JPH0821721B2 - Force detection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a force detection device used in, for example, a force sensor for a robot or a three-dimensional input device as a man-machine interface.

2. Description of the Related Art A conventional force detecting device is configured such that a plurality of detecting elements that change electric resistance by mechanical deformation of the strain generating element are formed on a strain generating element that elastically deforms when an external force is applied thereto. The electric resistance change is extracted as an electric signal to detect the strength of the external force.

Generally, in this type of force detection device, the external force acts on a fixed point, and X, Y, Z at that point of action.
The individual component forces of the forces F _X , F _Y , F _{Z in the} coordinate system and the moments M _X , M _Y , M _Z act as shown in FIG.

In order to detect each of these component forces, there is one in which the flexure element of the force detection device is formed into a three-dimensional block structure, and external force is separated and detected as a multiaxial force component. JP-B-54-11903, JP-B-54-21021,
It is disclosed in JP-A-59-95433, JP-A-61-57825 and JP-A-61-79129. Especially,
The detection surface of each component force independent of the forces F _X , F _Y , F _Z of the X, Y, Z coordinate system and the moments M _X , M _Y , M _Z at the above-mentioned action points, that is, the sticking surface of the strain gauge is The characteristic is that a plane perpendicular to the component force is used, and the flexure element is inevitably a three-dimensional structure as a block structure as described above.

In the case of such a structure, the strain-generating body is manufactured by cutting or electric discharge machining and must be manufactured from a block-shaped material. Therefore, processing is difficult and complicated. In addition, it is common to attach a detection element using a strain gauge to each force detection element of each component, and these electrical connections are bridge-bonded, so the lead wire is complicated to twist and compact. However, it is difficult to reduce the cost and the mass productivity is low. In particular, since the flexure element and the strain gauge are made of different materials, it is not possible to prevent the occurrence of hysteresis during force detection.

There is also a structure in which a three-dimensional block is formed by combining structures and plates in order to separate external force as a multiaxial force component, and this structure is disclosed in JP-A-61-83929. ing. In such a structure,
Since the detection body for each component is fastened with screws,
There is a problem of poor reproducibility. That is, the deformation of the fastening portion causes hysteresis and non-linearity.

In this respect, it is possible to form a flat strain generating element by integrally forming a central support, an outer peripheral support, and a plurality of beams connecting the two with a common semiconductor material. twenty two
It is disclosed in Japanese Patent No. 3626. At this time, it is also disclosed that a semiconductor gauge resistor (detection element) is integrally formed on each beam by using a well-known semiconductor technique. According to this, it is easy to manufacture the flexure element including the detection element, and it is possible to prevent the occurrence of hysteresis at the time of force detection. Further, it is also disclosed that the sensitivity is improved by making the rigidity of the beam portion smaller than the rigidity of the central support and the outer peripheral support.

According to the sensor structure described in Japanese Patent Laid-Open No. 61-223626, the first and second detection elements are arranged on the outer peripheral support side of the first beam among the plurality of beams, and Third and fourth detection elements are disposed on the inner peripheral support side of the beam, and further, a fifth detection element is disposed on the outer peripheral support side of the second beam on the same line as the first beam and a fifth detection element is disposed on the inner peripheral support side. Is provided with a sixth detection element. Then, the second, fourth, fifth, and sixth detection elements arranged on the same line are connected so as to generate an output when these balances are lost, and a bridge circuit for force detection is formed. A bridge circuit for moment detection is formed by connecting the 1st, 3rd, 5th, and 6th detection elements, which are arranged in a twisted position with respect to the center of the peripheral support, so as to generate an output when these balances are lost. Has been done.

This makes the directions of the first and second beams the X-axis direction,
If the direction orthogonal to the X axis in the plane of the flexure element is the Y axis direction and the direction orthogonal to these X axis and Y axis is the Z axis direction, the force in the Z axis direction applied to the flexure element is for force detection. The bridge circuit for moment detection detects the force in the Y-axis direction as a moment acting around the X-axis.

Further, if a similar detecting element is arranged on the beam in the Y-axis direction orthogonal to the X-axis to form a bridge circuit for moment detection, the force in the X-axis direction is a moment acting as a moment acting around the Y-axis. It also describes that it can be detected by a bridge circuit for detection.

However, according to the sensor structure described in Japanese Patent Laid-Open No. 61-223626, the second, fourth, and fourth sensors arranged on a line deviating from the center line passing through the center of the inner peripheral support in detecting the force in the Z-axis direction.
Since the detection is performed based on the detection elements 5 and 6, the force applied to the center of the inner peripheral support in the Z-axis direction cannot be accurately detected. Further, a detection element for detecting a force in the Z-axis direction and a force (X-axis direction) (X
Since the detection element for detecting the moment around the axis is also used for the same beam, an interference output due to the force in the other axis occurs when these forces are detected. The accuracy is poor.

Purpose The present invention uses a flat plate strain element that is easy to manufacture,
An object of the present invention is to obtain a force detection device capable of highly accurately detecting forces in the three axis directions forming the X, Y, Z coordinate system in a state where interference of forces in the other axis directions is small.

Configuration According to the present invention, one of a central portion and a peripheral portion is a supporting portion and the other is an operating portion, and the X-axis direction, the Y-axis direction, and the X-axis in the XY plane are between the central portion and the peripheral portion. And a detection surface having arms separated in at least eight for four directions with respect to the direction having an angle of 45 degrees with respect to the Y axis, and the rigidity of the central portion and the peripheral portion with respect to this detection surface. Is formed on the center line passing through the center of the central portion with respect to each of the eight arms for the four directions. , And at least two are provided separately for the central part side and the peripheral part side of the arm so that an output is generated when the balance of the four detection elements provided on the arm in the X-axis direction is lost. Connect these four detector elements to form the first bridge circuit , A second bridge circuit is formed by connecting these four detection elements so that an output is produced when the balance of the four detection elements provided on the arm in the Y-axis direction is lost, and a second bridge circuit is formed. On the other hand, these eight detection elements are connected to form an output when the eight detection elements provided on the arm in a direction having an angle of 45 degrees are unbalanced, and a third bridge circuit is formed. The first, second and third
Each output of the bridge circuit is used to detect the force in the Y-axis direction, the X-axis direction, and the Z-axis direction orthogonal to the XY plane. Accordingly, since the respective forces in the three axis directions are independently detected by using the individual arms, the interference output due to the forces in the other axis directions is configured to be performed with high accuracy in a state as small as possible. .

An embodiment of the present invention will be described with reference to FIGS. First, the flat plate strain generating element 1 is made of a single crystal substrate, and the flat plate strain generating element 1 has a thick and highly rigid peripheral portion 2 formed in a ring shape. There are eight mounting holes 3 formed on the same circumference and penetrating in the thickness direction. The peripheral portion 2 is connected to a support portion 4 fixed to a fixing portion (not shown).

A thick disk-shaped central portion 5 is formed at the center, and four mounting holes 6 are formed in the central portion 5 so as to penetrate in the thickness direction. A member (not shown) is attached to the central portion 5, and the central portion 5 serves as an action portion 7 for receiving an external force.

Further, a thin flat plate portion 8 is formed between the support portion 4 and the acting portion 7, and the surface of the flat plate portion 8 serves as a detection surface 9. Eight holes 10 having a relatively large diameter are formed in the flat plate portion 8 at equal intervals. Eight arms 11 connecting the inner and outer circumferences are radially formed by these holes 10. These arms 11 are composed of a narrowest portion 12 having the narrowest width in the central portion thereof and a substantially trapezoidal widening portion 13 located at both ends of the narrow portion 12. The arm portion 11 is positioned along the four directions of the X-axis direction, the Y-axis direction, and the direction having an angle of 45 degrees with respect to the X-axis and the Y-axis within the XY plane defined by the detection surface 9. .

Then, Y ₁ , Y ₂ ,
A detection element 14 using a strain gauge, which is represented by Y ₃ and Y _4, is formed by the semiconductor planar process technology described later. Among these detection elements 14, Y ₁ and Y ₄ are located in the outer expanded portion 13 and Y ₂ and Y ₃ are located in the inner expanded portion 13. These detecting elements 14 are bridge-coupled as shown in FIG. 5, and an output V _Y is generated when the detecting elements 14 Y ₁ , Y ₂ , Y ₃ , Y ₄ are out of balance. It is connected. As a result, the first bridge circuit is formed.

Further, a detection element 14 by a strain gauge, which is indicated by X ₁ , X ₂ , X ₃ , and X ₄ , is formed on the expanded portion 13 on the X axis orthogonal to the X axis by a semiconductor planar process technique described later. Has been done. Of these detection elements 14, the
The X ₁ and X ₄ are located in the outer expanding portion 13, and the X ₂ and X ₃ are located in the inner expanding portion 13. These detection elements 14 are the sixth
As shown in the figure, they are bridge-bonded, and X ₁ , X ₂ , X ₃ , X ₄
Is connected so that the output V _X is generated when the balance of the detection element 14 is lost. As a result, the second bridge circuit is formed.

Further, in the expanding portion 13 located on the arm 11 in the direction having an angle of 45 degrees with respect to the X axis and the Y axis, Z ₁ , Z ₂ , Z ₃ , Z ₄ ,
Eight detection elements 14, designated as Z ₅ , Z ₆ , Z ₇ , and Z ₈ , are formed by the semiconductor planar process technology described later. Of these detection elements 14, Z ₁ , Z ₄ , Z ₅ , and Z ₈ are the outer expanded portions 13 on the outside.
And Z ₂ , Z ₃ , Z ₆ , and Z ₇ are located in the expanding portion 13 inside. These detecting elements 14 are connected as shown in FIG. As a result, the third bridge circuit is formed. That is, Z ₁ , Z ₄ and Z ₂ , Z ₃ and Z ₅ , Z ₈ and Z ₆ , and Z ₇ are united and bridge-coupled, and when these balances are lost, the output V _Z is generated. To do.

The detecting element 14 positioned as described above is formed by the semiconductor planar process technique as shown in FIG. That is, the flat plate strain element 1 is formed of a single crystal, that is, a Si n-(110) wafer. First, the process will be described next.

(Oxidation Step) The Si n − (110) wafer is oxidized to form SiO ₂ on the surface. This SiO ₂ is used as a mask for diffusion in the next step.

(Diffusion window brightening step) In order to perform selective diffusion, SiO ₂ is removed and diffusion window brightening is performed.

(Diffusion process) Diffusion is performed with a B / N plate, Bcl ₃ or the like. Boron diffuses only where the silicon surface is exposed and changes from n-type to p-type.

(CVD, Si ₃ N ₄ deposition process) The front surface is used as a barrier against external contamination, and the back surface is used as a mask when etching a silicon substrate.

(Contact hole etching process) The contact hole is etched to electrically connect the gauge resistance, and the window is opened.

(Aluminum deposition process) Aluminum is used to interconnect gauge resistors and to electrically connect to external circuits.

(Sintering) Sintering is performed to improve the ohmic contact between aluminum and gauge resistance.

After passing through such a process, if necessary, dicing to separate the flat strain element 1 is performed, and the shape of each part described above is formed.

The detection principle of the flat strain element 1 in such a configuration will be described based on FIGS. 8 (a) and 8 (b). First, in FIG. 8, a flexure element 15 formed of a beam or a plate is attached between a fixed portion 16 and a movable portion 17,
A strain gauge 18 as a detecting element is provided on the upper and lower surfaces of the flexure element 15 at equal distances from the center.
In the state shown in FIG. 8 (a), the movable portion 17 is not loaded, and in the state shown in FIG. 8 (b), a downward load F is applied to move the movable portion 17. Is in a state of moving downward. At this time, in the flexure element 15, the upper surface on the fixed portion 16 side extends, the lower surface contracts, the upper surface on the movable portion 17 side contracts, and the lower surface extends. That is, in the strain gauge 18, strain having the same absolute value and the opposite sign +-is generated, and the resistance changes accordingly. Generally these four strain gauges
By connecting 18 bridges, the sensitivity is quadrupled compared to the case of a single strain gauge, and the output is taken out.

Next, what is shown in FIG. 9 has the same cross section as that of the flat plate-shaped strain-generating body 1 in the present embodiment, and the surrounding support 4
Is fixed to a fixed portion (not shown), and an external force acts on the central action portion 7. Now, FIG. 9 (a) shows the action portion 7
Fig. 9 (b) shows that F _Z
It is a state in which a vertical load is applied. In this state, one side from the central action portion 7 is shown in FIG.
This is the same as the state shown in (2), in which the two inner detection elements 14 are contracted (-) and the two outer detection elements 14 are expanded (+). The state shown in FIG. 9C is a state in which the moment M acts on the acting portion 7. In this state,
Left and right antisymmetrical bending state, showing the detection elements inside and outside
Each of the 14 flexed states is now in the opposite sign.

In the flat plate strain element 1 showing such a detection principle,
An important point in terms of operation is that the detecting element 14 is formed as the same member in the flat strain element 1 itself.
The feature is that hysteresis does not occur during force detection.
Therefore, even if the strain generating element and the detection element are integrated by adhesion or the like as in the conventional case, it is impossible to avoid occurrence of hysteresis or creep as long as they are composed of separate members. Compared to this, it brings a remarkable effect.

Furthermore, the rigidity of the support portion 4 and the action portion 7 is higher than that of the flat plate portion 8, and moreover, the support portion 4, the action portion 7, and the flat plate portion 8 are integrally formed. It is an important requirement for the body. That is, the fixed portion and the load detection body are coupled to the support portion 4 and the action portion 7. However, if deformation or play may occur in these fastening portions due to an external force, hysteresis may occur in the output, Non-linearity may occur. Therefore, since the supporting portion 4 and the acting portion 7 have higher rigidity than the flat plate portion 8 and the supporting portion 4, the acting portion 7 and the flat plate portion 8 are integrally formed, hysteresis and non-linearity are generated. Does not occur. Further, the support portion 4 as the fastening portion and the action portion 7 are likely to generate stress on the detection surface 9 due to stress due to screw tightening or the like. Since the rigidity is much higher than that of the flat plate portion 8, the detection element 14 will not be distorted due to the fastening of other members.

Generally, a pressure-sensitive member protruding in the Z-axis direction is attached to the action portion 7 located at the center, but if a force F _X acts on the tip of the pressure-sensitive member, the action portion 7
If the moment becomes M _{Y and the} force F _Y acts on the tip of the pressure-sensitive member, the moment becomes M _{X in the} acting portion 7. Therefore, the three external forces of M _Y , M _X , and F _Z are representative.

This stress relationship will be described with reference to FIG. First, there is an action point O _{0 at} the center of the detection surface 9, and at this action point O ₀ the height L
The pressure-sensitive member is attached, and an external force acts on the pressure-sensitive member at the point of action O ₁ . Therefore, F _X, F _Y acting on the point O ₁ of the pressure-sensitive member, F _Z, M _X, components of M _Y is the acting point O ₀ of the detection surface _{9, F Z, M X,} 3 of M _Y It is detected as a component force.

Next, a typical state in which an external force acts on the flat plate strain element 1 will be described with reference to FIGS. 11 to 13. First, a state in which only the moment M _Y acts on the acting portion 7 as an acting force is shown in FIGS. 11 (a), (b), (c) and (d). At this time, as shown in FIG. 11 (a), there is no deformation in the M _X component detecting section, and the bridge circuit shown in FIG. 6 is constituted by the detecting elements 14 of X ₁ , X ₂ , X ₃ and X ₄ . The output V _{X of} is 0. In addition, the M _Y component detection unit is in the deformation mode as shown in FIG. 11 (b), and the detection element 1 labeled Y ₁ , Y ₂ , Y ₃ , Y ₄ is displayed.
Outputs V of the bridge circuit shown in FIG.
_Y indicates a value corresponding to the moment M _Y. Further, the _FZ component detecting section is in a deformation mode as shown in FIGS. 11 (c) and (d), and Z ₁ , Z ₂ , Z ₃ , Z ₄ , Z ₅ , Z ₆ , Z ₇ , Z ₈ The eight detected elements 14 displayed are respectively deformed. However, the degree of deformation is small, and its output is almost "0" because it is obtained by the bridge circuit shown in FIG.
That is, the directions of expansion and contraction of Z ₁ and Z ₄ , Z ₂ and Z ₃ , Z ₅ and Z ₈ and Z ₆ and Z ₇ are opposite directions, and each side of the bridge circuit shown in FIG. Since the combined resistances of 1 and 2 are canceled by each other and become “0”, the output V _Z becomes “0”.

Here, although with eight strain gauges in F _Z component detection, X, Y-axis or X, detected using the Y-axis and four strain gauges in one axial direction of the shaft in 45 ° direction Is possible. However, employing the present method in order to reduce the interference force other than F _Z (moment).

Next, a state in which only the moment M _X acts is shown in FIGS. 12 (a), (b), (c), and (d). In this case, M _X
The output V _X of the component detection unit is generated, and the output V _Y of the M _Y component detection unit becomes “0”. Also, regarding the output V _Z of the F _Z component detection,
It becomes "0" for the same reason as in the case of FIGS. 11 (c) and (d) described above.

Further, when only the force F _Z acts, it is shown in Fig. 13 (a).
As shown in (b), (c), and (d), in the M _X component detection unit, X ₁ and X ₄ are positive side deformations, and X ₂ and X ₃ are negative side deformations. The output V _{X of the} bridge circuit shown in the figure is "0". Also, the output V _Y of the M _Y component detector is "0" for the same reason.
Is. On the other hand, the output V _Z of the F _Z component detector is one detector
8 times the output of 14 is obtained.

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

Thus, the deformation in the direction of maximum sensitivity can be detected by the detecting element 14 as a strain gauge, and the output of other interference components can be made "0" by the bridge circuit.

Next, by forming the holes 10 in the flat plate portion 8 of the flat plate strain generating element 1, the stress separation of each component is favorably performed.
For example, if the flat plate portion 8 has no holes 10 and is formed of a circular diaphragm, the bending stress generated in the flat plate portion 8 will be generated in the radial direction when an external force acts on the acting portion 7. However, the stress is generated in the circumferential direction in the same degree. The occurrence of the stress in the circumferential direction greatly interferes with other components when detected for each component. However, by forming a plurality of holes 10 at equal intervals on the circumference at an equal distance from the center as described above,
The circumferential bending stress generated in the flat plate portion 8 is reduced so that the strain is mainly generated only in the radial direction. By such an action, there is no interference of the stress of each component, and the stress separation is favorably performed.

Further, an arm 11 is formed by the hole 10 formed in the flat plate portion 8 of the flat plate strain generating element 1, and the detection element 14 is located in the expanded portion 13 of the arm 11. The widened portion 13 is formed by two holes 10 adjacent to each other, and has a substantially trapezoidal shape. And, with respect to the circumferential direction, it has a shape separated from the adjacent widened portion 13,
As described above, the interference due to the bending stress in the circumferential direction does not occur. Moreover, since the expanding portion 13 is located at the base of the arm 11, it is a portion where bending stress in the radial direction is easily generated, and is an appropriate position for detecting strain generated by an external force. Further, looking at the distribution of bending stress generated in the expanded portion 13, the stress distribution in the expanded portion 13 at the base of the arm 11 is relatively uniform, and
There is little interference. Therefore, when the detecting element 14 is attached as a strain gauge to the flat plate strain body 1, even if there is some displacement, there is no variation in the accuracy of strain detection, and this allows some displacement. , It is not necessary to place strict conditions on the accuracy of the sticking position.

Next, since eight holes 10 are formed in the flat plate portion 8 of the flat plate strain generating pair 1, a position having an angle of 45 degrees with them with respect to the radial directions of the X axis and the Y axis. To Z ₁ ,, Z ₂ , Z ₃ , Z ₄ ,
It becomes possible to dispose the detection elements 14 composed of Z ₅ , Z ₆ , Z ₇ , and Z ₈ . The arrangement of such a detecting device 14, the detection of F _Z components as shown in Table 1 is made good, moreover, M _X, effectively erasing the detection value other than the components upon detection of M _Y component Is what you can do.

In addition, in the above-mentioned embodiment, the flat strain element 1 is described as a disc shape, but the outer peripheral shape is not limited to the disc shape, and a square shape, a rectangular shape, a polygonal shape or any other arbitrary shape. It is possible to form it.

Advantageous Effects of Invention The present invention is, as described above, provided on the detection surface of the flat strain element in the XY plane, in the X-axis direction, the Y-axis direction, the X-axis, and the Y-axis.
At least eight arms for four directions with respect to the direction having an angle of 45 degrees with respect to the axis are formed separately, and are located on the center lines of these eight arms, and are formed on the center side and the inner peripheral side, respectively. At least two detection elements separated from each other are provided,
A first bridge circuit is formed by the four detection elements on the X-axis direction arm, and a second bridge circuit is formed by the four detection elements on the Y-axis direction arm. A third bridge circuit is formed by the combination of eight detection elements on the arm in the direction having an angle of 45 degrees, and the Y-axis direction and the X-axis are formed by the respective outputs of the first, second and third bridge circuits. Since the force in the Z-axis direction that is orthogonal to the XY plane and the XY plane is detected, it is possible to accurately detect each force in the three-axis directions as the force acting on the center of the central portion of the flat strain element. In particular, since the detection of each force in the three axis directions is independently performed by using the detection elements provided on the separate arms, the interference output due to the forces in the other axis directions is highly accurately performed. It is possible to achieve such effects.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a sectional view taken along the line AA in FIG.
FIG. 4 is a sectional view taken along line BB in FIG. 2, and FIG. 5 is
Fig. 6 is an electric circuit diagram showing the bridge circuit of the M _Y component detector, Fig. 6 is an electric circuit diagram showing the bridge circuit of the M _X component detector, Fig. 7
FIG electric circuit diagram showing a Buritsuji circuit F _Z component detection section, FIG. 8 is a side view showing the detection principle, FIG. 9 is a side view showing the detection principle of a state where an external force to the plate-shaped flexure element acts, FIG. 10 is a perspective view showing the state of the force acting on the action portion, FIG. 11 is a side view showing the deformed state of the flat strain element when the moment M _Y acts, and FIG. 12 shows the moment M _X FIG. 13 is a side view showing the deformed state of the flat plate strain-generating body when it is applied, FIG. 13 is a side view showing the deformed state of the flat plate-shaped strain body when a force F _Z is applied, and FIG. 14 is an external force. FIG. 15 is a flow chart showing the thin film process, which is a vector diagram showing each component force in the case. 1 ... Flat-shaped strain element, 2 ... peripheral part, 4 ... support part, 5
...... Center part, 7 ...... action part, 9 ...... Detection surface, 14 ...... Detection element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroshi Yamazaki, 1-3-3 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Kouji Izumi, 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Within Ricoh Company (56) Reference JP 61-223626 (JP, A) JP 63-21531 (JP, A) JP 63-75533 (JP, A) JP 63-21530 (JP, A) JP 63-153441 (JP, A) JP 63-210633 (JP, A) JP 63-226073 (JP, A) JP 63-226074 (JP, A) JP 59 -95433 (JP, A) JP-A-61-57825 (JP, A) JP-A-61-79129 (JP, A) JP-A-61-83929 (JP, A) JP-B-54-11903 (JP, Y2) ) Actual public Sho 54-21021 (JP, Y2)

Claims (1)

[Claims] 1. A center part and a peripheral part, one of which is a supporting part, and the other part is an acting part, and the X-axis direction, the Y-axis direction and the X-axis are defined in the XY plane between the center part and the peripheral part. And a detection surface having arms separated in at least eight for four directions with respect to the direction having an angle of 45 degrees with respect to the Y axis, and the rigidity of the central portion and the peripheral portion with respect to this detection surface. Is formed on the center line passing through the center of the central portion with respect to each of the eight arms for the four directions. , And at least two are provided separately on the center side and the peripheral side of the arm so that an output is generated when the balance of the four detection elements provided on the arm in the X-axis direction is lost. Connecting these four detector elements to form a first bridge circuit, A second bridge circuit is formed by connecting these four detection elements so that an output is generated when the balance of the four detection elements provided on the axial arm is lost, and a second bridge circuit is formed. A third bridge circuit is formed by connecting these eight detection elements so that an output is produced when the balance of the eight detection elements provided on the arm in the direction having an angle of 45 degrees is lost. By each output of the bridge circuit of 1, 2 and 3,
A force detection device, which is configured to detect a force in a Y-axis direction, an X-axis direction, and a Z-axis direction orthogonal to the XY plane.