JP2987929B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus capable of switching image densities.

[Prior Art] Conventionally, this type of apparatus includes a laser beam printer using a semiconductor laser. Generally, a laser beam printer capable of recording at an image density of 240, 300, and 400 dpi is often used. Recently, a laser beam printer with a high pixel density of 480, 600, 800, 1200 dpi or the like is often used in order to make oblique lines or curved portions of characters beautiful. In the case of a photographic image or the like, halftones are usually expressed by so-called area gray scales. Even if the number of gray scales is increased, the size of one pixel representing halftones is reduced to output a beautiful photographic image. If you want to output characters with a large number of strokes, such as Chinese characters, clearly, use a high pixel density laser beam printer.

However, when connecting and using peripheral devices, host computers, etc. using conventional software, it is necessary to consider compatibility with conventional laser beam printers. Even a beam printer needs to be able to use the conventional image density. For this reason, one laser beam printer can use a plurality of image densities (for example, 300 dpi and 600 dpi or 300 dpi and 800 dpi).
pi) can be executed by executing the printing process.

When changing the image density in a laser beam printer, it is necessary to change the reading speed of the image data and also change the scanning line density of the laser. To change the scanning line density, change the rotation speed of the polygon mirror. ,
This is performed by changing the rotation speed of the photoconductor.

[Problems to be solved by the invention]

However, in the above conventional example, when the pixel density is changed to a high pixel density, the pixel density on the electric signal is changed, but the performance of the photoconductor and the developing device (hereinafter, referred to as printing performance) corresponds to the high pixel density. There are many that do not have high quality output. In such a device, the output of oblique lines and curves of large characters is probably high-density, but characters with a large number of strokes such as kanji, especially thin lines of small characters cannot be printed. It was broken or crushed. In addition, binarization processing such as dithering is generally used for photographic image output processing. However, by changing to a high pixel density, one dot of the dither pattern has a smaller area, and the electric power is simply reduced. It is difficult to faithfully reproduce a photographic image only by changing the signal to a high pixel density, and in such a case, the photographic image is rather degraded in quality.

SUMMARY An advantage of some aspects of the invention is to provide an image forming apparatus capable of changing a pixel density according to printing performance.

[Means for solving the problem]

In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus that forms an image according to image data from an external device, comprising: an image forming unit in which a process cartridge including at least a developing unit is detachable. Detecting means for detecting the type of the mounted process cartridge; controlling means for controlling the image forming means such that images having different pixel densities are formed according to the type of the process cartridge detected by the detecting means. Having.

Further, in an image forming apparatus for forming an image according to image data from an external device, an image forming unit in which a process cartridge including at least a developing unit is detachable, and a pixel density of an image formed by the image forming unit is determined. Setting means for setting, means for limiting the pixel density that can be set by the setting means according to the type of the process cartridge to be mounted, and an image having the pixel density set by the setting means is formed. A control unit for controlling the image forming unit;

The image forming apparatus preferably further includes a unit that outputs pixel density information of an image formed by the image forming unit to the external device.

[Action]

According to the present invention, it is possible to prevent printing at a pixel density that does not correspond to the printing performance of the mounted process cartridge, and to form a high-quality image corresponding to the printing performance of the process cartridge.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view illustrating the configuration of an image forming apparatus according to an embodiment of the present invention. A laser beam emitted from a semiconductor laser passes through a collimator lens to become parallel light, then enters a polygon mirror, is reflected by a high-speed rotating polygon mirror, and scans the photosensitive drum 3. . 2 is fθ
This is an optical system including a lens, a folding mirror, and the like.
The laser beam enters the photosensitive drum 3 via the optical system 2. The wavelength of the semiconductor laser in this embodiment is 770 to 800 nm, and the photosensitive drum 3 uses a photosensitive member sensitive to this wavelength, for example, a phthalocyanine-based organic photoconductor or a selenium-based photoconductor.

Reference numeral 4 denotes a primary charger, which is a photosensitive drum 3 made of an organic photoconductor.
The top is uniformly charged.

In this embodiment, the grid 17 is provided at a certain distance from the photosensitive drum 3 in order to make the primary charging more uniform and to stabilize the potential on the photosensitive drum 3. The grid 17 is grounded via a self-voltage generating member. When a corona discharge current flows, the grid 17
Is generated to control the surface potential of the photosensitive drum 3. The photosensitive drum 3 charged by the primary charger 4 is connected to the scanner units 1 and 2 described above.
Scanning is performed by the laser beam guided by the optical system 2, and an electrostatic latent image is formed.

In this embodiment, a portion to be visualized is scanned with a laser beam. That is, a so-called image scanning method of developing a portion irradiated with the laser beam is used.
This is because the image scan method has clearer image quality than the background scan method, requires less laser emission time, and is advantageous for the life of the semiconductor laser. This electrostatic latent image is made remarkable by the next developing device 5. In this embodiment, a one-component magnetic developing system is adopted as a developing method, and the developing device 5 can be simplified and downsized, so that a developing device with less toner contamination can be configured. An AC voltage on which a DC voltage is superimposed is applied to a sleeve of the developing device 5 by a power supply (not shown).

On the other hand, the sheet P on the loading table S is fed onto the photosensitive drum 3 by the feed roller 6 and the registration roller 7 which rotates at a timing synchronized with the image on the photosensitive drum 3. Then, the toner image on the photosensitive drum 3 is transferred onto the sheet P by the transfer charger 8. Thereafter, the sheet P separated from the photosensitive drum 3 by the separating unit 9a is guided to the fixing device 10 by the guide 9, and after the toner image on the sheet P is fixed, is discharged onto the tray 12 by the discharge roller 11. . Reference numeral 13 denotes a cleaner.

Incidentally, the photosensitive drum 3, the primary charger 4, the developing unit 5, the cleaner 13
Constitutes an integrated process cartridge 14. The process cartridge 14 is provided detachably with respect to the main body. When the process cartridge 14 is loaded into the main body, the sliding portion 1 of the frame 14a of the process cartridge 14 is attached to the main body guide 15.
4b is engaged and guided. Reference numeral 16 denotes pre-exposure means for irradiating the photosensitive drum 3 with light before primary charging, and a halogen lamp, an incandescent bulb, an LED, or the like may be used as a light source. The light of the pre-exposure is applied to the surface of the photosensitive drum 3 through the opening of the process cartridge 14.

Reference numeral 18 denotes a controller, which controls the overall operation of the image forming apparatus.

FIG. 2 is a control block diagram for explaining the configuration of the control section 18 shown in FIG. 1. A controller 30 on the image forming apparatus side is connected to a computer 39 on the host side via a connector.

The signal from the controller 30 is the main motor driver
It is sent to a main motor 32 via a 31 or a scanner motor 34 via a scanner motor driver 33, and the respective motors 32 and 34 are driven.

The controller 30 receives a signal from a pixel density designation signal receiving circuit 40 that receives a pixel density designation signal from the process cartridge 14 as described later, and receives a designated scanning line density,
For example, a switching signal of 600 dpi or 300 dpi is sent to the scanner motor driver 33, and the scanner motor driver 33 controls the scanner motor 34 to the scanner motor rotation speed corresponding to the scanning line density.

Further, the controller 30 includes a pixel density designation signal receiving circuit 40.
When a pixel density designation signal is received from the controller 39, a signal is sent to the scanner motor driver 33 and the host computer 39
Also outputs a signal of the specified pixel density.

On the other hand, the semiconductor laser 35 is driven according to an image signal by a laser driver 30a included in the controller 30. The laser driver 30a modulates the laser light from the semiconductor laser 35 with image data at a transmission speed according to the pixel density. A high-voltage power supply 36 applies a high voltage to a charger such as a primary charger based on a control signal from the controller 30. 37
Denotes a pre-exposure unit that performs pre-exposure processing based on a control signal from the controller 30. A developing bias power supply 38 applies a predetermined developing bias to the developing sleeve based on a control signal from the controller 30.

Next, the process cartridge 14 will be described with reference to FIGS.

FIG. 3 shows a case where the process cartridge 14 in which a photosensitive drum, a charger, a developing device, a cleaner, and the like, which are main parts of image formation, can be replaced collectively, is detached from the image forming apparatus.

The developing performance of the developing unit 5 built in the process cartridge 14 greatly changes depending on the particle size or material of the toner used therein. In particular, the toner particle size has a large effect on the development performance. In the process cartridge of this embodiment, about 240 dpi, 300 dpi, and 400 dpi
A toner having a particle diameter of 12 μm is used, and a toner having a particle diameter of about 6 μm is used for 600 dpi and 800 dpi.

As shown in FIG. 4, one or a plurality of frames 220b-
224b is installed. This frame has the image density dp
It indicates i, and the attachment position, number, etc. are determined corresponding to each dpi.

Then, when the process cartridge 14 is inserted into the image forming apparatus main body, the tops 220b to 224b turn on the micro switches 220a to 224a mounted in the main body,
With this switch ON, the pixel density signal is input to the pixel density designation signal receiving circuit 40.

The optimum sensitivity of the photosensitive drum used in the electrophotographic image forming apparatus may vary depending on the image recording density. The higher the pixel density, the lower the sensitivity. In such a case, as for the photosensitive drum, a photosensitive cartridge having an optimum sensitivity according to the pixel density can be used as in the above-described embodiment.

In this embodiment, a photosensitive drum is used as a process cartridge.
Although the charger, developing device, cleaner, etc. are configured as one,
The developing device may be replaced with a replaceable integrated structure, and may be a cartridge.

In this embodiment, the pixel density may be determined according to the type of the process cartridge as described above. However, the pixel density that can be set according to the type of the process cartridge may be limited as described below. Good.

FIG. 5 is an operation flowchart of such an image forming apparatus. In this embodiment, in step S1, the pixel density is changed by a pixel density change command from the host computer or the operation of key input means (not shown) provided in the image forming apparatus. If data other than the pixel density change command is received in step S1, a process corresponding to the data is performed in step S2.

In step S3, it is determined whether or not the pixel density specified by the received pixel density change command corresponds to the mounted process cartridge. That is, for example, if the installed process cartridge is 24
This determination is negative when a pixel density change command specifying 600 dpi is received when recording is performed at a pixel density of 0 dpi, 300 dpi, or 400 dpi. In such a case, the process proceeds to step S4 to return an error to the host computer, and the pixel density is not changed.

If the determination in step S3 is affirmative, a change to the pixel density specified by the received pixel density change command, that is, a change in the number of rotations of the scanner, a change in the clock for reading image data, and the like are performed.

Note that in this embodiment, the initial pixel density is
Depending on the currently installed process cartridge, when the process cartridge is replaced when the power is turned on, when a new process cartridge is installed, the default value is set in accordance with the new process cartridge.

In the above-described embodiment, the scanning line density is switched by changing the rotation speed of the scanner motor.For example, when it is difficult to greatly increase the rotation speed of the scanner motor, the image forming process speed, that is, This may be performed by changing the rotation speed of the photosensitive drum 3. However, in this case, it is necessary to change various process conditions such as the amount of laser light, the high voltage output for the primary charger, the developing bias, the high voltage output for the transfer charger, and the set temperature of the fixing device.

Further, the present invention is not limited to the above example, and when the scanning line density is switched, the process speed may be switched simultaneously with the rotation speed of the scanner motor. By doing so, the amount of change in the rotational speed of the scanner motor and the amount of change in the process speed can be reduced. This eliminates the need for a scanner motor that can rotate at a high speed, and reduces the amount of change in the process speed, thereby reducing the change in process conditions and contributing to the stability of the formed image.

In the above embodiment, the mechanical method using a microswitch as a means for receiving the image density signal of the process cartridge has been described.However, the dpi information is printed as a barcode on a part of the process cartridge. Alternatively, an optical method of reading the data by a bar code reader method or other magnetic methods may be used.

〔The invention's effect〕

According to the present invention, it is possible to prevent printing at a pixel density that does not correspond to the printing performance of the mounted process cartridge, and to form a high-quality image corresponding to the printing performance of the process cartridge.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating the configuration of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a control block diagram illustrating the configuration of a controller unit illustrated in FIG. 1, and FIG. FIG. 4 is a view for explaining a mode of attachment / detachment of the cartridge from the main body, FIG. 4 is a perspective view showing a configuration of a process cartridge, and FIG. 5 is an operation flowchart of an embodiment of the present invention. 1 Scanner unit 2 Photosensitive drum 4 Primary charger 5 Developing device 8 Transfer charger 10 Fixer 14 Process cartridge 18 Controller 40 Image density designation signal reception Circuits 220a to 224a ... Micro switches.

Claims (3)

(57) [Claims] 1. An image forming apparatus for forming an image in accordance with image data from an external device, wherein an image forming means in which a process cartridge including at least a developing means is detachable, and a type of the mounted process cartridge is detected. An image forming apparatus comprising: a detection unit; and a control unit that controls the image forming unit so that images having different pixel densities are formed according to the type of the process cartridge detected by the detection unit. 2. An image forming apparatus for forming an image in accordance with image data from an external device, comprising: an image forming unit in which a process cartridge including at least a developing unit is detachable; Setting means for setting the pixel density; means for limiting the pixel density that can be set by the setting means according to the type of the process cartridge to be mounted; and an image having the pixel density set by the setting means is formed. As described above, the image forming apparatus includes a control unit that controls the image forming unit. 3. The image forming apparatus according to claim 1, further comprising means for outputting pixel density information of an image formed by said image forming means to said external device.