JP2856448B2 - Fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a fixing device, and more particularly, to a copy in which a single-color or plural-color toner image is transferred to one side and a toner image in which a toner image is transferred to both sides. The present invention relates to a temperature control structure in a fixing device for performing heat fixing of a copy.

(Prior Art) As is well known, in a fixing device for heating and fixing a visible image transferred onto a transfer paper by an electrophotographic process,
Some of the pair of rollers capable of nipping and transporting the transfer paper have a built-in heating heater in the roller facing the visible image surface, and perform image fixing by setting the temperature of the heater.

In the above-described fixing device, a heating mode at the time of fixing, that is, a temperature setting is made different depending on a copying mode of an image on a transfer sheet.

That is, with respect to the above-described temperature setting, when a single-color image is formed on one side of the transfer paper, when a single-color image is formed on both sides of the transfer paper, the fixing heat received at the time of fixing on one side is used. However, when the other surface is fixed, the fixing temperature increases, which may cause hot offset or wrinkles.
When a so-called color image is formed, the heat energy required for fixing must be increased by the amount of the toner layer, and a higher fixing temperature is required.

Therefore, conventionally, when an image is formed on both sides using a fixing device having a heater provided on one of the pair of conveying and holding rollers described above, the fixing temperature on the remaining one side after finishing the image on one side is lowered. Settings (for example,
No. 62-86384), the front side copying is continuously performed, the heater used for fixing at that time is once turned off, and after a predetermined time has elapsed, the heater is turned on again and the temperature used for fixing the front side is set again, and then the back side fixing is performed. Or (for example, see
-156270), and, apart from the structure described above,
A heater for heating is incorporated in each of the pair of rollers,
At the time of fixing a color image, both heaters are turned on, and at the time of fixing a single color image, only the heater on the side of the fixing roller facing the image surface is turned on (see, for example, JP-A-62-157079). No.).

(Problems to be Solved by the Invention) However, in the above-described fixing structure, any of the above-mentioned fixing structures can be applied only to those having limited copy formats, and can be applied to all of these copy formats. At present, it is impossible to prevent the occurrence of hot offset and wrinkles.

In view of the above-described problems in the fixing device, an object of the present invention is to provide a fixing device that does not cause hot offset or wrinkles regardless of a copy format for transfer paper. Another object of the present invention is to provide a fixing device capable of performing temperature setting in accordance with a copying mode set for a surface of a transfer sheet and performing copying without occurrence of the above-described hot offset, wrinkles, or fixing defects. It is in.

(Means for Solving the Problems) In order to achieve this object, the present invention provides a method of directly transferring a toner image from a photoreceptor to transfer paper, and a method of temporarily transferring the toner image from a photoreceptor to a transfer member. Then, a method of re-transferring to transfer paper is adopted, so as to correspond to an unfixed image carried on one or both sides of the transfer paper,
A fixing device that includes a first fixing unit disposed on the one surface side and a second fixing unit disposed on the other surface side, and heats and fixes the transfer paper while nipping and transporting the transfer paper by each of the fixing units. A heating source provided in each of the first and second fixing means, a temperature detecting means for detecting a surface temperature of the fixing means, an input side connected to the temperature detecting means, And a control unit connected to the heating source. The control unit sets the temperature of the second fixing unit independently of the first fixing unit, and controls the temperature of the second fixing unit in accordance with each of the methods. It is proposed that the temperature settings of the two fixing units be made different.

Further, according to the present invention, the control unit selects a set temperature for each of the first fixing unit and the second fixing unit according to the one-sided single-color copying mode, the two-sided single-color copying mode, and the other-sided color copying mode. Is proposed.

(Operation) According to the present invention, the temperatures in the first and second fixing units are selected according to each copy mode, and the fixing is performed at a temperature suitable for the mode.

Embodiment An embodiment of the present invention will be described below in detail with reference to FIGS. 1 to 5.

FIG. 1 is a schematic diagram showing the overall configuration of a fixing device according to an embodiment of the present invention.

That is, the fixing device according to the present embodiment is a fixing device used for a copying machine capable of performing two-color copying on one surface of a transfer sheet, and the copying machine 1 includes a drum-shaped photoconductor 2 therein.

Around the photosensitive member 2, a charging device 3, an optical writing device 4, developing devices 5 and 6, a transfer belt 7, and a cleaning device 8 are arranged along the rotation direction of the photosensitive member 1 indicated by an arrow. is there.

The above-described optical writing device 4 irradiates the original image with the laser beam to the photosensitive member 2.
The developing devices 5 and 6 are magnetic brush developing devices in which one developing unit 5 contains a black developer and the other developing unit 6 contains, for example, a red developer other than black.

On the other hand, the transfer belt 7 is wrapped around a pair of pulleys 7A and 7B. For example, when forming a plurality of color images on one side of a transfer paper or when forming a color image, images of different colors are formed. In order to combine the images, the image that has been subjected to the visible image processing by the developing device is electrostatically transferred by a transfer charger 9 disposed inside a position facing the photoreceptor 2 once, having a function of once transferring the previously formed image. It has become so.

A fixing device 10 having a pair of rollers is disposed behind the transfer direction (the direction of the arrow in the drawing) of the transfer paper obtained by the movement direction of the transfer belt 7.

The above-described fixing device 10 includes a first fixing roller 10A and a second fixing roller 10B which face each other across a transfer path of the transfer sheet.
The first fixing roller 10A is usually
A heating roller used in this type of fixing device, which has a coating layer of Teflon (trade name) on the surface and is disposed at a position facing an image formed on only one side of the transfer paper, as described later. .

The second fixing roller 10B is configured as a pressurizing / heating roller having a Teflon (trade name) coating layer on a silicon rubber layer, and has a back surface corresponding to the opposite side of one side of the above-described transfer paper. They are opposed to each other.

Further, heaters 10C and 10D as first and second heating sources are disposed inside the fixing rollers 10A and 10B, and the heaters 10C and 10D are controlled in temperature by a control unit described later. It has become.

Further, as shown in FIG. 2, a thermistor 10E, 1E for detecting the surface temperature is provided on the surface of each fixing roller.
0F is in contact, and the thermistors 10E and 10F are also connected to a control unit described later.

On the other hand, a paper feed mechanism is disposed in the forward direction of the transfer paper set by the above-described movement direction of the transfer belt 7, and the paper feed mechanism transfers the paper fed from a paper feed cassette (not shown). There is provided a registration roller 11 for temporarily holding the paper and setting the timing with respect to the image position on the photoconductor 2.

In the drawing, reference numeral 12 denotes a cleaning blade 12A and a static elimination brush 12B which are provided so as to be able to contact and separate from the transfer belt 7.
Reference numeral 13 denotes a transfer charger used for transferring an image on the transfer belt 7 to transfer paper.

In the copying machine 1 having such a structure, depending on the copy mode of an image formed on a transfer sheet, for example, in a mode of forming a single-color copy on a transfer sheet (hereinafter, referred to as a mode), the photosensitive When the body 2 rotates, the charging device 3
After the uniform writing, the writing of the current structure is performed by the optical writing device 4, and the supply is performed through visible image processing by the developing device 5 containing, for example, a black developer among the developing devices 5 and 6. The transfer is performed on the transfer paper fed from the paper mechanism, and the transferred transfer paper is transferred to the fixing device 10.

In the case of a copy mode in which a multi-color copy, for example, a copy copy of two colors of black and red is formed on a transfer sheet (hereinafter, referred to as a mode), the copy is formed on the photoconductor 2 by the first writing. The developed electrostatic latent image is subjected to a visible image processing by a developing device 5 containing a black developer among the developing devices, and the visible image is once transferred to a transfer belt 7 and again transferred onto the photoreceptor 2. After the electrostatic latent image obtained by writing is processed with a developing device 6 containing a red developer different from the previous developer, the electrostatic latent image is processed into a visible image, and the image is transferred to a transfer belt 7. The image on the transfer belt 7 is transferred to a transfer sheet, and the transfer sheet is transferred to the fixing device 10.

On the other hand, in the fixing device 10 described above, as shown in FIG. 2, the first fixing roller 10A and the second fixing roller
The first thermistor 10C and the second heater 10D, which are arranged inside of the fixing unit 0B, are provided on the output side of the control unit 12 and the thermistors 10E, 10F provided in contact with the surfaces of the respective fixing rollers.
It is connected to the input side of the control unit 12 respectively.

The control unit 14 is connected to the main control unit 15 of the copying machine, and the fixing rollers are connected to each other in accordance with a control signal based on a mode signal from the mode selection switches 16, 17, and 18 input to the main control unit 15. Are set independently.

That is, the temperature setting of the fixing roller in the control unit 14 is as shown in Tables 1 and 2 below.

In Tables 1 and 2, the symbol I means the first fixing roller 10A, and the symbol II means the second fixing roller 10B.
As shown in FIG. 3 (A), the mode is a mode for performing single-sided single-color copying using the first fixing roller 10A, and the mode is as shown in FIG. 3 (B).
A mode for performing single-sided multi-color copying, and a mode for, as shown in FIG. 3C, a mode for inverting the transfer paper using the first fixing roller 10A and performing double-sided single-color copy of the transfer paper, respectively. ing.

Table 2 shows specific values of the temperatures of the first and second fixing rollers 10A and 10B in each mode.

That is, in the mode, the first fixing roller 10
By setting the surface temperature (T ₀ ) of A to 160 degrees and the surface temperature (T ₀ ′) of the second fixing roller 10B to 140 degrees, the required temperature for one-sided copying is satisfied.

Further, in the mode, the surface temperatures (T ₁ , T ₁ ′) of the first fixing roller 10A and the second fixing roller 10B are both set.
By setting the temperature to 160 degrees, the temperature setting is set higher than in the case of the mode. This is because the amount of heat required for fixing is increased by the increase in the thickness of the toner layer in the developer because of color copying.

Further, in the mode, the first fixing roller 10A
And the surface temperature of the second fixing roller 10B (T ₂ ,
By setting both T ₂ ') to 140 degrees, the temperature setting is lower than in the case of the mode.

This is because, in the heat fixing on the back surface performed after the heat fixing on one surface, the amount of heat on the transfer paper side received at the time of the previous heat fixing affects the first fixing roller 10A, and the heat of the roller 10A is changed. Since the temperature tends to rise excessively, the temperature is set to a low value in view of the rise in order to maintain the predetermined temperature, and the temperature approaches the predetermined temperature. When such a low temperature is set, the amount of heat for fixing seems to be insufficient. However, since the heat is passed twice between the fixing rollers, insufficient fixing does not occur.

Based on the above-mentioned temperature setting, the control unit 14 detects the surface temperature of each fixing roller by a thermistor, and sets the energization state to the heater by a detection signal from the thermistor based on the above-mentioned mode selection. Temperature setting.

It is needless to say that the difference between the set temperatures should be made as small as possible in order to shorten the standby time required for the temperature to rise when the mode is switched.

Further, the fixing device 10 described above is not limited to the structure shown in FIG. 1, but can swing a part of the transfer belt 7 in the extending direction as shown in FIG. The first fixing roller 10A and the second fixing roller 10B for setting the nipping conveyance path of the transfer paper with the pressure roller 14 interposed therebetween are arranged in each section, and the transfer when passing through each conveyance path is arranged. A structure in which the heating surface of the paper is set upside down, or a second fixing roller 10B as shown in FIG.
Is not placed in contact with the first fixing roller 10B, a pressure roller 15 is brought into contact with the first fixing roller 10A, and a transfer roller is applied to the pressure roller 15 around its peripheral surface. Heat belt
Needless to say, the present invention can be applied to a structure in which heat from the second fixing roller 10B is transmitted through the second fixing roller 10B.

(Effects of the Invention) As described above, according to the present invention, it is possible to independently set the temperature setting in the pair of fixing units for nipping and conveying the transfer paper according to the transfer mode for the transfer paper, and to set the temperature in accordance with each transfer method. (1) Since the temperature settings of the first and second fixing means are made different, the amount of heat required for fixing in each copy mode can be secured, and the occurrence of hot offset and wrinkles due to the supply of excess heat is prevented. And good image fixation becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an entire configuration of a fixing device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a control structure in the fixing device shown in FIG. 1, and FIG. 3 is a diagram shown in FIG. FIGS. 4 and 5 are model diagrams for explaining a fixing mode when the temperature is set by the control section, and FIGS. 4 and 5 correspond to FIG. 1 showing a partially modified example of the structure of the fixing device shown in FIG. It is a schematic block diagram. 1 ... copying machine, 2 ... photoconductor, ... 5, 6 ... developing device, 7
... Transfer belt, 10 fixing device, 10A first fixing roller, 10B second fixing roller, 10C, 10D first, second
Heaters, 10E, 10F… Thermistors, 14 ……
Control unit, 16, 17, 18 ... Mode selection switch.

Claims (2)

(57) [Claims] 1. A method in which a toner image is directly transferred from a photoreceptor to a transfer sheet, and a method in which the toner image is once transferred from a photoreceptor to a transfer body and then re-transferred to a transfer sheet, is adopted. A first fixing unit disposed on the one surface side and a second fixing unit disposed on the other surface side so as to correspond to an unfixed image carried on one or both surfaces of the transfer paper. A fixing device that heats and fixes the transfer paper while nipping and transporting the transfer paper by each of the fixing units; a heating source provided in each of the first and second fixing units; and a surface temperature of the fixing units. And a control unit connected to the input side of the temperature detection unit and connected to the heating source on the output side. The control unit is configured to be connected to the first fixing unit. Independently setting the temperature of the second fixing means And fixing the temperature of the fixing means in accordance with each of the methods. 2. The fixing device according to claim 1, wherein the control unit controls the first fixing unit and the second fixing unit in accordance with a single-sided single-color copying mode, a double-sided single-color copying mode, and a second-sided color copying mode. A fixing device, wherein a set temperature is selected.