JPH10171314A - Electrophotographic printer and transferring part abnormality detecting method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently check the resistance value, etc., of a transferring part by printing a test pattern while applying a transfer voltage easily causing a printing thining to the transferring part. SOLUTION: A control part (MPU) 11 switches a device to a test mode, when the test mode changeover switches 12a and 12b of an operation panel 12 are depressed. A switching circuit 14 reduces the voltage of a transfer bias control signal and a check voltage is applied to a transfer roller from a transfer power source 15. The check voltage is made half of the transfer voltage at the time of executing printing, so that the printing thining conspicuously appears. The control part 11 reads out test pattern data (painting out data) from a ROM 13, to execute a printing operation. Then, the difference in density between a printed part and a thined part is measured and when the difference in the density is >=50%, a failure in the transfer roller is decided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic printer for printing using toner and a method for detecting a transfer abnormality of the printer.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic printer for printing using a toner, a toner image formed by an image forming unit is transferred to a printing sheet by a transfer unit.

[0003]

In the conventional electrophotographic printer, when an abnormality occurs in the transfer section, the housing is disassembled and the resistance value and the like are checked by a measuring instrument, which takes time and effort. There is a problem that the number of steps in the evaluation and the production line increases.

An object of the present invention is to provide an electrophotographic printer capable of efficiently checking the resistance value and the like of a transfer portion and a method of detecting a transfer portion abnormality.

[0005]

In order to achieve the above object, in an electrophotographic printer according to the present invention, a test pattern is applied to a transfer section by applying a transfer voltage which easily causes print blurring.
A print mode, and a test mode changeover switch for switching the apparatus to a test mode as a specific means. The transfer mode is a method for detecting an abnormality in the transfer section based on a density difference between a printed portion and a blurred portion. , Test pattern
Test pattern data storage means for storing data, a switching circuit for switching a transfer voltage to be applied to the transfer unit to a check voltage at which print fading is likely to occur, and a transfer unit based on the output of the test mode switch. Is switched to the check voltage, and the test pattern
Control means for outputting the contents of the data storage means to the image forming unit and printing a test pattern.

[0006]

Embodiments of the present invention will be described with reference to the drawings. Elements common to the drawings are denoted by the same reference numerals. FIG. 2 is a block diagram showing a main configuration of the electrophotographic printer according to the embodiment. Image forming unit 1
A charging roller 3, a printing head 4, and a developing roller 5 are arranged around the photosensitive drum 2, and the charging roller 3, the developing roller
A negative high voltage is applied to the battery 5 from the power supplies 6 and 7, respectively.

A transfer roller 9 is disposed between the photosensitive drum 2 and the paper transporting path, and receives a high positive voltage from a transfer power supply 8.

The surface of the photosensitive drum 2 is uniformly charged with a negative charge by a charging roller 3 and is exposed by a print head 4 based on print data to form an electrostatic latent image. The electrostatic latent image is transferred from the developing roller 5 to a toner having a negative charge.
Is supplied and developed.

The transfer roller 9 supplies a positive charge to the printing paper 10 to transfer toner development to the printing paper by an electrostatic effect. The toner transferred to the printing paper is heated and fused by a fixing unit (not shown) arranged at the next stage.

By the way, if the transfer roller 9 has a resistance value within a predetermined variation range, the toner can be almost uniformly transferred to the printing paper to maintain the print quality, but the variation in the resistance value is within a predetermined range. Above the range, shading appears. In particular, when there is a portion having a large resistance value, it is difficult for a transfer current to flow from the portion to the printing paper, and a portion having a small charge is generated on the printing paper, so that the toner is not transferred to the printing paper and print blur occurs.

FIG. 1 is a control block diagram of a main part configuration shown in FIG. The control unit 11 is composed of a microprocessor (hereinafter referred to as MPU) including a control program, an operation panel 12 having operation keys and a display unit, and test pattern data storage for storing test pattern data. Read-only memory 13 (hereinafter referred to as ROM 13)
), And is connected to the transfer power supply unit 15 via the print head 4 and the switching circuit 14.

The operation panel 12 is provided with a test mode changeover switch for switching the apparatus to a test mode, for example, as a combination key by operating keys 12a and 12b.

FIG. 3 is a detailed diagram of a switching circuit for switching the transfer power supply to the check voltage. The collector terminal of the transistor Qx is connected to a signal line for inputting a transfer bias control signal to the transfer power supply 8 via the buffer 16.

The emitter terminal of the transistor Qx is grounded, and a transfer roller check signal is input to the base terminal from the control unit. By inputting the transfer roller check signal to the base terminal, the voltage of the transfer bias control signal drops and the current also decreases. The transfer voltage and the transfer current also decrease and decrease respectively due to the voltage drop of the transfer bias control signal.

FIG. 4 is a diagram showing the relationship between the transfer voltage and the transfer current. The good transfer range differs depending on the type of printing paper as shown by the solid line. (A broken line indicates a transfer failure range such as blurred printing.) In the present embodiment, since the voltage range surrounded by the one-dot chain line is a transfer voltage with good transfer to the printing paper 10a, 10b, 10c, an intermediate value of the range is printed. The transfer voltage VTR at the time, and VTR / 2 is the check voltage.

As described above, when a portion of the transfer roller 9 having a large resistance value is present, it becomes difficult for the transfer current to flow to the printing paper, and the toner is not transferred to the printing paper, causing print blurring. The print fading becomes remarkable when the transfer voltage decreases.

According to the present invention, the check voltage is reduced to half of the transfer voltage at the time of printing so that the print blur is remarkably exhibited, and the defect of the transfer roller is checked without disassembling the housing. This reduces the man-hours required for evaluation and production lines.

FIG. 5 is a flowchart of the present invention. Each step is an operation of the control unit (MPU), and is executed by interrupt processing.

Next, the operation will be described with reference to FIG. Press the power switch to start up the device. When the test mode changeover switch is depressed in step S1, an interrupt process is started.

In step S2, the apparatus is switched to the test mode, and a transfer roller check signal is output to the base terminal of the transistor Qx. The transistor Qx lowers the voltage of the transfer bias control signal by inputting the transfer roller check signal to the base terminal. When the voltage of the transfer bias control signal drops, a check voltage VTR / 2 is applied from the transfer power supply 8 to the transfer roller 9.

In step S3, test pattern data (painting data) is read from the ROM 13, and in step S4, a printing operation is performed, and the interrupt processing is terminated.

When printing is completed, the density difference between the printed portion and the blurred portion is measured using a density measuring device or an image sensor. If the density difference is 50% or more, the transfer roller is defective. Is determined.

In this embodiment, the transfer section is described by using a transfer roller. However, the present invention can be applied to an electrophotographic printer using a transfer belt.

[0024]

Since the present invention is configured as described above, it has the following effects. A test mode changeover switch for switching the apparatus to a test mode, a test pattern data storage means for storing test pattern data, and a transfer voltage applied to the transfer section to a check voltage which is likely to cause printing blur. The transfer voltage applied to the transfer unit is switched to the check voltage by the switching circuit based on the output of the switching circuit and the test mode changeover switch, and the contents of the test pattern data storage unit are output to the image forming unit for test pattern. Control means for printing a print pattern, a test pattern is printed by applying a transfer voltage that easily causes print blur to the transfer section, and the transfer section is determined by the density difference between the printed portion and the blurred portion. Abnormalities can be determined, so transfer roller defects can be checked without disassembling the housing, reducing design evaluation and man-hours on the production line. To.

[Brief description of the drawings]

FIG. 1 is a control block diagram of a main part configuration shown in FIG.

FIG. 2 is a block diagram showing a main configuration of the embodiment.

FIG. 3 is a detailed diagram of a switching circuit.

FIG. 4 is a relationship diagram between a transfer voltage and a transfer current.

FIG. 5 is a flowchart of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming part 9 Transfer roller 11 Control part 13 ROM 14 Switching circuit

Claims (2)

[Claims] An electrophotographic printer for transferring a toner image formed by an image forming unit onto printing paper at a transfer unit, comprising: a test mode changeover switch for switching an apparatus to a test mode; and a test pattern data. A test pattern data storage means for storing, a switching circuit for switching a transfer voltage applied to the transfer unit to a check voltage that easily causes printing blur, and a switching circuit for applying the transfer voltage based on an output of the test mode switch to the transfer unit. And a control unit for switching the transfer voltage to be applied to a check voltage, outputting the contents of the test pattern data storage unit to the image forming unit, and printing the test pattern. 2. A transfer abnormality detecting method for an electrophotographic printer in which a toner image formed by an image forming unit is transferred to printing paper by a transfer unit, wherein a transfer voltage that easily causes print blur is applied to the transfer unit. A transfer error detection method for an electrophotographic printer, which prints an image and determines a transfer portion error based on a density difference between a printed portion and a blurred portion.