JPS6092670A - Kinetic force converter - Google Patents

Abstract

PURPOSE:To produce a highly precise kinetic force converter easily by a method wherein a distorted body is located in the linear direction i.e. only in the free boundray direction of the distorted body in terms of a kinetic force transmitter, a distorting body and the locational relation between the distorting body and gauge resistors. CONSTITUTION:Gauge resistors 1 are buried in the main surface of a rectangular distorting body 30 comprising a semiconductor substrate by impurity diffusing process. Multiple gauge resistors 1 are arranged in parallel with and perpendicular to the short side ends 40 of the rectangular distorted body 30 to be connected to leads 12 by small metallic wires 11. The multiple gauge resistors 1 are provided with the means to constitute the Wheastone bridge circuit. The four sides of the distorting body 1 comprise a pair of long side ends with free boundary and a pair of short side ends 40 rigidly adhering to a square-shaped supporting base 31 making the distorted body 30 vertically flexible. A kinetic force transmitter 7 is provided with a knife-shaped blade at the end while its edge 32 in the direction perpendicular to the free boundary side of the distorting body 30 i.e. in parallel with the short side direction comes into contact with the distorted body 30 at the central line of the free boundary side of said distorted body 30.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a force transducer, and in particular, to a force transducer, and particularly to a force transducer for positioning a pressure-sensitive element formed on the surface of a force transmitting strain body that transmits a force applied from the outside to a strain body. The present invention relates to a structure of a force transducer that can be easily implemented.

Recently, in the field of pressure transducers, the use of diaphragm-type silicon pressure sensors that utilize piezoresistive effects has become widespread in place of conventional metal gauges. This sensor has the advantage of having several tens of times higher sensitivity than a metal gauge, and can be made smaller. Therefore, by using this sensor, it has become possible to provide a high-performance semiconductor pressure transducer simply by forming a temperature compensation circuit around it. Moreover, by utilizing semiconductor processing technology for silicon and the like, it has become possible to manufacture the sensors in large quantities at low cost. On the other hand, from the side of systems such as robotics, there has recently been a particularly strong demand for force transducers that directly detect force in addition to pressure. Recently, it has been devised to utilize the semiconductor pressure transducers mentioned above to provide force transducers. This has the same configuration as a conventional semiconductor pressure transducer in that it uses a piezoresistance effect to detect strain generated in a silicon diaphragm, which is a strain-generating body, with a gauge resistance. It differs from conventional semiconductor pressure transducers in that it has a structure that directly transmits force rather than applying the pressure of gas or other fluid. below,
A conventional example of a force transducer will be explained with reference to the drawings.

FIG. 1 shows the configuration of a conventional force transducer. A gauge resistor 1 is formed by diffusing impurities into a semiconductor substrate such as silicon, and a protective film is applied to the surface. After this, it is immersed in an etching solution such as KOH or hydrazine, and the surface opposite to the surface on which the gauge resistor 1 is formed is anisotropically etched to form a diaphragm 2 and a pressure sensor 3. Pedestal portion 2 of the pressure sensor 3
1 and glass 6 having a thermal expansion coefficient close to that of the substrate material (for silicon, 774 manufactured by Corning Co., Ltd.
Furthermore, this glass 6 is bonded to the stem 4 with a eutectic alloy 14 such as gold and tin, and is sealed with a package 5. A gauge resistor 1 formed on 3 is connected to a lead 1 by a thin metal wire 11.
2, thereby allowing electrical signals to be taken out to the outside. The stem 4 is provided with an opening 13 to make the pressures of the upper and lower air chambers of the diaphragm 2 the same.

Typically, 13 openings are open to the atmosphere. A force transmitting body 7 having a sharply cut tip is in contact with the surface of the diaphragm 20, and is led to the outside through the package 5. The force transmitting body 7 is made of a hard metal such as stainless steel, an insulator such as Teflon, and is provided with a protrusion 9. On the other hand, the package 5 has a support 8 and the force transmitting body 7 is placed on the diaphragm 2.
The diaphragm 2 has a function of standing approximately vertically and colliding with the protrusion 9 before the diaphragm 2 breaks, thereby limiting the force acting on the diaphragm 2. The inside of the support 8 is made of materials such as Teflon, rubber, metal, etc., and is configured to allow the force transmitting body 7 to move smoothly. A pressurizing section 10 to which an external force is applied is formed at the end of the force transmitting body 7. Moreover, the shape of the pressurizing part 10 is round, square, oval, or the like.

FIG. 2 is a plan view of the pressure sensor 3. In the pressure sensor 3, a diaphragm 2 is formed inside the broken line in the figure by anisotropically etching silicon on the (100) plane. The portion outside the broken line is electrostatically bonded to the glass 6 at the pedestal portion 21 of the pressure sensor 3, and is further attached to the stem. Gauge resistors l are created in the (+'to:> direction) by impurity diffusion around the diaphragm 2. Two sets of the gauge resistors are arranged parallel to and perpendicular to the sides of the diaphragm 2, and aluminum wiring (not shown) is used. A Wheatstone bridge circuit is constructed by the above.The sharply cut tip of the force transmitting body 7 contacts the center 20 of the diaphragm 2- to transmit the force from the pressurizing section to the diaphragm 2. Due to the strain generated in the entire diaphragm, the two sets of gauge resistors in different directions with respect to the sides of the diaphragm exhibit opposite positive and negative resistance change rates.As a result, a large bridge output voltage is detected, and the bridge output Since the voltage is proportional to the force applied to the pressurizing part 10, the magnitude of the nuclear force can be known by reading the bridge output voltage. However, in such a structure, the force transmitting body and the diaphragm It is important to accurately determine the contact position of the diaphragm and the gauge resistor, and any deviation in the positional relationship between the diaphragm and the gauge resistor greatly affects the accuracy of the force transducer.In particular, the structure of the conventional example described above is The force transducer is designed to accurately control the position of the gauge resistor on the two-dimensional plane of the diaphragm, and to position the tip of the force transmitting body that contacts the diaphragm correctly on the two-dimensional plane of the diaphragm. There was a difficulty in having to assemble it.

The purpose of the present invention is to eliminate such conventional drawbacks and to develop a new principle that can operate with high precision by considering the positioning of the gauge resistance, the strain body, the force transmitting body, and the strain body in one dimension. According to the present invention, a rectangular strain-generating body having two fixed sides and a free boundary on the other two sides, and a main force transducer on one or both sides of the strain-generating body are provided. A resistive element provided on a surface and responsive to strain in the strain-generating body, a means for detecting a change in resistance value of the resistive element, and one tip of which is in contact with the strain-generating body and the other tip of which has a pressurizing portion. A force transducer is obtained, characterized in that the force transmitting body is provided, and the force applied to the pressure section is detected by the detection means.

The present invention will be described below with reference to drawings showing embodiments.

Figure 3 (a), (bl, (cl is a diagram showing one embodiment of the present invention, the same figure (at is a diagram conceptually showing the cross section of the force transducer, the same figure (bl is the same figure) This is a conceptual diagram of the plan view of Figure (a), and C1 is a conceptual diagram of a cross section taken about AA in the figure (bl). In the figure, the same numbers as in Figure 1 refer to the same components. In Fig. 3 (al), 30 is a thin rectangular strain-generating body made of a semiconductor substrate such as silicon, and one or both main surfaces of 30 are treated by well-known techniques such as thermal diffusion and ion implantation. A gauge resistor 1 is buried by impurity diffusion.

A plurality of the gauge resistors are arranged parallel to and perpendicular to the short side end 40 of the rectangle (FIG. 2(b)), and are connected to the lead 12 through the thin metal wire 11. Via the leads, the plurality of gauge resistors 1 have means for forming a Wheatstone bridge circuit. The four sides of the strain-generating body are connected to a set of long side ends with free boundaries and a support base 3 according to well-known technology.
1 (FIG. 1(b)).

31 has a 10" shape with an opening inside,
The strain body 30 has a structure that allows it to bend up and down (FIG. 3(C)), and the material of the strain body 31 is not limited, but may be Pyrex glass having a coefficient of thermal expansion similar to that of the strain body 30. etc. are preferred. In such cases, 30.3
Electrostatic bonding technology can be used for adhesion between the two. Of course, other materials may be used, and as for the bonding method, glass bonding, eutectic alloy, organic adhesive, etc. may be used. 30,
The structure of 31 is fixed to the stem 4 using a eutectic alloy, an adhesive, etc., and the package 5 is sealed in the stem 4. Note that even if 4.31 is integrally constructed of the same material, In such a case, there is an advantage that the configuration is greatly simplified. When the strain body is made of silicon, (
A silicon single crystal with a 100) plane can be used, and the side direction of the rectangle is in the (110) direction, and the gauge resistance is in the (110) direction.
When selecting the plane direction or axial direction, the force transmitting body 7 is set at the end, which is known to maximize the rate of change in resistance based on the piezoresistance effect of the gauge resistance. A contact surface 32 at the end of the knife 33 has a blade 33 in the shape of a knife in a direction perpendicular to the side of the free boundary of the strain-generating body, that is, parallel to the short side direction, The material of 33, which is in contact with the flexure body 30 on the center line of the free boundary side of the flexure body 30, is a metal, an insulator, etc., and is not particularly limited. It may be integrally molded with the same material as 7.

FIG. 4 is a diagram conceptually showing the plane of the contact portion between 7 and 8 in FIG. 3 (al). In the figure, the same numbers as in FIG. The support 8 formed on the package 5 is connected to the protrusion 9 (third
By colliding with Figure (a)), there is a function of stopping the nuclear force applied to the strain body and limiting the magnitude of the deflection of the strain body. In addition, in order to prevent the blade 33 from rotating, the support 8 has a long side that is not circular but has a long side that is in a certain relationship (for example, parallel) with the direction of the nuclear force. It has a structure such as a rectangle. Of course, since this shape prevents rotation of 33, various modifications are possible.

The force transducer according to one embodiment of the present invention has been described above. Next, the bending moment and shear force distribution of the above embodiment and the distribution of the shear force of the present invention are shown using FIG. 5 (at, fbl, (cl). Describing Effects 0 Fig. 5 (Al is a diagram showing the main components of the force transducer of the above embodiment, and the same numbers as in Fig. 3 indicate the same components. Pressurizing part l
The force applied to O is applied to the center position of the long side of 30 via 7 and 32 with a force of W per unit line length. The length of the free boundary of the long side is l, and reaction forces of R+ and k are acting on the places where the strain-generating body and the support stand touch each other, respectively. At this time, the distribution of the bending moment in the long side direction is shown in the same figure (, bl), and the distribution of shear force is shown in the same figure (C
When the ratio of the long side to the short side of the O flexure body shown in 1 is sufficiently large, the moment of the bend and the magnitude of the shear force change by #1 in the direction perpendicular to the long side direction. It is constant. In addition, the following relationship exists between the moment of the song and the reaction force.

Ml == M3 = 100 W/ M, =--W/ R, = 几2 = 2 On the other hand, when the thickness of the strain-generating body is h, the stress and bending moment generated on the surface of the 30 are as follows. , 2g = 100M. From the above, the stress acting on the gauge resistance formed on the surface of the flexure element 30 changes linearly in the direction of the long side of the flexure element 30, but on the other hand, in the direction perpendicular to the long side. It can be seen that there is almost no change. Therefore, a highly accurate force transducer can be obtained by simply aligning the gauge resistance l formed on the surface of the strain body 3o by observing only the position in the long side direction of the strain body. Further, in the force transmitting body 7, it is sufficient to align the contact surfaces only in the long side direction of the strain generating body. In the conventional example described above, the gauge resistor 1 was formed near the support base 31, but by protecting the surface of the strain body with a protective film, etc., it is also possible to arrange the gauge resistor near the center of the strain body. It is. Further, the force transducer having the structure of the present invention differs from the conventional example in that the upper and lower air chambers of the strain body 30 communicate with each other through the lateral surface of the free side of the boundary, so that the pressure is always the same. Therefore, there is no need to open the opening 13 in the stem, and there is an advantage that the configuration is simplified.

FIG. 6 (al a (bl) shows another example of the shape of the contact surface.

The same figure (81 is a plane, the same figure (b) is the same figure (al A A
' is a diagram showing the concept of a cross section. In the figure, the same numbers as in FIG. 4 indicate the same components. In this embodiment, by increasing the length of the contact surface 32, when the displacement of the strain body 30 reaches a certain displacement or more, 32 and 3
In such a case, as shown in the same figure (bl), part of the above-mentioned 9 and 8 is unnecessary, and the structure is simplified. There is an advantage.

FIG. 7 (at v (bl) is also a diagram showing other shapes of the contact surface; FIG.
! The same reference numerals as in FIG. 4, which is a diagram illustrating the concept of the cross section of AAI in I), indicate the same components. This embodiment is characterized by the fish-shaped contact surface. Even in such a case, as described above, since the changes in the moment and stress distribution in the short side direction of the strain-generating body 30 are small, it is possible to realize the advantages of positioning in the present invention described above. In the case of such a structure, there is an advantage that the structure having the function of preventing rotation is unnecessary and the work is easy.

FIG. 8 is a diagram showing another embodiment of the present invention.

In the figure, the same numbers as in FIG. 3 indicate the same components. This embodiment has a configuration similar to that of the first embodiment (FIG. 3), but in contrast to FIG. 8th
In the figure, the thick fixing part 60 and the thin strain body part 61 are formed of the same material using anisotropic etching of a semiconductor such as silicon. Fixing part 6 of the strain body
0 is fixed to the stem 4 via a glass 6 or the like.

Since the operation in this embodiment is similar to the operation described above, the following explanation will be omitted.

FIG. 9 is a diagram showing another embodiment of the present invention, in which the same numbers as those in FIG. 3 indicate the same components. In this embodiment, a base 91 made of silicon, etc. A capacitor is formed by a cavity 93 provided between a substrate 92 made of a metal material and a metal 90 made of gold or the like deposited on both sides of the inside of the cavity. The lead 90 is connected to the lead 12 via the thin metal wire 11.
and means (not shown) for detecting the capacitance t of the nuclear capacitor. The force applied to the force transmitting body 7 is transmitted to the strain body 3o via 32, which induces vertical displacement of 30. This displacement changes the capacitance value of the capacitor, so that the capacitance value An electrostatic force transducer may be configured to detect the force by detecting a change in the force.

The present invention has been described above in detail using examples. Note that the strain body is made of metal, and one of the surfaces of the metal,
Alternatively, the nuclear force applied to the strain body is detected by pasting strain gauges on both sides or depositing strain gauges made of metal or semiconductor, etc., and the strain body is made of a semiconductor such as silicon. The present invention also includes a structure in which the surface is protected with an oxide film such as silicon, a nitride film, etc., and a structure in which a peripheral circuit is formed on the surface.

In addition, the force/voltage conversion efficiency in the above embodiment increases as the length of the side with free boundaries of the strain-generating body increases and as the film thickness decreases, and it becomes possible to detect a slight force. ,
When the force to be detected is large, the vertical movement of the force transmitting body is provided with an elastic action such as a spring, so that a part of the applied force from the outside is absorbed by the spring, and only the remaining applied force is used to generate the force. It is sufficient if the voltage is applied to the strained body. It is also possible to reduce the sensitivity by reducing the ratio of the length of the side with a free boundary to the length of the fixed side of the strain-generating body, or by making the tip of the knife of the force transmitting body blunt. The film thickness, the ratio of the length of the free side to the fixed side, the shape of the spring, the tip of the knife, etc. may be selected in various combinations depending on the force to be measured.

Further, if design considerations are taken into consideration, such as the arrangement of the gauge resistor and the detection means, the contact surface does not necessarily come into contact with the strain-generating body on the center set in the direction of the free boundary side of the strain-generating body. There's no need.

1. According to the present invention, by aligning only the -dimensional direction, that is, the free boundary direction of the strain body, with respect to the positional relationship between the force transmitting body and the strain body, and the strain body and the gauge resistance. A highly accurate force transducer can be easily realized.The present invention has great effects in that it can provide a durable, highly accurate, and high-quality psychokinetic transducer, including the advantages of labor saving and manufacturing cost reduction. It is something.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional force transducer, Fig. 2 is a plan view of a pressure sensor, and Fig. 3 (at is a sectional view of an embodiment of the present invention;
The same figure (b) is the plane of the same figure (!I), the same figure (c) is the conceptual diagram of the cross section at A in the same figure (bl), and Fig. 4 is the same figure (! Conceptual diagram of the plane of the part shown in Fig. 5 (a).
)・Distribution diagram of shearing force, FIG. The figure is a sectional view of another embodiment of the present invention. 1... Gauge resistance, 2... Diameter 72m, 3...
Pressure sensor, 4... Stem, 5... Package, 6
... Gala, Su, 7... Force transmission body, 8... Support, 9.
...Protrusion, 1o...Pressure part, 11...Thin metal wire, 1
2...-Lead, 13... Opening, 14... Eutectic alloy such as gold and tin, 15... Electrostatic bonding, 20...
・Contact end, 21... Pedestal part, 3°... Strain body, 31
...Support stand, 32...Contact surface, 33...Blade, 40
...Short side end, 6o...Fixing part, 61...Strain body part, 90...Metal, 91...Base, 92...Substrate, 93...Cavity. Figure 1 Figure 2! 0 Pressure ℃'73 Figure 3 (Rihai 3I sword (b) Figure 4 Figure 5 Figure 6 ((1) Figure 7 (a) - Figure 8 n

Claims (2)

[Claims] (1) A rectangular flexure element with two fixed sides and a free boundary on the other two sides, and a resistor that is provided on one or both main surfaces of the flexure element and responds to strain of the flexure element. an element, a means for detecting a change in the resistance value of the resistance element, and a force transmitting body having one tip in contact with the strain-generating body and the other tip having a pressurizing part, and applying the force to the pressurizing part. A force transducer characterized in that force is detected by the detection means. (2) The thickness of the flexure element on the fixed two sides of the flexure element is larger than the thickness of the flexure element in the region in contact with the force transmitting body, and the flexure element is the same. The force transducer according to claim 1, which is integrally constructed of a material.