JP2919561B2 - Image forming device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming apparatus capable of forming a black-and-white image and a color image.

(Prior Art) The following is known as a fixing device for fixing a toner image by passing a recording paper carrying an unfixed toner image between a pair of heated rollers.

A fixing device for fixing a toner image on a toner carrier by pressing a toner carrier having a plurality of color toner images on the surface thereof with a heating roller and a pressure roller which presses against each other, and relates to a temperature of the heating roller. Is set to be higher than the temperature of the pressure roller to satisfy the high glossiness at the time of full-color copying and to prevent the occurrence of fixing offset (see, for example, JP-A-1-244488).

In order to increase the gloss of a color image, two sets of fixing means, in which only one of the rollers is a heating roller, are provided in series on a recording paper conveying path so as to continuously feed paper (Japanese Patent Laid-Open No. 55-55). No. 43596).

Spray coating for enhancing the glossiness of an image surface (see Japanese Patent Application Laid-Open No. Sho 60-52861).

(Problems to be Solved by the Invention) For a fixed toner image, a user requests various gloss levels depending on his / her preference, but generally, a color image requires a high gloss level, and a black and white image requires a low gloss level. .

On the other hand, in the prior art, the glossiness of the color image is good, but the black-and-white image also has high gloss, and the heat shrinkage, image misalignment, wrinkles, paper folding, etc., caused by passing the paper twice are considered. Concerned, the above requires spray coating means. In addition, since all of the above-mentioned methods apply a large amount of silicone oil to a black-and-white image, there is a problem that it is not possible to expect a commonly required addition to a black-and-white image.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which solves the above-mentioned problems, allows a user to easily select the glossiness of an image, and improves the retouching of a monochrome image. .

(Means for Solving the Problems) In order to achieve the above object, in the image forming apparatus of the present invention, a recording sheet carrying an unfixed toner image is passed between a pair of heated rollers. An image forming apparatus provided with a fixing device for fixing the toner image includes a heat roller having a fine roller surface roughness, a heat roller having a rough roller surface roughness, and a pressure roller.
Each of the three heat rollers has a heat source. Two of the three rollers are disposed adjacent to each other, and the pressure roller is disposed so as to press any one of the heat rollers. A drive control means for controlling the direction of the heat roller so as to be capable of reversing the direction; and providing a first fixing area by a facing pressure contact portion between the two heat rollers, and a facing pressure contact between any one of the heat rollers and the pressure roller. A second fixing area is formed by each of the first fixing area and a recording paper receiving port for guiding a recording sheet carrying an unfixed toner image with respect to the first fixing area and a second fixing area. A recording paper receiving port for guiding the recording paper carrying the unfixed toner image, and when the recording paper to be fixed carries a color unfixed toner image, the toner surface thereof is roughened on the roller surface. So that it contacts the heat roller Further, when the recording paper to be fixed is one carrying only black toner, one of the two recording paper receiving ports is selected so that the toner surface thereof is in contact with the heat roller having a rough surface. The recording paper to be fixed is transferred to perform fixing.

(Operation) A fixing area dedicated to high glossiness and a fixing area dedicated to low glossiness can be selectively used according to the type of a recorded image.

(Examples) Example 1 (see FIG. 1) Generally, the higher the gloss of an image, the higher the gloss of the image (for example, the glossiness is 20%), due to the vividness of color, transparency, and color reproducibility.
Conversely, a black-and-white image, on the other hand, is preferred by the user as the glossiness is lower (for example, 5% or less).

The so-called thermal fixing roller system, in which paper is fixed between a pair of heated rollers, is considered to be superior to other systems in terms of thermal efficiency, cost, safety, and the like, and the present invention also belongs to this category.

Regarding the gloss of the fixed image, not only the material of the roller for heat fixing, but also the surface roughness of the roller greatly influences.

In other words, when the surface roughness is reduced, the glossiness of the image fixed in contact with the roller increases, and conversely, the gloss decreases.

Therefore, in this embodiment, rollers having different surface roughness are selectively used according to the desired glossiness of the fixed image.

In FIG. 1, reference symbol S denotes a heat roller having a fine roller surface roughness, reference symbol L denotes a heat roller having a rough roller surface roughness,
Reference symbol P indicates a pressure roller. The heat roller has a heat source inside. In each case described below, the opposed pressure contact portion between the two heat rollers is referred to as a first fixing region T1, and the opposed pressure contact portion between the heat roller and the pressure roller is referred to as a second fixing region T2.

Case 1 (see FIG. 1 (a)) In this example, the heat roller S, the heat roller L, and the pressure roller P are arranged in such a manner that these rollers are pressed against each other in this order from the top.

Here, for the recording paper CS carrying the color (full-color to multi-color) toner CT, the first fixing area T1 is passed with the toner surface facing the heat roller S, and only the black toner BT is carried. It is assumed that the recording paper BS passed through the second fixing area T2 with the toner surface facing the heat roller L.

When passing each recording sheet, it is necessary to switch the rotation direction of each roller forward and backward freely so as to be suitable for the sheet passing. For this purpose, a drive control means for switching between forward and reverse rotation, for example, a motor or gear mechanism capable of forward and reverse rotation is provided.

Further, a silicon oil applying means 1 for supplying silicon oil to the heat roller S when the first fixing area T1 is used is provided above the fine roller S.

Case 2 (see FIG. 1 (b)) In this example, in the configuration of the roller in the case 1,
The arrangement is such that the positions of the heat roller S and the heat roller L are interchanged. The silicone oil applying means 1 is provided above the heat roller L or diagonally above the heat roller S. In the former case, that is, when provided above the heat roller L, it is supplied indirectly to the heat roller S via the heat roller L, which is indirect. Except for special cases, the former is generally applied. The same applies to the applying means for the heat roller L in case 4 described later.

Here, for the recording paper CS, the toner surface is
The second fixing area T2 is passed through to the transfer paper BS.
About the first fixing area with the toner surface facing the heat roller L.
We will pass T1.

Case 3 (see FIG. 1 (c)) In this example, the configuration of the roller in the case 1 is as follows.
In this configuration, the pressure roller P is moved to the upper portion of the heat roller L, and is arranged in opposing pressure contact. Silicone oil application means 1
Is provided below the heat roller S.

Here, the first fixing area T1 is passed through the recording paper CS with the toner surface facing the heat roller S, and the second fixing area T2 is passed with the recording paper BS facing the toner surface toward the heat roller L.
And let the paper pass.

Case 4 (see FIG. 1 (d)) This example is based on the configuration of the roller in Case 3 described above.
The arrangement is such that the positions of the heat roller S and the heat roller L are interchanged.

The silicone oil applying means 1 is provided diagonally above the heat roller L or diagonally above the heat roller L.

Here, it is assumed that the second fixing region T2 passes through the second fixing region T2 with the toner surface facing the heat roller S for the recording paper CS, and the first fixing region T1 faces with the toner surface facing the heat roller L for the recording paper BS.
And let the paper pass.

In the above, in each case, a heat roller with a fine surface roughness is used for fixing a color image requiring glossiness, and a heat roller with a rough surface roughness is used for fixing a black and white image not requiring glossiness. To meet the intended demands.

Example 2 (see FIG. 2) FIG. 2 is an enlarged view of the roller portion of the case (FIG. 1 (a)), and the structure of each roller will be described using this as an example. The same applies to the cases 2 to 4.

The heat roller S includes a halogen heater as a heat source H provided inside, a cylindrical core 2 made of Al, Fe or the like surrounding the heat source H, and an intermediate layer 3 of a Si rubber layer covering the periphery of the core. And an outer peripheral layer 4 formed by spray coating Si-based rubber on the surface of the intermediate layer. The outer peripheral layer 4 has a very small surface roughness. In order to make the surface roughness fine, surface polishing, spray coating with a release material, or the like is performed.

Next, the heat roller L also has a heat source H and a cylindrical cored bar 2 surrounding the heat source H. Further, an outer peripheral layer 50 made of a Si rubber layer or a carbon-containing Teflon (trade name) layer is provided around the cored bar 2. The outer layer 50 has a rough surface rougher than that of the heat roller S.

Next, the pressure roller P has a hollow cored bar 3 and an outer peripheral layer 6 of a Si rubber layer covering the outer periphery thereof.

As the Si rubber used for each roller, HTV, RTV,
Various rubbers such as LTV can be used, and are appropriately selected in consideration of a toner release material, a fixing temperature range, durability, and the like.

Example 3 (See FIG. 3) FIG. 3 shows an example in which the configuration of the roller shown in FIG. 2 is combined with other members to realize a fixing device 5. Therefore, the configuration and the like of each roller are in accordance with the above-described example.

The silicone oil applying means 1 includes a pressurizing member 1 made of an elastic material and the silicone oil in the silicone oil tank 1-1.
-2 oil-coated felt member 1 provided along
The suctioned silicone oil is supplied through the oil-applied felt member 1-3 that slides on the heat roller S by utilizing the capillary effect through the suction roller 3. Further, a cleaner device 1 composed of a blade member and the like.
-4 realizes a cleaning action of the heat roller surface, a further uniform application of the Si oil, and an appropriate quantity action, thereby improving and maintaining the fixing performance.

The pressing member 1-2 is an oil-coated felt member 1-
3 and is engaged with the rotation support member 17. The rotation support member 17 has a base end attached to a rotation shaft 18,
The rotating shaft 18 is connected to a rotary solenoid or the like. Therefore, the oil-applied felt member 1 is changed according to the rotation of the rotating shaft.
-3 can be controlled to approach and separate from the heat roller. Therefore, the configuration including the rotation support member 17 and the rotation shaft 18 is referred to as a means for interrupting the supply of Si oil. Further, the pressure roller cleaner 16 removes foreign substances and prevents contamination on the back surface of the recording paper.

The fixing device 5 has upper and lower two independent recording paper receiving ports for receiving recording paper carrying toner for fixing.

The upper recording inlet 6u is located at the upper part and is for guiding recording paper to the first fixing area T1. When high glossiness is required for the recorded image, for example, full-color or multi-color, etc., a clear and high color Used when reproducibility is required.

Further, the lower recording paper receiving port 6d is located below the upper recording paper receiving port 6u, and is for guiding the recording paper to the second fixing area T2. Used when fixing.

The transfer of the recording paper to each of these recording paper receiving ports is performed by the transport device 7.
This is done by the displacement of The position of the conveying device 7 is switched up or down according to the recording mode such as color image or black and white image, and the recording paper receiving port is selected.

This displacement is performed by moving the end of the conveyance device 7 by using a solenoid, a motor, or the like (not shown) so that the end of the conveyance device 7 is located near each recording paper receiving port.

The transport device 7 ensures that the recording paper is transported by the transport belt 7-1, the air vacuum device 7-2, the guide claws 7-3, and the like.

The rotational drive control of each of the heat rollers S and L and the pressure roller P is optimally controlled by a motor, a clutch and the like (not shown) in the direction of rotation, speed, timing and the like.

At the time of fixing, thermistors 8, 9 are used to fix each heat roller S, L
And the optimum temperature control of the heat roller is performed by a fixing temperature controller (not shown) based on these detection signals.

For the pressure roller P, a pressure lever 10 and a spring
By applying the pressing force by 11, an optimum pressing force is applied to each roller. The upper separating claw 12, the lower separating claw
13, the guide plate 14 prevents the recording paper from being wound around the rollers, and the recording paper is fixed to the discharge rollers 15
As a result, the sheet is reliably discharged to the next step.

This embodiment is a specific example of a fixing device to which the case 2 (see FIG. 1B) is applied by replacing the arrangement of the heat roller S and the heat roller L.

Example 4 (see FIG. 4) FIG. 4 corresponds to an example of a fixing device that embodies case 3 (FIG. 1 (c)). The function of each member conforms to the example of FIG. 3 described using the same reference numerals.

This embodiment is a specific example of a fixing device to which the case 3 (see FIG. 1C) is applied by exchanging the arrangement of the heat roller S and the heat roller L.

Example 5 (See FIG. 5) The state of the surface roughness of each heat roller used in the present invention will be discussed.

In FIG. 5, curve B1 is a roller with a fine surface roughness (0.3
0.80.8 μm Rz) (where Rz is the average roughness), characteristics when an image with a toner adhesion amount of 1.2 mg / cm ² was fixed, curve B
2 shows the characteristics when the same roller was used to fix an image having a toner adhesion amount of 0.3 mg / cm ² .

Similarly, the curve A1 shows a roller having a rough surface roughness (1 to 4 μm).
using MRZ), shows characteristics when the fixing for the image of the toner adhesion amount 1.2 mg / cm ^2, curve A2 uses the same roller, characteristic when the fixing for the image of the toner adhesion amount 0.3 mg / cm ^2, respectively.

When the above-mentioned rollers are used in opposition, the temperatures in the opposing portions including the roller nip portion are common, and this is the fixing temperature. The fixing temperature t ₁ following the cold offset occurrence region, the fixing temperature t ₄ or more hot offset generating region and the temperature region excluding and safe watching fixing was set to the inner ring slightly than the respective areas Temperature Temperature t ₂ temperature range of ~t ₃ each roller common capable of avoiding offset said to be "preferred fixing temperature region".

On the other hand, as for gloss,
It is considered that 20% or more is a preferable area for a full-color image, and 5% or less is a preferable area for a black-and-white image.

As in this example, if a roller having a rough surface roughness and a fine roller face each other to form a pair of fixing rollers, as described above, the temperature of the facing portion of both rollers, that is, the fixing portion temperature, becomes a common temperature, and the temperature becomes the fixing temperature. Become. At this common fixing temperature, a full-color image is fixed for a roller with a fine surface roughness, and a black and white image is fixed for a roller with a rough surface roughness, so that a glossiness corresponding to the image characteristics can be obtained for each image. The fixing temperature _{t 1 ~t 2, t 3 ~t} 4
Are margin temperatures.

Next, an example of a recording apparatus suitable for carrying out the present invention will be described with reference to FIG. It should be noted that the seventh symbol indicated by the same reference
The example in the figure also complies with the following description.

Original 21 placed on contact glass 20 for recording
Is illumination lamp 22, mirror group 23, reduction lens 24, color CC
A color scanner device including a D image sensor 25, a scanner controller 26, and the like converts the color image into electric signals corresponding to blue, green, red, and black original images.

This electric signal is further processed by the image processing unit 27,
It is sent to the writing unit 28. The electric signal sent to the writing unit 28 is converted into an optical signal there, and is radiated as a laser beam onto the photoconductor 32 via the polygon mirror 29, the fθ lens 30, and the mirror 31. Photoconductor 32
Around the, there are a static eliminator 33, a charger 34, and five developing units, that is, a yellow developing unit 35Y, a magenta developing unit 35M, a cyan developing unit 35C, a black developing unit 35CB for black and a black developing unit 35BB for black and white copying. And a photoconductor cleaning device 36.

Reference numeral 37 denotes an intermediate transfer member belt, which has a first transfer portion facing the photosensitive member 32, a first transfer device 38 corresponding to the first transfer portion, and a second transfer device (bias). Roll) 39, an intermediate transfer member belt cleaner 40, a bias roll cleaner 41, a waste toner bottle 42, and a plurality of support rollers 43 around the belt.

On the intermediate transfer belt 37, a single-color image, a two-color image, a three-color image, a four-color image (for example, a single-color copy, a multi-color copy, a full-color copy) and the like are formed in accordance with the recording mode. These operations are performed by re-transferring the toner image on the photoreceptor from the first transfer unit 38 onto the intermediate transfer belt 37 through a normal color electrophotographic image forming cycle.

At the time of recording, the recording paper 44 to be the recording paper CS or the recording paper BS is fed one by one by a feed roller 45.

Special size paper or the like can be fed using the manual feed table device 46.

The recording paper relating to the paper feeding is transferred by a guide plate, a conveying roller, a registration roller, and the like to a second transfer unit where the second transfer unit 39 is disposed, where a toner image corresponding to the original image is formed.
The image is transferred onto the recording paper from the intermediate transfer belt. If this toner is only black toner BT, the recording paper 44 is used as the recording paper BS.
In the case of the color toner CT, the recording paper CS is fixed as described above.

The recording paper 44 is sent to the fixing device 5 via the transport device 7.

After the fixing, the sheet is discharged by a fixing discharge roller 15 and further stored in a copy stacker 49 via a discharge roller 48.

 The following advantages can be obtained by the above embodiment.

The glossiness of the image desired by the user can be freely selected.

A high gloss color image can be obtained, and high image quality can be achieved.

As for the high gloss image, the recording paper and the image are not spoiled as compared with the case where the fixing unit continuously passes a plurality of stages.

Rollers with rough surface roughness (for example, Teflon (trade name) rollers,
Teflon (trade name) roller containing carbon, high-strength Si rubber, etc.) can be used, and reliability and economy can be improved.

In the case of a black-and-white image as described above, the recording paper does not come into contact with the fine roller of the roller surface. Therefore, the roller surface is not damaged due to the paper powder, and the roller surface characteristics are not deteriorated due to the paper sticking due to the abrasion and scratch of the roller due to the recording paper, and the high quality image is stabilized and maintained.

It is very important to improve the releasability between the toner image and the heat roller by applying the Si oil to the heat roller in order to improve the durability and the quality of the heat roller. Especially in full-color images, large amounts of Si oil are required compared to conventional black-and-white image fixing in order to instantly and uniformly fix the unfixed toner image with a large amount of toner and a multilayer structure over the entire image. I have.

Also, in order to obtain a high gloss image, application of a large amount of Si oil is effective.

However, the application of the Si oil causes problems such as deterioration of the retouching property to the finished image and deterioration of the feel. In particular, black and white images are mostly used mainly for line images, and thus it is demanded to further improve the quality of the retouchability and tactility.

In the above example, a large amount of Si oil is applied to a roller having a small roller surface roughness, and a small amount is applied to a roller having a rough roller surface roughness. For a heat roller with a rough roller surface, the roller surface roughness once passes through a finer heat roller. Less is. Therefore, this problem can be most rationally, efficiently, and economically solved for a color image, a monochrome image, a high gloss image, and a low gloss image.

In relation to the above, the application amount of the Si oil to the heat roller can be controlled by operating the interruption means of the Si oil supply as necessary, and a desired proper amount of application or no application can be obtained, and It is possible to more reliably improve the retouching property of the image and the high gloss of the color image.

(Effects of the Invention) According to the present invention, it is possible to reliably obtain a high-quality recorded image satisfying desired glossiness or rewriting property according to image characteristics with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating various examples of an arrangement configuration of a fixing roller.
FIG. 2 is a diagram illustrating the structure of the roller, FIGS. 3 and 4 are diagrams illustrating the overall configuration of the fixing device, FIG. 5 is a diagram illustrating the fixing characteristics, FIG. 6, and FIG. FIG. 1 is a diagram illustrating an outline of a recording apparatus suitable for implementing the present invention. 1 Silicon oil application means, 6u Upper recording paper receiving port, 6d Lower recording paper receiving port, 7 Conveyor, S, L
… Heat roller, P… Pressure roller, CS, BS …… Recording paper.

Claims (1)

(57) [Claims] An image forming apparatus having a fixing device for fixing a toner image by passing a recording sheet carrying an unfixed toner image between a pair of heated rollers, wherein the roller surface roughness is The heat roller has a fine heat roller, a heat roller having a rough surface roughness, and a pressure roller. Each of these two heat rollers has a heat source.
Drive control means for arranging the two heat rollers adjacent to each other, arranging the pressure roller so as to press any one of the heat rollers, and controlling the rotation directions of these three rollers to be freely reversible; A first fixing area formed by an opposing pressure contact portion between two heat rollers, and a second fixing area formed by an opposing pressure contact portion between any one of the heat rollers and the pressure roller; A recording paper receiving port for guiding the recording paper carrying the unfixed toner image to the first fixing area, and a recording paper receiving receptacle for guiding the recording paper carrying the unfixed toner image to the second fixing area. When the recording paper to be fixed carries a color unfixed toner image, an entrance is provided, so that the toner surface of the recording paper is in contact with the heat roller having a small surface roughness of the roller, and the recording paper to be fixed is provided. Is the one carrying only black toner The recording paper to be fixed is transported and fixed by selecting one of the two recording paper receiving ports so that the toner surface thereof contacts the heat roller having a rough surface. Image forming device.