JPH11352816A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of executing fixation while always applying appropriate oil on a heating roller. SOLUTION: In this fixing device 33, the pressure roller 46 is held in press contact with the heating roller 45 provided with a halogen heater 52 in a hollow center part, and fixation is performed by inserting the paper sheet 53 therein and transporting. The paper sheet 53 is guided by an approach guide 51, a toner image is fixed thereon by heat and pressure, separated from the heating roller 45 by a separating pawl 47, and ejected outside the device by ejecting roller pair 34. During preliminary rotation of the fixing device 33 at the operation starting time of the device main body 1, the cleaning roller 49 supported by a bottom end of a turning arm 56 supported at the top end by a supporting shaft 55 is turned/driven by a driving mechanism not shown in the figure and brought into contact with the heating roller 45, and then separated when the surface temp. of the heating roller 45 becomes to the temp. allowed to obtain satisfactory fixing property or to the temp. in the vicinity thereof. In such a manner, an oil stain on the first sheet of the OHP paper sheet or the like is prevented from being caused by absorbing the excessive oil at the operation initial stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for optimally applying oil to a heat roller at an early stage of operation.

[0002]

2. Description of the Related Art Conventionally, in most types of color page printers, oil is applied to a heat generating roller of a fixing device in order to improve the releasability between a toner image on paper and a fixing roller. Generally, silicone oil is used for this oil.

FIG. 5A shows an example of such a fixing device. The fixing device 1 shown in FIG. 1A is provided in a large color page printer. In this type of fixing device, a large amount of oil is stored in an oil tank 2. The oil is supplied abundantly from the oil tank 2 to the felt 3. A large amount of oil is applied to the peripheral surface of the heat generating roller 4 via the felt 3. Excess oil is scraped off by a scraping plate 5 and stored in a waste oil tank 6. This oil application prevents the toner image transferred to the sheet 7 from adhering to the peripheral surface of the heat roller 4. The paper 7 is conveyed while being nipped by the heat generating roller 4 and the pressing roller 8 while the toner image is fixed on the paper surface by heat and pressure by the fixing device 1, and is conveyed by the discharge roller pair 9 via the discharge path 10. Is discharged outside the machine.

The use of a large amount of oil as described above can be said to be a preferable configuration which addresses various problems in the printing process such as improvement of the color developing property of the color toner. There is a problem that it is not possible to meet the recent demand for downsizing OA equipment. In addition, there is a problem that the amount of used oil is too large and wasteful economically. Further, problems such as oil spilling from the waste oil tank 6 when the printer of the main body is moved or the like occur. Further, it is necessary to provide a valve and a packing for preventing oil outflow, and there is a problem that the cost is increased.

For this reason, a small color page printer employs a fixing device shown in FIG. Same figure
In the fixing device 11 shown in (b), an oil application roller 13 is pressed against a heating roller 12. This oil application roller 1
Reference numeral 3 is formed by covering a roller-shaped sponge body (or felt body) containing a fixed amount of oil with a Teflon tube or the like having a large number of fine holes on its surface.
The oil inside the roller oozes out from the fine holes on the tube surface and is applied to the peripheral surface of the heat generating roller 12. As a result, all of the problems of the large-sized device are solved.

[0006]

By the way, in the early stage of the operation of the color page printer, a period from when the power is turned on to when the temperature of the heat generating roller rises to a predetermined temperature.
Pre-rotation (idling without actual fixing) is performed. During this time, the oil is continuously applied from the oil applying roller 13 to the heat generating roller 12, so that the oil on the surface of the heat generating roller 12 becomes excessive. Is formed. Such oil stains are not a problem because ordinary office paper (plain paper) is absorbed inside the paper.
In the case of P (projector) paper, the oil stain does not disappear,
There is a problem that shadows are formed in the projected image.

As a solution to this, an oil application roller 1
Although it is considered that the heating roller 12 contacts the oil application roller 13 containing oil after the temperature of the heating roller 12 becomes high, thermal damage to the sponge body (or felt body) may occur. This causes a problem that the service life of the oil application roller 13 is shortened, which is not preferable.

In addition, the oil is rapidly applied at the moment when the oil application roller 13 comes into contact with the heat roller 12, so that the amount of oil at the contact portion between the heat roller 12 and the paper 14 is appropriately controlled. There was also a problem that it could not be done.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional circumstances,
An object of the present invention is to provide a fixing device that performs fixing while always applying appropriate oil to a heat generating roller.

[0010]

The construction of the fixing device of the present invention will be described below. The fixing device of the present invention has a conveyance unit that conveys a sheet carrying an unfixed toner image, and has a heat source, inherits the sheet conveyed by the conveyance unit, and rotates while applying heat and pressure to the sheet. In a fixing device having a pair of heat fixing rollers for nipping and conveying, and an oil applying member pressed against the heat fixing roller to supply releasable oil to the heat fixing roller, the surface temperature of the heat fixing roller is Heat source control means for controlling the heat source to be turned on and off so as to maintain a temperature suitable for fixing an unfixed toner image; and rotating the heat fixing roller until at least a temperature suitable for the fixing after the heat source is turned on. A roller rotation control means for controlling the heat fixing roller, and a roller rotation control means for controlling the rotation of the heat fixing roller at a position downstream of the oil applying member in a rotational direction of the heat fixing roller and in front of a holding portion of the heat fixing roller. An oil application adjusting member that adjusts an amount of oil applied on the heat fixing roller by absorbing a part of the oil applied by the oil applying member at the time of contact, and a surface temperature of the heat fixing roller that is suitable for the fixing. When the predetermined temperature is lower than the above, the oil application adjusting member is pressed against the heat fixing roller, and when the surface temperature of the heat fixing roller exceeds the predetermined temperature, the oil application adjusting member is moved from the heat fixing roller. And an oil application adjusting member operation control means for separating the oil application adjusting member.

The oil applying member is constituted by an elastic roller, for example. Further, the oil application adjusting member operation control means comprises, for example, a bimetal as described in claim 3, and comprises, for example, a temperature sensor and a solenoid as described in claim 4.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a fixing device according to an embodiment and a configuration in the vicinity thereof.
FIG. 2 is a side sectional view illustrating a configuration of an image forming apparatus including the fixing device. First, the overall configuration will be described. The image forming apparatus 1 shown in FIG. 2 is a tandem type full color printer. The full-color printer 1 has an upper lid 3 on the upper surface of a main body housing 2, and a paper cassette 4 that is detachable from the front (right side in the figure) at the lower part. A large number of sheets are placed and stored in the sheet cassette 4.

An open / close sheet feed tray 5 is provided on the front surface of the main body housing 2, and a power switch (not shown), a liquid crystal display device, a plurality of input keys and the like are arranged on the front upper surface 6, and the rear side. The upper cover 3 is provided so as to cover almost the entire surface. The upper cover 3 is provided with a paper discharge stopper 7 at the front part, and a rear part is provided with an upper paper discharge tray 8 together with a rear upper surface of the main body housing 2.
, And open and close vertically with the hinge 9 as a fulcrum.

A transport belt 11 formed in a flat loop shape in the front and rear direction is disposed substantially in the center of the main body 2 in a horizontal plane. The transport belt 11 is stretched between a driving roller 12 and a driven roller 13,
And circulates counterclockwise as indicated by arrow A in the figure. Above the conveyor belt 11, four image forming and transferring sections 14 (14a, 14b, 14c, 14d) are arranged in a multistage manner along the sheet conveying direction of the conveyor belt 11 (from right to left in the drawing). I have.

These image forming / transferring sections 14 (hereinafter, only the image forming / transferring sections 14a are numbered and shown) surround the photosensitive drum 15 and the peripheral surface of the photosensitive drum 15 in a clockwise direction. Then, cleaner 16, initialization charger 1
7, an exposure head 18, a developing device 19, a developing roller 21, and various devices such as a transfer brush 22 are arranged with the transport belt 11 interposed therebetween.

The four photosensitive drums 15 are arranged in contact with the upper circulating portion (paper transport surface) of the transport belt 11, respectively. In addition, magenta, cyan,
Yellow and black color toners are stored respectively. Further, the four exposure heads 18 are supported on the back surface of the upper lid 3 via the support member 23, and move up and down in an arc-shaped trajectory as the upper lid 3 opens and closes. As a result, the photosensitive drum 15 is arranged to face the photosensitive drum 15.

A standby roller pair 24 and a paper feed sensor 25 are disposed on the upstream side (right side in the drawing) of the transport belt 11 in the paper transport direction. Are provided with a paper feed roller 26, a separating member 27, and the above-mentioned open / close paper feed tray 5. Further, a feed path 28 composed of two guide plates is formed below, and its upstream (lower) side.
A transport roller pair 29 is disposed at the end, and the paper feed end of the paper cassette 4 described above is located below the transport roller pair 29. Above the paper feed end of the paper feed cassette 4, a paper feed roller 31 having a half-moon cross section is disposed.

On the other hand, a paper separating claw 32 is disposed on the downstream side of the transport belt 11 in the paper transport direction in contact with the end thereof, and a fixing device 33 which will be described in detail later is disposed downstream thereof. A discharge roller pair 34 is provided downstream of the fixing device 33, and a switching flap 35 is provided downstream thereof.

Downstream from the switching flap 35, a paper discharge path 36 is formed in the upward direction and is inverted from top to front.
At the end of 6, an upper discharge port including a discharge roller 37 and a discharge roller 38 is formed above a rear portion of the upper discharge tray 8.
Further, a rear opening / closing tray 39 is disposed in a lateral direction downstream of the switching flap 35. This rear opening / closing tray 39
FIG. 1 shows a closed state, and FIG. 2 shows an open state.

A cleaning blade 41 and a cleaner bottle 42 supporting the cleaning blade 41 are provided between the conveyor belt 11 and the paper cassette 4 at the front thereof in contact with the lower circulation portion of the conveyor belt 11. Has been established. An electrical unit 43 to which a predetermined number of circuit boards can be mounted is disposed behind the cleaner bottle 42. A control device including a plurality of electronic components is mounted on a circuit board provided in the electrical component unit 43.

The above-mentioned control device comprises a controller unit and an engine unit (not shown). The controller unit includes a CPU (central processing unit), a ROM (read only memory), an EEPROM (rewritable read memory), a frame memory, an image data transfer circuit, and the like, and print data input from a host computer or the like. Is analyzed, and print data is created and transferred to the engine unit.

The engine unit includes a CPU, a ROM, and the like.
On the input side, data and command signals from the controller unit, the output of the temperature sensor, the output of the paper detection sensor, etc. are input. On the output side, a motor driver that drives a motor (not shown), and the drive of the motor is transmitted to each unit. Such as a clutch driver for switching a driving system to be driven, a print driver for driving the exposure head 18 based on the print data, a bias power supply driver for supplying a predetermined bias current to the initialization charger 17, the developing roller 21, the transfer brush 22, and the like. Is connected.
The engine unit receives data and command signals from the controller unit,
Each unit is drive-controlled based on the output of the temperature sensor, the output of the paper detection sensor, and the like.

Next, the basic operation of the image forming apparatus (apparatus main body) 1 having the above configuration will be described with reference to FIG. 2 again.
First, power is turned on to the apparatus main body 1 and printing (printing) is started when the number of sheets to be used, a print mode, and other designations are input as a key input or a signal from a connected host device.

First, the paper feed roller 31 makes one rotation to take out one sheet of the topmost sheet stored in the paper cassette 4,
The sheet is fed to the standby roller pair 24 via the conveying roller pair 29 and the feeding path 28. Alternatively, the paper feed roller 26 is
The uppermost one of the sheets placed on the open / close sheet feed tray 5 is fed to the standby roller pair 24 in cooperation with the above. Paper feed sensor 25
Detects the leading edge of the fed sheet and confirms that the paper has been fed normally, and detects the trailing edge of the conveyed sheet to confirm the size of the sheet.

The standby roller pair 24 temporarily stops rotating,
The advance of the sheet is stopped by abutting the leading end of the sheet against the holding portion, the skew of the sheet is corrected, and the transfer timing is waited. The drive roller 12 rotates counterclockwise to start the circulating movement of the transport belt 11. Each image forming unit 14 is sequentially driven in accordance with the printing timing, and the photosensitive drum 15 rotates clockwise.

The initialization charger 17 applies a uniform high negative charge while sliding on the peripheral surface of the photosensitive drum 15 to initialize the photosensitive drum 15. The exposure head 18 is arranged opposite to the photosensitive drum 15 while keeping a predetermined distance.
Exposure according to the image signal is performed on the peripheral surface of the photosensitive drum 15 to form an electrostatic latent image including a high negative potential portion by initialization and a low negative potential portion by the exposure. Developing roller 2
1 is rotatably supported by the lower opening of the housing of the developing device 19, presses against the photosensitive drum 15, and transfers the toner in the developing device 19 to a low potential portion of the electrostatic latent image to expose the photosensitive drum 15. A toner image is formed on the peripheral surface of the body drum 15 (reversal development).

The image forming and transferring section 14 at the uppermost stream in the sheet conveying direction
At the timing when the leading end of the magenta toner image on the peripheral surface of the photosensitive drum 15 is rotated and conveyed to the portion facing the conveyor belt 11, the standby position is set so that the printing start position of the paper coincides with the facing portion. The roller pair 24 starts rotating and feeds the paper toward the transport belt 11. Paper is in feed path 2
8, the transport path 73 formed by the transport belt 11 and the like
(See FIG. 2), and the image forming and transferring section 1
4a is transported to the first transfer section formed by the photosensitive drum 15 and the transfer brush 22.

The transfer brush 22 applies a transfer current output from a transfer bias power supply (not shown) to the sheet via the transport belt 11. As a result, the magenta toner image on the photosensitive drum 15 is transferred to the paper. Subsequently, the cyan toner image is transferred by the photosensitive drum 15 of the second image forming / transferring unit 14b and the transfer brush 22 from the upstream in the sheet transport direction, and further transferred to the photosensitive drum 15 of the third image forming / transferring unit 14c. The yellow toner image is transferred by the brush 33, and the black toner image is transferred by the photosensitive drum 15 and the transfer brush 33 of the most downstream image forming and transferring unit 14d.

The sheet on which the toner images of the four colors are transferred in a superimposed manner is separated from the conveyor belt 11 by the sheet separating claws 32 and is carried into the fixing device 33. The fixing device 33 presses and holds the sheet by the heat generating roller 74 and the pressing roller 75 and applies heat and pressure to the sheet to discharge the toner image backward while fixing the toner image on the sheet. The sheet discharged from the fixing device 33 is
The sheet is nipped by the unloading roller pair 34 and is unloaded.

When the switching flap 35 is rotating downward as shown in FIG. 2, the sheet is guided upward along the sheet discharge path 35, and is further turned forward at the end to be forwardly moved to the upper sheet discharge section. The paper is discharged onto the upper paper discharge tray 8 with the image forming surface facing downward from the mouth. When the switching flap 35 is rotating upward, it is fed out substantially horizontally rearward, and is discharged onto the rear opening / closing tray 39 with the image forming surface facing upward.

The full-color printer 1 operating as described above
In the fixing device 33, a special member that operates only at the beginning of the operation in order to perform appropriate oil application is provided. Hereinafter, this will be described.

The fixing device 33 is, as shown in FIG.
The heating roller 45 and surrounding the heating roller 45,
Pressing roller 46, fixing separation claw 47, oil application roller 4
8, a cleaning roller 49, an entrance guide 51, and the like are provided.

The heating roller 45 has a rubber roller whose surface layer is covered with a tube made of PFA (perfluoroalkoxy copolymer: tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), and a halogen heater is provided at the center of the hollow. 52 are provided.

The pressing roller 46 is formed by coating a surface layer of a rubber roller having a lower hardness than the heat generating roller 45 with a PFA tube. The pressing roller 46 is in pressure contact with the heat generating roller 45 to form a fixing portion there.

The four color toner images shown in FIG. 2 are transferred onto the paper surface and are separated from the conveyor belt 11 as shown in FIG.
As shown in the figure, the paper 53 carried into the fixing device 33 from the right outside of the figure is guided by the entry guide 51 and sandwiched by the fixing unit in a stable posture, and is heated and pressed to apply the toner image to the paper surface. The paper is transported backward while being fixed on the paper.

The fixing separation claw 47 is in contact with the heat generating roller 45 on the downstream side in the rotation direction of the heat generating roller 45 as shown by the arrow B in the drawing from the fixing unit, and causes the sheet 53 sent out from the fixing unit to the rear. To prevent the paper 53 from being wound around the heat generating roller 45. Fixing separation claw 4
The roller 54 coaxially supported by the roller 7 prevents the toner image forming surface of the sheet 53 separated from the heat roller 45 from being rubbed against the fixing / separating claw 47 and being scratched, and also allows the sheet 53 to be transported to the rear discharge roller. Guide to pair 34.

The oil application roller 48 is formed by impregnating a heat-resistant paper roller with silicon oil (hereinafter simply referred to as oil) and covering the surface with a tube made of a porous film. The oil application roller 48 is pressed against the heat roller 45 with a light load at a position downstream of the fixing separation claw 47 in the rotation direction of the heat roller 45 to apply oil to the surface of the heat roller 45. The amount of oil applied (consumed) by the oil application roller 48 is usually about 0. 4 per A4 size sheet.
5 mg.

As the oil, a type having a viscosity of 1000 cs is used. The surface temperature of the heating roller 45 is
Since the temperature rises to approximately 190 ° C., the viscosity of the oil applied to the heat generating roller 45 decreases to about 100 cs at the fixing portion, that is, the portion in contact with the paper 53, due to the high temperature.

By the way, as described above, in the initial stage of the operation of the apparatus main body 1, the heat roller 45 is pre-rotated until the temperature reaches a fixing temperature at which the toner can be fixed on the paper. At this time, the oil applied from the oil application roller 48 to the heating roller 45 has no place (paper) to permeate, so it is applied on the heating roller 45 in a multiplex manner, adheres in a large amount, and forms an image on the OHP film. As described above, a problem may occur if this is done.

The cleaning roller 49 of the fixing device 33 according to the present embodiment prevents such a problem from occurring. That is, the cleaning roller 49
Is made of a material into which oil can penetrate (any material can be used as long as the material can penetrate oil), under conditions where the oil that seeps from the oil application roller 48 to the peripheral surface of the heat generation roller 45 is not absorbed by the paper 53 or the like. Only the oil on the peripheral surface of the heat generating roller 45 is absorbed. For example, at the beginning of operation when printing on OHP paper.

For this purpose, the cleaning roller 49
Is rotatably driven by a driving mechanism (not shown) supported by a lower end of a rotating arm 56 whose upper end is supported by a support shaft 55, and comes into contact with and separates from the heat generating roller 45 at a certain timing.
The driving mechanism may drive the solenoid according to a control signal from a control device, or may be set to operate at a predetermined temperature using a bimetal or a shape memory alloy. The contact / separation may be driven.

FIGS. 3A to 3D are timing charts of the contact and separation of the cleaning roller 49 controlled by the control device of the electrical unit 43. FIG. FIG. 2A shows the timing of power on or rise from sleep mode.
(B) shows the start and end of the pre-rotation and the timing of the start of the main rotation, (c) shows the transition of the surface temperature of the heating roller, and (d) shows the timing of the contact and separation of the cleaning roller. Is shown.

In this control, the cleaning roller 49 is brought into contact with and separated from the heat generating roller at a low temperature at a position shown by a solid line in FIG. 1 and at a high temperature at a position shown by a broken line 57 in FIG. This temperature condition is determined to be low when the fixing device is at the same temperature as the outside air temperature, such as immediately after the power is turned on or when the fixing device rises from the sleep mode. When the temperature reaches a temperature at which a sufficient fixing property can be obtained or a temperature in the vicinity thereof, it is determined that the temperature is high.

In FIG. 5A, the power supply is first turned on at time t1 (or started from the sleep mode), and in response to this, the pre-rotation is started as shown in FIG. , And the heat generating roller 45 is heated. The cleaning roller 48 has been in contact with the heat generating roller 45 before the start of operation, as shown in FIG. Thus, at the start of the pre-rotation, the oil applied from the oil application roller 48 to the heat generation roller 45 is absorbed by the cleaning roller 48 and does not remain on the heat generation roller 45.

At time t2, when the surface temperature of the heat roller 45 has not reached the fixing temperature but has reached a predetermined temperature, the cleaning roller 48 is separated from the heat roller 45.

After the surface temperature of the heat generating roller 45 has risen to the fixing temperature at time t3, a slight time t4 has passed.
To stop the pre-rotation, and start the main rotation at the following time t5 with almost no pause.

As described above, the cleaning roller 49 contacts the peripheral surface of the heat generating roller 45 to absorb the oil until the heat generating roller 45 and the pressing roller 46 are appropriately warmed.
Even when fixing the first sheet of paper, the amount of oil applied to the heat generating roller 45 does not become excessive.

Immediately after the cleaning roller 48 is separated from the heat generating roller 45, oil spots remain on the surface of the heat generating roller 45. However, when a print start signal is input, the sheet is conveyed by the conveying belt while the toner image is transferred, and is fixed. Since there is time to arrive at the part, there is no problem because the oil spots described above are wiped out and the application is uniformized.

The cleaning roller 48 may be rotated following the heating roller 45, or may be rotated by forced driving. Further, the shape of the member that regulates the amount of oil may not be a roller shape but may be a cube. In such a case, it is only necessary to adopt a configuration in which they are simply separated from each other without being rotated. Further, instead of absorbing the oil on the heat generating roller in the early stage of operation as described above, the oil may be scraped off.

FIG. 4 is a view showing another embodiment in which the oil on the heat generating roller is scraped off at the beginning of the operation. The fixing device 60 shown in FIG. 6 includes a blade member 61 instead of the cleaning roller 48 shown in FIG. The blade member 61 has a rear end rotatably supported by a support shaft 62, and has a front end in contact with the surface of the heat generating roller 45 when the temperature is low, and separates to a position shown by a broken line 63 in the figure when the temperature is high. This rotation drive is performed by the bimetal 64 and the opening spring 65. Also in this case, the deformation temperature of the bimetal 64 for rotating the blade member 61 is:
The surface temperature of the heating roller 45 at time t3 in FIG. 3 is set. Other configurations are the same as those in FIG.

[0051]

As described above in detail, according to the present invention, the cleaning member having a simple structure is moved toward and away from the heat roller in synchronization with the pre-rotation of the fixing device. The oil applied to the heat roller can be forcibly absorbed, thereby preventing excess oil at the beginning of the main rotation. Therefore, even in the case of special paper such as OHP, it is possible to prevent oil stain from the first sheet. It is possible to form no normal images.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a fixing device and a configuration in the vicinity thereof according to an embodiment;

FIG. 2 is a side sectional view illustrating a configuration of an image forming apparatus including the fixing device of FIG. 1;

FIGS. 3A to 3D are timing charts of the contact and separation of a cleaning roller controlled by a control device of an electrical unit;

FIG. 4 is a diagram illustrating a configuration of a fixing device according to another embodiment and its vicinity.

5A is a diagram illustrating an example of a fixing device provided in a conventional large color page printer, and FIG. 5B is an example of a fixing device provided in a conventional small color page printer. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image forming apparatus (full color printer) 2 Main body base body 3 Top cover 4 Paper cassette 5 Openable paper feed tray 6 Front upper surface 7 Paper discharge stop 8 Upper paper discharge tray 9 Hinge 11 Conveyor belt 12 Drive roller 13 Follower Roller 14 (14a, 14b, 14c, 14d) Image forming and transferring unit 15 Photoconductor drum 16 Cleaner 17 Initializing charger 18 Exposure head 19 Developing unit 21 Developing roller 22 Transfer brush 23 Support member 24 Standby roller pair 25 Feed sensor 26 Paper feed roller 27 Separation member 28 Feed path 29 Conveyor roller pair 31 Paper feed roller 32 Paper separation claw 33 Fixing device 34 in one embodiment 34 Discharge roller pair 35 Switching flap 36 Paper discharge path 37 Paper discharge roller 38 Paper discharge roller 39 Rear opening / closing tray 41 Cleaning blade 42 Cleaner board Le 43 electrical component section 45 heat roller 46 pressing roller 47 fixing separation claws 48 oil applying roller 49 cleaning roller 51 enters the guide 52 halogen heater 53 Paper 54 roller 55 support shaft 56 rotating arm 60 other fixing device in an embodiment

Claims (4)

[Claims] 1. A transporting means for transporting a sheet carrying an unfixed toner image, and having a heat source, taking over the sheet transported by the transporting means, and applying heat and pressure to the sheet to rotate and pinch and transport the sheet. A pair of heat-fixing rollers, and an oil application member that presses against the heat-fixing roller to supply releasable oil to the heat-fixing roller, wherein the surface temperature of the heat-fixing roller is unfixed. Heat source control means for controlling the heat source to be turned on / off so as to maintain the temperature suitable for fixing the toner image; and controlling the rotation of the heat fixing roller until at least a temperature suitable for the fixing after the heat source is turned on. A roller rotation control means, which is provided at a position downstream of the oil applying member in the rotation direction of the heat fixing roller and in front of a holding portion of the heat fixing roller, so as to be able to freely contact and separate from the heat fixing roller. An oil application adjusting member that adjusts an amount of oil applied on the heat fixing roller by absorbing a part of the oil applied by the oil applying member, and a surface temperature of the heat fixing roller is higher than a temperature suitable for the fixing. When the temperature is too low, the oil application adjusting member is pressed against the heat fixing roller, and when the surface temperature of the heat fixing roller exceeds the predetermined temperature, the oil application adjusting member is separated from the heat fixing roller. And a control unit for controlling operation of an oil application adjusting member. 2. The fixing device according to claim 1, wherein the oil applying member is an elastic roller. 3. The fixing device according to claim 1, wherein said oil application adjusting member operation control means is made of bimetal. 4. The fixing device according to claim 1, wherein said oil application adjusting member operation control means comprises a temperature sensor and a solenoid.