JP2021162588A - Load sensor - Google Patents

Abstract

To improve load resistance and measurement precision of a load sensor.SOLUTION: A lower rigid member 2 has a dent 2a. An upper rigid member 3 is disposed opposite to the lower rigid member 2. The upper rigid member 3 has a pressure receiving part 3c for receiving a load, a dent 3a corresponding to it positionally, and a projecting part 3b projecting from the dent 3a. An elastic plate 4 is clamped partially by the upper and lower rigid members 2, 3, and is flexible within an internal space formed by the dents 2a, 3a. An open end of the elastic plate 4 corresponds to the projecting part 3b positionally. A strain sensor 5 is provide in the elastic plate 4, and detects the amount of strain of the elastic plate 4 bent by operation of a load applied to the pressure receiving part 3b via the projecting part 3b.SELECTED DRAWING: Figure 1

Description

The present invention relates to a load sensor that measures a load received from the outside.

Conventionally, a load sensor that measures a load received from the outside is known. For example, Patent Document 1 discloses a load meter having two disc-shaped rigid plates, a plurality of disc-shaped elastic members, a disc-shaped pressure receiving plate, and a strain gauge. The two rigid plates are provided so as to be in contact with the object to be measured on one surface and to face each other so that the other surfaces are parallel to each other. One surface of each of the plurality of elastic members is fixed to the other surface of the rigid plate. The pressure receiving plate is sandwiched and fixed between the other surfaces of each elastic member. The strain gauge is fixed to the pressure receiving plate.

Japanese Patent No. 3001577

An object of the present invention is to improve the load bearing capacity and measurement accuracy of a load sensor.

In order to solve such a problem, the present invention provides a load sensor having a first rigid member, a second rigid member, an elastic plate material, and a strain sensor. The first rigid member has a first recessed portion. The second rigid member is arranged so as to face the first rigid member. Further, the second rigid member has a pressure receiving portion that receives a load, a second recessed portion that is positionedly corresponding to the pressure receiving portion, and a protruding portion that protrudes from the second depressed portion. The elastic plate material is partially sandwiched by the first rigid member and the second rigid member, and is flexible in the internal space formed by the first recessed portion and the second depressed portion. Further, the open end of the elastic plate material is positionedly corresponding to the protruding portion. The strain sensor is provided on the elastic plate material, and detects the amount of strain of the elastic plate material that is bent by the load applied to the pressure receiving portion acting through the protruding portion.

Here, in the present invention, a third rigid member arranged so as to surround the second rigid member and fixed to the first rigid member may be provided. The third rigid member projects laterally from around the upper portion toward the pressure receiving portion side and comes into contact with the upper surface of the second rigid member. In this case, it is preferable that the third rigid member is provided in the center of the upper portion thereof and has an opening facing the pressure receiving portion.

In the present invention, the pressure receiving portion may have a flat surface raised from the surface of the second rigid member. In this case, the horizontal cross-sectional area of the raised flat surface is preferably equal to or larger than the horizontal cross-sectional area of the internal space.

In the present invention, it is preferable that the strain sensor is provided on one side or both sides of the elastic plate material. Further, it is preferable that a plurality of the elastic plate materials are arranged point-symmetrically and at equal intervals with respect to the protruding portion.

In the present invention, a hollow spacer and a fastening member may be further provided. The spacer is attached to the first mounting hole provided in one of the first rigid member and the second rigid member. One end of the spacer extends until it reaches the facing surface of the first rigid member and the second rigid member, and the other end protrudes from the first mounting hole. The fastening member engages with the second mounting hole provided on the other of the first rigid member and the second rigid member via the spacer attached to the first mounting hole, and its axial force thereof. To fasten the first rigid member and the second rigid member. In this case, a ring-shaped elastic body may be further provided. This ring-shaped elastic body is provided on the outer peripheral side of a portion of the spacer that protrudes from the first mounting hole, and one end thereof is one of a first rigid member and a second rigid member. And the other end abuts with the head of the fastening member.

In the present invention, a plate-shaped elastic body may be further provided. The plate-shaped elastic body is provided between this portion and the elastic plate material along a portion of at least one of the first rigid member and the second rigid member that sandwiches the elastic plate material.

According to the present invention, since the second rigid member having high rigidity receives a load, the load bearing capacity can be improved. Further, instead of directly detecting the deformation of the second rigid member caused by the load, after converting this into the bending of the elastic plate material, the degree of this bending (strain amount) is detected by the strain sensor. By detecting the amount of strain of the elastic plate material that is flexible in the internal space, it is possible to improve the measurement accuracy of the load as compared with the case of directly detecting the amount of strain of the second rigid member.

Schematic diagram showing the deployed state of the load sensor according to the first embodiment Schematic diagram showing another example of the tip shape of the protrusion Cross-sectional view of the load sensor in the assembled state Top view showing an arrangement example of a plurality of elastic plates Top view showing the tip shapes of a plurality of elastic plates Schematic diagram of the upper rigid member according to the modified example Cross-sectional view of the load sensor according to the first modification Cross-sectional view of the load sensor according to the second modification Cross-sectional view of the load sensor according to the second embodiment Cross-sectional view in which the arrangement of the fastening members in the configuration of FIG. 9 is turned upside down. Cross-sectional view of the load sensor according to the modified example of the second embodiment Schematic diagram showing the deployed state of the load sensor according to the third embodiment

(First Embodiment)
FIG. 1 is a schematic view showing a deployed state of the load sensor according to the present embodiment. The load sensor 1 is mainly composed of upper and lower rigid members 2 and 3 constituting a housing, at least one elastic plate material 4, and at least one strain sensor 5, which are bolts, adhesives, or the like. Is integrated by. The load sensor 1 is used for measuring the load (force) applied to the upper rigid member 3.

The upper and lower rigid members 2 and 3 are made of a highly rigid material such as a steel material, and have a circular or square plate shape. The lower rigidity member 2 is a plate-shaped member and has a predetermined thickness in order to secure sufficient rigidity for practical use. The upper surface of the lower rigid member 2 is provided with a recessed portion 2a that is recessed downward in a stepped shape and has a circular or square opening shape.

On the other hand, the upper rigid member 3 has a plate shape corresponding to the lower rigid member 2, and has a sufficient thickness for the same reason as the lower rigid member 2. On the lower surface of the upper rigid member 3, a recessed portion 3a that is recessed upward in a stepped shape is provided. The depressed portion 3a is positionally corresponding to the depressed portion 2a on the lower rigid member 2 side, and has an opening shape similar to that of the depressed portion 2a. Further, at substantially the center of the depressed portion 3a, a protruding portion 3b protruding downward (vertically) from the top surface of the depressed portion 3a is provided.

The tip shape of the protruding portion 3b may be a flat shape as shown in the figure, or may be a curved surface shape (hemispherical shape) as shown in FIG. Further, a pressure receiving portion 3c that receives a load is provided on the upper surface of the upper rigid member 3. The pressure receiving portion 3c corresponds in position to the depressed portion 3b, and in the present embodiment, the pressure receiving portion 3c has a flat surface raised from the upper surface of the upper rigid member 3. Further, the horizontal cross-sectional area of the raised flat surface has a size equal to or larger than the horizontal cross-sectional area of the depressed portion 3b (internal space A described later), that is, equal to or larger than the depressed portion 3b. The larger the size of the pressure receiving portion 3c, the more the load bearing capacity and durability of the load sensor 1 can be improved.

The elastic plate material 4 is a flat plate-shaped elastic member, and is made of a metal material having higher elasticity than the rigid members 2 and 3. The elastic plate material 4 is interposed between the upper and lower rigid members 2 and 3. Further, the strain sensor 5 is provided on the elastic plate material 4 and detects the amount of strain of the elastic plate material 4. As the strain sensor 5, for example, a strain gauge that detects a change in resistance value according to expansion and contraction of the elastic plate material 4 can be used.

FIG. 3 is a schematic cross-sectional view of the load sensor 1 in the assembled state. The upper and lower rigid members 2 and 3 are arranged so as to face each other, and are integrated by an adhesive or a fastening member (bolt or the like). Further, one continuous internal space A is formed by facing the depressed portion 2a on the lower rigid member 2 side and the depressed portion 3a on the upper rigid member 3 side. A part of the elastic plate member 4 is sandwiched between the upper surface of the lower rigid member 2 and the lower surface of the upper rigid member 3, and the other portion faces the internal space A and extends in the horizontal direction. .. As a result, the elastic plate member 4 is held in a state of being flexible in the internal space A, that is, being able to bend in a vertical bow shape. The open end of the elastic plate member 4 is arranged so as to correspond in position with the protrusion 3b, in other words, to overlap the protrusion 3b at the top and bottom, and is in light contact with the protrusion 3b. Further, the strain sensor 5 is arranged at a portion of the elastic plate material 4 facing the internal space A.

Here, the strain sensor 5 is preferably attached to both sides of the elastic plate material 4 as shown in FIG. 1 from the viewpoint of improving the load measurement accuracy, but from the viewpoint of reducing the size of the load sensor 1, one of them is used. It may be attached only to the surface (upper surface or lower surface) of the.

At least one elastic plate material 4 is sufficient, but a plurality of elastic plate materials 4 may be used in order to improve the load detection accuracy. In this case, the plurality of elastic plate members 4 are preferably arranged point-symmetrically and at equal intervals with respect to the protruding portions 3b. For example, as shown in FIG. 4, when four elastic plate materials 4a to 4d are used, the open ends of the elastic plate materials 4a to 4d are arranged point-symmetrically so as to correspond to the protrusions 3b in position. It seems that each is arranged at equal intervals with a rotation angle of 90 degrees. Further, the tip shape of the elastic plate material 4 at the open end may be flat as shown in FIG. 4, but may be triangular as shown in FIG. By forming the triangular shape, the open ends of the plurality of elastic plate members 4 can be made closer to the vicinity of the protrusions 3b, so that the load detection accuracy can be further improved.

The mechanism by which the load sensor 1 measures the load is as follows. First, when the pressure receiving portion 3c receives a load, the upper rigid member 3 is deformed. As a result, the protruding portion 3b is pushed downward, and the open end of the elastic plate material 4 in contact with the protruding portion 3b is also pushed downward. As a result, the elastic plate material 4 facing the internal space A is bent and strained, and the strain amount is detected by the strain sensor 5. The amount of strain of the elastic plate member 4 has a correlation with the amount of displacement of the protruding portion 3b, that is, the amount of deformation of the upper rigid member 3, and this amount of deformation corresponds to the amount of load applied to the upper rigid member 3. Therefore, if the strain amount of the elastic plate material 4 is detected, the load amount is uniquely specified, so that the load can be measured.

As described above, according to the present embodiment, since the highly rigid upper rigid member 3 receives the load, the load bearing capacity can be improved. Further, instead of directly detecting the deformation of the upper rigid member 3 caused by the load, after converting this into the bending of the elastic plate material 4, the degree of this bending (strain amount) is detected by the strain sensor 5. By detecting the amount of strain of the elastic plate material 4 that is flexible in the internal space A, it is possible to improve the measurement accuracy of the load as compared with the case of directly detecting the amount of strain of the upper rigid member 3.

In the above-described embodiment, the pressure receiving portion 3c is defined as a flat surface raised from the surface of the upper rigid member 3 in order to improve the measurement accuracy. However, as shown in FIG. 6, the pressure receiving portion 3c is defined as a flat surface. In order to improve the load bearing capacity, the upper rigid member 3 may be flush with the surface.

Further, in the above-described embodiment, an example in which the housing of the load sensor 1 is composed of two rigid members 2 and 3 has been described, but as shown in the following modification, the housing is made of three or more rigid members. It may be configured.

FIG. 7 is a cross-sectional view of the load sensor according to the first modification. The load sensor 1A is provided with a lateral rigid member 6 in addition to the upper and lower rigid members 2 and 3 as members constituting the housing. The laterally rigid member 6 is arranged so as to surround the upper rigid member 3. The lower portion of the laterally rigid member 6 is fixed to the upper surface of the lower rigid member 2 projecting laterally from the periphery of the upper rigid member 3 with bolts, adhesives, or the like. Further, a protruding portion 6a is provided around the upper portion of the laterally rigid member 6. The protruding portion 6a projects laterally toward the pressure receiving portion 3c side and extends, and by abutting with the upper surface of the upper rigid member 3, the displacement of the upper rigid member 3 is regulated. Further, an opening 6b is provided in the center of the upper portion of the laterally rigid member 6, and the shape of the opening is defined by the continuous tip of the protruding portion 6a. A raised pressure receiving portion 3c faces the opening 6b. Since the other points are the same as those in the above-described embodiment, the same reference numerals are given and the description thereof will be omitted here.

FIG. 8 is a cross-sectional view of the load sensor according to the second modification. The difference between the load sensor 1B and the load sensor 1A shown in FIG. 7 is that the lateral rigidity member 6 extends to the lower surface of the load sensor 1B (lower rigidity member 2), and only the upper rigidity member 3 is used. The point is that the lower rigid member 2 is also arranged so as to surround it. The lateral rigid member 6 and the lower rigid member 2 are fixed to each other by bolts, adhesives, or the like. Since the other points are the same as those of the load sensor 1A shown in FIG. 7, the same reference numerals are given and the description thereof will be omitted here.

(Second Embodiment)
Next, as a second embodiment, a fastening structure of the constituent members 2 and 3 suitable for the load sensor 1 (including various modified examples; the same applies hereinafter) will be described. FIG. 9 is a cross-sectional view of the load sensor according to the second embodiment, and shows a cross-sectional state seen from a viewpoint different from that of FIG. 1 and the like. In the load sensor 1C, the upper and lower rigid members 2 and 3 are fastened and fixed by using a hollow cylindrical spacer 7 and a fastening member 8 such as a bolt. The same members as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted here. This point is the same for the third embodiment.

Specifically, the lower rigid member 2 is provided with a mounting hole 2b in which a screw groove is formed. Further, the upper rigid member 3 is provided with a recess 3d and a mounting hole 3e that are positionally corresponding to the mounting hole 2b. The recess 3d is recessed with respect to the flat upper surface of the upper rigid member 3 and has a diameter and a depth capable of accommodating the head portion 8a (for example, a diameter of 9 mm) of the fastening member 8. Further, the mounting hole 3e penetrates vertically between the bottom portion of the recess 3d and the lower surface of the upper rigid member 3, and is formed to have a diameter larger than that of the mounting hole 2b. On the other hand, the spacer 7 is made of metal, resin, or the like, and has a height larger than the depth of the mounting hole 3e. The spacer 7 is mounted in the large diameter mounting hole 3e without reaching the small diameter mounting hole 2b. In this state, one end (lower end) of the spacer reaches the stepped portion of the two mounting holes 2b and 3e due to the difference in diameter, in other words, the facing surfaces of the upper and lower rigid members 2 and 3. Along with extending, the other end (upper end) protrudes upward by a predetermined height from the upper opening of the mounting hole 3e.

The fastening member 8 inserted from above penetrates the hollow portion of the spacer 7 attached to the attachment hole 3e and engages only with the attachment hole 2b in which the screw groove is formed. As a result, the upper and lower rigid members 2 and 3 are integrated by the axial force of the fastening member 8 housed in the recess 3d. Here, the axial force means a force at which the fastening member 8 that is pulled in the axial direction and slightly extended when the fastening member 8 is tightened tries to return to its original position, and is a force that fixes the upper and lower rigid members 2 and 3. Acts as. In this way, the spacer 7 prevents the head portion 8a of the fastening member 8 from directly contacting the upper rigid member 3, so that the upper and lower rigid members do not apply the axial force of the fastening member 8 to the upper rigid member 3. A few are fixed.

As shown in FIG. 10, the arrangement of the fastening members 8 is turned upside down, and the fastening members 8 inserted from below fix the upper and lower rigid members 2 and 3 without applying an axial force to the lower rigid member 2. You may.

As described above, according to the present embodiment, the spacer 7 is attached to one of the upper and lower rigid members 2 and 3, and the end portion of the spacer 7 is extended until it reaches the facing surface of the rigid members 2 and 3. The other end is projected from the mounting hole 3e. By interposing such a spacer 7, the upper and lower rigid members 2 and 3 are fastened without applying the axial force of the fastening member 8 to the rigid member (for example, the rigid member 3) on the side to which the spacer 7 is attached. It becomes possible to fix at 8.

As shown in FIG. 11, as a modification of the second embodiment, a ring-shaped elasticity is formed on a part of the spacer 7, more specifically, on the outer peripheral side of the portion protruding from the upper opening of the mounting hole 3e. A body 9 (for example, outer diameter 11.5 mm, inner diameter 8.5 mm, height 0.5 mm) may be interposed. The elastic body 9 may be formed of an elastic material such as rubber or silicon, or may have a spring force such as a spring washer. One end of the elastic body 9 is in contact with the upper rigid member 3 (lower rigid member 2 in the configuration of FIG. 10), and the other end is in contact with the head 8a of the fastening member 8 to sandwich the elastic body 9. Shrinks and deforms. The restoring force of the deformed elastic body 9 makes it possible to reduce rattling between members derived from the space B as shown in FIGS. 9 and 10.

(Third Embodiment)
Next, as a third embodiment, an example in which a plate-shaped elastic body is interposed in the load sensor 1 will be described. FIG. 12 is a cross-sectional view showing a deployed state of the load sensor according to the third embodiment. In this load sensor 1D, a plurality of plate-shaped elastic bodies 10 are provided along a part of the upper and lower rigid members 2 and 3, that is, a portion for sandwiching the elastic plate member 4 (hereinafter referred to as “holding portion”). There is. The elastic body 10 is formed of an elastic material such as rubber or silicon. By interposing the elastic body 10 instead of directly sandwiching the elastic plate member 4 between the upper and lower rigid members 2 and 3, it is possible to reduce the restraint of the rigid member (for example, the upper rigid member 3) due to the axial force of the fastening member 8. At the same time, the influence of the deformation of the rigid member on the elastic plate material 4 can be reduced.

The plate-shaped elastic body 10 may be provided not on both of the upper and lower rigid members 2 and 3, but on only one of them. Further, the plate-shaped elastic body 10 may be provided on a part of the holding portion, but it is possible to obtain a higher effect when the plate-shaped elastic body 10 is provided on the entire surface of the holding portion as shown in FIG.

1,1A to 1D Load sensor 2 Lower rigid member 2a Depressed part 2b Mounting hole 3 Upper rigid member 3a Depressed part 3b Protruding part 3c Pressure receiving part 3d Recessed part 3e Mounting hole 4, 4a to 4d Elastic plate material 5 Strain sensor 6 Lateral rigid member 6a Projection 6b Opening 7 Spacer 8 Fastening member 8a Head 9 Ring-shaped elastic body 10 Plate-shaped elastic body

Claims (10)

In the load sensor
A first rigid member having a first recess and
A pressure receiving portion that is arranged so as to face the first rigid member and receives a load, a second recessed portion that is positionedly corresponding to the pressure receiving portion, and a protruding portion that protrudes from the second depressed portion. A second rigid member having and
A part is sandwiched by the first rigid member and the second rigid member, and is flexible and open in the internal space formed by the first recessed portion and the second depressed portion. An elastic plate whose ends correspond to the protrusions
A load provided on the elastic plate material and having a strain sensor for detecting the amount of strain of the elastic plate material that is bent by the load applied to the pressure receiving portion acting through the protruding portion. Sensor. Further having a third rigid member arranged so as to surround the second rigid member and fixed to the first rigid member.
The third rigid member according to claim 2, wherein the third rigid member projects laterally from around the upper portion thereof toward the pressure receiving portion side and has a protruding portion that abuts on the upper surface of the second rigid member. The load sensor according to claim 1. The load sensor according to claim 2, wherein the third rigid member is provided in the center of the upper portion thereof and has an opening facing the pressure receiving portion. The load sensor according to any one of claims 1 to 3, wherein the pressure receiving portion has a flat surface raised from the surface of the second rigid member. The load sensor according to claim 4, wherein the horizontal cross-sectional area of the raised flat surface is equal to or larger than the horizontal cross-sectional area of the internal space. The load sensor according to any one of claims 1 to 5, wherein the strain sensor is provided on one side or both sides of the elastic plate material. The load sensor according to any one of claims 1 to 5, wherein a plurality of the elastic plate materials are arranged point-symmetrically and at equal intervals with respect to the protruding portion. It is attached to a first mounting hole provided in one of the first rigid member and the second rigid member, and one end thereof is a first rigid member and the second rigid member. A hollow cylindrical spacer extending until it reaches the facing surface of the above, and the other end projecting from the first mounting hole.
Through the hollow hole of the spacer attached to the first mounting hole, the first rigid member and the second mounting hole provided on the other of the second rigid members are engaged with each other. The load sensor according to any one of claims 1 to 7, further comprising a fastening member for fastening the first rigid member and the second rigid member by the axial force. Provided on the outer peripheral side of a portion of the spacer that protrudes from the first mounting hole, one end abuts on one of the first rigid member and the second rigid member, and the other end. The load sensor according to claim 8, wherein the portion further has a ring-shaped elastic body that abuts on the head of the fastening member. A plate-shaped elastic body provided between the elastic plate material and the portion along the portion sandwiching the elastic plate material in at least one of the first rigid member and the second rigid member. The load sensor according to any one of claims 1 to 9, further comprising.

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