JP2001004656A - Force sensor and adjustment of sensitivity thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-sensitive force sensor capable of increasing and adjusting the sensitivity of detection, and preventing the force sensor from being damaged and destroyed by the action of an impact force or a large external force applied to the force sensor. SOLUTION: This impact resistant force sensor 31 is provided with a supporting base 3 having a hollow part 4, a flexible plate 5 which has at least one detecting element 6 and is horizontally laid on the hollow part 4 in the supporting base 3, and an acting body 2 suspended from the flexible plate 5 at the hollow part 4 in the supporting base 3. A visco-elastic body 10 is attached so as to come into contact with at least the acting body 2 and the flexible plate 5, at least the acting body 2 and the wall surface of the hollow part 4 in the supporting base 3, or at least the part of the substrate on which the acting body 2 and the force sensor 31 are disposed or part of a can body on which the substrate is disposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of detecting the direction and magnitude of a physical quantity acting from the outside by detecting the displacement of an actuating body itself or the bending of a flexible plate due to the displacement of an actuating body by a sensing element. This is a force sensor originally measured, which can increase the detection sensitivity and can adjust the detection sensitivity, and furthermore, the force sensor can be damaged by an impact force applied to the force sensor or a large external force. The present invention relates to a highly reliable force sensor for preventing destruction and a method for adjusting the sensitivity of the force sensor.

[0002]

2. Description of the Related Art In the fields of the automobile industry and the machine industry, demands for force sensors capable of accurately detecting physical quantities such as acceleration and magnetism are increasing. In particular, a small force sensor capable of detecting these physical quantities for each of two-dimensional or three-dimensional components is desired. For example, an acceleration sensor is one of such force sensors, and adjusts the self-standing stability of a mechanism that automatically adjusts the posture, a collision sensing mechanism, and a crane when the vehicle loses its position due to a sudden steering wheel, side wind, or the like. Or a mechanism that senses a change in the velocity of the fluid flowing in the piping and adjusts the flow rate or opens and closes a valve.

Further, in a joystick used for a computer game or the like, a small force sensor capable of faithfully reproducing not only the amount of displacement at the time of operation but also the degree of force application is desired. .

As such a force sensor, Japanese Patent Laid-Open No.
No. 25744 discloses a weight 96 as shown in FIG.
A force sensor 95 is disclosed in which a plurality of piezoelectric elements 98 are arranged on a flexible plate 97 that supports the force. Further, Japanese Unexamined Patent Publication No.
No. 94661 discloses an abutment 93 as shown in FIG.
A flexible plate 92 and a weight 94 disposed inside the force sensor are force sensors 90 integrally formed of a piezoelectric material,
One end surface of the cylindrical abutment 93 is closed by a flexible plate 92, and a column-shaped weight 94 is supported by the flexible plate 92 at the center of the hollow portion of the abutment 93. A force sensor 90 in which a plurality of upper electrodes 91A to 91E are provided, and a lower electrode 91F is provided on the lower surfaces of the support 93, the flexible plate 92, and the weight 94 is disclosed.

[0005] These force sensors are configured such that the flexible plate bends by a force corresponding to a physical quantity such as a direct force externally acting on the weight, an inertial force due to acceleration, or an attractive force due to magnetism. By detecting the charge generated in the piezoelectric body in accordance with the deflection of the body, the direction and magnitude of the physical quantity (force) acting on the weight can be detected.

Three-dimensional force detection by a force sensor,
That is, the force detection in each of the X, Y, and Z axes representing the rectangular coordinate system is performed by taking the force sensor 90 shown in FIG. When the displacement occurs, the displacement amount can be detected by the electric charge generated in the upper electrode 91E. At this time, the upper electrode 91A
The charges generated in the upper electrodes 91A and 91B cancel each other, and the charges generated in the upper electrodes 91C and 91D also cancel each other, so that the upper electrodes 91A to 91D do not detect the force in the Z-axis direction. . Similarly, when the weight is displaced in the X-axis direction, the charge generated on the upper electrodes 91A and 91B is used. When the weight is displaced in the Y-axis direction, the charge is generated on the upper electrodes 91C and 91D. The amount of displacement in each direction can be measured. In this way, when the weight is displaced in an arbitrary direction, the direction and magnitude of the force applied to the weight can be known by combining the detected axial components.

[0007]

In such a force sensor, it is essential to improve the reliability in use while maintaining the detection sensitivity and the detection accuracy. Here, since it is necessary to form many sensing elements and electrodes such as piezoelectric elements on the surface of the flexible plate, the flexible plate is required to secure an area necessary for disposing these sensing elements and the like. (In the above-described force sensor 90 shown in FIG. 11, the distance D indicates the distance D from the outer periphery of the weight 94 to the inner wall of the hollow portion of the support 93.
The same applies hereinafter. ) Must be equal to or larger than a predetermined value.

Further, in order to cause a desired flexure in the flexible plate, it is necessary to set the width and the thickness of the flexible plate to predetermined values according to the weight of the weight. In other words, when the width of the flexible plate is reduced and when the thickness of the flexible plate is large, the rigidity of the flexible plate is increased. Although it is preferable in that the destruction of the plate is prevented, the weight is hardly displaced, and the flexible plate is not sufficiently distorted. As a result,
There is a problem that the detection sensitivity is lowered.

Conversely, when the width of the flexible plate is large and the thickness thereof is small, the mechanical strength of the flexible plate is reduced, so that the impact resistance is reduced and the flexible plate is easily broken. Although a problem occurs, the amount of distortion of the flexible plate increases, which is preferable in terms of improvement in detection sensitivity and detection accuracy. Therefore, conventionally, the width and thickness of the flexible plate are appropriately determined in consideration of securing the space for disposing the sensing element and the like, detection sensitivity, reliability, and also considering the shape and weight of the weight. I was

In addition, even when the width of the flexible plate is large and the thickness thereof is thin, a stopper is provided around the working body to restrict the displacement of the working body from being unnecessarily large, and A method of suppressing the destruction of the plate is also conceivable. However, when trying to limit the displacement of the weight in all directions, there is a problem that the structure becomes complicated.

Further, if a force sensor is formed by assembling members (flexible plates, weights, abutments) made of different materials and made as separate bodies using an adhesive or the like, these members are incompatible with each other. Although it is possible to satisfy the characteristics, there is a problem that a decrease in productivity cannot be denied because many parts and man-hours are required.

By the way, when arranging a sensing element, there may be a case where characteristics vary among a plurality of sensing elements, and in this case, it is necessary to adjust the sensitivity of the sensing element. For example, when a piezoelectric element is used, it is necessary to adjust the electrode area by trimming or the like using a YAG laser or the like. Since an expensive machine or the like must be used for such trimming, if the sensitivity can be adjusted by a simpler alternative method, it is advantageous in the manufacturing process.

[0013]

Means for Solving the Problems The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to change the shape and material of the main components of a force sensor. Another object of the present invention is to provide a force sensor capable of adjusting the detection sensitivity by providing simple additional means and further improving the shock resistance.

That is, according to the present invention, an abutment having a hollow portion, at least one sensing element is provided, and
A force sensor having a flexible plate suspended in the hollow portion of the abutment and an actor supported by the flexible plate in the hollow portion of the abutment, wherein the viscoelastic body is at least The working body and the flexible plate, or at least the working body and the hollow wall surface of the abutment, or at least a part of the substrate on which the working body and the force sensor are disposed or A force sensor is provided, wherein the substrate is attached so as to contact a part of a can body in which the substrate is provided.

In this force sensor, silicone gel or silicone rubber is preferably used as the viscoelastic body. In addition, it is preferable that the working body is embedded in the viscoelastic body because the sensitivity is most improved. In addition, the force sensor of the present invention is preferably used as an acceleration sensor that detects an externally applied acceleration by using an operating body as a weight.

In such a force sensor of the present invention, the green sheet laminating method is suitably used, whereby the working body, the abutment and the flexible plate can be easily formed integrally, and As a material, it is preferable to use zirconia as a main component. Further, it is preferable that the flexible plate and the sensing element are formed integrally, and when a green sheet laminating method is used, an integral structure without using an adhesive or the like can be easily obtained by integral firing. .
A piezoelectric element is preferably used as the detecting element.

According to the present invention, an abutment having a hollow portion and at least one sensing element are provided, and
A method for adjusting the sensitivity of a force sensor including a flexible plate suspended in a hollow portion of the support and an operating body supported by the flexible plate in the hollow portion of the support, the method comprising: A substrate on which the operating body and the force sensor are arranged so that at least the operating body and the flexible plate are in contact with each other, or at least the operating body and the hollow wall surface of the support are in contact with each other. A method of adjusting the sensitivity of a force sensor, wherein the method is provided so as to be in contact with a part of the substrate or a part of a can body on which the substrate is provided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a force sensor according to the present invention will be described with reference to the drawings, taking a case where a piezoelectric element is used as a sensing element as an example. These various force sensors are suitably used as an acceleration sensor for detecting acceleration acting from the outside by using the acting body as a weight.

FIG. 1 is a sectional view (b) and plan views (a) and (c) showing an embodiment of the force sensor of the present invention.
The plan view (a) is a view seen from the upper side of the sectional view (b), and the plan view (c) is a view seen from the lower side of the sectional view (b).

The force sensor 31 includes an abutment 3 having a hollow portion 4, a flexible plate 5 laid over the hollow portion 4, and an operating body 2 supported by the flexible plate 5 in the hollow portion 4. ing. Further, a piezoelectric element (detection element) is provided on the upper surface of the flexible plate 5 (the surface opposite to the surface on which the action body 2 is supported).
6 are provided. The action body 2, the support 3, the flexible plate 5, and the piezoelectric element (detection element) 6 are the basic constituent members of the force sensor 31. Note that the working body 2 is supported by the force sensor 31 at the center of the hollow portion 4 (the flexible plate 5), but is not necessarily limited to such a position.

Here, the working body is a member that is displaced by receiving an external force, and the abutment is a base member for holding the working body and the flexible plate. Therefore, the working body and the abutment are made of a material having high rigidity which is not deformed by force,
For example, it is preferable to be formed using ceramic or metal, and if a material having a large specific gravity is used for the working body, there is an advantage that downsizing becomes easy.

On the other hand, the flexible plate is a plate-like member suspended from the support while supporting the working body, and is bent based on the displacement of the working body. Therefore, as long as the flexible plate is not elastically deformed as long as it is not broken by the displacement of the working body, the sensitivity of the force sensor can be improved, which is preferable. Specifically, metals, ceramics, glass, resins, and the like can be used, but it is preferable to use ceramics having a high Young's modulus, easily inducing distortion in the piezoelectric element, and easily disposing the piezoelectric element. In the case where a metal material is used for the flexible plate, the piezoelectric element may have an electrode, and thus may need to be insulated from the piezoelectric element. Further, the entire flexible plate can be made of a piezoelectric material.

In the force sensor 31, the direction in which the working body 2 is supported is defined as the Z-axis direction, and an X-axis and a Y-axis that are orthogonal to each other are set in the plane direction of the flexible plate 5 perpendicular to the Z-axis. The setting of such coordinate axes is the same for various force sensors described later. When such coordinate axes are set, in the force sensor 31, the piezoelectric element disposed at a position corresponding to the inner peripheral side of the hollow portion 4 can be suitably used for detecting a force in the Z-axis direction. The piezoelectric element disposed at a position corresponding to the outer peripheral side of the hollow portion 4 can be used for detecting a force in the direction inside the XY plane.

Now, in the force sensor 31, the viscoelastic body 10 is filled in the hollow portion 4, and the operating body 2 is
Buried in In the present invention, "embedment of the working body"
The expression does not mean only the state in which the operating body 2 exists in the viscoelastic body 10 without being exposed, and the lower surface of the operating body 2 may be exposed from the viscoelastic body 10.

In the present invention, the density of the viscoelastic body has a positive correlation with the sensitivity of the sensor, and the viscosity and elastic modulus of the viscoelastic body have a negative correlation with the sensitivity of the sensor. In other words, the density of the viscoelastic body acts as a function of an additional weight to the working body like the working body, so that the sensor sensitivity is increased. On the other hand, the viscosity and elastic modulus of the viscoelastic body have the function of reducing the displacement of the working body due to the external force, and thus the function of reducing the distortion of the sensing element on the flexible plate caused by the displacement of the working body. As a result, the sensor sensitivity is reduced. For this reason, the viscoelastic body has a function as a sensitivity adjusting material.

For example, by selecting a viscoelastic material having a moderately high density, a low viscosity, and a low elastic modulus, it is possible to provide a sensor that is relatively resistant to impact while improving the sensitivity. By selecting a viscoelastic body having a high density, a high viscosity, and a high elastic modulus, it is possible to provide a sensor which is extremely resistant to impact and has a sensor sensitivity suppressed to a desired value. Therefore, the form of attachment of the viscoelastic body is not limited to the form of the force sensor 31.

For example, the viscoelastic body 10 has a structure similar to a force sensor 32 shown in a sectional view (a) and a plan view (b) of FIG.
It may be provided so as to be in contact with at least the working body 2 and the flexible plate 5, and the sectional view (a) and the plan view (b) of FIG.
The force sensor 33 may be attached so as to contact at least the wall surface of the hollow portion 4 of the working body 2 and the support 3 as shown in FIG. However, as described later, since the weight of the viscoelastic body 10 contributes to the increase rate of the detection sensitivity, when the amount of the viscoelastic body 10 attached is small, the change rate of the detection sensitivity also becomes small.

Further, in the case where the amount of contact of the viscoelastic body 10 is small, the portion of the operating body 2 where the viscoelastic body 10 is attached to a portion closer to the weight tip having a large displacement amount is the weight. High displacement suppressing effect. Therefore, the embodiment of FIG. 3 is more preferable than the embodiment of FIG. 2 from the viewpoint of impact resistance. 2 and 3
Are drawn in the same manner as the cross-sectional view of FIG. 1B and the plan view of FIG. In addition, although the form of the surface of the viscoelastic body 10 is drawn by a curve, it is not limited to such a shape.

By the way, in the present invention, “the viscoelastic body is attached” means that “the viscoelastic body is disposed so as to be in contact with the constituent member, or is disposed so as to adhere the constituent member”. It will be used at will. Therefore, the filling of the viscoelastic body 10 into the hollow portion 4 is only one mode of mounting the viscoelastic body 10.

Since the viscoelastic body 10 has the same effect as the working body 2, the viscoelastic body 10 is not only required to be in contact with at least a part of the working body 2 but also , Must also be in continuous contact with other members. Therefore, a state in which the viscoelastic body 10 is attached only to the acting body 2 is excluded from the embodiment of the present invention.

The viscoelastic body 10 includes a polymer gel (gel body) such as silicone gel, agar, konjac, silicone rubber, natural rubber, butadiene rubber, styrene rubber, butyl rubber, ethylene propylene rubber, nitrile rubber, acrylic Polymer rubber (rubber-like body) such as rubber, urethane rubber, fluorine rubber, or foam with good elasticity (sponge-like body), vinyl chloride, polystyrene, AB
Plastics such as S, polyethylene, polypropylene, nylon, acrylic resin, fluororesin, polycarbonate, methylpentene resin, polyurethane, phenolic resin, melamine resin, and epoxy resin are preferably used.

Among them, the silicone gel, in particular, is a sol (liquid) having excellent fluidity before curing, so that the silicone gel can be easily filled into the hollow portion 4, and the viscosity can be adjusted to make the silicone gel free-standing. It has characteristics that are favorable for mounting on a force sensor in various shapes, for example, it can be arranged as a shape. As the rubber-like body, there are a liquid state and a paste state as properties before curing, but it is preferable to use a liquid state which can be easily filled into the hollow portion 4.

Each cross-sectional view shown in FIG. 4 shows another embodiment of the present invention in the same manner as FIG. 1B. The force sensors 34A to 34D are attached to the substrate 8,
In addition, there is a form in which the auxiliary working body 7 is attached to the working body 2 using a hole formed in the substrate 8. Each of the force sensors 34A to 34D has a form in which the amount of the viscoelastic body 10 attached to the hollow portion 4 is different.

FIG. 5 shows the rate of change of the detection sensitivity of each of the force sensors 34 A to 34 D shown in FIG. 4 in the X-axis, Y-axis, and Z-axis directions, as shown in FIG. The graph shows the effect of the difference in the amount of the viscoelastic body 10 attached to the detection sensitivity on the basis of the detection sensitivity of the force sensor 34E in which the elastic body 10 is not attached at all. As shown in Table 1, the effect of the amount of the viscoelastic body 10 on impact resistance is as follows.
All of the force sensors 34A to 34D are equivalent.

[0035]

[Table 1]

As shown in FIG. 4, the shape of the acting body 2 is not limited to the columnar shape shown in FIG. 1, and it is also preferable to partially provide irregularities. Also, the form of the auxiliary action body 7 is not limited to a columnar shape. However, when using the same shape of the sensing element so as not to make a difference between the detection sensitivity in the X-axis direction and the detection sensitivity in the Y-axis direction, the operating body 2 and the auxiliary operating body 7 have shapes that are line-symmetric with respect to the Z axis. It is preferable that

As is clear from FIG. 5, the viscoelastic body 10
It can be seen that the detection sensitivity increases as the amount of attachment increases. In other words, the viscoelastic body 10 functions in the same manner as the working body 2, and as the amount of attachment increases, the mass acting as the working body increases, so it is considered that the detection sensitivity is increased. In addition, even if bubbles are included in the viscoelastic body 10, when the volume ratio is small, it does not particularly adversely affect the increase in the detection sensitivity.

Meanwhile, when the fluidity of the viscoelastic body 10 is large, the detection sensitivity changes over time due to a change in the contact area between the acting body 2 and the viscoelastic body 10. It is also clear. Therefore, the hardness of the viscoelastic body 10 is set to be appropriate so that the contact area between the viscoelastic body 10 and the working body 2 is constant, or the viscoelastic body 10 is prevented from flowing out to the outside. In addition, it is preferable to devise the structure of the force sensor.

For example, the force sensor 3 shown in FIG.
4D arranges the substrate 8 on another substrate 11 and
The viscoelastic body 10 is injected into the hollow portion 4 by using the hole portion 12 formed in 1 and then cured, and the hole portion 12 is closed with the resin 13. Of course, the structure for preventing the viscoelastic body 10 from flowing out is not limited to such a form.

Conventionally, in adjusting the detection sensitivity in each axial direction, a method has been used in which a part of the sensing element is deleted by laser or dicing to change the effective operating area of the sensing element. However, by utilizing the fact that the rate of increase in the detection sensitivity varies depending on the amount of the viscoelastic body attached as in the present invention, the detection sensitivity can be reduced without using a process that requires expensive mechanical equipment such as a laser device. Adjustment can be easily performed. Such a trimming method of changing the attachment amount of the viscoelastic body does not require mechanical costs,
Further, since the work is easy, it greatly contributes to shortening and simplification of the manufacturing process and cost reduction of the product.

Next, regarding the form of attachment of the viscoelastic body,
A description will be given of a specific example in which the basic components are the same as the force sensor 31. First, FIG. 6 (FIG. 6 (a)
6B corresponds to the cross-sectional view, and FIG. 6B corresponds to the plan view of FIG. 2) shows a form in which the viscoelastic body 10 is attached to a part of the operating body 2 and a part of the flexible plate 5, and the viscoelastic body 10 is compared with the force sensor 32 shown in FIG. The only difference is that the elastic body 10 is not in contact with the wall of the hollow portion 4 of the support 3.

Viscoelastic body 1 in force sensors 31 to 35
As is clear from the mounting state of No. 0, the viscoelastic body 10 does not need to be mounted so as to fill the hollow portion 4 of the support 3, but may be mounted with good symmetry with respect to the working body 2. preferable. This is different from the case where the viscoelastic body 10 is partially attached so as to be asymmetric with respect to the working body 2, and the position of the center of gravity of the combination of the working body 2 and the viscoelastic body 10 is only the working body 2. This is because the position is shifted to a different position, and as a result, a difference occurs in the detection sensitivity in each axis direction. Conversely, by utilizing this, it is also possible to intentionally change the detection sensitivity only in a predetermined axial direction.

Next, FIGS. 7A and 7B show the viscoelastic body 1.
0 is a force sensor 36A.3 having a configuration in which it is attached so as to contact a part of the substrate 8 on which the acting body 2 and the force sensor are disposed.
FIG. 6B shows a cross-sectional view of FIG. 7A and 7B correspond to the cross-sectional view of FIG. 1B.

The force sensors 36A and 36B have a configuration in which the attached state of the viscoelastic body 10 in the above-described force sensors 34B to 34D is changed, and the auxiliary action body 7 is not provided. That is, the force sensor 36A contacts the operating body 2 and the substrate 8 while the force sensor 36B
The viscoelastic body 10 is provided so as to be in contact with the support 3 and the substrate 8.

On the substrate 8, other wiring components, arithmetic elements, electric control elements, and the like can be provided. Therefore,
The substrate 8 is one of the static members like the abutment 3, and is provided with the viscoelastic body 10 so as to be in contact with the operating body 2 and the substrate 8, so that the substrate 8 is similar to the force sensors 31 to 35 described above. Thus, the effect of adjusting the detection sensitivity can be obtained.

The force sensor 34 shown in FIGS. 4 and 7
When B-34D is combined with 36A / 36B, it can be easily conceived that the auxiliary working body 7 can be provided in the state where the viscoelastic body 10 is attached to the force sensors 36A / 36B.

As described above, when the force sensor of the present invention is provided on a substrate, by covering the entire substrate with a can body, the environment that adversely affects the force sensor, such as humidity and dust, is removed. Can be protected. The force sensor is preferably incorporated into various devices and apparatuses in such a package state (hereinafter, the form in which the force sensor is disposed in the can body is referred to as a “sensor package”). Therefore, since the can body of the sensor package can also be one of the static members, the force sensor can also be provided by attaching the viscoelastic body so as to contact the working body and the can body (wall surface of the can body). Can be adjusted.

FIGS. 8A to 8C show the viscoelastic body 10.
Is a sectional view (similar to FIG. 7) of force sensors 37A to 37C attached so as to come into contact with the operating body 2 and a part of the can body 9 on which the substrate 8 is disposed. The force sensor 37A is in contact with the working body 2 and the can 9; the force sensor 37B is in contact with the working body 2 and the support 3 and the can 9; Are filled and the viscoelastic bodies 10 are respectively contacted with the substrate 8 and the can 9.
Is provided.

As described above, the detection sensitivity can be adjusted by attaching the viscoelastic body at a predetermined position and controlling the attachment amount. In addition, in the force sensor of the present invention, When a large external force acts on the force sensor, the viscoelastic body suppresses the excessive displacement of the acting body, and does not extremely lower the detection sensitivity at the measurement frequency (several Hz to several tens Hz) without changing the resonance frequency. The effect of lowering the Q value at (several kHz to several tens kHz) can also be obtained. Therefore, the force sensor of the present invention also has a feature of being excellent in impact resistance.

Next, a method for manufacturing the force sensor of the present invention will be described. The force sensor 31 and the like can be manufactured by individually manufacturing each member using various materials, and then bonding and using an adhesive or the like. In this case,
There is a problem that the number of parts is large and the production process is likely to be complicated.
Therefore, in the present invention, a method in which the working body 2, the support 3, and the flexible plate 5 are integrally fired and formed by a green sheet laminating method using a ceramic green sheet is suitably adopted.

A green sheet is prepared from a slurry prepared by mixing a binder, a solvent, a plasticizer, and the like with ceramic powder using a doctor blade method (slip casting) or a calendar roll method. Alternatively, the green sheet can also be prepared by adding a binder, a solvent, and a plasticizer to a ceramic powder and kneading the mixture, using an extrusion molding method or the like. The green sheet is a thin sheet having a predetermined thickness, and is characterized by having excellent flexibility and workability, and being easy to cut, punch, and adhere. Therefore,
A plurality of green sheets punched and cut into a desired tomographic shape are laminated at a predetermined position, integrated by thermocompression bonding (hot press) or the like, and then fired to obtain the working body 2.
It is possible to obtain a force sensor integrally formed with the support 3 and the flexible plate 5 in a predetermined shape. Hereinafter, such a method of manufacturing a force sensor is referred to as a “green sheet laminating method”.

When the green sheet laminating method is used, it is easy to reduce the thickness of the force sensor itself, and the thickness reproducibility of each green sheet and the uniformity of the entire green sheet are excellent. In addition, there is an advantage that precise control of the thickness of the flexible plate is easy. Therefore, the force sensor manufactured by the green sheet laminating method can improve the detection sensitivity by forming the flexible plate so as to be easily bent, and also has a variation in the deflection of each flexible plate or each part of the flexible plate. It has a feature that it is small, and therefore, the characteristic variation of each force sensor can be reduced.

Further, by controlling the thickness of the green sheet,
Alternatively, even when a green sheet having a predetermined thickness is used, the thickness of each part can be easily adjusted by appropriately selecting the number of stacked green sheets. That is, unlike the case where the working body and the like are manufactured separately, there is no need to manufacture parts having different sizes for each design shape. In this way, it is easy to balance the detection sensitivity in the Z-axis direction by adjusting the thickness of the acting body, which particularly affects the detection sensitivity in the X-axis and Y-axis directions, by the number of stacked green sheets. This makes it possible to reduce or eliminate the labor required for objective calibration.

Further, when thin plates cut into a tomographic shape are laminated for each of the working body, the abutment, and the flexible plate, it becomes possible to select a green sheet having a different thickness for each member. Can be selectively used, such as using a thin green sheet having high flexibility, and using a green sheet having high rigidity for the weight and abutment. The flexible portion is easily bent while being integrally formed. The body and the abutment make it possible to obtain a highly sensitive and accurate force sensor with high rigidity.

When the green sheet laminating method is used, many sheet components can be obtained from one green sheet by punching using a die or the like, so that the productivity is excellent and the precision is high. The advantage that force sensors can be provided at low cost, and the manufacturing process can be shortened by forming the lower electrode, piezoelectric body, and upper electrode using green film technology such as screen printing on the green sheet and firing them integrally. There is also an advantage that it can be easily achieved.

Hereinafter, a method for manufacturing the force sensor of the present invention will be described in detail. First, FIG. 9 shows an example of a green sheet member (hereinafter, referred to as a “sheet member”) prepared for manufacturing a force sensor by punching a green sheet.
Shown in Here, the sheet member 21 of the first layer mainly forms a flexible plate, but also forms the upper surface portion of the abutment. The sheet member 22A of the second layer forms an abutment, and the sheet member 22B forms an action body. These sheet members 22A and 22B are preferably used by laminating a plurality of layers so as to obtain a predetermined thickness. The sheet members 21, 22A and 22B are provided with reference holes 25 used for positioning during lamination.

Various sheet members 2 thus prepared
1.2A and 22B are connected to the respective sheet members 21 and 2
The reference holes 25 formed in the 2A and 22B are sequentially laminated while passing through the positioning pins set on the lower base of the crimping fitting, and finally, the upper base of the crimping fitting is superimposed, and hot pressing or the like is performed in the laminating direction to perform sheet pressing. 21 / 22A / 22B are integrated. By degreasing and firing the laminated body (bulk) thus obtained, the working body of the force sensor, the support, and the flexible plate can be integrally formed.

Subsequently, a piezoelectric element is formed on the outer surface (upper surface) of the flexible plate in the obtained fired body. In forming the piezoelectric element, an electrode paste is printed and fired using a screen printing method, then a piezoelectric ceramic paste is printed and fired, and then the electrode paste is printed and fired. A printing method is preferably used in which an electrode paste and a piezoelectric ceramic paste are stacked and printed and fired at one time. Further, it can be formed by a sputtering method or the like. Although it is necessary to draw out electrode leads from the piezoelectric element, it is preferable in terms of production process to form the electrode leads simultaneously with the formation of the electrodes of the piezoelectric element.

It is also possible to form a piezoelectric element on the surface of the sheet member 21 in advance by laminating printing, and to form the piezoelectric element simultaneously with firing of the bulk. However, in this case, it is necessary to adjust the firing temperature of the piezoelectric element to the firing temperature of the bulk.

Next, when the viscoelastic body 10 is filled in the hollow portion 4 as in the case of the force sensors 31 and 34B to 34E,
The viscoelastic body 10 can be attached by a method of injecting the liquid raw material into the hollow portion 4 using a syringe or the like and then hardening. This method is also suitably used for attaching the viscoelastic body 10 in the force sensors 32 and 37C. If the viscosity of the liquid raw material is appropriately adjusted so that the shape can be maintained to some extent and the surface remains viscous, the force sensor 3
It is also possible to mount the viscoelastic body 10 in the form of the viscoelastic body 3 and 35. This method is based on the force sensors 36A and 36B provided on the substrate 8 and the force sensor 37A provided on the can body 9 as well. -37B can be similarly used.

Next, materials and the like suitably used for each member (excluding the viscoelastic body) when the above-described green sheet laminating method is used will be described. As the ceramic material constituting the green sheet, a material mainly composed of zirconia, which has good sheet formability, has high toughness in a sintered body, and has high strength, is suitably used. Any of stabilized zirconia can be used, but it is also possible to use various different ceramic materials in combination as long as the laminated and integrated bulk can be integrally fired. Thus, it is possible to easily improve the measurement sensitivity and the reliability against mechanical destruction.

Next, for a piezoelectric element which is one element of the piezoelectric element, lead zirconate titanate (PZT), lead magnesium niobate (PMN), and lead nickel niobate (PN)
Piezoelectric ceramics having excellent piezoelectric characteristics such as N) are preferably used. In addition, silver (Ag), gold (A
u), palladium (Pd), platinum (Pt) or an alloy thereof is preferably used. In particular, when a high melting point metal such as Pd or Pt is used, simultaneous firing with a piezoelectric body is easy and integral firing with a flexible plate or the like can be easily performed, which is preferable. In addition, although it depends on the manufacturing process, copper (Cu), nickel (Ni), aluminum (A
Various metal materials such as 1) can be used for the electrode and the electrode lead.

In the present invention, any of a piezoelectric material and an electrostrictive material may be used as the piezoelectric body. The porosity of the piezoelectric body is preferably 50% or less, more preferably 20% or less. If the porosity is too high, it is difficult to obtain sufficient piezoelectric / electrostrictive characteristics. The porosity in this case is defined as the ratio occupied by the area of the porosity portion with respect to the visual field area when the cross section of the piezoelectric body is mirror-polished so as not to fall off, and the cross section is observed using an SEM or the like. Point.

As described above, the embodiments of the force sensor according to the present invention have been described using a piezoelectric element as a sensing element as an example, but the present invention is not limited to these embodiments. Needless to say. That is, regarding the structure of the force sensor, the features of each embodiment can be combined with each other, and various changes can be made to the shape of each part without departing from the gist of the present invention. Should be understood.
For example, the present inventors previously disclosed in Japanese Patent Application No. 10-87133 a force sensor (three-axis sensor) in which the shape and composition of a flexible plate were varied in various ways. Also for the (three-axis sensor), it is possible to increase the detection sensitivity by attaching the viscoelastic body, which is the main purpose of the present invention.

In the above-described embodiment,
External shape of abutment in XY plane (shape of upper surface and lower surface)
Is a square, and the hollow portion is a column, but the shape is not limited to such a shape. For example, XY
It is possible to make the outer shape of the abutment in a plane circular or elliptical, and as described above, the shape of the acting body may be various shapes such as a prismatic shape in addition to the columnar shape described above. it can.

As for the flexible plate, in all of the above-described embodiments, a single plate having a constant thickness has been illustrated, but the thickness of the flexible plate does not necessarily have to be constant. In addition, the flexible plate does not need to be laid on the support so as to completely close the hollow portion on the support. For example, a flexible plate that is thick near the joint with the working body and the abutment and thin in the middle is used, or a beam is provided on the flexible plate to suppress the displacement of the working body in a certain axial direction. It is possible to use a flexible plate having portions having different thicknesses, and further, a plate-like flexible plate having a predetermined width is straddled over the hollow portion without completely closing the upper surface of the abutment. It does not matter. Such a shape of each member may be appropriately determined according to the selection of the number of detection directions of the force to be detected and the use of the force sensor.

The detecting element is not limited to the piezoelectric element, and may be any element that detects the displacement of the working body itself or the bending generated on the flexible plate based on the displacement of the working body, and converts the amount of bending to an electric signal. I just need. For example, a device using a change in capacitance, a device using a change in piezoresistance, and the like can be used. As a method using the change in capacitance,
It has a pair of electrodes provided on the surface of a flexible plate or a working body, a dielectric sandwiched between the electrodes, and an electronic circuit connected to the electrodes, and the capacitance charged in this specific space is expressed by an electronic circuit. That are detected by the following method. An element typified by a strain gauge can be used as a device utilizing a change in piezoresistance. In addition, a device utilizing a resistance change due to expansion and contraction of a conductor can also be used.

[0068]

As described above, according to the force sensor and the sensitivity adjustment method of the present invention, since the detection sensitivity can be adjusted by controlling the filling amount of the viscoelastic body, the conventional laser in the manufacturing process can be adjusted. Instead of trimming using, for example, the detection sensitivity can be adjusted easily and inexpensively. Furthermore, the force sensor according to the present invention has excellent impact resistance because the Q value at the resonance frequency is reduced.
It is also excellent in reliability. By using the green sheet laminating method, it is possible to improve the production efficiency while homogenizing the characteristics of the individual force sensors, and there is also an excellent effect that the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view showing an embodiment of a force sensor of the present invention.

FIG. 2 is a sectional view and a plan view showing another embodiment of the force sensor of the present invention.

FIG. 3 is a sectional view and a plan view showing still another embodiment of the force sensor of the present invention.

FIG. 4 is a sectional view showing still another embodiment of the force sensor of the present invention.

FIG. 5 is a graph showing how the sensitivity of the force sensor of the present invention increases.

FIG. 6 is a sectional view and a plan view showing still another embodiment of the force sensor of the present invention.

FIG. 7 is a sectional view showing still another embodiment of the force sensor of the present invention.

FIG. 8 is a sectional view showing still another embodiment of the force sensor of the present invention.

FIG. 9 is a plan view showing one embodiment of a shape of a green sheet used for a green sheet laminating method.

FIG. 10 is a cross-sectional view showing a mode in which a viscoelastic body is not provided in the force sensor shown in FIG. 4;

FIG. 11 is a perspective view showing one embodiment of a conventional force sensor.

FIG. 12 is a sectional view showing an embodiment of a conventional force sensor.

[Explanation of symbols]

2 ... Working body (weight), 3 ... Abutment, 4 ... Hollow part, 5 ... Flexible plate, 6 ... Piezoelectric element, 7 ... Auxiliary working body, 8 ... Substrate, 9 ... Can body, 10 ... Viscoelastic body , 11 ... substrate, 12 ... hole, 13 ...
Resin, 21 / 22A / 22B: Sheet member, 25: Reference hole, 31-37C: Force sensor, 90: Force sensor, 91A
-91E: upper electrode, 91F: lower electrode, 92: flexible plate, 93: support, 94: weight, 95: force sensor, 96:
Weight, 97: flexible plate, 98: piezoelectric element.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Fumitake Takahashi 2-56, Suda-cho, Mizuho-ku, Nagoya-shi, Aichi Japan F-term (reference) 2F051 AA10 AB08 AC01 DA03 DB05

Claims (9)

[Claims] 1. An abutment having a hollow portion, a flexible plate provided with at least one sensing element, and laterally suspended in the hollow portion of the abutment; A force sensor having an operating body supported by a flexible plate, wherein the viscoelastic body is in contact with at least the operating body and the flexible plate, or at least a hollow in the operating body and the support. That it is attached so as to be in contact with the inner wall surface, or at least to be in contact with a part of a substrate on which the operating body and the force sensor are disposed or a part of a can body on which the substrate is disposed. Characteristic force sensor. 2. The force sensor according to claim 1, wherein the viscoelastic body is a silicone gel or a silicone rubber. 3. The force sensor according to claim 1, wherein the action body has a structure embedded in the viscoelastic body. 4. The force sensor according to claim 1, wherein the acting body is used as a weight and used as an acceleration sensor for detecting an externally applied acceleration. 5. The force sensor according to claim 1, wherein the working body, the abutment, and the flexible plate are integrally formed by a green sheet laminating method. 6. The force sensor according to claim 5, wherein a green sheet containing zirconia as a main component is used. 7. The force sensor according to claim 5, wherein the flexible plate and the sensing element are formed integrally. 8. The force sensor according to claim 1, wherein the sensing element is a piezoelectric element. 9. An abutment having a hollow portion, a flexible plate on which at least one sensing element is provided, and which is laterally bridged in the hollow portion of the abutment; A method for adjusting the sensitivity of a force sensor having an operating body supported by a flexible plate, wherein the viscoelastic body is brought into contact with at least the operating body and the flexible plate, or at least the operating body and the It is attached so as to be in contact with the hollow part wall surface of the abutment, or at least to be in contact with a part of the substrate on which the operating body and the force sensor are disposed or a part of a can body on which the substrate is disposed. A method for adjusting the sensitivity of a force sensor.