JP6794230B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus such as a copier, a laser beam printer, and a facsimile.

In image formation by the electrophotographic method, the following printing process is generally performed. That is, in the image forming unit, each step of charging, exposure, and developing is performed, an electrostatic latent image is formed on the photosensitive drum charged to a predetermined potential by the exposure step, and the electrostatic latent image is developed by the developing step. , A toner image is formed. Then, the toner image on the photosensitive drum is transferred to the paper by the transfer step, and finally the toner image is heated and pressurized at the fixing portion to perform a printing process consisting of a fixing step of fixing the toner image on the paper. It has been

When the image forming apparatus performs the printing operation of the first sheet, the preprocessing is performed as a preliminary preparation prior to the printing operation of the image forming portion and the fixing portion in order to satisfy the image quality in the printing process. In the image forming unit, the start-up control of a high-voltage power supply that applies a high voltage to various rollers, such as a charging roller, a developing roller, and a transfer roller, and a scanner used for exposure has been completed by the timing of starting the printing process. There is a need. Further, the timing at which the paper reaches the fixing portion can be satisfied only after the heater of the fixing portion is sufficiently heated and the fixing property of the toner image on the paper can be sufficiently guaranteed. .. Therefore, the fixing portion also requires pretreatment such as the heater reaching a predetermined temperature before starting the paper feeding operation or performing a preheating operation for a predetermined time.

Since the above preprocessing is required, the time from when the user of the image forming apparatus instructs the start of printing until the first sheet is ejected is the printing time per sheet during continuous printing. It takes a long time compared to the above and forces the user to wait. The time from instructing the start of the printing operation until the first sheet of paper is ejected is referred to as the first printout time (FPOT), and will be abbreviated as FPOT below. As a technique for shortening FPOT, for example, in Patent Document 1, a technique of increasing the transport speed in a section excluding a section where paper passes through an image forming portion and shortening the time from paper feeding to ejection. Has been proposed.

Japanese Unexamined Patent Publication No. 4-320866

However, since the method of the prior art described above focuses only on shortening the paper transport time, the influence on the image quality due to the shortened transport time is not considered. That is, when the transport time is shortened by increasing the transport speed, the timing at which the paper reaches the image forming portion becomes earlier. As a result, it is time to start the printing process before the start-up control of the image forming portion is completed, which affects the image quality or the paper arrives before the fixing portion is preheated to a predetermined temperature. , The fixing property of the toner image on the paper may be insufficient. Therefore, it is conceivable to reduce the amount of increase in the transport speed or delay the paper feed timing, but the time required for the preprocessing varies depending on the state of the image forming portion and the fixing portion. As a result, the acceleration section of the paper transport speed is constant, and the reduction amount of the transport time is designed to have a margin so that the image quality is not affected even when the preprocessing time is maximum. The effect of shortening cannot be obtained sufficiently. Further, by increasing the transport speed, there is a concern that the driving noise of the motor or gear may increase, the torque margin may be insufficient, or the temperature of the driver IC of the motor may rise, which may lead to an increase in cost.

Further, in the case where the paper transport speed is not increased as in Patent Document 1, the first sheet is fed in consideration of the time from the paper feeding to the image forming portion and the fixing portion. Control is performed to start before a predetermined time when the preprocessing of the image forming portion and the fixing portion is completed. However, as described above, the time required for the pretreatment and the time for the paper to reach the image forming portion and the fixing portion vary. Therefore, it is necessary to determine the timing of the start of paper feeding so that the image formation is not started before the preprocessing is completed or the timing of starting the heat fixing at the fixing portion is not reached. Therefore, it is assumed that the preprocessing will be the longest time, and that the time it takes for the paper to reach the image forming section and fixing section from the start of paper feeding will be the shortest time, and the printing process will always start after the preprocessing is completed. The paper feed timing is determined so that However, in reality, the time required for preprocessing is always the longest, and the time to reach the image forming portion and the fixing portion is not always the shortest. Therefore, as a result, the paper feed timing is unnecessarily delayed by the difference between the assumed time and the actual time, which is a factor that increases the FPOT.

The present invention has been made under such circumstances, and an object of the present invention is to shorten FPOT while maintaining image quality at the time of image formation without adding a new configuration.

In order to solve the above-mentioned problems, the present invention includes the following configurations.

(1) A photosensitive drum, a charged portion that charges the photosensitive drum to a predetermined potential, an exposed portion that forms an electrostatic latent image on the photosensitive drum, and an exposed portion that develops the electrostatic latent image to form a toner image. It has a developing unit, a transfer unit that transfers the toner image to the paper, an image forming unit that forms an image on the paper, and a heater, and the toner image transferred to the paper is heated by the heater. A fixing unit for fixing the paper to the paper, a transporting means for transporting the paper from the paper feeding unit for storing the paper at a first transport speed or a second transport speed faster than the first transport speed, and the transport means. The control means is provided with a control means for controlling the timing at which the paper reaches the transfer portion and the fixing portion, and the control means is such that when the heater of the fixing portion rises to a target temperature, the paper is said. The first timing at which the transport means can start paper transport so as to reach the fixing portion, the charging portion starts charging the photosensitive drum, and the toner image formed on the photosensitive drum is transferred. A second timing at which the transport means can start paper transport and the exposure section start forming the electrostatic latent image on the photosensitive drum so that the paper reaches the transfer section at the timing of reaching the section. The third timing at which the transfer means can start the transfer of the paper and the transfer so that the paper reaches the transfer portion at the timing when the toner image formed on the photosensitive drum reaches the transfer portion. Based on the paper feed start timing at which the paper transfer is started by the means, the accelerating distance until the paper reaches the transfer unit is calculated, and the first accelerating distance is calculated according to the calculated accelerating distance. An image forming apparatus comprising controlling the transport means so as to transport paper at the transport speed of 1 or the second transport speed.

(2) A photosensitive drum, a charged portion that charges the photosensitive drum to a predetermined potential, an exposed portion that forms an electrostatic latent image on the photosensitive drum, and an exposed portion that develops the electrostatic latent image to form a toner image. It has a developing unit, a transfer unit that transfers the toner image to the paper, an image forming unit that forms an image on the paper, and a heater, and the toner image transferred to the paper is heated by the heater. A fixing unit for fixing the paper to the paper, a transport means for transporting the paper from the paper feed unit for storing the paper at a first transport speed or a second transport speed slower than the first transport speed, and the paper feed. A detection means provided in the transfer path between the unit and the transfer unit to detect the transferred paper, and a control means for controlling the transfer means to control the timing at which the paper reaches the transfer unit and the fixing unit. The control means has a first timing at which the paper transport means can start paper transport so that the paper reaches the fixed portion when the heater of the fixing portion rises to a target temperature. The transport means transports the paper so that the charged portion starts charging the photosensitive drum and the paper reaches the transfer portion at the timing when the toner image formed on the photosensitive drum reaches the transfer portion. The paper is released at the second timing at which the paper can be started and at the timing when the exposed portion starts forming the electrostatic latent image on the photosensitive drum and the toner image formed on the photosensitive drum reaches the transfer portion. The first transfer of paper is performed at a third timing at which the transfer means can start paper transfer so as to reach the transfer unit, and at a paper feed start timing determined based on the transfer start timing. When the paper is conveyed at a high speed and the paper is detected by the detection means, the time from the first timing until the paper is detected by the detection means, and the paper is detected by the detection means from the second timing. The time until the paper is detected by the detection means from the third timing, and the predetermined time until the paper is fed from the paper feed unit and reaches the detection means. Based on the difference, the distance required for deceleration from the detection means to the transfer unit is calculated, and the first transfer speed or the first transfer speed is calculated according to the calculated distance required for deceleration. An image forming apparatus characterized in that the transport means is controlled so as to transport paper at a transport speed of 2.

According to the present invention, the FPOT can be shortened while maintaining the image quality at the time of image formation without adding a new configuration.

Sectional drawing which shows the structure of the image forming apparatus of Examples 1 to 3. Schematic diagram showing the relationship between various rollers and motors of Examples 1 to 3 Block diagram showing the configuration of the control system of Examples 1 to 3 Timing chart for explaining the preprocessing and paper feed timing of the first embodiment The figure explaining the scanner start-up control of Example 1. Timing chart for explaining the paper feed timing of the first embodiment Timing chart for explaining the preprocessing and paper feed timing of the third embodiment

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Configuration of image forming apparatus]
FIG. 1 is a cross-sectional view showing the configuration of the image forming apparatus 100 of the first embodiment. In FIG. 1, the photosensitive drum 122 is made of an organic photosensitive member or an amorphous silicon photosensitive member, and is rotationally driven at a predetermined peripheral speed (process speed) in the arrow direction (clockwise direction) in the drawing. The surface of the photosensitive drum 122 is charged to a predetermined polarity and potential by the charging roller 123, which is a charging unit. The scanner unit 108, which is an exposure unit that exposes the photosensitive drum 122, is a drive unit that rotationally drives a laser light source (not shown) that emits laser light, a rotary multifaceted mirror 110 that deflects the laser beam, and a rotary multifaceted mirror 110. The scanner motor 112 is housed. From the laser light source (not shown), laser light modulated (on / off conversion) according to image information input from an image signal generator such as an image reader or a computer is emitted. The emitted laser light is deflected by the rotating multifaceted mirror 110 and output from the scanner unit 108, and is reflected by the laser light reflecting mirror 107 to irradiate the surface of the photosensitive drum 122. As a result, the surface of the photosensitive drum 122 is exposed, and an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 122. The electrostatic latent image formed on the photosensitive drum 122 is developed by adhering toner to the developing roller 121, which is a developing unit, to form a toner image. The photosensitive drum 122, the charging roller 123, and the developing roller 121 are housed in the toner cartridge 120. The image forming unit for forming an image is composed of a scanner unit 108, a photosensitive drum 122, a charging roller 123, and a developing roller 121.

Only one sheet of paper P is fed from the paper feed cassette 114 by the paper feed roller 102, and the fed paper P is conveyed to the transfer roller 106, which is a transfer unit, by the transfer roller 103 and the registration roller 104. By applying a voltage having a polarity opposite to that of the toner from the high-voltage power supply to the transfer roller 106, the toner image formed on the photosensitive drum 122 is transferred to the paper P. The paper P on which the toner image is transferred is conveyed to the fixing device 130. The fuser 130 includes a heater 132 that heats the fixing film 133, a fixing film 133 that heats the toner image on the paper P, a pressure roller 134, and a thermistor 131 that detects the temperature of the heater 132. The toner image of the paper P conveyed to the fuser 130 is heated and pressurized by the fixing film 133 and the pressure roller 134, and is fixed to the paper P. The paper P on which the toner image is heat-fixed is discharged to the discharge tray 113 by the discharge roller 111. The top sensor 105 and the discharge sensor 109, which are detection means, are provided to detect the paper P to be conveyed.

[Delivery motor, fixing motor, drive relationship with each roller]
In the image forming apparatus 100 of this embodiment, as motors used for image forming, in addition to the scanner motor 112 provided in the scanner unit 108 described above, there are a transfer motor 301 and a fixing motor 302. FIG. 2 is a schematic view showing the relationship between the transfer motor 301 and the fixing motor 302, and each roller driven by the transfer motor 301 and the fixing motor 302. The transfer motor 301 (indicated as M in the figure) drives the paper feed roller 102, the transfer roller 103, and the registration roller 104. On the other hand, the fixing motor 302 (indicated as M in the figure) drives the photosensitive drum 122, the transfer roller 106, the fixing film 133, the pressure roller 134, and the discharge roller 111.

[Structure of control system of image forming apparatus]
FIG. 3A is a block diagram showing a relationship between a control system in the image forming apparatus 100 of the present embodiment, that is, a control device that controls image formation, and devices such as various circuits, sensors, and motors controlled by the control device. Is. The control device 200 that controls the image forming apparatus 100 includes an image forming control unit 201, a paper conveying control unit 202, and a conveying speed calculation unit 203.

The image formation control unit 201 controls the high voltage power supply, the scanner unit 108, and the fuser 130 in order to transfer the toner image formed on the photosensitive drum 122 to the paper P and heat and fix the toner image on the paper P. By doing so, the image formation operation is controlled. That is, the image formation control unit 201 applies a high voltage applied to the charging roller 123 and the developing roller 121 for forming the toner image on the photosensitive drum 122, and the transfer roller 106 for transferring the toner image on the photosensitive drum 122 to the paper P. Controls the high voltage generation circuit 126 that supplies Further, the image formation control unit 201 controls the temperature of the heater 132 to raise the temperature of the fuser 130 in order to heat and fix the toner image on the paper P according to the detection result of the thermistor 131 that detects the temperature of the heater 132. I do. Further, the image formation control unit 201 controls the scanner motor 112 via the scanner / laser control circuit 400 for controlling the scanner unit 108.

The paper transport control unit 202 detects the position of the paper P during transport based on the detection results of the top sensor 105 and the discharge sensor 109 arranged in the paper transport path. Further, the paper transport control unit 202 controls the transport motor 301 and the fixing motor 302 that perform paper transport based on the information from the image formation control unit 201 and the calculation result of the paper transport speed calculated by the transport speed calculation unit 203. To do. The transport speed calculation unit 203 calculates the acceleration amount / deceleration amount of the paper transport speed by the transport motor 301 based on the information from the image formation control unit 201 and the paper transport control unit 202.

FIG. 3B is a block diagram showing a hardware configuration of the control device 200. The control device 200 has a CPU 200a, a ROM 200b, and a RAM 200c. The CPU 200a collectively controls the image forming operation of the image forming apparatus 100 based on a control program or the like stored in the ROM 200b. Further, the control device 200 has a timer 200d for measuring the time, which is controlled by the CPU 200a. The RAM 200c is used as the main memory, work area, etc. of the CPU 200a. The image formation control unit 201, the paper transfer control unit 202, and the transfer speed calculation unit 203 described above are also functions executed by the CPU 200a.

[Pre-processing and paper feed timing]
FIG. 4 is a timing chart for explaining the relationship between the pre-processing state of the fixing unit and the image forming unit in this embodiment and the paper feeding timing at which the paper P is started to be fed from the paper feed cassette 114. In FIG. 4, (a) shows the state transition in the pretreatment of the fuser 130. (B) to (d) show state transitions in the preprocessing of the image forming unit. (B) shows the driving state of the fixing motor 302, (c) shows the driving state of the scanner motor 112 of the scanner unit 108, and (d) shows the charging state of the surface of the photosensitive drum 122 by the charging roller 123. (E) shows the driving state of the transfer motor 301 that drives the paper feed roller 102, the transfer roller 103, and the registration roller 104 to transfer the paper P. The horizontal axis of FIG. 4 indicates time. In FIG. 4, the box shown by the solid line (for example, “waiting for fixed paper feed Ready” in (a)) indicates the state of preprocessing. Further, the box shown by the dotted line (for example, "Paper feeding time Min" in (a)) indicates a time factor that determines the timing of feeding, and the transport path length of the paper P of the image forming apparatus 100 and the like. This is a predetermined time parameter based on the performance of the high voltage generation circuit 126 and the like.

[Paper Ready Timing]
The fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready of FIG. 4 are conditions under which the state of the fuser 130 and the scanner motor 112 and the charged state of the photosensitive drum 122 can start paper transfer from the paper feed cassette 114, respectively. Is the timing to show that is established. The paper transport control unit 202 sets the paper feed roller 102 at the timing when all the paper feed Readys are established (paper feed start timing) based on the respective timings of the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready. Drive to feed the first sheet. The timing of the paper feed Ready in the fuser 130, the scanner motor 112, and the photosensitive drum 122 from the start of the printing operation will be described below.

(Fixed paper feed Ready timing)
The image formation control unit 201 starts the fixing motor 302 by starting the printing operation (see FIG. 4B), heats the fixing motor 132, adjusts the temperature by detecting the temperature by the thermistor 131, and heats the fixing film 133. .. The “fixed paper feed Ready waiting” state shown in FIG. 4 indicates this state. Subsequently, the timing at which the detection temperature of the thermistor 131 reaches a predetermined temperature lower than the target temperature is the "fixing paper feed Ready" timing (first timing). The state from the “fixing paper feed Ready” timing to the timing when the detection temperature of the thermistor 131 reaches the target temperature is the “fixing Ready waiting” state. Then, in the "fixing Ready" of FIG. 4, the fixing film 133 and the pressure roller 134 are sufficiently heated, and the paper P rushes into the nip portion (hereinafter, referred to as the fixing nip portion) of the fixing film 133 and the pressure roller 134. However, it shows a state in which the toner image can be heat-fixed. The state of the fixing Ready is a state determined in advance by an experiment. For example, the state after the timing when the detection temperature of the thermistor 131 reaches the target temperature at the time of temperature adjustment is referred to as the “fixing Ready” state in this embodiment.

The “fixing paper feed Ready” timing is a timing at which paper feeding is started so that the paper P rushes into the fixing nip portion after the fixing device 130 transitions to the “fixing Ready” state. Therefore, the timing of transitioning to the "fixed paper feed Ready wait" is, for example, the thermistor 131 in consideration of the temperature rise in the "fixed ready wait" state from the paper P being fed to the time when the paper P is rushed into the fixing nip portion. It is the timing when the detected temperature of is reached the target temperature of -10 ° C. In addition, "-10 ° C." is a value determined in advance by an experiment in consideration of the usage environment of the image forming apparatus 100, the variation in the performance of the heater 132, and the like. It should be noted that the timing of the "fixed paper feed Ready" may be determined by using a temperature other than this from the degree of increase in the detection temperature of the thermistor 131 or the like. Further, in the “paper feed time Min”, which is a predetermined time surrounded by the dotted line in FIG. 4 (a), the tip of the paper P is at the top after the paper P is started to be conveyed by driving the paper feed roller 102. The time (predetermined value) when the time until detection by the sensor 105 is minimized is shown. Further, "Top-fixing" indicates the time required from the detection of the tip of the paper P by the top sensor 105 until the tip of the paper P reaches the fixing nip portion.

(Scanner paper feed Ready timing)
Next, the scanner paper feed Ready timing (third timing) will be described. When the fixing motor 302 is started by the start of the printing operation and the fixing motor 302 transitions to the "steady rotation" state (FIG. 4B), the image formation control unit 201 rotates the rotary multifaceted mirror 110 of the scanner unit 108. Drive 112. The state of preprocessing of the scanner motor 112 changes in the order of "waiting for entry" state, "waiting for convergence" state, and "scanner Ready" state. The "waiting for entry" state indicates a state from the start of activation of the scanner motor 112 to the arrival at a predetermined rotation speed (hereinafter, referred to as a state transition threshold value) slower than the target speed. The "waiting for convergence" state indicates a state from when the rotation speed of the scanner motor 112 reaches the state transition threshold value to when it reaches the target speed. The "scanner Ready" state indicates a state in which the rotation speed of the scanner motor 112 is stable at the target speed. When the speed of the scanner motor 112 fluctuates during the exposure process in which the laser beam is emitted from the scanner unit 108 to expose the surface of the photosensitive drum 122, an electrostatic latent image formed on the photosensitive drum 122 is formed. Distortion and image quality deteriorate. Therefore, the exposure step needs to be performed after the rotation speed of the scanner motor 112 has changed to the stable "scanner Ready" state.

Further, in this embodiment, an oil bearing motor is used for the scanner motor 112. In the case of the scanner motor 112 of the oil bearing, the viscosity of the oil changes depending on the temperature. As a result, the way the scanner motor 112 rises changes depending on the temperature environment when the scanner motor 112 is started. FIG. 5 is a graph showing a waveform showing a change in the rotation speed of the scanner motor 112 at the start-up in the minimum temperature and maximum temperature environment where the image forming apparatus 100 is assumed to be used. In FIG. 5, the solid line shows the rotation speed of the scanner motor 112 when started in a low temperature environment, the alternate long and short dash line shows the rotation speed of the scanner motor 112 when started in a high temperature environment, and the vertical axis shows the rotation speed of the scanner motor 112. The horizontal axis indicates time.

Further, the time t0 indicates the timing when the scanner motor 112 is started in a low temperature environment, and the time t1 indicates the timing when the scanner motor 112 is started in a high temperature environment. Further, the time t2 indicates the timing when the rotation speed of the scanner motor 112 reaches the state transition threshold value, and the time t3 indicates the timing when the rotation speed of the scanner motor 112 reaches the target speed. In FIG. 5, the time t3, which is the timing at which the rotation speed of the scanner motor 112 stabilizes at the target speed in the high temperature environment and the low temperature environment, is shown in an overlapping manner. Further, the states of FIG. 5 corresponding to the “waiting for entry” state of FIG. 4C are time t0 to time t2 (in the case of a low temperature environment) and time t1 to time t2 (in the case of a high temperature environment). Similarly, the states of FIG. 5 corresponding to the “waiting for convergence” state and the “scanner Ready” state of FIG. 4C are time t2 to time t3 and time t3 to, respectively.

In this embodiment, the state transition threshold value for determining that the low-speed region of the scanner motor 112, which is most affected by the temperature change, is in the “waiting for entry” state and the state is in the “waiting for convergence” state is affected by the temperature of the oil. Is set to, for example, 95% of the target speed so that By setting in this way, it is possible to reduce the variation in the time from the time t2 to the time t3 (hereinafter referred to as the convergence waiting time) from the transition to the "convergence waiting" state to the "scanner Ready" state. it can. Thereby, the convergence waiting time can be set to a predetermined time determined based on the measurement result measured in advance by the experiment.

As shown in FIG. 4C, consider a case where the exposure is started at the timing when the scanner motor 112 transitions to the “scanner Ready” state. In this case, an electrostatic latent image is formed on the photosensitive drum 122, the electrostatic latent image is developed by the developing roller 121, and a toner image on the photosensitive drum 122 is formed. Then, the toner image on the photosensitive drum 122 reaches the nip portion (hereinafter, referred to as the transfer nip portion) of the photosensitive drum 122 and the transfer roller 106. On the other hand, even when the paper P is started to be fed at the "scanner paper feed Ready" timing and the paper P is conveyed within the paper feed time Min, it is necessary to satisfy the following timing relationship. That is, the paper P reaches the transfer nip portion after the timing at which the exposure is started at the timing of transition to the above-mentioned "scanner Ready" state and the tip of the toner image formed on the photosensitive drum 122 reaches the transfer nip portion. There is a need to. In other words, it is necessary to satisfy the time relationship of FIG. 4 (c) shown in the following equation (1).
[Convergence waiting transition-scanner paper feed Ready] ≥ [convergence waiting time] + [exposure-transfer drum rotation time]-[paper feed time Min]-[Top-transfer nip transfer time] ... (1)
[Convergence waiting transition-scanner paper feed Ready] is from the transition of the scanner motor 112 in FIG. 4C from the “rush waiting” state to the “convergence waiting” state until the “scanner paper feeding Ready” timing is reached. Indicates the time. [Convergence waiting time] indicates the time from the transition of the scanner motor 112 to the “convergence waiting” state to the transition to the “scanner Ready” state. [Exposure-Transfer drum rotation time] corresponds to "Exposure-Transfer" in FIG. 4C, and is the time required for the photosensitive drum 122 to rotate from the exposure position on the circumference of the photosensitive drum 122 to the transfer nip portion. Is shown. [Top to transfer nip transfer time] corresponds to "Top to transfer" in FIG. 4C, and after the tip of the paper P is detected by the top sensor 105, the tip of the paper P reaches the transfer nip portion. Shows the time required to complete.

The above equation (1) is due to reasons such as a long transport path for the paper P from the paper feed cassette 114 to the transfer nip, and a short time from the start of the scanner motor 112 until the rotation speed stabilizes. The calculation result on the right side of) may be a negative value. In this case, if the timing at which the scanner motor 112 transitions to the "waiting for convergence" state is set as the "scanner paper feed Ready" timing, the paper feed timing will be delayed from the "scanner paper feed Ready" timing in the fastest case, and the FPOT. Becomes larger. Therefore, in such a case, the state transition threshold value indicating the rotation speed for transitioning to the "waiting for convergence" state of the scanner motor 112 is lowered to a lower rotation speed, and the calculation result on the right side of the equation (1) becomes 0 or more. Must be. However, as can be seen from FIG. 5, as the rotation speed of the scanner motor 112 indicated by the state transition threshold becomes slower, the fluctuation of the convergence waiting time due to the temperature environment becomes large, and the [convergence waiting time] is uniquely determined from the scanner rotation speed. It becomes difficult to decide. In such a case, the timing of the scanner paper feed Ready may be determined as follows so that the order of the transition to the “scanner Ready” state and the exposure start timing is not reversed. That is, the start profile storing the rotation control procedure when starting the scanner motor 112 at the lowest temperature in the temperature environment of the image forming apparatus 100 is stored in the ROM 200b, and the scanner paper feed Ready is set based on the start profile. Determine the timing. However, when the temperature fluctuation of how the scanner motor 112 rises is large, the paper feed time is Min, the transport time from the top sensor 105 to the transfer nip is large, and it is necessary to significantly lower the state transition threshold value, the following The scanner paper feed Ready may be set to. That is, depending on the configuration of the image forming apparatus 100, it is better to set the scanner paper feed Ready at the timing of 95% of the state transition threshold than to lower the state transition threshold to lengthen the convergence waiting time. It is also possible that the timing of becoming is early. In this embodiment, it is assumed that the calculation result on the right side of the equation (1) becomes negative, and the scanner paper feed Ready is set to the timing when the convergence transition threshold reaches 95%.

(Charged Paper Ready Timing)
Next, the charged paper feed Ready timing will be described. Regarding the charging process, depending on the state of the surface potential of the photosensitive drum 122 at the start of printing, the surface potential of the photosensitive drum 122 may not be uniform even if the charging voltage is applied once by the charging roller 123, and the image quality may deteriorate. There is. Therefore, in this embodiment, the "charged paper feed Ready" timing (second timing) is set so as to form a toner image on the surface of the photosensitive drum 122 after the charging voltage is applied by the charging roller 123 at least twice. To do.

Specifically, as shown in FIG. 4D, in the pretreatment of charging, the high voltage generation circuit 126 is activated and the charging voltage is started up (“startup” in FIG. 4C). Then, when the start-up of the charging voltage is completed, the state transitions to the "waiting for one round of charging" state, and the charging voltage is applied to the surface of the photosensitive drum 122 by the charging roller 123 in order to make the surface potential of the photosensitive drum 122 uniform. To. When the first application of the charging voltage by the charging roller 123 is completed by making one round of the photosensitive drum 122, the state transitions to the "charging Ready" state. In the "charged ready" state, the scanner unit 108 performs an exposure process from the surface on which the second charging voltage is applied to the photosensitive drum 122 that has returned after one round, and an electrostatic latent image is formed on the photosensitive drum 122. It is formed. Then, the electrostatic latent image is developed by the toner by the developing roller 121, the toner image is formed on the photosensitive drum 122, and the toner image on the photosensitive drum 122 moves to the transfer nip portion.

On the other hand, even when the paper P is started to be fed at the “charged paper feed Ready” timing and the paper is conveyed within the paper feed time Min, the tip of the toner image formed on the photosensitive drum 122 reaches the transfer nip portion. After that timing, the paper P needs to reach the transfer nip portion. That is, it is necessary to satisfy the time relationship of FIG. 4 (d) represented by the following equation (2).
[Charging 1-lap waiting transition-Charging paper feed Ready] ≥ [Photosensitive drum 1-round rotation time] + [Charging-Transfer drum rotation time]-[Paper feeding time Min]-[Top-Transfer nip transport time] ... (2 )
[Charging 1-lap waiting transition-Charging paper feed Ready] indicates the time from the transition to the “charging 1-lap waiting” state in FIG. 4 (d) to reaching the “charged paper feed Ready” timing. [One-turn rotation time of the photosensitive drum] corresponds to the “waiting for one round of charging” in FIG. 4D, and indicates the time for the charging roller 123 to apply a charging voltage to the entire surface (entire circumference) of the photosensitive drum 122. There is. [Charging-transfer drum rotation time] corresponds to "charging-transfer" in FIG. 4D, and the photosensitive drum 122 rotates from the position where the charging roller 123 on the circumference of the photosensitive drum 122 contacts to the transfer nip portion. Shows the time it takes to do this. In this embodiment, the timing at which the equal sign of the right side and the left side is established in the equation (2) is defined as the timing of the “charged paper feed Ready”.

In this embodiment, regarding the developing process and the transfer process, it is sufficient to secure the start-up time for raising the developing voltage and the transfer voltage applied to the developing roller 121 and the transfer roller 106 in the high voltage generation circuit 126. Therefore, the developing process and the transfer process do not require a time sufficient to be a constraint on the paper feeding time as compared with the charged state of the fuser 130, the scanner motor 112, and the photosensitive drum 122. Therefore, from FIG. 4, the description of the pretreatment state of the developing process and the transfer process is omitted.

As described above, in this embodiment, the paper feed operation is performed at the timing when all the paper feed Ready timings of the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready are established. However, as described above, the calculation result on the right side of the equation (1) may be negative, and in that case, the "waiting for convergence" state, which is later than the timing originally desired to set the scanner paper feed Ready timing. It is the same timing as the transition to. FIG. 6 is a timing chart obtained by extracting (a), (c), and (d) of FIGS. 4 in order to explain the time relationship between the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready. The horizontal axis of FIG. 6 indicates time. 6 (a), (b), and (c) of FIG. 6 show a state transition in the pretreatment of the fuser 130, a state transition in the pretreatment of the scanner motor 112 of the scanner unit 108, and a pretreatment of the surface of the photosensitive drum 122, respectively. It shows the transition of the charged state. Each state shown in FIGS. 6A to 6C is the same as that in FIG. 4, and the description thereof will be omitted here.

Further, in FIG. 6, the time TA indicates the timing of the scanner paper feed Ready that was originally desired to be set. The time TB indicates the timing at which the paper feeding operation is started when the timing of the scanner paper feeding Ready is the time TA, which is the timing originally desired to be set. That is, the time TB is the timing at which the three paper feed Readys of the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready are established. In this case, the timing of the fixed paper feed Ready becomes the bottleneck timing. ing. The time TC indicates the timing at which the timing of the scanner paper feed Ready becomes a bottleneck and the paper feed operation is started. For example, as described above, in the case of a low temperature environment, the timing of the scanner paper feed Ready may be determined from the activation profile in the case of the lowest temperature in the temperature environment in which the image forming apparatus 100 is used. In such a case, the scanner paper feed Ready timing becomes a bottleneck, and the paper feed operation is started at the time TC. As a result, the paper feed timing is delayed from the time TA or the time TB, which causes a problem that the FPOT becomes large.

[Calculation of accelerating distance]
Therefore, in this embodiment, by performing control for accelerating the transport speed of the paper P, the transport time from when the paper P is fed from the paper feed cassette 114 until it reaches the transfer nip portion is shortened. Usually, the transport speed of the paper P by the transport motor 301 is the same speed as the transport speed of the paper P by the fixing motor 302 (hereinafter, referred to as a steady speed) _VPS (first transport speed). In this embodiment, the transfer speed of the paper P by the transfer motor 301 is set to the second transfer speed V _Acc (in consideration of the timing at which the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready are established at the start of paper feed. Acceleration control to increase V _Acc > V _PS ) is performed. As a result, even if the start of the paper feed operation is delayed, the transport time until the paper feed P reaches the transfer nip portion is shortened, and the FPOT is improved. The calculation for controlling the transport speed of the paper P is executed by the transport speed calculation unit 203.

(Accelerating distance of fixing factor)
First, the acceleration control is possible distance when the pretreatment is a bottleneck (rate-limiting) of the fixing unit 130 (hereinafter, referred to as the acceleration distance) D _Fsr will be described. Fixing feeding Ready starts paper feeding at a steady rate V _PS at the timing when the sheet P reaches the fixing nip portion, the fixing device 130 has reached the target temperature, sufficient heat to the sheet P This is the timing when the fixing ready state is reached. Therefore, if paper feeding is started at the timing of the fixing paper feed Ready and the acceleration control of the conveying speed of the paper P is performed, the paper P is placed on the fixing nip portion before the fixing device 130 is in the fixing ready state. I will rush. As a result, the toner image on the paper P cannot be sufficiently heated by the fuser 130, so that the toner image may be poorly fixed on the paper P.

なお、時間Ｔ_{ＦｓｒＲｄｙＴｏＰｉｃｋ}は、定着給紙Ｒｅａｄｙとなったタイミングから定着給紙Ｒｅａｄｙ、スキャナ給紙Ｒｅａｄｙ、帯電給紙Ｒｅａｄｙの各タイミングが成立して、用紙Ｐの給紙が開始されるまでの経過時間（待ち時間）を示している。 On the other hand, it is assumed that the timing at which the fixing device 130 becomes the fixing paper feed Ready is the latest timing (fixing rate-determining) among the fixing paper feeding Ready, the scanner paper feeding Ready, and the charged paper feeding Ready. Then, the transport from the timing of the fixing feeding Ready, if further delay the paper feeding operation is started, by conveying the paper P at a faster transport speed V _Acc than the steady speed V _PS, at a steady rate V _PS FPOT can be improved as compared with the case where. Based on the above, the distance _DFsr that can be accelerated by the fixing factor can be _expressed by the following equation (3).

In the time _{TFsrRdyToPick} , the elapsed time from the timing when the fixed paper feed is set to the time when each timing of the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready is established and the paper P is started to be fed. Indicates the time (waiting time).

(Accelerating distance of scanner factor)
Next, the accelerating distance _DScn , which is the distance at which acceleration control is possible when the preprocessing of the scanner motor 112 becomes a bottleneck (rate limiting), will be described. As described with reference to FIG. 6, the timing originally desired to be the scanner paper feed Ready and the timing to be the actual scanner paper feed Ready may be different. As a result, it is assumed that the timing at which the scanner motor 112 becomes the scanner paper feed Ready is the latest timing (scanner rate-determining) among the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready. When the further delayed feeding operation from the timing of the scanner feed Ready is initiated, by conveying the sheet P at a faster transport speed V _Acc than the steady speed V _PS, it was conveyed at a constant speed V _PS FPOT can be improved as compared with the case.

This factor in accelerating coverage distance _{D Scn} of the scanner motor 112 in this case can be calculated by Time to the scanner feeding Ready~ feeding starting] × constant velocity _{V PS.} Then, [time from scanner paper feed Ready to paper feed start] can be calculated by [convergence waiting transition-time until paper feed start]-[convergence wait transition-scanner paper feed Ready time]. Further, from FIG. 4C and Equation (1), [Convergence waiting transition-scanner paper feed Ready time] = [convergence waiting time] + [exposure-transfer drum rotation time]-[paper feed time Min]-[ Top ~ transfer nip transfer time] can be expressed. Therefore, [scanner paper feed Ready-time to paper feed start] = [convergence waiting transition-time to paper feed start]-([convergence waiting time] + [exposure-transfer drum rotation time]-[paper feed time Min ]-[Top ~ transfer transfer time]). As a result, the accelerating distance _DScn due to the exposure by the scanner motor 112 can be expressed by the following equation (4).

In the formula (4), the time T _{ScanWaitRdyToPick} indicates the _total time of the time of [convergence waiting transition-scanner paper feed Ready] and the time of [scanner paper feed Ready-paper feed start] of the formula (1). Further, the time T _ScanWaitRdy and T _PickMin indicate the [convergence waiting time] and the [paper feed time Min] of the equation (1), respectively. The distance D _ExpToTr indicates the distance from the exposure position on the photosensitive drum 122 where the exposure is started by the laser beam from the scanner unit 108 to the transfer nip portion. Distance D _TopTopTr indicates the distance on the transport path from the top sensor 105 to the transfer nip.

(Acceleration distance of charging factor)
Next, the accelerating distance D _Pr , which is the distance at which acceleration control is possible when the charging process of the photosensitive drum 122 by the charging roller 123 becomes a bottleneck (rate-determining), will be described. The charged paper feed Ready state starts paper feeding at that timing, and when the paper P reaches the transfer nip portion at a steady speed _VPS , a charging voltage is applied twice to the surface of the photosensitive drum 122. It is set so that the timing is. As a result, an electrostatic latent image can be formed on the surface of the photosensitive drum 122 having a stable charging potential by exposure by the scanner unit 108. Therefore, when the paper feeding is started at the same time as the charging paper feeding Ready, when the acceleration control of the conveying speed of the paper P is performed, the charging voltage is applied twice to the surface of the photosensitive drum 122 in the charging Ready state. Before, the paper P reaches the transfer nip portion. As a result, the surface of the photosensitive drum 122 to which the charging voltage is not applied twice is started to be exposed by the scanner unit 108, and after the exposure is started, the surface is switched to the surface of the photosensitive drum 122 to which the charging voltage is applied twice. Therefore, the charging potential varies, and the electrostatic latent image may not be formed normally.

なお、時間Ｔ_{ＰｒＲｄｙＴｏＰｉｃｋ}は、帯電給紙Ｒｅａｄｙから、定着給紙Ｒｅａｄｙ、スキャナ給紙Ｒｅａｄｙ、帯電給紙Ｒｅａｄｙの各タイミングが成立し、用紙Ｐの給紙が開始されるまでの経過時間（待ち時間）を示している。 On the other hand, it is assumed that the timing of the charged paper feed Ready is the latest timing (charge rate-determining) among the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready. When the further delayed feeding operation from the timing of the fixing feeding Ready is started, by conveying the sheet P at a faster transport speed V _Acc than the steady speed V _PS, it was conveyed at a constant speed V _PS FPOT can be improved as compared with the case. Based on the above, the distance D _Pr that can be accelerated by the charging factor can be expressed by the following equation (5).

In the time T _PrRdyToPick , the elapsed time (waiting time) from the charged paper feed Ready to the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready timings to start feeding the paper P. ) Is shown.

(Accelerating distance due to transport path factors)
Finally, the accelerating distance D _AccEnb , which is the distance at which acceleration control is possible when the distance of the transport path on which the paper P is conveyed becomes a bottleneck (rate-determining), will be described. By the present embodiment for implementing the acceleration control to increase the conveying roller 103, the speed _{V Acc} the conveying speed of the registration roller 104 from the steady speed _{V PS,} compared to the case of transport at a steady rate _{V PS,} to improve the FPOT be able to. By the way, the section in which acceleration control can be performed is a section from the paper feed section to the transfer nip section. Therefore, the total of the distance at which the paper P is conveyed at the steady speed _VPS and the distance at which the paper P is conveyed by the acceleration control is the distance of the transfer path from the paper feed section to the transfer nip section. Based on the above, the distance D _AccEnb that can be accelerated due to the transport path factor can be _expressed by the following equation (6).

In the formula (6), the distance D _AccEnb is the time of performing the acceleration control of the sheet P (period), compared with the case of conveying the sheet P at a steady rate V _PS, shows the increase in distance which is conveyed There is. The distance _{D AccSlowUpDown} the period from the steady speed _{V PS} until it reaches the speed _{V Acc,} and the period from the speed _{V Acc} to decelerates a steady speed _{V PS,} than when transporting the paper P at a constant velocity _{V PS} Refers to the increased transport distance. The distance _{D SlowUpDown} shows a steady rate _{V PS} period until reaching the velocity _{V Acc,} and the distance the sheet P is transported in the period from the speed _{V Acc} to decelerates a steady speed _{V PS.} That is, the distance D _SlowUpDown is the _sum of the distance D _{AccSlowUpDown} , the period from the steady speed V _PS to the speed V _Acc , and the distance that the paper P is conveyed at the steady speed V _ps during the period from the speed V _Acc to the steady speed V _PS. It is the distance. (D _PickToTr −D _SlowUpDown ) of the formula (6) indicates the distance at which the paper P is conveyed by the speed V _Acc or the steady speed V _PS . _{Furthermore, (V Acc -V PS) /} V Acc , of the distance the sheet P is transported by the velocity _{V Acc,} the ratio, excluding the distance when it is transported at a steady rate _{V PS,} i.e. accelerated by the speed _{V Acc} It shows the percentage of the transport distance increased by the treatment.

Above, fixing, exposure, charging, acceleration distance _D Fsr of the transport path distance _factor, D _{Scn, D Pr,} has been described _{D AccEnb.} In this embodiment, the timings of the three paper feed Readys of the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready are established, and each accelerating distance is calculated when the paper feed operation of the paper P is started. .. Then, by _setting the minimum value of the accelerating distances D _Fsr , D _Scn , D _Pr , and D _AccEnb calculated at the time of paper feeding as the accelerating distance in the acceleration control, the FPOT is shortened within a range that does not affect the image quality. can do. Acceleration distance _{D Fsr, D Scn, D Pr} , the minimum value _Min of the _{D AccEnb (D Fsr, D Scn} , D Pr, D AccEnb) and. Period carrying the sheet P (time) at a velocity _{V Acc,} be calculated by _{((Min (D Fsr, D} Scn, D Pr, D AccEnb) -D AccSlowUpDown) / (V Acc -V PS) Further, a table in which the minimum value of the determined accelerating distance and the control information of the paper transport control unit 202 according to the determined accelerating distance are associated with each other is stored in the ROM 200b of the control device 200, and the paper is transported. The control unit 202 may perform acceleration control of paper transport based on the control information. The control information of the paper transport control unit 202 includes, for example, acceleration control from a steady speed V _PS to a speed V _Acc , or deceleration. Control, transport time at speed V _Acc , etc.

Further, in this embodiment, regarding the developing process and the transfer process, it is sufficient to secure the development voltage applied to the developing roller 121 and the transfer roller 106 and the start-up time for raising the transfer voltage in the high voltage generation circuit 126. Omitted. For example, when performing a process that requires time, such as determining a reference voltage to be applied as a transfer voltage by ATVC control as a preprocessing of the transfer process, the paper feed Ready and acceleration can be performed in the same manner as the scanner unit 108 and the charging process. The distance may be calculated.
As described above, according to the present embodiment, the FPOT can be shortened while maintaining the image quality at the time of image formation without adding a new configuration.

In the first embodiment, when the paper P reaches the transfer nip portion or the fixing nip portion so as not to affect the image quality even in the minimum case in which the feeding time of the first sheet is considered to vary. The accelerating distance is calculated so that each member is in the Ready state. However, in the image forming apparatus 100, as the period of use of the image forming apparatus 100 becomes longer, for example, the paper feed roller 102 and the transfer roller 103 wear out. As a result, the transport distance of the paper P transported by these rollers is shortened, and the paper feed time from the start of transporting the paper P to the arrival of the paper P at the top sensor 105 is gradually lengthened (delayed). .. In addition, there may be a difference between the actual paper feed time and the paper feed time Min due to factors such as using paper that easily slips on the paper P. As a result, when any of the pretreatment of the fixing device 130 and the scanner motor 112 and the charging treatment of the charging roller 123 becomes the rate-determining process, from the transition of the rate-determining member to the Ready state to the start of use. , There is a waiting time due to the time difference between the paper feed time and the paper feed time Min.

Therefore, in the second embodiment, in addition to the control of the first embodiment, when the tip of the paper P is detected by the top sensor 105, the accelerationable distance described below is recalculated. Then, as a result of the recalculation, further acceleration control is performed in consideration of the time difference between the acquired actual paper feed time and the paper feed time Min to shorten the FPOT. The configuration of the image forming apparatus 100 and the configuration of the control device 200 in this embodiment are the same as those in the first embodiment, and the description thereof will be omitted here.

[Calculation of accelerating distance]
First, the accelerating distance _DFsrFromTop , which is the distance at which acceleration control is possible from the top sensor 105 when the pretreatment of the fuser 130 becomes a bottleneck (rate-determining), can be _expressed by the following equation (7).

Incidentally, formula _{(T FsrRdyToPick} × _{V PS)} is an equation for calculating the acceleration distance _{D Fsr} of the fixing factors described in the first embodiment. Further, the equation ((T _PickMsr −T _PickMin ) × V _PS ) indicates the distance that the paper P can accelerate by the time delayed from reaching the top sensor 105. From the equation (7), it is possible to calculate the distance to be further accelerated in the section from the top sensor 105 to the transfer nip portion. Incidentally, the distance _{D AccToTop,} for example _Min in Example _{1 (D Fsr, D Scn,} D Pr, D AccEnb) if is 0, to the tip of the sheet feeding is started sheet P reaches the top sensor 105 time is multiplied by the constant velocity V _PS to a, it can be calculated. _{Furthermore, Min (D Fsr, D Scn} , D Pr, D AccEnb) if the is greater than 0, executed based on the control information table sheet conveyance control unit 202 described above is stored in ROM200b controller 200 It may be calculated according to the state of acceleration control.

なお、式（（Ｔ_{ＳｃｎＷａｉｔＲｄｙＴｏＰｉｃｋ}−Ｔ_{ＳｃｎＷａｉｔＲｄｙ}＋Ｔ_{ＰｉｃｋＭｉｎ}）×Ｖ_ＰＳ−Ｄ_{ＥｘｐＴｏＴｒ}＋Ｄ_{ＴｏｐＴｏＴｒ}）は、実施例１で説明したスキャナモータ１１２が要因での加速可能距離Ｄ_Ｓｃｎを算出する式である。式（８）により、トップセンサ１０５から転写ニップ部までの区間において、更に加速すべき距離を算出することができる。 Next, the accelerating distance D _ScnFromTop , which is the distance at which acceleration control is possible from the top sensor 105 when the preprocessing of the scanner motor 112 becomes a bottleneck (rate-determining), can be _expressed by the following equation (8). ..

Incidentally, the formula _{((T ScnWaitRdyToPick -T ScnWaitRdy + T} PickMin) × V PS -D ExpToTr + D TopToTr) a scanner motor 112 described in Embodiment 1 is an equation for calculating the acceleration distance _{D Scn} of a factor. From the equation (8), it is possible to calculate the distance to be further accelerated in the section from the top sensor 105 to the transfer nip portion.

なお、式（Ｔ_{ＰｒＲｄｙＴｏＰｉｃｋ}×Ｖ_ＰＳ）は、実施例１で説明した帯電要因での加速可能距離Ｄ_Ｐｒを算出する式である。式（９）により、トップセンサ１０５から転写ニップ部までの区間において、更に加速すべき距離を算出することができる。 Subsequently, the accelerating distance D _PrFromTop , which is the distance at which acceleration control is possible from the top sensor 105 when the charging process of the photosensitive drum 122 by the charging roller 123 becomes a bottleneck (rate-determining), is _expressed by the following equation (9). Can be represented.

The formula (T _PrRdyToPick × V _PS ) is a formula for calculating the accelerationable distance D _Pr due to the charging factor described in the first embodiment. From the equation (9), it is possible to calculate the distance to be further accelerated in the section from the top sensor 105 to the transfer nip portion.

なお、式（Ｄ_{ＡｃｃＳｌｏｗＵｐＤｏｗｎ２}＋（Ｄ_{ＴｏｐＴｏＴｒ}−Ｄ_{ＳｌｏｗＵｐＤｏｗｎ２}）×（Ｖ_Ａｃｃ−Ｖ_ＰＳ）／Ｖ_Ａｃｃ）は、実施例１で説明した搬送路要因での加速可能距離Ｄ_{ＡｃｃＥｎｂ}を算出する式である。式（１０）により、トップセンサ１０５から転写ニップ部までの区間において、更に加速すべき距離を算出することができる。 Finally, the accelerating distance D _{AccEnbFromTop} , which is the distance that acceleration control is possible from the top sensor 105 when the distance of the transport path through which the paper P is conveyed becomes a bottleneck (rate-determining), is _expressed by the following equation (10). Can be represented.

The equation (D _{AccSlowUpDown2} + (D _TopTopTr −D _SlowUpDown2 ) × (V _{Acc −} V _PS ) / V _Acc ) is an equation for calculating the accelerating distance D _AccEnb due to the transport path factor described in Example 1. .. From the equation (10), it is possible to calculate the distance to be further accelerated in the section from the top sensor 105 to the transfer nip portion.

Above, fixing, exposure, charging, acceleration distance _{D FsrFromTop} of the transport path distance factor, _{D ScnFromTop, D PrFromTop,} was described _{D AccEnbFromTop.} In this embodiment, when the tip of the paper P reaches the top sensor 105, the accelerating distances D _FsrFromTop , D _ScnFromTop , D _PrFromTop , and D _{AccEnbFromTop} are calculated, and the minimum value among the calculated accelerating distances is determined. .. Then, further acceleration control is performed by using the determined minimum value as a further acceleration possible distance in the acceleration control in the section from the top sensor 105 to the transfer nip portion. As a result, the paper feed roller 102 and the transfer roller 103 are worn away, and the transfer distance per rotation is shortened. As a result, even if the transfer time of the paper P is long, the FPOT is performed within a range that does not affect the image quality. Can be shortened.
As described above, according to the present embodiment, the FPOT can be shortened while maintaining the image quality at the time of image formation without adding a new configuration.

In the third embodiment, a deceleration control for switching the transport speed of the paper P by the transport motor 301 from the steady speed V _PS to the slower transport speed V _Slow will be described. As a result, the FPOT can be shortened even by the deceleration control opposite to the acceleration control described in the first and second embodiments.

In Examples 1 and 2, the paper feed Ready timing of each member was determined based on the case of the paper feed time Min in consideration of the paper feed variation. On the other hand, in the present embodiment, the paper feed Ready timing of each member is determined based on the paper feed time Max, which is a predetermined time in consideration of the paper feed variation. That is, when the paper feed time reaches the maximum (Max), the timing at which the member that has become the rate-determining (bottleneck) that determines the paper feed start timing enters the Ready state and the timing at which the member actually starts to be used are determined. Make sure they match. Here, the paper feed time Max is the opposite of the paper feed time Min of Examples 1 and 2, and after the paper feed roller 102 is driven to start the transfer of the paper P, the tip of the paper P is the top sensor. It refers to the time (predetermined value) when the time until detection by 105 becomes the maximum (Max). As described above, in this embodiment, the paper feed Ready timing is advanced as compared with the first and second embodiments, so that the paper P can be started to be fed earlier. As a result, when the actual paper feed time (the time from the start of paper feed to the tip of the paper P reaching the top sensor 105) is shorter than the paper feed time Max, before each member is in the Ready state. It will be the start timing of use, and the image quality will deteriorate. Therefore, in this embodiment, the deceleration control of the transport motor 301 that decelerates the transport speed of the paper P by the time difference between the actual paper feed time and the paper feed time Max is performed, and the Ready timing and use of each member of the fixing, the scanner, and the charging are performed. Controls to guarantee the order of start timing.

[Calculation of Paper Feed Rady Timing]
FIG. 7 is a timing chart for explaining the relationship between the pre-processing state of the fixing unit and the image forming unit and the paper feeding timing at which the paper P is started to be fed from the paper feed cassette 114 in this embodiment. In FIG. 7, (a) shows the state transition in the pretreatment of the fuser 130. (B) to (d) show state transitions in the preprocessing of the image forming unit. (B) shows the driving state of the fixing motor 302, (c) shows the driving state of the scanner motor 112 of the scanner unit 108, and (d) shows the charging state of the surface of the photosensitive drum 122 by the charging roller 123. (E) shows the driving state of the transfer motor 301 that drives the paper feed roller 102, the transfer roller 103, and the registration roller 104 to transfer the paper P. The horizontal axis of FIG. 7 indicates time. FIG. 7 is the same as in FIG. 4 except that the “paper feed time Min” in FIG. 4 of the first embodiment is changed to the “paper feed time Max”, and the description thereof is the same as that in FIG. Omit.

Next, the timings of the fixed paper feed Ready, the scanner paper feed Ready, and the charged paper feed Ready in this embodiment will be briefly described. The timing of the fixing paper feed Ready is the timing when the detection temperature of the thermistor 131 reaches (target temperature −15 ° C.). The “fixing paper feed Ready” timing is a timing at which paper feeding is started so that the paper P rushes into the fixing nip portion after the fixing device 130 transitions to the “fixing Ready” state. Therefore, at "-15 ° C", the temperature rise is guaranteed to the target temperature in consideration of the temperature rise variation in the fixing Ready waiting state from the time when the paper P is fed to the time when the paper P is rushed into the fixing nip. The value.

Next, at the timing of the scanner paper feed Ready, when the paper P is started to be fed and the paper is conveyed at the paper feed time Max, the tip of the toner image formed on the photosensitive drum 122 is brought to the transfer nip portion. This is the timing at which the paper P reaches the transfer nip portion at the timing of arrival. Therefore, it is necessary to satisfy the time relationship of FIG. 7 (c) shown in the following formula (11).

[Convergence waiting transition-scanner paper feed Ready] ≥ [convergence waiting time] + [exposure-transfer drum rotation time]-[paper feed time Max]-[Top-transfer transfer time] ... (11)
In this embodiment, for the sake of simplicity, the result on the right side of the equation (11) is set to 0 or more, and the timing at which the scanner paper feed Ready is established is the timing at which the equal sign is established (left side = right side).

Finally, at the timing of the charged paper feed Ready, when the paper P is started to be fed and the paper is conveyed within the paper feed time Max, the tip of the toner image formed on the photosensitive drum 122 is brought to the transfer nip portion. This is the timing at which the paper P reaches the transfer nip portion. Therefore, the timing of the charged paper feed Ready needs to satisfy the time relationship of FIG. 7 (d) shown in the following equation (12).
[Charging 1-lap waiting transition-Charging paper feed Ready] ≥ [Photosensitive drum 1-round rotation time] + [Charging-Transfer drum rotation time]-[Paper feeding time Max]-[Top-Transfer nip transport time] ... 12)

[Calculation of the distance required to reduce the transport speed]
Next, the distance required to reduce the paper transport speed when the pretreatment of the fuser 130, the pretreatment of the scanner motor 112, and the charging treatment of the photosensitive drum 122 by the charging roller 123 becomes a rate-determining (bottleneck) will be described. .. In this embodiment, at the start of feeding the paper P, the paper P is conveyed at a steady speed _VPS . Then, at the timing when the top sensor 105 detects the tip of the paper P, the deceleration amount of the paper P transfer speed is determined, and based on the determined deceleration amount, the transfer speed V _Slow (No. 1) at the time of deceleration of the transfer motor 301. 2 transport speed) is determined. Also in this embodiment, the paper feeding of the paper P is started at the timing when all three timings of the fixing paper feeding Ready, the scanner paper feeding Ready, and the charged paper feeding Ready are satisfied.

時間Ｔ_{ＰｉｃｋＭａｘ}は、給紙を開始してから用紙Ｐの先端がトップセンサ１０５により検知されるまでの時間が最大となる場合の時間（給紙時間Ｍａｘ）を指している。時間Ｔ_{ＰｉｃｋＭｓｒ}は、給紙を開始してからトップセンサ１０５が用紙Ｐの先端を検知するまでの時間を示し、時間Ｔ_{ＦｓｒＲｄｙＴｏＰｉｃｋ}は、定着給紙Ｒｅａｄｙのタイミングから給紙が開始されるまでの時間を示している。したがって、式（Ｔ_{ＰｉｃｋＭａｘ}−Ｔ_{ＰｉｃｋＭｓｒ}−Ｔ_{ＦｓｒＲｄｙＴｏＰｉｃｋ}）は、用紙Ｐが給紙時間Ｍａｘよりもトップセンサ１０５に早く到達した時間の差分（時間差）を示している。算出された時間差に用紙Ｐの搬送速度である定常速度Ｖ_ＰＳを乗じることにより、用紙Ｐをトップセンサ１０５から転写ニップ部まで搬送する間に、減速が必要な距離を求めることができる。 First, the distance _DFsrSlow that requires deceleration due to the fixing factor can be obtained by the following equation (13).

The time T _PickMax refers to the time when the maximum time from the start of paper feeding to the detection of the tip of the paper P by the top sensor 105 (paper feeding time Max). The time T _PickMsr indicates the time from the start of paper feeding until the top sensor 105 detects the tip of the paper P, and the time T _FsrRdyToPick is the time from the timing of the fixing paper feed Ready to the start of paper feeding. Is shown. Therefore, formula _{(T PickMax -T PickMsr} -T _{FsrRdyToPick),} the sheet P indicates a difference (time difference) of the time has been reached sooner top sensor 105 than the paper feed time Max. The calculated time difference by multiplying the constant velocity V _PS is the conveyance speed of the paper P, while conveying the sheet P from the top sensor 105 to the transfer nip portion, it is possible to obtain the deceleration is required distances.

Next, the distance D _ScnSlow that requires deceleration due to the cause of the scanner motor 112 can be _obtained by the following equation (14).

用紙Ｐの先端がトップセンサ１０５を通過してから、転写ニップ部に到達するまでに減速が必要な距離は、３つの減速が必要な距離Ｄ_{ＦｓｒＳｌｏｗ}、Ｄ_{ＳｃｎＳｌｏｗ}、Ｄ_{ＰｒＳｌｏｗ}のうちの最大の距離である。 Similarly, the distance D _PrSlow that requires deceleration due to the charging factor can be _obtained by the following equation (15).

The distance required for deceleration from the tip of the paper P passing through the top sensor 105 to reaching the transfer nip is the maximum distance among the three deceleration required distances D _FsrSlow , _DSknSlow , and _DPrSlow. Is.

Next, the deceleration control of this embodiment will be described. In the first embodiment, the transport speed at the time of acceleration control of the paper P is set to V _Acc in advance, and the control is performed so as to accelerate the paper transport as much as possible in the section where the acceleration control from the paper feed section to the transfer nip section of the paper P is performed. It is carried out. As a result, the acceleration coverage distance _{D AccEnb} the transport path, relationship _{(D AccEnb <MIN (D Fsr} , D Scn, D Pr)) in some cases to satisfy the. In such a case, acceleration cannot be performed by the amount of acceleration determined from the accelerationable distances of the fixing, the scanner, and the rate-determining charge. However, in that case, there is only a waiting time from the transition of the state of each member to the Ready state until the member is used, and the image quality is not affected.

On the other hand, regarding the deceleration control of the present embodiment, if the minimum speed V _Slow of the paper P conveying speed is set in advance, the following problems occur. The maximum values of the distances D _FsrSlow , _DScnSlow , and _DPrSlow are set to MAX (D _FsrSlow , _DScnSlow , _DPrSlow ). If the maximum required deceleration distance cannot be decelerated in the deceleration control execution section, the paper P reaches the transfer nip portion or the fixing nip portion before the fixing, scanner, and charging states transition to Ready. As a result, it is time to start using the product, which affects the image quality. In order to avoid the occurrence of such a state, in this embodiment, the following deceleration control is performed at the minimum speed for transporting the paper P. That is, based on the deceleration distance determined by MAX ( _DFsrSlow , _DScnSlow , _DPrSlow ) and the distance from the top sensor 105 on which deceleration control is performed to the transfer nip portion, the minimum speed V _Slow of the paper P transport speed. Is calculated. Here, the minimum speed V _Slow is a speed that satisfies the relational expression (deceleration amount by the minimum speed V _Slow ≧ Max ( _DFsrSlow , _DScnSlow , _DPrSlow )).

For example, a table in which the determined deceleration distance and the control information of the paper transport control unit 202 according to the determined deceleration distance are associated with each other is stored in the ROM 200b of the control device 200, and the paper transport control unit 202 controls. The deceleration control of the paper transport may be performed based on the information. Note that the control information of the sheet conveyance control unit 202, for example, accelerating the minimum speed _{V Slow} corresponding to deceleration distance, from the deceleration control or speed _{V Slow} from steady rate _{V PS} to the speed _{V Slow} to a steady speed _{V PS} Control, transfer time at the minimum speed V _Slow , etc.

In this embodiment, the deceleration control described above, that is, the paper feed timing of the paper P is advanced, and then the deceleration control is performed according to the paper feed time detected by the top sensor 105. Thus, without accelerating the conveying motor 301 than the constant speed V _PS, to the extent that does not affect the image quality, it is possible to shorten the FPOT. If the calculation result on the right side of the equation (11) is a negative value and it is desired to shorten the FPOT by performing only the deceleration control of the transfer motor 301, the convergence waiting time and the state are as follows. The transition threshold may be determined. That is, in accordance with the rise timing in the high temperature environment of FIG. 5 described in the first embodiment, the convergence waiting time and the rush waiting state are changed to the convergence waiting state so that the calculation result on the right side of the equation (11) becomes 0. Determine the state transition threshold at the time. In this case, it is necessary to reflect the difference between the actual rise time of the scanner motor 112 and the rise time in the high temperature environment in the deceleration control. What is the convergence waiting time? It refers to the time required to transition from the convergence waiting state to the scanner Ready state.
As described above, according to the present embodiment, the FPOT can be shortened while maintaining the image quality at the time of image formation without adding a new configuration.

106 Transfer roller 108 Scanner unit 122 Photosensitive drum 123 Charging roller 130 Fixer 200 Control device 301 Conveyor motor

Claims (17)

A photosensitive drum, a charging unit that charges the photosensitive drum to a predetermined potential, an exposure unit that forms an electrostatic latent image on the photosensitive drum, and a developing unit that develops the electrostatic latent image to form a toner image. An image forming unit that has a transfer unit that transfers the toner image to the paper and forms an image on the paper.
A fixing portion having a heater and heating the toner image transferred to the paper with the heater to fix the toner image on the paper.
A transporting means for transporting paper from a paper feeding unit that stores paper at a first transport speed or a second transport speed faster than the first transport speed.
A control means that controls the transport means to control the timing at which the paper reaches the transfer portion and the fixing portion.
With
The control means has a first timing at which the transport means can start paper transport and the charged portion so that the paper reaches the fixed portion when the heater of the fixing portion rises to a target temperature. The transfer means can start the transfer of the paper so that the photosensitive drum is charged and the paper reaches the transfer portion at the timing when the toner image formed on the photosensitive drum reaches the transfer portion. The paper reaches the transfer portion at the timing of 2 and the timing when the exposed portion starts forming the electrostatic latent image on the photosensitive drum and the toner image formed on the photosensitive drum reaches the transfer portion. By the time the paper reaches the transfer unit, based on the third timing at which the transport means can start the paper transport and the paper feed start timing at which the paper transport is started by the transport means. It is characterized in that the accelerating distance is calculated and the transport means is controlled so as to transport the paper at the first transport speed or the second transport speed according to the calculated accelerating distance. Image forming apparatus. The image forming apparatus according to claim 1, wherein the first timing is a timing at which the temperature of the heater reaches a predetermined temperature lower than the target temperature. A detection means provided in the transport path between the paper feed unit and the transfer unit to detect the paper to be transported is provided.
The second timing is the time from when the charging unit starts charging the photosensitive drum to when the photosensitive drum makes one revolution and until the exposure position of the photosensitive drum by the exposure unit moves to the transfer unit. It is determined based on the time, a predetermined time until the paper is fed from the paper feed unit and reaches the detection means, and the paper transport time from the detection means to the transfer unit. The image forming apparatus according to claim 2. The exposed unit includes a rotating multi-sided mirror that deflects light from a light source and a driving unit that drives the rotating multi-sided mirror.
The third timing includes the time from when the rotation speed of the drive unit reaches a predetermined speed to when the target speed is reached, which is faster than the predetermined speed, and the exposure by the exposure unit can be started. It is determined based on the time until the exposure position of the photosensitive drum by the exposure unit moves to the transfer unit, the predetermined time, and the paper transport time from the detection means to the transfer unit. The image forming apparatus according to claim 3. The calculated accelerating distance is the first distance when the paper is conveyed at the first conveying speed from the first timing to the feeding start timing, and the feeding from the second timing. The second distance when the paper is conveyed at the first transfer speed to the start timing, and the second when the paper is conveyed at the first transfer speed from the third timing to the paper feed start timing. The image forming apparatus according to claim 4, wherein the distance is the smallest of the three distances. In the control means, the minimum distance is the time required when the paper is conveyed from the paper feeding unit to the transfer unit at the first conveying speed, and when the paper is conveyed at the second conveying speed. When the transport distance is larger than the fourth distance, which is larger than the transport distance at the first transport speed, the paper is transported at the second transport speed based on the fourth distance. The image forming apparatus according to claim 5, wherein the transport means is controlled. The image forming apparatus according to claim 5, wherein the control means controls the transfer means so that the paper is conveyed at the first transfer speed when the minimum distance is 0. When the transport time from when the paper is fed from the paper feed unit to when the paper is detected by the detection means is longer than the predetermined time, the control means has the same transfer time and the predetermined time. According to the distance obtained by multiplying the difference by the first transport speed and the distance increased from the distance transported by the first transport speed before the paper reaches the detection means, the first The image forming apparatus according to claim 6 or 7, wherein the transport means is controlled so as to transport the paper at the transport speed of 2. The image forming apparatus according to claim 8, wherein the predetermined time is the minimum time from when the paper is fed from the paper feeding unit until it is detected by the detecting means. A photosensitive drum, a charging unit that charges the photosensitive drum to a predetermined potential, an exposure unit that forms an electrostatic latent image on the photosensitive drum, and a developing unit that develops the electrostatic latent image to form a toner image. An image forming unit that has a transfer unit that transfers the toner image to the paper and forms an image on the paper.
A fixing portion having a heater and heating the toner image transferred to the paper with the heater to fix the toner image on the paper.
A transport means for transporting paper from a paper feed unit that stores paper at a first transport speed or a second transport speed slower than the first transport speed.
A detection means provided in the transport path between the paper feed unit and the transfer unit to detect the conveyed paper,
A control means that controls the transport means to control the timing at which the paper reaches the transfer portion and the fixing portion.
With
The control means has a first timing at which the transport means can start paper transport and the charged portion so that the paper reaches the fixed portion when the heater of the fixing portion rises to a target temperature. The transfer means can start the transfer of the paper so that the photosensitive drum is charged and the paper reaches the transfer portion at the timing when the toner image formed on the photosensitive drum reaches the transfer portion. The paper reaches the transfer portion at the timing of 2 and the timing when the exposed portion starts forming the electrostatic latent image on the photosensitive drum and the toner image formed on the photosensitive drum reaches the transfer portion. The paper is conveyed at the first transfer speed at the third timing at which the transfer means can start the paper transfer and at the paper feed start timing at which the paper transfer is started, which is determined based on the above.
When the paper is detected by the detection means, the time from the first timing until the paper is detected by the detection means, the time from the second timing until the paper is detected by the detection means, Based on the difference between the time from the third timing until the paper is detected by the detection means and the predetermined time from the third timing until the paper is fed from the paper feed unit and reaches the detection means. The distance required for deceleration from the detection means to the transfer unit of the paper is calculated, and the calculated deceleration is performed at the first transfer speed or the second transfer speed according to the required distance. An image forming apparatus, characterized in that the transport means is controlled so as to transport paper. The image forming apparatus according to claim 10, wherein the first timing is when the temperature of the heater reaches a predetermined temperature lower than the target temperature. The second timing is the time from when the charging portion starts charging the photosensitive drum to when the photosensitive drum makes one revolution and until the exposure position of the photosensitive drum by the exposure portion moves to the transfer portion. The image forming apparatus according to claim 11, wherein the image forming apparatus is determined based on the time, the predetermined time, and the paper transport time from the detection means to the transfer unit. The exposed unit includes a rotating multi-sided mirror that deflects light from a light source and a driving unit that drives the rotating multi-sided mirror.
The third timing includes the time from when the rotation speed of the drive unit reaches a predetermined speed to when the target speed is reached, which is faster than the predetermined speed, and the exposure by the exposure unit can be started. It is determined based on the time until the exposure position of the photosensitive drum by the exposure unit moves to the transfer unit, the predetermined time, and the paper transport time from the detection means to the transfer unit. The image forming apparatus according to claim 12. The calculated distance required for deceleration is calculated by multiplying the difference between the time from the first timing until the paper is detected by the detection means and the predetermined time by the first transport speed. The first distance, the second distance calculated by multiplying the difference between the time from the second timing until the paper is detected by the detection means and the predetermined time by the first transport speed, and The maximum distance among the third distances calculated by multiplying the difference between the time from the third timing until the paper is detected by the detection means and the predetermined time by the first transport speed. The image forming apparatus according to claim 13, wherein the image forming apparatus is provided. The image forming apparatus according to claim 14, wherein the predetermined time is the maximum time from when the paper is fed from the paper feeding unit until it is detected by the detecting means. The image forming apparatus according to claim 15, wherein the control means controls the transfer means so that the paper is conveyed at the first transfer speed when the maximum distance is 0. The control means is determined so that the distance at which the paper is conveyed is reduced by the maximum distance during the time when the paper is conveyed from the detection means to the transfer unit at the first transfer speed. The image forming apparatus according to claim 16, wherein the transport means is controlled so as to transport the paper at the transport speed of 2.

Images