JP2014041078A - Manufacturing method of strain detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a strain detector having a load transmission part disposed in an axial direction of cylindrical strain generation member capable of reducing variations in characteristics at mass production stage.SOLUTION: The strain detector has a load transmission part 2 welded to a cylindrical strain generation member 1 in an axial direction thereof. A communication path 14 communicating the inner side and the outer side of the strain generation member 1 is formed in a contact point between the load transmission part 2 and the strain generation member 1. When welding the load transmission part 2 and the strain generation member 1, the opening of the communication path 14 is sealed in the last stage of the welding.

Description

  The present invention relates to a method for manufacturing a strain detecting device in which a load transmitting portion is arranged in the axial direction of a cylindrical strain generating body.

  Conventionally, in this type of weight sensor, a load transmitting part for external attachment is inserted into an opening of a cylindrical strainer having a strain resistance element arranged on the outer peripheral surface, and the inner peripheral end of the opening and the load transmitting part These were integrated by welding the outer peripheral end of the.

  Then, the load applied to the detected body is transmitted to the strain generating body via the load transmitting portion, and the strain component of the strain generating body caused by this load is detected by the strain resistance element provided on the outer peripheral side surface. ing. In such a strain detection device, since it is important to ensure the detection accuracy that the detection axis of the strain generating body and the load transmission direction of the load transmitting portion match, the opening of the strain generating body And the offset with the load transmission part inserted in this opening part is set very small.

  As prior art document information related to the invention of this application, for example, Patent Document 1 is known.

JP 2011-58813 A

  However, when performing welding with the load transmitting portion inserted into the opening of the strain generating body, the closed space formed by the strain generating body and the load transmitting portion is small because the offset between the opening and the load transmitting portion is small. The air tightness of the air is increased and the air in the closed space expands due to heat during welding, which acts in the direction of pushing up the load transmission part. Variations occurred, resulting in variations in the characteristics of the strain detection apparatus.

  SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to solve such problems and to suppress characteristic variation at the mass production stage in a strain detection device in which a load transmitting portion is arranged in the axial direction of a cylindrical strain generating body.

  In order to achieve this object, the present invention provides a strain detecting device in which a load transmitting portion is welded in the axial direction of a cylindrical strain generating body, and a strain generating body is provided at a contact portion between the load transmitting portion and the strain generating body. A communication passage connecting the inside and the outside of the housing is provided, and when the load transmitting portion and the strain body are welded, the communication passage is sealed at the final stage of welding.

  According to this method, the present invention can suppress variation in characteristics at the mass production stage in the strain detection device in which the load transmitting portion is arranged in the axial direction of the cylindrical strain generating body.

Cross section of strain detector Circuit diagram of the distortion detector Development view of the strain-generating body constituting the strain detection device (A), (b) Schematic diagram showing the detection principle of the strain detection device The figure which shows the welding method of the strain body and load transmission part in the same strain detection apparatus

  Hereinafter, a strain detection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a cross-sectional structure of a strain detection apparatus. The basic structure of the strain detection apparatus is a cylindrical strain body 1, and a body to be detected (particularly FIG. 1) arranged on a central axis 1a of the strain body 1. The load transmitting portion 2 is integrated by inserting a lower end portion of the load transmitting portion 2 into the opening of the strain generating body 1 and welding the joint portion. In addition, 3 shown with a broken line has shown the supporting member which attaches a distortion | strain detector.

  Further, on the outer peripheral side surface of the strain generating body 1, the power supply electrode 4, the output electrodes 5 and 6, the GND electrode 7 and the four strain resistance elements 8, 9, 10, and 11 constituting the bridge circuit shown in FIG. It is arranged. As shown in FIG. 3, the strain resistance elements 8 and 9 are arranged symmetrically with respect to the central axis 1 a of the strain generating body 1 in these electrodes, and the strain resistance element 8 is One end is connected to the power electrode 4 and the other end is connected to the output electrode 5. The strain resistance element 9 has one end connected to the output electrode 6 and the other end connected to the GND electrode 7. The strain resistance elements 10 and 11 are arranged symmetrically with respect to the central axis 1 a of the strain generating body 1 in the upper portion of the strain generating body 1, and one end of the strain resistance element 10 is connected to the strain resistance element 8 and the output electrode 5. The other end is connected to the GND electrode 7. The strain resistance element 11 has one end connected to the strain resistance element 9 and the output electrode 6 and the other end connected to the power supply electrode 4.

  As shown in FIG. 1, the strain body 1 is supported by a column portion 12 having a T-shaped cross section, and the disc-shaped head portion 13 of the column portion 12 is a cylindrical strain body. Welded in the middle of 1.

  Next, the detection principle of this strain detection apparatus will be described. In this strain detection apparatus, in an initial state where a detected load is not applied to the load transmitting portion 2, as shown in FIG. 4A, the shape change of the strain body 1 supported by the head portion 13 of the column portion 12 is achieved. There is no potential difference between the output electrodes 5 and 6 in the bridge circuit connected between the power supply electrode 4 and the GND electrode 7.

  On the other hand, when a detected load in the direction of the central axis 1a as shown by the arrow in FIG. 1 is applied to the load transmitting portion 2, as shown in FIG. 4B, the head integrated inside the strain generating body 1 A shear load is applied to 13. Then, due to the shear load, a moment force acts on the outer surface of the strain body 1 supported by the head 13, and thereby a tensile force acts on the outer peripheral side surface on the upper end side of the strain body 1. A compressive force acts on the outer peripheral side surface on the lower end side. Accordingly, the resistance values of the strain resistance elements 10 and 11 provided on the upper outer peripheral side surface of the strain generating body 1 are increased, and the resistance values of the strain resistance elements 8 and 9 provided on the lower outer peripheral side surface are decreased. A potential difference is generated between the output electrodes 5 and 6 in the bridge circuit, and an output signal corresponding to the detected load can be formed by performing signal processing on the potential difference with a processing circuit (not shown) in the subsequent stage.

  Next, a method for assembling the strain detection device will be described. First, after printing a glass paste (not shown) on the outer peripheral side surface of a stainless steel cylinder constituting the strain generating body 1, the stainless steel surface is insulated by baking at about 550 ° C. for about 10 minutes. Next, a silver paste (not shown) for forming the power electrode 4, the output electrodes 5, 6 and the GND electrode 7 is printed on the surface of the baked glass paste and baked at about 550 ° C. for about 10 minutes. Next, a metal glaze paste (not shown) for forming the strain resistance elements 8, 9, 10, 11 is printed and baked at about 550 ° C. for about 10 minutes. Next, after inserting the column part 12 into the inside of the strain body 1 and welding the outer peripheral part of the head 13 and the inner periphery part of the strain body 1, the load transmitting part 2 is attached to the opening of the strain body 1. Weld.

  In this strain detection device, as shown in FIG. 5, a communication path 14 is provided in the welded portion 15 between the load transmitting portion 2 and the strain body 1, and a path that communicates the inside and the outside of the strain body 1. When welding the welded portion 15 that hatches the load transmitting portion 2 and the strain generating body 1, the welding is started from the vicinity of the communication passage 14, and the communication passage 14 is sealed at the final stage of welding. Thus, it is possible to suppress variation in characteristics at the mass production stage in the strain detection device.

  That is, when attaching the load transmission part 2 after attaching the column part 12 to the strain body 1, the inside of the strain body 1 is connected to the head 13 of the pillar part 12 and the load transmission part at the stage of welding the load transmission part 2. 2, a closed space 16 is formed with the lower portion, and when welding is performed in a state in which the closed space 16 is formed, the internal air of the closed space 16 expands due to heat during welding as described above, and the load Acting in the direction in which the transmission unit 2 is pushed up causes variations in the characteristics of the strain detection apparatus. However, since the closed space 16 is structured to communicate with the outside through the communication path 14 and the communication path 14 is sealed at the final stage of welding, the internal air expanded by the welding heat is discharged from the communication path 14 to the outside. As a result, the push-up action of the load transmission part 2 is suppressed, and as a result, the installation system of the load transmission part 2 at the welding stage can be improved, and the characteristic variation at the mass production stage can be suppressed.

  In this strain detection device, the communication path 14 is formed by providing a notch on the load transmitting portion 2 side, but this is easier than providing a notch in the inner peripheral portion of the strain generating body 1. Not only can it be formed, but it also leads to deterioration of detection accuracy by losing the axial symmetry of the intensity distribution by partially providing a notch in the cylindrical strain body 1, thereby forming the communication path 14. The cutout is preferably provided on the load transmitting portion 2 side.

  The strain detection apparatus according to the present invention can suppress characteristic variations at the stage of mass production, and is particularly useful in a strain detection apparatus for measuring a load on a vehicle seat or the like.

DESCRIPTION OF SYMBOLS 1 Strain body 2 Load transmission part 8, 9, 10, 11 Strain resistance element 14 Communication path

Claims (2)

A cylindrical strain generating body, a strain resistance element disposed on an outer peripheral surface of the strain generating body, and a load transmitting portion connected by welding to an opening of the strain generating body, the load transmitting portion and the In a strain detection apparatus in which a communicating path that connects the inside and outside of the strain generating body is provided at a contact portion with the strain generating body, the strain generating body and the load transmitting portion are welded along an outer periphery of the load transmitting portion. And a method of manufacturing a strain detecting device, wherein the communication path is sealed at a final stage of the welding. 2. The method of manufacturing a strain detection apparatus according to claim 1, wherein the communication path is provided in the load transmission portion.

Images