JPS6321530A - Force detector - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of a strain generator by forming the flat plate-shaped object to be strained that is formed with a detecting surface between a central portion and a periphery both having a high rigidity, masking either the central portion or the periphery a supporting portion and the other a point of action and forming detecting elements on the detecting surface. CONSTITUTION:A supporting portion 4 and an acting portion 7 have a higher rigidity than that of a flat plate portion 8 and, furthermore, the supporting, acting and flat plate portions 4, 7 and 8, respectively, are integrally formed in a flat plate-shaped object 1 to be strained. Thus, a fixed portion and a load detector are connected to the supporting and acting portions 4 and 7, respectively, whereby neither hysteresis nor nonlinearity is generated. Although a strain is liable to be produced in a detecting surface 9 by a stress produced by a thread fastening 3 or the like in the supporting and the acting portions 4 and 7 as fastening portions, since the supporting and acting portions 4 and 7, respectively, have a far higher rigidity than that of the flat plate portion 8, the strain caused by the fastening of other members is not produced in detecting elements 14.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a force detection device used, for example, in a force sensor for a robot, a three-dimensional input device as a man-machine interface, and the like.

2. Description of the Related Art A conventional force detection device includes a strain body that elastically deforms when an external force is applied thereto, and a plurality of detection elements that change electrical resistance through mechanical deformation of the strain body. The strength of the external force is detected by extracting the change in electrical resistance as an electrical signal.

-i, in this type of force detection device, the external force acts on a fixed point, and the x, y,
Forces Fx, Fy, Fz and moment M x in the z coordinate system,
The independent component forces of M y and M z act as shown in FIG. 14.

In order to detect each component force, there is a force detection device in which the strain body is formed into a three-dimensional block structure so that the external force can be detected separately as multi-axial force components. Publication No. 54-11903, Publication No. 54-210
No. 21, JP-A-59-95433, JP-A-Sho 6
This method is disclosed in Japanese Patent Application Laid-open No. 1-57825, Japanese Patent Application Laid-Open No. 61-79129, and the like. In particular, the detection surface of the independent force components of the x, y, z coordinates of the forces Fx, Fy, Fz and moments M x , M y , M z at the point of application, that is, the surface to which the strain gauge is attached is as follows. , which is characterized by the use of a plane perpendicular to the component force, and the strain-generating body must have a three-dimensional structure as a block structure as described above.

In such a structure, the means for manufacturing the strain-generating body is cutting or electric discharge machining, and the strain body must be manufactured from a block-shaped material.

Therefore, processing is difficult and complicated. In addition, it is common to attach a strain gauge detection element to each force detection element of each component, and to connect these electrically with a bridge, which makes it complicated to run lead wires around, making it difficult to downsize. However, it is difficult to reduce costs and has low mass productivity.

In addition, there are also structures that combine structures and plates to form a three-dimensional block in order to separate external forces into multiaxial components, and this structure is disclosed in Japanese Patent Application Laid-Open No. 83929/1983. There is. In devices with such a structure, the detection bodies for each component are fastened together with screws, etc., and it is reported that reproducibility is poor. That is, hysteresis and nonlinearity occur due to the deformation of the fastening portion.

Furthermore, as for another structure, JP-A-60-221
No. 288 discloses a so-called octagonal stress ring. Such an octagonal stress sensor has a problem in that it can be used as a pressure sensor for applying external force in one direction, but cannot be used for multi-axial force.

Purpose The present invention aims to provide a force sensing element whose strain-generating body is easy to manufacture and whose sensing element can also be easily formed.

Structure The present invention forms a plate-shaped flexural body in which a detection surface is formed between a highly rigid center portion and a peripheral portion, and uses one of the center portion and the peripheral portion as a supporting portion and the other as an acting portion. A detection element is formed on the detection surface. This results in
Since the strain body has a flat plate shape, it can be formed with only a slight cutting process during production, and can also be processed by press processing such as fine blanking, casting, or injection molding. By forming the detection surface into a flat surface, the detection element can be formed using a thin film semiconductor.

A first embodiment of the present invention will be described based on FIGS. 1 to 13. First, the plate-shaped flexure element 1 has a ring-shaped peripheral part 2 that is thick and has high rigidity. Eight mounting holes 3 are formed. This peripheral portion 2 serves as a support portion 4 that is fixed to a fixed portion (not shown).

Further, a thick disc-shaped central portion 5 is formed in the center, and four attachment holes 6 are formed through the central portion 5 in the thickness direction. A member (not shown) is attached to this central portion 5, and this central portion 5 serves as an acting portion 7 for receiving an external force.

Further, a thin flat plate part 8 is formed between the support part 4 and the action part 7, and the surface of this flat plate part 8 is used as a detection surface 9. Eight holes 10 having a relatively large diameter are formed in such a flat plate portion 8 at equal intervals. Eight arms 11 are formed radially through these holes 10 to connect the inner and outer peripheries. These arms 11 have a narrowest part 12 at the center thereof and substantially trapezoidal expanded parts 13 located at both ends of the second narrow part 12. The arm portion 11 is positioned along the X-axis direction, the Y-axis direction, and the Z-axis direction having an angle of 45 degrees with respect to the X-axis and the Y-axis.

Next, the expanded portion 13 on the X axis has Y,...
Detection elements 14 are formed by strain gauges labeled Y, , Y, , Y,. These detection elements 14
Of these, Y, , Y4 are located in the outer expanded portion 13, and Y, , Y, are located in the inner expanded portion 13. These detection elements 14 are bridge-coupled as shown in FIG. 5, and are connected so that when the balance of the detection elements 14 Y, , Y, , Y, , Y4 is lost, an output Vy is generated. ing.

Further, detection elements 14 made of strain gauges are formed in the expanded portion 13 on the Y axis perpendicular to the X axis, and are labeled x, , x, , x, , x. Of these detection elements 14, the X, .

is located in the inner expanded portion 13. These detection elements 14 are bridge-coupled and arranged as shown in FIG.
When the detection elements 14 consisting of x, , x, , x, , x are out of balance, they are connected so that an output Vx is generated.

Further, in the expanded portion 13 located on the Z axis having an angle of 45 degrees with respect to the X axis and the Y axis, Z l lz, z
, , z, , z, , z, , z, , eight detection elements 14 are formed. Among these detection elements 14, z, , z4 . z,, z, are located in the expanded portion 13 on the outside, and z,, z,, z,, z, are located in the expanded portion 1 on the inside.
It is located at 3. These detection elements 14 are connected as shown in FIG. That is, 2. ．． 2. and 2.
．． 2. and 2. ．． 2. and 2. ．． 2. are bridge-coupled as a unit, and when the balance between these is disrupted, an output Vz is generated.

The detection element 14 positioned as described above is formed by thin film technology. That is, the plate-shaped strain body 1 is made of aluminum alloy or stainless steel.
A buffer layer is deposited on the buffer layer. Specifically, this buffer layer is made of SiN or a-
A 5i:H film is created by a 2,000 to 10,000-person plasma CVD method.

Next, a semiconductor thin film is laminated on this buffer layer to a thickness of 5,000 to 20,000 A, and a highly conductive material (for example, Al) is added to serve as an electrode material.

metal thin film such as Ni-Cr, Mo) from 2000 to 5000
Laminate layers one after another to a human thickness. Specifically, the semiconductor thin film is μC-3i (microcrystalline silicon) created by plasma CVD method or photoexcitation CVD method.
or n”a-3i: H is used, and A is used as the electrode material.
1-3L (Si: 2 to 3 wt%) is produced by a vapor deposition method or a sputtering method.

Next, the electrode material is patterned into a predetermined shape by photolithography and etching methods. As etching,
Although both the wet method and the dry method have no effect on the shape, dry etching is preferable in order to avoid any influence on the device characteristics. In addition, in the case of a-5i:H, CF4-0□ (3 to 20 wt%
) Etching with good reproducibility and precision is possible by using a mixed gas.

Further, since detection of the six force components Fx, Fy, Fz, Mx, My, and Mz and a bridge circuit for the detection element 14 are required, the wiring density becomes high, so multilayer wiring is required. For this purpose, an interlayer insulating material such as photosensitive polyimide or SiN is laminated. When photosensitive polyimide is used, it is applied using a roll coater or spinner, and contact holes are created through photolithography and etching processes. In the case of S i N 4, a film is formed by plasma CVD, and after resist coating, a contact hole portion is created by photolithography and etching steps.

Furthermore, secondary electrode materials (e.g. AI, Ni-Cr.

MO, etc.) is laminated thereon, and predetermined wiring and pad portions are formed by photolithography and etching processes.

Next, as a passivation film to improve moisture resistance and prevent mechanical damage, for example, parylene or S
I Q * + S Ll N 4 is deposited.

The primary electrode pattern, the interlayer insulating part, and the secondary electrode pattern may be formed in advance of such a means for forming the detection element 14. By doing this,
Defective products up to this step can be excluded, and the yield in the final step can be improved. The failure mode in the detection element 14 portion is 25% short-circuit or disconnection of the primary and secondary electrode materials, and about 20% is short-circuit due to poor insulation in the interlayer insulation part or disconnection due to defective contact hole. , the majority of defects occur up to this stage. Therefore, the effect of eliminating these defects at an early process stage is significant.

Further, when depositing the semiconductor thin film, a metal mask having openings only in necessary parts may be used to form the semiconductor thin film only in predetermined positions. This eliminates the need for photolithography and etching steps for the semiconductor thin film, simplifies the process, and makes it possible to manufacture the detection element 14 portion at low cost.

In such a configuration, the principle of detection of the flat strain body 1 will be explained based on FIGS. 8(a) and 8(b).

First, in FIG. 8, a strain body 15 such as a beam or a plate is installed between a fixed part 16 and a movable part 17, and the upper and lower surfaces of this strain body 15 are arranged at equal distances from the center. A strain gauge 18 is provided as a detection element. The state shown in FIG. 8(a) is a state in which no load is applied to the movable part 17, and the state shown in FIG.
) is a state in which a downward load F is applied and the movable portion 17 has moved downward. At this time, the upper surface of the strain body 15 on the fixed part 16 side is elongated, the lower surface is reduced, the upper surface on the movable part 17 side is reduced, and the lower surface is elongated.

That is, a strain having the same absolute value and an opposite sign occurs in the strain gauge 18, and the resistance changes accordingly.

Generally, these four strain gauges 18 are bridge-coupled to quadruple the sensitivity and output.

Next, the one shown in FIG. 9 has a cross section similar to that of the flat plate-shaped flexure element 1 in this embodiment, and the surrounding support part 4 is fixed to a fixed part (not shown), and the central acting part 7 An external force acts on it. Now, FIG. 9(a) shows a state where no load is acting on the acting part 7, and FIG. 9(b) shows a state where Fz
This is a state where a vertical load of In this state, one side from the central acting part 7 is shown in FIG. 8(b).
The state is similar to that shown in FIG. 1, in which the two inner detection elements 14 are contracted (-) and the two outer detection elements 14 are expanded (+). The state shown in FIG. 9(c) is a state in which a moment M is applied to the acting portion 7. In this state, the left and right sides exhibit antisymmetrical deflection states, and the deflection states of the inner and outer detection elements 14 have opposite signs.

In the plate-shaped flexure element 1 exhibiting such a detection principle, the support part 4 and the action part 7 have higher rigidity than the flat part 8, and the support part 42 and the action part 7. An important requirement is that the flat plate portion 8 be integrally formed. That is, the support part 4
A fixed part and a load detection body are connected to the and acting part 7, but if deformation or play occurs in these fastened parts due to external force, hysteresis may occur in the output.
Nonlinearity may occur. Therefore, the supporting portion 4 and the acting portion 7 have higher rigidity than the flat plate portion 8, and the supporting portion 42 has higher rigidity than the flat plate portion 8.
Action part 7. Since the flat plate portion 8 is integrally formed, hysteresis and nonlinearity do not occur. In addition, the support part 4 and the action part 7, which serve as fastening parts, are likely to be subject to stress due to screw tightening, etc., which may easily cause distortion in the detection surface 9. Since the rigidity is much higher than that of the flat plate portion 8, the detection element 14 will not be distorted due to fastening of other members.

Generally, a pressure-sensitive member protruding in the Z-axis direction is attached to the centrally located acting part 7, but if a force Fx is applied to the tip of the pressure-sensitive member, My If a force Fy is applied to the tip of the pressure-sensitive member, a moment Mx will be generated in the acting portion 7. Therefore, three external forces My, Mx, and Fz are representative.

This stress relationship will be explained based on FIG. 10.

First, a point of action ○ is placed at the center of the detection surface 9. A pressure sensitive member with a height L is attached to the second point of action 0°, and an external force is applied to this pressure sensitive member at the point of action 0°. It shall act on Therefore, the point of action of the pressure sensitive member is 0. < Fx, Fy, Fz, M
The components of x and My are Fz,
This is detected as a three-component force of Mx and My.

Next, a typical state in which an external force is applied to the flat nine-plate strain body 1 will be explained based on FIGS. 11 to 13. First, FIGS. 11(a), (b), (c), and (d) show a state in which only the moment MY acts on the acting portion 7 as an acting force. At this time, as shown in FIG. 11(a), there is no deformation in the Mx component part, and the output Vx of the bridge circuit shown in FIG. is "OJ". Also, the My component detection section is in a deformation mode as shown in FIG. 11(b), and Y,
, Y, , Y, , Y4 are respectively deformed, and the output Vy of the bridge circuit shown in FIG. 5 shows a value corresponding to the moment MY. The deformation mode is as shown in Figures (c) and (d), z,,z,,z,,z,,z,,z,,z,,z
, the eight detection elements 14 are deformed.

However, since the degree of this deformation is small and the output is determined by the bridge circuit shown in FIG. 7, it becomes almost "0". That is, Z, and 24.2.
and 23.2. and 2. ．． 2. The directions of expansion and contraction of and Z are opposite directions, and in the bridge circuit shown in Figure 7, the combined resistances of each side cancel each other out and become "0", so the output Vz becomes "0". Become.

Next, the state where only moment Mx acts is the 12th
As shown in Figures (a), (b), (c), and (d), in this case, the output Vx of the Mx component detection section is generated, and the output Vy of the My component detection section is "0". Further, the output Vz of the Fz component detection section becomes rQJ for the same reason as in the case in FIGS. 11(C) and (d) described above.

Furthermore, when only force Fz acts, Fig. 13(a)
As shown in (b), (c), and (d), in the Mx component detection section, X,,X4 is a + side deformation, and X,,X,
is a negative side modification, and the output Vx of the bridge circuit shown in FIG. 6 is "0". In addition, the output VY of the My component detection section
is also "O" for the same reason. On the other hand, the output Vz of the Fz component detection section is eight times that of one detection element 14.

The output states shown in FIGS. 11 to 13 are summarized as shown in Table 1.

Table 1 In this way, deformation in the direction of maximum sensitivity is detected by the detection element 14 as a strain gauge, and the output of other interference components can be set to "0" by the bridge circuit.

Next, by forming the hole 1o in the flat plate portion 8 of the flat plate-shaped strain-generating body 1, stress separation of each component is performed well. For example, if the flat plate part 8 does not have a hole 10 and is formed by a circular diaphragm, when an external force is applied to the acting part 7, the bending stress generated in the flat plate part 8 will naturally occur in the radial direction. Although approximately the same stress is generated in the circumferential direction, when the generation of stress in the circumferential direction is detected for each component, it greatly interferes with other components. However, as described above, by forming the plurality of holes 10 at equal intervals on the circumference at equal distances from the center, the bending stress in the circumferential direction generated in the flat plate part 8 is reduced,
The generation of strain is made to appear mainly only in the radial direction. Due to such an effect, there is no interference between the stresses of each component, and the stress separation is performed satisfactorily.

Further, an arm 11 is formed by a hole 10 formed in the flat plate part 8 of the flat plate-like strain body 1, and an enlarged part 1 of this arm 11 is formed.
A detection element 14 is located at 3.

This expanded portion 13 is formed by two holes 10 adjacent to each other, and has a shape approximately approximating a trapezoid. In the circumferential direction, the expanded portions 13 are separated from each other, and as described above, interference due to bending stress in the circumferential direction does not occur. However, since the expanded portion 13 is located at the base of the arm 11 portion, it is a portion where bending stress in the radial direction is likely to occur.
This is an appropriate position for detecting strain caused by external force.

Furthermore, looking at the distribution of bending stress generated in the expanded portion 13, the stress distribution is relatively uniform in the expanded portion 13 at the base of the arm 11, and there is little interference. Therefore, when the sensing element 14 is attached as a strain gauge to the flat plate-like strain body 1, there is no variation in the accuracy of strain detection even if there is some positional deviation, and therefore, some positional deviation is tolerated. Therefore, there is no need to impose strict conditions on the accuracy of the pasting position.

Next, since the eight holes 10 are formed in the flat plate part 8 of the flat plate-like strain body 1, a position having an angle of 45 degrees with respect to the radial direction of the X-axis and the Y-axis is formed. niz, , ,
z , z , , z , , z , , z ,
, z , , z , it becomes possible to arrange the detection elements 14 . By arranging the detection element 14 in this way, as shown in Table 1, the Fz acid component can be detected well, and when the Mx and My acid components are detected, detected values of other components are effectively erased. It is something that can be done.

Next, a second embodiment of the present invention will be described based on FIG. 15. This embodiment employs the same configuration as the first embodiment described above, and also has the following features:
9 with a detection element 14 attached thereto. That is, X
A detection element 14 for FY detection is attached to the side surface 19 of the arm 11 along the axis, and the side surface 19 of the arm 11 along the Y axis is attached to the detection element 14 for FY detection.
A detection element 14 for detecting Fx is attached to 9, and a detection element 14 for detecting moment Mz is attached to a side surface 19 of arm 11 that forms an angle of 45 degrees with the X and Y axes.

Therefore, according to this embodiment, the moment Mz around the X-axis can also be detected.

In each of the above-mentioned embodiments, the plate-shaped strain-generating body 1 is described as having a disk shape, but the outer peripheral shape thereof is not limited to a disk shape, and may be square, rectangular, polygonal, etc. It is possible to form it in any shape.

In addition, although the explanation has been made regarding the case in which holes 10 are formed in the flat plate portion 8 of the flat plate-shaped strain body 1, if a simple type that allows interference of various stresses is sufficient as described above, those holes 10 may be formed. It is also possible to leave it in the shape of a diaphragm without forming it.

Furthermore, regarding the direction of the detection axis, instead of detecting all three directions, x, y, and z, as in the previous embodiment, it may be configured to detect only two directions, for example, the X axis and the Y axis. It is a good thing.

Effects As described above, in the present invention, one of the center part and the peripheral part is used as a support part and the other part is used as an action part, and a detection surface is formed between these two parts, and the detection surface is larger than the center part and the peripheral part. A flat plate-shaped 8-distortion body with increased rigidity with respect to the peripheral portion is formed, and a detection element that changes the electrical resistance by mechanical deformation of this detection surface is formed on the detection surface of this flat plate-shaped distortion body. It is extremely easy to manufacture the strain-generating body, and it is possible to use a manufacturing method that would not be possible with conventional block-shaped objects, and the detection element can also be formed using thin film semiconductors. Due to this.

It is possible to arrange detection elements with uniform performance,
Their positions are also more accurate, and in particular, the wiring of complicated lead wires for bridging each component is facilitated.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a cross-sectional view of the A-A Ia section in FIG. A cross-sectional view of the line B-B,
FIG. 5 is an electric circuit diagram showing the bridge circuit of the My component detection section, FIG. 6 is an electric circuit diagram showing the bridge circuit of the Mx component detection section, and FIG. 7 is an electric circuit diagram showing the bridge circuit of the Fz component detection section. , Fig. 8 is a side view showing the detection principle, Fig. 9 is a side view showing the detection principle when an external force is applied to the flat plate-like strain body, and Fig. 10 is a perspective view showing the state of the force acting on the acting part. Figure 11 is a side view showing the deformation state of the flat plate-like strain body when moment My acts on it, and Figure 12 is a side view showing the deformation state of the flat plate-shaped flexure element when moment My acts on it.
Fig. 13 is a side view showing the deformation state of the flat plate-like flexure body when force Fz is applied, and Fig. 14 is a side view showing the deformation state of the plate-like flexure body when force Fz is applied. FIG. 15 is a vector diagram showing each component force in the case where the force is applied, and FIG. 15 is a perspective view showing a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Flat strain body, 2... Peripheral part, 4... Support part, 5... Center part, 7... Acting part, 9... Detection surface, 14... Detection Element 3'' Figure 37Figure 3.3Figure h 3. Person making the amendment 1t l'l: What relationship Patent applicant's office Nakamagome 1-3-6-4, 11.1-ku, University of Tokyo 1-3-6 Agent Address: 107 Tokusho No. 61-166391 Amendment Regarding this application, the description in the specification is amended as follows: "Multiaxial component" in the third line of page 4 is amended to "multiaxial force component". 2, page 4 Delete the sentences from line 12 to line 17. 3. Delete "or injection molding J" in line 12 of page 5. 4. Delete "or injection molding J" in line 5 of page 6. ” is changed to “
It is connected to the support part 4. ”. 5. Add the following sentence between the first and second lines of page 9.6 The flat plate-like strain body sensing element 14 shown above is a conventional metal foil strain gauge. It was also possible to use The necessity of flattening the strain-generating body is also important for the thin film formation technology of strain sensors. 6. Correct rsiN, J on page 9, line 8 to rsi, N, J. 7, page 9, line 8, ra-5i:H film” with rsiOx
Correct to “membrane”. 8, page 9, line 16, rltC-5iJ is “μC-3
Correct to iJ. 96 page 10 line 15 rSiN,J is rSi,N,
Correct to J. 10, "SiN4" in the first line of page 11 is rsi, N4
”. 11, page 13, line 12, "combining to increase sensitivity" is corrected as follows. "Compare the sensitivity with the case of combining one strain gauge and set it to the r M x component part of J12, page 16, line 15".
to the Mx component detection section. 13. Add the following sentence to the 15th line of page 17.

Claims (2)

[Claims] 1. A flat plate in which one of a center part and a peripheral part is used as a support part and the other part is used as an action part, a detection surface is formed between the two, and the rigidity of the center part and the peripheral part is greater than that of the detection surface. 1. A force detection device comprising: a flat flexure body; and a detection element that changes electrical resistance by mechanical deformation of the detection surface, is formed on the detection surface of the flat flexure body. 2. 2. The force detection device according to claim 1, wherein a plurality of detection elements are formed in the same plane.