JP2000180274A - Force sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a force sensor with excellent reliability in which the direction and mass of a physical amount acting from outside can be measured three- dimensionally and prevention of damage or breakage caused by impact applied rapidly or by the action of a great external force is realized. SOLUTION: A force sensor 1 is constituted of a support stand 3 having a cavity part 4, a flexible plate 5 that has at least one detecting device and is laid horizontally on the cavity part 4 of the support stand 3, and an operant 2 pulled and supported by the flexible plate 5 in the cavity part 4 of the support stand 3. Then clearance parts 7A and 7B with a predetermined width are formed between the operant 2 and the support stand 3 and/or deterrent members 8A and 8B mounted on the support stand 3 so that the operant 2 is not deformed to exceed the predetermined distance.

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. The present invention relates to a sensor that is originally measured and is a highly reliable force sensor that prevents damage / breakage of a flexible plate due to the action of a sudden impact force or a large external force.

[0002]

2. Description of the Related Art In the fields of the automobile industry and the machine industry, there is an increasing demand for sensors capable of accurately detecting physical quantities such as acceleration and magnetism. In particular, a small sensor capable of detecting these physical quantities for each two-dimensional or three-dimensional component is desired. For example, an acceleration sensor is a mechanism that automatically adjusts the posture when a vehicle loses its position due to a sudden steering wheel, a side wind, or the like, a collision sensing mechanism, a mechanism that adjusts autonomous stability such as a crane, or a fluid velocity flowing through piping. It can be used for a mechanism or the like that adjusts the flow rate or opens and closes a valve by sensing a change in the pressure.

As such a sensor, Japanese Patent Application Laid-Open No. H5-25-2
Japanese Patent No. 5744 discloses a sensor 95 in which a plurality of piezoelectric elements 98 are arranged on a flexible plate 97 on which a weight 96 is supported, as shown in FIG. In addition, Japanese Patent Application Laid-Open No. 8-94
No. 661 discloses a sensor 90 in which a support 93, a flexible plate 92, and a weight disposed inside the sensor are integrally formed of a piezoelectric material, as shown in FIG. One end surface of the abutment 93 is closed by the flexible plate 92, and the abutment 93 is closed.
In the center of the hollow portion, a column-shaped weight is supported by the flexible plate 92, and a plurality of upper electrodes 91A to 91A are provided on the surface of the flexible plate 92.
A sensor 90 is disclosed in which E is provided, and a lower electrode 91F is provided on the lower surface of the support 93, the flexible plate 92, and the weight.

[0004] These 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. Physical quantity (force) acting on the weight by detecting the charge generated in the piezoelectric body according to the bending
Direction and size can be detected. Hereinafter, such a sensor is referred to as a “force (power) sensor”.

A three-dimensional force detection by a force sensor,
That is, in the detection of the forces in the X, Y, and Z axis directions (hereinafter, referred to as “three-axis directions”) representing a rectangular coordinate system, taking the sensor shown in FIG. When the displacement occurs in a certain Z-axis direction, the displacement amount can be detected by the electric charge generated in the upper electrode 91E. At this time, the electric charges generated in the upper electrodes 91A and 91B cancel each other, and
Wiring is performed so that the charges generated in the upper electrodes 91C and 91D are also offset from each other, so that the forces in the X-axis direction and the Y-axis direction are not detected. 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.

[0006]

In such a force sensor, it is essential to improve the reliability in use while maintaining the detection accuracy. Here, in order to cause a desired bending of the flexible plate, it is necessary that the width of the flexible plate be equal to or larger than a predetermined width. Further, since it is necessary to form many sensing elements and electrodes such as piezoelectric elements on the surface of the flexible plate, the width of the flexible plate is required to secure an area necessary for disposing these sensing elements and the like. Must be equal to or larger than a predetermined width. Further, when the width of the flexible plate is reduced, the rigidity around the flexible plate is increased, so that the weight becomes difficult to swing and the displacement is hindered. Therefore, sufficient stress is not generated in the flexible plate. There is a problem that the detection sensitivity is reduced. For this reason, in the conventional force sensor, the distance between the outer periphery of the weight and the inner peripheral surface of the abutment is designed to be equal to the width of the flexible plate.

On the other hand, the weight only has to be displaced within a predetermined detection range and a range where detection accuracy can be obtained, and there has been a problem that an excessive displacement may cause a failure of the sensor. For example,
If the sensor shown in FIGS. 16 and 15 is dropped due to an error or the like and collides with the ground, excessive acceleration is applied to the weight, and cracks occur at the boundary between the weight and the flexible plate. (Cracks) and the like, and the sensor was sometimes damaged.

In addition, during normal use, it is also assumed that a force that induces a displacement exceeding a desired displacement amount is applied to the weight. In such a case, even if the sensor is not damaged by one force application, the strength is gradually deteriorated between the weight and the flexible plate due to the large number of such large forces. Eventually, it can be destroyed.

Further, in the force sensor, the flexible plate is required to have high flexibility in order to obtain sufficient sensitivity, while the weight and the abutment are rigid in order to purely detect the received acceleration. Is required to be high and difficult to bend. Therefore, if the sensor is constructed by assembling the weight, abutment, and flexible plate members that are separately manufactured, it is possible to satisfy these contradictory characteristics, but many parts and man-hours are required. And
There is a problem that productivity cannot be denied.

[0010]

Means for Solving the Problems The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a larger force than normally expected, such as a fall or a collision. It is an object of the present invention to provide a highly reliable force sensor that does not break down even when applied to a sensor and that maintains good measurement accuracy. That is, according to the present invention, an abutment having a hollow portion, a flexible plate having at least one sensing element, and being laterally suspended in the hollow portion of the abutment, and a hollow portion of the abutment A force sensor comprising an operating body supported by the flexible plate, wherein the operating body is attached to the supporting body and / or the support so that the operating body is not displaced beyond a predetermined distance. A force sensor, wherein a gap having a predetermined width is formed between the force sensor and the stopping member. The force sensor according to the present invention includes a force sensor capable of detecting a force only in a uniaxial direction (linear direction) and a force sensor capable of detecting a force only in an arbitrary biaxial direction (plane direction). Sensors, as well as force sensors that detect forces in three axes, are included. Selection of the detection direction in these force sensors can be performed by changing the arrangement state and the wiring state of the sensing elements according to the application of the force sensor.

[0011] In the force sensor of the present invention, the above-described portion is provided between the convex portion and / or concave portion formed on the working body and the convex portion and / or concave portion formed on the abutment and / or the restraining member. It is preferable to have a structure in which a gap is formed. Further, it is preferable that the stopping member is attached to the upper surface and / or the lower surface of the abutment. INDUSTRIAL APPLICABILITY The force sensor of the present invention uses an operating body as a weight, and is suitably used as an acceleration sensor for detecting an externally applied acceleration.

Now, as a method of manufacturing the force sensor of the present invention, it is preferable to use a green sheet laminating method and integrally form the abutment, the working body, and the flexible plate by firing. here,
It is preferable that the burned material is formed at a predetermined position on the green sheet by printing or the like, and the burned material is burned out during firing to form a gap, thereby simplifying the manufacturing process. As the green sheet, one containing zirconia as a main component is preferably used, and in particular, the flexible plate is preferably formed by integrally firing the green sheet and the sensing element. As the detecting element, a piezoelectric element is preferably used. Also, in particular,
The composition of the flexible plate, 0.1 to 0.6 in terms of TiO ₂
0.005 to 0.005% by weight of titanium and / or MgO
It is preferable to use zirconia ceramics containing magnesium 0.1% by weight, 0 in terms of TiO _2.
2 to 0.5% by weight of titanium and / or 0.
It is more preferable that the zirconia ceramic contains magnesium in an amount of from 0.01 to 0.05% by weight.

By the way, in the force sensor of the present invention,
When the acting body has a cylindrical shape having a diameter of 2b and the abutment has a cylindrical inner peripheral wall having an inner diameter of 2a, when the thickness of the flexible plate is h, the Young's modulus is E, and the breaking stress is σ. The width L of the gap is preferably in the range of L = ± σαa ² / βEh (α: coefficient of maximum deflection, β: coefficient of maximum stress). A more preferable range of the width L of the gap is L = ± 0.9.
σαa ² / βEh, and a more preferable range is L
= Is between ± 0.7σαa ² / βEh, most preferred, L = in the range of ± 0.5σαa ² / βEh.

[0014]

Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking as an example a case where a piezoelectric element suitably employed in the present invention is used as a sensing element. 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 showing an embodiment of a force sensor (hereinafter, referred to as “sensor”) of the present invention. The basic constituent members of the sensor 1 are an abutment 3 having a hollow portion 4,
A flexible plate 5 laid horizontally in the hollow portion 4 of the support 3 and the working body 2 supported by the flexible plate 5 in the hollow portion 4 of the support 3.
The operating body 2 is supported by the sensor 1 at the center of the hollow portion 4 (flexible plate 5), but is not necessarily limited to such a position.

Although at least one sensing element is provided on the upper surface of the flexible plate 5, it is omitted in FIG. 1 and is not shown. In the sensor 1,
The direction in which the weight 2 is supported is defined as the Z-axis direction, and the Z-axis direction is defined as the vertical direction of the sensor 1. Further, the X-axis and the Y-axis are set in the transverse direction of the flexible plate 5 perpendicular to the Z-axis. The setting of such coordinate axes is the same for various sensors described later.

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 that is not deformed by force, for example,
It is preferably formed using ceramic or metal,
When 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 on the abutment 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 damaged by the displacement of the working body, the easier the elastic deformation, the higher the sensitivity of the 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 may be made of a piezoelectric material.

In the sensor 1, the flexible plate 5 has a width sufficient to dispose a piezoelectric element for detecting a force applied in each of the three axial directions. This makes it possible to secure the desired detection accuracy and measurement range. In order to limit the amount of displacement of the working body 2 in the vertical direction (Z-axis direction), the upper and lower end surfaces of the support 3 are provided with restraining members 8A.
8B are adhered using an adhesive or the like via spacers 9A and 9B, respectively, and the gaps 7A and 7B are formed by the thickness of the spacers 9A and 9B. The adhesive itself can be used as a spacer and an adhesive by mixing beads or the like having a predetermined diameter into the adhesive or the like.

In the sensor 1, a dicer line 6 is formed below the working body 2 and the support 3,
The dicer line is a gap formed by dicing (cutting) using a diamond cutter (wheel) or the like. When the sensor 1 is manufactured by using a green sheet laminating method described later, first, the operating body 2 and the support 3
Is integrally formed with a single plate, and then the above-described single plate is so formed that the dicer lines in the X-axis direction and the Y-axis direction intersect each other on the extension of the hollow portion 4 in the Z-axis direction. By cutting, the dicer line 6 is formed. By the formation of the dicer line 6, the working body 2
And the abutment 3 are separated from each other, and the working body 2 is supported by the flexible plate 5, and the stopping members 8A and 8B are
Is adhered to the abutment 3 after the formation.

The dicer line 6 can be used to limit the amount of displacement of the working body 2 in the XY plane direction. However, the dicer line 6 formed by dicing has a gap 7A Since the width is generally wider than that of 7B, it is not used to positively limit the displacement of the acting body 2 in the XY plane direction. In other words, it is preferable that the sensor 1 be provided with another portion for controlling the displacement of the operating body 2 in the XY plane direction. However, if the dicer line 6 can be formed to have the same width as the gaps 7A and 7B by using a diamond cutter with a small blade width, dicing using a wire saw, or laser processing, the dicer line 6 Can be used to limit the displacement of the action body 2 in the XY plane direction.

In the sensor 1, while maintaining the flexible plate 5 at a predetermined width, the gaps 7 A and 7 B allow the action body 2
Is prevented from being extremely displaced in the Z-axis direction.
It is highly reliable because damage and destruction are prevented. However,
In the sensor 1, there remains a problem that the displacement is not limited in the XY plane direction. Also, the stopping members 8A and 8A
B has the advantage that the working body 2, the abutment 3 and the flexible plate 5 are formed separately from each other, and that any material different from the main body can be used as the stopping members 8A and 8B. From the viewpoint, the number of parts and the number of steps are increased, and the gaps of the gaps 7A and 7B are difficult to be constant.

Next, FIG. 2 shows another embodiment of the force sensor of the present invention. The sensor 10 has a columnar concave portion 2A formed in the center of the lower surface of the operating body 2 of the sensor 1 described above, and a columnar convex portion 8C formed in a central portion of a stopping member 8B attached to a lower portion of the support 3. It has a formed structure. A gap 7C having a predetermined width is formed in the Z-axis direction between the recess 2A and the projection 8C, and a gap 7D having a predetermined width is also formed in the XY plane direction. have.

XY of the operating body 2 is formed by the gap 7D.
The displacement in the plane direction is limited. By setting the width of the gap 7C equal to or less than the width of the gap 7B, the gap C can be used to limit the displacement of the working body 2 in the Z-axis downward direction. Is preferably equal to or greater than the width of the gap 7B, and the displacement of the working body 2 in the Z-axis downward direction is preferably limited mainly by the gap 7B. In the sensor 10 as well, since the restraining member 8B is prepared separately, the restraining member 8B having the convex portion 8C may be prepared according to the shape of the concave portion 2A formed in the operating body 2.

In such a sensor 10, since the displacement of the working body 2 is restricted in three axial directions, the sensor 10 is more reliable than the sensor 1. However, it cannot be denied that the number of parts and the number of steps are large, and that the gaps of the gaps 7A to 7D are difficult to be constant.

FIG. 3 shows still another embodiment of the force sensor of the present invention. The sensor 11 is the sensor 1 described above.
Has a structure in which an annular convex portion 3A is formed at a central portion on the inner peripheral side of the abutment 3 so as to form a gap portion 7E at a predetermined interval from the outer periphery of the working body 2. 7E restricts the displacement of the action body 2 in the XY directions. In the Z-axis direction, similarly to the sensor 1, the stopping member 8
The displacement of the working body 2 is limited by A · 8B. The demerit of the sensor 11 is the same as that of the sensor 1, but has an advantage that the gap portion 7E can be easily and accurately formed by a green sheet laminating method described later.

Next, FIG. 4 shows still another embodiment of the force sensor of the present invention. In the sensor 11 described above,
While the displacement control in the XY plane direction is performed by the convex portion 3A formed integrally with the support 3, the sensor 12 has an annular convex portion 2B formed on the outer periphery of the operating body 2. Thereby, a gap 7F is formed between the support 3 and the inner peripheral wall,
The displacement of the action body 2 in the XY plane direction is limited. Note that the sensor 12 is manufactured using the same manufacturing method as that of the sensor 11.

The sensor 13 shown in FIG. 5 shows still another embodiment of the force sensor according to the present invention. A restraining member 8B is adhered to a lower portion of the support 3 via a spacer 9B, and displacement of the working body 2 in the Z-axis downward direction is restricted. Further, a convex portion 2C formed by forming the dicer line 6 at the lower portion of the working body 2 and a convex portion 3B integrally formed so as to protrude radially from the inner peripheral surface of the support 3.
By forming a gap 7G in the Z-axis direction between
The displacement of the working body 2 in the axial direction is limited. In addition,
In the sensor 13, by setting the interval of the gap 7 </ b> H between the projection 3 </ b> B and the outer periphery of the operation body 2 to be equal to the gap 7 </ b> G, the projection 3 </ b> B restricts the displacement of the operation body 2 in the XY plane direction. Can also be used.

The sensor 13 is superior in productivity to the sensor 1 and the sensors 10 to 12 in that the sensor 13 does not require one stop member 8A. In addition, if the gap control of the gap 7G is performed by using a green sheet laminating method described later, a method of applying a member that burns down on the green sheet or a method of laminating a sheet that burns down can be easily used. There are advantages that can be done.

In the sensor 13 described above, the abutment 3 is provided with the convex portion 3B. However, like the sensor 14 shown in FIG. 2D, and a gap 7J in the Z-axis direction between the projection 3C formed below the support 3 by the dicer line 6, thereby displacing the working body 2 in the negative direction in the Z-axis direction. Can be restricted.

Therefore, in comparison with the sensor 13, the sensor 14 does not require the stopping member 8 B for limiting the displacement of the operating body 2 in the Z-axis downward direction, and instead, does not require the operating body 2 in the Z-axis upward direction. 8A is attached to the upper surface of the working body 3 via the spacer 9A. By setting the gap 7K formed between the convex portion 2D and the inner peripheral wall of the support 3 to have a predetermined width, the convex portion 2D also serves to limit the displacement of the working body 2 in the XY plane direction. It can be used.

Next, still another embodiment of the force sensor according to the present invention is shown in FIG. In the sensor 15, an annular convex portion 2 </ b> E having a larger outer diameter is formed at a central portion of the working body 2, and an annular concave portion 3 </ b> D is formed at an inner peripheral side central portion of the support 3. A gap 7M is formed at a predetermined width in the Z-axis direction and a gap 7L is formed at a predetermined width in the XY plane direction between the projection 2E and the recess 3D. Therefore, the three-dimensional displacement of the working body 2 is restricted by the convex portion 2E and the concave portion 3D.
Breakage due to sudden external force or the like is avoided, and reliability is improved.

Such a convex portion 2E and a concave portion 3D can integrally form the main body of the operating body 2 and the abutment 3, respectively, even when the green sheet laminating method is used. Further, as compared with the above-described sensor 1 and the like, the sensor 15 does not require the stopping members 8A and 8B. For this reason, the manufacture of the sensor 15 does not require a separate component, and does not require the assembly of a separate component.
It is possible to simplify the manufacturing process and improve the productivity. Further, there is an advantage that the gap control of the gaps 7L and 7M is easy.

In the sensor 15, the operating body 2 and the abutment 3
It is also possible to form the convex portion 2E and the concave portion 3D respectively formed in opposite directions. That is, as in the case of the sensor 16 shown in FIG.
F and an annular convex portion 3 at the center of the support 3.
It is also preferable to form the gaps 7K and 7L by forming E. Thus, the displacement of the working body 2 in the three axial directions is limited.

In the above-described sensors 15 and 16, the convex portions and the concave portions formed on the operating body 2 and the support 3 are both annular, but the shapes of the convex portions and the concave portions are not limited. . For example, the sensor 17 shown in FIG. 9 is different from the sensor 15 in that the annular convex portion 2
In this embodiment, E is formed as a substantially prismatic convex portion 2G that protrudes in the X-axis direction and the Y-axis direction.

Here, the recess 3D formed in the support 3
May be formed in an annular shape as in the case of the sensor 15. Corresponding to the shape of the concave portion 3D, the distal end surface of the convex portion 2G is formed into a curved surface so as to form a gap 7L. Of course, it is also preferable to provide the support 3 with a concave portion in which a gap is formed at a predetermined interval on the outer periphery of the convex portion 2G so as to suppress the rotational displacement of the convex portion 2G in the XY plane.

The sensor 18 shown in FIG.
6, instead of the annular convex portion 3E formed on the support 3, substantially prismatic convex portions 3F are provided in the X-axis direction and the Y-axis direction, respectively. The recess 2H is formed such that a gap 7L is formed between the gap 7L and the gap 7M between the surface (upper and lower surfaces) of the protrusion 3F in the Z-axis direction.
Is formed on the action body 2. With such a structure, it is also possible to limit an unnecessarily large displacement of the working body 2.

Meanwhile, the various sensors 1.1 described above
The width L of the gaps 7A to 7M (hereinafter, referred to as “gap 7”) formed in 0 to 18 (hereinafter, “sensor 1 etc.”) is formed on the flexible plate 5 by the displacement of the working body 2. It is preferable that the generated stress is set so as not to break the flexible plate 5. In other words, it is necessary to set the width L so that the flexible plate 5 is not broken even when the working body 2 is displaced by the width L of the gap 7.

Therefore, when the working body 2 has a cylindrical shape with a diameter 2b and the support 3 has a cylindrical inner peripheral wall with an inner diameter 2a, the thickness of the flexible plate 5 is h and the Young's modulus is E. When the breaking stress is σ, the width L of the gap 7 is L = ± σαa ²
/ ΒEh. Here, α indicates the coefficient of maximum deflection, and β indicates the coefficient of maximum stress. In addition, in order to further increase the safety and avoid the destruction of the flexible plate 5, the width L of the gap 7 is a narrower range L.
= Preferably be between ± 0.9σαa ² / βEh, still more preferably in the range of L = ± 0.7σαa ² / βEh
And the most preferable is L = ± 0.5σαa ² /
Within the range of βEh. However, it is needless to say that the width L of the gap portion 7 needs to be narrowed as far as a desired detection accuracy and a desired detection range can be obtained.

Now, a method for manufacturing the sensor 1 and the like will be described. The sensor 1 and the like can be manufactured by individually manufacturing each member using various materials and then bonding them using an adhesive or the like. In this case, however, the number of parts is large and the production process is also large. There is a problem in that the gap 7 is likely to be complicated and the dimensional accuracy of the gap 7 is reduced. 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.

The green sheet is prepared by mixing a slurry prepared by mixing a binder, a solvent, a plasticizer, and the like with a ceramic powder, using slip casting such as a doctor blade method or a calendar roll method, or adding a binder, a solvent, and a plasticizer to the ceramic powder. It is a thin sheet of predetermined thickness produced by extrusion molding or the like obtained by adding and kneading, and is characterized by being flexible, easy to process, easy to cut, perforate, and adhere. . Therefore, a plurality of green sheets punched or cut into a desired tomographic shape are laminated at a predetermined position, integrated by thermocompression bonding (hot press) or the like, and then fired, whereby the working body 2 and the support 3 and It is possible to obtain a sensor in which the flexible plate 5 has a predetermined shape and is integrally formed. Hereinafter, such a method is referred to as “green sheet lamination method”.

When the green sheet laminating method is used, the thickness of the sensor itself can be easily reduced, and the reproducibility of the thickness of each green sheet and the uniformity of the thickness of the entire green sheet are excellent. There is an advantage that precise control of the thickness of the flexible plate is easy. Therefore, the 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 has a small deflection variation for each flexible plate or each portion of the flexible plate. For this reason, there is a characteristic that the characteristic variation between the sensors is reduced.

Further, by controlling the thickness of the green sheet,
Alternatively, even when a green sheet having a predetermined thickness is used, by appropriately selecting the number of stacked green sheets,
The thickness of each part can be easily adjusted. 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. Thus, in particular, the thickness of the acting body which affects the detection sensitivity in the X-axis and Y-axis directions is adjusted by the number of stacked green sheets,
It is also easy to balance with the detection sensitivity in the Z-axis direction, and it is possible to reduce or eliminate the trouble of electrical calibration by an electric circuit.

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. As for the body and the abutment, it is possible to obtain a highly sensitive and highly accurate sensor having high rigidity.

When the green sheet laminating method is used, many sheet components can be obtained from one green sheet by punching using a mold or the like.
Excellent productivity and the ability to provide high-precision sensors at low cost. Lower electrode, piezoelectric body, and upper electrode are formed on a green sheet using a thick film technique such as screen printing, and are integrally fired. By doing so, there is an advantage that the manufacturing process can be easily shortened.

Hereinafter, a method for manufacturing the above-described sensor 1 and sensor 15 will be described in detail. First, FIG. 11 shows an example of a green sheet member (hereinafter, referred to as a “sheet member”) prepared for manufacturing the sensor 1 by punching a green sheet. Here, the sheet member 21 of the first layer forms the flexible plate 5, the sheet member 22 A of the second layer is the support 3, and the sheet member 22 B is the operating body 2.
Are formed respectively. These sheet members 2
The layers 2A and 22B are laminated in a plurality of layers so as to obtain a predetermined thickness. The third-layer sheet member 23 is for producing the operating body 2 and the lower part of the support 3 by a single plate. These sheet members 21 to 23 are provided with a reference hole 25 for positioning at the time of lamination, and the sheet member 23 is preferably provided with a degreasing hole 26 to facilitate degreasing at the time of firing. .

FIG. 12 shows a sheet member prepared in manufacturing the sensor 15. Seat member 21
(1st layer) ・ 22A ・ 22B (2nd / 4th layer) ・ 23 (5
The layer is used in common with the production of the sensor 1. As described above, in the sensor 15, since the convex portion 2E is formed at the center of the operating body 2, the sheet member 24B having an outer diameter larger than the sheet member 22B is provided in the middle of the sheet member 22B. It is sandwiched between eyes and laminated. Of course, a plurality of these sheet members 22B and 24B can be used.

In addition, corresponding to the convex portion 2E of the operating body 2,
Since the recess 3D is formed in the support 3, the sheet member 24 </ b> A having a large inner diameter is sandwiched as a third layer in the middle of the sheet member 22 </ b> A with the sheet member 24 </ b> B of the same stacking position. I do. At this time, the inner peripheral side of the sheet member 22A and the outer peripheral side of the sheet member 24 come into contact with each other at two upper and lower portions of the third layer. Here, at least one contact portion of the sheet members 22A and 24B that come into contact with each other, By printing a burnt material that burns off during firing, integration during firing can be avoided, and the gap 7M can be favorably formed. The burnt material is an organic substance in many cases, and as an example, theopromine (manufactured by Shiratori Pharmaceutical Co., Ltd., chemical name: 3,7-Dihydro-3,7-
dimethyl-1H-purine-2,6-di
one). Further, instead of printing the burnt material, a sheet having a predetermined thickness made of the burnt material may be inserted and laminated.

The reference holes 25 of the various sheet members thus prepared are sequentially laminated while passing through the positioning pins set on the lower base plate (crimp metal fittings). Finally, the upper base plate is superimposed and hot-pressed in the laminating direction. By performing the above, the sheet member is integrated. The stacked body (bulk) obtained in this way is degreased and fired, whereby the working body 2 of the sensors 1 and 15, the support 3 and the flexible plate 5 are integrally formed.

Subsequently, a piezoelectric element is formed on the outer surface of the flexible plate 5 in the obtained fired body. In forming the piezoelectric element, the electrode paste and the piezoelectric ceramic paste can be sequentially printed and fired by a screen printing method, or can be fired by lamination printing, or can be formed by a sputtering method or the like. Although it is necessary to draw out electrode leads from each piezoelectric element, it is preferable in terms of production process that the formation of the electrode leads be performed simultaneously with the formation of the piezoelectric elements.

A piezoelectric element is previously formed on the surface of the sheet member 21 serving as the flexible plate 5 by laminating printing.
It is also possible to shape 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.

Now, the sensor 1.1 thus manufactured
At this point, the intermediate 5 is still in a state in which the operating body 2 is connected to the support 3 at the lower portion. FIG.
As shown in the figure, a single plate below the sensor 1.15 (intermediate body) is diced using a diamond cutter, a wire saw, or the like so as to intersect on the extension of the hollow portion 4 in the stacking direction (Z-axis direction). Only the part of is cut. Thus, a dicer line 6 as a space is formed, and the working body 2 is supported by the flexible plate 5. After dicing, the sensor 15 becomes a product as it is.

FIG. 13A is a perspective view of the sensors 1 and 15 (intermediate body) before dicing, and FIG. 13B is a perspective view of the sensors 1 and 15 (intermediate body) after dicing. FIG. 13 (c) is a plan view of the sensor 1 (intermediate body) / 15 (product) after dicing as viewed from the lower surface, and the part number 27 in FIG. 13 (a) indicates a piezoelectric element. Is shown. The shape of the piezoelectric element 27 is not limited to the illustrated one, and the electrode leads are omitted.

Finally, in the sensor 1, it is necessary to attach the stopping members 8 A and 8 B to the upper and lower surfaces of the support 3. FIG. 14 is an explanatory diagram showing one example of the method. In the sensor 1 (intermediate) after dicing, the lower part is divided into several sections by the dicer line 6. Here, spacers 9A and 9
B using an adhesive, and further stopping members 8A and 8B
The sensor 1 having the gaps 7A and 7B formed while supporting the working body 2 by sticking is provided.

Next, materials and the like suitably used for each member 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 the stabilized zirconia can be used.

Here, regarding the flexible plate 5, in order to improve the required bending characteristics, only the sheet member 21 that becomes the flexible plate 5 has a titania (TiO ₂ ) equivalent of 0.1.
1 to 0.6% by weight of Ti and / or magnesia (Mg
O) It is preferable to use zirconia ceramics containing 0.005 to 0.1% by weight of Mg in terms of Mg. Ti
Alternatively, if the weight ratio of Mg is smaller than the above range, the flexible plate 5 is unlikely to bend, which causes a problem that the sensor sensitivity is reduced. Further, when the weight ratio is larger than the above range, the toughness of the flexible plate 5 is reduced, so that the flexible plate 5 is easily broken, and there is a problem that the reliability of the sensor is reduced. Thus, the flexible plate 5 is also a range, a further 0.2 to 0.5 wt% of Ti and / or terms of MgO in terms of TiO ₂ 0.01 to 0.05
It is preferable that the content of Mg be in the range containing Mg by weight.

On the other hand, it is preferable that the abutment 3 and the working body 2 have high rigidity without mixing such additives. By using the green sheet lamination method, it is easy to design a sensor in which the composition of each sheet member is changed, and a variety of different ceramic materials can be used in combination as long as the laminated and integrated bulk can be integrally fired. It is also possible to easily improve the measurement sensitivity and the reliability against mechanical destruction. The method of controlling the characteristics of a flexible plate or the like by such a chemical composition is not limited to the case of using ceramics, but is also useful in the case of integral molding using metal or resin.

Next, as for the piezoelectric material forming the piezoelectric element, lead zirconate titanate (PZT), lead magnesium niobate (PMN), lead nickel niobate (PNN)
Piezoelectric ceramics having excellent piezoelectric characteristics, such as, for example, are preferably used. In addition, silver (Ag), gold (A
When u), palladium (Pd), platinum (Pt), or an alloy thereof is used, simultaneous firing with the piezoelectric body is easy, and integral firing with the flexible plate 5 and the like can be easily performed. . In addition, copper (C
Various metal materials such as u), nickel (Ni), and aluminum (Al) can be used for the electrodes and the electrode leads.

In the present invention, either a piezoelectric material or an electrostrictive material may be used. 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. This porosity is mirror-polished so that the cross section of the piezoelectric body does not fall off,
The cross section is defined by the ratio of the area of the pore portion to the area of the visual field when the cross section is observed using an SEM or the like.

The stopping members 8A and 8B and the spacer 9A
As a material of 9B, a metal plate, a ceramic plate, or a glass plate can be suitably used. As the adhesive, an epoxy resin or the like having a strong adhesive force and a high hardness of itself is suitably used. Also, by mixing glass beads or polymer beads having a predetermined diameter into the adhesive, the adhesive itself can have a function as a spacer.

As described above, the embodiments of the force sensor according to the present invention have been described with reference to the case where a piezoelectric element is used as a sensing element, but the present invention is not limited to these embodiments. Needless to say. That is, regarding the structure of the 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 spirit of the present invention. It should be understood. For example, the inventors previously described in Japanese Patent Application No. 10-87133,
Although a force sensor (triaxial sensor) in which the shape and composition of the flexible plate are variously disclosed, such a force sensor (triaxial sensor) is also disclosed as the main object of the present invention. It goes without saying that it is possible to provide a member for limiting the displacement, or to provide an uneven portion on the working body or the abutment.

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 circular, but is not limited to such a shape. For example, various forms such as a polygonal shape such as a quadrangle, a circular shape, or an elliptical shape in the XY plane may be employed. The selection of such a shape is the same for the shape of the acting body, and it is possible to use acting bodies having various shapes such as the above-mentioned columnar shape and a prismatic shape. As for the flexible plate, in all of the above-described embodiments, a single plate having a constant thickness has been exemplified. However, the thickness of the flexible plate does not necessarily have to be constant, and the flexible plate is provided on the upper surface of the abutment. In this case, it is not necessary to lie on the support so as to completely close the hollow portion. For example, in order 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, such as providing a beam on the flexible plate, and a plate-like flexible plate having a predetermined width. The flexible plate may be laid over the hollow portion without completely closing the upper surface of the abutment. 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 sensor.

Further, the sensing element is not limited to a piezoelectric element,
Any method may be used as long as it detects the displacement of the working body itself or the bending generated in the flexible plate based on the displacement of the working body and converts the amount of bending into an electric signal. For example, a change in capacitance is used. One that uses a change in piezoresistance can be used. As a device utilizing the change in capacitance, a pair of electrodes provided on the surface of a flexible plate or an operating body, a dielectric material sandwiched between the electrodes, and an electronic circuit connected to the electrodes are provided. One that detects an electrostatic capacitance charged in a space by an electronic circuit. An element typified by a strain gauge can be used as a device utilizing a change in piezoresistance. It should be noted that, in addition to the above, there are those utilizing a change in resistance due to expansion and contraction of the conductor.

[0064]

As described above, according to the force sensor of the present invention, since an unnecessary large displacement of the working body is restricted, even if a large external force is applied to the working body such as an impact or a collision, A large stress that would cause the flexible plate to break is not generated on the flexible plate, and damage to the sensor is avoided. As a result, a remarkable effect of extremely excellent reliability is obtained.
Further, by using the green sheet laminating method, it is possible to improve the production efficiency while homogenizing the characteristics of each sensor. Therefore, an excellent effect that a low-cost and high-accuracy sensor can be provided at low cost is also achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a force sensor of the present invention.

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

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

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

FIG. 10 is a sectional view showing still another embodiment of the force sensor of the present invention.

FIG. 11 is a plan view showing one embodiment of a shape of a green sheet used in a green sheet laminating method.

FIG. 12 is a plan view showing another embodiment of the shape of the green sheet used in the green sheet laminating method.

FIG. 13 is an explanatory diagram relating to dicing of a sintered body.

FIG. 14 is an explanatory diagram relating to sticking of a stopping member.

FIG. 15 is a perspective view showing an embodiment of a conventional force sensor.

FIG. 16 is a sectional view showing another embodiment of the conventional force sensor.

[Explanation of symbols]

1 ... force sensor (sensor), 2 ... acting body (weight), 2A
2F · 2H ··· Recesses formed in the working body 2; 2B · 2C ·
2D, 2E, 2G: convex portions formed on the working body 2, 3: abutment, 3A, 3B, 3C, 3E, 3F: convex portions formed on the abutment 3, 3D: formed on the abutment 3 Recessed part, 4 ... hollow part,
Reference numeral 5: flexible plate, 6: dicer line, 7A to 7K: gap, 8A and 8B: stop member, 8C: convex portion formed on stop member 8B, 9A and 9B: spacer, 10 to 18: sensor, 21 22A / 22B / 23 / 24A / 24B: sheet member, 25: reference hole, 26: degreasing hole, 27: piezoelectric element, 90: sensor, 91A to 91E: upper electrode, 91F
... Lower electrode, 92 ... Flexible plate, 93 ... Abutment, 95 ... Sensor, 96 ... Weight, 97 ... Flexible plate, 98 ... Piezoelectric element.

Claims (15)

[Claims] 1. An abutment having a hollow portion, a flexible plate having at least one sensing element and being laterally suspended in the hollow portion of the abutment; A force sensor comprising an operating body supported by a flexible plate, wherein the operating body and the abutment and / or a restraint attached to the abutment are mounted such that the operating body is not displaced beyond a predetermined distance. A force sensor, wherein a gap having a predetermined width is formed between the force sensor and a member. 2. The gap portion is formed between a convex portion and / or a concave portion formed on the working body and a convex portion and / or a concave portion formed on the support and / or the stopping member. The force sensor according to claim 1, wherein 3. The method according to claim 1, wherein the stopping member is provided on an upper surface of the support and / or
Or affixed to the lower surface.
Or the force sensor according to 2. 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 operating body, the support, and the flexible plate are integrally fired by a green sheet laminating method. 6. The force sensor according to claim 5, wherein the gap is formed by a burnt material formed at a predetermined position of the green sheet. 7. The force sensor according to claim 5, wherein a green sheet containing zirconia as a main component is used. 8. The force sensor according to claim 5, wherein the flexible plate is formed by integrally firing a green sheet and a sensing element. 9. The force sensor according to claim 1, wherein the sensing element is a piezoelectric element. 10. The flexible plate has a TiO ₂ equivalent of 0.1.
-0.6% by weight of Ti and / or MgO as 0.00
The force sensor according to any one of claims 1 to 9, comprising a zirconia ceramic containing 5 to 0.1% by weight of Mg. 11. The flexible plate has a TiO ₂ equivalent of 0.2.
To 0.5% by weight of Ti and / or MgO in terms of 0.01
11. The force sensor according to claim 10, wherein the force sensor is a zirconia ceramic containing 0.05 to 0.05% by weight of Mg. 12. When the working body has a cylindrical shape with a diameter of 2b and the abutment has a cylindrical inner peripheral wall with an inner diameter of 2a, the thickness of the flexible plate is h and the Young's modulus is E. When the breaking stress is σ, the width L of the gap is L = ± σαa ² / β
The force sensor according to any one of claims 1 to 11, wherein the force sensor is within a range of Eh (α: coefficient of maximum deflection, β: coefficient of maximum stress). 13. The width L of the gap is L = ± 0.9σ.
13. The force sensor according to claim 12, wherein the force is in the range of αa ² / βEh. 14. The width L of the gap is L = ± 0.7σ.
14. The force sensor according to claim 13, wherein the force is in the range of αa ² / βEh. 15. The width L of the gap is L = ± 0.5σ.
The force sensor according to claim 14, wherein the force is in the range of αa ² / βEh.