JPS62130321A - Pressure detector - Google Patents

Abstract

PURPOSE:To accurately detect the pressure by providing a resistance circuit base having a couple of electrodes and a block contact forming a parallel variable resistance circuit electrically keeping contact with the base at all times. CONSTITUTION:The resistance circuit base 11 can form freely an optional pattern as occasion arises by the printing, etc., and on the other hand, the block contact 12 consisting of conductive and elastic material can form each type of point contact, line contact and surface contact, etc., in accordance with the pattern of the resistance circuit. Further, a plunger 13 transmits the external force to the contact 12 accurately in order to bring stably the block contact 12 into contact with the resistance circuit base 11. Then, the contact 12 is in contact with the resistance circuit base 11 in a nonpressure state and the pressure from zero can be detected. Further, since the resistance circuit sets an initial value, it has the stable pressure detecting ability. Moreover, a change of a resistance value is measured only at a contact part between the contact 12 and the resistance circuit and the linear pressure/resistance value characteristic is obtained by determining each shape most suitably and the accurate pressure can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure sensor that can be used as a pressure sensor or a pressure switch.

[Conventional technology]

Figures 11 and 12 show a conductive rubber switch as a conventional pressure detector shown in, for example, Japanese Utility Model Application Publication No. 60-39523.
is another conductive rubber sheet having at least three insulating protrusions 3 protruding from each other at appropriate intervals, and both conductive rubber sheets 1.2 are separated by insulating protrusions 3 so as not to contact each other under no pressure. It is laminated. 4 is a flexible sheet made of rubber or synthetic resin in which at least one tapered elastic protrusion 5 is provided at a position that does not overlap the insulating protrusion 3; be. 6.
7 is an electrode, 8 is a power source, and 9 is an ammeter.

The composite conductive rubber switch 10 with the laminated structure configured as described above has the following characteristics: when no pressure is applied to the flexible sheet 4;
The resistance between the isolated electrodes 6 and 7 is infinite, and no current flows at all. When pressure is applied to the flexible sheet 4, the conductive rubber sheet 2 bends as shown by the chain line (conductive rubber sheet) 1 A series resistance circuit is formed between the electrodes 6 and 7, and a current flows. This current I^ changes in accordance with the resistance of the contact portion which changes with the pressure applied to the flexible sheet 4, so by measuring this current it is possible to know the magnitude of the applied pressure.

[Problem that the invention seeks to solve]

The contact that deforms due to external pressure and comes into contact with the fixed electrode is a conductive rubber sheet, and the conductive rubber sheet is insulated and isolated via an insulating protrusion so that it does not come into contact with the fixed electrode in a non-pressure state. For this reason.

(b) Pressure detection at low pressures is not possible; (b) the distance between the electrodes changes over time due to permanent distortion of the conductive rubber sheet, resulting in large variations in pressure detection; and (c)
Because the change in resistance value with respect to pressure change is not linear,
There are obvious defects that require correction using arithmetic circuits, etc., and although it can be used for fairly rough load detection (for example, detecting the number of passing cars), it can be used for load detection that requires accuracy (for example, object detection). There was a problem that it could not be used for measuring the weight of

The present invention has been made in view of these conventional problems, and aims to provide a pressure detector that is accurate and highly reproducible.

[Means for solving problems]

The present invention, which achieves the above object, comprises a resistive circuit board having at least one pair of electrodes formed by means such as printing, and a conductive elastic material, which maintains constant contact with the resistive circuit board, and This pressure sensor is characterized by comprising a block contact whose contact area gradually changes from a non-pressurized state to a pressurized state to form an electrically parallel variable resistance circuit.

[Effect]

The resistance circuit board according to the present invention can be easily adjusted in advance to a required resistance value by means such as printing, and can be freely formed into any pattern as required. On the other hand, block contacts made of conductive elastic material can be of various types, such as one-point contact, line contact, and surface contact, depending on the pattern of the resistance circuit. These contacts are in pressureless contact with the resistor circuit board, and pressure can be detected from zero. In addition, since the initial value is set using a resistor circuit, it has stable pressure detection ability. Moreover, the change in resistance value is measured only at the contact portion between the contactor and the resistance circuit, and linear pressure/resistance value characteristics can be obtained by optimally determining each shape.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 is a longitudinal side view of the pressure detector.

In the figure, 11 has at least one pair of electrodes E, E2,
The resistive circuit board 12, on which a predetermined circuit pattern is formed by means such as printing, is always in elastic contact with the resistive circuit board 11, and its contact area changes from a non-pressure state to a pressurized state. The block contactor 13 is designed to bring the block contactor 12 into stable contact with the resistance circuit board 11.

A plunger 14 for accurately transmitting external force to the contact 12 is a case that accommodates each of the above components 11 to 13.

More specifically, the resistance circuit board 11 includes electrodes E+ and E2 made of copper or the like (plated with gold or the like as necessary) on the surface of the board 11a made of an electrically insulating resin material. The electrodes E, E2 are connected by a printed circuit 15 using conductive ink. 2 to 4 illustrate printed resistor circuit patterns formed in this way, and the one in FIG. 2 shows a pair of electrodes 81 to 22.
They are connected by a printed circuit 15 having a single linear pattern of uniform dimensions. The one in Figure 3 has a pair of electrodes 8
1 to 22 are connected by a printed circuit 15 having a non-uniform pattern that is narrowest at the center and widens as it approaches the electrode. The one in FIG. 4 has two pairs of electrodes E1 to E2, each connected by a printed circuit 15 having a single linear pattern of uniform width, similar to the one in FIG. 2, and printed circuits formed in parallel. The circuits 15 and 15 are insulated.

The blow 2-shaped contact 12 is molded from a known conductive elastic material obtained by adding a conductivity imparting agent such as carbon black to a polymeric elastic material such as rubber. The shape of the contact portion with the resistance circuit board 11 is preferably a point contact (or line contact) when no pressure is applied, and a shape in which the area of the contact portion increases as the pressure increases. The figure shows an example of the shape, and the one in Figure 5 has a solid structure having a cylindrical body 12a and a conical head 12b with an angle of inclination α, while the one in Figure 6 is the same as above. The wall thickness (
d) The recessed portion 12c is formed in the structure shown in FIG. The specific resistance of such a contactor 12 is preferably much smaller than the resistance between the electrodes El and E2 of the printed resistance circuit 11.

The plunger 13 is made of an insulating material such as synthetic resin, and has a recess 13a at one end for attaching the contact 12, and a protrusion 13b for applying external pressure at the other end. 13c is a concave portion that serves as a relief when the contactor 12 is deformed under pressure. When the plunger 13 is pressed by the projection 13b protruding from the case 14.

It slides while being guided by the inner wall of the case 14 and pressurizes the contactor 12.

Various pressure/resistance characteristics can be obtained depending on how the block contactor 12 and each pattern of the resistance circuit board 11 are combined. That is, when combining the block contactor 12 with the resistance circuit pattern shown in FIG. 2 (hereinafter referred to as "A pattern") and the resistance circuit pattern shown in FIG. 3 (hereinafter referred to as "B pattern"), There is also a block contact 1 in the center 0 of the printed circuit 15 of each pattern.
2 conical apex 12Pt - assembled in contact. In this case, the initial resistance of the pressure sensor is the resistance Ro of the printed resistance circuit itself (resistance between the electrodes of the pattern),
By dividing the line width, line length, etc. into 21 sections, it is easy to control the line width, line length, etc. to accurate values in advance.

As the pressure load increases from this initial state via the plunger 13, the contact area between the printed circuit 15 and the tip 12F of the contactor 12 increases, and the mutually contacting parts electrically form a parallel circuit. As a result, the inter-electrode resistance decreases.

Now, the initial resistance of the printed resistance circuit is Ro, the resistance at load F is R, the contact diameter between the contact 12 and the printed circuit 15 at this time is L, the distance between the electrodes of one circuit is L, and the volume of the contact 12 is When the specific resistance value is σ, it is expressed as.

Since the contact radius is proportional to the load F, the resistance between the terminals decreases as the load increases. If the contact diameter changes by ΔD when the load changes ΔF, then the change in resistance between the terminals ΔR is.

Therefore, even though ΔD increases, ΔR decreases and Δ
If D decreases, ΔR increases.

Moreover, when RO is very large with respect to σ, it becomes easy.

On the other hand, when the block contactor 12 is combined with the resistance circuit pattern shown in FIG. In this way, when the contact 12 is crushed under a certain pressure state and the two printed circuits 15 and 15 are connected, it becomes conductive and can be used for pressure detection that also functions as a switch.

Next, the effects will be explained based on various experimental examples.

<Experiment example 1> Guidance? Using LT silicone rubber KE-360IU (manufactured by Shin-Etsu Chemical), a contact (Fig. 5) with an outer diameter of 12 m and an inclination angle of α = 20 degrees was fabricated, and a line width W = 0.5 and a weight electrode distance L.
= When brought into contact with a resistance circuit board having a 12m layer A pattern, the inter-electrode resistance value, which was 12Ω when no pressure was applied, gradually decreased to 8Ω when applied with IKg, showing good pressure response. was obtained (see Figure 7, line 20).

<Experimental example 2> The line width at the center is W H - 0.5 mm, and the line width widens as it approaches the electrode, and the line width W2 at the electrode part is 8 ■ layers, and the distance between the electrodes is 12 ■ ■. Resistance of pattern B When the circuit board was brought into contact with the contactor (Fig. 5), the resistance value between the electrodes, which was 5Ω when no pressure was applied, changed almost linearly to IKΩ when the pressure was applied to IKg, which was very good. A good pressure response was obtained (see line 21 in FIG. 7).

(Experimental Example 3) A contactor (Fig. 5 ), the interelectrode resistance value, which was 12Ω in a closed circuit and infinite in an open circuit when no pressure was applied, gradually decreased to 8.5Ω with a pressure of 1 kg, resulting in a good pressure response. (Figure 7, line 22)
reference).

In this case, there is no change in the electrode resistance value in the case of a closed circuit until a pressure of 0.2 kg is applied, and the resistance value remains infinite in the case of an open circuit. In the case of an open circuit, the interelectrode resistance value matched that in the case of a closed circuit, and a pressure detector that also behaved as a switch was obtained.

<Experimental Example 4> Using conductive silicone rubber 5RX-539UF (manufactured by Toray Silicone), a contactor (Fig. 6) having an outer diameter of 12 mm and a concave portion 12c with an inclination angle α of 15 degrees was molded. Contact pressure was applied to the B-pattern resistor circuit board (FIG. 3) used, and the influence of the difference in wall thickness d on the pressure responsiveness of the interelectrode resistance was investigated. FIG. 8 is a graph showing the relationship between pressing force and contact area when the thickness of d is ■4■■, ■3m layer, ■2 layer, and ■1++v+,
It can be seen that the contact area increases as the pressure increases, and the thinner the wall thickness, the higher the rate of increase in the contact area with respect to pressure.

FIG. 9 is a graph showing changes in the pressure responsiveness of the interelectrode resistance value as the thickness of d changes. According to this, the wall thickness d of the contact has a large influence on the pressure response, and it is necessary to change the dimensions and shape depending on the pressure range. It can be seen that the contact area changes as the contact area deforms in response to the change in resistance between the electrodes.

In addition, the pressure sensor is configured such that the contactor 12 is deformed by applying a load of 1 kg via a spring and brought into contact with the resistance circuit board 11, and when external pressure is applied, the load due to the spring decreases. (not shown), a characteristic was obtained in which the inter-electrode resistance value gradually increased when the external pressure exceeded 1 kg (see Fig. 10).

〔Effect of the invention〕

As explained above, according to this invention.

(a) Since the contact is in contact with the resistance circuit board in a pressure-free state, pressure detection is possible from O. - (b) Since the initial value is set by the resistance circuit, stable pressure detection ability is achieved. be. In addition, (c) changes in resistance are measured only at the contact area between the contact and the resistance circuit, and pressure changes can be responded to by determining the shape of the contact and the shape of the resistance circuit according to the pressure detection range requirements. It is possible to make the resistance value change linear. This invention is achieved by such improvements.

It is possible to provide a pressure detector that is more cost-effective and more practical than conventional general pressure sensors such as metal sensors and semiconductor sensors, which enables accurate pressure detection that has not been possible in the past.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional side view of one embodiment of the present invention, FIGS. 2, 3, and 4 are plan views showing examples of the resistor circuit pattern of the present invention, and FIG. 5, respectively. FIG. 6 is a half-sectional side view showing an example of the contactor of the present invention, FIGS. 7 to 10 are graphs of experimental data related to the present invention, and FIG. 7 is a load (pressure) for each resistance circuit pattern.
/resistance characteristic diagram, Figure 8 is a load/contact area characteristic diagram with the contact wall thickness (d) as a parameter, and Figure 9 is a load/contact area characteristic diagram with the contact thickness (d) as a parameter.
) as a parameter, Figure 10 is a load/resistance characteristic diagram with another configuration, Figure 11 is a plan view showing an example of a conventional pressure detector, and Figure 12 is a double diagram of Figure 11. −
■It is a sectional view. In the figure, E, E2 are electrodes, 11 is a resistance circuit board, and 12 is a (block) contact. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 11 Fig. 12 Procedural amendment document February 5, 1986 Director General of the Patent Office Uga Michibe 1. Display of the case 1985 Patent Application No. 269544 2, Name of the invention Pressure detector 3, Person making the amendment Relationship to the case Patent applicant Name 2-7 Kojimachi, Chiyoda-ku, Tokyo Name Name Kokoku Rubber Industries Co., Ltd. Representative: Tomoaki Eno 4, Agent address: 5 Tamuracho Building, 3-3-14 Shinbashi, Minato-ku, Tokyo Date of amendment order (All columns of "Complete drawings") 7. Contents of the amendment (1) Details of the description Correct "dimensions" in the third line of page 6 to "width". (2) r3130IJ on page 10, line 3 of the same book as l'36
Corrected to 01J. (3) “Explain” in the third line of page 13 of the same book as “explain”
Correct to. (4) Figure 8 of the drawings will be corrected as shown in the attached sheet. (5) Figure 11 of the drawings will be corrected as shown in the attached sheet.

Claims (1)

[Claims] It consists of a resistive circuit board having at least one pair of electrodes formed by means such as printing, and a conductive elastic material, which maintains constant contact with the resistive circuit board and changes from a non-pressure state to a pressurized state. A pressure sensor comprising a block contact whose contact area gradually changes to form an electrically parallel variable resistance circuit.