JP2012128261A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which achieves both excellent FPOT (First Page Out Time) and life elongation of an image heating device by maintaining the excellent FPOT and also suppressing unnecessary standby time of the image heating device.SOLUTION: Detection means is for detecting a state of on-demand image heating means or a surrounding state of the image heating means, and according to the state of the heating means detected by the detection means, relative drive start timing is changed between driving means for image formation means and driving means and energization means of the image heating means.

Description

  The present invention relates to an image forming apparatus equipped with an image heating apparatus capable of forming an image on a recording material by an image forming process such as a copying machine, a printer, or a facsimile, such as an electrophotographic system or an electrostatic recording system. Examples of the image heating device include a fixing device that fixes an unfixed image formed on a recording material, and a gloss processing heating device that improves the glossiness of an image by heating the image fixed on the recording material.

  In an image forming apparatus using an image forming process such as an electrophotographic system or an electrostatic recording system, an electrostatic latent image is formed on a photoreceptor, and the latent image is developed using a developer to be visualized as a toner image. The toner image is transferred onto a recording material such as paper, and then the recording material onto which the toner image has been transferred is formed by a fixing roller and a pressure roller provided in a fixing device that is an image heating device. Pass through the nip. As a result, the toner image is heat-fixed as an image on the recording material.

  Recently, a quick start on-demand heating device has been proposed and put into practical use as a fixing device which is an image heating device. In other words, on-demand heating is a system in which an endless heat-resistant, thin-walled flexible member is slid and moved to a heating body, and the heat of the heating body is applied to the recording material through the flexible member. Device.

  By the way, in such an image forming apparatus, in recent years, in order to improve productivity, FPOT (First Page Out Time: time from the start of printing until the first recording material is discharged) is emphasized. Although there are many factors that determine FPOT, it is roughly divided into the following four items. That is, image information generation / development time by image information processing means such as a video controller, rise time of a motor for rotating a scanner mirror in the exposure apparatus, length and speed of a conveyance path from paper feeding to conveyance, and image heating It is the temperature rise time of the device.

  Here, the temperature rise time of the image heating apparatus is the time required for the energization of the fixing heater provided in the image heating apparatus to start up the temperature of the heating member to a predetermined temperature at which image heating is possible. is there. The temperature rise time of the image heating apparatus has the largest variation among the FPOT variation factors on the image forming apparatus side excluding the image development time. The temperature of the image heating apparatus at the start of printing, the ambient environmental temperature, the power supply Varies greatly depending on voltage.

  As one of the methods for shortening the FPOT, it is conceivable to shorten the start-up time of the fixing device, and the use of the on-demand heating device is suitable for this.

  On the other hand, an image forming apparatus equipped with an image heating apparatus has been increased in speed and lifetime year by year, and higher durability is required for the component parts than in the past. One of the biggest factors that determine the life of an image forming apparatus is an image heating apparatus, and the life is determined by deterioration of parts such as rollers and wear of roller shafts and bearings due to long-term use. A major factor for the life of such an image heating apparatus is the number of rotations of the roller. The higher the number of rotations, the more the image heating apparatus deteriorates. In particular, in recent high-speed image forming apparatuses, even if the time of one printing is very short, it becomes a very large value when converted to the number of rotations of the roller.

  In addition, there is a demand for downsizing at the same time as the speed of the image forming apparatus. If the diameter of the roller is reduced for downsizing, a larger number of rotations are required even for the same amount of printing, and the rotation of the roller The speed is even faster.

  As a proposal for shortening the FPOT, as disclosed in Patent Document 1, a recording material conveyance timing is changed in accordance with the heating condition of the heating device, the power supply voltage, and the environmental temperature. That is, the fewer the unfavorable conditions for securing the fixing property, the faster the sheet feeding is started, the FPOT is shortened as much as possible, and conversely the more the unfavorable conditions are increased, the more the feeding start timing is delayed.

  Further, as in Patent Document 2, there is a configuration in which the heating device is operated at a temperature lower than the target temperature until the image is developed, and is raised to the target temperature after the image development is completed. In Patent Document 2, in an image forming apparatus having a video controller, the video controller issues a start signal to the engine controller before the generation / development of image information. That is, while the image is being developed, the fixing device is started up at a low temperature and waits, and the waiting time until the image forming operation is completed is shortened while preventing an excessive temperature rise.

  Further, as in Patent Document 3, an apparatus has been proposed in which the output of the temperature detection element is detected at the start of printing, and unnecessary heating is suppressed to prevent excessive temperature rise. That is, when the detected temperature is high and the difference from the target temperature of the heating device is small, the heating start timing of the heater is delayed as compared with the case where the detected temperature is low.

JP 2007-108297 A JP 2002-091230 A JP 2002-169411 A

  However, in the configurations described in Patent Documents 1 and 3, the image heating apparatus starts to be driven when printing is started. Therefore, if the image heating apparatus starts up earlier than the exposure apparatus or the time until the recording material is conveyed to the image heating apparatus, a time for waiting while the image heating apparatus is driven is generated. Waiting while the image heating apparatus is driven affects the life of the image heating apparatus because the number of rotations of the roller increases as described above. Further, in the configuration described in Patent Literature 2, the time required for image development cannot be predicted, and the image heating device is driven during that time. Time may be generated.

  In the on-demand heating device as the image heating device, even if only the heating body is energized with the driving of the image heating device stopped, temperature unevenness occurs in the members in the heating device and the temperature is increased to a uniform temperature. I can't let you. This is because the range in which the heating body applies heat is limited to the vicinity of the fixing nip. Therefore, even when trying to obtain a good FPOT by using the on-demand heating device, it is easy to generate a wasteful waiting time while the image heating device is driven, and there is a problem of temperature rise due to unnecessary heating. The life of the image heating device, such as the number of rotations, was affected.

  An object of the present invention is to form an image that can maintain a good FPOT, suppress unnecessary waiting time of the image heating device, and suppress unnecessary driving and unnecessary heating of the image heating device to extend the life of the image heating device. To provide an apparatus.

  To achieve the above object, a typical configuration of an image forming apparatus according to the present invention includes an image forming unit that is driven by a first driving unit to form a toner image on a recording material, and the image forming unit includes the image forming unit. Image information processing means for generating image information for forming the toner image on the recording material, control means for controlling the image forming means based on the image information processing status of the image information processing means, and second driving means And an image heating means for receiving and heating the recording material on which the toner image is formed from the image forming means in a state where the energization means drives and raises the temperature and is maintained at a predetermined image heating temperature; In the image forming apparatus, the image heating unit heats the energization unit to generate heat and is maintained at a predetermined image heating temperature, and slides in contact with the heating unit. A flexible member whose surface is in contact with the recording material, and a pressure member that is pressed against the heating body via the flexible member to form a nip with the flexible member, and is rotated by the second driving means. An on-demand image heating unit that sandwiches and conveys the recording material at the nip and heats it with the heat of the heating body via the flexible member. And detecting means for detecting a state around the image heating means, wherein the control means is configured to detect the first drive means and the second drive according to the state of the image heating means detected by the detection means. The drive start timing relative to the means and the energization means is changed.

  According to the present invention, on-demand image heating means is used, and the start timing of drive and temperature rise of the image heating apparatus can be adjusted according to the state of the detected image heating means, and unnecessary driving and unnecessary heating are suppressed. be able to. This makes it possible to achieve both shortening of the FPOT and extending the life of the image heating apparatus. By using the present invention, it is possible to cope with the case where the start timing of the image forming apparatus is advanced in order to shorten the FPOT or the print signal is transmitted to the image forming apparatus before the image processing is completed.

(A) is a case where the fixing heater temperature is 150 ° C. or higher at the start of printing, with respect to the start of driving of the image forming apparatus, the start of driving of the image heating apparatus, and the start of energization in the first embodiment of the present invention. When the time required for development is relatively short, (b) is a diagram illustrating a case where the time required for image information development is relatively long. (A) is a case where the fixing heater temperature is less than 100 ° C. at the start of printing, and is related to image information in the first embodiment of the present invention. When the time required for development is relatively long, (b) is a diagram showing a case where the time required for image information development is relatively short. FIG. 4A shows the start of driving of the image forming apparatus, the start of driving of the image heating apparatus, and the start of energization according to the first embodiment of the present invention. FIG. When the time required for image information expansion is relatively short, (b) is a diagram showing the case where the time required for image information expansion is relatively long. 1 is a cross-sectional view illustrating an image forming apparatus according to a first embodiment. FIG. 2 is a cross-sectional view illustrating a fixing device that is an image heating device according to the first embodiment. It is a block diagram for demonstrating the control part in 1st Embodiment. FIG. 3 is a diagram illustrating a temperature rising curve of the fixing device according to the first embodiment. FIG. 5A is a diagram showing the start of driving of the image forming apparatus, the start of driving of the image heating apparatus, and the start of energization in the first comparative example, and FIG. 5B is the start of driving of the image forming apparatus in the second comparative example, and the image heating apparatus. It is a figure which shows the drive start and energization start. It is a block diagram for demonstrating the control part in the 2nd Embodiment of this invention. FIG. 10 is a diagram illustrating a rising curve according to an input current value of a fixing device according to a second embodiment. It is a block diagram for demonstrating the control part in the 3rd Embodiment of this invention. FIG. 10 is a diagram illustrating a rising curve according to a use environment of a fixing device according to a third embodiment. It is a figure which shows the operation | movement sequence of an image forming apparatus.

<< First Embodiment >>
(Image forming device)
FIG. 4 is a schematic cross-sectional view of a laser beam printer as the image forming apparatus according to the first embodiment of the present invention. An image reading scanner 30 is provided so as to be connectable, and the read image information can be input to the CPU 11 as control means. In the figure, 1 is an organic photosensitive drum as an image carrier, 2 is a charging roller as a charging member, 3 is a laser scanner as a laser exposure device, 4 is a developing device comprising a developing sleeve, a developing blade, and a one-component magnetic toner. It is. Reference numeral 5 denotes a cleaning blade and a cleaning device including a waste toner container, 6 denotes a transfer roller, and 7 denotes a heat fixing device. In the figure, the general flow of the recording material is indicated by a solid line, and the specific flow is indicated by a broken line.

  The drum 1 is driven by a main motor (not shown), is uniformly charged with negative charges by the charging roller 2, and an electrostatic latent image is formed on the drum 1 by the laser beam from the laser scanner 3. The laser scanner 3 functions as an image information processing unit that generates image information for forming a toner image on a recording material.

  Next, the toner charged in the developing device 4 adheres to the electrostatic latent image on the drum 1 to become a visible image, and is transferred onto a sheet as a recording material P on the transfer roller 6 and fixed as a fixing device. Fixing is performed by the device 7. The sheet is conveyed in the direction of the arrow in the drawing by a sheet feeding unit driven by a sheet feeding motor (not shown). The cleaning device 5 removes the toner remaining on the organic photosensitive drum 1. An image is formed by the function of each unit described above.

(Image heating device)
FIG. 5 is a schematic cross-sectional view of a fixing device 7 which is an on-demand fixing device as an example of an image heating device in the present embodiment. A fixing heater 72 as a heating body that is energized by the energizing means and generates heat and is maintained at a predetermined image heating temperature, and a flexible member 13 that slides in contact with the fixing heater 72 on one surface and contacts the recording material on the other surface And a thermistor 73 serving as temperature detecting means. Then, a pressure roller 16 as a pressure body that is pressed against the fixing heater 72 via the flexible member 13 to form a nip with the flexible member 13 and is rotationally driven by the driving means of the image heating apparatus. Have. The recording material is nipped and conveyed by the nip formed as described above, and heated by the heat of the fixing heater 72 via the flexible member 13.

  As the flexible member 13, an endless belt shape or a cylindrical shape is used, and at least a part of the circumference of the flexible member 13 is always tension-free (a state in which no tension is applied). The pressure roller 16 is rotationally driven by the rotational driving force. The endless flexible member 13 is externally fitted to a stay 15 which is a guide member of a flexible member including a fixing heater 72 as a heating body.

  The inner peripheral length of the endless flexible member 13 and the outer peripheral length of the stay 15 including the fixing heater 72 are slightly larger than those of the flexible member 13. It fits with a margin. The stay 15 is made of a high heat-resistant resin such as polyimide, polyamideimide, PEEK, PPS, or liquid crystal polymer, or a composite material of these resins and ceramics, metal, glass, or the like. In this embodiment, a liquid crystal polymer is used.

  Since the flexible member 13 has a small heat capacity and improves quick start properties, a single layer flexible member such as PTFE, PFA, FEP having a heat resistance of 100 μm or less can be used. Alternatively, a composite layer flexible member in which PTFE, PFA, FEP or the like is coated on the outer peripheral surface of a flexible member such as polyimide, polyamideimide, PEEK, PES, or PPS can be used. In addition, a composite layer flexible member in which the outer peripheral surface of a stainless steel flexible member having a film thickness of 50 μm or less is coated with PTFE, PFA, FEP or the like can also be used. In this embodiment, a polyimide flexible member having a film thickness of about 50 μm coated with a release layer blended with PTFE / PFA on the outer peripheral surface is used.

  The pressure roller 16 forms a nip N with the flexible member 13 sandwiched between the pressure roller 16 and the pressure roller as a flexible member outer surface contact driving means for driving the flexible member 13 to rotate. It is. A rotational force acts on the flexible member 13 by the frictional force between the pressure roller 16 and the outer surface of the flexible member 13 and the rotational driving of the pressure roller 16. The flexible member driving roller / pressure roller 16 is composed of a cored bar, an elastic layer, and an outermost release layer. The flexible member 13 has a predetermined pressing force by bearing means and biasing means (not shown). Is placed in pressure contact with the surface of the fixing heater 72.

(Control means for image forming apparatus)
FIG. 6 is a block diagram schematically illustrating a control unit of the image forming apparatus according to the present embodiment. The CPU 11 includes a laser scanner 3, a main motor 20, a paper feed motor 12, a fixing device motor driving device (hereinafter referred to as “fixing motor”) 71 inside the fixing device 7, and fixing as a heating body of the heating device. The heater 72 is controlled. The CPU 11 receives scanner rotation speed information indicating the driving state of a motor built in the laser scanner from the laser scanner 3, and receives an output signal from a thermistor 73 as temperature detection means of the fixing heater 72. Based on the information, the sheet feeding motor 12 as the first driving means, the main motor 20 in the image forming means for driving the laser scanner 3, and the fixing device as the second driving means for driving the image heating device 7 are used. Temperature control of the motor 71 and the fixing heater 72 is performed.

  As will be described later, the start timing of driving and energization of the image heating device is the same time, and this same time is the time when the image heating device reaches a predetermined image heating temperature before the recording material enters the image heating means. CPU11 which is a control means determines. This control means controls the image forming means based on the image information processing status of the scanner 3 which is the image information processing means. The control means changes the relative drive start timing of the image forming means driving means, the image heating means driving means, and the energization means depending on the state of the image heating means detected by the thermistor 73 as the detecting means. Be made.

(Image development as a base for drive control of the image forming apparatus)
Image development is processing in which each color of a color image to be printed is analyzed and developed by a controller. The image information expansion means 17 for expanding the image information transmits a drive signal (hereinafter referred to as “preprint command”) to the image forming apparatus before the image information is expanded, and the image information expansion ends. It is possible to start driving the image forming apparatus before. Further, at the end of image development, a signal for instructing start of printing (hereinafter referred to as “print signal”) is transmitted to the image forming apparatus, and the control unit can start driving the image forming apparatus based on the print signal. It becomes.

(Temperature rise time, which is the base for energization control of the image heating device)
FIG. 7 shows a temperature rise curve of the fixing device as the image heating apparatus in the present embodiment. The horizontal axis indicates the time from the start of the start, and the vertical axis indicates the fixing heater temperature. When the fixing device was started up from room temperature (20 ° C.), the time to reach the target temperature (180 ° C.) was about 8 seconds. Similarly, it took about 6 seconds when it was raised from 50 ° C., 4 seconds when it was raised from 100 ° C., and 2 seconds when it was raised from 150 ° C. The time from feeding A4 size paper to the image forming apparatus and entering the fixing unit was measured, and it was about 5 seconds. Further, when the time from when the paper entered the fixing device to when the paper was discharged out of the image forming apparatus was measured, it was about 4 seconds.

  The control unit of the image forming apparatus drives the image heating unit and controls the image heating unit to reach a predetermined image heating temperature before the recording material enters the image heating unit based on the detection result by the thermistor 73 which is a temperature detection unit. The start timing of energization is defined as “3 seconds before entry”.

(Image heating device drive and energization start timing)
Hereinafter, the description will be made assuming that the driving and energization of the image heating device start at the same time,
Both may deviate from each other within a predetermined time within the scope of the present invention. 1 to 3 are sequence diagrams showing control contents of the image forming apparatus according to the present embodiment. In this embodiment, there are three stages of heating device drive start timings based on the fixing heater temperature detected by the thermistor 73 at the start of printing.

(1) First Control Sequence A control sequence in the case where the fixing heater temperature is 150 ° C. or higher at the start of printing is shown below. FIG. 1A is a sequence diagram showing the control contents of the image forming apparatus when the temperature of the fixing heater 72 is 150 ° C. or higher. In FIG. 1A, image development is started at the timing of T113, and a preprint command is also transmitted at the same time. However, the image forming apparatus main body waits for the end of image development without particularly starting the operation. At T114, when the image development is completed and a print signal is output, the scanner motor, the main motor, and the paper feed motor start to rotate. The scanner becomes scanner ready at the timing of T115, and drawing becomes possible.

  The fixing device motor 71 and the fixing heater 72 start to rotate and energize at timing T116 3 seconds before the paper enters the fixing device. The time point “3 seconds ago” is determined as follows. That is, after the scanner that is the image information processing unit starts generating the image information, the detection result by the thermistor 73 that is the temperature detection unit is input to the control unit. Based on the result, the control unit determines that the start timing of driving and energization of the image heating unit is “3 seconds ago” so that the recording material reaches a predetermined image heating temperature before the recording material enters the image heating unit.

  In this case, since the temperature of the fixing heater 72 sufficiently rises until the sheet enters the fixing device at the timing of T117, a sufficient fixing ability can be secured. The paper is ejected from the image forming apparatus at the timing of T118, and printing ends.

  In the example shown in FIG. 1A, the time required for image development is relatively short, and the fixing device temperature hardly changes between the start of image development and the driving of the fixing device motor 71 and the fixing heater 72 and energization. Assumed. However, depending on the time required for image development, the fixing device temperature may decrease, and when the control shown in FIG. 1A is used, the fixing device temperature does not rise sufficiently until the paper enters the fixing device. There can be. FIG. 1B shows control for preventing such a problem from occurring. In FIG. 1B, image development is started at T119.

  Even during image development, the thermistor 73 monitors the temperature of the fixing heater 72 and starts driving the fixing device motor 71 and the fixing heater 72 when the temperature of the fixing heater 72 is detected to be less than 150 ° C. (T120). When the fixing heater temperature reaches 180 ° C. (T121), the fixing device motor 71 and the fixing heater 72 are turned off again, and the fixing device 7 returns to the standby state. Further, when the image development continues and the fixing heater temperature again becomes lower than 150 ° C. (T122), the fixing heater 72 and the fixing device motor 71 are similarly driven until the fixing heater temperature reaches 180 ° C. Control is performed so that the temperature is maintained at 150 ° C or higher.

  When the image development is completed at T124, driving of the paper feed motor 12, the main motor 20, and the scanner motor is started. At T125, the scanner is ready and drawing is possible. Thereafter, the driving of the fixing heater 72 and the fixing device motor 71 is started at T126, and the sheet enters the fixing device 7 at T127. At T128, the sheet is discharged out of the image forming apparatus, and the printing operation ends.

(2) Second Control Sequence A control sequence when the fixing heater temperature is less than 100 ° C. at the start of printing is shown below. As shown in FIG. 2A, expansion of image information is started at the timing of T101. At the same time, a preprint command is transmitted to the printer engine, and the printer is ready for printing. The fixing device motor 71 and the fixing heater 72 start to rotate and energize at the same timing as T101. At T102, a heater ready signal is output when the temperature reaches a temperature that can be expected to reach the fixable temperature (180 ° C.) from the start of feeding to the time when the fixing device enters, and the apparatus waits as it is.

  When the image development is completed at T103, a print signal to the printer engine is sent. At the same time, the scanner motor starts to rotate, enters the scanner ready state after about 2 seconds, and enables image drawing at T104. As with the scanner motor, the main motor 20 and the paper feed motor 12 start rotating at T103, and the paper feed operation is started. The sheet passes through the image forming apparatus, and the sheet is discharged out of the image forming apparatus about 4 seconds after the sheet enters the fixing device at the timing of T105, and the operation of the image forming apparatus ends at T106.

  In the example shown in FIG. 2A, the heater ready signal is output in the middle of image development, but in practice, the time required for image development cannot be predicted in advance and is uncertain. Therefore, there is a possibility that the image development ends before the heater ready signal is output and the print signal is output. A sequence diagram in such a case is shown in FIG.

  In FIG. 2B, the image development is started at the timing of T107, and at the same time, the fixing device motor 71 and the fixing heater 72 start to rotate and energize, respectively. Before the heater temperature rises sufficiently, image development ends at the timing T108, and at the same time, the scanner motor and main motor 20 start rotating. That is, although the print signal is output at the timing of T108, the image forming apparatus is in a standby state for a while because the heater temperature has not risen.

  When the fixing heater 72 rises to a temperature at which it can be expected to reach the target temperature before the paper enters the fixing device 7 from the start of paper feeding, the heater ready is output at the timing of T110. Immediately after the heater ready, the scanner motor, the main motor 20, and the paper feed motor 12 start rotating, the paper is fed, and rushed and fixed to the fixing device 7 at the timing of T111, and then at the timing of T112. The image is discharged out of the image forming apparatus and printing is finished.

(3) Third Control Sequence A control sequence when the fixing heater temperature is 100 ° C. or higher and lower than 150 ° C. at the start of printing is shown below. As shown in FIG. 3A, image development starts at T129, and image development ends at T130. During this time, the image forming apparatus is not driven, and after the print signal is transmitted at T130, the scanner motor, the main motor 20, the paper feed motor 12, the fixing device motor 71, and the fixing heater 72 start driving. Since the heater ready is output at the timing of T132 before the paper enters the fixing device at T133, the fixing property of the paper can be sufficiently secured. The fixed sheet is discharged out of the image forming apparatus at timing T134, and the printing is finished.

  In FIG. 3A, it is assumed that the time required for image development is short and the fixing heater temperature hardly decreases. FIG. 3B shows an outline of control corresponding to the case where the fixing heater temperature decreases during image development. In FIG. 3B, image development is started at the timing of T135. Meanwhile, the temperature of the fixing heater 72 is monitored by the thermistor 73, and when the fixing heater temperature becomes less than 100 ° C., driving of the fixing device motor 71 and the fixing heater 72 is started during the image development time (T136).

  That is, the driving of the fixing device motor 71 and the fixing heater 72 is continued until the fixing heater temperature rises to 180 ° C., and when the fixing heater temperature reaches 180 ° C., the driving of the fixing device motor 71 and the fixing heater 72 is stopped (T137). ). From the second time onward, when the fixing heater temperature falls below 150 ° C., the driving of the fixing device motor 71 and the fixing heater 72 is resumed (T138). Also in this case, when the fixing heater temperature reaches 180 ° C., the driving of the fixing heater 72 and the fixing device motor 71 is stopped (T139).

  That is, the control means adjusts the drive timing of the image heating means and the start of energization so that the image heating means reaches a predetermined image heating temperature before the recording material enters the image heating means. Furthermore, when image information generation by the image information processing means has not been completed when the image heating means reaches a predetermined image heating temperature, the driving and energization of the image heating means are stopped again. Then, in accordance with the degree of decrease in the temperature of the image heating unit from the predetermined image heating temperature, the operation of starting driving and energizing the image heating unit again is repeated until the recording material enters the image heating unit.

  With respect to the image heating unit, as for the image forming unit, a print signal is output simultaneously with the completion of image development at T140, and the paper feed motor 12, the main motor 20, and the scanner motor start rotating. At T141, the scanner ready is issued and drawing with the image forming apparatus becomes possible. In the meantime, the sheet is fed through the conveyance path and enters the fixing device at T143.

  Returning to the image heating means, at T142 before the paper enters the fixing device, the fixing device motor 71 and the fixing heater 72 start driving and rise to a predetermined temperature by T143, so that the fixing property of the paper is sufficiently secured. it can. The paper is discharged out of the image forming apparatus at T144, and the printing operation ends.

  Here, a durability test of the image forming apparatus was performed using the fixing device 7 of the present embodiment. A one-sheet intermittent endurance test in which one sheet is printed and the next printing is started at the moment when the sheet is ejected is performed. No abnormality occurred.

(Comparative Example 1)
FIG. 8A shows a sequence diagram showing the control contents of an image forming apparatus as a comparative example of the present invention. FIG. 8A shows a sequence diagram when the fixing heater temperature is 150.degree. As shown in FIG. 8 (a), the fixing device starts up the image development at T601, and whenever the preprint command is transmitted, the fixing device is started up, and the fixing heater 72 is turned on before the paper enters the fixing device. When the target temperature is reached, the target temperature is maintained and kept as it is.

  Using the fixing device of this comparative example, a one-sheet intermittent durability test similar to that of the first embodiment was performed. After about 100,000 sheets were passed, the paper slipped with respect to the fixing roller, and the paper was not passed. An impossible phenomenon occurred. This is because the torque increased because the pressure roller rotated at high temperature for a long time, and when the paper entered, the drive by the fixing roller was not applied and the rotation of the pressure roller stopped. It is done.

(Comparative Example 2)
FIG. 8B is a sequence diagram showing the control contents of the image forming apparatus as the second comparative example of the present invention. Also in this comparative example, it is assumed that the fixing heater temperature starts from the time of 150 ° C. In FIG. 8B, the image forming apparatus does not operate when image development is started in T701, and a print signal is transmitted when image development is completed in T702. Here, for the first time, the scanner motor, the main motor 20, the paper feed motor 12, the fixing device motor 71, and the fixing heater 72 start to be driven simultaneously.

  In this comparative example, when the time until the sheet is discharged from T702 to T705 is measured except for the image development time, it varies depending on the initial temperature of the fixing heater 72, and the fixing heater 72 is at room temperature (20 ° C.). The FPOT was 12 seconds. Further, the FPOT from the state where the fixing heater temperature was 50 ° C. was 10 seconds, and the FPOT from the state where the fixing heater temperature was 100 ° C. or higher was 9 seconds. This means that, in the first embodiment, the FPOT after the end of image development is always 9 seconds, but there is a case where the FPOT is delayed.

  In the first embodiment, although an example in which the temperature of the fixing device 7 is divided into three stages is shown, the number of stages is arbitrary and may be more or less than that of the present embodiment. In this embodiment, although a margin of about 2 seconds is expected from the heater ready until the paper fixing device enters, this time can be further reduced, or only the first sheet can be printed before the heater ready temperature. A sequence that enters the fixing device may be used. This is because the pressure roller temperature tends to be higher on the first sheet than when a plurality of sheets are continuously passed, so that sufficient fixability can be achieved even if the heater ready temperature is not reached. This is because it can often be ensured.

  Further, although the rising condition of the scanner is not considered in the present embodiment, the time required for starting the scanner may be predicted by looking at the rising speed of the scanner motor. The start-up timing of the fixing device may be determined based on a combination of the difference from the predicted start-up time and the fixing roller temperature.

<< Second Embodiment >>
FIG. 9 is a block diagram schematically illustrating a control unit of the image forming apparatus according to the present embodiment. As in the first embodiment, the CPU 11 controls the laser scanner 3, the paper feed motor 12, the fixing motor 71 in the fixing device 7, and the fixing heater 72. The CPU 11 receives scanner rotation speed information indicating the driving state of a motor built in the laser scanner from the laser scanner 3, and receives an output signal from a thermistor 73 as temperature detection means of the fixing heater 72. Based on the information, the sheet feeding motor 12, the main motor 20, the motor for driving the laser scanner 3, the driving of the heating device 7, and the temperature control are performed.

  Further, information from the image information expansion means 17 is input to the CPU, and a drive signal can be sent to the image forming apparatus depending on the expansion state of the image information. Further, in the present embodiment, a current amount detection unit 18 capable of detecting a current value as a current amount flowing through the fixing heater 72 is provided. The current amount detection means 18 can determine the amount of power that can be used by the fixing heater 72 by monitoring the value of the current flowing through the fixing heater 72.

  In this embodiment, the center value of the resistance value of the fixing heater 72 is 10Ω, and the center value of the input voltage is 100V. In this case, the current value is 10 A, and the power is 1000 W. The fixing heater resistance value may fluctuate at a rate of 10%. Similarly, since the voltage value also has a fluctuation range of about 10%, the current value may fluctuate from 12.2 A at the maximum to 8.17 A at the minimum. Similarly, the power value may vary from 1340W to 740W.

  FIG. 10 shows a graph of rising of the fixing heater temperature from room temperature (20 ° C.) in the case of the maximum power value, the minimum power value, and the center value. As shown in the figure, when the current value is the center value (10 A), the current temperature rises up to the target temperature (180 ° C.) in 8 seconds, whereas when the current of 12 A flows, it rises in about 4 seconds. When a current of 9 A flows, it takes about 12 seconds.

  In this embodiment, the sequence showing the operation of the image forming apparatus when the current value is less than 12 A is the same as that in FIG. That is, expansion of image information is started at the timing of T101. At the same time, a preprint command is transmitted to the printer engine, and the printer is ready for printing. The fixing device motor 71 and the fixing heater 72 start to rotate and energize at the same timing as T101, and when the temperature reaches the fixable temperature (180 ° C.) at T102, the heater ready signal is output and waits as it is.

  When the image development is completed at T103, a print signal to the printer engine is sent. At the same time, the scanner motor starts to rotate, enters the scanner ready state after about 2 seconds, and enables image drawing at T104. As with the scanner motor, the main motor 20 and the paper feed motor 12 start rotating at T103, and an image forming operation and a paper feed operation are started. The sheet passes through the image forming apparatus, and the sheet is discharged out of the image forming apparatus about 4 seconds after the sheet enters the fixing device 7 at the timing of T105, and the operation of the image forming apparatus ends at T106.

  In this embodiment, the sequence showing the operation of the image forming apparatus when the current value is 12 A or more is the same as that shown in FIG. That is, the image forming apparatus is not driven until the image development is completed at T129, and after the print signal is transmitted at T130, the scanner motor, the main motor 20, the paper feed motor 12, the fixing device motor 71, and the fixing heater 72 are Start driving each one. Since the heater ready is output at the timing of T132 before the paper enters the fixing device at T133, the fixing property of the paper can be sufficiently secured. The fixed sheet is discharged out of the image forming apparatus at timing T134, and the printing is finished.

  As shown in the present embodiment, by changing the operation sequence of the image forming apparatus according to the detection result by the current value detection unit, as in the first embodiment, both good FPOT and long life of the fixing device can be achieved. be able to.

  It should be noted that the sequence can be determined by combining the current value detection result by the current detection unit shown in the present embodiment and the fixing heater temperature shown in the first embodiment. As in the first embodiment, when the fixing heater temperature is lowered during image development, it is possible to introduce a sequence in which the fixing device is repeatedly driven and stopped up to a predetermined temperature. Furthermore, in this embodiment, although it classify | categorizes into two types, less than 12 A of current values and 12 A or more, it is also possible to divide into three or more cases.

<< Third Embodiment >>
FIG. 11 is a block diagram schematically illustrating a control unit of the image forming apparatus according to the present embodiment. As in the first embodiment, the CPU 11 controls the laser scanner 3, the main motor 20, the paper feed motor 12, the fixing motor 71 inside the fixing device 7, and the fixing heater 72. The CPU 11 receives scanner rotation speed information indicating the driving state of a motor built in the laser scanner from the laser scanner 3, and receives an output signal from the thermistor 73 serving as a heater temperature detection means. Based on the information, the sheet feeding motor 12, the main motor 20, the motor for driving the laser scanner 3, the driving of the heating device 7, and the temperature control are performed.

  Information from the image information expansion means 17 is input to the CPU 11, and a drive signal can be sent to the image forming apparatus depending on the expansion state of the image information. Further, in the present embodiment, an environment sensor 19 is provided as an environment detection unit that detects the temperature around the image forming apparatus. The environment sensor 19 measures the temperature of the surrounding environment where the image forming apparatus is placed, and transmits the information to the CPU 11 as needed.

  FIG. 12 is a graph showing a difference in rising of the fixing heater temperature depending on the ambient temperature of the image forming apparatus. When the ambient temperature is 20 ° C., the time required for the fixing heater temperature to rise from the state where the fixing heater 72 is 100 ° C. to the target temperature (180 ° C.) is 4 seconds. On the other hand, when the ambient temperature of the image forming apparatus is 10 ° C., it takes 5 seconds for the fixing heater temperature to rise from 100 ° C. to 180 ° C.

  The sequence diagram showing the operation of the image forming apparatus at the room temperature of 20 ° C. in the present embodiment is the same as FIG. That is, the image forming apparatus is not driven until the image development is completed at T129, and after the print signal is transmitted at T130, the scanner motor, the main motor 20, the paper feed motor 12, the fixing device motor 71, and the fixing heater 72 are Start driving each one. Since the heater ready is output at the timing of T132 before the paper enters the fixing device at T133, the fixing property of the paper can be sufficiently secured. The fixed sheet is discharged out of the image forming apparatus at timing T134, and the printing is finished.

  In addition, the sequence diagram showing the operation of the image forming apparatus when the room temperature is 10 ° C. or lower in the present embodiment is the same as FIG. That is, expansion of image information is started at the timing of T101. At the same time, a preprint command is transmitted to the printer engine, and the printer is ready for printing. The fixing device motor 71 and the fixing heater 72 start to rotate and energize at the same timing as T101, and when the temperature reaches the fixable temperature (180 ° C.) at T102, the heater ready signal is output and waits as it is.

  When the image development is completed at T103, a print signal to the printer engine is sent. At the same time, the scanner motor starts to rotate, enters the scanner ready state after about 2 seconds, and enables image drawing at T104. As with the scanner motor, the main motor 20 and the paper feed motor 12 start rotating at T103, and the paper feed operation is started. The sheet passes through the image forming apparatus, and the sheet is discharged out of the image forming apparatus about 4 seconds after the sheet enters the fixing device at the timing of T105, and the operation of the image forming apparatus ends at T106.

  As shown in the present exemplary embodiment, by changing the operation sequence of the image forming apparatus according to the detection result by the surrounding environment detecting unit of the image forming apparatus, as in the first exemplary embodiment, a favorable FPOT and a long lifetime of the fixing apparatus are achieved. Can be compatible.

  In this embodiment, the detection unit for the environment around the image forming apparatus detects only the ambient temperature, but it may detect not only the temperature but also information such as humidity. Further, the sequence of the image forming apparatus may be determined in conjunction with the temperature detected by the thermistor 73 in the first embodiment and the second embodiment and the detection result of the current value input to the fixing heater 72. Absent. That is, the detection means may be any combination of an environmental sensor, a temperature detection means, and a current amount detection means.

(Overall operation sequence of image forming apparatus)
Here, the overall operation sequence of the image forming apparatus will be described with reference to FIG. The steps in the figure mean operations. The pre-command output that is the print start in the above-described embodiment corresponds to the time point of the print start signal S in FIG.

  a. Pre-multi-rotation operation: A start operation period (start operation period, warming period) of the image forming apparatus. When the main power switch is turned on, the main motor of the apparatus is driven to rotationally drive the photosensitive drum 1 to execute a preparatory operation for a predetermined process device.

  b. Pre-rotation operation: a period during which the pre-print operation is executed. This pre-rotation operation is executed following the pre-multi-rotation operation when a print signal is input during the pre-multi-rotation operation. When the print signal is not input, the drive of the main motor is temporarily stopped after the completion of the previous multi-rotation operation, the rotation of the photosensitive drum 1 is stopped, and the image forming apparatus is in a standby (standby) state until the print signal is input. Kept. When the print signal is input, the pre-rotation operation is executed.

  c. Printing operation: When a predetermined pre-rotation operation is completed, an image forming process for the photosensitive drum 1 is subsequently executed, and the toner image formed on the surface of the rotating photosensitive drum is transferred to the recording material P, and the toner image is formed by the fixing device 7. Fixing processing is performed, and the image formed product is printed out. In the continuous print mode, the above-described printing operation is repeatedly executed for a predetermined set number of prints.

  d. Between sheets: In the continuous printing mode, after the trailing edge of one recording material has passed through the transfer nip, the recording material in the transfer nip until the leading edge of the next recording material reaches the transfer nip. This is a non-paper passing period.

  e. Post-rotation operation: This is a period during which a predetermined post-operation is executed by continuing to drive the main motor for a while after the printing operation of the last recording material is completed to rotate the photosensitive drum 1.

  f. Standby (standby): When a predetermined post-rotation operation is completed, the main motor is stopped and the photosensitive drum 1 is stopped, and the image forming apparatus is kept in a standby state until the next print start signal is input. . In the case of printing only one sheet, after the printing is completed, the printer goes into a standby state through a post-rotation operation. When a print start signal is input in the standby state, the printer shifts to a pre-rotation operation.

  The printing operation of c is the time of image formation, and the pre-multi-rotation operation of a, the pre-rotation operation of b, the sheet interval of d, and the post-rotation operation of e are non-image formation (non-printing).

1 .... photosensitive drum, 2 .... charging roller, 3 .... laser scanner, 4 .... developing device, 5 .... cleaning device, 6 .... transfer roller, 7 .... fixing device, 11 .... CPU, 12 .... Feeding motor, 13 ... Flexible member, 15 ... Stay, 16 ... Pressure roller, 18 ... Current value detection means, 19 ... Environmental sensor, 20 ... Main motor, 30 ... Reading scanner, 71 ... Fixer motor 72 ... Fixing heater 73 ... Thermistor P ... Recording material N ... Nip

Claims (8)

Image forming means for forming a toner image on a recording material by being driven by a first driving means; image information processing means for generating image information for forming the toner image on the recording material by the image forming means; A state in which the image forming means is controlled by the control means for controlling the image forming means based on the image information processing status, the second driving means and the energizing means are driven and the temperature is raised and maintained at a predetermined image heating temperature. In the image forming apparatus, comprising: an image heating unit that heats upon receiving the introduction of the recording material on which the toner image is formed from the image forming unit.
The image heating means includes a heating body that is energized by the energization means and generates heat and is maintained at a predetermined image heating temperature, a flexible body that slides in contact with the heating body on one side and contacts the recording material on the other side. A pressure member that is pressed against the heating body via the flexible member to form a nip with the flexible member and is rotationally driven by the second driving means, and On-demand image heating means for sandwiching and conveying the recording material at a nip and heating it with the heat of the heating body via the flexible member,
The image heating unit or a detection unit that detects a surrounding state of the image heating unit, and the control unit includes the first driving unit according to the state of the image heating unit detected by the detection unit, An image forming apparatus, wherein a relative drive start timing of the second drive unit and the energization unit is changed.   The image forming apparatus according to claim 1, wherein the detection unit is a temperature detection unit configured to detect a temperature of the heating unit.   The image forming apparatus according to claim 1, wherein the detecting unit is an environment detecting unit that detects a temperature or humidity around the heating unit or the image forming apparatus.   The image forming apparatus according to claim 1, wherein the detection unit is a current amount detection unit configured to detect a current amount when the heating unit is energized.   The detection means detects a temperature detection means for detecting the temperature of the heating means, an environment detection means for detecting the temperature or humidity around the heating means or the image forming apparatus, and a current amount when the heating means is energized. The image forming apparatus according to claim 1, wherein the image forming apparatus is an arbitrary combination of current amount detection means.   After the image information processing unit starts generating image information, at least a detection result by the detection unit is input to the control unit, and based on the result, the control unit rushes the recording material into the image heating unit. 6. The drive timing of the image heating unit and the start timing of energization are adjusted to the same time point so that the image heating unit reaches a predetermined image heating temperature by the time. The image forming apparatus described in the item.   After the image information processing unit starts generating image information, at least a detection result by the detection unit is input to the control unit, and based on the result, the control unit rushes the recording material into the image heating unit. Until the image heating means reaches a predetermined image heating temperature, the drive timing of the image heating means and the start timing of energization are adjusted to the same time point, and the image heating means reaches the predetermined image heating temperature. 6. When the image information generation by the image information processing means is not completed at the time of arrival, driving and energization of the image heating means are stopped again. Image forming apparatus.   After the image information processing unit starts generating image information, at least a detection result by the detection unit is input to the control unit, and based on the result, the control unit rushes the recording material into the image heating unit. Until the image heating means reaches the predetermined image heating temperature, the drive timing of the image heating means and the start timing of energization are adjusted to the same time point, and further, the image heating means reaches the predetermined image heating temperature. When the image information generation by the image information processing means has not been completed at the time of arrival, the driving and energization of the image heating means are stopped again, and the degree of decrease in the temperature of the image heating means from a predetermined image heating temperature The operation of starting driving and energizing the image heating unit again is repeated until the recording material enters the image heating unit. The image forming apparatus according to any one of Itaru 5.