JP2001092337A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which can suppress the rise of temperature in the device by making the fan control appropriate and which can prevent a cockle of recording paper and a picture blurring. SOLUTION: A control part driving/controlling fan for limiting the driving of a cooling fan 70 until the leading end of recording paper 10 enters a fixing device 30 after it passes through a transfer part is installed. The control part drives/controls the fan when recording paper transport speed is slow.

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 for transferring a toner image formed on an image carrier to recording paper and fixing the transferred recording paper by a fixing device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer or a copying machine, a fan is driven to discharge air in the apparatus main body to the outside to suppress a rise in temperature in the apparatus main body. However, there has been a problem that the recording paper is pushed up from the transfer to the fixing due to the influence of the airflow from the fan, and the recording paper enters the fixing nip at a position different from the target position. When such a phenomenon occurs, wrinkles may occur on the recording paper, or the recorded image may be blurred.

As an example of a countermeasure for solving this problem, by controlling the drive of the fan to be stopped until the recording sheet enters the fixing state from the transfer, the influence of the air flow upon entering the fixing nip can be prevented. It is known to Further, there is also known an apparatus which controls an airflow control plate or the like to obtain a similar effect.

[0004]

However, as the miniaturization of the apparatus progresses, the distance between the fixing device, which is a heat generating part in the apparatus, and other parts becomes shorter, and the temperature rise becomes more severe. In addition, as the speed increases, the fan drive control described above takes into account the time difference between receiving the fan stop signal and stopping the air flow to such an extent that the air flow does not affect the recording paper. Becomes very large, and it is difficult to suppress the temperature rise in the apparatus. Therefore, in recent years, it is approaching a situation where it is difficult to suppress a rise in the internal temperature of the apparatus by fan drive control.

[0005] It is known that, in an image forming apparatus such as a printer, the conveying speed is reduced to half when performing high-resolution printing compared to when performing normal low-resolution printing. Even in the normal printing in this case, it is currently difficult to suppress the temperature rise in the apparatus by controlling the fan.

The present invention has been made in view of the above-mentioned conventional circumstances, and provides an image forming apparatus capable of suppressing a rise in temperature inside the apparatus by optimizing fan control and preventing wrinkles and image blurring of recording paper. That is the task.

[0007]

In order to solve the above-mentioned problems, the present invention transfers a toner image formed on an image carrier to recording paper, and fixes the transferred recording paper by a fixing device. An image forming apparatus capable of changing a recording paper conveyance speed by switching modes, wherein an image forming apparatus in which a cooling fan is provided in an apparatus main body is used after an end of the recording paper passes through a transfer unit. A control unit for performing fan drive control for restricting the driving of the cooling fan until entering the fixing device, wherein the control unit performs the fan drive control when the recording paper transport speed is low. It is characterized by.

It is to be noted that the present invention is also directed to the fan drive even when the recording paper transport speed is low and the resolution is high when the recording paper transport speed is high. When control is selectable,
It is effective.

Further, the present invention is effective when it is possible to select whether or not to execute the fan drive control according to the type of the recording paper.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating an embodiment of a printer as an image forming apparatus according to the present invention.

In FIG. 1, a photosensitive drum 1 serving as a latent image carrier is uniformly charged by a charging means 2 while being rotated in a counterclockwise direction, and then, based on image information from a laser optical device 3. The laser beam is scanned and exposed to form an electrostatic latent image on the surface. The electrostatic latent image formed on the photosensitive drum 1 is developed with toner by the developing unit 5, whereby an image is formed on the photosensitive drum 1.

The image formed on the photosensitive drum 1 is transferred onto a transfer material 10 which is conveyed from an automatic paper feed cassette 7 or a manual paper feed tray 7a to a transfer section via paper feed rollers 8, 8a and registration rollers 9. Is transferred under the action of the transfer means 6. After the transfer, the transfer material 10 is fixed with a toner image by a fixing device 30 having a pair of rollers of a fixing roller 32 and a pressure roller 33. Thereafter, the sheet on which the image has been formed is moved down the image surface by a pair of discharge rollers 34. And the output tray 4
Drained above zero. The toner on the photoconductor drum 1 that has not been transferred is removed from the photoconductor drum 1 by the photoconductor cleaner 13.

The printer according to the present embodiment prints at a resolution of 600 dpi or less, but is a device capable of selectively printing at a high resolution of 1200 dpi. At the time of printing at a high resolution of 1200 dpi, the printing is performed at half the conveying speed as compared with the printing of 600 dpi or less. This is mainly because there is a restriction due to the high-speed rotation performance of the polygon motor of the laser optical system 4. Accordingly, it is necessary to reduce the amount of heat applied to the recording paper at a low speed in the fixing unit 30. Ideally, it is desirable to reduce the pressing force of the pressing roller 33 against the fixing roller 32 to reduce the nip width of the roller pair. However, there is a problem of space and cost for separately providing a mechanism for changing the pressure. In many cases, measures are taken to lower the set temperature, which can be easily achieved.

Further, a fan 70 is provided in the apparatus in order to prevent an excess amount of heat mainly generated from the fixing apparatus 30 from adversely affecting other parts in the apparatus. Cooling around. As a result, it is inevitable that an air current indicated by an arrow S is generated near the fixing device 30. The air flow S usually has an adverse effect on the recording paper 10 that is to be sent to the nip between the pair of fixing rollers 32 and 33, as shown in FIG.
As shown in FIG. 3, 0 may not enter the target position of the fixing roller pair. Thus, the recording paper 1
If 0 is not correctly fed to the fixing device 30, the recording paper itself may undulate and wrinkle, or an unfixed image may be blurred if carelessly touches the fixing roller 32 before entering the nip. That was explained earlier. Note that, as in the printer shown in FIG. 1, the recording paper passing through the transfer means 6 is sent upward (vertically) and the fixing device 1
In the case of the type of entering into 2, the airflow S tends to be easily affected.

To prevent this problem, the recording paper 10
It has been proposed to perform fan drive control to stop the rotation of the fan 70 or to limit the drive to reduce the number of rotations until the leading end passes through the transfer means 6 and enters the nip of the fixing roller pair. I have.

This control is performed by a control unit (not shown), and the fan 70 can be stopped by, for example, turning on the clutch 21 of the registration roller 9 as a trigger. As shown in FIG. 4, the fan stop timing has an optimum value which varies depending on the transport speed and the like. Is set after a lapse of a predetermined time B in which the above is recalled. The fan 70
Is re-driven after a predetermined time A has elapsed since the clutch 21 was turned on, or when the paper discharge sensor 72 provided after fixing is turned on. As shown in FIG. 5, the fan drive control uses sensors 73 and 74 disposed immediately after the transfer unit 6 and immediately after the pair of fixing rollers. The control may be performed at the timing at which is detected.

The inventor of the present application has found that the difference between low-speed printing and high-speed printing based on the level of image resolution causes the relationship between cooling in the apparatus, which is the original function of the fan 70, and adverse effects on recording paper, which is a side effect, to be different. I found it. That is, in the case of low-speed printing, recording paper 10
Is likely to be affected by the airflow S and is likely to cause an abnormal image, but the fixing set temperature is low and the temperature rise in the apparatus is at a level that does not cause any problem. On the other hand, in the case of high-speed printing, the recording paper 10 is transported by the airflow S
It has been found that it is hardly affected by the image and the possibility of generating an abnormal image is low. Also, the fixing temperature at this time is high,
The temperature rise inside the device is also high. In addition, when the fan drive control is performed, the fan stop time is constant irrespective of the size of the recording paper 10, but when the length of the recording paper itself is shortened, the interval between the next recording paper leading edge is shortened and recording is performed at high speed. In the case where horizontal paper passing with a short length of paper is performed, the time during which the fan 70 is stopped becomes too long, and the cooling function is not performed. Further, it is more preferable to stop the fan 70 early in consideration of the time difference from when the stop signal of the fan 70 is sent to the time when the fan 70 actually stops due to the inertia force and the time until the air flow stops after the fan 70 stops. .

In view of the above, it is preferable to perform the above-described fan drive control at the time of low-speed printing. It turned out to be.

Therefore, in the present embodiment, control is performed based on the flowchart shown in FIG. It is determined whether the image data of Step 1 has a resolution of 1200 dpi (Step 2). If the resolution is not 1200 dpi,
Since the resolution is 600 dpi or less, high-speed printing is performed (step 3), and at this time, the fan 70 is normally rotated (step 4). In step 2, when the resolution is 1200 dpi, low-speed printing is performed (step 5), and the fan 70 is operated until the leading end of the recording paper 10 passes through the transfer means 6 and enters the nip of the fixing roller pair.
Fan drive control is performed to stop the rotation of 0 or to limit the drive to reduce the number of rotations (step 6).

As described above, the above-described problem can be solved by executing the fan drive control only at the time of low-speed printing in which an abnormal image easily occurs due to the airflow S and there is room for temperature rise in the apparatus. it can.

In high-speed printing in which an abnormal image or the like is unlikely to occur even if fan drive control is not performed, a problem may occur depending on the type of recording paper and the installation environment of the apparatus. In preparation for such a case, the fan drive control can be selectively performed by a user's panel operation even during high-speed printing.

Further, the trouble of the recording paper due to the air flow S is remarkable on thin paper which is easily affected, and hardly occurs on thick paper. Therefore, in the present invention, the fan 70 is controlled based on the thickness of the recording paper as shown in the flowchart of FIG.

In FIG. 7, Steps 1 and 2 are the same as those in FIG.
Is determined to be the thin paper mode, and if not, the fan 70 is driven normally (step 5). In the thin paper mode in step 4, fan drive control is performed (step 8).

In step 2, the resolution is 12
At 00 dpi, low-speed printing is performed (step 5).
Next, it is determined whether the mode is the thick paper mode (step 7). If the mode is the thick paper mode, the fan 70 is driven normally (step 5).
If the mode is not the thick paper mode in step 7, fan drive control is performed (step 8).

In this control example, usually, in such an apparatus, there are many cases in which a thick paper mode, a thin paper mode, and the like are set due to a problem such as fixability, and the apparatus is linked to these modes. Further, if the apparatus is capable of automatically detecting the paper thickness, a configuration in which fan control is automatically performed when thin paper is detected is also possible. It is also possible for the user to change the setting relating to the presence or absence of the fan drive control by himself according to the recording paper used.

[0026]

According to the first aspect of the present invention, the driving of the fan is controlled when the recording paper enters and enters the high-resolution printing mode. In both modes at the time of low-speed printing where blur is likely to occur, it is possible to suppress the temperature rise in the apparatus and to prevent wrinkles on the recording paper and image blur.

According to the second aspect of the present invention, the fan drive control can be selectively performed even at the time of high-speed printing, so that the fan drive control can be performed depending on the installation environment of the apparatus, and wrinkles and image blurs on the recording paper can be achieved. Can be further prevented.

According to the third aspect of the present invention, the execution or non-execution of the fan control is selected according to the type of recording paper.
It is possible to achieve both more reliably suppressing the temperature rise in the apparatus and preventing wrinkles and image blurring of the recording paper.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram illustrating a state in which a recording sheet enters a fixing device of the image forming apparatus correctly.

FIG. 3 is an explanatory diagram illustrating a recording paper entering state when affected by an airflow to a fixing device.

FIG. 4 is a timing chart of fan drive control according to the present invention.

FIG. 5 is an explanatory diagram showing an example of arrangement of sensors for performing fan drive control.

FIG. 6 is a flowchart illustrating an embodiment of the present invention.

FIG. 7 is a flowchart showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 6 Transfer means 10 Recording paper 30 Fixing device 70 Fan

Claims (3)

[Claims] An image forming method in which a toner image formed on an image carrier is transferred onto a recording sheet, and the recording sheet after the transfer is fixed by a fixing device. In the image forming apparatus, wherein a cooling fan is provided in the apparatus main body, the driving of the cooling fan is performed until the leading end of the recording sheet passes through the transfer unit and enters the fixing device. An image forming apparatus, comprising: a control unit for performing a fan drive control for limiting, wherein the control unit performs the fan drive control when the recording paper conveyance speed is low. 2. The image forming apparatus according to claim 1, wherein the recording paper transport speed is low when high-resolution printing is performed.
An image forming apparatus, wherein the fan drive control is selectable even at the time of low-resolution printing in which the recording paper conveyance speed is high, while the printing speed is high at the time of low-resolution printing. 3. The image forming apparatus according to claim 1, wherein whether to execute the fan drive control can be selected according to the type of the recording paper.