JP2607096B2 - Force / moment detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a force / moment detecting device, and more particularly to a force / moment detecting device using a resistance element formed on a semiconductor substrate.

[Conventional technology]

In recent years, semiconductor sensors have been devised as new force and moment sensors. For example, Japanese Patent Application No. 62-1012
67-101270 disclose some such sensors. Such a semiconductor sensor is more suitable for miniaturization and mass production than a sensor using a strain gauge, and great demand is expected in the future.

[Problems to be solved by the invention]

However, the above-described semiconductor sensor has a problem that the same semiconductor substrate cannot be used for both the force sensor and the moment sensor. That is, the semiconductor substrate for use as a product as a force sensor and the semiconductor substrate for use as a product as a moment sensor must be formed separately, and there is a problem that cost performance is poor.

Therefore, the present invention provides a force sensor using the same semiconductor substrate.
It is an object of the present invention to provide a force / moment detecting device applicable to any of the moment sensors.

[Means for solving the problem]

The present invention provides a force / moment detecting device, comprising: a transducer capable of detecting mechanical deformation in a plurality of directions by arranging elements for converting mechanical deformation into electric signals in a plurality of different directions; A first strain body fixed to the transducer so as to cause mechanical deformation of the transducer based on a displacement of the action portion with respect to the support section; and a support section of the first strain body. On the other hand, a fixing portion fixed at least in the direction of the force to be detected, a flexible portion connected to the fixing portion and having flexibility, and one end fixed to the action portion of the first strain body, A second strain body having an arm-shaped portion having a start end extending away from the transducer and having an other end connected to the flexible portion, and the other end of the arm-shaped portion being connected to the transducer. Against A moment force is generated at one point on the transducer when a force is applied in a direction to cause a sliding motion, and the moment force is applied to the one point when a rotational force is applied to the other end with respect to the one point. It is configured to generate a force in the direction along the transducer.

(Operation)

The transducer and the flexure element form a sensor. This sensor can detect a force or a moment acting on one point on the sensor surface based on the strain of the flexure element. The sensor used in the detection device according to the present invention,
A mechanism that detects only one of a force and a moment acting on one point on the sensor surface may be used.
If a mechanism for detecting a force is used as it is, it becomes a force sensor if it is used as it is, and if it has a configuration in which an arm-shaped portion is attached as in the device according to the present invention, it becomes a moment sensor. Conversely, if it is a mechanism for detecting a moment, it will be a moment sensor if it is used as it is, and if it has a structure in which an arm is attached as in the device according to the present invention, it will be a force sensor.

In short, if a sensor capable of detecting only one of the force and the moment is mass-produced, the detection of the other can be performed by adding the arm.

〔Example〕

 Hereinafter, the present invention will be described based on the illustrated embodiments.

1 (a) is a side sectional view of a force detecting device according to an embodiment of the present invention, and FIG. 1 (b) is a partial bottom view of the device. Here, it is assumed that the X axis, the Y axis, and the Z axis are defined in the direction of the drawing.
FIG. 1A is a sectional view of the device shown in FIG. 1B cut along the X-axis.

This device is roughly divided into three parts: a semiconductor substrate 10, a first strain body 20 (indicated by single-line hatching), and a second strain body 30 (indicated by double-line hatching). I have. FIG. 1B shows only the semiconductor substrate 10 and the first strain body 20 among them.

In this apparatus, on a silicon single crystal substrate 10,
A total of 12 resistance elements R are formed, and constitute a transducer for converting mechanical deformation into an electric signal.
The resistance elements Rx1 to Rx4 are arranged on the X axis and used for detecting moment about the Y axis. The resistance elements Ry1 to Ry4 are arranged on the Y axis and used for detecting moment about the X axis.
1 to Rz4 are arranged on an axis parallel to and in the vicinity of the X axis and used for detecting a force in the Z axis direction. The specific structure of each resistance element R and its manufacturing method will be described later in detail, but these resistance elements R are elements having a piezoresistance effect in which the electric resistance changes due to mechanical deformation.

The single crystal substrate 10 is bonded to a first strain body 20. In the device according to the present embodiment, the first strain body 20 includes a disc-shaped support portion 21, a flexible portion 22 having a reduced thickness for providing flexibility, and an action portion 23 projecting to the center. Consists of The material of the first strain body 20 is Kovar (iron,
Alloys of cobalt and nickel) are used. Since Kovar has a coefficient of thermal expansion substantially equal to that of the silicon single crystal substrate 10, it has an advantage that even when bonded to the single crystal substrate 10, the thermal stress generated by a temperature change is extremely small. The material and shape of the first strain body 20 are not limited to those described above, and the embodiment shown here is merely an optimal embodiment. The first strain body 20 is fixed toward the mounting hole 34 of the second strain body 30 by the set screw 14 inserted through the mounting hole 24.

A protection cover 40 for protecting the single crystal substrate 10 is attached to a lower portion of the first strain body 20 (FIG. 1B).
In the illustration). The protective cover 40 may be of any type as long as it has a protection function, and may not be provided depending on the usage of the device.

Each resistance element is provided with wiring as shown in FIG.
That is, the resistance elements Rx1 to Rx4 are assembled in a bridge circuit as shown in FIG. 2A, the resistance elements Ry1 to Ry4 are assembled in a bridge circuit as shown in FIG.
1 to Rz4 are assembled in a bridge circuit as shown in FIG. 2 (c). A predetermined voltage or current is supplied to each bridge circuit from a power supply 50, and each bridge voltage is measured by voltmeters 51 to 53. In order to perform such wiring for each resistance element R, bonding pads 11 electrically connected to each resistance element R on a single crystal substrate 10 as shown in FIG.
And an electrode 13 for external wiring are connected by a bonding wire 12. The electrode 13 is led out to the opposite side of the first strain body 20 through the wiring hole 25. Thereafter, a wiring is made from the outside of the second strain body 30 to the electrode 13, but this wiring is omitted in FIG.

In the above-described embodiment, the strain body 20 and the single crystal substrate 10 are separate bodies. However, if the strain body 20 is formed of a single crystal, both can be formed integrally.

The second strain body 30 has a hollow columnar shape as can be seen from the cross section of FIG. 1A, and has a fixing portion 31 serving as a base and a flexible portion for providing flexibility. It is composed of a part 32 and an arm part 33 protruding inward at the center. Here, the arm portion 33 has an elongated cylindrical shape, the tip of which is flat, and is adhered by brazing to the tip of the working portion 23 of the flattened first flexure element 20. . In essence, the arm 33 and the working part, such as screwing instead of brazing
Any means may be used as long as it is a means to which the fixing member 23 is fixed.

The first strain body 20 and the second strain body 30 are connected after being formed separately. Focusing on the connection relationship, the support portion 21 of the first strain body 20 is connected to the fixing portion 31 of the second strain body 30, and the working portion of the first strain body 20.
23 is connected to the arm 33 of the second strain body 30. Moreover, regarding the first strain body 20, since the action portion 23 is connected to the support portion 21 via the flexible portion 22, the action portion 23 is displaced with respect to the support portion 21 by the bending of the flexible portion 22. be able to. The second strain body 30 has an arm-shaped portion.
33 is connected to the fixing portion 31 via the flexible portion 32,
The arm portion 33 can be displaced with respect to the fixed portion 31 by bending of the flexible portion 32.

In FIG. 1 (a), when a force is applied to the displacement point S above the arm 33, a stress strain corresponding to the applied force is generated in the second flexure element 30. As described above, the flexible portion 32 bends, and a displacement occurs between the arm-shaped portion 33 and the fixing portion 31, and this displacement is transmitted to the action portion 23 of the first strain body 20. Here, the flexible portion 22 bends, and a displacement occurs between the flexible portion 22 and the support portion 21 of the action portion 23,
Displacement occurs near the action point P on the semiconductor substrate 10, and each resistance element R is mechanically deformed. Due to this deformation, the electric resistance of each resistance element R changes, and eventually, the applied force is detected as a change in each bridge voltage shown in FIG.

FIG. 3 shows the relationship between the stress strain and the change in the electric resistance of the resistance element R. Here, for convenience of explanation, the single crystal substrate 10
And only the action portion 23 of the first strain body 20 is illustrated.
It will be displayed upside down in FIG. Now, consider a case where four resistance elements R1 to R4 are formed from left to right in the drawing. First, as shown in FIG.
When no force is applied to the single crystal substrate 10, no stress strain is applied to the single crystal substrate 10, and the resistance change of all the resistance elements is zero. However, when a downward force F is applied, the single crystal substrate 10 is mechanically deformed as shown in FIG. Now, assuming that the conductivity type of the resistive element is P-type, this deformation causes the resistive elements R1 and R4 to expand and increase the resistance (indicated by a + sign), and the resistive elements R2 and R3 to contract and reduce the resistance. (Denoted by a minus sign). When a counterclockwise moment M is applied, the single crystal substrate 10 is mechanically deformed as shown in FIG. Due to this deformation, the resistance elements R1 and R3 expand and increase the resistance, and the resistance elements R2 and R4 contract and reduce the resistance. Since each resistance element R is a resistance element whose longitudinal direction is in the horizontal direction of the drawing, when a force or moment is applied in a direction perpendicular to the plane of the drawing, the change in the resistance value of each resistance element can be ignored. . As described above, the present apparatus utilizes the fact that the resistance change characteristic of the resistance element differs depending on the direction of the applied force, and independently detects the force in each direction.

Operation of the Device as a Moment Detecting Device Hereinafter, referring to FIGS. 4 to 6, the semiconductor substrate 10 and the first
The operation of the device including the flexure element 20 will be described. Both figures show the semiconductor substrate 10 and the first strain body 20 in an upside-down relationship with respect to FIG. FIG. 4 shows a case where a moment My about the Y axis is applied to the action point P, and FIG.
FIG. 6 shows the stress applied to each resistive element when a moment Mx around the axis is applied and a force Fz in the Z-axis direction is applied (the extending direction is indicated by +, the contracting direction is indicated by −, and no change is indicated by 0). Are respectively shown. In each figure, (a) is a cross section of the device shown in FIG. 1 taken along the X axis, (b) is a cross section taken along the Y axis, and the element Rz1 is parallel to the X axis.
A cross section taken along Rz4 is shown as (c).

First, considering the case where a moment about the Y axis is applied as shown by an arrow My in FIGS. 4 (a), (b), and (c), stresses of the polarities shown are generated. The polarity of this stress can be easily understood from the description of FIG. A resistance change corresponding to this stress occurs in each resistance element R. For example, the resistance of the resistance element Rx1 decreases (-), the resistance of the resistance element Rx2 increases (+), and the resistance of the resistance element Ry1 does not change (0). When a moment about the X-axis and a force in the Z-axis direction are applied as indicated by arrows Mx and Fz in FIGS. 5 and 6, respectively, a stress as illustrated is generated.

Finally, Table 1 summarizes the relationship between the applied moment or force and the change of each resistance element.

Here, taking into account that each resistance element R forms a bridge as shown in FIG. 2, the applied force and the presence or absence of a change in each of the voltmeters 51 to 53 have a relationship as shown in Table 2. .

Note that the resistance elements Rz1 to Rz4 receive substantially the same stress change as the resistance elements Rx1 to Rx4, but have different responses from the voltmeters 51 and 53 because the bridge configurations are different as shown in FIG. I want to. After all, the voltmeters 51, 52, 53
Will respond to My, Mx, Fz. Although only the presence or absence of a change is shown in Table 2, the polarity of the change is controlled by the direction of the applied moment or force, and the amount of change is controlled by the magnitude of the applied moment or force.

As described above, the device composed of the semiconductor substrate 10 and the first strain body 20 is provided around the X axis and Y
It can be used as a device for detecting the moment around the axis (in this embodiment, it also has a function of detecting the force acting in the Z-axis direction, but this function is an additional function from the viewpoint of the basic idea of the present invention). is there). Actually, since the point of action P is a point on the semiconductor substrate, the moment acting directly on the point of action P is not detected, but, for example, the moment acting on one point in the acting portion 23 is detected as the moment acting on the point of action P. Will do.

Operation as Force Detection Device As described above, the device including the semiconductor substrate 10 and the first strain body 20 functions as a moment detection device, and the second strain body 30 is added thereto. By doing so, it becomes possible to function as a force detection device.

FIG. 7 is a view for explaining the function as this force detecting device. FIG. 7 (a) is a sectional view showing only a main part of the device shown in FIG. Here, the semiconductor substrate 10 and the first strain body 20 constitute a moment detecting device as described above. The action point P of the first strain body 20 and the displacement point S of the second strain body 30 are separated by a distance l along the arm 33 as shown in FIG. 7 (b). I have. Now, FIG. 7 (c)
Let us consider a case where the displacement point S is displaced to the position of the point S 'by a force Fx parallel to the X axis as shown in FIG. As a result of this displacement, the second strain body 30 bends as shown by the broken line in the figure, and as a result, a moment My about the Y axis is generated at the point of action P. As described above, this moment My can be detected as a change in the resistance value of the resistance element. In short, the force Fx applied to the displacement point S can be detected as the moment My applied to the action point P. Force Fx and moment
Conversion with My can be easily performed by using the distance l as a coefficient.

The advantage of the force detection device according to the present invention lies exactly in this point. That is, a semiconductor substrate as a moment detecting device
If a combination of 10 and the first strain body 20 is prepared,
By adding the second strain body 30 to this, it can be made into a force detecting device. Therefore, at the time of manufacturing the semiconductor substrate 10, mass production of the same bridge wiring with the same pattern is always performed without considering whether the device will be used as a moment detector or a force detector in the future. can do.

Embodiment in which the reverse application is performed The embodiment described so far is to mass-produce the semiconductor substrate 10 functioning as a moment detecting device for the time being,
When this is used as a force detecting device, a second flexure element is further provided.
Although the application of adding 30 has been performed, it is also possible to perform the opposite application. That is, the semiconductor substrate 10 functioning as a force detecting device is first mass-produced, and when the semiconductor substrate 10 is used as a moment detecting device, the second strain body 30 is further added.

If the bridge wiring shown in FIG. 8 is performed instead of FIG. 2 for each resistance element R of the device shown in FIG. 1, the semiconductor substrate 10 and the first strain body 20 function as a force detecting device. Will fulfill. Note that there is no change in the bridge configuration for the resistance element Rz, but there are some changes in the bridge configuration for the resistance elements Rx and Ry. If such a bridge is configured, when the forces Fx, Fy, Fz in the X-axis, Y-axis, and Z-axis directions are applied to the point of action P, the resistance changes of the respective resistance elements as shown in Table 3 are received. Table 4 shows whether or not each of the voltmeters 51 to 53 has changed.

As described above, the device including the semiconductor substrate 10 and the first strain body 20 forming the bridge as shown in FIG. 8 is a device for detecting the X-axis and Y-axis forces acting on the action point P. (This embodiment also has a function of detecting a force acting in the Z-axis direction, but this function is an additional function from the viewpoint of the basic idea of the present invention). Actually, since the point of action P is a point on the semiconductor substrate, the force acting directly on the point of action P is not detected.
The force acting on one point in 23 is detected as the force acting on the action point P.

By adding the second strain body 30 to the device for detecting the force acting on the point of action P, the device can be used as a moment detecting device. FIG. 7 (d) is a diagram for explaining the function as this force detecting device. Now, consider a case where the second strain body 30 is bent around the displacement point S by a moment My about a straight line passing through the displacement point S and parallel to the Y axis. As a result, the second strain body 30 bends as shown by the broken line in the figure, and as a result, generates a force Fx in the X-axis direction such that the point of action P moves to the point P '. This power
Fx can be detected as a change in the resistance value of the resistance element as described above. In short, the moment My acting on the displacement point S can be detected as the force Fx acting on the acting point P. The conversion between the force Fx and the moment My can be easily performed by using the distance l as a coefficient.

Minimum Resistive Element Configuration In the above embodiment, an example was shown in which twelve resistive elements Rx1 to Rz4 were formed on the semiconductor substrate 10, but not all of these resistive elements are necessarily required. In particular, Rz1 to Rz4
The four resistance elements are for detecting the force in the Z direction, and are not necessary for detecting the forces and moments on the X axis and the Y axis. If the moment about the Y axis acting on the action point P on the semiconductor substrate 10 is to be detected, as can be seen from Tables 1 and 2, the resistance element Rx
It is sufficient if there are two elements, Rx1 and Rx3, and if detecting the force in the X-axis direction, it is sufficient if there are two elements, resistance elements Rx1 and Rx2.

Production of Resistive Element Having Piezoresistance Effect An example of a method for producing a resistive element used in the present invention will be briefly described below. This resistive element has a piezoresistive effect and is formed on a semiconductor substrate by a semiconductor planar process. First, as shown in FIG. 9A, an N-type silicon substrate 101 is thermally oxidized to form a silicon oxide layer 1 on the surface.
Form 02. Subsequently, as shown in FIG. 1B, the silicon oxide layer 102 is etched by photolithography to form an opening 103. Subsequently, boron is thermally diffused from the opening 103 to form a P-type diffusion region 104, as shown in FIG. Note that the silicon oxide layer 105 is formed in the opening 103 during the heat diffusion process.
Next, as shown in FIG. 3D, silicon nitride is deposited by a CVD method, and the silicon nitride layer 106 is formed as a protective layer. Then, as shown in FIG. 3E, contact holes are opened in the silicon nitride layer 106 and the silicon oxide layer 105 by photolithography, and then, as shown in FIG. I do. Finally, the aluminum wiring layer 107 is patterned by photolithography to obtain a structure as shown in FIG.

The above-described manufacturing process is shown as an example, and the present invention can be realized by using any resistance element having a piezoresistance effect.

Other Embodiments Although the present invention has been described based on the embodiments illustrating the present invention,
The present invention is not limited to the embodiments described above, and various applications are possible.

For example, in the above-described embodiment, the central portion of the first strain body is the acting portion, the peripheral portion is the support portion, the center portion of the second strain body is the arm, and the peripheral portion is the fixing portion. However, the present invention is not limited to such a configuration, and a mode in which the central portion and the peripheral portion have an opposite relationship can be implemented.

Further, in the above embodiments, a resistance element formed on a semiconductor substrate is used as a transducer, but any transducer having a function of converting mechanical deformation into an electric signal may be used as the transducer. Good.
For example, a sensor using a strain gauge can be applied.

〔The invention's effect〕

As described above, according to the present invention, a transducer capable of detecting mechanical deformation in a plurality of directions by arranging elements for converting mechanical deformation into electrical signals in a plurality of different directions, and a A first flexure element that performs a flexure operation, a fixed section that is fixed to at least a direction of a force to be detected with respect to a support section of the first flexure element, and a flexible section that is connected to the fixed section. A flexible portion having one end fixed to the action portion of the first strain body, and an arm-shaped portion having the one end as a starting end and extending away from the transducer and having the other end connected flexibly. And the second strain body is provided so that the force or moment applied to the other end of the arm-shaped portion can be converted into the moment or force at the action portion and detected, so that either the force or the moment can be detected. If a sensor capable of detecting only one of them is mass-produced, the other can be detected by adding a second flexure element (arm-shaped part). That is, the same transducer can be used and the force sensor can be used. It can be applied to any of the moment sensors.

[Brief description of the drawings]

1 (a) and 1 (b) are a sectional view and a partial bottom view, respectively, of a force / moment measuring device according to the present invention, FIG. 2 is a circuit diagram showing a bridge configuration of a resistance element of the device shown in FIG. 1, FIG. 3 is a principle diagram showing the relationship between stress strain and resistance change of a resistance element in the device shown in FIG. 1, FIG.
FIG. 6 and FIG. 6 show Y and Y respectively in the apparatus shown in FIG.
FIG. 7 is a diagram showing a moment generated around an axis, a moment about an X axis, and a stress generated when a force is applied in a Z axis direction.
The figure shows a mechanism for converting force and moment in the device shown in FIG. 1, FIG. 8 is a circuit diagram showing another bridge configuration of the resistance element of the device shown in FIG. 1, and FIG. 9 is FIG. FIG. 4 is a process chart of a process for forming a resistive element used in the device shown in FIG. 10 ... single crystal substrate, 11 ... bonding pad, 12 ...
Bonding wire, 13 ... electrode, 14 ... set screw, 20
... First flexure element, 21... Support part, 22... Flexible part, 23.
.. Acting part, 24 mounting hole, 25 wiring hole, 30 second strain body, 31 fixing part, 32 flexible part, 33 arm part,
34 ... Mounting hole, 40 ... Protective cover, 50 ... Power supply, 51-53
... Voltmeter, 101, N-type silicon substrate, 102, silicon oxide layer, 103, opening, 104, P-type diffusion region, 105
... silicon oxide layer, 106 ... silicon nitride layer, 107 ...
Aluminum wiring layer, R: resistance element, S: displacement point,
P: action point.

Claims (6)

(57) [Claims] 1. A transducer capable of detecting mechanical deformation in a plurality of directions by arranging elements for converting mechanical deformation into electric signals in a plurality of different directions, a support portion and an operating portion, A first strain body fixed to the transducer so as to cause mechanical deformation of the transducer based on a displacement with respect to the support portion; and a force to be detected at least with respect to the support portion of the first strain body. And a flexible portion connected to the fixed portion and having flexibility, and one end is fixed to the action portion of the first strain body, and the one end is a starting end and A second strain body having an arm-shaped portion having the other end extended away from the flexible portion, and a sliding motion of the other end of the arm-shaped portion with respect to the transducer. Force in the direction When applied, a moment force is generated at one point on the transducer, and when a moment force is applied in a direction that causes the other end to rotate with respect to the one point, a force in a direction along the transducer is applied at the one point. A force / moment detecting device characterized in that it is configured to generate a force / moment. 2. A force / force transducer according to claim 1, wherein said transducer is formed of a semiconductor substrate having at least one surface formed with a resistance element whose electric resistance changes by mechanical deformation. Moment detection device. 3. A central portion of the first strain body is a working portion, a peripheral portion is a supporting portion, a peripheral portion of the second strain body is a fixing portion, and the arm state is as described above. 3. The force / moment detecting device according to claim 1, wherein the force / moment detecting device is formed at a central portion of the second strain body. 4. The apparatus according to claim 1, wherein said second strain body is made of metal, and said working portion and said arm are fixed to each other by brazing or screwing. Item 3. The force / moment detecting device according to item 3. 5. The force / moment according to claim 2, wherein said semiconductor substrate comprises a single crystal substrate of silicon, and said resistance element is formed on said silicon substrate by a semiconductor planar process. Detection device. 6. The force detecting device according to claim 5, wherein said semiconductor substrate and said first strain body are integrally formed in the same silicon chip.