JP7510157B2 - Sensor unit and sensor - Google Patents

Description

The present invention relates to a sensor unit and a sensor.

The introduction of robots is progressing to solve the problems of a decline in the productive labor force and a shortage of workers in medical, nursing, and caregiving fields. In the future, it is hoped that robots will be densely equipped with sensors to give them advanced senses so that they can perform complex tasks in the same way as humans. In the area of robot sensors, there has been remarkable progress in vision sensors based on LSI (Large-Scale Integrated circuit) technology, and progress is being made with the development of robots with eyes that surpass those of humans in functionality and performance.

For a robot to perform the same tasks as a human, it is important that the robot has sensors that sense other than vision, such as force, pressure, temperature, and cold. A variety of sensors have been proposed to measure the force acting on an object, acceleration, spatial pressure, and sound. In particular, progress has been made in the development of small, highly sensitive sensors (accelerometers, pressure sensors, and sound sensors) that use silicon and MEMS (Micro Electro Mechanical Systems) technology.

Patent document 1 discloses a strain detection element that has a substrate and a magnetic layer made of a conductor layer and a magnetostrictive material laminated on the substrate. It is described that the strain detection element in patent document 1 detects strain caused by an external force as an impedance change.

JP 2000-356505 A

However, the strain detection element in Patent Document 1 was unable to adequately detect the applied force depending on the direction of the external force.

The present invention was made in consideration of the above problems, and aims to provide a sensor unit and sensor that can detect external forces in various directions. It also aims to provide a sensor unit that can obtain various information with a single element.

The inventors have discovered that by using a magnetostrictive film that protrudes in a first direction relative to a reference plane, it is possible to detect forces in various directions. That is, in order to solve the above problem, the following means are provided.

(1) A sensor unit according to one aspect of the present invention comprises a continuous magnetostrictive film having a plurality of protrusions protruding in a first direction perpendicular to a reference plane , and contacts arranged on both ends of the protrusions, and a sensor signal processing circuit connected to the contacts for measuring at least one impedance of each of the plurality of protrusions, each of the plurality of protrusions being a sensor.

(2) At least one of the plurality of protrusions of the sensor unit according to the above aspect may further include an insulator filled between the rear surface of the magnetostrictive film and the reference surface.

(3) In the sensor unit according to the above aspect, the convex portion having the insulator may have a minimum width of 1 mm or less when viewed in a planar view from the first direction.

(4) In the sensor unit according to the above aspect, at least one of the convex portions having the insulator may have a length in a second direction along the reference surface that is different from a length in a third direction that is along the reference surface and perpendicular to the second direction.

(5) In the sensor unit according to the above aspect, at least one of the plurality of protrusions may have a space between the rear surface of the magnetostrictive film and the reference surface.

(6) In the sensor unit according to the above aspect, at least one of the plurality of protrusions may have a hole penetrating the magnetostrictive film.

(7) In the sensor unit according to the above aspect, the convex portion among the plurality of convex portions having an insulator filled between the back surface of the magnetostrictive film and the reference surface is defined as a first convex portion, the convex portion among the plurality of convex portions having a space between the back surface of the magnetostrictive film and the reference surface and having a hole penetrating the magnetostrictive film is defined as a second convex portion, and the convex portion among the plurality of convex portions having a space between the back surface of the magnetostrictive film and the reference surface and not having a hole penetrating the magnetostrictive film is defined as a third convex portion, and the height of the first direction of the first convex portion may be greater than the height of the second convex portion and the third convex portion in the first direction.

(8) In the sensor unit according to the above aspect, the magnetostrictive film may be an amorphous material.

(9) The sensor unit according to the above aspect may further include a circuit board that forms at least a portion of the reference surface.

(10) In the sensor unit according to the above aspect, the Young's modulus of the circuit board may be 3 GPa or less.

(11) A sensor according to a second aspect of the present invention comprises a magnetostrictive film having a convex portion protruding in a first direction perpendicular to a reference plane , and contacts arranged on both ends of the convex portion, and has a sensor signal processing circuit connected to the contacts and measuring the impedance of the convex portion .

The sensor unit and sensor according to the above aspect can detect external forces in various directions.

FIG. 2 is a schematic perspective view of the sensor unit according to the first embodiment. FIG. 2 is a schematic cross-sectional view of the sensor unit according to the first embodiment. FIG. 11 is a schematic diagram showing a sensor unit according to a comparative example. 4 is a graph showing the correlation between force F1 and the magnetostrictive film in the sensor unit shown in FIG. 5A and 5B are schematic diagrams illustrating characteristic parts of the sensor unit according to the present embodiment. FIG. 2 is a schematic diagram of a circuit for reading out a sensor unit according to the present embodiment. FIG. 11 is a top view showing an example of an arrangement of sensors in a sensor unit according to a first modified example. FIG. 11 is a top view showing the arrangement of the sensor unit according to the second modified example. FIG. 13 is a schematic cross-sectional view of a sensor unit according to a third modified example. 1A to 1C are diagrams for explaining an example of a manufacturing method for a sensor unit according to the present embodiment, showing the first half of the manufacturing method. 10A to 10C are diagrams for explaining an example of a method for manufacturing a sensor unit according to the present embodiment, showing a latter half of the manufacturing method. FIG. 1 is a schematic diagram of a robot arm equipped with a sensor unit according to an embodiment of the present invention.

The present invention will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, arrangements, numbers, values, configurations, etc. exemplified in the following description are merely examples, and the present invention is not limited to them, and may be modified as appropriate within the scope of the present invention.

First, the directions are defined. The z direction is the stacking direction in which the magnetostrictive film is stacked on the circuit board 20 described later (see FIG. 1). The z direction is an example of a first direction. The x direction and y direction are directions perpendicular to the z direction. In FIG. 1, they are directions approximately parallel to one surface of the circuit board 20 described later. The x direction and y direction intersect perpendicularly.

[Sensor unit]
Fig. 1 is an enlarged perspective view of a main portion of a sensor unit 100 according to a first embodiment. Fig. 2 is a cross-sectional view of the sensor unit 100. The sensor unit 100 includes a circuit board 20 and a magnetostrictive film 10. The magnetostrictive film 10 is laminated on the circuit board 20.

The magnetostrictive film 10 includes a magnetic material such as an amorphous magnetic alloy thin film that exhibits the Villari effect. The amorphous magnetic alloy thin film is, for example, an iron-based amorphous alloy or a cobalt-based amorphous alloy thin film that exhibits soft magnetic properties. The iron-based amorphous alloy is, for example, Fe-Si-B or Fe-Si-B-P. The cobalt-based amorphous alloy is, for example, Co-Si-B, Co-Si-B-P, Fe-Co-B, or Fe-Co-B-P. These magnetic materials have a high gauge factor, which increases the sensitivity of the sensor unit. The gauge factor is an index of the stress impedance effect.

Amorphous alloys have high tensile strength. When an amorphous alloy is used for the magnetostrictive film 10, the magnetostrictive film 10 is less likely to break even if it has a complex shape such as a three-dimensional structure. In addition, the magnetostrictive film 10 of an amorphous alloy can be easily manufactured because it can be produced by sputtering, etc.

The thickness T of the magnetostrictive film 10 is, for example, 0.5 μm or more and 10 μm or less.

The magnetostrictive film 10 is a continuous magnetostrictive film having multiple protrusions 1a, 1b, 2, and 3 that protrude in a first direction relative to a reference plane RP. In FIG. 1, the multiple protrusions 1a, 1b, 2, and 3 protrude in the z direction from the continuous magnetostrictive film 10 relative to the reference plane RP. Here, the reference plane RP is, for example, the main surface of the circuit board 20 in the z direction. The x and y directions are directions along the reference plane. When the circuit board 20 is flat as in FIG. 1, the reference plane RP is also a flat surface, but when the circuit board has a curved three-dimensional structure, the reference plane RP is curved along the circuit board 20.

The magnetostrictive film 10 has a front surface 10a and a back surface 10b. The back surface 10b is the surface of the magnetostrictive film 10 that is closest to the reference plane RP.

For ease of explanation, below, convex portions 1a and 1b may be referred to as the "first convex portion," convex portion 2 may be referred to as the "second convex portion," and convex portion 3 may be referred to as the "third convex portion."

Details will be described later, but the first convex parts 1a and 1b function as tactile sensors, the second convex part 2 functions as an acoustic sensor (microphone), and the third convex part 3 functions as a pressure sensor.

(First convex portion)
The first convex portions 1a and 1b have an insulator 11 between the rear surface 10b of the magnetostrictive film 10 and the reference plane RP.

The first convex portion 1a has a substantially equal length in the x direction and a substantially equal length in the y direction when viewed from the z direction. The first convex portion 1a has, for example, a circular shape when viewed from the z direction. The first convex portion 1b has a longer length in the y direction than in the x direction when viewed from the z direction. The first convex portion 1b has, for example, an elliptical shape when viewed from the z direction. The x direction is an example of the second direction, and the y direction is an example of the third direction. The sensor unit 100 may have only the first convex portion 1a or only the first convex portion 1b, but it is preferable that the sensor unit 100 has both the first convex portion 1a and the first convex portion 1b.

The first convex portion 1b, for example, has a different length in the x direction and a different length in the y direction. The first convex portion 1b has a shape that is long in the y direction. Such a first convex portion 1b experiences different reaction forces from the insulator 11 depending on the direction in which an external force is applied. For example, the reaction force against a force applied from the x direction is different from the reaction force against a force applied from the y direction. As a result, the first convex portion 1b can read the difference in magnitude depending on the direction of the external force.

The minimum width of the first convex portions 1a and 1b in plan view from the z direction is, for example, 1 mm or less. That is, when Fig. 2 passes through the center and center of gravity of the first convex portions 1a and 1b in plan view from the z direction, the widths _w1a and _w1b of the first convex portions 1a and 1b are 1 mm or less. By setting the widths in this manner, it is also possible to make the density of the first convex portions 1a and 1b in the sensor unit 100 equal to or greater than the density of sensory points on human skin.

The height of the first protrusions 1a and 1b in the z direction is preferably smaller than the minimum width in the direction perpendicular to the z direction. That is, the height _h1a of the first protrusion 1a from the reference plane RP in the z direction is preferably equal to or smaller than the width _w1a , and the height _h1b of the first protrusion 1b from the reference plane RP in the z direction is preferably equal to or smaller than the width _w1b . Note that, although the height _h1a is greater than the height _h1b in FIG. 2, the present invention is not limited to this example, and the height _h1b may be greater than the height _h1a .

(Insulator)
The insulator 11 is in contact with at least a portion of the back surface 10b. The insulator 11 is located between the reference surface RP and the back surface 10b corresponding to the first convex portions 1a, 1b. The insulator 11 fills the space between the reference surface RP and the back surface 10b of the magnetostrictive film 10 corresponding to the first convex portions 1a, 1b. That is, the insulator 11 is disposed in close contact with the magnetostrictive film 10 and the circuit board 20. The shape of the insulator 11 corresponds to the shape of the area surrounded by the reference surface RP and the first convex portions 1a, 1b, for example.

The insulator 11 is an element that greatly affects the feel of the tactile sensor, because the insulator 11 is in close contact with the thin magnetostrictive film 10. The material of the insulator 11 is preferably selected so that the hardness (feel) of the first convex portions 1a, 1b is similar to that of human skin. Specifically, the material of the insulator 11 preferably has a Young's modulus in the range of 1×10 ³ Pa to 5×10 ⁶ Pa. An example of such a material for the insulator 11 is polydimethylsiloxane (PDMS).

As described above, the first convex portions 1a and 1b are provided with an insulator 11, and when an external force is applied, a reaction force is generated from the insulator 11. The reaction force from the insulator 11 causes stress to act on the magnetostrictive film 10, which distorts the magnetostrictive film 10, changing the impedance of the first convex portions 1a and 1b. By measuring the impedance of the magnetostrictive film 10, the first convex portions 1a and 1b function as tactile sensors that detect the applied force.

(Second convex portion)
The second convex portion 2 has a space _R2 between the back surface 10b of the magnetostrictive film 10 and the reference plane RP. The space _R2 is formed along the reference plane RP.

The second protrusion 2 has at least one through hole H penetrating the magnetostrictive film 10. The number of through holes H may be two or more.

The shape of the second convex portion 2 in plan view from the z direction does not matter. The second convex portion 2 has, for example, a circular shape in plan view from the z direction. The width _w2 of the second convex portion 2 in plan view from the z direction is, for example, 0.5 mm or more and 5 mm or less. The height _hR2 of the space _R2 is preferably large, for example, 2 mm or more. On the other hand, when the second convex portion ₂ is provided in a sensor unit having at least one of the first convex portions 1a and 1b, from the viewpoint of strength, for example, the height h2 of the second convex portion 2 from the reference plane RP in the z direction is designed to be lower than the height h1a of the first convex portion _1a and the height _h1b of the first convex portion 1b.

Although details will be described later, the space _R2 is a space connected to the outside by the through hole H, so that stress due to external pressure does not normally act on the magnetostrictive material. When the pressure outside the second convex portion 2 changes due to the action of acoustic waves, the magnetic material vibrates in response to the change in pressure, and a change in stress acts on the second convex portion 2. At this time, the impedance of the second convex portion 2 changes due to the stress impedance effect. Therefore, the second convex portion 2 functions as an acoustic sensor (microphone) by measuring the impedance.

(Third convex portion)
The third convex portion 3 has a space _R3 between the back surface 10b of the magnetostrictive film 10 and the reference plane RP. The space _R3 is sealed along the reference plane RP.

The shape of the third convex portion 3 in plan view from the z direction does not matter. The third convex portion 3 has, for example, a circular shape in plan view from the z direction. The width _w3 of the third convex portion 3 in plan view from the z direction is, for example, 0.5 mm or more and 5 mm or less. The height _hR3 of the space _R3 is preferably large, for example, 1 mm or more. On the other hand, when the third convex portion 3 is provided in a sensor unit having at least one of the first convex portions 1a and 1b, the height h3 of the third convex portion ₃ from the reference plane RP in the z direction is designed to be lower than, for example, the height _h1a of the first convex portion 1a and the height _h1b of the first convex portion 1b. Note that, although FIG. 2 illustrates a case in which the height _h2 is higher than the height _h3 , the present invention is not limited to this example, and the height _h3 may be higher than the height _h2 .

Although details will be described later, as described above, the space _R3 is a sealed space, and a pressure corresponding to the pressure difference between the pressure inside the space _R3 and the external pressure acts on the magnetic material of the third convex portion 3, distorting the magnetic material and changing the impedance of the third convex portion 3. Therefore, the third convex portion 3 functions as a pressure sensor by measuring the impedance.

(contact)
The contacts are located at both ends of each of the multiple protrusions 1a, 1b, 2, and 3 in a predetermined direction. The sensor unit 100 connects a sensor signal processing circuit (described later) to the contacts located at both ends of each protrusion to measure the impedance of each protrusion. For example, in the configuration shown in FIG. 2, the contacts C _1a1 and C _1a2 , the contacts C _1b1 and C _1b2 , the contacts C ₃₁ and C ₃₂ , and the contacts C ₂₁ and C ₂₂ are connected to the sensor signal processing circuit. The sensor unit 100 measures the impedance of the first protrusion 1a, the first protrusion 1b, the third protrusion 3, and the second protrusion 2, respectively, by the sensor signal processing circuit.
Hereinafter, the contacts _C1a1 , _C1a2 , _C1b1 , _C1b2 , _C31 , _C32 , _C21 and _C22 will be collectively referred to as contacts C.

(Circuit board)
The circuit board 20 forms at least a part of the reference plane RP. The circuit board 20 is located on the side of the magnetostrictive film 10 closer to the rear surface 10b. The circuit board 20 is a board having at least a part of a sensor signal processing circuit. The entire sensor signal processing circuit may be formed within the circuit board 20. Here, the sensor signal processing circuit is a circuit that connects the contacts C of each of the multiple protrusions to an AC circuit and reads out the impedance of each of the multiple protrusions 1a, 1b, 2, and 3.

The circuit board 20 may be a flat board as shown in FIG. 1 and FIG. 2, but the sensor unit of this embodiment preferably uses a flexible board or other flexible board. For example, the sensor unit preferably uses a board with a Young's modulus of 3 GPa or less. By using such a flexible board as the circuit board 20, the sensor unit 100 can be used in a wide range of fields.

In Figures 1 and 2, a sensor unit 100 having first convex portions 1a, 1b, second convex portion 2, and third convex portion 3 is illustrated as an example, but the sensor unit 100 according to this embodiment may have multiple convex portions and is not limited to this example.

1 and 2 show an example in which the shape of the multiple protrusions 1a, 1b, 2, and 3 is dome-shaped (the cross-sectional shape is arc-shaped), but the shape of the multiple protrusions 1a, 1b, 2, and 3 is not limited to this example. For example, the shape of the multiple protrusions 1a, 1b, 2, and 3 may be a part of a polyhedron, the cross-sectional shape may be asymmetric, and the protrusions may be inclined so as to be perpendicular to the slip direction. In addition, the microstructure of the surface of the magnetostrictive film 10 may be changed to improve sensitivity to slip.
1 and 2 show an example in which the insulator 11 fills the gap between the rear surface 10b and the reference surface RP at the positions corresponding to the first convex portions 1a and 1b, but the sensor unit according to the present embodiment is not limited to this example. The insulator 11 only needs to be in close contact with the rear surface 10b at the positions corresponding to the first convex portions 1a and 1b, and does not have to be configured to fill the gap between the rear surface 10b and the reference surface RP.

The thickness T of the magnetostrictive film 10 is not limited to the above example. The thickness T of the magnetostrictive film 10 is preferably as thin as possible from the viewpoint of compatibility with flexible substrates, throughput in manufacturing, and economical viewpoints. On the other hand, the thickness of the magnetostrictive film 10 is preferably thick from the viewpoint of strength. The thickness T of the magnetostrictive film 10 is selected arbitrarily, taking into consideration the sensitivity of the sensor and economical issues. In addition, other materials may be deposited in close contact with a predetermined position on the surface of the magnetostrictive film 10, as long as the sensitivity of the magnetostrictive film 10 to stress is not hindered. By depositing other materials in close contact with the surface 10a of the magnetostrictive film 10, the friction coefficient can be changed, and depending on the material, the sensitivity to slip can be improved. Examples of materials that can be deposited on the surface 10a of the magnetostrictive film 10 include SiO films and organic parylene films. These materials are deposited by plasma CVD, for example.

In this embodiment, for convenience of explanation, a sensor unit 100 having a small number of convex portions as shown in FIG. 1 has been described as an example, but the sensor unit according to this embodiment is not limited to this example. The sensor unit according to this embodiment may be a sensor unit arranged with a large number of configurations as shown in FIG. 1. Note that a unit sensor unit having one second convex portion 2 and one third convex portion 3, and other areas covered with first convex portions 1a and 1b, can be approximately 5 mm x 5 mm, 5 mm x 10 mm, and 10 mm x 10 mm in plan view from the z direction, for example.

<Sensor unit operation>
The sensor unit 100 according to this embodiment can detect forces applied from the outside in various directions, and can sense various sensations.
The operating principle of the sensor unit 100 will now be described.

Each sensor in the sensor unit 100 is a sensor that utilizes the stress impedance effect (SI effect). The stress impedance effect occurs when force is applied to a magnetic material. The stress impedance effect occurs when impedance changes due to the Villari effect and the skin effect of a conductor are affected by changes in magnetic permeability.

Specifically, when stress acts on the sensor, the magnetostrictive film on the surface is distorted. When the magnetostrictive film is distorted, its magnetic permeability changes due to the Villari effect. The following formula (1) represents the Villari effect. The following formula (1) represents the magnetic permeability μ of a magnetostrictive film when the magnetic permeability in a vacuum is μ ₀ and the magnetostrictive film has magnetic anisotropy constant K _U , saturation magnetization M _S , saturation magnetostriction λ _{S , and} Young's modulus E _F and is distorted by (Δl/l) due to stress.

The following equation (2) expresses the skin effect. The following equation (2) expresses the depth (skin depth) δ through which current flows when a current of frequency ω flows through a conductor with electrical resistivity ρ.

From the above formula (1), it is confirmed that the magnetic permeability μ depends on the stress that the magnetic material receives due to the Villari effect. Furthermore, from the above formula (2), it is confirmed that the skin depth δ depends on the magnetic permeability μ of the magnetostrictive film. When the skin depth δ changes, the impedance of the conductor changes. Therefore, when the stress applied to the magnetostrictive film changes, the impedance of the magnetostrictive film changes. Therefore, by measuring the impedance of the magnetostrictive film, the magnitude of stress can be detected, and it can be used as a force sensor.

Fig. 3 shows an example of a main part of a force sensor according to a comparative example. The force sensor shown in Fig. 3(a) has a magnetostrictive film 10', contacts _C1 ' and _C2 ' formed in the magnetostrictive film 10', and an AC circuit including a configuration that connects the contacts _C1 ' and _C2 ' and can measure the impedance between the contacts _C1 ' and _C2 '.

Even the force sensor shown in FIG. 3(a) can detect forces parallel to the z direction, such as force F1. FIG. 4 is a graph showing the correlation between the strength of force F1 and impedance Z. On the other hand, the force sensor shown in FIG. 3(a) cannot accurately detect forces having an x-direction component, such as force F2. It also cannot detect forces perpendicular to the z direction, such as force F3.

The force sensor shown in FIG. 3(b) is a force sensor used in a strain detection element such as that described in Patent Document 1 (JP Patent Publication No. 2000-356505). The force sensor shown in FIG. 3(b) has a substrate 1h that detects external strain, a magnetic layer made of a magnetic material 2h, a conductor layer 3h, and a magnetic material 4h laminated on the substrate 1h, and an electrode pad portion 5h. Patent Document 1 discloses that strain applied to the end of the substrate 1h is transmitted to the magnetic layer, causing an impedance change.

The force sensor shown in FIG. 3(b) cannot accurately detect forces such as force F2 and force F3.

In contrast, FIG. 5 shows an example of a main part of a force sensor included in this embodiment. The force sensor shown in FIG. 5 has a configuration in which the insulator 11 has been removed from the tactile sensor 1a, and the magnetostrictive film has a convex portion that protrudes in the z direction relative to the xy plane. In other words, it has a three-dimensional shape that is convex in the direction in which the force acts. Therefore, it can accurately detect not only forces parallel to the z direction such as force F1, but also forces having an x-direction component such as force F2 and forces perpendicular to the z direction such as force F3. In other words, if the shape of the sensor is a structure that protrudes in a first direction relative to the reference plane (convex structure), it can accurately detect forces in any direction that cannot be detected with a flat structure, such as forces parallel to the reference plane.

In addition, by utilizing the principles of the force sensor, it can be used as a tactile sensor, pressure sensor, and acoustic sensor (microphone).

(Tactile sensor operation)
An example of a tactile sensor is the first convex portions 1a and 1b. When the magnetostrictive material of the tactile sensor comes into contact with an external object, an external force acts on the tactile sensor. When a force acts on the tactile sensor, a reaction force is generated from the insulator 11. That is, stress acts on the magnetic material, causing it to distort. Therefore, the impedance of the magnetic material changes due to the stress impedance effect. By determining the correlation between the impedance of the magnetic material and the external force in advance and comparing it with the measured impedance, the tactile sensor can detect the applied force.

The tactile sensor here has a three-dimensional structure that protrudes in a first direction relative to the reference plane, and the magnitude of the in-plane direction is minute. Therefore, the force applied to the tactile sensor can be considered to be applied perpendicular to the minute surface of the convex structure of the tactile sensor. In particular, in the case of a sensor such as the first convex portion 1a, whose size is equal in the x and y directions, the direction of the external force is highly likely to be perpendicular to the surface of the tactile sensor.

When a force inclined from the z direction acts on a tactile sensor such as the first protrusion 1b, which has different lengths in the x and y directions, a reaction force of different magnitudes depending on the direction is generated from the insulator 11 to the magnetic material. Therefore, a tactile sensor such as the first protrusion 1b has high directional resolution.

(Operation of pressure sensor)
An example of a pressure sensor is the third convex portion 3. In the magnetostrictive material of the pressure sensor, the external pressure and the pressure in the space between the magnetostrictive material of the pressure sensor and the reference surface are generated in opposite directions. That is, a stress equivalent to the pressure difference between the external pressure and the pressure in the internal space acts on the magnetostrictive material of the pressure sensor, distorting the magnetostrictive material. Therefore, the impedance of the magnetostrictive material changes due to the stress impedance effect. By grasping the correlation between the impedance of the magnetostrictive material and pressure in advance and comparing it with the measured impedance, the pressure sensor can detect the external pressure. When the space between the magnetostrictive material of the pressure sensor and the reference surface is almost a vacuum, the pressure sensor operates as a barometer.

(Acoustic sensor operation)
An example of an acoustic sensor is the second convex portion 2. When the pressure outside the second convex portion 2 changes due to the action of acoustic waves, the magnetostrictive material vibrates, and a stress change acts on the second convex portion 2. The way in which the second convex portion 2 distorts changes with the change in stress. Therefore, the impedance of the second convex portion 2 changes due to the stress impedance effect. By measuring this change in impedance, the acoustic sensor can detect sound.

(Reading the sensor unit)
6 is a schematic diagram showing an example of a sensor signal processing circuit that reads out the sensor units 100. In this example, the sensor units 100 are arranged in a 3×3 matrix.

The sensor signal processing circuit has a drive circuit and a detection circuit. The drive circuit has drive wiring La1 to La3. Each of the drive wiring La1 to La3 is electrically connected to each of the sensors via a contact. The detection circuit has detection wiring Lb1 to Lb3. Each of the detection wiring Lb1 to Lb3 is electrically connected to each of the sensors via a contact that is not connected to the drive wiring La1 to La3.

The sensor signal processing circuit is connected to an AC power source (not shown). Such a sensor signal processing circuit can measure the impedance of each sensor.

Based on the above principles, the sensor unit 100 can detect external forces in various directions. The sensor unit 100 also has a continuous magnetostrictive film 10 with multiple protrusions 1a, 1b, 2, 3 that protrude in a first direction relative to a reference plane, allowing it to sense various sensations. For example, the sensor unit 100 is equipped with a tactile sensor, an acoustic sensor, and a pressure sensor, allowing it to sense various sensations.

When combining independent sensors that sense a single sensation and mounting them on a substrate, the manufacturing process can become complicated because the reading methods and sensor structures are different for each sensor. The sensor unit 100 of this embodiment can solve this problem.

The impedance of the magnetostrictive film is also correlated with temperature and an external magnetic field. Therefore, the sensor unit 100 according to this embodiment can sense the sensations of temperature and external magnetic fields by grasping in advance the correlation between impedance and temperature and the correlation between impedance and an external magnetic field. In other words, the sensor unit 100 according to this embodiment can also be equipped with a temperature sensor and a magnetic field sensor in addition to a tactile sensor, a pressure sensor, and an acoustic sensor.

<First Modification>
Next, a first modified example of the embodiment will be described.
Fig. 7(a) is a schematic plan view of a sensor unit according to a first modified example of the first embodiment. The sensor unit 101 according to the first modified example is different from the sensor unit 100 shown in Fig. 1 in that it is made up of a plurality of convex portions 1a and 1b. The sensor unit 101 may be made up of the same type of convex portions as long as it has a plurality of convex portions. The same components as those in the first embodiment are denoted by the same reference numerals and will not be described.

The sensor unit 101 is arranged such that the first convex portion 1a is surrounded by multiple first convex portions 1b. The multiple first convex portions 1b include those whose major axis direction is in the x direction and those whose major axis direction is in the y direction when viewed in a plan view from the z direction. The first convex portion 1b whose major axis direction is in the x direction and the first convex portion 1b whose major axis direction is in the y direction are arranged adjacent to each other.

The sensor unit 101 can achieve the same effect as the tactile sensor of the sensor unit 100. Furthermore, the sensor unit 101 can further improve the resolution and strength of the stress for each direction and position of the tactile sensor.

The type and arrangement of the multiple convex portions in the first modified example are not limited to the example shown in the figure. For example, the arrangement may be such that multiple second convex portions or third convex portions are lined up, or such that only multiple first convex portions 1a are lined up, or such that only multiple first convex portions 1b are lined up. In addition, the sensor unit may be arranged as shown in the schematic plan view of FIG. 7(b).

In the sensor unit 101' shown in FIG. 7(b), the first convex portions 1b are arranged repeatedly in parallel like a human fingerprint. Specifically, in the sensor unit 101', the multiple first convex portions 1b with the same longitudinal direction are aligned perpendicular to the longitudinal direction. For example, the longitudinal direction of the first convex portions 1b located in the region Ax is the y direction and they are arranged in parallel in the x direction, and the longitudinal direction of the first convex portions 1b located in the region Ay is the x direction and they are arranged in parallel in the y direction.

Even with sensor unit 101', the same effect as sensor unit 101 can be obtained. Furthermore, in area Ax, it is possible to improve sensitivity when the sliding direction is the x direction, and in area Ay, it is possible to improve sensitivity when the sliding direction is the y direction. Sensor unit 101' is not limited to the example shown in the figure. It may be configured such that the entire unit is area Ax, or may be the entire unit, or the first convex portion 1b may have a distorted shape such as a crescent shape.

<Second Modification>
Next, a second modification of the embodiment will be described.
Fig. 8 is a schematic plan view of a sensor unit according to a second modified example of the first embodiment. The sensor unit 102 according to the second modified example differs from the sensor unit 100 shown in Fig. 1 in that the second convex portion 2 and the third convex portion 3 are not adjacent to each other.

The sensor unit 102 has first convex portions 1a and 1b between the second convex portion 2 and the third convex portion 3. In addition, each of the second convex portion 2 and the third convex portion 3 is arranged so as to be surrounded by the first convex portion when viewed in a plan view from the z direction.

Sensor unit 102 provides the same effect as sensor unit 100. Compared to an arrangement such as sensor unit 100, sensor unit 102 provides the function of a tactile sensor evenly in the in-plane direction. Furthermore, sensor unit 102 has improved strength compared to sensor unit 100.

<Third Modification>
Next, a third modified example of the embodiment will be described.
Fig. 9 is a schematic cross-sectional view of a sensor unit according to a third modified example of the first embodiment. The sensor unit 103 according to the third modified example differs from the sensor unit 100 shown in Fig. 2 in that the circuit board 20A has a locally recessed structure.

In the sensor unit 103, the positions corresponding to the second convex portion 2A and the third convex portion 3A of the circuit board 20A are formed to be deeper than the reference plane RP. For example, the circuit board 20A has grooves 202 and 203. The grooves 202 and 203 overlap the second convex portion 2A and the third convex portion 3A, respectively, in a plan view from the z direction. Due to the groove 202, the height _hR2 of the space _R2 is higher than the height _h2 minus the thickness T of the magnetostrictive film 10. Similarly, the height _hR3 of the space _R3 is higher than the height _h3 minus the thickness T of the magnetostrictive film 10.

The shape of the grooves 202 and 203 is, for example, semicircular, rectangular, or polygonal when viewed in a plan view from the y direction.

The sensor unit 103 can achieve the same effect as the sensor unit 100. The heights h _R2 and h _R3 of the sensor unit 103 can be increased without increasing the heights h ₂ and h _3. In other words, the sensitivity of the acoustic sensor and pressure sensor can be increased while maintaining the strength of the sensor unit.

The position of the groove in the third modified example is not limited to the example shown in the figure. For example, groove 202 may be formed only at a position that overlaps second convex portion 2A in a plan view from the z direction, and groove 203 may be formed only at a position that overlaps third convex portion 3A.

[Method of manufacturing the sensor unit]
The sensor unit according to this embodiment is manufactured, for example, by the following method. Figures 10 and 11 are views for explaining the manufacturing method of the sensor unit according to this embodiment. Figure 10 shows the first half of the process of an example of the manufacturing method of the sensor unit according to this embodiment, and Figure 11 shows the second half of the process of an example of the manufacturing method of the sensor unit according to this embodiment. Note that the terms "first half" and "second half" of the manufacturing method are used here for convenience of explanation, and do not limit the invention.

The manufacturing method of the sensor unit according to this embodiment includes a magnetostrictive film forming process in which a magnetostrictive film is formed on a resist layer having multiple recesses, an adjustment process in which an insulating material is filled into the protrusions of the magnetostrictive film or through holes are formed according to the desired sensor, and an electrical connection process in which the circuit board and the magnetostrictive film are electrically connected.

As a more specific example, the method for manufacturing the sensor unit according to this embodiment includes a first step of forming a resist layer P on the substrate S, a second step of forming a plurality of recesses of a predetermined shape in the resist layer P, a third step of forming a magnetostrictive film 10' on the resist layer P, a fourth step of forming an insulating material PD at a predetermined position on the magnetostrictive film 10', a fifth step of forming a hole H penetrating the magnetostrictive film 10', a sixth step of removing unnecessary material in contact with the back surface 10b' of the magnetostrictive film 10', a seventh step of electrically connecting the circuit board 20' and the magnetostrictive film 10' via the contact C', and an eighth step of removing unnecessary material on the front surface 10a' of the magnetostrictive film 10'.

(First step)
First, a resist layer P is formed on an arbitrary substrate S by a known method. Figures 10(a) and 10(b) show the state before and the state after the first step, respectively. The resist layer P is, for example, a positive photoresist layer. The substrate S is, for example, a Si substrate having a thickness of 2 mm. The thickness of the resist layer P is, for example, 1000 μm. This substrate S and resist layer P are not included in the final sensor unit 100' because they are removed in the fifth step described later.

(Second step)
Next, a plurality of recesses having a predetermined shape are formed in the resist layer P. When a positive photoresist layer is formed as the resist layer P in the first step, a predetermined positive pattern is exposed and developed. For example, a pattern of a plurality of recesses is formed in the photoresist layer P by grayscale lithography. Fig. 10(c) shows the state after the second step.

The shape of the recesses formed in the second step corresponds to the shape of the protrusions of the magnetostrictive film in the completed sensor unit. The minimum width and depth of each recess in plan view from the z direction are designed, for example, as follows:
Part corresponding to the tactile sensor: minimum width 500 μm, depth 500 μm
Part corresponding to pressure sensor: diameter 1500 μm, depth 450 μm
Part corresponding to the acoustic sensor: diameter 1000 μm, depth 450 μm

(Third process)
Next, a magnetostrictive film 10' is formed on the resist layer P. The third step is performed by, for example, a sputtering method. FIG. 10(d) shows the state after the third step. Any magnetic material exhibiting a stress impedance effect is used as the magnetostrictive film 10', and it is preferable to use an amorphous magnetic alloy, and it is preferable to use a soft magnetic amorphous magnetic alloy. The magnetostrictive film 10' is, for example, Fe ₇₉ Si ₇ B _14. The thickness of the magnetostrictive film 10' is, for example, 1 μm. The magnetostrictive film 10' is formed by, for example, a sputtering method.

(Fourth step)
Next, the fourth step is performed. In the fourth step, an insulating material PD is formed in a region including at least one of the multiple protrusions of the magnetostrictive film 10'. The insulating material PD is formed, for example, so as to flatten the entire surface. FIG. 10(e) shows the state after the fourth step.
When manufacturing a sensor unit that does not include a tactile sensor, it is not necessary to form an insulating material on the convex portion of the magnetostrictive film 10'. As the insulating material PD, PDMS (polydimethylsiloxane) or the like is used.
The insulating material PD may be formed over the entire surface so that the magnetostrictive film 10' is not exposed, as shown in Fig. 10(e). In this case, the unnecessary portions of the insulating material PD are removed in a later process.

(Fifth step)
Next, a hole H' is formed penetrating the magnetostrictive film 10'.
10(e), when insulating material PD is formed over the entire surface so that magnetostrictive film 10' is not exposed in the fourth step, it is necessary to expose the portion of magnetostrictive film 10' where hole H' is to be formed in advance. Therefore, insulating material PD is removed at a predetermined position before etching to form groove PDH as shown in FIG.
The hole H' is formed by, for example, etching. The etching is performed by, for example, a technique of irradiating an ion beam. Fig. 11(a) is a diagram showing the state after the fifth step, and is the diagram following Fig. 10(f). Note that the hole H' formed in the fifth step becomes the hole H of the acoustic sensor. Therefore, when manufacturing a sensor unit that does not include an acoustic sensor, the fifth step is omitted.

(Sixth step)
Next, unnecessary material in contact with the rear surface 10b' of the magnetostrictive film 10' is removed. Fig. 11(b) shows the state after the sixth step. The unnecessary material is, for example, the insulating material PD filled in the convex portion that will become a pressure sensor or an acoustic sensor, and the insulating material PD present at the position where the contact C' is to be formed. A space PDCH is formed at the position where the contact C' is to be formed. The sixth step is performed by a known method such as plasma etching.

(Seventh step)
Next, the circuit board and the magnetostrictive film 10' are electrically connected via the contacts C'. Fig. 11(c) shows the state in which the circuit board 20' having the contacts C' is prepared. Fig. 11(d) shows the state after the seventh step. The contacts C' are disposed between each of the multiple protrusions.
When a sensor unit having a locally recessed circuit board such as the sensor unit 103 is used, a locally recessed circuit board is used in the seventh step.

(Step 8)
Next, unnecessary material on the surface 10a' of the magnetostrictive film 10' is removed. The unnecessary material is, for example, the resist layer P and the substrate S deposited on the surface 10a'. Fig. 11(e) shows the state after the eighth step has been performed. The eighth step uses, for example, a lift-off process.

Using this method, the sensor unit 100' shown in FIG. 11(f) is manufactured.

[Application example]
Fig. 12 is a schematic diagram of a robot arm according to an application example. In the robot arm shown in Fig. 12, a sensor unit is mounted on the surface of the hand or arm. The robot arm and a circuit board 20' are in contact with each other, and the sensor unit is disposed so that the surface 10a is exposed.

The density of tactile sensory points on human skin is about 30 per ^cm2 . Therefore, in order to obtain a sensation equal to or greater than that of a human with a robot arm, it is preferable to set the density of the first convex portions 1a, 1b in the sensor unit equal to or greater than the tactile sensory points on human skin. To achieve this, as described above, it is preferable to set the minimum width of the first points 1a, 1b in plan view from the z direction to 1 mm or less.

The part where the sensor unit is mounted is not limited to the example shown in the figure. The type and arrangement of the sensor in the sensor unit can be appropriately selected depending on the part where it is mounted. For example, the density of tactile sensors on the fingertip can be made higher than other parts, or a temperature sensor can be provided depending on the application. The sensor unit according to this embodiment can also be mounted on an uneven surface.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to specific embodiments and modifications, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims.

1a: First protrusion (tactile sensor)
2: Second protrusion (acoustic sensor)
3: Third protrusion (pressure sensor)
10: Magnetostrictive film 10a: Surface of magnetostrictive film 10b: Back surface of magnetostrictive film 11: Insulator 20: Substrate 100, 101, 102: Sensor unit C: Contact

Claims (11)

a continuous magnetostrictive film having a plurality of protruding portions protruding in a first direction perpendicular to a reference plane ; and contacts disposed on both ends of each of the plurality of protruding portions,
a sensor signal processing circuit connected to the contact and configured to measure at least one impedance of each of the plurality of protrusions;
The sensor unit, wherein each of the plurality of protrusions is a sensor. The sensor unit according to claim 1, further comprising an insulator filled between the back surface of the magnetostrictive film and the reference surface in at least one of the plurality of convex portions. The sensor unit according to claim 2, wherein the protrusion having the insulator has a minimum width of 1 mm or less when viewed in a plan view from the first direction. The sensor unit according to claim 2 or 3, wherein at least one of the convex portions having the insulator has a length in a second direction along the reference surface that is different from a length in a third direction that is a direction along the reference surface and perpendicular to the second direction. The sensor unit according to any one of claims 1 to 4, wherein at least one of the plurality of protrusions has a space between the rear surface of the magnetostrictive film and the reference surface. The sensor unit according to claim 5, wherein at least one of the plurality of protrusions has a hole penetrating the magnetostrictive film. Among the plurality of protrusions, a protrusion having an insulator filled between the rear surface of the magnetostrictive film and the reference surface is defined as a first protrusion,
Among the plurality of protrusions, a protrusion having a space between the back surface of the magnetostrictive film and the reference surface and having a hole penetrating the magnetostrictive film is defined as a second protrusion,
Among the plurality of protrusions, a protrusion having a space between the rear surface of the magnetostrictive film and the reference surface and having no hole penetrating the magnetostrictive film is defined as a third protrusion,
7. The sensor unit according to claim 1, wherein a height of the first convex portion in the first direction is greater than heights of the second convex portion and the third convex portion in the first direction. The sensor unit according to any one of claims 1 to 7, wherein the magnetostrictive film is an amorphous material. The sensor unit according to any one of claims 1 to 8, further comprising a circuit board forming at least a part of the reference surface. The sensor unit according to claim 9 , wherein the circuit board has a Young's modulus of 3 GPa or less. a magnetostrictive film having a protrusion protruding in a first direction perpendicular to a reference plane , and contacts disposed on both ends of the protrusion;
The sensor includes a sensor signal processing circuit connected to the contact and measuring an impedance of the protrusion .

Images