JP2001228747A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the fixing device which realizes the speeding-up of operation such as the reduction of a warm-up time, the reduction of a starting time from standby, and the speeding-up of fixing, and realizes stabilization and low power consumption of the output of a power unit, and to provide an image forming device equipped with the same. SOLUTION: Turning on and off of heaters 46, 47 and 49 connected to the power unit 55 is controlled by a controller 54. The heater 49 is turned off during the warm-up, starting-up and printing, electric power is concentrated on the heaters 46 and 47 in a heating roller, and sufficient heat is supplied to a moving fixing belt through the heating roller. On standby, the heater 47 is turned off and the temperature of the heating roller and a pressure roller is maintained by the heater 46 in the heating roller and the heater 47 in the pressure roller. The timing when the heaters 46, 47 and 49 are turned on is controlled so as not to coincide mutually.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt-type fixing device used in an electrophotographic image forming apparatus and an image forming apparatus having the same.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, a laser beam printer, and a facsimile, an electrostatic latent image is formed on a photosensitive member and then developed with toner to form a toner image. Is heated and melted and pressed to fix it on paper. Such an image forming apparatus incorporates a fixing device for fixing a toner image to a sheet.

As such a fixing device, a heat roller system and a belt system have been proposed. In a fixing device of a heat roller type, a fixing roller and a pressure roller rotate while being pressed against each other, and a paper having a toner image carried on a pressure contact portion (referred to as a nip portion) between the fixing roller and the pressure roller. Is inserted. A heater is built in the fixing roller. Thus, when the sheet passes through the nip portion, heat is applied from the fixing roller and pressure is applied from the pressure roller. As a result, the unfixed toner image on the sheet is melted and softened and fixed on the sheet.

In such a heat roller type fixing device,
Since the heater is provided in the fixing roller in contact with the unfixed toner image, there is a limit to the rubber thickness on the surface of the fixing roller. Therefore, in order to secure the shape of the nip portion that is advantageous for separating the paper and the width of the nip portion necessary for fixing,
It is necessary to increase the diameter of the fixing roller, which increases the size of the fixing device. Also, as the diameter of the fixing roller increases, the heat capacity increases, and the warm-up time increases.

On the other hand, for example, JP-A-6-318001 discloses a belt-type fixing device. This belt-type fixing device includes an endless fixing belt, a fixing roller,
A heating roller and a pressure roller are provided.

A heating roller and a fixing roller are arranged in parallel with each other, and a fixing belt is stretched over the heating roller and the fixing roller. The pressure roller is provided in parallel with the fixing roller with the fixing belt interposed therebetween, and is urged toward the fixing roller. Thereby, pressure is generated between the fixing roller and the fixing belt. When the pressure roller rotates, the fixing belt running around the heating roller and the fixing roller runs. A main heating source is provided inside the heating roller, and an auxiliary heating source is provided inside the pressure roller.

A sheet carrying a toner image is inserted into a portion (called a nip portion) where the pressure roller and the fixing roller sandwich the fixing belt. When the sheet passes through the nip portion, heat is applied from the fixing belt and pressure is applied from the pressure roller. At this time, heat is also supplementarily applied from the pressure roller. The unfixed toner image is fixed on the sheet by the heat and pressure applied when the sheet passes through the nip.

[0008] As a fixing belt, there is shown a fixing belt in which a surface layer of silicone rubber is provided on a surface of a polyimide base material. Such a surface layer of the fixing belt plays a role of preventing toner from adhering to the fixing belt.

In such a belt-type fixing device, since no heater is provided in the fixing roller in contact with the unfixed toner image, there is no limitation on the rubber thickness on the surface of the fixing roller. Therefore, by using a fixing roller having a relatively small diameter, it is possible to secure the shape of the nip portion which is advantageous for separating the paper and the width of the nip portion necessary for fixing. Therefore, the size of the fixing device can be reduced. Further, since the heat capacity of the fixing belt is very small and the diameter of the heating roller is also small, the warm-up time can be shortened.

[0010]

In the above-mentioned conventional belt-type fixing device, a heating roller and a pressure roller are heated by a main heating source and an auxiliary heating source, and the fixing belt is heated via the heating roller and the pressure roller. Is heated. The main heating source and the auxiliary heating source heat the fixing device so that fixing can be performed at the time of warm-up after turning on the power, and the heating roller and the pressure roller in a standby state in which the fixing belt is stopped without performing fixing. Temperature is maintained.
At the time of startup from the start of the operation of the fixing belt in the standby state to the start of fixing, reheating is performed so that the fixing device can perform fixing, and the temperature of the fixing belt is maintained during fixing.

In recent years, there has been a demand for a faster operation of the fixing device, such as a shorter warm-up time, a shorter startup time from a standby state, and a faster fixing. In order to shorten the warm-up time in response to these demands, it is necessary to supply sufficient heat so that the fixing device can be warmed in a short time. Further, in order to reduce the time required for starting up from the standby state, it is necessary to supply sufficient heat so as to quickly recover the temperature of the fixing device, which decreases as the fixing belt runs. Further, in order to speed up the fixing, it is necessary to supply sufficient heat to the fixing belt to stabilize the temperature of the fixing belt even during the continuous fixing.

In order to respond to demands for faster operation of the fixing device, such as shortening the warm-up time, shortening the startup time from the standby state, and speeding up the fixing, the main heating source and the auxiliary heating source have high output. When sufficient heat is supplied by the conversion, the load fluctuation of the power supply device becomes large due to the turning on and off of the main heating source and the auxiliary heating source, and the output of the power supply device largely fluctuates. Generally, a power supply device that supplies power to the main heating source and the auxiliary heating source also supplies power to other parts of the image forming apparatus, and fluctuations in the output of the power supply device adversely affect image formation.

Further, when the output of the main heating source and the auxiliary heating source is increased, the size of the power supply device for supplying power to the main heating source and the auxiliary heating source is increased, and the height of the main heating source, the auxiliary heating source, and the power supply device is increased. Outputting is costly. Further, increasing the power of the main heating source and the auxiliary heating source to consume extra energy is not preferable from the viewpoint of energy saving.

An object of the present invention is to shorten the warm-up time, reduce the time required to start up from a standby state, and speed up the operation of fixing, and stabilize the output of the power supply unit. An object of the present invention is to provide a fixing device and an image forming apparatus including the same.

Another object of the present invention is to shorten the warm-up time, reduce the time required for starting up from a standby state, and speed up the operation of fixing, and stabilize the output of the power supply device. Another object of the present invention is to provide a fixing device with low power consumption and an image forming apparatus provided with the fixing device.

[0016]

Means for Solving the Problems (1) First invention A fixing device according to a first invention comprises a first roller for fixing and a second roller spaced apart from the first roller. , An endless fixing belt stretched over the first roller and the second roller, a third roller for pressing an unfixed sheet against the first roller via the fixing belt, and running on the fixing belt. Driving means for heating the fixing belt, three or more heating sources provided in the second roller and the third roller for heating the fixing belt, and at least two of the three or more heating sources are parallel to the heating source. And a power supply unit capable of supplying electric power to the at least two heating sources.

In the fixing device according to the present invention, the fixing belt can be heated at the same time by at least two heating sources that receive power supply from the power supply means in parallel. By simultaneously heating the fixing belt with two or more heating sources provided in the second and third rollers, a large amount of heat is efficiently supplied to shorten the warm-up time, and to start up from the standby state. Therefore, it is possible to increase the operation speed of the fixing device such as shortening of the fixing speed and the fixing speed. At this time, by shifting the start timings of power supply to at least two heating sources from each other, the timing of instantaneous power consumption at the start of power supply can be dispersed. This makes it possible to stabilize the output of the power supply unit while suppressing the load fluctuation of the power supply unit.

(2) Second Invention In the fixing device according to the second invention, in the configuration of the fixing device according to the first invention, three or more heat sources are provided by a plurality of heating sources provided in a second roller. A first heating source, and a second heating source provided in the third roller, wherein the power supply means comprises:
Power is supplied to the plurality of first heating sources in parallel during the first period, and power supply start timings to the plurality of first heating sources are shifted from each other in the first period.

In this case, during the first period, the electric power supplied from the electric power supply means is concentrated on the plurality of first heating sources in the second roller, and the fixing belt is efficiently moved via the second roller. Heating can be performed well, and the operation of the fixing device can be accelerated. At this time, by staggering the start timings of the power supply to the plurality of first heating sources, the output of the power supply unit can be stabilized.

(3) Third Invention In the fixing device according to the third invention, in the configuration of the fixing device according to the first invention, the three or more heating sources include a plurality of heating sources provided in a second roller. A first heating source, and a second heating source provided in the third roller, wherein the power supply means comprises:
In the second period, power is supplied in parallel to some of the first heating sources and the second heating sources of the plurality of first heating sources, and some of the first heating sources are supplied in the second period. The start timings of the power supply to the second heat source and the second heat source are shifted from each other.

In this case, during the second period, power is supplied from the power supply means to a part of the first heating source in the second roller and the second heating source in the third roller. Since the second roller and the third roller are heated, it is possible to reduce power consumption of the first heating source that is not supplied with power from the power supply unit. At this time, by staggering the start timing of the power supply to some of the first heating source and the second heating source, the output of the power supply unit can be stabilized.

(4) Fourth Invention In the fixing device according to the fourth invention, in the fixing device according to the second invention, the fixing belt is driven while driving the fixing belt during the first period. This is the heating period.

In this case, when the fixing belt is heated by the plurality of first heating means via the second roller, the fixing belt is driven by the driving means. The entire belt can be efficiently heated.

(5) Fifth Invention A fixing device according to a fifth invention is the fixing device according to the third invention, wherein the fixing belt is stopped and the temperature of the fixing belt is maintained during the second period. It is a period to do.

In this case, the fixing belt around the second roller is heated by a part of the first heating means while the third belt is heated by the third heating means.
The fixing belt around the first roller can be heated by the second heating means, and heat is supplied from a plurality of locations via the second roller and the third roller even when the fixing belt is stopped, so that the fixing is performed. Maintaining the belt temperature is performed effectively with less heat, and power consumption is reduced.

(6) Sixth Invention A fixing device according to a sixth invention is a fixing device comprising: a first roller for fixing; a second roller spaced apart from the first roller; , A third roller for pressing an unfixed sheet against the first roller via the fixing belt, and a second roller for heating the fixing belt. A plurality of first heating sources provided in the roller, a second heating source provided in the third roller for heating the fixing belt, a driving unit for running the fixing belt, and a driving unit. During a first period in which the fixing belt is heated while the fixing belt is running, a plurality of first
A first heating source and a second heating source of a part of the plurality of first heating sources during a second period for supplying power to the heating source and stopping the fixing belt to maintain the temperature of the fixing belt. And power supply means for supplying power to the power supply.

In the fixing device according to the present invention, since the fixing belt runs during the first period, the entire fixing belt can be heated. In the first period, the supply of power to the second heating source is stopped, and the power supply from the power supply unit is concentrated on the plurality of heating sources. This effectively heats the fixing belt with less heat, reduces excess power consumption and reduces power consumption, shortens warm-up time, shortens startup time from standby mode, and increases fixing speed. For example, it is possible to increase the speed of the operation of the fixing device. Further, by reducing excess power, the output of the power supply means can be stabilized.

(7) Seventh invention A fixing device according to a seventh invention is the fixing device according to the fifth invention, wherein the first period is a time of warm-up.
The second period includes at least one of a start-up period and a fixing period, and a standby period.

In this case, the temperature of the fixing belt is efficiently maintained by a part of the first heating source and the second heating source during standby, and the warm-up time, the start-up time and the fixing speed are reduced. Is achieved, and the operation of the fixing device is speeded up.

(8) Eighth Invention In the fixing device according to the eighth invention, in the configuration of the fixing device according to the sixth or seventh invention, the power supply means includes a power supply device having a predetermined maximum allowable power consumption. Including a plurality of first
, The sum of the power capacities of the heating sources is equal to the maximum allowable power consumption of the power supply unit, and the sum of the power capacities of some of the first heating source and the second heating source is equal to the maximum allowable power consumption of the power supply unit It is.

In this case, at the time of warm-up, start-up and fixing, a plurality of first heating sources consume a predetermined maximum allowable power consumption to generate sufficient heat to further speed up the operation of the fixing device. In the standby state, the power of some of the first heating source and the second heating source can be consumed so that the predetermined maximum allowable power consumption can be consumed by some of the first heating source and the second heating source. Since the capacity is large, the temperatures of the second and third rollers can be reliably maintained.

(9) Ninth Invention An image forming apparatus according to a ninth invention has a toner image forming means for forming a toner image on a recording medium and a fixing means for fixing the toner image formed on the recording medium. And a fixing device according to any one of the first to eighth inventions.

In the image forming apparatus according to the present invention, since the fixing device according to any one of the first to eighth aspects is provided, a large amount of heat is efficiently supplied to the fixing belt from a plurality of heating sources. Speed up the operation of the fixing device, such as shortening the warm-up time, shortening the startup time from the standby state, and increasing the fixing speed, and stabilizing the output of the power supply by minimizing the load fluctuation of the power supply. Can be planned.

[0034]

FIG. 1 is a schematic sectional view showing the structure of an image forming apparatus having a fixing device according to an embodiment of the present invention. FIG. 2 is a sectional view of the fixing device according to the embodiment of the present invention.

First, the configuration of the image forming apparatus will be described with reference to FIG. 1, and then the configuration of the fixing device will be described with reference to FIG. The image forming apparatus in FIG. 1 is, for example, a full-color laser beam printer.

As shown in FIG. 1, in the apparatus main body 100,
The photoreceptor belt 1 is tuned and supported by three photoreceptor belt support / conveyance rollers 2, 3, and 4 so as to form a horizontal plane. On the surface of the photoreceptor belt 1, an organic photoreceptor (OP
C) and the like, and a photosensitive receiving layer is applied in a thin film form. The photoreceptor belt 1 is driven to rotate in the direction of arrow A along the photoreceptor belt supporting and conveying rollers 2, 3, and 4 by a driving device (not shown).

Below the photoreceptor belt 1, a photoreceptor cleaning device 6, a static eliminator 7 and a charger 8 are sequentially arranged in the moving direction of the photoreceptor belt 1. A laser beam generator 9 is provided below the static eliminator 7 and the charger 8.

The static eliminator 8 includes a charging wire 10 made of a tungsten wire or the like, a shield plate 11 made of a metal plate, and a grid plate 12. When a high voltage is applied to the charged wire 10, the charged wire 10 causes corona discharge,
The surface of the photoreceptor belt 1 is uniformly charged via the grid plate 12.

The laser beam generator 9 irradiates the surface of the photoreceptor belt 1 with a laser beam 13 according to the image data.
An electrostatic latent image corresponding to each of the plurality of color components is formed on the photoreceptor belt 1. When the image forming apparatus is a laser beam printer, the laser beam generator 9 is controlled by a signal from a host computer (not shown).

On the upper portion of the photoreceptor belt 1, one-component developing devices 5B and 5Y for storing negatively charged toners of black (B), yellow (Y), magenta (M) and cyan (C), respectively. , 5M and 5C are provided. These one-component developing devices 5B, 5Y, 5M, 5C
Are horizontally arranged along the surface of the photoreceptor belt 1 at equal intervals and detachably in predetermined storage sections provided in the apparatus main body 100.

The one-component developing device 5B has a toner supply roller 14, a developing roller 15, and a doctor blade 16. The toner supply roller 14 is formed by forming a conductive elastic body made of a foamed material such as urethane or silicone on a peripheral surface of a base material made of a metal such as stainless steel. The toner replenishing roller 14 is a one-component developing device 5B
Are rotatably supported at both ends thereof and are driven to rotate counterclockwise to supply toner to the surface of the developing roller 15. The toner replenishing roller 14 has a predetermined digging amount with respect to the developing roller 15, thereby stabilizing the charge amount due to friction with the toner.

The developing roller 15 is formed by forming a conductive elastic material such as urethane or silicone in a layer on the outer peripheral surface of a base material made of metal such as stainless steel. The developing roller 15 is rotatably supported at both ends of the one-component developing device 5B and is driven to rotate clockwise.

The doctor blade 16 is formed of a conductive member such as silicone or urethane which is formed simultaneously with a stainless steel leaf spring. The doctor blade 16 frictionally charges the toner supplied by the toner supply roller 14 and forms the charged toner on the outer peripheral surface of the developing roller 15 in a thin layer state.

The configuration of the one-component developing devices 5Y, 5M and 5C is the same as the configuration of the one-component developing device 5B except for the toner housed inside.

On the upper surface of the apparatus main body 100, a developing device attaching / detaching cover 19 is provided. Developing device removable cover 19
Is rotatably supported on a developing device attaching / detaching cover shaft 20 fixed to the apparatus main body 100 so as to be freely opened and closed. The developing device attaching / detaching cover 19 has contact cams 17B, 17Y, 17M, 17M.
C is provided. These contact cams 17B, 17
When developing an electrostatic latent image of a predetermined color component, Y, 17M, and 17C are used to develop one-component developing devices 5B, 5Y, 5M, and 5M, respectively.
5C is brought into contact with the photoreceptor belt 1. One-component developing device 5
B, 5Y, 5M, and 5C have separation springs 18B,
18Y, 18M and 18C are provided. These separation springs 18B, 18Y, 18M, and 18C separate the one-component developing devices 5B, 5Y, 5M, and 5C to standby positions, respectively.

The intermediate transfer unit 21 comprises an intermediate transfer belt 22 made of a conductive resin or the like and three intermediate transfer belt support rollers 23, 24 and 25. The intermediate transfer belt 22 is tuned and supported by the intermediate transfer belt support rollers 23, 24, and 25. In order to transfer (first transfer) the toner image on the photosensitive belt 1 onto the intermediate transfer belt 22, the intermediate transfer roller 26 supports and transports the intermediate transfer belt with the photosensitive belt 1 and the intermediate transfer belt 22 interposed therebetween. It is arranged so as to face the roller 23. A first pre-transfer static eliminator (PT) including an LED (light emitting diode) array or the like is provided between the one-component developing device 5C and the intermediate transfer body unit 21 so as to face the photosensitive belt 1.
L) 27 is arranged.

Here, the length of the outer peripheral surface of the intermediate transfer belt 22 is set to be equal to the length of the outer peripheral surface of the photosensitive belt 1. The intermediate transfer member belt cleaning device 2 is arranged so as to face the outer peripheral surface of the intermediate transfer member belt 22.
8 are provided. The intermediate transfer body belt cleaning device 28 is separated from the intermediate transfer body belt 22 when a synthetic image is formed on the intermediate transfer body belt 22, and comes into contact with the intermediate transfer body belt 22 only at the time of cleaning. The residual toner on the body belt 22 is scraped off.

The laser beam generator 9 in the apparatus main body 100
A paper cassette 29 for storing the paper 30 is provided below the paper cassette 29. The paper 30 is sent out one by one from a paper cassette 29 to a paper transport path 32 by a paper feed roller 31. A registration roller 33 is provided in the paper transport path 32 so as to be in pressure contact with a driven roller 34. The registration roller 33 temporarily stops the sheet 30 and waits for the sheet 30 to coincide with the position of the synthesized image formed on the intermediate transfer belt 22.

A paper transfer roller 35 is provided so as to face the intermediate transfer belt supporting and conveying roller 25 with the intermediate transfer belt 22 interposed therebetween. The paper transfer roller 35 rotates in contact with the intermediate transfer belt 22 only at the time of transfer, in order to transfer the composite image formed on the intermediate transfer belt 22 to the paper 30.

Above the paper transfer roller 35, a belt-type fixing device 36 is provided. This fixing device 36
Presses and heats the sheet (unfixed sheet) 30 on which the composite image is transferred from the intermediate transfer belt 22 to fix the unfixed toner image on the sheet 30. The detailed configuration of the fixing device 36 will be described later. A sheet discharge roller pair 39 is provided downstream of the fixing device 36. Also, the device body 100
A paper discharge tray 40 is provided on the upper surface of the printer. The fixed paper 30 is accumulated in the paper discharge tray 40.

In the present embodiment, the photosensitive belt 1, the one-component developing devices 5B, 5Y, 5M, 5C, the charger 8, the laser beam generator 9, and the intermediate transfer unit 21 constitute a toner image forming means.

As shown in FIG. 2, in the fixing device 36,
The fixing roller 44 and the heating roller 45 are spaced apart and parallel to each other. An endless fixing belt 50 is looped around the fixing roller 44 and the heating roller 45 in a loop shape. Further, a pressure roller 48 is provided so as to be in rolling contact with the fixing roller 44 at a predetermined pressure.

The fixing roller 44 is a metal core having a thickness of 5 mm.
Is formed. The heating roller 45 is
It is a metal core coated with fluororesin,
Inside the metal core, a total of two heaters of 500 W capacity and 500 W capacity 47 are provided as first heating sources.

The pressure roller 48 is obtained by coating a metal core with silicone rubber and further coating with a fluorocarbon resin-containing fluoro rubber latex. The metal core has a capacity of 500 W as a second heat source. Heater 49 is provided. The fixing belt 50 is formed by coating 200 μm of silicone rubber on polyimide.

The pressing roller 48 presses the fixing roller 44 with the fixing belt 50 interposed therebetween. Nip portion 41 in which fixing belt 50 is sandwiched between fixing roller 44 and pressure roller 48
The paper 30 is inserted through.

The pressure roller 48 is rotated by the drive motor 58 in the direction of the arrow R1 (counterclockwise). When the sheet 30 carrying the unfixed toner image 43 is inserted into the nip portion 41 as shown by an arrow Z, the fixing belt 50 is moved by the pinching force between the fixing roller 44 and the pressure roller 48.
0 is securely pressed against the surface. As the pressure roller 48 rotates, the fixing belt 50 travels in the direction of arrow X due to frictional force, and the fixing roller 44 also rotates in the direction of arrow R2 (clockwise) due to frictional force with the fixing belt 50. further,
The heating roller 45 also rotates in the direction of the arrow R3 (clockwise) due to the frictional force with the fixing belt 50.

While the fixing belt 50 travels along the sheet 30 along the nip 41 between the fixing roller 44 and the pressure roller 48, the unfixed toner image 43 on the sheet 30 is heated and melted and fixed on the sheet 30. You.

A temperature measuring device 51 such as a thermistor is arranged on the fixing belt 50. The temperature of the fixing belt 50 during traveling is measured by the temperature measuring device 51. Also,
A temperature measuring device 52 such as a thermistor is disposed on the heating roller 45. The temperature of the heating roller 45 when the fixing belt 50 is stopped is measured by the temperature measuring device 52. Further, a temperature measuring device 5 such as a thermistor is attached to the pressing roller 48.
3 are arranged. The temperature of the surface of the pressure roller 48 is measured by the temperature measuring device 53.

Temperature measuring devices 51, 52, 5 disposed on the fixing belt 50, the heating roller 45 and the pressure roller 48.
3 is connected to the control device 54. The heaters 46 and 47 in the heating roller 45 and the heater 49 in the pressure roller 48 are connected to a control device 54 via a power supply device 55. The control device 54 includes temperature measurement devices 51, 52,
On / off control of the heaters 46, 47, 49 is performed based on the output of 53.

In this embodiment, the fixing roller 44 is
The heating roller 45 corresponds to a second roller, and the pressing roller 48 corresponds to a third roller. Further, the heaters 46, 47, 49 correspond to three or more heating sources, the heaters 46, 47 correspond to a first heating source, the heater 49 corresponds to a second heating source, and the driving motor 58 is driven. The power supply 55 corresponds to a power supply unit.

Next, the outline of the operation of the image forming apparatus of FIG. 1 will be described. In FIG. 1, first, a high voltage is applied to a charging line 10 in a charger 8 by a high-voltage power supply (not shown).
By causing corona discharge, the surface of the photoreceptor belt 1 is uniformly charged to -600V.

In this state, while the photoreceptor belt 1 is rotated in the direction of arrow A by a driving device (not shown), a plurality of laser beams are applied from the laser beam generator 9 to the uniformly charged surface of the photoreceptor belt 1. The laser beam 13 is emitted corresponding to an image of a predetermined color component among the color components.

Here, first, a laser beam 13 is applied to the surface of the photoreceptor belt 1 corresponding to the black (B) image. As a result, the charge of the portion irradiated with the laser beam 13 on the surface of the photoreceptor belt 1 disappears, and an electrostatic latent image is formed. The energy per unit area given by the laser beam 13 to the surface of the photoreceptor belt 1 is 1.0 μJ / c.
m ² . The surface potential of the portion irradiated with the laser beam 13 drops to -80V.

On the other hand, a one-component developing device containing black (B) toner contributing to development by half rotation of the contact cam 17B based on a color selection signal from a host computer (not shown). 5B comes into contact with the surface of the photoreceptor belt 1. At this time, 0.5 m
g / cm ² . A bias voltage of −250 V was applied to the developing roller 15, and the laser beam 13 on the photosensitive belt 1 was irradiated by an electric field acting between the surface of the developing roller 15 and the surface of the photosensitive belt 1. The toner is transferred only to the portion, and a toner image is formed. Thereby, development is performed.

After the development by the one-component developing device 5B is completed,
The contact cam 17B further makes a half turn, and the one-component developing device 5B moves from the contact position with the photosensitive belt 1 to the standby position by the urging force of the separation spring 18B. During the development by the one-component developing device 5B, the other one-component developing devices 5Y, 5M, 5C
Is separated from the photosensitive belt 1.

On the other hand, the intermediate transfer belt 22 has +500
A bias voltage of V is applied. One-component developing device 5
The toner image formed on the photosensitive belt 1 by B is transferred onto the intermediate transfer belt 22 by the bias voltage.

At this time, the surface potential of the portion of the photoreceptor belt 1 not irradiated with the laser beam 13 is -600 V, and the potential difference from the surface of the intermediate transfer belt 22 is as large as 1100 V. As a result, the toner is reversely charged due to the release of the positive charge from the intermediate transfer belt 22, and the transfer efficiency from the photosensitive belt 1 to the intermediate transfer belt 22 is significantly reduced. In order to prevent this, the surface potential of the photosensitive belt 1 is reduced by the first pre-transfer static eliminator 27 before the transfer, and the potential difference with the intermediate transfer belt 22 is suppressed. Thereby, the transfer efficiency is improved.

Next, when cyan (C) is selected based on a color selection signal from the host computer, the one-component developing device 5C comes into contact with the photosensitive belt 1 and starts development using cyan toner. . Similarly, the one-component developing device 5
Development using magenta toner by M and development using yellow toner by the one-component developing device 5Y are sequentially performed. As a result, the four color toner images of black, cyan, magenta, and yellow are superimposed on the intermediate transfer belt 22 to form a composite image.

On the other hand, the paper 30 is fed from the paper cassette 29 along the paper transport path 32 between the intermediate transfer belt 22 and the paper transfer roller 35. At this time, a high voltage of about +1 kV having a polarity opposite to that of the toner is applied to the paper transfer roller 35. Thereby, the intermediate transfer body belt 22
The composite image formed thereon is collectively transferred to the sheet 30 by the electric field between the intermediate transfer belt 22 and the sheet transfer roller 35 and the pressure by the sheet transfer roller 35. Thus, an unfixed toner image is formed on the sheet 30.

Subsequently, the sheet 30 is sent to the fixing device 36. In the fixing device 36, the unfixed toner image is fixed on the sheet 30 by the heat of the fixing belt 50 and the nipping force between the fixing roller 44 and the pressure roller 48, and a color image is formed on the sheet 30. Paper 30 that has passed through fixing device 36
Is passed between the paper discharge roller pair 39 and discharged to the paper discharge tray 40.

Next, the operation of the fixing device 36 of FIG. 2 will be described with reference to FIG. FIG. 3 is a timing chart for explaining control of the heaters 46, 47, and 49 in the fixing device 36 of FIG. Here, it is assumed that the maximum power that can be used for heating the fixing belt 50 in the fixing device 36 is 1000 W due to the capacity of the high-voltage power supply.

First, when the power is turned on at time t1, the fixing device 36 operates and warm-up is started. At the time of warm-up, the fixing roller 44 and the heating roller 45
Further, while rotating the pressure roller 48 and running the fixing belt 50, both of the heaters 46 and 47 are turned on, and a total of 1000 W of electric power is concentrated on the heating roller 45 to supply heat. Thereby, the fixing device 36 is warmed up. In this case, after the heater 46 is first turned on, the heater 47 is turned on after a predetermined delay time Δt. Thereby, the instantaneous maximum power consumption can be reduced. The predetermined delay time Δt is 500 msec. By shifting the timing at which the heaters 46 and 47 are turned on in this manner, load fluctuation of the power supply device 55 can be suppressed, and output fluctuation of the power supply device 55 can be reduced.

After the completion of the warm-up, when the apparatus enters the standby state at time t2, the fixing device 36 is operated until a print command is input.
Has stopped. At this time, the temperature control of the heating roller 45 and the pressure roller 48 is performed using the heater 46 and the heater 49, respectively. That is, the control device 54 controls the heater 46 on and off based on the temperature measured by the temperature measuring device 52 disposed on the heating roller 45, thereby keeping the heating roller 45 at a predetermined temperature. Further, the control device 54 controls the heater 49 on and off based on the temperature measured by the temperature measuring device 53 disposed on the pressure roller 48, thereby maintaining the pressure roller 48 at a predetermined temperature. Also at this time, the timing at which the heaters 46 and 49 are turned on is shifted, so that the load fluctuation of the power supply device 55 is suppressed and the output fluctuation of the power supply device 55 is reduced.

When a print command is input at time t3, the fixing device 36 starts operating. Thereby, the fixing roller 4
4. The fixing roller 50 runs while the heating roller 45 and the pressure roller 48 rotate. At this time, since the temperature of the fixing device 36 temporarily decreases, the fixing device 36 is started to recover the temperature. That is,
Both the heaters 46 and 47 are turned on, and the power is concentrated on the heating roller 45 to supply heat. In this case, after the heater 46 is first turned on, the heater 47 is turned on after a predetermined delay time Δt. Also in this case, the delay time Δt is 500 msec as in the warm-up. By shifting the timing at which the heaters 46 and 47 are turned on, load fluctuations of the power supply 55 are suppressed, and output fluctuations of the power supply 55 are reduced.

When the start-up is completed at time t4, printing is started. At the time of printing, the paper 30 and the unfixed toner image 43 deprive the fixing belt 50 of heat.
In order to keep 0 at a predetermined temperature, it is necessary to supply heat. Therefore, at the time of printing, the heaters 46 and 47 are turned on, electric power is concentrated on the heating roller 45, and heat is supplied. The control device 54 controls the heater 4 based on the temperature measured by the temperature measurement device 51 disposed on the fixing belt 50.
By controlling the on and off of the fixing belts 5 and 47, the fixing belt 5
0 is maintained at a predetermined fixing temperature. In this case, the timing for turning on the heater 47 is shifted from the timing for turning on the heater 46 by a predetermined delay time Δt. The predetermined delay time Δt is 500 msec. By shifting the timing at which the heaters 46 and 47 are turned on, the load fluctuation of the power supply device 55 is suppressed, and the output fluctuation of the power supply device 55 is reduced.

In this state, the sheet 30 carrying the unfixed toner image 43 is supplied from the lower opening of the fixing device 36 in the direction of arrow Z. The paper 30 is inserted between the fixing belt 50 and the pressure roller 48 at the nip portion 41. The unfixed toner image 43 on the sheet 30 is melted by the heat given from the fixing belt 50, and is further fixed on the sheet 30 by the pressing force between the pressing roller 48 and the fixing roller 44. The sheet 30 that has been fixed in the nip portion 41 is carried out from the upper opening of the fixing device 36.

In the fixing device 36 of the present embodiment,
At the time of warm-up, at the time of startup from the standby state to the start of fixing, and at the time of fixing, the heater 49 is turned off, and the fixing belt 5 driven by the drive motor 58 is turned off.
0 can be intensively heated by the heaters 46 and 47, effectively heating the fixing belt 50 with a small amount of heat, shortening the warm-up time, shortening the startup time from the standby state, and increasing the fixing speed. Is being planned. In the standby state, the maximum allowable power consumption of 1000 W can be consumed by the heaters 46 and 49 in the standby state, so that the temperatures of the heating roller 45 and the pressure roller 48 can be reliably maintained.

By heating the fixing belt 50 by using the electric power efficiently as described above, it is possible to suppress unnecessary power consumption and to reduce power consumption, and to reduce the output fluctuation of the power supply device 55. The heaters 46, 47,
By shifting the timing at which 49 is turned on, the number of heaters that are turned on at one time can be reduced, and the timing of instantaneous power consumption at the start of power supply can be dispersed. This makes it possible to stabilize the output of the power supply device 55 while keeping the load fluctuation of the power supply device 55 small.

[0079]

As described above, according to the present invention, a large amount of heat is efficiently supplied from a plurality of heating sources to the fixing belt to shorten the warm-up time, shorten the startup time from the standby state, and fix the fixing speed. As a result, it is possible to stabilize the output of the power supply device while speeding up the operation of the fixing device, such as increasing the speed of the power supply, and suppressing the load fluctuation of the power supply device.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus including a fixing device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a fixing device according to an embodiment of the present invention.

FIG. 3 is a timing chart for explaining control of a heater in the fixing device of FIG. 2;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoreceptor belt 5B, 5Y, 5M, 5C one-component developing device 8 charger 9 laser beam generator 21 intermediate transfer body unit 30 paper 36 fixing device 44 fixing roller 45 heating roller 46, 47, 49 heater 48 pressure roller 50 Fixing belt 51, 52, 53 Temperature measuring device 54 Control device 55 Power supply device 58 Drive motor

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Daimitsu Shimazaki 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Norihito Tanaka 1006 Okadoma Kadoma Kadoma City Osaka Prefecture Inside Matsushita Electric Industrial Co. (72) Inventor Seiichi Kitagawa 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Keiichi Matsuzaki 1006 Odaka Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Yuichiro Higashi 1-5-12 Shiba, Minato-ku, Tokyo Nitto Kogyo Co., Ltd. (72) Inventor Yasuhide Hamada 1-5-12 Shiba, Minato-ku, Tokyo Nitto Kogyo Co., Ltd. F-term (reference) 2H027 EA12 EA16 ED25 EE02 EE07 EF01 2H033 AA20 AA30 AA41 BA11 BA25 BB01 CA03 CA48

Claims (9)

[Claims] A first roller for fixing; a second roller spaced apart from the first roller; and a first roller fixed to the first roller and the second roller. An endless fixing belt, a third roller for pressing an unfixed sheet against the first roller via the fixing belt, a driving unit for driving the fixing belt, and a second roller for heating the fixing belt. Two or more heating sources provided in the second roller and the third roller, and power supply means capable of supplying power in parallel to at least two of the three or more heating sources. Wherein the power supply unit shifts the start timing of power supply to the at least two heating sources from each other. 2. The three or more heating sources include a plurality of first heating sources provided in the second roller and a second heating source provided in the third roller. The power supply unit is configured to be able to supply power to the plurality of first heating sources in parallel during a first period, and to supply power to the plurality of first heating sources during the first period. 2. The fixing device according to claim 1, wherein the start timings of the fixing operations are shifted from each other. 3. The three or more heating sources include a plurality of first heating sources provided in the second roller and a second heating source provided in the third roller. Wherein the power supply means is configured to be capable of supplying power in parallel to a part of the first heating sources and the second heating sources of the plurality of first heating sources during a second period, 2. The fixing device according to claim 1, wherein in the second period, start timings of supplying power to the first heating source and the second heating source are shifted from each other. 3. 4. The fixing device according to claim 2, wherein the first period is a period in which the fixing belt is heated while the fixing belt is driven by the driving unit. 5. The fixing device according to claim 3, wherein the second period is a period in which the fixing belt is stopped to maintain the temperature of the fixing belt. 6. A fixing roller, a second roller spaced apart from the first roller, and a first roller fixed to the first roller and the second roller. An endless fixing belt, a third roller for pressing an unfixed sheet against the first roller via the fixing belt, and a plurality of rollers provided in the second roller for heating the fixing belt. A first heating source, a second heating source provided in the third roller for heating the fixing belt, a driving unit for moving the fixing belt, and the fixing belt driven by the driving unit. Power is supplied to the plurality of first heating sources during a first period in which the fixing belt is heated while running, and the plurality of first heating sources are stopped to maintain the temperature of the fixing belt in a second period. Of some of the first heating sources A fixing device comprising: a first heating source; and a power supply unit configured to supply power to the second heating source. 7. The method according to claim 1, wherein the first period is a warm-up period.
7. The fixing device according to claim 6, wherein at least one of a start-up period and a fixing period is included, and the second period includes a standby period. 8. The power supply unit includes a power supply having a predetermined maximum allowable power consumption, wherein a total of the power capacities of the plurality of first heating sources is equal to the maximum allowable power consumption of the power supply, 8. The power supply device according to claim 6, wherein the sum of the power capacities of the first heating source and the second heating source is equal to a maximum allowable power consumption of the power supply device.
The fixing device as described in the above. 9. A toner image forming unit for forming a toner image on a recording medium, and a fixing device according to claim 1, for fixing the toner image formed on the recording medium. An image forming apparatus comprising: