JPH0629809B2 - Pressure sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pressure sensor, and more specifically, to a distributed pressure sensor attached to a robot hand or the like and capable of detecting a vertical load distribution applied to the sensor. Regarding

[Conventional technology]

The conventional pressure sensor of this type is arranged in a robot hand or the like, and has been developed in various fields for the purpose of obtaining information on the strength of gripping force, surface pressure distribution, etc. by detecting the pressure sensation. FIG. 9 shows an example of such a pressure sensor. Here, in the pressure sensor 1, the individual pressure detection elements 2 are arranged in a matrix through grooves 3 provided in a grid pattern. An elastic body 4 is mounted on the substrate 5, and has an appropriate Young's modulus so as to obtain flexibility. Further, a single crystal silicon plate 6 is further adhered to each surface of the elastic body 4 which is separated by the cross groove 3 and a strain gauge is provided on the upper surface of the single crystal silicon plate 6 as shown in FIG. 7A and 7B are formed.

Further, a load carrying portion 8 is attached to the central portion of the upper surface of the single crystal sillcon plate 6 by adhesion or eutectic bonding (for example, Sn / 10Au), and the semiconductor strain gauges 7A and 7B described above are not connected to each other. Wiring and signal extraction solder pads 9A and 9B are formed, and these pads 9A and 9B and the flexible printed board 1 are formed.
Solder pads 11A and 11B formed on the 0 side are welded to each other. The flexible printed board 1
The window 10 in which the load carrying portion 8 of 0 is projected is cut out.
It is A.

In the pressure sensor 1 configured as described above, when a vertical load is applied to the load carrying portion 8, the single crystal silicon plate 6 is deformed together with the elastic body 4, and the deformation provides the upper surface 6A of the single crystal silicon plate 6. Since the electric resistance value in the strain gauges 7A and 7B changes, it is possible to detect the magnitude of the vertical load applied to each detection element 2 by extracting the changed value as a voltage change by the Wheatstone bridge circuit. You can

Therefore, it is possible to know the distribution of the vertical load applied to the entire pressure sensor 1 by appropriately performing scanning on these detection elements 2 arranged in a matrix. The pressure sensor 1 configured as described above has the following problems.

That is, in the pressure sensor 1, since the area of the pressure receiving surface 8A of the load carrying portion 8 is small, there is no problem when the contact surface of the pressure side object is relatively smooth, but contact occurs as shown in FIG. 11, for example. If a sharp protrusion 11A is present on the contact surface 11 of the object, the protrusion 11A may be pressed against a portion other than the load carrying portion 8 and a concentrated load may be applied, so that the load is not accurately detected. In addition, the pressure sensing element 2 may be damaged, such as the flexible printed board 10 being damaged.
In other words, there was a lack of reliability in terms of detection accuracy and durability.

In particular, in order to study the stress distribution generated in the single crystal silicon plate 6 for the configuration in which the load carrying portion 8 is arranged on the single crystal silicon plate 6 as described above, the single crystal silicon plate 6 in this case and the single crystal silicon plate 6 are held. The relationship with the elastic body 4 can be expressed in a modeled form as shown in FIG. That is, 6M is a silicon plate considered as a beam,
Assuming that the silicon plate 6M as a beam of such a finite length is laid horizontally on the floor 4M of an elastic body having an infinite spread, if a concentrated load P is applied to the central portion thereof, the silicon plate 6M Negative strain ε, that is, compressive stress as shown in FIG. 13 is generated on the upper surface 6MA, and tensile stress corresponding thereto is generated on the lower surface 6MB side.

However, the single-crystal silicon plate is originally a brittle material, and in particular, the lower surface, that is, the surface in contact with the elastic body is rougher than the upper surface subjected to the semiconductor process, and numerous scratches such as minute cracks due to machining etc. However, the strength is inferior to that of the upper surface. Therefore, the tensile stress as described above easily causes damage from the lower surface side.

Furthermore, a pressure sensor that uses a strain gauge and incorporates these into a bridge circuit to obtain an output usually requires a combination of a strain gauge that exhibits a positive resistance value change and a strain gauge that exhibits a negative resistance value change. However, as described above, in the pressure sensor 1 of the form shown in FIG. 9, since only the compressive stress, and thus the negative strain, is distributed on the upper surface 6A side thereof,
As shown in FIG. 10, one set of the strain gauges 7A and 7B is arranged so that the direction is changed like 7B, and the lateral strain in which the positive and negative are reversed from the main strain is detected by the principle of Poisson's ratio. There is. However, the Poisson's ratio of metal is about
It is 0.3, which means that the amount of lateral strain is only about 1/3 of the amount of main strain, and the bridge output is inevitably small, so in the conventional pressure sensor 1 like this. There is a drawback that a very high detection sensitivity cannot be obtained.

[Problems to be solved by the invention]

The object of the present invention is to detect the stress distribution with high accuracy without being affected by the unevenness of the object surface that keeps contact with the sensor, in order to solve the above-mentioned conventional problems. An object of the present invention is to provide a distributed pressure sensor having excellent durability and reliability.

[Means for solving problems]

In order to achieve such an object, the present invention has a single crystal silicon plate arranged in a matrix on an elastic body, and the single crystal silicon plate is formed by a vertical load applied to each of the single crystal silicon plates. In a pressure sensor that changes the electric resistance value of a plurality of semiconductor strain gauges provided and detects the vertical load by the change of the electric resistance value to detect the load distribution, it has a flat surface capable of carrying the vertical load. The two legs of the U-shaped vertical carrying member are respectively adhered and fixed to the ends of the single crystal silicon plate along the groove, and the individual vertical loads are distributed to the ends of the single crystal silicon plate by the vertical carrying member. It is characterized in that it is carried.

[Work]

According to the pressure sensor of the present invention, the load applied to the flat portion of the U-shaped vertical load carrying member is shared by both ends of the single crystal silicon plate through the legs thereof, and the upper surface of the silicon plate is thus supported. The detection output obtained via the bridge circuit can be made highly sensitive by the change of the resistance value obtained from the strain gauge arranged in the above, and at the same time, the load receiving area by the flat portion of the vertical load carrying member can be reduced. It can be widely held, and it is possible to eliminate the risk of detection failure and damage to the sensor.

〔Example〕

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

FIG. 1 shows an embodiment of the present invention. Here again, the single crystal silicon plate 6 is mounted on the elastic body 4 having an appropriate Young's modulus such as plastic or rubber, but in this example, the flexible printed board 20 only has the window 20A as shown in FIG. Covers the front surface of the pressure sensor 21. Thus, although not shown here, a strain cage is provided on the single crystal silicon plate in a manner substantially similar to that shown in FIG. 10, solder pads 9A and 9B are provided, and solder provided on the lower surface side of the flexible printed board 20 is provided. A connection is made between pads 11A and 11B.

Reference numeral 28 denotes a load carrying member provided with the flexible printed board 20 mounted thereon as shown in FIG. 2 and straddling between the windows 20A thereof. The load carrying member 28 is formed of, for example, alloy steel in a U-shape. Both legs 28A are fixed to the edge of the single crystal silicon plate 6 with an adhesive 29 such as epoxy.

Next, in the pressure sensor 21 configured as described above, the strain generated on the single crystal silicon plate 6 will be described with reference to FIG. Here again, the single crystal silicon plate 6 is shown as a beam 6M having a finite length. That is, in the case of this example, the shared load P / 2 is applied to both ends of the beam 6M placed on the elastic floor 4M. In this example, however, the thick adhesive 29 is present in the load carrying portion, but since the adhesive area is relatively small, both ends can be regarded as free supporting beams, and the strain generated on the upper surface of the supporting beam can be considered. The distribution of quantity is as shown in Fig. 4.

That is, as is apparent from FIG. 4, tensile stress is generated not on the lower surface 6MB side of the silicon plate 6M but on the upper surface 6MA side thereof. Therefore, in the case of the pressure sensor 21 as shown in FIG. 1, the upper surface 6A of the single crystal silicon plate 6 is smooth as described above, and it is less likely to be damaged by tensile stress and high strength can be maintained. Therefore, it is possible to reduce the thickness of the single crystal silicon plate 6 by that amount, and even if the strain gauge is arranged as shown in FIG.
Larger strain can be generated on the upper surface 6A of the single crystal silicon plate, and the detection sensitivity can be increased.

FIG. 5 shows another embodiment of the present invention. In this example, when the load carrying member 28 is bonded to the upper surface 6A of the single crystal silicon plate 6, the bonding layer 29A is formed sufficiently thinly.
The formation of such an adhesive layer 29A can be achieved by eutectic bonding with, for example, Sn / 10Au. Note that FIG. 6 shows one of the detection elements 30 taken out and viewed from the upper surface, where 7A is a strain gauge.

This embodiment can be regarded as a beam supported in a state where both ends are fixed, and when modeled as shown in FIG. 7,
The shared load P / is applied to both ends of the silicon plate 6M regarded as such a beam.
It may be considered that 2 is added to each, and at this time, distortion as shown in FIG. 8 occurs on the upper surface 6MA of the silicon plate 6M. That is, since positive and negative strains ε are generated in this way, by arranging the strain gauge 7A as shown in FIG. 6, for example, it is possible to obtain positive and negative corresponding resistance value changes in the strain gauge 7A. Becomes
A large output can be obtained from the bridge circuit, and higher detection sensitivity can be maintained as compared with the conventional one.

〔The invention's effect〕

As described above, according to the present invention, the elastic body has the single crystal silicon plates arranged in a matrix through the grooves, and the vertical load applied on each single crystal silicon plate causes In the pressure sensor that can detect the load distribution by changing the electric resistance value of multiple semiconductor strain gauges arranged on the single crystal silicon plate and detecting the individual vertical load from the change in the electric resistance value, Two leg portions of a U-shaped vertical load carrying member having a flat surface capable of carrying and two leg portions are respectively bonded and fixed to the end portions along the groove of the single crystal silicon plate, and the Since the load is distributed to and carried by the single crystal silicon plate through these vertical load carrying members, the vertical load carrying area as a whole can be kept wider than before, and the contacted object surface can be maintained. Irregularities and can keep a high degree of detection accuracy no matter regrettable, it has become possible to provide a pressure sensation sensor durability and reliability superior distributed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of the configuration of the pressure sensor of the present invention, FIG. 2 is a plan view of the flexible printed board seen from above, and FIG. 3 is a single crystal silicon plate of the pressure sensor considered as a beam. Fig. 4 is a schematic diagram showing how the load is applied, Fig. 4 is a distribution diagram of the amount of strain generated on the upper surface of the silicon plate in the state of Fig. 3, and Fig. 5 is a sectional view showing the configuration of another embodiment of the present invention. FIG. 6 is a top view of the single crystal silicon plate, FIG. 7 is a schematic view showing how a load is applied when the silicon plate of the pressure sensor shown in FIG. 5 is regarded as a beam, and FIG. FIG. 7 is a distribution diagram of the amount of strain generated on the upper surface of the silicon plate in the state of FIG. 7, FIG. 9 is a cross-sectional view showing an example of the configuration of a conventional distributed pressure sensor, and FIG. 10 is a top view of the single crystal silicon plate. FIG. 11 is a plan view showing that the conventional pressure sensor comes into contact with a contacted object having a protrusion. FIG. 12 is a cross-sectional view showing a state, FIG. 12 is a schematic diagram showing how a load is applied when the single crystal silicon plate of the pressure sensor of FIG. 9 is regarded as a beam, and FIG. 13 is a silicon plate in the state of FIG. It is a distribution diagram of the amount of strain generated on the upper surface. 2 ... Pressure sensing element, 3 ... Groove, 4 ... Elastic body, 6 ... Single crystal silicon plate, 6A ... Top surface of single crystal silicon plate, 10, 20 ... Flexible printed board, 21 ... Pressure sensor , 28 ... Load-carrying member, 28A ... Leg part, 29 ... Adhesive agent, 29A ... Adhesive layer.

Claims (1)

[Claims] 1. A plurality of semiconductor strains having single crystal silicon plates arranged in a matrix on an elastic body and provided on the single crystal silicon plates by a vertical load applied to each of the single crystal silicon plates. A pressure sensor that changes an electric resistance value in a gauge and detects the vertical load by detecting the change in the electric resistance value to detect a load distribution, which is a substantially U-shape having a flat surface capable of carrying the vertical load. The two legs of the vertical carrying member are fixedly bonded to the ends of the single crystal silicon plate along the groove, and the vertical loads are individually distributed to the ends of the single crystal sillcon plate by the vertical carrying member. A pressure sensor characterized in that the pressure sensor is configured to be carried as a carrier.