JP2005025041A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an advanced energy-saving oriented apparatus in which one of a medium speed printing mode, a low speed printing mode and a rated high-speed printing mode can be selected. <P>SOLUTION: In the case of rated high-speed printing, an upper fixing heater and a lower fixing heater are alternatively heated and driven from the time (t0) and printing is started at the time (ts) when temperature of a roller becomes a rated temperature Ts°C. In the case of printing in a energy saving mode, only the upper fixing heater is heated and driven from the time (t0) and printing is started at the time (t1) when temperature of the roller becomes a first temperature T1°C for low speed which is lower than the rated temperature Ts°C and heating driving of the upper fixing heater is controlled so as to maintain the first temperature T1°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to paper conveyance driving in an image forming apparatus and temperature control of a thermal fixing device. More specifically, energy saving orientation is promoted in addition to a rated high-speed printing mode and a medium-speed or low-speed printing mode can be selected. The present invention relates to an image forming apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic printer, toner is used for image formation, and even if a toner image is formed on an image carrier such as a photosensitive drum by this toner, the toner image is transferred to a sheet. The sheet onto which the toner image has been transferred is carried into a heat fixing device, and the toner image is heated and melted to be fixed to the sheet with pressure. To be discharged.
[0003]
FIG. 10 is a diagram schematically showing the configuration of the main part of such a conventional electrophotographic color image forming apparatus. As shown in the figure, the color image forming apparatus 1 includes a paper feed cassette 2 in which paper P is stacked and stored, a paper feed roller (not shown) that takes out the paper P from the paper feed cassette 2 one by one, and this paper feed roller. A sheet conveyance guide (not shown) for guiding the sheet P fed by the sheet as shown by an arrow A in the figure, a pair of standby rollers (not shown) disposed at the end of the sheet conveyance guide, and the standby roller pair at the printing timing. A conveyance belt 3 that conveys and feeds the fed paper in a counterclockwise direction in the figure is provided, and drive rollers 4 a and 4 b that drive the conveyance belt 3.
[0004]
Further, four image forming units 5 (5-1, 5-2, 5-3, 5-4) are arranged in a multistage manner in the vicinity of the sheet conveying surface of the conveying belt 3 from the upstream side to the downstream side in the sheet conveying direction. The fixing device 6 is disposed on the downstream side of the conveyance belt 3 in the sheet conveyance direction indicated by the arrow B in the drawing.
[0005]
All of the four image forming units 5 have the same configuration, and the cleaner 8, the charger 9, the recording head 10, the developing device 11, and the transport belt 3 are arranged around the photosensitive drum 7 and in the vicinity of the peripheral surface thereof. The transfer devices 12 are sequentially arranged with the image interposed therebetween. The developing unit 11 stores yellow (Y), magenta (M), and cyan (C) color toners, which are three subtractive primary colors, and black (K) toner mainly used for character portions. The developing roller 13 is disposed in the opening on the lower side surface. In addition, an electrical component 14 on which a control circuit board is mounted is disposed near the lower portion of the drive roller 4a.
[0006]
The photosensitive drum 7 rotates in the clockwise direction indicated by the arrow C, the peripheral surface thereof is cleaned by the cleaner 8, and a uniform negative high charge is given to the cleaned peripheral surface by the charger 9. The initialized peripheral surface is exposed by the recording head 10 to form an electrostatic latent image composed of a minus high potential portion by the initialization and a minus low potential portion in which the potential is attenuated by the exposure. The
[0007]
The toner stored in the developing device 11 is transferred to the minus low potential portion by the developing roller 13, and the electrostatic latent image is developed (developed). The developed toner image is transferred onto the paper P conveyed by the conveying belt 3 in such a manner that it is sequentially superimposed and transferred by the transfer device 12. The sheet P onto which the four color toner images are transferred in such a manner as described above is carried into a fixing device, where the toner image is fixed on the paper surface by heat and pressure, and discharged to the outside by a paper discharge roller (not shown). Is done. As a result, a color image based on a composite color of the four colors of toner is formed on the paper P.
[0008]
As described above, when the four-color toner images are sequentially transferred and overlapped as in the color image forming apparatus 1, in order to perform correct image formation on the paper P, the toner images are overlaid and transferred at the fixing unit. Proper supply of heat for melting the four-color toner images is essential.
[0009]
FIG. 11 is a block diagram of a fixing temperature control circuit in such a conventional color image forming apparatus. As shown in FIG. 11, the fixing temperature control circuit includes a print controller (hereinafter referred to as “PR_CONT”) 15, a CPU (central processing unit) 16, a ROM (read only memory) 17, a fixing SW (switch) power supply 18, and a fixing device 19. It is made up of.
[0010]
The fixing device 19 is supplied with a heat roller power source and a pressure roller power source from a fixing SW power source 18 and drives the heat roller heater 19-2a and the pressure roller heater 19-2b to generate heat. The surface temperatures of the heat roller 19-1a and the pressure roller 19-1b are sent to the PR_CONT 15 as a heat roller temperature signal and a pressure roller temperature signal, respectively, by a temperature sensor (not shown). The PR_CONT 15 performs analog / digital conversion processing on each signal and outputs it to the CPU 16.
[0011]
The CPU 16 compares the converted signal input from the PR_CONT 15 with a value set in the ROM 17 in advance, and outputs a fixing control command to the PR_CONT side according to a program stored in the ROM 17 in advance.
The PR_CONT 15 outputs a fixing temperature control signal to the fixing SW power supply 18 in accordance with the fixing control command input from the CPU 16. The fixing SW power supply 18 supplies a heat roller power supply and a pressure roller power supply to the fixing device 19 based on a fixing temperature control signal input from the PR_CONT 15.
[0012]
In the past, the fixing temperature was obtained by the heat roller heater 19-2a provided only on the heat roller 19-1a. However, the demand for double-sided printing and high-speed printing has increased, and in response to this demand, double-sided printing and high-speed printing can be performed. In order to realize this, now the pressure roller 19-1b is also provided with a pressure roller heater 19-2b so that the fixing temperature is obtained from both the heat roller 19-1a and the pressure roller 19-1b.
[0013]
However, in this case, if both the heat roller 19-1a and the pressure roller 19-1b are heated at the same time, the power consumption becomes excessively large. In general, the heat roller power supply and the pressure roller power supply are switched alternately. However, a method is adopted in which the heat roller 19-1a and the pressure roller 19-1b are alternately heated to increase the temperature of both.
[0014]
From the heat roller 19-1a and the pressure roller 19-1b, a heat roller temperature signal and a pressure roller temperature signal are notified to the CPU 16 via the PR-CONT 15 by a temperature sensor (not shown). The CPU 16 controls the fixing SW power source 18 via the PR-CONT 15 so that the fixing temperature of the fixing device 19 is maintained at the rated fixing temperature compared with the rated fixing temperature data stored in advance in the ROM 17. .
[0015]
FIG. 12 shows the progress of the temperature rise up to the printable fixing temperature of the heat roller heater 19-2a (upper heater) of the heat roller 19-1a and the pressure roller heater 19-2b (lower heater) of the pressure roller 19-1b. FIG.
In the figure, the horizontal axis indicates time T, and the vertical axis indicates the two upper and lower roller temperatures Tn ° C. of the fixing device 19. Tx ° C. (n = x) indicates the temperature of the fixing device 19 at the time when the print command is input to the color image forming apparatus 1 (upper and lower two roller temperatures, the same applies hereinafter). If Tx ° C. is room temperature, if the print command is from standby mode, Tx ° C. is the standby temperature, for example, 90 ° to 100 ° C. If the print command is from sleep mode, Tx ° C. is standby This is a temperature during natural cooling from the standby temperature of 90 ° to 100 ° C. to room temperature after the fixing power source is turned off after a predetermined time has elapsed from the mode.
[0016]
At the printing command time Ts, the heating by the fixing power source is started from the temperature Tx ° C. before the heating start, and the upper heater and the lower heater are alternately heated by repeatedly turning on / off the fixing power source. When the temperature of the fixing device 19 reaches the fixable temperature Tt ° C. at time Tp, printing is started. (For example, see Patent Documents 1 and 2)
Here, the fixable temperature Tt ° C. controlled and maintained by the control device shown in FIG. 11 varies depending on the properties of the toner used and the paper conveyance speed. If A4 size paper is printed at a rate of 31 sheets per minute (31 ppm (print-per-minute)) in the horizontal direction, the temperature is in the range of 180 ° C. to 185 ° C.
[0017]
In such an image forming apparatus, it is extremely important to properly maintain the fixing temperature of the fixing device (fixing device), and various proposals have been made. For example, by setting dedicated fixing temperatures (first fixing temperature and second fixing temperature) for each of normal paper and thick paper, favorable fixing can be performed regardless of the thickness of the paper. There is something called. In this method, the fixing temperature is set according to the thickness of the paper, and the feeding of the paper is started after confirming that the temperature of the heat roller of the fixing device has reached the set fixing guarantee temperature. (For example, see Patent Document 1.)
In general, the specification of an image forming apparatus is, for example, “A4 size paper is horizontally (or vertically) continuously several times per minute” or “what is the first print time”. This first print time refers to the waiting time when printing is started from room temperature. In recent years, the number of continuous prints has been increased to, for example, 31 ppm so that a comfortable printing environment can be obtained. It has become.
[0018]
As described above, high-speed printing is increasingly required in recent printers. However, heaters are provided in both the heat roller and the pressure roller, rather than for double-sided printing. Often used for high-speed printing.
[0019]
[Patent Document 1]
Japanese Utility Model Publication No. 62-037245 (<Technical Field>, FIG. 5)
[Patent Document 2]
Japanese Patent Laid-Open No. 06-337616 ([Summary], FIG. 1)
[0020]
[Problems to be solved by the invention]
By the way, in the image forming apparatus as described above, the higher the speed of printing, the higher the driving load for high-speed conveyance of the paper, and the higher the temperature load for maintaining the temperature of the heat fixing device at 180 ° C. to 185 ° C. That is, an increase in energy is inevitable.
[0021]
The increase in energy is related to the depletion of resources and environmental problems, and in recent years, energy saving (energy saving, the same applies hereinafter) has been screamed in various devices. For this reason, in the color image forming apparatus as described above, various devices for low-melting-point toner and heat fixing devices have been studied in order to save energy.
[0022]
For example, as one of the contrivances of the thermal fixing device, a power consumption reduction mode in which a heat source such as a heater is stopped or maintained at a low temperature when there is no print command for a while has been put into practical use. However, the increase in overall energy has not necessarily been stopped.
[0023]
As for temperature control of the thermal fixing device, Japanese Patent Application Laid-Open No. 2003-228561 proposes that the fixing temperature is changed between thick paper and thin paper and appropriate printing is performed on each paper. However, this does not suggest energy saving. This is because energy saving is achieved if the fixing temperature is changed (lowered) for the same type of paper, but it does not lead to energy saving because it is a necessary countermeasure for different types of paper.
[0024]
Even if the fixing temperature is changed for energy saving, the energy consumption is not limited to the thermal fixing device, so the contribution to energy saving is small. For example, in the color image forming apparatus having the configuration shown in FIG. 10, the feeding system of the drive system that drives the four image forming units 5 (5-1, 5-2, 5-3, 5-4) simultaneously is high. If it is a load and, moreover, high-speed driving is true for all driving systems in the world, the energy used increases geometrically as the speed increases.
[0025]
By the way, the high-speed image forming apparatus as described above is generally often used for office work of companies and the like. However, looking closely, it is limited to special workplaces that perform dozens of prints with one print command (print job). There is not always much printing of a sheet. Rather, it is more common when there are fewer than a few.
[0026]
In addition, at present, the host device and the image forming apparatus are often connected via a LAN or the like, but although the print command is issued in such a LAN environment, the person who issued the print command immediately picks up the printed matter. There are many cases where you do not go. In such a case, high-speed print output is not always effective. Therefore, it can be said that high-speed printing with the highest specifications of the image forming apparatus is not always necessary.
[0027]
SUMMARY OF THE INVENTION In view of the above-described conventional situation, an object of the present invention is to provide an image forming apparatus that promotes energy saving and is capable of selecting a medium-speed or low-speed print mode in addition to a rated high-speed print mode.
[0028]
[Means for Solving the Problems]
The configuration of the image forming apparatus according to the present invention will be described below.
An image forming apparatus according to the present invention includes a sheet feeding conveyance unit that conveys a sheet from a sheet feeding unit to a sheet discharging unit, a sheet conveyance speed by the sheet feeding conveyance unit, and a rating that is faster than the first speed. A transfer speed switching means for switching to a speed, a transfer means for transferring a toner image onto the paper while the paper is being transported by the paper feeding and transport means, and a toner image transferred by the transfer means having a heat source. A heat fixing unit that fixes the toner image on the sheet while the conveyed sheet is continuously conveyed by the sheet feeding conveyance unit, a power supply unit that supplies power to the heat source, and the heat source of the power supply unit Power supply switching means for switching between power supply to and interruption of the power supply, fixing temperature detection means for detecting the temperature of the heat fixing means, power is supplied from the power supply means to the heat source, and the temperature of the heat fixing means is reduced. Rise When the fixing temperature detecting means detects that the temperature of the thermal fixing means is equal to or higher than the first fixing temperature that enables the fixing of the toner image onto the paper conveyed at the first speed. Similarly to the first paper feed mode in which the paper is conveyed by the paper feeding / conveying means at the first speed, the fixing temperature detecting means applies the temperature of the heat fixing means to the paper conveyed at the rated speed. A rated paper feed mode for starting the transport of the paper by the paper feed transport means at the rated speed when it is detected that the toner has a rated fixing temperature at which the toner image can be fixed. A sheet feeding / conveying control means for selectively switching each sheet feeding mode by controlling the means; and when the first sheet feeding mode is selected, the temperature of the heat fixing means is maintained at the first fixing temperature. Power supply switching means When the rated paper feed mode is selected by controlling the power supply and shutoff by the power supply, the fixing temperature is maintained to control the power supply and shutoff by the power supply switching means so as to keep the temperature of the heat fixing means at the rated fixing temperature. And a control means.
[0029]
For example, according to a second aspect of the present invention, the sheet feeding / conveying control means includes three speeds of the first speed, the rated speed, and a second speed that is an intermediate speed between the first speed and the rated speed. The conveying speed switching means is controlled to switch to any one of the above, and the conveying speed switching means is set to the first feeding mode as the initial feeding mode, for example, as in claim 3. And a selection instruction manual operation means, for example, according to claim 4, wherein the conveyance speed switching means is controlled based on a manual operation input from the selection instruction manual operation means to Each of the paper feed modes is configured to be switched, and for example, as in claim 5, a selection automatic instruction for automatically switching to the rated paper feed mode when the designated number of prints of the paper exceeds a predetermined number Configured to include a stage.
[0030]
Further, in this image forming apparatus, for example, as described in claim 6, the heat source is a heater, and the heat fixing unit is a pair of rollers including a heat inlet roller and a pressure roller in which a heater is incorporated in at least one of them. And a sheet on which the toner image is transferred between the pair of rollers.
[0031]
The heater is provided in the heat roller, for example, as in claim 7, and a first heater that heats the heat roller, and a first heater that is provided in the pressure roller and heats the pressure roller. And the power supply means is configured to supply power to one of the first and second heaters.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the following description, the paper feeding / conveying means includes, for example, a motor drive circuit 67, a motor 60, a paper feeding roller 42, a standby roller pair 46, a conveying belt 40, and the like. CPU 62, PR_CONT 61, motor drive circuit 67, and the like. The transfer means includes, for example, a photosensitive drum 34, a transfer device 41, and the like. The heat fixing means includes, for example, a fixing unit 50. The power supply switching means includes, for example, PR_CONT 61, a fixing SW power supply 65, etc., and the fixing temperature detecting means includes, for example, two temperature sensors (not shown) for the heat roller 51 and the pressure roller 52, and these The PR_CONT 61 and the like that receive the heat roller temperature signal Th and the pressure roller temperature signal Tp from the temperature sensor, and the first constant described above. The temperature is made up of a temperature such as ** ° C., for example, and the rated fixing temperature is made up of a temperature such as ** ° C., for example, and the paper feeding / conveying control means is made up of, for example, the CPU 62, PR_CONT 61, motor drive circuit 67, etc. The fixing temperature maintenance control means includes, for example, PR_CONT 61, fixing SW power supply 65, and the like. The selection instruction manual operation means includes, for example, an operation panel 23, a key operation unit 23a, and the like. Consists of a ROM 63, an EPROM 64, a CPU 62, and the like.
[0033]
In the following description, printing and printing are used synonymously.
FIG. 1 is a perspective view showing an appearance of a color image forming apparatus (hereinafter simply referred to as a printer) according to an embodiment. The printer of this example is an example of a tandem color printer. The printer of this example is an example of a color printer for duplex printing.
[0034]
In the figure, the printer 20 is connected to a host device such as a personal computer (not shown) by a cable. The printer 20 includes an apparatus main body upper part 21 and an apparatus main body lower part 22. An operation panel 23 is disposed on the upper surface of the apparatus main body upper part 21, and a paper discharge unit 24 for printing paper is further formed.
[0035]
The operation panel 23 includes a key operation unit 23a provided with a plurality of keys and a liquid crystal display 23b that performs display based on display information output from a CPU (not shown). In addition, paper on which a color image has been formed by an image forming unit, which will be described later, is discharged onto the paper discharge unit 24 and is sequentially stacked on the paper discharge unit 24.
[0036]
A double-sided printing conveyance unit and a paper feed cassette, which will be described later, are set in the lower part 22 of the apparatus main body. For example, by opening a lid (not shown) provided on the side surface of the printer 20 It is a possible configuration. The apparatus main body lower part 22 is provided with a front cover 26 that can be opened and closed on the front surface thereof and a paper feed cassette 27 that is detachable from the apparatus main body lower part 22. For example, the front cover 26 is opened for jam processing, maintenance, or the like.
[0037]
Further, on the right side surface of the lower part 22 of the apparatus main body, a mounting portion cover 28 is provided at a mounting portion of an MPF (multi paper feeder) tray, and a maintenance cover 29 is provided below the mounting portion cover 28. However, in FIG. 1, the MPF tray is not attached to the attachment portion cover 28. The maintenance cover 29 is a cover for checking a paper conveyance path, which will be described later, and the maintenance cover 29 is opened to perform maintenance such as a paper jam.
[0038]
Note that the paper feed cassette 27 is housed in the lowermost stage of the printer 20 of the present example as described above, and when the paper is supplied to the paper feed cassette 27, for example, the paper feed cassette 27 is pulled by pulling the handle 27a forward. Can be pulled out in the direction of the arrow.
FIG. 2 is a cross-sectional view illustrating the internal configuration of the printer 20 having the above-described external configuration. As shown in the figure, the printer 20 includes an image forming unit 30, a duplex printing transport unit 31, and a paper feed unit 32. The image forming section 30 has a configuration in which four image forming units 33 (33-1, 33-2, 33-3, 33-4) are arranged in a multistage manner.
[0039]
Of the four image forming units 33, three image forming units 33-1, 33-2, and 33-3 on the upstream side in the sheet conveying direction are magenta (M) and cyan (C), which are subtractive three primary colors, respectively. ), Yellow (Y) color toner is formed, and the image forming unit 33-4 forms a monochrome image mainly using black (K) toner such as characters.
[0040]
Each of the image forming units 33 includes a drum set C1 and a toner set C2, and has the same configuration except for the developer (color) stored in the developing container. Accordingly, the configuration of the yellow (Y) image forming unit 33-3 will be described below as an example.
[0041]
The drum set C1 is provided with a photoconductive drum 34. The photoconductive drum 34 has a peripheral surface made of, for example, an organic photoconductive material, and surrounds the vicinity of the peripheral surface of the photoconductive drum 34. The cleaner 35 and the charger 36 that constitute the drum set C1 together with the photosensitive drum 34 are disposed, and then the print head 37 supported by the frame of the main body device is disposed, and the developing container that further constitutes the toner set C2. 38 and the developing roller 39 are arranged, and a transfer belt 41 and a transfer device 41 are arranged below the conveyance belt 40 with the conveyance belt 40 interposed therebetween. The developer container 38 contains toner therein and supports a developing roller 39 in the opening on the lower side surface.
[0042]
The photosensitive drum 34 rotates in the clockwise direction in the figure, the peripheral surface is cleaned by the cleaner 35, and the peripheral surface of the photosensitive drum 34 is uniformly charged by the charge application from the charger 36. Next, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 34 by optical writing based on print information from the print head 37. The electrostatic latent image is converted into a toner image by yellow (Y) toner stored in the developing container 38 by developing processing by the developing roller 39.
[0043]
The toner image formed on the peripheral surface of the photosensitive drum 34 in this way reaches the transfer portion where the photosensitive drum 34 and the transfer device 41 face each other as the photosensitive drum 34 rotates. The toner image that has reached the transfer portion is transferred onto a sheet that moves from the upstream side to the downstream side in the sheet conveyance direction immediately below the photosensitive drum 34.
[0044]
The sheet is carried out of the sheet feeding cassette 27 by one rotation of the sheet feeding roller 42, and is fed to the standby roller pair 46 through the guide roller pair 43, the guide path 44, and the feeding roller pair 45. Alternatively, the paper is fed by the paper feed roller 28b from the MPF tray 28a attached to the opened attachment portion cover 28. The standby roller pair 46 feeds the sheet onto the conveying belt 40 at a timing when the printing start position of the sheet coincides with the leading end of the toner image on the photosensitive drum 34 of the image forming unit 33-1 at the most upstream in the sheet conveying direction.
[0045]
The conveyor belt 40 is stretched between a driving roller 47 and a driven roller 48, driven by the driving roller 47, and circulated in the counterclockwise direction in the figure. The sheet is electrostatically attracted to and conveyed by the upper surface of the circulating and conveying belt 40, and the magenta (M) toner image is transferred by the transfer unit of the image forming unit 33-1, and the image forming unit 33-2. The cyan (C) toner image is transferred at the transfer portion, the yellow (Y) toner image is transferred at the transfer portion of the image forming unit 33-3, and the black ( The toner image of K) is transferred.
[0046]
The paper onto which the four color toner images are transferred in this manner is carried into a fixing unit 50 as a fixing device. The fixing unit 50 includes a heat roller 51, a pressure roller 52, an oil application roller 53, and the like. And fix. The oil application roller 53 has a function of applying toner releasing oil to the peripheral surface of the heat roller 51 and removing toner remaining on the heat roller 51.
[0047]
As described above, the sheet on which the toner image is fixed by the fixing unit 50 is formed by the carry-out roller pair 55 from the side discharge port 56 when the switching plate 54 is rotated upward as shown by the solid line in the figure. When the switching plate 54 is rotated downward as indicated by the broken line in the figure, it is guided upward by the conveying roller pair 57 and the image forming surface is moved by the paper discharge roller 25. The paper is discharged downward to the paper discharge unit 24.
[0048]
The double-sided printing transport unit 31 is configured to be detachable from the apparatus main body, and is a unit that is mounted when performing double-sided printing by the printer 20 of the present example. Has been.
In the case of duplex printing, the sheet is once sent upward by the switching plate 54. For example, when the trailing edge of the sheet reaches the pair of conveying rollers 57, the conveyance of the sheet is stopped and the sheet is further conveyed in the reverse direction. . By this control, the sheet is conveyed downward on the left side of the switching plate 54 set at the position indicated by the dotted line, is carried into the sheet conveyance path of the duplex printing conveyance unit 31, and is conveyed by the conveyance rollers 58a to 58e. It reaches the standby roller pair 46 via the guide path 44 and the feed roller pair 45 and is sent to the transfer unit at the same timing as the toner image as described above, and the toner image is transferred to the back surface of the paper.
[0049]
A near-infrared regular reflection sensor 59 provided in the vicinity of the drive roller 47 is for measuring the toner density and the print position of a toner image directly formed on the peripheral surface of the transport belt 40 as a resist patch. It is.
FIG. 3 is a diagram showing an arrangement relationship between the gear train of the drive system of the printer 20 and each rotation load unit. As shown in FIG. 3, the photosensitive drum 34 of each of the image forming units 33-1 33-2 33-3 and 33-4 shown in FIG. Drum gears 34M, 34C, 34Y, and 34K that mesh with the drive gears of the drive system are provided on the side surfaces. Although not shown, each drum gear engages with the gear of the developing drum 39 in each image forming unit 33. The gear of the developing drum 39 is not described in FIG. These members are driven by being connected to a drive system such as a stirrer, a toner supply roller, and a charger 36.
[0050]
As described above, the four drum gears 34M, 34C, 34Y, and 34K are subjected to a large load for driving each member in each of the assembled image forming units 33, and this large load is applied 4. In addition to driving the drum gears 34M, 34C, 34Y, 34K, the sheet feeding roller 42, the standby roller pair 46, the conveying belt 40, the guide roller pair 43, the feeding roller pair 45, the heat roller 51 of the fixing unit 50 and the pressure As shown in FIG. 3, the drive system for driving the rollers 52 and the like has approximately 34 gears including an idle gear, a reduction gear, a clutch gear and the like on a drive shaft gear 60-1 of one motor 60. It consists of a drive system consisting of rows.
[0051]
The power consumed by this drive system increases geometrically as the drive speed is increased as described above.
FIG. 4A is a view showing the inside by opening the front cover 26 of the printer 20 and removing the side mounting portion cover 28 and the maintenance cover 29 shown in FIG. 1, and FIG. It is a figure which shows the state which opened the apparatus main body upper part 21. FIG.
[0052]
As shown in FIG. 4B, the upper part 21 of the apparatus main body is opened while being kept substantially horizontal with respect to the lower part 22 of the apparatus main body. Therefore, at the time of opening, the drum set C1 and the toner set C2 can be inserted and removed in a substantially horizontal direction. That is, as shown in the figure, it is possible to easily extract the drum set C1 and insert a new drum set C1.
[0053]
FIG. 5A is a diagram showing a state in which the fixing unit 50 is detached from the state of FIG. 4B, and FIG. 5B shows the configuration of the fixing unit 50 removed from the printer 20 main body. It is sectional drawing shown in detail.
The fixing unit 50 shown in FIG. 5A is fixed to the main body of the printer 20 by a fixing mechanism (not shown), and is configured to be easily removable to the outside as indicated by an arrow A in the figure. Further, if the reverse operation is performed, the fixing unit 50 can be easily attached to the printer 20 main body. That is, the fixing unit 50 is a so-called unit.
[0054]
As shown in FIG. 5B, the fixing unit 50 includes a heat roller 51, a pressure roller 52, and an oil application roller 53 as shown in FIG. As indicated by a broken line arrow D in FIG. 5B, for example, a plurality of color toner images transferred onto the sheet are melted while the sheet is nipped and conveyed by the heat roller 51 and the pressure roller 52, and a large number of images are obtained. Thermally fixed on paper as a color image.
[0055]
FIG. 6 is a block diagram of a fixing temperature control circuit in the printer 20 of this example. As shown in FIG. 6, the fixing temperature control circuit includes a PR_CONT 61, a CPU 62, a ROM 63, an EPROM (erasable and programmable ROM) 64, a fixing SW power supply 65, a motor driving circuit 67, and a fixing unit 50.
In the following description, the “fixing temperature” refers to the temperature of the sheet nipping portion (fixing portion) of the heat roller 51 and the pressure roller 52 that nipping and conveying the sheet.
[0056]
As shown in FIGS. 5B and 6, the fixing unit 50 is supplied with a heat roller power source Vh and a pressure roller power source Vp from a fixing SW power source 65. The heat roller heater 66a and the pressure roller heater 66b are supplied to the fixing unit 50, respectively. The heat is driven alternately.
The heat roller 51 and the pressure roller 52 of the fixing unit 50 are each provided with a temperature sensor for measuring the temperature of the roller surface (not shown), and the heat roller 51 detected by these temperature sensors. The surface temperature of the pressure roller 52 is sent to the PR_CONT 61 as a heat roller temperature signal Th and a pressure roller temperature signal Tp, respectively. The PR_CONT 61 performs analog / digital conversion processing on each signal and outputs it to the CPU 62.
[0057]
The CPU 62 compares the analog / digital converted heat roller temperature signal Th and pressure roller temperature signal Tp input from the PR_CONT 61 with values set in advance in the ROM 63, and the calculation results are stored in the EPROM 64 in advance. Whether it is a rated fixing temperature for high-speed conveyance according to the set rated paper feeding mode, or another fixing temperature corresponding to conveyance in a paper feeding mode whose conveyance speed is slower than the rated paper feeding mode, and According to the program stored in the ROM 63, a fixing control command and a conveyance control command are output to the PR_CONT 61.
[0058]
Further, the CPU 62 compares the predetermined number of sheets registered in advance in the EPROM 64 with the designated number of prints specified in advance by key input or job information from the host device, and feeds paper to start printing. Determine the mode.
The PR_CONT 61 outputs the temperature control signal Tc to the fixing SW power source 65 in accordance with the fixing control command input from the CPU 62 and also transfers the transport speed control signal Sp to the motor drive circuit 67 in accordance with the transport control command similarly input from the CPU 62. Output.
[0059]
The fixing SW power source 65 supplies the heat roller power source Vh and the pressure roller power source Vp to the fixing unit 50 based on the temperature control signal Tc input from the PR_CONT 61. On the other hand, based on the conveyance speed control signal Sp input from the PR_CONT 61, the motor drive circuit 67 moves the heat roller 51 and the pressure roller 52 together with other rotational drive units through the gear train of the drive system shown in FIG. The number of rotations of the motor 60 that rotates is controlled.
[0060]
In the above configuration, the conveyance speed by the conveyance speed control signal Sp is controlled to high-speed conveyance and low-speed conveyance. High-speed conveyance is a rated speed corresponding to the rated paper feed mode and is a high-speed conveyance mode of the highest specification. On the other hand, the low-speed conveyance is a conveyance mode set regardless of the highest-specification printing mode, and one type or two types can be set.
[0061]
In addition, the initial paper feed mode setting is not the rated paper feed mode in which printing is performed in the highest specification high-speed transport mode, but the paper feed mode in which printing is performed at low speed transport (the slower one when there are two types). Is set.
Hereinafter, when there is one type of paper feed mode by low-speed conveyance, the conveyance speed is called a first speed, and the paper feed mode is called a first paper feed mode. The slower transport speed is the first speed, the paper feed mode is the first paper feed mode, the faster speed (that is, the intermediate speed between the first speed and the rated speed) is the second speed, and the paper feed mode is the first speed. The two-feed mode is assumed. That is, in the initial setting, the first paper feed mode at the first speed is always set.
[0062]
The first feed mode based on the first speed in the initial setting is not canceled unless printing in the rated feed mode is designated in the job information from the key input or the host device, and the first speed is always set. Printing is started in the first paper feed mode.
However, when automatic setting is specified separately in advance, when the specified number of prints specified in the job information from the key input or host device is greater than the specified number, the printer automatically enters the rated feed mode at the rated speed. Is printed.
[0063]
Further, the high-speed conveyance at the rated speed corresponding to the rated paper feed mode in this example is a conveyance speed of 31 ppm with, for example, A4 size paper sideways, and the rated fixing temperature in that case is about 180 ° C. On the other hand, the low-speed conveyance at the first speed corresponding to the first paper feeding mode is, for example, a conveyance speed of 17 ppm with an A4 size paper sideways, and the first fixing temperature in this case is about 160 ° C.
[0064]
Further, when the second paper feed mode by the low speed conveyance at the second speed is set, the conveyance speed is, for example, a conveyance speed of 22 ppm with the A4 size paper sideways, and the second fixing temperature in that case is About 170 ° C.
That is, in the first paper feed mode (or second paper feed mode, the same applies hereinafter) of this example, it is noted that printing can be performed even if the fixing temperature is lower than the rated fixing temperature for low-speed conveyance. In addition to the rated paper feed mode for printing on the paper with the highest specification high-speed conveyance of the original image forming device, to save energy, the fixing temperature for the highest specification high-speed conveyance is not required. The feeding is started and printing is performed at low speed, and the fixing temperature is maintained.
[0065]
The user can manually select the rated paper feeding mode and the first paper feeding mode by operating the key operation unit 23a from the operation panel 23 on the upper surface of the upper part 21 of the apparatus body shown in FIG. It is.
In addition, as will be described in detail later, whether or not the CPU 62 matches various conditions specified in advance in key input or job information from the host device with conditions set in the ROM 63 or EPROM 64 in advance. It can also be done automatically.
[0066]
FIG. 7A is a diagram schematically illustrating control up to a fixing temperature at which printing can be performed at a rated speed of a thermal roller heater (on the fixing heater) and a pressure roller heater (on the fixing heater) of the printer in the embodiment. This characteristic is the same as in FIG. 12, but the time on the horizontal axis and the temperature on the vertical axis are shown based on the notation of this example. FIG. 4B is a diagram schematically showing temperature control at a fixing temperature at which printing can be performed at a low first speed other than the rated speed.
[0067]
In the printing by the high-speed rated conveyance in the rated paper feed mode of this example shown in FIG. 5A, when the printing operation is started at the temperature Tx ° C. and the time t0, the fixing is performed by the control from the CPU 62 performed through the PR_CONT 61. The SW power source 65 turns on the heat roller heater 66a (on the fixing heater) and the pressure roller heater 66b (on the fixing heater) alternately to start heating.
[0068]
At time ts, when the roller temperature reaches the rated temperature Ts ° C. at which printing can be performed at the rated printing speed of 31 ppm, printing is started.
On the other hand, in the case of printing at the first speed in the first paper feed mode shown in FIG. 5B, when the printing operation is started at the temperature Tx ° C. and the time t0, the fixing SW power source 65 is connected to the heat roller heater 66a (fixing heater). Start heating only on top). Since the heating is not performed alternately but only by the heat roller heater 66a (on the fixing heater), the amount of heat is small, but the temperature rises rapidly, and the time t1 that is earlier than the print start time ts at the rated temperature Ts ° C. Thus, the roller temperature rises to T1 ° C., which is a predetermined first temperature.
[0069]
The first temperature T1 ° C. is a temperature that can sufficiently cope with printing at a printing speed of 17 ppm by the first speed in the first paper feeding mode, and the heat amount for fixing at the printing speed of 17 ppm is determined by the heat roller heater 66a (fixing). It is also a temperature that can be sufficiently supplied by heating only on the heater). At this time t1, execution of printing in the first paper feed mode is started. Thereafter, the fixing SW power supply 65 controls the opening and closing of the power switch to the heat roller heater 66a so as to maintain the first temperature based on the control from the CPU 62.
[0070]
FIG. 8 schematically shows temperature control at a fixing temperature at which printing can be performed by the heat roller heater (on the fixing heater) and the pressure roller heater (on the fixing heater) when printing is performed at a second speed other than the rated speed. FIG. 6 shows a case of printing at a second speed in the second paper feed mode. In the case of printing at the second speed in the second paper feed mode shown in the figure, when the printing operation is started at the temperature Tx ° C. and the time t0, the fixing SW power source 65 also turns on the heat roller heater 66a (on the fixing heater). ) Only start heating. In this case as well, heating is not performed alternately but only by the heat roller heater 66a (on the fixing heater), so that the temperature rises rapidly although the amount of heat is small, and from the printing start time t1 at the first temperature T1 ° C. However, at a time t2 earlier than the print start time ts at the rated temperature Ts ° C., the roller temperature rises to a predetermined second temperature T2 ° C.
[0071]
The second temperature T2 ° C. is a temperature that can sufficiently cope with printing at a printing speed of 22 ppm at the second speed in the second paper feed mode, and the amount of heat for fixing at the printing speed of 22 ppm is determined by the heat roller heater 66a (fixing). It is a temperature that can be sufficiently supplied by heating only on the heater). At time t2, execution of printing in the second paper feed mode is started. Thereafter, the fixing SW power supply 65 controls opening and closing of the power switch to the heat roller heater 66a so as to maintain the second temperature based on the control from the CPU 62.
[0072]
By the way, if the initial setting is set to the first paper feed mode for energy saving, even if a large amount of printing is performed, the initial setting of the first paper feed mode certainly saves energy. The printing speed is slow and the completion of the total number of printed sheets is slowed, making it meaningless to have the highest specifications. In preparation for such a case, it is preferable to automatically switch from the initially set first paper feed mode to the rated paper feed mode that performs printing at the highest specification at a high speed, depending on the designated number of prints.
[0073]
For this purpose, it is preferable to check the relationship between the command print number and the time required for completion of printing in the first paper feed mode and the rated paper feed mode in advance.
First, in an environment of room temperature of 25 ° C., the print execution start time in the first paper feed mode is T1, the print execution start time in the rated paper feed mode is Ts, the number of low-speed prints per minute is NL, and the high-speed print per minute Assuming that the number of sheets is NH and the number of command printed sheets is n, the respective printing completion required times tl and th are:
tl = 60 / NL × n + TQ (1)
th = 60 / NH × n + TS (2)
It is represented by
[0074]
Here, if the command print number n is the number of prints required for the same print completion time regardless of which paper feed mode is used, that is, “tl = th”, the above formula ( From 1) and formula (2)
60 / NL × n + TQ = 60 / NH × n + TS
And can be put. Solving this for n,
60n (1 / NL-1 / NH) = TS-TQ
60n ((NH-NL) / (NL × NH)) = TS-TQ
n = ((NL × NH) × (TS−TQ)) / (60 × (NH−NL)) (3)
It becomes.
[0075]
That is, it is confirmed that there is a number of sheets having the same required time for completion of printing regardless of the paper feeding mode. Conversely, it turns out that the first paper feed mode should be selected for energy saving when the number of sheets is n or less where the above equation holds. When the number exceeds n, it can be said that it is preferable for the customer to select the rated paper feeding mode in order to finish the printing operation in a short time by making use of the highest specification.
[0076]
FIG. 9 is a graph showing the relationship between the command print number and the print completion time in each of the first paper feed mode and the rated paper feed mode. In the figure, the horizontal axis indicates the number of printed sheets, and the vertical axis indicates time. The time axis shows the print execution start time T1 in the first paper feed mode and the print execution start time TS in the rated paper feed mode. Starting from these times T1 or TS, two graphs indicated by diagonally upward straight lines show the relationship between the command print number and the required print completion time tl or th in the first paper feed mode or the rated paper feed mode, respectively. It is a graph.
[0077]
N shown in the figure is n indicating a specific number in this case. When this specific number of sheets is n, the two graphs intersect, and it is found that the time required for completion of printing is reversed when the number of sheets exceeds that.
The above formulas (1) and (2) are not limited to when the power is input, and the printer main body has a ready state, a standby state, a sleep state, or an intermediate state between them. In the state of the printer main body as described above, the fixing temperature at the time of the print command is detected, and the print execution start times TS and T1 and the number of print commands n that are obtained in advance through experiments or the like corresponding to the fixing temperature at the time of the print command are obtained. Based on the above formulas (1) and (2), the print completion required times tl and th for the print command number n are calculated, and as described above, the energy saving paper feed mode or the print completion required time is short. The paper feed mode is automatically selected to execute printing.
[0078]
The waiting times T1 and TS acquired in advance by the above experiments are the print execution start times corresponding to the initial temperature, intermediate temperature, final temperature, etc. of the roller temperature in the standby state and the sleep state, respectively, starting with the room temperature at the time of power input. The table is stored in the ROM 63 or the EPROM 64 as a table of T1 and TS.
[0079]
In the color printer 20 configured as described above, the CPU 62 performs printing as follows.
First, it is determined whether or not the initially set first paper feed mode has been canceled. If the initial setting of the first paper feed mode has not been canceled, it is next determined whether the number of print commands is n or less, and if n or less, printing is performed in the initial setting of the first paper feed mode. To do. On the other hand, if the number of print commands exceeds n, the paper feed mode is switched to the rated paper feed mode and the printing operation is started.
[0080]
When the initial first paper feed mode is cancelled, the paper feed mode instructed by manual input or JOB from the host device is checked, and the printing operation is started in the instructed paper feed mode. To do.
As described above, the present invention pays attention to the fact that printing is possible at low speed conveyance even at a fixing temperature lower than the maximum specification fixing temperature of the apparatus. Low-speed transport printing (printing in the first paper feeding mode or the second paper feeding mode) that is slower than that, regardless of the printing function of the highest specification, while having the rated specifications for printing in the paper mode) In order to prevent the increase in overall energy as much as possible, it is possible to selectively use different specifications consisting of the energy saving mode specifications for the same type of paper. Thereby, in addition to energy saving, the secondary effect of improving the durability of the apparatus is also obtained.
[0081]
【The invention's effect】
As described above, according to the present invention, the image forming apparatus having the highest-specification high-speed printing function includes the energy-saving mode in which printing is performed at a low speed regardless of the highest-specification rated high-speed printing function. It is possible to provide an image forming apparatus that can prevent an increase in overall energy as much as possible, thereby addressing the demand for energy saving and improving the durability of the apparatus. It becomes.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating an appearance of a color image forming apparatus (printer) according to an embodiment.
FIG. 2 is a cross-sectional view illustrating an internal configuration of a printer according to an embodiment.
FIG. 3 is a diagram illustrating an arrangement relationship between a gear train of a printer drive system and rotation load units according to an embodiment.
4A is a diagram showing the inside of the printer according to an embodiment with the front cover opened and the side MPF mounting portion cover and the maintenance cover removed, and FIG. FIG.
5A is a diagram illustrating a state in which the fixing device is detached from the state in which the upper portion of the printer main body is opened according to the embodiment; FIG. 5B is a detailed configuration of the fixing device removed from the printer main body. It is sectional drawing shown.
FIG. 6 is a block diagram of a fixing temperature control circuit in the printer according to the embodiment.
7A is a diagram schematically illustrating control up to a fixing temperature at which printing can be performed at a rated speed of a heat roller heater (on a fixing heater) and a pressure roller heater (on a fixing heater) of a printer according to an embodiment. FIG. (B) is a figure which shows typically the temperature control in the fixing temperature which can be printed at the 1st speed of low speeds other than a rating.
FIG. 8 is a printable fixing temperature of a heat roller heater (on the fixing heater) and a pressure roller heater (under the fixing heater) when printing is performed at a second low speed other than the printer rating in the embodiment. It is a figure which shows typically temperature control of this.
FIG. 9 is a graph showing the relationship between the command print number and the print completion time in each of the first paper feed mode and the rated paper feed mode.
FIG. 10 is a diagram schematically illustrating a configuration of a main part of a conventional color image forming apparatus.
FIG. 11 is a block diagram of a fixing temperature control circuit in a conventional color image forming apparatus.
FIG. 12 is a diagram schematically showing the progress of the temperature rise up to a printable fixing temperature of a conventional heat roller heater (upper heater) and pressure roller heater (lower heater).
[Explanation of symbols]
1 Color image forming device
2 Paper cassette
P paper
3 Conveyor belt
4a, 4b Driving roller
5 (5-1, 5-2, 5-3, 5-4) Image forming unit
6 Fixing device
7 Photosensitive drum
8 Cleaner
9 Charger
10 Recording head
11 Developer
12 Transfer device
13 Developing roller
14 electrical equipment
15 PR_CONT
16 CPU
17 ROM
18 Fixing SW power supply
19 Fixing device
19-1a Heat roller
19-1b Pressure roller
19-2a Heated roller heater
19-2b Pressure roller heater
20 Printer
21 Upper part of main unit
22 Lower part of main unit
23 Operation Panel
23a Key operation unit
23b liquid crystal display
24 Paper output unit
25 Paper discharge roller
26 Front cover
27 Paper cassette
27a Toride
28 Mounting part cover
28a MPF tray
28b Paper feed roller
29 Cover for maintenance
30 Image forming unit
31 Transport unit for duplex printing
32 Paper feed unit
33 (33-1, 33-2, 33-3, 33-4) Image forming unit
C1 drum set
C2 toner set
34 Photosensitive drum
35 Cleaner
36 Charger
37 Print head
38 Development container
39 Developing roller
40 Conveyor belt
40a Paper transport surface
41 Transfer device
42 Feed roller
43 Guide roller pair
44 guideway
45 Feeding roller pair
46 Waiting roller pair
47 Driving roller
48 Followed roller
50 Fixing unit
51 Heat roller
52 Pressure roller
53 Oil application roller
54 switching plate
55 Unloading roller pair
56 Side outlet
57 Conveying roller pair
58a-58e Conveyance roller
59 Near-infrared specular reflection sensor
60 motor
60-1 Drive shaft gear
61 PR_CONT
62 CPU
63 ROM
64 EPROM
65 Fixing SW power supply
66a Heat roller heater
66b Pressure roller heater
67 Motor drive circuit

Claims (7)

Paper feeding and conveying means for conveying paper from the paper feeding unit to the paper discharging unit;
Transport speed switching means for switching the transport speed of the paper by the paper feed transport means between a first speed and a rated speed faster than the first speed;
Transfer means for transferring a toner image onto the paper while the paper is being conveyed by the paper feeding and conveying means;
A heat fixing means for fixing the toner image on the paper while the paper on which the toner image is transferred by the transfer means and having the heat source is continuously conveyed by the paper feed conveying means;
Power supply means for supplying power to the heat source;
Power supply switching means for switching between power supply to the heat source of the power supply means and interruption;
Fixing temperature detecting means for detecting the temperature of the thermal fixing means;
In the process in which power is supplied from the power supply means to the heat source and the temperature of the heat fixing means rises, the fixing temperature detecting means causes the toner on the sheet to be conveyed at the first speed. A first paper feed mode for starting transport of the paper by the paper feed transport means at the first speed when it is detected that the temperature is equal to or higher than a first fixing temperature enabling image fixing;
Similarly, when the fixing temperature detecting means detects that the temperature of the thermal fixing means is a rated fixing temperature that enables the fixing of the toner image onto the paper conveyed at the rated speed, the paper feeding / conveying means A rated paper feed mode for starting conveyance of the paper at the rated speed;
With
A paper feed transport control means for controlling the transport speed switching means to selectively switch the paper feed modes;
When the first paper feed mode is selected, the rated paper feed mode is selected by controlling the power supply switching by the power supply switching means to maintain the temperature of the heat fixing means at the first fixing temperature. A fixing temperature maintaining control means for controlling power supply and shutoff by the power supply switching means to maintain the temperature of the thermal fixing means at the rated fixing temperature.
An image forming apparatus comprising: The sheet feeding / conveying control means switches the conveying speed so as to switch to one of the three speeds of the first speed, the rated speed, and the second speed which is an intermediate speed between the first speed and the rated speed. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled. 2. The image forming apparatus according to claim 1, wherein the sheet feeding / conveying control unit controls the conveying speed switching unit with the first sheet feeding mode as an initial setting sheet feeding mode. The sheet feeding / conveying control unit includes a selection instruction manual operation unit, and controls the conveyance speed switching unit based on a manual operation input from the selection instruction manual operation unit to switch each sheet feeding mode. The image forming apparatus according to claim 1 or 2. 3. The automatic feeding control unit includes an automatic selection instruction unit that automatically switches to the rated paper feeding mode when the designated number of prints of the paper exceeds a predetermined number. Image forming apparatus. The heat source is a heater, and the heat fixing unit includes a pair of rollers including a fuser roller and a pressure roller that incorporate a heater in at least one of them, and a sheet on which the toner image is transferred between the pair of rollers. The image forming apparatus according to claim 1, wherein the fixing is performed by nipping and conveying. The heater includes a first heater that is provided in the heat roller and heats the heat roller, and a second heater that is provided in the pressure roller and heats the pressure roller. 7. The image forming apparatus according to claim 6, wherein electric power is supplied to one of the first and second heaters.

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