JPH0546052A - Image forming device - Google Patents

Abstract

PURPOSE:To replenish the toner of a proper quantity into a developing unit even if a toner concentration inside the developing unit tentatively has dispersion and to shorten the energizing time of an electromagnetic solenoid changing the housing capacity of a container housing the toner completely used by intermittently operating it. CONSTITUTION:The toner concentration inside the developing unit is detected by a magnetic sensor 3c, the replenishing quantity of the toner from a toner box 4 is controlled based on the detected toner concentration and its changing quantity, and simultaneously, the switching of the operation/nonoperation of the electromagnetic solenoid 9b changing the housing capacity of a waste toner bottle 9a is controlled.

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 using toner, such as an electrophotographic copying machine and a laser printer, and more particularly to a toner box for supplying toner to a developing unit provided in the image forming apparatus and the use thereof. The present invention relates to the operation control of a used toner and a member that changes the storage capacity of a waste toner container that stores waste toner.

[0002]

2. Description of the Related Art In an electrophotographic copying machine which is most widely used in such an image forming apparatus, the outer peripheral surface of a photosensitive drum is uniformly charged and the object to be copied is exposed to expose the photosensitive drum. An electrostatic latent image is formed on the outer peripheral surface, and a toner is attached to the electrostatic latent image by a developing unit to form a toner image, which is transferred to a copy sheet to perform a copying operation. After such a copying operation, the toner remains on the outer peripheral surface of the photoconductor drum, so that the residual charged toner is removed by the cleaning device.

Toner is supplied to the developing unit from a toner box containing a large amount of toner. Also,
The waste toner removed by the cleaning device is stored in the waste toner bottle as used toner, and the storage capacity of the waste toner bottle is adjusted by the electromagnetic solenoid. Then, specifically, the toner concentration in the developing unit is detected, and when the detected toner concentration falls below a predetermined value, a certain amount of toner is replenished from the toner box to the developing unit, and Accordingly, the electromagnetic solenoid is operated to increase the storage capacity of the waste toner bottle.

[0004]

As described above, in the prior art, since the toner replenishment is controlled only based on the toner density, it is not sufficient to deal with the case where the toner density temporarily varies. The deterioration of image quality cannot be denied. In addition, when the toner concentration falls below a predetermined value, a certain amount of toner is supplied, and the electromagnetic solenoid of the waste toner bottle operates accordingly, so the electromagnetic solenoid operates even for a small consumption of toner, There has been a problem that the electromagnetic solenoid continues to operate continuously and its energization time becomes long, which leads to a reduction in suction force and causes abnormal noise.

The present invention has been made in view of the above circumstances, and includes a control mechanism for controlling the toner replenishment amount and the waste toner bottle accommodating capacity based on the toner concentration and the toner concentration change amount. , It is possible to replenish the developing means with an appropriate amount of toner even if the toner density varies.
An object of the present invention is to provide an image forming apparatus capable of solving the above-mentioned problems in the electromagnetic solenoid by only intermittently operating the changing means (electromagnetic solenoid).

[0006]

SUMMARY OF THE INVENTION An image forming apparatus according to the present invention comprises a developing means for accommodating a developer containing a mixture of toner and a carrier, and a detecting means for detecting the toner concentration of the developer in the developing means. Replenishing means for replenishing the developing means with toner, accommodating means for accommodating waste toner after image formation, changing means for changing the accommodating capacity of the accommodating means, and calculating means for calculating the amount of change in the toner density. And a first control means for controlling the amount of toner replenished from the replenishing means to the developing means based on the amount of change in toner density calculated by the calculating means and the toner density detected by the detecting means. And second control means for controlling the operation of the changing means according to the control operation of the first control means.

[0007]

In the image forming apparatus according to the present invention, the detecting means detects the toner concentration of the developer in the developing means, and the calculating means calculates the change amount of the toner concentration in the developing means. Then, the first control unit controls the replenishing unit based on the detected toner concentration and the calculated change amount of the toner concentration,
The amount of toner supplied to the developing means is controlled. Further, the second control means controls the operation of the changing means in accordance with the control operation of the first control means, and the operating state and the non-operating state of the changing means are intermittently repeated.

[0008]

Embodiments of the present invention will be specifically described below by taking an electrophotographic copying machine as an example.

FIG. 1 is a schematic view showing a main part of an electrophotographic copying machine which is an embodiment of an image forming apparatus according to the present invention.
In FIG. 1, reference numeral 1 is a photosensitive drum as an electrostatic latent image carrier that rotates in the direction a in the figure, and a charging corotron 2 for charging the surface of the photosensitive drum 1 uniformly above the photosensitive drum.
Is provided, and an exposure device (not shown) that exposes a light beam in the direction c in the drawing is disposed on the downstream side thereof. A developing unit 3 is provided on the downstream side of this exposure device. The developing unit 3 contains a developer, which is a known mixture of toner 3e and carrier 3d. The developing unit 3 includes a developing roller 3a and a developer stirring roller 3b, and a magnetic sensor 3c for detecting the toner concentration in the developing unit 3 is provided below the developer stirring roller 3b. A toner box 4 is provided above the developing unit 3, and a toner replenishing roller 4a for supplying the toner 3e in the toner box 4 to the developing unit 3 is installed between the developing unit 3 and the toner box 4. There is.

Below the photoconductor drum 1, a transfer for transferring the electrostatic latent image formed on the surface of the photoconductor drum 1 to a sheet (not shown) conveyed from the direction b in the figure. A corotron 5 and a separating corotron 6 for separating the transferred sheet from the photosensitive drum 1 are provided respectively. Further, on the downstream side (upper left side in the figure) of the separating corotron 6, there are a cleaning device 7 for removing the residual toner on the photoconductor drum 1, a charge eliminating lamp 8 and a waste toner bottle 9a for collecting the residual toner. It is provided.
In the Carlson process, the residual toner remaining on the photosensitive drum 1 after the transfer processing onto the paper is removed by the cleaning device 7, and the removed residual toner is stored in the waste toner bottle 9a as used toner. The waste toner bottle 9a is provided with an electromagnetic solenoid 9b in order to increase the waste toner storage capacity.

FIG. 2 is a schematic side view of the toner box 4. The toner replenishing roller 4a is connected to a toner replenishing motor 4b for rotating the toner replenishing roller 4a.
The toner replenishing roller 4a is rotated by rotating, and the toner 3e in the toner box 4 is dropped into the developing unit 3 (in the direction of the white arrow in the figure).

Generally, in the two-component developing system, the toner density in the developing unit 3 (the mixing ratio of the carrier 3d and the toner 3e has a great influence on the image density. In this embodiment, the toner density is read by the magnetic sensor 3c. A required amount of toner is replenished from the toner box 4 into the developing unit 3. This toner replenishment amount is obtained by fuzzy reasoning.
It is a graph which shows the detection characteristic of. The specific toner density control is based on a fuzzy inference from the absolute value of the toner density and its change amount in order to converge the toner density in the developing unit 3 to 6.5% and the output voltage of the magnetic sensor 3c to 2.3V. The toner is replenished only for the time determined by using the toner.

Next, this fuzzy inference will be described with reference to FIG. 4 showing membership functions and FIG. 5 showing rules. The fuzzy inference in this embodiment is a 2-input 1-output type in which the front companion part is 2 and the back companion part is 1. Front companion 1
Is used as the output value of the magnetic sensor 3c, that is, the toner density. Here, the output value of the magnetic sensor 3c is set to 2.3 by experiment.
In order to converge to V, it can be said that the membership function should be dense at 2.4 to 2.5 V as shown in Fig. 4 (a), and should be sparse as it gets away from it. Further, as the front companion portion 2, a change amount of the output value of the magnetic sensor 3c, that is, a change amount of the toner density is used. The antecedent part 2 has a relatively uniform membership function as shown in Fig. 4 (b). The trailing part uses the toner replenishment time, and its membership function becomes dense at long replenishment times and sparse at long replenishment times as shown in FIG. 4 (c).

FIG. 5 shows the above membership function.
Make 21 rules. This rule basically means that the lower the toner concentration, the longer the replenishment time, the replenishment is stopped when the target toner concentration is reached, and the toner concentration is reduced if the toner concentration is about the same. When the amount is increased, the supply amount is increased. However, when the amount of change in the output value of the magnetic sensor 3c is large, it means that a large amount of toner is being consumed and a large amount of toner is being replenished.
If replenishment is stopped at the time when the toner density reaches the target value, the toner density immediately decreases and, as a result, the toner density is controlled at a low level. To prevent this, the toner concentration control value can be brought closer to the target value by continuing the replenishment even if the toner concentration increases and reaches the target value only when the change amount of the toner concentration is large.

The inference method uses the max-min centroid calculation method. At this time, the toner density of the front companion is given with a 6-bit resolution between the toner sensor output value of 0% and 13%, and the toner density variation is given with a 4-bit resolution between minus 0.4% and plus 0.4%. .. Further, the toner replenishment time of the trailing portion is expressed by 5 bit resolution from 0 second to 2 seconds.

If the electromagnetic solenoid 9b provided for increasing the storage capacity of the waste toner bottle 9a is always operated, the energization time of the solenoid becomes long, the suction force is lowered, and abnormal noise is generated. Therefore, it is desirable to intermittently perform the operation of the electromagnetic solenoid 9b. less than,
An example of effective intermittent operation of the electromagnetic solenoid 9b will be described.

A3 size, solid black ratio 30%, toner consumption 50
When a 0 mg original is copied, the transfer efficiency is generally 66.4%.
Therefore, the amount of waste toner is about 168 mg. Assuming that 10 such documents (generally, the maximum amount used by the user at one time) is copied, the amount of waste toner is 1.68 g.
Becomes If the electromagnetic solenoid 9b is operated once at this time, when the toner supply amount is 0.65 to 0.75 g / sec, the amount of waste toner is (0.65 to 0.75) × (1-0.664) = 0.195 to 0.225. (g / sec), and the operation cycle of the electromagnetic solenoid 9b may be 1.68 (g) ÷ (0.195 to 0.225) (g / sec) = 8.6 to 7.5 (sec). Therefore, the cumulative time is used for the membership function that uses the toner replenishment time for the trailing part, and 8.6 ~ 7.5 sec
The electromagnetic solenoid 9b is operated once every time. If there is no replenishment toner or the amount of toner consumption is too high and the toner density is below a certain level, the copying operation is automatically stopped, the developing unit 3 is replenished with toner, and the target value is reached. When the time is reached, the copying operation is started again, so that proper toner density control can be performed on any original.

FIG. 6 is a block diagram of the control unit of the copying machine main body. The copier is controlled by a microcomputer system including MPU100. This microcomputer system includes a ROM 102 connected to the MPU 100 for storing control programs and the like, a temporary storage of data during control by the MPU 100, and various flag areas necessary for control. RAM 104 and I / O interface 10 for MPU 100 to control input and output of internal devices
Contains 6 and.

The RAM 104 is backed up by a backup battery 114 such as a lithium battery connected to the voltage V _CC . When the voltage V _CC is no longer supplied, the voltage of the backup battery 114 is applied to the RAM 104. Therefore, even if the main switch of the copying machine is turned off, the data in the RAM 104 is retained. The I / O interface 106 is connected with a key matrix 109 for performing input / output with the outside. The input port of the I / O interface 106 includes a sensor group including a magnetic sensor 3c for detecting the toner concentration in the developing unit 3.
110 is connected via an A / D converter 108 that converts an analog value of the sensor output into a digital value. Also, I / O
To the output port of the interface 106, drive devices 111 and 112 including a toner replenishing motor 4b for replenishing toner in the developing unit 3 or an electromagnetic solenoid 9b for increasing the storage capacity of the discharged toner bottle 9a are connected.

Next, the control procedure of the MPU 100 will be described with reference to the flow charts shown in FIGS.

FIG. 7 is a flow chart showing the main routine. First, in the copy operation 1 in step S101, an initial process such as permission of interruption, rotation of the main motor, and scan start is performed. Then step S103
Controls the toner replenishment and operation of the electromagnetic solenoid 9b.
Details of these controls will be described later with reference to FIGS. 9 and 10. Then, a series of copying processes are performed in the copy operation 2 of step S105, and the process proceeds to the next step S107. In step S107, it is determined whether the copy is continuous copy.
If YES, the process returns to step S101, and if NO, the main routine is ended.

FIGS. 8, 11 and 12 show a part of interrupt routines. These interrupt routines are MPUs.
An internal timer of 100 interrupts the main routine at a predetermined cycle to perform processing. 9 and 10 show a subroutine of the process of step S103 of FIG. 7, that is, the control process of toner replenishment and operation of the electromagnetic solenoid 9b.

The interrupt routine A of FIG. 8 is for obtaining the "current toner concentration" used when determining the toner concentration change amount (= "previous toner concentration"-"current toner concentration"), and is eight consecutive times. Then, the toner density is read and added. Explaining along the flowchart, it is determined in step S201 whether or not the flag provided in the predetermined area of the RAM 104 is zero, and if it is zero, the step is performed.
Proceed to S203. In step S203, the counter of the RAM 104 and the memory 1 are initialized to zero, the flag is set to 1, and this interrupt is exited.

Next, when this interrupt routine is entered, since the flag of the RAM 104 is set to 1 in step S201 and step S205, the process proceeds to step S207. In step S207, the toner concentration in the developing unit 3 is read by the magnetic sensor 3c, the analog value is converted into a digital value by the A / D converter 108, and the digital value is added to the contents of the memory 1 and stored in the memory 1 again. deep. Also, the counter is counted once. In step S209, it is determined whether the counter is 8. That is, it is determined whether the process of step S207 has been performed eight times. If NO, exit the interrupt routine, and if YES, proceed to step S211. Step S207
The toner density value obtained by adding 8 times is stored in the memory 2 of the RAM 104, the flag is reset, and the interrupt routine is exited. In this way, in the interrupt routine A, the "current toner density" is always stored in the memory 2 of the RAM 104.

Next, the processing of step S103 in FIG.
In other words, regarding toner replenishment and control of the electromagnetic solenoid 9b,
This will be described with reference to FIGS. First, in step S301, it is determined whether the copy is the first copy after the power is turned on. Since there is no information on the "previous toner density" in the first copy after the power is turned on, the toner density change amount cannot be obtained. Therefore, in order to divide the control for the first copy after the power is turned on and the subsequent copies, this step S3
The judgment at 01 is made.

When the first copy is made after the power is turned on, the process proceeds to steps S305, S307 and S309. Here, the memory 3 provided in a predetermined area in the RAM 104 stores the "previous toner density", and the memory 4 stores the "current toner density". At this time, the contents of the memory 2 obtained in the interrupt routine A are put into the memory 3 and the memory 4, and the toner density change amount (= “previous toner density” − “current toner density” = content of the memory 3−memory 4 I am trying to set the content to zero.

On the other hand, except for the first copy after the power is turned on, the value of the memory 4 is put in the memory 3 and the "current toner density" is set.
The old information of is set to “previous toner density”, and the “current toner density” is changed to the latest “current toner density” obtained by the interrupt A in the contents of the memory S30.
3 and S307 to proceed to the next step S309. Step S309
Then, the content of the memory 4 is subtracted from the content of the memory 3, and the subtracted value is divided by 8 and placed in the memory 5 of the RAM 104. In addition,
The reason for dividing by 8 is that the content of the memory 2 obtained by the interrupt routine A is an added value obtained by successively adding the sensor input values read eight times in succession, and is averaged at this point. The memory 5 stores the toner density change amount.

Next, in step S311, the magnetic sensor
The toner density is detected at 3c, and the value passed through the A / D converter 108 is used as the absolute value of the toner density at the time of copying. Steps S313 and S315 are steps for determining whether or not the fuzzy control application range is outside the application range when the toner density is determined from about 5.8% to about 8%.

In step S313, it is determined whether the toner density obtained in step S311 is higher than 8%. If YES, do nothing and return from this subroutine. If NO, the process proceeds to step S315. Here, as in the previous step, it is determined whether the toner density is lower than 5.8%. YE
If it is S, in steps S317, S318, S319, data for a fixed time for replenishing toner is set in the memories 6 and 7 of the RAM 104, and the toner replenishing motor 4b is started. That is, by rotating the toner replenishing motor 4b for a certain period of time, the toner replenishing roller 4a is rotated and the toner 3e in the toner box 4 is dropped into the developing unit 3 to replenish the toner.

If NO in step S315, the flow advances to step S321, which is a fuzzy control area. A solution obtained by performing fuzzy inference calculations on the absolute value of toner concentration and the amount of change in toner concentration in advance, that is, the data of toner replenishment time is stored in the form of a data table, and in step S321, in steps S309 and S311. Data of the toner replenishment time that matches the obtained absolute value of the toner density and the amount of change in the toner density is extracted from this data table. Such a data reading method is a lookup table method. Then, in steps S323, S324, and S325, the toner replenishment time is set in the memory 6 and the memory 7 of the RAM 104, and the toner replenishment motor 4b is started and rotated to rotate the toner 3e.
Is dropped into the developing unit 3 to replenish the toner 3e.
In this control, the time for rotating the toner replenishing motor 4b is varied based on the two information of the toner density and its change amount.

Next, in step S327, steps S318 and S324 are performed.
The contents of the memory 7 storing the toner replenishment time are added to the memory 8. After that, in step S329, it is determined whether or not the content of the memory 8, which is the sum of the memory 7, is equal to or larger than a certain set value. If NO, return without doing anything. If YES, the contents of the memory 8 are cleared in step S331, the solenoid flag is set to 1 in step S333 to turn on the electromagnetic solenoid 9b in the subsequent processing, and the process returns. This processing utilizes the fact that some percentage of the replenished toner is discharged as waste toner, and aims to pull the electromagnetic solenoid 9b when the amount of waste toner reaches a certain amount. That is, the total amount of toner replenishment is stored in the memory 8, and the toner replenishment amount corresponding to the amount of discharged toner for which the electromagnetic solenoid 9b is desired to be pulled is set as the set value in step S329. When the set value is reached, the electromagnetic solenoid 9b is pulled, To make the degree of accumulation of toner in the waste toner bottle 9a uniform.

FIG. 11 shows a flowchart of an interrupt routine B for pulling the electromagnetic solenoid 9b. In step S401, it is determined whether or not the solenoid flag in the RAM 104 is 0, and if YES, this interrupt is exited. Similarly, in step S403, it is determined whether the solenoid flag is 1 and YE
If it is S, the electromagnetic solenoid 9b is turned on in step S405, the time for which the electromagnetic solenoid 9b is turned on is set in the memory 8 in step S407, and the solenoid flag is set to 2 in step S409 to exit this interrupt. Step S411
If the flag is 2 at step S413, the process proceeds to step S413, the content of the memory 8 of the RAM 104 is decremented by 1, and at step S415 the memory 8
It is determined whether the content of is 0. If YES, step
The electromagnetic solenoid 9b is turned off in S417, the solenoid flag is set to 0 in step S419, and this interrupt is exited. If NO in step S415, this interruption is repeated until the memory 8 becomes zero.

FIG. 12 shows a flow chart of an interrupt routine C for stopping the toner replenishment time motor 4b.
In step S501, it is determined whether the content of the memory 6 is zero.
This determination is made based on that the memory 6 is 0 unless the data of the rotation time of the toner replenishing motor 4b is set in steps S317 and S323. If NO, step S5
Go to 03, decrement the contents of memory 6 by 1 and return. If YES, the process proceeds to step S405. In step S505, the toner supply motor 4b is stopped and the process returns.

Although the electrophotographic copying machine has been described in the above embodiment, it goes without saying that the present invention can be applied to other image forming apparatuses such as a laser printer.

[0035]

As described above, in the image forming apparatus of the present invention, the toner replenishment amount is set based on the toner density and the toner density change amount, and the operation of the electromagnetic solenoid of the waste toner bottle is controlled. Even if the toner concentration varies, the toner can be replenished in an appropriate amount, and even if the toner is slightly consumed, the electromagnetic solenoid will operate from the cumulative time of the toner replenishment supply time, and the state of continuous operation will continue. It is possible to solve all of the conventional problems that the energization time of the solenoid becomes long and the suction force is reduced to cause abnormal noise.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part of an electrophotographic copying machine that is an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a schematic side view of a toner box in the electrophotographic copying machine of FIG.

FIG. 3 is a characteristic diagram of a magnetic sensor incorporated in a developing unit.

FIG. 4 is a diagram showing a membership function in fuzzy inference used in an embodiment.

FIG. 5 is a table showing rules in fuzzy inference.

FIG. 6 is a block diagram showing a configuration of a control mechanism in the electrophotographic copying machine.

FIG. 7 is a flowchart showing a main routine of control operation of the embodiment.

FIG. 8 is a flowchart showing an interrupt routine of the embodiment.

FIG. 9 is a flowchart showing a control routine of toner replenishment amount and electromagnetic solenoid operation in the embodiment.

FIG. 10 is a flowchart showing a control routine for the toner replenishment amount and the electromagnetic solenoid operation in the embodiment.

FIG. 11 is a flowchart showing another interrupt routine of the embodiment.

FIG. 12 is a flowchart showing still another interrupt routine according to the embodiment.

[Explanation of reference signs] 1 photoconductor drum 3 developing unit 3a developing roller 3b developer stirring roller 3c magnetic sensor 3d carrier 3e toner 4 toner box 4a toner replenishing roller 4b toner replenishing motor 7 cleaning device 9a waste toner bottle 9b electromagnetic solenoid

Claims (1)

[Claims] 1. A developing means for accommodating a developer containing a mixture of toner and carrier, a detecting means for detecting a toner concentration of the developer in the developing means, and a supplying means for supplying toner to the developing means. Storage means for storing the waste toner after image formation, changing means for changing the storage capacity of the storage means, and calculation means for calculating the amount of change in the toner density.
First control means for controlling the amount of toner replenished from the replenishing means to the developing means based on the amount of change in toner concentration calculated by the calculating means and the toner concentration detected by the detecting means, An image forming apparatus comprising: a second control unit that controls an operation of the changing unit according to a control operation of the first control unit.