Sensor Unit

Abstract

To provide a sensor unit that can be suitably attached to the object to be detected.SOLUTION: A sensor unit 1 pertaining to the present invention comprises a base member 5, a linear sensor 2 that is disposed in contact with the underside of the base member 5 and that detects vibration, a counter member 4 that is disposed facing the base member 5 across the linear sensor 2, and a cover member 3 that has a top plate 31 that covers the top face of the base member 5. The base member 5 has a first base through-hole 55 that penetrates in the vertical direction. The counter member 4 has a counter through-hole 401 that penetrates in the vertical direction, at a position facing the first base through-hole 55. The cover member 3 has a cylindrical part 33 that is inserted into the first base through-hole 55 and extends to a height position at which the lower end touches a member located below.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a sensor unit having a linear sensor. [Background technology]

[0002] A linear sensor is known that uses an internal conductor, a piezoelectric body provided in contact with the outer peripheral surface of the internal conductor, and an external conductor provided in contact with the outer peripheral surface of the piezoelectric body as a sensor wire (see, for example, Patent Document 1). This linear sensor has the property that the piezoelectric body is deformed when an external load is applied, and a voltage is induced between the internal conductor and the external conductor. Utilizing this property, it is being considered to use the linear sensor as a pressure sensor for detecting pressure or a vibration sensor for detecting vibration. It is also being considered to configure a linear sensor using a resistance wire such as conductive rubber or a capacitor wire as the sensor wire instead of a sensor wire using a piezoelectric body.

[0003] This linear sensor has been used to detect vibrations on objects such as machine tools, robots, agricultural machinery, vehicles, and home appliances, as well as on their components. The collected and analyzed vibration data can be used to predict failures and improve work efficiency. However, when a linear sensor is attached to an object with tape to detect vibrations, the force of the linear sensor pressing against the object is weak, resulting in a low transmission rate of vibrations generated by the object to the linear sensor. Furthermore, when the linear sensor is attached to multiple locations along its length with multiple fasteners, such as screws or clips, to increase the pressing force, variations in the fastening forces of the fasteners are directly reflected in the detection results, making accurate measurement difficult. Furthermore, the portions of the linear sensor that are far from the fasteners do not exert a pressing force on the object, making it difficult to detect vibrations from the object. As a countermeasure against these problems, it has been proposed to attach a linear sensor to a support having a base member with higher rigidity than the linear sensor to form a sensor unit, and to press the linear sensor against the object to be detected using the support, thereby increasing the detection sensitivity of the linear sensor (see, for example, Patent Document 2, etc.). Patent Document 2 discloses a sensor unit that attaches the sensor unit to the object to be detected by inserting a screw into a through-hole formed in the sensor unit, and a sensor unit that attaches the sensor unit to the object to be detected by using the screw, and a sensor unit that has a magnet placed inside the sensor unit and uses magnetic force to attach the sensor unit to the object to be detected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2019 / 117037 [Patent Document 2] Patent Publication No. 2021-124506 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when attempting to firmly attach the sensor unit to the object to be detected using screws, a fastening force of tens of thousands to hundreds of thousands of newtons may be applied to the sensor unit, and this fastening force may be applied to the linear sensor, causing it to be crushed too much. If the linear sensor is crushed too much, the sensitivity of the linear sensor will decrease, and in the worst case, the linear sensor may be damaged. Furthermore, it is desirable to attach the sensor unit to the object to be detected in a suitable manner, not just using screws.

[0006] SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a sensor unit that can be suitably attached to an object to be detected. [Means for solving the problem]

[0007] The sensor unit of the present invention that solves the above problems comprises: A base member; a linear sensor disposed in contact with the lower surface of the base member and detecting vibrations; an opposing member disposed opposite the base member with the linear sensor interposed therebetween; a cover member having a top plate portion that covers an upper surface of the base member, The base member has a first base through-hole that penetrates in the vertical direction, the opposing member has an opposing through-hole penetrating in the up-down direction at a position opposing the first base through-hole, The cover member is characterized by having a cylindrical portion that is inserted into the first base through-hole and extends to a height position where its lower end contacts a member positioned below.

[0008] With this sensor unit, the cylindrical portion receives the fastening force of the screw, thereby substantially preventing that fastening force from acting on the linear sensor, so that the linear sensor is not crushed too much and the sensor unit can be suitably attached to the object to be detected.

[0009] Here, the cylindrical portion may have a hollow portion (cylindrical bore) inside for passing a screw that attaches the sensor unit to the object to be detected. The cylindrical portion may also receive a fastening force from the screw by contacting the underside of the screw seat or the underside of the screw head with its upper surface. Additionally, the base member and the linear sensor may be sandwiched between the cover member and the opposing member.

[0010] In this sensor unit, The cylindrical portion may have a lower end that contacts the opposing member.

[0011] According to this aspect, the fastening force applied to the cover member can be received by the cylindrical portion via the opposing member.

[0012] In this sensor unit, The cylindrical portion may be inserted into the opposing through-hole and extend to a lower surface of the opposing member.

[0013] According to this aspect, the fastening force applied to the cover member can be received by the cylindrical portion.

[0014] In addition, in this sensor unit, the cover member has a peripheral wall portion hanging down from a peripheral edge portion of the top plate portion, The peripheral wall portion may extend to the lower surface of the opposing member.

[0015] Since the fastening force applied to the cover member can be received not only by the cylindrical portion but also by the peripheral wall portion, the fastening force can be more reliably prevented from being transmitted to the linear sensor.

[0016] In addition, in this sensor unit, the cover member has a peripheral wall portion hanging down from a peripheral edge portion of the top plate portion, The opposing member has a disk-shaped portion and a lateral protrusion protruding laterally from the disk portion, The peripheral wall may have a peripheral wall notch into which the lateral protrusion is inserted.

[0017] When the rotational force of the tightening screw is applied to the cover member, the rotational force is also transmitted to the base member, while the opposing member is difficult to rotate due to the frictional force between the base member and the object to be detected. This causes relative rotation between the base member and the opposing member, which could twist and damage the linear sensor. According to this aspect, because the lateral protrusions are inserted into the peripheral wall notches, when the cover member rotates, the opposing member also rotates, preventing relative rotation between the base member and the opposing member. This prevents the linear sensor from being damaged by rotation of the screw used to attach the sensor unit to the object to be detected.

[0018] In addition, in this sensor unit, The base member has a base protrusion that protrudes downward, The opposing member may have a first opposing recess into which the base protrusion is inserted.

[0019] The base convex portion and the first opposing concave portion prevent relative rotation from occurring between the base member and the opposing member, thereby preventing the linear sensor from being damaged by rotation of the screw used to attach the sensor unit to the object to be detected.

[0020] In addition, in this sensor unit, The base member has a second base through-hole that penetrates in the vertical direction, the top plate portion has a top plate recess at a position facing the second base through hole, the opposing member has a second opposing recess at a position opposing the second base through-hole, The base may include a shaft member that passes through the second base through-hole, has an upper end inserted into the top plate recess, and has a lower end inserted into the second opposing recess.

[0021] With this configuration, the shaft member prevents relative rotation between the cover member, the base member, and the opposing member, thereby preventing the linear sensor from being damaged by rotation of the screw used to attach the sensor unit to the object to be detected. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a sensor unit that can be suitably attached to an object to be detected. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a cross-sectional view showing the structure of a linear sensor according to an embodiment of the present invention. [Figure 2] FIG. 1A is a plan view of the sensor unit of this embodiment, and FIG. 1B is a front view of the sensor unit shown in FIG. [Figure 3] 3(a) is a bottom view of the sensor unit shown in FIG. 2, and (b) is a bottom view showing the sensor unit shown in FIG. 3(a) with the opposing member removed. [Figure 4] FIG. 3 is a plan view of the sensor unit shown in FIG. 2(a) seen through a cover member. [Figure 5] FIG. 2(b) is a cross-sectional view taken along the line AA in FIG. [Figure 6] FIG. 2 is a block diagram showing the configuration of a circuit board. [Figure 7] FIG. 3 is an attachment diagram showing an example of a state in which the sensor unit shown in FIG. 2(a) is attached to a detection object by a fixture. [Figure 8] FIG. 6 is a cross-sectional view similar to FIG. 5, showing a sensor unit according to a first modified example. [Figure 9] FIG. 6 is a cross-sectional view similar to FIG. 5, showing a sensor unit according to a second modified example. [Figure 10] FIG. 6 is a cross-sectional view similar to FIG. 5, showing a sensor unit according to a third modified example. [Figure 11] FIG. 10 is a cross-sectional view similar to FIG. 5, showing a sensor unit according to a fourth modified example. [Figure 12] FIG. 10 is a cross-sectional view similar to FIG. 5, showing a sensor unit according to a fifth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The sensor unit of this embodiment is mainly used to detect vibration waves propagating on the surface of a detection object. First, a linear sensor used in the sensor unit of this embodiment will be described.

[0025] FIG. 1 is a cross-sectional view showing the structure of the linear sensor of this embodiment.

[0026] As shown in Fig. 1, the linear sensor 2 includes a sensor wire 20, an inner sheath 24, a shield coating 25, and an outer sheath 26. The sensor wire 20 is composed of an inner conductor 21, a piezoelectric element 22, and an outer conductor 23. The inner conductor 21 is disposed at the center of the linear sensor 2 and is composed of seven conductor wires 211. The piezoelectric element 22 is disposed on the outer periphery of the inner conductor 21. The outer conductor 23 is disposed on the outer periphery of the piezoelectric element 22.

[0027] Each of the seven conductor wires 211 has a diameter of 50 μm, of which four are stainless steel conductor wires 211S and the remaining three are copper conductor wires 211C. In FIG. 1, the stainless steel conductor wires 211S are indicated by hatching slanting downward to the left, and the copper conductor wires 211C are indicated by hatching slanting downward to the right. In the internal conductor 21 shown in FIG. 1, the conductor wire arranged in the center is a stainless steel conductor wire 211S, and the conductor wires arranged on the periphery are alternately made of stainless steel conductor wires 211S and copper conductor wires 211C. The copper conductor wire 211C has lower electrical resistance and is softer than the stainless steel conductor wire 211S. Conversely, the stainless steel conductor wire 211S has higher electrical resistance but higher mechanical strength (e.g., tensile strength) and rigidity than the copper conductor wire 211C.

[0028] The seven conductor wires 211 are arranged at the vertices of a regular hexagon and at the center of the regular hexagon. These seven conductor wires 211 are twisted together. That is, the internal conductor 21 is formed by twisting the seven conductor wires 211 together after arranging them in a close-packed structure in their cross sections. In this case, the maximum thickness of the internal conductor 21 is 150 μm. By twisting the multiple conductor wires 211 in this manner with a loose twist or a medium twist, loosening in the direction opposite to the twisting direction is permitted, thereby providing flexibility to the linear sensor 2.

[0029] The diameter of the conductor wire 211 is not limited to 50 μm, but may be 8 μm or more and 130 μm or less, and is preferably 8 μm or more and 100 μm or less. The thinner the conductor wire 211, the higher the flexibility but the lower the strength and rigidity, and the thicker the conductor wire 211, the lower the flexibility but the higher the strength and rigidity. If the diameter of the conductor wire 211 is 20 μm or more, it can be manufactured at low cost and easily. Furthermore, the inner conductor 21 may be formed by twisting together conductor wires 211 of different diameters.

[0030] Although the inner conductor 21 shown in FIG. 1 is formed by twisting seven conductor wires 211, the number does not have to be seven. Twisting multiple conductor wires 211 together can increase the flexibility of the linear sensor 2. Alternatively, for example, multiple bundles of twisted conductor wires may be prepared and further twisted together. For example, seven bundles of twisted seven thin conductor wires 211 may be prepared and further twisted together. Twisting the conductor wires in multiple stages increases the flexibility of the linear sensor 2, making it more likely to deform in response to vibrations or other forces applied to the linear sensor 2. As a result, the detection sensitivity of the linear sensor 2 can be improved. When multiple twisting processes are performed, such as when twisting in multiple stages, the twisting directions may be different. Alternatively, multiple conductor wires 211 may be bundled in a straight line without being twisted. Furthermore, these configurations may be combined, for example, by twisting together a bundle of multiple untwisted conductor wires 211 and multiple twisted conductor wires 211. Even in these cases, by applying a piezoelectric material, the multiple conductor wires 211 are bonded and bundled together, and a single piezoelectric fiber can be produced.

[0031] In the sensor wire 20 described above, multiple types of conductor wires with different mechanical strengths and electrical resistances are used as the conductor wires 211 constituting the internal conductor 21. However, to further increase flexibility or further decrease electrical resistance, the central conductor wire 211 may be replaced with a copper conductor wire 211C, or all seven conductor wires 211 may be copper conductor wires 211C. Conversely, to further increase mechanical strength and rigidity, all seven conductor wires 211 may be stainless steel conductor wires 211S. Furthermore, instead of the stainless steel conductor wire 211S, a conductor wire made of tungsten, high-tensile steel such as tungsten or its alloy, or ultra-high-tensile steel may be used. Instead of the copper conductor wire 211C, a conductor wire made of titanium, titanium alloy, magnesium, magnesium alloy, or the like may be used. Furthermore, a conductor wire containing carbon nanotubes or a conductor wire containing pitch-based carbon fiber may be used. Alternatively, a conductor wire made of spring steel that is easily elastically deformed may be used.

[0032] The piezoelectric body 22 is formed by applying a piezoelectric material such as polyvinylidene fluoride (PVDF) to the internal conductor 21. Polyvinylidene fluoride is a lightweight polymer material that generates a piezoelectric effect, and has the property of generating voltage when pressure is applied to it, and generating distortion when voltage is applied. The piezoelectric body 22 has been subjected to polarization treatment, and when deformation occurs in the piezoelectric body 22 due to vibration or the like, a voltage is induced between the internal conductor 21 and the external conductor 23.

[0033] 1, examples of the piezoelectric material constituting the piezoelectric body 22 include, in addition to polyvinylidene fluoride, trifluoroethylene (TrEF), a mixed crystal material of PVDF and TrEF, and polymeric materials having a dipole moment, such as polylactic acid, polyuric acid, and polyamino acid. The piezoelectric material may be applied by immersion coating, spray coating, brush coating, or application using a coating device such as a coater. The piezoelectric material is not limited to a coating configuration, and may be, for example, a configuration in which a strip-shaped PVDF film is spirally wound around the internal conductor 21.

[0034] The thickness of the piezoelectric body 22 is preferably equal to or greater than the diameter of the conductor wire 211. The thickness of the piezoelectric body 22 shown in FIG. 1 is 75 μm at its thinnest point, but is preferably 10 μm to 150 μm. The thicker the piezoelectric body 22, the better the detection sensitivity, but the limit of the thickness of the piezoelectric body 22 is determined by the viscosity of the applied piezoelectric material and the application method. Also, if the thickness of the piezoelectric body 22 is too thick, the linear sensor 2 becomes too hard and lacks flexibility, which is a drawback.

[0035] 1, multiple conductor wires 211 are twisted together, resulting in depressions at the boundaries between the conductor wires 211. These depressions can support more piezoelectric material, making the volume of the piezoelectric material larger (thicker), and therefore improving detection sensitivity compared to other areas. These depressions create six areas in the circumferential direction where the piezoelectric material is thicker than other areas, evenly spaced apart, which is why the internal conductor 21 functions as a highly sensitive piezoelectric fiber regardless of the direction in which it is bent.

[0036] While adjacent conductor wires 211 shown in FIG. 1 are almost in contact with each other, the piezoelectric material penetrates through small gaps due to capillary action, filling the gaps between adjacent conductor wires 211 (inside the internal conductors 21). However, depending on the viscosity of the piezoelectric material and the application method, the piezoelectric material may not penetrate into the gaps between adjacent conductor wires 211. Even in this case, it is sufficient that the piezoelectric material is supported on the portion facing the outer periphery of the internal conductor 21. Note that in a configuration using the strip-shaped PVDF film described above as the piezoelectric body 22, the linear sensor 2 has no piezoelectric material penetrating into the gaps between adjacent conductor wires 211. This linear sensor 2 has greater flexibility than one in which the piezoelectric material penetrates into the gaps between adjacent conductor wires 211, thereby improving the detection sensitivity of the linear sensor 2.

[0037] The external conductor 23 shown in FIG. 1 is formed by applying a polymeric conductive material containing carbon, such as carbon nanotubes, to the outer periphery of the piezoelectric body 22. The conductive material forming the external conductor 23 may be a polymeric conductive material containing silver particles, silver paste, or the like. The conductive material may be applied by immersion coating, spray coating, brush coating, or application using a coating device such as a coater. The thickness of the external conductor 23 is preferably equal to or less than the diameter of the conductor wire 211 and is also preferably equal to or less than the thickness of the piezoelectric body 22. The thickness of the external conductor 23 shown in FIG. 1 is 30 μm, but is preferably equal to or greater than 5 μm and equal to or less than 80 μm. Alternatively, a conductive wire may be used for the external conductor 23 without using a conductive material.

[0038] The inner sheath 24 covers the outer periphery of the outer conductor 23 to improve abrasion resistance, chemical resistance, and rust prevention. The inner sheath 24 is formed to a thickness of 30 μm. The inner sheath 24 is made of a material that is softer than the outer sheath 26. The inner sheath 24 is formed by applying a polyamide synthetic resin, but it may also be formed by applying a polyvinyl chloride resin.

[0039] The shield coating 25 is a tubular shield made by braiding thin wires made of a metal such as nickel-plated copper or stainless steel. The shield coating 25 may be formed by depositing copper, aluminum, or the like on the inner sheath 24, which contains the inner conductor 21, the piezoelectric element 22, and the outer conductor 23. The shield coating 25 may also be attached to the inner sheath 24 by other methods such as sputtering, electron beam deposition (EBD), chemical vapor deposition (CVD), coating, dipping, electroless plating, or bonding with an adhesive, or may be formed by wrapping a metal foil around the inner sheath 24.

[0040] The outer sheath 26 is made of a material that is more abrasion-resistant than the inner sheath 24. The outer sheath 26 is formed by coating with polytetrafluoroethylene (PTFE). However, it may also be formed by coating with tetrafluoro-hexafluoropropylene resin (FEP), tetrafluoroethylene ethylene copolymer (EPFE), or tetrafluoroethylene perfluoroalkoxyethylene copolymer fluororesin (PFA). The coating here may be by immersion coating, spray coating, brush coating, or application using a coating device such as a coater. It is preferable to apply the coating multiple times to prevent pinholes from forming. Additionally, the outer sheath 26 may be thicker than the inner sheath 24. Furthermore, while the inner sheath 24 may be made of a flammable material, the outer sheath 26 is preferably made of a flame-retardant, non-flammable, or flame-resistant material.

[0041] The diameter of the linear sensor 2 shown in Fig. 1 is 0.5 mm. However, the diameter of the linear sensor 2 may be larger or smaller, and is preferably 0.1 mm or more and 3.0 mm or less.

[0042] FIG. 2(a) is a plan view of the sensor unit of the embodiment, FIG. 2(b) is a front view of the sensor unit shown in FIG. 2(a), and FIG. 3(a) is a bottom view of the sensor unit shown in FIG. 2(a). FIG. 2(b) is a view showing the basic posture of the sensor unit 1, and the following description will be based on the up-down direction in this basic posture. Note that the sensor unit 1 may be attached to the object to be detected in an attachment posture different from the basic posture, in which case the up-down direction will be the direction corresponding to the attachment posture. For example, if the sensor unit 1 is attached to the object to be detected in a posture inverted 180 degrees from the basic posture, the up-down direction in the attachment posture will be reversed compared to the basic posture.

[0043] As shown in FIGS. 2(a) and 2(b), the sensor unit 1 has a hollow cylindrical shape with a height of 7.4 mm and a diameter of 25 mm. The center of the sensor unit 1 is provided with a cylindrical bore 331 formed by a cylindrical portion 33 (see FIG. 3(b)), which will be described later. This cylindrical bore 331 has a diameter of 6.2 mm. Sensor units 1 of any size can be used depending on the conditions of use, etc. The sensor unit 1 includes the linear sensor 2 described above, a cover member 3, an opposing member 4, a base member 5, a circuit board 7, and a signal cable 8. When the sensor unit 1 is attached to the object to be detected, the bottom side of FIG. 2(b) faces the object to be detected. Both ends of the linear sensor 2 are on the top surface of the base member 5, but the majority of the linear sensor 2 is on the bottom surface of the base member 5 and is disposed in contact with the bottom surface of the base member 5. The arrangement of the linear sensor 2 will be described later.

[0044] As shown in FIG. 2(b), the cover member 3 is made of stainless steel and includes a top plate portion 31, a peripheral wall portion 32, and a cylindrical portion 33 (see FIG. 3(b)) integrally formed therewith. However, the cover member 3 may be made of a metal other than stainless steel, or may be made of resin. The top plate portion 31 covers the upper surface of the base member 5. In FIG. 2(b), the base member 5 is drawn slightly smaller so that the inner surface of the cover member 3 and the base member 5 can be distinguished from each other. However, in reality, the lower surface of the top plate portion 31 is in contact with the upper surface of the base member 5. The base member 5 and the linear sensor 2 on the lower surface of the base member 5 are fixed by being sandwiched between the top plate portion 31 and the opposing member 4. There is only a small gap between the side surface of the base member 5 and the inner surface of the peripheral wall portion 32.

[0045] The top plate 31 is disk-shaped. This top plate 31 forms the upper surface of the sensor unit 1. The peripheral wall 32 hangs down from the peripheral edge of the top plate 31. Furthermore, the cylindrical portion 33 (see FIG. 3(b)) extends in the vertical direction in the central portion of the top plate 31. The top plate 31, the peripheral wall 32, and the cylindrical portion 33 form a storage space that is open downward. That is, the storage space is defined by the underside of the top plate 31, the inner peripheral surface of the peripheral wall 32, and the outer peripheral wall of the cylindrical portion 33. The linear sensor 2, the upper portion of the opposing member 4, the base member 5, and the circuit board 7 are housed in this storage space.

[0046] The peripheral wall 32 is formed with two first peripheral wall cutouts 321 recessed upward from the lower end. FIG. 2(b) shows one of the two first peripheral wall cutouts 321. The other first peripheral wall cutout 321 is formed at a position 180 degrees apart in the circumferential direction of the peripheral wall 32. These first peripheral wall cutouts 321 correspond to an example of a peripheral wall cutout. The two first peripheral wall cutouts 321 have the same shape, and their upper ends are located higher than the upper surface of the opposing member 4. The peripheral wall 32 is composed of a thick portion 32a and a thin portion 32b at the lower end, and a peripheral wall abutment portion 322 is formed at the boundary between the thick portion 32a and the thin portion 32b. 3(a), the peripheral wall 32 is formed with a second peripheral wall notch 323 that is recessed upward from the lower end and through which the signal cable 8 passes. The upper end of the second peripheral wall notch 323 is higher than the upper end of the first peripheral wall notch 321. The peripheral wall abutment portion 322 shown in FIG. 2(b) is formed around the entire periphery of the peripheral wall 32 except for the portions where the first peripheral wall notch 321 and the second peripheral wall notch 323 are formed.

[0047] As shown in FIG. 2(b), the opposing member 4 is a plate-like member that is disposed at the lower end of the sensor unit 1, facing the base member 5 across the linear sensor 2, and closes the opening of the storage space formed by the cover member 3. This opposing member 4 is made of aluminum with a plate thickness of 1.0 mm. The opposing member 4 may also be made of other metals or resins. The plate thickness may be any thickness depending on the material, etc.

[0048] As shown in Fig. 3(a), the opposing member 4 has a disk portion 40 having an opposing through-hole 401 penetrating vertically in the center portion, and two lateral protrusions 41 protruding laterally from the disk portion 40. The opposing through-hole 401 is formed at a position opposing the cylindrical inner hole 331 (see Fig. 2(a)) and a first base through-hole 55 (see Fig. 3(b)) described below, and is connected to the cylindrical inner hole 331. The opposing through-hole 401 has the same diameter as the cylindrical inner hole 331. The cylindrical inner hole 331 and the opposing through-hole 401 form a hole penetrating vertically in the center portion of the sensor unit 1.

[0049] The outer diameter of the disk portion 40 is slightly larger than the inner diameter of the thin-walled portion 32b of the peripheral wall portion 32. The disk portion 40 is inserted into the thin-walled portion 32b of the peripheral wall portion 32. That is, the disk portion 40 is press-fitted into the thin-walled portion 32b. As shown in FIG. 2(b), the peripheral edge of the disk portion 40 contacts the peripheral wall abutment portion 322. This prevents the opposing member 4 from moving further upward. The peripheral wall portion 32 extends to a position slightly above the lower surface of the opposing member 4. In other words, the opposing member 4 protrudes downward from the lower end of the peripheral wall portion 32. This protrusion is approximately 0.1 to 0.2 mm, but is exaggerated in FIG. 2(b) for clarity. It is preferable that the peripheral wall portion 32 extend downward from the upper surface of the opposing member 4, and it is also preferable that the lower surface of the peripheral wall portion 32 be positioned above the lower surface of the opposing member 4. That is, it is more preferable that the lower surface of the peripheral wall portion 32 is within the thickness range of the opposing member 4. The peripheral wall portion 32 may extend downward below the opposing member 4. However, compared to when the peripheral wall portion 32 protrudes downward beyond the opposing member 4, when the opposing member 4 protrudes downward beyond the peripheral wall portion 32, the linear sensor 2 is more likely to deform in response to vibration of the object to be detected, thereby increasing the detection sensitivity of the sensor unit 1. Furthermore, the thin portion 32b of the peripheral wall portion 32 may face the opposing member 4 with a gap between it and the side surface of the opposing member 4, but it is preferable that the gap be as small as possible, and it is more preferable that the thin portion 32b contacts the side surface of the opposing member 4.

[0050] The width of the lateral protrusion 41 is slightly smaller than the inner width of the first peripheral wall notch 321. The lateral protrusion 41 is inserted into the first peripheral wall notch 321. This prevents the cover member 3 and the opposing member 4 from rotating relative to each other in the circumferential direction of the sensor unit 1. The first peripheral wall notch 321 is cut out above the upper surface of the lateral protrusion 41. When disassembling the sensor unit 1 for maintenance or the like, the cover member 3 and the opposing member 4 can be separated by inserting a plate-shaped member formed on the tip of a tool such as a flat-head screwdriver into the first peripheral wall notch 321 and twisting the tool. The lateral protrusion 41 increases the hook length of the tip of the tool during the separation operation, thereby improving the ease of separation.

[0051] FIG. 3(b) is a bottom view showing the sensor unit shown in FIG. 3(a) with the opposing member removed.

[0052] As shown in FIG. 3(b), the base member 5 is made of resin and has a generally hollow cylindrical shape. A first base through-hole 55 is formed in the center, penetrating the base member 5 in the vertical direction. The first base through-hole 55 has a diameter slightly larger than the outer diameter of the cylindrical portion 33. The cylindrical portion 33 is inserted into the first base through-hole 55. The outer diameter of the base member 5 is slightly smaller than the inner diameter of the thick portion 32a of the peripheral wall portion 32. A spiral groove 56 is formed on the underside of the base member 5. The spiral groove 56 is formed in a spiral shape, with approximately four turns. More precisely, the spiral groove 56 is formed slightly longer than four turns. Two extraction holes 52 are formed at both ends of the spiral groove 56, penetrating the base member 5 in the vertical direction, on the inner and outer peripheries, respectively. The linear sensor 2 extends along the spiral groove 56. One end of the linear sensor 2 penetrates an extraction hole 52 formed on the outer periphery of the base member 5 and reaches the upper surface of the base member 5, while the other end of the linear sensor 2 penetrates an extraction hole 52 formed on the inner periphery of the base member 5 and reaches the upper surface of the base member 5. The portion of the spiral groove 56 closest to the extraction hole 52 is curved upward in a side view to prevent the linear sensor 2 from bending abruptly. A portion of the linear sensor 2 in this curved portion does not contact the opposing member 4. By forming the spiral groove 56 longer than four times to account for this non-contact length, the functional portion of the linear sensor 2 located on the underside of the base member 5 is designed to have four revolutions. The number of revolutions of the linear sensor 2 is not limited to four, but is preferably a multiple of 0.5 revolutions. A multiple of 0.5 revolutions allows vibrations transmitted from any radial direction of the sensor unit 1 to be detected under the same conditions. This eliminates the directivity of the detection direction of the linear sensor 2.

[0053] FIG. 4 is a plan view of the sensor unit shown in FIG. 2(a) seen through the cover member.

[0054] As shown in FIG. 4, a base top recess 51 is formed on the top surface of the base member 5, defining a space in which both ends of the linear sensor 2, the circuit board 7, one end of the signal cable 8, and the like are disposed. Two lead-out holes 52 penetrating in the vertical direction are connected to the base top recess 51. Both ends of the linear sensor 2 passing through these lead-out holes 52 are connected to input-side terminal members 27 disposed in the base top recess 51. The input-side terminal members 27 are so-called flexible printed wiring boards in the form of a film that is folded to enclose both ends of the linear sensor 2 and overlapped. The internal conductor 21, external conductor 23, and shield coating 25 of the linear sensor 2 shown in FIG. 1 are each individually connected to the input-side terminal member 27 by soldering. The input-side terminal member 27 is connected to the circuit board 7.

[0055] The base upper surface recess 51 has a cable guide portion 51a extending to the outer peripheral edge of the base member 5. One end portion of the signal cable 8 is fitted into the cable guide portion 51a. The cable guide portion 51a has multiple protrusions formed thereon that protrude toward the center in the groove width direction. The signal cable 8 is sandwiched between these protrusions, thereby preventing the signal cable 8 from moving in the longitudinal direction and also preventing the signal cable 8 from slipping out of the cable guide portion 51a. In addition, two base cutouts 53 are formed on the peripheral edge portion of the base member 5 at positions spaced circumferentially apart and rotated 180 degrees. These base cutouts 53 are formed in positions facing the first peripheral wall cutout 321 (see FIG. 2(b)). The base cutouts 53 are bottomed cutouts that are recessed in a direction away from the first peripheral wall cutout 321 and are open upward and to the sides. During maintenance, etc., the cover member 3 (see FIG. 2) and the base member 5 can be separated by inserting a plate-shaped member formed on a tool such as a flat-head screwdriver into this base cutout 53 through the first peripheral wall cutout 321 and twisting the tool. However, the base cutout 53 may be omitted. When disassembling the sensor unit 1 during maintenance, etc., a two-stage operation is performed: first, the opposing member 4 is removed from the cover member 3, and then the base member 5 is separated from the cover member 3 as described above. It is possible to simultaneously remove both the opposing member 4 and the base member 5 from the cover member 3 by inserting a tool into the base cutout 53 and twisting it while the opposing member 4 is press-fitted into the cover member 3; however, it is preferable to remove them in two stages to avoid the risk of crushing the linear sensor 2.

[0056] The circuit board 7 is disposed in the base upper surface recess 51. Various electronic components are mounted on this circuit board 7. A wiring pattern is formed on the upper surface of the circuit board 7, and a ground pattern is formed on the lower surface. The configuration of the circuit board 7 will be described in detail later.

[0057] The signal cable 8 contains a signal line, a signal ground line, a ground line, and a power line, and is covered on the outside with a protective tube. The signal cable 8 transmits signals obtained by the linear sensor 2 and conditioned by the circuit board 7 to external devices. One end of the signal cable 8 is connected to an output terminal member 81 located in the base upper surface recess 51. The output terminal member 81 is similar to the input terminal member 27 and is a film-like flexible printed wiring board that is folded to enclose one end of the signal cable 8 and overlapped. The signal line, signal ground line, ground line, and power line of the signal cable 8 are each individually connected to the output terminal member 81 by soldering. The output terminal member 81 is connected to the circuit board 7. The protective tube is a stainless steel tube covered with PVC or an olefin-based elastomer. This protective tube protects the signal lines and other components inside. The protection tube extends from the outside of the cover member 3 (see Figure 2) to the inside of the cover member 3. The portion of the signal cable 8 immediately extending from the cover member 3 is susceptible to strong bending stress, but by protecting this portion with the protection tube, breakage of the internal signal lines and the like is prevented.

[0058] FIG. 5 is a cross-sectional view taken along line AA in FIG. 2(a).

[0059] As described above, the cylindrical portion 33 extending in the vertical direction is formed in the center of the cover member 3. An inner cylindrical hole 331 communicating with the opposing through-hole 401 is formed inside the cylindrical portion 33. As shown in FIG. 5 , the upper end portion of the cylindrical portion 33 is connected to the top plate portion 31. The lower end of the cylindrical portion 33 is in contact with the upper surface of the opposing member 4. In other words, the cylindrical portion 33 extends to a height position where it contacts the opposing member 4.

[0060] As shown in the enlarged view circled in FIG. 5 , the linear sensor 2 is compressed in the height direction by being sandwiched between the opposing member 4 and the base member 5, resulting in a diameter in the height direction of h1. In this embodiment, the height of the base member 5, the depth of the spiral groove 56, and the distance from the top plate portion 31 to the peripheral wall abutment portion 322 are set so that the height of the linear sensor 2 is h1. This h1 roughly coincides with the depth of the spiral groove 56. The depth of the spiral groove 56 is preferably greater than 0 and less than or equal to h1 so that the linear sensor 2 can be further deformed slightly after being compressed to h1. Furthermore, because the linear sensor 2 is deformed into an elliptical shape and its width is expanded by being sandwiched between the opposing member 4 and the base member 5, the width of the spiral groove 56 is set wider than the diameter of the linear sensor 2. In FIG. 5 , the linear sensor 2 before being sandwiched (in an unloaded state) is shown by a dashed line.

[0061] The linear sensor 2 in the unloaded state has an outer diameter of h2, and h1 is 90% of h2. The linear sensor 2 has the characteristic of being most sensitive to vibrations and other signals when sandwiched so that its radial height is between 80% and 90% of its unloaded state. If the linear sensor 2 is sandwiched so that its radial height is less than 80% of its unloaded state, the linear sensor 2 is less likely to deform, resulting in reduced detection sensitivity. On the other hand, if the linear sensor 2 is sandwiched so that its radial height is more than 90% of its unloaded state, the linear sensor 2 separates from the opposing member 4 or the base member 5 when large displacement due to vibration occurs, preventing detection of some of the vibration, resulting in reduced detection sensitivity. Therefore, it is preferable to sandwich the linear sensor 2 so that h1 / h2 is between 80% and 90%. Furthermore, because the depth of the spiral groove 56 is equal to h1, even if the opposing member 4 attempts to bend upward, the bending is prevented by the underside of the base member 5, and the linear sensor 2 is not crushed beyond h1. This prevents the linear sensor 2 from breaking or breaking down due to bending of the opposing member 4. In this embodiment, the lower surface of the base member 5 is flat except for the spiral groove 56, but the depth of the spiral groove 56 may be made shallower and a base protrusion may be formed on the lower surface of the base member 5 such that the height position of the protruding surface is at a position h1 from the bottom surface of the spiral groove 56.

[0062] The top and side surfaces of the circuit board 7 are covered with a shielding sheet 79, which is made of two insulating layers and a shielding layer sandwiched between them. The shielding sheet 79 is a so-called flexible substrate. The shielding layer is electrically connected to the ground formed on the circuit board 7. The bottom surface of the shielding sheet 79 is attached to the bottom surface of the base top surface recess 51 with an adhesive. The bottom surface of the circuit board 7 is also attached to the shielding sheet 79 with an adhesive. The overlapping upper portions of the shielding sheet 79 may be fixed together with adhesive tape. The circuit board 7 is entirely covered with the shielding sheet 79, making it less susceptible to external noise. Instead of the circuit board 7 and shielding sheet 79, a rigid-flexible substrate in which the circuit board 7 and shielding sheet 79 are integrated may be used. The shielding layer of the rigid-flexible substrate is electrically connected to the ground of the circuit portion. Using a rigid-flexible substrate eliminates the need to attach the bottom surface of the circuit board 7 to the shielding sheet 79, which is expected to reduce the number of manufacturing processes.

[0063] FIG. 6 is a block diagram showing the configuration of the circuit board.

[0064] As shown in FIG. 6 , the circuit board 7 includes a preamplifier 71, an A / D converter 72, an equalizer 73, a memory 74, a correction value selector 76, a temperature sensor 77, and a protocol processor 78. The preamplifier 71 amplifies the output signal of the linear sensor 2. The preamplifier 71 amplifies the signal voltage from the linear sensor 2 with a gain adjusted to fall within a range of approximately ±5 V. The gain of the preamplifier 71 can be adjusted using a knob provided on the circuit board 7. The preamplifier 71 has a high impedance on the input side, which is the linear sensor 2 side, and a lower impedance on the output side. The input impedance is preferably 10 kΩ or more and 10 MΩ or less. The output impedance is preferably 10 Ω or more and 100 kΩ or less. In this embodiment, the input impedance is set to 1 MΩ, and the output impedance is set to 50 Ω. This allows the signal input to the preamplifier 71 to be amplified and output from the preamplifier 71. The A / D converter 72 converts the signal amplified by the preamplifier 71 into a digital signal.

[0065] The memory unit 74 stores correction information based on the characteristics of the linear sensor 2. Due to the sensor configuration, the linear sensor 2 has frequencies with high sensitivity and frequencies with low sensitivity. For this reason, variations occur in the output level of the signal obtained from the linear sensor 2 based on the characteristics of the linear sensor 2. Furthermore, the characteristics of the linear sensor 2 change depending on the ambient temperature. The memory unit 74 stores, as correction information for each ambient temperature, information for correcting the variation in the output level of the signal obtained from the linear sensor 2 for each frequency. Here, a digital value indicating the amplification degree for each frequency is saved in the memory unit 74 as this correction information.

[0066] The correction value selection unit 76 acquires information on the ambient temperature obtained from the temperature sensor 77. Then, it selects correction information corresponding to the ambient temperature information from the correction information stored in the storage unit 74 and transmits the selected correction information to the equalizer 73.

[0067] The equalizer 73 corrects the frequency characteristics using the correction information received from the correction value selection unit 76, thereby correcting for variations in output level due to the characteristics of the linear sensor 2 and outputting the corrected signal. Therefore, data can be output under the same conditions for each frequency, regardless of the characteristics of the linear sensor 2. This equalizer 73 corresponds to an example of a correction output unit. Note that although the equalizer 73 of this embodiment is configured by a CPU and a program, a part or all of it may be configured by an FPGA. Here, the correction information stored in the storage unit 74 may be a coefficient (amplification factor) by which each frequency is multiplied. In that case, if 0 is stored for frequencies for which no data is required, the equalizer 73 can also be used as a band-pass filter.

[0068] The protocol processing unit 78 converts the digital signal corrected by the equalizer 73 into a format suitable for communication standards such as TCP / IP and outputs the converted signal. Note that instead of the protocol processing unit 78, a D / A conversion unit may be provided to output an analog signal.

[0069] Next, a method for assembling this sensor unit 1 will be described.

[0070] First, a temporary adhesive is applied to the bottom surface of the spiral groove 56 of the base member 5, and one end of the linear sensor 2 is inserted into the outlet hole 52 and wired along the spiral groove 56. Note that instead of using adhesive, double-sided tape may be attached to the bottom of the spiral groove 56 to temporarily secure the linear sensor 2. Then, the other end of the linear sensor 2 is passed through the other outlet hole 52, and both ends of the linear sensor 2 are connected to the input terminal member 27. In addition, an output terminal member 81 is connected to one end of the signal cable 8. Then, the circuit board 7 is fitted into the base upper surface recess 51, and the input terminal member 27 and the output terminal member 81 are connected to the circuit board 7, respectively.

[0071] Next, the base member 5 assembly incorporating the linear sensor 2, circuit board 7, and signal cable 8 is fitted into the cover member 3 with the base upper surface recess 51 facing the top plate portion 31, and the cylindrical portion 33 is inserted into the first base through-hole 55. At this time, the relative rotational positions of the cover member 3 and the base member 5 assembly are adjusted so that the signal cable 8 enters the second peripheral wall notch 323.

[0072] Finally, the opposing member 4 is press-fitted into the thin portion 32b of the peripheral wall portion 32 so as to close the opening of the storage space formed by the cover member 3. At this time, the relative rotational positions of the cover member 3 and the opposing member 4 are adjusted so that the lateral protrusions 41 of the opposing member 4 enter the first peripheral wall notch 321, and then the opposing member 4 is press-fitted until the peripheral edge of the disk portion 40 abuts against the peripheral wall abutment portion 322. After the opposing member 4 abuts against the peripheral wall abutment portion 322 formed on the peripheral wall portion 32, it is prevented from moving further upward. This completes the assembly of the sensor unit 1.

[0073] FIG. 7 is an attachment diagram showing an example of a state in which the sensor unit shown in FIG. 2(a) is attached to a detection object by a fixture.

[0074] As shown in FIG. 7, the sensor unit 1 is attached to the object to be detected DB by a washer screw SS. This washer screw SS is an example of a fastener. Note that a screw without a washer SSa or a screw with a washer may be used instead of the washer screw SS. A screw hole DBa is provided at the measurement location of the object to be detected DB. The threaded portion of the washer screw SS passes through the cylindrical inner hole 331 of the cover member 3 and the opposing through-hole 401 of the opposing member 4 and screws into the screw hole DBa. The sensor unit 1 is pressed against the object to be detected DB and fixed by the washer screw SS. This pressing force is received mainly by the cylindrical portion 33 (see FIG. 5), which is sandwiched between the washer screw SS and the object to be detected and into which the threaded portion of the washer screw SS is inserted, and the disk portion 40 (see FIG. 5).

[0075] According to the sensor unit 1 of the embodiment described above, the fastening force (pressing force against the detectable object DB) of the washer screw SS is received by the cylindrical portion 33 mainly via the disk portion 40 of the opposing member 4, thereby substantially preventing the fastening force from acting on the linear sensor 2. Therefore, even if the washer screw SS is overtightened, the linear sensor 2 is not overly crushed, and the sensor unit 1 can be suitably attached to the detectable object DB. Furthermore, because the peripheral wall portion 32 of the cover member 3 extends to the underside of the opposing member 4, even if the cylindrical portion 33 or the disk portion 40 is about to be compressed by the fastening force of the washer screw SS, the peripheral wall portion 32 also receives the fastening force, thereby more reliably preventing the fastening force from being transmitted to the linear sensor 2.

[0076] Furthermore, when a rotational force is applied to the cover member 3 from the washer screw SS when the washer screw SS is tightened, that rotational force is also transmitted to the base member 5, while the opposing member 4 is difficult to rotate due to the frictional force between it and the object to be detected DB, causing relative rotation between the base member 5 and the opposing member 4, which could twist and damage the linear sensor 2. In this embodiment, the lateral protrusion 41 is inserted into the first peripheral wall cutout 321, preventing the cover member 3 and the opposing member 4 from rotating relative to each other in the circumferential direction of the sensor unit 1. Therefore, when the cover member 3 rotates, the opposing member 4 also rotates, and no relative rotation occurs between the base member 5 and the opposing member 4. This prevents the linear sensor 2 from being twisted and damaged when the washer screw SS is tightened.

[0077] Furthermore, the peripheral wall abutment portion 322 of the peripheral wall portion 32 and the cylindrical portion 33 prevent the opposing member 4 from moving upward more than necessary, so even if the opposing member 4 is forcefully pressed into the cover member 3 during assembly of the sensor unit 1, the linear sensor 2 will not be crushed too much and damaged. Similarly, even if a foreign object is caught between the sensor unit 1 and the detectable object DB or if a small protrusion is present on the surface of the detectable object DB during attachment of the sensor unit 1, the linear sensor 2 will not be crushed more than necessary by tightening the washer screw SS and damaged. In addition, by pressing the opposing member 4 until it abuts against the cylindrical portion 33 and the peripheral wall abutment portion 322, the linear sensor 2 will be crushed with an appropriate pressing force, thereby enabling the formation of a sensor unit 1 with high detection sensitivity.

[0078] Furthermore, when the opposing member 4 moves laterally, a load is applied to the linear sensor 2, which may result in damage or a break in the linear sensor 2. In contrast, in the sensor unit 1 of this embodiment, the lateral movement of the opposing member 4 is restricted by the peripheral wall portion 32, so that the linear sensor 2 can be prevented from being damaged by the lateral movement of the opposing member 4. This increases the durability of the sensor unit 1. In particular, in this embodiment, the opposing member 4 is press-fitted into the peripheral wall portion 32 and fixed to the cover member 3, so that the opposing member 4 does not move laterally and the linear sensor 2 can be reliably prevented from being damaged.

[0079] Furthermore, during maintenance and the like, the cover member 3 and the opposing member 4 may need to be separated, but because they are joined by press-fitting, separation can be difficult. Similarly, separation can be difficult if the cover member 3 and the opposing member 4 are joined in a direction other than press-fitting, for example, by adhesive or the like. In this embodiment, the first peripheral wall cutout 321 is formed in the peripheral wall 32, and the cover member 3 and the opposing member 4 can be easily separated by inserting a plate-shaped member of a tool such as a flat-head screwdriver into the first peripheral wall cutout 321 and twisting the tool.

[0080] Next, a description will be given of the sensor unit 1 of the first modified example. In the following description, components having the same names as components described so far will be assigned the same reference numerals as those used so far, and duplicate descriptions may be omitted.

[0081] FIG. 8 is a cross-sectional view similar to FIG. 5, showing a sensor unit according to a first modified example.

[0082] The sensor unit 1 shown in FIG. 8 differs from the sensor unit 1 of the previous embodiment in the shape of the cover member 3 and the shape of the opposing member 4. The protruding length of the cylindrical portion 33 of the cover member 3 is longer than that of the previous embodiment, and the cylindrical portion 33 extends to the underside of the opposing member 4. The opposing member 4 has an opposing through-hole 401 that is larger than that of the previous embodiment and is slightly larger than the outer shape of the cylindrical portion 33. The lower end portion of the cylindrical portion 33 is inserted into the opposing through-hole 401.

[0083] This first modified example also achieves the same effects as the previous embodiment, except that the fastening force of the washer screw SS is mainly received only by the cylindrical portion 33, and the prevention of upward movement of the opposing member 4 is solely performed by the peripheral wall abutment portion 322.

[0084] FIG. 9 is a cross-sectional view similar to FIG. 5, showing a sensor unit according to a second modified example.

[0085] The sensor unit 1 shown in FIG. 9 differs from the sensor unit 1 of the previous embodiment in the shapes of the facing member 4 and the base member 5. A cylindrical base convex portion 58 that protrudes downward is formed on the lower end surface of the base member 5. A first facing recess 402 having an inner diameter substantially the same as the outer diameter of the base convex portion 58 is formed in the facing member 4 at a position opposite the base convex portion 58. The depth of the first facing recess 402 is slightly deeper than the protruding length of the base convex portion 58. The base convex portion 58 is inserted into the first facing recess 402. Note that in this embodiment, only one pair of the base convex portion 58 and the first facing recess 402 is formed, but two or more pairs may be formed.

[0086] This second modified example also has the same effects as the previous embodiment. Furthermore, the base convex portion 58 and the first opposing concave portion 402 can prevent relative rotation between the base member 5 and the opposing member 4. This more reliably prevents the linear sensor 2 from being twisted and damaged when the washer screw SS is tightened.

[0087] The following inventive concept can be extracted from the sensor unit 1 of the second modified example described above.

[0088] A base member; a linear sensor disposed in contact with the lower surface of the base member and detecting vibrations; an opposing member disposed opposite the base member with the linear sensor interposed therebetween, The base member has a base protrusion that protrudes downward, The sensor unit is characterized in that the opposing member has a first opposing recess into which the base protrusion is inserted.

[0089] FIG. 10 is a cross-sectional view similar to FIG. 5, showing a sensor unit according to a third modified example.

[0090] The sensor unit 1 shown in FIG. 10 differs from the sensor unit 1 of the previous embodiment in the shapes of the cover member 3, the opposing member 4, and the base member 5. It also differs from the sensor unit 1 of the previous embodiment in that it is provided with a rotation stop pin 6. This rotation stop pin 6 corresponds to an example of a shaft member. A second base through-hole 59 penetrating vertically and downwardly is formed in the base member 5. The inner diameter of this second base through-hole 59 is approximately the same as the outer diameter of the rotation stop pin 6. A top plate recess 311 recessed upward is formed in the underside of the top plate portion 31 of the cover member 3 at a position facing the second base through-hole 59. The inner diameter of this top plate recess 311 is approximately the same as the outer diameter of the rotation stop pin 6. Furthermore, a second opposing recess 403 is formed in the opposing member 4 at a position facing the second base through-hole 59. The inner diameter of the second opposing recess 403 is also approximately the same as the outer diameter of the rotation stop pin 6. The rotation stop pin 6 is inserted into the second base through-hole 59. The rotation stop pin 6 is longer than the second base through-hole 59 , passes through the second base through-hole 59 , and has its upper end inserted into the top plate recess 311 and its lower end inserted into the second opposing recess 403 .

[0091] This third modified example also has the same effects as the previous embodiment. Furthermore, the rotation stop pin 6 prevents the cover member 3, the opposing member 4, and the base member 5 from rotating relative to each other. This more reliably prevents the linear sensor 2 from being twisted and damaged when the washer screw SS is tightened.

[0092] The following inventive concept can be extracted from the sensor unit 1 of the third modified example described above.

[0093] A base member; a linear sensor disposed in contact with the lower surface of the base member and detecting vibrations; an opposing member disposed opposite the base member with the linear sensor interposed therebetween; a cover member having a top plate portion that covers an upper surface of the base member, The base member has a base through-hole that penetrates in the vertical direction, the top plate portion has a top plate recess at a position facing the second base through hole, the opposing member has a second opposing recess at a position opposing the second base through-hole, The sensor unit comprises a shaft member that passes through the base through-hole, the upper end of which is inserted into the top plate recess, and the lower end of which is inserted into the opposing recess.

[0094] FIG. 11 is a cross-sectional view similar to FIG. 5, showing a sensor unit according to a fourth modified example.

[0095] The sensor unit 1 shown in FIG. 11 differs from the sensor unit 1 of the previous embodiment in the shape of the cover member 3 and the shape of the opposing member 4. The length of the peripheral wall portion 32 of the cover member 3 is shorter than that of the previous embodiment. The lower end of the peripheral wall portion 32 is located at approximately the same position as the lower end of the cylindrical portion 33. However, the lower end of the peripheral wall portion 32 may be located slightly higher. The opposing member 4 is larger than that of the previous embodiment and is disk-shaped without lateral protrusions 41 (see FIG. 3(a)), with an outer diameter approximately the same as that of the top plate portion 31. Therefore, the lower end of the peripheral wall portion 32 faces the upper surface of the opposing member 4. This facing portion is bonded with an adhesive, thereby connecting the cover member 3 and the opposing member 4. Note that double-sided tape may be used instead of an adhesive. Furthermore, instead of the above-mentioned facing portion, the contact portion between the lower end of the cylindrical portion 33 and the opposing member 4 may be bonded with an adhesive or the like, or both the contact portion and the above-mentioned facing portion may be bonded with an adhesive or the like.

[0096] This fourth modified example also has the same effects as the previous embodiment. In addition, since there is no need to form the thin-walled portion 32b (see FIG. 2(b)), and the tolerance of the outer diameter of the opposing member 4 can be loose, the cover member 3 and the opposing member 4 can be formed inexpensively.

[0097] FIG. 12 is a cross-sectional view similar to FIG. 5, showing a sensor unit according to a fifth modified example.

[0098] The sensor unit 1 shown in FIG. 12 differs from the sensor unit 1 of the previous embodiment in the shapes of the cover member 3 and the opposing member 4. The cover member 3 does not have a thin portion 32b (see FIG. 2(b)) and has a uniform thickness down to its lower end. The opposing member 4 is smaller than that of the previous embodiment and is disk-shaped with no lateral protrusions 41 (see FIG. 3(a)), with an outer diameter approximately equal to the inner circumferential surface of the peripheral wall portion 32. However, the outer diameter of the opposing member 4 may be slightly smaller than that of the inner circumferential surface of the peripheral wall portion 32. The opposing member 4 is bonded to the cover member 3 by bonding the contact portion with the lower end of the cylindrical portion 33 with an adhesive or the like. Note that double-sided tape may be used instead of adhesive. Furthermore, instead of the contact portion, the inner circumferential surface of the lower end portion of the peripheral wall portion 32 and the side circumferential surface of the opposing member 4 may be bonded with an adhesive or the like, or both the contact portion and the contact portion may be bonded with an adhesive or the like.

[0099] This fifth modified example also has the same effects as the previous embodiment. Furthermore, since there is no need to form the thin portion 32b (see FIG. 2), the cover member 3 and the opposing member 4 can be formed inexpensively.

[0100] The present invention is not limited to the above-described embodiment and various modifications can be made within the scope of the claims. For example, in this embodiment, the linear sensor 2 using a piezoelectric element 22 has been described. However, the linear sensor 2 may be modified to use a resistor wire or capacitor wire made of conductive rubber or the like. Furthermore, while the linear sensor 2 is arranged in a spiral shape between the opposing member 4 and the base member 5, the linear sensor 2 may be arranged in a corrugated or zigzag shape, or may be arranged in a star shape or gear tooth shape by winding multiple times around the base member 5 toward the inner and outer peripheries. Furthermore, the circuit board 7 may be omitted, and the linear sensor 2 and the signal cable 8 may be connected directly or via a terminal member. Furthermore, an elastic material such as rubber or foam rubber may be disposed at the contact point between the cover member 3 and the base member 5. Additionally, the cover member 3 and the opposing member 4 may be joined with adhesive or double-sided tape, and the cover member 3 and the base member 5 may also be joined with adhesive or double-sided tape. Furthermore, the base member 5 may be an assembly of multiple members. Moreover, instead of the equalizer 73 on the circuit board 7, an FFT and a correction output unit that corrects the frequency spectrum signal output from the FFT using correction information from the correction value selection unit 76 may be provided. Furthermore, the circuit board 7 may process and output the signal from the linear sensor 2 as an analog signal.

[0101] It should be noted that even if a constituent element is included only in the description of each of the modified examples described above, that constituent element may be applied to other modified examples. [Explanation of symbols]

[0102] 1 sensor unit 2 Linear sensors 3 Cover material 4 opposing members 5 Base material 31 Top plate 33 Cylindrical part 55 First base through hole 401 Opposite through holes

Claims

1. A base member; a linear sensor disposed in contact with the lower surface of the base member and detecting vibrations; an opposing member disposed opposite the base member with the linear sensor interposed therebetween; a cover member having a top plate portion that covers an upper surface of the base member, the base member has a first base through-hole penetrating in the up-down direction, the opposing member has an opposing through-hole penetrating in the up-down direction at a position opposing the first base through-hole, The sensor unit is characterized in that the cover member has a cylindrical portion that is inserted into the first base through-hole and extends to a height position where its lower end contacts a member located below.

2. 2. The sensor unit according to claim 1, wherein the cylindrical portion has a lower end that contacts the opposing member.

3. 2. The sensor unit according to claim 1, wherein the cylindrical portion is inserted into the opposing through-hole and extends to a lower surface of the opposing member.

4. the cover member has a peripheral wall portion hanging down from a peripheral edge portion of the top plate portion, 4. The sensor unit according to claim 1, wherein the peripheral wall portion extends to a lower surface of the opposing member.

5. the cover member has a peripheral wall portion hanging down from a peripheral edge portion of the top plate portion, The opposing member has a disk-shaped portion and a lateral protrusion protruding laterally from the disk portion, 4. The sensor unit according to claim 1, wherein the peripheral wall has a peripheral wall notch into which the lateral protrusion is inserted.

6. The base member has a base protrusion that protrudes downward, 5. The sensor unit according to claim 1, wherein the opposing member has a first opposing recess into which the base protrusion is inserted.

7. the base member has a second base through-hole penetrating in the up-down direction, the top plate portion has a top plate recess at a position facing the second base through hole, the opposing member has a second opposing recess at a position opposing the second base through-hole, A sensor unit according to any one of claims 1 to 4, characterized in that it comprises an axial member that passes through the second base through-hole, has an upper end inserted into the top plate recess, and has a lower end inserted into the second opposing recess.

Images