JPH1164093A - Vibration detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve contact resonance frequency characteristic, processability, etc., of the mobile section of a vibration detecting device which comes into contact with a vibrating object. SOLUTION: The mobile section of a vibration detecting device is constituted of a head chip 1, which is a contacting member that is brought into contact with a vibrating object and a base 5 which is jointed with the chip 1, made of a material having a specific gravity lower than that of the material of the heat 1 has or a softer material than the material of the head 1, and holds a vibration detecting element. Therefore, the resonance frequency of the mobile section can be mode higher by making the mobile section lighter in weight as a whole and, in addition, the durability of the head chip 1 and good processability of the base 5 can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration detecting device for converting a vibration into an electric signal by contacting with a vibrating object and detecting a vibration state of the vibrating object.

[0002]

2. Description of the Related Art Conventionally, as a vibration detecting device of this type,
A part that comes into contact with the vibrating object is a movable part that is biased by a spring. A piezoelectric element that converts vibration into an electric signal is provided in the movable part, and one that uses the movable part against a vibrating object is known. Have been. The apparatus disclosed in Japanese Utility Model Laid-Open No. 4-75924 is an example of this, in which a ceramic detection needle forms the main part of the movable part, and an end opposite to the side where the detection needle contacts the vibrating object. Is provided with a piezoelectric element.

[0003]

In the above prior art, since the detecting needle is made of ceramic, the detecting needle is processed into a complicated shape to make it easier to hold the vibration detecting element or to mount the vibration detecting element. It is difficult to hold the circuit board that has been used.

In general, the following characteristics are required for the movable part of the vibration detecting device. (1) The entire movable part is light in order to increase the resonance frequency of the movable part that contacts the vibrating object.
(2) The part of the movable part that comes into contact with the vibrating object must be hard to obtain durability. (3) The part of the movable part holding the vibration detecting element has good workability so that a complicated shape can be formed.

Accordingly, an object of the present invention is to provide a vibration detecting device in which a movable portion that comes into contact with a vibrating object has at least a part of the above-mentioned characteristics, and a high contact resonance frequency, excellent workability, and the like can be obtained. .

[0006]

According to a first aspect of the present invention, there is provided a vibration detecting apparatus according to the present invention, comprising: a fixed portion; a movable portion which is movable with respect to the fixed portion; A vibration detecting device comprising: a movable portion that vibrates by moving the movable portion; and a biasing unit that biases the movable portion against the fixed portion; wherein the movable portion includes a vibration detection element that converts vibration into an electric signal. Is characterized by having a contact member that contacts a vibrating object, and a base member that is joined to the contact member and that is made of a material having a lower specific gravity than the contact member and holds a vibration detecting element.

In the present invention, the movable portion is constituted by the contact member having a relatively large specific gravity and the base member having a relatively small specific gravity. In addition, the whole movable section can be made lighter, and the resonance frequency of the movable section can be increased. Further, it is easy to select a hard material suitable as a material for the contact member from materials having a large specific gravity, and to select a material having good workability suitable as a material for the base member from a material having a small specific gravity. Is easy. For example, stainless steel can be selected as the material of the contact member and aluminum can be selected as the material of the base member.

[0008] The joining between the contact member and the base member is performed as follows.
It is preferable to use a method of obtaining high rigidity after joining such as press fitting and screw fitting. The holding of the vibration detecting element by the base member may be a direct holding for directly fixing the vibration detecting element to the base member, or an indirect holding for fixing the vibration detecting element to the base member via a circuit board.

According to a second aspect of the present invention, a vibration detecting device according to the present invention comprises a fixed portion, and a movable portion movable with respect to the fixed portion and in contact with a vibrating object when detecting vibration. And a biasing means for biasing the movable portion against the fixed portion, wherein the movable portion comes into contact with a vibrating object in a vibration detecting device including a vibration detecting element for converting vibration into an electric signal in the movable portion. A contact member and a base member joined to the contact member and made of a material softer than the contact member and holding the vibration detecting element are provided.

In the present invention, since the movable portion is constituted by the relatively hard contact member and the relatively soft base member, the durability of the contact member and the good workability of the base member can be realized. . In addition, it is easy to select a material having a small specific gravity suitable as a material for the base member from soft materials. For example, stainless steel can be selected as the material of the contact member and aluminum can be selected as the material of the base member. Also, ceramic can be selected as the material of the contact member. However, ceramics have problems such as that they are too hard and may damage the vibrating object, are easily cracked, are difficult to cut, and tend to be costly. Is advantageous.

There are various methods for defining or measuring hardness, and any method may be used. In short, here, the hardness indicates the ease of cutting (soft materials are easy to cut). Therefore, it is not important to specify the definition of hardness or the method of measurement.

In a preferred embodiment, the base member has a vibration detecting element holding structure formed by cutting. By doing so, the vibration detection element can be accurately and easily fixed to the base member. Cutting includes lathing, drilling, end milling, thread cutting, and the like.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. What is described here is a vibration detection device that has a function of converting vibration into an electric signal, but does not include means for analyzing a vibration waveform signal. From such a function, the vibration detecting device of this embodiment is referred to as a sensor head. The contact member is referred to as a head chip, and the base member is referred to as a base.

FIG. 1 is a front view of the sensor head 30, and FIG. 2 is a left side view thereof. The sensor head 30 has a substantially cylindrical shape, and the cable 15 is drawn out from the right end in FIG. 1, and the movable part 31 protrudes from the left end. The movable portion 31 described here is a portion that is pressed against the object to be measured for vibration, and moves rightward in accordance with a force applied to the tip from the left. A screw is engraved on the outer periphery of a region near the left end of the sensor head 30. The screw and the two nuts 23 are used to fix the sensor head to a structure (not shown) that supports the sensor head 30 (for example, a robot arm).

FIG. 3 is a sectional view taken along line AA of FIG. 2, and FIG.
FIG. 7 is a sectional view taken along line BB of FIG. Describing the internal structure of the sensor head 30, the fixed part is the housing 3 and the part fixed thereto. The movable section 31 includes a base 5, a head chip 1, a spring seat 7, and the like. The movable portion 31 is provided so as to be movable in the axial direction of the housing 3 while receiving a leftward force by compressing the spring 8 as the urging means. A printed circuit board 16 on which a piezoelectric element and an amplifier circuit for an output signal of the piezoelectric element are mounted is attached to a base 5 of the movable portion 31 by a screw 17 and a rivet 20. The head chip 1 is made of stainless steel and is press-fitted and fixed to a base 5 made of aluminum. The spring seat 7 made of acetal resin is locked by the pins 22 after being fitted to the base 5. One end of the spring 8 is in contact with the spring seat 7 of the movable portion 31, and the other end is in contact with the spring seat 9. The spring seat 9 is fixed to the housing by being sandwiched between a step on the inner surface of the housing 3 and a cap 11 screwed and fixed to the housing 3, and is prevented from rotating by a pin 22.

Ring-shaped rubber dampers 4 and 6 are provided between the base 5 and the housing 3. The rubber dampers 4 and 6 prevent the movable portion 31 from moving in a direction other than the axial direction of the housing 3 and also prevent the vibration from being transmitted to the piezoelectric element when vibration is applied to the housing 3 from outside. ing. Rubber damper 4 is housing 3
And is fixed between the step on the inner surface of the base and the cap 2 pressed into the housing. When the base 5 moves leftward, the shock when the base 5 stops on the step of the base 5 is reduced. I do. Rubber damper 6 is base 5
Are fixed by being sandwiched between the stepped portion of the spring member and the spring seat 7, and constitute a part of the movable portion.

Flexible printed wiring board (FPWB)
That. ) 21 is the printed circuit board 16 of the movable portion 31
And the cable 15 are electrically connected. One end of the FPWB 21 is soldered to the printed circuit board 16 and fixed by crimping to the base 5 with rivets 20, and the other end is soldered to the connector 10 attached to the end of the cable 15. The connector 10 is fitted into a groove provided in the spring seat 9 and is fixed to the spring seat 9 by a pressing rubber 25. The cable 15 is penetrated and fixed to the cap 11 via the bush 13 and the clamp 14.

FIG. 5 shows an equivalent circuit of the piezoelectric element and the amplifier circuit mounted on the printed circuit board 16. When a force is applied to the piezoelectric element, charges are charged, and the charges are converted into a voltage by a charge amplifier, which is a kind of integrator. In FIG. 5, -A is the amplification degree of the operational amplifier (A≫1), Cd is the capacitance of the piezoelectric element, Cc is the floating capacitance of the circuit, Cf is the feedback capacitance, Rf is the feedback resistance, and qd is the charge generated by the piezoelectric element. , qf the electrical charge to be stored in Cf, q ₀ represents the electric charge to be stored in Cd and Cc. At this time, the relationship e ₀ = − (qf / Cf) · (A / (1 + A)) ≒ −qf / Cf ≒ −qd / Cf holds, and the output voltage is proportional to the charge qd generated by the piezoelectric element. e ₀ is obtained.

When a product inspection is performed using the sensor head 30, the sensor head 30 is attached to a support structure such as a robot arm using the screw portion on the outer periphery of the housing 3 as described above, and Tip (head chip 1)
Can be pressed against and released from the product to be inspected. The product to be inspected is, for example, a laser beam printer, and the sensor head 30 analyzes the vibration generated by the rotation of the polygon mirror inside the laser beam printer to determine whether the product is normal or abnormal. Used for detection. When the product to be inspected is transported to a predetermined inspection position, the tip of the movable portion 31 of the sensor head 30 is pressed against a location suitable for detecting the vibration of the product, and the vibration is detected. When the vibration detection is completed, the sensor head 30 is separated from the product, and then the sensor head 30 waits until the next product to be inspected is conveyed.

Next, the vibration detecting operation by the sensor head 30 will be described. When the tip of the movable part 31 is pressed against the product to be inspected, the movable part 31 moves rightward in FIG. The limit of the movement is until the spring seat 7 and the spring seat 9 come into contact with each other. The amount by which the sensor head 30 is pressed against the product to be inspected is determined so that the movable portion 31 moves to approximately the middle of the movable distance when the vibration is detected. When detecting the vibration, the vibration of the product to be inspected is transmitted to the piezoelectric element via the head chip 1, the base 5, and the printed circuit board 16, where it is converted into an electric charge. The charge amount corresponding to this vibration is converted into a voltage by the charge amplifier, and this voltage signal is provided to an apparatus (not shown) for analyzing vibration via the FPWB 21 and the cable 15. The power required for the operation of the circuit on the printed circuit board 16 is supplied from a device for analyzing vibration via the cable 15 and the FPWB 21.

6 to 10 show details of the shape of the base 5. FIG. 6 is a plan view of the base 5, FIG. 7 is a front view, FIG. 8 is a bottom view, FIG. 9 is a right side view, and FIG. 10 is a cross-sectional view taken along line CC of FIG. In making this shape, first, a shape combining the cylindrical shapes is formed by aluminum die casting, and then a two-step step shape 51, 5 engraved from the side of the central cylindrical portion.
2 (the part to which the printed circuit board 16 is fixed), a groove 53 (FPW) extending from the center column to the right column.
B21), holes 54, 54 for riveting the printed circuit board 16, a lower hole for a screw hole 55 for screwing the printed circuit board 16, and a hole 56 in the left cylindrical portion (head). The part into which the chip 1 is press-fitted) is formed by end milling, and finally the screw in the screw hole 55 is cut with a tap. Steps 51 and 52 and hole 5
4, 54 and the screw hole 55 are holding structures of the vibration detecting element.

According to the embodiment described above, the movable portion 3
Since the base 5 (made of aluminum) and the spring seat 7 (made of acetal resin), which occupy a large part of the volume of 1, are made of a material having a small specific gravity, the movable part 31 is light as a whole, so that the resonance frequency of the movable part 31 is small. Since the head chip 1 that contacts the vibrating object is made of stainless steel, the portion that contacts the vibrating object is hard and durable, and has high contact rigidity. Thereby, the contact resonance frequency (the natural resonance frequency of a system formed in a state where the movable portion is in contact with the vibrating object) also increases. Since the base 5 holding the vibration detecting element is made of aluminum, the cutting workability is good, and the printed circuit board 16 on which the vibration detecting element is mounted can be processed into a shape that can be accurately and easily fixed.

The embodiment of the present invention described above can be variously modified. For example, the head chip may be made of ceramic. As means for biasing the movable portion with respect to the fixed portion, various elastic structures such as a leaf spring other than a helical spring such as the spring 8 can be used. Further, the amplifier circuit for the output signal of the vibration detecting element may be provided on the fixed part side. Further, means such as a microcomputer system for analyzing a vibration waveform signal may be incorporated in the sensor head.

[Brief description of the drawings]

FIG. 1 is a front view of a vibration detection device (sensor head) according to an embodiment of the present invention.

FIG. 2 is a left side view of the same.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a sectional view taken along line BB of FIG. 2;

FIG. 5 is an equivalent circuit diagram of a piezoelectric element and an amplifier circuit mounted on a printed circuit board.

FIG. 6 is a plan view of a base 5;

FIG. 7 is a front view of the base 5. FIG.

FIG. 8 is a bottom view of the base 5. FIG.

9 is a right side view of the base 5. FIG.

FIG. 10 is a sectional view taken along line CC of FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Head chip (movable part) 3 Housing (fixed part) 5 Base (base member: movable part) 16 Printed circuit board (mounted with vibration detecting element) 30 Sensor head 31 Movable part

Claims (3)

[Claims] 1. A fixed portion, a movable portion movable with respect to the fixed portion and vibrating upon contact with a vibrating object when vibration is detected, and biasing means for biasing the movable portion against the fixed portion. A vibration detecting device that includes a vibration detecting element that converts vibration into an electric signal in the movable portion, wherein the movable portion includes a contact member that contacts a vibrating object, and the contact member that is joined to the contact member. And a base member made of a material having a smaller specific gravity than the base member for holding the vibration detecting element. 2. A fixed portion, a movable portion movable with respect to the fixed portion and vibrating by contacting a vibrating object when vibration is detected, and a biasing means for biasing the movable portion against the fixed portion. A vibration detecting device that includes a vibration detecting element that converts vibration into an electric signal in the movable portion, wherein the movable portion includes a contact member that contacts a vibrating object, and the contact member that is joined to the contact member. And a base member made of a softer material and holding the vibration detecting element. 3. The vibration detection device according to claim 2, wherein the base member has a structure for holding the vibration detection element formed by cutting.