JPH026006B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin and lightweight weighing scale that uses an elastic body having conductivity.

[Conventional technology]

Conventional weight scales detect the weight of an object based on changes in the length of a coil spring, bending or twisting of a bar, etc.
These displacements were mechanically converted and displayed, or converted into electrical signals using a load cell or the like and then displayed in analog or digital form.
Therefore, these devices have to be large in size to some extent due to their structure and are also heavy, making them inconvenient to store and carry when not in use.

For this reason, with the recent trend towards downsizing of products, it has been desired to make weight scales smaller and lighter.

[Problem that the invention seeks to solve]

In view of the above circumstances, it is an object of the present invention to provide a thin plate weighing scale that has not existed in the past by making the weight detection mechanism smaller, lighter, and simpler.

[Means for solving problems]

The technical means taken by this invention to achieve the above object are as follows.

In a first aspect of the present invention, there is provided a substantially plate-shaped main body including a substrate and a movable plate disposed to be displaceable with respect to the substrate and on which an object to be measured is placed; a pressure sensor whose electrical resistance value changes by elastic deformation in response to pressure acting on a movable plate; a signal processing means for processing an electrical signal based on a change in electrical resistance value of the pressure sensor; and an output signal of the signal processing means. and display means for displaying the weight of the object to be weighed based on the pressure sensor, the pressure sensor including a substantially cylindrical conductive elastic body formed by dispersing and mixing conductive fine particles in an insulating elastic body. Further, the conductive elastic body is in contact with another conductive elastic body or a hard conductive plate material, and the contact area thereof gradually changes with displacement of the movable plate. It is characterized by the fact that

In a second aspect of the invention, there is provided a substantially plate-shaped main body including a substrate and a movable plate disposed to be displaceable with respect to the substrate and on which an object to be measured is placed; a pressure sensor whose electrical resistance value changes by elastic deformation in response to pressure acting on a movable plate; a signal processing means for processing an electrical signal based on a change in the electrical resistance value of the pressure sensor; and an output signal of the signal processing means. and display means for displaying the weight of the object to be weighed based on the pressure sensor, the pressure sensor being made of conductive fine particles dispersed and mixed in an insulating elastic body, and having a substantially semi-cylindrical or substantially hemispherical shape on at least one side. The conductive elastic body is configured to include a conductive elastic body formed in a plate shape having a protrusion, and the conductive elastic body is in contact with the other conductive elastic body or the hard conductive plate material, and the conductive elastic body is in contact with the other conductive elastic body or the hard conductive plate material. It is characterized in that the contact area is gradually changed by the displacement of the movable plate.

[Effect]

As a result of taking the above technical measures, when an object to be measured is placed on the movable plate, the movable plate is displaced by its weight, causing the pressure sensor to elastically deform. Then, the contact area between the conductive elastic bodies that make up the pressure sensor or between the conductive elastic bodies and the hard conductive plate gradually increases, so the electrical resistance value of the pressure sensor gradually decreases (the conductivity increases). do. Moreover, at the same time, the density of the conductive fine particles dispersed inside the conductive elastic body increases, and the electrical resistance value also decreases due to this.

In this way, the electrical resistance value of the pressure sensor changes due to changes in the contact area between conductive elastic bodies or conductive hard materials and changes in the density of conductive particles inside the conductive elastic bodies. If this change is detected and processed by the signal processing means to display the weight, the weight of the object to be weighed can be displayed on the display section.

Furthermore, since the pressure sensor can be constructed by simply bringing conductive elastic bodies into contact with each other or a conductive elastic body and a hard conductive plate material, it can be easily made compact by being housed in a plate-shaped body, and can be configured easily. It can be very simplified. Therefore, the weight detection mechanism can be made smaller, lighter, and simpler, and the entire weighing scale can be made into a plate shape to provide a thin and lightweight weighing scale.

〔Example〕

Embodiments of the present invention will be described below based on the accompanying drawings.

1 and 2 show an embodiment of the weighing scale of the present invention, in which a movable plate 2 on which an object to be weighed is placed is fitted into a recess formed on the upper surface of a substrate 1 so as to be vertically displaceable. There is. A pressure sensor 4 is interposed in a space 3 between the substrate 1 and the movable plate 2, and the pressure sensor 4 is elastically deformed in response to the pressure acting on the movable plate 2 and whose electrical resistance value changes. The substrate 1 and the movable plate 2 constitute the main body of this weighing scale.

As shown in FIG. 3, the sensor 4 is constructed by stacking four cylindrical conductive elastic bodies 5 in a grid pattern, and the upper and lower surfaces thereof are in contact with the movable plate 2 and the substrate 1, respectively. It is arranged to do so. An insulating sheet 6 is adhered to the surfaces of the substrate 1 and the movable plate 2 that are in contact with the conductive elastic body 5 .

As the conductive elastic body 5, CR, SBR, NBR,
Carbon, iron,
A mixture of dispersed conductive particles such as silver can be used. Since the conductive elastic body 5 is formed in a cylindrical shape, the contact area between the upper and lower conductive elastic bodies 5 is very small when no load is applied, and the electrical resistance value of the contact portion is very large. When a load is applied, each conductive elastic body 5 is elastically deformed and the contact area is expanded, so that the electrical resistance value of the contact portion is reduced.
In this case, since the conductivity and the load of the sensor 4 change almost proportionally, the weight of the object can be measured by detecting the change in conductivity. When the conductive elastic body 5 is a mixture of conductive fine particles dispersed in an insulating polymeric elastic body,
At the same time as the contact area changes, the density of the conductive fine particles dispersed inside the conductive elastic body 5 changes, and this also changes the electrical resistance value (conductivity).

In this embodiment, four conductive elastic bodies 5 are stacked, but it is also possible to use the two conductive elastic bodies 5 on either the upper or lower side as metal electrodes. Also,
The number of cylindrical conductive elastic bodies 5, the manner of contact, etc. can be arbitrarily changed depending on the sensitivity and purpose, as long as the contact area gradually changes as the conductive elastic bodies 5 are elastically deformed.

7 is a signal processing circuit embedded in the board 1, which includes a current/voltage converter 8, an A/D converter 9, and a CPU.
It consists of 10. 11 is a display section, a liquid crystal,
The weight is displayed using LEDs, etc. still,
12 and 13 are interfaces, and 14 is a power supply housed within the board 1.

Next, the usage condition of the weighing scale according to the present invention will be explained.

First, when an object to be measured is placed on the movable plate 2, the movable plate 2 is displaced downward and presses the sensor 4. Then, the conductive elastic body 5 is elastically deformed according to the load, and the conductivity of the sensor 4 increases due to the increase in the contact area and the increase in the density of the conductive particles, so this change is detected as a voltage signal, Signal processing circuit 7
Enter. The signal processing circuit 7 outputs a signal corresponding to the current load based on this input signal, and the display section 11 displays the weight.

When the object to be weighed is removed from the movable plate 2, the movable plate 2 is displaced upward by the elastic force of the conductive elastic body 5 and returns to its original state.

The conductivity of the sensor 4 increases almost linearly in accordance with the load when a load is applied, but does not return through the same path when the load is removed, and there is hysteresis. Since only the solid line portion in Figure 6 is used, there is no problem.

Note that the substrate 1 and the movable plate 2 can be manufactured from metal or hard plastic plates or molded products.

7 to 9 show other embodiments of the sensor 4 used in the present invention. In FIG. 7, two cylindrical conductive elastic bodies 5 are arranged side by side, and metal A hard conductive plate material 15 such as a plate or a conductive plastic plate is provided. In this case,
As the contact area between the conductive elastic body 5 and the conductive plate material 15 changes, the conductivity of the sensor 4 changes.

8 and 9 show a conductive elastic body 5 in the form of a plate having semi-cylindrical and hemispherical protrusions 16 on one side, respectively.
is held between two conductive plates 15. In these cases, the contact area between each protrusion 16 and the upper conductive plate 15 changes, so that the conductivity of the sensor 4 changes. It is preferable that the protrusion 16 has a semi-cylindrical or hemispherical shape, but a similar shape, for example a parabolic cross section, is preferable in view of the characteristics of the sensor 4.

In this invention, "substantially cylindrical" includes not only a cylinder but also a similar shape such as an elliptical cylinder,
The same applies to "approximately semi-cylindrical shape". Furthermore, the term "substantially hemispherical" includes not only a hemisphere but also a shape resembling a hemisphere, such as a semi-ellipsoid and a parabolic cross section.

〔Effect of the invention〕

In the present invention, as a weight detection mechanism, substantially cylindrical conductive elastic bodies 5 or the conductive elastic bodies 5 and a hard conductive plate material such as the conductive plate material 15 are brought into contact with each other, or at least on one side thereof. A pressure sensor 4 is used in which the conductive elastic bodies 5 each having a substantially semi-cylindrical or semi-spherical protrusion 16 are brought into contact with each other or the conductive elastic bodies 5 and a hard conductive plate are brought into contact with each other. Therefore, the weight detection mechanism can be made very small, lightweight, and simple in structure, and can be made compact so that it can be accommodated in a thin plate-like main body.

Therefore, it is possible to provide a weight scale that is thin, lightweight, and extremely convenient to carry and store.

[Brief explanation of drawings]

FIG. 1 is a plan view of a weighing scale according to the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is an overall view of the sensor. FIG. 4 is a partially enlarged sectional view of the weighing scale. FIG. 5 is a block diagram of a circuit used in the present invention. FIG. 6 is a characteristic diagram showing the load-conductivity characteristics of the sensor. 7 to 9 are partially cutaway perspective views showing other embodiments of the sensor. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Movable plate, 4...Sensor, 5...Electroconductive elastic body, 15...Electroconductive plate material, 16...Protrusion.

Claims (1)

[Scope of Claims] 1. A substantially plate-shaped main body including a substrate and a movable plate on which an object to be measured is placed, which is displaceable with respect to the substrate, and which is interposed between the substrate and the movable plate. a pressure sensor whose electrical resistance value changes by elastic deformation in accordance with the pressure acting on the movable plate; a signal processing means for processing an electrical signal based on a change in the electrical resistance value of the pressure sensor; and an output of the signal processing means. and display means for displaying the weight of the object to be weighed based on the signal, and the pressure sensor includes a substantially cylindrical conductive elastic body formed by dispersing and mixing conductive fine particles in an insulating elastic body. Further, the conductive elastic body is in contact with another conductive elastic body or a hard conductive plate material, and the contact area thereof gradually changes with displacement of the movable plate. A weighing scale characterized by: 2. A substantially plate-shaped main body including a substrate and a movable plate that is displaceable with respect to the substrate and on which an object to be measured is placed; and a main body that acts on the movable plate that is interposed between the substrate and the movable plate. A pressure sensor whose electrical resistance value changes by being elastically deformed in response to pressure; a signal processing means for processing an electrical signal based on a change in electrical resistance value of the pressure sensor; and display means for displaying the weight of the object, the pressure sensor being made of conductive fine particles dispersed and mixed in an insulating elastic body, and having a substantially semi-cylindrical or semi-spherical protrusion on at least one side. The conductive elastic body is configured to include a conductive elastic body formed in a plate shape, and the conductive elastic body is in contact with another conductive elastic body or a hard conductive plate material, and due to the displacement of the movable plate. A weighing scale characterized by being configured such that its contact area gradually changes.