JPH063914A - Image forming device - Google Patents

Abstract

(57) [Summary] [Configuration] It is determined whether or not the value of the read image density is 7% or less (step S3). And if 7% or less,
When it is judged that the character information of the typewriter original is mainly selected, the high speed process speed is selected and the condition is set (step S4), and the copying operation is performed faster than before without changing the machine configuration (step S4). S6). Further, when the image density is high, the fixing property is uncertain, so the slow process speed determined by assuming the worst condition as usual is selected and the condition setting is performed (step S5), and thereafter the copying operation is performed as usual ( Step S6). According to the present invention, the image forming speed can be increased without changing the mechanical structure of the apparatus by switching the process speed according to the image density of the original and always exerting the ability of the machine.

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 capable of changing a process speed, as found in, for example, a medium or low speed copying machine.

More specifically, the present invention relates to an image forming apparatus in which the process speed is variable except for a device such as a high speed machine in which the limit process speed is determined by the driving speed of the mirror of the image reading section. Is.

[0003]

2. Description of the Related Art In a conventional image forming apparatus, the process speed of image forming is changed when a reduction copy or the like is performed or when the compression rate becomes low due to the influence of the compression processing of image information like a facsimile. However, none of them detected the image density of the original and the process speed changed accordingly.

That is, even if the image is thin, the image formation is set under the same conditions as when the image is solid black.

Specifically, under the image forming conditions of a copying machine or the like, the fixability is affected by the image density, and when the image density is high, the fixability becomes poor. The conditions are set, and the process speed is also one of the image forming conditions. Even when the image density is low, the image is formed at a speed adapted to the case of solid black.

[0006]

However, as described above, it is rare that copying is performed under the worst conditions, and in the case of a normal document, although the image forming speed can be made a little faster, this is set as a constant speed. The drawback was that the equipment was not fully utilized.

Further, there is a method in which the user determines the image density of the original document in consideration of the above and switches the process speed according to the user's determination. However, if the setting is erroneous, the fixing property is poor. There were some drawbacks such as poor usability.

Therefore, in view of the above points, an object of the present invention is to provide an image forming apparatus in which the original image forming ability of the apparatus is improved while maintaining the usability.

[0009]

In order to achieve the above object, the present invention comprises a detection means for detecting the image density of an original,
When the image density of the document detected by the detection unit is low, the process speed of image formation is increased to form the image at high speed, and when the image density of the document is high, the process speed is decreased to form the image at low speed. And means.

[0010]

According to the present invention, a detecting means for detecting the image density of the original is provided, and the process speed is changed in accordance with the signal from the detecting means of the image density (a method of switching some preset speeds may be adopted. ), Always trying to operate at a speed that makes the best use of the ability of the machine.

Further, since the process speed is automatically set without depending on the user's judgment, a copy having bad fixing property is not obtained due to a mistake, and there is no problem in usability.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

Embodiment 1 FIG. 2 shows an overall view of a copying machine according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a document feeder, which separates the document 2 from the lower side and conveys it onto the platen glass 21 from the right side of the figure. Reference numeral 3 denotes a document reading CCD for illuminating the document on the platen glass 21 with the document illumination lamp 10 and reading the reflected light beam to convert it into an electric signal.

An image density detection sensor 4 is provided inside the document feeder. With this, the image density can be read in advance when the document is conveyed onto the platen glass 21, and it is effective when it is desired to increase the first copy speed.

In the case of a document feeding device capable of handling both-sided documents, a sensor is also required in the document reversing path portion in the document feeding device, as shown at 4'in FIG.

Reference numeral 5 denotes a potential sensor for measuring the surface potential of the photosensitive drum 6 of the copying apparatus, which measures the surface potential of the photosensitive drum 6 after the image information of the original is written. Therefore, the image density information of the document can be obtained from this signal as well.

Reference numeral 7 is a heater of a fixing device, 8 is an upper fixing roller for melting and fixing the toner on the copy image surface, 9 is a lower fixing roller, 10 is an original illumination lamp, 11 is a photosensitive drum, and the photosensitive drum is charged to a uniform potential. A primary charging device 12 is a separation charging device for separating and separating the copy paper onto which the toner is transferred from the photosensitive drum 6 by eliminating electrostatic attraction, and a reference numeral 13 is for transferring the toner on the photosensitive drum 6 to the copy paper. Transfer charger,
Reference numeral 14 is a developing unit cylinder, and 22 is a double-sided copying unit.

FIG. 1 is a flow chart showing the operation of the copying machine shown in FIG. Here, an example is shown in which copying is performed using the document feeding device, but when a document is directly placed on the platen glass 21, the same operation is performed.

First, when the document stack 2 is set on the document feeding device 1 and the copy start key is pressed, the document feeding device 1 measures the image density of the document with the image density detection sensor 4, and the document is placed on the platen glass 21. Transport. Then, prescan is performed, the original is read by the CCD 3 and the potential sensor 5, and the image density is reconfirmed (steps S1 and S2).

The above operation itself is the same as that conventionally known as an automatic density adjusting mechanism (AE) of a copying machine, and the measurement itself is relatively established and can be easily carried out.

Next, it is judged whether or not the read image density value is 7% or less (step S3). If it is 7% or less, it is determined that the character information of the typewriter original is mainly, and the high speed process speed is selected to set the condition (step S4). A copying operation is performed at high speed (step S6).

That is, in some conventional medium to low speed copying machines, the copying speed is selected by the ability of the fixing device, and further, the worst condition is set so that the fixing performance is sufficiently improved even when copying solid black. I had selected and set the upper limit of the process speed. Conversely, this means that the image density of a normal manuscript is over-quality, and the process speed can be made a little faster.

Further, when the image density is high, the fixing property is uncertain, and the slow process speed determined by assuming the worst condition as usual is selected and the condition setting is performed (step S5). After that, the copying operation is performed as usual. Is performed (step S6).

In the flow chart shown in FIG.
According to the image density information of the original, it is divided into two stages, a high speed mode and a conventional low speed mode, but the same operation can be performed by dividing it into five stages or more.

FIG. 3 is a control block diagram for performing the condition setting described in FIG. In the figure, reference numeral 15 is a controller unit that controls the entire copying apparatus. This controller unit 15 is a CC
D3, the image density detection sensor 4 of the document feeding device, and the potential sensor 5 for measuring the potential of the photosensitive drum are connected to detect the image density of the document.

The controller unit 15 makes the judgment shown in FIG. 1 based on the information, and sets the conditions in accordance with the selected process speed. That is, (1) switching of the driving speed of the main motor 16 that drives the photosensitive drum 6, the developing cylinder 14, the fixing device rollers 8 and 9, the conveying unit, the cleaner, and the like.

(2) Switching of the driving speed of the paper feeding motor driving the paper feeding device 23.

(3) Switching of the speed of the optical system drive motor driving the original illumination lamp 10 and the scanning mirror.

(4) Switching the speed of the double-sided unit drive motor when performing double-sided copying.

(5) Switching of the light quantity of the document illumination lamp 10.

(6) Primary charger 11, separation charger 12,
Switching of various high voltages such as the developing bias applied to the transfer charger 13 and the developing cylinder 14.

The controller unit 15 performs the above operation, and thereafter, the copying operation is performed as usual.

Embodiment 2 In the above embodiment, the average value of the image density of the original document is used as the criterion for the condition judgment. However, in the case of the original document in which the black portion is concentrated only in a part, the continuous copying is performed. When the number of sheets is large, the fixing property of that portion may deteriorate.

When there are many such documents, it is dangerous to judge only by the average image density. Therefore, in addition to the average, if the maximum area of the concentrated portion of the solid black image is added to the judgment material, Better. This embodiment is shown in FIG.

Further, in the conventional apparatus in which the user can select a high process speed, the machine further judges whether or not the judgment of the user's image density is appropriate, and when it is dangerous, prohibits it or displays a message. Can also be used.

In the above-mentioned embodiments, the judgment of the process speed switching is explained with the image density of 7% as a boundary, but this value is experimentally obtained, and other values may be used. good.

Summary In the embodiment of the present invention, "(1) In the apparatus for reading and forming an image, the process speed is configured to be variable, the means for detecting the image density of the original document, and the detected image density of the original document according to the means. When the density is low, the process speed of the image forming apparatus is increased to perform high-speed image formation, and when the image density of the document is high, the process speed is decreased from that when the density of the original is low, and image formation is performed at low speed. By adopting the "characteristic image forming apparatus", it is not always necessary to fix the process speed assuming the worst condition.

Therefore, when a document having an ordinary image density of about 7% or less is copied, the copy can be performed at a higher speed, and 100% of the capacity of the image forming apparatus can be exhibited.

Further, as the document image density detecting means, the means listed below can be adopted.

1) The original reading section is equipped with a CCD, and the average value of the signals is used.

2) Using the image density detecting means provided in the document feeding device, the document is read just before it is placed on the platen glass of the image forming device and the average value thereof is used.

3) An electrophotographic copying machine equipped with a photosensitive drum or a photosensitive belt is used as an image forming apparatus, and a potential sensor for measuring the surface potential of the photosensitive drum or photosensitive belt is provided as an image density detecting means of a document. The average value of the detection signals is used.

4) An image density detecting sensor is provided as the image density detecting means, and instead of the average value of the detected signals,
The area of the maximum solid black portion is obtained and used as a reference for image density (1) 2) 3) above).

[0044]

As described above, according to the present invention, the process speed is switched according to the image density of the original so that the ability of the machine is constantly exhibited, thereby increasing the image forming speed without changing the mechanical structure of the apparatus. be able to.

That is, it is possible to improve the specifications substantially without changing the cost.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating the operation of an embodiment of the present invention.

FIG. 2 is an overall view of a copying apparatus according to an embodiment of the present invention.

FIG. 3 is a block diagram showing a control unit according to an embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of another embodiment of the present invention.

[Explanation of symbols]

 3 CCD of the document reading section 4 Image density detection sensor of the document feeder 5 Potential sensor for measuring the surface potential of the photosensitive drum 7 Heater of the fixing device 8 Upper fixing roller 9 Lower fixing roller 10 Original illumination lamp

Claims (5)

[Claims] 1. A detection unit for detecting an image density of an original, and when the image density of the original detected by the detection unit is low, the process speed of image formation is increased to form an image at high speed, An image forming apparatus comprising: a control unit that slows the process speed when the temperature is high and forms an image at a low speed. 2. The image forming apparatus according to claim 1, wherein the detecting unit for detecting the image density of the original includes a CCD in an image reading unit and uses an average value of output signals of the CCD. 3. The image density detecting means provided in a document feeding device as the detecting means for detecting the image density of a document, wherein the document is read immediately before being placed on the platen glass, and an average value thereof is read. An image forming apparatus characterized by using. 4. An electrophotographic copying machine equipped with a photosensitive drum or a photosensitive belt is used as the image forming apparatus according to claim 1,
An image forming apparatus characterized in that an electric potential sensor for measuring the surface potential of the photosensitive drum or photosensitive belt is provided as the detecting means for detecting the image density of the original, and the average value of the detection signal is used. 5. The image density detection sensor according to claim 2, wherein an image density detection sensor is provided as the detection means for detecting the image density, the maximum area of the solid black portion is obtained from the detected signal, and the value is used as the image density. An image forming apparatus characterized by being used as a standard of.