JPH0660855B2 - Pressure sensor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor, and more particularly to a pressure sensor mounted on a hand of a robot or the like and suitable for detecting a force received from a grasped object.

[Prior Art] Many conventional robots, such as manipulators, sequence-type robots, and playback-type robots, work in a fixed place. Therefore, their working range and functions are limited. The welding robot for use is installed at a specific place on the production line and welds the vehicle body by moving the welding arm, and the robot itself does not perform the welding on its own judgment.

However, in recent years, so-called intelligent robots having sensory and cognitive functions equivalent to the five senses of humans have been developed and gradually put into practical use.

By the way, these intelligent robots need to be equipped with sensors for detecting various sensations. Typical sensors are a visual sensor and a pressure sensor (tactile sensor), and in particular, the pressure sensor can be said to be indispensable for work such as grasping and grasping an object.

The functions required for such a pressure sensor for an intelligent robot include the following items.

(1) High sensitivity: Sensitivity to detect force is high, for example, one element can detect a load of several grams.

(2) Wide dynamic range: The operating range is as wide as possible.

(3) High reliability and durability: To withstand harsh environments.

(4) Linearity and little hysteresis: Pressure and output are proportional and there is little hysteresis.

(5) Response speed: High response speed of signal processing.

(6) Flexibility: Flexibility is maintained like the skin of human hands,
Be able to grasp the grasped object softly.

(7) Slip feeling: Not only the pressure but also the slip can be detected if possible.

(8) Small size and low cost: Thin and small size with low manufacturing cost and material cost.

A pressure sensor that satisfies some of these requirements has been proposed or put into practical use so far, for example, one that uses on / off of a microswitch or one that uses a pressure-sensitive rubber sheet (conductive rubber sheet). Alternatively, there is one that utilizes a change in the amount of light reflection.

[Problems to be Solved by the Invention] However, the one utilizing the on / off of the microswitch is such that the sensor, which is normally in the “off” state, turns into the “on” state when a force is applied, This only detects the presence or absence of force, and is not suitable for continuously detecting the magnitude of the force.

In addition, the one using a pressure-sensitive rubber sheet is one in which one conductive rubber sheet is sandwiched between two electrodes and the sheet resistance is changed by applying a force to the electrodes. There is a problem that linearity cannot be obtained between the force and the sensor signal output, hysteresis is likely to occur, and the heat resistance is low because a rubber sheet is used.

Furthermore, in the case of utilizing the change in the reflection amount of light, a transparent acrylic plate is coated with a rubber sheet having a large number of conical projections, and a mirror body or a light receiving element is arranged on the back surface of the acrylic plate. Then, when the acrylic plate is irradiated with light from the lateral direction of the acrylic plate, the protrusion of the rubber sheet changes according to the magnitude of the external force.Therefore, the degree of dent should be detected by a mirror or a light receiving element. is there. However, it is difficult for the pressure sensor that uses the reflection of light to know the absolute value of the external force accurately, and there is a problem that the detection accuracy is poor.

In addition to the pressure sensor as described above, pressure sensors of various forms have been proposed or prototyped, but none of them have sufficiently satisfied the above-mentioned functions, and therefore have high sensitivity and are truly practical. The development of a high pressure sensor is strongly desired.

The present invention has been made in view of the above problems, and an object thereof is to provide a pressure sensor that has high practical performance, has a simple structure, is easy to manufacture, and can be thinly and densely arranged.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a support platform in which window form parts are formed in a matrix, a bridge circuit incorporating a semiconductor strain gauge, and the bridge. With the surface on which the switch means and the terminals for the circuit are arranged facing down,
A plurality of rectangular silicon cells, both ends of which are supported by the supporting portion of the window frame, and a common arrangement on the upper surfaces of the plurality of rectangular silicon cells, which are electrically connected to predetermined terminals of the terminals. And a conductive rubber sheet that has been formed.

[Operation] According to the present invention, both ends of the rectangular silicon cell are supported by the respective supporting portions of the supporting table having the frame portion in a matrix shape, and the Wheatstone bridge in which the semiconductor strain gauge is incorporated and the switch means. , The flexible printed wiring board is bonded to the lower surface side of the silicon cell on which the ground terminal is formed together with the solder bump via the electrode, and the ground terminal provided on the lower surface side of the silicon cell is connected via the conductive silicon cell itself. Since it is electrically connected to the conductive rubber sheet laid on the upper surface side so that grounding can be obtained, it is not necessary to provide a ground terminal for each silicon cell and draw a ground wire from each ground terminal. It is possible to simplify the signal lines in the printed circuit board that are arranged across the silicon cells, contributing to cost reduction. It is possible to provide a thin and highly practical pressure sensor that can be arranged in high density.

Embodiments Embodiments of the present invention will be described in detail and specifically below with reference to the drawings.

First, referring to FIGS. 6A and 6B, the principle of bending of the silicon cell according to the present invention, which is a support beam for both ends, will be described. Now, as shown in FIG. 6A, both ends of the silicon cell 1 having the solder bumps 3 are shown in FIG. 6A. Assuming that a force is applied to the central portion of the upper surface of the silicon base 1 while being supported by the support base 2, as shown in FIG. 6B, the silicon cell 1 bends to generate tensile stress on the lower surface side.

Therefore, as shown in FIG. 7A, four strain gauges R ₁ , R ₂ , R ₃ and R ₄ are arranged on the lower surface side of the silicon cell 1 as described above, and these strain gauges R _{1 to} R ₄ are further arranged. Is incorporated in a bridge circuit as shown in FIG. 7C, a voltage V is applied between opposite vertices, one end thereof is grounded (G), and the output lines drawn from between the other opposite vertices are connected to each other. By disposing the switching elements S1 and S2, it is possible to take out the resistance change generated in the strain gauges R _{1 to} R _{4 due} to the above-mentioned deflection as an output signal from the terminals T and t by turning on the switching elements S1 and S2. it can. In addition,
E is a voltmeter.

In FIG. 7A, the silicon cell 1 is thus formed of the semiconductor silicon material, and the strain gauges R _{1 to} R ₄ and the switching elements S1 and S2 are connected to the output line from the bridge circuit.
Furthermore, output terminals T and t, a switch signal terminal S, a ground terminal G, and a voltage terminal V are provided. These T, t, S and V are formed by solder bumps 3 as shown in FIG. 7B.

The reason why semiconductor silicon is used for the beam member as shown in FIGS. 6A and 6B is that the strain gauges R _{1 to} R ₄ are formed by the wafer process in the case of semiconductor silicon.
And switching elements S1, S2, wiring, T, t,
This is because the solder bumps 3 formed on each of the S and V terminals can be formed by a consistent process of film forming technology. Furthermore, by forming such a silicon cell, the beam member can be made smaller and thinner.
The switching elements S1 and S2 formed here are, for example, field effect transistors.

FIG. 1 is a diagram showing a basic configuration of the present invention, in which:
Reference numeral 4 denotes a support base, and the support base 4 is a window-shaped frame portion 5 and a support portion 6 for supporting both ends of the silicon cell 1 fitted in the frame portion 5.
And an insulating member. Further, here, in the silicon cell 1, as shown in FIG. 2, an insulating layer 7 by what is called a PN junction is formed on the surface of the conductive portion 1A (P layer) which is the base thereof.
(N layer) is formed in advance, and the strain gauge 8 is formed as a P layer on the insulating layer 7, a wiring pattern 9 made of aluminum or the like is further formed, and the grounding terminal 10 is made conductive by a semiconductor process. The part 1A is left as it is, and is formed thereon.

Therefore, the silicon cell 1 thus constructed is supported on the support portion 6 as shown in FIG. 1 with the surface on which the strain gauges 8 and the like are formed facing downward, and the conductive rubber sheet 11 is attached to the silicon cell. The upper surface (corresponding to the lower surface side in FIG. 2) of 1 is closely adhered by, for example, a conductive adhesive 21, and a film 12 made of, for example, an insulating rubber sheet for soft protection is further provided thereon.
Is provided to electrically and thermally protect the conductive rubber sheet 11.
That is, with this configuration, the grounding terminal 10 shown in FIG. 2 is electrically connected to the conductive rubber sheet 11 via the conductive portion 1A of the silicon cell 1, and therefore the silicon cell 1 It is not necessary to provide a through hole in itself, and the conductive rubber sheet 11 carries the role of grounding wiring.

Reference numeral 13 denotes a flexible printed wiring board disposed on the lower surface side of the silicon cell 1. The flexible printed wiring board 13 has printed wiring on both surfaces thereof, which will be described later, and is provided on the lower surface side of the silicon cell 1. The solder bumps 3 of each terminal are connected to electrodes (not shown) on the flexible printed wiring board 13 by soldering.

Although the configuration of the pressure sensor as a single unit has been described above, such a pressure sensor is generally used as an array in which a plurality of the above single units are arranged in a matrix. Therefore, the configuration of the pressure sensor in an array will be described below.

FIG. 3A to FIG. 3C are diagrams showing the case where three pressure sensors are arranged in three rows, three pressure sensors each. In FIG. 3A, the support base 4 is formed of a rigid body having electrical insulation, and has a groove 14 formed in the column direction on the lower surface side thereof as shown in FIG. 3B, for example. Further, FIG. 3C shows that the flexible printed wiring board 13 is arranged in the column direction in the groove 14 on the lower surface side of the support, after the silicon cell 1 is fitted into the support portion 6 of each frame of the support 4.
Is attached, and 15 is a conductor circuit formed on both sides of the flexible printed wiring board 13.

Next, the signal line to be drawn out from one silicon cell 1 will be examined with reference to FIGS. 4A to 4C, and Wheatstone configured on one silicon cell 1 as shown in FIG. 4A will be described. For the bridge circuit, terminals V, S, T, t
And G are provided, the electrodes corresponding to the terminals are provided on the flexible printed wiring board 13 corresponding to the silicon cell 1 as shown in FIGS. 4B and 4C.
V _E , S _E , T _E , t _E and the lead wiring LV from each of the electrodes,
LS, LT, LT must be provided. However, here, the ground terminal G does not require an electrode and wiring as described above, and one wiring is saved.

However, when the silicon cells 1 are arranged in a matrix form instead of one, the number of wirings increases in the column direction, so that the flexible printed wiring board 13 as shown in FIGS. It becomes impossible to use only one side. Therefore, the case where five silicon cells 1 are arranged in the column direction will now be described with reference to FIGS. 5A and 5B.

FIG. 5A and FIG. 5B show the installation state of the electrodes and the lead wiring on the flexible printed wiring board 13 in this case, where 1-1 to 1-5 are connected to this flexible printed wiring board 13. The position of five silicon cells 1 in the column direction to be performed is shown. That is, as described above, the electrodes V _E , S _E , T _E, and t _E are provided at the positions opposite to the terminals provided individually for the five silicon cells 1-1 to 1-5, but the switch signal Since the electrode S _E for use in must be turned on / off for each individual unit, a through hole 20 is provided in the electrode S _E corresponding to the silicon cells 1-1 to 1-4.
Wirings LS1 to LS4 for driving the switches are arranged on the back surface side through the through holes 20. LV, Lt, and LT are lead wires for V _E , t _E, and T _E provided on the upper surface side, respectively.

Signal processing in the pressure sensor configured in a matrix like this will be described. First, by transmitting a signal to the switch signal terminal S provided in one silicon cell, two signals from the silicon cell 1 are transmitted to the terminals T and t. However, if signals are simultaneously obtained from the five silicon cells 1-1 to 1-5 as shown in FIGS. 5A and 5B, signal processing is difficult. Therefore, first, when a signal is taken out from the silicon cell 1-1, the switching element is turned on via the signal line LS1, but in this case, no signal is sent to the other signal lines LS2 to LS5. Thus, the switching elements in each silicon cell may be sequentially turned "on" via the signal lines.

In the example of FIGS. 5A and 5B, the silicon cell 1 is used.
Although an example in which five pieces are arranged is described above, this is because up to five pieces of signal processing can be performed by wiring four rows on the flexible printed wiring board 13 for double-sided use.
Therefore, it is much easier to use four or three silicon cells 1 arranged in the column direction. Thus, the array of pressure sensors can be obtained by fitting the silicon cells 1 into the frames formed on the support base 4 in the row and column directions.

[Effects of the Invention] As described above, according to the present invention, the lower surface of a rectangular silicon cell in which a bridge circuit incorporating a semiconductor strain gauge, its switch means and various terminals is arranged is formed in a matrix. Since both ends are supported by the frame support part of the support base that includes the frame part and the deflection of the silicon cell is detected, the detection sensitivity can be kept high, and the flexible print on the lower surface side of the silicon cell. Joining the wiring boards, supplying electric signals to the switch means and taking out signals from the strain gauge, and connecting the conductive rubber sheet to the upper surface of the silicon cell over the entire surface of the supporting base, Since the conductive rubber sheet is electrically connected to the ground terminal provided on the lower surface side through the conductive silicon cell itself, the ground wire should be Since it is not necessary to dispose on the flexible printed wiring board, the wiring on the flexible printed wiring board can be easily performed by itself, and it is possible to provide a pressure sensor that is thin as a whole and has excellent detection accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view showing the basic structure of a pressure sensor of the present invention, FIG. 2 is a partial sectional view of a silicon cell thereof, and FIGS. 3A, 3B and 3C are examples of a support base according to the present invention. FIG. 4 is a perspective view showing a partially enlarged view and a perspective view of a state in which a silicon cell is mounted on the support, FIG. 4A is a wiring diagram on the silicon cell, and FIGS. 4B and 4C are flexible printed wiring boards according to the present invention. A plan view and a side view showing an example of the above basic wiring state, and FIGS. 5A and 5B show a plan view and an example of wiring on a flexible printed wiring board according to the present invention respectively for each silicon cell unit. Sectional views, FIGS. 6A and 6B are schematic views showing the supported state and the loaded state of the silicon cell, respectively, and FIGS. 7A and 7B are the diagrams showing the circuit arranged on the silicon cell. FIG. 7C is a configuration diagram of a bridge circuit on the silicon cell, and FIG. 1,1-1～1-5 ... silicon cell, 1A ... conductive portion, 3 ... solder bumps, S1, S2 ... switching element, R ₁ to R _4, 8 ... strain gauge, 4 ... support stand, 5 ... frame portion , 6 ... Supporting part, 7 ... Insulating layer, 9 ... Wiring pattern, 10 ... Grounding terminal, 11 ... Conductive rubber sheet, 12 ... Film, 13 ... Flexible printed wiring board, 14 ... Groove, 15 ... Conductor circuit, V, S, T, t, G ... _{terminal, V E, S E, T} E, t E ... electrode, LV, LS, LS1~LS4, LT , Lt ... wire, 20 ... through hole.

Claims (4)

[Claims] 1. A support base in which window form parts are formed in a matrix shape, a bridge circuit incorporating a semiconductor strain gauge, and a surface on which switch means and terminals for the bridge circuit are arranged is set to a lower side. A plurality of rectangular silicon cells whose both ends are supported by the supporting portions of the window frame, and a plurality of rectangular silicon cells, which are commonly disposed on the upper surfaces of the plurality of rectangular silicon cells and which have predetermined terminals among the terminals. A pressure sensor comprising a conductive rubber sheet electrically connected. 2. The pressure sensor according to claim 1, wherein the conductive rubber sheet covers the plurality of rectangular silicon cells over the entire surface of the support base. 3. The pressure sensor according to claim 1 or 2, wherein the predetermined terminal is a ground terminal, and the conductive rubber sheet is used for grounding wiring. . 4. The pressure sensor according to any one of claims 1 to 3, wherein a flexible printed wiring board is arranged on a lower surface side of the rectangular silicon cell, and the flexible printed wiring board is provided. The electrode according to claim 1 is electrically connected to a terminal other than the predetermined terminal.