JP2005241610A - Crew load detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crew load detector whose load measurement errors are few, in spite of being small in size, low in height, and having a simple structure. <P>SOLUTION: The crew load detector is provided with a strain-sensing portion being a component for uniting a seat and a car body, and is composed of a beam-like strain element, two sheets of stiffening plates, strain gauges, ladder-shaped resistors, and gauge tabs; a circuit portion composed of a gauge input/output circuit, a terminal block, and input/output cables; and a wiring portion for connecting between the strain sensing portion and the circuit portion. In the detector, a first strain gauge forming an angle of approximately +45 degrees, with respect to the longitudinal direction of the beam-like strain element; and a second strain gauge forming an angle of approximately -45 degrees, with respect to the longitudinal direction of the beam-like strain element are arranged on a side surface of the beam-like strain element; a third strain gauge and a fourth strain gauge are arranged on its different side surface so as to be rotation-symmetric to the first and second strain gages; and a Wheatstone bridge circuit is formed by the use of the four strain gauges. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an occupant detection system for detecting an occupant's situation in order to appropriately deploy an airbag according to the physique and posture of the occupant, and in particular, a method for measuring the weight on a seat. The present invention relates to an occupant load detection device.

As a method of measuring the seat and the load on the seat, a system that measures the pressure distribution on the seat by arranging a number of pressure sensitive elements in the seat cushion has been commercialized, but the correct physique cannot be identified depending on the posture of the occupant There was a problem. Thus, in recent years, a method of installing a load detection device in the seat attachment device portion has been often employed. With this method, the weight of the occupant can be measured to some extent accurately regardless of the occupant posture and the seat position. However, because the products currently offered use the bending stress detection method, the measurement is likely to cause errors in measurement due to the effects of twisting, fulcrum movement, and horizontal load when the strain generating body is subjected to a load. In order to reduce the load, the mounting structure of the load detection device is complicated, and the shape of the strain body is complicated (Patent No. 3448810, No. 3468728). In addition, since the minute strain is amplified at a high magnification, there are problems such as zero point variation, large output drift due to temperature, which hinders measurement, and output characteristics vary from product to product. Is also sought. Japanese Patent Application Laid-Open No. 11-304579 and Japanese Patent Application Laid-Open No. 11-351952 show a mode in which a strain gauge is provided on the side surface of a strain generating body and a shear force is detected. Then, there is a problem that distortion due to torsion is also output.
Japanese Patent No. 3444810 Japanese Patent No. 3468728 JP-A-11-304579 JP 11-351952 A

  An object of the present invention is to provide an occupant load detection device that is small and has a low profile and a simple structure, and that has little load measurement error.

  In order to solve the above-described problem, an occupant detection device according to claim 1 has grid patterns for detecting biaxial shear stress on each of two side surfaces of a beam-shaped strain body, and the two-side grid pattern. Is characterized in that strain gauges are arranged so as to be asymmetric with each other, and a Wheatstone bridge circuit is constituted by a total of four-axis gauges. According to the first aspect of the present invention, since the value of the shear stress generated in the strain generating body does not change even if the fulcrum fixed state of the strain generating body is changed as the load increases, from no load to the rated load. Measurement errors such as output nonlinearity and hysteresis do not occur. In addition, since the shear stress distribution in the longitudinal direction of the strain generating body is uniform (the shear strain per unit length is uniform in any part of the longitudinal direction), output performance is affected even if there is a longitudinal attachment position error when attaching the gauge. do not do. Furthermore, by attaching a biaxial gauge for measuring shear stress to both sides of the strain-generating body and constructing a bridge circuit with these 4 gauges, even if tensile or compressive stress is applied to the gauge due to expansion and contraction of the strain-generating body due to temperature changes Canceled by the bridge circuit configuration, temperature effect is not output (self-temperature compensation function). Furthermore, according to the gauge arrangement and the bridge wiring according to the present invention, even if a load that twists the strain generating body is applied, the strain due to torsion is canceled by the bridge circuit and is not output.

  The occupant load detection device according to claim 2, wherein the beam-shaped strain body has two or more bolt through holes, a fulcrum that fastens only the vehicle body side, and a fulcrum that fastens only the seat side, A strain gauge is provided between the fulcrums, the shear strain at the place where the gauge is placed at the rated load is ± (300 to 2000) x 10-6, and the maximum bending stress generated on the upper and lower surfaces of the strained body at the maximum measured load is The tensile strength of the strain-generating material is 0.1 to 0.3, and the yield strength of the strain-generating material is 0.2 to 0.8. By selecting the material and dimensions of the strain generating body so as to fall within this claim range, both load durability and output securing can be achieved.

  The occupant load detection device according to claim 3 is characterized in that the beam-shaped strain generating body has a portion having a small cross section in part and a strain gauge on a side surface of the portion having a small cross section. According to the third aspect of the present invention, the strain distribution can be changed so that the strain is concentrated at a portion having a small cross-sectional area, and the output can be improved by arranging the strain gauge at the portion.

  In the occupant load detection device according to claim 4, the strain gauge provided on the side surface of the beam-shaped strain generating body has a ladder-like pattern whose resistance value can be adjusted, and this is continuously formed integrally with the same material as the strain gauge. It is characterized by being. According to the invention described in claim 5, when the zero balance of the bridge is adjusted, the resistance value of each of the two gauges is measured, and the ladder resistance of the gauge having the lower resistance value is cut to thereby increase the resistance value. It can be set to the same resistance value as the gauge. Since the inside of the bridge can be constituted only by resistors having the same resistance temperature coefficient, a load detection device with a small output temperature drift can be obtained. According to this method, the work can be greatly simplified as compared with a correction method in which a fixed resistor is inserted into a bridge that is generally performed.

  In the occupant load detection device according to claim 5, the strain gauge provided on the side surface of the beam-shaped strain body is a metal resistor, the thickness of the resistor is 0.2 to 6 μm, and the uniaxial gauge resistance Is 350 to 5000Ω. By using a high resistance gauge within the range described in claim 6, the gauge current can be kept small, so that the measurement stability is obtained without being affected by the heat generated by the gauge itself due to Joule heat. Moreover, since the high resistance gauge can be realized with a small area by setting the thickness of the resistor to be within the scope of the claims, it can be mounted even when the area of the shear surface of the strain generating body is small.

  The occupant load detection device according to claim 6, wherein the bridge circuit is formed on a circuit board disposed adjacent to the beam-shaped strain body, and a diameter between the gauge side terminal and the circuit side terminal is 0.1 to 0.4 mm. It is characterized by being bonded with aluminum wire. Since the strain gauge and the circuit wiring are connected by wire bonding, the reliability of the wiring is improved as compared with bonding by solder or the like.

  As described above, the present invention can measure with a simple structure in which biaxial shear strain gauges are arranged on both side surfaces of a beam-shaped strain body and a bridge circuit is wired, so that less errors can be measured. Can be made smaller and thinner than other products. Since the portion for fastening the seat and the vehicle body has a simple structure, it can be applied to various vehicle types and seat sizes.

  Hereinafter, an embodiment in which the present invention is applied to a vehicle seat and a vehicle body will be described with reference to the drawings.

  FIG. 22 shows an embodiment of the present invention.

  A metal sintered body was used as the strain generating body, and spring stainless steel was used as the reinforcing plate. The metal sintered body was produced by press-molding and sintering raw material powder having a composition of 3% Cr-0.5% Mo-0.3% C by weight and the balance substantially consisting of Fe. As a result, a sintered metal body having a density of 7.05 g / cm3, a longitudinal elastic modulus of 140 GPa, a yield strength of 320 MPa, and a tensile strength of 810 MPa was obtained. The shape of the metal sintered body was an I shape having a bolt fastening portion and a constricted portion as shown in FIG. The overall dimensions are 6mm thick, 20mm wide and 55mm long. The bolt fastening part has two Φ8.5mm bolt holes with a pitch of 30mm, and the width between the bolt holes is 4.0mm wide and 8mm long. A constricted part was provided. On the other hand, for the reinforcing plate, stainless steel SUS301-CSP 3 / 4H temper rolled material for spring was punched out with a press to obtain two reinforcing plates, an upper reinforcing plate and a lower reinforcing plate. The upper reinforcing plate is 27mm wide, 60mm long, and two Φ8.5mm bolt holes with a pitch of 30mm. There are two types of lower reinforcement plates: 27mm wide, 95mm long, and two Φ8.5mm bolt holes with a pitch of 30mm. Then, the strain body and the two reinforcing plates were overlapped and fixed with an adhesive to form a three-layer composite structure.

  Calculate the stress and strain generated in the material by the load from the longitudinal elastic modulus of the material, and calculate the overload safety factor from the material's yield strength and tensile strength values, and determine the appropriate strain body and reinforcement plate dimensions. Asked. In the configuration of FIG. 22, the maximum strain generated in the strain body under the rated load of 100 kg is approximately 750 × 10−6, the strain factor safety factor is 1.9 and the reinforcement plate safety factor is 1.5 when the overload is 500 kg. It was.

  Although the example of the sintered body of the Fe-based alloy is shown in the embodiment as the material of the strain generating body, it can be made of an aluminum alloy. In the embodiment, the reinforcing plate is made of stainless steel for springs, but can be made of steel or non-ferrous rolled material. However, the material of the reinforcing plate is preferably a material having a longitudinal elastic modulus equal to or higher than that of the strain-generating material. Specifically, it is preferable to use a material having a longitudinal elastic modulus of 30 to 180 GPa for the strain body and a material 1.0 to 3.5 times the longitudinal elastic coefficient of the strain body for the reinforcing plate. If the elastic modulus of the reinforcing plate material is smaller than the longitudinal elastic modulus of the strain-generating body material, the stress applied to the strain-generating body will increase, so the strain output will improve, but it will pull on the reinforcing plate and the strain-generating body at an overload of 500 kg. Since stress exceeding the strength is applied, the function as a fastening part is not satisfied.

  A strain gauge is a metal resistance foil obtained by rolling an alloy having a composition of 20% Cr-2.8% Al-2.0% Cu with the balance substantially consisting of Ni to a thickness of 5 μm, and a polyimide film with a thickness of 25 μm. Bonded with thermosetting adhesive, and using this, as shown in Fig. 15, two gauges R1 and R2 with different sensitive axis directions are provided, ladder resistance is attached to the gauges, and wiring is connected. A pattern having a gauge tab for use was formed by a photolithography process. When a strain gauge pattern is formed from a metal resistance foil, one gauge axis direction is substantially + θ in the resistance foil rolling direction, as shown in FIG. The other gauge axis direction was formed so as to form approximately -θ in the resistance foil rolling direction.

  Ladder resistance is formed so that it can be adjusted in the range of 0.2 to 50Ω, and the resistance value between the gauge tabs including the ladder resistance is approximately 1000Ω, and the difference between the two gauge resistance values is within 0.2Ω. Produced. In addition, two biaxial gauges with R1 and R2 and rotationally symmetric biaxial gauges with R3 and R4, and similar ladder resistors and gauge tabs for wiring connection were created. These two types of biaxial strain gauges were bonded to the two side surfaces of the strain generating body with a thermosetting adhesive, respectively. Further, two reinforcing plates were laminated and fixed with an adhesive.

  Then, on the lower reinforcing plate, the printed circuit board on which the circuit components were mounted was bonded and fixed to the portion where there was no strain generating body. On the circuit board, an amplifier (op-amp), offset voltage shift circuit, sensitivity correction circuit, AD converter, noise filter, and other circuit components necessary for signal processing are mounted, and the strain generator side of the circuit is connected to the gauge by wiring. A terminal block was installed.

  FIG. 1 shows the overall configuration of a state in which an occupant load detection device according to the present invention is attached to a vehicle seat and a vehicle body. The seat has a structure that can slide back and forth on the seat rail, and has a reclining structure in which the backrest moves back and forth. The occupant load detection device is attached under the two seat seat rails, one for the front and one for the rear per rail, and a total of four on the seat. The load on the seat can be obtained by calculating the sum of each measurement value using four load detection devices. Load measurement is possible by using a load detection device capable of detecting both the gravity direction load and the gravity reverse direction load regardless of the seating position and posture, the seat back, and the seat slide. The load on the seat can be detected even in a dynamic environment when the vehicle is running by repeatedly taking in the measurement data of the four load detection devices in a short cycle.

  2 and 3 show the mounting structure of the occupant load detection device. One fulcrum of the occupant load detection device is fixed to the seat rail of the seat, and the other fulcrum is fixed to the vehicle body bracket. Since there is a gap between the fixed part of the seat rail and the vehicle body and there is a gap between the fixed part of the vehicle and the seat rail, the vehicle body and the seat are fastened by a beam-shaped occupant load detection device. Has been. When an excessive load is applied to the sheet, this gap is eliminated and the sheet can function as a stopper. The occupant load detection device may have a structure that is mounted on the body bracket as shown in FIG. 2, or may be a structure that is mounted under the body bracket as shown in FIG. According to the present invention, if the tightening torque of the bolt is managed, the occupant load detection device can be easily attached to the vehicle body and the seat and with less variation in fastening strength. When fixing the occupant load detection device between the vehicle body and the seat rail, bolts, nuts, and washers with a strength category equivalent to 10.9 or higher are used to stabilize the fulcrum fixing conditions and to obtain output linearity due to the load. It is done.

  FIG. 4 shows the configuration of the occupant load detection device. The strain generating body is provided with a load fulcrum and a round hole for penetrating a bolt to be a load point, and strain gauges are disposed on two surfaces having no round hole in the longitudinal direction. The two surfaces having no round holes in the longitudinal direction are surfaces on which shear stress occurs when a load is applied, that is, shear surfaces. The strain gauge includes a biaxial grid on one side of the shear surface, and each axis forms approximately 45 degrees in the longitudinal direction. By arranging a strain gauge having a biaxial grid forming approximately 45 degrees in the longitudinal direction of the strain generating body, the shear strain can be efficiently measured. The biaxial grid may be arranged on the shear plane as “<<” or “>>” or “\\\ ///”.

  The strain gauge is provided with 2 grids on one side of the shear surface of the strain generating body and 4 grids on both sides. These 4 grids are wired with lead wires so as to form a Wheatstone bridge (FIG. 5). In each grid, the resistors are formed in a folded pattern by photolithography using thin lines so that they have substantially the same resistance value. When a load is applied to a load point, the grid arranged to receive a positive shear stress increases its resistance value due to a tensile stress, and the grid arranged to receive a negative shear stress has a resistance value due to a compressive stress. Lower (Figure 6). In response to the load, the bridge circuit is assembled so that the grid portion where the resistance value increases becomes the opposite sides of the bridge circuit, and the grid portion where the resistance value decreases becomes the opposite sides of the bridge circuit. When an input voltage is applied to the bridge circuit, a voltage is output according to the magnitude of the load. Therefore, the load can be measured by calibrating the relationship between the load value and the output.

  FIGS. 7 and 8 show another configuration for the mounting structure shown in FIGS. Even in this configuration, the strain hole has a round hole serving as a fulcrum of the strain generating body and a load point, and a strain gauge, but the round hole and the strain gauge are arranged on the same plane. In this configuration, the vehicle body side frame and the load detection device, and the bolt for fastening the load detection device and the seat rail penetrate substantially horizontally with the vehicle body. Also with this configuration, the strain body is distorted by the sheet load, and the amount of strain is detected as a shear strain.

  In any of FIGS. 2, 3, 7, and 8, the distribution of shear stress (strain) is constant in the longitudinal direction of the strain generating body as shown in FIG. If the load W is constant, the same measurement value can be obtained no matter where the shear strain is detected in the longitudinal direction of the strain generating body. Further, even if the position of the fulcrum varies when the load detection device is fastened with a bolt or washer, or the position of the fulcrum moves during use, the shear stress does not change if the load W is constant. FIG. 10 shows a method of detecting a bending stress (strain) in which strain gauges are arranged on the front and back surfaces of a plate-like strain body that has been conventionally employed. In this case, a bending moment distribution is generated, and therefore, depending on the position in the longitudinal direction. The stress applied to the strain body is different. Furthermore, in the case of the configuration shown in FIG. 10, the stress changes due to the influence of variations in the fastening positions of the bolts and washers. Therefore, there is a problem that load detection is not properly performed because of the influence of the deviation of the position where the gauge is attached and the variation in the distance between the fulcrums. In order to avoid such a problem, it is necessary to adopt an extremely troublesome fastening direction such as riveting a fulcrum or welding, or to increase the distance between fulcrums as an S-shaped (Z-shaped) strain generator. It was necessary to devise such as keeping constant (FIG. 11). According to the strain-generating body structure according to the present invention, it is possible to realize an occupant load detection device with a small measurement error by simply fixing a strain-generating body having a simple structure with a bolt.

  FIG. 12 shows a measurement example according to the present invention. A human sits on a seat with four load detection devices attached, and the occupant load is measured. Even when the occupant changed the seating position on the seat and changed the center of gravity, the total output values of the four load detection devices were almost the same. Here, if the measurement data for each load detection device is taken individually, it is possible to recognize the state of the occupant's posture. FIG. 13 shows the measurement results obtained by changing the seat position and the reclining state in a normal posture. When several passengers with different weights were evaluated, almost correct load measurement was performed without being affected by the condition of the seat. FIG. 14 shows load measurement results when the vehicle is stationary and when the vehicle is traveling. It has been confirmed that an almost correct load can be obtained by averaging the measured values within a certain time even in a dynamic state. Therefore, according to the occupant load detection device of the present invention, it is possible to accurately identify the occupant's posture and physique.

  FIG. 15 shows a ladder resistance pattern for adjusting the resistance of a strain gauge according to the present invention. It is created by patterning from the same resistor material at once by photolithography. When a resistance value difference between the biaxial grids occurs, the biaxial resistance values can be made uniform by cutting a predetermined ladder portion according to the magnitude of the difference. As a method of aligning the resistance value of each gauge in the bridge, there is a method of adding a constantan wire or nichrome wire to one side of the bridge circuit where the resistance is low, but this method is easier to implement and automates the correction work. Is also possible. According to this aspect, it is possible to easily obtain an occupant load detection device with a small bridge offset voltage.

  As shown in FIG. 16, the strain generating body can be increased in the output value due to the load by reducing a part of the cross section and disposing a strain gauge in a portion having a small cross section. As a method of reducing the cross-sectional area, there is a method of dividing the cross-section into two by opening a window in the center, but it is preferable to make one cross-section as shown in FIG.

  In addition, the strain generating body may have a composite laminated structure. FIG. 17 shows a structure in which stainless steel plates for springs are stacked on two upper and lower surfaces of an aluminum alloy strain body. According to this structure, it is possible to reduce the weight while maintaining the load durability and the output characteristics equivalent to the case where the strain body is composed of only steel or stainless steel. FIG. 18 shows a structure in which a sintered alloy strain body having a portion having a small cross section in part and a stainless steel plate for springs stacked on top and bottom thereof. Even in such a structure, it is possible to increase an output value due to a load by disposing a strain gauge in a portion having a small cross section. Even a complicated shape with a small cross section at the center of the strain body can be easily manufactured by extrusion molding of aluminum or sintering powder, and the stainless steel plate can also be easily punched by pressing, so it is efficient. Can be produced.

  The load measurement results of these examples are shown in FIG.

  When fixing a car seat with four fastening parts, even if a load of 500 kg per place is applied, destruction is not permitted, and measurement performance is not allowed to deteriorate within a load of up to 150 kg. On the other hand, when trying to obtain a resolution of 1 kg or less in load measurement, it is preferable to secure a strain output of about 300 × 10 −6 or more. If it is set as the structure by the claim of this invention, the conflicting request | requirement of load durability ensuring and distortion output improvement can be satisfied.

FIG. 20 is a grid pattern of a biaxial strain gauge disposed on one side surface of the beam-shaped strain body. This gauge was manufactured by the method described below. A foil of 20% Cr-2.8% Al-2.0% Cu in weight ratio, which is made of the remaining Ni and rolled to a thickness of 5μm, is bonded to a polyimide film with a thickness of 12.5μm using an adhesive, and this is photolithography A gauge pattern having a resistance value of 1000Ω was formed by the above process. Of the two-axis gauge sensing parts arranged in close proximity, one gauge axis direction forms approximately + θ in the resistance foil rolling direction, and the other gauge axis direction forms approximately −θ in the resistance foil rolling direction. ing. If the grid directions of the biaxial gauges are patterned at the same angle with respect to the rolling direction, the resistance value and the temperature resistance coefficient between the biaxial gauges can be easily aligned. The smaller the difference in resistance between the two gauges, the smaller the bridge offset voltage, making the zero balance adjustment work easier or unnecessary. Further, the smaller the difference in temperature resistance coefficient between the two gauges, the smaller the drift due to the temperature of the output, and the measurement accuracy improves.
As another manufacturing method, after forming an insulating layer of polyimide resin, Al2O3, SiO2, etc. on the gauge placement surface of the strain generating body, a 20% Cr-Ni alloy thin film with a thickness of about 1 μm is formed on this surface by sputtering, It is also possible to obtain a gauge pattern with a gauge resistance of 4000Ω by photolithography.

  When the bridge voltage is 5V, when the gauge resistance is 350Ω or less, the current is 14mA or more, and the measured value becomes unstable due to the effect of resistor heating by Joule heat. When trying to form a smaller strain gauge with a resistance higher than 350Ω, use a Ni-Cr alloy with a high specific resistance, or use a constantan foil with a small thickness.

  FIG. 21 shows a wiring between a gauge side terminal and a circuit side terminal in order to electrically connect a circuit board having a circuit such as a bridge circuit wiring or an amplifier circuit and a strain generating body provided with a strain gauge. The state which performed wire bonding is shown. The resistor material of the gauge has poor solder wettability due to the oxide film on the surface, and it is difficult to connect lead wires with solder. Bonding aluminum wires with a diameter of 0.2 to 0.4 mm improves the reliability against dynamic environments such as vibration and impact in cars. Since the circuit board bonded to the reinforcing plate is located outside the plurality of fulcrums of the strain generating body, the circuit board may be inclined depending on the rigidity of the fastening member of the strain generating body. Therefore, the circuit side strain body fulcrum is fastened with the highly rigid vehicle body side. As a result, vibrations and impact loads applied to the circuit board are reduced.

  FIG. 22 shows a state where the circuit board is mounted and assembled on the strain-generating body and a plate-like board obtained by extending a part of the strain-generating body. The circuit is equipped with an amplifier (op-amp), offset voltage shift circuit, sensitivity correction circuit, AD converter, and other necessary components. Since it has various correction functions and signal conversion functions required when using a load transducer that uses a strain gauge, offset zero point adjustment and sensitivity adjustment are completed in advance, and there is little need for correction and performance variation is small. The load detection device can be assembled to the seat / body. The gauge mounting portion and the circuit component mounting portion are resin-molded, and the power supply line and signal line are drawn out by a cable with a connector. Since the gauge mounting portion and the circuit component mounting portion are molded with the same rubber-like elastic resin, the waterproofness required for the vehicle seat is satisfied, and the strain detection function by the gauge is not impaired. Further, since the signal can be digitized in the load detection device, it is less susceptible to electromagnetic noise.

It is a figure of the form attached to the vehicle body and a seat. It is the figure which showed the detail of the attaching part of FIG. It is a figure of another form attached to the vehicle body and a seat. It is the figure which showed the grid direction of the strain gauge arrange | positioned in a strain body. It is the figure which showed the wiring diagram of a gauge. It is the figure which showed the principle which outputs a shearing strain as a voltage. It is a figure of another form attached to the vehicle body and a seat. It is the figure which showed the detail of the attaching part of FIG. It is the figure which showed the stress distribution and moment distribution when a load is applied to the strain body. It is the figure which showed the stress distribution in the conventional bending strain detection system. It is the figure which showed the bending body structure of the conventional bending strain detection system, and its stress distribution. It is the figure which showed the result of having measured the passenger | crew's load attached to the seat and the vehicle body. It is the figure which showed the result of having changed and measured the position of the occupant's physique and the seat / backrest. It is the figure which showed the measurement result of the stop state of a car, and a driving state. It is the figure which showed the shape of the strain gauge which has ladder resistance for resistance adjustment. It is the figure which showed the strain body which has a location with a small cross section. It is the figure which showed the structure which laminated | stacked the several plate-shaped strain body. It is the figure which showed the laminated structure containing the strain body which has a location with a small cross section. This is the result of calculating strain output and load durability by changing the material and dimensions of the strain generating body. It is the figure which showed the grid pattern of the strain gauge. It is the figure which showed the wiring connection of a strain gauge and a circuit. It is the figure which showed the whole structure of the load detection apparatus. It is the figure which showed the output characteristic by a load. It is the figure which showed the temperature influence of a zero point.

Claims (6)

  A part that fastens the seat and the vehicle body. It is composed of a beam-shaped strain body, two reinforcing plates, a strain gauge, a ladder-like resistor, a strain sensing part consisting of a gauge tab, and a gauge input / output. In an occupant load detection device comprising a circuit portion comprising a circuit, a terminal block, and an input / output cable, and a wiring portion connecting the strain sensing portion and the circuit portion, an angle of approximately +45 degrees in the longitudinal direction of the beam-shaped strain generator And a second strain gauge having an angle of about −45 degrees in the longitudinal direction of the beam-like straining body are arranged on the side surface of the beam-like straining body, and the first strain gauge is arranged on the side surface of the beam-like straining body. An occupant load detection device, wherein a third and a fourth strain gauge are arranged so as to be rotationally symmetric with the second strain gauge and the second strain gauge, and a Wheatstone bridge circuit is constituted by four strain gauges.   The strain sensing part has a bolt hole for fastening only the vehicle body side and a bolt hole for fastening only the seat side, and the longitudinal elastic modulus of the strain body material is 30 to 180 GPa, and the top and bottom of the strain body The longitudinal elastic modulus of the reinforcing plate laminated on the reinforcing plate is 1.0 to 3.5 times that of the strain-generating material, and the first to fourth strain gauges are disposed on the side surfaces between the bolt holes of the strain-generating portion. The occupant load detection device according to Item 1.   The beam-shaped strain generating body has a concave constricted portion between bolt holes, and the first to fourth strain gauges are disposed on a side surface of the concave constricted portion. The occupant load detection device described in 1.   The occupant load according to any one of claims 1 to 3, wherein the strain gauge provided on the side surface of the beam-shaped strain generating body has a ladder-like resistance, and is formed integrally and continuously by the same material as the strain gauge. Detection device.   The strain gauge provided on the side surface of the beam-shaped strain generating body is characterized in that the resistor is a metal resistor, the thickness of the resistor is 0.2 to 6 μm, and one gauge resistance is 350 to 5000 Ω. The passenger | crew load detection apparatus of Claim 1 thru | or 4.   6. The occupant load detection device according to claim 1, wherein the gauge tab and the circuit side terminal are bonded with an aluminum wire having a diameter of 0.05 to 0.4 mm.