JPH05113722A - Developer layer thickness detecting device - Google Patents

Abstract

PURPOSE:To provide a developer layer thickness detecting device capable of detecting the layer thickness of a developer with high accuracy. CONSTITUTION:A developer layer thickness detecting device is provided with a developing sleeve 22 at least one longitudinal part of which is formed of a transparent member; a light projecting means 51 disposed either inside or outside the developing sleeve 22 so as to inject light toward the transparent part 42 of the developing sleeve 22; and a light receiving means 52 disposed opposedly to the light projecting means 51, either inside or outside the developing sleeve 22, that is, on the opposite side to the light projecting means 51, so as to receive the light emitted from the light projecting means 51 and transmitted through the transparent part 42 of the developing sleeve 22. The developer layer thickness detecting means then detects the developer layer thickness on the basis of the detection output of the light receiving means 52.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer layer thickness detecting device for detecting the layer thickness of a developer on a developing sleeve in an image forming apparatus such as a printer or a copying machine.

[0002]

2. Description of the Related Art In a printer, a copying machine, etc., a developing sleeve supplies a developer to a photosensitive drum. Since the thickness of the developer layer on the developing sleeve affects the image density, it is necessary to keep the developer layer thickness at an appropriate level in order to obtain a suitable image density.

Therefore, a technique has been developed in which the developer layer thickness on the developing sleeve is detected and the pressing pressure of the blade for regulating the developer layer thickness against the developing sleeve is adjusted based on the detected value.

Conventionally, the developer layer thickness is detected by irradiating the surface of the developing sleeve obliquely with light by a light projecting element and receiving the light reflected by the surface of the developing sleeve by a light receiving element. (Japanese Patent Laid-Open No. 2-16583
(See the official gazette). That is, the thicker the developer layer on the developing sleeve, the smaller the amount of light reflected by the surface of the developing sleeve, and the smaller the amount of light received by the light receiving element. There is.

[0005]

However, the conventional method of detecting the developer layer thickness has the following problems. That is, the light emitted from the light projecting element onto the surface of the developing sleeve in an oblique direction is also reflected on the surface of the developer particles on the developing sleeve, and a part of the reflected light is incident on the light receiving element. Therefore, in addition to the reflected light from the surface of the developing sleeve, the reflected light from the particle surface of the developer enters the light receiving element. Therefore, the relationship between the thickness of the developer layer on the developing sleeve and the amount of light received by the light receiving element is not uniformly determined, and the developer layer thickness cannot be accurately detected.

It is an object of the present invention to provide a developer layer thickness detecting device capable of detecting the developer layer thickness with high accuracy.

[0007]

SUMMARY OF THE INVENTION A developer layer thickness detecting device according to the present invention includes a developing sleeve having a transparent member at least a part of which is formed in a length direction, and one of an inner side and an outer side of the developing sleeve. A light projecting means that is disposed and emits light toward the transparent portion of the developing sleeve, and a light projecting means that is disposed on the opposite side of the inner side and the outer side of the developing sleeve where the light projecting means is disposed. And a light receiving unit for receiving the light emitted from the light projecting unit and transmitted through the transparent portion of the developing sleeve, and the developer layer thickness is detected based on the detection output of the light receiving unit.

[0008]

The light is emitted from the light projecting means toward the transparent portion of the developing sleeve. This light is received by the light receiving means through the transparent portion of the developing sleeve and the gap between the particles of the developer on the outer surface of the transparent portion. Then, the developer layer thickness is detected based on the detection output of the light receiving means.

As the thickness of the developer layer on the outer surface of the transparent portion of the developing sleeve increases, the amount of light received by the light receiving means decreases, so that the developer layer thickness can be detected based on the detection output of the light receiving means.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a developing unit of a copying machine.

The developing unit 1 comprises a developing device 20 for supplying the developer to the photosensitive drum 10, and a hopper 30 for supplying the developer to the developing device 20. A developer replenishing roller 31 for replenishing the developer in the hopper 30 into the developing device 20 is provided below the hopper 30.

The developing device 20 includes a housing 21 having an opening facing the photosensitive drum 10. The photosensitive drum 10 is rotationally driven in the direction of arrow A by a drive source (not shown). A non-magnetic one-component developer is stored in the housing 21.

A developing sleeve 22 for transferring the developer to the photosensitive drum 10 is rotatably arranged in the opening of the housing 21. The developing sleeve 22 is rotationally driven in the direction of arrow B by a drive source (not shown).

In the housing 21, the developer is pressed against the developing sleeve 22, the developer is supplied to the developing sleeve 22, and the developer is charged to a predetermined polarity, in this example, a conveying roller 23 for negatively charging. Are rotatably arranged. The rotation shaft of the conveyance roller 23 is connected to the output shaft of the drive motor 71 via the belt 24, and
3 is rotationally driven by the drive motor 71 in the direction of arrow C.

In the vicinity of the opening of the housing 21, a developer layer thickness regulating blade 25 for forming a uniform developer layer on the surface of the developing sleeve 22 is provided. The blade 25 is attached to a blade holding member 27 fixed to a rotary shaft 26 rotatably supported by the housing 21. The rotating shaft 26 is connected to an output shaft of a pulse motor 72 via a belt 28.

When the pulse motor 72 is rotated to change the rotation angle of the pulse motor 72, the blade 25 swings around the rotation shaft 26, and the pressing pressure of the blade 25 against the developing sleeve 22 changes.

A negative bias having the same polarity as that of the developer is applied to the developing sleeve 22 by a power source 73. A negative bias having the same polarity as the developer is applied to the transport roller 23 by the power supply 74. The absolute value of the applied voltage to the transport roller 23 is larger than the absolute value of the applied voltage to the developing sleeve 22, and the negatively charged developer is attracted to the developing sleeve 22 by the electric field formed by the potential difference.

2 and 3 show the vicinity of one end of the developing sleeve 22.

The developing sleeve 22 is composed of a cylindrical aluminum developing sleeve main body 41 whose both ends are closed, and a cylindrical transparent sleeve portion 42 attached to one end of the developing sleeve main body 41. A rotary shaft 43 extending outward is provided on both end surfaces of the developing sleeve body 41.

The transparent sleeve portion 42 has a transparent cylindrical base material 44.
And a transparent conductive layer 45 formed on the outer peripheral surface of the transparent cylindrical base material 44, and a low electric resistance transparent protective layer 46 formed on the outer peripheral surface of the transparent conductive layer 45. As a material for the transparent cylindrical base material 44, a synthetic resin such as acrylic resin is used. As the transparent conductive layer 45, for example, a TiO vapor deposition film is used. As the material of the low electric resistance transparent protective layer 46, antistatic paint Synctron C-4402 or C-442 is used.
2 (trade name) or the like is used.

The transparent conductive layer 45 and the developing sleeve body 41 are electrically connected. Low electrical resistance transparent protective layer 46
The outer surface of is subjected to surface treatment so as to have the same roughness as the outer surface of the developing sleeve body 41. Therefore, the thickness of the developer layer formed on the outer surface of the transparent sleeve portion 42 is equal to the thickness of the developer layer formed on the outer surface of the developing sleeve body 41.

In the main body of the copying machine, a U-shaped optical system holder having two arms 50a and 50b which are fitted from the end of the transparent sleeve portion 42 and are arranged to face the outside and the inside of the transparent sleeve portion 42, respectively. 50 is attached so as not to interfere with the transparent sleeve portion 42.

The optical system holder 50 is located downstream of the rotational angle position of the developing sleeve 22 where the blade 25 is located in the rotational direction of the developing sleeve 22, and the developing sleeve 22 is close to the photosensitive drum 10 and the developing sleeve 22. It is fitted to the end of the transparent sleeve portion 42 on the upstream side in the rotation direction of the developing sleeve 22 with respect to the rotation angle position.

On the outer arm 50a of the optical system holder 50,
A light projecting means 51 for emitting light toward the central axis of the transparent sleeve portion 42 and in a direction perpendicular to the surface of the transparent sleeve portion 42 is arranged. On the inner arm 50b of the optical system holder 50, at a position facing the light projecting means 51,
Light receiving means 52 for receiving the light emitted from the light projecting means 51 and transmitted through the transparent sleeve portion 42 is arranged.
The light projecting means 51 comprises a light projecting element such as a light emitting diode and a light projecting lens. The light receiving means 52 includes a light receiving element such as a photodiode and a light receiving lens.

FIG. 4 shows the electrical construction of the copying machine.

The copying machine is controlled by the CPU 61. The CPU 61 is a ROM that stores the program and the like.
62 and a RAM 63 for storing necessary data. The CPU 61 includes a drive circuit 64 for the light projecting means 51,
The amplifier circuit 65 of the light receiving means 52, the drive circuit 66 of the drive motor 25 of the transport roller 23, the drive circuit 67 of the pulse motor 72, etc. are connected via input / output interfaces 68, 69.

In the ROM 62, the light receiving means 52 corresponding to the proper range of the developer layer thickness obtained by the experiment in advance.
The data regarding the detection output of is stored.

FIG. 5 shows a developer layer thickness control processing procedure by the CPU 61.

When the print key of the copying machine is turned on, the developing device 20 is preliminarily operated (step S1). That is, the developing sleeve 22 and the conveying roller 23 are driven to rotate, the developer in the housing 21 adheres to the developing sleeve 22, and the blade 25 forms a uniform developer layer on the surface of the developing sleeve 22.

At this time, the rotational angular position of the pulse motor 72 is adjusted to the previously determined position. That is, the pressing pressure of the blade 25 against the developing sleeve 22 is adjusted to the previously determined pressing pressure.

In the course of the preliminary operation of the developing device 20, the developer layer thickness is detected (step S2). That is, the light projecting means 51 is driven, and light is emitted from the light projecting means 51. Of the light emitted from the light projecting means 51, the light that has passed through the gap between the particles of the developer on the outer surface of the transparent sleeve portion 42 is transmitted through the transparent sleeve portion 42 and is received by the light receiving means 52.

The thicker the developer layer on the outer surface of the transparent sleeve portion 42, the more the amount of light emitted from the light projecting means 51 that passes through the gap of the developer particles on the outer surface of the transparent sleeve portion 42. As the developer layer on the outer surface of the transparent sleeve portion 42 becomes thicker, the detection output of the light receiving means 52 becomes smaller. The detection output of the light receiving means 52 is the amplification circuit 65.
Is amplified and the output of the amplifier circuit 65 is read.

Then, the read output value S of the amplifier circuit 65 is set to a predetermined reference range (S _min ~
Whether the S _max) within the reference range (S _min to S _max) is greater than or less is determined (step S3).

The read output value S is based on the reference range (S _min
When to S _max) is greater than (S> S _max), that is, when layer developer is thinner than the proper range, the predetermined rotation angle rotation pulse motor 72 in the counterclockwise direction (direction indicated by the arrow D in FIG. 1) The blade holder 27 is driven to rotate the rotary shaft 2
It swings counterclockwise about the center of 6 by a predetermined rotation angle. As a result, the pressing pressure of the blade 25 against the developing sleeve 22 is weakened (step S4). That is, the pressing pressure of the blade 25 is adjusted so that the developer layer thickness becomes thick.

The read output value S is the reference range (S _min
.About.S _max ) (S <S _min ), that is, when the developer layer thickness is thicker than the appropriate range, the pulse motor 72 is rotationally driven in the clockwise direction by a predetermined rotation angle, and the blade holder 27 is rotated. It swings clockwise about the center of a predetermined rotation angle. This allows the blade 25
The pressing pressure on the developing sleeve 22 is strengthened (step S5). That is, the pressing pressure of the blade 25 is adjusted so that the developer layer thickness becomes thin.

The read output value S is the reference range (S _min
~ S _max ) (S _min ≤ S ≤ S _max ),
That is, when the developer layer thickness is within the proper range, the rotation angle position of the pulse motor 72 is maintained as it is.

When the pressing pressure of the blade 25 against the developing sleeve 22 is controlled according to the detection output of the light receiving means 52, copying processing for the set number of sheets is executed (step S6).

In the above embodiment, the pressing pressure of the blade 25 against the developing sleeve 22 is controlled based on the detection output of the light receiving means 52, but the rotation speed of the conveying roller 23 is controlled based on the detection output of the light receiving means 52. You may do so.

That is, when the read output value S of the amplifier circuit 65 is larger than the reference range (S _{min to} S _max ), the drive motor 71 is controlled and read so that the rotation speed of the carry roller 23 becomes faster. When the output value S of the amplifier circuit 65 is smaller than the reference range (S _{min to} S _max ), the drive motor 71 is controlled so that the rotation speed of the carry roller 23 becomes slow.

Further, the voltage applied to the conveying roller 23 may be controlled based on the detection output of the light receiving means 52. That is, the read output value S of the amplifier circuit 65
Is larger than the reference range (S _{min to} S _max ), the absolute value of the negative applied voltage applied to the carrying roller 23 is increased, that is, the applied voltage to the carrying roller 23 and the developing sleeve 22 are applied. The applied voltage to the transport roller 23 is controlled so that the potential difference from the applied voltage becomes large. When the read output value S of the amplifier circuit 65 is smaller than the reference range (S _{min to} S _max ), the conveyance roller 2
3 is applied to the transport roller 23 so that the absolute value of the negative applied voltage applied to the transport roller 23 is small, that is, the potential difference between the voltage applied to the transport roller 23 and the developing sleeve 22 is small. The voltage is controlled.

In the above embodiment, of the light emitted from the light projecting means 51, the light which has passed through the gap of the developer particles on the outer surface of the transparent sleeve portion 42 is received by the light receiving means 52,
The developer layer thickness is detected based on the detection output of the light receiving means 52. Therefore, unlike the conventional case, the influence of the light reflected by the surface of the developer particles is less likely to occur, and the accurate developer layer thickness can be detected.

In the above embodiment, only one end of the developing sleeve 22 is transparent, but the developing sleeve 22 may be entirely transparent. Further, the light projecting means 51 is arranged inside the developing sleeve 22, and the light receiving means 52 is provided.
May be arranged outside the developing sleeve 22.

[0044]

According to the present invention, the developer layer thickness can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a developing unit of a copying machine showing an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing the vicinity of one end of the developing sleeve.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is an electrical block diagram showing an electrical configuration of the copying machine.

[Explanation of symbols]

 22 developing sleeve 42 transparent sleeve part 51 light projecting means 52 light receiving means

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[Procedure amendment]

[Submission date] October 22, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a configuration diagram of a developing unit of a copying machine showing an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing the vicinity of one end of a developing sleeve.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is an electrical block diagram showing an electrical configuration of the copying machine.

FIG. 5 is a flowchart showing a developer layer thickness control processing procedure by a CPU.

[Explanation of reference numerals] 22 developing sleeve 42 transparent sleeve portion 51 light emitting means 52 light receiving means

Claims (1)

[Claims] 1. A developing sleeve, at least a part of which in the lengthwise direction is formed of a transparent member, and a light which is arranged on one of an inner side and an outer side of the developing sleeve and emits light toward a transparent portion of the developing sleeve. The light projecting means and the inner side and the outer side of the developing sleeve, which are opposite to the side on which the light projecting means is arranged, are arranged so as to face the light projecting means, and are emitted from the light projecting means to cover the transparent portion of the developing sleeve. A developer layer thickness detecting device comprising: a light receiving means for receiving the transmitted light, and detecting the developer layer thickness based on a detection output of the light receiving means.