JPH04278Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a powder sensor that can be suitably implemented mainly for detecting the remaining amount of toner in a copying machine.

2. Description of the Related Art As shown in FIG. 5, a conventional toner remaining amount sensor utilizes a unimorph type vibrator 5 provided facing inside the side wall of a toner tank 4.

The principle of this sensor is as shown in FIG.
The toner is self-oscillated when supported by the toner, and the oscillation stops due to mechanical damping due to the contact load with the toner.The oscillation when the toner runs out is extracted as an electrical output to detect the remaining amount of toner. That's what I do.

Here, the periphery of the metal plate 5b of the unimorph vibrator 5 is supported by the casing 1 so as to be flush with the inner surface of the toner tank 4, as shown in FIG. The reason why the metal plate 5b is made flush with the inner surface of the toner tank 4 is that the vibration of the metal plate is suppressed by the adhesion of fine powder toner, and as a result,
This is to prevent malfunctions in which it is reported that there is no toner remaining when there is no remaining amount.

Problems to be Solved by the Invention Incidentally, the above-described unimorph type vibrator 5 generates bending vibration when voltage is applied, but the node line of the vibration mode is located at the metal plate 5b of the vibrator.
Since the metal plate 5b is located slightly inside the periphery of the metal plate 5b, if a structure is adopted in which the periphery of the metal plate 5b is supported by the casing, vibrations will be suppressed and vibrations will leak through the casing and the toner tank. It turns out.

In order to solve this problem, conventionally, as shown in FIG. 6, a heavy metal ring 9 is provided as additional mass on the casing 1 near the periphery of the metal plate, or
Alternatively, the casing 1 itself has been made of heavy die-casting, but all these methods do nothing but prevent vibration leakage by suppressing vibrations, and such means cannot increase the detection sensitivity of the remaining amount of toner. However, it is undeniable that the cost increases due to the provision of additional mass.

Furthermore, static electricity flows from the charged toner to the circuit through the metal plate, causing malfunctions and circuit damage. In order to prevent this, the surface of the metal plate is coated with resin or the like, but this is not perfect and is expensive.

The purpose of this invention is to solve the above technical problems,
It is an object of the present invention to provide a powder sensor that has a simple structure, has high detection sensitivity, and can reliably prevent circuit damage and malfunction due to static electricity in the powder.

Means for Solving the Problems In order to achieve the above object, the present invention provides a powder sensor using a unimorph type vibrator in which a piezoelectric ceramic is provided on one surface of a metal plate, the metal plate being The metal plate is bent in a direction approaching the piezoelectric ceramic at a position near the node line, an insulating thin plate is attached to the other surface of the metal plate, and this insulating thin plate is attached to the sensor casing.

Effect According to the present invention, the metal plate of the unimorph type vibrator is bent in the direction approaching the piezoelectric ceramic at a position near the node line, and the metal plate is bent on the side opposite to the side where the piezoelectric ceramic is provided. Since a thin insulating plate is attached and this thin insulating plate is attached to the sensor casing, the vibration energy of the metal plate is attenuated within the thin insulating plate and is not transmitted to the sensor casing. In addition, since the thin plate attached to the metal plate has insulating properties, it is difficult for powder to adhere to it, and even if the powder is charged, static electricity is blocked, preventing static electricity from flowing into the circuit inside the sensor. This will be prevented.

Embodiment FIG. 1 is a sectional view of the powder sensor 10, and the second
The figure is a plan view seen from the arrow A side in FIG. The casing 30 of the powder sensor is made of synthetic resin and has a first cylindrical portion 31 , an outward flange 32 connected to the first cylindrical portion 31 , and a second cylindrical portion 33 connected to the outward flange 32 . A printed circuit board 34 is attached to the lower end of the first cylindrical portion 31 . A plurality of circuit components 36 are mounted on this printed circuit board 34 to form an oscillation circuit 35. A sheet body 37 made of silicone rubber is attached to the upper surface of the outward flange 32. The outward flange 32 has an insertion hole 39 into which the screw 38 is inserted.
is formed. The front surface of the second cylindrical portion 33 has a perfect circular opening 4 having a common axis with the second cylindrical portion 33.
0 is formed, and an insulating thin plate 4 is formed to cover this opening 40 and cover almost the entire front surface of the second cylindrical portion 33.
1 is attached. The insulating thin plate 41 is made of an electrically insulating material such as synthetic resin, ceramic, or glass.

A unimorph type vibrator 42 is provided on the inner side of the thin insulating plate 41. This unimorph type vibrator 4
2 is composed of a piezoelectric ceramic 43 and a metal plate 44. As shown in FIG. 3, the metal plate 44 has a substantially truncated conical portion 45 bent near the portion where the node line is located, and an outward flange 46 formed at the large diameter end of the truncated conical portion 45. and has. The truncated conical portion 45 has a small diameter portion 45a and a peripheral wall portion 45b, and the angle θ formed by the small diameter portion 45a and the peripheral wall portion 45b is equal to the angle θ formed by the peripheral wall portion 45b during vibration.
is selected to a value that does not abut against the inner wall of the casing 30. A piezoelectric ceramic 43 is adhered to the inner surface of the small diameter portion 45a with an adhesive 48 such as epoxy resin. As shown in FIG. 4, an electrode 47 having an input electrode 47a and an output electrode 47b is provided on the surface of the piezoelectric ceramic 43 opposite to the small diameter portion 45a. In addition, the input/output electrode 47
Various patterns may be used for the arrangement of a and 47b, and the piezoelectric ceramic 43 itself may be of a known type, for example PZT. Further, in FIG. 3, 49 is a lead wire connected to the input electrode 47a and the metal plate 44, and 50 is a lead wire connected to the output electrode 47b, from which vibration output is extracted.

Unimorph type vibrator 4 having such a configuration
2, make sure that the peripheral wall portion 45b is located inside the casing 30, and that the center point of the small diameter portion 45a and the center point of the thin insulating plate 41 match. Then, the outer surface of the small diameter portion 45a is attached to the inner surface of the thin insulating plate 41 using an adhesive 50 such as epoxy. In this way, the vicinity of the periphery of the small-diameter portion 45a of the metal plate 44 is configured to be a node line, so that the vibration energy generated in the metal plate 44 is attenuated within the thin insulating plate 41 and transmitted to the casing 30. can be prevented as much as possible.

Next, the second cylindrical portion 33 is inserted into the opening 16 so that the insulating plate 41 is almost flush with the inner surface of the side wall 15a of the toner supply tank 15, and in this state, the screw 38 is screwed into the side wall 15a. and fix the sensor casing 30 to the toner supply tank 15. At this time, the sheet body 37 is in tight contact with the outer surface of the side wall 15a, so that the toner 13 in the toner supply tank 15 does not leak to the outside, thereby preventing the inside of the copying machine from being contaminated. is prevented.

Further, the thin insulating plate 41 blocks static electricity from the toner 13 and prevents it from flowing into the circuit components 36, thereby preventing damage to the circuit components 36 and malfunctions. Furthermore, since the metal plate 44 and the insulating thin plate 41 are coaxial, detection sensitivity can be increased.
For reference, when the metal plate 44 and the thin insulating plate 41 are not coaxial but are shifted, the amount of attenuation of vibration energy by the thin insulating plate 41 is partially different, and due to this, the metal plate 44 Deteriorates the vibration characteristics of.

Furthermore, according to the experimental results of the inventor of this case, the opening 4
The diameter of 0 is taken as 1, and the small diameter portion 45a of the metal plate 44
When the diameter of the metal plate 41 is 2, the vibration energy of the metal plate 41 could be effectively absorbed in the range of 1:2=1:1 to 3:1. Also 1:2=3:2
The best case was

In the above-described embodiment, the remaining toner amount sensor 10 was used to detect the amount of toner remaining in the toner replenishment tank 15. It may also be used to detect the remaining amount of discharged toner. Further, the present invention can be suitably implemented to detect not only the remaining amount of toner but also other powders.

Effects of the invention As described above, according to the invention, the vibration energy of the metal plate is attenuated within the thin insulating plate and is not transmitted to the sensor casing. There is no need for the sensor itself to be made of a metal or the like having a high specific gravity, and therefore manufacturing costs can be reduced, and Q at no load can be maintained high, thereby increasing detection sensitivity.

In addition, by providing a thin insulating plate, it is difficult for powder to adhere, and therefore malfunctions caused by incidental adhesion can be reliably prevented, and static electricity from charged powder can not flow into the circuit. First, circuit damage and malfunctions caused by static electricity can be reliably prevented.

[Brief explanation of the drawing]

1 is a sectional view of a remaining toner amount sensor 10 as an embodiment of the present invention, FIG. 2 is a plan view seen from the arrow A side in FIG. 1, and FIG. 3 is a unimorph type vibrator 4.
2 is an enlarged sectional view of the vicinity of 2, FIG. 4 is a plan view seen from the arrow B side of FIG. 3, FIG. 5 is a sectional view of a toner tank to which a conventional remaining toner amount sensor is applied, and FIG. FIG. 3 is a cross-sectional view showing the remaining toner amount sensor of FIG. 10... Toner remaining amount sensor, 15... Toner supply tank, 30... Sensor casing, 41...
Insulating thin plate, 42...Unimorph type resonator.

Claims (1)

[Claims for Utility Model Registration] A powder sensor using a unimorph type vibrator in which a piezoelectric ceramic is provided on one surface of a metal plate, wherein the metal plate is moved in a direction approaching the piezoelectric ceramic at a position near a node line of the metal plate. A powder sensor characterized in that the metal plate is bent, a thin insulating plate is attached to the other surface of the metal plate, and the thin insulating plate is attached to a sensor casing.