JPH07302013A - Fixing device of image forming device - Google Patents

Abstract

PURPOSE:To speed up the fixing speed of a recording medium on which a color image, etc., are recorded with many toner layers, in a fixing device for an image forming device for fixing plural toner layers on one recording medium such as a full color electrophotographic device. CONSTITUTION:Toner layer number detecting means 30 and 31 for partially detecting the number of the toner layers on a sheet-like recording medium 100 stuck to only one toner layer on a part of the surface and plural superimposed toner layers on the other part are provided, the carrying speeds of the recording medium carrying means 21 and 22 of a fixing part are controlled according to the results of the detections on the toner layer number detecting means 30 and 31 and the carrying speeds when the toner is not present on the recording medium 100 in a position where it receives heat from a heating means 23, when no toner layer is present, when only one toner layer is present and when plural toner layers are present are defined as V0, V1 and V2 respectively, the carrying speeds are controlled to V0>V1>V2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus, such as a full-color electrophotographic apparatus, for fixing a plurality of toner layers to a recording medium.

The toner layer transferred to the recording medium needs to be fixed by heating or the like, but in the case of a color image having a plurality of toner layers, the toner layer becomes thicker, so that a large amount of heat is required for fixing. Become.

[0003]

2. Description of the Related Art In order to increase the amount of heat for fixing, it is necessary to increase the amount of heat generated by a heating device or slow the conveying speed of a recording medium passing through a fixing section.

However, if the amount of heat generated is increased, a difficult problem occurs on the cooling surface and the like, so that the conveying speed of the recording medium is slowed down. Therefore, the fixing speed is slowed in the conventional full-color electrophotographic apparatus and the like, and as a result, the recording speed is slowed down.

However, since there are quite a few cases in which a monochrome image is recorded by a full-color electrophotographic apparatus, it is very inefficient that the fixing speed becomes slow even in such a case.

Therefore, conventionally, in the case of a recording medium for recording a color image, the conveying speed in the fixing section is slowed, and in the case of a recording medium for recording a single color image, the conveying speed is increased.
The carrying speed is switched depending on the recording medium (Japanese Patent Laid-Open No. 3-288171).

[0007]

However, even in the above-mentioned device, the fixing speed is slow in the case of a recording medium for recording a color image, and the slowing of the recording speed due to the fixing speed is not improved at all. Was bad.

Therefore, an object of the present invention is to provide a fixing device of an image forming apparatus capable of increasing the fixing speed of a recording medium for recording a color image or the like with a plurality of toner layers.

[0009]

In order to achieve the above object, the fixing device of the image forming apparatus of the present invention has a toner layer on a part of the surface as shown in FIG. 1 for explaining the embodiment. Is adhered to only one layer, and at some other portion, a plurality of toner layers are superposed and adhered to one sheet-shaped recording medium 100.
The toner layer number detecting means 30 and 31 for detecting the number of upper toner layers for each part, the heating means 23 for applying heat to heat and fix the toner layer to the recording medium 100, and the recording medium 100 are Medium transporting means 21, 22 for transporting the recording medium 100 so as to pass while receiving heat from the heating means 23, and the toner layer number detecting means 30, 3
In response to the detection result in 1, the medium conveying means 21,
The transport speed of 22 is controlled so that the transport speed when there is no toner layer on the recording medium 100 at the position where heat is received from the heating means 23 is V0, the transport speed when there is only one toner layer is V1, and the toner speed is V1. A fixing speed control means 30 is provided so that V0>V1> V2, where V2 is the transport speed when there are a plurality of layers.

The medium conveying means 21 and 22 are a pair of rollers 21 and 22 which are rotatably driven by sandwiching the recording medium 100 from the front and back sides, and the heating means 23 is
It may be provided in the roller 21 of the pair of rollers 21, 22 on the side in contact with the toner layer.

The toner layer on the recording medium 100 is transferred onto the recording medium 100 from an image carrier 1 which first forms a latent image on the surface and then develops and conveys the latent image. Yes, the toner layer number detecting means 30, 3
1 detects the number of toner layers on the image carrier 1 and calculates the timing when the toner layers reach the heating means 23, whereby the recording medium 100 at the position where the heat is received from the heating means 23. The number of upper toner layers may be detected.

[0012]

The recording medium 100 by the medium conveying means 21 and 22
The conveyance speed of is faster when there is only one toner layer than when there are multiple toner layers on the recording medium 100 at the position where heat is received from the heating means 23, and when there is no toner layer at that position. It is controlled to be even faster than that.

[0013]

Embodiments will be described with reference to the drawings. Figure 2
1 illustrates a full color electrophotographic printer to which the present invention is applied. However, the present invention can be applied to a fixing device of various image forming apparatuses for recording by superposing a plurality of layers of toner.

In FIG. 2, around the photosensitive drum 1 which is rotationally driven in the arrow direction at a constant speed A, first, a pre-charger 2 for pre-charging the surface of the photosensitive drum 1 to a constant potential, and a photosensitive drum The photosensitive drum 1 by irradiating the drum 1 with image light
An exposure device 3 for forming an electrostatic latent image is arranged on the surface of the.

The image light irradiation from the exposure device 3 is divided into four exposures corresponding to the development with four color toners of yellow (Y), magenta (M), cyan (C) and black (B). One rotation is performed for each color of the drum 1.

Next, a developing device 4 for developing the latent image on the photosensitive drum 1 with toner is arranged around the photosensitive drum 1. The developing device 4 has four developing units 4Y,
4M, 4C and 4B are formed side by side.

Reference numeral 5 is a transfer device for transferring the toner image on the photosensitive drum 1 onto the recording paper 100, and 6 is a cleaner for removing the toner remaining on the photosensitive drum 1 without being transferred onto the recording paper 100. And are arranged around the photosensitive drum 1 in order.

The recording paper 100 is in the form of a thin sheet, and is fed from the paper cassette 11 and conveyed by a conveyance roller (not shown) so as to come into contact with the photosensitive drum 1 between the transfer device 5 and the photosensitive drum 1. To be done.

During the development with the four color toners, a paper path control device (not shown)
As indicated by the broken line arrow, the same recording paper 100 is repeatedly fed four times so as to pass through the transfer portion, and when the transfer of the toner image of the fourth color is completed, the recording paper 100 is fixed by the paper conveying belt 12 to the fixing device. It is transported to 20.

The fixing device 20 is provided with a pair of rollers 21 and 22 which are rotatably driven with the recording paper 100 sandwiched therebetween, and by the rotation thereof, the recording paper 100 is further conveyed and sent to the stacker 15.

Of the pair of rollers 21 and 22 of the fixing device 20, the heating roller 21 in contact with the surface of the recording paper 100 on which the toner layer is adhered is heated by using a xenon lamp or another heating element. The container 23 is arranged.

Therefore, the heat of the heater 23 is transferred to the toner layer on the recording paper 100 which is in contact with the heating roller 21 through the heating roller 21, and the toner image is heated and fixed on the surface of the recording paper 100.

With the apparatus thus constructed, a toner image of one color is formed on the recording paper 100 every time the photosensitive drum 1 makes one revolution, and the photosensitive drum 1 makes four revolutions.
Recording paper 100 with one toner layer of four colors of Y, M, C and B
It is transferred on top of each other. Then, the recording paper 100 is sent to the fixing device 20, and the toner image is heated and fixed on the recording paper 100.

FIG. 1 shows the control portion of the fixing speed of the apparatus of the above embodiment. A control signal from the exposure unit 3 is read into the control unit 30 having a central processing unit (CPU) or the like, and each dot is developed in a plurality of layers with toner of a plurality of colors for each row of the exposure unit. It is detected whether it is a color portion, a single-color portion that is developed in a single layer with only one color toner, or a white portion that is not developed at all. Reference numeral 31 is the detection unit.

The read-only memory (ROM) in the control unit 30 stores data such as the rotation speed A of the photosensitive drum 1 and the distance L between the photosensitive drum 1 and the fixing device 20. Three types of designated speeds of the motor 24 that rotationally drives the rollers 21 and 22 so that the fixing speed of the fixing device 20 can be changed in three stages of high-speed fixing speed V0, medium-speed fixing speed V1, and low-speed fixing speed V2. Value etc. are stored.

From these data, the photosensitive drum 1
The timing at which the upper toner layer reaches the fixing device 20 is constantly calculated, and each dot of one line on the recording paper 100 at the position where it comes into contact with the heating roller 21 and receives the heat of the heating device 23, the toner of a plurality of colors is detected. It is detected whether it is a multi-colored portion that is superimposed on a plurality of layers, a single-colored portion that has only one toner layer, or a white portion that does not have toner.

FIG. 3 is a control processing flow chart of the fixing speed control in the control unit 30. S indicates a processing step. Here, first, the heater 23 is brought into contact with the heating roller 21.
It is determined whether or not one line of the recording paper 100 at the position receiving the heat from the white line is a white line (S1), and when the line is the white line, the motor 24 is rotated at a high speed, and the recording paper 100 in the fixing device 20 is rotated. The transport speed of the high speed V0 (S
2).

If the line is not a white line, it is judged whether or not there are multicolor dots, that is, dots of a plurality of toner layers in the line (S3). If there is no multi-layer portion, that is, there is only one toner layer. In this case, the motor 24 is rotated at a medium speed, and the conveyance speed of the recording paper 100 in the fixing device 20 is set to the medium speed V1 (S4).

When the multi-colored dots of a plurality of toner layers are in that row, the motor 24 is rotated at a low speed so that the conveyance speed of the recording paper 100 in the fixing device 20 is V2 which is a low speed.
(S5).

Such fixing speed control is performed by the recording paper 1
The process is performed line by line until 00 passes (S6), and the same fixing speed control is performed on the next recording paper 100 if there is one (S7), and if there is no next recording paper 100, the process ends.

Three fixing speeds V0, V1 and V2
Is V0>V1> V2, and the ratio is, for example, 6 :.
It is 4: 1.

[0032]

According to the present invention, the conveyance speed of the recording medium in the fixing unit is only a single toner layer than when there are a plurality of toner layers on the recording medium at the position where heat is received from the heating means. Is faster, and is faster than when there is no toner layer, so the fixing speed can be made as fast as possible for each line of the recording portion, and as a result,
The fixing speed of a recording medium for recording a color image or the like can be efficiently increased without increasing the heat generation amount of the fixing device.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fixing speed control portion of an embodiment.

FIG. 2 is an overall configuration diagram of a full-color printer according to an embodiment.

FIG. 3 is a control processing flowchart of the embodiment.

[Explanation of symbols]

 20 Fixing Device 21 Heating Roller 22 Roller 23 Heating Device 30 Control Unit 31 Toner Layer Number Detection Unit 100 Recording Paper

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Claims (3)

[Claims] 1. The number of toner layers on a sheet-shaped recording medium (100) in which only one toner layer is attached to a certain portion of the surface and a plurality of toner layers are attached to another portion of the sheet. Toner layer number detection means (3
0, 31), heating means (23) for applying heat to heat and fix the toner layer to the recording medium (100), and the recording medium (100) receives heat from the heating means (23). The medium conveying means (21, 22) that conveys the recording medium (100) so as to pass therethrough, and the medium conveying means (21, 22) corresponding to the detection results of the toner layer number detecting means (30, 31). Is controlled to control the transport speed when there is no toner layer on the recording medium (100) at the position where heat is received from the heating means (23), and the transport speed when there is only one toner layer. V1, the transport speed when there are multiple toner layers is V
The fixing device of the image forming apparatus is characterized in that a fixing speed control means (30) for setting V0>V1> V2 is provided when the number is 2. 2. The medium transporting means (21, 22) is a pair of rollers (21, 22) rotatably driven by sandwiching the recording medium (100) from the front and back sides, and the heating means (23). The fixing device of the image forming apparatus according to claim 1, wherein the fixing device is provided in the roller (21) of the pair of rollers (21, 22) on the side in contact with the toner layer. 3. The toner layer on the recording medium (100) comprises:
First, a latent image is formed on the surface, and then the latent image is developed and conveyed, and then transferred from the image carrier (1) to the recording medium (100).
0, 31) first detects the number of toner layers on the image carrier (1), and the toner layers are detected by the heating means (23).
The number of toner layers on the recording medium (100) located at a position where heat is received from the heating means (23) is detected by calculating the timing to approach.
A fixing device for an image forming apparatus as described above.