Image forming apparatus

Abstract

To start printing without switching an ADF reading speed from the normal speed to a low speed mode in a warm-up operation.SOLUTION: An image forming apparatus 100 has an automatic document feeder 102 that automatically conveys a document; a scanner 103 that reads an image of the document; and a fixing device 18 that applies heat and pressure to a toner image formed on a recording medium. When the automatic document feeder 102 operates during the warm-up of the fixing device 18, the image forming apparatus can change the warm-up time of the fixing device 18 according to the document conveyance speed of the automatic document feeder 102.SELECTED DRAWING: Figure 4A

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus such as a multi-function peripheral (MFP) equipped with an automatic document feeder having at least two operation modes with different power consumption. [Background technology]

[0002] Office multifunction peripherals (MFPs) are not only capable of copying and printing, but also have functions such as automatic document reading with an automatic document feeder (ADF) and post-processing with a finisher. Meanwhile, the power supply situation for MFPs is usually 100V in Japan, and the upper limit of a single power source is often 1500W.

[0003] For this reason, power is usually supplied to the main unit and peripheral devices at a specified power level per power source (1,500 W in Japan). However, the ADF and finisher may operate simultaneously with printing, and the power allocated to the fixing device may be insufficient for the power required.

[0004] In the invention of Patent Document 1 (JP Patent Publication 2005-24899 A), in order to increase the power supplied to the fixing device during warm-up operation when the temperature of the fixing device is low, the ADF is switched to a low-speed operation mode with low power consumption. However, when the reading speed is slower than the printing speed, image creation starts after reading is completed, which causes a problem of a long waiting time until the job is completed. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and has an object to make it possible to start printing during the warm-up operation without switching the ADF reading speed to a lower speed mode than the normal speed. [Means for solving the problem]

[0006] In order to solve the above problem, the image forming apparatus of the present invention has an automatic document feeder that automatically transports a document, a scanner that reads an image of the document, and a fixing device that heats and pressurizes a toner image formed on a recording medium, and is characterized in that when the automatic document feeder operates during warm-up of the fixing device, the warm-up time of the fixing device can be changed depending on the document transport speed of the automatic document feeder. Effect of the Invention

[0007] According to the present invention, printing can be started without switching the ADF reading speed to a lower speed operation mode than the normal speed during the warm-up operation. [Brief description of the drawings]

[0008] [Figure 1A] 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 1B] FIG. 1 is a block diagram of an image forming apparatus. [Diagram 2] FIG. 2 is a schematic diagram of a fixing device used in the image forming apparatus. [Diagram 3] This shows the power distribution of an image forming device, with (a) the ADF at low speed during warm-up, (b) the ADF at high speed during warm-up, (c) the ADF at low speed during printing, and (d) the ADF at high speed during printing. [Figure 4A] 11 is a flowchart showing a process from warming up the image forming apparatus to starting printing, in which the warm-up time is changed according to the ADF reading speed. [Figure 4B] 13 is a flowchart showing a process from warming up the image forming apparatus to the start of printing, in which the print speed is changed from the first to fifth sheets after the start of printing in accordance with the ADF reading speed. [Figure 4C] 11 is a flowchart showing a process from warming up the image forming apparatus to starting printing, in which the warm-up time is changed depending on the fixing device temperature and the ADF reading speed before the warm-up starts. [Figure 4D] 11 is a flowchart showing a process from warming up the image forming apparatus to starting printing, in which the warm-up time is changed depending on the paper discharge destination of a print job. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of an electrophotographic MFP will be described below as an example of an image forming apparatus to which the present invention is applied. Fig. 1A is a schematic diagram of an MFP 100 according to this embodiment. Fig. 1B is a block diagram of the MFP 100. This MFP 100 is composed of a main body 101, an automatic document feeder (ADF) 102, a scanner 103 as an image reading means, and a post-processing device (finisher) 104. The main body 101 and the scanner 103 may be configured as an integrated unit or as separate units.

[0010] The MFP 100 has an operation panel that allows the user to change recording paper settings, copy image quality, scanner settings, etc. Furthermore, the MFP 100 can receive and print print jobs sent from an external device, such as a personal computer (PC), as shown in FIG 1B.

[0011] As shown in Fig. 1B, the MFP 100 has a controller, an engine control unit, a paper transport unit, an image forming unit, a fixing device 18, a scanner 103, an ADF 102, and a finisher 104. Printing is performed according to a print mode set by the printer driver in response to a signal from the controller. As shown in Fig. 1A, the ADF 102 includes an original feed tray 110 on which an original is set, a pickup roller 111 that picks up the original from the original feed tray 110, and an output tray 112 to which the original is discharged.

[0012] 1A, the scanner 103 includes a carriage 109 that can move in the left-right direction indicated by the double arrow, a light source 114 such as an LED that is built into the carriage 109 and irradiates the document with light through a contact glass 113, a plurality of reflecting mirrors 115, a photoelectric conversion element (CCD sensor) 116 that receives light from the document and converts it into an electrical signal, an A / D converter that converts the electrical signal into digital data, etc. The finisher 104 has a stapler, punch, paper folding function, etc. as a post-process for recording paper after image formation is completed.

[0013] The stapler can staple the recording papers discharged from the main body 101 in groups of a predetermined number of sheets in accordance with instructions based on the print job information. Also, the punch can punch holes in the recording papers discharged from the image forming apparatus 100 in predetermined locations for each sheet or for every predetermined number of sheets in accordance with instructions based on the print job information.

[0014] The image forming section in the main body 101 forms a toner image on a recording paper P, and includes first to fourth photoconductors 1 (a to d) as image carriers. Furthermore, the image forming section in the main body 101 includes an intermediate transfer device 60, which is a belt device provided with an intermediate transfer belt 3 as a belt member, above the four photoconductors 1.

[0015] On the four photoconductors 1(a-d), toner images of different colors are formed. On the four photoconductors 1(a-d) of this embodiment, a black toner image, a cyan toner image, a magenta toner image, and a yellow toner image are formed, respectively. Although the photoconductors 1(a-d) shown in FIG. 1A are formed in a drum shape, an endless belt-shaped photoconductor that is wound around a plurality of rollers and driven to rotate can also be used as the photoconductor.

[0016] An intermediate transfer belt 3 serving as an intermediate transfer body is disposed facing the first to fourth photoconductors 1(a-d), and in the state shown in Fig. 1A, the four photoconductors 1(a-d) are in contact with the surface of the intermediate transfer belt 3. The intermediate transfer belt 3 shown in Fig. 1A is wound around a secondary transfer opposed roller 4, a tension roller 5, a backup roller 6, and an entrance roller 7. One of these support rollers, the secondary transfer opposed roller 4, is configured as a drive roller driven by a drive source, and the intermediate transfer belt 3 is driven to rotate in the direction of arrow A in Fig. 1A by the drive of this secondary transfer opposed roller 4.

[0017] The intermediate transfer belt 3 may be of a multi-layer structure or a single-layer structure, but if it is of a multi-layer structure, it is preferable that the base layer is made of, for example, a fluororesin, a PVDF sheet, or a polyimide resin with low elongation, and the surface is covered with a smooth coating layer of a fluororesin, etc. If it is of a single layer, it is preferable to use materials such as PVDF, PC, polyimide, etc.

[0018] The formation of a toner image on the photoreceptor 1 and the transfer of each toner image to the intermediate transfer belt 3 are all substantially the same for all four photoreceptors 1(a-d), and only the colors of the toner images formed are different. For this reason, only the formation of a yellow toner image on the yellow photoreceptor 1d, which is located on the most upstream side in the surface movement direction of the intermediate transfer belt 3, among the four photoreceptors 1(a-d), and the transfer of the yellow toner image to the intermediate transfer belt 3 will be described.

[0019] 1A, the surface of the yellow photoconductor 1d is irradiated with light from a charge removing device, and the surface potential of the yellow photoconductor 1d is initialized. The initialized surface of the yellow photoconductor 1d is uniformly charged to a predetermined polarity (negative polarity in this embodiment) by a charging device 8.

[0020] The surface of the yellow photoconductor 1d thus charged is irradiated with a light-modulated laser beam emitted from an exposure device, and an electrostatic latent image corresponding to the written information is formed on the surface of the yellow photoconductor 1d. In the MFP100 shown in Fig. 1A, an exposure device made of a laser writing device that emits a laser beam is used, but an exposure device having an LED array and an imaging means can also be used.

[0021] The electrostatic latent image formed on the yellow photoconductor 1d is visualized as a black toner image by a yellow developing device. On the other hand, a yellow transfer roller 11d is disposed on the inner side of the intermediate transfer belt 3 at a position facing the yellow photoconductor 1d with the intermediate transfer belt 3 therebetween.

[0022] This yellow transfer roller 11d comes into contact with the rear surface of the intermediate transfer belt 3, and an appropriate transfer nip is formed between the yellow photoconductor 1d and the intermediate transfer belt 3. A transfer voltage of the opposite polarity (positive polarity in this embodiment) to the toner charge polarity of the toner image formed on the yellow photoconductor 1d is applied to the yellow transfer roller 11d.

[0023] As a result, a transfer electric field is formed between the yellow photoreceptor 1d and the intermediate transfer belt 3, and the black toner image on the yellow photoreceptor 1d is electrostatically transferred onto the intermediate transfer belt 3, which is rotated in synchronization with the yellow photoreceptor 1d. Residual toner adhering to the surface of the yellow photoreceptor 1d after the black toner image is transferred to the intermediate transfer belt 3 is removed by a yellow cleaning device, and the surface of the yellow photoreceptor 1d is cleaned.

[0024] Similarly, a magenta toner image, a cyan toner image and a black toner image are formed on the other three photoconductors 1 (c, b, a), respectively, and these toner images of each color are electrostatically transferred in succession onto the intermediate transfer belt 3 to which the yellow toner image has been transferred.

[0025] The MFP 100 has two drive modes: a full-color mode that uses four colors of toner, and a black monochrome mode that uses only black. In the full-color mode, the intermediate transfer belt 3 comes into contact with the four photoconductors 1 (a to d), and the four-color toner image is transferred onto the intermediate transfer belt.

[0026] On the other hand, in the black monochrome mode, only the black photoconductor 1a contacts the intermediate transfer belt 3, and only the black toner is transferred to the intermediate transfer belt 3. At this time, the three photoconductors 1(b-d) for cyan, magenta, and yellow are not in contact with the intermediate transfer belt 3, and the three primary transfer rollers 11(b-d) are separated from the photoconductors 1(b-d) by a contact / separation mechanism. At this time, in order to reliably separate the intermediate transfer belt 3 from the three photoconductors 1(b-d) for cyan, magenta, and yellow, the backup roller 6 is moved to change the profile of the intermediate transfer belt 3.

[0027] As shown in Fig. 1A, a paper feeder 14 that transports paper is disposed at the bottom of the main body 101. The paper feeder 14 includes a paper feed roller 15, and the rotation of the paper feed roller 15 feeds recording paper P, which is a recording medium, in the upward direction in Fig. 1A. The fed recording paper P hits a pair of registration rollers 16 that transport paper and stops temporarily.

[0028] A portion of the intermediate transfer belt 3 that is wrapped around the secondary transfer opposing roller 4 comes into contact with a secondary transfer roller 17 that is disposed opposite the intermediate transfer belt 3 and serves as a secondary transfer member. This contact portion forms a secondary transfer nip.

[0029] The recording paper P that hits the registration roller pair 16 is transported to the secondary transfer nip at a predetermined timing. At this time, a predetermined transfer voltage is applied to the secondary transfer roller 17, so that the toner images transferred onto the intermediate transfer belt 3 are secondarily transferred onto the recording paper P.

[0030] The recording paper P onto which the toner image has been secondarily transferred is transported further upward and passes through a fixing device 18, at which time the toner image on the recording paper P is fixed by the action of heat and pressure in the fixing device 18. The recording paper P that has passed through the fixing device 18 is discharged outside the MFP 100 by a pair of paper discharge rollers 19 provided in the paper discharge section, and is stacked on a paper discharge tray 112 on the top surface of the device. After the toner image has been transferred to the recording paper P, a small amount of toner remains on the intermediate transfer belt 3 as residual toner, but this residual toner is removed from the intermediate transfer belt 3 by a belt cleaning device.

[0031] Fixing device Next, the fixing device 18 of this embodiment will be described. Fig. 2 is a schematic diagram showing the fixing device 18 of this embodiment.

[0032] Fixing device 18 of the present embodiment includes an endless fixing belt 181, a nip forming plate 184 and a pressure roller 182 as nip forming members arranged opposite each other via the fixing belt 181, and two heat sources 183 as heating means for heating fixing belt 181. Nip forming plate 184 is arranged so as to be in contact with the inner circumferential surface of fixing belt 181, and by sandwiching fixing belt 181 between nip forming plate 184 and pressure roller 182, a fixing nip N is formed between the fixing belt portion in contact with the nip forming surface of nip forming plate 184 and the pressure roller.

[0033] Fixing belt 181 is a belt-like or film-like endless member made of a metal belt such as nickel or SUS, or a resin belt using a resin material such as polyimide, etc. The surface layer of fixing belt 181 has a release layer made of PFA or PTFE, etc., and has releasability so that toner does not easily adhere to it.

[0034] An elastic layer made of silicone rubber or the like may be provided between the base material and the surface layer of the fixing belt 181. If no elastic layer is provided, the heat capacity is small and the fixing performance can be improved, but minute irregularities on the fixing belt surface may appear on the image, causing problems such as citrus peel-like uneven gloss (citrus peel image) in solid parts of the image.

[0035] To improve such a problem, it is preferable to provide an elastic layer having a thickness of, for example, 100 μm or more, because the deformation of the elastic layer absorbs minute irregularities on the fixing belt surface, improving the orange peel image.

[0036] Heat source 183 is disposed on the inner circumferential surface side of fixing belt 181, and heats fixing belt 181 by radiant heat. Heat source 183 in this embodiment is configured with a halogen heater, but the type of heater and the number of heaters are optional. For example, instead of a halogen heater, an IH (Induction Heating) configuration may be adopted, or a resistance heating element, a carbon heater, or the like may be adopted.

[0037] Pressure roller 182 is an elastic roller in which elastic rubber layer 182b covers the periphery of core metal 182a, and the hardness of the surface layer is lower than that of the nip forming surface of nip forming plate 184. Elastic rubber layer 182b of pressure roller 182 may be solid rubber, but it is preferable to use sponge rubber.

[0038] Sponge rubber is more preferable because it has higher heat insulation properties and is less likely to lose heat from fixing belt 181 to pressure roller 182. In addition, pressure roller 182 is provided with a release layer (PFA or PTFE layer) on its surface to obtain releasability.

[0039] The pressure roller 182 is axially supported by the housing of the fixing device 18, and is rotated by a driving force transmitted via gears from a driving source such as a motor provided in the MFP body. The fixing belt 181 receives a rotational driving force from the pressure roller 182 at the fixing nip N, rotates in association with the rotation of the pressure roller 182, and travels while being guided by holding members (flanges) at both ends other than the nip portion.

[0040] At this time, fixing belt 181 rotates while its inner circumferential surface slides against the nip forming surface of nip forming plate 184. A sliding performance improving member such as a sliding sheet may be interposed between the nip forming surface of nip forming plate 184 and the inner circumferential surface of fixing belt 181 to improve sliding performance.

[0041] The nip forming plate 184 is fixed and supported on a stay member 185. The stay member 185 also has a function of suppressing bending of the nip forming plate 184 due to pressure from the pressure roller 182, and forming a uniform fixing nip N in the width direction of the fixing belt 181.

[0042] The pressure from the pressure roller 182 is received by the stay member 185, so that the surface pressure at the fixing nip N required for melting and fixing the toner can be obtained. In addition, the stay member 185 is held and fixed at its both ends by holding members for positioning.

[0043] The stay member 185 is formed by bending iron or stainless steel, and has a large heat capacity because it uses an iron plate or SUS plate with a thickness of about 2 to 4 mm. Therefore, in this embodiment, a reflecting member 186 is provided between the heat source 183 and the stay member 185, and the stay member 185 is prevented from being heated by radiant heat from the heat source 183, which would result in wasted energy consumption. Instead of providing the reflecting member 186, the surface of the stay member 185 may be subjected to a heat insulating treatment or a mirror finish.

[0044] In this embodiment, the nip forming surface of the nip forming plate 184 is substantially flat. Since the nip forming surface of the nip forming plate 184 has a higher hardness than the elastic rubber layer 182b of the pressure roller 182, the elastic rubber layer 182b of the pressure roller 182 elastically deforms along the nip forming surface of the nip forming plate 184.

[0045] Therefore, the fixing nip N of this embodiment is substantially flat along the nip forming surface (plane) of the nip forming plate 184. The nip forming surface does not need to be a completely flat surface, and may have a slightly convex or concave curved shape as long as the curvature is sufficiently smaller than that of a conventional fixing nip formed by two rollers, which has a curved shape.

[0046] In this embodiment, by using the fixing device 18 having the above-mentioned configuration, a low heat capacity is realized in the structure on the fixing belt side, and heating is performed efficiently in a short time. In this embodiment, a warm-up operation is performed to raise the temperature of the fixing belt 181 to a specified fixing temperature, and then an image forming operation is started. In the fixing device 18 of this embodiment, since the structure on the fixing belt side has a low heat capacity, the fixing belt 181 can be raised to the fixing temperature in a short time, and the warm-up time can be shortened.

[0047] The surface temperature of the fixing belt 181 is detected by a thermopile 187, and the amount of current supplied to the heating source 183 is determined according to the difference between the fed back temperature and the target temperature. Also, at the start of printing or warm-up, a predetermined amount of current may be input. The rated power of the heating source is 1200W, and when the power supply voltage is 100V and current is constantly supplied, a current of 12A flows, resulting in a power consumption of 1200W.

[0048] Distributed power The MFP 100 consumes power in each of the controller, engine control unit, paper transport, image forming unit, fixing device 18, scanner 103, ADF 102, and finisher 104 shown in Fig. 1B, and a predetermined amount of power is allocated to each of these units. The fixing device 18 consumes the most power, but the maximum power consumption of the MFP 100 varies depending on the operating speed of the ADF 102 and whether or not the finisher is used. The power allocated to the ADF 102 is explained below. The ADF reading resolution, ADF reading speed, operating mode, and power allocation are as shown in Table 1. The operating modes in the top row of Table 1 (ADF reading resolution 600 dpi, ADF reading speed 300 mm / s) are used for both scanning and copying. 100 W is allocated to the operating modes in the top row.

[0049] [Table 1]

[0050] The lower operation modes in Table 1 (ADF reading resolution 300 dpi, ADF reading speed 600 mm / s) are not used in copy mode. The lower operation modes are used only when scanning and saving or sending documents. The lower operation modes are high speed, so 150 W is allocated to them.

[0051] 3 shows an example of power distribution to each device in the MFP 100. In the case of MFPs sold in Japan, the maximum power consumption of the entire MFP 100 is often 1500W.

[0052] FIG. 3(a) shows an example of power distribution during low-speed warm-up, where the ADF reading resolution is 600 dpi and the ADF reading speed is 300 mm / s. In this case, 100 W is distributed to the ADF 102. In FIG. 3(a), the ADF: 100 W, the fixing device: 1200 W, and others (fixing device drive, control device, etc.): 100 W. In this case, the maximum power consumption is 1400 W.

[0053] FIG. 3(b) shows another example of power allocation during high-speed warm-up, where the ADF reading resolution is 300 dpi and the reading speed is 600 mm / s. In this case, 150 W is allocated to the ADF 102. In FIG. 3(b), the ADF: 150 W, the fixing device: 1200 W, and others (fixing device drive, control device): 100 W. The maximum power consumption is 1450 W.

[0054] FIG. 3(c) shows an example of power allocation during low-speed printing, where the ADF reading resolution is 600 dpi and the reading speed is 300 mm / s. In this case, 100 W is allocated to the ADF 102. In FIG. 3(c), the ADF: 100 W, the finisher: 100 W, the fixing device: 1000 W, and others (paper transport, developing device, transfer device, fan, control device): 300 W. The maximum power consumption is 1500 W.

[0055] The rated power of the heating source 183 is 1200 W, but in this case it is limited to an upper limit of 1000 W. Even if the heating source 183 is limited to 1000 W, it is designed to be possible to print at the specified printing speed and print quality (fixability).

[0056] Figure 3(d) shows the power allocation during high-speed printing, with an ADF reading resolution of 300 dpi and an ADF reading speed of 600 mm / s. In this case, 150 W is allocated to the ADF 102. In Figure 3(d), the ADF: 150 W, the finisher: 100 W, the fixing device: 1000 W, and others (paper transport, developing device, transfer device, fan, control device): 300 W. The maximum power consumption is 1500 W.

[0057] The rated power of the heating source 183 is 1200 W, but in this case it is limited to an upper limit of 950 W. Even when limited to 950 W, it is designed to be possible to print with the specified print quality (fixability), but there are cases where it is necessary to reduce the printing speed or extend the warm-up time.

[0058] Flowchart Each embodiment of the present invention will be described with reference to the flow charts of Figures 4A-4D. <Embodiment 1> 4A shows a flowchart of the first embodiment, which is a flowchart for changing the warm-up time according to the ADF reading speed. When the machine receives a return signal from the energy saving mode or power off, the warm-up of the fixing device 18 starts (step S11).

[0059] In step S12, the ADF 102 operates (scanning begins). For a copy job, the ADF reading resolution is automatically set. That is, for a copy job, the ADF resolution is automatically set to 600 dpi and the ADF reading speed is automatically set to 300 mm / s. This is because the copy image quality can be improved with high resolution (600 dpi) and low speed (300 mm / s), and there is no need to reduce the data volume by saving image data (scanned data). For a copy job, the warm-up is not extended (step S13 ⇒ step S15), and copy printing begins after warm-up is complete (step S16).

[0060] In the case of a printer job, there are cases where the printer job is sent from the PC and only printing is performed, and cases where the printer job is sent from the PC and printing is performed while the document scan is performed independently (scanning and copying). When scanning, the user can select the resolution. That is, the user can select one of two operation modes, for example, ADF resolution: 300 dpi, ADF reading speed 600 mm / s, and ADF resolution: 600 dpi, ADF reading speed 300 mm / s.

[0061] In the power-consuming mode of ADF reading speed 600 mm / s and ADF resolution: 300 dpi, the power allocated to the fixing device 18 during printing must be set to 950 W (total 1500 W) as shown in Fig. 3(d). The maximum power required by the fixing device 18 is 1000 W, so there is a shortage of 50 W. Therefore, the process moves from step S13 to step S14, and the warm-up time is extended to compensate for the power shortage of 50 W while storing heat in the fixing device 18.

[0062] In this way, the power required and the power distribution of the fixing device 18 during printing are predicted, and the warm-up time is determined according to the ADF reading speed. This makes it possible to shorten the warm-up time for copying and scanning with a reading resolution of 600 dpi (speed 300 mm / s), which is frequently used and consumes little power (100 W).

[0063] If a printer job and a scan (resolution: 300 dpi, ADF reading speed 600 mm / s) are run simultaneously and independently of each other, the warm-up time is extended in step S14. However, the probability that a printer job and a scan (resolution: 300 dpi, ADF reading speed 600 mm / s) will run simultaneously in this way is low. Therefore, the probability that the warm-up time for the printer job will be extended in step S14 is also low. Since the user's waiting time is limited, this does not pose any particular problem.

[0064] <Embodiment 2> 4B shows a flowchart of the second embodiment, which changes the print speed for the first to fifth sheets after printing starts according to the ADF reading speed. Similar to steps S11 ⇒ S12 ⇒ S13 in FIG. 4A described above, the process proceeds in the order of steps S21 ⇒ S22 ⇒ S23.

[0065] When the ADF reading speed is determined to be 600 mm / s in step S23, the power allocated to the fixing device 18 during printing is 950 W, as shown in Fig. 3D. This allocated power of 950 W is 50 W short of the maximum required power of 1000 W.

[0066] For this reason, after it is determined in step S24 that the warm-up is complete, printing starts in step S25, but the print speed is reduced to 80% for the first five sheets after printing starts (step S26). By reducing the print speed in this manner, the fixing failure (low-temperature fixing failure) caused by the 50W power shortage described above is prevented without extending the warm-up time.

[0067] From the sixth sheet onwards, printing is performed at 100% print speed, shortening the user's waiting time. Since sufficient heat can be stored in the fixing device 18 by the reduced speed printing from the first to fifth sheets, it becomes possible to print from the sixth sheet onwards at 100% print speed, eliminating the need to extend the warm-up time.

[0068] The printing speed deceleration rate is not limited to 80%, and the number of sheets printed at reduced speed is not limited to 1 to 5 sheets. Even if the deceleration rate is around 80% or the number of sheets printed at reduced speed is around 5 sheets, it is sufficient as long as the fixing failure (low-temperature fixing failure) caused by the above-mentioned 50W power shortage can be prevented. The printing speed or deceleration rate can be calculated from the transport speed of the recording paper and the rotation speed of the transport motor that transports the recording paper.

[0069] In this way, the power required and the power allocation of the fixing device 18 during printing are predicted, and the print speed is determined according to the ADF reading speed. In this way, regardless of whether the ADF operation mode in Table 1 is "scan / copy" or "scan," it is possible to prevent a drop in the fixing temperature without extending the warm-up time and without changing the ADF reading speed (from high speed to low speed). This makes it possible to shorten the user's waiting time.

[0070] On the other hand, if it is determined in step S23 that the ADF reading speed is not equal to 600 mm / s (low speed), it is determined in step S27 that the warm-up is complete, and then printing starts (step S23). These steps S27 and S28 are the same as steps S15 and S16 in FIG. 4A.

[0071] The printing speed at this time is 100%. Since the ADF is slow, the power allocated to the ADF 102 is 100 W, and the power allocated to the fixing device 18 is 1000 W, as shown in FIG. 3C. Therefore, a printing speed of 100% is possible.

[0072] <Embodiment 3> 4C shows a flowchart of the third embodiment, which changes the warm-up time according to the fixing device temperature before the start of warm-up and the ADF reading speed. In step S31 before the start of warm-up, if the determination of "fixing device temperature T≦60° C.?" is No, that is, if it is determined that heat has already been stored in the fixing device 18, steps S31 ⇒ S36 ⇒ S37 are bypassed and printing is started. The fixing device temperature T is the temperature detected by the thermopile 187 when warm-up is about to start.

[0073] This reduces the maximum power required during printing, and whether the ADF operation mode in Table 1 is "scan / copy" or "scan," it is possible to prevent a drop in the fixing temperature without extending the warm-up time and without changing the ADF reading speed (from high speed to low speed). This makes it possible to shorten the user's waiting time.

[0074] On the other hand, if it is determined in step S31 before the start of warm-up that the temperature of fixing device 18 is, for example, 60° C. or lower, the process proceeds in the order of steps S32 ⇒ S33 ⇒ S34 ⇒ S35 ⇒ S36 ⇒ S37. These steps are the same as steps S11 ⇒ S12 ⇒ S13 ⇒ S14 ⇒ S15 ⇒ S16 in Fig. 4A described above. Note that the temperature in step S31 is not limited to 60° C., but can be changed according to the machine configuration.

[0075] <Embodiment 4> 4D shows a flowchart of the fourth embodiment, which changes the warm-up time depending on the destination of the print job. If the destination of the print job is the finisher, the finisher consumes 100 W of power. In contrast, if the print job is the main body destination and the finisher does not operate, the 100 W of power is not required.

[0076] Therefore, even if the ADF reading speed is 600 mm / s, which consumes a lot of power, there is a margin of 100 W that is not needed, so there is no need to reduce the power allocated to the fixing device 18. Therefore, in the case of main body paper ejection, the warm-up time can be shortened, and printing can be started in step S47 via step S41 ⇒ step S46. This makes it possible to shorten the user's waiting time.

[0077] When the print job's paper output destination is the finisher, the finisher consumes 100 W of power, so when the ADF reading speed is 600 mm / s, which consumes a lot of power, the power allocated to the fixing device 18 is reduced to 950 W as shown in Fig. 3(d). This keeps the power consumption of the entire MFP 100 to a maximum of 1500 W or less. In this way, with the power allocated to the fixing device 18 reduced to 950 W, warm-up of the fixing device 18 is started (step S42), and reading of the ADF 102 is started (step S43).

[0078] Thereafter, the process proceeds in the order of steps S42->S43->S44->S45->S46->S47. These steps are similar to steps S11->S12->S13->S14->S15->S16 in Fig. 4A and steps S32->S33->S34->S35->S36->S37 in Fig. 4C.

[0079] Although the present invention has been specifically described based on the embodiment, it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways within the scope of the technical ideas described in the claims. For example, the ADF reading speed can be three stages by adding 400 mm / s between 300 mm / s and 600 mm / s, or it can be four or more stages by adding less than 300 mm / s and more than 600 mm / s. It is also possible to configure the warm-up time of the fixing device 18 to be extended according to these multiple stages of document transport speed.

[0080] The document transport speed in ADF 102 includes speeds in three sections: 1) the speed at which the document is transported from document feed tray 110 to scanner 103, 2) the speed at which the document passes through scanner 103 (ADF reading speed), and 3) the speed at which the document is transported from scanner 103 to discharge tray 112, and the speeds 1), 2), and 3) may differ. In the present invention, the operation of changing the warm-up time according to the speed 2) (ADF reading speed) out of 1), 2), and 3) has been described, but the warm-up time may be changed according to the speed 1) or 3).

[0081] 1) The operation of changing the warm-up time depending on the speed will be explained. 1) By making the speed at which the original document is transported from the original document feed tray 110 to the scanner 103 faster than 2) the speed at which the original document passes through the scanner 103 (ADF reading speed), the transport time from the original document feed tray 110 to the output tray 112 can be shortened.

[0082] For example, 2) if the speed at which the document passes through scanner 103 (ADF reading speed) is 300 mm / s, 1) the speed at which the document is transported from document feed tray 110 to scanner 103 is set to 500 mm / s. 2) if the speed at which the document passes through scanner 103 (ADF reading speed) is 600 mm / s, 1) the speed at which the document is transported from document feed tray 110 to scanner 103 is set to 800 mm / s.

[0083] In this case, 1) the speed at which the document is transported from document feed tray 110 to scanner 103 is the fastest and consumes the most power, so 1) it is desirable to change the warm-up time according to the speed at which the document is transported from document feed tray 110 to scanner 103. The operation when changing according to the speed in 3) is similar to that when changing according to the speed in 1).

[0084] <Additional Notes> Preferred aspects of the present invention will be described below. <First aspect> The first aspect is an image forming apparatus having an automatic document feeder that automatically transports a document, a scanner that reads an image of the document, and a fixing device that heats and pressurizes a toner image formed on a recording medium, characterized in that when the automatic document feeder operates during warm-up of the fixing device, the warm-up time of the fixing device can be changed depending on the document transport speed of the automatic document feeder. <Second aspect> A second aspect is an image forming apparatus having an automatic document feeder that automatically transports a document, a scanner that reads an image of the document, and a fixing device that heats and pressurizes a toner image formed on a recording medium, characterized in that when the automatic document feeder operates during warm-up of the fixing device, the conveying speed of the recording medium in the fixing device can be changed in accordance with the document conveying speed of the automatic document feeder. <Third aspect> A third aspect is the image forming apparatus of the first aspect, characterized in that the warm-up time of the fixing device can be changed according to the document transport speed of the automatic document feeder only when the temperature of the fixing device is lower than a predetermined temperature before the start of warm-up, and when the temperature of the fixing device is higher than the predetermined temperature before the start of warm-up, the fixing device is operated after warm-up is completed to start printing. <Fourth aspect> In a fourth aspect, only when the discharge destination of the recording medium is a finisher, the warm-up time of the fixing device can be changed according to the document conveying speed of the automatic document feeder, In the image forming apparatus of the first aspect, when the discharge destination of the recording medium is not a finisher, the fixing device is operated after warm-up is completed to start printing. <Fifth aspect> A fifth aspect is an image forming apparatus according to any one of the first to fourth aspects, characterized in that the automatic document feeder has at least two operating modes, a first operating mode in which the document transport speed and power consumption are low, and a second operating mode in which the document transport speed and power consumption are high, and the warm-up time is longer in the second operating mode than in the first operating mode. [Explanation of symbols]

[0085] 1(a-d): photoconductor 3: intermediate transfer belt 4: Secondary transfer opposing roller 5: Tension roller 6: Backup roller 7: Entrance roller 8: Charging device 11 (a-d): Primary transfer roller 14: Paper feed device 15: Paper feed roller 16: Registration roller pair 17: Secondary transfer roller 18: fixing device 19: paper discharge roller pair 60: intermediate transfer device 100: image forming device 101: Main unit 102: Automatic document feeder (ADF) 103: Scanner 104: Post-processing device (finisher) 109: Carriage 110: Document feed tray 111: Pickup roller 112: Paper output tray 113: Contact glass 114: Light source 115: Reflecting mirror 116: Photoelectric conversion element (CCD sensor) 181: Fixing belt 182: Pressure roller 182a: Core metal 182b: Elastic rubber layer 183: Heat source 184: Nip forming plate 185: Stay member 186: Reflective member 187: Thermopile N: Fixing nip P: Recording paper [Prior art documents] [Patent documents]

[0086] [Patent Document 1] JP 2005-24899 A

Claims

1. An image forming apparatus having an automatic document feeder that automatically transports a document and a fixing device that heats and pressurizes a toner image formed on a recording medium, characterized in that when the automatic document feeder operates during warm-up of the fixing device, the warm-up time of the fixing device can be changed according to the document transport speed of the automatic document feeder.

2. An image forming apparatus having an automatic document feeder that automatically transports a document and a fixing device that heats and pressurizes a toner image formed on a recording medium, characterized in that when the automatic document feeder operates during warm-up of the fixing device, the image forming apparatus is capable of changing the transport speed of the recording medium in the fixing device in accordance with the document transport speed of the automatic document feeder.

3. only when the temperature of the fixing device is lower than a predetermined temperature before the start of the warm-up, the warm-up time of the fixing device is variable in accordance with the document transport speed of the automatic document feeder; 2. The image forming apparatus according to claim 1, wherein, if the temperature of said fixing device is higher than a predetermined temperature before the start of warm-up, said fixing device is operated after the warm-up is completed to start printing.

4. Only when the discharge destination of the recording medium is a finisher, the warm-up time of the fixing device can be changed according to the document transport speed of the automatic document feeder; 2. The image forming apparatus according to claim 1, wherein, when the destination of the recording medium is not a finisher, the fixing device is operated after warm-up is completed to start printing.

5. the automatic document feeder has at least two operation modes, a first operation mode in which the document transport speed and power consumption are low, and a second operation mode in which the document transport speed and power consumption are high, 5. The image forming apparatus according to claim 1, wherein the warm-up time is longer in the second operation mode than in the first operation mode.

Images