JP5003430B2 - Vehicle seat load detection device - Google Patents

Description

  The present invention relates to an occupant load detection device that detects the weight of an occupant seated on a vehicle seat.

  In recent years, in order to improve the performance of various safety devices such as seat belts and airbags, the operation of these safety devices may be controlled in accordance with the weight of an occupant seated in a vehicle seat.

  As such an apparatus for detecting the weight of a seated person, one described in Patent Document 1 is known. The first fixing member press-fitted into the first fixing hole of the sensor substrate and causes an external force to act on the end of the detection member press-fitted into the detection hole of the sensor substrate as a strain generating body. In addition, a reaction force is applied to the end portion of the second fixing member press-fitted into the second fixing hole of the sensor substrate that contacts the sensor substrate.

By adopting such a configuration, the positions of the ends of the detection member, the first fixing member, and the second fixing member that contact the sensor substrate are not displaced, so that the bending stress applied to the strain detection element is stabilized. As a result, the output accuracy of the strain sensor can be improved.
JP 2003-83707 A

  However, in the sensor of Patent Document 1, each of a fixing member (bracket) and a detection member (connecting member) is an individual member, and all of them are press-fitted and fixed to the sensor substrate (strain body). In order to fix the detection device, the fixing members at both ends are fastened and fixed to the vehicle frame with bolts and nuts. In this case, since the fixing member is press-fitted into the sensor substrate and is in contact with the surface of the sensor substrate, the rotation caused by the axial force (force in the central axis direction of the bolt) and frictional force generated when fastening the nut. The force is transmitted to the sensor substrate through the fixing member. For this reason, internal stress is generated in the sensor substrate, and there is a problem that accuracy as a sensor is lowered.

  The present invention has been made in view of the conventional problems, and when a detection device to be attached is attached to a vehicle, the axial force and the rotational force generated by the frictional force when fastened are passed through the fixing member to the sensor substrate (starting up). It is an object of the present invention to provide a vehicle seat load detection device capable of maintaining high accuracy as a sensor by preventing internal stress generated by being transmitted to a strain body from being transmitted to a sensor substrate.

  In order to solve the above-described problem, the structural feature of the invention according to claim 1 is interposed between a floor-side fixing member and a seat-side fixing member for fixing a seat to a vehicle floor, and the seat In a vehicle seat load detection device for a vehicle for measuring a load of a passenger seated on a seat, a mounting surface formed on one of the floor side fixing member and the seat side fixing member is spaced from the mounting surface by a predetermined distance. A strain generating body fixed at both ends, a connecting member fixed by being press-fitted in a vertical direction into the center of the strain generating body and fixed to the other of the floor side fixing member and the seat side fixing member, and A strain gauge affixed to the surface of the strain body between each of the both end portions and the center portion, and fixed by being press-fitted into fixing holes formed at both end portions of the strain generating body, and the floor side fixing member And seat side fixing member An insertion hole for inserting a fixed shaft fixed to one side is formed, a pair of fixed support members for supporting the strain body at a predetermined interval from the mounting surface, and mounting holes for mounting the fixed support member at both ends. A bracket member having a pair of attachment portions formed, and an amplifier case attachment portion extending to the side of the strain generating body continuously to the pair of attachment portions, and press-fitted into the fixed support member. A washer member that is overlapped and clamped on each mounting portion of the bracket member between the fixed strain body and a tightening nut that is screwed to the fixed shaft, and the bracket member and the washer Of the members, one member provided on the side of the tightening nut is press-fitted into each of the fixed support members, and the other member is inserted into each of the fixed support members with a gap therebetween. is there.

  The structural feature of the invention according to claim 2 is that, in claim 1, the bracket member is disposed on the side of the tightening nut, and at least one of the mounting holes of the bracket member is arranged with both the mounting holes. That is, it is formed in a long hole shape that is long in the direction.

  The structural feature of the invention according to claim 3 is that, in any one of claims 1 and 2, the strain gauge is affixed to the surface of the strain body opposite to the side to be tightened by the tightening nut. It is that.

  According to the first aspect of the present invention, when the tightening nut is tightened, the rotational force generated by the frictional force of the tightening nut is transmitted from the tightening nut to the washer member, for example. Relative sliding between the contact surfaces reduces the rotational force transmitted, and further reduces the rotational force transmitted when the washer member and the bracket member slide between the mutual contact surfaces. Accordingly, the internal stress (stress strain) due to the frictional force generated in the strain generating body can be reduced by providing the washer member in addition to the bracket member between the tightening nut and the strain generating body. . Further, the force (axial force) in the central axis direction of the fixed shaft increases the contact area to the bracket member or the strain body by the washer member as compared to the tightening nut, and the washer member is compatible with the member to be contacted. It is possible to make it difficult for internal stress to be generated in the strain generating body without causing stress concentration in the contacting member. Therefore, by fixing the both ends of the strain generating body with the tightening nut, it is possible to make it difficult to affect the deformation of the strain generating body during the load, and the load can be detected with high sensitivity.

  In addition, the connecting member and the fixed support member are press-fitted and fixed to the strain-generating body, and the bracket member or washer member disposed on the tightening nut side is press-fitted and fixed to the fixed supporting member, so that the strain-generating body, the connecting member and the fixed member are fixed. Since the support member, bracket member and washer member are formed as a single unit, it is possible to detect the occupant load with high accuracy without being affected by variations in manufacturing dimensions of the position of the fixed shaft to which the strain body is attached. It can be carried out. Moreover, it can handle collectively in each production process, and can improve productivity.

  In particular, when the washer member is provided on the fastening nut side, if the washer member is press-fitted into the fixed support member and the bracket member is inserted into the fixed support member with a gap, the mounting hole of the bracket member is dimensioned. It can be set as the loose fitting hole which can absorb an error. Therefore, it is not necessary to strictly match the manufacturing dimension between the two mounting holes with the mounting dimension between the fixed shafts inserted into the mounting holes. Therefore, since it is not necessary to use a bracket member with high manufacturing accuracy, a low-cost vehicle seat load detection device can be provided. Further, when the bracket member is provided on the fastening nut side, the bracket member is press-fitted into the fixed support member, and the washer member is inserted into the fixed support member with a gap therebetween, so that the washer member is moved to the strain body side. Will be provided. For this reason, if what is generally used as a washer member is used, it is inexpensive, and it is not necessary to process the bracket member to uniformly generate strain on the strain generating body, so that the arc shape of the washer member is eliminated. Strain can be uniformly generated on the strain generating body at the edge.

  According to the invention according to claim 2, since the variation in the manufacturing dimension between the two mounting holes of the bracket member can be compensated by the elongated hole shape of one mounting hole, the bracket member can be manufactured without high accuracy. It is possible to easily match the mounting dimensions between the pair of fixed shafts into which the fixed support members are inserted. Therefore, since it is not necessary to use a bracket member with high manufacturing accuracy, a low-cost vehicle seat load detection device can be provided.

  According to the invention of claim 3, since the strain gauge is affixed to the opposite side of the strain generating body on the side to be tightened with the tightening nut, the influence due to the tightening of the tightening nut, especially the effect of stress strain due to torsion is reduced. And high accuracy as a sensor can be maintained.

  Hereinafter, a vehicle seat load detection apparatus 10 according to a first embodiment of the present invention will be described with reference to the drawings. The vehicle seat load detection device 10 measures the load of an occupant seated on the vehicle seat 11 shown in FIG. In FIG. 1, a seat slide device 13 for fixing a seat 11 to a floor 12 of a vehicle so as to be adjustable is supported by a pair of lower rails 14 fixed to the floor 12 and extending in the front-rear direction of the vehicle, and movably supported by the lower rails 14. And upper rail 16 and the like.

  As shown in FIGS. 1 and 2, the lower portion of the seat 11 is composed of a frame 17 (seat-side fixing member) assembled to the lower surface of the seat cushion. Are fixed to a mounting surface 18 (see FIG. 2) formed on the upper surfaces of the pair of upper rails 16 (floor side fixing members) via the vehicle seat load detection device 10. A pair of fixed shafts 19 for fixing the vehicle seat load detection device 10 on the mounting surface 18 are provided in the longitudinal direction of the vehicle at each end portion of each upper rail 16 to which the vehicle seat load detection device 10 is fixed. It protrudes vertically by a distance.

  As shown in FIG. 3, the vehicle seat load detection device 10 includes a strain body 20, strain gauges G <b> 1 and G <b> 2 attached to the lower surface of the strain body 20, and the strain body 20 at both ends. A pair of lower bushes 21 as fixing support members fixed to the mounting surface 18 and a connecting shaft as a connecting member fixed to the frame 17 of the seat 11 by being fixed to the central portion of the strain body 20 by a ring member 48 in the vertical direction. 23, a bracket member 24 engaged with the upper surface of the strain body 20 at both ends, a washer member 22 disposed on both ends of the bracket member 24 and inserted into the lower bush 21 together with the bracket member 24, An amplifier board 26 (see FIG. 6) which is attached to the amplifier case attachment portion 47 of the bracket member 24 along with the strain generating body 20 and amplifies signals from the strain gauges G1 and G2 is accommodated. An amplifier case 27, which is, and a strain gauge G1, G2 and amplifier board 26 FPC board 28 connected to the (see FIG. 6) (described later) or the like.

  First, as shown in FIGS. 3 and 4, the lower bush 21 is press-fitted into a base portion 29 having a predetermined thickness and fixing holes 30 that protrude from the base portion 29 and are formed on both ends of the strain body 20. The center shaft portion 31, the tip shaft portion 32 protruding from the center shaft portion 31, and the insertion hole 33 formed through the center.

  Here, in this embodiment, “press-fit” means that the diameter of the shaft portion to be fitted is larger than the diameter of the hole portion to be fitted, and when the shaft portion is fitted into the hole portion, For example, when the hole (fixed hole 30) is formed in the strain generating body 20, the stress strain generated around the hole when the shaft (middle shaft 31) is fitted does not reach the strain gauge. The shaft portion and the hole portion are held to each other to the extent that they are not easily dropped during handling in production operations (the same applies hereinafter).

  Next, fixing holes 30 are formed at both ends of the strain body 20, and both fixing holes 30 are formed by a predetermined distance that is the same as the interval between the fixing shafts 19 protruding from the both ends of the upper rail 16. ing. As shown in FIG. 4, the fixing hole 30 is press-fitted into the middle shaft portion 31 until the surface abuts the base portion 29 of the lower bush 21 as shown in FIG. A central hole 38 is formed in the central portion of the strain body 20, and the central shaft portion 39 of the connecting shaft 23 is press-fitted into the central hole 38. A flange 40 having a thickness smaller than that of the base portion 29 of the lower bush 21 is formed at the end of the connecting shaft 23 and is in contact with the surface of the strain generating body 20. A front middle shaft portion 41 projects from the end surface of the middle shaft portion 39, and a fixing screw portion 42 projects from the end surface of the front middle shaft portion 41. When the ring member 48 is press-fitted into the front middle shaft portion 41 in a state where the middle shaft portion 39 of the connecting shaft 23 is press-fitted into the central hole 38 of the strain body 20, the connection shaft 23 is interposed between the flange 40 and the ring member 48. The strain body 20 is sandwiched between the two and the base body is fixed to the strain body 20.

  Moreover, the front-end | tip part of the said connection shaft 23 is connected with the sheet | seat 11 as follows. First, a connecting surface 62 is formed on the frame 17 of the seat 11, and a connecting hole 63 is formed in the connecting surface 62. A connection hole 63 is fitted in the fixing screw portion 42 of the connection shaft 23, the lower surface of the connection surface 62 comes into contact with the upper surface of the ring member 48, and the frame 11 is placed on the upper rail 16 via the strain body 20, The nut 65 screwed to the fixing screw portion 42 presses the connecting surface 62 to the ring member 48, whereby the connecting shaft 23 of the vehicle seat load detection device 10 is fixed to the frame 17 of the seat 11.

  Further, as shown in FIG. 5, for example, steel plate bracket members 24 are assembled to both ends of the upper surface of the strain body 20. Attachment portions 43 are integrally provided at both ends of the bracket member 24, and attachment holes 45 are formed in the attachment portions 43 as shown in FIG. These mounting holes 45 are inserted into the front shaft portion 32 of the lower bush 21 protruding from the bracket member 24 by inserting the front shaft portions 32 of the lower bush 21 protruding from the upper surface of the strain body 20 with gaps. Each washer member 22 is press-fitted.

  The strain body 20 is sandwiched with the bracket member 24 between the washer member 22 and the base portion 29 of the lower bush 21 at both ends thereof.

  As shown in FIG. 2, the insertion hole 33 of the lower bush 21 is fitted to the fixed shaft 19 projecting vertically from the end of the upper rail 16, and the bottom surface of the base portion 29 is the mounting surface 18. Sit on top. The tightening nut 60 screwed into the threaded portion engraved at the tip of the fixed shaft 19 presses the mounting portion 43 of the bracket member 24 described later, whereby the strain body 20 of the vehicle seat load detection device 10. Is fixed at both ends to the mounting surface 18 of the upper rail 16 with a predetermined gap corresponding to the thickness of the base portion 29 from the mounting surface 18.

  As described above, the strain body 20 whose central portion is fixed to the frame 17 via the connecting shaft 23 and whose both end portions are fixed to the upper rail 16 has the load of the occupant seated on the seat 11 connected to the connecting shaft. 23, when both ends thereof are supported by the lower bush 21 at both ends and bent, the surface of the strain generating body 20 is interposed between each lower bush 21 and the connecting shaft 23. In proportion to the load, compressive strain is generated on the lower bush 21 side, and tensile strain is generated on the connecting shaft 23 side. Further, in order to detect these compressive strain and tensile strain, a half bridge is formed between each end portion and the center portion of the strain generating body 20, that is, between each lower bush 21 and connecting shaft 23. Strain gauges G1 and G2 each having an element are attached. These strain gauges G <b> 1 and G <b> 2 are affixed to the surface of the strain generating body 20 on the side opposite to the side to be tightened by the tightening nut 60. A full bridge is formed by the half bridges of the strain gauges G1 and G2, and the load of the occupant seated on the seat 11 is measured as the bending of the strain generating body 20.

  As shown in FIG. 5, the bracket member 24 is formed with an amplifier case mounting portion 47 that integrally connects the mounting portions 43 at both ends so as to extend to the side of the strain body 20. As described above, the bracket member 24 affects the deformation of the strain body 20 by preventing the bracket member 24 from overlapping with the strain body 20 except for the mounting portions 43 at both ends, that is, the amplifier case mounting portion 47. The occupant's load can be accurately measured.

  Further, as shown in FIGS. 3 and 6, for example, an amplifier case 27 made of PBT (polybutylene terephthalate) resin is attached to the amplifier case mounting portion 47 along with the strain body 20 by screws (not shown). Yes. By making the amplifier case 27 made of PBT resin, it is possible to reduce the weight and cost as compared with the conventional aluminum case. The amplifier case 27 is provided with a connector 59 for connecting a communication line for transmitting the output of the amplifier board to an unillustrated electronic control unit, as shown in FIG.

  Further, as shown in FIG. 6, the U-shaped FPC (Flexible Printed Circuits) substrate 28 is placed between the strain gauges G1 and G2 at the ends of both leg portions between the both ends and the central portion of the strain body 20. Four through holes 46 connected to the wiring pattern of the FPC board 28 are provided in the intermediate portion of the FPC board 28, and these through holes are connected to the terminals 59 of the amplifier board, respectively.

  According to the vehicle seat load detection device configured as described above, when the occupant load detection device 10 is attached to the fixed shaft 19 attached to the attachment surface 18, the connecting shaft 23 and the lower bush 21 are attached to the strain body 20. The washer member 22, which is press-fitted and disposed on the side of the tightening nut 60, is press-fitted and fixed to the lower bush member 21, so that the strain body 20, the connecting shaft 23, the lower bush 21, the bracket member 24, and the washer member 22 are formed. Since it is formed as a single unit, it is possible to detect the occupant load with high accuracy without being affected by manufacturing dimensional variations in the position of the fixed shaft 19 to which the strain generating body 20 is attached. Moreover, since it can handle collectively as a unit in a production process, productivity can be improved.

  The pair of fixed shafts 19 erected on the upper rail 16 at predetermined intervals are respectively inserted through the insertion holes 33 of the lower bush 21 serving as the unit, and the fixed shaft 19 protruding from the insertion hole 33 of the lower bush 21. The fastening nut 60 is screwed into the threaded portion of the screw, and the fastening nut 60 is fastened to fix the unit. When tightening with the tightening nut 60, the rotational force generated by the frictional force due to the tightening of the tightening nut 60 is transmitted from the tightening nut 60 to, for example, the washer member 22, but the tightening nut 60 and the washer member 22 are mutually connected. Relative sliding between the contact surfaces reduces the transmitted rotational force, and further reduces the rotational force transmitted by the washer member 22 and the bracket member 24 sliding between the contact surfaces. Therefore, the internal stress due to the frictional force generated in the strain body 20 can be reduced by providing the washer member 22 in addition to the bracket member 24 between the tightening nut 60 and the strain body 20. it can. Further, the force (axial force) in the direction of the central axis of the fixed shaft 19 has a larger contact area with the bracket member 24 or the strain body 20 than the tightening nut 60 by the washer member 22, and the washer member 22 is used by use. Since it is compatible with the bracket member 24, the tightening nut 60, or the strain body 20 in contact with each other, stress concentration on the bracket member 24 and the strain body 20 is not caused, and internal stress is hardly generated in the strain body 20. be able to. Therefore, it is possible to detect the same load with high sensitivity without fixing the both ends of the strain body 20 by the tightening nut 60 without affecting the deformation of the strain body 20 during the load.

  Further, if the washer member 22 is press-fitted into the lower bush 21 and the washer member 22 is inserted into the lower bush 21 with a gap, both the mounting holes 45 of the bracket member 24 can absorb the dimensional error. It can be a fitting hole. Therefore, it is not necessary to strictly match the manufacturing dimension between the two mounting holes 45 with the mounting dimension between the fixed shafts 19 inserted into the mounting holes 45. Therefore, since it is not necessary to use the bracket member 24 with high manufacturing accuracy, the low-cost vehicle seat load detection device 10 can be provided. Further, since the mounting hole 45 on the side in contact with the strain generating body 20 is a loose fitting hole, it is not constrained by the lower bush 21, so that it can abut on the surface of the strain generating body 20, and stress is applied to the strain generating body 20. Can be reduced.

  In addition, since the attachment portions 43 that form a pair of the bracket members 24 are integrally formed, the attachment portions 43 have a relationship of preventing the rotation of each other. For this reason, even if the tightening nut 60 is tightened, each mounting portion 43 stays within the elastic deformation and is prevented from rotating by the tightening nut 60. The influence of torsional stress can be further reduced.

  In addition, since the strain gauges G1 and G2 are attached to the opposite side of the strain generating body 20 on the side to be tightened by the tightening nut 60, the influence of the tightening of the tightening nut 60, particularly the occurrence of stress strain due to torsion, is caused. It is possible to decrease and maintain high accuracy as a sensor.

  When the occupant sits on the seat 11, the occupant's load is applied to the frame 17 fixed to the seat cushion. As a result, a load is applied to each strain body 20 via the connecting shaft 23 of the vehicle seat load detection device 10. As shown in FIGS. 6 to 7, when the strain generating body 20 is deformed, the electrical resistance of the strain gauges G <b> 1 and G <b> 2 is changed, and the change in the voltage that changes is amplified by the amplifier circuit of the amplifier substrate 26. This detects the occupant's load.

  Next, the vehicle seat load detection apparatus 80 according to the second embodiment of the present invention will be described below. In the present embodiment, the bracket member 82 is disposed on the tightening nut 60 side, and the washer member 22 is inserted into the lower bush 21 with a gap and provided on the strain generating body 20 side. Further, one of the mounting holes 83 of the bracket member 82 (the right side in FIG. 7) is formed into a long hole shape having a short diameter and a long diameter (the direction in which the two mounting holes 83 are aligned) is long, and an edge portion of the short diameter In 83a, it press-fits in contact with the outer periphery of the front shaft portion 32 of the lower bush 21. The other mounting hole 84 is a circular hole, but the front shaft portion 32 of the lower bush 21 is press-fitted. In these respects, the second embodiment is different from the first embodiment, and the other configuration is the same as that of the first embodiment.

  According to the vehicle seat load detecting device 80 having the above-described configuration, the manufacturing dimension variation between the two mounting holes 83, 84 of the bracket member 82 can be compensated by the long mounting hole 83. Even if it is not manufactured with high accuracy, it is possible to match the dimension between the fixed shafts 19 in which the lower bush 21 is inserted. For this reason, if what is generally used as the washer member 22 is used, it is inexpensive, and it is not necessary to process the bracket member 82 to uniformly generate strain on the strain generating body 20, and the washer member 22. It is possible to uniformly generate the strain S on the strain generating body 20 with the arc-shaped edges (see FIG. 7).

  Further, the mounting portions 43 of the bracket member 82 are respectively continuous with the amplifier case mounting portion 47, and the pair of mounting portions 43 are integrally formed so as not to move relative to each other. They are in a relationship to prevent each other. For this reason, even when tightened by the tightening nut 60, the mounting portions 43 are prevented from rotating by the tightening nut 60, so that internal stress generated in the strain body 20 due to tightening of the tightening nut 60 is further reduced. Can be made.

  In the above embodiment, the strain body is sandwiched between the bracket member located above the strain body and the lower bush located below the strain body. However, the present invention is not limited to this. For example, these configurations may be arranged upside down.

  Moreover, although the bracket member is made of a steel plate, the bracket member is not limited to this, and may be made of an aluminum alloy, for example.

The perspective view of the sheet | seat in which the vehicle seat load detection apparatus of the vehicle in 1st Embodiment is used. The figure which shows the attachment state of the vehicle seat load detection apparatus. The exploded perspective view of the load detection apparatus. The figure which shows the assembly | attachment to the strain body of the same bracket member and a connection shaft. The perspective view of the vehicle seat load detection apparatus assembled in the same. The figure which shows the seat load detection apparatus for vehicles from the back side. The perspective view of the assembled vehicle seat load detection apparatus in 2nd Embodiment. The figure which shows the assembly | attachment state of the vehicle seat load detection apparatus The figure which shows the shape of the attachment hole of the bracket member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Vehicle seat load detection apparatus, 11 ... Seat, 12 ... Floor, 16 ... Floor side fixing member (upper rail), 17 ... Seat side fixing member (frame), 18 ... Mounting surface, 19 ... Fixed shaft, 20 ... Starting Distorted body, 21 ... fixed support member (lower bush), 22 ... washer member, 23 ... connecting member (connecting shaft), 24 ... bracket member, 30 ... fixing hole, 33 ... insertion hole, 43 ... mounting portion, 45 ... mounting Hole 47: Amplifier case mounting portion 60: Clamping nut G1: Strain gauge G2: Strain gauge

Claims (3)

In a vehicle seat load detection device for a vehicle that is interposed between a floor side fixing member and a seat side fixing member for fixing a seat to a vehicle floor and measures a load of an occupant seated on the seat,
A strain body that is fixed at both ends of the floor-side fixing member and the seat-side fixing member at a predetermined interval from the mounting surface.
A connecting member that is press-fitted and fixed in the vertical direction to the center of the strain generating body and is fixed to the other of the floor side fixing member and the seat side fixing member;
A strain gauge affixed between the both end portions and the central portion on the surface of the strain generating body;
An insertion hole is formed through which a fixing shaft fixed to one of the floor side fixing member and the seat side fixing member is inserted and fixed to fixing holes formed at both ends of the strain generating body, A pair of fixed support members for supporting the strain body from the mounting surface at a predetermined interval;
A pair of mounting portions formed with mounting holes for mounting the fixed support member at both ends, and an amplifier case mounting portion extending to the side of the strain generating body continuously to the pair of mounting portions. A bracket member;
A washer member that is overlapped and clamped on each mounting portion of the bracket member between the strain body press-fitted and fixed to the fixed support member and a tightening nut screwed to the fixed shaft; Prepared,
Of the bracket member and the washer member, one member provided on the tightening nut side is press-fitted into each of the fixed support members, and the other member has a gap with respect to each of the fixed support members. A vehicle seat load detection device, wherein the vehicle seat load detection device is inserted. In Claim 1, the bracket member is disposed on the side of the tightening nut,
At least one of the mounting holes of the bracket member is formed in an elongated hole shape that is long in a direction in which the mounting holes are aligned. 3. The vehicle seat load detection device according to claim 1, wherein the strain gauge is affixed to a surface of the strain body opposite to a side to be tightened by the tightening nut. 4. .

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