JP3907407B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a laser printer, a copying machine, and a facsimile using an electrophotographic process , and a fixing device provided in the image forming apparatus .
[0002]
[Prior art]
As shown in FIG. 5, this type of fixing device 14a has a fixing roller 16 and a pressure roller 17 that presses and rotates with the fixing roller 16. The fixing roller 16 has a cleaning roller having cleaning and oil application functions. 40a is rotatably contacted. In recent years, in order to reduce the power consumption of the fixing device used in the image forming apparatus due to energy saving, low-melting-point toner has been used as the toner to be used, and such a fixing device 14a. Then, fixing conditions are changed depending on the type of paper used (plain paper, trepe paper). In other words, when using plain paper, the fixing operation is performed under fixing conditions that match the low-melting toner used, but when using Trepe paper, the amount of heat supplied to prevent ripple-like wrinkles that occur when fixing paper is passed. The fixing conditions have been changed, such as increasing the number. Here, in the case of a low melting point toner, hot offset may occur under the fixing conditions in which the amount of heat is increased as described above. Therefore, as shown in FIG. Further, a cleaning roller 40a for cleaning paper dust is brought into contact with the fixing roller 16 to prevent hot offset.
[0003]
However, the following problems occur when the cleaning roller 40a remains in contact with the fixing roller. That is, if the cleaning roller 40a is not very dirty, there is no problem in cleaning performance. However, if the contamination becomes severe, oil that has oozed out from the cleaning roller 40a during the standby time adheres to the pressure roller 17 from the fixing roller 16. There is a fear. Here, dirt and oil adhering to the fixing roller 16 are removed again by the cleaning roller 40a. However, when dirt and oil adhering to the pressure roller 17 are not provided on the pressure roller 17 side, The dirt and oil may adhere to the back side of the passed paper. In order to prevent such backside soiling of the paper, for example, in Japanese Patent Laid-Open No. 5-88579, the cleaning roller is configured to be able to come into contact with and separate from the fixing roller, and the above-mentioned fixing roller is only in contact with the fixing roller. A technique for pressing the cleaning roller is disclosed.
[0004]
[Problems to be solved by the invention]
However, the fixing device described above has the following problems. That is, as shown in FIGS. 5 and 6, in the fixing device 14a, a small amount of silicon oil that has oozed out from the cleaning roller 40a and the scraped offset toner are re-transferred to the surface of the fixing roller 16 at the X portion during the fixing standby. Thus, the retransferred toner and the exuding oil adhere to the surface of the pressure roller 17 at the nip portion (Y portion) of the pressure roller 17 when the fixing roller 16 rotates. In the case of this conventional example, since no cleaning means is disposed on the pressure roller 17 side, the oil or toner adhering to the paper will clean the paper. Cause. Further, conventionally, when a fixing jam occurs, the pressure of the pressure roller 17 is released, the pressure roller 17 is moved away from the fixing roller 16, and when the jammed paper is removed, the pressure of the pressure roller 17 is increased. The pressure roller 17 was in contact with the fixing roller 16 at a predetermined pressure. Therefore, unfixed toner from jammed paper adheres to the fixing roller 16, and the toner adheres to the pressure roller 17 at the fixing nip, and the pressure roller 17 is applied to the back surface of the first sheet after the jammed paper is removed. There is a problem that the toner adhering to the toner adheres again.
[0005]
Further, in the conventional fixing device, when a fixing jam occurs, the pressure applied by the pressure roller 17 is reduced so that the jam paper is removed from the fixing roller 16 so as to be improved. However, unfixed toner may adhere to the fixing roller 16 when removing jammed paper. In the conventional case, when the jam processing is completed and the cover of the machine is closed, when the jam detection sensor or the like confirms that there is no jammed paper, the pressurizing force of the pressure roller 17 is set to a predetermined value at the time of fixing. The pressure was restored. However, at this time, there is a problem that unfixed toner adheres to the pressure roller 17 side, and the dirt is attached to the back surface of the first sheet after the jam processing.
[0006]
The cleaning roller 40a is provided with a one-way clutch for preventing the cleaning roller 40a from being driven to rotate in the same direction as the fixing roller 16 in order to improve the cleaning performance. For this reason, the cleaning surface of the cleaning roller 40a that is in contact with the fixing roller 16 is always the same surface, and the contamination of that portion is accelerated, resulting in a problem that the cleaning performance is deteriorated.
[0007]
During the fixing standby, the dirt or oil exuding from the cleaning roller 40a is retransferred from the cleaning roller 40a to the fixing roller 16 in contact with the cleaning roller 40a, and the dirt or oil is pressed from the fixing roller 16. Transfer to the roller 17 may occur. For this reason, conventionally, before the start of the fixing driving (rotation driving in the paper conveyance direction), the fixing roller 16 is rotated in the reverse direction (within a range not reaching the contact position of the pressure roller 17 from the cleaning roller 40a contact position). The oil or dirt that has oozed out to the fixing roller 16 is once cleaned. Then, at the time of the reverse rotation, the cleaning roller 40a is rotated, and the surface in contact with the fixing roller 16 is changed. However, in the conventional fixing device, the pressure roller 17 at the time of reverse rotation presses and rotates with the fixing roller 16, so that the pressure roller 17 also rotates at the time of reverse rotation. As a result, the durability of the thermistor serving as the temperature detecting means in contact with the pressure roller 17 is significantly reduced.
[0008]
With respect to this, a problem with the thermistor 50 when the pressure roller 17 rotates reversely will be described with reference to FIG. That is, the surface of the fixing roller 16 is made of a heat-resistant release layer such as PFA or PTFE, and the surface of the pressure roller 17 is made of silicon rubber. One end of the thermistor 50 is fixed to the fixing unit frame, and the other end is pressed against the surface of the pressure roller 17 by the elastic force of the leaf spring 51. Since a small amount of oil is supplied from the cleaning roller 40a to the fixing roller 16 and the pressure roller 17, the pressure roller 17 and the contact portion of the thermistor 50 that is in contact with the pressure roller 17 Frictional resistance is relatively low. However, since a small amount of oil supplied from the cleaning roller 40a almost adheres to the paper during the passage of paper to the fixing device, the pressure is applied to the thermistor 50 that is in contact with the pressure roller 17 due to insufficient oil. The frictional resistance with the roller 17 is very high compared to the fixing roller 16 side. Here, in the normal rotation direction during fixing, when the contact resistance between the thermistor 50 and the pressure roller 17 is high, it is attached so that the pressing force escapes so that the contact pressure of the thermistor 50 does not increase. Yes. However, when the pressure roller 17 rotates in the reverse direction, the thermistor 50 may bite into the pressure roller 17 and deform the thermal foam rubber 53 provided at the tip of the thermistor 50. The temperature detecting element used in the thermistor 50 is disposed inside the heat-resistant foamed rubber 53. Due to the deformation of the rubber, the thin electric wire (jimet wire 52) connecting the temperature detecting element is stressed. This may cause disconnection, or cause the surface of the pressure roller 17 to be damaged by the biting of the thermistor 50.
[0009]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the problems of the conventional fixing device as described above, and to prevent the pressure roller from being soiled, thereby preventing oil and toner stains from adhering to the paper. In addition, the present invention provides a fixing device and an image forming apparatus that can prevent the occurrence of stains on the back of the paper after the jam processing.
[0010]
[Means for Solving the Problems]
To achieve the above object, the present invention includes a fixing roller for fixing an unfixed toner image, pressed against the peripheral surface of the fixing roller to clean toner, paper dust or the like adhering to the circumferential surface of the fixing roller cleaning an oil application roller for applying the oil to the roller or the fixing roller, the fixing roller opposite to and a fixing roller and a detachably arranged the pressure roller, the axis end of the cleaning roller or the oil application roller part way clutch is provided, the cleaning roller or the oil coating roller to the reverse rotation of the fixing roller is configured to rotate together with the fixing roller, is biased in a direction away said pressure roller from the fixing roller An urging means, a pressure mechanism that presses the pressure roller against the fixing roller against the urging force of the urging means, and a contact surface of the pressure roller. In the fixing device and the temperature sensing means is provided for, the pressure mechanism includes a stepping motor, a feed screw rotated by the driving force of the motor, the anchor moves horizontally in accordance with the feed amount of the screw, The anchor has one end connected to swing around the fulcrum as the anchor moves horizontally, and a link connected to the other end of the link that swings around the fulcrum as the link swings. During the reverse rotation of the fixing roller, the lever of the pressure mechanism swings away from the fixing roller, so that the urging force of the urging means wins and the pressure roller and the fixing roller are separated from each other. It is characterized by. A second aspect of the present invention is an image forming apparatus including the fixing device according to the first aspect.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of an image forming apparatus A to which the present invention is applied. That is, the apparatus main body is provided with paper feed means 4 and 4 having a plurality of paper feed cassettes 2 and paper feed rollers 3, and the paper 5 fed by each of the paper feed means 4 and 4 is stored in registration rollers 6. The photosensitive member 7 is conveyed to the rotationally driven photosensitive member 7 at a timing, and the surface of the photosensitive member 7 is uniformly charged by the charging charger 8 when the photosensitive member 7 is rotationally driven. On the other hand, the scanner unit 9 reads the reflected light of the original from the exposure lamp, and the read data is subjected to image processing and transmitted to the laser optical system. The laser optical system then irradiates the charged photoconductor 7 with laser light to form an electrostatic latent image. The electrostatic latent image is visualized by a developer (toner) when passing through the developing device 12, and the visible image is transferred to the paper 5 transported to the photoreceptor 7, and the paper 5 is transported to the transport belt 13. Is conveyed to the fixing device 14.
[0012]
As shown in FIG. 2, the fixing device 14 has a fixing roller 16 and a pressure roller 17 that presses and rotates with the fixing roller 16. The surface of the fixing roller 16 is coated with a heat-resistant release layer such as PFA or PTFE. Inside, a heat source 20 such as a fixing heater is provided. As the heat source 20, a halogen heater, an infrared heater (nichrome wire), or the like is used. The fixing roller 16 is provided with a fixing temperature sensor 21 as a temperature detecting means on the peripheral surface of the fixing roller 16, and the pressing temperature sensor 22 is provided as a temperature detecting means on the peripheral surface of the pressure roller 17. 21. Based on the temperature detection signal from the pressure temperature sensor 22, the energization to the heat source 20 is controlled so that the temperature of the fixing roller 16 and the pressure roller 17 becomes a certain temperature, In order to control the amount of heat supplied, the press mechanism 24 is controlled so that the nip width can be changed. The fixing roller 16 is rotationally driven by a driving mechanism (not shown), and performs a fixing process by applying heat and pressure to the paper 5 while conveying the paper 5 by being in pressure contact with the pressure roller 17. The surface of the pressure roller 17 is composed of a heat-resistant rubber layer such as silicon rubber, and both ends of its shaft are rotatably supported and separated from the fixing roller 16 by an urging means (not shown). It is always urged in the direction to do. On the other hand, the pressure roller 17 is lifted from below the shaft by the pressure mechanism 24 and pressed against the lower portion of the fixing roller 16.
[0013]
In the pressurizing mechanism 24, the stepping motor 25 rotates in the forward direction (A direction), and the gear 28 is driven from the coaxial gear 26 through the idler gear 27. The shaft of the gear 28 is a feed screw 29, and pulls the anchor 30 in the horizontal direction (C direction). A spring 32 is hung on the anchor 30 and one is hung on a link 33. As the anchor 30 moves horizontally, the link 33 rotates about the fulcrum 34. A lever 35 is fitted to one end of the link 33 and rotates around a fulcrum 36 to push up the pressure roller 17 and apply pressure. When the stepping motor 25 is rotated in the reverse direction (B direction), the anchor 30 is pushed back in the horizontal direction (D direction), the lever 35 rotates about the fulcrum 36, and the pressure roller 17 is pulled down to release pressure. At this time, the anchor 30 is provided with a home position detection sensor 31, and an instructed pressure can be applied to the pressure roller 17 by adjusting the movement amount of the anchor 30. The amount of movement of the anchor 30 at this time is such that the pressure of the maximum pressure roller 17 is released and the pressure roller 17 can be moved to a position away from the fixing roller 16. Note that the pressure mechanism 24 configured in this manner is provided at both ends of the pressure roller 17.
[0014]
Reference numeral 40 denotes a cleaning roller. The cleaning roller 40 has a configuration in which a heat-resistant felt 41 impregnated with a small amount of silicon oil is wound around the surface of a metal core. At the time of fixing, paper dust and toner adhering to the surface of the fixing roller 16 are wiped off by the heat-resistant felt 41 in a non-rotating state with respect to the peripheral surface of the fixing roller 16. That is, the cleaning roller 40 is attached to one end via a one-way clutch, and the other end is attached to a fixing unit frame (not shown) with a heat-resistant bearing. For this reason, when the fixing roller 16 rotates forward (during fixing), the cleaning roller 40 does not rotate with the fixing roller 16 (in a locked state), and offset toner or paper dust adhering to the surface of the fixing roller 16 Etc. can be cleaned. On the other hand, when the fixing roller 16 rotates in the reverse direction, the cleaning roller 40 is rotated and the contact surface of the cleaning roller 40 that is in contact with the fixing roller 16 can be changed.
[0015]
Here, the feature of the present invention is that the pressure roller 24 is controlled to a position separated from the fixing roller 16 by the pressure mechanism 24 during the standby of the fixing device 14, so that the oil oozed out during the standby or To prevent dirt from adhering to the pressure roller, when the fixing roller starts rotating, the pressure applied to the pressure roller is released and the pressure roller is separated from the fixing roller. The cleaning of the pressure roller is prevented by pressing the pressure roller after being cleaned by the cleaning roller. That is, as shown in FIG. 5, the pressure roller 17 is separated (between L parts) until the silicone oil and the toner that have been transferred and exuded from the cleaning roller 40 waiting during fixing driving pass through the nip part Y part. The pressure roller 17 is controlled to come into pressure contact with the fixing roller 16 after dirt such as adhering oil or toner passes through the Y portion (first embodiment). In this case, the oil and toner adhering to the fixing roller 16 are cleaned again by the cleaning roller 40, and the pressure roller 17 is separated from the pressure roller 17, so that oil and toner stains do not occur. Here, the cleaning unit of this embodiment employs a cleaning roller system, but another cleaning system, for example, a heat-resistant felt pad system that is fixedly pressed against the fixing roller 16 and impregnated with high-viscosity silicon oil. Even when (not shown) is employed, the same effect as in the present embodiment can be expected.
[0016]
FIG. 4 shows a flowchart of a processing procedure according to the present invention (second embodiment). That is, in the present embodiment, after the jam processing is completed, the fixing roller 16 is at least moved after the jam processing so that the unfixed toner adhered to the fixing roller 16 is cleaned by the cleaning roller 40 and then the pressure roller 17 is pressed. By rotating once, the pressure of the pressure roller 17 is increased to a predetermined pressure. In order to prevent the back side of the first sheet after the jam processing from occurring, the fixing roller is rotated before the pressure applied to the pressure roller after the jam processing is returned to a predetermined pressure, and is adhered to the surface of the fixing roller. An object of the present invention is to prevent the occurrence of back-stain after jamming and improve the quality by pressing the pressure roller against the fixing roller after cleaning the toner. The occurrence of a jam is detected by a jam detection element installed in a conveyance path (not shown), and when the jam removal is completed, the cover is opened and closed by a detection means (sensor or switch) that detects opening and closing of the cover of the main body. After that, it is confirmed by the jam detection means that there is no remaining paper, and it is determined that the jam removal is completed. In this case, the first embodiment and the cleaning unit described above are not a cleaning roller system, but another cleaning system, for example, a heat-resistant felt pad system that is fixedly pressed against the fixing roller 16 and impregnated with high-viscosity silicon oil ( Adopting (not shown) has the same effect.
[0017]
Further, the present invention is characterized in that the pressure applied by the pressure roller 17 is released during the reverse rotation of the fixing roller 16 (third embodiment). In this case, the reverse rotation driving of the fixing roller 16 is not transmitted to the pressure roller 17, thereby preventing the pressure roller 17 from rotating reversely. In order to solve this problem, in this embodiment, when the fixing roller is driven in reverse rotation, the pressure of the pressure roller is released so that the pressure roller does not rotate reversely. The cleaning roller used in this embodiment is a system in which a small amount of oil is applied to improve the releasing action between the fixing roller and the toner, the offset is prevented, and the toner offset to the fixing roller is cleaned. is there. In the present embodiment, the configuration of the cleaning roller has been described, but the same effect can be obtained with an oil application roller.
[0020]
【The invention's effect】
The present invention is as described above, and the invention described in claim 1 includes a fixing roller that fixes an unfixed toner image, and a toner that is in pressure contact with the peripheral surface of the fixing roller and adheres to the peripheral surface of the fixing roller, It has an oil coating roller for applying the oil to the cleaning roller or the fixing roller to clean the paper powder, and a pressure roller which is disposed to be fixing roller separable to face the fixing roller, the cleaning roller or the one-way clutch is provided in the axial end portion of the oil application roller, the cleaning roller or the oil coating roller to the reverse rotation of the fixing roller is configured to rotate together with the fixing roller, the pressure roller from the fixing roller An urging means for urging in the separating direction; a pressure mechanism for pressing the pressure roller against the fixing roller against the urging force of the urging means; In the fixing device abutting temperature detecting means is provided on the peripheral surface of the roller, said pressing mechanism includes a stepping motor, a feed screw rotated by the driving force of the motor, depending on the feed amount of the screw An anchor that moves horizontally, a link that has one end connected to the anchor and swings around the fulcrum as the anchor moves horizontally, and a link that is connected to the other end of the link and swings around the fulcrum as the link swings A lever that moves, and when the fixing roller rotates in the reverse direction, the lever of the pressure mechanism swings in a direction away from the fixing roller, so that the biasing force of the biasing means wins and the pressure roller and the fixing roller since the roller is spaced apart, never pressure roller is reversely rotated, for thereby thermistor which is a temperature detecting means can be prevented damage to the damaged or the surface of the pressure roller, resistance There is an effect that it is possible to improve the quality and copy quality. The invention according to claim 2 can achieve the effect in the image forming apparatus.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing an example of a copying machine equipped with a fixing device of the present invention.
FIG. 2 is an overall configuration diagram showing an identification wearing apparatus.
FIG. 3 is a diagram for explaining the first embodiment;
FIG. 4 is a flowchart showing a processing procedure of the embodiment.
FIG. 5 is a diagram illustrating a configuration of a conventional fixing device.
FIG. 6 is a diagram illustrating a conventional fixing device (first example).
FIG. 7 is a diagram illustrating a conventional fixing device (second example).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper feed cassette 3 Paper feed roller 4 Paper feed means 5 Paper 6 Registration roller 7 Photoconductor 8 Charging charger 9 Scanner part
12 Developer
13 Conveyor belt
14 Fixing device
16 Fixing roller
16a Oil application roller
17 Pressure roller
18 Heat source
19 Pressure lever
20 Pressure spring
21 Fixing temperature sensor
22 Pressurized temperature sensor
24 Pressurization mechanism
25 Stepping motor
26 Gear
27 idler gear
29 Lead screw
30 anchor
31 Home position detection sensor
33 links
35 lever
40, 40a Cleaning roller
41 heat resistant felt
50 thermistor

Claims (2)

A fixing roller that fixes an unfixed toner image, and a cleaning roller that presses against the peripheral surface of the fixing roller and cleans toner, paper dust, etc. attached to the peripheral surface of the fixing roller, or an oil application roller that applies oil to the fixing roller When, and a pressure roller which is disposed to be fixing roller separable to face the fixing roller, the one-way clutch is provided in the axial end portion of the cleaning roller or the oil application roller, the fixing roller the cleaning roller or the oil application roller during reverse rotation are configured to rotate together with the fixing roller, and biasing means for biasing in a direction away said pressure roller from the fixing roller, the biasing force of the biasing means It provided a pressure mechanism for pressing the pressure roller in the fixing roller against the abutting temperature detecting means on the peripheral surface of the pressure roller In wearing equipment,
The pressurizing mechanism includes a stepping motor, a feed screw that is rotated by the driving force of the motor, an anchor that horizontally moves in accordance with the feed amount of the screw, and one end of the anchor that is connected to the horizontal movement of the anchor. A link that swings around a fulcrum, and a lever that is connected to the other end of the link and swings around the fulcrum as the link swings;
At the time of reverse rotation of the fixing roller, a lever of the pressure mechanism swings in a direction away from the fixing roller, whereby the urging force of the urging means is won and the pressure roller and the fixing roller are separated from each other. A fixing device. An image forming apparatus comprising the fixing device according to claim 1.

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