JP7046333B2 - Load cell - Google Patents

Description

The present invention relates to a load cell for detecting a load, and more particularly to a load cell capable of detecting a load in a triaxial direction using carbon fibers such as CFRP.

At present, a strain gauge type load cell is generally widely used as a sensor for detecting a load. This strain gauge type load cell attaches a strain gauge to a strain-causing body made of a thin metal plate, forms a Wheatstone bridge using the strain gauge, and can detect the load by the electric signal output from the strain gauge. It is something like that. Such a strain gauge type load cell has the advantages of extremely high accuracy and little influence of temperature changes.

However, such a strain gauge type load cell has a drawback that it is costly and difficult to reduce because of its complicated structure.

On the other hand, a load cell in which a load is detected by using a conductive material such as carbon fiber has also been proposed. For example, in Patent Document 1 below, the load can be detected by paying attention to the change in electrical resistance when a load is applied to the carbon fiber, and as shown in FIG. 7, the movable plate 61 can be detected. It has been proposed that carbon fibers 62 are attached to the upper and lower parts of the carbon fiber 62 so that the load can be detected by the change in the electric resistance of the carbon fiber 62 pressed and pulled by the movement of the movable plate 61. According to such a load cell, since it is not necessary to provide a strain gauge or the like, there is an advantage that the load cell itself can be made small and the cost can be reduced.

Japanese Unexamined Patent Publication No. 57-191526

However, the load cell using the carbon fiber described in Patent Document 1 has the following problems.

That is, the load cell described in Patent Document 1 can detect only the load in the uniaxial direction along the working body 63. Therefore, when detecting a load in the three-axis direction, the load cell must be directed in three directions. However, when the load cell is directed in the three-axis direction in this way, there are three action elements 63 for applying the load. There is a problem that the load in the three axial directions acting at one point cannot be detected at the same time.

Further, in the load cell shown in Patent Document 1, the carbon fiber 62 is brought into contact with the movable plate 61 in a planar manner to detect an increase or decrease in electrical resistance, but when a load is applied to the working body 63, it is mechanically applied. There is a possibility that the movable plate 61 will be tilted due to the error and a load will be applied locally. However, when the carbon fiber 62 is locally loaded in this way, the pressure at that portion becomes stronger, so that the electric resistance is detected to be small. On the other hand, even if the load is the same, when they come into contact with each other in a plane, the pressure becomes small and the electric resistance becomes large. Therefore, even if the load is the same, different loads will be detected.

Therefore, the present invention has been made by paying attention to the above-mentioned problems, and is a load cell capable of detecting a load in three axial directions by using a conductive material such as carbon fiber and capable of detecting a load with high accuracy. The purpose is to provide.

That is, in order to solve the above problems, the present invention has an insert body inserted with a gap in the upper, lower, left and right sides between the case main body having a hole inside and the hole portion of the case main body, and an upper portion of the insert body. A working body configured by providing a flange body, a conductive material provided in a direction orthogonal to the inner wall of the hole portion, and an insertion direction of the hole portion as a normal line. The conductive material provided on the upper surface of the case body and the conductive material provided on the upper surface of the case body are sandwiched by being inserted toward the upper surface of the case body through the holes provided in the flange body. It is provided with a bolt to be pressed and a bolt to be inserted toward the insertion body through a hole provided on the side surface of the case body and to sandwich and press a conductive material provided on the inner wall of the case body. By pressing the respective conductive materials with the flange body and the insert body, the electric resistance of each of the conductive materials is changed to detect the load in the triaxial direction.

Further, in such an invention, a pair of upper and lower holes are provided on the inner wall of the hole so that the protrusion provided on the side surface of the insert is at an intermediate position, and the conductive material is pressed by the bolt. Let me do it .

According to the present invention, it is possible to simultaneously detect a load in three axial directions from a load acting on one actuator, and it is possible to simplify the structure and construct a load cell at low cost.

An exploded perspective view of a load cell according to an embodiment of the present invention. Schematic cross-sectional view in the same form The figure which shows the lower surface of the flange body in the same form. The figure which shows the relationship between the pressure of the carbon fiber and the resistance value in the same form. The figure which shows the load cell in another embodiment. The figure which shows the load cell in another embodiment. The figure which shows the load cell using the carbon fiber in the conventional example.

Hereinafter, the load cell 1 according to the embodiment of the present invention will be described.

The load cell 1 in this embodiment is designed so that a load can be detected by paying attention to a change in electrical resistance when a carbon fiber such as CFRP is pressed, and as shown in FIG. 1, a hole portion is provided inside. A pair of electrodes 52 (FIG. 2) are provided in the direction orthogonal to the case main body 2 having the 22, the action body 3 insertable into the hole portion 22 of the case main body 2, and the inner wall 21a of the hole portion 22. The conductive material 5 sandwiched between the working elements 3 and the upper surface 21b of the case body 2 is provided between the conductive material 5 and the conductive material 5 sandwiched between the pair of electrodes 52. Therefore, when a load is applied to one working body 3 in the triaxial direction, the load in the triaxial direction can be simultaneously detected based on the change in the electric resistance of the conductive material 5. Hereinafter, the load cell 1 in the present embodiment will be described in detail.

First, as shown in FIGS. 1 and 2, the case body 2 constituting the load cell 1 has a hole portion 22, and the action body 3 can be inserted into the hole portion 22. The hole portion 22 of the case body 2 has a circular cross section, and the upper surface 21b of the case body 2 has a flat surface.

The actuating body 3 inserted into the case main body 2 includes a columnar insert body 31 inserted into the hole portion 22 of the case main body 2 with a slight gap, and a flange body 32 provided on the upper portion of the insert body 31. Is configured to have. A hemispherical protrusion 33 is provided on the outer peripheral surface of the insertion body 31 in the orthogonal direction, and a hemispherical protrusion 33 is also provided on the lower surface of the flange body 32 at regular intervals (see FIG. 2). ). Then, these are made to press the conductive material 5 by the protrusion 33.

The conductive material 5 is composed of a conductive sheet 51 (see FIG. 2) whose electrical resistance changes by pressing and a pair of electrodes 52 that sandwich the conductive sheet 51, and is, for example, CFRP or the like. A carbon fiber sandwiched between thin metal plates is used. Among such carbon fibers, especially PAN-based carbon fibers are known to have a large change in electrical resistance when a pressing force or a tensile force is applied. Therefore, the load can be detected by sandwiching the carbon fiber between thin electrodes 52 and detecting the difference in electrical resistance. Here, the carbon fiber is sandwiched between the thin electrodes 52, but the case body 2 and the working body 3 are made of a non-conductive material (for example, ceramics), and the hemispherical protrusion 33 is made of metal. It may be configured to sandwich the conductive sheet 51.

Such a conductive material 5 is provided in a direction orthogonal to the inner wall 21a of the hole 22 of the case body 2 (XY axis direction) or on the upper surface 21b of the case body 2, and is 3 at the protrusion 33 of the action body 3. It is designed to be pressed in the axial direction. A cable (not shown) extends from the electrode 52 of the conductive material 5, and an electric resistance can be detected by applying a voltage to the electrode 52 so that a load can be detected.

By the way, when the change in the electric resistance of the conductive material 5 is detected in this way, as shown in FIG. 4, the resistance value changes to a non-linear state in the initial pressing state, and from the state where a constant pressing force is applied. The resistance value changes linearly. Therefore, in this embodiment, an offset portion is provided so that the resistance value can be detected in the region where the electric resistance changes linearly.

This offset portion makes it possible to detect the resistance value in the linear region of the resistance curve of the conductive material 5 by pressing the working body 3 against the case body 2 in advance. A bolt 4 is passed through a slightly larger hole 32b provided on the upper surface of the working body 3, the flange body 32 is pressed toward the case body 2 by the head 41 of the bolt 4, and the body portion 42 of the bolt 4 is pressed. The flange body 32 is displaced in the Z-axis direction within the range. As a result, the resistance value can be detected in the linear region by pressing the conductive material 5 in advance with the bolt 4. Further, when the flange body 32 is pressed in the Z-axis direction with the bolt 4 in this way, it is necessary to displace the flange body 32 in the Z-axis direction while maintaining the flat state. For this reason, the bolts 4 are provided intermittently at regular intervals (90 degrees) so that the flange body 32 is displaced in the Z-axis direction while maintaining a flat surface, so that the pressed state by the protrusion 33 is adjusted. Try to stabilize.

Similarly, for the offset portion 30 in the X-axis direction and the Y-axis direction, the conductive material 5 is pressed in the X-axis direction and the Y-axis direction by passing the bolt 4 from the side surface of the case body 2 through the insertion body 31 and pressing the body. It is designed so that it can be displaced within the range of the portion 42. At this time, since it is necessary to allow a slight displacement in the X-axis direction and the Y-axis direction in the other axial directions, a gap between the body portion 42 of the bolt 4 and the hole portion 23 of the case body 2 is provided. Leave it slightly open so that the conductive material 5 is pressed in the axial direction of the bolt 4 while allowing displacement in the other axial direction. Further, when the gap is left in this way, the insert body 31 may be shaken. Therefore, a pair of upper and lower holes 23 are provided in each of the X-axis direction and the Y-axis direction, and the bolt 4 is passed through. The protrusion 33 is positioned at an intermediate position of the bolt 4. By doing so, the upper and lower bolts 4 can prevent the shake in the X-axis direction and the Y-axis direction, and the pressed state by the protrusion 33 can be stabilized.

Next, the operation of the load cell 1 configured in this way will be described.

First, when the load P acts on the upper surface 21b of the working body 3, the Z-axis component of the load P acts in the Z-axis direction of the flange body 32. Then, the flange body 32 is pressed downward, and the conductive material 5 is pressed by the protrusion 33 provided on the flange body 32. At this time, since the conductive material 5 is already pressed by the offset portion 30 in the Z-axis direction, the change in electrical resistance within the range of the linear region in FIG. 3 is detected and the Z-axis load is applied. Will be able to be detected. The bolt 4 provided in the X-axis direction and the Y-axis direction of the insert body 31 in which the acting body 3 is displaced in the Z-axis direction is displaced in the Z-axis direction within a slight gap in the hole 23 of the case body 2. It will be like.

On the other hand, the action body 3 is displaced in the coaxial direction by pressing the load P in the Y-axis direction. Then, the conductive material 5 is pressed by the protrusion 33 provided on the insert body 31. At this time, since the conductive material 5 is already pressed by the offset portion 30 in the Y-axis direction, it becomes possible to detect the resistance change in the linear region. When the insert body 31 is displaced in the Y-axis direction in this way, the bolt 4 attached along the Z-axis direction and the bolt 4 attached along the X-axis direction have a hole portion 32b provided in the flange body 32. And within the range of the hole 23 provided in the case body 2, the displacement is in the Y-axis direction.

Similarly, in the X-axis direction, the acting body 3 is displaced based on the component of the load P in the X-axis direction. Then, the conductive material 5 is pressed by the protrusion 33 provided on the insert 31. Also at this time, since the state is already pressed by the offset portion 30 in the X-axis direction, the resistance change can be detected in the linear region. Also at this time, the bolt 4 attached along the Z-axis direction and the bolt 4 attached along the Y-axis direction are within the range of the hole portion 32b provided in the flange body 32 and the hole portion 23 provided in the case body 2. It will be displaced in the X-axis direction within.

Then, the load in the coaxial direction is calculated and output based on the difference change in the electric resistance in the XYZ axis direction detected in this way.

With this configuration, it becomes possible to simultaneously detect a load in the triaxial direction from the load P acting on one working body 3 by using the conductive material 5.

<Second embodiment>

Next, the second embodiment will be described. In the above embodiment, the flange body 32 is provided on the upper part of the working body 3, but in the second embodiment, the configuration as shown in FIG. 5 is used.

The load cell 1 shown in FIG. 5 has a case body 2 configured in the same manner as in the above embodiment, and a conductive material 5 for detecting a load in the Z-axis direction is attached to the bottom surface 21c of the hole portion 22. be. Even in such a configuration, it becomes possible to simultaneously detect the load acting on the working body 3 in the triaxial direction. In the figure, those with the same reference numerals are assumed to have the same configuration as that of the above embodiment, and the description thereof will be omitted.

When the conductive material 5 is pressed by the bottom surface of the insert body 31 in this way, the protrusion 33 may be provided on the bottom surface 21 c of the insert body 31 and the pressure may be applied in advance by the same offset portion 30. .. Alternatively, the bottom portion 21c of the insert 31 may be sharpened and the initial pressure may be applied at this pressure.

<Third embodiment>

Further, the case body 2 as shown in FIG. 6 can also be used. The case body 2 shown in FIG. 6 has a square hole portion 22 and has a columnar insert body 31 inserted therein. Then, the conductive material 5 is provided on the inner wall 21a of the hole portion 22, and the conductive material 5 is also provided on the surface whose insertion direction is the normal direction. Then, when the working body 3 having the circular insert body 31 is inserted into the square hole portion 22, the columnar insert body 31 comes into contact with the inner wall 21a of the hole portion 22 in a single point line, and the protrusion portion. It is possible to concentrate the load and detect the change in the resistance value without providing 33 or the like. When the insert 31 is formed into a cylindrical shape in this way, it is in linear contact with the hole 22 along the Z-axis direction. May be good.

As described above, according to the above embodiment, the insertion body 31 inserted with a gap in the vertical and horizontal directions between the case main body 2 having the hole portion 22 inside and the hole portion 22 of the case main body 2 and the insertion thereof. An actuating body 3 having a flange body 32 provided on the upper portion of the body 31, a conductive material 5 provided in a direction orthogonal to the inner wall of the hole portion 22, and a hole portion 22. It is inserted toward the upper surface of the case body 2 via the conductive material 5 provided on the upper surface of the case body 2 having the insertion direction as the normal line and the hole portion 32b provided in the flange body 32, and is inserted toward the upper surface of the case body 2. The case body 2 is inserted toward the insertion body 31 via a bolt 4 that sandwiches and presses the conductive material 5 provided on the upper surface of the case 2 and a hole portion 23 provided on the side surface of the case body 2. Each of the conductive materials 5 is provided with a bolt 4 for sandwiching and pressing the conductive material 5 provided on the inner wall of the above, and by pressing the respective conductive materials 5 with the flange body 32 and the insertion body 31. Since the load in the triaxial direction is detected by changing the electric resistance of the load cell, the load in the triaxial direction acting on one working body 3 can be detected at the same time, the structure is simplified, and the load cell is low cost. 1 can be configured.

The present invention is not limited to the above embodiment, and can be carried out in various embodiments.

For example, in the above embodiment, carbon fiber such as CFRP is used as the conductive material 5, but the present invention is not limited to this, and the electrical characteristics (resistance value, electromotive force value, etc.) change due to pressing or pulling. Other materials such as piezo film may be used.

Further, in the above embodiment, the protrusion 33 is provided on the working body 3, but it may be provided on the case body 2 side.

1 ... Load cell 2 ... Case body 21a, b, c ... Top surface, inner wall, bottom surface 22 ... Hole 23 ... Hole 3 ... Acting body 31 ... Inserting body 32.・ ・ Flange body 32b ・ ・ ・ Hole 33 ・ ・ ・ Protrusion 4 ・ ・ ・ Bolt 41 ・ ・ ・ Head 42 ・ ・ ・ Body 5 ・ ・ ・ Conductive material 51 ・ ・ ・ Conductive sheet 52 ・ ・·electrode

Claims (2)

The case body with a hole inside and
An insert body inserted with gaps in the vertical and horizontal directions between the case body and the hole portion, and an actuating body configured by providing a flange body on the upper portion of the insert body .
Conductive materials provided in the directions orthogonal to the inner wall of the hole, and
A conductive material provided on the upper surface of the case body whose normal is the insertion direction of the hole, and
A bolt that is inserted toward the upper surface of the case body through a hole provided in the flange body and that sandwiches and presses a conductive material provided on the upper surface of the case body.
A bolt that is inserted toward the insert through a hole provided on the side surface of the case body and that sandwiches and presses a conductive material provided on the inner wall of the case body is provided.
A load cell in which the electric resistance of each of the conductive materials is changed by pressing the respective conductive materials with the flange body and the insert body to detect a load in the triaxial direction. According to claim 1, a pair of upper and lower holes are provided on the inner wall of the hole so that the protrusion provided on the side surface of the insert is at an intermediate position, and the conductive material is pressed by the bolt. Described load cell.

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