JPH09211952A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent toner from dropping, overflowing and flowing into a developing unit, at the time of supplying the toner by supplying the toner to a first toner supplying container from a second toner supplying container, with a control means, when a second detecting member for detecting the quantity of the toner in the second toner supplying container detects the deficiency of the toner. SOLUTION: When the absence of the toner is detected by a remaining amount detecting sensor 113 for a second toner supplying device, during consecutive copying, a second screw 112 is driven for the time up to the completion of the operation of a device (postrotation) after the formation of the image in a drum part is completed. In other words, the second screw 112 is driven for a specified time, to supply the toner from a second hopper to a first hopper and the upper space V (upper space from a toner sensor) of the first hopper is filled with the toner. Thus, the toner is supplied from the second hopper to the first hopper and after this first hopper becomes full, a device final control element is urged to supply the toner to the second hopper by a toner bottle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image of a copying machine or a printer such as an electrophotographic system or an electrostatic recording system in which toner is attached to an electrostatic image formed on an image carrier to make it visible. Forming apparatus

[0002]

2. Description of the Related Art Conventionally, a developer concentration control device (ATR) for controlling toner replenishment from a hopper as a toner replenishing container into a developing device in order to maintain a predetermined toner concentration in a two-component developer in a developing device. Are known. For toner replenishment control, for example, a method is known in which the toner concentration in the developing device is detected by irradiating the toner in the developing device with light and detecting the amount of reflected light.

When the toner in the developing device is less likely to reflect light, a toner patch as a reference toner image corresponding to a predetermined density is formed on the image carrier to measure the toner density in the developing device. However, it is known that the density of this toner patch is optically detected by a sensor.

Although various other control methods are known,
In any case, it is strongly desired that the accuracy of the replenishment amount to the developing device is higher than that of the toner hopper in order to stabilize the toner concentration.

In order to improve the replenishment accuracy of the toner replenishment amount from the hopper to the developing device, a first hopper that replenishes the developing device with toner and a second hopper that replenishes the toner to the first hopper are provided. It is known to provide.

[0006]

When the amount of toner in the second hopper decreases below a predetermined amount, the operator replenishes the second hopper with toner from the outside.

The following problems may occur when the toner is replenished by the operator.

That is, when replenishing the toner from the toner bottle to the hopper, if the toner is hardened and the fluidity is poor, the toner is not discharged from the toner bottle. It is a general practice to replenish the hopper with toner in this state. At this time, the toner in the lower part of the hopper has a function of preventing the toner having a good fluidity supplied from above from leaking outside, that is, from the hopper outlet. However, depending on the tightness of the residual toner in the hopper and the fluidity of the toner to be replenished,
In rare cases, the flow of toner cannot be stopped, and toner flows from the outlet of the second hopper to the developing device connected through the first hopper, and a fog image is generated during subsequent image formation, or the amount of inflow. If the amount is large, the problem may occur that the developer overflows from the developing device.

The same phenomenon (problem) occurs in both the normal single tank hopper and the above-mentioned two-stage hopper.

As a measure against this problem, a method of increasing the amount of residual toner at the time of detection by raising the position of the toner remaining amount detection sensor of the second hopper can be considered, but if the size of the hopper in the height direction is the same. Therefore, there is a drawback that the space above the detection surface is reduced, that is, the amount of toner that can be replenished from the outside is reduced.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an image carrier, a developing device for developing an electrostatic image on the image carrier, and a first toner for supplying toner to the developing device. The replenishment container, the first detection member for detecting the amount of toner in the first toner replenishment container, the second toner replenishment container for replenishing the toner in the first toner replenishment container, and the first detection member. An image forming apparatus comprising: a control unit that controls replenishment of toner from a second toner replenishing container according to an output; and a second detecting member that detects the amount of toner in the second toner replenishing container. An image forming apparatus, wherein the control means replenishes toner from the second toner replenishing container to the first toner replenishing container when the second detecting member detects the toner shortage.

[0012]

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

First, the overall configuration of an embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. Although a four-drum type digital full-color copying machine is shown in the present embodiment, it goes without saying that the present invention is equally applicable to various other image forming apparatuses such as a monochrome electrophotographic type and an electrostatic recording type.

This color image forming apparatus is capable of forming a visible image (toner image) of each color of yellow, magenta, cyan and black in the main body of the apparatus.
The fourth four image forming sections Pa, Pb, Pc and Pd are arranged linearly, and each of the image forming sections Pa to Pd is arranged.
Are dedicated photoconductor drums 1a, 1b, 1 serving as image carriers.
c and 1d, respectively. Each photoconductor drum 1a to 1d
Are driven to rotate in the direction of the arrow shown in the figure, and there are dedicated image forming process means around them, for example, the charging means 2.
a, 2b, 2c, 2d, image exposure means 3a, 3b, 3c, 3d such as a laser scanner, developing means 4a, 4b, 4c,
4d, and cleaning means 5a, 5b, 5c, 5d, etc. are provided.

A recording material carrying means, in this example, an endless recording material carrying belt 8 is provided between a plurality of rollers below the photosensitive drums 1a to 1d of each image forming portion Pa to Pd. The transfer charging means 6a, 6b, 6c, and 6d are arranged in the interior. Further, a sheet feeding section is arranged on the right side of the recording material carrying belt 8 in the figure, and a fixing means 7 is arranged on the opposite side, that is, on the left side of the figure. Further, a pair of registration rollers 13 for feeding the recording material P at a timing is arranged between the paper feeding portion and the recording material carrying belt 8. The recording material P is fed from the paper feeding portion to the registration rollers. The recording material carrying belt 8 is fed and held via the recording material carrying belt 13.
Of the image forming units Pa to
The Pd is sequentially transferred to the transfer area.

In the above-mentioned structure, the recording material P sent out from the paper feeding section is temporarily stopped when its front end is slightly sandwiched by the registration rollers 13, and the first image forming section P is then stopped.
It is sent out at the same timing as the image forming process a, and is fed onto the recording material carrying belt 8. This first
In the image forming portion Pa, the image data of the yellow component color in the original image is scanned with a laser beam or the like on the photosensitive drum 1a uniformly charged by the charging means 2a to form an electrostatic latent image of the yellow component color. To be done. This electrostatic latent image becomes a yellow visible image with yellow toner attached by the developing means 4a.

On the other hand, the recording material P is carried while being carried on the recording material carrying belt 8, and in the transfer area below the photosensitive drum 1a of the first image forming portion Pa, the photosensitive member is actuated by the transfer charging means 6a. The yellow visible image formed on the drum 1a, that is, the toner image is transferred onto the recording material P. While the yellow toner image is thus transferred onto the recording material P, an electrostatic latent image of a magenta component color is formed on the second image forming portion Pb, and this electrostatic latent image is magenta by the developing means 4b. The recording material P is a toner image, and the recording material P is the second image forming portion Pb.
When the magenta toner image is conveyed to the lower transfer area of the photosensitive drum 1b, the magenta toner image is transferred to the transfer area, and is transferred in a state of being superposed on the yellow toner image on the recording material P by the action of the transfer charging means 6b. To be done.

Hereinafter, the third and fourth image forming portions Pc and Pd will be described.
In the same manner, similarly to the first and second image forming portions Pa and Pb, cyan and black toner images are sequentially formed, and these are sequentially formed on the recording material P conveyed by the recording material carrying belt 8. Toner images are multi-transferred.

When the image forming process is completed, the recording material P is separated from the recording material carrying belt 8 and fixed by the fixing means 7.
Then, the desired full-color image is obtained by batch fixing. The residual toners are removed from the photosensitive drums 1a to 1d of the image forming portions Pa to Pd after the transfer by the cleaning units 5a to 5d to prepare for the subsequent latent image formation.

A two-component developing system is used in which each color of yellow (Y), magenta (M), cyan (C), and black (Bk) is provided with a toner and a carrier, and the mixing ratio of the toner and the carrier is maintained at a predetermined ratio. Developer concentration control device (A
TR).

In the Y, M and C image forming stations,
The optical ATR sensors 9a, 9 are used to correct the changed toner density in the developing devices 4a, 4b, 4c by developing the latent image.
b and 9c are provided in the developing devices for the respective colors, and toner is supplied to the developing devices from a toner hopper (not shown) based on the detection signal thereof.

As described above, each of Y, M, and C adopts the optical ATR system and has a density detection sensor (hereinafter referred to as an ATR sensor) in the developing device. The optical ATR method utilizes the property that the toner reflects the infrared light and the carrier absorbs the infrared light,
The amount of light reflected by light irradiation is detected. Bk uses a carbon toner having a high cost merit. Since the carbon toner absorbs infrared light, it is not suitable to use this optical ATR method in the developing device.

Therefore, it is preferable that BK adopt a method different from the optical ATR method. The BK ATR method will be described below.
FIG. 3 is a diagram showing an image processing unit for forming a latent image and a fourth image forming station (Bk) including a toner hopper. (First to third stations are omitted from the drawing.) The latent image formation will be described in detail with reference to the drawing. First, the image of the original 80 is read by the CCD 81, the obtained analog image signal is amplified to a predetermined level by the amplifier 82, and the analog-digital converter (A / D converter) 8
3 converts into a digital image signal of 8 bits (0 to 255 gradations). Next, this digital image signal is supplied to a .gamma. Converter (a converter which is composed of a 256-byte RAM in this example and performs density conversion by a look-up table method) 84, and is .gamma. Input to the device (D / A converter) 85. Here, the digital image signal is converted again into an analog image signal and supplied to one input of the comparator 87. The other input of the comparator 87 is supplied with a triangular wave signal of a predetermined cycle generated from the triangular wave generating circuit 86, and the analog image signal supplied to one input of the comparator 87 is compared with this triangular wave signal and pulsed. It is width modulated. This pulse-width-modulated binary image signal is directly input to the laser drive circuit 88, and the laser diode 8
9 is used as a signal for on / off control of light emission. The laser light emitted from the laser diode 89 is scanned in the main scanning direction by a well-known polygon mirror 90, and f / θ
It is irradiated onto the photosensitive drum 1d, which is an image carrier rotating in the direction of the arrow, through the lens 91 and the reflection mirror 92,
An electrostatic latent image will be formed.

Further, in order to correct the toner density which has changed in the developing device 4d due to the development of the latent image, a video count type developer density control device is provided for controlling the output level of the digital image signal for each pixel. The toner has been added up and the toner is being predicted to be replenished. That is, the analog-digital converter 8
The output level of the image signal converted into the digital signal by 3 is integrated for each pixel, and the output level is calculated by the video counter 93.
Is converted into a video count number and sent to the CPU 94. CP
U94 converts the video count number into a replenishment amount, drives the motor 104 for a corresponding time, and rotationally drives the toner conveying screw 102 in the toner replenishment tank 101 that contains the toner T. An appropriate amount of toner is replenished therein to keep the toner density in the developing device 4d constant.

However, since the above-mentioned video count system is a predictive replenishment, if the toner replenishment amount from the hopper deviates from the expected value due to a change in the fluidity of the toner in the hopper, etc. The toner density of the developer deviates from the initial setting value.

A second developer concentration control device is provided for the purpose of correcting the deviation of the toner concentration of the developer.
It is used in combination with the first developer concentration control device of the video count system. This second developer concentration control device is operated at a predetermined timing to perform laser exposure and development on the photoconductor drum 1d to form a patch-shaped reference image, and to determine the toner concentration of the patch-shaped reference image. It is detected by the optical detection means 10 to determine whether the toner is over-replenished or insufficient, and the next video count number from the video counter 93 is corrected based on this determination, and the CPU
The toner replenishment signal from 94 is corrected.

The detecting means 10 is preferably provided downstream of the transfer position in the moving direction of the photosensitive drum 1d in order to prevent toner contamination, but may be provided upstream of the transfer position in the moving direction of the drum 1d. is there.

The timing at which the reference image is formed on the photosensitive drum is the timing at which the reference image is not transferred onto the transfer material. Normally, a plurality of images are continuously formed by inputting a single image formation start signal to the apparatus (for example, pressing a copy button once). During continuous copying, before the image formation on the first sheet or after the image formation on the last sheet is completed,
Alternatively, the reference image may be formed between the sheets (between the transfer materials). However, a system using a transfer belt has a problem in forming a reference image between sheets. In other words, there is a problem that a part of the toner, which is the reference image, is transferred to the belt, and when the belt makes a round, the back side of the next transfer material is stained. In order to avoid this problem, it is preferable that the photosensitive drum and the transfer belt are once separated at the time of forming the reference image (when passing the transfer nip). The separating operation is performed by lowering the transfer belt. During this time, Bk
Not only the transfer process of other colors cannot be performed, but image formation is temporarily interrupted even during continuous copying.

As described above, it is not preferable to frequently perform the above-described patch detection ATR because the image forming operation is interrupted. In this embodiment, the patch detection ATR is set to be performed at intervals of 100 sheets of transfer material during continuous copying. In this way, the density is corrected by the patch detection ATR, but the stability of the developer density is limited to the predictive replenishment performance by the video count method for 100 sheets without the patch detection operation during continuous copying. As a result, the toner replenishment amount from the toner hopper is required to be highly accurate.

Here, how much accuracy is specifically required will be described. The highest replenishment accuracy is required when the toner consumption amount (replenishment amount) is the largest. That is, the severest condition is that the original image is a solid image (about 1 g / sheet) and the maximum number of settable continuous copies is performed. Further, the narrower the toner density allowable range, the more severe the replenishment accuracy is required. The maximum number of continuous copies is 100, which is the patch detection interval, and the toner density allowable range is ± 1.
If the weight% and the amount of the developer in the developing device are 500 g, the toner replenishment accuracy is required to be about ± 5%.

Therefore, by forming the toner hopper in two stages in series and controlling the powder surface height of the lower hopper within a predetermined range, changes in the bulk density of the toner (fluidity change) are suppressed and the replenishment accuracy is improved. I am measuring.

According to the experiment conducted by the inventor, the replenishment accuracy of the conventional toner hopper (hopper having a single toner tank) is about ± 20 to 30%, whereas this toner hopper is about ± 5%. The accuracy has improved dramatically.

Next, the structure and operation of the toner hopper will be described with reference to FIGS.

The first toner replenishing device A includes a first toner container 101 for containing the toner T and a first carrying screw 102 for carrying the toner T in the container to the developing device 4d.
And a powder surface detection sensor 103 for detecting the powder surface (level surface) of the toner T in the container. Further, the second toner replenishing device B stores the toner T in a first toner container 111 and a second toner container 111 having a toner capacity larger than that of the first toner container 101.
Second conveying screw 1 for conveying to the toner replenishing device A
12, a remaining amount detection sensor (second sensor) 113 for detecting that the remaining amount of toner in the container is low, a stirring member 114 for loosening the toner in the container, and the like. As shown in FIG. 2, the stirring member 114 has a diameter of 1.4 m.
It is rotatably provided on the shaft 116 in a linear shape of m. A wiper 117 for cleaning the detection surface of the sensor 113 is rotatably provided on the shaft 116.

Next, the operation of this embodiment will be described.
When the copying process starts, as described above, the toner replenishment time is calculated based on the video count number, the first motor 104 is driven only during the calculated time, and the first conveying screw 102 is driven through the drive transmission member. Is rotatively driven, and a part of the toner T stored in the first toner container 101 is conveyed and replenished to the developing device 4d.

By supplying the toner to the developing device 44, the powder surface of the toner T in the first toner container 101 is lowered. Therefore, when the powder surface detection sensor (first sensor) 103 detects the powder surface, the second toner replenishing device B supplies a predetermined amount of toner. For example, the detection output of the powder surface detection sensor 103 is supplied to the CPU, a drive signal is sent from this control circuit to the second motor 115 to drive the second motor 115 for a predetermined time, and the second conveying screw 112 is moved to the predetermined direction. It is rotationally driven for a time, and a predetermined amount (small amount) of the toner T stored in the second toner container 111 is conveyed and replenished into the toner container 101 of the first toner replenishing device A.

By carrying out this operation, the height of the powder surface of the toner T in the toner container 101 of the first toner replenishing device A can be constantly kept approximately constant.

As a result, the fluctuation of the pressure applied to the lower toner in the first toner container 101 becomes small, and the fluctuation of the bulk density becomes small. Therefore, highly accurate toner supply can be performed.

Next, the operation related to the detection of the absence of toner by the remaining amount detection sensor 113 of the second toner supply device B will be described.

FIG. 1 is a sequence chart showing the operation of the two screws during continuous copying. First, FIG.
A case where the residual detection sensor 113 does not detect during continuous copying will be described with reference to FIG.

The paper as the transfer material is of A3 size and 15 CPM (1 cycle in 4 sec).
Further, the image will be described on the assumption that a solid image with the largest replenishment amount (an image in which toner is attached to the entire image formable region) is formed.

In FIG. 1A, the first screw 102 replenishes about 1 g of toner for 1 second based on the video count amount. The first sensor 103 is 1s from the start of image formation.
After ec, it is detected whether or not there is a predetermined amount of toner, and if it is detected that there is no toner, the second screw 112 is rotated for a predetermined time. The predetermined time is 1 sec. 2nd screw 1
The toner transport capacity of 12 is 1.5 of the first screw 102.
The toner is replenished to the first hopper 101 for about 1.5 g in 1 second. The first screw 102 turns three times (3 seconds) and the second screw 112 turns twice (2 seconds
ec) As it rotates, 3 g is replenished, and the amount of coming and going of the first hopper 101 is balanced. Therefore, the toner presence / absence determination by the first sensor 103 is based on the fact that the presence of the toner is repeated twice in the time series. In reality, since the amount of replenishment varies, the number of times the first sensor 103 does not continue toner is 1 to 4 times. It has been experimentally confirmed that toner is present once or twice.

Next, with reference to FIG. 1B, the operation when the residual detection sensor 113 detects the absence of toner during continuous copying will be described. The same operation as that of FIG. 1A is performed during image formation on the drum unit. Then, while the image formation on the drum portion is completed and the operation of the apparatus is completed (hereinafter, referred to as post-rotation), the operation of driving the second screw 112 is performed. Second
By driving the screw 112 for a predetermined time, the second
Toner is supplied from the hopper to the first hopper, and the space V (space above the toner sensor) above the first hopper is filled with toner.

For example, if the space V is about 10 cc, the bulk density of the toner is about 0.45 g / cc, so 4.5 g of toner should be replenished. In this example, the second
Since the screw has a carrying capacity of 1.5 g / sec, it may be driven for 3 sec.

In this way, after toner is supplied from the second hopper to the first hopper and the first hopper is full, a toner-less display is displayed on the operation portion of the apparatus, and the toner bottle for the second hopper is displayed to the operator. Prompt replenishment.

By filling the space above the first hopper with toner, the toner remaining in the hopper up to now becomes the first
The hopper and the second hopper, which were separated from each other, will be connected. As a result, the height of the powder surface of the toner becomes higher, and the same effect is obtained, and the resistance to block the flow of the toner with good fluidity flowing from the toner bottle is increased, and the leakage of toner from the hopper outlet is prevented. It will be prevented.

[0047]

As described above, according to the present invention, the toner leakage from the hopper outlet which may occur at the time of replenishing toner from the toner bottle to the hopper can be prevented without increasing the size of the second hopper or the phenomenon of the replenishment toner amount. This has the effect of preventing problems such as overflow of developer from the developing device.

[Brief description of drawings]

FIG. 1 is a timing chart illustrating an embodiment of the present invention.

FIG. 2 is an enlarged view of first and second hoppers.

FIG. 3 is a schematic diagram showing a latent image forming and fourth image forming station.

FIG. 4 is a sectional view of the image forming apparatus.

[Explanation of symbols]

 A first toner replenishing device B second toner replenishing device 102 first screw 112 second screw 103 first toner sensor 113 second toner sensor 4d Bk developing device

Claims (5)

[Claims] 1. An image bearing member, a developing device for developing an electrostatic image on the image bearing member, a first toner replenishing container for replenishing the developing device with toner, and a first toner replenishing container A first detection member that detects the amount of toner, a second toner supply container that supplies toner to the first toner supply container, and a toner from the second toner supply container according to the output of the first detection member. An image forming apparatus having a control unit for controlling replenishment of the toner and a second detection member for detecting the amount of toner in the second toner replenishment container, when the second detection member detects a toner shortage. The image forming apparatus is characterized in that the control means supplies toner from the second toner supply container to the first toner supply container. 2. The image forming apparatus according to claim 1, wherein when the second detection member detects the toner shortage, the toner is supplied to the first toner supply container after the image formation is completed. 3. When the second detection member detects a toner shortage, the control means replenishes the toner from the second toner supply container so that the first toner supply container is substantially full. The image forming apparatus according to claim 1 or 2. 4. The apparatus further comprises replenishment instructing means for instructing an operator to replenish toner to the second toner replenishing container, and the second detection member detects the toner shortage and detects the second toner. 4. The image forming apparatus according to claim 1, wherein a toner replenishing instruction is issued after replenishing the toner from the replenishing container to the first toner replenishing container. 5. The control means controls the toner replenishment so that the toner amount in the first toner replenishing container becomes a predetermined amount based on the output of the first detection member. Image forming device.