JP3416232B2 - Image recording device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording device such as a laser printer, and more particularly to an electrophotographic image recording device using a heating means for fixing an image.

[0002]

2. Description of the Related Art In a conventional image recording apparatus such as a laser printer, the toner is fixed on the recording paper by using a heating device such as a halogen heater and a pressure roller to perform the heat and pressure fixing. Further, in recent years, one using a thin film and a ceramic heater has been introduced. In a heating device using a ceramic heater, a drive source is usually provided on the pressure roller side, the thin film is driven by the drive source, and the conveying force of the recording paper is given by the pressure roller.

[0003]

However, in the conventional example as described above, the pressure roller is heated by the ceramic heater to cause thermal expansion of the pressure roller, which causes the pressure roller to expand. This causes an inconvenience that the outer diameter increases, and the conveyance speed of the recording paper increases correspondingly. As a result, normally, when recording / printing on a recording paper by an image signal is mistakenly performed, control is performed to detect the trailing edge of the recording paper so as not to protrude from the trailing edge of the recording paper and mask the image signal. I am doing it, but since the paper conveyance speed increases, I can not mask at regular timing,
There is a problem that an image or a print protrudes from the recording paper, and the toner is scattered in the machine at the time of transfer on the photosensitive drum.

The present invention has been made in view of the above problems of the conventional example. In order to solve the above problems of the conventional example, the trailing edge mask is always performed at an appropriate timing, It is an object of the present invention to provide means for preventing the toner scattering situation as described above.

[0005]

Therefore, in the present invention, an image recording apparatus for recording an image on a recording paper by using an electrophotographic process in accordance with an image signal from the outside is used. A moving drive means for the film, a heater having a constant temperature controlled and arranged on one surface side with the film inside, and a constant temperature controlled heater arranged on the other surface side so as to face the heater. On the other hand, in an image recording apparatus using a fixing unit having a roller-shaped pressure member that makes a recording paper surface on which an image is fixed through the film, a trailing edge detection for detecting the trailing edge of the recording paper. Means and a masking means for masking the image signal in accordance with the detection timing of the trailing edge detecting means, and the number of recorded images on the recording paper by the image recording apparatus or the addition amount. Depending on the detected temperature of the member, and the trailing-edge detector, by configuring so as to vary the image mask timing by said masking means, is intended to achieve the object.

[0006]

With the configuration of the present invention as described above, the trailing edge mask can be always performed at an appropriate timing by detecting the change in the recording sheet conveying speed due to the thermal expansion of the pressure roller. Can be prevented.

[0007]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 shows a schematic sectional view of a first embodiment of an image recording apparatus according to the present invention, and FIG. 2 shows a block diagram of its construction. Figure 1,
In reference numeral 2, 1 is the above-mentioned ceramic heater, 2 is a thin film, and 3 is a pressure roller combined with them. An image controller 4 in FIG. 2 develops an image based on code data from a host computer (not shown) to generate an image signal. Reference numeral 5 denotes a CPU, which controls the entire image recording apparatus of this embodiment. 6 is the CPU 5
The number-of-prints counting means provided therein, 7 is an image mask timing generating means, and 8 is a trailing edge detection sensor.

After the trailing edge of the recording paper is detected by the trailing edge detection sensor 8, a mask signal is generated from the mask timing generation means 7 after a predetermined time has passed, and the image signal generated from the image controller 4 is masked. A laser driver 9 is a semiconductor laser 1 shown in FIG. 1 based on an image signal.
1 is on / off modulated and horizontally scanned by the polygon mirror 12 to form an electrostatic latent image on the photosensitive drum 13.

By the way, the pressure roller 3 is heated by heat from the ceramic heater during continuous printing,
Thermal expansion occurs and the outer diameter increases. An example of the relationship between the number of prints and the amount of change (expansion rate of the pressure roller 3) is shown in FIG. The increase in the outer diameter of the pressure roller 3 causes the paper conveyance speed to increase after the leading edge of the recording paper reaches the pressure roller 3, so that the mask signal for the recording paper is delayed, so that the image signal is erroneously output outside the printing area. If the toner is discharged, the toner may be scattered in the machine during transfer.

In order to prevent this state from occurring, C
When the PU 5 detects that continuous printing has been performed by the print number counting means 6, the PU 5 predicts the expansion rate of the pressure roller 3 in accordance with the number of prints, and the image mask timing generating means 7 causes the PU 5 to generate the result as shown in FIG. The mask timing is appropriately advanced by an amount corresponding to the increase in the conveyance speed due to the change amount of the outer diameter, and the fixing control unit 10 in FIG. 2 controls the mask timing.

By performing the control as described above, it is possible to prevent an image signal from being output outside the printing area of the recording paper and prevent toner from scattering inside the machine.

(Other Embodiments) FIG. 4 shows a block diagram of a control configuration of the second embodiment of the image forming apparatus according to the present invention (the same as FIG. 2). In FIG. 4, 14 is a temperature detecting means for detecting the temperature of the pressure roller 3. FIG. 5 shows an example of the relationship between the temperature of the pressure roller 3 and the amount of change in the expansion coefficient of the pressure roller 3. As in the first embodiment, C
The PU 5 detects the temperature of the pressure roller 3 by the temperature detection means 14 and predicts the expansion rate of the pressure roller 3 according to the temperature, and the image mask timing generation means 7 causes the outer diameter as shown in FIG. The mask timing is advanced by an amount corresponding to the increase in the conveyance speed due to the change amount of.

By performing the control as described above, as in the case of the first embodiment, it is possible to prevent the image signal from being output outside the image recording area and prevent the accident of the toner scattering in the machine. You can

Further, in this embodiment, the pressure roller 3
The temperature of the pressure roller 3 is directly detected by a sensor or the like, but not limited to this, the temperature of the ceramic heater 1 detected by a thermistor (not shown) normally used for temperature control of the ceramic heater 1 determines the temperature of the pressure roller 3. It is also possible to infer the temperature, and this estimated value may be used in place of the sensed value.

[0015]

As described above, by changing the mask timing of the trailing edge of the paper according to the change of the recording paper conveying speed due to the thermal expansion of the pressure roller in this type of image recording apparatus, The protrusion from the recording paper is eliminated, an appropriate image mask can always be performed, and good recording can be performed without causing the toner to be scattered in the apparatus.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a first embodiment.

FIG. 2 is a block diagram of the control configuration of FIG.

FIG. 3 is an example diagram of the relationship between the number of prints and the expansion ratio of the pressure roller.

FIG. 4 is a block diagram of a control configuration according to a second embodiment.

FIG. 5 is a diagram showing an example of the relationship between temperature and expansion coefficient of a pressure roller.

[Explanation of symbols]

1 Ceramic heater 2 thin film 3 pressure roller 4 image controller 5 CPU 6 Print number counting means 7 Image mask timing generation means 8 Rear end detection sensor 9 Laser driver 10 Fixing control means 11 Semiconductor laser 12 polygon mirror 13 Photosensitive drum 14 Temperature detection means

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 1/23-1/31 B41J 3/00 G03G 13/04-13/056 G03G 15/00 G03G 15 / 04-15/056 G03G 21/00

Claims (2)

(57) [Claims] 1. An image recording apparatus for recording an image on a recording paper by using an electrophotographic process according to an image signal from the outside, comprising a thin heat-resistant film, a moving driving means for the film, and the film. A heater having a constant temperature which is fixedly supported on one side of the inside, and a heater which is fixed on the other side of the heater so as to face the heater, and the image should be fixed to the heater through the film. In an image recording apparatus using a fixing unit having a roller-shaped pressure member that brings the recording paper surface into close contact, a trailing edge detecting unit for detecting the trailing edge of the recording sheet, and a detection timing of the trailing edge detecting unit. Accordingly, a mask means for masking the image signal is provided, and the trailing edge detecting means and the image by the masking means are provided in accordance with the number of recorded images in which the image recording apparatus records an image on the recording paper. Image recording apparatus is characterized in that the disk timing configured to variable. 2. A temperature detecting means for detecting or estimating the temperature of the pressing member, and the image mask timing by the trailing edge detecting means and the masking means according to the detected temperature of the temperature detecting means. The image recording apparatus according to claim 1, wherein the image recording apparatus is configured to be variable.