JPH051408B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device manufactured using silicon integrated circuit technology, and more particularly to a force direction detection device using a silicon diaphragm type sensor.

In the field of measurement, load measuring devices called so-called load cells have been widely used for a long time. Such a load cell usually includes a mechanical part that converts a load applied from the outside world into mechanical strain, a strain/electrical signal conversion element provided in the mechanical part, and a circuit that processes the electrical signal obtained from the conversion element. It consists of two parts. The mechanism section is composed of a metal cantilever and a circular diaphragm. As the conversion element, an element called a strain gauge that utilizes a change in resistance value due to a change in shape of a deposited metal film has been widely used. Recently, semiconductor strain gauges that use the piezoresistance effect of semiconductors that have a large strain/resistance value change coefficient (so-called gauge factor) have also come into use. Bridge circuits are widely used in this circuit section, and settings of output signal values under no load, temperature compensation, etc. are performed. In order to change the measurement load range in the load cell, it is sufficient to change the rigidity of the mechanism. Such changes can be easily made by changing the cross-sectional area of the cantilever, the thickness of the diaphragm, and the like. However, in conventional load cells, it has not been possible to detect the direction of the force, that is, from which direction the force is being applied to the load cell.

On the other hand, with factory automation now in the spotlight, there are high hopes for the practical application of intelligent robots. Intelligent robots are characterized by the ability to take in information from the outside world and autonomously decide on operations. The external information includes visual sense, tactile sense, etc., and the latter is particularly important when grasping an object. It is said that there are various types of tactile sense, but
Force sensation is defined as the sensation of force exerted from a target object to a grasping unit, such as a robot hand. That is, not only the magnitude of the force but also the direction of the force are important factors. Conventionally, there is no simple sensor as a force direction detector, and the direction of force is determined by attaching strain gauges that detect force components in desired directions to multiple locations on the hand and calculating the output of the strain gauges. was. This conventional example has disadvantages in that the number of output lines of the plurality of strain gauges increases and the burden of calculation processing increases.

The present invention has been made in order to avoid such conventional drawbacks, and provides an element capable of detecting the direction of a force applied to the element from the outside using a single element.

According to the present invention, there is provided a thin-walled diaphragm, a support for fixing the periphery of the diaphragm, a cap provided on the support and covering the diaphragm, and a center of rotation of the cap and a tip that contacts the diaphragm. There is a pin, a part of which protrudes outside the cap, which receives an external force and transmits the direction of this force to the diaphragm, and a pin which is placed on both sides of this pin and which causes the pin to move in translation. A force direction detector is obtained, comprising means for converting asymmetrical strain or stress induced in the diaphragm into an electrical signal as a deviation from equilibrium when the diaphragm is rotated by a small angle that can be approximated.

Next, the present invention will be explained in detail using the drawings.

FIG. 1 is a diagram illustrating a conventional silicon diaphragm pressure transducer, and shows a structural cross-sectional view of the transducer. In the figure, reference numeral 1 denotes a silicon die, and a thin diaphragm 2 is formed in the center by a well-known method such as ultrasonic machining, electrical discharge machining, anisotropic etching, or the like. A plurality of diffusion layers 3 are buried in one main surface of the die by a well-known diffusion process so as to partially include the diaphragm region. The conductivity type of the diffusion layer is selected to be different from that of the die, and is configured to form a PN junction between 3 and 1 . In the diffusion layer 3,
A wiring 5 made of metal, polycrystalline silicon, etc. is electrically connected through a region where a portion of the insulating film 4 such as an oxide film covering the main surface is removed. The die 1 is fixed to the package 7 by an adhesive layer 6. The material of 7 may be the same as that of a typical integrated circuit package, or may be of a material having a coefficient of thermal expansion similar to that of the die. Further, the adhesive layer 6 may be an inorganic or organic adhesive such as low melting point glass,
Furthermore, a structure using anodic bonding via a glass layer may be used. As is well known, adhesive layers and packages should be selected with consideration to thermal strain and residual stress. Furthermore, a through hole is provided in a part of the package cage 7,
A first pressure introduction pipe 8 is fixed to 7.
A cap 9 is hermetically sealed around the package 7, and a portion thereof forms a second pressure introduction pipe 10. In addition, some parts of package 7 include
A plurality of hermetically sealed conductive terminals 11 are provided, and are connected to the metal wiring 5 described above with thin metal wires 12. In the configuration of FIG. 1, fluid pressure is applied via first and second pressure introduction pipes. For example, when it is desired to measure the pressure of a single fluid, the pressure is led to the second introduction pipe, and the first introduction pipe is open to atmospheric pressure. When the fluid pressure is higher than atmospheric pressure, the diaphragm 2 bends upward in the figure, while when it is low, it bends downward in the figure. Such deflection results in mechanical strain of the diaphragm, and stress corresponding to the strain is generated in the diaphragm portion. The piezoresistance effect is a phenomenon in which when stress is induced in a semiconductor material such as silicon, a resistance value change proportional to the stress occurs, and is well known to those skilled in the art. Since the value of the diffused resistor 3 changes due to the stress in the diaphragm portion described above, a voltage output signal can be obtained by connecting the resistor to either a quarter bridge, a half bridge, or a full bridge. If the deflection is a small amount, the relationships between pressure and strain, strain and stress, stress and resistance change, and resistance change and voltage output are all linear, so an output signal proportional to pressure can be obtained. . This operating principle achieves fluid pressure detection. However, as mentioned above, fluid pressure is a force per unit area, ie, in units of Kg/cm ² , and is applied as a distributed load to the first major surface of the diaphragm. On the other hand, the tactile sense of the robot hand is
Detection of force (i.e. in Kg) is required and the first
The pressure transducer shown in the figure is not applicable.

FIG. 2 is a diagram showing an embodiment of the present invention, and the same numbers as in FIG. 1 indicate the same components. In the figure, reference numeral 20 acts as a support for fixing the peripheral portion of the diaphragm 2, and the diaphragm is configured to deform while satisfying the support conditions of a so-called built-in edge.
21 is a pin whose lower end in the same drawing is in contact with a part of the diaphragm 2, and the upper end of this pin in the same drawing penetrates the cap 29 (the peripheral part is fixed to 7). It protrudes from the top so that a lateral force, for example the force shown at 28, can be applied from the outside. The portion where 21 passes through 29 has, for example, a ball joint structure 22, and 21 can be rotated about 22 by 28. Of course, but
A portion of the cap 29 corresponding to 22 is machined into the shape of a ball joint bearing. According to this structure, the point of contact of the pin 21 with the diaphragm 2 changes to the left in the figure, depending on the direction of application of the external force illustrated in 28.

The length of the pin 21 on the lower side of the pole joint 22 is the length of the pole joint 22 before the pin 21 touches it.
and diaphragm 2.
Then, the pin 21 comes into contact with a point A in the center of the diaphragm 2 shown in FIG. 3 and pushes the diaphragm 2 downward with a constant force. In this state, when a lateral force 28 is applied to the pin as shown in FIG. 2, the pin 21 rotates about the joint 22. When this rotation angle is small, that is, when the displacement is small, the pin 21 can be kept in contact with the diaphragm 2. The force along the axis of the pin 21 that pushes the diaphragm 2 can be decomposed into two components, a component perpendicular to the diaphragm 2 and a component parallel to it, but since the rotation angle is small, this parallel component is small. It is considered that the force by which the pin 21 vertically pushes the diaphragm 2 after rotation is approximately the same magnitude as before rotation. However, the position where the pin 21 contacts the diaphragm 2 changes due to this rotation. That is, in the sense that the force with which the pin 21 pushes the diaphragm 2 is the same, but the position is shifted laterally, an approximation of the translational motion as shown in FIG. 3 holds true. In Figure 3, 2
The stress distribution acting on the upper surface of 2 when 21 is in contact with the center of , that is, point A, and is pushing down 2 with a constant force is shown by the curve 40 in FIG. The horizontal axis of the figure is the position coordinate on the top surface of 2,
The vertical axis is the stress, with compressive force shown as the positive direction. Since point A is the center of 2, the stress curve 40 has symmetrical characteristics. On the other hand, 21 moves laterally in translation and comes into contact with point B in Fig. 3,
2 is pushed down with the constant force,
The stress distribution acting on the top surface of 2 is shown by the curve 41 in FIG. It is clear that, unlike 40, it has asymmetrical characteristics. As mentioned above, the piezoresistance effect in semiconductors is described by the product of the piezoresistance coefficient and stress, and the change in resistance value of the diffused resistor 3 provided at the end of the diaphragm in Fig. 2 is proportional to the stress shown in Fig. 4. value. That is,
21 is in contact with point A, 3 in Figure 2
The resistance value changes of will be equal. On the other hand, when 21 is in contact with point B, the resistance value change of 3 is different. This difference in resistance value change corresponds to the position of the contact point on 2 of 21, so if the resistance value change is detected, it is possible to know the position of the contact point on 2. . That is, the direction 28 in FIG. 2, in other words, the direction of the force applied from the outside can be determined, and a force direction detector has been realized. Although the shape of the lower contact portion 21 is not an important issue, it is preferable that the shape does not damage the surface of 2, for example, a spherical shape. Furthermore, a wide range of materials can be used for the material 21, such as metal, plastic, and Teflon.

FIG. 5 is a diagram showing another embodiment of the present invention, and shows a case where 21, 22, and 29 are integrally molded. Note that this figure only shows the main parts of FIG. 2, and it is clear that the other configurations can be the same as those of FIG. 2. In this embodiment, the rotational movement of 21 is achieved by the mechanical rigidity of a thin wall portion 50 provided in a portion of 29. In such a configuration, a portion of the externally applied force indicated by 28 will be spent on the deformation of 50, and the remaining portion will contribute to the rotational movement of 21. In other words, since the mechanical attenuator of the applied force is realized by 50, it is possible to set the amount of change in the contact point position on 2 of 21 small even when the applied force is large. . The attenuation factor in the attenuator can be changed by changing the shape of 50, that is, the thickness of 50, the lateral dimension, or the length of 21 that protrudes above 29, or the position at which 28 is applied. It is possible to achieve the desired attenuation rate.

FIG. 6 is a diagram showing another embodiment of the present invention.
In this figure, the same numbers as in FIG. 2 indicate the same components. In the figure, 60 is a diaphragm made of a metal thin film, etc., 61 is a support made of metal etc. that fixes the peripheral part of 60, and 62 is 6
A transducer that converts the strain and stress induced in the 60 into electrical signals and changes in resistance, such as a strain gauge made of a thin metal film or semiconductor. Fixed. 63 is a cap fixed to 60 or 61. The present embodiment is characterized in that the constituent material of the diaphragm 60 is other than a semiconductor, and the means for converting into an electric signal is arranged on the surface of the diaphragm 60, and the operation is the same as that described above, so a description thereof will be omitted. It should be noted that using the same construction method as in this embodiment, 62 may be a piezoelectric element, or 60
A piezoelectric material is used as a piezoelectric material, and a piezoelectric detection means 62 from the piezoelectric material, for example, a metal electrode, is easily deduced by those skilled in the art and is included in the present invention.

The present invention has been described in detail above. In the present invention, for convenience of explanation, all drawings are shown in cross-sectional views, and the direction of force is limited to one dimension only. However, detecting the two-dimensional direction of force is clear from the description of the invention. That is,
Since the diaphragm has a two-dimensional extent, it is possible to move the contact point of the pin 21 two-dimensionally on the diaphragm, and convert the strain or stress induced in the diaphragm into an electrical signal. By disposing a plurality of means on the diaphragm and processing a plurality of signals from the means, it is possible to determine the position of the contact point or the two-dimensional direction of the force applied from the outside. It is clear that this will become possible and the practicality will be even higher. Furthermore, the structures of the respective parts mentioned in the examples are merely exemplified, and various structures can be used without changing the spirit of the present invention.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a conventional silicon diaphragm type pressure transducer. FIG. 2 is a diagram for explaining an embodiment of the present invention, FIG. 3 is a diagram showing only the movable parts in FIG. 2, and FIG. 4 is a diagram showing the stress distribution on the diaphragm. FIG. 5 is a diagram for explaining another embodiment of the present invention, and only the main parts corresponding to FIG. 2 are shown. FIG. 6 is a diagram illustrating another embodiment of the present invention. In the figure, 1 ...Silicon die, 2, 60...Diaphragm, 3...Diffusion layer, 4...Insulating film, 5...Wiring, 6...Adhesive layer, 7...Package, 8, 10...Pressure introduction pipe, 9, 29, 63 ...cap, 11
Terminal, 12 Thin metal wire, 21 Pin, 22 Ball joint structure, 28 Force, 40, 41 Stress distribution, 50 Thin wall portion, 61 Support, 62 Transducer.

Claims (1)

[Claims] 1. A thin diaphragm, a support that fixes the periphery of the diaphragm, a cap that is provided on the support and covers the diaphragm, and a cap that has a center of rotation and whose tip is set in contact with the diaphragm. , a pin whose part protrudes outside the cap and which receives an external force and transmits the direction of this force to the diaphragm; A force direction detector comprising means for converting asymmetric strain or stress induced in the diaphragm when it rotates into an electrical signal as a deviation from equilibrium.