JP2603076Y2 - Toner density detector - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner density detecting device using an LC resonance circuit of an image forming apparatus such as a copying machine, and more particularly to a structure which can sufficiently bring a coil having inductance and a developer close to each other.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image is formed on a photosensitive drum by an exposure optical system, and the electrostatic latent image is developed with toner by a developing device, and then the toner image is transferred to recording paper. An image forming apparatus for fixing is known (Japanese Patent Laid-Open No.
-38482, JP-A-62-157070, etc.).

[0003] Developers used for development in the above-mentioned developing apparatus include a one-component developer and a two-component developer. The two-component developer is formed by mixing magnetic carrier particles and non-magnetic synthetic resin toner particles at an appropriate mixing ratio. The toner particles having an appropriate mixing ratio mixed with the carrier particles are developed. The toner is conveyed by a magnet roller of the apparatus, and slidably contacts or jumps onto a latent image portion on the drum, which is a photosensitive member surface, to form a toner image.

When a two-component developer is used, only the toner is consumed and the carrier is circulated and used repeatedly in the developing device. Therefore, a detecting device for detecting the toner concentration in the developing device is provided. The toner is replenished from the toner replenishing device at any time based on the detection result of the detecting device, and is appropriately charged in the developing device and stirred so as to have a uniform mixing ratio.

Several methods have been devised for detecting the toner concentration. One of the methods is to use a change in the oscillation frequency of an LC oscillation circuit.

[0006] The apparent magnetic permeability of a developer, which is a mixture of iron powder as a carrier and toner, changes depending on the toner concentration. When the coil is approached by a method such as embedding in the developer, the inductance of the coil changes depending on the magnetic permeability of the atmosphere. Since the oscillation frequency of the LC oscillation circuit is given by f = 1 / 2π (LC) ^1/2 , the toner density can be detected by measuring the frequency f.

In FIG. 6 showing a developing section of the image forming apparatus, reference numerals 1 and 2 denote the aforementioned drum and magnet roller, respectively. In the developer case 3, the above-described two-component developer 4 is stored. A hole 5 is provided in a side surface of the developer case 3, and a conventional toner density detecting device 6 using the above-described method is attached to the hole 5.

[0008] The toner concentration detecting device 6 has a configuration as shown in FIG. In FIG. 7, a core 8 having a ferromagnetic coefficient such as iron or ferrite is provided on a substrate 9 in a winding coil portion 7 having an inductance, and a winding coil 10 wound with a fine wire is provided around the core 8. It is established. Therefore, the toner density detecting device 6 has a shape in which the winding coil portion 7 protrudes from the substrate 9.

The projecting coil portion 7 is inserted into the hole 5 of the developer case 3. Further, if there is a protrusion in the developer case 3, the flow of the developer 4 is obstructed, which is not desirable. Therefore, the toner concentration detecting device 6 is configured such that only the tip of the winding coil portion 7 follows the wall of the developer case 3. Will be arranged.

[0010] In addition, as the toner concentration detecting device, a device having a structure in which a developer is used as a flow path in a coil has been devised.

[0011]

In a conventional toner density detecting device of an image forming apparatus, a winding coil is used as an inductance. Therefore, the structure shown in FIG. Can contact the developer 4 only, and the sensitivity is low.

In a configuration using a method of forming a flow path for the developer in the coil, the sensitivity is improved because the developer is present in the coil which has the greatest influence on the inductance of the coil. There are problems such as the structure of the agent case becoming complicated and the size thereof increasing.

The present invention has been made in view of such a conventional problem, and it is possible to bring the coil and the developer sufficiently close without obstructing the flow of the developer, and to stabilize the inductance and the magnetic flux of the coil. It is an object of the present invention to provide a toner concentration detecting device capable of exhibiting a highly accurate detecting ability by the development.

[0014]

An object of the present invention is to provide a detecting coil.
Oscillating circuit components and oscillating circuit wiring patterns
In the toner concentration detecting device having a substrate provided with an oscillation circuit configured by, detecting the concentration of the toner component in the developer by the inductance change of the detection coil,
The detection coil is a spiral planar coil, a substrate
The oscillation circuit wiring pattern formed on the surface of
Formed on the back surface of the plate, the planar coil, and the oscillation circuit wiring pattern are formed by etching,
The oscillation circuit wiring pattern is removed on the back surface of the substrate.
The present invention is attained by a toner density detecting device, wherein a flat magnetic material for shielding the planar coil is provided in a region on the back surface and a region on the front surface covering the planar coil. Further, the planar coil is formed.
To etch the oscillation circuit wiring pattern
Sometimes etching is a preferred embodiment.

[0015]

According to the above arrangement, since the spiral planar coil is disposed on the substrate of the resonance circuit, if the substrate is placed in the developer case, the planar coil and the developer can be sufficiently brought close to each other. In addition, the sensitivity of the toner concentration is improved due to the stabilization of the detection capability, and the size of the toner is reduced without obstructing the flow of the developer.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 6 and 7 are denoted by the same reference numerals and description thereof will be omitted.

FIG. 4 is a circuit diagram of the oscillation circuit of this embodiment. This oscillation circuit is a typical Colpitts oscillation circuit composed of an inductance coil L, capacitors C ₁ and C ₂ , a transistor Q, and a resistor R. The inductance coil L is formed of a planar coil. When a voltage V is applied to this circuit, an oscillation signal is output from the source of the transistor Q. The oscillation circuit is not limited to the Colpitts oscillation circuit, but may be another LC oscillation circuit.

FIG. 1 (a), (b) are each a plan view of a toner concentration detecting device 20 of the image forming apparatus in this embodiment is a rear view. In FIG. 1 ( a ), a planar coil 21 having the above-described inductance is spirally arranged on a surface of a printed board 22 made of, for example, glass epoxy, from a coil electrode 23 which is a through-hole to a coil electrode 24. ing. The upper part of the planar coil 21 is covered with a protective layer such as a green resin. On the back surface of the printed circuit board 22, components 26a, 26b and 26c such as capacitors C ₁ and C ₂ , a transistor Q and a resistor R of the oscillation circuit 26 are mounted, and the plane coil 21 is connected via coil electrodes 23 and 24. Component parts 26a-26c
Is connected to Also, on the back surface of the printed circuit board 22, electrodes 27a and 27 for connecting to a power supply of voltage V and outputting to the outside are provided.
b is provided.

In order to form the planar coil 21, when etching the oscillation circuit wiring pattern on the back surface of the printed circuit board 22, the copper foil on the surface of the printed circuit board 22 is also etched. Thereby, the planar coil 21 is formed of a copper foil. still,
The planar coil 21 may be formed by spirally arranging a copper wire on a printed circuit board 22.

When the planar coil 21 is formed of a copper foil on the printed circuit board 22, it is appropriate that the width of the planar coil 21 is about 50 to 100 μm and the pitch is about 100 to 200 μm. That is, to increase the inductance, the number of turns is increased, and to increase the inductance per unit area, the wiring pitch may be reduced. However, if the wiring pitch is reduced, the cross-sectional area of the wiring pattern is reduced, and as a result, coil
Since the resistance component of 21 becomes large and the LC circuit does not oscillate, the above-mentioned values are appropriate for the width and pitch of the planar coil 21.

Furthermore backside region on the back surface excluding the oscillating circuit wiring pattern of the printed circuit board 22, and the back surface of the area covering the flat <br/> surface coil 21 of the surface, the flat plate magnetic material 25
Is provided.

The magnetic body 25 is formed by etching at the same time as the above-mentioned oscillation circuit wiring pattern, or provided separately by attaching a magnetic metal sheet.

The magnetic member 25 has an effect of magnetically shielding the planar coil 21. When a magnetic member such as a screw existing around the detecting device changes its distance from the planar coil due to vibration of equipment or the like, the magnetic member 25 has a flat surface. The shield effect prevents the output of the coil 21 from fluctuating and lowering the detection accuracy. Therefore, the planar coil 21 can detect the toner concentration with high accuracy by a stable inductance and magnetic flux without being affected by other magnetic members.

FIG. 2 shows a toner concentration detecting device 20 according to this embodiment.
2 shows a state where the developer case 30 is attached to the developer case 30. As shown in the enlarged sectional view of FIG. 3, the developer case 30 is provided with two holes 31a and 31b. The toner concentration detecting device 20 is disposed in the developer case 30 and has two holes each.
The electrodes 27a and 27b are inserted through 31a and 31b.

Thus, the coil electrode 23 to the coil electrode 24 of the planar coil 21 come close to the developer 4 via the protective layer, and the toner density can be detected with high sensitivity.

According to this configuration, the spiral planar coil 21 having the inductance coil L of the LC oscillation circuit is arranged on the printed circuit board 22 so that
Even if 22 is placed in the developer case 30, the flow of the developer is not obstructed, the planar coil 21 and the developer 4 can be brought sufficiently close to each other, and the detection sensitivity of the toner density is improved. Further, since the planar coil 21 is formed integrally with the oscillation circuit on the printed circuit board 22, the shape becomes small,
When etching is performed, the planar coil 21 and the magnetic body 25 are formed at the same time, so that the cost can be reduced.

As shown in FIG. 5, the developer case 30 '
A concave portion 32 may be formed in a part of the device, and the toner concentration detecting device 20 of the present embodiment may be disposed in the concave portion 32. By doing so, the planar coil 21 and the inner surface of the developer case 30 'are flush with each other, so that the flow of the developer 4 is preferably not obstructed.

In this embodiment, a printed board made of glass epoxy is used. However, the present invention is not limited to this. For example, a ceramic board or a plastic board may be used as long as the board can be processed so as to be arranged in a coil spiral shape. Good.

[0029]

As described above, according to the present invention, the coil having the inductance of the toner concentration detecting device of the image forming apparatus having the resonance circuit based on the inductance and the capacitance is constituted by a spiral planar coil. Further, the flow of the developer is not obstructed, and the planar coil and the developer can be sufficiently brought close to each other, so that the detection sensitivity of the toner density is improved. Further, by providing a shield member on the back surface of the substrate of the toner concentration detecting device, highly accurate concentration detection can be performed, the size of the toner concentration detecting device can be reduced, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a state in which the toner concentration detecting device of FIG. 1 is attached to a developing unit.

FIG. 3 is a partially enlarged sectional view of FIG. 2;

FIG. 4 is a circuit diagram of the oscillation circuit of FIG. 1;

FIG. 5 is a diagram illustrating an application example of a developer case.

FIG. 6 is a cross-sectional view of a developing unit of a conventional image forming apparatus.

FIG. 7 is a diagram illustrating a configuration of a conventional toner density detection device.

[Explanation of symbols]

 20 Toner concentration detector 21 Planar coil 22 Printed circuit board 23, 24 Coil electrode 25 Magnetic material 30, 30 'Developer case L Inductance coil

Claims (2)

(57) [Scope of request for utility model registration] (1)Detection coil, oscillation circuit components, and
Oscillation circuit consisting of oscillation circuit wiring pattern
Having a substrate,Detector coil inductance
Toner that detects the concentration of the toner component in the developer
-In the concentration detection device, the detection coil is,A spiral planar coil,substrate
Formed on the surface of The oscillation circuit wiring pattern is formed on the back surface of the substrate.
And The plane coil and the oscillation circuitWiring pattern
Is formed by etching, on the back surface of the substrateExcludes the front oscillation circuit wiring pattern.
Area on the back side and the front sideCover the planar coil
ToOn the backIn the area, a flat plate that shields the front flat coil
A toner concentration detecting device comprising a magnetic material
Place. 2. The method according to claim 1 , further comprising the step of forming the planar coil.
When etching the wiring pattern,
2. The toner concentration detecting device according to claim 1, wherein the toner density is detected.