JPH0697194B2 - Piezoelectric pressure distribution sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure sensor using a piezoelectric element, and more particularly to a structure of a sensor for detecting a pressure distribution.

[Prior Art] Conventionally, as a pressure sensor, one using a change in resistance value or capacitance of a silicon semiconductor, one using a pressure-sensitive conductive rubber whose resistance value changes according to a pressing force, and a light emitting element and a light receiving element It is known to dispose and detect changes in the thickness of the silicon rubber layer due to pressure reception as changes in the amount of light.

[Problems to be Solved by the Invention] However, the one using a silicon semiconductor is excellent in sensitivity and accuracy as a pressure sensor, but cannot accurately measure the pressure distribution. This is because one sensor chip has a relatively large diameter of several mm, so that even if many sensor chips are arranged, the pressure distribution cannot be accurately measured. Therefore, a pressure distribution sensor using a silicon semiconductor has not been realized.

On the other hand, in the case where the pressure-sensitive conductive rubber is used, it is considered that the pressure distribution can be detected, but since it depends on the elasticity of the conductive rubber, there is a problem in reliability, stability and accuracy.

Further, the combination of the silicone rubber and the optical measuring means utilizes the deformation of the silicone rubber layer, so that there is a problem that the recovery after depressurization requires a relatively long time. . Further, there is a problem that the silicone rubber layer deteriorates with time or the mechanism becomes complicated because it is a combination of optical means.

Therefore, an object of the present invention is to provide a pressure distribution sensor that can accurately detect the pressure distribution and that is excellent in reliability and stability.

[Means for Solving Problems] The pressure distribution sensor of the present invention uses a highly rigid piezoelectric element. That is, a plurality of high-rigidity piezoelectric elements arranged at a contact portion with an unknown object and having extraction electrodes connected to the electrodes and electrodes formed on the surfaces facing the contact portions respectively, and one end outputs A switch which is connected to the end and which can be selectively connected to each extraction electrode of a plurality of high-rigidity piezoelectric elements, and each of the charges generated in each high-rigidity piezoelectric element is read out by switching the switches. This makes it possible to detect the pressure distribution at the contact portion.

As the high-rigidity piezoelectric element, for example, piezoelectric ceramics,
Alternatively, a piezoelectric single crystal or the like can be used.

[Operation] In the present invention, the piezoelectric element made of a piezoelectric material having relatively high rigidity such as piezoelectric ceramics or piezoelectric single crystal comes into contact with an unknown object, and the piezoelectric effect of each piezoelectric element causes the contact of each piezoelectric element. The pressure in the open part is detected. A plurality of piezoelectric elements are arranged, and by switching a switch, the pressure change in each of the plurality of piezoelectric elements with which an unknown object comes into contact is read, and the pressure distribution is detected based on this.

Description of Embodiments FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention. In the embodiment shown in FIG. 1, a plurality of piezoelectric elements 2 are fixed on a support member 1 (shown by an imaginary line) made of a conductive material. Each piezoelectric element 2 has an electrode 3 on the surface opposite to the surface in contact with the support member 1, and is connected to each electrode 3
The extraction electrode 4 is formed on the side surface.

Although not shown in FIG. 1, the other electrode of each piezoelectric element 2 is formed on the surface that comes into contact with the support member 1.

Each piezoelectric element 2 is made of a highly rigid piezoelectric material such as piezoelectric ceramics or piezoelectric single crystal.

Each extraction electrode 4 of the plurality of piezoelectric elements 2 is connected to a switch 7, while the other electrode of each piezoelectric element 2 is electrically connected to an output extraction connection line 8 via a support member 1. It is connected. The switch 7 and the output end are electrically connected by a connection line 9, and a capacitor 10 is inserted between the connection line 9 and the connection line 8. That is, the capacitor 10 is connected in parallel to each piezoelectric element 2.

In the pressure distribution sensor shown in FIG. 1, an unknown object is brought into contact with each piezoelectric element 2 from the electrode 3 side. At this time, an unknown object contacts and pressurizes each piezoelectric element 2, so that a piezoelectric effect is generated in the piezoelectric elements 2 in contact with each other. Therefore, the pressure in each piezoelectric element 2 can be detected by sequentially switching the switches 7, and therefore each piezoelectric element 2 can be detected.
The pressure distribution can be known by sequentially detecting the pressure at.

In addition, the extraction electrode 4 of each piezoelectric element 2 is used as the switch 7.
A pressure change in each piezoelectric element 2 can be detected by connecting a multiplexer between the output terminal and the output terminal and applying a control signal for selecting the input line of the multiplexer to the piezoelectric element 2. In this case, each piezoelectric element 2 can be detected. By sequentially operating, the pressure distribution can be known instantly.

Although the capacitor 10 is inserted in parallel with all the piezoelectric elements 2 in the embodiment shown in FIG. 1, a capacitor may be inserted in parallel with each piezoelectric element 2. This is because the capacitor 10 completes the discharge in a short time with a voltage of several to several tens of kV only with the piezoelectric element 2, and is inserted to prevent this. Therefore, in the embodiment of FIG. 1, as the capacitor 10, a capacitor having a capacity of several hundred to several thousand times the total capacity of the plurality of piezoelectric elements 2 is used.

FIG. 2 is a perspective view for explaining another embodiment of the present invention. Here, the piezoelectric elements 12 are arranged in a matrix of 5 rows and 5 columns. Although not particularly shown, each piezoelectric element
The other end of 12 is fixed to an appropriate support member. The one electrode 13 of the piezoelectric element 12 is electrically connected by a connection line A for each row, and the other electrode 14 is electrically connected by a connection line B for each column.

Therefore, in the embodiment shown in FIG. 2, the pressure distribution can be detected by sequentially operating the connection lines A of 5 rows and the connection lines B of 5 columns using, for example, two multiplexers. .

As described above, according to the embodiment of the present invention, since the piezoelectric elements 2 and 12 that can reduce the shape thereof are used, the pressure distribution can be accurately detected, and further, as the piezoelectric elements 2 and 12, It is understood that since a piezoelectric material having high rigidity is used, problems such as deterioration with time do not occur.

In the embodiment shown in FIGS. 1 and 2, the electrodes 3 and 13 were exposed on the surfaces of the piezoelectric elements 2 and 12 that contact the unknown object. An elastic member such as a silicon thin film may be attached to the surface of the.

Next, in the present invention, since a piezoelectric element made of a highly rigid piezoelectric material is used, it is possible to estimate the material and shape of an unknown object to be contacted by applying elastic contact theory. Will be explained. In the following description, as shown in the perspective view of FIG. 3, a case is assumed in which the spherical unknown object 21 is contacted.

According to Hertz's theory of elastic contact, when the rigidity on the pressure sensor side is larger than the rigidity of the sphere 21, from FIG. 4, the radii a and the center O of the contact portion (circular region D in FIG. 3) O The pressure distribution p at a distance r from is given by equations (1) and (2).

In the equation (2), Note that R ₀ represents the radius of the sphere, E ₁ and ν ₁ represent the Young's modulus (longitudinal elastic modulus) and Poisson's ratio of the sphere 21, and E ₂ and ν ₂ represent the Young's modulus and Poisson's ratio on the sensor side.

By the way, according to the pressure distribution sensor of the present invention, (a, p,
p ₀ ) can be measured and (E ₂ , ν ₂ ) is given beforehand. Therefore, the contact load P is given by the equation (4).

_{P = ∫ D Pdxdy ... (4} ) On the other hand, in a general material is Poisson's ratio of about 0 to 0.3, ^{_{therefore, 1 >> ν 2 2, 1}} >> ν 1 2 ... (5) Therefore, the following equation (6) and (7) are established.

Therefore, since E ₂ is known, it can be seen that E ₁ and R ₀ can be obtained if a, P and p at each r can be measured by the sensor. As described above, according to the pressure distribution sensor of the present invention, since a, P and p at each r are obtained, E ₁ , R _0, that is, the Young's modulus of the unknown object and the radius of curvature of the contact portion can be calculated. it can.

As described above, by using the pressure distribution sensor of the present invention, it is possible to estimate the material and curvature of the unknown object.

Next, concrete experimental results using a configuration corresponding to the embodiment shown in FIG. 1 will be described.

FIG. 5 is a perspective view for explaining the experimental conditions using the embodiment shown in FIG. Here, a plate-shaped member 31 made of stainless steel is used as the support member 1 in FIG. 1, and an unknown object 32 made of synthetic resin is used as the unknown object, which is obtained by vertically cutting a cylinder having a diameter of 100 mm. . Also in the following examples, although the diameter of the basic cylinder is changed, an unknown object having the same shape is used. An elastic member 33 made of silicon rubber was arranged between the unknown object 32 and the piezoelectric element 2. In the example shown in FIG. 5, a load of 20 kg was applied from above the unknown object 32. As a result, the output voltage distribution shown in FIG. 6 was obtained.

Since the piezoelectric elements on the supporting member 31 shown in FIG. 5 are arranged in 3 rows and 3 columns, in FIG. 6, 9 piezoelectric elements are numbered 1 to 9 in order from the upper left, The position of the piezoelectric element was plotted on the water surface according to each row and column, and the output voltage was plotted above the plotted position of the piezoelectric element.

From the results of FIG. 6, it can be seen that the output voltage is high in the piezoelectric elements (piezoelectric elements of Nos. 2, 5, and 8) located in the portion where the unknown object 32 is in strong contact.

FIG. 7 shows a state in which an unknown object is formed by cutting a cylindrical body with a diameter of 50 mm and has a diameter smaller than that of the unknown object 32 shown in FIG. 5, and a load of 20 kg is applied from above as well. . The results are shown in Fig. 8. From FIG. 8, it can be seen that in this example, the curvature of the contact portion of the unknown object is small, so that the load from the unknown object is more strongly applied to the piezoelectric elements No. 2, 5, and 8.

FIG. 9 is a perspective view showing a state in which an unknown object is formed of a cylindrical body having a diameter of 30 mm, that is, when it is made thinner than the experimental examples shown in FIGS. 5 and 7. The results of the experiment shown in FIG. 9 are shown in FIG. From FIG. 10, it can be seen that in this experimental example, the load is applied more strongly to the piezoelectric elements of Nos. 2, 5, and 8 than in the case shown in FIG.

FIG. 11 shows an unknown object 32 used in the experiment shown in FIG.
FIG. 6 is a perspective view showing an experimental result in which a load of 20 kg is applied from above and the contact is made obliquely. The results are shown in Fig. 12. From FIG. 12, in this experiment, Nos. 1, 5, 9 in contact with the unknown object 32
It can be seen that a strong load is applied to the piezoelectric element.

FIG. 13 shows the diameter in place of the unknown object used in FIG.
An unknown object formed from a 30 mm cylinder is brought into contact with the same direction and a load of 20 kg is applied. The results in this case are shown in FIG. It can be seen from FIG. 14 that a larger load is applied to the piezoelectric elements of Nos. 1, 5, and 9 as compared with the case of FIG.

As described above, the experiments shown in FIGS. 5 to 14 show that the pressure distribution sensor of the present invention can accurately know the pressure distribution of an unknown object.

[Effects of the Invention] According to the present invention, a plurality of high-rigidity piezoelectric elements arranged in a contact portion with an unknown object are provided, and a switch is switched while the high-rigidity piezoelectric elements are contacted and pressed by the unknown object. As a result, the pressure distribution at the contact portion can be detected.
In the present invention, since the piezoelectric element having high rigidity is used as the detection element, it is possible to realize a pressure distribution sensor which is less deteriorated with time and is therefore excellent in reliability and stability. Furthermore, since the piezoelectric element is a rigid body, the material and curvature of the unknown object can be accurately estimated by applying elastic contact theory. Further, relatively large displacement does not occur on the sensor side unlike silicon semiconductors or pressure-sensitive conductive rubbers, so that the positioning of each piezoelectric element can be performed with extremely high precision.

INDUSTRIAL APPLICABILITY The present invention can be generally used for applications in which pressure distribution measurement is required. For example, when installed in a grasping part of a robot, when grasping an unknown object, selection of the unknown object or control of grasping force is performed. It is possible to perform advanced work.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. FIG. 2 is a perspective view for explaining another embodiment of the present invention. 3 and 4 are perspective views for explaining the elastic contact theory. 5 to 14 are
FIG. 3 is a diagram showing conditions and results of a specific experiment conducted using a configuration corresponding to the example shown in FIG. 1. In the figure, 2 and 12 are piezoelectric elements, 10 is a capacitor, 32 is an unknown object, and 33 is an elastic member.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-94029 (JP, A) JP-A-55-4548 (JP, A) Actually opened 63-29740 (JP, U) Actually opened 61- 123948 (JP, U)

Claims (4)

[Claims] 1. A plurality of high-rigidity piezoelectric elements which are arranged in a contact portion with an unknown object, and each of which has an electrode formed on a surface facing the contact portion and an extraction electrode which is connected to each of the electrodes, A switch having one end connected to the output end and selectively connectable to each of the extraction electrodes of the plurality of high-rigidity piezoelectric elements, and each of the charges generated in each of the high-rigidity piezoelectric elements, A piezoelectric pressure distribution sensor capable of detecting the pressure distribution of the contact portion by reading by switching the switch. 2. The piezoelectric pressure distribution sensor according to claim 1, wherein the plurality of high-rigidity piezoelectric elements are arranged in a matrix. 3. The piezoelectric pressure distribution sensor according to claim 1, wherein a capacitor is connected in parallel with the piezoelectric element. 4. The piezoelectric pressure distribution sensor according to claim 1, wherein an elastic member is attached to a portion of the piezoelectric element that comes into contact with an unknown object.