JPH0713450A - Image forming device - Google Patents

Abstract

(57) [Summary] [Object] The present invention solves the problem of temperature rise in the non-sheet passing portion and reduces the temperature rise in the non-sheet passing portion to fix the fixing roller even when fixing recording materials of different sizes. Another object of the present invention is to provide an image forming apparatus capable of heating a heating element uniformly and uniformly and controlling the fixing temperature appropriately. [Structure] A small-size paper moving cassette 70 that moves to the left and right of arrows c and d and is located at positions H, I, and J is provided in the paper feed cassette 14, and small-size paper is continuously passed. At this time, the recording material sheet passing area at the fixing portion of the fixing roller 51 is changed.

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 having a fixing device for heating and fixing a toner image on a recording material.

[0002]

2. Description of the Related Art An example of a conventional reversal development type image forming apparatus is shown in FIG. In FIG. 7, reference numeral 1 is a photosensitive drum, and the photosensitive drum 1 has a photosensitive layer 1a on a conductive base material 1b such as a grounded metal, and is driven to rotate in the direction of arrow A. . A charging roller 2 having an elastic layer 2b on a core metal 2a to which a voltage is applied by a charging bias power source 11 is arranged above the photosensitive drum 1.
The surface of the photosensitive drum 1 is uniformly and uniformly charged to a predetermined potential (dark potential) by the charging roller 2. Then, when the surface thus charged is exposed by the exposure light 3 such as a laser beam, the potential of the surface is a predetermined potential (bright potential).
And an electrostatic latent image is formed. Further, the electrostatic latent image is visualized by the toner of the developing device 4 including the developing sleeve 4a to which the voltage is applied from the developing bias power source 12.

On the other hand, the recording material 61 in the paper feeding cassette 14
Are taken out one by one from the paper feed cassette 14, guided by the inlet guide 6, and transferred to the transfer roller 5 having the elastic layer 5a on the core metal 5b to which the voltage is applied by the transfer bias power source 13, and the photosensitive drum 1. The toner image on the photosensitive drum 1 is transferred onto the recording material 61, and the recording material 61 carrying the toner image is guided by the conveyance guide 8 and introduced into the fixing device 9 to form the toner image. Is fixed on the recording material 61.

Further, the transfer residual toner on the photosensitive drum 1 which has completed the transfer process is removed from the photosensitive drum 1 by the cleaning blade 7a and collected by the cleaning device 7. The cleaned photosensitive drum 1 is charged again. An image is formed by sequentially repeating the image forming process from the process.

Conventionally, the fixing device 9 used in the image forming apparatus as described above has a structure as shown in FIG. In FIG. 8, a fixing roller 51 is provided with a releasable resin layer 54 such as PFA or PTFE on a core metal 53 such as aluminum or iron, and the inside is heated by a heater 50. . The temperature of the fixing roller 51 is detected by a temperature detecting element 58 that is in contact with the fixing roller 51, and is controlled to a predetermined temperature by intermittently operating the heater 50 by a temperature control device (not shown).

On the other hand, reference numeral 52 is a pressure roller that rotates in pressure contact with the fixing roller 51, and is made of metal such as iron or stainless steel.
An elastic layer 57 and a release layer 59 such as silicone rubber or fluororubber having good release properties are formed on the surface 6.

The recording material 61 carrying the toner image 60 is guided to the fixing portion (nip portion) between the fixing roller 51 and the pressure roller 52 by the fixing inlet guide 63, and heated and pressed to cause the toner. After the image 60 is fixed on the recording material 61, the recording material 61 is separated from the fixing roller 51 by the separation claw 55.

Therefore, although toner and paper dust may adhere to the surface of the fixing roller 51, in the above conventional example, the cleaning pad 62 is brought into contact with the fixing roller 51 to remove the toner and paper dust. .

However, this cleaning pad 6
Even if 2 is used, some toner and paper dust remain on the surface of the fixing roller 51.
If it is disposed so as to be close to or in contact with the substantially central portion in the axial direction of the toner, toner or paper powder will adhere to the surface of the temperature detecting element 58 with use for a long time, and the release layer on the surface of the fixing roller 51 will be removed. It was worn and scratched, sometimes resulting in black streaks on the image.

Therefore, the temperature detecting element 58 is installed at the end of the fixing roller 51 to prevent image defects.

Further, according to such a conventional fixing device, there is a problem that the speed of raising the temperature of the fixing roller to a predetermined fixing temperature is slow.

Therefore, in recent years, the fixing roller 5 shown in FIG.
The thickness of the core metal 53 of 1 is 0.5 m from the conventional 3 mm
A “thin fixing roller” thinned to about m, or the heating member 20 is adhered to one surface side of the heat resistant film 24 and the recording material 61 is adhered to the other surface side thereof as shown in FIG. A “fixing device of film fixing type” that applies the thermal energy of the heating body 20 to the recording material 61 has been proposed.

This film fixing type fixing device is shown in FIG.
The endless belt-shaped fixing film 24 shown in FIG. 3 is suspended and stretched on three members of the driving roller 25, the driven roller 26, and the low heat capacity linear heating element 20 as a heating element, which are parallel to each other. The roller 28 is pressed against the fixing film 24. The fixing film 24 and the pressure roller 28 are rotationally driven at the same speed as the conveying speed of the recording material 61, and the recording material 6 carrying the unfixed toner image 60.
1 is introduced into the nip portion N from the conveyance guide 29 and heated.
The toner image 60 is fixed on the recording material 61 under pressure.
The low-heat-capacity linear heating element 20 as a heating element includes an electric heating element 2 having a glass layer 30 for insulation / protection as a surface layer.
2. A heater substrate 21 having a temperature detecting element 23 and the like, and is fixed and supported by heating body supports 27 and 27a having rigidity, heat resistance, and heat insulation.

According to this conventional example, the fixing device easily warms up, and when the power is turned on, printing can be started immediately.

[0015]

However, in each of the above-mentioned conventional examples, it is common to use several kinds of recording materials having different sizes. For example, a maximum A3 (sheet passing width of 297 mm) size longitudinal feed is possible. Image forming apparatuses such as A4 (sheet passing width 211 mm) and B5 (sheet passing width 1
82 mm), envelopes (paper passing width 105 mm), business cards (paper passing width 55 mm), etc.
A non-sheet passing portion is generated in the fixing section of the fixing device, and the amount of heat is not absorbed by the recording material in the non-sheet passing section. Part temperature rise "occurs. As a result, there were the following problems.

In the non-sheet passing portion, the temperature of the fixing roller becomes high and the rubber material of the pressure roller deteriorates. The thermal expansion of the pressure roller becomes non-uniform between the paper passing portion and the non-paper passing portion, and an outer shape difference occurs in the axial direction, which causes wrinkling or skewing of the recording material. After passing a small size recording material, the non-sheet passing area becomes higher than the fixing roller setting temperature.Therefore, if a larger size recording material is passed after passing a small size recording material, At the non-sheet passing portion, the toner is in an excessively melted state and hot offset occurs. This is the case when the temperature detection element is installed in the paper passing area, but when it is installed in the non-paper passing area, the paper passing area becomes lower than the set temperature and fixing failure occurs. Or cold offset occurs. As a measure to prevent the temperature rise in the non-sheet passing area, a method has been proposed in which the sheet passing interval of the recording material is set to be larger than that in normal continuous sheet feeding to prevent the local temperature rise of the fixing roller. According to the method, when printing small size paper, it takes a very long time and the printing speed becomes slow. According to the “thin-wall fixing roller” and the “fixing device of film fixing method” as described above, since the heat capacity of the fixing roller and the fixing film is small, the problem of the temperature rise in the non-sheet-passing portion becomes very remarkable, The temperature difference between the printing area and the non-paper feeding area could reach 200 ° C.

The present invention solves the above-mentioned problem of temperature rise in the non-sheet-passing portion and reduces the temperature rise in the non-sheet-passing portion so that the fixing roller or the heating member can be used even when fixing recording materials of different sizes. An object of the present invention is to provide an image forming apparatus capable of uniformly heating and appropriately controlling the fixing temperature.

[0018]

According to the present invention, the above object is to provide a nipping / conveying means for nipping and conveying a recording material, a heating means arranged inside the nipping / conveying means for generating heat by energization, and the nipping / holding means. The temperature detecting means arranged in contact with or close to the conveying means or the heating means, and the sandwiching conveying means or the heating means by controlling the energization amount to the heating means based on the temperature detected by the temperature detecting means. In an image forming apparatus equipped with a temperature control unit for maintaining the temperature of the unit at a predetermined temperature, an image forming operation of a recording material having a width narrower than the maximum recording material sandwiched and conveyed by the sandwiching and conveying unit is continuously performed. In this case, it is achieved by providing a recording material conveying path selecting means for bringing the recording material having the narrow width into contact with the sandwiching conveying means over an area substantially similar to the maximum recording material.

[0019]

According to the present invention, when the image forming operation of the recording material having a width narrower than the maximum recording material is continuously performed, for example, when the image is formed on one surface of the recording material, a plurality of recording materials are recorded. When the material is transported, the recording material transport path selection means is configured so that the position where the first recording material comes into contact with the sandwiching transport means and the position where the second recording material comes into contact with the sandwiching transport means are different. To
Since the recording material is supplied so that the contact position of each recording material with respect to the nipping / conveying means changes, the recording material comes into contact with the surface of the nipping / conveying means in almost the entire nipping portion of the nipping / conveying means. The temperature distribution in the longitudinal direction of the conveying means or the heating means becomes uniform.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS. Note that FIG. 7 and FIG.
The same parts as those of the conventional example shown in FIG.

FIG. 1 is an explanatory diagram of Embodiment 1 of the present invention.
The apparatus of this embodiment has substantially the same configuration as the conventional image forming apparatus shown in FIG. 7, and FIG. 1 is a view seen from above (direction of arrow B) in FIG. The charging roller 2, the developing device 4, the guides 6 and 8 and the like are omitted.

In this embodiment, a small-size sheet moving cassette 70 that can move to the left and right of the arrows c and d is provided in the sheet feeding cassette 14, and when the small-sized sheets are continuously fed, the fixing roller is used. The recording material sheet passing area of the fixing unit 51 is changed. That is, the present embodiment is provided with the conveyance path changing means for changing the conveyance path of the recording material to prevent the temperature rise of the non-sheet passing portion.

This procedure will be described. First, when the small-size paper moving cassette 70 carrying a plurality of recording materials 61 is at the home position H, the first recording material 61 is fed, and then moved to the dotted line position I in the direction of arrow c. At that time, the second recording material 61a is fed and passed on the left side of the photosensitive drum 1 and the fixing roller 51 as shown in FIG.
Next, the small-size sheet moving cassette 70 moves to the alternate long and short dash line position J in the direction of the arrow d to move the third recording material 61b.
Is fed and passed on the right side of the photosensitive drum 1 and the fixing roller 51 as shown in FIG. At this time, the recording material 61
The image position formed on the photosensitive drum 1 is also changed to an appropriate position by an image writing position control device (not shown) in accordance with the conveyance path of the.

In this way, the small size moving cassette 7
To feed the recording material 61 continuously while 0 moves in the directions of the arrows c and d (positions H → I → J → H ...), and to change the recording material passage area in the fixing unit of the fixing device. In addition, the conveyance path of the recording material is changed so as to minimize the continuous non-sheet passing portion in the fixing unit, and the temperature rise of the non-sheet passing portion is prevented.

FIG. 2 shows the results of measuring the temperature distribution of the fixing roller in this embodiment. In FIG. 2, K is a temperature distribution when a small-size sheet is continuously fed in the conventional image forming apparatus in which only the T2 side is the transport reference. The temperature is much higher than Tf.

Further, L in FIG. 2 is a temperature distribution when small size paper is continuously fed by using the small size moving cassette system of the present embodiment, and is kept at the set temperature Tf in the entire fixing roller. ing.

In this embodiment, the cassette position is set to H,
Although the case of moving to three positions of I and J has been described, in the case of using a recording material of a smaller size such as an envelope feeder, the moving method is performed by gradually moving and using a plurality of positions. Is the width of the recording material,
It may be arbitrarily adjusted depending on the material, the thickness, and the degree of temperature rise in the non-sheet passing portion of the fixing device.

As described above, according to the conveying path varying means as in the present embodiment, it is possible to prevent the temperature rise of the non-sheet passing portion, the pressure roller is not deteriorated, and the wrinkles of the recording material and the hot offset are caused. It was possible to obtain a clear image with no difference. Further, since continuous paper feeding is possible, the printing speed of small size paper is also improved, and particularly when applied to the above-described thin-wall fixing roller or film fixing type fixing device, the effect of preventing the temperature rise of the non-paper passing portion is great.

In the present embodiment, the feeding path of the recording material is changed by changing the feeding position, but the feeding position is fixed and the feeding path of the recording material is changed after feeding. May be used. For example, the recording material conveyance path changing means may be installed before the transfer process after the paper feeding or before the fixing process after the completion of the transfer process.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 3, reference numeral 80 designates 61 for small size paper.
It is a continuous type paper feed cassette that is arranged in parallel on the left and right of c and 61d. By feeding the recording materials 61c and 61d alternately from the left and right from the continuous type paper feeding cassette 80, the recording material passing area of the fixing portion of the fixing device is appropriately changed to reduce the continuous non-sheet passing portion. As a result, the temperature rise of the non-sheet passing portion can be prevented.

Moreover, as shown in FIG.
By feeding the sheets with a slight time difference as shown in FIG. 5, the printing speed is improved and the temperature rise of the non-sheet passing portion can be prevented. Also in this embodiment, image writing position control (not shown) is necessary, and as shown in FIGS.
When forming an image over two or more pages, for example, in a laser printer, two or more pages of images may be simultaneously processed by the controller.

Although FIGS. 3 to 5 have described the example of the two-cassette cassette, a plural-cassette cassette or a plurality of envelope feeders may be used. Further, the size of the recording material to be connected may be different. Further, by combining with the movable sheet feeding cassette as in the first embodiment of the present invention, there is no problem even if the width becomes larger than the width of the fixing roller 51 in the longitudinal direction when they are continuously mounted.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. 6, and a conventional image forming apparatus will also be described with reference to FIG. 10 for comparison with the present embodiment. To do. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the present embodiment, in an image forming apparatus for forming a double-sided image or a multiplex image, the conveyance path is changed between the image formation of the first side and the formation of the second side or the multiplex image to fix the fixing device. Since the sheet passing area of the recording material in the fixing unit is changed, it is possible to prevent the temperature rise of the non-sheet passing portion in the fixing unit.

FIG. 10 shows an example of a conventional image forming apparatus having an image forming function for double-sided images or multiple images.
In FIG. 10, the arrow line drawn from the paper feed cassette 14 toward the fixing device 9 indicates the moving path of the recording material. The recording material 61 in the paper feed cassette 14 is the entrance guide 6
Is inserted into the nip portion between the photosensitive drum 1 and the transfer roller 5, carries a toner image, is conveyed to the fixing device 9, and the toner image is fixed on the first surface of the recording material 61. After that, it passes through the path of the arrow line in the direction of the arrow D, is inverted by the reversing device 90, is inserted again into the entrance guide 6, an image is formed on the second surface similarly to the first surface, and the toner image is fixed by the fixing device 9. A double-sided image is formed through the path of the arrow line in the direction of arrow U. Here, the reversing device 90 is turned off,
A multiple image is formed by forming an image on the first side again without inverting.

In this image forming apparatus capable of forming a double-sided image or a multiplex image, as shown in FIG. 6, the small-sized recording material on which the image is formed on the first side is passed through the reversing device 90 and then the conveying path changing device 91. By changing the conveying path by the above, it is possible to prevent the temperature rise of the non-sheet passing portion by eliminating the continuous non-sheet passing portion of the recording material in the fixing device.

Further, the transport path changing device 91 may be arranged at any position after the first side image is fixed on the recording material and before the second side (or double side) image is fixed. 9
0 may be provided with a transport path variable function.

[0040]

As described above, according to the present invention,
Since the recording material passing position in the nipping and conveying means is appropriately changed by using the conveying path changing means and the continuous feed cassette, the recording material non-passing area in the nipping and conveying means or the heating means is eliminated, and the ascending position in the non-passing area is increased. It is possible to prevent the temperature, and solve the problems due to the temperature rise in the non-passage area of the recording material, such as the deterioration of the rubber of the pressure roller as the nipping / conveying means, the wrinkling of the recording material, the hot offset, and the decrease in the image forming speed. It is possible, regardless of the size of the recording material,
A clear image can be provided for a long period of time.

Further, the amount of abrasion of the fixing roller and the pressure roller as the nipping / conveying means due to the friction with the recording material and the toner in the nipping portion is not made uneven, and the sliding of the fixing material and the pressure roller with the end portion of the recording material is prevented. It is possible to prevent non-uniformity of fixing property, image stain, and the like caused by scratches and the like due to rubbing.

Particularly, in a fixing device having a fixing portion having a small heat capacity such as a thin fixing roller or a fixing device of film fixing type, the temperature rise of the recording material non-passing area is surely suppressed, and the temperature of the fixing portion is easily and uniformly made. It became possible to keep it.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an image forming apparatus according to a first exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a temperature distribution on the surface of a fixing roller in Example 1 of the present invention.

FIG. 3 is a diagram illustrating an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram for explaining another image forming apparatus according to the second embodiment of the invention.

FIG. 5 is a diagram illustrating another image forming apparatus according to a second embodiment of the invention.

FIG. 6 is a diagram illustrating an image forming apparatus according to a third exemplary embodiment of the present invention.

FIG. 7 is a vertical sectional view of an example of a conventional image forming apparatus.

FIG. 8 is a vertical sectional view of an example of a conventional roller type fixing device.

FIG. 9 is a vertical cross-sectional view of an example of a conventional film-type fixing device.

FIG. 10 is a diagram for explaining a conventional image forming apparatus capable of forming double-sided and multiple images.

[Explanation of symbols]

50 Heater (Heating Means) 51 Fixing Roller (Pinching and Conveying Means) 52 Pressure Roller (Pinching and Conveying Means) 58 Temperature Detecting Element (Temperature Detecting Means) 70 Moving Cassette for Small Size Paper (Recording Material Conveying Path Selection Means) 80 Continuous Type Cassette (recording material conveying path selecting means) 91 Conveying path changing device (recording material conveying path selecting means)

Claims (4)

[Claims] 1. A nipping and conveying means for nipping and conveying a recording material,
A heating means disposed inside the sandwiching and conveying means to generate heat when energized, a temperature detecting means disposed in contact with or close to the sandwiching and conveying means or the heating means, and a temperature detected by the temperature detecting means. In the image forming apparatus provided with the temperature control means for maintaining the temperature of the nipping and conveying means or the heating means at a predetermined temperature by controlling the amount of electricity supplied to the heating means by the nipping and conveying means. When the image forming operation of a recording material having a width narrower than the maximum recording material is continuously performed, the recording material having the narrow width is brought into contact with the nipping and conveying means over an area substantially similar to the maximum recording material. An image forming apparatus comprising a recording material conveyance path selecting means. 2. The image forming apparatus according to claim 1, wherein the recording material conveyance path selecting means is a recording material storage container that is movably arranged in the width direction of the recording material. 3. The image forming apparatus according to claim 1, wherein the recording material transport path selecting means is a recording material storage container having a plurality of supply ports arranged in parallel in the width direction of the recording material. 4. When the image forming operation which is continuously performed is an image forming operation on both sides of the recording material or a multiple image forming operation on one side, the recording material conveying path selecting means,
The image forming apparatus according to claim 1, wherein a contact position of the recording material with respect to the nipping / conveying means on the first surface or the single surface and a contact position on the second surface or the double surface are changed.