JPH10282782A - Toner density detector for developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To move a detecting coil of toner density sufficiently close to a developer, without disturbing its flowing and to detect the density of toner, without being affected by other magnetic materials, with high accuracy. SOLUTION: This toner density detector is constituted to detect the density of a toner component in the developer received in a developing device, by a change in the frequency of a resonance circuit by the inductance L of a detecting coil and the capacitance C of a capacitor. In such a case, the detecting coil is a spirally arranged plane coil 41 and at least, a base plate for constituting the detecting coil is a flexible base plate 42.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile, and the like, and more particularly to a toner density detecting apparatus using an LC resonance circuit having a planar coil, and particularly to improving performance. Related to improved technology.

[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. An image forming apparatus for fixing is known (Japanese Unexamined Patent Publication No.
7-38482, JP-A-62-157070, etc.).

[0003] Developers used for development in the developing device 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, and developing toner particles having an appropriate mixing ratio mixed with the carrier particles. The toner is conveyed by the developing sleeve of the apparatus and adheres to the latent image portion on the photosensitive drum by sliding or non-contact, thereby forming 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 by the detecting device, and is appropriately charged in the developing device and stirred so as to have a uniform mixing ratio.

Several methods for detecting the toner concentration have been proposed. One of the methods is to use a change in the resonance frequency of an LC resonance 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 (1), the toner density can be detected by measuring the frequency f. By the way, when using a winding coil in which a fine wire is wound around a rod-shaped core such as iron or ferrite having a high magnetic permeability, only the tip of the winding coil can be brought into contact with the developer, and the sensitivity is low. There is a problem that it becomes dull.

In view of this, a toner density detecting device in which the detecting coil is a planar coil has been proposed by the present applicant (see Japanese Utility Model Laid-Open No. 6-79661 and Japanese Patent Laid-Open No. 7-248676). The toner concentration detecting device of the image forming apparatus described in Japanese Utility Model Laid-Open No. 6-79661 is a device in which a coil having an inductance is formed by a planar coil spirally arranged on a resonance circuit board. JP-A-7-248676
In the toner concentration detecting device described in Japanese Patent Application Laid-Open No. H10-209, the detecting coil is formed by connecting a plurality of spiral planar coils formed on the substrate surface in series, and the directions of magnetic fluxes generated by adjacent planar coils are opposite to each other. It was made.

The use of the planar coil not only improves the sensitivity but also makes it possible to reduce the size.

[0009]

However, even in the toner density detecting device of the image forming apparatus using such a planar coil, there is a point to be further improved in order to improve the performance such as the detection sensitivity.

That is, it is necessary to further improve the detection level. It is also necessary to provide a configuration in which the toner concentration detecting device can be easily attached to the housing of the developing device. Further, it is necessary to reduce the size of the planar coil of the detection unit and the resonance circuit including the capacitor.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and has been further improved in order to improve detection performance and to achieve easy installation and miniaturization, and further improved toner density detection of a developing device. It is intended to provide a device.

[0012]

According to a first aspect of the present invention, there is provided a toner concentration detecting device for a developing device, comprising:
In the toner concentration detecting device of the developing device for detecting the concentration of the toner component in the developer housed in the developing device by the frequency change of the resonance circuit due to the inductance of the detecting coil and the capacitance of the capacitor, the detecting coil Are planar coils arranged in a spiral shape, wherein at least the substrate forming the detection coil is a flexible substrate.

According to a second aspect of the present invention, there is provided a toner concentration detecting device for a developing device, wherein a toner in a developer contained in the developing device is changed by a frequency change of a resonance circuit due to an inductance of a detecting coil and a capacitance of a capacitor. In the toner concentration detecting device of a developing device for detecting the concentration of a component, the detecting coil is configured by arranging a plurality of planar coils spirally arranged on a flexible substrate in a stacked manner with an insulating layer interposed therebetween. Are connected in series, and the directions of magnetic fluxes generated by a plurality of stacked planar coils are made the same.

According to an eighth aspect of the present invention, there is provided a toner concentration detecting device for a developing device, wherein a toner in a developer contained in the developing device is changed by a frequency change of a resonance circuit due to an inductance of a detecting coil and a capacitance of a capacitor. In the toner concentration detecting device of the developing device for detecting the concentration of the component, the detecting coil is a planar coil spirally arranged on a flexible substrate, and a coil surface of the detecting coil rotates in the developing device. The developing device is characterized in that it is closely attached to the outer surface of the housing of the developing device so as to be substantially equidistant from the outer peripheral locus of the developer stirring member.

According to a ninth aspect of the present invention, there is provided a toner concentration detecting device for a developing device, wherein a toner in a developer contained in the developing device is changed by a frequency change of a resonance circuit due to an inductance of a detecting coil and a capacitance of a capacitor. In the toner concentration detecting device of the developing device for detecting the concentration of the component, the detecting coil is a planar coil spirally arranged on a flexible substrate, and a coil surface of the detecting coil rotates in the developing device. The image forming apparatus is characterized in that the developing device is attached in close contact with the inner surface of the housing of the developing device or in a state protruding from the inner surface of the housing so as to be substantially equidistant from the outer peripheral locus of the developer stirring member.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of an embodiment of the present invention, an image forming section of an image forming apparatus equipped with a developing device of the present invention will be described with reference to a sectional view of FIG.

In FIG. 1, reference numeral 10 denotes a photosensitive drum as an image carrier, 11 denotes a scorotron charger, 12 denotes a pre-charging static eliminator (PCL), 13 denotes an exposure light path by an image exposure means (not shown), and 14 denotes a charge erasing device. LED array, 15A is a pair of registration rollers of the paper feeding device, 15B is a pair of paper feeding rollers, 16
Is a transfer electrode, 17 is a separation electrode, 18 is a separation claw, 19 is a cleaning device, and 20 is a developing device.

FIG. 2 is a longitudinal sectional view showing the structure of the developing device 20, FIG. 3 is a sectional view taken along line AA of the developing device 20, and FIG.

In these figures, reference numeral 21 denotes a developing device housing (housing) for accommodating a two-component developer composed of a toner and a carrier; 22, a lid for closing an upper opening of the housing 1;
Reference numeral 23 denotes a developer carrier (developing sleeve) which is a developer conveying means having a magnetic field generating means (magnet roll) 24 having a fixed magnet body therein, and reference numeral 25 denotes a supply member (developer supply roller, hereinafter referred to as a supply roller). Reference numeral 26 denotes a developer layer thickness regulating member that regulates the thickness of the developer layer on the developing sleeve 23 to a predetermined amount, and reference numerals 27 and 28 denote developer stirring members (developer stirring screws, hereinafter referred to as stirring screws). .

Stirring screw 27 and stirring screw 28
Is a first stirring chamber 21B formed on both sides of a partition wall 21A standing upright from the bottom of the developing device housing 21.
And in the second stirring chamber 21C.

The longitudinal space in which the photosensitive drum 10 and the developing sleeve 23 are close to and opposed to each other is the photosensitive drum 10
This is a development area E where the electrostatic latent image formed thereon is developed with the developer conveyed by the development sleeve 23.

Reference numeral 29 denotes a toner supply port opened at an upper portion of the developing device housing 21, which receives toner supplied from a toner cartridge (not shown) through a toner storage means and a toner transport means and puts the toner into the first stirring chamber 21B. .

In FIG. 3, the vicinity of both shaft ends of the developing sleeve 23 is rotatably supported by bearings 30A and 30B. In the vicinity of both shaft ends of the developing sleeve 23, butting rollers 31A and 31B are rotatably supported. The outer peripheral surfaces of the abutting rollers 31A and 31B abut against a drum cartridge abutting surface (not shown) to keep the gap between the photosensitive drum 10 and the developing sleeve 23 constant. Both ends of the magnetic field generating means 24 having a plurality of magnetic poles are fixedly supported. A driving gear G0 connected to a drive source (not shown)
Is a gear G fixed to one shaft end of the supply roller 25.
1, G2 is driven and rotated. The gear G1 is the developing sleeve 2
The driving force is transmitted to a gear G3 fixed to the shaft end of No.3. The gear G2 is a gear G fixed to the rotation shaft of the stirring screw 27.
Drive 4 is reached. Gear G5 fixed coaxially with G4
Transmits the drive to a gear G6 fixed to the rotation shaft of the stirring screw 28. In this manner, the driving rotation of the driving gear G0 causes the developing sleeve 23, the supply roller 25, and the stirring screws 27 and 28 to be simultaneously rotated in the directions indicated by the arrows in FIG. The surface of the developing sleeve 23 is located at a position facing the photosensitive drum
Is rotated in the same direction as.

From the toner cartridge to the toner storage means,
The toner supplied to the toner supply port 29 of the developing device 20 via the toner conveying means is conveyed in the direction indicated by the arrow in FIG.
After passing through the terminal opening 21D, it is fed into the second stirring chamber 21C. The toner sent into the second stirring chamber 21 </ b> C is conveyed in the direction of the arrow by the stirring screw 28, stirred and mixed with the developer accommodated in the second stirring chamber 21 </ b> C, and supplied to the supply roller 25. You.

At the bottom of the housing 21 of the developing device 20, a toner density detecting device 40 is fixed. The toner concentration detecting device 40 is attached to the second stirring chamber 21C or the first stirring chamber 21B of the housing 21, and the toner concentration detecting device 4
Based on the detection result of “0”, toner is supplied from the toner supply port 29 into the developing device 20.

FIG. 5 is a circuit diagram showing an example of a resonance circuit of the toner concentration detecting device 40. In this figure, the resonance circuit is composed of an inductance coil L, capacitors C ₁ , C ₂ ,
This is a typical Colpitts oscillation circuit composed of a transistor Q and a resistor R, and the inductance coil L is composed 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 resonance circuit is not limited to the Colpitts oscillation circuit.

6A and 6B show a toner concentration detecting device 40 according to the present embodiment. FIG. 6A is a plan view, FIG. 6B is a side view, FIG. 6C is a perspective view, and FIG. () Is an enlarged plan view of the planar coil portion.

In these figures, the planar coil 41 is
Flexible substrate (Flexible printed circuit board, FP
C) On the surface of 42, spirally arranged from the central coil electrode 43 to the peripheral coil electrode 44. As the flexible substrate 42, an extremely thin polyester film, a polyimide film, or the like is used. A copper foil is formed on the flexible substrate 42 by spiral pattern etching. Alternatively, a conductive layer is formed on the flexible substrate 42 by vapor deposition of aluminum or copper. The planar coil 41 has a line width of about 50 to 100 μm and a pitch of about 100 to 200 μm. This surface becomes the detection coil surface. Note that a thin copper wire may be spirally wound and arranged on the printed circuit board 22, and this may be used as the planar coil 41.

One end of the flexible board 42 is connected to a printed board 45 on which capacitors C ₁ and C ₂ , a transistor Q and a resistor R are mounted. A connector 46 having connection terminals is fixed to an upper portion of the printed board 45.
The connector 46 is provided with an electrode 47 that is connected to a power supply of a voltage V and outputs a detection signal to the outside.

The upper surface of the planar coil 41 is covered with a protective layer 48, as shown in FIG. The protective layer 48 is formed of, for example, a resist such as an insulating resin or any one of polyimide, polycarbonate, aramid, polyethylene terephthalate, and the like, and covers the surface of the planar coil 41 with insulation.

On the back side of the flexible substrate 42, an adhesive layer 49 made of a double-sided adhesive tape or the like is provided. By bonding this adhesive layer 49 to the housing 21 of the developing device 20 at a predetermined position, the toner concentration detecting device 40 having the planar coil 41 is fixed.

FIG. 7A is a sectional view showing a first embodiment in which the planar coil 41 of the toner density detecting device 40 is installed on the outer wall surface of the housing 21 of the developing device 20. In this embodiment, a part of the bottom outer wall of the housing 21 is formed on a thin outer wall mounting surface 21E, and a flexible substrate 42 having a planar coil 41 is bonded to the outer wall mounting surface 21E using a double-sided adhesive tape or the like. Bonded by layer 49. In addition,
By providing the planar coil 41 facing the adhesive layer 49 and disposing the flexible substrate 42 on the outermost layer, it is possible to eliminate the need for a protective layer.

FIG. 7B is an enlarged sectional view showing details of the mounting portion of the planar coil 41 and the stirring screw 28.

The outer wall mounting surface 21E to which the flexible substrate 42 is adhered is formed into a cylindrical shape by making it thin in a groove shape so as to be substantially equidistant from the outer peripheral trajectory of the stirring screw 28 rotating in the developing device 20. I have. Therefore, the planar coil 4 attached in close contact with the outer wall mounting surface 21E is used.
Distance d from the surface of No. 1 to the outer trajectory of the stirring screw 28
1 are substantially equally spaced.

Further, since the outer wall mounting surface 21E is formed in a thin groove shape within the allowable limit of the strength of the housing 21, the distance d1 from the surface of the flat coil 41 to the outer trajectory of the stirring screw 28 is set. Is set to a short distance. As described above, since the distance d from the curved surface of the planar coil 41 attached in close contact with the cylindrical outer wall mounting surface 21E to the outer peripheral trajectory of the stirring screw 28 is set at equal intervals and at a short distance, The toner concentration detection level when the stirring screw 28 rotates can be made sufficiently high.

Next, a second embodiment according to the present invention will be described.

FIG. 8A shows a state in which the planar coil 41 of the toner density detecting device 40 is connected to the inner peripheral surface 21 of the housing 21 of the developing device 20.
It is sectional drawing which shows 2nd Embodiment installed in the B side.
FIG. 8B is a partial perspective view of the housing 21.

In this embodiment, the inner wall mounting surface 2 is formed by thinning a part of the inner peripheral surface 21F at the bottom of the housing 21 in a groove shape.
1G, and a flat coil 41 is attached to the inner wall mounting surface 21G.
Is adhered by an adhesive layer 49 made of a double-sided adhesive tape or the like.

FIG. 8C is an enlarged sectional view showing details of the mounting portion of the planar coil 41 and the stirring screw 28.

The inner wall mounting surface 21 G to which the flexible substrate 42 is adhered is formed in a cylindrical shape so as to be equidistant from the locus of the outer circumference of the stirring screw 28 rotating in the developing device 20. Therefore, the distance d2 from the surface of the flat coil 41 attached in close contact with the outer wall attachment surface 21G to the outer trajectory of the stirring screw 28 is equal.

The upper surface of the planar coil 41 is
The distance d2 from the upper surface of the planar coil 41 to the outer trajectory of the stirring screw 28 is d by setting the same surface as the inner peripheral surface 21F or slightly protruding from the inner peripheral surface 21F.
The distance is set shorter than 1. As described above, since the distance d2 from the curved surface of the planar coil 41 attached in close contact with the cylindrical inner wall mounting surface 21G to the outer peripheral trajectory of the stirring screw 28 is equidistant and close to each other, The toner concentration detection level when the stirring screw 28 rotates can be made sufficiently high. Further, by disposing the upper surface of the planar coil 41 on substantially the same plane as the inner peripheral surface 21F of the housing 21, the flow of the developer is not obstructed, and the developer does not stay on the surface of the planar coil 41, and the detection is performed. The sensitivity is improved.

FIG. 9 (a) is a perspective view showing another embodiment of the toner concentration detecting device, FIG. 9 (b) is a plan view as viewed from the direction of arrow A, and FIG. 9 (c) is a sectional view. FIG. 10 is a circuit diagram of an oscillation circuit including a planar coil.

The toner density detecting device 50 of this embodiment
Is formed by forming planar coils 51A and 51B on both front and back surfaces of one flexible substrate 52. FIG. 9 (a),
In (b), for explanation, one flexible substrate 52 is used.
Is shown in two parts.

On the front side (front side) of the flexible substrate 52, a planar coil 51A having a spiral pattern in a counterclockwise direction indicated by an arrow A was formed. Flexible substrate 5
A flat coil 51B (shown by a broken line) having a spiral pattern in the counterclockwise direction indicated by the arrow A is formed on the back surface side (back surface) of No. 2. In FIG. 9, the center coil electrode 5
3. The peripheral coil electrodes 54A and 54B are
The electrodes (terminals) at the ends of 1A and 51B correspond to the terminal positions in the oscillation circuit of FIG.

As shown in these figures, two planar coils 51A and 51B are arranged on the front and back surfaces of the same flexible substrate 52, are connected by electrodes 53, 54A and 54B, and are electrically connected in series. This is used as a toner density detecting unit. At this time, the directions of the magnetic fluxes generated by the planar coils 51A and 51B overlapping on the front and back sides in the vertical projection direction are set to be the same directions indicated by arrows. As described above, the inductance of the detection coil can be made larger than that of the single planar coil 41 by connecting the plurality of planar coils 51A and 51B in series, so that the detection level is improved.

FIG. 11A is an exploded perspective view showing still another embodiment of the toner concentration detecting device, and FIG. 11B is an exploded sectional view thereof.

The toner density detecting device 60 according to this embodiment
In this example, planar coils 61A and 61B are formed on both front and back surfaces of a first flexible substrate 62, and planar coils 61C and 61D are formed on both front and rear surfaces of a second flexible substrate 65. In FIG. 11A, for the sake of explanation, the flexible substrates 62 and 65 are illustrated in two parts as in FIG. The first flexible substrate 62 and the second flexible substrate 65 are formed with planar coils having the same pattern shape as in FIG.

In FIG. 11, the central coil electrode 63A and the peripheral coil electrodes 64A and 64B on the first flexible substrate 62 are electrodes (terminals) at the ends of the planar coils 61A and 61B. A central coil electrode 63B on the second flexible substrate 65, a peripheral coil electrode 64C,
64D is an electrode (terminal) at the end of the planar coils 61C and 61D.

As shown in these figures, four plane coils 61A, 61A formed on two flexible substrates 62,
61B, 61C, 61D are electrodes 63A, 63B, 64
Those connected by A, 64B, 64C, and 64D and electrically connected in series are defined as a toner density detecting unit.
At this time, the directions of the currents of the planar coils 61A, 61B, 61C, 61D overlapping on the front and back surfaces in the vertical projection direction are set to be the same directions indicated by small arrows. When the current direction is the direction indicated by the arrow, according to the right-hand screw rule of ampere,
The direction of the magnetic flux (strong line) generated by these planar coils is as indicated by the arrow. Thus, the inductance of the detection coil is four plane coils 61A, 61B, 61C,
By connecting 61D in series, it is possible to increase the detection level since it can be larger than the single planar coils 51A and 51B.

FIG. 12A is an exploded perspective view showing still another embodiment of the toner concentration detecting device, FIG. 12B is an exploded sectional view thereof, and FIG. 12C is a sectional view of a laminated state. .

The toner density detecting device 70 according to this embodiment
Is formed by laminating a plurality of, for example, three, flexible substrates each having a planar coil formed on one surface as shown in FIG.

A flat coil 71A, a central coil electrode 73A and a peripheral coil electrode 74A are formed on one surface of a first flexible substrate 72, and a second flexible substrate 75
, A planar coil 71B, a central coil electrode 73B, and a peripheral coil electrode 74B are formed on one surface thereof, and a planar coil 71C, a central coil electrode 73C, and a peripheral coil electrode 74C are formed on one surface of a third flexible substrate 76. .

These planar coils 71A, 71B, 71
C, the central coil electrodes 73A, 73B, and 73C and the peripheral coil electrodes 74A, 74B, and 74C are electrically connected in series as shown in FIG. At this time, the planar coils 7 overlapping in the vertical projection direction
The directions of the magnetic fluxes generated by 1A, 71B, and 71C are set to be the same directions indicated by arrows. As described above, the inductance of the detection coil is three plane coils 71A and 71A.
By connecting 1B and 71C in series, it is possible to increase the detection level since it can be made larger than the single planar coil 41A.

The number of flexible substrates on which the planar coils are formed is not limited to the three-sheet configuration shown.

FIG. 13A is an exploded perspective view showing still another embodiment of the toner concentration detecting device, FIG. 13B is an exploded sectional view thereof, and FIG. 13C is a sectional view of a laminated state. .

The toner density detecting device 70 of this embodiment
Is formed by laminating a plurality of flexible substrates each having a planar coil formed on one surface as shown in FIG. 6 via an intermediate connection flexible substrate and connecting them.

A planar coil 81A, a central coil electrode 83A and a peripheral coil electrode 84A are formed on one surface of a first flexible substrate 82, and a second flexible substrate 85
A planar coil 81B, a central coil electrode 83B, and a peripheral coil electrode 84B are formed on one surface of the printed wiring board 86. A printed wiring 86A for connection, a central coil electrode 83C, and a peripheral coil electrode 84C are formed on one surface of an intermediate flexible substrate 86 for connection. To form

These planar coils 81A, 81B, central coil electrodes 83A, 83B, 83C, peripheral coil electrodes 84A, 84B, 84C and printed wiring 8 for connection.
6A are electrically connected in series as shown in FIG. At this time, the directions of the magnetic fluxes generated by the planar coils 81A and 81B overlapping in the vertical projection direction are set to be the same directions indicated by arrows. As described above, the inductance of the detection coil can be made larger than that of the single planar coil 41A by connecting the two planar coils 81A and 81B in series, so that the detection level is improved.

The number of flexible substrates on which the planar coils are formed is not limited to the two-layer configuration shown.

It is also possible to adopt a configuration in which a flexible substrate 52 having a planar coil formed on both surfaces and a flexible substrate 72 having a planar coil formed on one surface are used together.

Generally, the magnetic flux is concentrated near the plane coil plane. Since the toner concentration detection is to detect a change in inductance in the developer, the detection range is limited to an area close to the plane coil surface. 7 and 8, the distance d2 or d1 from the upper surface of the planar coil 41 to the outer trajectory of the stirring screw 28 is in the range of 0.05 to 2.0 mm where the magnetic flux is dense, preferably 0.3 to 1.
It is preferable to set it in the range of 0 mm. In order to secure this distance, as shown in FIG.
Is suitably installed on the inner surface side of the housing 21.

When the distance d2 or d1 is 0.3 mm or less, the toner concentration detecting surface is easily damaged by the influence of the developer stirring by the stirring screw 28.
There is difficulty in durability. Further, if the distance d2 or d1 is 1.
If it is 0 mm or more, the magnetic permeability decreases and the detection sensitivity becomes insufficient.

Even when a plurality of planar coils of the present invention are connected in series, the sensitivity rapidly decreases with an increase in the distance d, and becomes undetectable if the distance from the outer peripheral surface of the stirring screw 28 is 3 mm or more.

As shown in the enlarged sectional view of FIG. 8C again, according to the configuration in which a concave portion is formed in a part of the housing 21 and the toner concentration detecting device 40 is disposed in the concave portion, By disposing the spiral planar coil 41 having the inductance coil L on the flexible substrate 42, the flow of the developer in the developing device 20 is not obstructed, and the planar coil 41 and the stirring screw 28 are sufficiently close to each other. And the detection sensitivity of the toner density is improved.

As shown in FIGS. 7 and 8, a planar coil 41 having an inductance L, a capacitor C ₁ ,
By separating the printed circuit board 45 on which a circuit component constituted by C ₂ , the transistor Q, and the resistor R is mounted and electrically connecting these with the flexible board 42, the detection unit is downsized, The degree of freedom in arranging parts is increased, and assembly is facilitated. In particular, a small image forming apparatus or a color image forming apparatus having a plurality of developing devices is advantageous in terms of space and the like.

[0066]

As described above, according to the toner concentration detecting device of the developing device of the present invention, the detecting coil is a flat coil arranged in a spiral shape, and forms at least the detecting coil. Since the substrate to be formed is a flexible substrate, it can be easily curved and attached to the outer wall surface or the inner wall surface of the housing of the developing device.

According to the toner concentration detecting device of the developing device of the present invention, the detecting coil is formed by stacking a plurality of planar coils spirally arranged on a flexible substrate via an insulating layer. The detection level can be remarkably improved by arranging, connecting the planar coils in series, and making the direction of the magnetic flux generated by the plurality of laminated planar coils the same.

According to the eighth aspect of the present invention, the detecting coil is a flat coil spirally disposed on the flexible substrate, and the coil surface of the detecting coil is formed by the developing device. The flat coil is easily and quickly attached to the housing by being closely attached to the outer surface of the housing of the developing device so as to be equidistant from the outer peripheral trajectory of the developer stirring member rotating in the inside, Since the coil surface of the detection coil is arranged at the same distance from the developer stirring member, the detection sensitivity is improved.

According to the ninth aspect of the present invention, the detecting coil is a flat coil spirally disposed on the flexible substrate, and the coil surface of the detecting coil is formed by the developing device. The developer agitating member rotating inside the developing device is attached in close contact with the inner surface of the housing of the developing device or in a state protruding from the inner surface of the housing so as to be equidistant from the outer trajectory of the developer stirring member. Since the plane of the plane coil can be placed close to the rotation locus of the stirring screw and arranged at equal intervals, the detection accuracy is significantly improved.

Further, the detection coil is installed in close proximity to the developer agitating section of the housing of the developing device, the circuit components are fixed at an arbitrary position in the housing of the developing device, and these are electrically connected by a flexible substrate provided with the detection coil. By connecting
Downsizing and easy assembly are possible. In particular, a small image forming apparatus or a color image forming apparatus having a plurality of developing devices is advantageous in terms of space and the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of an image forming unit of an image forming apparatus.

FIG. 2 is a longitudinal sectional view illustrating a configuration of a developing device.

FIG. 3 is a sectional view taken along line AA of the developing device.

FIG. 4 is a perspective view of a developing device.

FIG. 5 is a circuit diagram showing an example of a resonance circuit of the toner concentration detection device.

FIG. 6 is a plan view, a side view, a perspective view, and an enlarged plan view of a planar coil of the toner concentration detecting device.

FIG. 7 is a cross-sectional view and an enlarged cross-sectional view illustrating a first embodiment of a toner concentration detection device.

FIG. 8 is a cross-sectional view, a partial perspective view of a housing, and an enlarged cross-sectional view of the toner concentration detection device, showing a second embodiment of the toner concentration detection device.

FIG. 9 is a perspective view, a plan view taken along an arrow A, and a cross-sectional view showing another embodiment of the toner concentration detecting device.

FIG. 10 is a circuit diagram of an oscillation circuit including a planar coil.

FIG. 11 is an exploded perspective view and an exploded cross-sectional view showing still another embodiment of the toner concentration detecting device.

FIG. 12 is an exploded perspective view, an exploded cross-sectional view, and a cross-sectional view of a stacked state showing still another embodiment of the toner concentration detecting device.

FIG. 13 is an exploded perspective view, an exploded cross-sectional view, and a cross-sectional view of a stacked state showing still another embodiment of the toner concentration detecting device.

[Explanation of symbols]

Reference Signs List 20 developing device 21 housing (developing unit housing) 21E outer wall mounting surface 21G inner wall mounting surface 27, 28 developer stirring member (developer stirring screw,
Stirring screw) 40, 50, 60, 70, 80 Toner density detection device 41, 51 (A, B), 61 (A, B, C, D) Planar coil 71 (A, B, C), 81 (A, B) B) Planar coils 42, 52, 62, 65, 72, 75, 76, 82, 8
5 Flexible substrates 43, 53, 63 (A, B), 73 (A, B, C), 8
3 (A, B, C) Central coil electrode (terminal) 44, 54 (A, B), 64 (A, B, C, D), 74
(A, B, C), 84 (A, B, C) Peripheral coil electrodes (terminals) 45 Printed circuit boards 48, 68 (A, B, C) Protective layer 86 Flexible board for connection 86A Printed wiring for connection d1, d2 distance

Claims (11)

[Claims] 1. A toner concentration detecting device of a developing device for detecting a concentration of a toner component in a developer housed in a developing device by a frequency change of a resonance circuit due to an inductance of a detecting coil and a capacitance of a capacitor. The detection coil is a planar coil arranged in a spiral shape, and at least a substrate on which the detection coil is formed is a flexible substrate. 2. A toner concentration detecting device of a developing device for detecting a concentration of a toner component in a developer housed in a developing device by a frequency change of a resonance circuit due to an inductance of a detecting coil and a capacitance of a capacitor. , The detection coil, a plurality of planar coils spirally arranged on a flexible substrate, arranged in a laminated manner via an insulating layer, connected in series with the planar coils, and
A toner concentration detecting device for a developing device, wherein the directions of magnetic fluxes generated by a plurality of stacked planar coils are made the same. 3. The toner concentration detecting device according to claim 1, wherein the detecting coil is formed on both surfaces of the flexible substrate. 4. The toner density detecting device according to claim 1, wherein the detecting coil is formed on one surface of the flexible substrate, and a plurality of the flexible substrates are arranged in a stacked manner. apparatus. 5. The toner density detecting device according to claim 1, wherein an adhesive layer is formed on at least one surface of the detecting coil. 6. The toner concentration detecting device according to claim 1, wherein a protective layer is formed on a surface of the planar coil. 7. The toner concentration detecting device according to claim 6, wherein the protective layer is made of any one of polyimide, polycarbonate, aramid, and polyethylene terephthalate. 8. A toner concentration detecting device of a developing device for detecting a concentration of a toner component in a developer housed in the developing device by a frequency change of a resonance circuit due to an inductance of a detecting coil and a capacitance of a capacitor. The detection coil is a planar coil spirally arranged on a flexible substrate, and the coil surface of the detection coil is substantially equidistant from the outer peripheral trajectory of the developer stirring member rotating in the developing device. A toner concentration detecting device for the developing device, the device being closely attached to an outer surface of a housing of the developing device. 9. A toner concentration detecting device of a developing device for detecting a concentration of a toner component in a developer housed in a developing device by a frequency change of a resonance circuit due to an inductance of a detecting coil and a capacitance of a capacitor. The detection coil is a planar coil spirally arranged on a flexible substrate, and the coil surface of the detection coil is substantially equidistant from the outer peripheral trajectory of the developer stirring member rotating in the developing device. A toner concentration detecting device for a developing device, wherein the toner concentration detecting device is mounted in close contact with the same surface as the inner surface of the housing of the developing device or protruding from the inner surface of the housing. 10. The distance between the surface of the detection coil and the outer peripheral track of the developer stirring member is 0.3 to 1.0 mm.
The toner concentration detecting device for a developing device according to claim 8, wherein the toner density detecting device is set to: 11. The toner density detecting device according to claim 8, wherein the developer stirring member is a transport screw.