JPH02254476A - Image forming device - Google Patents

Abstract

PURPOSE:To maintain toner concn. to a specified reference value and to stabilize it without the toner repenishing quantity from becoming insufficient when the toner consuming quantity is great by controlling the toner replenishing quantity responding to the varied quantity from the specified reference concn. of the detected toner concn. CONSTITUTION:The toner concn. detecting voltage of a toner supplying controlling device 100 is read into CPU 102 and stored in RAM 103. That data is compared with the toner concn. reference value 2.5V. When the toner concn. is lower than the reference value, and the detected voltage is greater than 2.5V, it is compared with a temporary set voltage of 3.75V, and if it is smaller than 3.75V, the toner concn. is thinner than the reference value but since there is little difference from the reference value, toner supplying time for one supplying cycle is made 0.5 seconds. On the other hand, if it is greater than 3.75V, since the toner concn. is extremely thin, the toner supplying time is set to be 2 seconds and a 2 seconds timer is set.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a laser printer, or a facsimile machine, and particularly to a toner density control means therefor.

In conventional toner replenishment systems for copying machines, etc., the toner concentration is detected, and when the detected toner concentration is lower than a predetermined concentration, the control device operates the toner replenishment device for a certain period of time.
It was common to replenish a certain amount of toner. For example, in the toner replenishment system of wet-type copying machines, when the toner concentration becomes low, the toner replenishment device is turned on for 0.5 seconds and turned off for 3 seconds based on the output voltage of the toner concentration detection sensor, and this operation is repeated until the toner concentration reaches a certain level. It was being replenished. However, in this method, since the replenishment time required for each toner replenishment series is a constant time of 0.5 seconds in 3.5 seconds, the initial toner replenishment time when the toner concentration is usually extremely low. When the amount of toner replenishment becomes large in such cases, it takes a long time to complete the toner replenishment, and there is a problem that the start-up time of the copying machine or the like becomes longer.

Also, during normal copying operations, when the image area of the document is large, the amount of toner consumed increases. In a toner replenishment cycle where the toner is turned on for 0.5 seconds and turned off for 3 seconds, toner replenishment does not follow the amount of toner consumed, resulting in insufficient replenishment, making it difficult to keep the toner concentration stable at the standard value. . As a result, there is a problem that the image quality is not stable.

The present invention solves the above-mentioned problems in the prior art, and claims I
An object of the invention is to provide an image forming apparatus that increases the amount of toner replenishment when the toner concentration is extremely low, such as during initial toner replenishment, and shortens the time until image formation becomes possible. The second invention aims to provide an image forming apparatus that can form an image with stable image quality without reducing the image density even when the amount of toner consumed is large, such as when forming an image with a large area of the image portion. Take it as a challenge.

In order to solve the above problems, the invention of claim 1 provides an electrostatic latent image formed on an image bearing member by a developing means that supplies a developer containing toner. An image forming apparatus that forms an image by developing with toner, which includes a toner replenishing means for replenishing toner to a developer, a toner concentration detecting means for detecting the toner concentration in the developer, and a toner concentration detecting means for controlling the toner concentration in the developer. n toner concentration control means, and the toner concentration control means controls the amount of toner replenishment by the toner replenishment means in response to the amount of change in the toner concentration detected by the toner concentration detection means from a predetermined reference concentration. death,
The invention according to claim 2 is characterized in that when the amount of change is large, the amount of toner replenishment is increased, and when the amount of change is small, the amount of toner replenishment is decreased. The toner concentration control means controls the toner replenishment amount by the toner replenishment means in accordance with the amount of change in toner concentration detected by the toner concentration detection means from a predetermined reference density. The present invention is characterized in that the amount of toner replenishment by the toner replenishing means is controlled in accordance with the amount of change between the detected toner concentrations.

According to the invention of claim 1, since the amount of toner replenishment by the toner replenishing means is controlled in accordance with the amount of change in the toner concentration detected by the toner concentration detecting means from the predetermined reference density,
For example, when the detected toner concentration is significantly lower than the predetermined reference density, the amount of toner replenishment becomes large, and the toner density can be quickly brought to the predetermined reference density.

According to the second aspect of the invention, since the amount of toner replenishment by the toner replenishing means is controlled in accordance with the amount of change between the toner densities detected by the toner density detecting means, when the density change is large, for example when the image area is large. When toner consumption is high, such as when forming images continuously, a large amount of toner is replenished, and the toner density can be maintained at a predetermined standard value and stabilized without causing insufficient toner supply. .

Practical L-Example FIG. 1 is a sectional side view of a main part of an electrophotographic copying machine using a wet type developing device, which is an example to which the present invention can be applied.

The surface of a photosensitive drum 1, which is an example of an image carrier rotating clockwise in the figure, is uniformly charged by discharge from a charging charger 2, and is then irradiated with light from an erase lamp 3 to form a non-image area. Charges in the image area are removed. Thereafter, an electrostatic latent image is formed on the surface of the photoreceptor drum 1 by irradiation of a light image from an optical system (not shown), and the electrostatic latent image is formed using the developer supplied from the developing device 4, which is an example of a developing means. For example, a toner in a developer containing toner is used to develop the image into a visible image.

The reference numeral 5 is a developing roller that conveys the developer to the photoreceptor drum l, and the reference numeral 6 is a squeeze roller that squeezes off the excess developer on the photoreceptor drum l.

Next, the visible image on the photosensitive drum I is superimposed on the transfer paper P fed by the paper feed rollerf, and is transferred onto the transfer paper P under the discharge of the transfer charger 8. The transferred paper P is separated from the photosensitive drum 1 by a separator roller 9 and a turn belt IO, and sent to a fixing device (not shown), where the toner image is fixed and then discharged to complete a copy image. The surface of the photoreceptor drum l after the transfer paper P has been separated is sent to a cleaning device F 11, where it is cleaned by a cleaning blade 12 and a cleaning roller 1.
3, the toner remaining on it is removed. Thereafter, the photoreceptor drum 1 is irradiated with light by the charge removal lamp 14 to remove the charge, and is prepared for the next copying process.

A developer supply section 15 is attached to the developing device 4 . As shown in FIG. 2, the developer supply unit I5 includes a developer tank 17 containing a developer 16 made by dissolving toner in a solvent, and a developer pump 18 that supplies the developer 16 to the developing device 4. , the developer 1 is sent to the cleaning device 11 and the toner concentration sensor 20, which is an example of toner concentration detection means.
6, a toner bottle 21 containing replenishment toner, and a solvent bottle 22 containing replenishment solvent.

Reference numeral 23 is a holder, and reference numeral 24 is a toner supply device which is an example of toner replenishment means.

FIG. 3(a) is a perspective view of the toner concentration sensor 20.
Figure (b) is an enlarged view of the detection section. The toner concentration sensor 20 includes a toner sensor lamp 20a and a Cd 520b that detects this light. The developer 16 supplied from the cleaning pump 19 shown in FIG.
The lamp 20aaCdS20b and the lamp 20a always emit constant light, and the Cd520b detects the light changed depending on the toner concentration in the developer 16 and outputs this as a toner concentration detection voltage. .

FIG. 4 is a graph showing the relationship between toner concentration and toner concentration detection voltage. When the toner concentration in the developer 16 is high, the light transmittance of the developer is low, so that the amount of light detected by the Cd 520b out of the light emitted by the toner sensor lamp 20a is reduced. On the other hand, when the toner concentration in the developer 16 is low, the light transmittance of the developer 16 is high, so the amount of light detected by the Cd 520b increases. In this case, the circuit configuration is such that when the toner concentration is high, the toner concentration detection voltage takes a low value, and when the toner concentration is low, the toner concentration detection voltage takes a high value. As a result, there is a difference between the toner concentration and the toner concentration detection voltage.
The relationship shown in FIG. 4 is obtained, and an output voltage corresponding to the toner concentration can be generated. In this embodiment, the toner concentration detection voltage is set to a maximum of 5.0■, a minimum of 0■, and a predetermined value!
! ! The circuit configuration is such that the reference value, which is an example of a voltage indicating the concentration, is 2.5■. However, this value can be determined freely.

FIG. 5 is an enlarged view of the toner replenishing section shown in FIG. 2. In this embodiment, the toner supply device 24 includes a driving means 24a, a fulcrum 24b, a lever 24c, etc., and includes a toner supply bag W2.
4, a solenoid, for example, as the drive means 24a is pulled in the direction of the arrow in the figure, the lever 24c rotates about the fulcrum 24b, the valve 21a built in the toner bottle 21 is pushed up, and the inside of the toner bottle 21 is pushed up. The +toner stored in the developer is supplied into the developer 16.

FIG. 6 is a block diagram showing the configuration of a toner supply control device 100, which is an example of toner concentration control means. The toner concentration sensor 20 and the toner supply device 24 are connected to the T10 boat 1.
01 to the CPU 102, and data is exchanged between them. Further, a RAM 103 and a ROM 104 are connected to the T10 boat 101 and the CPU 102.

Flow 1 in FIG. 7 shows a control flow by the toner supply control device 100 when the operating state of the copying machine is in the initial state. The toner concentration detection voltage is read into the CPU I O2, and this value is stored in the RAM 103 as data. This data is then compared with a voltage of 2.5V, which corresponds to the reference value of toner density, and as a result, if the toner density is lower than the reference value and the detected voltage is greater than 2.5V, proceed to the next step. In the 0th step, which returns when the voltage is smaller than 2.5■, the data stored in the RAM 103 is compared with the temporary setting voltage of 3.75 V, and if the data is smaller than 3.75 V as a result of the comparison, Although the toner concentration is lower than the standard value, the difference from the standard value is small, so: 1. Set the toner supply time in the supply cycle to 0.5 seconds. Turn on the solenoid (if the driving means 24a is a solenoid, the same applies hereinafter) for 0.5 seconds. Processes "timer set" and returns.

On the other hand, if the comparison result data is greater than 3.75 V, it means that the toner concentration is extremely low, so a "solenoid on 2 second timer set" process that sets the toner supply time in one supply cycle to 2 seconds is performed. and return.

As described above, in this embodiment, there are two types of timers that determine the solenoid on time during one supply cycle, so that two types of toner supply times can be set. And based on the temporary setting voltage! 1! Value 2.5v +2.5/2 V =
It is set at 3.75V. By providing two types of toner supply times, when the toner concentration is extremely low, such as when starting a copying machine, a timer set with a long toner supply time is used to supply a large amount of toner and bring the toner concentration closer to a predetermined reference value quickly. It is possible to make copies possible in a short time. In this embodiment, the difference between the voltage corresponding to the toner concentration and the predetermined value is used as the amount of change in the detected toner concentration from the predetermined reference concentration, and the toner replenishment amount is controlled to be 2 Jll in accordance with this difference. However, other amounts can be used as the amount of change, such as using the ratio of the voltage corresponding to the toner concentration to a predetermined value.Also, when using a voltage difference, the temporarily set voltage can be set to 2.5V+2. .5V/
It is also possible to perform more fine control by setting n to 2 or more as nV.

Flow 2 in FIG. 8 shows the flow when making continuous copies of a large number of sheets. Determine whether the copier is in its initial state,
When it is not in the initial state, it is checked whether the copy number counter is 1 or not, and when it is (2), the toner density detection voltage detected by the toner density sensor 20 is read into the CPU 102 and stored in the A register in the RAM 103 as data.

When the copy number counter is 2, the toner-density detection voltage is similarly read into the CPU 102 and stored in the B register in the RAMIO 3 as data. Next, in order to calculate the amount of toner consumed per copy, each data stored in the A and B registers is subtracted from A-B, ie [
The calculation of "data stored in A register" - "data stored in B register" is performed. This subtraction value is compared with the provisional setting voltage of 0.5■, and as a result of the comparison, the subtraction value is 0.5
If it is smaller than v, it means that the amount of toner consumed per copy is relatively small, so! “Solenoid on 0.5” to set toner supply time to 0.5 seconds during supply cycle
Second timer set” process and return.Meanwhile,
As a result of the comparison, if the subtraction value is larger than the temporary setting voltage of 0.5V, it means that the amount of toner consumed per copy is extremely large, so the toner supply time in one supply cycle is set to 1 second. Processes "Solenoid on 1 second timer set" and returns.

As described above, in this embodiment, the temporarily set voltage is set to 0.5V, which is l/10 of 5.0■, which is the maximum value of the toner concentration detection voltage.
Since there are two types of timers that determine the solenoid on time, if the image area of the document is large and the amount of toner consumed per sheet is large, by selecting a timer set with a long solenoid on time, the toner can be reduced. By increasing the supply amount, it is possible to prevent a decrease in toner concentration in the developer and stabilize the toner concentration.

In this embodiment, the difference between the detected voltage values is taken as the amount of change between the detected toner concentrations, and two types of toner replenishment amounts are set corresponding to this difference, but other methods can be used to determine the amount of change. For example, it is possible to take a ratio between detected values, or by setting multiple temporary voltage settings and setting multiple toner replenishment times using a timer, more detailed toner replenishment control can be performed in response to changes in toner concentration. It becomes possible. In addition, in this example,
Although an example has been shown in which the toner density is detected between the number of copies 1 and 2, the amount of toner consumed during this period is calculated, and the supply amount is controlled, it is also possible to detect the toner density after copying a plurality of sheets.

Flow 3 in Figure 9 is based on the flow in Figure 7 or Figure 8.
When the "solenoid on timer" that determines the toner supply time is set, the "solenoid on timer" is activated by turning on the timer at the set timing.
The flowchart shows the flow of executing the process and supplying toner. When the "solenoid on timer" ends, that is, when toner supply ends, a "solenoid on timer clear" process is performed and the process returns.

Although the image forming apparatus using a wet developing device has been described above, the present invention can also be applied to a developing device using a two-component developer consisting of toner and carrier.

Effects As described above, according to the present invention, in the invention of claim 1, a large amount of toner can be replenished when the amount of change in toner density from a predetermined reference density is large in the initial state of the image forming apparatus, etc. This reduces the time it takes for the toner density to reach the standard value, making it possible to form images in a short time.
According to the invention of claim 2, when images having a large image area are continuously formed, the image density is detected at an appropriate image forming interval and the amount of toner replenishment is controlled in accordance with the amount of change during that time. By doing so, it is possible to stabilize the toner density without causing insufficient toner supply, and it is possible to create an image with stable quality without any change in toner density.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main parts of a copying machine showing an embodiment of the present invention, FIG. 2 is a schematic diagram of its developer supply section, FIG. Figure (b) is a side view of the detection unit, Figure 4 is a curve diagram showing the relationship between toner concentration and toner concentration detection voltage, Figure 5 is a side sectional view of the toner replenishment unit in Figure 2, and Figure 6. is a block diagram of the toner supply control device, and FIGS. 7 to 9 are flowcharts. 1... Photosensitive drum (image carrier) 4... Developing device (developing means) 16... Developing solution (developer) 20... Toner concentration sensor (toner concentration detection means) 24
... Toner supply device (toner supply means) 100 ... Toner supply control device (toner concentration control means) +02 ... CP
U () Toner concentration control means) Fig. 6 Fig. 7 Fig. Fig.

Claims (2)

[Claims] (1) An image forming apparatus that forms an image by developing an electrostatic latent image formed on an image carrier with toner by a developing means that supplies a developer containing toner, and a toner that replenishes the developer with toner. The toner concentration control means includes a replenishing means, a toner concentration detection means for detecting the toner concentration in the developer, and a toner concentration control means for controlling the toner concentration in the developer. The amount of toner replenishment by the toner replenishing means is controlled in response to the detected amount of change in toner concentration from a predetermined reference density, and the response is to increase the amount of toner replenishment when the amount of change is large and to increase the amount of toner replenishment when the amount of change is small. An image forming apparatus characterized in that the amount of toner replenishment is sometimes reduced. (2) The toner concentration control means may control the toner replenishment amount by the toner replenishment means in accordance with the amount of change in the toner concentration detected by the toner concentration detection means from a predetermined reference density. 2. The image forming apparatus according to claim 1, wherein the amount of toner replenishment by said toner replenishing means is controlled in accordance with the amount of change between toner densities detected by a density detecting means.