JP4214935B2 - Load sensor calibration method - Google Patents

Description

  The present invention relates to a load sensor calibration method using a strain gauge, and relates to a load sensor calibration method in which a predetermined load is applied and the output of the load sensor is calibrated during manufacture.

  A seat load measurement system using a load sensor is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-14528 (Patent Document 1).

  FIG. 5A shows a conventional representative that is attached to the lower part of the seat of the vehicle and detects the weight of a seated person sitting on the seat, similarly to the load sensor in the seat load measuring system disclosed in Patent Document 1. It is a perspective view which shows the load sensor 90. FIG.

The load sensor 90 shown in FIG. 5A includes an upper arm (movable arm) 92 that transmits a load, a lower arm (fixed arm) 93 that supports the load, a load detection plate 91 to which a strain gauge is attached, and an output of the strain gauge. And a signal processor 94 for processing a signal. The load due to the weight of the seated person seated on the seat is transmitted to the load detection plate 91 by the upper arm 92, and the load detection plate 91 is deformed. This deformation strain is detected by a strain gauge attached to the load detection plate 91. The output signal of the strain gauge is input to a signal processor 94 attached to the load detection plate 91, subjected to signal processing such as amplification, and output from the signal processor 94.
JP 2003-14528 A

  The load sensor 90 shown in FIG. 5A needs to calibrate the output of the signal processor 94 by applying a predetermined load to the load detection plate 91 in the course of manufacturing.

  FIG. 5B is a perspective view showing a calibration operation during the manufacture of the load sensor 90 of FIG.

  As shown in FIG. 5 (b), the load sensor 90 is calibrated by attaching a case bottom plate 94b on which a circuit board 94a for processing an output signal of a strain gauge is mounted to the load detection plate 91, and the signal shown in FIG. 5 (a). This is performed in a state before the case cover 94c of the processor 94 is covered. The calibration is performed by bringing the probe P into contact with a predetermined position of the circuit board 94a and applying a predetermined load F to the upper arm 92. However, in the above calibration method, when the load F is applied to the upper arm 92, the load detection plate 91 is deformed, and the circuit board 94a attached to the load detection plate 91 is also displaced accordingly. Accordingly, since the probe P is separated from the circuit board 94a when the calibration load F is changed, it is necessary to bring the probe P into contact with the circuit board 94a every time the calibration load F is changed. For this reason, it takes time for the calibration work, which causes an increase in the cost of the load sensor 90.

  SUMMARY OF THE INVENTION Accordingly, the present invention provides a load sensor calibration method using a strain gauge and calibrating its output in the middle of manufacturing, and can provide a load sensor calibration method that can shorten the calibration work time and reduce the manufacturing cost. It is an object.

The invention according to claim 1, I and the load detection plate for detecting a strain gauge affixed deformation strain caused by the load, the signal processor is assembled for mounting a circuit board for processing the output signal of the strain gauge that a calibration method of the load sensor, at the time of calibration of the load sensor, is fixed in front Symbol load detection plate on a foundation for a jig for holding the load sensor, the load detection plate on the base The signal processor is mounted separately from the fixed position , the probe is brought into contact with a predetermined position of the circuit board in the signal processor mounted at the different position , and the load is fixed on the substrate. by applying a predetermined load to the detection plate, and calibrate the output of the signal processor, after completion of calibration of the load sensor, set the signal processor to said load detection plate It is characterized in that attach.

According to this, at the time of calibration of the load sensor, the signal processor on which the circuit board on which the probe abuts and the load detection plate to which the load is applied are separated at different positions on the base of the jig. Are attached and calibrated. For this reason, even if a calibration load is applied and the load detection plate is deformed, the circuit board mounted on the signal processor is not displaced. Therefore, once the probe is brought into contact with the circuit board, the probe need not be brought into contact again with the circuit board even if the calibration load is changed. For this reason, compared with the conventional calibration method performed in the state which attached the signal processor which mounts a circuit board to the load detection plate, working time can be shortened and the manufacturing cost of a load sensor can be reduced by it.
The signal processor is assembled to the load detection plate after the calibration of the load sensor is completed.

In the load sensor calibration method, as described in claim 2, the load sensor includes a movable arm that transmits a load and a fixed arm that supports the load, and one end of the load detection plate. The movable arm is attached, the fixed arm is attached to the other end of the load detection plate, and the strain gauge is disposed at an intermediate position between the two ends of the load detection plate, At the time of calibration of the load sensor, the fixed arm is fixed by being sandwiched by a toggle clamp provided on the jig wall and the base , the load detection plate is fixed on the base, and the movable arm is interposed. Preferably, a predetermined load is applied to the load detection plate.

Even for a load sensor with a movable arm or a fixed arm, as described above , the load detection plate is fixed on the base by fixing the fixed arm between the jig wall and the toggle clamp provided on the base. The signal processor is attached separately from the load detection plate on the base . In this state, even if a calibration load is applied to the load detection plate via the movable arm and the load detection plate is deformed, the circuit board mounted on the signal processor is not displaced as described above. Therefore, once the probe is brought into contact with the circuit board, the probe need not be brought into contact again with the circuit board even if the calibration load is changed. For this reason, the calibration method can shorten the work time and thereby reduce the manufacturing cost of the load sensor, compared with the conventional calibration method in which the signal processor on which the circuit board is mounted is attached to the load detection plate. be able to.

  When the signal processor has a case bottom plate on which the circuit board is mounted and a case cover that covers the case bottom plate, the signal processor is in a state where the case cover is removed. Calibration is performed by bringing the probe into contact with a predetermined position on the circuit board. If the case bottom plate and the case cover are bonded after calibration, damage to the circuit board after calibration due to external force or the like can be prevented.

  The calibration method according to claim 4, wherein the signal processor includes a case bottom plate on which the circuit board is mounted and a case cover that covers the case bottom plate, and a hole is provided at a predetermined position of the case cover. The probe is brought into contact with a predetermined position on the circuit board through the hole.

  When the calibration is performed with the case cover removed as described above, and the case bottom plate and the case cover are bonded after the calibration, since the entire body of the load sensor is large, it is difficult to apply the adhesive. It takes time to dry, and this increases the cost of the load sensor. On the other hand, when the signal processor case cover is provided with a calibration hole as in the above calibration method, the signal processor itself must be bonded in advance to the case bottom plate and the case cover before calibration. Can do. Since the signal processor itself has a small physique, it is easy to apply the adhesive to the case bottom plate, and a large number of adhesives can be dried in a short time. Therefore, this makes it possible to reduce the manufacturing cost of the load sensor.

  Calibration is performed by bringing the probe into contact with a predetermined position on the circuit board through a hole provided in a case cover of a signal processor that is attached to a jig separately from the load detection plate. Therefore, as described above, the circuit board mounted on the signal processor is not displaced, and the calibration method can reduce the manufacturing cost of the load sensor. The hole provided in the case cover is preferably covered with an inexpensive seal film after the calibration is completed. As a result, the circuit board can be protected from dust and dirt.

  Preferably, the number of the holes is one.

  By concentrating the contact points of the probes on the circuit board in one limited area and arranging the holes on the limited area, only one hole is required in the case cover. This facilitates formation of a hole in the case cover, facilitates contact of the probe and attachment of a seal film to the hole, and can provide an inexpensive load sensor.

  According to a sixth aspect of the present invention, in the calibration method, the load detection plate is a load detection plate formed by attaching four strain gauges constituting a bridge, and the signal processor It is suitable for use in a load sensor that is a signal processor for processing an output signal.

  A load sensor using four strain gauges constituting the bridge can detect a load with high accuracy. In this load sensor, it is necessary to calibrate the output accurately by bringing a probe having a large number of pins into contact with the circuit board. When calibration is performed using a probe having a large number of pins as described above, the contact condition between the probe and the circuit board becomes more severe as the number of pins increases. Therefore, the above-described calibration method in which the circuit board is not displaced by applying a calibration load is suitable for highly accurate load sensor calibration using a probe having a large number of pins whose contact conditions with the circuit board are severe.

  As described in claim 7, when the circuit board is a circuit board having an amplifier circuit that amplifies the output signal of the strain gauge and a ROM that stores the calibration result, a strain gauge or a bridge A calibration result obtained by amplifying a minute output voltage signal and accurately calibrating the signal can be stored in the ROM. The calibration result can also be written to the ROM using the probe.

  As described in claim 8, the calibration method described above is suitable for calibration of a load sensor that is attached to the lower part of a vehicle seat and detects the weight of a seated person sitting on the seat.

  Vehicles are equipped with seat belts and airbag systems as devices that ensure the safety of passengers on board. To control the operation of the above safety devices according to the weight (weight) of the passengers, A number of load sensors are attached. Since the load sensor attached to the lower part of the seat is required to have high accuracy, the output must be calibrated during the manufacturing process.

  As described above, the calibration method described above, in which the probe is brought into contact with the circuit board in the signal processor mounted on the jig separately from the load detection plate, can shorten the calibration work time and reduce the manufacturing cost. Since it is a calibrating method that can be performed, high accuracy is required and it is suitable for calibrating the above-described on-vehicle load sensor manufactured in large quantities.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  First, the structure and load detection principle of a load sensor using a strain gauge will be described with reference to FIGS. 1 (a) and 1 (b) and FIGS. 2 (a) to 2 (c).

  FIG. 1A is a perspective view showing a load sensor 100 in which each component is assembled. FIG.1 (b) is the figure which decomposed | disassembled the load sensor 100 of Fig.1 (a) and showed each component.

  The load sensor 100 shown in FIGS. 1A and 1B is attached to the lower part of the seat of the vehicle and detects the weight of the seated person sitting on the seat, similarly to the load sensor 90 shown in FIG. It is a load sensor. The vehicle is provided with a seat belt and an airbag system as a device for ensuring the safety of a passenger on board. In order to control the operation of the safety device according to the weight (weight) of the passenger, FIG. Many load sensors 100 shown in a) and (b) are attached to the lower part of the seat. Since the load sensor 100 attached to the lower portion of the seat is required to have high accuracy, output calibration is necessary during the manufacturing process.

  A load sensor 100 shown in FIGS. 1A and 1B includes, as main components, an upper arm (movable arm) 12, a lower arm (fixed arm) 13, and a load detection plate 11 to which strain gauges G1 to G4 are attached. And a signal processor 14 for processing output signals of the strain gauges G1 to G4.

  The upper arm 12 is fastened to a seat frame (not shown) and transmits a load based on the weight of the seated person seated on the seat to the load detection plate 11. The upper arm 12 is attached to one end portion of the load detection plate 11 with a screw, as shown in FIG. The lower arm 13 is fastened to a seat rail (not shown), functions as a fixed end of the load detection plate 11, and supports the load transmitted to the load detection plate 11. As shown in FIG. 1B, the lower arm 13 is attached to the end of the load detection plate 11 opposite to the attachment end of the upper arm 12 with a screw together with the plate 15a. In addition, the convex part 13t of the lower arm 13 is inserted and assembled into a through hole 12h provided in the upper arm 12, and these serve as a stopper when overloaded.

  As shown in FIG. 1B, the signal processor 14 is attached to the load detection plate 11 via the plate 15b. By attaching the signal processor 14 to the load detection plate 11, the strain gauges G1 to G4 and the wiring 14g of the signal processor 14 can be shortened, and the influence of noise and the like entering from the wiring 14g can be reduced. In the load sensor 100 in FIG. 1A and the load sensor 90 in FIG. 5A, the signal processors 14 and 94 are attached to the left and right opposite sides with respect to the load detection plates 11 and 91, respectively. The mounting direction in the vertical direction is also reversed. Moreover, the code | symbol 16 shown in FIG.1 (b) is a protective cover.

  The detail of the load detection plate 11 is shown to Fig.2 (a)-(c). FIG. 2A is a bottom view of the load detection plate 11. FIG. 2B is a schematic cross-sectional view of the load detection plate 11 to which the upper arm 12 and the lower arm 13 are attached. FIG. 2C is a circuit diagram showing connections of strain gauges G1 to G4 attached to the load detection plate 11. As shown in FIG.

  As shown in FIGS. 2A to 2C, four strain gauges G <b> 1 to G <b> 4 constituting a bridge are attached to the load detection plate 11 of the load sensor 100. As shown in FIG. 2 (a), the four strain gauges G1 to G4 are provided with the center line A-A in between the attachment ends of the upper arm 12 and the lower arm 13 in the load detection plate 11. It is arranged one by one. As shown in FIG. 2B, when a load F is applied to the upper arm 12, the applied load F is transmitted to the load detection plate 11, and the load detection plate 11 is deformed. At this time, in the structure shown in FIG. 2B, the deformation strain of the load detection plate 11 becomes tensile strain at the positions of the strain gauges G1 and G3 on the left side, and compressive strain at the positions of the strain gauges G2 and G4 on the right side. It becomes.

  The strain gauges G1 and G3 that are tensile strains and the strain gauges G2 and G4 that are compressive strains form a bridge in the arrangement shown in FIG. A constant voltage Vcc is applied to the strain gauges G1 to G4 constituting the bridge. When a load is applied, the resistance values R1 to R4 of the strain gauges G1 to G4 change, and the balance of the bridge changes. The output signal Vout having a minute voltage is output from the bridge. The output signal Vout of the bridge composed of the strain gauges G1 to G4 is input to the signal processor 14 shown in FIGS. 1A and 1B, subjected to signal processing such as amplification, and output from the signal processor 14 again. The

  The load sensor 100 shown in FIGS. 1A and 1B and FIGS. 2A to 2C using four strain gauges G1 to G4 can detect a load with high accuracy. However, the characteristics of a load sensor using a strain gauge vary depending on the state of the strain gauge attached to the load detection plate. For this reason, it is necessary to calibrate the output of the signal processor by applying a predetermined load to the load detection plate during the manufacturing process.

  Next, the load sensor calibration method of the present invention will be described with reference to FIG.

  FIG. 3 is a perspective view showing a calibration operation in the course of manufacturing the load sensor 100 shown in FIGS. 1 (a) and 1 (b).

  In the load sensor calibration method of the present invention, the load detection plate 11 of the load sensor 100 and the signal processor 14 are separated and attached to the jig 200, and the load sensor 100 is calibrated.

  In the jig shown in FIG. 3, the load sensor 100 in a state where the upper arm 12 and the lower arm 13 are assembled to the load detection plate 11 is placed on the base 20s of the jig 200, and the convex portion 13t of the lower arm 13 shown in FIG. Is sandwiched between the wall 20w of the jig 200 and the toggle clamp 20c, and the lower arm 13 is fixed to the jig 200. The signal processor 14 is assembled to the plate 15b of the load sensor 100 shown in FIG. 3 after completion of the calibration. At the time of calibration, the signal processor 14 is attached and fixed to another position of the jig 200 as shown in the figure.

  4 is an enlarged perspective view of the signal processor 14 used in the load sensor 100 shown in FIG.

  The signal processor 14 shown in FIG. 4 includes a circuit board 14a that processes the output signal of the strain gauge, a case bottom plate 14b that mounts the circuit board 14a, and a case cover 14c that covers the case bottom plate 14b. Further, a hole 14ch for contacting the calibration probe P shown in FIG. 3 is provided at a predetermined position of the case cover 14c. The case bottom plate 14b and the case cover 14c are bonded in advance before the calibration work process. Further, the hole 14ch provided in the case cover 14c is covered with an inexpensive seal film after the calibration work is finished. As a result, the circuit board 14a can be protected from dust and dirt.

  The circuit board 14a has an amplifier circuit that amplifies the output signal of the bridge composed of the strain gauges G1 to G4 shown in FIGS. 1 and 2, and a ROM that stores the calibration result. As described above, in a load sensor using a circuit board having an amplifier circuit and a ROM, a minute output voltage signal of a strain gauge or a bridge is amplified, and a calibration result accurately calibrated by a calibration process described later is stored in the ROM. It can be memorized. Further, the contact points of the pins of the probe P on the circuit board 14a are concentrated in one limited area, and the hole 14ch is disposed on the limited area. Accordingly, the number of the holes 14ch provided in the case cover 14c is one. This facilitates the formation of the hole 14ch in the case cover 14c, and facilitates the contact of each pin of the probe P and the application of the seal film to the hole 14ch.

  In the conventional calibration method shown in FIG. 5B, an example in which calibration is performed before the case cover 94c of the signal processor 94 is covered is shown. Also in the calibration method of the present invention using the jig 200 shown in FIG. 3, it is possible to perform calibration with the case cover 14c removed without providing the hole 14ch in the case cover 14c of the signal processor 14. .

  However, when the calibration is performed with the case cover removed, and the case base plate and the case cover are bonded after calibration, the entire application of the load sensor is difficult, and it is difficult to apply the adhesive. Takes a long time, and this increases the cost of the load sensor. On the other hand, when the calibration cover 14ch is provided in the case cover 14c of the signal processor 14, the case bottom plate 14b and the case cover 14c are bonded in advance as described above before the calibration. I can keep it. Since the signal processor 14 has a small size, the signal processor 14 can be easily applied to the case bottom plate 14b, and a large number of adhesives can be dried in a short time. . Accordingly, this can reduce the manufacturing cost of the load sensor 100.

  Calibration is performed according to the following procedure. As shown in FIG. 3, the probe P is placed at a predetermined position on the circuit board 14a through a hole 14ch provided in the case cover 14c of the signal processor 14 attached to the jig 200 separately from the load detection plate 11. Abut. At the same time, a predetermined load F is applied to the load detection plate 11 attached to another position of the jig 200 via the upper arm 12 to calibrate the output of the signal processor 14. The procedure for contacting the probe P to the circuit board 14a and applying the load to the upper arm 12 may be reversed. As described above, the circuit board 14a of the signal processor 14 has a ROM for storing the calibration result together with the amplifier circuit for amplifying the bridge output signal composed of the strain gauges G1 to G4 shown in FIGS. Have. The calibration result is written into the ROM simultaneously using the probe P.

  According to the calibration method described above, the signal processor 14 on which the circuit board 14a with which the probe P is abutted and the load detection plate 11 to which the load F is applied are separately attached to the jig 200. Calibration is performed. Therefore, even if the calibration load F is applied via the upper arm 12 and the load detection plate 11 is deformed, the circuit board 14a mounted on the signal processor 14 is not displaced. Therefore, once the probe P is brought into contact with the circuit board 14a, the probe P need not be brought into contact again with the circuit board 14a even if the calibration load F is changed. For this reason, compared with the conventional calibration method performed in the state which attached the signal processor 94 which mounts the circuit board 94a shown in FIG.5 (b) to the load detection plate 91, working time can be shortened, and, thereby, the load sensor 100 can be shortened. The manufacturing cost can be reduced.

  As shown in FIGS. 1A and 1B and FIGS. 2A to 2C, the load sensor 100 shown in FIG. 3 has high accuracy using four strain gauges G1 to G4 constituting a bridge. Load sensor. In this highly accurate load sensor 100, as shown in FIG. 3, the output of the probe P having a large number of pins is accurately calibrated so that each pin simultaneously abuts each predetermined position of the circuit board 14a. . For this reason, the larger the number of pins, the more severe the contact condition between the probe P and the circuit board 14a. Therefore, the above-described calibration method in which the circuit board 14a is not displaced by the application of the calibration load F is suitable for the calibration of the high-precision load sensor 100 using the probe P having a large number of pins whose contact conditions with the circuit board 14a are severe. is there.

  As described above, the load sensor calibration method of the present invention is a load sensor calibration method in which the output is calibrated in the middle of manufacturing using a strain gauge, which can shorten the calibration work time and reduce the manufacturing cost. It is a load sensor calibration method that can be reduced. For this reason, the calibration method is suitable for use in calibration of a load sensor for a vehicle that detects the weight of a seated person seated on a seat that is attached to the lower part of the seat of the vehicle and is manufactured in large quantities with high accuracy. is there.

(A) is the perspective view which shows the load sensor with which each component was assembled | attached, (b) is the figure which decomposed | disassembled the load sensor of (a) and showed each component. (A) is a bottom view of the load detection plate, and (b) is a schematic cross-sectional view of the load detection plate to which an upper arm and a lower arm are attached. (C) is a circuit diagram which shows the connection of a strain gauge. It is a figure explaining the calibration method of the load sensor of this invention, and is a perspective view which shows the calibration operation in the middle of manufacture about the load sensor shown to Fig.1 (a), (b). It is the perspective view which expanded and showed the signal processor used for the load sensor shown in FIG. (A) is a perspective view which shows the conventional typical load sensor, (b) is a perspective view which shows the calibration operation in the middle of manufacture of the load sensor of (a).

Explanation of symbols

90, 100 Load sensor 11, 91 Load detection plate 12, 92 Upper arm (movable arm)
13,93 Lower arm (fixed arm)
14, 94 Signal processor 14a, 94a Circuit board 14b, 94b Case bottom plate 14c, 94c Case cover 14ch Hole 15a, 15b Plate G1-G4 Strain gauge 200 Jig 20s Base 20w Wall 20c Toggle clamp

Claims (8)

The load detection plate for detecting the pasted strain gauge deformation strain due to a load, a method of calibrating load sensors ing the signal processor is assembled for mounting a circuit board for processing the output signal of the strain gauge ,
During calibration of the load sensor, it is fixed in front Symbol load detection plate on a foundation for a jig for holding the load sensor, the signal processor in a fixed position and the other position of the load detecting plate on the base Separately install,
The probe is brought into contact with a predetermined position of the circuit board in the signal processor attached to the different position , and a predetermined load is applied to the load detection plate fixed on the base, so that the signal processor Calibrate the output ,
After the calibration of the load sensor is finished, the signal processor is assembled to the load detection plate . The load sensor includes a movable arm that transmits a load and a fixed arm that supports the load,
The movable arm is attached to one end of the load detection plate,
The fixed arm is attached to the other end of the load detection plate,
The strain gauge is disposed at an intermediate position between the two ends of the load detection plate;
At the time of calibration of the load sensor, the fixed arm is fixed by sandwiching it with a toggle clamp provided on the wall of the jig and the base, and the load detection plate is fixed on the base .
The load sensor calibration method according to claim 1, wherein a predetermined load is applied to the load detection plate via the movable arm. The signal processor has a case bottom plate for mounting the circuit board, and a case cover for covering the case bottom plate,
The load sensor calibration method according to claim 1, wherein the probe is brought into contact with a predetermined position on the circuit board in a state where the case cover is removed. The signal processor has a case bottom plate for mounting the circuit board, and a case cover for covering the case bottom plate,
A hole is provided at a predetermined position of the case cover,
The load sensor calibration method according to claim 1, wherein the probe is brought into contact with a predetermined position on the circuit board through the hole.   The load sensor calibration method according to claim 4, wherein the number of the holes is one. The load detection plate is a load detection plate in which four strain gauges constituting a bridge are attached,
6. The load sensor calibration method according to claim 1, wherein the signal processor is a signal processor that processes an output signal of the bridge.   7. The circuit board according to claim 1, wherein the circuit board includes an amplifier circuit that amplifies an output signal of the strain gauge and a ROM that stores the calibration result. 8. Load sensor calibration method. The load sensor is attached to the lower part of the vehicle seat,
The load sensor calibration method according to any one of claims 1 to 7, wherein the load sensor is a load sensor that detects the weight of a seated person sitting on the seat.

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