JP2006118978A - Seat load detection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seat load detection apparatus which measures an accurate seat load regardless of the seating conditions of an occupant. <P>SOLUTION: The seat load detection system comprises a fixed bracket 31 fixed to a floor 5; a torsion bar 34 of which a fixed-side end 34a, or one end, is fixed to the fixed bracket 31 and which has a horizontal torsional axis O; an arm bracket 32 which is fixed to an arm-side end 34b, or the other end, of the torsion bar 34 and has a load acting section 38a on which the seat load acts at a position deviated from the torsional axis O of the torsion bar 34; and a torsional condition measurement means 50 which measures the torsional condition of the torsion bar 34. On the basis of measurement results of the torsional condition measurement means 50, the seat load acting on seating sections (10a, 10b) of a seat 10 can be detected. The detection system is provided with a ball bearing 60 which surrounds the one end of the torsion bar 34 and an auxiliary fixing bracket 61 which is fixed to the ball bearing 60. The auxiliary fixed bracket 61 is connected to the fixed bracket 31. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a seat load detection device capable of measuring the weight of an occupant.

  In recent years, in order to improve safety for passengers of vehicles such as automobiles, the vehicle has a seat belt holding function and an air bag depending on whether the passenger is seated on the seat or the weight of the seated passenger. It is carried out to control the operation function. In performing these controls, it is necessary to accurately detect the seat load as the weight of the passenger acting on the seat.

And, as such a seat load detection device, a strain generating plate composed of a flat body extending in the horizontal direction and having a strain gauge attached to the surface is provided, and one end side of the strain generating plate is fixed to the vehicle body side. In addition, the seat load detecting device configured to detect the seat load by fixing the other end side of the strain generating plate to the seat side and detecting a change in the electrical resistance of the strain gauge accompanying the bending of the strain generating plate. It is known (see, for example, Patent Document 1).
JP 2003-83798 A

  However, in the above-described seat load detection device, a flat plate-shaped strain generating plate extending in the horizontal direction is used, and further, in the horizontal direction for fixing each end of the strain generating plate to the vehicle body side and the seat side. Since an extended bracket or the like is required, the width in the horizontal direction is relatively large. Such an increase in the size of the seat load detection device causes, for example, interference with other devices added to the seat. In addition, since the strain plate receives a relatively large sheet load in a cantilever state, the thickness of the strain plate is also relatively thick. For example, the strain plate is attached to the strain plate with respect to the sheet load. In some cases, the change rate of the electrical resistance of the attached strain gauge becomes small, leading to a decrease in detection accuracy.

  Further, in the sheet load detection device using the strain generating plate as described above, the strain state of the strain gauge attached to the surface of the strain generating plate with respect to the sheet load changes depending on the distance from the point of application of the sheet load. In order to improve the sheet load detection accuracy, it is necessary to accurately manage the position where the strain gauge is attached on the surface of the strain generating plate. In addition, since the bending state of the strain plate is relatively complicated, the change state of the electrical resistance of the strain gauge attached to the surface of the strain plate with respect to the change of the sheet load is relatively complicated. Therefore, the seat load may not be detected widely and accurately.

  In this regard, a seat load detection device capable of measuring a seat load by measuring a twisted state of the torsion bar using a torsion bar has been developed (Japanese Patent Application No. 2004-281906). With such a seat load detection device, it is possible to reduce interference with other devices added to the seat, and to detect the seat load widely and accurately without causing a decrease in detection accuracy. Can do.

  However, when a seat load detection device using a torsion bar is attached to a seat, the seat load may not be accurately measured. This is the case, for example, when the occupant sits extremely biased toward the corner of the seat. In such a case, the sheet load applied to one sheet load detection device is unevenly distributed. Usually, in order to measure the torsional state of the torsion bar, the purpose is to measure the rotational stress generated in the torsion bar. However, when the occupant is seated as described above, bending stress is generated in the torsion bar. That is, the seat load detection device measures the torsional state of the torsion bar including not only rotational stress but also bending stress. For this reason, it is impossible to measure the torsional state of the torsion bar consisting only of rotational stress, and in the seated state of the occupant as described above, there is a case where an accurate seat load cannot be measured. Such a situation can also occur when an extremely heavy passenger sits on the seat.

  The present invention has been made in view of the above-described conventional situation, and an object to be solved is to provide a seat load detection device capable of measuring an accurate seat load regardless of the seating state of the occupant.

  The technical means taken in the present invention in order to solve the above-described problem is that, as described in claim 1, a fixing member fixed to the floor side, and a fixing side end portion, which is one end side, are fixed to the fixing member. And a torsion bar having a horizontal torsion axis, and a load that is fixed to an arm side end that is the other end of the torsion bar and that a seat load acts on a position displaced from the torsion axis of the torsion bar It has an arm member having an action part and a torsional state measuring means for measuring the torsional state of the torsion bar, and can detect the seat load acting on the seating part of the seat based on the measurement result of the torsional state measuring means A seat load detecting device, comprising: a bearing member provided around one end of the torsion bar; and an auxiliary fixing member fixed to the bearing member, wherein the auxiliary fixing member is fixed It is characterized in that it is connected to the timber.

  The technical means taken in the present invention is characterized in that, as described in claim 2, the auxiliary fixing member is connected to the fixing member by welding.

  In addition to welding, the auxiliary fixing member may be connected to the fixing member by bolting, caulking, rivet fastening, or the like.

  Furthermore, the technical means taken in the present invention is characterized in that the bearing member is a ball bearing.

  In addition to the ball bearing, a roller bearing, a bush or a collar may be used as a bearing member.

  Further, the bearing member and the auxiliary fixing member may be fixed by welding. In addition to welding, the space between the bearing member and the auxiliary fixing member may be fixed by caulking or bolting.

  According to the first aspect of the present invention, a torsion bar having a horizontal torsion center, for example, a fixing member fixed to the floor side which is the vehicle body side and an arm member fixed to the vehicle seat side, for example, It is necessary to provide a bracket that extends horizontally compared to a conventional seat load detection device that uses a flat plate-shaped strain generating plate that extends in the horizontal direction. Therefore, it is possible to reduce the size and avoid problems such as interference with other devices added to the sheet. The twisted state of the torsion bar changes approximately proportionally to the seat load as compared to the bent state of the strain body in the conventional seat load detecting device. Therefore, the torsion bar measured by the twisted state measuring means The seat load can be accurately derived by a relatively simple calculation based on the torsional state of the seat, and the ratio of the torsional state to the seat load can be set to be small so that it can correspond to a relatively wide range of seat loads. .

  In particular, when the occupant is seated extremely biased toward the corner of the seat, the generation of bending stress generated in the torsion bar by the bearing member and the auxiliary fixing member can be reduced. That is, for example, even if the occupant is seated with a bias toward the corner of the seat, if the bending stress acting on the torsion bar is reduced by the bearing member and the auxiliary fixing member, the rotational stress acts on the torsion bar greatly. . For this reason, the rotational stress which is not reduced by the influence of a bending stress arises in a torsion bar. An accurate seat load can be derived by performing a calculation based on the torsional state of the torsion bar using such rotational stress.

  Therefore, with the seat load detection device of the present invention, an accurate seat load can be measured regardless of the seated state of the occupant.

  According to the second aspect of the present invention, since the auxiliary fixing member is connected to the fixing member by welding, the auxiliary fixing member can be connected to the fixing member while adjusting the fixing position with respect to the bearing member.

  Furthermore, according to the invention described in claim 3, since the ball bearing is used as the bearing member, the bending stress generated in the torsion bar can be reliably reduced.

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

(Embodiment)
The seat load detection device 30 of the embodiment is attached to a vehicle seat 10 as shown in FIG. The seat 10 includes a seat cushion 10a as a seating portion and a seat back 10b. When an occupant is seated, the weight of the occupant acts on the seat cushion 10a as a seat load.

  The seat 10 is provided with seat load detection devices 30 for detecting the seat load acting on the seat cushion 10a at four positions on the front, rear, left and right of the seat 10, and the total load detected by each seat load detection device 30 is provided. Is detected as a seat load. The seat load detection device 30 is preferably arranged at the four locations as described above in consideration of the stability of the seat 10 and the like, but the number of arrangement and the arrangement location may be changed as appropriate. The seat load detection device 30 located on the front side of the seat 10 is covered with a tilt pan 10 c, and the tilt pan 10 c is connected to the cushion frame 11. The cushion frame 11 is made of a thin metal plate for weight reduction.

  A lower rail 13 is fixed to the floor 5 side of the vehicle, and the lower rail 13 holds the upper rail 12 in a slidable state.

  A fixing bracket (fixing member) of the seat load detection device 30 is fixed to the upper rail 12, while an arm bracket 32 (arm member) of the seat load detection device 30 is seat cushioned via a load acting portion 38a. It is connected to the cushion frame 11 in 10a.

  As shown in FIG. 2, the seat load detection device 30 includes a fixing bracket 31 as a fixing member fixed to the floor 5 side shown in FIG. In addition, a torsion bar 34 to which a fixed side end 34a, which is the upper center side of the fixed bracket 31, is fixed and has a horizontal twist axis O is also provided. Further, an arm as an arm member having a load acting portion 38a which is fixed to the arm side end portion 34b which is the other end side of the torsion bar 34 and where the seat load acts at a position displaced from the torsional axis O of the torsion bar 34. A bracket 32 is provided. Further, a twist state measuring means 50 for measuring the twist state of the torsion bar 34 is provided. And it is comprised so that a seat load may be detected based on the measurement result of the twist state measuring means 50. That is, when the seat load acts on the load acting portion 38a of the arm bracket 32, the torsion bar 34 is twisted according to the seat load. Therefore, the seat is based on the twist state measured by the twist state measuring means 50. The load can be detected.

  As shown in FIG. 3, a load pin 38 is screwed to the arm bracket 32 and a cylindrical limit pin 41 welded and fixed to the arm bracket 32. A bush 38b is provided around the load pin 38, and one end 42a of the indirect bracket 42 is swingably connected via the bush 38b. The cushion frame 11 is fastened and fixed by a pin 37 on the other end 42 b side of the indirect bracket 42. The position of the load pin 38 that connects the cushion frame 11 and the indirect bracket 42 to the arm bracket 32 becomes the load acting portion 38a on which the seat load acts.

  Here, in the load acting part 38 a or the load pin 38, when the center of engagement with the arm bracket 32 is a load center point, the distance from the arm bracket 32 to the load center point is the offset amount L. The offset amount L and the torsional strength of the torsion bar 34 shown in FIG. 2 are appropriately set in consideration of the stability of the sheet 10 shown in FIG.

  As shown in FIG. 4, the fixed bracket 31 is fixed to the upper rail 12 on the floor 5 side (see FIG. 1) with screws in a state of extending upward along the vertical plane, while the arm bracket 32 is In addition, it is fixed to the arm side end 34b of the torsion bar 34 in a state of extending sideways along the vertical plane. And the fixed bracket 31 and the arm bracket 32 are comprised by the plate-shaped object which opposes a horizontal direction mutually, The installation dimension in the thickness direction becomes comparatively small, Furthermore, it extends along a vertical surface. The shape is easy to attach to the arm bracket 32 and the upper rail 12.

  Further, a cylindrical member 36 is provided which is fixed at one end to the arm side end 34 b of the torsion bar 34 and surrounds the side surface of the torsion bar 34, and the arm bracket 32 is fixed to the other end of the cylindrical member 36. Yes.

  That is, by providing the cylindrical member 36, the distance between the fixing bracket 31 and the arm bracket 32 becomes shorter than the length of the torsion bar 34, and the installation dimension in the thickness direction of the fixing bracket 31 and the arm bracket 32 is further increased. Get smaller.

  Further, the inner surface of the cylindrical member 36 and the side surface of the fixed side end portion 34a of the torsion bar 34 are disposed in a loosely fitted state, and the inner surface of the cylindrical member 36 and the side surface of the fixed side end portion 34a of the torsion bar 34 are arranged. As a result of the contact, excessive bending of the torsion bar 34 is suppressed. Since the inner surface of the cylindrical member 36 and the fixed side end 34a of the torsion bar 34 are each circular, it is easy to process them so that they fit together in a loosely fitted state.

  The torsion bar 34 has a torsion part 34c in which torsion due to a seat load occurs. Further, by providing the torsion bar 34 with the twisted portion 34c, an unstable factor such as a change in the twisted state of the torsion bar 34 due to welding or the like when the torsion bar 34 is fixed to the fixing bracket 31 or the arm bracket 32 is removed. Thus, the torsion bar 34 can be accurately and stably twisted with respect to the seat load.

  Although not shown, the torsion portion 34c of the torsion bar 34 is preferably formed to have a cross-shaped cross section that protrudes in the vertical direction and the horizontal direction. That is, the cross-section of the torsion bar 34 is formed of elements having cross-shaped cross-sectional shapes having mutually different cross-sectional secondary moments in a plurality of directions perpendicular to the torsion axis O, and further has the cross-shaped cross-section. The element is formed such that the cross-sectional secondary moment is maximized in a predetermined direction perpendicular to the torsional axis O, and the cross-sectional secondary moment is discontinuous in the circumferential direction around the torsional axis O. Therefore, the torsion bar 34 having such a cross-sectional shape has a relatively low torsional rigidity although the bending rigidity is high, and the torsion bar 34 can be satisfactorily twisted with respect to the seat load. Since it has difficult characteristics, it is possible to suppress damage of the torsion bar 34 due to bending and a decrease in detection accuracy of the seat load.

  Further, the torsion portion 34c of the torsion bar 34 has an action direction of the seat load, that is, a moment of inertia of the section along the vertical direction is larger than a moment of inertia of the section along the direction intersecting the action direction. It becomes difficult to bend.

  Further, in the cross-shaped cross section of the twisted portion 34c of the torsion bar 34, the width in the vertical direction may be the same as the width in the horizontal direction. For example, the width in the vertical direction is greater than the width in the horizontal direction. Also, the bending of the torsion bar 34 can be further suppressed.

  In addition, the cross-sectional shape of the twisted portion 34c of the torsion bar 34 can adopt any shape such as a circle, an ellipse, and a rectangle in addition to the cross shape as described above. Further, the twisted portion 34c of the torsion bar 34 can be Further, it may be configured by a plurality of rod-like bodies arranged in the vertical direction or the like, and the cross-sectional shape thereof may be a shape composed of a plurality of element parts spaced apart from each other.

  In particular, as shown in FIGS. 2 and 4, a ball bearing 60 as a bearing member is provided around one end side (tip side) of the torsion bar 34. The ball bearing 60 is fitted into the outer periphery of the cylindrical member 36 of the torsion bar 34 by press fitting. The position of the ball bearing 60 can be adjusted to a position where bending stress is likely to occur in the torsion bar 34. As the bearing member, a bush, a collar or the like can be adopted. Such bushes and collars may be made of metal, wood or resin, and are preferably coated with grease, lubricating oil, or the like. The upper side of an auxiliary fixing bracket 61 as an auxiliary fixing member is fixed to the outer periphery of the ball bearing 60. The auxiliary fixing bracket 61 is fitted into the outer periphery of the ball bearing 60 by press fitting and then fixed by welding. The lower side of the auxiliary fixing bracket 61 is fixed to the fixing bracket 60 by welding. In this way, the auxiliary fixing bracket 61 is connected to the fixing bracket 60.

  As shown in FIG. 2, the torsional state measuring means 50 is a displacement that measures the displacement of the arm bracket 32 around the torsional axis O relative to the fixed bracket 31 as a torsional state at a position away from the torsional axis O of the torsion bar 34. The displacement sensor 50a includes a magnet 52 fixed to the arm bracket 32 side, and a Hall element 51 that faces the magnet 52 and is fixed to the fixed bracket 31 side. The Hall element 51 having electrical connection with the outside such as an output terminal is provided on the side of the fixed bracket 31 that is not displaced, and the magnet 52 having no electrical connection with the outside is provided on the side of the arm bracket 32 that is displaced. The magnet 52 may be provided on the fixed bracket 31 side, and the hall element 51 may be provided on the arm bracket 32 side.

  In the seat load detection device 10 configured as described above, when the occupant sits on the seat 10 of FIG. 1, the seat load is detected as follows.

  That is, stress is generated in the fixed bracket 31 due to the weight of the occupant. When the arm bracket 32 is displaced about the torsional axis O with respect to the fixed bracket 31, the magnet 52 is displaced with respect to the hall element 51, so that the magnetic flux density measured by the hall element 51 is equal to the displacement amount. On the other hand, it changes approximately proportionally. Therefore, the magnetic flux density is measured as the displacement by the hall element 51, and the seat load due to the weight of the occupant can be detected based on the displacement.

  Further, the magnet 52 and the hall element 51 of the displacement sensor 50a extend from the arm bracket 32 and the fixed bracket 31 so as to face each other in a direction perpendicular to the torsional axis O of the torsion bar 34. It is fixed to a bracket whose normal direction is a direction perpendicular to the lead twist axis O.

  That is, the displacement sensor 50a measures the displacement of the pair of facing surfaces facing each other with the direction perpendicular to the torsional axis O of the torsion bar 34 as the normal direction in each of the arm bracket 32 and the fixed bracket 31. The distance between the magnet 52 and the Hall element 51 is prevented from changing due to, for example, twisting of the arm bracket 32.

  For example, when the occupant is seated extremely biased toward the corner of the seat cushion 10a of the seat 10, the seat load is transmitted to the tilt pan 10c and the cushion frame 11 as shown in FIG. Then, the seat load is transmitted to the indirect bracket 42 via the pin 37. At this time, for example, when the occupant sits extremely biased, the cushion frame 11 (side surface of the cushion frame 11) bends outward or inward. If the cushion frame 11 is bent, the indirect bracket 42 is also bent outward or inward via the pins 37. Thus, if the indirect bracket 42 bends, the load pin 38 will be pulled. When the load pin 38 is pulled, the arm bracket 32 is also pulled, and bending stress is easily generated in the torsion bar 34 via the arm bracket 32 as shown in FIG. Further, when the arm bracket 32 is pulled, rotational stress is generated in the torsion bar 34 via the arm bracket 32. At that time, it is possible to reduce only the generation of bending stress generated in the torsion bar 34 by the ball bearing 60 and the auxiliary fixing plate 61 fixed to the torsion bar 34. For this reason, only the rotational stress is easily generated in the torsion bar 34 without being affected by the bending stress. An accurate seat load can be derived by performing a calculation based on the torsional state of the torsion bar using such rotational stress.

  Therefore, with the seat load detection device 30 of the embodiment, an accurate seat load can be measured regardless of the seated state of the occupant.

  If the seat load detection device 30 does not include the ball bearing 60 or the auxiliary fixing bracket 61, the following configuration is required.

  That is, as shown in FIG. 4, the displacement sensor 50a is arranged to measure the displacement of the arm bracket 32 relative to the fixed bracket 31 on a line that passes through the torsion center X0 of the torsion bar 34 and is perpendicular to the torsion axis O. There must be.

  That is, it is assumed that the arm bracket 32 rotates about the axis passing through the vicinity of the torsion center X0 and the vicinity of the torsion center X0 as the torsion bar 34 is bent by the seat load. Accordingly, the position at which the displacement sensor 50a measures the displacement is set on a line that passes through the torsion center X0 of the torsion bar 34 and is perpendicular to the torsion axis O, so that the displacement caused by the deflection of the torsion bar 34 at that position. Therefore, the displacement due to torsion of the torsion bar 34 can be accurately measured. The load acting portion 38a is also arranged on a line that passes through the torsion center X0 of the torsion bar 34 and is perpendicular to the torsion axis O, whereby the torsion bar 34 is bent by the seat load acting on the load acting portion 38a. Furthermore, the displacement at the measurement position of the displacement sensor 50a due to the bending can be suppressed.

  In this respect, if the seat load detection device 30 includes the ball bearing 60 and the auxiliary fixing bracket 61 as in the present embodiment, as shown in FIG. The same effect as described above can be obtained without being arranged on a line perpendicular to the twist axis O through X0. This is because bending of the torsion bar 34 due to the seat load acting on the load acting portion 38a is suppressed, and the torsional state of the torsion bar 34 can be measured in a wide range. In addition, since it is not necessary to limit the measurement position of the twisted state of the torsion bar 34, the size of the torsion bar 34 can be reduced.

1 is an overall side view of a sheet according to an embodiment. 1 is a perspective view of a seat load detection device according to an embodiment. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 1 according to the seat load detection device of the embodiment. FIG. 4 is a cross-sectional view taken along arrows IV-IV in FIG. 1 according to the seat load detection device of the embodiment. It is a cross-sectional view of the seat load detection device compared with the embodiment.

Explanation of symbols

5 ... Floor 31 ... Fixing bracket (fixing member)
34a ... Fixed side end O ... Twist axis 34 ... Torsion bar 34b ... Arm side end 38a ... Load acting part 32 ... Arm bracket (arm member)
50 ... Twist state measuring means 10 ... Seat 10a ... Seat cushion (sitting part)
10b ... Seat back (sitting part)
30 ... Seat load detection device 60 ... Ball bearing (bearing member)
61 ... Auxiliary fixing bracket (auxiliary fixing member)

Claims (3)

A fixing member fixed to the floor side, a torsion bar having a fixed side end fixed to the fixing member and having a horizontal twist axis, and an arm side which is the other end side of the torsion bar An arm member having a load acting portion that is fixed to an end and is displaced from the torsion axis of the torsion bar, and a seat load acts on the torsion bar; A seat load detection device capable of detecting the seat load acting on the seating portion of the seat based on the measurement result of the twist state measuring means,
A seat load detection comprising: a bearing member provided around one end of the torsion bar; and an auxiliary fixing member fixed to the bearing member, the auxiliary fixing member being connected to the fixing member. apparatus.   The seat load detection device according to claim 1, wherein the auxiliary fixing member is connected to the fixing member by welding.   The seat load detection device according to claim 1, wherein the bearing member is a ball bearing.

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