JPH05158357A - Automatic transfer current varying device - Google Patents

Abstract

PURPOSE:To always transfer an optimum toner image on a medium without depending on the number of printed sheets by previously measuring an optimum transfer current corresponding to the transition of specific charge by the use of a developing device in order to automatically vary the transfer current and setting the optimum transfer current based on the measured value. CONSTITUTION:This device is provided with a transfer current table 22 which previously obtains and stores the optimum transfer current accompanied with the transition of the specific charge of toner corresponding to the number of printed sheets corresponding to the stirring of the developer, and a printed sheet number measuring part 23 which measures the number of printed sheets corresponding to the stirring of the developer, and high voltage is impressed on a transfer charger 5 so that the optimum transfer current is obtained by referring to the transfer table 22 based on the number of printed sheets measured by the part 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transfer current changing device for automatically changing a transfer current of a transfer device for transferring a toner image on an image carrier onto a medium in an image forming apparatus such as an electrophotographic apparatus. It is about.

[0002]

2. Description of the Related Art Generally, when printing is repeated in an electrophotographic apparatus, the charge amount of the developer gradually changes. When the charge amount changes, the optimum value of the transfer current flowing to the transfer charger changes in order to transfer the toner image from the image carrier to the print medium, but the transfer current is always kept constant during printing. It was

Further, as described in JP-A-59-121364, the charge amount of toner is measured (to be exact,
There is also a method of measuring the bias current) and determining the transfer current.

[0004]

When the above-mentioned conventional transfer current is always kept constant for printing, the charge amount of the developer gradually changes as the printing is repeated, and the toner is transferred from the photosensitive drum to the print medium. When the image is transferred, there is a problem that the optimum value of the transfer current supplied to the transfer charger remains constant despite the change, and the optimum printing cannot be performed as the printing is repeated.

Further, if the toner charge amount (bias current) is measured and the transfer current is controlled to an optimum value based on this, good printing can be performed, but a mechanism for detecting the toner charge amount is provided. It is necessary to provide the device, and there is a problem that the device becomes large and the cost increases.

In the present invention, the optimum transfer current corresponding to the transition of the specific charge due to the use of the developing device is measured in advance, and based on this, the optimum transfer current corresponding to the use of the developing device is set, The objective is to always be able to transfer an optimum toner image onto a medium, regardless of the number of printed sheets.

[0007]

[Means for Solving the Problems] Means for solving the problems will be described with reference to FIG. In FIG. 1, a transfer current table 22 is a table in which an optimum transfer current associated with the transition of the specific charge of the toner is previously obtained and stored in association with the number of printed sheets corresponding to the stirring of the developer.

The number-of-printed-sheet counting unit 23 counts the number of printed sheets corresponding to stirring of the developer. The transfer current setting section 24 refers to the transfer table 22 on the basis of the number of printed sheets measured by the printed sheet number measuring section 23, and sets so that an optimum transfer current is supplied from the high voltage power source to the transfer charger 5. is there.

[0009]

According to the present invention, as shown in FIG. 1, the optimum transfer current according to the transition of the specific charge of the toner is obtained in advance in association with the number of printed sheets corresponding to the agitation of the developer and the like, and is stored in the transfer current table 22. The number of printed sheets is stored and the number of printed sheets is measured by the printed sheet count unit 23, and the transfer current setting unit 24 refers to the transfer table 22 based on the number of printed sheets measured by the printed sheet count unit 23. Then, the transfer charger 5 is set to supply an optimum transfer current from the high-voltage power supply, and the optimum toner image is transferred onto the medium.

Here, a developer consisting of two components of carrier and toner, or a developer consisting of one component of toner is used, and when the developer is replaced, the number of printed sheets corresponding to stirring of the developer is set. I am trying to start the measurement.

Therefore, the optimum transfer current corresponding to the transition of the specific charge due to the stirring of the developer is measured in advance, and based on this, the optimum transfer current corresponding to the use of the developing device is set. It is possible to always transfer the optimum toner image onto the medium without depending on the number of printed sheets.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the construction and operation of an embodiment of the present invention will be described in detail with reference to FIGS.

FIG. 1 shows a block diagram of an embodiment of the present invention.
FIG. 1A shows a block diagram. In FIG. 1A, the ROM 21 stores a table and a program in advance. Here, the transfer current table 22 is a table, and the print number measuring unit 2 is a program.
3. The transfer current setting unit 24 and the like are stored in advance. These programs are read and executed by the MPU 25 to measure the number of printed sheets (S2 in FIG. 3).
To S6), an optimum transfer current is set (see S8 in FIG. 3).

The transfer current table 22 is a table in which an optimum transfer current according to the transition of the specific charge of the toner is previously obtained and stored in association with the number of printed sheets corresponding to the agitation of the developer. As shown in FIG. 2A, the optimum transfer current is previously measured and stored in association with the number of printed sheets.

The number-of-printed-sheet counting unit 23 measures the number of printed sheets corresponding to the stirring of the developer (S2 in FIG. 3).
To S6). The transfer current setting section 24 refers to the transfer table 22 based on the number of printed sheets measured by the printed sheet number measuring section 23, and sets a predetermined value in the DA converter 28. By setting a predetermined value in the DA converter 28, a high voltage is applied from the high voltage power supply 29 to the transfer charger 5 to supply a predetermined transfer current. As a result, the toner image on the photosensitive drum 2 can be transferred onto the sheet 4 always in good condition.

The MPU 25 is a microprocessor, which reads out and executes a program stored in the ROM 21 to perform a predetermined process. Here, the number of printed sheets is measured based on the rotation signal of the drum, or the time during which the agitating roller 12 of the developing device 1 agitates the developer 11 is the time for printing one sheet on the paper 4 (for example, 1 In the case of an electrophotographic device that prints 50 sheets per minute, 1.2
In seconds, the number of printed sheets is counted as one sheet. In the latter, since the transition of the specific charge of the toner of the developer 11 in the developing device 1 is determined by the time for stirring the toner, the time for stirring the toner is divided by 1.2 seconds to obtain the number of printed sheets of paper 4. The number of printed sheets is converted and measured.

The RAM 26 is a random access memory and has a backup power supply. This RAM26
A print number counter 27 is provided in the inside, and S2 of FIG.
From S to S6, the number of printed sheets is measured.

The DA converter 28 converts the transfer current value sent from the MPU 25 into an analog DC voltage and sends it to the high voltage power supply 29. The high voltage power supply 29 is
A high voltage is generated so that a current corresponding to the transfer current value sent from the DA converter 28 flows to the transfer charger 5. The generated high voltage is applied to the corona wire of the transfer charger 5 to flow a predetermined transfer current.

FIG. 1B shows a configuration diagram (cross section) of the electrophotographic apparatus. In FIG. 1B, the developing device 1 is
The toner of the developer (magnetic carrier and toner) is adhered to the latent image on the photosensitive drum 2 by the magnet roll 13 while stirring the developer 11.
At this time, the developer 11 is rotated by the agitating roller 12 in the direction of the arrow shown in the drawing, and the developer 11 is agitated in the forward and backward directions by a screw (not shown). With respect to the developer 11 being stirred, the toner is attached onto the magnet roll 13 together with the magnetic carrier as shown in the figure, and is rotated, and further, a thin uniform layer is formed by the blade, and the latent image on the photosensitive drum 2 is formed. Only the toner is attached to and developed. In this way, the developer 11
When the toner is agitated, the specific charge of the toner changes as measured by the experiment of FIG. 2 described later.

Further, the developer 11 is replenished from the cartridge mounting portion 1-1 by the replenishing roller 1-2 as needed. To replace the developer 11, the developer bottom plate is opened and the developer 11 is discharged to the developer discard bottle 15. After discharging, the developing device bottom plate is closed, and new developer (carrier and toner) 11 is supplied from a supply port (not shown). By the exchange operation of these developers 11, the developing device bottom plate open detection switch 14 operates (turns on / off), and notifies the MPU 25 of the exchange completion signal.
Upon receiving the notification of the exchange completion signal, the MPU 25 resets the print sheet number counter 27 by YES in S2 of FIG.

The photosensitive drum 2 is exposed in accordance with an image to be printed and character information to form an electrostatic latent image,
This is developed by the developing device 1 to adhere toner, and the transfer charger 5 applies a voltage having a polarity opposite to that of the toner to transfer the toner image on the photosensitive drum 2 to the paper 4. The toner image transferred onto the sheet 4 is transferred to the heat roller 7
It is heated and melted to fix it.

The pre-charger 3 charges the photosensitive layer whose conductivity changes in response to the light applied to the photosensitive drum 2. The sheet 4 is a sheet on which the toner image on the photosensitive drum 2 is transferred and printed.

The transfer charger 5 reversely charges the toner image on the photosensitive drum 2 and transfers it onto the sheet 4. The backup roller 6 conveys the paper 4 in the direction of the arrow.

The heat roller 7 conveys the paper 4 in the direction of the arrow and heats it to fix the toner image on the paper 4. FIG. 2 shows an operation explanatory diagram of the present invention.

FIG. 2A shows the transfer current table 22. This is to prepare a new developer and a developer printed with the number of sheets shown in the drawing, and actually measure the optimum transfer current and the amount of charge of the toner. Here, the optimum transfer current is, when the print density and quality on the paper 4 become optimum,
It was measured as a current (μA) supplied to the transfer charger 5.

FIG. 2B shows the current supplied to the transfer charger 5 based on the actual measurement result of FIG. 700μA from the beginning to 10,000 sheets, 62 from 10,000 to 30,000 sheets
0μA, 50,000μA from 30,000 sheets to 50,000 sheets
It was set according to the experimental result of (a) and printed up to 500,000 sheets. The result is shown in FIG.

FIG. 2C shows the printing result of printing under the transfer current of FIG. Here, the variable is
(B) is the printing result printed under the transfer current,
Constant is the printing result obtained by printing under a constant constant transfer current. As can be seen from these printing results, in the case of the variable according to the present invention, ◎ (good) printing quality is obtained from the initial stage up to 200,000 sheets, and even at 200,000 sheets or more, the printing quality is improved as compared with the conventional case. It was found that good print quality was obtained over a wide range of the number of printed sheets, as compared with the conventional case where the transfer current was constant.

FIG. 3 shows an example of the transfer current of the present invention. This is one in which the transfer current is continuously changed instead of the stepwise transfer current in FIG. In this way, the transfer current may be continuously and sequentially set according to the number of printed sheets, and the transfer current may be changed more finely in association with the number of printed sheets to improve the printing quality.

Next, the operation of the configuration of FIG. 1 will be described in detail in the order shown in the flowchart of FIG. In FIG. 4, in step S1, data of the number of prints for which the transfer current switching process is performed and transfer current data at that time are read from the ROM. For this, for example, the number of printed sheets and the optimum transfer current (μA) shown in FIG. 2A are read from the transfer current table 22 in the ROM 21 shown in FIG.

In step S2, it is determined whether a developer replacement completion signal has been received. If YES, the number of printed sheets counter 27 in S3.
Is reset and the process proceeds to S4. If NO, the process proceeds to S4. In S4, it is determined whether the developing device 1 has rotated for 1.2 seconds or more. This is the same time as when the developing device 1 prints 1.2 seconds, that is, 60 seconds / 50 sheets = 1.2 seconds / sheet as an electronic copying apparatus capable of printing 50 sheets per minute here. In the meantime, it is determined whether or not the developer 11 is stirred by the stirring roller 12 of the developing device 1. Y
In the case of ES, the process proceeds to S5. If NO, the process waits in S4.

In step S5, the rotation time of the developing device 1 is reset to 0 seconds. In step S6, the print count value is read from the RAM 26. This is to read the print number value of the print number counter 27 of the RMA 26 shown in FIG.

In step S7, the number of printed sheets is incremented by 1 by reading in step S6.
To do. In S8, the number of printed sheets is written back to the RAM 26. In this case, the value of the print number counter 27 of the RAM 26 is incremented by 1 and written back.

In step S9, it is determined whether the number of printed sheets matches the number of printed sheets for which transfer switching processing is performed. This is because the number of printed sheets counted in S6 to S8 is, for example, (a) in FIG.
It is determined whether the number of printed sheets matches the value of the number of printed sheets in the transfer current table 22 of FIG. YES
In the case of, a signal is sent to the DA converter 28 so as to set the transfer current according to the number of printed sheets in S10. As a result, a high voltage is applied to the transfer charger 5 from the high voltage power supply 29,
The set transfer current is made to flow, and the optimum transfer current is made to flow. Then, the process returns to S2. On the other hand, if NO, the process returns to S2.

From the above, the rotation time of the developing device 1 is 1.
The number of printed sheets is incremented by 1 for 2 seconds (1 sheet, printing time), and the number of printed sheets is measured. The measured number of printed sheets is, for example, stored in advance in FIG.
When the number of printed sheets is equal to 2, the corresponding optimum transfer current is made to flow to the transfer charger 5 so that the toner image is transferred from the photosensitive drum 2 to the paper 4 with good quality.

FIG. 5 shows another configuration diagram (one component) of the present invention. This is the configuration when the developing device 1 uses the one-component developer 11. In the case of the one-component developer 11, the replacement of the developer 11 does not occur like the two-component replacement, but the cartridge replacement (replacement of the developing device 1) is performed, and the replacement is detected by the illustrated cartridge replacement detection switch 16, The MPU 25 is notified of the exchange completion signal (1) (1) and the print sheet number counter 27 is reset (YES in S2 of FIG. 4, S
3). Note that the other configurations are the same as those in FIG.

[0036]

As described above, according to the present invention,
Since the optimum transfer current corresponding to the transition of the specific charge due to agitation of the developer is measured in advance and the optimum transfer current corresponding to the use of the developing device is set based on this, the structure is adopted. The optimum transfer current can be supplied to the transfer charger 5 without depending on the number of printed sheets to always transfer a toner image of good quality onto the medium. As a result, by repeating printing, even if the charge amount of the toner changes, transfer is always performed with an optimum transfer current, so that a stable and good toner image can be obtained. Also, measure the change in the amount of charge in advance,
Since the optimum transfer current corresponding to this is stored, it is not necessary to have a means for measuring the optimum transfer current of toner, and the configuration is simpler than that of an apparatus having a mechanism for measuring the toner charge amount. Thus, the cost can be reduced and the size can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the present invention.

FIG. 3 is an example of a transfer current according to the present invention.

FIG. 4 is a flowchart explaining the operation of the present invention.

FIG. 5 is another configuration diagram (one component) of the present invention.

[Explanation of symbols]

 1: Developing device 11: Developer 12: Stirring roller 13: Magnet roll 14: Developing device bottom plate open detection switch 16: Cartridge replacement detection switch 2: Photosensitive drum 3: Pre-charging device 4: Paper 5: Transfer charging device 7: Heat Roller 21: ROM 22: Transfer current table 23: Printed sheet count section 24: Transferred current setting section 25: MPU 26: RAM 27: Printed sheet counter 28: DA converter 29: High voltage power supply

Claims (2)

[Claims] 1. A transfer current automatic variable device for automatically changing a transfer current of an image forming apparatus, which is an optimum transfer according to a transition of a specific charge of a toner in association with the number of printed sheets corresponding to stirring of a developer and the like. A transfer current table (22) for preliminarily obtaining and storing electric current and a print number measuring section (23) for measuring the number of printed sheets corresponding to stirring of the developer, etc. were provided and measured by this print number measuring section (23). A transfer current automatic variable characterized in that a high voltage is applied to the transfer charger (5) so as to obtain an optimum transfer current by referring to the transfer table (22) based on the number of printed sheets. apparatus. 2. The number of printed sheets measurement unit (23) is configured to start counting the number of printed sheets corresponding to stirring of the developer and the like when the developer is exchanged as a starting point. The automatic transfer current variable device according to item 1.