JP2002278180A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which can solve the problems of a ground-stained image, a toner gush, etc., possibly occurring to, specially, a user device having a plurality of machine bodies of the same kind through easy soft control without requiring any cost. SOLUTION: Being equipped with a toner replenishing means which replenishes a development part of a developing device with toner, a toner density detecting means 5 which detects the toner density in the developing device, a toner replenishment control means which controls the toner replenishing means according to the result of comparison between the output value Vt of the toner density detecting means and a reference value Vr, and a means which corrects Vr to Va by using the result of the comparison between Vt and Vr, the image forming device detects a door 30 being opened and closed to attach and detach the developing device 4 and is characterized by the relation that V2>V1>Vr and (V2-V1) > constant α, Va>Vr, where V1 and V2 are the output values that the toner detecting means obtains before and after the door is opened and closed.

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 a copying machine, a facsimile, a printer, and the like using an electrophotographic system.

[0002]

2. Description of the Related Art In a copying machine, a facsimile, and a printer, the largest factor affecting the image density is the toner density in a developer. Therefore, in order to maintain a stable image density, it is desirable to keep the toner density constant. . As the most common toner concentration detection sensor for controlling the toner concentration to be constant, a magnetic detection sensor (T sensor) for detecting the ratio of toner and carrier in the developing unit is used.

However, the characteristic of the T sensor, which is a magnetic detector, has a problem that the detection output value fluctuates depending on the amount of charge of the developer. For example, it is assumed that there are two types of developers having the same toner concentration and different charge amounts. At this time, the detection value of the T sensor is lower for the developer having a higher charge amount, and conversely, for the developer having a lower charge amount, the T sensor value is lower.
The sensor detection value increases. To compensate for this problem,
Many machines use a P sensor that optically detects the density of a toner pattern image (P pattern) formed on an image carrier together with a sensor (Japanese Patent Application Laid-Open No. 8-11070).
Reference).

[0004] Regardless of whether only the T sensor or the T / P sensor is used, the toner supply control reference value Vr of the T sensor is corrected based on the detection results of these sensors, and Va is newly set as the toner supply control reference value. By re-establishing the target and determining the toner density, a stable image can be obtained.

[0005] As an example, T.
There is the following method for toner density control using a P sensor together. At each image forming operation, the toner concentration in the developing device is detected by the T sensor, and the toner replenishment amount is controlled in accordance with the comparison result between the output value Vt and the control reference value Vr. here,
Due to a change in the physical properties of the developer itself at the time of splicing, or a change in physical properties due to environmental conditions such as temperature and humidity, development conditions, and the like, the T sensor detects a different Vt even though there is no change in the toner concentration. Oversupply or undersupply can occur. Therefore, every time a predetermined number of images are formed, P
A pattern is formed, and the image density is detected by a P sensor,
A correction amount ΔVr of the control reference value Vr is calculated based on the output value. Then, the new reference value Va (= V
r + ΔVt) is determined and set as a new control target value (see JP-A-8-110700). As an example here, a matrix for determining the correction amount ΔVr is listed in Table 1.

[0006]

[Table 1]

The toner supply amount is determined from the difference between the corrected T sensor control target value Va and the T sensor output value Vt output at each image forming operation or at a certain timing. The toner supply amount can be replaced with, for example, the bottle rotation time (toner supply clutch ON time) if the toner supply is performed by rotating the bottle. (Vt-V
Generally, the larger the value of r), the longer the toner bottle rotation time (toner replenishment clutch ON time), assuming that the toner concentration is insufficient with respect to the target value.

Here, for example, after continuous multi-copy copying is completed or when multi-copy copying is performed in a low-temperature and low-humidity environment,
Normally, the charge amount Q / M per unit weight of the toner increases, and the image density ID decreases. At this time, the correction amount ΔVr (<＜) determined from the P sensor output value and the T sensor output value
In accordance with 0), the toner supply reference value Vr is controlled so that the toner supply is sufficiently performed, and so that the TC is increased. Conversely, when a small number of copies are made on a daily basis or when a small number of copies are made under high temperature and high humidity, the Q / M of the normal toner decreases and the image ID increases. At this time, according to the correction amount ΔVr (> 0) determined from the P sensor output value and the T sensor output value, the toner supply reference value V
r is increased, and TC is controlled to be low so that toner replenishment is not performed excessively.

[0009]

It is not unusual to install a plurality of main units of the same type in the market due to the recent price reduction of printers and copiers. In such a user, when one machine excessively outputs an image and the toner Q / M becomes high and the image density ID becomes low, there is a case where a developing device of another machine is transferred and supplied.

[0010] Here, in a machine in which an image is excessively output,
It is clear from the above description that the toner replenishment reference value Vr has been lowered by the correction. It is assumed that a developing device including a T sensor of another machine, which has regularly made a small number of copies, is put into this machine. The toner Q in this developing device
Since / M is decreasing, Vr is corrected to be higher, and the T sensor output Vt should be higher. At this time, the aforementioned machine main body is set at a low Vr so as to perform a high toner density control in order to adapt to the developing device that has been loaded just before. Therefore, when a developing device of a machine described later with a low Q / M and a high Vt is turned on, the toner is replenished until the (Vt−Vr) difference becomes close to 0, resulting in an excessive toner density and a background contamination. Problems such as image / toner ejection occur.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a background image / toner ejection which is particularly likely to occur to a user who has installed a plurality of machine bodies of the same type. It is an object of the present invention to provide an image forming apparatus which can solve the above-mentioned problems without any cost by simple software control.

[0012]

According to an aspect of the present invention, there is provided a developing apparatus for supplying a toner to a latent image formed on an image carrier to visualize the latent image. And a toner replenishing unit for replenishing toner to the developing unit of the developing device, a toner concentration detecting unit for detecting a toner concentration in the developing device, and comparing an output value Vt of the toner concentration detecting unit with a reference value Vr. In the image forming apparatus provided with a toner replenishment control means for controlling the toner replenishment means based on the result obtained, and a means for correcting Vr to Va by using the result of comparing Vt and Vr, the attachment and detachment of the developing device The opening / closing of the door necessary to perform the operation is detected, and the output values of the toner concentration detecting means detected before and after the opening / closing of the door are respectively V1 and V
When V2>V1> Vr and (V2-V1)> constant α, Va> Vr.

According to a second aspect of the present invention, there is provided a developing device for supplying toner to a latent image formed on an image carrier to visualize the latent image, and supplying toner to a developing section of the developing device. Toner supply means, a toner concentration detection means for detecting the toner concentration in the developing device, and controlling the toner supply means based on a result of comparing the output value Vt of the toner concentration detection means with a reference value Vr. Toner replenishment control means, Vt and Vr
In the image forming apparatus provided with means for correcting Vr to Va using the result of comparison, the opening and closing of the door necessary for attaching and detaching the developing device is detected, and detected before and after the opening and closing of the door. Assuming that the output values of the detected toner density detection hands are V1 and V2, respectively, (V2>Vr> V1) and (V2
−V1)> constant α, (Va> Vr).

The invention described in claim 3 is characterized in that, in the invention described in claim 1 or claim 2, the constant α can be arbitrarily changed.

Further, according to the invention described in claim 4, in the invention described in claim 1 or claim 2, the constant α is V
It is characterized by being a value that changes according to the value of r.

According to a fifth aspect of the present invention, in the first aspect of the present invention, a reference image for detecting image density is formed on an image carrier. An image density detecting means for detecting an image density of a reference image, and a reference value correcting means for correcting the reference value Vr based on an output value of the image density detecting means are provided.

In any of the above constructions, problems such as background image contamination and toner ejection, which can occur particularly for a user who has installed a plurality of machine bodies of the same type, are costly by simple software control. Can be solved without

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine as an image forming apparatus will be described below.

FIG. 1 is a schematic view of the copying machine. An electrostatic latent image is formed on the photoconductor 1 by a writing unit not shown. A charging device R2 for uniformly charging the surface of the photoconductor 1 to a negative polarity, a developing device for visualizing an electrostatic latent image formed on the photoconductor 1, and a developing device A transfer device R3 for transferring to a transfer paper is disposed.

The developing device includes a toner hopper (not shown) serving as a toner replenishing unit for replenishing toner into the developing device 4 and a toner concentration of a two-component developer composed of a carrier and negatively charged toner in the developing device 4. The apparatus includes a magnetic permeability sensor (hereinafter, referred to as a T sensor) 5 as a detecting unit, a developing sleeve 6 as a developer carrying member that carries the developer in the developing section and supplies the toner onto the photoreceptor 1. A negatively charged developing bias is applied to the developing sleeve 6 from a power source (not shown), and a predetermined developing potential is formed between the developing sleeve 6 and the photosensitive member. Reference numeral 7 denotes a reflection type photo sensor (hereinafter referred to as a P sensor) as a means for detecting the image density on the photoconductor.
It is. Here, the T sensor output value Vr outputs a lower value as the toner concentration TC in the developer increases, and the P sensor output value Vsp outputs a lower value as the image density on the photoconductor increases. I do. In the drawing, reference numeral 10 denotes a cleaning blade.

FIG. 2 is a block diagram of an electrical unit for controlling the toner density using the T sensor and the P sensor. The control unit 12 as a control means includes a CPU, a RAM, a ROM, an I / O interface, and the like. A main motor 14 and a toner supply clutch 16 are connected to the I / O interface via a driver, respectively. The I / O interface has a PWM controller 1 for supplying a predetermined voltage to the T sensor and the P sensor.
8, an A / D converter 20 for converting an analog signal output from the T sensor and the P sensor into a digital signal is connected.

As described above, for example, after a continuous multi-copy operation is completed or when a multi-copy operation is performed in a low-temperature and low-humidity environment, the charge amount of the developer increases, and the normal image density ID decreases. At this time, the toner supply reference value Vr is Va (= Vr + ΔV) according to the correction amount determined from the P sensor output value.
t), ΔVt <0, and the ON time of the toner replenishment clutch is extended so that toner replenishment is sufficiently performed (see Table 1).

The Vsp value at the appropriate ID is 0.40 ≦ Vsp <
0.52 (V) is satisfied. If Vsp is 0.52 (V) or more, it is determined that the ID is low, and the toner supply reference value Vr is corrected to be lower by 0.05 (V) to 0.20 (V) according to Vsp at that time. The P sensor determines the level of image density on the photoreceptor as Vs
Vr is corrected each time confirmation is made by p. At this time,
Depending on the use environment of the machine, etc., Vr may be corrected small each time. Here, by setting the lower limit value of Vr to 1.10 (V), it is possible to prevent the developer from overflowing in the developing container due to excessive toner replenishment or excessive toner concentration, and to prevent toner drop, background contamination, toner dust, etc. No abnormal image is generated. Conversely, Vsp is 0.40 (V)
In the following cases, it is determined that the ID is high, and the toner supply reference value Vr is corrected to be higher by 0.05 (V) to 0.20 (V) according to Vsp at that time. Here, the upper limit value of Vr is set to 2.80 (V) to prevent a shortage of the developer in the developing device and to prevent an abnormal image such as image unevenness from occurring.

Assuming a user who has installed two machines of this machine, 2K sheets / day is copied for 20 days for machine armor, Vr is set to the lower limit of 1.10 (V), and machine machine is copied at 50 sheets / day. Copying was performed for 20 days, and Vr was adjusted to the upper limit of 2.80 (V). At this time, the TC of the developer in the PCU of Machinery A is 6.4 (wt%), and the TC of the developer in the PCU of Machinery B is
C was 3.6 (wt%).

Here, the door 30 of the machine main body is opened (FIG. 3), and the PCU of the machine shell is pulled out.
I put in the second party. Incidentally, the developing case and the PCU are usually blocked by a door 30 to prevent dust and light from entering from outside and to improve the appearance of the machine main body. In order to adapt to the optimum condition of the machine B which was turned on immediately before, the T sensor output Vt of the PCU B is controlled so that Vt becomes the upper limit value of Vr 2.80 (V) so as to perform low TC control. It is a thing. Therefore, by introducing PCU B to the machine armor with a low Vr of 1.10 (V), (2.80 (V)-1.
10 (V)), the amount of toner supply corresponding to the difference is performed for each copy, and the TC eventually rises from 3.6 (wt%) to 6.8 (wt%), and the amount of TC generated when excessive TC occurs Dirty images, toner bleeding, etc. have occurred on the copied images.

Therefore, just before the PCU shell is pulled out, the PC
The value V1 output from the T-sensor of U-U at the machine A (step S3 in FIG. 4), and the T-sensor of U-U of U-U immediately after the door of the machine body is opened and PCU B is turned on The value V2 (step S4 in FIG. 4) is compared. At this time, V2>V1> Vr and (V2-V1)> α
(Α is a constant) or V2>Vr> V1 and (V2-
V1)> α (steps S6 and S11 in FIG. 4), the toner supply reference value Vr is changed to Va (> V
r) (steps S7 and S in FIG. 4).
12) By doing so, excessive replenishment is not performed in the next toner replenishment.

That is, in the related art, it is possible to prevent the toner supply corresponding to the difference of (V2−Vr) from entering, and
-Va) (steps S8 and S13 in FIG. 4). Obviously, the larger the Va value, the smaller the toner replenishment. If Vr> V2, which is outside the above condition, toner supply is not performed without correcting Vr.
Vr correction is not performed (step S16 in FIG. 4).

If V1>V2> Vr, there is no risk of excessive toner replenishment, so Vr correction is not performed (step S16 in FIG. 4). When the door is not opened and closed, the PCU cannot be replaced.
Is not corrected to make Va (> Vr) (step S16 in FIG. 4). Α is a value for discriminating the magnitude of the difference between V2 and V1, and when (V2−V1)> α, the difference between the continuously detected T sensor output values is large, that is, This is for recognizing that the charging characteristics of the developer are significantly different due to the fact that the PCU has been inserted or a sudden environmental change has occurred.

The reference value α may be a fixed value or a variable value so that it can be arbitrarily changed (see FIG. 4). Α may be a value that changes depending on the value of Vr. For example, when Vr <1.5, α =
When 0.7 and 1.5 ≦ Vr, α = 1.4. That is, especially when Vr <1.5, the TC originally targeted by the machine is
Is higher, the Vr correction is easily performed, and the margin for excessive toner supply is increased.

The detection timing of V1 and V2 is effective at any timing, such as every time an image forming operation is started or every certain time. However, when forming images continuously, the detection values of the continuous V1 and V2 do not greatly differ. Even when forming images one by one, the detection values of the continuous V1 and V2 are small when the job interval is short. Not much different. Therefore,
The invention is useful only when the PCU is replaced.

The present invention is carried out based on the result of comparison between the output value Vt of the T sensor and the toner supply reference value Vr. However, as in the present embodiment, the image density detection on the image carrier is performed. Density detection means (P sensor) for forming a reference image for use and detecting the image density of the reference image, and means for correcting Vr by using a T sensor in combination, the effect is more effective. TC control is possible.

[0032]

As described above, according to the image forming apparatus of the present invention, problems such as background image contamination and toner ejection that can occur particularly for a user who has installed a plurality of machine bodies of the same type. It can be solved without cost by simple software control.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus to which the present invention is applied.

FIG. 2 is a block diagram of a toner density control system of the image forming apparatus of FIG.

FIG. 3 is a perspective view of a door opening and closing unit of the image forming apparatus of FIG. 1;

FIG. 4 is a flowchart of a control operation according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 photoconductor (image carrier) 4 developing device 5 T sensor (toner density detecting means) 7 P sensor (image density detecting means) 30 door

Claims (5)

[Claims] 1. A developing device for supplying toner to a latent image formed on an image carrier to visualize the latent image, a toner supply unit for supplying toner to a developing unit of the developing device, A toner density detecting means for detecting the toner density of the toner, a toner replenishing control means for controlling the toner replenishing means based on a result of comparing the output value Vt of the toner density detecting means with a reference value Vr, and Vt and Vr. Vr using the result of comparing
In the image forming apparatus provided with a means for correcting to a, the opening and closing of the door necessary for attaching and detaching the developing device is detected, and the output value of the toner density detecting means detected before and after the opening and closing of the door is detected. V1 and V2 respectively, V2> V1
> Vr and (V2−V1)> constant α, V
An image forming apparatus, wherein a> Vr. 2. A developing device for supplying toner to a latent image formed on an image carrier to visualize the latent image, a toner replenishing means for replenishing toner to a developing section of the developing device, and A toner density detecting means for detecting the toner density of the toner, a toner replenishing control means for controlling the toner replenishing means based on a result of comparing the output value Vt of the toner density detecting means with a reference value Vr, and Vt and Vr. Vr using the result of comparing
In the image forming apparatus provided with means for correcting to a, the opening and closing of the door necessary for attaching and detaching the developing device is detected, and the output value of the toner density detection hand detected before and after the opening and closing of the door is detected. When V1 and V2, respectively, (V2>Vr>
V1) and (V2−V1)> constant α,
An image forming apparatus, wherein (Va> Vr). 3. The image forming apparatus according to claim 1, wherein the constant α can be arbitrarily changed. 4. The image forming apparatus according to claim 1, wherein the constant α is a value that changes according to the value of Vr. 5. An image density detecting means for forming a reference image for image density detection on an image carrier and detecting an image density of the reference image, and the reference value based on an output value of the image density detecting means. The image forming apparatus according to claim 1, further comprising a reference value correction unit that corrects Vr.