adjustment is performed using both of a plurality of resistors, one can be roughly adjusted and then the other can be finely adjusted to reach a desired value, which enables more accurate offset adjustment. There is an effect. Further, in the case of the offset adjustment by cutting the resistor, there is an effect that the adjustment can be performed more accurately without being affected by the heat of the laser light during the trimming.

According to the invention described in claim 4,
In any one of the third aspect, since the resistance value ratios of the plurality of resistors have different values, there is an effect that the offset adjustment can be performed more accurately.

According to the invention described in claim 5,
In any one of the fourth aspect, since the plurality of resistors are thick film resistors, there is an effect that offset adjustment can be performed with higher accuracy.

In the displacement detecting device according to the invention of claim 6, in the invention of any one of claims 1 to 5, the magnetic detecting element is used as the detecting element, so that the resistance value changes due to the change of the applied magnetic field, and Moreover, there is an effect that the displacement of the object to be detected can be detected.

[Brief description of drawings]

FIG. 1 is a first embodiment of a displacement detecting device according to the present invention.
It is a block diagram which shows.

FIG. 2 is a second embodiment of the displacement detecting device according to the present invention.
It is a block diagram which shows.

FIG. 3 is a third embodiment of the displacement detecting device according to the present invention.
It is a block diagram which shows.

FIG. 4 is a characteristic diagram showing an embodiment of a displacement detecting device according to the present invention and a conventional example in comparison.

FIG. 5 is a configuration diagram showing a conventional displacement detection device.

FIG. 6 is a characteristic diagram for explaining the operation of a general magnetic detection element.

[Explanation of symbols]

1, 2 magnetic detection elements, 7 differential amplifier circuits, 10a to 1
0n, 11a-11n thick film resistors.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Wataru Fukui 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Corporation (72) Inventor Yutaka Ohashi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Rishi Electric Co., Ltd.

Claims (6)

[Claims] 1. A displacement detection device comprising a bridge circuit using a detection element as at least one of the four side components, wherein at least one of the above components comprises an offset adjusting means composed of a plurality of resistors. Displacement detection device characterized by. 2. The displacement detecting device according to claim 1, wherein the plurality of resistors are connected in series, and offset adjustment is performed using at least one of the plurality of resistors. 3. The displacement detection device according to claim 1, wherein the plurality of resistors are connected in parallel, and offset adjustment is performed using at least one of the plurality of resistors. 4. The displacement detection device according to claim 1, wherein the resistance value ratios of the plurality of resistors are different values. 5. The displacement detecting device according to claim 1, wherein the plurality of resistors are thick film resistors. 6. The displacement detection device according to claim 1, wherein a magnetic detection element is used as the detection element.