JPH11231714A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently carry out copying even under a power saving mode without being left only for warm-up time at the start of the copying with respect to a copying machine capable of forming images on a plurality of copying sheets carried in parallel. SOLUTION: In a fixing device, a heater and a temperature detection sensor, which correspond to a front carrying path area and a rear carrying path area, are provided, and control is exerted so that the surface temperature of the front carrying path area of a fixing roller is always maintained at a fixing temperature T1 and that of the rear carrying path area is maintained at a power saving temperature T2, which is lower than the fixing temperature T1, when the power saving mode is executed. To start copying under the power saving mode, a copying operation is carried out using the front carrying path, and also the rear carrying path area of the fixing roller is heated [an interval between (c) and (d)]. When the rear carrying path area reaches the fixing temperature T1 [point (d)] copying by parallel carrying is carried out by the use of both the carrying paths afterwards.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a laser printer capable of forming an image on a plurality of recording sheets conveyed in parallel, and more particularly, to a toner formed on a recording sheet. The present invention relates to an improvement in a fixing device for fixing an image.

[0002]

2. Description of the Related Art Hitherto, in the field of image forming apparatuses, especially in the field of copying machines, there has been a demand for an increase in copy speed in order to make more copies in a short time. As described above, in order to increase the copy speed, it is necessary to increase the overall speed of each part related to the copy process such as the rotation speed of the photosensitive drum and its peripheral portion, the scanning speed of the optical system,
As a result, copiers have become larger, more complex, and more expensive.

For example, Japanese Patent Laid-Open Publication No. Hei 2-24673 discloses a copying machine that conveys two copy sheets in parallel and forms an image on each copy sheet. In the copying machine capable of parallel conveyance, it is possible to form an image on two copy sheets in one image forming operation, so that the copy processing speed can be doubled and the efficiency of the copy operation can be increased.

[0004] On the other hand, the copier is transported in parallel.
A fixing device having a heating value sufficient to reliably heat-fix a toner image on a copy sheet is required, and accordingly, a large amount of power needs to be supplied to a heater in the fixing device. By the way, recently, there is a strong demand for energy saving based on the energy situation, and the above-mentioned parallel transportable copier which requires a large amount of power consumption by using a heater is also required to have a power saving function. Have been.

This power saving function automatically lowers the temperature in the fixing device to a temperature lower than the fixing temperature (about 160 ° C., for example, 60 ° C.) when an input operation is not performed by an operator within a predetermined time after printing is completed. The power consumption is reduced as much as possible to achieve energy saving by lowering the temperature to about ℃ and suspending the supply of power to the heater in the fixing device. This is called "power saving mode."

[0006]

However, the use of the power saving mode as described above contributes to energy saving, but hinders the efficiency of the copying operation. That is, in the state where the above-described power saving mode is being executed, even if the operator gives a copy start instruction on the operation panel, the temperature in the fixing device is about 160 ° C. which is the fixing temperature.
(Hereinafter, this time is referred to as "warming-up time"), and this time hinders the copying work efficiency, and is a copier that can be conveyed in parallel for high-speed copy processing. There is no point in adopting.

The present invention has been made in view of such a problem, and in an image forming apparatus capable of carrying in parallel, even when a power saving mode is executed, a warm-up time is required when starting copying. It is an object of the present invention to provide an image forming apparatus capable of performing a copying operation efficiently without waiting.

[0008]

In order to achieve the above object, the present invention conveys a recording sheet to each of a plurality of conveying paths provided in parallel, and transfers an image on an image carrier to each recording sheet. An image forming apparatus for forming an image by transferring the image and thermally fixing the image, wherein a first heat fixing unit provided corresponding to at least one conveyance path, and an image forming apparatus provided corresponding to another conveyance path A heat fixing unit including a second heat fixing unit;
Temperature control means for controlling the temperatures of the first and second heat fixing sections, wherein the temperature control means controls the temperature of the first heat fixing section to always maintain a predetermined fixing temperature. The temperature of the second heat fixing unit is at least
When the image forming operation is performed on the corresponding transport path, the fixing temperature is raised to the predetermined fixing temperature, and then the fixing temperature is maintained during the image forming operation. Otherwise, the temperature is controlled to be lower than the fixing temperature. It is characterized by doing.

Further, the present invention provides a method for forming an image,
If the second heat fixing unit has not reached the fixing temperature, the first
The image formation is performed only on the transport path corresponding to the heat fixing unit, and when the second heat fixing unit reaches the fixing temperature, the image formation is performed on at least one transport path corresponding to the second heat fixing unit. The image forming apparatus further includes an image forming control unit that controls the image forming apparatus to execute the image forming apparatus.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described using a digital copying machine capable of carrying in parallel as an example. FIG. 1 is a diagram showing the overall configuration of the digital copier (hereinafter, simply referred to as “copier”).

As shown in FIG. 1, the copying machine includes an automatic document feeder 10, an image reading unit 30, a printer unit 40, and a paper feeding unit 60. The automatic document feeder 10 includes:
A plurality of documents set on a document feed tray 11 are fed one by one by a feed roller 12, a separating roller 13, and a separating pad 14, and the image reading unit 3 is transported by a transport belt 15.
After the document is read by the image reading unit 30, the document is conveyed again by the conveyance belt 15 rightward in FIG.
The document is then discharged onto a document discharge tray 17 through the document tray 6.

The image reading section 30 includes a scanner 31 which moves in the direction of the arrow in FIG. 1 by driving the scanner motor M1. The scanner 31 includes an exposure lamp 32 for irradiating a document, and a contact type CCD image sensor (hereinafter, simply referred to as a “CCD sensor”) 33 for converting reflected light from the document to an electric signal. The image of the document illuminated by the exposure lamp 32 of the scanner 31 is
3, the electric signal is converted into an electric signal by the control unit 100.
Sent to The electric signal is transmitted to the control unit 100 by A
The digital signal is converted into a digital signal, stored in an image memory 131 (see FIG. 5) in the control unit 100, read out as needed, and converted into a drive signal for the laser diode 41.

The printer section 40 is composed of an optical system for exposing the surface of the photosensitive drum 45 around the photosensitive drum 45, and an image processing system for visualizing the exposed image and reproducing it on copy paper. In the optical system, the output of the laser diode 41 of the optical system is modulated by the drive signal output from the control unit 100. The output laser light is transmitted to the polygon motor 4
The light is reflected by the mirror surface of the polygon mirror 42 rotated at a constant speed by 3, passes through the fθ lens 44, is reflected by a predetermined folding mirror, exposes and scans the surface of the photosensitive drum 45, and writes an electrostatic latent image.

The image processing system includes a charging charger 46,
Developing device 47, transfer charger 48, separation charger 4
9, a cleaner 50, and an eraser lamp 51 are arranged around the photosensitive drum 45, and form an image on a copy sheet fed from the sheet feeding unit 60 by a well-known electrophotographic technique. That is, after the residual toner and the residual charge on the surface of the photoconductor are removed by the cleaner 50 and the eraser lamp 51, the photoconductor drum 45 is charged.
6, the electrostatic latent image is formed by exposure scanning by the optical system. The electrostatic latent image on the photoconductor drum 45 is developed by a developing device 47 to form a toner image, and then the formed toner image is fed out of the paper feeding unit 60 by a transfer charger 48 below the photoconductor drum 45. Is transferred to the copied paper.

The paper supply section 60 includes, for example, paper supply cassettes 64a and 64b for setting A4 size copy paper 63a and 63b in parallel in the vertical direction and a paper supply cassette 65 for storing A3 size copy paper 66 in the horizontal direction. And pick-up rollers 61a, 61b,
62 and the like. When any one of the paper feed cassettes is selected, the copy paper set in the paper feed cassette is fed by the corresponding pickup roller, and is passed through the timing roller 55 to the photosensitive drum 45.
It is conveyed to the lower transfer position.

The copy paper on which the toner image is formed by the image processing system is conveyed to a fixing device 70 by a conveyance belt 52, and is heated and pressed by fixing rollers 71 and 72 having heaters 73a and 73b therein. As a result, the toner is fixed. The copy paper after fixing is discharged to a discharge roller 53.
And discharged to the discharge tray 54. In addition,
SE1a, SE1b, SE2a, SE2b, SE3a,
SE3b is a jam detection sensor that detects the passage of the copy paper transported to each transport path. Further, an easy-to-operate position on the front surface of the image reading unit 30 (broken line in FIG. 1).
Is provided with an operation panel 34 for the operator to set various copy modes. The operation panel 34 is used to input a number of copies, a copy magnification, and the like, and to start a copy operation. A start key, a display unit for displaying the set copy mode, and the like are provided.

FIG. 2 is a perspective view showing the structure of a main part around the photosensitive drum 45 in the printer unit 40.
This figure shows a state in which an image is formed on an A4-size copy sheet conveyed in parallel. Note that, for convenience of description, the folding mirror, the cleaner 50, and the like are omitted. The laser light output from the laser diode 41 is
2, through the fθ lens 44, the paper feed cassette 64a,
Copy paper 63a, 6 fed from the paper 64b and conveyed in parallel
3b, an electrostatic latent image is written at the image forming positions Sa and Sb on the surface of the photoconductor drum 45 (hereinafter, the conveying path of the copy paper conveyed corresponding to the image forming position Sa is referred to as “forward conveying”. The transport path corresponding to the “path” and Sb is referred to as the “rear-side transport path.”

The electrostatic latent images formed on the front and back sides of the photosensitive drum 45 are developed by a common developing device 47 and transferred to copy paper 63a, 63b by a transfer charger 48. The copying paper 63a, 63b after the transfer is
And heat-fixed. FIG. 3 is a sectional view showing the configuration of the fixing device 70. The fixing device 70
A pair of fixing rollers 7 for fixing a toner image on copy paper
1, 72, heaters 73a, 73b disposed inside the fixing roller 71, temperature detection sensors 74a, 74b for detecting the surface temperature of the fixing roller 71, and an abnormally high temperature in the apparatus, for example, about 200 ° C. Thermal switches 75a and 75b, which become non-conductive when detected and cut off power supply to the heaters 73a and 73b, are provided. Note that the temperature detection sensors 74a and 74b and the thermal switch 75a,
75b is a perspective view of the fixing roller 71 in FIG.
They are provided at positions corresponding to the transport paths on the near side and the far side, respectively.

On the upper part of the fixing device 70, a web roller 763 around which a long nonwoven fabric containing silicone oil is wound around a rotating shaft, a web winding roller 761 which winds the nonwoven fabric around a rotating shaft, An oil application roller 762 for pressing the nonwoven fabric against the surface of the fixing roller 71
Are supported by a frame (not shown), and the fixing rollers 71, 7
(2) While supplying silicon oil to the surface, dirt on the surface is wiped off.

Further, a lower portion of the fixing device 70 is provided with a spring 78 for lifting the fixing roller 72 and pressing the fixing roller 71 against the fixing roller 71, and separating claws 771, 772 for separating the copy paper from the surfaces of the fixing rollers 71, 72. I have. In addition,
The fixing roller 71 is rotatably supported by a frame (not shown) of the fixing device 70 via a bearing.
A and 73b are fixed to a supporting member attached to the frame so that the fixing roller 71 does not come into contact even when rotated.

FIG. 4 is a perspective view of the fixing roller 71 when viewed from the front upper right in FIG. As shown in the figure,
The heater 73a has a heating filament 731a only at a portion corresponding to the front-side conveyance path region from the longitudinal center to the left end of the fixing roller 71, and does not heat the back-side conveyance path region from the longitudinal center to the right end. And a temperature detection sensor 74a and a thermal switch 75a
Is the fixing roller 7 heated by the heater 73a.
The temperature of the front-side transport path area is detected.

On the other hand, the heater 73b has a heating filament 731b only in a portion corresponding to the back side conveyance path area of the fixing roller 71, and is configured not to heat the front side conveyance path area. And the thermal switch 75b detect the temperature of the rear side transport path area. Each of the heaters 73a and 73b is longer than the fixing roller 71 and is fixed by supporting members (not shown) provided at both ends thereof. However, the present invention is not limited to such a configuration. With respect to the road area, a configuration may be adopted in which a heater having a length from the left end to the vicinity of the center in the longitudinal direction is fixed by the support member only at the left end portion so as not to contact the inner surface of the fixing roller 71. Further, in the rear side transport path region, a heater having a length from the right end to the vicinity of the center in the longitudinal direction is configured to be fixed by the support member only at the right end portion so as not to contact the inner surface of the fixing roller 71.

As described above, the fixing device 70 is provided with a heater for heating each transport path, a temperature detection sensor, and the like, and the surface temperature of the fixing roller 71 is controlled to a predetermined temperature by the control unit 100. Next, the configuration of the control unit 100 installed inside the copying machine will be described with reference to the block diagram of FIG.

As shown in FIG. 1, the control unit 100 includes an image reading control unit 110, an image signal processing unit 120, a memory control unit 130, a printer control unit 140, a fixing temperature control unit 150, a main control unit. 160 and others. Each control unit is configured around a CPU,
A ROM storing programs necessary for the respective controls and a RAM serving as a work area when executing the programs are provided, and data and commands are mutually exchanged via a command line CL.

The image reading control section 110 controls the operation of the automatic document feeder 10 and the image reading section 30 to execute reading of a document. The image data of the document read by the CCD sensor 33 is sent to the image signal processing unit 120. The image signal processing unit 120 includes an A / D converter, a shading correction unit, an MTF correction unit,
The image data of the input document is processed by the respective units, and then processed by the memory control unit 130.
Is forwarded to

The memory control unit 130 binarizes or further encodes the image data, and
1 and read image data from the image memory 131 in response to an instruction from the main control unit 160,
This is sent to the printer control unit 140. Printer control unit 140
Outputs a drive signal to the laser diode 41 based on a control program stored in an internal ROM for the image data read from the image memory 131 to form an electrostatic latent image on the photosensitive drum 45 . Further, the image processing system and the sheet feeding operation from each sheet cassette are controlled to execute printing on copy paper.

The fixing temperature control section 150 includes a fixing roller 71.
Is controlled for each of the transport path areas on the near side and the far side.
Further, the main control unit 160 receives various key inputs from the operation panel 34, reports the set copy mode to the control units 110 to 160, and controls the entire system in a unified manner.

FIG. 6 is a block diagram showing the structure of the fixing temperature control section 150. As shown in the figure, the fixing temperature control unit 150 includes a CPU 151 and an SSR (Solid State Relay) 15 that starts or stops energization of the heaters 73a and 73b in response to an instruction from the CPU 151.
3, 155 and the analog detection signals output from the temperature detection sensors 74a and 74b are converted into digital signals,
It is composed of A / D converters 152 and 154 to be sent to the PU 151, a ROM 156 for storing a temperature control program, a RAM 157 for temporarily storing the current operation state, instructions from the main control unit 160, and the like.

The RAM 157 stores a temperature (fixing temperature) T1 required for fusing toner to copy paper at the time of copying.
And the temperature to be maintained in the power saving mode (power saving temperature) T2
(More precisely, a digital signal value corresponding to the temperature), and the CPU 151 transfers the digital signal value as a reference temperature for temperature control according to the currently set operation state (whether or not the power saving mode is set). The above T1 and T2 are selected for each road, and a digital signal value corresponding to the reference temperature and the A / D converter 15 detected by the temperature detection sensors 74a and 74b.
The digital signal values obtained by the conversion in step 2 and 154 are compared (hereinafter, in order to avoid such a roundabout expression, the comparison between the two digital signal values is simply referred to as “compare the reference temperature and the detected temperature”. Do it. ").

The CPU 151 compares the reference temperature with the detected temperature, and if the detected temperature is lower than the reference temperature,
An ON signal (energization start signal) for turning on the heaters 73a and 73b is output to R153 and 155, and an OFF signal (energization stop signal) for turning off the heaters 73a and 73b is output if the temperature is higher than the reference temperature. By performing such control, the surface temperature of the fixing roller 71 is maintained substantially at the reference temperature for each of the two conveyance path regions.

FIG. 7 is a temperature control diagram showing how the surface temperature of the fixing roller 71 is controlled by the CPU 151 at the time of turning on the power of the copying machine, at the time of copying, at the time of the power saving mode, and the like. When the power of the copying machine is turned on, the fixing roller 71 is heated by the heaters 73a and 73b and is heated (section (a) in FIG. 3).

When the surface temperatures of the two conveyance paths of the fixing roller 71 reach the fixing temperature T1, the CPU 151 maintains the fixing temperature T1. Next, when an instruction to start copying, for example, when a print key is pressed by the operator, copying by parallel conveyance is started using the front side and back side conveyance paths (point (b) in the figure). During this time, the surface temperature of both the conveyance paths of the fixing roller 71 is maintained at the fixing temperature T1.

After the copying by the parallel conveyance is completed,
Even when the predetermined time t has elapsed, if no instruction to start copying or the like is given by the operator, the surface temperature of the back side conveyance path area of the fixing roller 71 becomes the power saving temperature T2 lower than the fixing temperature T1. And the power saving mode is executed. However, the front side transport path area is maintained at the fixing temperature T1.

When a copy start instruction is given by the operator during the execution of the power saving mode, copying is started in the front transport path, and the rear transport path area is heated by the heater 73.
b (point (c) in the figure). While copying is being performed on the front side transport path, the fixing roller 71
When the surface temperature of the back side conveyance path area reaches the fixing temperature T1,
Copying is also started on the back side transport path ((d) in FIG.
Point), and thereafter, copying by parallel conveyance is performed.

As described above, the power supply to the heater 73b is reduced by controlling the inner side conveyance path area of the fixing roller 71 to the power saving temperature T2 when the power saving mode is executed, thereby realizing energy saving. In addition, since the front side transport path area is maintained at the fixing temperature T1 even during execution of the power saving mode, the operator can efficiently perform copying without waiting for the warm-up time. At this time, when the rear transport path area of the fixing roller 71 is heated by the heater 73b and reaches the fixing temperature T1, copying is started not only in the front transport path but also in the rear transport path. There is no extreme decrease in speed.

After the copying by the parallel conveyance is completed,
If the operator does not give any instruction to start copying even after the predetermined time t has elapsed, the copier enters the power saving mode as described above, and Is controlled so that the surface temperature becomes the power saving temperature T2, and the front side transport path area becomes the fixing temperature T1. The fixing temperature T1, the power saving temperature T2, and the predetermined time t are determined in advance based on a copy processing speed, toner fixing characteristics, a power saving effect, and the like.
60 ° C., the power saving temperature T2 is 60 ° C., and the predetermined time t is 10
Set to about a minute.

Next, a control operation for forming an image by transporting copy paper in parallel will be described with reference to flowcharts shown in FIGS. FIG. 8 is a flowchart showing a main routine of the control operation of the copying machine. First, when the power of the copier is turned on, each of the control units 11 in the control unit 100 is controlled.
Initial settings such as initialization of CPUs and ROMs of 0 to 160 are performed (step S1).

Thereafter, a repetitive loop process of S2 to S7 is executed. That is, an internal timer for managing the execution time of one routine is set (step S2), and the setting contents such as the number of copies, the copy paper size, and the copy mode input by operating the keys on the operation panel 34 are stored in the RA.
A key input process (step S3) for receiving an input of a print key or the like stored in the M157, reading a document, and storing the image data in the image memory 131 (step S4). After executing the print processing for reading out the stored image data and forming an image on copy paper (step S5) and the fixing temperature control processing for controlling the surface temperature of the fixing roller 71 (step S6), the internal timer is terminated. It waits (step S7), and then returns to step S2 to repeat the above processing. Next, the contents of steps S5 and S6 will be described in detail.

FIG. 9 is a flowchart showing the contents of the print processing in step S5. In the flowchart, the “print flag” is a flag that determines whether or not the copying machine is performing a copy operation.
When the print key is pressed by the operator, “1” is set. The “standby flag” is a flag for determining whether or not the printing process can be performed on the back side conveyance path, and is a temperature at which the surface temperature of the back side conveyance path area of the fixing roller 71 is lower than the fixing temperature T1. Is set to "1" when print processing cannot be performed. The setting timing of the standby flag will be described later.

The print flag and the standby flag are R
It is stored in a management table inside the AM 157. Also,
The “power saving timer” is an internal timer of the CPU 151 provided to measure the above-mentioned predetermined time t. In addition,
In the initial setting of step S1 in FIG. 8, the print flag and the standby flag are set to "0", and the power saving timer is reset.

First, in step S51, the CPU 1
51 determines whether or not the print flag is “1”. If it is determined that the print flag is "1", it is next determined whether or not the standby flag is "1" (step S52). When the standby flag is “1”, since the surface temperature of the back side conveyance path area of the fixing roller 71 is lower than the fixing temperature T1, the printing process is started using only the front side conveyance path. (Step S53). This corresponds to point (c) in FIG. 7 described above.

On the other hand, if the standby flag is not "1",
The surface temperature of the rear conveyance path area of the fixing roller 71 is the fixing temperature T.
1, the printing process is performed by the parallel transport using the transport paths on the near side and the far side (step S54). This corresponds to (b) in FIG.
(D) It corresponds to a point. Next, the CPU 151 refers to the management table to determine whether or not all copies of the image data of the document stored in the image memory 131 have been completed, and if not completed, returns to the main routine. , The process proceeds to the next copy (step S55).

On the other hand, if all copies have been completed, the print flag is set to "0" (step S56), and the copy sheet on which an image has been formed last is detected by the jam detection sensor SE3.
(a) After a predetermined time has passed after passing through SE3b, the power saving timer is reset once, and the counting is started (steps S57 and S58). FIG. 10 is a flowchart showing a main routine of the fixing temperature control process in step S6.

In the fixing temperature control process, the CPU 151 performs the temperature control of the front conveyance path area of the fixing roller 71 and the temperature control of the rear conveyance path area in parallel, and returns (steps S60 and S61). In the near-side transport path temperature control in step S60, the SSR1 is controlled so that the surface temperature of the near-side transport path area of the fixing roller 71 always becomes the fixing temperature T1.
A signal for turning on / off the heater 73a is output to the controller 53.

The temperature control of the back side transport path in step S61 will be described with reference to the flowchart of the next subroutine shown in FIG. First, in step S611, the CPU 151 determines whether the print flag is “1”. If the print flag is not "1", that is, if the copy operation is not being performed, it is determined in step S612 whether the power saving timer has counted up. If the power saving timer has not counted up, that is, if counting is in progress or has not started counting, it is determined whether or not the surface temperature T of the fixing roller 71 is higher than the fixing temperature T1 as a reference temperature. If it is lower than T1, the heater 73b is turned on and the process returns (steps S613 and S615).

On the other hand, if the surface temperature T is higher than the fixing temperature T1, the heater 73b is turned off and the process returns (step S614). As described above, the surface temperature T of the fixing roller 71 in the rear side conveyance path area is maintained at substantially the fixing temperature T1. If the power saving timer reaches the predetermined value t and counts up in step S612, the CPU 1
51 sets the standby flag to “1” (step S61)
6).

The CPU 151 determines the fixing temperature T1
Using the lower power saving temperature T2 as a reference temperature, the fixing roller 71
It is determined whether or not the surface temperature T is higher than the power saving temperature T2. If the surface temperature T is higher than the power saving temperature T2, the heater 73b is turned off (steps S617 and S618). If the surface temperature T is lower than the power saving temperature T2, the heater 73b is turned on. The process returns (steps S617 and S619). As a result, the surface temperature T of the fixing roller 71 in the rear conveyance path region is maintained at the power saving temperature T2, and the power saving mode is executed.

If the print flag is "1" in step S611, that is, if the copying machine is performing a copying operation, the CPU 151 determines whether or not the standby flag is "1" (step S620). ).
If the standby flag is "1", after the power saving mode is canceled, the heater 73b is turned on to increase the surface temperature T of the fixing roller 71 in the rear side conveyance path area. If the fixing temperature T1 has not been reached, the heater 73b is turned on and the process returns ("N" in step S621, S622). (Sections (c) to (d) in FIG. 7 described above) When the back side conveyance path area of the fixing roller 71 is heated by the heater 73b and the surface temperature T reaches the fixing temperature T1,
The heater 73b is turned off, the standby flag is set to “0”, and the process returns (“Y” in step S621, S62
3, S624). (Point (d) in FIG. 7 described above) If the standby flag is not “1” in step S620, the process proceeds to step S613, and the above-described temperature control in steps S613 to S615 is performed.

When the routine goes round after the standby flag is set to "0" in step S624, the determination in step S52 in the print processing of FIG. 9 becomes "N", and the print processing by parallel conveyance is started. Will be. For example, if one original is to be continuously copied 100 times during execution of the power saving mode, first, the image data of the original stored in the image memory 131 is read, and the printing process is started on the near side transport path (FIG. 9, "Y" in step S52, and S53), and heats the heater 73b by turning on the heater 73b ("Y" in step S620, "N" in S621, S).
622). If the surface temperature T in the rear conveyance path area reaches the fixing temperature T1 at the time when, for example, 20 print processes are completed in the front conveyance path, the standby flag is set to “0” at this time.
(Steps S621, S623, S624),
From the print processing for the 21st sheet, print processing for 40 sheets is performed by parallel conveyance using the front side and the back side conveyance paths (“N” in step S52 of FIG. 9, S54). During the printing process by the parallel transport, step S62 in FIG.
The determination of 0 becomes “N”, and the process proceeds to step S613.
The rear side transport path area is maintained at approximately the fixing temperature T1 (steps S613 to S615).

The temperature of the back side transport path in step S61 is controlled in addition to the above-mentioned control. After (from section (a) in FIG. 7), the power saving mode may be started even when the operator does not give an instruction to start copying even after a predetermined time has elapsed. In this case, the count of the power saving timer is started after the surface temperature of both the conveyance paths of the fixing roller 71 reaches the fixing temperature T1, and the standby flag is set to “1” after a predetermined time has elapsed.
Then, the rear side transport path area is maintained at the power saving temperature T2.

In the flowcharts of FIG. 8 to FIG. 11, the control operation when the copy paper is conveyed in parallel to form an image has been described. When the power saving mode is executed, the A3-size copy paper is passed in the horizontal direction. In this case, the copying is started after the surface temperature of the rear conveying path region of the fixing roller 71 reaches the fixing temperature T1. Although the copying machine according to the present invention has been described based on the embodiment, the content of the present invention is not limited to the above-described embodiment, and the following modified examples can be considered.

(1) In the present embodiment, a copying machine that simultaneously transports two sheets of copying paper in parallel has been described.
The present invention is also applicable to a copying machine capable of carrying three or more copy sheets in parallel and forming an image on each copy sheet. A heater having heating filaments corresponding to three or more conveyance paths and a temperature detection sensor for detecting a surface temperature of each conveyance path area of the fixing roller 71 are arranged in the fixing device 70,
The fixing temperature T1 is always set for at least one conveyance path area.
To maintain. The other transport path areas are maintained at the power saving temperature T2 when the copy operation is not performed, and at least the corresponding transport path areas are fixed at the fixing temperature T1 when the copy operation is performed.
And the fixing temperature T1 is maintained during the copying operation.

(2) In the above embodiment, the control is performed such that the rear conveying path area of the fixing roller 71 is maintained at the power saving temperature T2 lower than the fixing temperature T1 when the power saving mode is executed. The power supply to the heater 73b corresponding to the back side conveyance path may be stopped when the power saving mode is executed, without being limited to the above method. In this case, power consumption is reduced as compared with the case where the power saving temperature T2 is maintained, and energy saving can be realized.

(3) In the above embodiment, heaters 73a and 73b having heating filaments corresponding to the conveyance path area are provided inside one fixing roller 71, so that a large-sized copy paper such as A3 size can be used. Although the fixing is enabled, the present invention is not limited to such a configuration. In an image forming apparatus dedicated to parallel conveyance, a fixing device may be independently provided for each conveyance path to perform temperature control. .

(4) In the above embodiment, the power saving mode is controlled to start after a predetermined time t has elapsed from the end of the copy operation. However, the present invention is not limited to such a method, and the control is performed immediately after the end of the copy operation. Control may be performed to start the power saving mode. In this case, since the power saving mode is started without waiting for the predetermined time, power consumption is reduced by that amount, and energy saving can be realized.

(5) The present invention is applicable not only to the above-described image forming apparatus in the digital copying machine but also to other image forming apparatuses such as a laser printer.

[0057]

As described above, according to the present invention, the temperature of the first heat fixing unit provided corresponding to at least one transport path is controlled so as to always maintain a predetermined fixing temperature,
Regarding the temperature of the second heat fixing unit provided corresponding to the other transport path, at least when the image is formed in the corresponding transport path, the temperature is raised to the predetermined fixing temperature and during the image forming operation. Since the fixing temperature is maintained and the temperature is controlled to be lower than the fixing temperature at other times, the power supplied to the second heat fixing unit can be reduced, and energy saving can be realized.

In forming an image, if the second heat fixing unit has not reached the fixing temperature, control is performed so that image formation is performed only on the transport path corresponding to the first heat fixing unit. Thus, the operator can start the image forming operation without waiting. Furthermore, if the second heat fixing unit reaches the fixing temperature, control is performed so that image formation is performed in at least one conveyance path corresponding to the second heat fixing unit, so that the processing speed is extremely reduced. Image formation can be performed efficiently without any problem.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a copying machine according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an image forming unit of the copying machine.

FIG. 3 is a sectional view showing a configuration of a fixing device of the copying machine.

FIG. 4 is a perspective view of a fixing roller in the fixing device.

FIG. 5 is a block diagram showing a configuration of a control unit in the copying machine.

FIG. 6 is a block diagram illustrating a configuration of a fixing temperature control unit in the control unit.

FIG. 7 is a temperature control diagram showing how the surface temperature of the fixing roller is controlled.

FIG. 8 is a flowchart showing a main routine of a control operation of the control unit.

FIG. 9 is a flowchart showing a print processing subroutine of the main routine.

FIG. 10 is a flowchart showing a subroutine of a fixing temperature control process of the main routine.

FIG. 11 is a flowchart showing a subroutine for controlling the temperature of the rear side conveyance path in the fixing temperature control process.

[Explanation of symbols]

 Reference Signs List 40 Printer unit 70 Fixing devices 71, 72 Fixing rollers 73a, 73b Heaters 74a, 74b Temperature detection sensors 75a, 75b Thermal switch 100 Control unit 150 Fixing temperature control unit 151 CPU 152, 154 A / D converter 153, 155 SSR 156 ROM 157 RAM 731a, 731b Filament for heating

Claims (2)

[Claims] An image for conveying a recording sheet to each of a plurality of conveying paths provided in parallel, transferring an image on an image carrier to each recording sheet, and thermally fixing the image to form an image. A heat fixing unit including: a first heat fixing unit provided corresponding to at least one conveyance path; and a second heat fixing unit provided corresponding to another conveyance path. A temperature control unit that controls a temperature in the first and second heat fixing units, wherein the temperature control unit constantly controls the temperature of the first heat fixing unit.
A predetermined fixing temperature is controlled to be maintained, and the temperature of the second heat fixing unit is raised at least to the predetermined fixing temperature when an image forming operation is performed in a corresponding conveyance path, and then the image of the second heat fixing unit is heated. An image forming apparatus, wherein the fixing temperature is maintained during a forming operation, and the temperature is controlled to be lower than the fixing temperature in other cases. 2. When forming an image, if the second heat fixing unit has not reached the fixing temperature, the image forming is performed only on the conveyance path corresponding to the first heat fixing unit, and the second heat fixing unit is operated. 2. The image forming apparatus according to claim 1, further comprising: an image forming control unit configured to control the image forming unit to execute image forming in at least one conveyance path corresponding to the second heat fixing unit when the fixing unit reaches a fixing temperature. Image forming apparatus.