JP2000076966A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase ease of assembly of a pressure sensor for use as the after-touch sensor of an electronic keyboard instrument. SOLUTION: A flexible sheet 14, having a moving contact 16 made from pressure-sensitive conducting ink, is bonded via a spacer 15 on a base 11 having a pair of comb-like fixed contacts 12, 13 made from carbon. The base 11 and the flexible sheet 14 are gripped by a frame 21. The frame 21 includes a soft pressure plate part 22 formed by two-color extrusion molding, etc., and has a protrusive part 22a, and a pair of hard grip parts 23. In assembling, the base 11 and the flexible sheet 14 are gripped by the pair of grip parts 23, than the position of the protrusive part 22a relative to the flexible sheet 14 is uniformly determined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor, for example, a pressure sensor used as an after touch sensor of an electronic keyboard instrument.

[0002]

2. Description of the Related Art For example, a conventional pressure sensor used as an after touch sensor of an electronic keyboard instrument is shown in FIGS. 7A and 7B. This pressure sensor has a strip-shaped substrate 1. On both sides in the width direction of the upper surface of the substrate 1, a pair of comb-shaped fixed contacts 2 and 3 made of carbon are formed so as to bite each other. A strip-shaped flexible sheet 4 is bonded on the substrate 1 via a spacer 5. On almost the entire lower surface of the flexible sheet 4, there is formed a movable contact 6 made of a pressure-sensitive conductive ink and having a resistance value that changes according to a pressing load and a change in the contact area with the pair of fixed contacts 2 and 3. At the center in the width direction of the upper surface of the flexible sheet 4, a pressing plate 7 made of a belt-like felt is adhered. In this case, the width of the pressing plate 7 is slightly smaller than the interval between the spacers 5. This is because when the pressing plate 7 is pressed by the flat lower surface of the key (not shown), the flexible sheet 4 is pressed by the pressed pressing plate 7.
Is bent downward symmetrically in FIG. 7A to improve the pressure-sensitive characteristics.

When the key is continuously pressed, the flexible sheet 4 at the portion corresponding to the key is pressed via the pressing plate 7 and bends downward. Then, the movable contact 6 displaced integrally with the flexible sheet 4 comes into contact with the pair of fixed contacts 2 and 3 according to the key pressing force, and the resistance value according to the contact state becomes the pair of fixed contacts 2 and 3. , And the tone is changed according to the detection result.

[0004]

Since the width of the pressing plate 7 is smaller than the width of the flexible sheet 4, the pressing plate 7 is accurately attached to the center of the upper surface of the flexible sheet 4 in the width direction. It is extremely difficult. On the other hand, when the position where the pressing plate 7 is pasted is shifted beyond the allowable range in the width direction, the resistance value between the pair of fixed contacts 2 and 3 greatly differs from the desired value even with the same key pressing force. Tone changes vary more than the allowable range. Therefore, considerable work is required for the work of attaching the pressing plate 7, and there has been a problem that the assembling workability is extremely poor. An object of the present invention is to facilitate assembly workability.

[0005]

According to the present invention, a pair of comb-shaped fixed contacts are formed on both sides in the width direction of a strip-shaped upper surface, and a pair of comb-shaped fixed contacts are attached to each other via a spacer. A flexible sheet having a band-shaped lower contact formed on a lower surface of the band, the resistance being changed by a pressing load and a change in the contact area with the pair of fixed contacts, and both side surfaces in the width direction of the substrate and the flexible sheet And a resin frame integrally provided with a hard gripping portion for gripping and a soft pressing plate portion disposed on the flexible sheet and having a protruding portion at the center in the lower surface width direction. is there. According to the present invention, when the gripping portion of the frame is gripped on both sides in the width direction of the substrate and the flexible sheet, the arrangement position of the pressing plate portion of the frame with respect to the flexible sheet is determined uniformly. It is sufficient that the gripping portion of the frame simply grips both sides in the width direction of the substrate and the flexible sheet,
Assembly workability can be facilitated.

[0006]

FIG. 1A is a longitudinal sectional side view of a pressure sensor according to a first embodiment of the present invention.
(B) is a sectional view taken along the line BB. This pressure sensor has a strip-shaped substrate 11. A pair of comb-shaped fixed contacts 12 and 13 made of carbon bite each other on both sides in the width direction of the upper surface of the substrate 11. A band-shaped flexible sheet 14 is bonded on the substrate 11 via a spacer 15. Almost the entire lower surface of the flexible sheet 14 is made of pressure-sensitive conductive ink,
A movable contact 16 whose resistance value changes due to a change in the contact area between the pressing load and the pair of fixed contacts 12 and 13 is formed.

[0007] Both sides in the width direction of the substrate 11 and the flexible sheet 14 are gripped by a frame 21. Frame 21
1A is formed symmetrically in FIG. 1A by two-color extrusion molding or the like, has a substantially U-shaped cross section, and has a soft pressing made of an elastomer or the like having a protruding portion 22a at the center in the width direction of the lower surface of the upper plate. A structure comprising a plate portion 22 and a pair of rigid grip portions 23 having a substantially L-shaped cross section and an inverted L-shaped cross section formed continuously at respective lower ends of both side plates of the pressing plate portion 22; Has become. The lower surface of the protruding portion 22a is a protruding surface that protrudes in an arc shape. The width of the protruding portion 22a is
The distance between them is almost the same. Then, both sides in the width direction of the substrate 11 and the flexible sheet 14 are gripped between the pair of hard gripping portions 23. In this state, the protrusion 22
The center of the lower surface width direction a is simply in contact with the center of the flexible sheet 14 in the upper surface width direction. A protective sheet 24 made of belt-like felt is attached to the upper surface of the pressing plate portion 22.

When a key (not shown) is continuously pressed, the pressing plate portion 22 at a portion corresponding to the key is pressed via the protective sheet 24 and elastically deforms downward. Then, the lower surface of the protruding portion 22a of the pressing plate portion 22 presses the flexible sheet 14, and the flexible sheet 14 bends downward. Then, the movable contact 16 displaced integrally with the flexible sheet 4 is turned into a pair of fixed contacts 1 according to the key pressing force.
2 and 13, the resistance value corresponding to the contact state is detected via the pair of fixed contacts 12 and 13, and the tone is changed according to the detection result. In this case, since the lower surface of the protruding portion 22a is a protruding surface that protrudes in an arc shape, the movable contact 1 increases as the key pressing force increases.
The contact area of the pair 6 with the pair of fixed contacts 12 and 13 gradually increases, so that better pressure-sensitive characteristics can be obtained.

When assembling the pressure sensor, when the both sides in the width direction of the substrate 11 and the flexible sheet 14 are gripped between the pair of gripping portions 23 of the frame 21, the pressing plate 22 of the frame 21 is The position of the projection 22a with respect to the flexible sheet 14 is determined uniformly. Therefore,
When assembling, the substrate 1 is
It is only necessary to simply hold the both sides in the width direction of the flexible sheet 14 and the flexible sheet 14, thereby facilitating assembly workability.

Next, FIG. 2A is a longitudinal sectional side view of a pressure sensor according to a second embodiment of the present invention, and FIG.
Is a sectional view taken along the line BB. This pressure sensor is different from the pressure sensor shown in FIG. 1 in that a central portion in the width direction of the movable contact 16 is formed of a pressure-sensitive conductive ink 16a having a relatively high resistance value, and both side portions in the width direction have a higher resistance value. However, this is a point formed by the slightly lower pressure-sensitive conductive ink 16b. By doing so, the protrusion 22
a, the lower surface of the pressure-sensitive conductive ink 16a having a high resistance value comes into contact with the pair of fixed contacts 12 and 13 and then the pressure-sensitive conductive ink 16b having a lower resistance value. Will come into contact with the pair of fixed contacts 12 and 13.

When the movable contact 16 is formed only of the pressure-sensitive conductive ink 16a having a high resistance value, the pressure-sensitive characteristic becomes as shown in FIG. 3A, and the pressure-sensitive conductive ink 16b having a low resistance value is obtained. When formed only by the pressure-sensitive characteristics, the pressure-sensitive characteristics are as shown in FIG. On the other hand, when the movable contact 16 is formed of the pressure-sensitive conductive ink 16a having a high resistance value and the pressure-sensitive conductive ink 16b having a low resistance value, the pressure-sensitive characteristic is as shown by a solid line in FIG. Therefore, better pressure-sensitive characteristics can be obtained. In addition,
In FIG. 3C, a dashed line indicates the pressure-sensitive characteristic of FIG. 3A, and a two-dot chain line indicates the pressure-sensitive characteristic of FIG.

FIG. 4A is a vertical sectional side view of a pressure sensor according to a third embodiment of the present invention, and FIG.
Is a sectional view taken along the line BB. This pressure sensor differs from the pressure sensor shown in FIG. 1 in that each tooth portion of the pair of fixed contacts 12 and 13 has a three-layer structure (for example, the number of times of printing carbon is three), and the center in the width direction. The point is that the height of the portion is made gradually higher than the height of both sides in the width direction. By doing so, the initial contact area of the movable contact 16 with the pair of fixed contacts 12 and 13 is small, and the contact area gradually increases as the key pressing force increases, and thus the resistance value changes gradually and smoothly. Good pressure-sensitive characteristics can be obtained.

FIG. 5A is a vertical sectional side view of a pressure sensor according to a fourth embodiment of the present invention, and FIG.
Is a sectional view taken along the line BB. This pressure sensor is different from the pressure sensor shown in FIG. 1 in that the central portion in the lower width direction of the protruding portion 22a has a substantially semicircular section 22 made of a resin that is slightly harder than the other portions.
b. By doing so, the pressure-sensitive characteristics of this embodiment are as shown by the solid line in FIG.
6, the pressure-sensitive characteristics of the pressure sensor are as shown by the dotted line in FIG. 6, but better pressure-sensitive characteristics can be obtained. In each of the embodiments shown in FIGS. 2 and 4, it is a matter of course that the structure of the protrusion 22a may be as shown in FIG.

[0014]

As described above, according to the present invention, when the gripping portion of the frame grips both sides in the width direction of the substrate and the flexible sheet, the arrangement of the pressing plate portion of the frame with respect to the flexible sheet is achieved. Since the positions are determined uniformly, when assembling, it is only necessary to make the holding portion of the frame simply hold both sides of the substrate and the flexible sheet in the width direction, so that assembling workability can be facilitated.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional side view of a pressure sensor according to a first embodiment of the present invention, and FIG. 1B is a sectional view taken along the line BB.

FIG. 2A is a longitudinal sectional side view of a pressure sensor according to a second embodiment of the present invention, and FIG. 2B is a sectional view taken along the line BB.

FIGS. 3A to 3C are views for explaining pressure-sensitive characteristics of the pressure sensor shown in FIG. 2;

FIG. 4 (A) is a longitudinal sectional side view of a pressure sensor according to a third embodiment of the present invention, and FIG. 4 (B) is a sectional view along line BB.

FIG. 5A is a longitudinal sectional side view of a pressure sensor according to a fourth embodiment of the present invention, and FIG. 5B is a sectional view taken along the line BB.

FIG. 6 is a view for explaining pressure-sensitive characteristics of the pressure sensor shown in FIG. 5;

FIG. 7A is a vertical sectional side view of a conventional pressure sensor,
(B) is a sectional view along the line BB.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12, 13 Fixed contact 14 Flexible sheet 15 Spacer 16 Movable contact 21 Frame 22 Pressing plate part 22a Protrusion part 23 Holding part 24 Protection sheet

Claims (6)

[Claims] 1. A substrate formed by a pair of comb-shaped fixed contacts biting each other on both sides in the width direction of a band-shaped upper surface, and bonded to each other via a spacer on the substrate. A flexible sheet on which a strip-shaped movable contact whose resistance value changes due to a change in the contact area with the pair of fixed contacts is formed, and a hard gripping portion that grips both sides in the width direction of the substrate and the flexible sheet. A pressure sensor comprising: a resin frame integrally provided with a soft pressing plate portion disposed on the flexible sheet and having a protruding portion at a central portion in a width direction of the lower surface. 2. The pressure sensor according to claim 1, wherein the resistance value of the movable contact at a central portion in the width direction is higher than the resistance value at both sides in the width direction. 3. The invention according to claim 1, wherein a height of a central portion of each of the teeth of the pair of fixed contacts that bites into each other in a direction along a width direction of the substrate is higher than a height of both side portions in the same direction. A pressure sensor characterized by being elevated. 4. The pressure according to claim 1, wherein a central portion in the lower width direction of the protruding portion is made of a resin that is slightly harder than other portions. Sensor. 5. The pressure sensor according to claim 1, wherein a protective sheet is attached on the pressing plate portion. 6. The pressure sensor according to claim 1, wherein the pressure sensor is used as an after touch sensor of an electronic keyboard instrument.