JPS6352161A - Image forming device - Google Patents

Abstract

PURPOSE:To always obtain a high-quality, image, by forming the detection window of a detector in a curved state and providing the window in such a state that the window is faced to the curved developing agent moving area of a developing device. CONSTITUTION:A detector 33 is constituted of glass and a dichromic mirror formed by performing vapor deposition on glass. The shape of the detector 33 on the side facing a sleeve 251 is formed in a curved state so that it can be provided along the surface of the sleeve 251. Since the detector 33 is formed along the peripheral surface of the sleeve 251 in such way, a thickness (l) of a developing agent is formed between the detection window 33 and sleeve 251 and, therefore, the detection window 33 can always be contacted with the developing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION A. [-U portion unreleased II] relates to image forming apparatuses such as electrophotographic copying machines and electrostatic recording devices 921 used for various purposes, especially toner A latent image holding member is formed by carrying a developer containing a mixture of and magnetic particles (carrier) on a development holding member! The present invention relates to an image forming apparatus equipped with a developing device for developing an image.

In general, a developing device included in an image forming device such as an electrophotographic copying device or an electrostatic recording device used for various purposes is a device that mixes toner and magnetic particles (carrier). However, the mixing ratio of toner and carrier (toner concentration) is an extremely important factor in stabilizing image quality. Therefore, in order to obtain good image quality, it is necessary to accurately detect the concentration of toner in the developer that is used and wasted, and to strictly control the amount of toner replenishment according to changes in the concentration of toner in the developer. (Developer concentration) must be kept constant.

Conventionally, various configurations have been proposed as a two-component developer developing device, but most commonly, as partially illustrated in FIG. The structure is such that a body 251 is arranged. The developer carrier 25
1 is usually, but not limited to, a non-magnetic sleeve as shown in the figure, with a magnet arranged inside. With this structure, when the sleeve 251 rotates in the direction of the arrow 52, the developer flows into the sleeve 2.
51 and conveyed to the opening of the developer container facing a latent image carrier (not shown). In the process, the developer T in the sleeve 251-h is regulated to a predetermined thickness by the doctor blade 51.

Although various devices have been proposed for accurately detecting toner concentration in a developing device having the above configuration, the most effective developer concentration detecting device is considered to be an optical type. It is schematically illustrated in FIGS. 7 and 8. In other words, developer concentration detection! I! The position c has a detection head 30 and a detection unit 40.

The detection head 30 has two optical fibers 32, 34 arranged at a predetermined angle and a reflection mirror 31. A detection unit 40 disposed adjacent to the entrance to the optical fiber 32
The white illumination light from the light source 42 reaches the reflection mirror 31 via the optical fiber 32, is reflected by the reflection mirror 31, and is formed on the detection head 30 to detect the developer concentration! ! 33 is illuminated. The detection window 33 includes a glass that reflects one spectral energy light and transmits another spectral energy light different from the spectral energy light, and a tN R on the glass.
It is made up of a dichroic mirror that has been subjected to, for example, white illumination light, so that it reflects the visible light component with a wavelength of about 700 nm or less, and transmits the near-infrared component with a wavelength of about 700 nm or more. configured. Therefore, the near-infrared light transmitted through the detection window 33 irradiates the developer on the developing sleeve 251, and the reflected light hits the detection window 33 again! The light is reflected by the reflection mirror 31 or transmitted through the detection window 33 and guided directly to the optical fiber 34, passes through the color separation filter 44 of the detection unit 40, and enters the light receiving element 45 of the silicon φ photodiode.

On the other hand, the light reflected on the surface of the guichroic mirror 33 is also reflected again on the reflection mirror 31 or directly transmitted to the optical fiber 34.
The light passes through a color separation filter 44 and enters a light receiving element 45, which is a silicon photodiode.

The color separation filter 44 consists of filter members 47 and 48 having an area that covers the light-receiving part of the light-receiving element 45, and the filter member 47 collects only the visible component of approximately 700 nm or less reflected on the surface of the dichroic mirror (hereinafter referred to as "reference"). The filter member 48 transmits light (hereinafter referred to as "detection light d") that is the near-infrared light of approximately 700 nm or longer that has passed through the detection window 33 and is reflected by the developer. To Penetrate.

The color separation filter 44 is movable in the direction of the arrow by a solenoid 49 and a spring (not shown), and at the beginning of the developing operation, a filter member 47 is placed in front of the light receiving element 45 to allow the reference light r to enter the light receiving element 45. In the second half of the developing operation, a filter member 48 is placed in front of the light receiving element 45 to allow the detection light d to enter the light receiving element 45. The operation timing and the detection timing of the reference light r and the detection light d are set to the first
Shown in Figure 3.

Here, the signal generated by the reference light r is a signal for detecting deterioration of the light source and dirt in the detection system, and the signal generated by the detection light d is a signal output corresponding to the developer concentration. A strong signal will give a large signal, and a small signal will give a small signal.

The operation of the developer concentration detection device having the above structure will be explained. Light received by the light receiving element 5 is outputted as a voltage from the amplifier circuit P through the amplifier circuit 41 shown in FIG. 1O. The voltage is input manually from 0 of the processing circuit shown in FIG. 11 and enters the A/D conversion circuit. A signal obtained by voltage conversion and A/D conversion of the light from the reference light r is converted into a reference light signal D1. If the signal obtained by voltage conversion and A/D conversion of the light from the detection light d is the detection light signal nz, then the signal D1. DZ enters the arithmetic circuit and produces a differential signal (D
3), that is, Dz −Dr =03 is obtained. This difference signal D3 becomes a developer concentration signal. The memory stores a difference signal D9. which should be taken when the developer concentration is normal. is stored as a standard developer concentration signal. 0
The 2 signal is a signal that becomes smaller when the developer concentration becomes thinner and becomes larger when the developer density becomes darker.Therefore, the developer concentration signal D3 similarly becomes smaller when the developer concentration becomes thinner and becomes larger when the developer density becomes darker.

The developer concentration signal D3 is sent from the arithmetic circuit, and the standard developer concentration signal D3o is sent from the memory to the comparison circuit. A comparison circuit compares D3 and 030, and when D3<D1°, it is determined that the developer concentration is low, and a replenishment signal is sent, and D3≧
At D3o, it is determined that the developer concentration is appropriate or excessive, and the replenishment signal is not sent. When the replenishment signal is sent, the toner replenishment device! ! (not shown) sends toner to the developing device and replenishes the toner.

Hereinafter, the developer concentration detection device described in Section 14 has the feature that it can prevent abnormal toner concentration detection due to changes in the illuminance of the light source lamp and changes in the sensitivity characteristics of the light receiving element, and can perform stable toner concentration detection. However, it had the following drawbacks.

Referring to FIG. 7, the detection window 33 of the developer concentration detection device
The relationship between the developing sleeve 251 and the developing sleeve 251 is shown. The developer T consisting of carrier and toner is exposed to the arrow 52 during development as described above.
The thickness of the developer on the sleeve is regulated by the doctor blade 51. As can be seen in FIG. 7, the developer T carried by the circular sleeve 251 is detected because the detection window 33 is located in the V row with respect to the tangent to the sleeve 251. Although the developer is in sufficient contact with substantially the lower half, the developer is not sufficiently contacted with the -L half of the detection window and is transported by the sleeve 251. This means that the developer conveyed from part A of the developing device passes between the sleeve 251 and the detection window 33.
The developer layer thickness is regulated at 2tc to the point where it is the shortest.
After that, the developer is transferred to section B while keeping its layer thickness approximately the same, so it is thought that the developer escapes from the upper part of the detection window.

According to the research and experiments conducted by the present inventors, the upper surface of the detection window is always kept free of developer, but in reality,
It has been found that when the developer is circulated in the developing device, the toner separated from the carrier and scattered adheres to the upper surface of the detection window, and a large amount of only toner adheres to the upper surface of the detection window, resulting in a quasi-accumulation.

If density detection is performed in such a state, there will be a lot of toner attached to the detection window, and the state will be the same as the state where the developer concentration is high, so even though the developer concentration is low, the detected light d As a result, the developer concentration signal D3 becomes larger than the standard developer concentration signal D10. Therefore, when the developer concentration changes, the developer concentration is controlled in a low concentration range.

The graph shown in FIG.
! This graph shows the change in developer concentration when the developer concentration signal is obtained at position A. As can be seen from the graph, the developer concentration decreases by 8% as the number of copies increases compared to the initial developer concentration of 10%. The developer concentration is controlled by the degree of Currency is
When the developer concentration is controlled by such a developer concentration detection device, the developer concentration decreases, resulting in a disadvantage that the copy becomes a pale image or the image has a blemish or the like, which deteriorates the image quality. occurs.

The purpose of ``& Bean 2 and No Blood 1'' is to eliminate the drawbacks of conventional developer concentration detection devices as described in E, to always control the developer concentration at the same concentration, and to prevent the appearance of blemishes, etc. An object of the present invention is to provide an image forming apparatus capable of obtaining high-quality images.

3I Old - The above [1] is achieved by the image forming apparatus according to the present invention. In summary, the present invention is a development method that develops a latent image formed on a latent image carrier using a two-component developer containing a mixture of toner and carrier! An image forming apparatus equipped with a position A has a developer concentration detection device that detects the concentration of developer by detecting a 72 ratio of toner and carrier, a detection window of the detection device is formed in a curved shape, and The image forming apparatus is characterized in that the image forming apparatus is installed so as to face the curved developer moving area of the apparatus.

Next, an image forming apparatus according to the present invention having a characteristic developer concentration detection device will be described in more detail.

The developer concentration detection device according to the present invention has the same structure as the developer concentration detection device 'A' described in connection with FIGS. 7 and 8 above. That is, in the present invention, the developer concentration detection device has a detection head 30 and a detection unit 40'J having the same configuration, and also has optical paths and processing methods for developer concentration detection light, reference light, etc., and a developer concentration detection device. The concentration control method is also the same as in the conventional example. However, the detection window 3 of the detection head 30
The shapes of the three are strikingly different.

According to the present invention, the detection window 33 is the same as the conventional example in that it is composed of glass and a dichroic mirror formed by vapor deposition on the glass, but as shown in FIGS. The shape of the side facing 251 is curved along the sleeve surface. As understood from 1IA, when the sleeve 251 rotates in the direction of the arrow 52, the developer T around the sleeve, for example, the developer T at point A is transported from point 11A to point C-+B. According to this, since the detection window 33 is formed along the circumferential surface of the sleeve, the thickness of the developer is different from the detection window 33 and the sleeve 2.
51, so that the detection window 33 is always in contact with the developer. Therefore, according to the configuration of the present invention, the detection window 33 as described in connection with FIG.
If only the toner is deposited in the upper half of the toner and the developer concentration is controlled in the low concentration range when the developer concentration changes, the five defects α will disappear.

3 and 4 show another embodiment of the developer concentration detection device according to the present invention. In the unimplemented example, the detection window 33
is curved along the sleeve by L1. Even with this shape, one half of the detection window 33 is brought into contact with the developer depending on the thickness of the developer at point B, and the same effect as in the previous embodiment can be obtained.

FIG. 5 shows still another embodiment of the developer concentration detection device according to the present invention. In this embodiment, the developer concentration detection device is of an electric type, and includes a detection unit disposed adjacent to the sleeve. ) 30E. The detection unit is formed by having a curved side facing the sleeve 251, and an electric coil is disposed inside, and the inductance of the coil changes according to changes in developer concentration. As the developer concentration decreases, the developer's apparent l-
When the magnetic permeability increases, this is detected by an internal electromagnetic circuit, and when it falls below the standard developer concentration, toner is replenished and the developer concentration is controlled. By curving the surface 33E along the sleeve 251, stable developer CIff detection becomes possible.

As described in 1-1 below, according to the present invention, since the developer is configured to hit the entire surface of the detection window 33 or 33E, reflected light corresponding to the developer concentration is always detected without causing the toner tti pattern. As a result, developer concentration detection can be stabilized.

The graph shown in FIG. 6 shows the change in developer concentration when the developer concentration was controlled using the developer concentration detection device according to the present invention. It will be understood that the developer concentration is always controlled stably.

In the above embodiments, the developer concentration detection method was explained using a specific optical developer concentration detection device and an electric developer concentration detection device. In the equation, other methods may be used to detect the toner concentration using changes in inductance occurring in the coil.

In addition, the sleeve can be attached to a latent image carrier such as an electrophotographic light source.
Although the description has been given as a developing sleeve that performs development on the surface of the sleeve, the developer concentration may be detected using a developer concentration detection sleeve that is provided separately from the development sleeve and does not perform development. A similar effect can also be obtained by providing a detection window in the developer container and forming the window into a curved shape. Furthermore, instead of the developing sleeve, a curved developer guiding member is provided somewhere in the developer movement area within the developing device, and a curved detection window is provided facing the curved member, thereby achieving the above-described method. Even if the same operation is performed, the same effect can be obtained by 4"l. Examples of the developer moving area include, for example, the stirring area of a developer mixing and stirring member (e.g. screw, stirring bar, etc.), and the developer moving area in the longitudinal direction. A developer transport path such as a moving screw or a temporary developer retention area 1
For example, the end of a screw can be mentioned.

Although the detection window 33 is made of glass and a dichroic mirror with a thin coating applied to it, it is also possible to use a resin that is easy to process, such as polycarbonate, which spectrally transmits visible light and near-infrared light. A reflective filter or the like may also be used.

The image forming apparatus according to the present invention configured as follows:
Detection by a developer concentration detection device in an image type l& device equipped with a development device that carries a developer consisting of a mixture of toner and magnetic particles (carrier) on a developer carrying member and develops an HII image formed on a layered image carrier. By curving the window so that the developer comes into contact with the entire surface of the detection window, there are no detection errors caused by toner accumulation on the detection window, and stable developer concentration control is always performed, resulting in consistently high image quality. This has the effect that it is possible to obtain images of

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of an embodiment of a developing device and a developer concentration detecting device included in an image forming apparatus according to the present invention. FIG. 2 is a perspective view of the detection head of the developer concentration detection device of FIG. 1. FIG. 3 is a partial cross-sectional view of another embodiment of the developing device and developer concentration detecting device used by the image forming I& device according to the present invention. 4 is a perspective view of the detection head of the developer concentration detection device of FIG. 3. FIG. FIG. 5 is a partial sectional view of still another practical example of a developing device and a developer concentration detecting device included in an image forming apparatus according to the present invention. FIG. 6 is a graph showing the result of developer concentration adjustment by the developer concentration detection device included in the image forming apparatus according to the present invention. FIG. 7 is a partial sectional view of a phenomenon device and a developer concentration detection device included in a conventional image forming apparatus. FIG. 8 is a partially sectional top view of the developer concentration detection device of FIG. 7. FIG. 9 is a timing chart showing the operation timing of the developer concentration detection device shown in FIG. 10 and 11 are a circuit diagram and a block diagram showing the electric circuit of the developer concentration detection device of FIG. 7. FIG. 12 shows that the conventional image forming apparatus is 1! Enjoy developer +i using developer concentration detection device:! It is a graph which shows the result of degree adjustment. 251, Developing sleeve 30.30E: Detection head 33.33E: Detection window 40, Detection unit Agent Patent attorney Akira Kurahashi - Figure 5 P Figure 6 Figure 1 Image Figure 8 Figure 9 Figure 1 O Figure 4 5 Figure 11

Claims (1)

[Scope of Claims] 1) In an image forming apparatus equipped with a developing device that develops a latent image formed on a latent image carrier using a two-component developer containing a mixture of toner and carrier, a developer concentration detection device for detecting the concentration of the developer by detecting the mixing ratio of the developer, the detection window of the detection device being curved;
An image forming apparatus characterized in that the image forming apparatus is installed facing a curved developer moving area in a developing device. 2) The device according to claim 1, wherein the detection window of the developer concentration detection device is arranged to face the developing sleeve of the developing device. 3) The device according to claim 1 or 2, wherein the developer concentration detection device is an optical developer concentration detection device that detects the reflective density of the developer using an optical system using a light source and a light receiving element. 4) The device according to claim 1 or 2, wherein the developer concentration detection device is an electrical developer concentration detection device that electrically detects the concentration of the developer.