Image forming apparatus

Abstract

To provide an image forming apparatus that can reduce the time in preparation processing during which the temperature of a polygon motor and a fuser is unnecessarily increased, compared to before.SOLUTION: An ASIC 10 executes preparation processing of executing a polygon motor preparation operation and a heater temperature increase maintaining operation in parallel, and printing processing of, according to print data, causing an image forming unit 4 to form an image on a sheet and causing a fuser 6 to fix the image formed on the sheet. In executing the polygon motor preparation operation and the heater temperature increase maintaining operation in parallel in the preparation processing, the ASIC 10 determines which of the polygon motor preparation operation and the heater temperature increase maintaining operation is to be executed first according to a predetermined condition.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus for forming an image on a sheet. [Background technology]

[0002] Patent Document 1 describes an image forming apparatus that shortens the time required from when an instruction to form an image on a sheet is given until the trailing edge of the first sheet is discharged, that is, the so-called first print time (FPOT). The image forming apparatus described in Patent Document 1 shortens the first print time by executing a preparatory process prior to execution of a printing process. The preparatory process is a process in which the rotation speed of the polygon motor is made to reach a predetermined speed, the temperature of the fixing unit is raised to the fixing temperature using a heater, and then the fixing temperature is maintained using the heater. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-41214 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the image forming apparatus described in Patent Document 1, the polygon motor starts to be driven after the heater is turned on, and if the time required to start the polygon motor is shorter than the time required to heat the heating rotor, it is necessary to maintain the polygon motor at least until the temperature of the heating rotor is completed. Also, if the time required to start the polygon motor is longer than the time required to heat the fixing unit, it is necessary to continue heating the fixing unit at least until the polygon motor reaches a predetermined rotation speed. Therefore, in the image forming apparatus, there is a problem that there is a period during which the polygon motor is unnecessarily driven and a period during which the fixing unit is heated wastefully during the execution of the preparation process.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an image forming apparatus that can reduce the time spent unnecessarily heating up the polygon motor and fixing unit during preparatory processing compared to conventional methods. [Means for solving the problem]

[0006] In order to solve the above problems, the image forming apparatus has a photosensitive drum, a polygon mirror that deflects a light beam emitted from a light source to expose the photosensitive drum, and a polygon motor that supplies driving force to rotate the polygon mirror, and is equipped with an image forming unit that forms an image on a sheet, a heating rotor, a heater that heats the heating rotor, and a pressure rotor that forms a nip portion that nips the sheet between the heating rotor and the pressure rotor, and is equipped with a fixer that fixes the image formed by the image forming unit to the sheet, a main motor that transmits driving force to rotate either the heating rotor or the pressure rotor, and a control unit. The control unit executes a preparatory process in which a polygon motor preparatory operation is performed in parallel, the polygon motor being turned on to cause the rotational speed of the polygon motor to reach a predetermined speed, and a heater temperature rise and maintenance operation is performed in parallel, the heater being turned on to cause the temperature of the heating rotor to rise to the fixing temperature using the heater, and then the heater is used to maintain the fixing temperature; and a printing process in which an image is formed on a sheet using an image forming unit based on print data, and the image formed on the sheet is fixed using a fixing unit.When the polygon motor preparatory operation and the heater temperature rise and maintenance operation are performed in parallel in the preparatory process, the control unit switches between which of the polygon motor preparatory operation and the heater temperature rise and maintenance operation is to be executed first, depending on predetermined conditions.

[0007] In the above configuration, when the polygon motor preparatory operation and the heater temperature maintenance operation are executed in parallel in the preparation process, the control unit switches whether to execute the polygon motor preparatory operation or the heater temperature maintenance operation first according to a predetermined condition. As a result, by executing the bottleneck operation of the polygon motor preparatory operation for setting the polygon motor to a predetermined speed and the heater temperature maintenance operation for raising the temperature of the heating rotor to the fixing temperature first, it is possible to reduce the time that was unnecessarily executed in the polygon motor preparatory operation and the heater temperature maintenance operation in the preparation process.

[0008] and a communication interface for receiving data from an external terminal, the control unit executes an acquisition process for acquiring a preceding command from the external terminal via the communication interface, and in a preparation process, upon receipt of the preceding command via the communication interface, switches between which of a polygon motor preparation operation and a heater temperature maintenance operation is to be executed first in accordance with a predetermined condition. In a printing process, after the preparation process is executed, an image is formed on a sheet using an image forming unit according to print data received via the communication interface, and the image formed on the sheet is fixed using a fixing unit. In the above configuration, when a precedence command is received from an external terminal via a communication interface, it is possible to switch between the polygon motor preparatory operation and the heater temperature maintenance operation to be executed first, depending on specified conditions.

[0009] In the acquisition process, the control unit acquires the printing conditions to be used in the printing process together with the preceding command via the communication interface, the specified conditions being the printing conditions, and in the preparation process, switches between turning on the polygon motor preparation operation and the heater temperature maintenance operation first depending on the printing conditions. In the above configuration, it is possible to switch between the polygon motor preparatory operation and the heater temperature maintenance operation to be executed first, depending on the content of the printing process.

[0010] In the preparation process, the control unit calculates a fixing temperature arrival time from when the heater is turned on until the heating rotator reaches the fixing temperature and a polygon motor start time from when the polygon motor is turned on until the rotation speed of the polygon motor reaches a predetermined speed, according to the printing conditions acquired in the acquisition process. If the fixing temperature arrival time is longer than the polygon motor start time, the heater temperature rise and maintenance operation is performed before the polygon motor preparation operation. On the other hand, if the polygon motor start time is longer than the fixing temperature arrival time, the polygon motor preparation operation is performed before the heater temperature rise and maintenance operation. In the above configuration, the fixing temperature arrival time indicating the time for the heating rotor to reach the fixing temperature and the polygon motor start time indicating the time for the polygon motor to reach a predetermined speed are calculated, and by comparing the two times, it is possible to switch between the heater temperature maintenance operation and the polygon motor preparation operation to be executed first. This makes it possible to accurately shorten the time for which the heating rotor is unnecessarily heated and the time for which the polygon motor rotates during the preparation process.

[0011] In the preparation process, when the fixing temperature reach time is longer than the polygon motor start time, the control unit calculates a first start time according to a value obtained by subtracting the polygon motor start time from the fixing temperature reach time, turns on the heater, and then executes the polygon motor preparation operation when the calculated first start time has elapsed.When the polygon motor start time is longer than the fixing temperature reach time, the control unit calculates a second start time according to a value obtained by subtracting the fixing temperature reach time from the polygon motor start time, and starts execution of the polygon motor preparation operation, and then starts a heater temperature rise maintenance operation when the calculated second start time has elapsed. In the above configuration, the first and second startup start times are calculated using the fixing temperature arrival time and the polygon motor startup time according to a comparison result between the fixing temperature arrival time and the polygon motor startup time.Then, the calculated first and second startup start times are used to set the time when the polygon motor is turned on and the time when the fuser is turned on.Therefore, in the preparation process, the time when the heating rotator is heated to the fixing temperature and the time when the polygon motor reaches a predetermined rotation speed are brought closer together, and it is possible to shorten the time that was unnecessarily executed in the polygon motor preparation operation and the heater temperature maintenance operation.

[0012] The printing conditions include a condition that specifies that the image forming unit forms an image on a sheet at a first speed during the printing process, and a condition that specifies that the image forming unit forms an image on the sheet at a second speed slower than the first speed, and the control unit calculates the fixing temperature reaching time and the polygon motor start time during the polygon motor preparatory operation according to the first speed or the second speed specified by the conditions included in the printing conditions. In the above configuration, the fixing temperature reaching time and the polygon motor start time are calculated according to the speed at which an image is formed on a sheet in the printing process, and thus the start times of the polygon motor preparatory operation and the heater temperature maintenance operation can be set according to the conditions of the printing process to be executed thereafter.

[0013] The image forming unit has a developing roller that supplies toner to the photosensitive drum and a transfer roller that transfers the toner image formed on the photosensitive drum to a sheet, and the main motor is capable of transmitting driving force to the heating rotor, the photosensitive drum, and the developing roller, and the control unit turns on the main motor during heater temperature maintenance operation to rotate the photosensitive drum and the developing roller in addition to the heating rotor. In a configuration in which the heating rotor, photosensitive drum, and developing roller are rotated by one main motor, if the time from when the polygon motor is turned on until the rotation speed of the polygon motor reaches a predetermined speed during the preparation process is longer than the time from when the heater is turned on until the heating rotor is heated to the fixing temperature, there is a concern that toner will be consumed unnecessarily due to the rotation of the photosensitive drum and developing roller in addition to the heating rotor. In the above configuration, the time that the main motor continues to rotate after the heating rotor reaches the fixing temperature during the preparation process is shortened, and the time that the developing roller rotates is also shortened, making it possible to suppress unnecessary consumption of toner.

[0014] The fixing devices include a first type fixing device and a second type fixing device. In the first type fixing device, the heating rotor is a heating roller and the pressure rotor forms a nip portion between the heating roller and the pressure rotor. In the second type fixing device, the heater is a flat substrate on which a heat generating pattern is formed, the heating rotor is a belt that rotates around the substrate, and the pressure rotor forms the nip portion by pinching the belt between the pressure rotor and the flat surface of the substrate. The specified condition is whether the type of the fixing device is a first type fixing device or a second type fixing device. In the preparation process, if the fixing device is a first type fixing device, the control unit executes a heater temperature increase maintenance operation before a polygon motor preparation operation, and if the fixing device is a second type fixing device, the control unit executes a polygon motor preparation operation before a heater temperature increase maintenance operation. In a configuration in which the fixing unit has a flat substrate as a heater, the heating rotator is a belt, so the time required for the belt to heat up to the fixing temperature is shorter than in a fixing unit of the first type. Therefore, in a fixing unit of this type, the control unit executes the polygon motor preparatory operation before the heater temperature maintenance operation in the preparation process. This reduces unnecessary time caused by the fixing unit type, and makes it possible to reduce the first print time in a way that is more suited to the situation. [Brief description of the drawings]

[0015] [Figure 1]FIG. 2 is a diagram illustrating the configuration of a printer. [Diagram 2] FIG. 2 is a block diagram of a printer. [Diagram 3] 11 is a flowchart illustrating a procedure of a process executed by an ASIC. [Figure 4] 11 is a flowchart illustrating a procedure of a preparation process. [Diagram 5] 10 is a flowchart illustrating a procedure for determining a fixing temperature reaching time. [Figure 6] FIG. 1 is a diagram illustrating an increase in temperature. [Figure 7] 4 is a timing chart illustrating a printing process. [Figure 8] 4 is a timing chart illustrating a printing process. [Figure 9] FIG. 13 is a diagram illustrating a fixing unit of a second type. [Figure 10] 10 is a flowchart illustrating a procedure of a preparation process according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (First embodiment) FIG. 1 is a cross-sectional view showing a schematic configuration of a laser printer 1 according to this embodiment. The laser printer 1 is an example of an image forming device. Hereinafter, the laser printer 1 will be abbreviated to printer 1. The printer 1 comprises a device main body 2, a conveying section 3, an image forming section 4, and a fixing unit 6. Hereinafter, for convenience of explanation, the up-down direction and the front-rear direction of the printer 1 will be defined as shown by the arrows in FIG. 1. In addition, the side of the paper will be defined as the left, and the other side of the paper will be defined as the right.

[0017] The device body 2 has a front cover 21, a supply tray 31, and a discharge tray 22. The front cover 21 is attached to the front of the device body 2 in an openable and closable state. The supply tray 31 is attached to the bottom of the device body 2 in a detachable state. A sheet S is placed on the supply tray 31. The sheet S is a standard size sheet such as A4 size. The sheet S is, for example, a paper medium such as plain paper or thick paper, but is not limited to these and may be an OHP film. The discharge tray 22 is provided on the top of the device body 2, and the sheet S on which an image is formed is placed thereon.

[0018] A conveying path is formed in the device body 2 for conveying the sheet S placed on the supply tray 31 toward the discharge tray 22. The conveying section 3 has a pickup roller 33, a separation roller 34, a registration roller 35, a conveying roller 36, a re-conveying roller 38, a discharge roller 85, and a main motor 20 (see FIG. 2).

[0019] The pickup roller 33 picks up the sheets S in the supply tray 31 that have been pushed upward by the sheet pressing plate 32, and transports them toward a transport path. The separation roller 34 separates the sheets S picked up by the pickup roller 33 one by one.

[0020] The registration rollers 35 are disposed upstream of a photoconductor drum 51 (described later) of the image forming unit 4 in the conveying path. The registration rollers 35 align the direction of the leading edge of the sheet S, and then convey the sheet S toward the image forming unit 4. The conveying rollers 36 convey the sheet S after passing through the fixing unit 6 to a discharge roller 85. The re-conveying rollers 38 re-convey the sheet S conveyed to the re-conveying path, toward the image forming unit 4.

[0021] The image forming unit 4 forms an image on the sheet S and is housed in the apparatus body 2. The image forming unit 4 has a drum cartridge 5 and a laser unit 7. The drum cartridge 5 has a photosensitive drum 51, a toner storage unit 57, a supply roller 56, a developing roller 55, a charger 52, a transfer roller 53, and a pinch roller 54. The drum cartridge 5 can be removed from the apparatus body 2 by opening the front cover 21. The pinch roller 54 of the drum cartridge 5 faces the registration roller 35. The pinch roller 54 rotates following the rotation of the registration roller 35, and transports the sheet S together with the registration roller 35.

[0022] The photoconductor drum 51 is rotated by a driving force transmitted from a main motor 20 (see FIG. 2) to transport the sheet S in the transport direction. Toner is stored in a toner storage section 57. A supply roller 56 supplies the toner in the toner storage section 57 to the developing roller 55. A charger 52 uniformly charges the surface of the photoconductor drum 51.

[0023] A transfer roller 53 is disposed at a position facing the photosensitive drum 51. The transfer roller 53 forms a transfer nip between itself and the photosensitive drum 51. Instead of the transfer roller 53, a transfer belt may be used.

[0024] The device body 2 has a laser unit 7 at an upper portion inside the device body 2. The laser unit 7 has a polygon mirror 131 (see FIG. 2), a laser emission unit 132 (see FIG. 2), a lens, a reflecting mirror, etc. The laser unit 7 exposes the surface of the photoconductor drum 51 by scanning the surface of the photoconductor drum 51 with a laser beam based on image data emitted from the laser emission unit 132.

[0025] An electrostatic latent image based on image data is formed on the surface of the photoconductor drum 51 by exposing the surface of the photoconductor drum 51 to light by the laser unit 7. The developing roller 55 supplies toner to the electrostatic latent image formed on the surface of the photoconductor drum 51, thereby forming a toner image on the surface of the photoconductor drum 51.

[0026] A transfer voltage is applied to the transfer roller 53 by a voltage application unit (not shown). The transfer roller 53 transfers the toner image formed on the surface of the photosensitive drum 51 to the sheet S passing through the transfer nip by transporting the sheet S between the transfer roller 53 and the photosensitive drum 51. In this manner, an image is formed on the sheet S.

[0027] A fixing unit 6 is disposed downstream of the image forming unit 4 on the conveying path. The fixing unit 6 is of a first type (two-roller type) and includes a heating roller 61, a pressure roller 62, a heater 63, and a temperature sensor 64 (see FIG. 2). The heating roller 61 heats the sheet S. The pressure roller 62 forms a nip portion NP between the heating roller 61 and the pressure roller 62, and presses the sheet S. The pressure roller 62 rotates by the driving force of the main motor 20.

[0028] The heater 63 is, for example, a halogen heater, and heats the heating roller 61. The temperature sensor 64 is provided near the heating roller 61 and detects the temperature of the heating roller 61. The temperature sensor 64 outputs a signal corresponding to the detected temperature to the ASIC 10, which will be described later.

[0029] Next, the control configuration of the printer 1 will be described with reference to Fig. 2. As shown in Fig. 2, the printer 1 further includes an ASIC (Application specific integrated circuit) 10, a ROM 12, a RAM 13, a NVRAM 14, a communication IF 16, a pre-registration sensor SE1, a post-registration sensor SE2, and a paper discharge sensor SE3. Note that IF is an abbreviation for Interface.

[0030] A CPU (not shown) is mounted on the ASIC 10. The ASIC 10 is an example of a control unit, and performs overall control over each part of the printer 1. The ASIC 10 is electrically connected to the ROM 12, the RAM 13, the NVRAM 14, the electromagnetic clutch 23, the main motor 20, the pre-registration sensor SE1, the post-registration sensor SE2, the paper discharge sensor SE3, the communication IF 16, the drum cartridge 5, the fixing unit 6, and the laser unit 7.

[0031] The ROM 12 stores various control programs and various settings for controlling the printer 1. The processes described below with reference to Figures 3, 4, and 5 are included in the control programs. The RAM 13 is used as a working area from which the various control programs are read, and as a storage area for temporarily storing image data included in a job. The ASIC 10 controls each part of the printer 1 while storing the processing results in the RAM 13 or NVRAM 14 according to the control programs read from the ROM 12 and the signals output from the various sensors.

[0032] The main motor 20 transmits driving force to the conveying unit 3, the pressure roller 62, and the drum cartridge 5. When the main motor 20 is driven, the driving force is transmitted from the main motor 20 to the pressure roller 62, the photosensitive drum 51, the developing roller 55, the pickup roller 33, the registration roller 35, the re-conveying roller 38, and the discharge roller 85. The pressure roller 62, the photosensitive drum 51, the developing roller 55, the pickup roller 33, and the registration roller 35 rotate in a direction to convey the sheet S in the conveying direction.

[0033] ASIC 10 turns on electromagnetic clutch 23 to transmit the driving force of main motor 20 to pickup roller 33, and turns off electromagnetic clutch 23 to prevent the driving force of main motor 20 from being transmitted to pickup roller 33.

[0034] The pre-registration sensor SE1 is disposed upstream of the registration rollers 35 on the conveying path, and is a sensor that detects the passage of the sheet S. The pre-registration sensor SE1 may be a sensor having an actuator that oscillates when the sheet S comes into contact with it, or an optical sensor. The pre-registration sensor SE1 outputs an ON signal when the sheet S is passing, and outputs an OFF signal when the sheet S is not passing. A detection signal by the pre-registration sensor SE1 is output to the ASIC 10.

[0035] The post-registration sensor SE2 is disposed upstream of the fixing unit 6 on the conveying path, specifically, between the registration roller 35 and the transfer roller 53, and is a sensor that detects the passage of the sheet S. The post-registration sensor SE2 has the same configuration as the pre-registration sensor SE1. A detection signal by the post-registration sensor SE2 is output to the ASIC 10.

[0036] The paper discharge sensor SE3 is disposed between the fixing unit 6 and the conveying roller 36 on the conveying path, and detects the passage of the sheet S. The paper discharge sensor SE3 has a configuration similar to that of the pre-registration sensor SE1. A detection signal by the paper discharge sensor SE3 is output to the ASIC 10.

[0037] The communication IF 16 is connected to a network such as a LAN, and enables connection to an external device such as a PC incorporating a driver for the printer 1. The ASIC 10 is capable of receiving print data via the communication IF 16. The print data includes image data for image formation, and option information indicating printing conditions required for forming an image on the sheet S, such as the size and type of the sheet S used for image formation.

[0038] Although not shown, a high-voltage power supply board for applying voltages to the charger 52, the transfer roller 53, and the developing roller 55 is connected to the ASIC 10.

[0039] Next, a process procedure will be described when the printer 1 receives print data from a PC and performs printing processing. The PC is equipped with a printer driver, and the printer driver can generate print data for the printer 1 to print an image.

[0040] Specifically, when the printer driver of the PC accepts the operation of the print execution button from the user, it generates a preceding command and sends it to the printer 1. The preceding command is a command that is sent to the printer 1 prior to sending print data to the printer 1. In this embodiment, the preceding command includes option information. The option information includes information related to the rotation speed (full speed, half speed) of the polygon motor 130 during the print process, information related to the paper transport speed (full speed, half speed), and information specifying the paper type used during the print process. Of the rotation speeds of the polygon motor 130, half speed is a speed slower than full speed. Of the paper transport speeds, half speed is a speed slower than full speed.

[0041] In this embodiment, full speed is an example of the first speed, and half speed is an example of the second speed. In addition, when the first speed is full speed, the second speed may be 75% of the full speed or 25% of the full speed.

[0042] For example, when the printer 1 and the PC are connected via a network by the communication IF 16, the option information may be written in Printer Job Language (PJL). On the other hand, when the printer 1 and the PC are connected via a wired USB connection by the communication IF 16, the option information may be written in commands in the USB control transfer format.

[0043] 3, when the ASIC 10 of the printer 1 receives a preceding command in step 10 (hereinafter, step will be abbreviated as "S") (S10: YES), the process proceeds to S11 and starts preparation processing. The preparation processing is processing that, prior to image formation on the sheet S, executes a polygon motor preparation operation for rotating the polygon motor 130 to a predetermined rotation speed, and a heater temperature increase and maintenance operation for increasing the temperature of the heating roller 61 to the fixing temperature by the heater 63 and maintaining the fixing temperature. In this embodiment, the processing that the ASIC 10 executes in S10 is an example of an acquisition processing.

[0044] 4 is a flowchart explaining the procedure of the preparation process. In S20, the ASIC 10 executes a fixing temperature reaching time determination for determining the time until the heating roller 61 reaches the fixing temperature. The fixing temperature is a temperature required for the heating roller 61 to thermally fix an image formed on the sheet S, and is an example of a target temperature.

[0045] 5 is a flowchart for explaining a procedure for determining the fixing temperature reaching time. In step S40, the ASIC 10 acquires the current temperature from the measurement value of the temperature sensor 64.

[0046] In S41, the ASIC 10 determines the paper conveying speed during the printing process used to determine the fixing temperature and the standby temperature, using the printing conditions indicated by the option information. The ASIC 10 determines the paper conveying speed to be either "full speed" or "half speed" from the printing conditions included in the option information. For example, when the paper type is specified as plain paper (PLAIN) and the print mode is specified as normal printing in the printing conditions included in the option information, the sheet conveying speed is determined to be "full speed". On the other hand, when the paper type is specified as plain paper (PLAIN) and the print mode is specified as a mode requiring high image quality such as photo printing, the sheet conveying speed is determined to be "half speed". In addition, the ASIC 10 may determine the sheet conveying speed to be "full speed" when the option information includes information related to the rotation speed of the polygon motor 130 and the rotation speed of the polygon motor 130 is specified as full speed by this information, and may determine the sheet conveying speed to be "half speed" when the rotation speed of the polygon motor 130 is specified as half speed.

[0047] In S42, the ASIC 10 determines a polygon activation time indicating the time required to activate the polygon motor 130 in the preparation process. As shown in Table 1, if the conveying speed determined in S41 is "full speed", the ASIC 10 determines the polygon activation time to be "3 seconds". On the other hand, if the conveying speed determined in S41 is "half speed", the ASIC 10 determines the polygon activation time to be "2 seconds". Note that the polygon activation times shown in Table 1 are merely examples, and the values ​​are set appropriately depending on the performance of the polygon motor 130 and the sheet conveying speed determined at full speed or half speed.

[0048] [Table 1]

[0049] In S43, the ASIC 10 determines a standby temperature that is a target temperature when the heater 63 heats up the heating roller 61. The standby temperature is a temperature lower than the fixing temperature. As will be described later, in the heater temperature rise maintenance process, the ASIC 10 heats up the heating roller 61 from the current temperature to the standby temperature at a first heating rate, and heats up the heating roller 61 from the standby temperature to the fixing temperature at a second heating rate slower than the first heating rate.

[0050] In S43, the ASIC 10 determines the standby temperature using, for example, the paper type (plain paper, thick paper) specified in the printing conditions and the sheet transport speed (full speed, half speed) determined in S40. Specifically, as shown in Table 2, if the paper type is "plain paper (PLAIN)" and the transport speed is "full speed," the standby temperature is determined to be "80°C." If the paper type is "plain paper (PLAIN)" and the transport speed is "half speed," the standby temperature is determined to be "125°C." If the paper type is "thick paper" and the transport speed is "half speed," the standby temperature is determined to be "125°C." Note that the standby temperatures shown in Table 2 are merely examples.

[0051] [Table 2]

[0052] In S44, ASIC 10 compares the standby temperature determined in S43 with the current temperature acquired in S40. If the standby temperature is equal to or higher than the current temperature (S44: YES), ASIC 10 proceeds to S45 and determines the fixing temperature arrival time. The fixing temperature arrival time is the time required for the heating roller 61 to be heated to the fixing temperature by the heater 63.

[0053] In S45, the ASIC 10 determines the fixing temperature reaching time using the following (Equation 1). Fixing temperature arrival time = (fixing temperature - standby temperature) / second rising temperature + (standby temperature - current temperature) / first rising temperature … (Formula 1)

[0054] The rising temperature indicates the temperature to which the heating roller 61 is raised in one second by the heater 63, and is a value shown in Table 3 in this embodiment. [Table 3]

[0055] In this embodiment, as shown in Fig. 6, the rising temperature indicating the rising speed of the heating roller 61 is made different between when the temperature of the heating roller 61 is equal to or higher than the standby temperature and when it is lower than the standby temperature. Specifically, when the temperature of the heating roller 61 is lower than the standby temperature, the amount of heat applied by the heater 63 is set so that the heating roller 61 rises at a first rising temperature of "35°C / s". On the other hand, when the temperature of the heating roller 61 is equal to or higher than the standby temperature, the amount of heat applied by the heater 63 is set so that the heating roller 61 rises at a second rising temperature of "28°C / s" which is lower than the first rising temperature. In this way, after the heating roller 61 exceeds the standby temperature, the rising temperature is lowered to suppress deterioration of the heating roller 61.

[0056] On the other hand, if the standby temperature is lower than the current temperature (S44: NO), the ASIC 10 proceeds to S46 and determines the fixing temperature reaching time. In S46, the ASIC 10 determines the fixing temperature reaching time using the following (Equation 2). Fixing temperature arrival time = (fixing temperature - current temperature) / second rising temperature ... (Equation 2)

[0057] When proceeding to S46, the temperature of the heating roller 61 is already equal to or higher than the standby temperature, so unlike the process in S45, the temperature of the heating roller 61 is increased only at the second increasing temperature "28° C. / s".

[0058] Returning to S21 in FIG. 4, the ASIC 10 judges whether the fixing temperature arrival time determined in S20 is equal to or longer than the polygon activation time. When the ASIC 10 judges that the fixing temperature arrival time is equal to or longer than the polygon activation time (S21: YES), the process proceeds to S22 and calculates the polygon motor activation start time. When the process proceeds to S22, the time required to raise the temperature of the heating roller 61 to the fixing temperature becomes longer than the time required to rotate the polygon motor 130 to a predetermined rotation speed. Therefore, as in "Case 1" shown in FIG. 7, it is preferable to start the heater temperature rise maintenance operation to raise the temperature of the heating roller 61 first and then start the polygon motor preparation operation to start the polygon motor 130, thereby shortening the time during which the polygon motor 130 continues to rotate unnecessarily. Therefore, in S22, the ASIC 10 calculates the polygon motor activation start time, which indicates the time from turning on the heater 63 to starting the drive of the polygon motor 130, using the following (Equation 3).

[0059] Polygon motor start time = Fixing temperature arrival time - Polygon start time ... (Equation 3)

[0060] That is, in S22, a value obtained by subtracting the polygon startup time from the fixing temperature reaching time is calculated as the polygon motor startup start time, which indicates the period from the start of driving the heater 63 to the start of driving the polygon motor 130. In this embodiment, the polygon motor startup start time is an example of the first startup start time.

[0061] In S23, the ASIC 10 turns on the heater 63 to start a heater temperature increase maintenance operation that starts increasing the temperature of the heating roller 61. In S24, the ASIC 10 starts driving the main motor 20 to rotate the pressure roller 62. As shown in Fig. 2, the main motor 20 supplies driving force to the photosensitive drum 51 and the developing roller 55 in addition to the pressure roller 62, so that the photosensitive drum 51 and the developing roller 55 also rotate due to the driving of the main motor 20 in S24.

[0062] In S25, ASIC 10 determines whether the time since heater 63 was turned on in S23 has reached the polygon motor startup start time. If the polygon motor startup start time has not been reached (S25: NO), ASIC 10 waits. If the polygon motor startup start time has been reached (S25: YES), ASIC 10 proceeds to S26, where it turns on polygon motor 130 to start a polygon motor preparatory operation for rotating polygon motor 130 up to a predetermined rotation speed.

[0063] In S32, the ASIC 10 determines whether the temperature of the heating roller 61 has reached the fixing temperature and whether activation of the polygon motor 130 has been completed based on the detection result of the temperature sensor 64. If the ASIC 10 determines S32 as negative (S32: NO), it waits. On the other hand, if the temperature of the heating roller 61 has reached the fixing temperature and activation of the polygon motor 130 has been completed (S32: YES), the ASIC 10 ends the process shown in FIG. 4. That is, the ASIC 10 ends the preparation process.

[0064] Proceeding to S12 in FIG. 3, the ASIC 10 determines whether print data has been received from the PC. The print data is also called a print job, and has header information, a body, and footer information. The header information includes the IP address of the PC that sent the print data, the name of the creator of the print data, the name of the print data, print setting information, etc. The body is the part that converts the characters and image data to be subjected to the image formation process into a language that can be interpreted by the printer 1. The footer information includes page information such as the page number, creation date, and creator name.

[0065] When the ASIC 10 receives the print data (S12: YES), the process proceeds to S13 and starts the print process. In the print process, the ASIC 10 executes the RIP process, which generates image data for forming an image on the sheet S by interpreting the print data stored in the RAM 13. In the RIP process, the ASIC 10 analyzes the print data stored in the RAM 13, generates one page of image data, and stores the image data in the page memory area of ​​the RAM 13. If the generation of one page of image data is completed, the ASIC 10 registers a print queue corresponding to the image data for one page. If the print data corresponds to one page of image data, the ASIC 10 determines the end of the RIP process by registering the print queue for one page. On the other hand, if the print data corresponds to multiple pages, the ASIC 10 repeats the determination of the generation of one page of image data and the registration of the print queue corresponding to the generated image data for one page if the print queue is not registered for all pages of image data analyzed from the print data.

[0066] When the registration of the print queue is completed, the ASIC 10 refers to the print queue and starts the image forming process on the sheet S using the image data stored in the page memory area. In the image forming process on the sheet S, a latent image is formed on the photosensitive drum 51 using the image data, and a toner image is formed on the photosensitive drum 51 by the toner supplied by the developing roller 55. Then, an image is formed on the sheet S passing through a transfer position between the photosensitive drum 51 and the transfer roller 53. Thereafter, the sheet S is heated and held by the nip portion NP between the pressure roller 62 and the heating roller 61, and the image formed on the sheet S is thermally fixed. When the image forming process on the sheet S is to be ended, the ASIC 10 stops driving the main motor 20 and the polygon motor 130.

[0067] Fig. 7 shows, in this embodiment, the transition of time from when a preceding command is generated by a PC to when a print process is executed by the printer 1. Fig. 8 shows, as a comparative example, the transition of time from when a preceding command is generated by a PC to when a print process is executed by the printer 1. In Figs. 7 and 8, "Case 1" shows a case where the fixing temperature reaching time required for the heating roller 61 to reach the fixing temperature is equal to or longer than the polygon start-up time required for the polygon motor 130 to reach a predetermined rotation speed.

[0068] 8, at time t11, heater 63 starts increasing the temperature of the heating roller, and at time t12, when a predetermined time, which is a fixed value, has elapsed, polygon motor 130 starts to be activated. Therefore, even after polygon motor 130 reaches a predetermined rotation speed, heating roller 61 does not reach the fixing temperature, and polygon motor 130 continues unnecessary rotation for period Td1.

[0069] 7, at time t1, heater 63 starts increasing the temperature of heating roller 61, and then at time t2, which is the time obtained by subtracting the polygon motor start time from the fixing temperature reach time, polygon motor 130 starts starting up. Therefore, the time when heating roller 61 reaches the fixing temperature and the time when polygon motor 130 reaches a predetermined rotation speed become closer, and the period during which polygon motor 130 continues unnecessary rotation becomes shorter than in "Case 1" of FIG.

[0070] Next, a process executed by the ASIC 10 when the fixing temperature reaching time determined in S20 of the preparation process shown in FIG. 4 is shorter than the polygon activation time will be described.

[0071] In FIG. 4, when the ASIC 10 determines that the fixing temperature arrival time is shorter than the polygon activation time (S21: NO), the process proceeds to S27 and calculates the heater activation start time. When the process proceeds to S27, the time required to heat the heating roller 61 to the fixing temperature is shorter than the time required to rotate the polygon motor 130 to a predetermined rotation speed. Therefore, as in "Case 2" shown in FIG. 7, starting the polygon motor preparatory operation to turn on the polygon motor 130 and then starting the heater temperature increase preparatory operation to turn on the heater 63 can shorten the time during which the heating roller 61 continues to be unnecessarily increased in temperature. Therefore, in S27, the ASIC 10 calculates the heater drive start time, which indicates the time from turning on the polygon motor 130 to starting the temperature increase of the heating roller 61, using the following (Equation 4).

[0072] Heater drive start time = Polygon start time - Fixing temperature arrival time ... (Equation 4)

[0073] That is, in S27, a value obtained by subtracting the "fixing temperature reaching time" from the "polygon activation time" determined in S20 is calculated as the heater drive start time, which indicates the period from the start of driving the polygon motor 130 to the start of driving the heater 63. In this embodiment, the heater drive start time is an example of the second activation start time.

[0074] In S28, ASIC 10 starts the polygon motor preparatory operation by starting the polygon motor 130. In S29, ASIC 10 determines whether the time since the start of the polygon motor 130 has reached the heater activation start time. If the heater activation start time has not been reached (S29: NO), ASIC 10 waits. If the heater activation start time has been reached (S29: YES), ASIC 10 proceeds to S30 and starts the heater temperature maintenance operation by turning on the heater 63.

[0075] In S31, the ASIC 10 starts driving the main motor 20, thereby rotating the pressure roller 62.

[0076] The ASIC 10 waits if the temperature of the heating roller 61 has not reached the fixing temperature or if the driving of the polygon motor 130 has not been completed (S32: NO). On the other hand, if the temperature of the heating roller 61 has reached the fixing temperature and the driving of the polygon motor 130 has been completed (S32: YES), the ASIC 10 ends the process shown in FIG.

[0077] 7 and 8, "Case 2" shows a case where the fixing temperature reaching time required for the heating roller 61 to reach the fixing temperature is shorter than the polygon start-up time required for the polygon motor 130 to reach a predetermined rotation speed.

[0078] 8, in "Case 2", similarly to "Case 1", at time t11, heater 63 starts increasing the temperature of the heating roller, and at time t12, when a predetermined time, which is a fixed value, has elapsed, polygon motor 130 starts to be activated. Therefore, even after heating roller 61 reaches the fixing temperature, polygon motor 130 does not reach a predetermined rotation speed, and heating roller 61 continues unnecessary temperature increase during period Td2.

[0079] 7, in "Case 2", at t1, polygon motor 130 starts to be driven, and then at time t3, when the heater start time, which is the polygon start time minus the fixing temperature arrival time, has elapsed, heater 63 starts to heat up heating roller 61. Therefore, the time when heating roller 61 reaches the fixing temperature and the time when polygon motor 130 reaches a predetermined rotation speed become closer, and the period during which heating roller 61 is unnecessarily heated becomes shorter than in "Case 2" of FIG.

[0080] Next, an example will be described in which the ASIC 10 of the printer 1 accepts a print command through operation of an operation panel (not shown) and performs print processing using print data stored in the NVRAM 14, etc. When the ASIC 10 accepts a print command through operation of the operation panel, it does not receive a preceding command from the PC.

[0081] 3, when a print command is received (S14: YES), the ASIC 10 proceeds to S15 and executes the preparation process as described in S11. In this example, the ASIC 10 determines the sheet transport speed used to determine the fixing temperature and standby temperature using the printing conditions included in the print data in determining the fixing temperature arrival time executed in S20 of FIG. 4 (S41). In this case as well, the ASIC 10 determines the paper transport speed to be either "full speed" or "half speed" based on the printing conditions included in the print data.

[0082] In S42, ASIC 10 uses the paper transport speed determined in S41 to determine a polygon start time indicating the time required to start polygon motor 130. In S43, ASIC 10 determines a standby temperature using the paper transport speed and paper type determined in S40. The processes executed by ASIC 10 in S44, S45, and S46 have already been described.

[0083] In S16 of Fig. 3, the ASIC 10 executes the print process in the same manner as in S13 already described. When S16 ends, the ASIC 10 ends the process in Fig. 3.

[0084] The present embodiment described above can provide the following advantages. The ASIC 10 executes a preparatory process in which a polygon motor preparatory operation for turning on the polygon motor 130 to make the rotation speed of the polygon motor 130 reach a predetermined speed and a heater temperature increase and maintenance operation for turning on the heater 63 to increase the temperature of the heating roller 61 to the fixing temperature and then maintaining the fixing temperature using the heater 63 are executed in parallel. In the preparatory process, the ASIC 10 switches whether to execute the polygon motor preparatory operation or the heater temperature increase and maintenance operation first according to a predetermined condition. This makes it possible to reduce the time that was unnecessarily executed in the polygon motor preparatory operation and the heater temperature increase and maintenance operation in the preparatory process.

[0085] Upon receiving a preceding command via communication IF 16, ASIC 10 switches whether to execute the polygon motor preparatory operation or the heater temperature maintenance operation first in the preparation process, according to a predetermined condition. After executing the preparation process, ASIC 10 forms an image on a sheet using image forming unit 4 according to print data received via communication IF 16, and fixes the image formed on the sheet using fixing unit 6. In this way, upon receiving a preceding command from the PC via communication IF 16, it is possible to switch whether to execute the polygon motor preparatory operation or the heater temperature maintenance operation first, according to a predetermined condition.

[0086] The ASIC 10 acquires the printing conditions used in the print process together with the preceding command via the communication IF 16, and in the preparation process, switches whether to execute the polygon motor preparation operation or the heater temperature maintenance operation first according to the printing conditions. This makes it possible to switch whether to turn on the polygon motor 130 or the heater 63 first according to the printing conditions used in the print process.

[0087] In the preparation process, the ASIC 10 calculates the fixing temperature arrival time and the polygon start-up time according to the acquired printing conditions, and if the fixing temperature arrival time is longer than the polygon start-up time, executes the heater temperature rise and maintenance operation before the polygon motor preparation operation, and if the polygon start-up time is longer than the fixing temperature arrival time, executes the polygon motor preparation operation before the heater temperature rise and maintenance operation. This makes it possible to switch which of the heater 63 and the polygon motor 130 is turned on first by comparing the fixing temperature arrival time and the polygon start-up time, and it is possible to accurately shorten the time for which the heating roller 61 is heated and the time for which the polygon motor 130 rotates, unnecessarily.

[0088] When the fixing temperature arrival time is longer than the polygon activation time, the ASIC 10 calculates the polygon motor activation start time according to the value obtained by subtracting the polygon activation time from the fixing temperature arrival time, and executes the polygon motor preparatory operation when the calculated polygon motor activation start time has elapsed after starting the heater temperature rise maintenance operation. On the other hand, when the polygon motor activation time is longer than the fixing temperature arrival time, the ASIC 10 calculates the heater activation start time according to the value obtained by subtracting the fixing temperature arrival time from the polygon activation time, and executes the polygon motor preparatory operation when the calculated heater activation start time has elapsed after starting the polygon motor preparatory operation. This makes it possible to shorten the time that was unnecessarily executed in the polygon motor preparatory operation and the heater temperature rise maintenance operation in the preparation process, while bringing the time when the heating roller 61 is heated to the fixing temperature closer to the time when the polygon motor reaches a predetermined rotation speed.

[0089] In the polygon motor preparatory operation, the ASIC 10 calculates the fixing temperature arrival time and the polygon motor start time according to the full speed or half speed determined by the printing conditions. By calculating the fixing temperature arrival time and the polygon motor start time according to the conditions of the printing process executed after the preparatory process, the time for the heating roller 61 to heat up and the time for the polygon motor to rotate can be shortened according to the contents of the printing process.

[0090] In a configuration in which the heating roller 61, the photosensitive drum 51, and the developing roller 55 are rotated by one main motor 20, if the time from when the polygon motor 130 is turned on until the rotation speed of the polygon motor 130 reaches a predetermined speed during the preparation process is longer than the time from when the heater 63 is turned on until the heating roller 61 is heated to the fixing temperature, there is a concern that toner will be consumed unnecessarily due to the rotation of the photosensitive drum 51 and the developing roller 55 in addition to the heating roller 61. In this embodiment, the time during which the main motor 20 continues to rotate after the heating roller 61 reaches the fixing temperature during the preparation process is shortened, and therefore the time during which the developing roller 55 rotates is also shortened, thereby suppressing unnecessary toner consumption.

[0091] Second embodiment In the second embodiment, the configuration different from the first embodiment will be mainly described. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

[0092] In the first embodiment, the fixing unit 6 is of a first type including a heating roller 61 which is a heating rotator and a pressure roller 62 which is a pressure rotator. In the present embodiment, the fixing unit 6 may be of a second type.

[0093] As shown in FIG. 9, the second type fixing device 6 includes a heating unit 160 and a pressure roller 165. One of the heating unit 160 and the pressure roller 165 is biased toward the other by a biasing mechanism (not shown). The heating unit 160 includes a flat heater substrate 161, a belt 162, and a holder 163. The heater substrate 161 is supported by the holder 163 with the flat surface on which the heating pattern is formed facing downward. The belt 162 is a heating rotating body, and is an endless belt having heat resistance and flexibility. The belt 162 is composed of, for example, a metal tube made of a metal such as stainless steel and a fluororesin layer that covers the metal tube. The heater substrate 161 is disposed inside the belt 162 by the holder 163. The belt 162 is configured to rotate around the heater substrate 161 supported by the holder.

[0094] The pressure roller 165 functions as a pressure rotating body. The pressure roller 165 sandwiches the belt 162 between itself and the heater substrate 161 to form a nip portion NP for applying heat and pressure to the sheet S. This nip portion NP has an area corresponding to the plane of the heater substrate 161. The pressure roller 165 is driven to rotate by the power from the main motor 20, and causes the belt 162 to rotate by the frictional force with the belt 162 (or the sheet S). As a result, the sheet S on which the toner image has been transferred is transported between the pressure roller 165 and the heated belt 162, whereby the toner image is thermally fixed.

[0095] 10 is a flow chart for explaining the procedure of the preparation process according to this embodiment. In S50, the ASIC 10 judges whether the type of the fixing unit 6 is the first type. For example, the ASIC 10 judges the type of the fixing unit 6 from information for identifying the model of the printer 1, which is the device itself. If the type of the fixing unit 6 is the first type (S50: YES), the process proceeds to S23, and the heater 63 is turned on to start the heater temperature maintenance operation. In S24, the ASIC 10 starts driving the main motor 20 to rotate the pressure roller 165.

[0096] In S26, the ASIC 10 starts the polygon motor preparatory operation by turning on the polygon motor 130. That is, in this embodiment, the ASIC 10 determines the time to turn on the polygon motor 130 without calculating the polygon activation start time. Alternatively, the ASIC 10 may proceed to S26 and start the polygon motor preparatory process when it determines that a predetermined period has elapsed.

[0097] On the other hand, if the type of the fixing unit 6 is the second type (S50: NO), the ASIC 10 proceeds to S28 and starts polygon motor preparation processing by turning on the polygon motor 130. Since the second type fixing unit 6 requires a shorter time for the belt 162 to reach the fixing temperature compared to the first type fixing unit, the polygon motor preparation operation starts before the heater temperature increase and maintenance operation.

[0098] In S30, the ASIC 10 starts the heater temperature maintaining operation by turning on the heater 63. In S31, the ASIC 10 starts the activation of the main motor 20.

[0099] In S32, the ASIC 10 determines whether or not the temperature of the belt 162 has reached the fixing temperature and the activation of the polygon motor 130 has been completed based on the detection result of the temperature sensor 64. If the temperature of the belt 162 has reached the fixing temperature and the activation of the polygon motor 130 has been completed (S32: YES), the ASIC 10 ends the process shown in FIG.

[0100] 9, the second type of fixing device 6 may have the following configuration. The fixing device 6 has a heater, a nip plate that receives radiant heat from the heater, a heating belt that rotates around the nip plate, and a pressure roller, and the heating belt is rotated by the main motor 20. The first type of fixing device 6 may have the following configuration. The fixing device 6 has a heating roller, a heater, and a pressure belt, and the pressure belt is rotated by the main motor 20.

[0101] In the embodiment described above, if the fixing unit 6 is of the second system, the ASIC 10 executes the polygon motor preparatory operation before the heater temperature maintenance operation in the preparatory process. This allows the operation required to rotate the polygon motor 130, which is a bottleneck, up to a predetermined rotation speed to be performed in advance in the preparatory process, thereby reducing unnecessary time and realizing a reduction in the first print time that is more suited to the situation.

[0102] (Other embodiments) The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. In the above embodiment, a halogen heater that uses radiant heat is used as the heater, but the heater is not limited to this and may be, for example, a ceramic heater or a carbon heater that uses heat generated by a resistor. Also, the heater may be disposed outside the heating rotor instead of inside the heating rotor.

[0103] In the above embodiment, the main motor 20 transmits the driving force to the transport unit 3, the pressure roller 62, and the drum cartridge 5. Alternatively, the transport unit 3, the pressure roller 62, and the drum cartridge 5 may be driven by separate motors.

[0104] The image forming apparatus is not limited to a printer, and may be, for example, a copying machine or a multifunction machine equipped with a document reading device such as a flatbed scanner. [Explanation of symbols]

[0105] 1... printer, 6... fuser unit, 10... ASIC, 61... heating roller, 62... pressure roller, 63... heater, 130... polygon motor

Claims

1. an image forming section including a photosensitive drum, a polygon mirror that deflects a light beam emitted from a light source to expose the photosensitive drum, and a polygon motor that supplies a driving force for rotating the polygon mirror, and that forms an image on a sheet; a fixing device including a heating rotator, a heater for heating the heating rotator, and a pressure rotator for forming a nip portion for nipping a sheet between the heating rotator and the pressure rotator, and fixing an image formed by the image forming unit onto the sheet; a main motor that transmits a driving force for rotating either the heating rotor or the pressure rotor; A control unit; Equipped with The control unit is a polygon motor preparatory operation for turning on the polygon motor so that the rotation speed of the polygon motor reaches a predetermined speed; a preparatory process for simultaneously executing a heater temperature increase and maintenance operation of turning on the heater to increase the temperature of the heating rotator to a fixing temperature and then maintaining the fixing temperature by using the heater; a printing process in which an image is formed on a sheet using the image forming unit based on print data, and the image formed on the sheet is fixed using the fixing device; Run an image forming apparatus characterized in that, when the polygon motor preparatory operation and the heater temperature maintenance operation are executed in parallel in the preparatory processing, which of the polygon motor preparatory operation and the heater temperature maintenance operation is executed first is switched depending on specified conditions.

2. A communication interface for receiving data from an external terminal; The control unit is execute an acquisition process for acquiring a preceding command from the external terminal via the communication interface; in the preparation process, switching whether to execute the polygon motor preparation operation or the heater temperature maintenance operation first in response to a predetermined condition, when the preceding command is received via the communication interface; The image forming apparatus according to claim 1, characterized in that in the printing process, after the preparation process is executed, an image is formed on a sheet using the image forming unit according to the print data received via the communication interface, and the image formed on the sheet is fixed using the fixing device.

3. The control unit is In the acquisition process, a printing condition used in the printing process is acquired together with the preceding command via the communication interface; the predetermined condition is the printing condition, 3. The image forming apparatus according to claim 2, wherein in the preparation process, whether the polygon motor preparation operation or the heater temperature maintenance operation is to be turned on first is switched in accordance with the printing conditions.

4. The control unit is In the preparation process, calculating a fixing temperature arrival time from when the heater is turned on until the heating rotator reaches the fixing temperature and a polygon motor start time from when the polygon motor is turned on until the rotation speed of the polygon motor reaches the predetermined speed according to the printing conditions acquired by the acquisition process; When the fixing temperature reaching time is longer than the polygon motor starting time, the heater temperature increasing and maintaining operation is performed prior to the polygon motor preparation operation; 4. The image forming apparatus according to claim 3, wherein when the polygon motor start time is longer than the fixing temperature reaching time, the polygon motor preparation operation is performed prior to the heater temperature increasing and maintaining operation.

5. The control unit is In the preparation process, when the fixing temperature arrival time is longer than the polygon motor start time, a first start time is calculated according to a value obtained by subtracting the polygon motor start time from the fixing temperature arrival time; After turning on the heater, when the calculated first startup start time has elapsed, the polygon motor preparation operation is executed; When the polygon motor start time is longer than the fixing temperature arrival time, a second start time is calculated according to a value obtained by subtracting the fixing temperature arrival time from the polygon motor start time; 5. The image forming apparatus according to claim 4, wherein the heater temperature maintaining operation is started when the calculated second startup start time has elapsed after the polygon motor preparatory operation is started.

6. the printing conditions include a condition that specifies that the image forming unit forms an image on the sheet at a first speed in the printing process, and a condition that specifies that the image forming unit forms an image on the sheet at a second speed that is slower than the first speed, The control unit is 6. An image forming apparatus according to claim 4, wherein in the polygon motor preparatory operation, the fixing temperature reaching time and the polygon motor start time are calculated according to the first speed or the second speed specified by conditions included in the printing conditions.

7. the image forming unit includes a developing roller that supplies toner to the photosensitive drum, and a transfer roller that transfers the toner image formed on the photosensitive drum onto a sheet; the main motor is capable of transmitting a driving force to the heating rotator, the photosensitive drum, and the developing roller; The control unit is 2. The image forming apparatus according to claim 1, wherein, in the heater temperature maintaining operation, the main motor is turned on to rotate the photosensitive drum and the developing roller in addition to the heating rotor.

8. The fixing devices include a first type fixing device and a second type fixing device, In the first type fixing device, the heating rotator is a heating roller, and the pressing rotator forms the nip portion between the heating roller and the pressing roller, In the second type fixing device, the heater is a flat substrate on which a heating pattern is formed, the heating rotator is a belt that rotates around the substrate, and the pressure rotator pinches the belt between itself and a flat surface of the substrate to form the nip portion; the predetermined condition is whether the type of the fixing device is a first type fixing device or a second type fixing device; The control unit, in the preparation process, When the fixing unit is a fixing unit of the first type, the heater temperature increasing and maintaining operation is performed prior to the polygon motor preparation operation; 3. The image forming apparatus according to claim 2, wherein if the fixing unit is a fixing unit of the second type, the polygon motor preparatory operation is executed prior to the heater temperature maintenance operation.

Images