JP2000234975A - Face pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a face pressure sensor whose rigidity is high, whose deformation amount with reference to compression is small, which is resistant to heat, which is flexible and which can measure the distribution of a face pressure. SOLUTION: Strain gages are pasted on side faces in central parts of quadratic prism-shaped bodies whose central parts are constricted. On the other hand, the quadratic prism-shaped bodies in which through holes in the X-direction and the Y-direction are made in their head parts and their bottom parts are arranged in a matrix shape as unit load cells 1. Thin wires 21, 22, 31, 32 and the like are passed through the through holes. Thereby, this face pressure sensor is constituted. Fig. (a) shows an example in which 2×2 pieces of the unit load cells 1 are arranged. Fig. (b) shows an example in which 4×4 pieces of the unit load cells 1 are arranged. In this manner, the face pressure sensor is constituted in such a way that the unit load cells in a plurality, whose rigidity is high are arranged in the matrix shape and that they are connected to each other by the thin wires. As a result the unit load cells are provided individually with high rigidity, and their deformation amount is small. The unit load cells are flexible as a whole. As a result, it is possible to obtain an advantage that a face pressure and the distribution of the face pressure can be measured precisely. In addition, since the face pressure sensor is resistant to heat, it can deal with a temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact surface pressure distribution when a highly rigid object such as a metal is contacted and pressed, and a contact surface pressure when the highly rigid objects are thermally deformed. The present invention relates to a surface pressure sensor that measures a distribution change with a sensor having the same high rigidity.

[0002]

2. Description of the Related Art The following three types are known as conventional examples of this type of surface pressure sensor. (1) Pressure Sensitive Paper FIGS. 5A and 5B are explanatory views for explaining the first example, in which FIG. 5A shows a cross-sectional structure, and FIG. That is, the pressure-sensitive paper shown in FIG.
On a base material (polyethylene terephthal) 51 of 1 μm, microcapsules 52 containing 5 to 15 μm of a medicine,
The drug 53, which develops a color when it reacts with the drug in the capsule, is dispersed and applied at an appropriate ratio (thickness L2 μm), and the total thickness L (L1 + L2) is about 100 to 120 μm.

When this is inserted into the contact boundary surface with the load body 55 and pressurized, it is deformed as shown in FIG.
The large capsule is crushed and broken according to the applied pressure (the broken microcapsule is indicated by reference numeral 54), and the medicine inside the capsule leaks and reacts with the surrounding medicine to develop color. If the applied pressure is large, the number of chemicals that break down even small capsules and leak increases, so that the color when the color develops becomes darker. That is, since shading of the color occurs due to the pressing force, the surface pressure is measured from the density difference.

(2) Pressure-sensitive film FIG. 6 is an explanatory view for explaining a second example, and FIG.
1 is a perspective view showing the whole. In (a),
61 is a pressure-sensitive film, 62 is an X-direction electrode, 63 is a Y-direction electrode, and 64 is a conductive particle. The pressure-sensitive film 61 is made of a relatively soft electric insulator such as polyester, nylon, epoxy, or rubber, and has an electrode 62 on its upper surface.
Are embedded insulated from each other, and these are aligned in the X direction. Similarly, a plurality of electrodes 63 are embedded in the lower surface of the pressure-sensitive film 61 so as to be aligned in the Y direction. Further, conductive particles 64 are embedded in the pressure-sensitive film 61.

FIG. 6B shows a sectional structure of the pressure-sensitive film 61.
, Xn and electrodes Y1 Y2
.. Yn (here, only Yn is displayed), the conductive particles 64 are embedded in the pressure-sensitive film 61. When no external force (pressure) is acting on the pressure-sensitive film 61, the conductive particles 6 between the electrode Xn and the electrode Yn are removed.
The electric resistance of No. 4 shows a high value. Here, as shown in FIG. 6C, when an external force from the load body 65 is applied, the conductive particles are compressed along with the deformation of the pressure-sensitive film 61, so that the contact area between the particles increases, and the electrode Xn And the electrode Yn exhibits a low value. From the change in this value, it is possible to know the magnitude of the external force, and further the distribution and the change due to the external force.

(3) Surface pressure sensor in which load cells are arranged FIG. 7 is an explanatory view for explaining a third example, and FIG. 7A is a perspective view showing the whole. In FIG. 9A, reference numeral 71 denotes a load cell, 72 denotes a strain gauge, 73 denotes a mounting screw, 74 denotes a base plate, 75 denotes a screw hole, and 76 denotes a strain generating portion. The load cell 71 which receives a compressive load from the vertical direction has a portion (also referred to as a strain generating portion) 7 having a reduced cross-sectional area.
6, a strain gauge 72 for detecting a compressive strain is attached thereto. A mounting screw 73 is formed at the lower end of the load cell 71, and a screw hole 75 is formed in the base plate 74. By screwing the mounting screw 73 into the screw hole 75, the load cell 71 is attached to the base plate 74. Fixed. Here, the gap between the load cells 71 is made large, but actually, they are fixed side by side so as to minimize the gap.

FIG. 7B shows an example of a bridge circuit for converting a change in electrical resistance due to a compressive strain detected by the strain gauge 72 into a voltage. That is, a strain gauge 72 and dummy gauges 77 and 78 are connected to each side of the bridge, and a gauge voltage is supplied from a bridge power supply 79. When the load cell 71 receives a compressive load in this state, the resistance of the strain gauge 72 changes and the balance of the bridge circuit is lost, so that an output voltage 80 is generated. Here, the strain gauge 72 is connected to only one side of the bridge. However, in practice, a strain gauge stuck in the horizontal direction is connected to the dummy gauge 77 for temperature correction, and the dummy gauge 78 is also vertically connected to increase the sensitivity. In many cases, strain gauges attached in the horizontal and vertical directions are connected and used.

[0008]

However, in the arrangement shown in FIGS. 5 and 6, the amount of deformation of the sensor is large,
It is not suitable for suppressing the displacement amount of No. 5 to a small value.
Therefore, FIG. 8 shows an example in which the surface pressure distribution is measured while suppressing the deformation amount to be small. As shown in FIG. 8A, a large piece in which metal A81 and metal B82 having different coefficients of linear expansion are joined and a small piece in which metal B83 and metal A84 are also joined are brought into contact with each other. Between the bolts 87
Suppose you tightened. Then, it is assumed that the whole is heated in this state.

The large piece and the small piece each have a structure in which metals having different coefficients of linear expansion are joined, that is, a so-called bimetal structure, and warpage occurs due to a temperature change. When the linear expansion coefficient of the metal A is larger than that of the metal B, the metal A is deformed by the temperature rise as shown by dotted lines 89 and 90 in FIG. 8B, and the contact surface pressure changes. In order to measure this surface pressure, if the above-described pressure-sensitive film is interposed as the surface pressure sensor 90 in FIG.
Since this film is soft and thermally weak, the amount of deformation of the film itself is large and it is not possible to measure an accurate surface pressure. That is, in such a case, the amount of deformation of the surface pressure sensor itself must be small and the surface pressure sensor must not be thermally affected.

When the contact surface is deformed both above and below as shown in FIG. 8 (b), it is necessary for the sensor itself to adapt to the deformation and measure the surface pressure. For example, when the large piece 91 and the small piece 92 deform as shown in FIG. 8C, in the surface pressure sensor in which the load cells are arranged on the base plate as described with reference to FIG. 7, the shape change of the lower contact surface is considered. Since it is not possible, it is not possible to measure an accurate surface pressure distribution. Therefore, an object of the present invention is to increase the rigidity to suppress the amount of deformation due to compression, and to make it thermally strong and flexible, so that the surface pressure distribution that can be adapted to the shape change of the upper and lower contact surfaces can be measured. It is to provide a sensor.

[0011]

According to the first aspect of the present invention, a strain gauge is attached to the center of a high-rigid square prism having a reduced cross-sectional area at the center, and a head and a bottom of the high-rigid square prism are attached. Are formed as a unit load cell in which through-holes are alternately penetrated in two orthogonal axes directions, are arranged in a matrix, and are connected to each other through thin wires in the through-holes.

According to the first aspect of the present invention, the contact surfaces of the head and the bottom of the quadrangular prism contacting the unit load cells can be formed of a material layer having a small coefficient of friction. In the invention of the second aspect, plastic or ceramic can be used as the substance having a small friction coefficient (the invention of the third aspect).

In any one of the first to third aspects of the present invention, a screw hole is formed to reach the through hole from the upper and lower ends of each unit load cell located at the end of the surface pressure sensor. The fine wire can be fixed by tightening with a set screw screwed from the screw hole (the invention of claim 4). In this case, it is advisable to insert a ball into the tip of the set screw.

[0014]

FIG. 1 is a schematic structural view showing an embodiment of the present invention, and FIG. 2 is a perspective view showing an example of a load cell used in FIG. First, FIG. 2 will be described. This shows a basic (unit) load cell structure, in which a square pillar having a narrow central portion is used as a basic type. The material is a highly rigid substance such as metal or ceramics. 1
Reference numeral 7 denotes a strain generating portion, on which a longitudinal strain gauge 18 and a transverse strain gauge 19 are attached as shown in the figure. The vertical strain gauge 18 is for detecting pressure, and the horizontal strain gauge 19 is for increasing the detection sensitivity and performing the function of temperature compensation. The pressure receiving head 11
The pressure receiving bottom 12 has through holes 13, 14 and 15, 16 that do not intersect at right angles to each other.

FIG. 1A shows a case where 2 × 2 load cells as described above are arranged, and FIG. 1B shows a case where 4 × 4 load cells are arranged. In FIG. 1A, the load cells 1 are arranged apart from each other, but this is for the purpose of explanation. Generally, as shown in FIG.
In these figures, 21 indicates a head X-direction thin wire (wire), 22 indicates a bottom X-direction wire, 31 indicates a head Y-direction wire, and 32 indicates a bottom Y-direction wire, by which the load cells 1 are connected to each other. And a surface pressure sensor. Further, the number of load cells is not limited to 2 × 2 or 4 × 4, but can be generally N (integer) × N.

FIG. 3 is an explanatory diagram showing a state in which the surface pressure of the contact surface where warpage due to thermal deformation has occurred is measured by a surface pressure sensor. The actual deformation is very small, but is illustrated assuming extremely large deformation for explanation. In this state,
The upper and lower surfaces of the load cell 1 do not come into full contact, and an upper surface contact point 27 and a lower surface contact point 28 are generated, and a moment for rotating the load cell 1 clockwise is generated. Then, since each bottom of the load cell 1 tends to separate, it is necessary to provide a method of fixing the wire so as to hold the load cell 1 with an appropriate tension so as not to separate it.

FIG. 4 is an explanatory diagram of the wire fixing method as described above. However, such a configuration is equivalent to four load cells in the outer peripheral portion of the sensor, that is, all four in FIG. 1A and the numeral 1 in FIG. 1B. First, the through-holes 13 and 1 from the upper and lower ends of the load cell 1
Drill a screw hole (only 42 is shown) reaching 5.
Next, the wires 41 are passed through the wires 21 and 22, and the ball 41 is put thereon. At this time, by tightening the screw 40 while applying an appropriate tension to the wire, it is possible to keep the load cells 1 from separating from each other even when the surface pressure is measured in the state shown in FIG. Note that the ball 41 may be omitted, and the ball 41 may be tightened only with the set screw 40.

When the above-described sensor is used in, for example, a heat cycle test, the coefficient of friction between the load cells increases, and the vertical movement may be deteriorated. Therefore, as shown in FIG. 3B by hatching, for example, material layers 111 and 121 having a small coefficient of friction such as plastics and ceramics (see hatched lines) are provided on the side surfaces of the head and the bottom of the load cell which contact and slide with each other. ) Is formed. By doing so, it becomes easy to move in the vertical direction, and good flexibility can be maintained.

[0019]

According to the present invention, a plurality of high-rigidity unit load cells are arranged in a matrix and are connected to each other by thin lines, so that each has a high rigidity, so that the amount of deformation is small, and In particular, since it has flexibility, an advantage that accurate measurement of surface pressure and surface pressure distribution can be obtained is obtained. Also, since it is strong against heat, it can cope with temperature changes.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a unit load cell used in FIG.

FIG. 3 is an explanatory diagram of a surface pressure measuring method according to the present invention when warpage occurs.

FIG. 4 is an explanatory diagram of a method for fixing a thin wire according to the present invention.

FIG. 5 is an explanatory diagram of a first conventional example.

FIG. 6 is an explanatory diagram of a second conventional example.

FIG. 7 is an explanatory diagram of a third conventional example.

FIG. 8 is an explanatory diagram of the reason why surface pressure measurement is required.

[Explanation of symbols]

1 ... load cell, 11 ... pressure receiving head, 12 ... pressure receiving bottom, 1
3-16: Through-hole, 17: Strain-generating part, 18: Vertical strain gauge, 19: Horizontal strain gauge, 21, 22, 3
1, 32 ... fine wire (wire), 25, 26 ... warp generator,
27: upper contact point, 28: lower contact point, 111, 121
... A material layer having a small coefficient of friction, 40... Set screws, 41... Balls, 42.

Claims (5)

[Claims] 1. A strain gauge is attached to a central portion of a high-rigidity rectangular column having a reduced cross-sectional area at a central portion, and the head and the bottom of the high-rigidity rectangular column are alternately penetrated in two orthogonal directions. A surface pressure sensor comprising: a unit load cell having a through-hole formed therein, arranged in a matrix, and connected to each other through a thin wire in the through-hole. 2. The surface pressure sensor according to claim 1, wherein each of the contact surfaces of the head and the bottom of the quadrangular prism body with which the unit load cells contact each other is formed of a material layer having a small coefficient of friction. 3. The surface pressure sensor according to claim 2, wherein plastic or ceramic is used as the material having a small coefficient of friction. 4. A screw hole reaching the through hole from the upper and lower ends of each unit load cell located at the end of the surface pressure sensor, and after passing through the fine wire, is tightened with a set screw screwed in from the screw hole. The surface pressure sensor according to claim 1, wherein the surface pressure sensor is fixed. 5. The surface pressure sensor according to claim 4, wherein a ball is inserted between the set screw and the fine wire, and the fine wire is fixed through the ball.