JPH0990804A - Image forming device - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide an image forming apparatus which can obtain an energy saving effect without impairing the fixing property of a fixing device. According to the present invention, when a standby state of a device exceeds a predetermined time, a display lamp or the like of an operation unit is turned off, and an exhaust fan 1 is provided.
In the image forming apparatus having the automatic preheating function of shifting to the preheating mode by performing control such as stop of No. 8 and control temperature decrease of the fixing device 13, if the duration of the preheating mode continues for a predetermined time or more, It is characterized in that the pair of fixing rollers (fixing roller 13a, pressure roller 13b) are rotated for a predetermined time. Further, it is characterized in that the time for rotating the pair of fixing rollers 13a and 13b is changed according to the fixing temperature in the preheating mode. As a result, it is possible to prevent the temperature on the pressure roller side from decreasing in the preheating mode, obtain a good fixed image even immediately after releasing the preheating mode, and obtain a sufficient energy saving effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile or a printer, and more particularly to an image forming apparatus having a preheating function.

[0002]

2. Description of the Related Art In recent years, energy-saving activities have been actively carried out on a global level as a part of global environmental protection. Naturally, energy-saving activities are also carried out for OA equipment, and many image forming apparatuses such as copiers and facsimiles have been put on the market for energy saving.

Generally, in an electrophotographic image forming apparatus such as a copying machine, an electrostatic latent image is formed on a charged photoconductor by exposure of a document image or optical writing, and the latent image is formed by toner of a developing device. It is developed to form a toner image, and the toner image is transferred to a transfer material such as transfer paper. Then, the toner image transferred onto the transfer paper is heated and fixed by a fixing device having a heater.In such an image forming apparatus, the fixing device is usually a fixing roller having a heater. A fixing roller pair including a pressure roller pressed against the fixing roller is provided, and energization of the heater is controlled so that the temperature of the fixing roller is maintained at a predetermined temperature.
Also, in order to prevent the temperature inside the machine from rising due to heat radiation from the fixing device, the image forming apparatus is equipped with an exhaust fan, and the exhaust fan is turned on during operation of the apparatus to replace the air inside the machine and cool it. It is supposed to do. But,
If the temperature of the fixing device is kept at a predetermined temperature even when the apparatus is in the standby state, or if the exhaust fan is kept on all the time, useless power consumption other than during the image forming operation significantly increases. Therefore, as a concrete method for energy saving in such an image forming apparatus, when the standby state of the apparatus continues for a predetermined time or more, the display lamp of the operation unit is turned off, the exhaust fan is stopped, and the control temperature of the fixing device is changed. Mainly has an automatic preheat function that controls the decrease etc. and shifts to the preheat mode,
Some products are available that allow users to set the time to the automatic preheating function and the control temperature of the fixing device.

[0004]

In the automatic preheating function in the conventional image forming apparatus, the fixing temperature continues to drop to the predetermined standby temperature no matter how many hours the preheating mode lasts. Only the fixing roller side with a built-in heater is controlled, and the temperature of the pressure roller side is not taken into consideration.Therefore, the temperature of the pressure roller is high only in the part in contact with the fixing roller, and The temperature of the part will be quite low. Therefore, the temperature of the pressure roller, which is an important factor that determines the fixing property, is lowered. Even if the preheat mode is released in such a situation, the pressure roller temperature will not be warmed up, and the fixing temperature may not be sufficient immediately after releasing the preheat mode, and the fixability may not be satisfactory, and a good fixed image cannot be obtained. , Is not really energy saving.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus which solves the conventional problems and can also achieve an energy saving effect without impairing the fixing property of the fixing device.

[0006]

In order to achieve the above object, the invention according to claim 1 is such that when the standby state of the device is longer than a predetermined time, the display lamp of the operation portion is turned off, the exhaust fan is stopped, In an image forming apparatus having an automatic preheating function that shifts to a preheating mode by performing control such as controlling the temperature of the fixing device, if the duration of the preheating mode continues for a predetermined time or more, the fixing roller pair of the fixing device is operated for a predetermined time. It is characterized by rotating.

According to a second aspect of the invention, in the image forming apparatus according to the first aspect, the time for rotating the pair of fixing rollers is changed according to the fixing temperature in the preheating mode.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a copying machine showing an example of an image forming apparatus according to the present invention. In FIG. 1, reference numeral 1 is a contact glass on which a document 23 is placed, and although not shown, this contact glass 1
A pressure plate for pressing the document or an automatic document feeder (ADF) is provided on the upper part of the. Reference numeral 2 is a scanner unit for reading a document, and the scanner unit 2 includes a halogen lamp 2a for illuminating a document and mirrors 2b, 2c, 2
d, an image forming lens 2e, and a light receiving section 2f including an image pickup device such as a CCD. The original image is formed on the light receiving section 2e while scanning the original surface, and an electric signal (image) is formed by the light receiving section 2e. It is adapted to be converted into a signal) and transmitted to an image processing unit (not shown). An image forming system for forming an image by an electrophotographic method is arranged below the scanner unit 2, and the image forming system is used for charging the photosensitive drum 4 as an image carrier and the photosensitive drum 4. Charger 5 and optical writing device 3 for performing electrostatic writing on the charged photoconductor drum 4 in accordance with an image signal from the image processing unit to form an electrostatic latent image, and are formed on photoconductor drum 4. A developing device 6 for developing the electrostatic latent image with toner, and a transfer for transferring the toner image on the photoconductor drum 4 onto a transfer sheet fed from a sheet feeding section 8 (or 9) through a registration roller 7. Part 11, a fixing device 13 for fixing the transfer paper on which the toner image is transferred by a fixing roller pair composed of a fixing roller 13a and a pressure roller 13b, a cleaning device 14 for removing the residual toner on the photosensitive drum 4 after the transfer, After cleaning It has a configuration including a discharger 15 and the like that discharges the photosensitive drum 4.

The optical writing device 3 includes, for example, a polygon mirror (polygon mirror) 3a that rotates a light flux from a laser light source (laser diode or the like) 3c whose light quantity is modulated by an image signal at a high speed by a polygon motor 3b. f
A system in which an image is formed on the photosensitive drum 4 by a scanning and image forming optical system 3d including a θ lens, and scanning is performed to perform writing is used. Further, reference numeral 10 in FIG. 1 is a double-sided tray, 16 is a paper ejection roller, 17 is a paper ejection tray, 18 is an exhaust fan, 19 is a human body detection sensor, and 22 is a manual feed table.

Next, the image forming operation in the copying machine having the configuration shown in FIG. 1 will be briefly described. Document 23 set on the contact glass 1 above the scanner unit 2
Is irradiated by a halogen lamp 2a that moves along the surface of the document at a predetermined speed, and the reflected light from the document 23 passes through the mirrors 2b, 2c, 2d and the image forming lens 2e, and the light receiving section 2 is emitted.
An image is formed on f, the presence / absence and shade of the original image are discriminated by a change in the amount of received light, and the light receiving portion 2f converts the electric signal into an electric signal and sends the electric signal to an image processing portion (not shown). In the image processing unit, the electric signal is subjected to predetermined calculation and image processing to form an image signal, which is then transmitted to the optical writing device 3 of the image forming system. In parallel with the operation of reading the original, the photosensitive drum 4 is charged by the charger 5, and the optical writing device 3 drives the laser light source 3c according to the image signal to convert it into a change in the light amount.
Polygon mirror 3 rotated at high speed by polygon motor 3b
Laser light is deflected and scanned onto the photosensitive drum 4 via a and the image forming optical system 3d to form an electrostatic latent image. Then, the latent image on the photosensitive drum 4 is developed with the toner of the developing device 6 to form a toner image.

In parallel with the operation of the image forming system, the paper feeding unit 8
The transfer paper fed from (or 9) by the paper feed roller 8a (or 9a) is conveyed by the transport roller 8b (or 9b, 9).
It is conveyed to the registration roller 7 by c). Then, the transfer sheet is conveyed to the transfer section 11 by the registration roller 7 in time with the toner image formed on the photosensitive drum 4, and the contact section (transfer section) between the photosensitive drum 4 and the transfer conveyance belt 12. The toner image is transferred by. Then, the transfer sheet on which the unfixed toner image is placed is conveyed to the fixing device 13 by the transfer conveying belt 12, and the fixing roller 13 a and the pressure roller 1 are conveyed.
The unfixed toner image is semi-permanently fixed on the transfer sheet by the pair of fixing rollers 3b, and is discharged to the discharge tray 17 via the discharge roller 16. On the other hand, after the toner image is transferred, the photosensitive drum 4 is cleaned by the cleaning device 14 to remove the residual toner, and then discharged by the charge eliminator 15 to move to the next image forming step.

The copying machine having the structure shown in FIG. 1 is provided with the double-sided tray 10, and in the double-sided copy mode, the transfer paper after the one-sided image is fixed in the above-mentioned step is the double-sided conveyance roller 20,
21 is conveyed to the double-sided tray 10 via the double-sided tray 1.
The reverse side of 0 and the paper feed roller 10a reverses the front and back, and is temporarily stocked in the tray 10b. Then, the sheet is fed by the reversing / sheet feeding roller 10a in accordance with the next image forming operation, and is conveyed toward the registration roller 7 via the conveying roller 9c. Then, the toner image is transferred to the back side through the image forming / transferring process similar to the above, the image is fixed by the fixing device 13, and the double-sided copy is ejected to the paper ejection tray 17.

In the copying machine having the structure shown in FIG. 1, when the standby state of the apparatus exceeds a predetermined time, the display lamp of the operation section (not shown) is turned off, the exhaust fan 18 is stopped, and the fixing device 13 is used. It is equipped with an automatic preheating function that shifts to the preheating mode by performing control such as control temperature drop. Further, the human body detection sensor 19 installed in the upper left of the apparatus is located on the panel surface or the like on the front surface of the apparatus. It is designed to be released to enable the image forming operation.

However, in this configuration, as in the above-described conventional apparatus, the fixing temperature is lowered to a predetermined standby temperature in the automatic preheating state, but the heater 36 is built in to be controlled to the standby temperature. Since only the fixing roller 13a side and the pressure roller 13b side temperature are not taken into consideration, the temperature of the pressure roller 13b is high only in the portion in contact with the fixing roller 13a, and the temperature of other portions is considerably low. Become. Therefore, the temperature of the pressure roller 13b, which is an important factor that determines the fixing property, is lowered. Even if the preheat mode is released in such a situation, the temperature of the pressure roller is not sufficiently warmed up, the fixing temperature is insufficient, and the fixability immediately after releasing the preheat mode is often unsatisfactory.

Therefore, in the present invention, by adding the function described below to the above structure, it is possible to achieve the fixability immediately after the preheating mode is released. As a first function thereof, when the duration of the preheating mode continues for a predetermined time or more, the fixing roller pair of the fixing device 13 is controlled to rotate for a predetermined time (claim 1). When the fixing roller pair is rotated for a predetermined time in this manner, the temperature of the pressure roller 3b becomes substantially equal to the temperature of the fixing roller 3a side,
The temperature of the pressure roller 13b can always be maintained above the fixing property attaining temperature.

Further, recently, in many cases, the fixing temperature in the preheating mode can be changed (the temperature is lowered) in order to further improve the energy saving effect. Therefore, the second function is to adjust the fixing temperature in the preheating mode. Control is performed so as to change the time for rotating the pair of fixing rollers. As a result, it is possible to prevent the temperature on the pressure roller side from decreasing, and it is possible to achieve the fixability immediately after the preheating mode is released (Claim 2).

[0017]

Embodiments of the control operation of the copying machine according to the present invention will be specifically described below. 2 is a block diagram showing an example of a control system of the copying machine shown in FIG. In FIG. 2, the main control unit 30 is composed of a microcomputer, an input / output device, etc., and controls the operation of the entire copying machine based on the input by the operation keys 41 of the operation unit 40 and the control information and control data stored in the memory 43. The image is formed under control.

In FIGS. 1 and 2, when the power of the copying machine is turned on, the main control section 30 detects the initial setting of each section and the presence / absence of abnormality, turns on the exhaust fan 18, and turns on the fixing device 13. The heater circuit 35 is turned on, the heater 36 is energized and controlled, the initial operation is performed until the fixing roller temperature of the fixing device 13 reaches a predetermined temperature, and when the initial temperature is reached, the standby state is set. Then, the operation keys 41 of the operation unit 40 are used to make settings (number of copies, paper size selection (paper supply unit selection), scaling ratio setting, single-sided / double-sided copy mode setting, etc.). When the start key is pressed, the control operation of each part is started according to the input information. Then, the scanner section drive system 31, the image forming section drive system (image forming system excluding the fixing device) 32, the sheet feeding / conveying section drive system 3
3 and the fixing device 13 are controlled to control the scanner unit 2 described above.
A series of operations of reading an original image by means of, the image forming operation on the photosensitive drum 4, the conveyance of the transfer sheet to the transfer section 11, and the transfer of the toner image are performed, and after transferring the toner image to the transfer sheet, the transfer is performed. The paper is conveyed to the fixing device 13, the fixing roller pair of the fixing device 13 is driven to fix the toner image on the transfer paper, and the paper is discharged to the paper discharge tray 17. Then, when the copy operation for the set number of sheets is completed, the scanner unit drive system 31 and the image forming unit drive system 3
2. The control operation of the paper feed unit drive system 33 is completed, and a standby state is set.

As described above, the time measurement by the timer 44 is started from the time of the standby state, and when the standby state exceeds a predetermined time, the display device 42 such as the display lamp of the operation unit 40 is turned off and the exhaust air is discharged. The fan 18 is stopped, the heater control temperature of the fixing device 13 is lowered, and the like, and the preheat mode is automatically entered.

Next, FIG. 3 is a flow chart showing an example of the control operation after the copying machine shifts to the preheating mode. Time counting is started by the timer 44 incorporated in the machine from the time when the copying machine enters the preheating mode (here, the preheating mode is automatically entered when the standby state of the machine continues for a predetermined time, The user may press the preheat mode key of the operation unit 40 to enter, but both are in the same preheat mode). And measurement time (preheating mode duration)
After a lapse of a predetermined time T or more, the temperature of the fixing roller at that time is detected by the temperature sensor 34, and the rotation time of the fixing roller pair is determined from the data table shown in Table 1 below stored in the memory 43 in advance. The pair drive system 38 is controlled to rotate the pair of fixing rollers. As a result, the temperature of the pressure roller 13b becomes substantially equal to the temperature of the fixing roller 13a, and the problem that the temperature on the pressure roller side is excessively lowered in the preheating mode is solved. Further, since this series of control operations is performed while the preheating mode continues, the pressure roller is always warmed to a temperature in a region where the fixing property can be satisfied, so that when the preheating mode is released (detected by the human body detection sensor 19). When the fixing roller temperature returns to a predetermined temperature, the temperature on the pressure roller side does not become too low, so that a stable fixed image can be obtained.

[0021]

[Table 1]

Here, in Table 1 above, the correlation between the temperature of the fixing roller and the temperature of the pressure roller is grasped by the duration of the preheating mode,
How many seconds to rotate the pair of fixing rollers,
It is data obtained experimentally as to how many times the temperature of the pressure roller can be guaranteed when the temperature of the fixing roller returns to the predetermined temperature and the fixing property can be guaranteed. Therefore, since it varies depending on the characteristics of each device, it is preferable to experimentally obtain data for each device and store it in the memory 43 as control data.

[0023]

As described above, in the image forming apparatus according to the first and second aspects, the fixing roller pair is rotated for a predetermined time when the preheating mode continuation time continues for a predetermined time or longer. Further, it is possible to prevent the temperature on the pressure roller side from decreasing, and it is possible to obtain a good fixed image even immediately after releasing the preheating mode. Further, since the time for rotating the pair of fixing rollers is changed according to the fixing temperature in the preheating mode, even if the fixing temperature is set low to increase the energy-saving effect, the pressure roller is applied to the fixing roller. It is possible to prevent the temperature on the side from dropping too much, and it is possible to obtain a good fixed image even immediately after releasing the preheating mode.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a copying machine showing an example of an image forming apparatus according to the present invention.

2 is a block diagram showing an example of a control system of the copying machine shown in FIG.

FIG. 3 is a flowchart showing an example of a control operation after the copying machine shifts to a preheating mode.

[Explanation of symbols]

 1: Contact glass 2: Scanner part 3: Optical writing device 4: Photosensitive drum 5: Charging device 6: Developing device 7: Registration roller 8, 9: Paper feeding part 10: Double-sided tray 11: Transfer part 12: Transfer conveyor belt 13: Fixing device 13a: Fixing roller 13b: Pressure roller 14: Cleaning device 15: Static eliminator 16: Paper discharging roller 17: Paper discharging tray 18: Air discharging fan 19: Human body detection sensor 23: Original document 30: Main controller 31 : Scanner unit drive system 32: Image forming unit drive system 33: Paper feed / transport unit drive system 34: Temperature sensor 35: Temperature detection circuit 36: Heater 37: Heater control circuit 38: Fixing roller pair drive system 40: Operation unit 41 : Operation key 42: Display device such as display lamp 43: Memory (ROM, RAM) 44: Timer

Claims (2)

[Claims] 1. When the standby state of the device exceeds a predetermined time,
In an image forming apparatus that has an automatic preheat function that switches to the preheat mode by controlling the turning off of the display lamps of the operation unit, stopping the exhaust fan, and lowering the control temperature of the fixing device, etc. If you continue,
An image forming apparatus, wherein a fixing roller pair of the fixing device is rotated for a predetermined time. 2. The image forming apparatus according to claim 1, wherein the time for rotating the pair of fixing rollers is changed according to the fixing temperature in the preheating mode.