JPH0456884A - Fixing device and image forming device - Google Patents

Abstract

PURPOSE:To prolong the service life of a fixing roller and to prevent the staining of a picture caused by the sticking of an offset developer to a transfer material by separating a cleaning member from a fixing roller relatively. CONSTITUTION:The cleaning member 6 sliding on the fixing rotating-body 2 for cleaning is employed. The developer-cleaning-member contact/uncontact means for bringing the cleaning member 6 into contact/uncontact with the surface of the fixing rotary body 2 is provided. This means is controlled in such a manner that when a transfer material is carried into the fixing device, the cleaning member 6 is in pressurized contact against the fixing rotary body 2 and when the transfer material passes through the fixing device, the cleaning member 6 is separated from the body 2. Thus, the unnecessary wear of the surface layer of the fixing rotary can be prevented, the service life of the fixing rotary body and cleaning member can be greatly prolonged and a clear picture can be obtained without staining the front and back of the transfer material.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, and particularly relates to a cleaning mechanism for a fixing roller and the image forming apparatus.

"Prior Art" Image forming apparatuses such as copying machines are usually provided with a fixing device for fixing a developer image formed on transfer paper to the transfer paper through a development process such as electrostatic photography. FIG. 8 shows an example of such a fixing device.

In the example shown in FIG. 8, a transfer material, such as a transfer paper, is introduced into a nip formed by a pair of pressure roller 3 and fixing roller 2 from the direction of the figure, and as it passes through the nip,
Pressure force and heat from the heater 4 built into the fixing roller are applied to melt the developer and fix it to the transfer paper.

In the fixing device having the above structure and operation, the fixing roller 2 is usually a roller with a hard surface such as metal, while the pressure roller 3 is a roller with a soft surface such as silicone rubber. The one formed as is used.

In the fixing operation as described above, it is known that some of the developer carried on the transfer paper and conveyed to the nip portion adheres to the fixing roller 2 in an offset manner. During the fixing operation, the offset developer adheres to the transfer paper, resulting in smearing of the image.

Therefore, in conventional general fixing devices, a cleaning mechanism for the fixing roller 2 is provided along with the fixing roller 2 (in the example shown in FIG. 8, on the upper part of the fixing roller). A thin sheet material made of non-woven fabric impregnated with a release agent such as silicone oil is rolled up from an elastic material such as rubber while being driven to be wound around the unwinding shaft 8 and the winding shaft 7 in conjunction with the passage of the transfer paper. The web roller 6 is pressed against the fixing roller 2 by a spring (not shown) to provide a certain nip width, thereby wiping off the dirt caused by the offset on the fixing roller 2, and applying silicone oil impregnated into the web 5 to the fixing roller 2. The coating is applied uniformly onto the surface of the roller 2.

In addition, in this two-linering mechanism, as shown in the example of FIG.
When the web 5 is wound up, the presser member 9 is pressed against the web 5 on the unwinding shaft 8 with a predetermined pressure by an appropriate spring member (not shown) to provide an appropriate unwinding resistance to the web 5. Usually, the web is given tension to prevent it from sagging or wrinkling.

``Problems to be Solved by the Invention'' By the way, in the fixing roller cleaning mechanism using a web as described above, the circumferential speed of the fixing roller is much larger than the web feeding speed, resulting in Generally, the fixing roller is constantly rubbed against the entire surface of the web. Therefore, the surface layer of the fixing roller is always slightly scraped off by the web. Usually, the metal or other hard surface of the fixing roller has a thickness of 20 to 30 mm to ensure releasability from the developer.
It is coated with a fluororesin (trade name: "Teflon") of approximately 0 um. Therefore, the fluororesin on the surface of the fixing roller is scraped off by the web that is rubbed over the entire surface, which is critical to the life of the fixing roller. Moreover, since the fixing roller is constantly rotating during the copying operation, the surface of the fixing roller is rubbed by the web even during times other than the fixing operation, further shortening the life of the fixing roller.

In addition, in recent years, due to advances in developer technology, so-called fixed @ devices with a cleaning mechanism that do not require a cleaning mechanism have appeared, thanks to developers that are less likely to cause offset than before, but they do not require cleaning completely. This has not yet been achieved. Therefore, if the amount of offset of the developer to the fixing roller increases, a cleaning mechanism is inevitably required.

A case where the offset amount increases will be explained below.

Generally speaking, when using a relatively thick type of transfer material (cardboard 80 gr/m2 or more), the heat from the fixing roller may not be sufficiently transmitted to the transfer material (thus, the fixing performance may deteriorate). As a result, the amount of developer offset to the fixing roller tends to increase (hereinafter referred to as "increased offset").Also, when forming an image with a high density ratio, the amount of developer offset on the transfer material increases. Since there is a large amount of developer, the offset of the developer to the fixing roller increases.

Furthermore, when the device is used in a low-temperature environment, the transfer material itself is in a low-temperature state, and furthermore, the constant @ device itself is also in a low-temperature state, so the fixing performance is likely to deteriorate. , the offset increases.

Furthermore, with the recent systemization of image forming apparatuses, duplex functions and multiple compositing functions have been added.

In the case of the double-sided function, since an image is formed once again on the back side of the transfer material surface on which the image has been formed on the first side, the pressure roller side and the image forming surface of the first side come into contact. Therefore, if the fixing performance on the first side is decreasing (for example, as shown above,
(in the case of thick paper, high image density ratio, or low-temperature environment), unfixed developer is likely to offset to the pressure roller, and in addition to the offset described earlier, the degree of the offset is even worse. , stains on the transfer paper increase.

In addition, in the case of multiple functions, since an image is formed once again on the same side of the transfer paper on which the image has already been formed on the first side, if the fixing performance of the first side has deteriorated (for example, as shown above) (in the case of thick paper, high image density ratio, or low-temperature environment), heat is applied to the fixed developer on the first side in addition to the second unfixed image. Fixability is more likely to deteriorate than surface grain, offset increases further, and surface stains worsen.

Furthermore, with the systemization of devices, in addition to the above-mentioned multiple compositing function, a multicolor function has been added in which, for example, a red copy is added to the conventional black copy to form an image in two or more colors. In this case, two or more developing devices are installed in the device, and the adhesion (offset) characteristics to the circumferential surface of the fixing roller are often different. Contains a non-Mag type developer (Mag type developer contains iron components, so it is difficult to produce bright colors and is not suitable as a color developer.) contains a mag-type developer that produces black color.The particle size of the red and black developers is almost the same, so the red developer has less iron than the black developer. It is easily charged and causes more charging offset to the fixing roller than black mag-based developer.Therefore, when producing an image in red, this charging offset is more likely to occur (in addition, when creating multiple images in conjunction with black) In this case, the offset described earlier is also added, and the degree of the offset is inconvenient.

As described above, the adhesion (offset) characteristics to the circumferential surface of the fixing roller are different, and when a developer with poor adhesion characteristics is used, offset tends to increase.

In addition, in order to improve the above-mentioned disadvantages in conventional embodiments, measures have been taken such as increasing the web feeding speed to improve the developer collection ability and preventing offset. To shorten the lifespan and the lifespan of the web,
Therefore, a long web is required, which has the drawback of increasing the cost of the web and the running cost.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems caused by the cleaning member being in constant sliding contact with the outer periphery of the fixing roller, and to provide a fixing device in which the fixing roller can be cleaned only when the transfer material performs a fixing action. do.

The present invention provides an image forming apparatus in which the fixing roller can be cleaned only when the developer on the transfer material is likely to be offset to the fixing roller, so that the cleaning member is constantly in sliding contact with the outer periphery of the fixing roller. The purpose is to better (resolve) the above-mentioned problems caused by

"Means and Effects for Solving the Problem" Therefore, according to the present invention, by providing a means for relatively contacting and separating the fixing roller as a rotating body for fixing and the cleaning member, fixing by sliding of the cleaning member is provided. Minimize scraping of the roller surface as much as possible,
In addition, it has made it possible to increase the lifespan of the fixing roller and prevent image (tBq) deviation caused by offset developer adhering to the transfer material.Furthermore, it has become possible to detect the thickness of the transfer material (paper). By providing a detection means for detecting the original density, a means for detecting the density of the document, and a means for detecting the ambient environment temperature, the means for moving the cleaning member toward and away from the cleaning member can be controlled according to these detection signals. This improves the ability of the cleaning member to capture the original and the developer at low temperatures, making it possible to prevent image stains due to offset and extend the life of the fixing roller.

Furthermore, only in the image forming mode where double-sided/multiple functions work, the means for moving the cleaning member toward and away from the fixing roller is controlled to improve the developer collection ability of the cleaning member and prevent image stains due to offset. In addition, it is possible to extend the life of the fixing roller.

Furthermore, when using a developer with poor adhesion (offset) characteristics to the circumferential surface of the fixing roller, specifically, when forming an image in a color other than black, the means for moving the cleaning member toward and away from the fixing roller is controlled. As a result, the ability of the cleaning member to collect the developer can be improved, and it is possible to prevent image staining due to charge offset peculiar to developers of colors other than black, and to extend the life of the fixing roller.

The first aspect of the present invention includes a fixing rotary body for fixing a developer image formed on a transfer material, and a developer offset from the fixing rotary body that is slid onto the circumferential surface of the fixing rotary body. The fixing device includes a cleaning member that comes into contact with and cleans, and a developer cleaning member contact/separation means that brings the cleaning member into contact with and away from the circumferential surface of the fixing rotating body.

A second aspect of the present invention provides a fixing rotary body for fixing a developer image formed on a transfer material and a fixing rotary body in an image forming apparatus that performs image formation, depending on the image forming mode. A cleaning member for cleaning the offset developer by sliding it on the circumferential surface of the fixing rotary body, and a developer cleaning member separating means for bringing the cleaning member into contact with and separating from the circumferential surface of the fixing rotary body. This is an image forming apparatus characterized by having a fixing device and a control section that controls the developer cleaning member separating means according to an image forming mode.

The third aspect of the present invention is a temperature detection means for detecting the environmental temperature, a transfer material thickness detection means for detecting the thickness of the transfer material, an original density detection means for detecting the density of the document, and a single-sided or double-sided image. a double-sided mode detecting means for detecting whether the mode is set, a multi-mode detecting means for detecting that the mode is for forming various images on one side, and a double-sided mode detecting means for detecting that the mode is for forming various images on one side; An image forming apparatus that has at least one detection means among developer detection means for detecting developers having characteristics with different degrees of characteristics, and performs image formation after detecting at least one signal from each of the detection means. The image forming apparatus according to the second invention is characterized in that the image forming apparatus is in a mode.

In a fourth aspect of the present invention, when the temperature detection means detects an environmental temperature or a value lower than a predetermined value, the transfer material thickness detection means detects that the thickness of the transfer material is thicker than a predetermined value. When detected, when the document density detection means detects that the document density is darker than a predetermined value, when the duplex mode detection means detects a double-sided image forming mode, and the multiple mode detection means detects a multiple image formation mode. or when the developer detection means detects a developer whose adhesion is larger than that of the fixing rotor, the developer cleaning member is activated by at least one of these detection signals. The image forming apparatus according to the second invention, further comprising a control section that controls the contact/separation means so as to press the developer cleaning member into contact with the fixing rotating body.

"Embodiment" Next, a first embodiment of the present invention will be described using FIG. 1 of the accompanying drawings. Note that parts common to the conventional device shown in FIG. 8 are designated by the same reference numerals, and explanations thereof will be omitted.

The present invention differs from conventional developer cleaning means (hereinafter referred to as cleaning mechanism).

Above the fixing roller 2, there is a web 5 which is a belt-shaped developer cleaning member that slides on the circumferential surface of the fixing roller 2 and moves in a tangential direction, and a pressurizing means which presses the web 5 against the fixing roller 2. A cleaning mechanism including a sponge-like web roller 6 is provided. The web roller 6 is rotatably supported by the arm 11 via a bearing (not shown) at one end of an arm 11 which is rotatable about a central shaft 10 attached to the frame of the developing device 1. An elongated hole 12 extending in the same direction as the longitudinal direction of the arm 11 is formed at the other end of the arm 11, and the elongated hole 12 is connected to a movable rod 14a of a solenoid 14 via a pin 13. Furthermore, arm 11
One end of a tension coil spring 15 is attached near the elongated hole 12, and the other end of the spring 15 is hooked to a spring hook 16 of a part of the fixing device 1. Therefore, arm 1
1 is always biased clockwise by the force of the spring 15, and normally when the solenoid 14 is deenergized, the first
The web 5 and the web roller 6 are in a state separated from the fixing roller 2, as shown by the two-dot chain line in the figure. When the solenoid 14 is in the energized state, the web 5 is brought into contact with the fixing roller 2 by the web roller 6, as shown by the solid line in FIG.

On the other hand, a gear 17 is fixed to the winding shaft 7.

A drive gear 18 is attached to mesh with this gear 17, and this drive gear 18 is directly connected to the output shaft of a web winding drive motor 19. Therefore, when web take-up drive motor 19 rotates counterclockwise, drive gear 18 rotates in the same direction causing gear 17 to rotate clockwise. As a result, the winding shaft 7 rotates clockwise and winds the web 5 in the direction of arrow B in the figure. Note that the feeding speed of the web 5 is extremely low compared to the circumferential speed of the fixing roller 2.

Next, the timing of the web 5 coming into contact with and separating from the fixing roller 2;
The timing of winding the web 5 will be explained using the time chart shown in FIG. 2.

The case of one copy will be explained. By pressing the copy start button from an operation unit (not shown), the copy start signal is turned on for seven hours as shown in FIG. 2A. Then, as shown in FIG. 2B, the transfer paper is fed, and the unfixed transfer paper on which image formation has been completed is conveyed to a location immediately before entering the fixing device after T1 time. Therefore, the web take-up drive motor 19 is energized and rotated counterclockwise to take up the web 5 and expose a clean web surface free of developer. As shown in the second section C, 13 hours after the web take-up drive motor 19 rotates, the web separating solenoid 14 is energized to bring the web 5 into contact with the fixing roller 2. Time T corresponding to the length of the transfer paper
After 4, the web take-up drive motor 19 and the web separation solenoid 14 are simultaneously deenergized. Here, the time T2 during which the web winding drive motor 19 is rotating is T2.
Same as a + T 4. T2 and T4 are
Varies depending on the length of the transfer paper. For long transfer paper, use T2
and T4 is long, and when using short transfer paper, T2 and T4 are long.
4 will be shorter.

For multiple copies, repeat the above sequence.

By doing this, the transfer paper is brought into pressure contact with the web-shaped fixing roller 2 only when it is passing through the fixing roller 2, making it possible to extend the life of the fixing roller 2 and the web 5. Become.

"Other Embodiments" FIG. 3 shows other embodiments. Common parts with Figure 1 include:
The same reference numerals are used to omit the explanation.

The web roller 6 is rotatably supported by one end of an arm 11 that is rotatable about a central axis 10 . An L1-shaped groove 20 is formed at the other end of one arm 11, and the tip 21a of the cam lever 21 is engaged with the groove 20. The cam lever 21 is connected to a web detachment drive motor 22 which is fixedly installed. Web winding drive motor 19
is fixed to a mounting plate 23, and the mounting plate 23 is fixed to a measuring plate 24 of the fixing device. When the motor 22 rotates in the direction of the solid arrow shown in the figure (counterclockwise when viewed from above), the arm 11 rotates clockwise around the central axis 10 when viewed from the right front in FIG. 3, and the web 5 It is separated from the fixing roller 2 (same as the state shown in the dashed line in FIG. 1). Conversely, the motor 22 moves in the direction of the line of force arrow shown in the figure (when viewed from above,
When the arm 11 rotates clockwise), the arm 11 rotates around the central axis 10.
Rotate counterclockwise when looking from the front of the third stationary center.
The web roller 6 advances toward the fixing roller 2, and the web 5
contacts the fixing roller 2.

Furthermore, by controlling the rotation angle using a step motor for the motor 22, it is also possible to change the width of the web 5 in pressure contact with the fixing roller 2. In other words, it is possible to make the state of pressure contact of the sponge-like web roller 6 variable, and it is also possible to further improve the ability of the web 5 to collect developer. In other words, by increasing the pressure welding, the way the web roller 6 collapses becomes larger (width).
Therefore, the contact area with the fixing roller 2 increases accordingly, and as a result, the developer collecting ability of the web can be improved.

Next, a third embodiment of the present invention is shown in FIGS. 4 to 7 (Fl
This will be explained using up to. This embodiment is an image forming apparatus having the fixing device according to the first embodiment, and the structure of the fixing device is the same as that of the first embodiment, so a description of the fixing device will be omitted.

This embodiment provides an image forming apparatus that is provided with the fixing device described in the first embodiment and various detection means for determining situations where offset is likely to occur, and that reliably prevents offset even under various conditions. It is something.

FIG. 4 is a sectional view of an image forming apparatus to which the present invention is applied. In FIG. 4, a primary charger 10 is placed above a photosensitive drum 100, which is a cylindrical latent image carrier rotating in the direction of arrow J.
1 is disposed, and the surface of the photosensitive drum 100 is uniformly charged.

The surface is exposed by exposure beam 102 to form an electrostatic latent image. The electrostatic latent image is developed as a toner image by one or both of developing devices 103 and 104 sequentially arranged in the rotational direction of the photosensitive drum 100. Since the developing device 103 stores non-magnetic chromatic toner, and the developing device 104 stores magnetic black toner, multicolor copying is possible. As the photosensitive drum 100 rotates, the toner image arrives at a transfer section where a transfer charger 105 is disposed below the photosensitive drum 100.

In the paper feeding section, cassettes C1 and C2 are provided with paper feeding rollers (not shown), respectively, and in the transfer section, cassettes C1 and C2 are provided with paper feeding rollers (not shown).
The transfer material selectively taken out by the paper feed roller C2 advances through a conveyance path 106, and is conveyed in synchronization with the toner image under the control of a pair of registration rollers 107. Then, the toner image is transferred onto the transfer material by the transfer charger 105.

Next, the separation charger 108 disposed in parallel with the transfer charger 105 removes the electric charge applied to the transfer material during transfer, and the transfer material is separated from the photosensitive drum 100 and transferred to the first transfer path 109. Fixing device 1 having the same configuration as the embodiment
At this point, the toner image is fixed and fixed on the transfer material.

When performing single-sided copying in the apparatus of this embodiment as described above, the flapper F1 is set at the position shown by the solid line in FIG. 4, and the transfer material is directly ejected to the outside of the machine in the direction of the arrow.

On the other hand, when performing double-sided or multiple copying, the transfer material coming out of the fixing device 1 is conveyed in the direction of the arrow with the flapper F1 set at the position shown by the two-dot chain line in FIG.

In the case of double-sided copying, the flapper F2 is further set to the position shown by the solid line in FIG. 100 and feed it again to the conveyance path 106. The toner image that has been formed on the photosensitive drum 100 by this time is formed in the same manner as described above, and by the time this transfer material passes through the fixing device 1, the flapper is moved to the position shown by the solid line in FIG. F1
It passes in the direction of the arrow and is ejected from the aircraft.

In addition, when performing multiple copies on one side, after the first copy is completed, the transfer material traveling in the direction of the arrow is moved in the direction of the arrow M with the flapper F2 at the position shown by the two-dot chain line in Fig. 4. It suffices to supply it to the conveyance path 106 and perform the second and subsequent image forming operations in the same manner as described above.

As described above, the apparatus of this embodiment can perform copying in each mode of single-sided copying, double-sided copying, multiplex copying, and multicolor copying. The determination is made by receiving the information by the CPU, which will be described later.

In such an image forming apparatus, a transfer material thickness detection sensor consisting of a light-emitting element 25a and a light-receiving element 25b is provided at an appropriate position on the conveyance path 106, and a temperature detection means is provided at an appropriate position in a sheet feeding portion where a cassette is disposed. A document density detection sensor 27 serving as document density detection means is provided near the temperature sensor 26 and the exposure beam 102 .

Each detection means will be explained below.

FIG. 5(A) shows an example of temperature detection means, and as the temperature sensor 26, an NTC type thermistor sensor or the like whose main component is Mn, Go, Ni, or Fe-based material can be used. This thermistor sensor has a characteristic that the resistance value changes depending on the relative temperature, and the resistance of the element is high when the temperature is low, and low when the temperature is high.

In a detection circuit using an operational amplifier ○Al as shown in FIG.
A signal that represents same as below. ) is Low below a certain temperature.
It is assumed that a signal (a signal representing O'' in a logic circuit; the same applies hereinafter) is output and input to a CPU, which will be described later.

Next, FIG. 5 (Bl shows the above-mentioned transfer material thickness detection means and its detection circuit).

As shown in FIG. 4, the detection means is disposed at a suitable position on the conveyance path 106, and includes a light source 25a which is a light emitting element, and a light receiving element 25b which is a CdS element.
or C2).

Therefore, depending on the thickness of the transfer material C, the amount of light that passes through this and is received by the light receiving element 25b changes.
In the case of , the amount of light received is small, so the resistance of the CdS element becomes large, and in the case of thin transfer material C, the amount of light received is large and the resistance value of the CdS element decreases, and in the former case, the operational amplifier If the Low signal from OA2 is the latter, it becomes Hi.
Each of the gh signals is input to a CPLI, which will be described later.

Further, as the document density detection means, a manual density setting device, which is provided in the image forming apparatus of this embodiment and which manually sets the density of a copy image to an arbitrary density, is used. In this embodiment, the amount of exposure to the photosensitive drum 100 is controlled based on the signal from the document density detection means, and the density of the copied image is automatically adjusted to an appropriate density.

That is, the document is irradiated with an exposure lamp (not shown) for document irradiation, the amount of light reflected from the document is detected by the document density detection sensor 27 to measure the density of the document, and based on this measurement result, the document is sent to the photosensitive drum 100. Automatic exposure (AE) control is performed to control the exposure amount.

The original density detection sensor 27 serving as the original density detection means is C
dS, and the amount of reflected light changes depending on the density of the original. If the original density is high, for example, the original density is 0.
．． In the case of 3 (gray), the amount of light received is small, so the resistance of the CdS element is large. Also, when the density of the original is low, for example, when the original density is 0.07 (standard white board), the amount of light received is large, so the CdS element is The resistance of the element becomes small. Therefore, the fifth
In the former case, in the detection circuit using the operational amplifier OA3 as shown in Figure (C), the L from the operational amplifier OA3 is
Either the OW signal or, in the latter case, the High signal, is input to the CPU, which will be described later.

FIG. 6 shows a block diagram of the entire control section.

Each of the detection means described above is connected to a CPU 505, and the CPU 505 controls the web separation solenoid 14 based on the signals from each detection means to move the web 5 toward and away from the fixing roller 2. The temperature detection sensor 26 also connects to the paper thickness detection sensors 25a and 2 via the detection circuit 500.
5b is connected to the CPU 505 via a detection circuit 501, and the document density detection sensor 27 is connected to the CPU 505 via a detection circuit 502. A signal is transmitted from the CPU 505 to the web separation solenoid 14 via the drive circuit 503, and the web separation solenoid 14 is driven.

Further, the CPU 505 is also connected to a panel control device (not shown) of the main body of the image forming apparatus, and determines whether the mode is one-sided, double-sided, multiplex, or multicolor.

Next, regarding each image forming mode of 11) to 1B), using the flowchart, the web 5 corresponding to the signal of each detection means is
The sequence for adjusting the timing of pressure contact with the fixing roller 2 will be explained.

A case where the separation and contact of the web 5 is controlled by signals from the fli paper thickness detection sensors 25a and 25b.

As shown in FIG. 7 (Al), first, it is checked whether the copy key on the panel of the image forming apparatus has been pressed (step 1a). When the copy key is pressed, the paper feed roller is rotated and paper feeding starts. (Step 2a).As shown in FIG. 4, before the transfer material is sent and reaches the pair of registration rollers 107, the transfer material passes through the positions of the paper thickness detection sensors 25a and 25b, so the paper thickness is determined at that position. (Step 3a). There, it is determined whether the signal from the paper thickness detection sensor is a Low signal or not. If it is a Low signal, it is determined that the paper is thick paper, and the web separation solenoid 14 is turned on.
The web 5 is brought into pressure contact with the surface of the fixing roller 2 by the web separating means. Therefore, collection of developer is started to prevent offset from occurring when cardboard is used (step 4a). If the paper thickness detection sensor 25a.

25b or a High signal, it is determined that the paper is thin and the web separation solenoid 14 is not activated (O
FF state), image formation is performed while the web 5 remains separated from the surface of the fixing roller 2 (step 5a).
).

(2) A case where the contact and separation of the web 5 is controlled by the signal from the temperature sensor 26.

As shown in FIG. 7fB), first, it is checked whether the copy key on the panel has been pressed (step lb). When the copy key is pressed, the signal from the temperature sensor 26 is sent to the CPU.
505, where the surrounding environment temperature is checked (step 2bl).

First, it is determined whether the signal from the temperature sensor is a Low signal or not. If the signal is low, it is determined that the temperature is low,
The web separating solenoid 14 is turned on, and the web 5 is brought into pressure contact with the surface of the fixing roller 2 by the web separating means.

Therefore, developer collection is started to prevent offset from occurring in a low temperature environment (step 3b). If the signal from the temperature sensor 26 is a High signal, it is determined that the temperature is high, and the web separation solenoid 14 is not activated (remains in the OFF state), and the web 5 is separated from the surface of the fixing roller 2. Paper feeding starts (step 4).
b). Image formation is then performed (step 5b).

(3) A case where the contact and separation of the web 5 is controlled by the signal from the document density detection sensor 27.

As shown in FIG. 7fcl, first, it is checked whether the copy key on the panel has been pressed (step lc). When the copy key is pressed, a signal from the document density detection sensor 27 is input to the CPU 505, and the document density is checked there (step 2c). First, it is determined whether the signal from the document density detection sensor 27 is a Low signal. If the signal is Low, it is determined that the document density is high, the web separation solenoid 14 is turned ON, and the web separation means
is pressed against the surface of the fixing roller 2. Therefore, collection of developer is started, and offset is prevented from occurring even if the original density is high (step 3c). If the signal from the document density detection sensor 27 is the old gh signal, it is determined that the document density is low, and the web solenoid 14 is not activated (OFF).
sheet feeding is started while the web 5 remains separated from the surface of the fixing roller 2 (step 4c). Then, image formation is performed (step 5c).

(4) When controlling the separation of the web by convenient mode (double-sided copy, multiple copy, single-sided copy).

As shown in FIG. 7 FD+, first, it is checked whether the copy key on the panel has been pressed (step ld). When the copy key is pressed, the mode of use is determined, and whether it is duplex mode or multiple mode is checked (step 2d).

If the double-sided mode or multiplex mode is used, the occurrence of offset increases, so the web separation solenoid 14 is turned on, and the web 5 is brought into pressure contact with the surface of the fixing roller 2 by the web separation means. Therefore, developer collection is started to prevent offset from occurring even in double-sided copying or multiple copying (step 3d). If it is in the single-sided mode, the web separation solenoid 14 is not activated (remains in the OFF state) because there is less offset, and paper feeding is started with the web 5 separated from the surface of the fixing roller 2. (Step 4d).

Then, image formation is performed (step 5dl).

(5) When controlling web separation using color mode (chromatic copy, achromatic copy).

As shown in FIG. 7 fEl, first, it is checked whether the copy key on the panel has been pressed (step le). When the copy key is pressed, the color mode is determined and it is checked whether it is a chromatic copy or an achromatic copy, that is, a black copy (step 2e). If the chromatic color copy mode is selected, that is, if the developing device 103 containing a non-magnetic (non-mag) chromatic developer shown in FIG.
Since offset occurs more frequently than with the black developer, the web separation solenoid 14 is turned on, and the web 5 is brought into pressure contact with the surface of the fixing roller 2 by the web separation means.

Therefore, collection of developer is started, and occurrence of offset is prevented even in chromatic copies (step 3).
e). If in the black copy mode, that is, if the black developing device 104 containing the magnetic developer shown in FIG.
When selected, the web separating solenoid 14 is not activated because offset occurs less than when using a chromatic color.
Paper feeding is started with the web 5 kept separated from the surface of the fixing roller 2 (step 4el), and image formation is performed (step 5el).

(6) Paper thickness, temperature, original density, duplex, multiple mode,
At least one signal in the color mode causes the web 5 to
If you want to control the disjunction of .

As shown in Figure 7 (Fl), first check whether the panel copy key is pressed (step if)
When the copy key is pressed, first, a signal from the temperature sensor 26 is input to the CPU 505. Then, check the environmental temperature (step 2f). The signal from the temperature sensor is Lo
Determine whether it is a w signal or not. If the signal is Low, it is determined that the temperature is low, and the web separating solenoid 14 is turned on to press the web 5 against the surface of the fixing roller 2 by the web separating means. Therefore, developer collection is started to prevent offset from occurring (step 3f).

If the temperature sensor signal is a High signal, then the signal from the document density detection sensor 27 is input to the CPU 505 . Then, the original density is checked (step 4f). It is determined whether the signal from the document density detection sensor is a Low signal. If the signal is Low, it is determined that the document density is high, and the process proceeds to step 3f described earlier. If the signal is High, then determine the usage mode (step 5f)
. It is determined whether the usage mode is double-sided or multiplex mode, and if it is double-sided or multiplex mode, the process proceeds to step 3f described above. If NO, the color mode is determined. Then, the color mode is checked (step 6f).

Therefore, if the color mode is selected, the process proceeds to step 3f described earlier. If No, that is, the mode is black copy, paper feeding is started (step 7f), and as shown in FIG. The transfer material passes through the position. Then, the paper thickness is checked (step 8f). It is determined whether the signal from the paper thickness detection sensor is a Low signal or not. If L
If it is an OW signal, it is determined that the paper is cardboard, the web separation solenoid 14 is turned on, and the web 5 is brought into pressure contact with the surface of the fixing roller 2 by the web separation means. Therefore, collection of developer is started, and occurrence of offset is prevented (step 9f). Then, the process advances to step llf, which will be described later. If the signal is High, it is determined that the paper is thin,
Image formation is performed while the web 5 remains separated from the surface of the fixing roller 2 without operating the web separation solenoid 14 (remains in the OFF state) (step 11f).

If at least one of the following conditions is met: low temperature environment, dark original, double-sided or multiple mode, color mode, the process proceeds to step 3f described above, and then paper feeding starts (
Step 10f), and then image formation is performed (step 11f). Furthermore, when operating the web separation solenoid 14 in duplex mode or multi-mode mode, it is also effective to operate the web separation solenoid 14 only during duplex or second copying.

Further, if the fixing device of the second embodiment shown in FIG. 3 is applied, it is also possible to continuously change the pressure applied to the web roller 6 by changing the rotation angle of the step motor 22. That is, analog signals such as paper thickness, temperature, and document density are A/D converted and input to the CPU, so that when the web 5 is in contact with the surface of the fixing roller 2, the optimum conditions are achieved. The pressing force of the web roller 6 may be continuously controlled. That is, by controlling the angle, the pressing force can be controlled and the nip width can be controlled by the position of the cam lever 21 in FIG. 3.

Note that the present invention is not limited to an image forming apparatus having a paper thickness detection sensor, a temperature sensor, a document density detection sensor, a duplex and multiple copy mechanism, or a multicolor copy mechanism; The present invention is also applied to an image forming apparatus having one.

[Effects of the Invention] As described above, a cleaning member that comes into sliding contact with the fixing rotor is used, a developer cleaning member separating means is provided for separating the cleaning member from the surface of the fixing rotor, and the transfer material is removed. The developer cleaning member separating means is controlled so that the cleaning member is brought into pressure contact with the fixing rotating body when the developer enters the fixing device, and the cleaning member is separated from the fixing rotating body when the transfer material passes through the fixing device. As a result, unnecessary wear of the surface layer of the fixing rotor can be prevented, and the life of the fixing rotor can be extended, and furthermore, the life of the cleaning member can be extended.

Therefore, it is possible to reduce running costs and simplify maintenance work. Furthermore, before the cleaning member is brought into pressure contact with the fixing rotor, the cleaning member can be sent to expose a clean surface free of developer, and then brought into pressure contact with the fixing rotor, so the cleaning member can be used for development. The agent collection ability is further improved, and the cleaning ability can be effectively demonstrated.

Further, in an image forming apparatus that is provided with a transfer material thickness detection means, a temperature detection means, and an original density detection means and has a double-sided/multiple copying mechanism and a multicolor copying mechanism, a developer cleaning member that slides into contact with a cleaning mechanism of a fixing device. is provided with a developer cleaning member separating means, and when at least one of the following conditions is satisfied: thick transfer material, low temperature, dark original, double-sided or multi-mode, color mode, the cleaning member separating means is controlled and cleaning is performed. By bringing the member into pressure contact with the surface of the fixing rotary body, the cleaning member starts collecting the developer, thereby providing a clean image free from dirt on the front surface and dirt on the back surface of the transfer material.

Furthermore, since the life of the cleaning member is extended, it is possible to reduce costs and simplify maintenance work.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of the first embodiment of the present invention, and FIG.
3 is a perspective view of the second embodiment of the present invention, FIG. 4 is a vertical sectional view showing a schematic configuration of the third embodiment of the present invention, and FIG. 5 is a time chart of the embodiment shown in FIG. , (C
1 is a detection circuit diagram of each detection means of the device shown in FIG. 4, FIG. 6 is a block diagram of a control device for the web separation means used in the device shown in FIG. 4, and FIG. iD
), +E), (F) is a flowchart showing the flow of operation of the apparatus shown in FIG. 4, and FIG. 8 is a longitudinal sectional view of the conventional example. 2.Fixing roller 3.Pressure roller 5.Web
6...Web roller 11...Arm 14...Web contact/separation solenoid 21...Cam lever 22...Web contact/separation drive motor 25a, 25b...Paper thickness detection sensor
26...Temperature sensor 27...Document density detection sensor 5
05...Control unit (CPU). Figure 1 Figure 21! ! TART 3rjA Ditch diagram Ditch diagram (D) Diagram (E)

Claims (1)

[Scope of Claims] 1. A fixing rotary body for fixing a developer image formed on a transfer material, and a developer offset from the fixing rotary body slidingly brought into contact with the circumferential surface of the fixing rotary body. A fixing device comprising: a cleaning member that cleans the fixing member; and developer cleaning member contact/separation means for bringing the cleaning member into contact with and away from the circumferential surface of the fixing rotating body. 2. In an image forming apparatus that performs image formation, depending on the image forming mode, a fixing rotary body for fixing a developer image formed on a transfer material and a developer offset to the fixing rotary body are attached to the fixing rotary body. A fixing device comprising a cleaning member that comes into sliding contact with and cleans the circumferential surface of a fixing rotary body, and a developer cleaning member separating means that makes the cleaning member come into contact with and separate from the circumferential surface of the fixing rotary body, and an image forming apparatus. An image forming apparatus comprising: a control section that controls the developer cleaning member separating means according to a mode. 3. Temperature detection means for detecting the environmental temperature, transfer material thickness detection means for detecting the thickness of the transfer material, document density detection means for detecting the document density, and detecting whether the image mode is single-sided or double-sided. a double-sided mode detection means for detecting a mode in which various types of images are formed on one side; and a multi-mode detection means for detecting a mode in which various types of images are formed on one side; It is characterized in that it has at least one detection means among developer detection means for detecting developer, and is in an image forming mode in which image formation is performed after detecting at least one signal of each of the detection means. The image forming apparatus according to claim 2. 4. The control unit controls the document density when the temperature detection means detects that the environmental temperature is lower than a predetermined value, and when the transfer material thickness detection means detects that the thickness of the transfer material is thicker than a predetermined value. When the detection means detects that the document density is darker than a predetermined value,
When the duplex mode detection means detects a double-sided image forming mode, when the multiplexed mode detecting means detects a multiplexed image forming mode, or when the developer detecting means detects adhesion to the circumferential surface of the fixing rotor. When the developer with a large degree of adhesion is detected, at least one of these detection signals controls the developer cleaning member separating means to press the developer cleaning member into contact with the fixing rotating body. The image forming apparatus according to claim 2, further comprising a control section for controlling the image forming apparatus.