JPH1130926A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To consecutively execute a large number of image forming operations at a high speed by preventing the drop of temp. caused by the relative deficiency of the heating quantity of a heating roller in a fixing device. SOLUTION: The fixing device 46 is provided with a first heater 46x provided to heat the heating roller, a second heater 46y whose power consumption and heating capacity are larger than those of the first heater 46x and which is provided to heat the heating roller and a controller 10 for monitoring the operation states of an automatic document feeder 30 and a document reading part 20 which exceed the feedable power of a digital copying machine provided with the fixing device 46, when power-feeding simultaneous with the second heater 46y is attained, to use the second heater 46y instead of the first heater 46x, when the automatic document feeder 30 and the document reading part 20 are not operated.

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 fixing a recording sheet onto which a toner image has been transferred by an electrophotographic method by pressing a heated fixing member against the recording sheet.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus is equipped with a fixing device for fixing a toner image transferred to a recording sheet. This fixing device generally includes a heat roller (heating roller) heated by an internal heater and a pressure roller pressed against the heat roller. The recording paper on which the toner image has been transferred is pressed against both rollers. The paper is drawn into the nip. One of the heat roller and the pressure roller is a driving roller, and the other is a driven roller.

[0003] A fixing device in which two heaters are provided inside a heat roller has been proposed or provided. For example, Japanese Patent Publication No. 3-41831 discloses that when the temperature of the fixing roller is raised, two heat sources are turned on, and when the set temperature for the fixing operation or the set temperature in the power saving mode is maintained. Any one
A technique for lighting individual heat sources is disclosed. Japanese Patent Publication No. 6-5427 discloses a first heater and a low-power-consumption second heater in which the heat generation distribution at the center is larger than at both ends. Sometimes, a technique of heating using only the first heater is disclosed.

[0004]

In the technique described in the above-mentioned publication, two heat sources are turned on at the time of startup, but only one heater is turned on during the operation of the fixing device.
For this reason, if a large amount of image forming operations are continuously performed in a high-speed machine, the temperature of the heat roller may be reduced due to a relative shortage of the heating amount, and the temperature may be lower than a fixable temperature. In this case, the operation of the heat roller is stopped until the temperature of the heat roller is restored to a predetermined set temperature, or the operation is switched to a low-speed operation when the temperature of the heat roller reaches a certain lower limit temperature, so that the temperature of the heat roller is equal to or lower than the feasible temperature. It is controlled so that it does not decrease to As a result, in the conventional apparatus, when a large number of image forming operations are performed continuously, a high-speed operation cannot be continued for a long time, resulting in a problem that productivity is reduced. Turning on the two heaters other than at the time of startup means that the power that can be supplied to the entire image forming apparatus is, for example, 1.5K due to the use of a commercial power supply.
Since it is limited to about W, it is practically impossible.

The present invention has been made in view of the above circumstances, and is intended to prevent a decrease in temperature due to a relative shortage of a heating amount of a heat roller and to perform a large number of image forming operations continuously and at a high speed. The purpose is to do.

[0006]

SUMMARY OF THE INVENTION The present invention is a fixing device for fixing a heated fixing member to a recording sheet on which a toner image has been transferred by electrophotography by pressing the fixing member, wherein the fixing member is heated. A first heater provided, a second heater having higher power consumption and heating capacity than the first heater and provided to heat the fixing member, and a fixing device provided when power is supplied simultaneously with the second heater. A fixing unit that monitors an operation state of a member exceeding power that can be supplied by the image forming apparatus and uses the second heater instead of the first heater when the member is not operating. .

The present invention is also a fixing device wherein the image forming apparatus is a digital copying machine and the members are an automatic document feeder and a document reading device.

[0008]

FIG. 2 shows the overall configuration of a digital copying apparatus according to an embodiment of the present invention. The illustrated copying machine is
A main body having a document reading unit 20 and a printer unit 40, and an automatic document feeder 30 set on a platen glass 21 of the main body.
And a large-capacity sheet feeding stacker 50 provided on the left side of the main body in the drawing, and a finisher 60 provided with a staple function and a punch function provided on the right side of the main body in the drawing,
The power that can be fed as a whole copying machine including these,
1.5 KW.

The main body of the copying apparatus reads an original on an original platen glass 21 and generates an image data.
Unit) 20, and a printer unit 40 that forms an image on recording paper based on the image data generated by the document reading unit 20.

An original reading unit 20 scans an original set at a predetermined position on an original platen glass 21 with a scanner 22 below the original platen glass 21, photoelectrically converts the original with a CCD 23, and further sends an image signal to an image signal processing unit 24. By performing known image signal processing, image data is generated and stored in the image memory unit 25.

A document transport system (so-called “panning shot”) for reading an image by transporting a document by the automatic document transport device 30 while the scanner is not moving can be controlled. In general, a panning mode is set. The automatic document feeder 30 can be opened and closed from the front side of the figure. When reading one document, the original is opened by opening the automatic document feeder 30 and the document table glass is manually operated.
Set on 21. Since the configuration of the automatic document feeder (FDH) 30 is known, the description thereof is omitted.

The image memory 25 stores image data of a document read by the document reading unit 20. This allows
The reading operation and the printing operation of the original image can be executed independently, and the fixing operation included in the printing operation is continued by switching from the first heater 46X to the second heater 46Y after the reading operation as in this embodiment. Can be controlled. In the image memory unit 25, scaling processing, synthesis processing,
An image editing process such as a rotation process is also performed as appropriate, but these processes are well-known and will not be described.

The printer section 40 reads out image data from the image memory section 25 to the control section 41 and drives a laser device 42 by a drive circuit in the control section 41 so that an electrostatic latent image is formed on the charged surface of the photosensitive drum 43. To form The electrostatic latent image is visualized by developing with a toner in the developing unit 44, and a large-capacity paper stacker is used.
The image is transferred onto recording paper fed at a predetermined timing from the paper feed tray 50, the paper feed trays 45a and 45b, or the re-feeding path 47 through a paper passing path. Further, the recording paper after the image transfer is sent to the fixing device 46, and the paper is passed between the heat roller 46a and the pressure contact roller 46b so that the image is fixed by thermocompression and discharged from the copying machine main body.

As shown in FIG. 3, a first heater 46X for heating the heat roller 46a is provided on the heat roller 46a.
And a second heater 46Y, and a thermistor 47SE for detecting the temperature of the heat roller 46a is provided on the peripheral surface thereof. The controller 10 (FIG. 1)
In addition to performing the switching control described later (switching control between the first heater 46X and the second heater 46Y), by controlling the power supply to the first heater 46X or the second heater 46Y based on the detection result of the thermistor 47SE, the heat roller Control to keep the surface temperature of 46a at the specified set temperature is also performed.

The first heater 46X and the second heater 46Y are constituted by halogen heaters in this embodiment. 1st heater 46X
Of the second heater 46Y is 850W. Also, the automatic document feeder 30 described above is used.
And the document reading section 20 have a total power consumption of 120 W. That is, the power consumption of the first heater 46X is reduced by the automatic document feeder 30.
The value obtained by adding the power consumption of the original reading section 20 to the
It is designed to be equal to the power consumption of Y.

The finisher 60 discharges the copied recording paper discharged from the copying machine main body to the paper discharge tray 61 or stores it in the reversing tray 62, and then sends it back to the re-feeding path 47 of the copying machine main body, or reverses. The stack basket 64 is stored in the staple tray 63 from the tray 62 and bound by a stapler (not shown).
Down to

FIG. 1 shows a power supply circuit of the copying apparatus. As shown in the drawing, the first heater 46X and the second heater 46Y are configured to be supplied with power to only one of them by a switch that is switched by a command from the controller 10. A design is made such that the sum of the power consumption a of the automatic document feeder 30, the power consumption b of the document reading section 20, and the power consumption x of the first heater 46X is substantially equal to the power consumption y of the second heater 46Y. Have been.

The controller 10 controls the power supply to the first heater 46X or the second heater 46Y based on the detection result of the thermistor 47SE as described above, and sets the surface temperature of the heat roller to the set temperature (standby temperature, standby temperature). In addition to the normal control of maintaining the standby temperature in the power saving mode, the automatic document feeder 30
And the operation state of the document reading unit 20 is monitored. If both are off and the fixing device 46 is operating, the first heater 46X
Instead, control is performed to switch the switch so as to supply power to the second heater 46Y. As a result, a large amount of printing operation can be continued at high speed.

A description will be given with reference to FIG. First, when a main switch (not shown) is turned on, power is supplied to the second heater 46Y having a large heating capacity for warming up. When the surface temperature of the heat roller 46a reaches the set fixing temperature and the warm-up is completed, the power supply is switched from the second heater 46Y to the first heater 46X, and the apparatus enters a standby state.

When a print switch (not shown) is turned on, a copy operation is started. Initially, the automatic document feeder (F
Since the DH) 30 and the document reading unit 20 are operating, the power supply to the first heater 46X is continued. Next, when the document reading operation is completed and the automatic document feeder 30 and the document reading unit 20 are in a non-operating state, the power supply destination is switched from the first heater 46X to the second heater 46Y, and the heating capacity is increased. High-speed and large-volume image forming operations can be continued. Thereafter, when the copy operation is completed, the mode is switched to the first heater 46X, and the standby state is resumed. If the surface temperature of the heat roller is lower than the standby temperature at the end of the copy operation, the power is supplied to the second heater 46Y to recover the standby temperature, and then the operation is switched to the first heater 46X.

On the other hand, when a jam occurs, the power supply to the first heater 46X and the second heater 46Y is turned off, and when the jam is reset, a large heating capacity is set so that the fixing temperature can be quickly returned to the set fixing temperature. The two heater 46Y is turned on.
When the warm-up is completed, the apparatus enters the standby state again and is switched to the first heater 46X. When returning from the power saving mode at a temperature lower than the standby state to the standby state, the second heater 46Y is first turned on, and then the first heater 46Y is turned on.
Switch to X.

Referring to the graph of FIG. 4, the control of this embodiment is compared with the control of the conventional example shown in FIG. Copy speed is 6
0 sheets / minute, the number of originals set is 100, the lower limit temperature for fixing is 160 ° C., the print operation is executed in parallel with the read operation until the 100 originals are read, and after the read operation is completed, Control was performed so that only the printing operation was performed. Further, as the configuration of the conventional example, the same configuration as that of the present embodiment was adopted except for the power supply to the first heater 46X and the second heater 46Y. That is, the power of the first heater 46X is 730W,
The configuration is such that the power of the heater 46Y is 850 W, and the total power of the automatic document feeder 30 and the document reading section 20 is 120 W.

As shown in FIG. 4, in the case of the conventional control, when the number of copies reaches 1,000, the surface temperature of the heat roller 46a falls below 160 ° C. (the lower limit temperature at which fixing is possible). . For this reason, in the case of the conventional example, the printing operation is temporarily stopped
It is necessary to wait until the surface temperature of the heat roller 46a recovers, or to switch the printing speed to a low speed before the surface temperature of the heat roller 46a decreases to 160 ° C. to stop the decrease in the surface temperature. In either case, the high-speed printing operation cannot be continued, and the productivity is inevitably reduced.

On the other hand, in the case of the present embodiment, the surface temperature of the heat roller 46a after switching from the first heater 46X to the second heater 46Y decreases not only gradually but also by 170 ° C. Stops around ℃. That is, the amount of heat applied to the heat roller 46a is balanced with the amount of heat taken from the heat roller 46a by paper passing or the like. Therefore, the lower limit temperature for fixing is not lowered to 160 ° C., the number of sheets that can be continuously printed at high speed is not limited, and the productivity does not decrease.

FIG. 4 shows a case where the number of originals is 100, but the same tendency is observed when this set value is changed. In FIG. 4, the original reading operation is started at the same time as the start of the copying operation. However, when the original reading operation is controlled to be started during warm-up, jam recovery, or returning from the power saving mode. Has a second heater
The switching time to 46Y can be further advanced. That is, the heating capacity can be increased from an earlier time.

[0026]

According to the present invention, when power is supplied simultaneously with the second heater, a member exceeding the maximum power of the image forming apparatus provided with the main fixing device (for example, a document reading section and an automatic document feeder)
Is not operating, the second heater is used instead of the first heater. For this reason, it is possible to prevent a temperature decrease due to a relative shortage of the heating amount of the heat roller, and it is possible to perform a large amount of image forming operations continuously and at a high speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of a power supply circuit of a digital copying machine according to an embodiment of the present invention.

FIG. 2 is a sectional view schematically showing a mechanism of the digital copying machine according to the embodiment of the present invention.

FIG. 3 is a sectional view schematically showing a mechanism of a fixing device of the copying machine shown in FIG. 2;

FIG. 4 is a graph showing measured values of the number of copies and the temperature of a heat roller during continuous copying in the case of the embodiment of the present invention and in the case of the conventional example.

FIG. 5 is a time chart illustrating temperature control of the fixing device according to the embodiment of the present invention.

FIG. 6 is a time chart illustrating temperature control of a fixing device of a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 20 document reading section 30 automatic document feeder 46 fixing device 46X first heater 46Y second heater

Claims (2)

[Claims] 1. A fixing device for fixing a heated fixing member to a recording sheet onto which a toner image has been transferred by an electrophotographic method by pressing the fixing member, comprising: a first heater provided to heat the fixing member; A second heater provided to heat the fixing member with higher power consumption and heating capacity than the first heater; and a power supplyable power of the image forming apparatus provided with the present fixing device when power is supplied simultaneously with the second heater. And a control means for monitoring the operation state of the member to be moved and, when the member is not operating, using the second heater instead of the first heater. 2. The fixing device according to claim 1, wherein the image forming apparatus is a digital copying machine, and the members are an automatic document feeder and a document reading device.