JP3081233B2 - Image forming device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming apparatus such as a page printer such as a laser printer and a digital copying machine.

[Prior art] In a conventional image forming apparatus such as a laser printer,
In general, the resolution is fixed, and it is not possible to meet the demand of the user. However, in recent years, the resolution can be changed.

[Problems to be solved by the invention]

However, the change of the resolution requires the operation of an operator, which is complicated.

Some resolutions can be automatically changed, but the resolution is not always changed to an optimum resolution. For example, if the print data from the host includes the content for specifying the resolution, the printer will be fixed at the specified resolution even if a higher resolution is possible.

The specified resolution is also 300dpi, 400dpi, 600dpi
… And because of the jumpy value, it was not optimized.

Generally, the higher the resolution, the higher the print quality tends to be. Therefore, it is desired that the resolution be as high as possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to automatically and optimally change the resolution to obtain high image quality without bothering the operator.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an image forming apparatus capable of changing the resolution, according to the amount of memory that can be used when developing print data into bit map data.
Automatic resolution changing means for automatically changing the resolution to the maximum resolution which can be developed, and means for prohibiting processing by the automatic resolution changing means when print data is bitmap data or when using bitmap fonts. It is provided.

(Operation)

In the image forming apparatus according to the present invention, when the print data is not bit map data or when the bit map font is not used, the print data is expanded according to the amount of memory available when developing the bit map data.
Since the automatic resolution changing means automatically changes the resolution to the maximum resolution at which the resolution can be developed (the maximum resolution possible), an image of the highest print quality can be obtained without bothering the operator.

Also, when the print data is bitmap data or when using bitmap fonts, the resolution cannot be changed, so the processing by the automatic resolution changing means is wastefully started by prohibiting the processing by the automatic resolution changing means. Since processing does not occur, processing efficiency is improved.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 2 is a sectional view showing a schematic configuration of a laser printer according to one embodiment of the present invention.

This laser printer has a paper feed tray 2 detachably mounted on a main body 1, a first paper discharge stacker 3 at the top, and a second paper discharge stacker 4 at the rear.

Normally, the first discharge stacker 3 is selected from the two discharge stackers 3 and 4. However, the second discharge stacker 3 is used in special cases, such as when using easily curlable paper such as envelopes and postcards. Statka 4 is selected.

The paper discharge to the two paper discharge stackers is performed by the switching claw 5.
Can be switched by means of

Further, in the main body 1, each process device constituting an image forming unit of the printer engine, that is, a photosensitive drum 6, a charging unit 7, an optical writing unit 8, a developing unit 9, a transfer unit 10, and a fixing unit 11, The paper feed unit includes a paper feed roller 12, a pair of registration rollers 13, and the like, and a paper discharge transport unit 14 including a transport roller and a paper guide plate.

On the upper part of the printer, boards for a controller section (printer controller) 20 and an engine control section (engine driver) 30, which will be described later, are mounted.

When a print sequence is started by a command from a host computer (to be simply referred to as a “host” hereinafter), paper is started to be fed from the paper feed tray 2 by the paper feed roller 12 and the leading edge of the paper is It stops temporarily at the position between the registration rollers 13.

On the other hand, electrophotographic processing is performed by each process device.

That is, the photosensitive drum 6 rotates in the direction of the arrow in FIG. 2, and the laser beam modulated on the surface charged by the charging section 7 by the optical writing section 8 in accordance with the video data from the controller section 20. Is irradiated while the main scanning is performed in the drum axis direction to form a latent image.

It is developed with toner in a developing unit 9, transferred to a sheet fed at a predetermined timing by a registration roller pair 13 by a transfer unit 10, and then the sheet heated and fixed by the fixing unit 11 is The sheet is discharged to the first sheet discharge stacker 3 via the second sheet discharge stacker 4 or the discharge section 14.

FIG. 1 is a block diagram showing a configuration of a control unit of the laser printer.

In the controller unit 20, when print data transferred from a host computer 19 such as a personal computer, a word processor, a data processing device, and an image forming device is received by a receiver 21, a processor (CPU) 22 is read from a ROM.
The print data is converted (developed) into bit map data using a memory (RAM) 24 in accordance with the control program in 23 and then sent to the engine control unit 30.

In the engine control unit 30, the bit map data from the controller unit 20 is received by the receiver 31, and the driver 32 drives the laser diode 40 to emit light according to the data.

Further, a processor (CPU) 33 sets a preset value corresponding to the resolution in a timer 36 using a memory (RAM) 35 according to a control program in a ROM 34.

The timer 36 outputs a pulse signal of a constant frequency in accordance with a preset value from the processor 33 to the polygon motor driver 41.
Continue sending to.

The polygon motor driver 41 uses the pulse signal as a reference clock to rotationally drive a polygon motor (not shown) that rotates the polygon mirror 42 at a rotational speed proportional to the frequency.

Thereby, the laser light from the laser diode 40 is deflected by the polygon mirror 42, and the charged photosensitive drum 6 is exposed through the lens 43 to form an electrostatic latent image.

In addition to the exposure process, the processor 33 causes the process device shown in FIG. 2 to perform an electrophotographic process such as paper feeding, charging, developing, transferring, and fixing to output a printed image.

By the way, the controller unit 20 uses the memory 24 to develop print data into bit map data.

In the case of the laser printer (page printer) according to this embodiment, if the full-bit map method is used, a letter size (8.5 "x 11") sheet requires a memory capacity of about 1 megabyte at a resolution of 300 dpi.

When the controller unit 20 has a memory capacity of one page or less, a partial bit map method is employed (in this case, printable contents are limited).

Conversely, if the memory capacity is one page or more, the remaining memory is used for the bit map of the next page (improves the printing speed) or used for storing soft fonts.

However, in this case, conventionally, the remaining memory of one page or more is not always used.

In general, the higher the resolution, the larger the required memory (about 4 megabytes, which is four times 300 dpi for 600 dpi). Conversely, the more memory you have, the higher your resolution will be.

As described above, if more than one page of memory is available at a certain resolution, the resolution is determined from the amount of available memory, and if printing is performed at that resolution, printing is always performed at the highest resolution, that is, at the highest printing quality. I can do it.

Therefore, when the processor 22 of the controller unit 20 receives one page of print data from the host computer 19, the processor 22 determines the resolution from the amount of data and the amount of memory available at that time, and transmits information on the determined resolution. The signal is transmitted to the processor 33 of the engine control unit 30. The resolution at this time does not need to be the discrete value as described above,
For example, a value such as 203 dpi may be used.

However, when the print data transferred from the host computer 19 is bit map data or when a bit map font is used, such resolution determination processing is not performed.

The processor 33 of the engine control unit 30 includes a controller unit.
According to the resolution information from 20, the preset value of the timer 36 is changed, the rotation speed of the polygon mirror 42 is changed, and the resolution is changed.

Thereafter, when bit map information corresponding to the set resolution is received from the controller 20, the above-described printing operation is performed.

As described above, in this embodiment, the resolution is automatically changed according to the amount of available memory, so that the resolution can be maximized as much as possible. can get.

Further, when the print data is bitmap data or when a bitmap font is used, the process of changing the resolution (determination process) is prohibited, so that the process is not started unnecessarily, and the processing efficiency is reduced. improves.

The embodiment in which the present invention is applied to a laser printer has been described above. However, the present invention is applicable to other page printers such as an LED printer and a liquid crystal shutter printer and image forming apparatuses such as a digital copying machine.

〔The invention's effect〕

As described above, according to the present invention, since the resolution can be maximized as much as possible, the highest image quality can be obtained without bothering the operator.

Further, when the print data is bitmap data or when a bitmap font is used, by prohibiting the process of changing the resolution, the process is not started unnecessarily, thereby improving the processing efficiency. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a control unit of the laser printer shown in FIG. 2, and FIG. 2 is a schematic configuration diagram showing a mechanism of a laser printer according to an embodiment of the present invention. 1 Laser printer, 6 Photoconductor drum 19 Host computer 20 Controller, 21, 31 Receiver 22, 33 Processor (CPU) 23, 24 ROM 24, 35 Memory (RAM) 30 ... Engine control unit, 32 ... Driver 36 ... Timer, 40 ... Laser diode 41 ... Polygon motor driver 42 ... Polygon mirror

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/44 B41J 2/485 B41J 5/30 G06T 11/00 H04N 1/387

Claims (1)

(57) [Claims] An image forming apparatus capable of changing the resolution, wherein the resolution is automatically changed to the maximum possible resolution in accordance with the amount of memory available when the print data is expanded into bit map data. An image forming apparatus comprising: an automatic changing unit; and a unit that prohibits the processing by the automatic resolution changing unit when print data is bitmap data or when a bitmap font is used.