JPH0968853A - Electrophotographic device and printing start position control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotogaphic device capable of printing at a fixed position at all times regardless of a printing density by offsetting a fault that a printing start position is deviated when the printing density is changed. SOLUTION: A laser light detecting mechanism 105 is irradiated with laser light for the timing of starting to print (at this time, this printing start means the starting of a horizontal scan with the laser light with printing data on a photoreceptor drum), emitted from a laser generating mechanism 601, with a rotary reflection mirror 602 for horizontally scanning. The timing of starting to print on the photoreceptor drum is set with a signal outputted from the laser light detecting mechanism 105 by the irradiation with the laser light. The timing of starting to print is corrected with time in accordance with the lumious power of the laser light for variably setting the printing density to always keep the printing start position on the photoreceptor drum in fixed position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the start of printing on a photosensitive drum of an electrophotographic apparatus (in this case, the start of printing means the start of horizontal scanning of laser light with print data on the photosensitive drum). Position control.

[0002]

2. Description of the Related Art In a laser type electrophotographic apparatus (for example, a laser beam printer), as shown in FIG.
04, and the like, and is reflected by a motor-driven polygon mirror (rotary reflection mirror) 602 that rotates at a constant speed, and then the photosensitive drum 603.
The surface is scanned horizontally. Photosensitive drum 603
Is controlled at a constant speed by a control device (not shown) by a vertical synchronizing signal generated by a crystal oscillator with high stability. Similarly, the polygon mirror 602 is controlled at a constant speed by a controller (not shown) according to the vertical synchronizing signal described above.

By the way, when horizontally scanning (starting printing) a laser beam accompanied by dot-developed print data,
A laser beam for printing start timing is emitted. The emitted timing laser light is received by the laser light detection mechanism 105 on the laser light path via the polygon mirror 602 (the laser light detection mechanism 105 is, for example, the photosensitive drum 60).
An output signal by receiving the laser beam is sent to the controller unit 101, and a timing signal (horizontal synchronization signal) for starting printing is generated based on the output signal. The print data is sent from the controller unit 101 to the laser generation mechanism 601, and the laser beam accompanied by the print data is applied to the photoconductor drum 603, so that a so-called electrostatic latent image is formed and the printing process is established. That is, the controller unit 101 determines the time when the laser beam accompanied by the print data is scanned at the target print start position, and sends the print data to the laser generation mechanism 601. For example, the controller unit 101, triggered by the reception of the output signal from the laser light detection mechanism 105, counts a certain time A required to reach a target print start position, generates a timing signal, and outputs a laser with print data. Output control of light. Here, the print data includes not only data that appears as characters and figures, but also data that relates to blank spaces (portions that should be non-latent images).

As described above, the laser light detecting mechanism 105 receives the laser light and generates a photocurrent, a photosensor 201, a resistor 202 for converting the photocurrent into a voltage, a light output and a specified voltage. It is composed of a comparator 203 for comparing The optical sensor 201 linearly generates a photocurrent according to the power of the laser described above. On the other hand, the laser input to the optical sensor 201 has a power distribution as shown in FIG. 3A (in FIG. 3A, two types of laser light S and L having different emission powers are illustrated. Then, the surface of the optical sensor 201 is scanned by the rotary reflection mirror 602. When the output from the optical sensor 201 is viewed in a time series, it generally shows the characteristics as shown in FIG. Therefore, depending on the strength (magnitude) of the laser power with which the surface of the photosensor 201 is irradiated, the output rise of the photosensor 201, that is, the time until the voltage reaches the specified voltage Vr varies.
That is, in the case of the laser light S, the time until the output of the optical sensor 201 reaches the specified voltage takes up to x as shown in FIG. The time required for the output of 201 to reach the specified voltage is y
It takes up to. As a result, the signal output from the comparator 203 in FIG. 2 (the signal serving as the base point of the timing) has the transmission timing deviated by the time T due to the intensity of the laser power, as shown in FIG. In particular, as the laser light becomes smaller, the signal output from the comparator 203 is delayed.

By the way, the user of the electrophotographic apparatus changes the printing density depending on the intended use or preference of the printing result. Generally, when the line width is changed depending on the exposure amount to the photosensitive drum 603, that is, the strength of the laser power, the apparent print density can be easily changed. Therefore, a method in which the laser power is arbitrarily changed and the print density is changed is generally used. However, when the print density is changed depending on the strength of the laser power, a shift occurs in the print start position, as can be understood from the above description of FIG.

[0006]

According to the above method, as shown in FIG.
As shown in (c), since the horizontal scanning start time (time until the print data is sent) A accompanied by the print data from the print start timing signal is constant, the print start position is set at a certain density. Even after adjustment, the print start position was misaligned when the print density was changed. Conventionally, visual correction was performed to correct the print start position.

The present invention has been made in view of the above points, and an object thereof is to provide an electrophotographic apparatus capable of automatically adjusting the print start position so that the print start position can always be kept constant regardless of the print density.

[0008]

In order to achieve the above object, the present invention provides a laser beam detecting mechanism for a laser beam for printing start timing emitted from a laser generating mechanism via a rotary reflecting mirror for horizontal scanning. The print density is variably set in the print start position control method of the electrophotographic apparatus, which determines the timing of starting the print on the photosensitive drum based on the signal output from the laser light detection mechanism by the irradiation of the laser light. Therefore, the print start timing is temporally corrected according to the emission power of the laser light so that the print start position on the photosensitive drum is always kept constant.

[0009]

According to the above configuration, when the print density is arbitrarily selected, the time A required for the above-mentioned timing setting is set by a predetermined amount according to the print density (in other words, the emission power of the laser beam). Since it is automatically variably adjusted (specifically, as the emission power of the laser light becomes smaller, the time A becomes shorter as shown in FIG. 5), automatic correction is performed so that the print start position is always kept constant. To be done.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
This will be described with reference to FIG. The basic configuration of the electrophotographic apparatus according to the present embodiment is as shown in FIG. 4 described above, but the points different from the conventional one are the configuration of the controller unit 101, the print density selection mechanism 104, and the laser beam as shown in FIG. It is in the form of signal processing from the detection mechanism 105. That is, the controller unit 10
1 is a print data transmission unit 103 and a timing generator 1
02, the timing generator 102 is
The setting status of the print density of the print density selection mechanism unit 104, that is, the set laser power is received as a signal from a print density control circuit (not shown) of the print density selection mechanism unit 104.

A programmable timer is used for the timing generator 102, and the timing of printing start on the photosensitive drum 603, in other words, the start timing (printing start position) in horizontal scanning of laser light accompanied by print data is set to a laser. The light reception signal of the timing laser light output from the light detection unit 105 (at the time when the specified voltage Vr in FIG. 2 is exceeded) is used as a trigger (base point) to perform time counting and determination.
Further, the timing generator 102 inputs the selection signal (selection signal) of the print density from the print density setting device (print density selection mechanism) 104, and determines the time required for the print start timing from the base point according to the print density. And a timing correction means for always keeping the print start position on the photosensitive drum constant. Therefore, the timing generator 102 is corrected so that the time count value (timer value) A becomes shorter as the print density becomes lighter (the laser light power becomes smaller) corresponding to the print density (laser light power). A coefficient has been set or has been set.

According to the above construction, when the printing density is selected and, for example, the laser light S having a large emission power becomes the timing laser light as shown in FIG. 5, the timer value A is long and the emission power is large. When the laser light S having a small value becomes the timing laser light, the time value A is automatically adjusted so that the timer value A is shortened. Even if the error occurs, the print data transmission timing (in other words, the horizontal start timing of the laser beam accompanied by the print data) can always be kept constant. That is, the print data transmitting unit 103 always permits the dot-developed print data to be transmitted (a so-called enable signal) at the time when the print start position reaches the specified print start position.
Is transmitted to the laser light generation mechanism 601.

[0013]

According to the present invention, in the electrophotographic printing apparatus of the type in which the laser beam is scanned on the surface of the photosensitive drum to print based on the dot-developed print data, the conventional problem (that is, depending on the print density) By solving the problem that the print start position is displaced) and automatically correcting the print start position, it is possible to always print at a fixed position.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an example of a main part according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a laser light detection mechanism section.

3A is a laser power distribution diagram, FIG. 3B is a relational diagram of laser power and laser light detection mechanism output voltage, and FIG.
Is a timing chart showing the relationship between the conventional laser power and the print start timing signal.

FIG. 4 is an overall schematic configuration diagram of the above embodiment.

FIG. 5 is a timing chart showing an operation example of a print start position control method according to the above embodiment.

[Explanation of symbols]

101 ... Controller, 102 ... Timing generator, 1
03 ... print data transmission unit, 104 ... print density selection mechanism,
105 ... Laser light detection mechanism, 201 ... Optical sensor, 202
... resistance, 203 ... comparator, 601 ... laser generation mechanism, 602 ... polygon mirror (rotating reflection mirror), 603 ... photosensitive drum, 604 ... lens

 ─────────────────────────────────────────────────── (72) Inventor Shigeo Nemoto 1060 Takeda, Hitachinaka City, Ibaraki Prefecture, Hitachi Koki Co., Ltd. (72) Inventor Hiroshi Ueno 1060 Takeda, Hitachinaka City, Ibaraki, Hitachi Koki Co., Ltd.

Claims (2)

[Claims] 1. A laser beam output from a laser generation mechanism for starting printing (horizontal printing means starting horizontal scanning of laser light with print data on a photosensitive drum) for horizontal timing of laser light. An electrophotographic apparatus that irradiates a laser beam detection mechanism via a rotary reflection mirror for scanning and determines the timing of starting printing on the photosensitive drum based on a signal output from the laser beam detection mechanism by this laser beam irradiation. In the print start position control method, the print start timing is temporally corrected according to the emission power of the laser light for variably setting the print density, and the print start position on the photosensitive drum is always maintained. A printing start position control method for an electrophotographic apparatus, which is characterized by keeping it constant. 2. A laser generating mechanism for generating a laser beam for printing start timing and a laser beam accompanied by dot-developed print data, and a motor-driven rotation for horizontally scanning the laser beam on a photosensitive drum surface which rotates at a constant speed. A reflection mirror, a laser light detection mechanism that receives a laser beam for printing start timing and generates a signal that serves as a base point of the printing start timing, and determines the timing of the printing start on the photosensitive drum by setting a time from the base point. In the electrophotographic apparatus provided with a timing generator for controlling and a printing density selecting mechanism for variably setting a laser light emission power to select a printing density, the timing generator inputs a printing density selection signal. , The time required for the print start timing from the base point is corrected according to the print density, and the print start position on the photosensitive drum is always kept constant. An electrophotographic apparatus having two timing correction means.