JP2021051037A - Detection device - Google Patents

Abstract

To provide a detection device provided with a function to detect by a simple structure the fault of each detection element constituting a bridge.SOLUTION: A detection device 1 is constituted by including: a detection unit 10 having a first detection unit 11 for detecting a first detection value V1 relating to a detection object, and a second detection unit 12 paired with the first detection unit 11, for detecting a second detection value V2 relating to the detection object; a differential amplification unit 20 provided with a first input unit 21 for the first detection value V1 and a second input unit 22 for the second detection value V2, for amplifying a difference between the first detection value V1 and the second detection value V2 and outputting the detection value of the detection object as an output value Vout; a bias potential application unit 30 for applying a bias potential Vb to either the first input unit 21 or the second input unit 22; and a control unit 40 having a fault detection unit 41 for determining the fault detection of the detection unit 10 on the basis of the output value Vout of the differential amplification unit 20. This configuration enables the fault detection function of each detection element constituting a bridge.SELECTED DRAWING: Figure 1

Description

The present invention relates to a detection device, and more particularly to a detection device having a failure detection function.

Conventionally, for example, a failure detection circuit for a pressure sensor, particularly a failure detection circuit for detecting a failure when a disconnection occurs (see, for example, Patent Document 1). The failure detection circuit of Patent Document 1 is located between a constant voltage source that applies a constant voltage to a bridge connecting a pressure sensitive element and three reference resistors, and a connection point on both sides of the connection point on which the constant voltage acts. In a pressure sensor including an amplifier that inputs a point potential and outputs according to the potential difference, a detection resistor that follows the connection point facing the connection point on which the constant voltage acts and the ground is connected. Means for setting the output voltage across the detection resistor and the output voltage of the amplifier as predetermined reference values in the event of a defect or disconnection, and the output voltage across the detection resistor or the output voltage of the amplifier as the corresponding reference value. It is configured to include a comparator for comparison.

This failure detection circuit has a detection resistor and detects the bridge configuration by comparing the amplifier output (sensor output) and constant voltage (Vcc), comparing the amplifier output (sensor output) with the reference value, and comparing the voltage across the detection resistor. It is said that it is possible to detect that a failure has occurred in the pressure sensor, which is an element.

Japanese Unexamined Patent Publication No. 1-272904

However, the failure detection circuit of Patent Document 1 requires a detection resistor and three comparators in order to detect a failure of the pressure sensor having a bridge configuration, and causes a failure by outputting three comparator outputs via an OR gate. Since the detection signal is obtained, there is a problem that the circuit configuration becomes complicated.

Therefore, an object of the present invention is to provide a detection device having a failure detection function of each detection element constituting the bridge with a simple configuration.

[1] In the present invention, a first detection unit that detects a first detection value related to a detection target and a second detection unit that is paired with the first detection unit and detects a second detection value related to the detection target are provided. A detection unit having a detection unit, a first input unit for the first detection value, and a second input unit for the second detection value are provided, and the difference between the first detection value and the second detection value is amplified and described. A differential amplification unit that outputs the detected value of the detection target as an output value, a bias potential application unit that applies a bias potential to either the first input unit or the second input unit, and the differential amplification unit. Provided is a detection device including a control unit having a failure detection unit for determining failure detection of the detection unit based on the output value.
[2] The detection unit has a full bridge configuration in which the first detection unit and the second detection unit are half bridges, respectively, and the first detection value and the second detection value are the same as the first detection unit. It may be a detection device which is the midpoint potential of each of the second detection units.
[3] Further, the differential amplification unit may be an operational amplifier, and the operational amplifier may be a detection device that operates with a single power source.
[4] Further, the detection unit may be a detection device composed of load sensor elements which are four first to fourth detection elements.
[5] Further, the bias potential may be set to be smaller than the midpoint potential during the non-detection operation of the detection unit, which may be a detection device.
[6] Further, the failure detection unit may be a detection device that detects an open failure of each of the four detection elements.

According to the present invention, a detection device having a failure detection function of each detection element constituting the bridge can be obtained by a simple configuration.

FIG. 1 is a circuit configuration diagram of the detection device 1 according to the embodiment of the present invention. FIG. 2 is a flowchart when failure detection is executed in the detection device 1 according to the embodiment of the present invention. FIG. 3A is a diagram showing that the output value Vout is 0V when the load sensor element Ra in the detection device 1 has an open failure, and FIG. 3B is a diagram showing the load sensor element in the detection device 1. It is a figure which shows that the output value Vout is + 5V when Rb has an open failure, and FIG. 3C is the figure which the output value Vout is + 5V when the load sensor element Rc has an open failure in the detection device 1. FIG. 3D is a diagram showing that the output value Vout is 0V when the load sensor element Rd in the detection device 1 has an open failure.

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

[Embodiments of the present invention]
Detecting device 1 according to the embodiment of the present invention, as shown in FIG. 1, a first detector 11 for detecting the first detection value V ₁ for the detection target, without the first detector 11 pairs, detection A detection unit 10 having a second detection unit 12 for detecting a _{second detection value V 2} related to an object, a first input unit 21 of the first _{detection value V 1} , and a second input unit of _{the second detection value V 2.} 22 is provided, a differential amplification unit 20 that amplifies the difference between the first detection value V ₁ and the second detection value V ₂ and outputs the detection value of the detection target as an output value Vout, and a first input unit 21 or a first It has a bias potential application unit 30 that applies a bias potential Vb to any one of the two input units 22, and a failure detection unit 41 that determines the failure detection of the detection unit 10 based on the output value Vout of the differential amplification unit 20. It is configured to include a control unit 40.

The detection device 1 according to the present embodiment is, for example, an in-vehicle switch mounted on a vehicle. Further, the detection unit 10 included in the detection device 1 is, for example, a force sensor (load sensor), which is a sensor using a diaphragm structure in which a bridge due to a piezoresistive effect is arranged. In such a configuration, the detection target (load) is a load. The detection unit 10 of the detection device 1 according to the present embodiment can be applied to other detection targets. For example, when a change in a magnetic field is a detection target, the detection unit is a magnetic resistance such as MR. It can be composed of elements.

(Detection unit 10)
As shown in FIG. 1, the first detection unit 11 is a half bridge of the load sensor element Ra and the load sensor element Rb, which are detection elements, and the second detection unit 12 is a load sensor element Rc and a load, which are detection elements. The sensor element Rd is a half bridge. The detection unit 10 is configured such that the first detection unit 11 and the second detection unit 12, which are half bridges, are full bridges, respectively.

In the case of the diaphragm structure as described above, the load sensor elements Ra, Rb, Rc, and Rd, which are the detection elements, have gauge resistance by diffusion or ion injection on the diaphragm (pressure receiving portion) in which the silicon substrate is thinned by etching or the like, for example. By forming (piezoresistive effect), the piezoresistive effect can be obtained.

Further, the load sensor elements Ra, Rb, Rc, and Rd can obtain a piezoresistive effect by attaching a metal strain gauge using an isotropic conductor on the diaphragm (pressure receiving portion) in a bridge shape. it can.

In this embodiment, the differential amplification unit 20 is used with a single power supply (for example, a + 5V power supply). Therefore, the detection unit 10 is used so that the output of the differential amplification unit 20, which will be described later, is output as a positive voltage by pressing the diaphragm (pressure receiving unit) in one direction such as downward. Is preferable.

As shown in FIG. 1, the load sensor elements Ra and Rb, which are the first detection units 11, are electrically connected at the connection point 13, one end 15 of Ra is connected to the power supply voltage Vcc, and one end 16 of Rb is ground GND. It is connected to the. Further, the load sensor elements Rc and Rd, which are the second detection units 12, are electrically connected at the connection point 14, one end 15 of Rc is connected to the power supply voltage Vcc, and one end 16 of Rd is connected to the ground GND. .. As described above, the first detection unit 11 and the second detection unit 12 have a bull bridge configuration. In this embodiment, the power supply voltage Vcc is + 5V.

As shown in FIG. 1, the connection point 13 of Ra and Rb of the first detection unit 11 outputs the first detection value _{V 1} as the midpoint potential. Also, Rc and Rd connection point 14 of the second detection unit 12 outputs the second detection value _{V 2} as the midpoint potential.

(Differential amplifier 20)
As shown in FIG. 1, the differential amplification unit 20 is configured as a differential amplifier (inverting amplifier) by an operational amplifier.

The non-inverting input terminal 21 is first input unit is connected to the resistor R _3, the first detection value V ₁ is inputted. One end of the resistor _{R 3} is at the connection point 13 is connected to the load sensor elements Ra and Rb, the other end 21 of the resistor _{R 3} is connected to the resistor _R 4, _{R 5.} Also, the non-inverting input terminal 21, the bias potential application unit 30 is connected, is connected to the resistor R ₄ and the resistor R _5, the power supply voltage Vcc is applied as a divided by bias potential Vb.

Inverting input terminal 22 which is the second input unit is connected to the resistor R _1, the second detection value V ₂ is input. One end of the resistor _{R 1} is in the connection point 14 is connected to the load sensor elements Rc and Rd, the other end 17 of the resistor _{R 1} is connected to the resistor _{R 2.} Further, the inverting input terminal 22 is _{connected to the resistor R 2} and is connected to the output terminal 23 via _{the resistor R 2.}

The output terminal 23 of the differential amplification unit 20 outputs the output value Vout. The output value Vout can be used as the detection result of the detection unit 10. Further, it is input to the control unit 40 and can be used to determine the failure detection of the detection unit 10.

A power supply voltage Vcc is connected to the power supply terminal 24 of the differential amplification unit 20, and the ground terminal 25 is connected to the ground GND. In the present embodiment, the operational amplifier (differential amplifier 20) is operated with a single power supply having a power supply voltage of Vcc = + 5 [V].

(Bias potential application unit 30)
As shown in FIG. 1, the bias voltage applying unit 30, the power supply voltage Vcc is divided by the resistor R ₅ resistor R _4, to apply a bias potential Vb to the non-inverting input terminal 21.

(Control unit 40)
As shown in FIG. 1, the control unit 40 has a failure detection unit 41 in which the output value Vout of the differential amplification unit 20 is input and the failure detection of the detection unit 10 is determined based on the input value Vout.

A command signal Sc for executing failure detection of the detection unit 10 is input to the control unit 40. This command signal Sc is input from the main body of the device on which the detection device 1 is mounted. When the detection device 1 is mounted on a vehicle, for example, a command signal Sc is input to the control unit 40 from the vehicle side when the vehicle is turned on, the engine is started, the driver operates the equipment, or the like. ..

A warning signal Sa can be output from the control unit 40. When the load sensor elements Ra, Rb, Rc, and Rd constituting the detection unit 10 fail in an open manner, the warning signal Sa can notify the failure by, for example, changing from the Low level to the High level.

The control unit 40 is, for example, a CPU (Central Processing Unit) that performs detection, determination, determination, etc. based on acquired data according to a stored program, a RAM (Random Access Memory) that is a semiconductor memory, and a ROM (Read Only Memory). ) And so on. In this ROM, for example, a program for operating the control unit 40 is stored. The RAM is used, for example, as a storage area for temporarily storing the calculation result and the like.

(Output value Vout of the differential amplifier 20)
In the detection device 1 having the configuration shown in FIG. 1, the output value Vout of the differential amplification unit 20 is obtained.

Consider the sum of currents at the non-inverting input terminal 21 in FIG. Since the input impedance of the non-inverting input terminal 21 is sufficiently large, assuming that no current flows in, from I ₁ + I ₂ = I _{3 shown in FIG.}

Similarly, considering the current passing through the terminal 17 connected to the inverting input terminal 22, from I ₄ = I ₅ ,

Since the non-inverting input terminal 21 and the inverting input terminal 22 have the same potential due to an imaginary short circuit,

The output value Vout of the differential amplification unit 20 is obtained from the equations (1) to (3) shown above. In the above equation, R ₁ = R ₃ and R ₂ = R ₄ . Further, since the gain of the differential amplification unit 20 is increased to, for example, about 10 times, R ₁ << R ₂ can be set. Further, the bias potential Vb is set to be smaller than _{the midpoint potential (first detection value V 1} , second detection value V ₂ ) during non-detection operation of the detection unit. For example, since the bias potential Vb is set to about 1 [V], R ₄ << R ₅ can be set. From the above settings, the output value Vout is as follows.

In equation (4), under _{the conditions of R 1} << R ₂ << R ₅ , for example, Vcc = 5 [V], R ₁ = R ₃ = 1 [kΩ], R ₂ = R ₄ = 10 [kΩ] , R ₅ = 55 [kΩ], and the following equation (5) can be summarized.

According to the equation (5), the output value Vout of the differential amplification unit 20 has a bias potential Vb = 1 [V], _{and the difference between the first detection value V 1} and the second detection value V ₂ is amplified 10 times. , 0-5 [V] is output so as to be amplified on the positive voltage side.

(Failure detection operation in detection device 1)
FIG. 2 is a flowchart when failure detection is executed in the detection device 1 according to the embodiment of the present invention. The control unit 40 executes a failure detection operation based on the command signal Sc or the like shown in FIG. In Eq. (5), it is assumed that the offset is adjusted and (V _{1 −} V ₂ ) is set to zero when the detection unit 10 is not loaded.

(Step1)
The failure detection unit 41 of the control unit 40 determines whether or not the output value Vout of the differential amplification unit 20 is the bias potential Vb. When the output value Vout of the differential amplifier 20 is according to the equation (5), it is determined whether or not the output value Vout is 1 [V]. The failure detection unit 41 can determine whether or not the output value Vout is within Vb ± a [V], where a [V] is a predetermined voltage error. If the output value Vout is the bias potential Vb, the process proceeds to Step 2 (Step 1: Yes), and if the output value Vout is not the bias potential Vb, the process proceeds to Step 3 (Step 1: No).

(Step2)
The control unit 40 determines that the detection unit 10 is normal. That is, it can be determined that the detection unit 10 is operating normally without any open failure or the like. During this normal operation, the control unit 40 does not output the warning signal Sa. Further, the output value Vout of the differential amplification unit 20 can be used as a load sensor signal.

(Step3)
The failure detection unit 41 of the control unit 40 determines whether or not the output value Vout of the differential amplification unit 20 is 0 [V]. If the output value Vout of the differential amplifier 20 is 0 [V], the process proceeds to Step 4 (Step 3: Yes), and if the output value Vout is not 0 [V], the process proceeds to Step 5 (Step 3: No).

(Step4)
When the output value Vout of the differential amplification unit 20 is 0 [V], the failure detection unit 41 of the control unit 40 can determine that the load sensor element Ra or Rd is an open failure.

FIG. 3A is a diagram showing that the output value Vout is 0V when the load sensor element Ra of the detection device 1 has an open failure. In FIG. 3A, when the load sensor element Ra has an open failure (marked with a cross in the figure to indicate an open failure), V ₁ is about 0 [V] and V ₂ is about 2.5 [. Since it is V], the output value Vout becomes 0 [V].

Further, FIG. 3D is a diagram showing that the output value Vout is 0V when the load sensor element Rd fails to open in the detection device 1. In FIG. 3D, when the load sensor element Rd has an open failure (marked with a cross in the figure to indicate an open failure), V ₁ is about 2.5 [V] and V ₂ is about 5 [. Since it is V], the output value Vout becomes 0 [V].

Therefore, the failure detection unit 41 of the control unit 40 can determine that the load sensor element Ra or Rd is an open failure when the output value Vout of the differential amplification unit 20 is 0 [V]. ..

When the control unit 40 determines that the load sensor element Ra or Rd is an open failure, the control unit 40 can output a warning signal Sa. Further, the output value Vout of the differential amplification unit 20 can be prevented from being used as the load sensor signal.

(Step 5)
The failure detection unit 41 of the control unit 40 determines whether or not the output value Vout of the differential amplifier unit 20 is 5 [V]. If the output value Vout of the differential amplifier 20 is 5 [V], the process proceeds to Step 6 (Step 5: Yes), and if the output value Vout is not 5 [V], the process proceeds to Step 7 (Step 5: No).

(Step 6)
When the output value Vout of the differential amplification unit 20 is 5 [V], the failure detection unit 41 of the control unit 40 can determine that the load sensor element Rb or Rc is an open failure.

FIG. 3B is a diagram showing that the output value Vout is + 5V when the load sensor element Rb fails to open in the detection device 1. In FIG. 3B, when the load sensor element Rb has an open failure (marked with a cross in the figure to indicate an open failure), V ₁ is about 5 [V] and V ₂ is about 2.5 [. Since it is V], the output value Vout is 5 [V].

Further, FIG. 3C is a diagram showing that the output value Vout is + 5V when the load sensor element Rc fails to open in the detection device 1. In FIG. 3C, when the load sensor element Rc has an open failure (marked with a cross in the figure to indicate an open failure), V ₁ is about 2.5 [V] and V ₂ is about 0 [. Since it is V], the output value Vout is 5 [V].

Therefore, the failure detection unit 41 of the control unit 40 can determine that the load sensor element Rb or Rc is an open failure when the output value Vout of the differential amplification unit 20 is 5 [V]. ..

When the control unit 40 determines that the load sensor element Rb or Rc is an open failure, the control unit 40 can output a warning signal Sa. Further, the output value Vout of the differential amplification unit 20 can be prevented from being used as the load sensor signal.

When any of the load sensor elements Ra, Rb, Rc, and Rd fails to open, the output value Vout of the differential amplification unit 20 is saturated to the power supply voltage Vcc (+5 [V]) level, and the ground is also reached. The resistance value of the load sensor element and other resistance values R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are set so as to be GND (0 [V]).

(Step7)
The control unit 40 returns to Step 1 on the assumption that the determination cannot be made.

The series of operations of the flow shown above can be repeatedly executed as needed.

[Effects of Embodiments of the present invention]
According to the embodiment of the present invention shown above, it has the following effects.
(1) The detection device 1 makes a _{pair with the first detection unit 11 that detects the first detection value V 1} regarding the detection target and the first detection unit 11, and detects the second detection value V ₂ regarding the detection target. A detection unit 10 having 2 detection units 12, a first input unit 21 of _{the first detection value V 1 , and a second input unit 22 of the second detection value V 2} are provided, and the first detection values V ₁ and the first are provided. 2 Bias potential Vb to either the differential amplification unit 20 that amplifies the difference from the detection value V ₂ and outputs the detection value to be detected as the output value Vout, or the first input unit 21 or the second input unit 22. The bias potential application unit 30 for applying the above and the control unit 40 having the failure detection unit 41 for determining the failure detection of the detection unit 10 based on the output value Vout of the differential amplification unit 20. There is. As shown above, since the detection device 1 includes the bias potential application unit 30 for applying the bias potential Vb, it operates normally when any of the load sensor elements Ra, Rb, Rc, and Rd fails to open. It can be distinguished from the unloaded state at the time. As a result, the detection device 1 can detect an open failure.
(2) The detection device 1 shown in the present embodiment can be applied not only to a force sensor (load sensor) but also to a magnetoresistive element such as an MR as a detection unit 10. Further, the detection device 1 is suitably applicable to devices and devices such as in-vehicle switches mounted on vehicles, which are prone to open failure of the detection element due to vibration or the like.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from or changing the technical idea of the present invention. Although typical embodiments and illustrated examples according to the present invention have been illustrated, the above-described embodiments and illustrated examples do not limit the invention according to the claims. Therefore, it should be noted that not all combinations of the above-described embodiments and features described in the illustrated examples are essential for the means for solving the problems of the invention.

1 ... Detection device 10 ... Detection unit, 11 ... First detection unit, 12 ... Second detection unit, 13, 14 ... Connection point, 15, 16 ... One end, 17 ... Other end 20 ... Differential amplification unit, 21 ... Non Inverted input terminal, 22 ... Inverted input terminal, 23 ... Output terminal, 24 ... Power supply terminal, 25 ... Ground terminal 30 ... Bias potential application unit 40 ... Control unit, 41 ... Failure detection unit Ra, Rb, Rc, Rd ... Load sensor Element GND ... Ground R ₁ , R ₂ , R ₃ , R ₄ , R ₅ ... Resistance Sa ... Warning signal Sc ... Command signal V ₁ ... First detection value V ₂ ... Second detection value Vb ... Bias potential Vcc ... Power supply voltage Vout ... Output value

Claims (6)

A detection unit having a first detection unit that detects a first detection value related to a detection target, a second detection unit that is paired with the first detection unit and detects a second detection value related to the detection target, and a detection unit.
The detection value of the detection target is provided with a first input unit of the first detection value and a second input unit of the second detection value, and the difference between the first detection value and the second detection value is amplified. And a differential amplifier that outputs as an output value
A bias potential application unit that applies a bias potential to either the first input unit or the second input unit, and a bias potential application unit.
A control unit having a failure detection unit that determines failure detection of the detection unit based on the output value of the differential amplification unit, and a control unit.
Detection device having. The detection unit has a full bridge configuration in which the first detection unit and the second detection unit are half bridges, respectively, and the first detection value and the second detection value are the first detection unit and the second detection unit. The detection device according to claim 1, which is the midpoint potential of each of the detection units. The detection device according to claim 1 or 2, wherein the differential amplification unit is composed of an operational amplifier, and the operational amplifier operates with a single power source. The detection device according to any one of claims 1 to 3, wherein the detection unit is composed of a load sensor element which is four first to fourth detection elements. The detection device according to any one of claims 2 to 4, wherein the bias potential is set to be smaller than the midpoint potential during the non-detection operation of the detection unit. The detection device according to any one of claims 1 to 5, wherein the failure detection unit detects an open failure of each of the four detection elements.

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