JPH05221025A - Image forming device - Google Patents

Abstract

PURPOSE:To effect efficiently draft printing by which high printing speed is obtained though its printing quality is not high, by using a laser printer or the like, which requires no remarkable change of hard ware. CONSTITUTION:In a controller 22, a sub-scanning speed changing-over part 26, at which feeding speed at a paper feeding section is changed over from or to normal speed to or from high speed, and an image thinning-out part 24, in which the repeating period of the image formation in main scanning direction is thinned-out, when the feeding speed is changed to high speed at the sub- scanning speed changing-over part, as compared with the period at the normal feeding speed, are provided.

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 such as a laser printer or a digital copy which forms a two-dimensional image by main scanning and sub scanning intersecting with the main scanning.

[0002]

2. Description of the Related Art In a conventional laser printer, a sheet conveying speed, that is, a sub-scanning speed is fixed by a printer engine. For example, a 6 ppm printer prints one sheet in 10 seconds during continuous printing. The speed was limited.

[0003]

By the way, recently, in drafting a document or the like, there is a demand for high speed printing, that is, draft printing, even if the print quality is not high. However, in the conventional laser printer, the printing speed is determined by the paper conveyance speed (sub-scanning), and the necessary number of main scans per time is determined from the conveyance speed and the print pixel density. Therefore, the main scanning speed must be changed accordingly.

However, in order to change the main scanning speed, it is necessary to change the control signal clock of the laser, so that it is necessary to have a plurality of oscillators, and there are problems of complication of the apparatus and cost increase. Also, as the main scanning speed increases,
There is a fear that the image forming speed of the print control device (hereinafter, referred to as a controller) may not catch up with the normal printing. On the other hand, in order to increase the processing speed of the controller, a significant increase in hardware cost was inevitable.

Therefore, a first object of the present invention is to make it possible to efficiently perform draft printing, which does not have high print quality but high printing speed, without requiring a major change in hardware in a laser printer or the like. It is in.

A second object of the present invention is to make it possible to efficiently perform fine printing at a slower printing speed without requiring a great change in hardware. is there.

[0007]

A first object of the present invention is to provide a sub-scanning speed switching unit capable of switching the carrying speed of the paper carrying unit between a normal speed and a high speed, and a sub-scanning speed switching unit for changing the carrying speed. This can be achieved by providing the controller with an image thinning unit that thins out the repetition cycle of image formation in the main scanning direction at a high speed than at the normal speed.

A second object is to provide a sub-scanning speed switching unit which can switch the carrying speed of the paper carrying unit between a normal speed and a low speed, and a normal speed when the sub-scanning speed switching unit makes the carrying speed low. This can be achieved by providing the controller with a correction image generation unit that generates a correction image during a repeated cycle of image formation in the main scanning direction.

[Action]

During normal printing, the controller conveys the paper at the normal speed with the paper conveying unit at the normal speed, and sets the bit map data for one page to 0, 1, 2, 3, ... In synchronization with the timing of the main scanning unit. .. is read line by line, and the light emitting unit is turned on and off according to the content (1 or 0) of the data. However, when the sub-scanning speed switching unit is set to a high speed, for example, the paper is conveyed at a speed twice as high as the normal speed, and the bitmap data for one page is thinned out every other row, and 0, 2, 4, 6 ,. , And read every other row to control the light emitting unit.

On the other hand, when the speed is set low, for example, the conveyance speed of the paper is set to half the normal speed, and scanning of correction dots is generated and inserted between each main scanning (half row) to form a fine image.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention applied to a laser printer will be described in detail with reference to the drawings. FIG. 1 shows an overall schematic configuration of a laser printer according to the present invention. In the figure, 10 is a paper feed unit for feeding paper from a paper feed tray 11, 12 is a paper feed sensor for detecting the fed paper,
Reference numeral 13 denotes a polygon mirror 15 for applying laser light from the light emitting section 14.
Is a main scanning unit for deflecting the main scanning on the photoconductor 16 and 17 is a developing unit, 18 is a transfer unit, 19 is a cleaning unit, 20 is a fixing unit, and 21 is a paper discharge unit. 22 is a controller that controls all of these.

The controller 22 has various functions. Among them, as shown in FIG. 2, the bitmap data creating section 23, the image thinning section 24, the corrected image creating section 25 and the sub-scanning speed switching section 26 are included in the present invention. It will be important.

The controller 22 creates bitmap data for one page by the bitmap data creation unit 23 based on the data received from the external host computer, and when it is completed, the paper feed unit 10 and the photoconductor 16 The drive motor 27 that collectively drives the developing unit 17, the fixing unit 20, and the paper discharge unit 21 is actuated to start feeding from the paper feed tray 11. FIG. 3 shows an example of a part of bitmap data at the time of normal printing. In the figure, the horizontal is the main scanning direction,
The vertical direction is the sub-scanning direction.

During normal printing, the controller 22 rotates the polygon motor 28 of the main scanning unit 13 when a preset delay time during normal printing has passed, with reference to the detection timing of the leading edge of the paper by the paper feed sensor 12. The light emission of the laser diode 29 of the light emitting unit 14 is controlled in accordance with the timing of the main scanning by. And the controller 22
Reads the data in the main scanning direction of the above-described bitmap data created by the bitmap data creating unit 1 bit by bit and repeats it line by line in the sub scanning direction to turn on the laser diode 29 for each bit. -By turning off, one page image is formed. For example, in FIG. 3, when the third row in the sub-scanning direction is read,
The laser diode 29 is turned on (emits light) at the 7th bit, 9th bit, and 10th bit in the main scanning direction, and turned off at other bits.

When the laser diode 29 emits light and the photoconductor 16 is exposed to the laser light, the exposed points are charged and a latent image corresponding to FIG. 3 is formed on the photoconductor 16. This latent image is generated by rotating the photoconductor 16 and developing unit 17
Since it is developed by adsorbing the toner, the image is transferred by the transfer unit 18 onto the fed paper. The sheet is heated and fixed on the transferred image by the fixing unit 20, and then discharged by the paper discharging unit 21.

Next, the printing operation when the draft mode printing command is received from the external host computer or the draft mode printing is selected on the operation panel will be described.

The controller 22 creates bitmap data for one page by the bitmap data creation unit 23 based on the data received from the external host computer. The bitmap data is as shown in FIG. 3 as in the normal printing. When the bitmap data for one page is completed, the controller 22 controls the sub-scanning speed switching unit 26.
Then, the speed of the drive motor 27 is doubled at the time of normal printing. As a result, not only the paper transport system including the paper feed unit 10 and the paper discharge unit 21, but also the operations of the photoconductor 16, the developing unit 17, and the fixing unit 20 are doubled.

In draft printing, the controller 22 uses the detection timing of the leading edge of the paper by the paper feed sensor 12 as a reference, and when a preset delay time in draft printing has passed, the timing of main scanning by rotation of the polygon motor 28. Laser diode 29 of the light emitting unit 14 according to
Control the emission of light. Then, the controller 22 sequentially reads the bitmap data created by the bitmap data creating unit 23 bit by bit in the main scanning direction.
In the sub-scanning direction, the image thinning unit 24 thins out every other line (main scanning is performed every other line), and in FIG.
The laser diode 29 is turned on / off only for the even-numbered rows 4, 6, ..., And the image of one page is formed at high speed.

The bit map data read at this time is as shown in FIG. 4, but since the paper transport system, the photoconductor 16, the developing section 17, and the fixing section 20 are driven at a double speed as described above, A latent image as shown in FIG. 5 is formed on the photoconductor 16 and printed on a sheet by the same process as above. In this case, since the polygon motor 28 rotates at the same speed as in normal printing, the main scanning speed does not change, and therefore the laser diode drive circuit of the controller 22 may be the same as in normal printing.

In the above example, the operation in which the bit map data is skipped line by line and transferred to the laser diode 29 has been described. However, the data is discarded every other line before the printing is started, and the bit map data is transferred as shown in FIG. If printing is started after compression as described above, the memory efficiency can be improved.

Further, the sub-scanning speed is doubled and the main scanning is set to 1
Although the data is thinned out every other line, the sub-scanning is tripled, and the main scanning of the bitmap data is thinned out every two lines out of three lines, so that higher speed printing is possible. Furthermore, for example, if the main scanning of the bitmap data is thinned out every four lines, it is possible to change the speed by a non-integer multiple such as 1.5 times.

On the other hand, when the fine mode printing command is received from the external host computer or when the fine mode printing is selected on the operation panel, the sub scanning speed switching unit 26 switches the sub scanning speed to half of the normal printing. ,
The paper transport system, the photoconductor 16, the developing unit 17, and the fixing unit 20 are driven at half speed. Then, at this time, the correction image generation unit 25 generates and inserts the scanning of the correction dots between each main scanning, and a fine image is formed at low speed. In this case, each main scan may be performed twice.

[0023]

According to the first aspect of the present invention, draft printing, which is not high in print quality but high in printing speed, can be efficiently performed without requiring a significant change in hardware.

According to the second aspect, even when the printing speed is slowed down and fine printing is performed, the printing can be efficiently performed without requiring a large change in the hardware.

According to the third aspect, both draft printing and fine printing can be efficiently performed with a simple structure.

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram of an example of a laser printer to which the present invention is applied.

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

FIG. 3 is a pattern diagram of bitmap data during normal printing.

FIG. 4 is a pattern diagram of bitmap data thinned out every other row.

FIG. 5 is a pattern diagram when the above bitmap data is printed.

[Explanation of symbols]

 10 Paper Feeding Section 11 Paper Feeding Tray 12 Paper Feeding Sensor 13 Main Scanning Section 14 Light Emitting Section 15 Polygon Mirror 16 Photoreceptor 17 Developing Section 18 Transfer Section 19 Cleaning Section 20 Fixing Section 21 Paper Discharging Section 22 Controller 23 Bitmap Data Creating Section 24 Image thinning unit 25 Corrected image generation unit 26 Sub-scanning speed switching unit 27 Drive motor 28 Polygon motor 29 Laser diode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 9211-2C B41J 3/10 101 H 9211-2C 101 F

Claims (3)

[Claims] 1. A light source is controlled by a controller to form an image in the main scanning direction in accordance with image data in synchronism with the main scanning of the main scanning unit, and a paper transport unit is controlled to transport the paper. In an image forming apparatus that repeats image formation in the main scanning direction at a predetermined cycle in the sub scanning direction, a sub scanning speed switching unit that can switch the carrying speed of the paper carrying unit between a normal speed and a high speed, and the sub scanning speed. An image forming apparatus, wherein the controller is provided with an image decimating unit that decimates a repetition cycle of image formation in the main scanning direction when a switching unit increases the conveyance speed from a normal speed. 2. A light source is controlled by a controller to form an image in the main scanning direction in accordance with image data in synchronism with the main scanning of the main scanning unit to form an image in the main scanning direction. In an image forming apparatus that repeats image formation in the main scanning direction in a predetermined cycle in a sub scanning direction, a sub scanning speed switching unit that can switch the carrying speed of the paper carrying unit between a normal speed and a low speed, and the sub scanning speed. The controller is provided with a correction image generation unit that generates a correction image during a repeated cycle of image formation in the main scanning direction when the transport speed is set to a low speed at the switching unit and at a normal speed. Forming equipment. 3. A light source is controlled by a controller to form an image in the main scanning direction by a controller according to image data in synchronism with main scanning of a main scanning unit, and a paper transport unit is controlled to transport a sheet. In an image forming apparatus that repeats image formation in the main scanning direction in a predetermined cycle in the sub scanning direction, a sub scanning speed switching unit capable of switching the carrying speed of the paper carrying unit between a normal speed, a high speed, and a low speed.
When the conveyance speed is increased by the sub-scanning speed switching unit, the image thinning unit that thins out the repetition cycle of image formation in the main scanning direction than when it is at the normal speed A correction image generation unit that generates a correction image during a repetition cycle of image formation in the main scanning direction at a speed, and the controller is provided with the correction image generation unit.
Image forming apparatus.