JPH0629808B2 - Pressure sensor - Google Patents

Description

The present invention relates to a pressure sensor, and more particularly to a pressure sensor mounted on a robot hand or the like and capable of detecting a pressure received from a grasped object.

[Conventional technology]

In recent years, the technical progress of industrial robots has been remarkably advanced, and the point of particular interest is that by attaching a pressure sensor to a robot hand, it becomes possible to obtain sensory information such as tactile sensation and pressure sensation. It is that. Therefore, the necessary conditions for a sensor to detect such pressure sensation are as follows: high sensitivity, high resolution, wide dynamic range, heat resistance, linearity, responsiveness, flexibility, slippery feeling, etc. It can be mentioned that it can be obtained at low cost and has high reliability.

Of the many types of pressure sensors of this type that have been proposed or developed, several typical types are shown in FIGS. 5A to 5A.
This is shown by the C diagram. FIG. 5A shows a push-button type sensor, in which 1 is its button, 2 and 3 are positive and negative electrodes, 4 is a coil spring, and its right side is in a non-contact state with a gripping object not shown, its left side. Shows the state where the button 1 is pressed by the grasped object.

That is, when an object is grasped by the hand, the button 1
When is pressed, the electrical connection between the positive electrode 2 and the negative electrode 3 is cut off, and the gripped state is detected.

FIG. 5B shows a sensor using a conductive rubber,
Here, 5 is the conductive rubber layer. Therefore, as shown in the right side of FIG. 5B, when a force is applied by the gripping object from the layer side of the plus pole 2, the conductivity at the position of the conductive rubber layer 5, in other words, the electrical resistance changes, and the gripping state is detected. To be done.

FIG. 5C shows an example of a pressure sensor configured in combination with optical detection means. In this example, a silicon rubber plate 7 and a light-receiving element array 8 are provided above and below the acrylic plate 6, and a light source 9 having the acrylic plate 6 as an optical path is arranged laterally. Further, the silicon rubber plate 7 is provided with a conical projection 7A on its lower surface side, and the tip end of the projection 7A is kept in light contact with the upper surface of the acrylic plate 6.

When the gripping object presses the silicon rubber plate 7, the protrusion 7A is compressed and deformed as shown in the figure. Now, in the state before pressurization, the light from the light source 9 is uniformly reflected in the acrylic plate 6, and the reflected light is received by each of the light receiving elements 8A forming the light receiving element row 8. When the pressing force is applied, the projection 7A is diffusely reflected at the deformed portion, and the light receiving sensitivity of the light receiving element 8A arranged at that portion changes, so that the magnitude and distribution of the force can be detected. .

However, of the pressure sensors as described above, the fifth
In the system shown in FIG. A, only the presence or absence of the pressing force is detected from the two states of "ON" and "OFF" by the button 1, and the strength of the force cannot be continuously detected. Further, in the system shown in FIG. 5B, there is a problem of non-linearity or hysteresis in the relationship between the force and the conductivity of the rubber layer 5,
It is difficult to accurately detect the magnitude of force and its distribution.
Furthermore, the system shown in FIG. 5C also has problems of non-linearity and hysteresis, and in this case, the structure is complicated and flexibility is poor. Further, although there are many pressure sensors proposed or disclosed by those not illustrated here, there are not many highly reliable pressure sensors that are particularly flexible and satisfy the various conditions described above. That is not a paraphrase.

[Problems to be solved by the invention]

The object of the present invention is to pay attention to the above-mentioned conventional problems, and in order to solve the problems, the relationship between pressure and output has linearity, there is no hysteresis, and the structure is simple and flexible. The purpose of the present invention is to provide an inexpensive and highly reliable pressure sensor.

[Means for solving problems]

In order to achieve such an object, according to the present invention, silicon chips divided by grooves are arranged in a matrix, and a concave portion is provided at the center of each pressure receiving surface of each silicon chip, and a pressure receiving button is fitted into this concave portion. , A bridge circuit with a plurality of semiconductor strain gauges is provided on the back surface of the silicon chip corresponding to the recess, switch means and connection electrodes connected to the bridge circuit are provided on the back side, and a plurality of strain gauges are provided with flexible elasticity. It is characterized in that it is supported by a substrate made of a material, and each of the silicon chips is electrically connected.

[Work]

In the pressure sensor of the present invention, the strain gauge incorporated in the bridge circuit, the switch means connected to the strain gauge, and the connecting electrode are provided on the back surface side of the silicon chip divided by the groove, and the range where the strain gauge is provided. Is supported by a flexible elastic substrate, high-sensitivity output can be obtained, and since it is divided by the above groove, flexibility can be maintained as a whole, and the size and thickness are small. Can be converted.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

FIG. 1A shows an embodiment of the present invention. Here, 11 is a semiconductor silicon chip, and a plurality of strain gauges 12 and electrodes 13 are formed on the lower surface side of the silicon chip 11. Reference numeral 14 is a molded substrate formed of epoxy resin or the like, and 15 is an elastic substrate which is provided in a range of the molded substrate 14 in contact with the strain gauge 12 and is formed of an elastic body such as silicon rubber. Further, the electrode 13 provided on the lower surface side of the silicon chip 11 is
Bonding wire 1 such as gold or aluminum for electrically connecting the adjacent sensor units 10
Bonded by 7.

Reference numeral 18 is a cut groove that defines the space between the sensor units 10. By providing the cut groove 18, the flexibility of the entire sensor is maintained.
In order to provide 8, the bonding wire 17 is bent so as not to be cut. Reference numeral 19 denotes a pressure receiving button, which is slidably held in a recess 11A provided on the upper surface of the silicon chip 11.

On the other hand, a Wheatstone bridge circuit as shown in FIG. 2A is formed between the plurality of strain gauges 12 described above. In FIG. 2A, the four strain gauges 12 are R ₁ , R 2.
It is shown as the resistance of ₂ , R ₃ and R ₄ . Further, here, S _V , S _A2 , S _A1 and S _G are analog switches by field effect transistor FET, and arrangement of these switches prevents signals from sneaking into the adjacent sensor unit 10 and prevents the individual units from being spilled. The independence of the signals at 10 is maintained. Note that S _X and S _{Y are} row and column command selection means, and by designating a predetermined row and column via these command selection means S _X and S _Y as described later, the bridge circuit can be changed. Output E can be obtained.

2B and 2C, the strain gauge 12 described above has a resistance R.
₁ , R ₂ , R ₃ , and R ₄ show the state of being disposed on the lower surface of the silicon chip 11 and the pressure receiving state thereof, and such pressure receiving causes the silicon chip 11 to bend and, as a result, the gauges R ₁ and R 4. ₃ is tensile stress, gauge R ₂
A compressive stress is generated in R ₄ and R ₄ , and a highly sensitive output E as shown in FIG. 2D can be obtained.

Therefore, the command S _{X is} issued to the strain gauge 12 indicated by R _{1 to} R ₄ and the analog switches S _V , S _A2 , S _A1 , and S _G.
And electrode 13 to supply S _Y Between the strain gauge 12 and the analog switch described above.
The output E can be obtained from each sensor unit 10 by providing the wiring as shown in FIG.

FIG. 3 shows, as an example, an overall wiring diagram between the sensor units 10 in which the circuit shown in FIG. 1B is arranged in a matrix of 3 × 3, and the row command selecting means S _X1.
Selects one of the to S _X3, by further selecting one of a command selection unit S _Y1 to S _Y3 column, 3 ×
An output can be optionally obtained from any one of the three sensor units 10 through the bridge circuit of any one of the sensor units 10, and the column command is selected at the time of one selection while sequentially selecting the command selection means of the rows. By sequentially selecting the command selecting means of, the sensor units 1 of one row and three columns
Outputs E ₁ , E ₂ , and E ₃ can be obtained one by one from 0 in that order.

Next, a procedure for manufacturing the pressure sensor of the present invention will be described with reference to FIGS. 4A to 4E.

First, as shown in FIG. 4A, a resist layer 111 is formed on one surface of a silicon wafer 110, and a strain gauge 12 and an electrode 13 are formed on the other surface by a thin film technique.
The portion indicated by the dotted line is removed by etching to form the recess 11A as shown in FIG. 4B. Next, the silicon wafer 110 thus obtained is turned upside down, and an elastic layer such as a thin silicon rubber film is provided on the strain gauge 12 and its bridge circuit.
5 is formed.

Furthermore, the bonding wire 17 is provided between the adjacent electrodes 13.
After the connection, the silicon wafer 110 is surrounded by an elastic frame 112 made of a relatively soft material as shown in FIG. 4C, and an elastic material such as a soft epoxy resin is molded on the upper surface to form the mold substrate 14. To do. Then, up and down again, the state shown in FIG. 4D is obtained.

Next, the cut groove 18 is engraved in the portion indicated by the dotted line. When forming the groove 18, it is only necessary to cut the bonding wire 17 previously arranged with a grindstone or the like so as not to cut it. By doing so, flexibility is given to the entire sensor and bending is possible, for example, a robot hand. It is also possible to wrap it around the finger part of. FIG. 4E shows the state shown in FIG. 4D in which the pressure receiving button 19 is fitted and the upper part thereof is covered with the film 1.
A state in which the pressure sensor is covered with 13 is shown, and thus a pressure sensor in a practical state can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the silicon chips divided by the groove are arranged in a matrix, and the concave portion is provided in the central portion of the pressure receiving surface of each silicon chip to fit the pressure receiving button. A plurality of semiconductor strain gauges incorporated in a bridge circuit are provided on the back surface side of the silicon chip corresponding to the recesses, and switch means and connection electrodes connected to the bridge circuit are provided on the back surface side and the plurality of strain gauges are provided. Since the gauge is supported by the flexible elastic material substrate and the individual silicon chips are electrically connected, it is possible to provide an ideal pressure sensor that is thin, flexible, and highly practical. It becomes possible, and if it is applied to a robot hand, high-level manipulation work is possible and it can contribute to the intelligence of the robot.

[Brief description of drawings]

FIG. 1A is a sectional view showing an example of the configuration of the pressure sensor of the present invention, FIG. 1B is a wiring diagram of the silicon chip, and FIG. 2A is between a bridge circuit incorporating a strain gauge applied to the present invention and a switch means. FIG. 2B is a schematic view showing an example of the arrangement of the strain gauge, FIG. 2C is a sectional view schematically showing one silicon chip, and FIG. 2D is generated in the strain gauge. Fig. 3 is a characteristic curve diagram showing an example of stress, Fig. 3 is a circuit diagram for driving the pressure sensor, and Figs. 4A to 4E show a process of manufacturing the pressure sensor of the present invention in order of its cross section. FIGS. 5A to 5C are cross-sectional views schematically showing three forms of a conventional pressure sensor. 11 ...... silicon chips, 11A ...... recesses, _12, R 1 to R ₄ ...... strain gauges, 13 ...... electrodes, 14 ...... mold board, 15 ...... elastic substrate, 17 ...... bonding wire, 18 ...... switching Komimizo, 19 ...... pressure _{button, S V, S Al, S} A2, S G ...... switch (means), 110 ...... silicon wafer, 111 ...... resist layer, 112 ...... elastic frame, 113 ...... film.

Claims (1)

[Claims] 1. A silicon chip divided by a groove is arranged in a matrix form, a recess is provided in the center of each pressure receiving surface of the silicon chip, and a pressure receiving button is fitted into the recess to correspond to the recess. A bridge circuit formed of a plurality of semiconductor strain gauges is arranged on the back surface of the silicon chip, switch means and connection electrodes connected to the bridge circuit are provided on the back surface side, and the plurality of strain gauges are made of a flexible elastic material. A pressure sensor, which is supported by the substrate and is electrically connected to each of the silicon chips.