JPH01150825A - Load sensor consisting of pressure sensitive conductive rubber - Google Patents

Abstract

PURPOSE:To obtain a load sensor which has increased the deviation quantity of pressure sensitive conductive rubber by providing a load detecting part which has laminated the pressure sensitive conductive rubber which contains dispersed conductive material grains and whose electric resistance value is varied in accordance with a load. CONSTITUTION:Pressure sensitive conductive rubber 3 consists of two layers 31, 32 and electrodes 2, 4 are provided with projection-like holding parts 81, 82 on the periphery so that the pressure sensitive conductive rubber layers 31, 32 are not shifted. Also, the holding parts 81, 82 are attached by a means for sticking a resin formed part to the electrodes 2, 4 etc. In such a state, a sensor 1 is held so as not to occur that the pressure sensitive conductive rubber layers 31, 32 are shifted from each other and the contact area is varied, by the holding parts 81, 82 and initial pressure. In such a way, by laminating lamellately the pressure sensitive rubber layers 31, 32, the load sensor which has increased effectively the deviation quantity of the pressure sensitive conductive rubber 3 can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a load sensor made of pressure-sensitive conductive rubber, and more particularly to a sensor in which the amount of deformation (deviation) for deforming the rubber is increased. be.

[Prior art]

Load can be measured using pressure-sensitive conductive rubber, in which conductive particles such as carbon are dispersed in silicone rubber, and the electrical resistance changes according to the compressive load.
It is well known that it is used as a sensor element for controlling equipment by adjusting the pressing force.

The pressure-sensitive conductive rubber is supplied to the market in the form of a sheet-like molded product or a paint that is applied as a liquid onto an electrode and solidified.

Load sensors made of pressure-sensitive conductive rubber have no moving parts and have an extremely simple structure, so they have come into practical use in various fields.

To apply a load to the pressure-sensitive conductive rubber, it is sufficient to apply a predetermined static load to the rubber surface, and a sensor 1 as shown in FIG. 6 has been developed. That is, the sensor 1 has a chip-shaped pressure-sensitive conductive rubber 3 arranged on an electrode 2, and an electrode 4 fixed thereon with a fixing member 5. The fixing member 5 is usually made of resin and is solidified while holding the picture electrodes 2 and 4 at a predetermined distance.

A force is transmitted to the pressure-sensitive conductive rubber 3 by applying a load to the free end 6 side of the electrode 4. Pressure-sensitive conductive rubber 3 at this time
The relationship between the resistance value R and the load W changes along the curve shown by the solid line in FIG. As is clear from the figure, when the load W is small, the amount of change in the resistance R increases and there is a problem in that the measured values vary.

Therefore, when the sensor 1 is manufactured, the pressure-sensitive conductive rubber 3 is usually fixed in a compressed state (hereinafter referred to as initial pressure) to a certain extent, and a finite initial resistance value RO is given under the condition that the load W=O. Therefore, the load W-resistance R curve has a shape in which the side Ws with the smaller load lies horizontally as shown by the dotted line in FIG.

Furthermore, since the rate of change in resistance R becomes small when the load WL is large, the range shown by a in FIG. 7 is designed to be the effective measurement range. The sheet-shaped pressure-sensitive conductive rubber 3 is usually made to have a thickness t of about 0.5 mm, and the deviation amount Δl of the pressure-sensitive conductive rubber 3 that provides the effective measurement range a is usually 30 mm.
It is about 0 μm.

By the way, printers have come into widespread use due to the spread of word processors, etc., but if a sensor made of pressure-sensitive conductive rubber is used as a paper pressure sensor or the like used therein, there is a problem that the above-mentioned deviation amount is insufficient. In other words, the stroke length Δ of the measuring section 6 required for this paper pressure measurement
L is determined by the length of the electrode 4, the length l of the arm between the fixing member 5, the pressure-sensitive conductive rubber 3, and the deviation amount Δl, but if Δl is fixed, L, 7! cannot be determined without limit, and it is necessary to create a pressure-sensitive conductive rubber with a large deviation amount Δl.

Naturally, in order to increase the deviation amount Δl, it is possible to increase the thickness of t. However, the thickness t of the pressure-sensitive conductive rubber 3
Even if the stroke length Δl is doubled, there is a problem that the stroke length Δl is not doubled, and there is also a problem that as the thickness increases, it becomes difficult to supply products of industrially stable quality.

[Purpose of the invention]

The present invention has been made focusing on the above problems,
The object of the present invention is to provide a load sensor in which the amount of deviation of pressure-sensitive conductive rubber is increased.

[Structure of the invention]

To achieve the above object, the load sensor made of pressure-sensitive conductive rubber of the present invention has a structure in which a pressure-sensitive conductive rubber containing dispersed conductive particles and whose electrical resistance value changes depending on the load is layered. The present invention is characterized by having a load detection section formed by laminating layers.

The configuration in which the pressure-sensitive conductive rubber is laminated in layers functions to effectively increase the amount of deviation of the pressure-sensitive conductive rubber.

Any pressure-sensitive conductive rubber used in the present invention can be used, such as one previously formed into a sheet or film, or a paint type (conductive ink) that is applied as a solution to the electrode surface.

〔Example〕

Hereinafter, the present invention will be described in detail by way of an embodiment with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of a sensor made of pressure-sensitive conductive rubber according to this embodiment, and its basic structure is the same as that shown in FIG. 6 above. Therefore, similar members are given the same numbers and their explanations will be omitted. The pressure-sensitive conductive rubber 3 of this embodiment has two layers 3. and 3□, and the electrode 2.4 has a holding portion 81.4 having a convex shape around the periphery to prevent the pressure-sensitive conductive rubber layer 31.32 from slipping.
82 are provided. The holding portions 8□, 82 can be attached by bonding resin molded products to the electrodes 2.4.

The sensor 1 of this embodiment can be held by the holding parts 81', 82 and the initial pressure described above so that the pressure-sensitive conductive rubber layers 31 and 32 do not shift from each other and the contact area does not change. Results of comparing the deviation amount Δl of this example shown in FIG. 1 with the deviation amount Δl of the conventional example shown in FIG. 6 using a true pressure-sensitive conductive rubber whose side is lQms + thickness 0° is shown in Figure 2. In FIG. 2, the horizontal axis represents the load W, the vertical axis represents the deviation amount Δl, curve A represents the example, and curve B represents the comparative example. As is clear from the figure, the conventional example had a maximum measurable load of about 260 g and a deviation of about 380 μ, but the maximum measurable load of the two stacked sheets was about 530 g' - that time. When the deviation amount is about 8
00μ, but if you compare the portion that changes almost linearly, that is, the portion a of the example and the portion b of the comparative example, it can be seen that the portion of the example is much larger. When this result is expressed as a load resistance value, it can be seen that the enlargement of the straight line portion has a remarkable effect of overlapping two sheets, as shown in FIG.

As an application of this embodiment, when using a paint type (conductive ink) that is difficult to give thickness, there is a method in which conductive ink is applied to each electrode and the electrodes are overlapped.

In this way, the measurement range can be expanded compared to applying the same thickness as the two sheets.

When further laminating, the electrode 2.4 has convex portions 81.82.
, it is not possible to hold intermediate layers.

Therefore, an embodiment in which four layers are laminated will be described with reference to FIGS. 4 and 5.

The basic structure of the sensor 1 is the same as that described above, and the pressure-sensitive conductive rubber layers 31 and 32, which are laminated in four layers, are held by a holder 1O so as not to shift. The holder 10 is made of, for example, a high expansion ratio molded product of a soft polyurethane resin, and includes a pressure-sensitive conductive rubber layer 3. A through hole 11 for accommodating .about.34 is provided. In the embodiment shown in FIGS. 4 and 5, the holder 10 can prevent the laminated pressure-sensitive conductive rubber layers 31 to 34 from shifting laterally without affecting the load-resistance characteristics. By adhering a part of the holder 10 to one of the electrodes 2.4, the holding state can be further stabilized.

According to the method of the present invention, it is possible to expand the range of resistance change due to a load in conductive rubber, which has a narrow resistance change range, making it possible to expand new fields of application.

〔Effect of the invention〕

As explained above, the load sensor made of pressure-sensitive conductive rubber of the present invention is a load sensor made of a layered layer of pressure-sensitive conductive rubber containing dispersed conductive particles and whose electrical resistance value changes according to the load. The structure has the effect of making the amount of deviation (deformation) of the pressure-sensitive conductive rubber larger than that of a similar thickness, and greatly expanding the measurement range of linearly changing loads. be.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a load sensor according to an embodiment, FIG. 2 is a load-deviation characteristic graph of the sensor in FIG. 1, and FIG. 3 is a load-resistance characteristic graph of the sensor in FIG. 1. FIG. 4 is a sectional view of a load sensor according to another embodiment, FIG. 5 is a partial perspective view thereof, FIG. 6 is a sectional view of a conventional load sensor, and FIG. 7 is a load-resistance characteristic of the sensor shown in FIG. 6. This is a graph of 1... Load sensor, 2, 4... Electrode, 3, 3. ~3
4...Pressure-sensitive conductive rubber. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] 1. A load sensor made of pressure-sensitive conductive rubber, characterized in that it has a load detection section made of layered pressure-sensitive conductive rubber that contains conductor particles dispersed therein and whose electrical resistance value changes according to the load.