JP2003194598A - Method and apparatus for detecting abnormality of sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormality detecting method and an abnormality detector for sensors by which abnormality of the output characteristics of the sensors can be detected. <P>SOLUTION: The abnormality detector 11 is provided with a pair of first and second sensors 12, 13 whose output values correspond to the changes of the directions of magnetic fluxes and have output characteristics reverse to each other, and amount to a constant sum output value when added. By the first and second sensors 12, 13, the directions of magnetic fluxes are detected by the first and second sensors 12, 13, both detected output values are added by an adder circuit 14, and a voltage V3 being the result of the addition is outputted to a central processing unit 15. When the voltage V3 is a specified (constant) value, the processing unit 15 determines that the first and second sensors 12, 13 are normal. When the voltage V3 is not a specified value, the processing unit determines that either the first or second sensor malfunctions. In this way, the abnormality detector 11 detects abnormality of the output characteristics of the first and second sensors 12, 13. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor abnormality detecting method and a sensor abnormality detecting device for determining whether or not a sensor itself outputs a normal signal.

[0002]

2. Description of the Related Art Generally, a sensor is required to have a linear output proportional to an input in order to obtain detailed information. In the case of a sensor having such a linear output, when the entire output range is used, all output values are treated as valid. Therefore, it is not possible to determine whether or not the output value of the sensor is abnormal based on the output signal of this sensor alone.

[0003]

For example, when the input is x and the output is y, the output characteristics of the sensor can be expressed by the following equation y = ax + b (a is a proportional coefficient, b is a constant).

In this case, as shown in FIG. 14, when the sensor is normal, if there is an input of x1, an output of y1 is obtained. However, when the sensor is abnormal and the constant b is changed, the output is y2 for the input x1. When the sensor is normal, this output y2 is the value at the time of x2, and therefore it is erroneously detected.

The same happens when the inclination a changes due to a sensor abnormality. Note that such a problem has a similar problem even in a sensor having a non-linear output characteristic, because it is difficult to determine whether or not the output value of the sensor is abnormal only by the output value.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a sensor abnormality detecting method and a sensor abnormality detecting device capable of detecting abnormality in the output characteristics of the sensor.

[0007]

In order to achieve the above object, the invention according to claim 1 has output characteristics in which output values corresponding to changes in a physical quantity are opposite to each other, and the output values are added. A method of detecting an abnormality of a pair of sensors at which a constant total output value is obtained, wherein one of the sensors is determined to be abnormal when the total output value of the both sensors is not a constant value.

According to a second aspect of the invention, in the sensor abnormality detecting method according to the first aspect, each of the sensors is 4
The gist is to include a magnetic detection unit that forms a bridge circuit with one magnetoresistive element, and an amplification unit that is connected to the magnetic detection unit and that amplifies a difference voltage between a pair of midpoints of the bridge circuit.

According to a third aspect of the invention, in the abnormality detecting method for the sensor according to the second aspect, the magnetic detecting means have mutually opposite output characteristics because the arrangement directions are different from each other. Is the gist.

According to a fourth aspect of the present invention, in the abnormality detecting method for the sensor according to the second aspect, the amplifying means includes an inverting input terminal and a non-inverting input terminal, and the pair of sensors includes each bridge circuit. When the arrangement directions of the magnetic detection means constituting the above are the same, they have the same output characteristics, and the connection between the inverting input terminal and the non-inverting input terminal for the pair of midpoint amplifying means in the bridge circuit is opposite to each other. That is the summary.

According to a fifth aspect of the present invention, in the method of detecting abnormality of a sensor according to any one of the first to fourth aspects, the pair of sensors have a linear output characteristic. To do.

According to a sixth aspect of the present invention, a pair of sensors having output characteristics in which output values corresponding to changes in a physical quantity are opposite to each other, and a constant total output value is obtained when the same output values are added, And a means for adding the outputs of the pair of sensors, and a means for judging that one of the sensors is abnormal when the total output value of both the sensors added by the addition means is not a constant value. Use as a summary.

According to a seventh aspect of the present invention, in the sensor abnormality detecting device according to the sixth aspect, each of the sensors is 4
The gist is to include a magnetic detection unit that forms a bridge circuit with one magnetoresistive element, and an amplification unit that is connected to the magnetic detection unit and that amplifies a difference voltage between a pair of midpoints of the bridge circuit.

According to an eighth aspect of the present invention, in the abnormality detecting device for a sensor according to the seventh aspect, the magnetic detecting means have mutually opposite output characteristics due to different arrangement directions. Is the gist.

According to a ninth aspect of the present invention, in the sensor abnormality detecting device according to the seventh aspect, the amplifying means includes an inverting input terminal and a non-inverting input terminal, and the pair of sensors includes each bridge circuit. When the arrangement directions of the magnetic detection means constituting the above are the same, they have the same output characteristics, and the connection between the inverting input terminal and the non-inverting input terminal for the pair of midpoint amplifying means in the bridge circuit is opposite to each other. That is the summary.

A tenth aspect of the present invention is the sensor abnormality detecting device according to any one of the sixth to ninth aspects, wherein the pair of sensors have a linear output characteristic. To do.

(Operation) Therefore, in the invention described in claim 1, when the same input signal is input to each sensor, each sensor outputs the output value of the output characteristic opposite to each other. The sum of the output values is set to a constant value regardless of the magnitude of the input signal. Therefore, if at least one of the two sensors becomes abnormal and the output value corresponding to the magnitude of the input signal is no longer present, the total output value will not be constant. That is, when the sum of the two output values is not constant,
It can be determined that at least one of the two sensors has an abnormality.

According to the invention described in claim 2, in addition to the operation of the invention described in claim 1, each magnetic detection means of each sensor detects the direction of the magnetic flux from the outside, and the detected magnetic flux direction. Each output value is output according to. Then, each output value is amplified by each amplification means, and it is determined whether or not the sensor is abnormal by determining whether or not the sum of the amplified output values is constant.

According to the invention described in claim 3, in addition to the function of the invention described in claim 2, by arranging the magnetic detection means of each sensor so that their directions are different from each other, the respective sensors are opposite to each other. Output characteristics.

According to the invention described in claim 4, in addition to the function of the invention described in claim 2, since the magnetic detection means have the same output characteristics, when the direction of the magnetic flux from the outside is detected, the magnetic flux is detected. The output value corresponding to the direction of is also the same.
When the respective output values are amplified by the respective amplifying means, the respective amplified output values have mutually opposite output characteristic values. Then, it is determined whether or not the sensor is abnormal by determining whether or not the sum of the amplified output values is constant.

In the invention described in claim 5, in addition to the operation of the invention described in any one of claims 1 to 4, each sensor outputs a linear output value, and each output The value is used to determine whether the sensor is abnormal.

According to the sixth aspect of the invention, when the same input signal is input to each sensor, each sensor outputs an output value having output characteristics opposite to each other. Then, the respective output values are added by the adding means. The total output value of both sensors is set to always be a constant value regardless of the magnitude of the input signal. Therefore, if at least one of the two sensors becomes abnormal and the output value corresponding to the magnitude of the input signal is no longer present, the total output value will not be constant. That is, when the sum of the two output values is not constant, it can be determined by the determination means that at least one of the two sensors has an abnormality.

According to the invention described in claim 7, in addition to the operation of the invention described in claim 6, each magnetic detection means of each sensor detects the direction of the magnetic flux from the outside, and the detected magnetic flux direction. Each output value is output according to. Then, each output value is amplified by each amplification means, and it is determined by the determination means whether or not the sensor is abnormal by determining whether the sum of the amplified output values is constant.

According to the invention described in claim 8, in addition to the operation of the invention described in claim 7, by arranging the magnetic detection means of each sensor so that their directions are different from each other, the respective sensors are opposite to each other. Output characteristics.

According to the invention described in claim 9, in addition to the operation of the invention described in claim 7, since each magnetic detection means has the same output characteristic, when the direction of the magnetic flux from the outside is detected, the magnetic flux is detected. The output value corresponding to the direction of is also the same.
When the respective output values are amplified by the respective amplifying means, the respective amplified output values have mutually opposite output characteristic values. Then, the determination unit determines whether or not the sum of the amplified output values is constant, thereby determining whether or not the sensor is abnormal.

In the invention described in claim 10, in addition to the operation described in any one of claims 6 to 9, each sensor outputs a linear output value, and each output value is output. The determination means determines whether or not the sensor is abnormal.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the sensor abnormality detecting device 11 of the present embodiment detects a change in the direction of the magnetic flux passing through the abnormality detecting device 11. Anomaly detection device 11
Includes first and second sensors 12 and 13 as sensors, an addition circuit 14 as addition means, and a central processing unit (hereinafter referred to as CPU) 15 as determination means. The first and second sensors 12, 13 and the adder circuit 14
Are known in the art. The first and second sensors 12 and 13 are detection circuits 20 as magnetic detection means,
21 and operational amplifiers 22 and 23 as amplifying means, respectively.

As shown in FIG. 2, the detection circuits 20 and 21 are arranged close to each other, and the detection voltage changes depending on the direction of the detected magnetic flux. As shown in FIG. 3, the detection circuits 20 and 21 include adjustment resistors R0 and R.
Each of the resistors R1 to R4 is a magnetoresistive element whose resistance value changes depending on the direction of the magnetic flux detected as 0 '. The resistors R1 to R4 are connected so as to form a 4-terminal bridge circuit B as a bridge circuit. Further, the adjusting resistor R is provided on the resistor R3 side.
0 is connected, and an adjusting resistor R0 ′ is connected to the resistor R1 side.

The connection point (middle point) a between the resistor R1 and the resistor R2 is an operational amplifier 22, 23 provided on the substrate.
Are respectively connected to the non-inverting input terminals T1. A connection point (midpoint) b between the resistors R3 and R4 is connected to the inverting input terminal T2 of the operational amplifiers 22 and 23.
Further, the adjusting resistors R0 and R0 ′ have a resistance value smaller than that of the resistors R1 to R4, and unlike the resistors R1 to R4, they are formed on the substrate with a material having a small temperature resistance change.

Further, as shown in FIG. 2, each of the resistors R1
˜R4 are arranged on the element surface f, and are configured to detect the magnetic flux in the direction parallel to the element surface f. Each of the resistors R1 to R4 is formed by forming a NiCo thin film in a polygonal line shape on the substrate and is set to have the same resistance value under the same temperature atmosphere. The resistors R1 to R4 have sensitivity temperature characteristics in which the sensitivity changes when the ambient temperature rises. In this sensitivity temperature characteristic, it is preferable that the sensitivity temperature change rate and the resistance temperature change rate match.

Next, the resistors R1 to R1 in the detection circuit 20.
The arrangement direction of R4 will be described. As shown in FIG.
The resistors R1 and R4 are arranged in the same direction, and the resistors R2 and R3 are arranged in a direction orthogonal to the direction in which the resistors R1 and R4 face. The center lines m1 and n1 in the figure indicate resistors R1 and R4 and resistors R2 and R2, respectively.
It shows the direction in which R3 is heading. The reference line s1 is
It is a bisector of the angle formed by the center lines m1 and n1 while passing through the base point at the point where the center lines m1 and n1 intersect.
In the present embodiment, the direction of the magnetic flux along the reference line s1 is 0 degrees, the direction of the magnetic flux along the center line m1 is +45 degrees, and the direction of the magnetic flux along the center line n1 is −45 degrees.

The detection circuit 20 has a range of -45 degrees to +45 degrees.
It is configured to detect the direction of magnetic flux up to degrees. When the detected magnetic flux is in the direction of -45 degrees, the resistors R1, R4
Has the maximum resistance value, and the resistance values of the resistors R2 and R3 have the minimum resistance value. As a result, the connection point a becomes an L level voltage, and the connection point b becomes an H level voltage. The difference voltage between the two connection points a and b is amplified by the operational amplifier 22, and the voltage V1 output from the operational amplifier 22 becomes the minimum voltage (see FIG. 4).

On the other hand, when the detected magnetic flux is in the direction of +45 degrees, the resistance values of the resistors R1 and R4 are minimum and the resistance values of the resistors R2 and R3 are maximum. As a result, the connection point a
Becomes an H level voltage, and the connection point b becomes an L level voltage. The difference voltage between the two connection points a and b is amplified by the operational amplifier 22 and output from the operational amplifier 22 as a voltage V1.
Is the maximum voltage (see FIG. 4).

Then, as the direction of the detected magnetic flux goes from -45 degrees to +45 degrees, the first sensor 1 outputs a linear voltage having a predetermined positive voltage V1.
2 is configured.

The output of the first sensor 12 is 5% of its maximum output when the direction of the detected magnetic flux is -45 degrees.
%, And the output is 50% of the maximum output of itself when the direction of the detected magnetic flux is 0 degree.
Further, the first sensor 12 detects that the direction of the detected magnetic flux is +45.
The output is 95% of the maximum output of itself.

That is, the following relational expression holds. Output of first sensor 12 (%) = 50 (%) + f
(Θ) Note that f (θ) is a function of θ and is (−45 (%)
≦ f (θ) ≦ + 45 (%)), and θ indicates the direction of the magnetic flux. When θ is 0, f (θ) = 0
(%).

Next, the resistors R1 to R1 in the detection circuit 21.
The arrangement direction of R4 will be described. As shown in FIG.
The arrangement direction of the resistors R1 to R4 of the detection circuit 21 corresponds to that of the resistors R1 to R4 of the detection circuit 20 rotated 90 degrees counterclockwise.

Therefore, the resistors R1 and R4 of the detection circuit 21.
Is the same as the center line n1 and the center line n2 is the same as the center line m1 in which the resistors R2 and R3 of the detection circuit 21 are directed.
The reference line s2 of the detection circuit 21 is in a direction orthogonal to the reference line s1.

The detection circuit 21 is operated from -45 degrees to +45 degrees.
It is configured to detect the direction of magnetic flux up to degrees. The resistors R1 to R4 in the detection circuit 21 have the same arrangement pattern as the resistors R1 to R4 of the detection circuit 20, and are changed by 90 degrees only in the arrangement direction. Therefore, the detected magnetic flux is -45
In the direction of the degree, the resistance values of the resistors R1 and R4 become the minimum, and the resistance values of the resistors R2 and R3 become the maximum. As a result, the connection point a becomes an H level voltage, and the connection point b becomes an L level voltage. The difference voltage between the two connection points a and b is amplified by the operational amplifier 23, and the voltage V2 output from the operational amplifier 23 becomes the maximum voltage (see FIG. 4).

On the other hand, the detection circuit 21 detects that the detected magnetic flux is +4.
When the orientation is 5 degrees, the resistance values of the resistors R1 and R4 are maximum, and the resistance values of the resistors R2 and R3 are minimum. As a result, the connection point a becomes an L level voltage and the connection point b becomes H level.
It becomes the level voltage. The difference voltage between the two connection points a and b is amplified by the operational amplifier 23, and the voltage V2 output from the operational amplifier 23 becomes the minimum voltage (see FIG. 4).

Then, as the direction of the detected magnetic flux goes from -45 degrees to +45 degrees, the second sensor 1 outputs a linear voltage having a predetermined negative voltage V2.
3 is configured.

The output of the second sensor 13 is 9% of its maximum output when the direction of the detected magnetic flux is -45 degrees.
The output is 5%, and the output thereof is 50% of the maximum output of itself when the direction of the detected magnetic flux is 0 degree. Further, the second sensor 13 detects that the direction of the detected magnetic flux is +
The output is 5% of its maximum output at 45 degrees.

That is, the following relational expression holds. Output of second sensor 13 (%) = 50 (%)-f
(Θ) Note that f (θ) is a function of θ and is (−45 (%)
≦ f (θ) ≦ + 45 (%)). Also, θ is 0
At that time, f (θ) = 0 (%).

In the present embodiment, the relationship "having opposite output characteristics" means that a line parallel to the X axis (hereinafter referred to as a symmetry line T) that passes through the intersection of the characteristic lines of the voltages V1 and V2. ), The two characteristic lines are line-symmetrical (see FIG. 4).

As shown in FIG. 1, the operational amplifier 22 is connected to the adder circuit 14 and the central processing unit 15, and the voltage V1 is added to the adder circuit 14 and the central processing unit 15.
Is configured to be input to. Further, the operational amplifier 23 is connected to the adder circuit 14 so that the voltage V2 is inputted to the adder circuit 14. The adder circuit 14 is connected to the central processing unit 15, and is configured to add the two voltages V1 and V2 that have been input and output a voltage V3 that is the addition result to the central processing unit 15. .

The central processing unit 15 receives the input voltage V3
Whether or not is a predetermined (constant) voltage is compared with data stored in advance in a ROM (read-only memory) not shown. Here, the predetermined means the first sensor 1
2 output, or 100% of the output of the second sensor 13. When the central processing unit 15 determines that the voltage V3 is a predetermined voltage, it is determined that the first sensor 12 is normal. That is, the voltage V1 input from the operational amplifier 22 is used as a control program for an external device (not shown) controlled by the central processing unit 15.

This is because the output characteristics of the voltage V1 and the voltage V2 are opposite to each other. Therefore, if both the voltages V1 and V2 are normal detection voltages, the output voltages are symmetrical with respect to the symmetry line T. As a result, the voltage V3, which is the sum of the two voltages V1 and V2, is always a predetermined value (constant value). Therefore, the first sensor 12 can be determined to be operating properly.

On the other hand, when the central processing unit 15 determines that the voltage V3 is not the predetermined voltage, the central processing unit 15
Outputs an abnormality signal to an abnormality warning device (not shown), and the abnormality warning device appropriately performs abnormality processing. This is because if the voltage V1 and the voltage V2 are not symmetrical with respect to the line of symmetry T, the added value of the two voltages V1 and V2 will not be a predetermined value (constant value).

Therefore, according to the abnormality detecting device 11 of the first embodiment, the following effects can be obtained. (1) In the present embodiment, the abnormality detection device 11 is provided with the first and second sensors 12 and 13 that detect changes in the direction of the magnetic flux passing through the element surface f. The first and second sensors 12 and 13 are configured so that their output values (voltages V1 and V2) have opposite output characteristics. The output values of the first and second sensors 12 and 13 are added by the adder circuit 14, and the voltage V3 which is the addition result is output to the central processing unit 15. Then, when the voltage V3 is a predetermined (constant) voltage, the central processing unit 15 operates the first and second sensors 12, 1
No. 3 was judged to be normal, and if it was not a predetermined voltage, one of the first and second sensors 12 and 13 was judged to be abnormal. Therefore, the abnormality detection device 11 can detect an abnormality in the output characteristics of the first and second sensors 12 and 13.

(2) In this embodiment, the detection circuits 20 and 21 of the first and second sensors 12 and 13 are composed of the resistors R1 to R4 and the adjusting resistors R0 and R0 ', respectively. A 4-terminal bridge circuit B is configured by the resistors R1 to R4. The direction of the magnetic flux is detected by the voltage difference between the voltage at the connection point (middle point) a of the resistors R1 and R2 and the voltage at the connection point (middle point) b of the resistors R3 and R4. . Therefore, the change in the direction of the magnetic flux passing through the element surface f can be detected by using the 4-terminal bridge circuit B including the resistors R1 to R4.

(3) In this embodiment, the first and second sensors 12 and 13 and the adder circuit 14 are constructed by known techniques. Therefore, when the abnormality detection device 11 is manufactured, there are almost no new parts to be manufactured by itself, and the manufacturing cost can be suppressed.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIGS. 5 and 6. The second embodiment and the third embodiment are modifications of the first embodiment, and the same components as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted. However, only different points will be described.

The abnormality detecting device 31 of this embodiment is different from that of the first embodiment only in the configuration of the second sensor. Specifically, in the first embodiment, the detection circuit 2
Although the arrangement direction of 1 is shifted by 90 degrees with respect to the detection circuit 20, the detection circuit 2 in the second sensor 32 of this embodiment is
The arrangement direction of 1 is the same as that of the detection circuit 20 (see FIG. 6). The second sensor 32 corresponds to a sensor.

The connection point a of the detection circuit 21 is connected to the inverting input terminal T2 of the operational amplifier 23, and the connection point b is connected to the non-inverting input terminal T1 of the operational amplifier 23.
As a result, the voltages V1 of the first and second sensors 12 and 32 are
The output values of V2 are configured to have opposite output characteristics.

Therefore, the abnormality detecting device 31 of the second embodiment
Also in the above, the same effects as the effects (1) to (3) of the first embodiment can be obtained. (Third Embodiment) A third embodiment of the present invention will be described below with reference to FIG.

The abnormality detection device 41 of the present embodiment does not have the addition circuit 14 as compared with the abnormality detection device 11 of the first embodiment. Instead, a central processing unit (hereinafter, referred to as a CPU) 42 as a determination means is provided with both voltages V1,
The difference is that the magnitude of V2 is detected and the value of the detection result is added and calculated by software. Therefore, in the present embodiment, the central processing unit 15 also corresponds to adding means.

Therefore, the abnormality detecting device 41 of the third embodiment
In the CPU 42, the addition operation of both voltages V1 and V2 is performed.
Other than that, since the same operation as the abnormality detection device 11 is achieved, the same effects as the effects (1) and (2) of the first embodiment can be obtained. At the same time, the following effects can be obtained.

(1) The abnormality detection device 41 of this embodiment is
Compared with the abnormality detection device 11 of the first embodiment, the adder circuit 14
Is omitted. Therefore, as compared with the abnormality detection device 11, the abnormality detection device 41 can reduce the number of parts by the amount that the addition circuit 14 is omitted.

(2) In this embodiment, the first and second sensors 12 and 13 are constructed by known techniques. Therefore, when manufacturing the abnormality detection device 41, there are almost no new parts to be manufactured by itself, and the manufacturing cost can be suppressed.

(Fourth Embodiment) A fourth embodiment of the present invention will be described below with reference to FIG. The fourth embodiment is a modification of the second embodiment, and the same components as those in the second embodiment are designated by the same reference numerals, detailed description thereof will be omitted, and only different portions will be described. Will be explained.

The anomaly detecting device 51 of this embodiment does not include the adding circuit 14 as compared with the anomaly detecting device 31 of the second embodiment. Instead, a central processing unit (hereinafter, referred to as a CPU) 52 serving as a determination unit is provided with both voltages V1,
The difference is that the magnitude of V2 is detected and the value of the detection result is added and calculated by software. Therefore, in the present embodiment, the central processing unit 15 also corresponds to adding means.

Therefore, the abnormality detecting device 51 of the fourth embodiment
In the CPU 52, the addition processing of both voltages V1 and V2 is performed.
Since the same operation as that of the abnormality detection device 31 is performed except that the above-described step is performed, the same effects as the effects (1) and (2) of the first embodiment can be obtained. At the same time, the following effects can be obtained.

(1) The abnormality detecting device 51 of this embodiment is
Compared to the abnormality detection device 31 of the second embodiment, the addition circuit 14
Is omitted. Therefore, as compared with the abnormality detection device 31, the abnormality detection device 51 can reduce the number of parts by the amount that the addition circuit 14 is omitted.

(2) In this embodiment, the first and second sensors 12 and 13 are constructed by known techniques. Therefore, when manufacturing the abnormality detection device 51, there are almost no new parts to be manufactured by itself, and the manufacturing cost can be suppressed.

(Other Embodiments) The above-described embodiments may be modified and embodied in the following other embodiments.

In the first and second embodiments, the operational amplifier 22 is connected to the CPU 15 so that the voltage V1 is applied to the CPU.
I input it to 15. Then, the CPU 15 determines that the first sensor 12 is normal when the voltage V3 is determined to be the predetermined value (constant value). That is, the voltage V1 input from the operational amplifier 22 is used as a control program for an external device (not shown) controlled by the central processing unit 15.

Not limited to this, by connecting the operational amplifier 23 to the CPU 15 instead of the operational amplifier 22, the voltage V2
Is input to the CPU 15. Then, the CPU 15 sets the voltage V
When it is determined that 3 is a predetermined value (constant value), the voltage V2 may be used for a control program for an external device (not shown) controlled by the central processing unit 15.

In the third and fourth embodiments, the CPU 4
Nos. 2 and 52 output the voltage V1 to the detection voltage utilization device when the voltage V3 is determined to be a predetermined value (constant value). Not limited to this, the CPUs 42 and 52 set the voltage V2 to the central processing unit 15 when the voltage V3 is determined to be a predetermined value (constant value).
It may be used for a control program for an external device (not shown) controlled by the.

The operational amplifiers 22 and 23 of each of the above embodiments
May be replaced with, for example, a differential amplification circuit 61 as a known amplification means shown in FIG. This differential amplifier circuit 61
Are input terminals Va and Vb, resistors R11 to R17, amplifiers 62 to 64, reference voltage terminal V _REF , and output terminal Vc.
Is equipped with. Then, the detection circuit 20 of the first embodiment,
21, the detection circuit 20 of the second embodiment, the detection circuits 20 and 21 of the third embodiment, and the detection circuit 20 of the fourth embodiment, the connection point a is the input terminal Va and the connection point b is the input terminal Vb.
Connect to. In addition, the detection circuit 21 of the second and fourth embodiments
In, the connection point a is connected to the input terminal Vb, and the connection point b is connected to the input terminal Va. In the resistance value, R11 =
The configuration is such that R14, R12 = R15, and R16 = R17. When the respective members are electrically connected as shown in this figure, the following relational expression holds.

Vc = (R16 / R12) × (1+ (2 ×
R11 / R13)) × (Va−Vb) + V _REF where V _REF is the voltage of the reference voltage terminal V _REF .

Hereinafter, this embodiment will be referred to as a first example. The operational amplifiers 22 and 23 of each of the above-described embodiments are shown in FIG.
The differential amplifier circuit 71 shown in FIG.
May be replaced with The differential amplifier circuit 71 includes input terminals Vd and Ve, resistors R21 to R24, amplifiers 72 and 7.
3, a reference voltage terminal V _REF , and an output terminal Vf. Then, the detection circuits 20 and 2 of the first and third embodiments
In the detection circuits 20 of the first, second and fourth embodiments, the connection point a is connected to the input terminal Vd and the connection point b is connected to the input terminal Ve. Further, in the detection circuit 21 of the second and fourth embodiments, the connection point a is the input terminal Ve and the connection point b is the input terminal V.
Connect to d. The resistance value is R23 = R2
2 and R21 = R24. When the respective members are electrically connected as shown in this figure, the following relational expression holds.

Vf = (1+ (R24 / R23)) × (V
d-Ve) + V _REF Vf is the terminal voltage of the output terminal, Vd and Ve are the terminal voltages of the input terminals, and R23 and R24 are the resistance values of the resistors R23 and 24. V _REF is the voltage of the reference voltage terminal V _REF .

Hereinafter, this embodiment will be referred to as a second example. The summing circuit 14 of the first and second embodiments may be replaced with a summing amplifier circuit 81 as a known addition means shown in FIG. This addition amplifier circuit 81 has an input terminal V
g, Vh, resistors R31 to R34, an amplifier 82, a reference voltage terminal V _REF , and an output terminal Vi. Then, the output terminals of the operational amplifiers 22 and 23 of the first and second embodiments are connected to the input terminals Vg and Vh, respectively. In addition,
The resistance value is configured such that R31 = R32. When the respective members are electrically connected as shown in this figure, the following relational expression holds.

Vi = − (R33 / R31) × (Vg + V
h) + V _REF × (1+ (2 × R33 / R3
1)) Vi is the terminal voltage of the output terminal, Vg and Vh are the terminal voltages of the input terminals, and R31 and R33 are the resistance values of the resistors R31 and 33. V _REF is the voltage of the reference voltage terminal V _REF .

In the first example, the second sensor 13 is
When the direction of the detected magnetic flux is 0 degree, the output is 50% of the maximum output of itself. Not limited to this, by adjusting the voltage of the reference voltage terminal V _REF shown in FIG. 9, the output becomes (50 + α)% of the maximum output of itself when the direction of the detected magnetic flux is 0 degree. The second sensor 13 may be configured. By doing so, the following effects can be obtained. Note that α> 0.

In the first example, when an abnormality occurs on the detection circuit side, it may be fixed at 50% output. Therefore, if both of the sensors 12 and 13 become abnormal and are fixed at 50% output, it may not be possible to determine that the sensor is in failure despite the failure. To prevent this, the voltage of the reference voltage terminal V _REF is added by, for example, α, and the sum in a normal state is set to “100 + α”. By doing so, even if the detection circuits of both sensors 12 and 13 both have a fixed output of 50% and both fail,
Both 2 and 13 do not settle at 50% output. In addition, such a change may be embodied in the second example.

Further, instead of adjusting the reference voltage terminal V _REF in this way, the detection circuit 21 in the second sensor 13 may be arranged with a shift of several degrees. Even in this case, the output of the second sensor 13 is, for example, (50 + α)% of the maximum output of itself when the direction of the detected magnetic flux is 0 degree.

In the first embodiment, both sensors 12,
13 has a characteristic of outputting linear voltages V1 and V2 having a predetermined slope. Not limited to this, both sensors having a non-linear output characteristic that draws a curve as shown in FIG. 13 may be used. What is essential is that the characteristic lines of the voltages V1 and V2 are line-symmetrical with respect to the line of symmetry T. Further, such changes may be embodied in the second to fourth embodiments.

In the abnormality detecting device 11 of the first embodiment, the output values corresponding to the detected magnetic flux directions have opposite output characteristics, and a constant total output value is obtained when the output values are added. A pair of sensors 12 and 13 are provided. Instead of the sensors 12 and 13 that detect the direction of the magnetic flux, a sensor that outputs the magnitude of the current and a pair of sensors that output a voltage according to the amount of received light are provided so that the abnormality detection device 11 is provided. May be configured. Even in this case, the pair of sensors employs output values corresponding to changes in the physical quantity having output characteristics opposite to each other and obtaining a constant total output value when the output values are added. With this configuration, it is possible to embody a sensor abnormality detection device that detects the magnitude of current, a sensor abnormality detection device that detects the amount of light, and the like.

[0081]

As described in detail above, according to the invention described in claims 1 to 10, it is possible to detect an abnormality in the output characteristic of the sensor.

[Brief description of drawings]

FIG. 1 is an electrical circuit diagram showing an electrical configuration of an abnormality detection device according to a first embodiment.

FIG. 2 is an explanatory diagram showing an arrangement state of each resistor in the first embodiment.

FIG. 3 is an equivalent circuit of a resistor according to the first embodiment.

FIG. 4 is a characteristic diagram showing the relationship between the direction of magnetic flux and the output characteristics of each sensor in the first embodiment.

FIG. 5 is an electrical circuit diagram showing an electrical configuration of an abnormality detection device according to a second embodiment.

FIG. 6 is an explanatory diagram showing an arrangement state of each resistor in the second embodiment.

FIG. 7 is an electrical circuit diagram showing an electrical configuration of an abnormality detection device according to a third embodiment.

FIG. 8 is an electrical circuit diagram showing an electrical configuration of an abnormality detection device according to a fourth embodiment.

FIG. 9 is an electric circuit diagram showing an electric configuration of a differential amplifier circuit according to another embodiment.

FIG. 10 is an electric circuit diagram showing an electric configuration of a differential amplifier circuit according to another embodiment.

FIG. 11 is an electric circuit diagram showing an electric configuration of a summing amplifier circuit according to another embodiment.

FIG. 12 is a characteristic diagram showing the relationship between the direction of magnetic flux and the output characteristics of each sensor in another embodiment.

FIG. 13 is a characteristic diagram showing the relationship between the direction of magnetic flux and the output characteristics of each sensor in another embodiment.

FIG. 14 is a characteristic diagram showing a relationship between an input and an output in the related art.

[Explanation of symbols]

11, 31, 41, 51 ... Sensor abnormality detection device, 12
... first sensor as sensor, 13, 32 ... second sensor as sensor, 14 ... adding circuit as adding means, 1
5 ... Central processing unit (CPU) as judging means, 2
0, 21 ... Detection circuit as magnetic detection means, 22, 23
... operational amplifier as amplifying means, B ... 4-terminal bridge circuit as bridge circuit, R1 to R4 ... resistor as magnetoresistive element, T1 ... non-inverting input terminal, T2 ... inverting input terminal.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Taiji Nishi             260-chome, Toyota, Oguchi-cho, Niwa-gun, Aichi             Tokai Rika Electric Co., Ltd. (72) Inventor Koichi Ichiko             10 Akane, Takane, Fujii-cho, Anjo City, Aichi Prefecture             N AW Co., Ltd. (72) Inventor Toru Shinya             10 Akane, Takane, Fujii-cho, Anjo City, Aichi Prefecture             N AW Co., Ltd. F term (reference) 2F076 AA06 AA18                 2G017 AA06 AD55 BA09 BA11

Claims (10)

[Claims] 1. An abnormality detection method for a pair of sensors, wherein output values corresponding to changes in physical quantity have output characteristics opposite to each other, and a constant total output value is obtained when the same output values are added, An abnormality detection method for a sensor, characterized in that when either of the total output values of the both sensors is not a constant value, one of the sensors is determined to be abnormal. 2. Each of the sensors includes a magnetic detection unit that forms a bridge circuit with four magnetoresistive elements, and an amplification unit that is connected to the magnetic detection unit and that amplifies a difference voltage between a pair of midpoints of the bridge circuit. The method for detecting abnormality of a sensor according to claim 1, further comprising: 3. The abnormality detecting method for a sensor according to claim 2, wherein the magnetic detecting means have mutually opposite output characteristics due to different arrangement directions. 4. The amplifying means includes an inverting input terminal and a non-inverting input terminal, and the pair of sensors have the same output characteristic when the magnetic detection means constituting each bridge circuit are arranged in the same direction. At the same time, the connection between the inverting input terminal and the non-inverting input terminal for the pair of midpoint amplifying means in the bridge circuit is opposite to each other. 5. The method for detecting abnormality of a sensor according to claim 1, wherein the pair of sensors have a linear output characteristic. 6. A pair of sensors, each having an output characteristic in which output values corresponding to a change in a physical quantity are opposite to each other, and a constant total output value is obtained when the output values are added, and outputs of the pair of sensors. Abnormality detection of the sensor, characterized by comprising: an addition unit for adding the above, and a determination unit for determining that one of the sensors is abnormal when the total output value of both the sensors added by the addition unit is not a constant value. apparatus. 7. Each of the sensors includes a magnetic detection unit that forms a bridge circuit with four magnetic resistance elements, and an amplification unit that is connected to the magnetic detection unit and that amplifies a difference voltage between a pair of midpoints of the bridge circuit. 7. The sensor abnormality detection device according to claim 6, further comprising: 8. The abnormality detecting device for a sensor according to claim 7, wherein the magnetic detecting means have output characteristics opposite to each other due to different arrangement directions. 9. The amplifying means includes an inverting input terminal and a non-inverting input terminal, and the pair of sensors have the same output characteristic when the magnetic detection means constituting each bridge circuit are arranged in the same direction. At the same time, the connection between the inverting input terminal and the non-inverting input terminal for the pair of midpoint amplifying means in the bridge circuit is opposite to each other, and the abnormality detecting device for the sensor according to claim 7. 10. The sensor abnormality detection device according to claim 6, wherein the pair of sensors have a linear output characteristic.