JP2014035228A - Sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor device capable of securing the operation range of a signal output during self-diagnosis even when a position of the zero point in the sensor circuit changes.SOLUTION: A sensor circuit 10 is connected to the negative electrode terminal 21 and the positive electrode terminal 22 of an amplifier circuit 20. A first resistive element 30 is connected to the negative electrode terminal 21 of the amplifier circuit 20, and a first switch circuit 50 is connected to this first resistive element 30. Further, a second resistive element 40 is connected to the positive electrode terminal 22 of the amplifier circuit 20, and a second switch circuit 60 is connected to this second resistive element 40. The on-off states of the first switch circuit 50 and the second switch circuit 60 are controlled by a zero point decision circuit 70. As a result, the amplitude of a signal output from the amplifier circuit 20 can be changed to a wider side in operation range among the operational potential side and the reference potential side during self-diagnosis, and the operation range of a signal output during self-diagnosis can be secured.

Description

  The present invention relates to a sensor device having a self-diagnosis function.

  Conventionally, for example, Patent Document 1 proposes a sensor device having a self-diagnosis function. Specifically, the sensor element, an amplifier circuit that amplifies the output voltage of the sensor element, a resistance element for determining the potential connected to the output terminal of the sensor element, and a connection between one end of the resistance element and the reference potential There has been proposed a configuration including a switched circuit.

  The resistance element is connected between one output terminal of the sensor element and the reference potential, and between the other output terminal of the sensor element and the reference potential. Further, the switch circuit is arranged between one end of each resistance element and the reference potential for any one of the resistance elements.

  According to such a configuration, the combined resistance value in the sensor device changes by operating the switch circuit during the self-diagnosis of the sensor device. For this reason, since the output of the amplifier circuit also changes, self-diagnosis based on the output becomes possible. That is, conventionally, the amplification polarity of a signal to be amplified at the time of self-diagnosis is a single polarity on either the plus side or the minus side.

JP 2010-85190 A

  However, when the signal amplitude at the time of self-diagnosis is a single polarity as in the above-described conventional technique, the output signal amplitude may be saturated to the reference potential or the operation potential because the output operation range of the amplifier circuit is narrow. There is sex. For this reason, there is a problem that it cannot be confirmed that a desired signal amplitude is output from the amplifier circuit.

  As a specific example, when the sensor element is configured as a strain gauge that detects pressure, the zero point of the sensor element changes according to a wide range of atmospheric pressure, that is, a high pressure environment or a low pressure environment. Here, the zero point is an output value when the sensor element is not measuring a physical quantity. The zero point when the sensor element detects pressure is atmospheric pressure.

  In the low pressure environment, the zero point shifts to the reference potential side, whereas in the high pressure environment, the zero point shifts to the operating potential side. When the switch circuit is operated at the time of self-diagnosis, the zero point is located on the reference potential side in a low-pressure environment, so the operation range to the reference potential side is narrow. For this reason, when the output of the amplifier circuit changes to the reference potential side, the output is saturated to the reference potential before reaching the maximum change value. Similarly, since the zero point is located on the operating potential side in the high pressure environment, the operating range to the operating potential side is narrow. For this reason, when the output of the amplifier circuit changes to the operating potential side, the output is saturated to the operating potential before reaching the maximum change value. As a result, it cannot be determined that a desired signal amplitude is output with respect to the zero point.

  In view of the above points, an object of the present invention is to provide a sensor device that can ensure an operation range of signal output during self-diagnosis even when the position of the zero point of the sensor circuit changes.

  In order to achieve the above object, according to the first aspect of the present invention, the sensor circuit (10) for detecting a physical quantity based on the operating potential and outputting a signal corresponding to the detected physical quantity is provided to the sensor circuit (10). It has a positive terminal (22) and a negative terminal (21) connected, and amplifies and outputs a voltage difference between the positive terminal (22) and the negative terminal (21) as a signal input from the sensor circuit (10). And an amplifier circuit (20).

  The first resistance element (30) having one terminal connected to the negative terminal (21), the second resistance element (40) having one terminal connected to the positive terminal (22), and the first resistance element The first switch circuit (50) connected between the other terminal of (30) and a reference potential lower than the operating potential, and connected between the other terminal of the second resistance element (40) and the reference potential. Second switch circuit (60).

  Furthermore, while the on / off state of the first switch circuit (50) and the second switch circuit (60) is fixed during normal operation, one of the first switch circuit (50) and the second switch circuit (60) is fixed during the self-diagnosis. A polarity control circuit (70, 80) is provided that changes the amplitude of the signal output from the amplifier circuit (20) to either the operating potential side or the reference potential side by controlling the on / off state. .

  According to this, the polarity control circuit (70, 80) selectively controls the polarity of the amplitude of the signal output from the amplifier circuit (20) during the self-diagnosis. For this reason, the amplitude of the signal output from the amplifier circuit (20) during the self-diagnosis can be changed to the wide operating range side of the operating potential side and the reference potential side. Therefore, it is possible to secure an operation range of signal output at the time of self-diagnosis.

  In the second aspect of the invention, the polarity control circuit obtains the output of the amplifier circuit (20) during normal operation during self-diagnosis and determines whether the output of the amplifier circuit (20) exceeds a reference value. When the output of the amplifier circuit (20) exceeds the reference value, the amplitude of the signal output from the amplifier circuit (20) is changed to the reference potential side by operating the first switch circuit (50). When the output of the amplifier circuit (20) does not exceed the reference value, the zero point determination circuit changes the amplitude of the signal output from the amplifier circuit (20) to the operating potential side by operating the second switch circuit (60). (70).

  As described above, the zero point determination circuit (70) determines whether the output of the amplifier circuit (20) in the normal operation exceeds the reference value, thereby reducing the amplitude of the signal output from the amplifier circuit (20). Can be amplified to the appropriate polarity side. For this reason, it is possible to prevent the amplitude of the signal output from the amplifier circuit (20) from being saturated to the operating potential or the reference potential.

  In the invention according to claim 4, the polarity control circuit changes the output of the amplifier circuit (20) when the amplitude of the signal output from the amplifier circuit (20) is changed to the reference potential side during the self-diagnosis. Is obtained as the first change amount, and the change in the output of the amplifier circuit (20) when the amplitude of the signal output from the amplifier circuit (20) is changed to the operating potential side is obtained as the second change amount. It is a circuit (80).

  Thus, the logic circuit (80) switches the direction of change in the amplitude of the signal output from the amplifier circuit (20) to both polarities. Therefore, even if the amplitude of the signal output from the amplifier circuit (20) is saturated to one of the operating potential and the reference potential and a signal having a sufficient amount of change cannot be obtained, a sufficient amount of change is not obtained for the other. A signal can be obtained.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a block diagram of the sensor apparatus which concerns on 1st Embodiment of this invention. It is the flowchart which showed the content of the self-diagnosis process which a zero point determination circuit performs. 3 is a timing chart showing changes in the output of an amplifier circuit in a high-pressure environment. 6 is a timing chart showing changes in the output of the amplifier circuit in a low-pressure environment. It is a timing chart showing a normal range in the abnormality determination process. It is a block diagram of the sensor apparatus which concerns on 2nd Embodiment of this invention. It is the flowchart which showed the content of the switch change process which concerns on 2nd Embodiment. 3 is a timing chart showing changes in the output of an amplifier circuit in a high-pressure environment. 6 is a timing chart showing changes in the output of the amplifier circuit in a low-pressure environment. It is the flowchart which showed the content of the self-contained process which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the sensor device according to the present embodiment includes a sensor circuit 10, an amplifier circuit 20, a first resistance element 30, a second resistance element 40, a first switch circuit 50, and a second switch circuit. A switch circuit 60 and a zero point determination circuit 70 are provided.

  The sensor circuit 10 is a circuit unit configured to detect a physical quantity based on the operating potential (Vcc) and output a signal corresponding to the detected physical quantity. In this embodiment, the sensor circuit 10 includes a bridge circuit configured by connecting four piezoresistive elements 11 in a square shape. One pair of diagonal points of the bridge circuit are connected to an operating potential and a reference potential (GND) lower than the operating potential. A signal corresponding to the physical quantity is output from the other pair of diagonal points of the bridge circuit. The reference potential is, for example, a ground potential. The sensor circuit 10 having such a configuration is built in a semiconductor chip by, for example, MEMS technology.

  In the present embodiment, the four piezoresistive elements 11 are laid out in a wave shape at the center portion and the outer edge portion of the diaphragm of the semiconductor chip. Thereby, when a pressure is applied to the diaphragm, the diaphragm is distorted, so that the resistance value of the piezoresistive element 11 that changes in accordance with the pressure is detected. That is, the sensor circuit 10 is a pressure sensor.

  The amplifier circuit 20 is a circuit unit for amplifying the signal input from the sensor circuit 10 with a predetermined amplification factor and outputting the amplified signal to the outside. As illustrated in FIG. 1, the amplifier circuit 20 includes a negative terminal 21 and a positive terminal 22. The amplifier circuit 20 is composed of various circuits such as an operational amplifier.

  The negative terminal 21 and the positive terminal 22 are connected to the other pair of diagonal points of the bridge circuit of the sensor circuit 10. Since the voltage difference between the negative terminal 21 and the positive terminal 22 becomes a signal output from the sensor circuit 10, the amplifier circuit 20 amplifies the voltage difference. Then, the amplifier circuit 20 outputs the amplified signal (Vout) from the output terminal to an external ECU (not shown). The external ECU is a control circuit device that acquires a pressure signal input from the sensor device and performs predetermined control.

  The first resistance element 30 is a resistor having one terminal connected to the negative terminal 21 of the amplifier circuit 20. The second resistance element 40 is a resistor having one terminal connected to the positive terminal 22 of the amplifier circuit 20. That is, the first resistance element 30 and the second resistance element 40 are pull-down resistors for the piezoresistive element 11. Thus, in the present embodiment, two systems of pull-down resistors are provided for the amplifier circuit 20.

  The first switch circuit 50 is a circuit unit connected between the other terminal of the first resistance element 30 and a reference potential. The second switch circuit 60 is a circuit unit connected between the other terminal of the second resistance element 40 and the reference potential. In the present embodiment, the first switch circuit 50 and the second switch circuit 60 are composed of, for example, MOS transistors. Therefore, the polarity of the signal output from the amplifier circuit 20 can be controlled corresponding to the on / off state of the first switch circuit 50 and the second switch circuit 60. Note that the ON state corresponds to the conduction state of the switch circuit, and the OFF state corresponds to the cutoff state of the switch circuit.

  The zero point determination circuit 70 is a circuit unit that controls the on / off state of the first switch circuit 50 and the second switch circuit 60. During a normal operation in which the sensor device detects pressure, the zero point determination circuit 70 controls both the first switch circuit 50 and the second switch circuit 60 to be in an on state. As a result, each potential of the positive terminal 22 and the negative terminal 21 of the amplifier circuit 20 is determined by the combined resistance value of the piezoresistive element 11, the first resistive element 30, and the second resistive element 40.

  Further, the zero point determination circuit 70 has a self-diagnosis function and an abnormality determination function. The self-diagnosis function is a function that causes the zero-point determination circuit 70 to output an output signal for self-diagnosis from the amplifier circuit 20 when the zero-point determination circuit 70 inputs a self-diagnosis signal from the external ECU. The period during which the zero point determination circuit 70 is inputting the self-diagnosis signal corresponds to the self-diagnosis, and the other period is the normal operation of the zero point determination circuit 70.

  Specifically, the zero point determination circuit 70 controls the on / off state of either the first switch circuit 50 or the second switch circuit 60 based on the output of the amplifier circuit 20 during the self-diagnosis. Accordingly, the zero point determination circuit 70 changes the combined resistance value of the piezoresistive element 11, the first resistive element 30, and the second resistive element 40, and changes the amplitude of the signal output from the amplifier circuit 20 to the operating potential side or the reference Change to potential side. That is, the zero point determination circuit 70 changes the polarity of the output of the amplifier circuit 20 not only to one polarity but also to the other polarity.

  The abnormality determination function is a function for determining whether a normal signal is output from the amplifier circuit 20. Since the zero point determination circuit 70 receives the output signal of the amplifier circuit 20, it can always determine abnormality.

  The amplifying circuit 20, the first resistance element 30, the second resistance element 40, the first switch circuit 50, the second switch circuit 60, and the zero point determination circuit 70 are formed in, for example, one IC chip.

  The above is the overall configuration of the sensor device according to the present embodiment. The sensor device is configured as a sensor device for a vehicle, for example, and is used by being mounted on a vehicle.

  Next, the self-diagnosis function of the zero point determination circuit 70 will be described with reference to FIGS. Normally, the zero point determination circuit 70 performs an operation during a normal operation, and controls both the first switch circuit 50 and the second switch circuit 60 to be in an on state. The zero point determination circuit 70 starts the self-diagnosis process shown in FIG. 2 when a self-diagnosis signal is input from the external ECU. Note that the timing at which the self-diagnosis signal is input to the zero point determination circuit 70 is, for example, when the vehicle is turned on or when the ignition is turned on.

  First, in step 100, a zero point is set. For this reason, the zero point determination circuit 70 fixes both the first switch circuit 50 and the second switch circuit 60 to the on state. Thereby, the external ECU acquires the output of the amplifier circuit 20 when the sensor circuit 10 is not measuring the pressure. That is, the external ECU acquires a zero point signal that is atmospheric pressure.

  Thereafter, in step 110, it is determined whether or not the zero point exceeds the reference value. The reference value is a potential between the operating potential and the reference potential. In this embodiment, when the operating potential is Vcc, the reference value is (1/2) Vcc. Therefore, the zero point determination circuit 70 acquires the output (Vout) of the amplifier circuit 20 and determines whether or not the condition of Vout> (1/2) Vcc is satisfied. Thereby, it is determined whether the zero point is the output value of the high pressure environment or the output value of the low pressure environment.

  When the condition of Vout> (1/2) Vcc is satisfied in step 110, the process proceeds to step 120. This indicates that the sensor device is placed in a high pressure environment.

  In step 120, the first switch circuit 50 is controlled to be in an OFF state while the second switch circuit 60 is maintained in an ON state. As a result, the combined resistance value of the resistors connected to the negative terminal 21 of the amplifier circuit 20 changes, so that the potential of the negative terminal 21 rises more than when the first switch circuit 50 is in the ON state. That is, the input potential difference to the amplifier circuit 20 changes. Thereby, the signal on the negative electrode side is amplified by the amplifier circuit 20, and the amplitude of the signal output from the amplifier circuit 20 can be changed from the zero point to the reference potential side. This is shown in FIG.

  As shown in FIG. 3, in the high voltage environment, the zero point (Vp1) of the amplifier circuit 20 is located on the operating potential (Vcc) side. When the output of the amplifier circuit 20 changes to the operating potential side, the range of change up to the headroom is limited. However, after time T10, the polarity of the output of the amplifier circuit 20 becomes negative, and the output signal of the amplifier circuit 20 changes from the zero point to the reference potential side. Since the output of the amplifier circuit 20 has a sufficient margin for the change to the minus side with respect to the zero point, the output reaches the maximum change value (Vout1). This maximum change value (Vout1) is acquired by the external ECU.

  Then, the zero point determination circuit 70 returns the first switch circuit 50 to the ON state at time T11, so that the output of the amplifier circuit 20 returns to the zero point at time T12. Thus, the self-diagnosis process ends. Note that the period of self-diagnosis from time T10 to time T12 is referred to as initial diagnosis.

  On the other hand, if the condition of Vout> (1/2) Vcc is not satisfied in step 110, the process proceeds to step 130. This indicates that the sensor device is placed in a low pressure environment.

  In step 130, the second switch circuit 60 is controlled to be in an off state while maintaining the on state of the first switch circuit 50. As a result, the combined resistance value of the resistors connected to the positive terminal 22 of the amplifier circuit 20 changes, so that the potential of the positive terminal 22 rises more than when the second switch circuit 60 is on. Thereby, the signal on the positive electrode side is amplified by the amplifier circuit 20, and the amplitude of the signal output from the amplifier circuit 20 can be changed from the zero point to the operating potential side. This is shown in FIG.

  As shown in FIG. 4, in the low pressure environment, the zero point (Vp2) of the amplifier circuit 20 is located on the reference potential side. When the output of the amplifier circuit 20 changes to the reference potential side, the range of change up to the reference potential is limited. However, after time T20, the polarity of the output of the amplifier circuit 20 becomes positive, and the output signal of the amplifier circuit 20 changes from the zero point to the operating potential side. Since the output of the amplifier circuit 20 has a sufficient margin for the change to the plus side with respect to the zero point, the output reaches the maximum change value (Vout2). This maximum change value (Vout2) is acquired by the external ECU.

  Then, when the zero point determination circuit 70 returns the second switch circuit 60 to the ON state at time T21, the output of the amplifier circuit 20 returns to the zero point at time T22. Thereafter, the self-diagnosis process ends.

  As described above, when the zero point exceeds (1/2) Vcc, the first switch circuit 50 on the negative input side of the amplifier circuit 20 is turned off, and the polarity of the signal amplitude of the amplifier circuit 20 is made negative. When the zero point is lower than (1/2) Vcc, the second switch circuit 60 on the positive input side of the amplifier circuit 20 is turned off, and the polarity of the signal amplitude of the amplifier circuit 20 is made positive. Thereby, the operation range of signal output at the time of self-diagnosis can be secured.

  Further, the external ECU calculates the amount of change with respect to the zero points (Vp1, Vp2). The external ECU calculates | Vout1-Vp1 | for the high pressure environment, and | Vout2-Vp2 | for the low pressure environment. Then, the external ECU determines whether the sensor device is operating normally by determining whether the calculated value exceeds a predetermined value.

  As described above, in the present embodiment, the zero point determination circuit 70 is configured to be able to selectively control the polarity of the amplitude of the signal output from the amplifier circuit 20 during self-diagnosis, and thus is output from the amplifier circuit 20. The signal amplitude can be changed to an appropriate polarity. For this reason, it is possible to prevent the amplitude of the signal output from the amplifier circuit 20 during the self-diagnosis from being saturated with the operating potential or the reference potential. Accordingly, it is possible to cause the external ECU to perform a reliable self-diagnosis.

  In particular, since the sensor device is configured as a pressure sensor, it is possible to always obtain a signal amplitude on the wide output operation range with respect to atmospheric pressure.

  Next, the abnormality determination function of the zero point determination circuit 70 will be described with reference to FIG. As shown in FIG. 1, the zero point determination circuit 70 is connected to the output terminal of the amplifier circuit 20. Therefore, the signal (Vp) output from the amplifier circuit 20 is always input to the zero point determination circuit 70.

  Then, the zero point determination circuit 70 determines whether or not the acquired output of the amplification circuit 20 is within the normal range. The normal range is an amplitude range in which the signal (Vp) output from the amplifier circuit 20 can be said to be normal.

  As shown in FIG. 5, the upper limit value on the operation potential side in the normal range is slightly smaller than the operation potential, and the lower limit value on the reference potential side in the normal range is slightly larger than the reference potential. That is, the normal range is a determination value for detecting High fixation where the output of the amplifier circuit 20 sticks to the operating potential and Low fixation where the output of the amplifier circuit 20 sticks to the reference potential.

  Therefore, the zero point determination circuit 70 determines that an abnormality has occurred when the output of the amplifier circuit 20 is larger than the upper limit value of the normal range or smaller than the lower limit value of the normal range. As described above, the abnormality of the output of the amplifier circuit 20 can be detected by the abnormality determination function of the zero point determination circuit 70.

  The zero point determination circuit 70 outputs the result of the abnormality determination to the external ECU. When the result of the abnormality determination input from the zero point determination circuit 70 indicates an abnormality, the external ECU notifies the sensor device that an abnormality has occurred using a diagnosis signal or the like.

  As described above, the sensor device has a configuration in which the zero point determination circuit 70 selectively controls the polarity of the amplitude of the signal output from the amplifier circuit 20. And since the zero point of a pressure sensor changes according to the environment where a pressure sensor is put, the composition of the sensor device concerning this embodiment is especially effective at the time of self-diagnosis of a pressure sensor. Further, since the vehicle receives a change in the atmospheric pressure according to the area where it is used, even if the atmospheric pressure received by the sensor circuit 10 changes, it is possible to cause the external ECU to perform a reliable self-diagnosis.

  As for the correspondence between the description of the present embodiment and the description of the claims, the zero point determination circuit 70 corresponds to the “polarity control circuit” of the claims.

(Second Embodiment)
In the present embodiment, parts different from the first embodiment will be described. As shown in FIG. 6, the sensor device according to the present embodiment includes a sensor circuit 10, an amplifier circuit 20, a first resistance element 30, a second resistance element 40, a first switch circuit 50, and a second switch circuit. A switch circuit 60 and a logic circuit 80 are provided. Among these, the configuration other than the logic circuit 80 is the same as that of the first embodiment.

  The logic circuit 80 is a circuit that alternately controls the on / off states of the first switch circuit 50 and the second switch circuit 60. In the normal operation, the logic circuit 80 fixes both the first switch circuit 50 and the second switch circuit 60 to the on state.

  Further, the logic circuit 80 has a switch switching function and an abnormality determination function. The switch switching function is a function of acquiring the amount of change in amplitude when the polarity of the signal output from the amplifier circuit 20 is alternately switched during the self-diagnosis of the logic circuit 80 for performing the function diagnosis of the sensor device.

  Specifically, at the time of self-diagnosis, the logic circuit 80 acquires the change in the output of the amplifier circuit 20 when the amplitude of the signal output from the amplifier circuit 20 is changed to the reference potential side as the first change amount. . In addition, the logic circuit 80 acquires, as the second change amount, a change in the output of the amplifier circuit 20 when the amplitude of the signal output from the amplifier circuit 20 is changed to the operating potential side. The first change amount and the second change amount are the change amount of the amplitude of the output signal of the amplifier circuit 20 based on the zero point, and are the absolute amount of change of the amplitude.

  The abnormality determination function of the logic circuit 80 is the same as the abnormality determination function provided in the zero point determination circuit 70. The above is the overall configuration of the sensor device according to the present embodiment.

  Next, the switch switching function at the time of self-diagnosis of the logic circuit 80 will be described with reference to FIGS. As in the first embodiment, the logic circuit 80 performs an operation during normal operation, and controls both the first switch circuit 50 and the second switch circuit 60 to be in an on state. When the logic circuit 80 receives a self-diagnosis signal from the external ECU, the logic circuit 80 executes the switch switching process shown in FIG.

  First, in step 200, a zero point is set. This is the same processing as step 100 described above.

  Subsequently, in step 210, the second switch circuit 60 is controlled to be in an off state while maintaining the on state of the first switch circuit 50. Thereby, the amplitude of the signal output from the amplifier circuit 20 is changed to the operating potential side, which is the plus side.

  In step 220, a first change amount that is a change in the output of the amplifier circuit 20 with respect to the zero point is acquired. Specifically, when the first change amount is V1, the amplitude of the output of the amplifier circuit 20 when the logic circuit 80 turns off the second switch circuit 60 is Vout1, and the zero point amplitude is Vp1, the first change The amount V1 is V1 = | Vout1-Vp1 |. After acquiring the first change amount V1, the logic circuit 80 returns the second switch circuit 60 to the on state.

  Subsequently, in step 230, the first switch circuit 50 is controlled to be off while maintaining the on state of the second switch circuit 60. Thereby, the amplitude of the signal output from the amplifier circuit 20 is changed to the reference potential side which is the minus side.

  In step 240, the logic circuit 80 with respect to the zero point obtains a second change amount that is a change in the output of the amplifier circuit 20. Specifically, when the second change amount is V2, the amplitude of the output of the amplifier circuit 20 when the logic circuit 80 turns off the first switch circuit 50 is Vout2, and the zero point amplitude is Vp2, the second change The amount V2 is V2 = | Vout2-Vp2 |. After obtaining the second change amount V2, the logic circuit 80 returns the first switch circuit 50 to the on state. Thus, the switch switching process is completed.

  The logic circuit 80 outputs the acquired first change amount and second change amount to the external ECU. The external ECU compares each change amount received from the logic circuit 80, and sets a large change amount as an effective change amount. Then, the external ECU determines whether or not the sensor device is operating normally by determining whether or not the effective change amount exceeds a predetermined value.

  In a high pressure environment, as shown in FIG. 8, the zero point of the amplifier circuit 20 is located on the operating potential side. For this reason, when the second switch circuit 60 is turned off at the time T30, the output of the amplifier circuit 20 changes to the plus side and is saturated to the operating potential. Therefore, the first change amount V1 cannot secure a sufficient change amount. At time T31, the second switch circuit 60 is returned to the on state.

  On the other hand, when the first switch circuit 50 is turned off at time T32, the output of the amplifier circuit 20 changes to the reference potential side which is the minus side. In this case, since there is a sufficient margin for the change to the minus side, the output of the amplifier circuit 20 reaches the maximum change value (Vout1). Therefore, the second change amount V2 having a sufficient amplitude can be acquired. At time T33, the first switch circuit 50 is returned to the on state. At time T34, the switch switching process ends.

  The external ECU determines that the second change amount V2 having a large change amount is effective among the first change amount V1 and the second change amount V2 shown in FIG. Then, the external ECU determines whether the sensor device is operating normally based on the second change amount V2.

  Further, in the low pressure environment, as shown in FIG. 9, the zero point of the amplifier circuit 20 is located on the reference potential side. Therefore, when the second switch circuit 60 is turned off at time T40, the output of the amplifier circuit 20 changes to the operating potential side, which is the positive side. Thereby, it is possible to secure the first change amount V1 having a sufficient amplitude. At time T41, the second switch circuit 60 is returned to the on state.

  On the other hand, when the first switch circuit 50 is turned off at time T42, the output of the amplifier circuit 20 changes to the reference potential side which is the minus side. For this reason, the output of the amplifier circuit 20 is saturated to the reference potential. Therefore, the second change amount V2 cannot secure a sufficient change amount. At time T43, the first switch circuit 50 is returned to the ON state. Then, the switch switching process ends at time T44.

  Then, the external ECU determines that the first change amount V1 having a large change amount is effective among the first change amount V1 and the second change amount V2 shown in FIG. Then, the external ECU determines whether the sensor device is operating normally based on the first change amount V1.

  As shown in FIGS. 8 and 9, the logic circuit 80 alternately switches the direction of change in the amplitude of the signal output from the amplifier circuit 20 to both polarities. For this reason, it is possible to always obtain a signal amplitude with a wide output operation range with respect to the atmospheric pressure. Therefore, even if the amplitude of the signal output from the amplifier circuit 20 is saturated to one of the operating potential and the reference potential and a sufficient amount of change cannot be obtained, a sufficient amount of change can be obtained for the other. . Accordingly, it is possible to cause the external ECU to perform a reliable self-diagnosis.

  As for the correspondence between the description of the present embodiment and the description of the claims, the logic circuit 80 corresponds to the “polarity control circuit” of the claims.

(Third embodiment)
In the present embodiment, parts different from the second embodiment will be described. In the present embodiment, the logic circuit 80 has a self-contained function that compares the first change amount and the second change amount, and outputs a large change amount as the effective change amount among the first change amount and the second change amount. I have.

  Specifically, the self-completion processing of the logic circuit 80 will be described with reference to FIG. As shown in FIG. 10, in step 250, the switch switching process in steps 200 to 240 is executed.

  Thereafter, in step 260, it is determined whether or not the condition of the first change amount V1> the second change amount V2 is satisfied. If the first change amount V1 is larger than the second change amount V2, the process proceeds to step 270. If the first change amount V1 is smaller than the second change amount V2, the process proceeds to step 280.

  In step 270, the fact that the first change amount V1 out of the first change amount V1 and the second change amount V2 is valid is output to the external ECU. This completes the self-contained process. On the other hand, in step 280, the fact that the second change amount V2 of the first change amount V1 and the second change amount V2 is valid is output to the external ECU. This completes the self-contained process. The external ECU determines whether the sensor device is operating normally based on the effective amount of change input from the logic circuit 80.

  As described above, the logic circuit 80 can not only acquire the amount of change in the amplitude of the signal at both poles, but also determine which amount of change is effective for self-diagnosis. In this manner, the amount of change effective for self-diagnosis can be output to the outside by self-completion.

(Other embodiments)
The configuration of the sensor device described in each of the above embodiments is an example, and the present invention is not limited to the configuration described above, and may be another configuration that can realize the present invention. For example, the zero point determination circuit 70 and the logic circuit 80 of the sensor device may not have an abnormality determination function.

  In the first embodiment, the reference value for determining whether the zero point is located in the high pressure environment or the low pressure environment is (1/2) Vcc, but this is an example of the reference value. Therefore, of course, other values may be used as the reference value.

  In the second embodiment, the second switch circuit 60 is turned off first, and then the first switch circuit 50 is turned off. However, this is only an example, and the order in which the first switch circuit 50 is turned off first and then the second switch circuit 60 is turned off may be used.

  The physical quantity detected by the sensor circuit 10 is not limited to pressure. That is, the sensor circuit 10 may be configured to detect other physical quantities such as acceleration that can be detected by the piezoresistive element 11.

  Furthermore, the application of the sensor device is not limited to the vehicle. The sensor device configured to detect the physical quantity can be applied to a device that performs self-diagnosis of the amplifier circuit 20.

DESCRIPTION OF SYMBOLS 10 Sensor circuit 11 Piezoresistive element 20 Amplifying circuit 21 Negative terminal 22 Positive terminal 30 1st resistive element 40 2nd resistive element 50 1st switch circuit 60 2nd switch circuit 70 Zero point determination circuit (polarity control circuit)
80 Logic circuit (polarity control circuit)

Claims (8)

A sensor circuit (10) for detecting a physical quantity based on the operating potential and outputting a signal corresponding to the detected physical quantity;
A positive terminal (22) and a negative terminal (21) connected to the sensor circuit (10) are provided, and a voltage difference between the positive terminal (22) and the negative terminal (21) is input from the sensor circuit (10). An amplification circuit (20) for amplifying and outputting the signal as
A first resistance element (30) having one terminal connected to the negative terminal (21);
A second resistance element (40) having one terminal connected to the positive terminal (22);
A first switch circuit (50) connected between the other terminal of the first resistance element (30) and a reference potential lower than the operating potential;
A second switch circuit (60) connected between the other terminal of the second resistance element (40) and the reference potential;
While the on-off state of the first switch circuit (50) and the second switch circuit (60) is fixed during normal operation, either the first switch circuit (50) or the second switch circuit (60) is used during self-diagnosis. A polarity control circuit (70, 80) for changing the amplitude of a signal output from the amplifier circuit (20) to either the operating potential side or the reference potential side by controlling the on / off state of A sensor device.   The polarity control circuit obtains an output of the amplifier circuit (20) during the normal operation at the time of the self-diagnosis and determines whether the output of the amplifier circuit (20) exceeds a reference value, When the output of the amplifier circuit (20) exceeds the reference value, the amplitude of the signal output from the amplifier circuit (20) is changed to the reference potential side by operating the first switch circuit (50), If the output of the amplifier circuit (20) does not exceed a reference value, the second switch circuit (60) is operated to change the amplitude of the signal output from the amplifier circuit (20) to the operating potential side. The sensor device according to claim 1, wherein the sensor device is a point determination circuit.   The zero point determination circuit (70) acquires the output of the amplifier circuit (20) and determines whether the output is within a normal range, and the output of the amplifier circuit (20) is within the normal range. The sensor device according to claim 2, further comprising an abnormality determination function that determines that an abnormality has occurred if not.   The polarity control circuit changes the output change of the amplifier circuit (20) when the amplitude of the signal output from the amplifier circuit (20) is changed to a reference potential side during the self-diagnosis. And a logic circuit (80) for acquiring a change in the output of the amplifier circuit (20) when the amplitude of the signal output from the amplifier circuit (20) is changed to the operating potential side as a second change amount. The sensor device according to claim 1, wherein:   The logic circuit (80) compares the first change amount and the second change amount, and outputs a large change amount of the first change amount and the second change amount as an effective change amount. The sensor device according to claim 4, comprising a function.   The logic circuit (80) acquires the output of the amplifier circuit (20), determines whether the output is within a normal range, and the output of the amplifier circuit (20) is not within the normal range 6. The sensor device according to claim 4, further comprising an abnormality determination function for determining that an abnormality has occurred.   The sensor device according to any one of claims 1 to 6, wherein the sensor circuit (10) is a pressure sensor constituted by a piezoresistive element (11).   8. The sensor device according to claim 1, wherein the sensor device is configured for a vehicle.

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