JP2001101947A - Device for sensing compressed force - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for sensing compressed force with enhanced durability to shock power, that can obtain stably a variation characteristic of resistance value to compressed force for long time. SOLUTION: In a device for sensing compressed force, characterized in that a front holder is formed with a through hole at an upper surface, one end of a sliding pole goes in and out of the through hole. A rear holder has a pair of measuring terminals on the bottom surface thereof, through which the measuring terminals extend outwardly from inside thereof. In the other end of the sliding pole, a pressing plate and a conductive resistor for sensing pressure are disposed adjacently. In the unloaded state, the pressing plate and the conductive resistor are biased in the sliding direction of the sliding pole by a resilient body for transferring the compressed force and a resilient body for releasing a load such that there is maintained a state that the conductive resistor is not contacted with the pair of measuring terminals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressive force sensing element, and an object of the present invention is to provide a compressive force sensor capable of stably obtaining characteristics of improvement in durability against impact force and resistance value change against compressive force for a long time. It is intended to provide a sensing element.

[0002]

2. Description of the Related Art Conventionally, there has been a compressive force sensing element which senses a compressive force applied from the outside as a change in electric resistance. For example, in Japanese Utility Model Application Laid-Open No. 56-41419, a pressure-sensitive conductive resistor is embedded in a plate-like insulator, and the pressure-sensitive conductive resistor and the contact electrode are covered with a protective film. There is disclosed a compressive force sensing element capable of preventing a contact electrode and a pressure-sensitive conductive resistor from coming into contact with air by pressing the contact electrode with air. In addition, Shokai 61
-56724 discloses a compressive force sensing element configured to generate an electrical output corresponding to a pressure change of a pressure-sensitive conductive resistor.

[0003]

However, these compressive force sensing elements have the following disadvantages. That is, the above-described compressive force sensing element applies a compressive force directly to the pressure-sensitive conductive resistor, and measures the change in surface electric resistance or the change in volume resistance due to the deformation or distortion caused by this. In the method, when a strong impact is applied or when used for a long time, there is a problem that internal collapse or breakage of the pressure-sensitive conductive resistor occurs,
There is a problem that the characteristic of the change in the electric resistance value also fluctuates greatly, and the change in the electric resistance value with respect to the compressive force becomes unstable. Therefore, it has been desired to create a compression force sensing element that can cope with a strong impact force and that exhibits a stable change in electric resistance value over a long period with respect to a compression force.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 is a compression force sensing element for sensing a compression force as a change in electric resistance. In the compression force sensing element, a sliding rod made of a non-conductive material slidable in the axial direction transmitting the compression force, a pressure-sensitive conductive resistor whose electric resistance value changes by the compression force, It consists of a pair of parallel measuring terminals for measuring the change in electric resistance value by contacting the pressure-sensitive conductive resistor, and a cylindrical holder made of a non-conductive material for holding and storing these. The holder part includes a front holder part and a rear holder part that can be engaged or screwed together, and an insertion hole into which one end of the sliding rod projects is provided on the upper surface part of the front holder part, The pair of measurements is located on the bottom of the rear holder. A terminal is provided so as to communicate from the inside to the outside, and a pressure plate and a pressure-sensitive conductive resistor are inserted into the other end of the sliding rod adjacent to each other on the bottom side thereof, so that The piezo-electrically conductive resistor and the pressing plate are formed by a compression force transmitting elastic body and a load reducing elastic body, so that the pressure-sensitive conductive resistor and the pair of measuring terminals are in a non-contact state in a non-pressurized state. The present invention relates to a compressive force sensing element characterized by being sandwiched in the sliding direction of a sliding rod. The invention according to claim 2 is
2. The pressure-sensitive conductive resistor is formed by dispersing and blending a conductivity-imparting material in a non-conductive elastomer.
The present invention relates to a compressive force sensing element described in (1). The invention according to claim 3 is characterized in that the sliding rod is provided with a protrusion for preventing the slide rod from falling off from the holder part, and the sliding force is sensed according to claim 1 or 2. Related to the element. The invention according to claim 4 relates to the compressive force sensing element according to any one of claims 1 to 3, wherein the pressing plate is made of a conductive material, and the surface thereof is provided with fine irregularities. The invention according to claim 5 relates to the compressive force sensing element according to any one of claims 1 to 4, wherein a curved portion is provided on a surface of the measurement terminal that contacts the pressure-sensitive conductive resistor. The invention according to claim 6 is characterized in that a bottom portion of the rear holder portion is provided with a groove for holding an elastic body and / or a sliding rod guide hole for holding a load reducing elastic body. Item 5 relates to a compressive force sensing element according to items 1 to 5.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A compressive force sensing element according to the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view of a compressive force sensing element according to the present invention, and FIG. 2 is a sectional view of the compressive force sense element according to the present invention. FIG. 3 is a sectional view when a compressive force is applied to the compressive force sensing element according to the present invention. FIG. 4 is an exploded perspective view showing another embodiment of the compression force sensing element according to the present invention. FIG. 5 is a sectional view showing a part of another embodiment of the compressive force sensing element according to the present invention, FIG. 6 is a plan view of a holder portion of the compressive force sense element according to the present invention, and FIG. FIG.
FIG. 4 is a sectional view taken along line AA of FIG. FIG. 8 is a sectional view showing a use state of the compressive force sensing element using the holder.

A compression force sensing element according to the present invention includes a sliding rod for sensing a compression force, an elastic body for transmitting a compressive force applied to the sliding rod, and an elastic body for transmitting a compression force. A pressure plate that presses the pressure-sensitive conductive resistor by the applied compressive force, a pressure-sensitive conductive resistor that changes the electrical resistance value when the compressive force is applied, and a load-reducing elastic body that absorbs the impact force And a pair of measurement terminals for measuring a change in the resistance value of the pressure-sensitive conductive resistor, and a holder unit for housing and holding these terminals.

The sliding rod (3) is for sensing an external compressive force, and one end of the sliding rod (3) is provided with a front end so as to be able to sense the external compressive force. The other end is housed inside the holder so as to protrude from the insertion hole (21) provided in the holder part (22), and slides in the axial direction of the slide rod (3). It is kept possible. As the material of the sliding rod (3), it is preferable to use a non-conductive material, and use a thermoplastic resin such as a polyacetal resin, a polycarbonate resin, an acrylic resin, or a polyamide resin, or a thermosetting resin such as a phenol resin. Can be. Ceramics can also be used for the purpose of improving the heat resistance of the sliding rod (3). The slide rod (3) in the illustrated example is provided with a projection (31) for preventing the slide rod (3) from falling off from the front holder (22). The protrusion (31) for preventing falling off is formed in the middle of the sliding rod (3). As this form,
A substantially disk-shaped one as shown in the illustrated example can be exemplified, but there is no particular limitation. Further, by adjusting the length of the insertion portion (32) provided on the bottom portion side of the holder portion of the sliding tube (3), the maximum value of the compressive force applied to the pressure-sensitive conductive resistor (6) can be reduced. It can be set freely.
For example, if the length of the insertion portion (32) is increased, the distal end portion of the insertion portion (32) comes into contact with the bottom of the rear holder portion with a weak compressive force. It is not added to (6).

[0008] A pressure-sensitive conductive resistor is a substance whose electric resistance value is reduced when a compressive force is applied to cause deformation or distortion. Generally, a material obtained by dispersing and blending a conductivity-imparting material in a non-conductive elastomer is used. When a compressive force is applied to the non-conductive elastomer by dispersing and blending the conductivity-imparting material in the non-conductive elastomer, the conductivity-imparting materials come into contact with each other or come into contact with each other, and in some cases, dielectric breakdown occurs and the electric resistance increases. The value decreases favorably.

The specific constitution of the material of the pressure-sensitive conductive resistor (6) having such properties is not particularly limited, but the non-conductive elastomer may be a natural material having rubber-like elastic deformation. Examples thereof include rubber, special synthetic rubbers such as urethane rubber and silicone rubber, general synthetic rubbers such as styrene rubber and butadiene rubber, thermoplastic elastomers, and high molecular substances such as polyethylene showing elastic deformation. Examples of the conductivity-imparting material include metal particles such as nickel, copper, gold, silver, stainless steel, aluminum, iron, chromium, and alloys thereof, and graphite, carbon black, and carbon particles. By forming such a pressure-sensitive conductive resistor into a plate shape, the pressure-sensitive conductive resistor (6) as shown in the illustrated example is formed.
Can be obtained. The cross-sectional shape of the plate-shaped pressure-sensitive conductive resistor (6) is not particularly limited. An insertion hole (61) is provided in the pressure-sensitive conductive resistor (6), and is inserted through one end of the sliding rod (3).

The measuring terminal (8) is brought into contact with the pressure-sensitive conductive resistor (6) to thereby form the pressure-sensitive conductive resistor (6).
For measuring the change in the resistance value of the sample, and transmitting the change in the resistance value to another device (not shown) connected to the measuring terminal (8), for example, a resistance value measuring device. In addition,
In the illustrated example, a plate-shaped measuring terminal (8) is used. In the compressive force sensing element (1) according to the present invention, the pair of measurement terminals (8) parallel to each other are provided so as to communicate from the inside to the outside of the bottom surface of the rear holder (24). In a non-pressurized state, the pressure-sensitive conductive resistor (6) and the measuring terminal (8) are provided in a non-contact state.

The form of the contact surface of the measuring terminal (8) with the pressure-sensitive conductive resistor (6) can be a linear one as shown in FIG. 4, but as shown in FIG. It is also possible to use one having a gentle curved portion (81). The radius of this curved portion (81) is about 3 to 5 m
m. By providing the curved portion (81) at the portion of the measuring terminal (8) in contact with the pressure-sensitive conductive resistor (6), a stable change in the resistance value can be measured, and the sensitivity can be improved. , A high compression force sensing element. The material used is not particularly limited. For example, copper or brass plated with nickel or gold, or stainless steel can be used, but stainless steel is used in view of strength and corrosion resistance. It is desirable.

In the compression force sensing element (1) according to the present invention, a pressure plate (5) is provided on the pressure-sensitive conductive resistor (6) side of the insertion hole (21) so as to be adjacent to each other, The pressure-sensitive conductive resistor (6) and the pressing plate (5) are inserted into one end of the sliding rod (3), and furthermore, the compressive force transmitting elastic body (4) and the load reducing elastic body (7). In the axial direction of the sliding rod (3), that is, in the sliding direction of the sliding rod (3), and in a non-pressurized state, the pressure-sensitive conductive resistor (6) and the measuring terminal (8) is held in a non-contact state. By being sandwiched between the two elastic bodies in this manner, when no compressive force is applied to the sliding rod (3), the measuring terminal (8) and the pressure-sensitive conductive resistor (6) are connected. Since the gaps are provided at a constant interval, the pressure-sensitive conductive resistor (6) does not show a change in the resistance value, and when a compressive force exceeding a certain level is applied, the pressure-sensitive conductive resistor (6) does not sense the resistance. The contact with the piezo-conductive resistor (6) comes into contact, and the change in the electric resistance value can be measured.

One of the two elastic bodies for holding and fixing the pressure-sensitive conductive resistor (6) and the pressing plate (5) in the sliding direction of the sliding rod (3) is one of the sliding rod (3). A compressive force transmitting elastic body that plays a role of transmitting the compressive force applied to the pressure-sensitive conductive member, and the other elastic body is used when the pressure-sensitive conductive resistor (6) and the measuring terminal (8) come into contact with each other. This is a load reducing elastic body (7) which serves to reduce the impact force and to return the sliding rod (3) to its original position when the external compressive force is removed. The form of the two elastic bodies used is not particularly limited, but is a coil spring in the illustrated example. When a coil spring is used, for example, a stainless steel wire, a spring steel wire, a piano wire, a phosphor bronze wire, or the like can be used as the material, but from the viewpoint of oxidation and corrosion resistance, use a stainless steel wire. Is desirable. When a coil spring is used, it is preferable to use a coil spring whose both end portions are formed so as to be substantially perpendicular to the axial direction of the sliding rod (3). Can be exemplified. This is because if a coil spring such as a non-grinding open end is used, the contraction becomes unstable, and a stable change in resistance cannot be measured. The two elastic bodies in the illustrated example are non-grinding closed-end coil springs.

In a normal case, the two elastic members are substantially equal, or the elastic member (7) for reducing the load contracts with a smaller force than the elastic member (4) for transmitting the compressive force. It is good to have composition. This is because when the compressive force transmitting elastic body (4) contracts more easily, the compressive force transmitting elastic body (4) reduces the compressive force when the compressive force is applied to the sliding rod (3). Since the pressure-sensitive conductive resistor (6) does not come into contact with the measuring terminal (8) with a weak compressive force due to absorption, the sensitivity of the compressive force sensing element (1) is lowered, which is not preferable. Because. Further, by changing the elasticity and size of the elastic body used, it is possible to arbitrarily set the sensitivity and the measurement limit of the compressive force sensing element (1).

By disposing the pressing plate (5) so as to be adjacent to the pressure-sensitive conductive resistor (6), the compressive force applied to the sliding rod (3) is reduced by the compressive force transmitting elastic member (4). ), The pressure is transmitted to the pressing plate (5), and the compressive force can be transmitted uniformly to substantially the entire surface of the pressure-sensitive conductive resistor (6) in contact with the pressing plate (5). For this reason, it is usually preferable that the outer diameter of the pressing plate (5) is substantially the same as or larger than that of the pressure-sensitive conductive resistor (6). The pressing plate (5) in the illustrated example is formed in a substantially cylindrical shape,
An insertion hole (51) for inserting the slide rod (3) is provided.

As the material of the pressing plate (5), a conductive material is used, and copper, brass, stainless steel, an alloy of copper or silver,
Nickel and gold-plated metals can be exemplified, and stainless steel and silver alloys are preferably used in terms of strength and corrosion resistance. Examples of the conductive resin include those obtained by blending carbon black with a thermoplastic resin such as a vinyl chloride resin, a polyethylene resin, or a polypropylene resin. It is also possible to provide a fine uneven shape on the surface of the pressing plate (5). By providing such a fine uneven shape, a gradual change in the electric resistance value with respect to the applied compressive force can be obtained. The compression force sensing element (1) shown in FIG. In addition, it is preferable that this uneven shape has a shape of several microns to several tens of microns.

As described above, each member described above is housed and held in a cylindrical holder comprising a front holder (22) and a rear holder (24). As shown in FIG. 2, the inner diameter of the holder is larger than the maximum diameter of the protrusion (31) for preventing the slide rod (3) from coming off, the pressing plate (5), and the pressure-sensitive conductive resistor (6). It is set large and is made of an electrically insulating material.
Thus, even if the pressure-sensitive conductive resistor (6) hits the holder portion, no electric leakage occurs, and the resistance value of the pressure-sensitive conductive resistor (6) can be accurately measured. The cross-sectional shape of the holder portion is not particularly limited, and may be, for example, a circular shape as shown in FIG. 1 or a polygonal shape such as a square shape as shown in FIG.

The material of the holder is not particularly limited as long as it is an electrically insulating material. For example, a thermoplastic resin such as a polycarbonate resin, a polyacetal resin, an acrylic resin, a polyamide resin, or a thermosetting resin such as a phenol resin is used. When it is possible to further improve heat resistance, glass, ceramic, or the like can be used. The holder in the illustrated example has a through hole (2) for the sliding rod (3).
A front holder (22) having 1) and a rear holder (24) to which the measuring terminal (8) is fixed;
The insertion hole (21) is provided on the upper surface of the front holder (22), and the measuring terminal (8) is provided on the bottom of the rear holder (24). Further, in the holder section shown in FIG. 1, the front holder section (22) and the rear holder section (24) are screwed together with a screw section (25), and the holder section shown in FIG. It is engaged by (26).

FIG. 6 shows the bottom of the rear holder.
As shown in FIG. 8 to FIG. 8, an elastic body holding groove (2) for holding a sliding rod guide hole (27) and a load reducing elastic body (7).
8) may be provided. As shown in FIG. 8, by providing the sliding rod guide hole (27), the sliding rod (3) can always slide stably with little blurring. Obtainable. Further, the provision of the elastic body holding groove (28) allows the load reducing elastic body (7) to perform stable contraction, so that the pressure-sensitive conductive resistor (6) has a stable electric resistance value. Can show change. In the illustrated holder portion, a male screw portion (23) for fixing the compressive force sensing element (1) to a base (not shown) or the like is formed.

The compressive force sensing element according to the present invention is characterized in that when a compressive force is applied to the sliding rod (3), the load reducing elastic body (7).
Contracts. When a compressive force is further applied, the pressure-sensitive conductive resistor (6) comes into contact with the measuring terminal (8) as shown in FIG.
At this time, since the load reducing elastic body (7) is used,
Even when a sudden load is applied, the impact force when the pressure-sensitive conductive resistor (6) comes into contact with the measuring terminal (8) can be reduced. Also, since the external compressive force is transmitted through the compressive force transmitting elastic body (4), it is possible to prevent an excessive compressive force from being applied to the pressure-sensitive conductive resistor (6). In addition, since the pressure-sensitive conductive resistor (6) is transmitted substantially uniformly to the entirety of the pressure-sensitive conductive resistor (6) through the pressing plate, a stable change characteristic of the electric resistance value can be exhibited.

[0021]

As described above in detail, according to the first aspect of the present invention, there is provided a compressive force sensing element for sensing a compressive force as a change in electric resistance value, wherein the compressive force sense element is arranged in an axial direction for transmitting the compressive force. A sliding rod made of a non-conductive material slidable on
A pressure-sensitive conductive resistor whose electric resistance value changes due to a compressive force, and a pair of parallel measurement terminals for measuring a change in electric resistance value by contacting the pressure-sensitive conductive resistor,
These are held and housed, and are formed of a cylindrical holder made of a non-conductive material, and the holder is formed of a front holder and a rear holder that can be engaged or screwed together,
An insertion hole through which one end of the sliding rod protrudes is provided on the upper surface of the front holder, and the pair of measurement terminals is provided on the bottom of the rear holder in such a manner as to extend from inside to outside. A pressure plate is inserted into the other end of the slide rod, and a pressure-sensitive conductive resistor is inserted adjacent to the bottom surface of the slide rod so as to be adjacent to each other. The sliding rod is slid by the compressive force transmitting elastic body and the load reducing elastic body so that the pressure-sensitive conductive resistor and the pair of measuring terminals are not in contact with each other in a non-pressurized state. Since the present invention relates to a compressive force sensing element characterized by being sandwiched in a direction, the following excellent effects can be obtained.

That is, since the pressure-sensitive conductive resistor is sandwiched between the two elastic members, the impact force is reduced, and the durability of the compressive force sensing element can be greatly improved. In addition, since the pressure plate is used, the pressure-sensitive conductive resistor can uniformly contact the measurement terminal in a well-balanced manner. Characteristics can be stabilized. Further, the sensitivity and the measurable area of the compressive force sensing element can be arbitrarily set depending on the elasticity of the elastic body used and the gap between the pressure-sensitive conductive resistor and the measurement terminal.

According to a second aspect of the present invention, the pressure-sensitive conductive resistor is formed by dispersing and blending a conductivity-imparting material in a non-conductive elastomer. Therefore, it is possible to obtain a compressive force sensing element exhibiting stable resistance value change characteristics.

According to a third aspect of the present invention, the sliding rod includes:
The compression force sensing element according to claim 1 or 2, wherein a protrusion for preventing the slide rod from falling off from the holder is provided. Dropout can be prevented.

The invention according to claim 4 is characterized in that the pressing plate is made of a conductive material, and the surface thereof is provided with fine irregularities, the compression force sensing according to any one of claims 1 to 3. Since it is related to the element, it can be a compression force sensing element showing a gradual change characteristic with respect to the compression force, and the change in the resistance value of the pressure-sensitive conductive resistor with respect to the change in the compression force can be increased. .

The invention according to claim 5 is characterized in that a curved portion is provided on a surface of the measuring terminal which contacts the pressure-sensitive conductive resistor, and the compressive force sensing device according to any one of claims 1 to 4, wherein Since the present invention relates to the element, a stable change in electric resistance value can be measured, and a highly sensitive compressive force sensing element can be obtained.

The invention according to claim 6 is characterized in that a groove for holding an elastic body and / or a sliding rod guide hole for holding an elastic body for reducing load is provided on the bottom surface of the rear holder. Since the present invention relates to the compressive force sensing element according to any one of claims 1 to 5, the sliding of the sliding rod and the contraction of the load reducing elastic body can be stabilized, and the measuring terminal and the pressure-sensitive conductive material can be stabilized. Due to the stabilized contact of the resistor, the characteristic of the resistance change of the pressure-sensitive conductive resistor with respect to the compressive force can be stabilized.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a compression force sensing element according to the present invention.

FIG. 2 is a sectional view of a compressive force sensing element according to the present invention.

FIG. 3 is a cross-sectional view showing a state when a compressive force is applied to the compressive force sensing element according to the present invention.

FIG. 4 is an exploded perspective view of a compressive force sensing element according to another embodiment of the present invention.

FIG. 5 is a side view showing a part of a compressive force sensing element using a measuring terminal provided with a curved portion.

FIG. 6 is a plan view of a holder of a compressive force sensing element according to another embodiment of the present invention.

FIG. 7 is a sectional view taken along line AA of the holder section shown in FIG. 6;

FIG. 8 is a cross-sectional view showing a state where a compressive force is applied to a compressive force sensing element using the holder shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Compressive force sensing element 21 ... Insertion hole 22 ... Front holder part 24 ... Rear holder part 27 ... Sliding rod guide hole 28 ... Elastic body holding groove part 3 ...・ Sliding rod 31 ・ ・ ・ Protrusion for preventing falling off 4 ・ ・ ・ Elastic body for transmitting compressive force 5 ・ ・ ・ Pressing plate 6 ・ ・ ・ Pressure-sensitive conductive resistor 7 ・ ・ ・ Elastic body for load reduction 8. ..Measurement terminals 81 ... Bending parts

Claims (6)

[Claims] 1. A compressing force sensing element for sensing a compressive force as a change in an electric resistance value, wherein the compressive force sensing element is a sliding rod made of a non-conductive material slidable in an axial direction for transmitting a compressive force. And, a pressure-sensitive conductive resistor whose electric resistance value changes by compressive force, and a pair of parallel measurement terminals for measuring a change in electric resistance value by contacting the pressure-sensitive conductive resistor, And a cylindrical holder made of a non-conductive material for holding and storing the front holder. The holder comprises a front holder and a rear holder which can be engaged or screwed together, and an upper surface of the front holder. The portion is provided with an insertion hole through which one end of the sliding rod projects, and the bottom portion of the rear holder portion is provided with the pair of measurement terminals so as to communicate from the inside to the outside. A pressure plate on the other end of the sliding rod and pressure-sensitive conductive on the bottom side The pressure-sensitive conductive resistor and the pressing plate are inserted by the compressive force transmitting elastic body and the load reducing elastic body in a non-pressurized state. A compressive force sensing element characterized in that the body and the pair of measuring terminals are sandwiched in a sliding direction of a sliding rod so as to be in a non-contact state. 2. The compressive force sensing element according to claim 1, wherein the pressure-sensitive conductive resistor is formed by dispersing a conductivity-imparting material in a non-conductive elastomer. 3. The compression force sensing element according to claim 1, wherein the slide rod is provided with a protrusion for preventing the slide rod from falling off from the holder. 4. The compressive force sensing element according to claim 1, wherein the pressing plate is made of a conductive material, and has a surface with fine irregularities. 5. The compressive force sensing element according to claim 1, wherein a curved portion is provided on a surface of the measuring terminal that contacts the pressure-sensitive conductive resistor. 6. A bottom surface portion of the rear holder portion is provided with a groove for holding an elastic body and / or a sliding rod guide hole for holding an elastic body for reducing load.
6. A compressive force sensing element according to any one of claims 1 to 5.