JP2000171312A - Load sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To property detect the presence or the absence of a load with a simple structure. SOLUTION: The load sensor optically detects the presence or the absence of a load. A light emitting part 33 and a light receiving part 34 are installed in cases 10, 20 made of an elastically deformable material. The load sensor is constituted such that when a load is applied to the cases 10, 20 in a direction nearly perpendicular to the light path from the light emitting part 33 to the light receiving part 34, the cases 10, 20 will be elastically deformed to block the light path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load sensor suitable for a seating sensor for a vehicle seat.

[0002]

2. Description of the Related Art Conventionally, as a load sensor for detecting the presence or absence of a load over a relatively large area, for example, a load sensor as disclosed in Japanese Patent Application Laid-Open No. 5-296709 is known. This sensor includes a pressure-sensitive conductive sheet 94 between an upper sheet 90 and a lower sheet 92, as shown in FIG.
Is sandwiched between the sheets. Upper sheet 90
A number of upper electrodes 96 extending in the vertical direction (depth direction in the figure) are arranged on the lower surface of the lower sheet 92, and a number of lower electrodes 98 extending in the horizontal direction (right and left direction in the figure) are arranged on the upper surface of the lower sheet 92. Have been. Then, for example, when a pressing load is applied to the upper sheet 90 from above, the pressure-sensitive conductive sheet 94 sandwiched between the electrodes 96 and 98 at the intersection of the upper electrode 96 and the lower electrode 98 applies pressure from above and below. In response, the resistance value changes from infinity to a finite value, and the presence or absence of a load can be recognized by a change in current accompanying the resistance value.

[0003]

In the load sensor having the above structure, a pressure-sensitive conductive material and a large number of electrodes must be used. In addition, it is necessary to form the pressure-sensitive conductive material into a sheet shape with high accuracy, and to accurately arrange each electrode at a predetermined position. Further, a complicated circuit is required to determine the presence or absence of pressure from the change in resistance of the pressure-sensitive conductive sheet 94. Therefore, the load sensor has a complicated structure as a whole and tends to be expensive, and is not suitable as a load sensor used for the purpose of simply detecting whether or not a predetermined load or more is applied, such as a seating sensor.

The present invention has been made in view of the above circumstances, and has as its object to provide a load sensor capable of accurately detecting whether or not a predetermined load or more is applied with a simple structure.

[0005]

As a means for solving the above problems, the present invention provides a light emitting section and a light receiving section for converting light emitted from the light emitting section into an electric signal. It is provided in a case made of a possible material, and the case is elastically deformed by applying a load to the case in a direction substantially orthogonal to the optical path from the light emitting unit to the light receiving unit, so that the optical path is blocked. It was done.

In this load sensor, when no more than a predetermined load is applied to the case and the case is in a non-deformed state or a state of small elastic deformation, the light emitted from the light emitting section reaches the light receiving section. On the other hand, when a load equal to or more than a predetermined value is applied to the case, the case elastically deforms and blocks the optical path, so that light from the light emitting unit does not reach the light receiving unit. Therefore, it is possible to accurately detect whether or not a load equal to or more than a predetermined value is acting on the case with a simple structure by the electric signal output from the light receiving unit.

In this sensor, the optical path from the light-emitting portion to the light-receiving portion may be directly blocked by the case itself. However, an elastically deformable tube is provided between the light-emitting portion and the light-receiving portion. Is configured so that light from the light emitting unit to the light receiving unit passes therethrough, and the tube is elastically deformed together with the case by applying a load in a direction substantially orthogonal to the light path, thereby blocking the light path. If this is the case, diffusion of light can be prevented by the tube, a better optical path can be formed more reliably, and the reliability of the sensor can be further improved.

Further, by providing the case with a pressing portion for locally pressing an intermediate portion of the tube along with the elastic deformation of the case to elastically deform the case, the sensitivity and reliability of the sensor can be further improved.

Further, if the pressing portion is provided at a plurality of positions on the tube or a plurality of sets of the light emitting portion and the light receiving portion are provided in the case, it is possible to detect the presence or absence of pressure reception over a wider area. For example, it is suitable for a seating sensor of an automobile seat.

Here, if a plurality of tube holding portions having tube fitting grooves into which the tubes are fitted are formed in the case, the tubes can be more stably fixed in the case. In this case, each pressing portion may be provided so as to press the position between the tube holding portions.

[0011]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG.

The load sensor shown here comprises a flat lower case 10 and a flat upper case 20, and these are stacked up and down to constitute the case according to the present invention.
Both cases 10 and 20 are formed of a material that can be elastically deformed (flexible), such as a synthetic resin or a synthetic rubber. As a specific material, foamed urethane or foamed EPDM is suitable.

As shown in FIG. 2, on the upper surface of the lower case 10, a plurality of (in the illustrated example, four in the vertical direction and two in the horizontal direction, a total of eight).
Projections 11A, 11B, 11C, 11D, 11E, 1
1F, 11G, and 11H are formed. A light emitting unit housing hole 13 is formed substantially at the center of the protrusions 11A and 11E at one end in the vertical direction, and the protrusion 11 at the other end in the vertical direction.
A light receiving portion storage hole 14 is formed at a substantially center of D and 11H. Then, as shown in FIG.
A light-emitting unit 33 composed of a light-emitting diode or the like is incorporated in 3, and a light-receiving unit 34 composed of a light-receiving element that receives light and converts it into an electric signal is incorporated in each light-receiving unit housing hole 14. The directions of the light emitting unit 33 and the light receiving unit 34 are set such that light is emitted from the light emitting unit 33 in the case vertical direction and received by the light receiving unit 34.

Each of the projecting portions 11A to 11H is formed with a tube fitting groove 15 for vertically connecting the light emitting portion housing hole 13 and the light receiving portion housing hole 14. The longitudinal elastic tubes 35 are fitted into the tube fitting grooves 15 arranged on the left side and the tube fitting grooves 15 arranged on the right side, respectively.

Each elastic tube 35 is formed in a long tubular shape by an elastically deformable material, and specific materials thereof include silicon rubber, EPM, EPDM,
A synthetic rubber such as urethane rubber, a relatively soft synthetic resin such as polyvinyl chloride, or the like is preferable. The elastic tube 35 is provided in the light emitting section 33 in the light emitting section housing hole 13.
The light receiving section 34 is disposed so as to connect the light receiving section 34 to the light receiving section 34 in the light receiving section housing hole 14, through which light from the light emitting section 33 to the light receiving section 34 passes.

Between the projection 11A and the projection 11E,
A rib 12A connecting these in the lateral direction is formed.
A rib 12B is formed between the protrusions 11D and 11H to connect them in the horizontal direction. Further, a rib 12C is formed in the center of the lower case 10 in the horizontal direction, extending from the rib 12B to the end of the case across the rib 12A in the vertical direction. A lead wire accommodating groove 16 is formed along the ribs 12A, 12B, and 12C, and a lead wire 36 connected to each of the light emitting unit 33 and the light receiving unit 34 is led out of the case 10 through the lead wire accommodating groove 16. Along with
The lead-out end is connected to each terminal of the connector 30.

FIG. 3 shows a state in which the upper case 20 is turned upside down (ie, a state in which the lower surface of the upper case 20 faces upward). A pair of left and right protruding portions 22A, 22B extending in the vertical direction and protruding downward (upward in FIG. 3) is formed at a substantially central portion in the horizontal direction of the upper case 20,
Next to the protrusion 22A, a plurality of protrusions 21 arranged in the vertical direction are provided.
A, 21B, and 21C are formed, and a plurality of protrusions 21E, 21F, and 21G arranged in the vertical direction also beside the protrusion 22B.
Are formed. When the upper case 20 is superimposed on the lower case 10, the protruding portion 22A enters between the rib 12C and the protruding portions 11A to 11D, and the protruding portion 22B forms the rib 12C and the protruding portions 11E to 11H. , The projection 21A enters between the projection 11A and the projection 11B, the projection 21B enters between the projection 11B and the projection 11C, and the projection 21C engages with the projection 11C. The projection 21D enters between the projection 11D and the projection 11E, the projection 21F enters between the projection 11F and the projection 11G, and the projection 21G enters between the projection 11F and the projection 11G. The position of each projection is set so as to enter between the projection 11G and the projection 11H.

Each projection 21A, 21B, 21C, 21
E, 21F, 21G, in the horizontal intermediate portion, that is, the portion located just above each elastic tube 35, these projecting portions 21A, 21B, 21C, 21E, 21F, 21
Pressing portions 23A, 23B, 23C, 23 one step lower than G
E, 23F and 23G are formed. These pressing parts 2
The height dimensions of 3A, 23B, 23C, 23E, 23F, and 23G are set so that the following operations can be obtained.

In this load sensor, cases 10, 2
When no load is applied to zero, that is, when the cases 10 and 20 are not elastically deformed, FIG.
And as shown in FIG. 5A, the pressing portions 23A, 23B,
Are positioned so as not to contact the elastic tube 35 or to lightly contact the upper surface of the elastic tube 35. Therefore, the elastic tube 35 is not pressed, and the elastic tube 35 is hardly elastically deformed. In this state, the light emitted from each light emitting section 33 reaches each light receiving section 34 through the elastic tube 35, and the light receiving section 34 receiving this light outputs an electric signal to the outside through the lead wire 36.

On the other hand, when a load equal to or more than a predetermined value is applied to the cases 10 and 20 from above (for example, when the occupant is seated on the seat with the seating sensor), the entire case receives the load and the entire case is as shown in FIG. As shown in FIG. 7B), the upper tube 20 is elastically deformed so that the pressing portions 23A, 23B,... Press the middle portion of the elastic tube 35 from above to crush it. As a result, the optical path from the light emitting section 33 to the light receiving section 34 is cut off, and the output of the electric signal from the light receiving section 34 to the outside is eliminated. Therefore, it can be determined whether or not a load equal to or greater than a predetermined value is acting on the basis of the presence or absence of the electric signal.

This load sensor does not require an expensive pressure-sensitive conductive sheet or a large number of electrodes as in the prior art, and has a simple structure in which the light-emitting portion and the light-receiving portion are incorporated in an elastically deformable case. Presence or absence can be accurately detected. Therefore, it is particularly suitable for a seating sensor or the like of an automobile seat.

However, the present invention can be widely applied irrespective of its specific use for the purpose of detecting the presence or absence of a predetermined load or more.

FIGS. 6 to 8 show a second embodiment. Here, in the lower case 10, the protrusions 11B, 11C, 11F, and 11H shown in the first embodiment are omitted, and each protrusion is also omitted in the upper case 20.

Even with such a simplified structure, the upper case is shifted from the undeformed state shown in FIG. 8A to the deformed state shown in FIG. It is possible to break the optical path by crushing the elastic tube 35 at the intermediate portion of 20. However, if the pressing portions 23A, 23B,... As shown in the first embodiment are formed in the case and the elastic tubes 35 are pressed locally by these pressing portions, the sensor sensitivity is improved. And the reliability can be further improved. Further, by forming the protruding portions 11B, 11C, 11F and 11G having the tube fitting grooves 15 shown in FIG.
The fixed state of the elastic tube 35 can be further stabilized.

In addition, the present invention can take the following embodiments.

In the present invention, the elastic tube 35 shown in each of the above embodiments is omitted, and the optical path from the light emitting section 33 to the light receiving section 34 is changed to a predetermined portion of the case (for example, the pressing sections 23A, 23B shown in FIG. 5). ,... Can be directly cut off. However, if the above-described elastic tube 35 is used, it is possible to prevent the diffusion of light from the light emitting unit 33 and to form the optical path to the light receiving unit 34 more reliably, thereby increasing the reliability of the sensor. There are advantages that can be increased.

In the present invention, regardless of the specific arrangement of the light-emitting unit and the light-receiving unit, they may be appropriately set according to the intended use and place of use. For example, as shown in FIG. 9 as a third embodiment, the light emitting sections 33 and the light receiving sections 34 may be arranged so that the optical paths run in the vertical and horizontal directions, or the optical paths are connected as shown in FIG. The light emitting units 33 and the light receiving units 34 may be arranged to cross each other. In the latter case, by providing a height difference between the optical paths, the elastic tube 35 shown in the first embodiment and the like can be used. When such a tube 35 is used, FIG.
The reliability of the sensor can be improved by providing the pressing portion 25 as shown by a two-dot chain line in FIG. 10 at a suitable position to locally press the middle part of the tube 35.

In the first embodiment, the lower case 1
0, the light emitting section 33, the light receiving section 34, and the elastic tube 35 are all incorporated, and the pressing sections 23A,... Are formed on the upper case 20. However, the upper section 20 may be upside down, or the sensor may be upright. It may be used. When a single light emitting unit and light receiving unit are used, the case may be formed in a long shape extending along the optical path.

[0029]

As described above, according to the present invention, the light-emitting portion and the light-receiving portion that receives light emitted from the light-emitting portion and converts the light into an electric signal are provided in a case made of an elastically deformable material.
When a load is applied to the case in a direction substantially perpendicular to the optical path from the light emitting unit to the light receiving unit, the case is elastically deformed to block the optical path. With a simple structure in which the unit and the light receiving unit are simply incorporated, there is an effect that it is possible to accurately detect whether or not a load equal to or more than a predetermined amount acts on the case.

[Brief description of the drawings]

FIG. 1 is a plan view seen through an upper case of a load sensor according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a lower case of the load sensor.

FIG. 3 is a perspective view showing an upper case of the load sensor.

4A is a cross-sectional view taken along the line AA of FIG. 1, and FIG.
1 is a sectional view taken along line BB of FIG. 1, and FIG. 2C is a sectional view taken along line CC of FIG.

5A is a cross-sectional view taken along the line DD of FIG. 1, and FIG. 5B is a cross-sectional view showing a state in which the entire case is bent and deformed from the state of FIG.

FIG. 6 is a perspective view showing a lower case of a load sensor according to a second embodiment of the present invention.

FIG. 7 is a perspective view showing an upper case of the load sensor of FIG. 6;

8A is a cross-sectional side view showing a state in which the load sensor of FIG. 6 is not deformed, and FIG. 8B is a cross-sectional view showing a state in which the entire case is bent and deformed from the state of FIG.

FIG. 9 is a schematic plan view of a load sensor according to a third embodiment of the present invention.

FIG. 10 is a schematic plan view of a load sensor according to a fourth embodiment of the present invention.

FIG. 11 is a diagram showing a schematic structure of a conventional load sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Lower case 11A-11H Projection part (tube holding part) 15 Tube fitting groove 20 Upper case 23A, 23B, 23C, 23E, 23F, 23G, 2
5 Pressing part 33 Light emitting part 34 Light receiving part 35 Elastic tube

Continued on the front page (72) Inventor Masahiro Kume 1-7-10 Kikuzumi, Minami-ku, Nagoya City, Aichi Prefecture Inside Harness Research Institute, Inc. (72) Inventor Masao Ito 1-7-10 Kikuzumi, Minami-ku, Nagoya City, Aichi Prefecture No. F-term in Harness Research Institute, Inc. (reference) 2F051 AA01 AB03 BA08

Claims (6)

[Claims] 1. A light-emitting portion and a light-receiving portion for receiving light emitted from the light-emitting portion and converting the light into an electric signal are provided in a case made of an elastically deformable material. A load sensor characterized in that the case is elastically deformed by applying a load in a direction substantially orthogonal to the optical path to the light receiving section, thereby blocking the optical path. 2. A load sensor according to claim 1, wherein an elastically deformable tube is provided between said light emitting portion and said light receiving portion, and light from said light emitting portion to said light receiving portion passes through said tube. A load applied in a direction substantially orthogonal to the optical path to elastically deform the tube together with the case to block the optical path. 3. The load sensor according to claim 2, wherein a pressing portion is provided inside the case to locally press an intermediate portion of the tube with the elastic deformation of the case to elastically deform the tube. Load sensor. 4. The load sensor according to claim 3, wherein the pressing portions are provided at a plurality of positions on the tube. 5. The load sensor according to claim 4, wherein a plurality of tube holding portions having a tube fitting groove into which the tube is fitted are formed in the case, and a position between the tube holding portions is pressed. A load sensor, wherein each pressing portion is disposed so as to perform a pressing operation. 6. The load sensor according to claim 1, wherein a plurality of sets of a light emitting unit and a light receiving unit are provided in the case.