JPH06201502A - Pressure sensor - Google Patents

Abstract

PURPOSE:To make it possible to measure the direction of pressure as well as the magnitude thereof by constructing one of counter electrodes out of a plurality of split electrodes insulated electrically from each other. CONSTITUTION:A capacitor is constructed of a flexible electrode 1 being a flexible conductor having such hardness as to be deflected by pressure and of fixed electrodes 2 and 3. When a voltage is impressed between an output terminal 6 and output terminals 4 and 5, capacitance C corresponding to a distance (d) between the flexible electrode 1 and the fixed electrodes 2 and 3 is generated between them. In other words, the capacitance C changes as the distance (d) changes, and by detecting this change of the capacitance, the distance (d) can be measured. The amount of change of the flexible electrode 1, i.e., the deflection thereof, by the pressure depends on the Young's modulus of the material of the flexible electrode 1 according to the Hooke's law. By measuring the Young's modulus of the material, therefore, the pressure is measured from the change in the capacitance measured from the output terminals 4, 5 and 6. By the split fixed electrodes 2 and 3, besides, the direction of application of the pressure is also detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor used in, for example, an endoscope, and more particularly to a pressure sensor (hereinafter referred to as a pressure sensor for detecting the magnitude and direction of a force received from an object by contacting the object. (Referred to as a pressure sensor).

[0002]

2. Description of the Related Art In recent years, endoscopes have come to emphasize the function of manipulating an observation object while observing, rather than the function as an instrument for observing the inside of the body.
This can be more easily deduced from the situation where a rigid endoscope is used for cholecystectomy surgery, and it is expected that surgery and diagnosis using an endoscope will continue to expand in the future. As described above, an endoscope capable of manipulating an object in a complicated manner is generally called a multi-functional endoscope, and one of the functions of the multi-functional endoscope is the pain to the patient when the endoscope is inserted. There is a function to soften.

As a structure that exhibits this function, it is possible to arrange a pressure sensor on the wall surface of the endoscope. Generally, there are many types, but the pressure sensors that can be used on the wall surface of the multifunctional endoscope are limited due to the area of the wall surface of the multifunctional endoscope and the volume of the multifunctional endoscope. come.

On the other hand, in an apparatus that uses light, such as an endoscope, it is considered possible to reduce the number of wires by utilizing the light. As a pressure sensor using this light, for example, there is a technique disclosed in Japanese Patent Application Laid-Open No. 60-120229, which is configured as shown in FIG. Further, as a conventional technique of a pressure sensor actually inserted in an endoscope, there is a technique disclosed in Japanese Patent Application Laid-Open No. 2-77226, which uses a pressure-sensitive conductive rubber and has a configuration as shown in FIG.

[0005]

However, as shown in FIG.
As shown in FIG.
2 and the change of the contact area of the protrusion 73a provided on the portion of the sheet 73 which is the pressure sensitive body in contact with the optical waveguide 72
The light is detected as scattered light from the optical waveguide 72 and the pressure is sensed by the scattered light.
The contact state of a is made uniform and the phototransistor array 74
It is very difficult to miniaturize because a light receiving element such as is required.

Further, as shown in FIG. 23, in the technique in which the pressure sensor 76 using the pressure-sensitive conductive rubber 75 is mounted on the endoscope 77, since the conductive rubber is a viscoelastic body, a large hysteresis is repeated and reproducibility is improved. It is said to be scarce. The present invention has been made in view of the above problems, and an object thereof is to provide a pressure sensor capable of measuring not only the magnitude of pressure but also the direction.

[0007]

In order to achieve the above object, according to the pressure sensor of the present invention, in a capacitance type pressure sensor having a counter electrode, one of the counter electrodes is electrically insulated from each other. It is characterized by comprising a plurality of divided electrodes.

[0008]

That is, the pressure sensor of the present invention is a capacitance type pressure sensor having a counter electrode, and one of the counter electrodes is composed of a plurality of divided electrodes electrically insulated from each other.

[0009]

First, prior to the description of the embodiments of the present invention, the basic principle of the present invention will be described. 2 (a) to 2 (c)
FIG. 4 is a diagram showing the basic principle of the pressure sensor of the present invention.

As shown in FIGS. 1 (a) to (c), the structure of the pressure receiving portion of the pressure sensor includes a flexible electrode 1 made of a flexible conductor having a hardness enough to bend with respect to pressure. , Fixed electrodes 2, 3 divided into at least two or more areas
The fixed electrodes 2 and 3 and the flexible electrode 1 are sequentially laminated.

In FIG. 2A, the flexible electrode 1 is a flexible material made of a conductive material, and the fixed electrodes 2 and 3 are provided with independent output terminals 4 and 5, respectively. Similarly, an output terminal 6 is provided. The flexible electrode 1 and the fixed electrodes 2 and 3 constitute a capacitor, and when a voltage is applied to the output terminal 6 of the flexible electrode 1 and the output terminals 4 and 5 of the fixed electrodes 2 and 3, the flexible electrode 1 An electrostatic capacitance C corresponding to the distance is generated between 1 and the fixed electrodes 2 and 3, and the electrostatic capacitance C is given by the following equation (1). C = εS / d (1) where ε is the relative permittivity of the substance between the electrodes, S is the area of the capacitor, and d is the distance between the electrodes.

That is, when the distance d changes, the electrostatic capacitance C changes, and the distance between the flexible electrode 1 and the fixed electrodes 2 and 3 can be measured by detecting this electrostatic capacitance change. The change amount of the flexible electrode 1 with respect to the pressure, that is, the strain mainly depends on the Young's modulus (elastic coefficient) of the material of the flexible electrode 1 according to Hooke's law. Therefore, if the Young's modulus of the material used for the flexible electrode 1 is accurately measured in advance, the output terminals 4, 5, 6
The pressure applied to the flexible electrode 1 can be measured by the change in capacitance measured from Also, by dividing the fixed electrodes 2 and 3, it is possible to detect the direction in which pressure is applied.

For example, as shown in FIG. 2B, the flexible electrode 1
When pressure is applied vertically to the fixed electrodes 2, 3
Since the average distances d1 between the flexible electrode 1 and the fixed electrodes 2 and 3 are the same, the electrostatic capacitances C1 and C2 of Eq.

On the other hand, as shown in FIG. 2 (c), when pressure is applied to the flexible electrode 1 with a certain inclination, the distance d2 between the fixed electrode 2 and the flexible electrode 1, the fixed electrode and the flexible electrode 1 Both of the distances d3 are different, and the electrostatic capacitances C2 and C3 output from the output terminals 4 and 5 are different. The capacitance C increases as the distance d decreases, and the capacitance C decreases as the distance d increases.

Therefore, as shown in FIG. 2C, the capacitance C3 becomes larger than C2 when pressure is applied,
By comparing the capacitances in this way, the fixed electrode 5
It can be judged that the pressure is applied from the direction. Also,
The magnitude of the pressure can be obtained from the sum of the electrostatic capacitances C2 and C3. That is, by dividing the fixed electrode, the direction in which the pressure is applied can be detected by comparing the magnitudes of the capacitances between the divided fixed electrodes, and the capacitance of the entire fixed electrode can be measured. The magnitude of pressure can be measured. Next, FIG. 3 is a diagram showing the configuration of a circuit for detecting the direction and magnitude of pressure based on the capacitance detected by such a principle.

In the figure, the electrostatic capacitance C output from the output terminals 4 and 5 is detected as a voltage by the electrostatic capacitance detection circuits 7a and 7b, and further, an impedance conversion circuit for converting the high impedance characteristic of the capacitor. 8
a, 8b. Then, based on the output here, the difference and sum of the electrostatic capacities of the capacitors composed of the fixed electrodes 2 and 3 are obtained using the determination circuit 9, and the direction and magnitude of the pressure are obtained. Here, electrostatic capacitance detection circuits 7a and 7b for detecting the electrostatic capacitance output from the fixed electrodes 2 and 3 shown in FIG.
The basic configuration of is as shown in FIG.

As shown in the figure, as a basic configuration, an AC power supply 11, a sensing capacitor C _S 12 composed of the fixed electrode 2 and the flexible electrode 1 or the fixed electrode 3 and the flexible electrode 1, and the sensing capacitor C Load capacitor C _L 1 for converting the electrostatic capacity of _S 12 into a voltage
3 and 3. In the circuit having such a configuration, the sensing capacitor C _S 12 has the output terminal 14
_Is output as a voltage V _L. Incidentally, instead of using the load capacitor C _L 13, it is also possible to use a load resistance R _L 15 as shown in FIG.

The output voltage V _L from the electrostatic capacitance detection circuits 7a and 7b has a high impedance and is very difficult to handle, so it is necessary to perform impedance conversion. Therefore, impedance conversion is performed using the impedance conversion circuit having the basic configuration shown in FIG.

In FIG. 6, 12 is a sensing capacitor C _S , 13 is a load capacitor C _L , 16 is a MOS transistor, 17 is a grounding resistor, 18 is an output terminal of the output voltage V _L ′, and the gate of the transistor 16 is shown. The electrode corresponds to the output terminal 14 in FIGS. Further, the load capacitor C _L 13 in FIG. 6 is shown in FIG.
It is also possible to set the load resistance R _L 15 as shown in FIG.

The voltage V _L ′ output from this circuit is compared and added with the output voltage V _L ′ from the capacitor composed of another fixed electrode and the flexible electrode, and therefore, FIG. Inputted to the differential operational amplifier 19 and the addition operational amplifiers 70a to 70e as shown in a) and (b), the direction and magnitude of the pressure are obtained based on the outputs of the operational amplifiers 19, 70a to 70e. Hereinafter, a pressure sensor according to an embodiment of the present invention based on such a basic principle will be described with reference to the drawings. FIG. 1 is an external view of a pressure sensor according to a first embodiment of the present invention when the pressure sensor is disassembled into layers, and FIG. 8 is a cross-sectional view when the respective parts of FIG. 1 are stacked.

As shown in the figure, the pressure sensor according to the first embodiment basically has a dome-shaped electrode 20 and an insulating film 21.
And fixed electrodes 24 to 27 that are divided and insulated by the gap 23 and electrically independent, and the fixed electrodes 24 to 2
The lower fixed electrodes 30 to 33 provided on the substrate 29 as the reference capacitance electrodes for detecting the capacitance change of the capacitor constituted by the substrate 28 on which 7 is arranged, the substrate 29, and the fixed electrodes 24 to 27. And a dielectric 34 laminated between the substrate and the substrate.

In such a configuration, the dome-shaped electrode 20 is a flexible body having a small amount of hysteresis, which is made by mixing carbon black, metal powder, metal fibers, etc. into a material such as urethane rubber, and the fixed electrode 24. Through 2
A portion of a portion 20 a parallel to the insulating film 21 is adhered to the upper portion of the substrate 28 on which the insulating film 7 is arranged via an electrically insulating film 21. Further, by providing the insulating film 21 also on the upper portions 21a of the fixed electrodes 24 to 27, an electrical short circuit with the fixed electrodes 24 to 27 can be prevented even if the dome-shaped electrode 20 is largely deformed due to excessive pressure. Moreover, since the insulating film 21 and the dome-shaped electrode 20 are in contact with each other, the insulating film 21 also functions as a stopper against an excessive pressure.

Further, there is a structure for forming the reference capacitors with the fixed electrodes 24 to 27 below the substrate 28, and the lower fixed electrodes 30 to 33 are arranged at positions facing the fixed electrodes 24 to 27. . The capacitor is composed of the dome-shaped electrode 20 and the fixed electrodes 24 to 27. Since it is used as a reference capacitor for detecting the change in capacitance of the capacitor, it is necessary to prevent the change in capacitance. Therefore, for the reason described above, the structure between the fixed electrodes 24 to 27 and the lower fixed electrodes 30 to 33 is configured to suppress the capacitance change due to the distance change between the electrodes, and the capacitance change between the electrodes due to temperature is minimized. It is filled with such substances.

If the above substance is a liquid, it is considered that the substance is absorbed and filled in paper or the like, and if it is a solid or gas, it may be filled as it is. Further, the distance change is eliminated by filling the paper or the solid, and it is possible to suppress the distance change by filling with high pressure in the case of gas.

The terminals 35, 40, 41 of the dome-shaped electrode 20 and the lower fixed electrodes 30 to 33,
An AC voltage is applied to 42 and 43 from an external AC power source, and the capacitance change of the capacitor formed by the dome-shaped electrode 20 and the fixed electrodes 24 to 27 is the same as that of the fixed electrode 2.
Detection is possible from the output terminals 36 to 39 connected to each of 4 to 27. Next, FIG. 9 is a diagram showing a configuration of an example of the output terminals from the fixed electrodes 24 to 27 shown in FIG. 2 and the judgment circuit 9 shown in FIG.

In the figure, the electrostatic capacitances output from the fixed electrodes 24 to 27 are converted into voltages by the circuits 45a to 45d composed of electrostatic capacitance detection circuits and impedance conversion circuits. The outputs from the fixed electrodes from the circuits 45a to 45d are connected to synchronously driven switches 46 to 49. Further, the switches 46 to 49
To output the outputs from the circuits 45a to 45d to the differential circuit 54
And the addition circuit 55. Also,
When the switch 47 and 49 are connected to the terminal 1, this terminal is connected to the switches 50 and 51. This switch 5
0 and 51 are driven in synchronization, and by driving the switches 50 and 51, the output voltage from the fixed electrodes to be compared in the differential circuit 54 is distributed. Therefore, a differential output is output from the differential output terminal 52, and the addition output terminal 53
Outputs an addition output. This makes it possible to detect the difference and sum of the electrostatic capacitances generated in the fixed electrodes, and to measure the direction and magnitude of the pressure applied to the pressure sensor.

Here, the output voltages from the fixed electrodes 24 to 27 are defined as V ₁ , V ₂ , V ₃ and V ₄ , respectively, and the direction and magnitude of the pressure applied are determined from the respective output voltages.

First, by setting all the terminals of the switches 46 to 49 to "1" and moving the switches of the switches 50 and 51, the difference between the sum of V ₁ and V _{2 and} the sum of V ₃ and V ₄ V ₁₂₃₄ and V ₁ And the difference V ₁₄₂₃ between the sum of V _{4 and} the sum of V ₂ and V ₃ is calculated, and the direction in which the pressure is applied is obtained from the value of each difference.
By setting the terminals of the switches 46 to 49 to “2”, V ₁ , V ₂ , V ₃ and V ₄ are connected to the adder circuit,
The sum of the output capacitances of the fixed electrodes 24 to 27 is output from the addition output 53.

FIG. 10 is a schematic diagram of an example of electrostatic capacitance distribution. When the direction and magnitude of pressure are obtained in the state of FIG. 10, the voltage output from the differential output is a positive voltage at V ₁₂₃₄ . It can be seen that is output and the direction of the applied pressure is from the negative direction of the X axis. Further, since a positive value is output at V ₁₄₂₃ , it can be seen that pressure is applied from the positive direction of the Y axis. Furthermore, by taking the ratio of both, not only the direction but also the angle can be measured. Next, FIGS. 11A and 11B are a cross-sectional view of the sensor when pressure is applied from the vertical direction and a top view schematically showing the charge distribution at that time. When pressure is applied to the pressure sensor of the present invention by touching an object or the like, the pressure received by the endoscope outer wall 56 is the dome-shaped electrode 20.
Transform.

At this time, as shown in FIG. 11A, when a pressure is applied to the pressure sensor in the vertical direction, the dome-shaped electrode 20 is deformed, and the electrostatic capacitance distribution in the fixed electrodes 24 to 27 at this time is It becomes as schematically shown in FIG. The capacitance change of the fixed electrodes 24 to 27 at this time is detected by the circuit shown in FIG. At this time, the detected capacitances become equal at the output terminals 36 to 39, and it can be determined that the pressure applied to the pressure sensor is the pressure in the direction perpendicular to the sensor. Moreover, since the total sum of the electrostatic capacitances detected from the output terminals 36 to 39 increases in proportion to the magnitude of the applied pressure, the total sum of the electrostatic capacitances corresponds to the applied pressure.

12 to 14 show the deformed state of the dome-shaped electrode 20 and the fixed electrodes 24 to 27 when the pressure applied to the pressure sensor is applied obliquely to the pressure sensor.
It is a figure which shows the electrostatic capacitance distribution in FIG. That is,
12A and 12B are a cross-sectional view of the sensor when pressure is applied from the right direction, a top view of the fixed electrode, and a top view schematically illustrating the distribution of charges at that time,
FIGS. 13A and 13B are a cross-sectional view of the sensor when pressure is applied from the left direction, a top view of the fixed electrode, and a top view schematically showing the charge distribution at that time.
(A) and (b) are cross-sectional views of the sensor when a pressure inclined further to the right from the pressure direction shown in FIG. 12 and a fixed electrode and an upper surface schematically showing the distribution of electric charges at that time are shown. It is a figure. At this time, the direction in which the pressure is applied can be detected by detecting the electrostatic capacitance from the output terminals 36 to 39 from each fixed electrode as described above and comparing each with the differential circuit 54. That is, in FIG. 12, the electrostatic capacitances of the output terminals 38 and 39 are larger than the electrostatic capacitances of the output terminals 36 and 37, and the pressure has a negative pressure direction in the X-axis direction. This corresponds to the total sum of the electrostatic capacitance changes detected in step S1 and the total output capacitance of the output terminals 36 to 39.

In FIG. 13, the output terminal 3
Since the electrostatic capacities of 6 and 37 are larger than the electrostatic capacities of the output terminals 38 and 39, the pressure direction is the direction toward the X-axis direction. Further, in FIG. 14, the output terminals 38, 39
14 is larger than the electrostatic capacitances of the output terminals 36 and 37, and is larger than that of the output terminals 38 and 39 in FIG. And
The reverse is true for the output terminals 36 and 37. That is, the pressure gradient appears as a difference in output capacitance between the fixed electrodes. Here, by making the pressure receiving surface 20b of the dome-shaped electrode 20 dome-shaped, that is, hemispherical, it is possible to detect a force in a wide range of directions and to keep the contact area constant in all directions. Since this is possible, the variation in pressure measured depending on the contact method is reduced.

As described above, the pressure sensor of the first embodiment can measure not only the magnitude of pressure but also the direction.
In particular, by attaching it to the wall surface of a multifunctional endoscope, it is possible to measure the direction and magnitude of pressure without being affected by pressure measurement due to unevenness of organs, and by outputting pressure data to the operator, Operability is improved, and the endoscope can be inserted without causing pain to the patient.

Next, the pressure sensor according to the second embodiment will be described with reference to FIG. As shown in the figure,
The pressure sensor of the second embodiment has a hollow structure in the pressure sensor of the first embodiment described above.
For this reason, when the ambient temperature decreases, the base body in the cavity contracts and the dome-shaped electrode 20 contracts in the radial direction, so that the pressure sensor may detect the pressure even if the pressure is not applied. Therefore, as shown in FIG. 15, the dome-shaped electrode 2
An air hole 57 is provided in a part of 0 so that the same atmospheric pressure as the outside air is applied to the hollow portion 22 of the dome-shaped electrode 20. Therefore, according to the pressure sensor of the present embodiment, it is possible to remove the influence of the pressure change due to the temperature change. Next, with reference to FIG. 16, a pressure sensor according to a third embodiment for removing the influence of the pressure change due to the temperature change described above will be described.

As shown in the figure, the pressure sensor according to the third embodiment has substantially the same basic structure as that of the first embodiment, but the cavity 58 of the dome-shaped electrode 20 is filled with the liquid 58. It is characterized by The enclosed liquid 58 uses a material having a low thermal conductivity and a high dielectric constant. As a result, in the pressure sensor of this embodiment, even if the ambient temperature changes, the distance between the dome-shaped electrode 9 and the fixed electrodes 24 to 27 hardly changes, and the influence of the temperature change on the pressure is very small. Become.
Also, the same effect can be obtained by enclosing a gas having a low coefficient of thermal expansion.

The fixed electrodes 24 to 27 can detect the direction of pressure with high accuracy by dividing into four, but if the direction of pressure does not require very high accuracy, it is not necessary to divide into four and other divisions. If the number is sufficient and the resolution in only one direction is sufficient, the direction can be measured in two divisions.

FIG. 17 is a diagram showing the structure of a circuit for converting the output voltage from the electrostatic capacitance detection circuit shown in FIGS. 3 and 4 into an oscillation frequency corresponding to the voltage value. Although a general Hartley circuit is adopted here, another circuit may be used as long as it is a circuit that performs the above-described differential. This Hartley circuit is composed of a transistor 59, a coil 60, and an antenna 61, and the base of the transistor 59 is shown in FIGS.
The output terminal 14 in is input. In this circuit, resonance occurs in the closed circuit composed of the transistor 59 and the coil 60 due to the electrostatic capacitance of the two capacitors C _S 12 and C _L 13. By connecting the antenna 61 to the closed circuit,
Radio waves are oscillated, the output voltage can be transmitted using the radio waves, and the number of wires of the endoscope can be significantly reduced.

Further, since the radio wave from the circuit shown in FIG. 17 transmits the change of the sensing capacitor C _S 12 as the frequency change, the output from each fixed electrode 24 to 27 can measure the pressure by comparing the frequencies. It becomes possible, and a high S / N ratio can be obtained because the frequency is transmitted. Next, an example in which the pressure sensor of the present invention is actually mounted on the endoscope 62 will be described with reference to FIGS. 18 to 21.

As shown in FIG. 18, by arranging the pressure sensors of the present invention in the circumferential direction, and arranging the pressure sensors at a certain interval in the axial direction, the pressure applied to the endoscope 62 is changed in the axial direction of the endoscope 62. The data can be detected as

Further, as shown in FIGS. 19 (a) and 19 (b), the pressure sensor of the present invention is arranged on a ring 63 made of a material which has substantially the same outer diameter as the endoscope 62 and is harder than the endoscope. Then, by fitting the ring 63 into the endoscope 62 as shown in FIG. 19B, even if the endoscope 62 bends, the ring 6
Bending does not occur in the three parts, the influence of the bending on the pressure sensor can be reduced, and the same effect as the mounting example shown in FIG. 18 can be obtained.

Besides, a structure 64 made of a material harder than the outer wall of the endoscope as shown in FIG. 20 (a) is used, and the present invention is provided between the rings 65, 66 at both ends as shown in FIG. 20 (b). It is also possible to arrange the pressure sensor. Then, the module 67 is fitted into the endoscope 62 as shown in FIG. 20C, and when the endoscope 62 is bent, the rings 6 at both ends are
It is possible to remove the force generated on the outer wall of the endoscope due to bending by 5, and 66, and the present pressure sensor between the rings 65 and 66 can accurately detect the pressure even when the endoscope is bent. .

Incidentally, these FIG. 18, FIG. 19 (a), (b),
In addition to the arrangement of the pressure sensors shown in FIGS. 20 (a) to 20 (c), a method of arranging the pressure sensor in the circumferential direction at equal intervals and other equal division numbers are also conceivable. It is determined according to the resolution of the pressure on the outer wall of the endoscope that the endoscope operator desires. It is also considered effective to arrange the pressure sensor in a spiral shape on the wall surface of the endoscope.

Next, a pressure sensor according to the fourth embodiment will be described with reference to FIG. This figure is an example of another shape of the dome-shaped electrode 20. The dome-shaped electrode 20 is formed into a flat plate shape, and the area of the counter electrode 68 of the fixed electrodes 24 to 27 is the whole area of the fixed electrodes 24 to 27. By making it smaller than this, the sensitivity of detection in the direction of the pressure is improved, and the amount of deformation is limited by the spacer 69 so as not to deform more than a certain amount. In addition, a restoring force can be obtained by forming the spacer 69 with an elastic material such as rubber. Further, the present pressure sensor is capable of detecting the pressure direction by dividing the fixed electrode of the substrate 28, but by dividing the fixed electrode of the substrate 28 and dividing the dome-shaped electrode 20. Also makes it possible to detect the direction of pressure. As described above in detail, the pressure sensor of the present invention has a structure capable of detecting the magnitude and direction of the pressure applied to the pressure-sensitive portion and has a simplified structure, so that the size can be easily reduced.

Further, the present pressure sensor is provided on the outer circumference of a cylindrical object such as a multi-function endoscope, and it becomes possible to detect the direction and magnitude of the pressure when these contact with the object.
Since this pressure sensor is small, it does not lead to an increase in the diameter of the endoscope due to pressure measurement.

Further, since the capacitor is used in the pressure detection circuit, the power consumption is reduced, the influence of heat on the pressure data can be removed, and a mechanism for preventing thermal expansion of the cavity is provided. By providing, the influence on heat can be further reduced. The present invention is not limited to the above-described embodiments, but can be widely applied to detection of pressure applied to the cylindrical structure.

[0046]

As described above, it is possible to provide a pressure sensor capable of measuring not only the magnitude of pressure but also the direction.

[Brief description of drawings]

FIG. 1 is a layered exploded perspective view of a pressure sensitive portion of a pressure sensor according to a first embodiment of the present invention.

2A to 2C are diagrams showing the basic principle of the pressure sensor of the present invention.

FIG. 3 is a block diagram of a circuit for detecting the direction and magnitude of pressure in the pressure sensor of the present invention.

FIG. 4 is a diagram showing a basic configuration of electrostatic capacitance detection circuits 7a and 7b for detecting the electrostatic capacitance output from the fixed electrodes 2 and 3 shown in FIG.

5 is a diagram showing a configuration of an improved example of the electrostatic capacitance detection circuits 7a and 7b shown in FIG.

FIG. 6 is a diagram showing a configuration of an impedance conversion circuit.

7A and 7B are differential operational amplifiers 1 respectively.
9a to 19c and FIG. 9 is a diagram showing a configuration of addition operational amplifiers 70a to 70c.

FIG. 8 is a cross-sectional view when the respective parts of the pressure sensor according to the first embodiment of the present invention are stacked.

9 is a diagram showing a configuration of an example of output terminals from the fixed electrodes 24 to 27 shown in FIG. 2 and a determination circuit 9 shown in FIG.

FIG. 10 is a diagram showing an example of capacitance distribution on a fixed electrode.

11A is a cross-sectional view of the sensor when pressure is applied in the vertical direction, and FIG. 11B is a top view of the fixed electrode and a top view schematically showing the charge distribution at that time. .

12A is a cross-sectional view of the sensor when pressure is applied from the right direction, and FIG. 12B is a diagram schematically showing a top view of the fixed electrode and charge distribution at that time. is there.

13A is a cross-sectional view of the sensor when pressure is applied from the left direction, and FIG. 13B is a diagram schematically showing a top view of a fixed electrode and charge distribution at that time. is there.

14 (a) is a cross-sectional view of the sensor when pressure is applied from the right side of the pressure direction shown in FIG. 12, and FIG. 14 (b) is a top view of the fixed electrode and electric charges at that time. It is the figure which showed typically distribution.

FIG. 15 is a cross-sectional view of a pressure sensor according to a second embodiment.

FIG. 16 is a sectional view of a pressure sensor according to a third embodiment for removing the influence of pressure change due to temperature change.

FIG. 17 is a diagram showing a configuration of a circuit that converts an output voltage from the electrostatic capacitance detection circuit shown in FIGS. 3 and 4 into an oscillation frequency according to the voltage value.

FIG. 18 is a diagram showing an example in which the pressure sensor of the present invention is mounted on an endoscope.

19A is a perspective view of a ring-shaped array of the pressure sensor of the present invention, and FIG. 19B is a diagram showing an example in which the ring-shaped array is mounted on an endoscope.

FIG. 20 (a) is a perspective view of a bending cancel ring,
(B) is the figure which attached the pressure sensor of this invention to the said bending cancellation ring, (c) is the perspective view which mounted the pressure sensor of this invention using the ring.

FIG. 21 is a diagram showing a configuration of a pressure sensor according to a fourth example.

FIG. 22 is a diagram showing a configuration of a conventional pressure sensor.

FIG. 23 is a diagram for explaining a conventional technique in which a pressure sensor using pressure-sensitive conductive rubber is mounted on an endoscope.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flexible electrode, 2, 3 ... Fixed electrode, 4,5 ... Fixed electrode output terminal, 6 ... Flexible electrode output terminal, 7 ... Capacitance detection circuit, 8 ... Impedance conversion circuit, 9 ... Judgment circuit, 10
... pressure sensitive part, 11 ... AC power supply, 12 ... sensing capacitor, 13 ... load capacitor, 14 ... output voltage, 15 ...
Load register, 16 ... MOS transistor, 17 ... Resistor, 18 ... Impedance converted output voltage, 19 ... Differential operational amplifier, 20 ... Dome-shaped electrode, 21 ... Insulating film, 22
... Cavity part, 23 ... Gap between fixed electrodes, 24-27 ...
Fixed electrode, 28 ... Fixed electrode substrate, 29 ... Lower fixed electrode substrate, 30-33 ... Lower fixed electrode, 34 ... Reference capacitor dielectric material, 35 ... Dome-shaped electrode output terminal, 36-
39 ... Fixed electrode output terminal, 40-43 ... Lower fixed electrode output terminal, 44 ... Lower fixed electrode gap, 45 ... Circuit,
46 to 51 ... Switch, 52 ... Differential circuit output terminal, 53
... addition circuit output terminal, 54 ... differential circuit, 55 ... addition circuit, 56 ... endoscope outer wall, 57 ... air hole, 58 ... liquid, 5
9 ... Transistor, 60 ... Coil, 61 ... Antenna, 6
2 ... Endoscope, 63 ... Ring, 64-66 ... Ring, 67
... Pressure sensor module, 68 ... Flat flexible electrode, 69
... Spacer, 70 ... Addition operational amplifier, 71 ... Flat plate, 72
... optical waveguide, 73 ... sheet, 74 ... phototransistor array, 75 ... pressure-sensitive conductive rubber, 76 ... pressure sensor, 77
…Endoscope.

Claims (1)

[Claims] 1. A capacitance type pressure sensor having a counter electrode, wherein one of the counter electrodes is composed of a plurality of divided electrodes electrically insulated from each other.