JP5017891B2 - Strain detector - Google Patents

Description

  The present invention relates to a strain detection device for measuring a load on a vehicle seat or the like.

  Hereinafter, a conventional strain detection apparatus will be described.

  As shown in FIG. 8, the conventional strain detection device is arranged between a plate-shaped metal strain generating body 2 having a plurality of through holes 1 and the through holes 1 of the strain generating body 2 to reduce the strain amount. A resistance element 3 whose resistance value changes accordingly, and a signal processing circuit (not shown) connected to the resistance element 3 are provided.

  For example, if the strain detection device is attached between the vehicle seat and the floor portion, the load of the person sitting on the vehicle seat can be measured. Among the plurality of through holes 1 provided in the strain generating body 2, a part of the vehicle seat is inserted into the inner through hole 1 to connect the strain generating body 2 and the vehicle seat, and the outer through hole 1 is connected. A part of the floor portion is inserted and the strain generating body 2 and the floor surface portion are connected and attached (for example, a part of the vehicle seat or a part of the floor surface portion is a screw portion, and the nut is interposed via the strain generating body 2). Tighten with and attach). Then, when a load is applied to the vehicle seat, the strain generating body 2 is distorted and the resistance value of the resistance element 3 changes, so that the load can be measured by processing this with a signal processing circuit. In this case, since the strain body 2 is connected to both the vehicle seat and the floor portion, the load in the compression direction and the load in the tension direction can be measured. In the signal processing circuit, four resistance elements 3 are connected in a ring shape to form a Hoyston bridge circuit and input to the signal processing circuit.

  As the shape of the strain generating body 2, there is a cylindrical shape in addition to the plate shape, and both are those in which a strain detecting device is attached by combining a plurality of attachment parts.

As prior art document information related to the invention of this application, for example, Patent Document 1 and Patent Document 2 are known.
JP 2003-240633 A JP-A-6-207865

  The signal processing circuit having the above configuration detects the load value based on the strain amount of the strain generating body. However, the strain amount of the strain generating body 2 varies depending on the temperature. The strain amount is large at a high temperature and the strain amount is small at a low temperature. When the temperature becomes low or low, an appropriate load value cannot be detected.

  An object of the present invention is to solve the above-mentioned problems and to provide a strain detection device that can detect an appropriate load value even if the temperature of a strain generating body changes without being affected by the ambient temperature used. .

In order to achieve the above object, the present invention particularly amplifies the signal processing circuit by inputting the first output signal and the second output signal and taking the differential between the first output signal and the second output signal. A second amplifier that inputs a first amplified signal output from the first amplifier and outputs a second amplified signal is provided, and the first amplified signal is input to the second amplifier via an input resistor unit and fed back. A part of the second amplified signal is input to the second amplifier together with the first amplified signal via a resistor, and is output based on an abnormal strain of the strain generating body caused by a temperature change. Correction means for correcting the abnormal first and second output signals is provided, and the correction means connects a plurality of temperature-sensitive resistors whose resistance values vary with temperature in parallel to form the input resistance unit. Input resistance section and feedback resistance consisting of It is obtained by a structure in which a switching means for switching Select and.

  With the above configuration, since the temperature sensitive resistor is used for the input resistance portion, the resistance value can be changed depending on the temperature. That is, when using a temperature-sensitive resistor whose resistance value increases as the temperature rises, even if the temperature rises and the strain amount of the strain generating body increases, the resistance value of the input resistance portion increases, The output values of the first and second output signals are reduced. Therefore, abnormal first and second output signals corresponding to the large strain amount of the strain generating body do not occur, and appropriate first and second output signals are output according to the resistance value of the input resistance unit, and appropriate The load value can be detected.

  On the other hand, even if the temperature decreases and the strain amount of the strain generating body decreases, the resistance value of the input resistance portion decreases, and the output values of the first and second output signals are relatively increased. Therefore, abnormal first and second output signals corresponding to the small strain amount of the strain generating body do not occur, and appropriate first and second output signals are output according to the resistance value of the input resistance unit, and appropriate The load value can be detected.

  Hereinafter, the invention described in all claims of the present invention will be described with reference to the drawings.

  1 is a cross-sectional view of a strain detection device according to an embodiment of the present invention, FIG. 2 is a side view of the strain detection device, FIG. 3 is a top view of the strain detection device, and FIG. 4 is a circuit block of the strain detection device. FIG. 5 is a side view of a seat unit in which a vehicle seat and a floor surface portion are connected using the strain detection device.

  1 to 3, the strain detection device according to the embodiment of the present invention is a cylindrical metal (precipitation hardening stainless steel) strain generating body 12 that is distorted by a load and has a cavity 10 in the axial direction. And a screw portion 14 disposed above and below the strain generating body 12 in the axial direction so as to sandwich the strain generating body 12. The screw portion 14 has a screw head portion 20 having a diameter larger than that of the screw barrel portion 18. The strain body 12 and the screw head portion 20 of the screw portion 14 are welded and joined together. Yes.

  Also, on the outer peripheral surface of the strain generating body 12, as shown in FIG. 4, the first to fourth resistance elements 13, 15, 17, 19 is provided, a power supply voltage is supplied between the first resistance element 13 and the fourth resistance element 19, the ground between the second resistance element 15 and the third resistance element 17, A Wheatstone bridge circuit 21 is formed that outputs a first output signal from between the second resistance element 15 and a second output signal from between the third resistance element 17 and the fourth resistance element 19. Further, a signal processing circuit 23 connected to the Wheatstone bridge circuit 21 and detecting the load value from the first and second output signals is arranged on the case 16 attached to the outer peripheral surface of the strain body 12 and the screw portion 14. Yes.

  For example, as shown in FIG. 5, if this strain detection device is attached between the vehicle seat 22 and the floor surface portion 24, the load of a person sitting on the vehicle seat 22 can be measured.

  A through hole for inserting the screw body 18 of the screw portion 14 is provided in the lower portion of the vehicle seat 22, and the screw body portion 18 is inserted into the rail portion 26 attached to the floor surface 28 in the floor surface portion 24. Through holes are provided, and the axial direction of each through hole is provided to be perpendicular to the floor surface 28. One screw body portion 18 is inserted into the through hole of the vehicle seat 22, and the other screw body portion 18 is inserted into the through hole of the rail portion 26, and the strain body 12 and the screw portion 14 are fastened with a nut 30. The vehicle seat 22 and the floor surface portion 24 are connected to each other.

  Then, when a load is applied to the vehicle seat 22, the load is applied to the screw portion 14 so that the load direction is the axial direction of the strain body 12 (the vertical direction with respect to the floor surface 28), and the shaft of the strain body 12 The strain body 12 is distorted due to the force. Since the resistance values of the first to fourth resistance elements 13, 15, 17, and 19 change due to the strain of the strain generating body 12, the load can be measured by processing this with the signal processing circuit 23.

  In the measurement of the load, the output values (voltage values) of the first and second output signals with respect to the load change are different when the temperature of the strain generating body 12 is high, normal, and low as shown in FIG. The strain amount of the strain generating body 12 is large at a high temperature, and the strain amount of the strain generating body 12 is small at a low temperature. The strain body 12 has an abnormal strain due to a temperature change compared to the normal temperature. And abnormal first and second output signals are output.

  Therefore, as shown in FIG. 7, the first temperature-sensitive resistor whose resistance value decreases as the temperature rises, or the resistance value as the temperature falls, with respect to the non-temperature-sensitive resistor (fixed resistor) whose resistance value does not change with temperature. The output values of the abnormal first and second output signals in FIG. 6 are increased or decreased by using the second temperature sensing resistor in which the output increases. And an appropriate load value is detected.

  As shown in FIG. 4, the specific signal processing circuit 23 includes a first amplifier 32 that receives the first and second output signals and outputs the first amplified signal, and receives the first amplified signal and receives the first amplified signal. A second amplifier 35 that outputs two amplified signals is provided, the first amplified signal is input to the second amplifier 35 through the input resistor unit 34, and a part of the second amplified signal is first input through the feedback resistor unit 36. The amplified signal is input to the second amplifier 35 together with the amplified signal. In addition, a correction circuit 37 is provided for correcting the abnormal first and second output signals output based on the abnormal strain of the strain generating body 12 caused by the temperature change. The temperature-sensitive resistor 38 whose value changes is corrected by using the input resistor unit 34. The input resistance unit 34 is a temperature sensing resistor group 44 in which a fixed resistor 40 and a plurality of temperature sensing resistors 38 that are one non-temperature sensing resistor are connected in parallel, and a non-temperature sensing resistor directly connected to the temperature sensing resistor group 44. The feedback resistor unit 36 includes a fixed resistor 47 that is one non-temperature-sensitive resistor, and the plurality of temperature-sensitive resistors 38 have different resistance value change rates with respect to temperature.

  In addition, the first switching means 48 for switching the input resistance unit 34 and the feedback resistance unit 36, and the temperature-sensitive resistor 38 is selected and switched according to the abnormal strain amount of the strain generating body 12 caused by the temperature change. 2 switching means 50 is provided. The first switching means 48 is a switching means for exchanging the input resistance section 34 and the feedback resistance section 36, and the first and second output signal polarities with respect to the load change in FIG. The first and second output signals with respect to the temperature change are switched according to the positive and negative states). The second switching means 50 increases or decreases the temperature gradient between the first temperature sensing resistor and the second temperature sensing resistor in FIG. 7 by switching so as to select or combine a plurality of temperature sensing resistors 38 connected in parallel. It is possible to correspond to various states of the first and second output signals with respect to the load change of FIG. In particular, the plurality of temperature sensitive resistors 38 can be made to correspond to various states by changing the resistance value change rate with respect to the temperature.

  With the above configuration, since the temperature sensitive resistor 38 is used for the input resistor section 34, the resistance value can be changed depending on the temperature. That is, when the temperature sensitive resistor 38 whose resistance value increases as the temperature rises is used, even if the temperature rises and the strain amount of the strain generating body 12 increases, the resistance value of the input resistance portion 34 increases. The output values of the first and second output signals are relatively lowered. Therefore, abnormal first and second output signals corresponding to the large strain amount of the strain generating body 12 do not occur, and appropriate first and second output signals are output according to the resistance value of the input resistance unit 34, Appropriate load value can be detected.

  On the other hand, even if the temperature decreases and the strain amount of the strain generating body 12 decreases, the resistance value of the input resistance unit 34 decreases, and the output values of the first and second output signals are relatively increased. Therefore, abnormal first and second output signals corresponding to the small strain amount of the strain generating body 12 do not occur, and appropriate first and second output signals are output according to the resistance value of the input resistance unit 34, Appropriate load value can be detected.

  Further, since the first switching means 48 for switching between the input resistance unit 34 and the feedback resistance unit 36 is provided, the polarity state of the first and second output signals with respect to the load change (temperature change when normal temperature is used as a reference) The first and second output signals with respect to the positive and negative states) can be switched.

  The input resistance unit 34 has a plurality of temperature sensitive resistors 38 connected in parallel, and is switched to select or combine the temperature sensitive resistors 38 according to the amount of abnormal strain of the strain generating body 12 caused by the temperature change. Since the switching means 50 is provided, the temperature gradient of the resistance value of the input resistance unit 34 can be changed, and various abnormal states of the first and second output signals can be dealt with. In particular, the plurality of temperature sensitive resistors 38 can be made to correspond to various states by varying the resistance value change rate with respect to the temperature.

  In the embodiment of the present invention, the cylindrical strain generating body 12 is used. However, the plate-shaped metal strain generating body 2 shown in FIG. 8 as described in the prior art may be used.

  In addition, the switching by the first switching unit 48 and the second switching unit 50 in the correction circuit 37 may be switched in advance in consideration of the temperature characteristics of the strain generating body 12 before being used as a strain detection device, or may be strain detection. During use of the apparatus, the temperature and ambient temperature related to the strain body 12 may be detected and automatically switched as needed. In the case of automatic switching, the temperature characteristics of the strain generating body 12 are stored in a memory in advance, and can be easily automatically controlled by comparing them whenever necessary.

  Furthermore, in one embodiment of the present invention, the strain detection device is used for load measurement of the vehicle seat 22, but may be used for torque measurement.

  As described above, the strain detection device according to the present invention is not affected by the ambient temperature to be used, can detect an appropriate load value even if the temperature of the strain generating body changes, and can be used as various sensors for measuring the load. Applicable to other equipment.

Sectional drawing of the distortion | strain detector in one embodiment of this invention Side view of the strain detector Top view of the strain detector Circuit block diagram of the distortion detector Side view of a seat unit in which a vehicle seat and a floor surface portion are connected using the strain detection device. A characteristic diagram showing the output values of the first and second output signals with respect to the load change Characteristic diagram showing resistance against temperature change Top view of a strain generating body of a conventional strain detection device

DESCRIPTION OF SYMBOLS 10 Cavity 12 Straining body 13 1st resistance element 14 Screw part 15 2nd resistance element 16 Case 17 3rd resistance element 18 Screw trunk | drum 19 4th resistance element 20 Screw head 21 Heystone bridge circuit 22 Vehicle seat 23 Signal Processing circuit 24 Floor surface portion 26 Rail portion 28 Floor surface 30 Nut 32 First amplifier 34 Input resistance portion 35 Second amplifier 36 Feedback resistance portion 37 Correction circuit 38 Temperature sensitive resistance 40 Fixed resistance 44 Temperature sensitive resistance group 46 Fixed resistance 47 Fixed resistance 48 1st switching means 50 2nd switching means

Claims (1)

A strain generating body that generates strain due to a load, a resistance element that is disposed on the strain generating body and has a resistance value that changes in accordance with the amount of strain, and the four resistance elements are connected to each other in a ring, and the first and second resistance elements A Wheatstone bridge circuit that outputs a first output signal from between and outputs a second output signal between the third and fourth resistance elements, and a load from the first and second output signals that is connected to the Wheatstone bridge circuit. A signal processing circuit for detecting a value, wherein the first output signal and the second output signal are input to the signal processing circuit, and the differential between the first output signal and the second output signal is amplified. A second amplifier that inputs a first amplified signal output from the first amplifier and outputs a second amplified signal is provided, and the first amplified signal is input to the second amplifier via an input resistor unit and fed back. Part of the second amplified signal via a resistor The first amplified signal is input to the second amplifier together with the first amplified signal, or the first amplified signal is input to the second amplifier via a feedback resistor, and a part of the second amplified signal is input via the input resistor. Is input to the second amplifier together with the first amplified signal, and the abnormal first and second output signals output based on the abnormal strain of the strain generating body caused by the temperature change are corrected. The correction means is configured to connect a plurality of temperature-sensitive resistors whose resistance values change with temperature in parallel to form the input resistance portion, and further, an input resistance portion and a feedback resistance portion having the same resistance value, A strain detection apparatus provided with switching means for selecting and switching.

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