JP2018054864A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image formation device with which it is possible to heighten quietness performance.SOLUTION: An image formation device of the present invention comprises: an image formation unit for forming a developer image on a recording medium; a fixation unit having an endless belt, a first roller arranged so as to be in contact with the outer circumferential surface of the belt, a second roller arranged so as to be in contact with the inner circumferential surface of the belt and pressed against the first roller across the belt and a press-contact member, a motor for driving the second roller to rotate, and a heater, the fixation unit fixing the developer image to the recording medium; and a control unit for adjusting the revolving speed of the second roller on the basis of both or one of a fixation temperature and a motor's motor current in a preparatory operation for causing the fixation temperature of the fixation unit to reach an intended temperature before the image formation unit forms the developer image.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus that forms an image.

  In the image forming apparatus, for example, a developer image is transferred to a recording medium, and the recording medium is supplied to a fixing device. In the fixing device, the developer on the recording medium is heated, melted, and pressurized. As a result, the developer image is fixed on the recording medium. For example, Patent Document 1 discloses a fixing device that forms a nip portion between a pressure roller, a fixing roller, and a nip forming member.

JP 2011-227377 A

  By the way, the image forming apparatus is desired to be able to operate quietly, and further improvement in quiet performance is expected.

  It is desirable to provide an image forming apparatus that can improve quiet performance.

  An image forming apparatus according to an embodiment of the present invention includes an image forming unit, a fixing unit, and a control unit. The image forming unit forms a developer image on a recording medium. The fixing unit is disposed so as to contact an endless belt, a first roller disposed so as to be in contact with the outer peripheral surface of the belt, and an inner peripheral surface of the belt, and be in pressure contact with the first roller across the belt. The second roller and the pressure contact member, a motor that rotationally drives the second roller, and a heater are provided to fix the developer image on the recording medium. In the preparatory operation for causing the fixing temperature of the fixing unit to reach the target temperature before the image forming unit forms the developer image, the control unit performs the second operation based on one or both of the fixing temperature and the motor current of the motor. The rotation speed of the roller is adjusted.

  According to the image forming apparatus in one embodiment of the present invention, in the preparation operation, the rotational speed of the second roller is adjusted based on one or both of the fixing temperature and the motor current. Can be increased.

1 is a configuration diagram illustrating a configuration example of an image forming system according to an embodiment. FIG. 2 is a configuration diagram illustrating a configuration example of a fixing unit illustrated in FIG. 1. 2 is a block diagram illustrating an example of a control mechanism of the image forming apparatus according to the embodiment. FIG. 4 is a timing diagram illustrating an example of a rotation speed of a fixing roller in an image forming apparatus according to an embodiment. FIG. 3 is a flowchart illustrating an operation example of the image forming apparatus according to the first embodiment. FIG. 6 is a timing diagram illustrating an example of a rotation speed of a fixing roller in an image forming apparatus according to a comparative example. FIG. 7 is a characteristic diagram illustrating a characteristic example in the image forming apparatus illustrated in FIG. 6. FIG. 6 is a characteristic diagram illustrating a characteristic example of load torque of the fixing motor. It is a characteristic view showing an example of an experimental result. It is a characteristic view showing an example of other experimental results. It is a characteristic view showing an example of other experimental results. It is a characteristic view which shows the experimental result shown to FIGS. FIG. 10 is a block diagram illustrating an example of a control mechanism of an image forming apparatus according to a modification of the first embodiment. FIG. 6 is a characteristic diagram illustrating a relationship between a load torque of a fixing motor and a motor current. 10 is a flowchart illustrating an operation example of an image forming apparatus according to a modification of the first embodiment. FIG. 10 is a block diagram illustrating an example of a control mechanism of an image forming apparatus according to another modification of the first embodiment. FIG. 6 is a timing diagram illustrating an example of characteristics of a motor current Im in a warm-up operation. 10 is a flowchart illustrating an operation example of an image forming apparatus according to another modification of the first embodiment. 10 is a flowchart illustrating an operation example of an image forming apparatus according to another modification of the first embodiment. 6 is a flowchart illustrating an operation example of an image forming apparatus according to a second embodiment. 10 is a flowchart illustrating an operation example of an image forming apparatus according to a modification of the second embodiment. 14 is a flowchart illustrating an operation example of an image forming apparatus according to another modification of the second embodiment. 14 is a flowchart illustrating an operation example of an image forming apparatus according to another modification of the second embodiment. FIG. 10 is a block diagram illustrating an example of a control mechanism of an image forming apparatus according to a third embodiment. 25 is a flowchart illustrating an operation example of the image forming apparatus illustrated in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The description will be given in the following order.
1. First Embodiment 2. FIG. Second Embodiment 3. FIG. Third embodiment

<1. First Embodiment>
[Configuration example]
FIG. 1 shows a configuration example of an image forming apparatus (image forming apparatus 1) according to a first embodiment of the present invention. The image forming apparatus 1 functions as a printer that forms an image on a recording medium made of, for example, plain paper using an electrophotographic method.

  The image forming apparatus 1 includes a pickup roller 12, a separation roller 13, a registration roller 14, a conveyance roller 15, an ID (Image Drum) unit 20, an exposure head 22, a transfer roller 23, a fixing unit 30, Conveying rollers 16 and 17 and a discharge roller 18 are provided. These members are arranged along a conveyance path 10 that conveys the recording medium 9.

  The pickup roller 12 is a member that takes out the recording medium 9 stored in the medium tray 11 one by one from the uppermost portion thereof, and sends out the taken recording medium 9 to the conveyance path 10. The separation roller 13 is a pair of rollers arranged with the conveyance path 10 interposed therebetween, and is a member that sends the recording medium 9 taken out by the pickup roller 12 to the conveyance path 10 one by one. The registration rollers 14 are a pair of rollers arranged with the conveyance path 10 interposed therebetween, and are members that correct the skew of the recording medium 9 that passes through the conveyance path 10. The conveyance rollers 15 are a pair of rollers arranged with the conveyance path 10 interposed therebetween, and are members that convey the recording medium 9 along the conveyance path 10.

  The ID unit 20 forms a toner image. The ID unit 20 has a photoconductor 21. The photoreceptor 21 is a member that carries an electrostatic latent image on the surface (surface layer portion). The exposure head 22 is a member that exposes the photoconductor 21 of the ID unit 20, and is configured using, for example, a plurality of LED (Light Emitting Diode) elements. An electrostatic latent image is formed on the photoreceptor 21 by exposure by the exposure head 22, and then a toner image is formed by supplying toner. The transfer roller 23 is a member for electrostatically transferring the toner image formed by the ID unit 20 onto the transfer surface of the recording medium 9.

  The fixing unit 30 is a member that fixes the toner image transferred onto the recording medium 9 to the recording medium 9 by applying heat and pressure to the recording medium 9. The fixing unit 30 is configured to be replaceable.

  FIG. 2 illustrates a configuration example of the fixing unit 30. The fixing unit 30 includes a fixing belt 31, a fixing roller 32, a pressure pad 33, a pad support 34, a coil spring 35, a temperature sensor 36, a heater 38, a heat transfer member 39, and a heater support. 40, a coil spring 41, and a pressure roller 43.

  The fixing belt 31 is an endless elastic belt, and is stretched (stretched) by a fixing roller 32, a pressure pad 33, guide members 37A and 37B, and a heat transfer member 39. The fixing belt 31 includes, for example, a base, an elastic layer formed on the base, and a release layer formed on the elastic layer. The base is configured using, for example, nickel, polyimide, stainless steel, or the like. The elastic layer is configured using, for example, silicon rubber or fluororesin. The release layer is configured using, for example, a fluororesin such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylene propene copolymer (FEP). The fixing belt 31 is stretched so that the release layer becomes an outer peripheral surface.

  The fixing roller 32 is a member that circulates and rotates the fixing belt 31 and forms a nip portion with the pressure roller 43. The fixing roller 32 has a cored bar part and an elastic layer covering the periphery of the cored bar part. The metal core portion has, for example, a pipe shape or a shaft shape, and is configured using, for example, aluminum, iron, stainless steel, or the like. The elastic layer is configured using a rubber material having high heat resistance such as sponge-like silicon rubber or fluorine rubber. However, the fixing roller 32 may further include a release layer that covers the periphery of the elastic layer in addition to the cored bar portion and the elastic layer. In this example, the fixing roller 32 rotates clockwise by power transmitted from a fixing motor 44 (described later). The fixing roller 32 is disposed in contact with the inner peripheral surface of the fixing belt 31. As a result, the fixing roller 32 circulates and rotates the fixing belt 31 in the direction of arrow A in FIG.

  The pressure pad 33 is a member that forms a nip portion with the pressure roller 43. The pressure pad 33 is configured using, for example, a rubber material. The pad support portion 34 is a member that supports the pressure pad 33. The coil spring 35 is a member that is inserted between the support member 42 and the pad support portion 34 and biases the pressure pad 33 in a direction away from the support member 42. Accordingly, the pressure pad 33 is in contact with the inner peripheral surface of the fixing belt 31 and is in pressure contact with the pressure roller 43 with the fixing belt 31 interposed therebetween. In this way, the pressure pad 33 forms a nip portion with the pressure roller 43.

  The temperature sensor 36 is a sensor that detects the belt temperature Tb of the fixing belt 31 and is configured using, for example, a thermistor.

  The heater 38 is a heat source for heating the fixing belt 31 and includes, for example, a resistance wire as a heating element. The heat transfer member 39 is a member that transfers heat generated in the heater 38 to the fixing belt 31. The heater support portion 40 is a member that supports the heater 38. The coil spring 41 is a member that is inserted between the support member 42 and the heater support portion 40 and biases the heater 38 and the heat transfer member 39 in a direction away from the support member 42. Accordingly, the heat transfer member 39 is in contact with the inner peripheral surface of the fixing belt 31 and stretches the fixing belt 31 by pushing the fixing belt 31 outward.

  The pressure roller 43 is a member that forms a nip portion NP between the fixing roller 32 and the pressure pad 33. The pressure roller 43 has, for example, the same configuration as the fixing roller 32. In this example, the pressure roller 43 is driven to rotate counterclockwise in accordance with the circulation rotation of the fixing belt 31.

  With this configuration, when the recording medium 9 on which the toner image is formed is supplied to the nip NP, the toner on the recording medium 9 is heated, melted, and pressurized. As a result, the toner image is fixed on the recording medium 9.

  The conveyance rollers 16 (FIG. 1) are a pair of rollers arranged with the conveyance path 10 interposed therebetween, and are members that convey the recording medium 9 supplied from the fixing unit 30 along the conveyance path 10. The conveyance rollers 17 are a pair of rollers arranged with the conveyance path 10 interposed therebetween, and are members that convey the recording medium 9 along the conveyance path 10. The discharge rollers 18 are a pair of rollers arranged with the conveyance path 10 interposed therebetween, and are members that discharge the recording medium 9 to the discharge tray 19.

  FIG. 3 illustrates an example of a control mechanism in the image forming apparatus 1. The image forming apparatus 1 includes a communication unit 51, an operation unit 52, a display unit 53, a storage unit 54, an exposure control unit 55, a voltage control unit 56, a motor control unit 57, and an image formation control unit 59. It has.

  The communication unit 51 performs communication using, for example, a USB (Universal Serial Bus) or a LAN (Local Area Network). For example, the communication unit 51 receives print data DP transmitted from a host computer. The operation unit 52 receives user operations and is configured using various buttons, for example. The display unit 53 displays an operation state of the image forming apparatus 1 and is configured using, for example, a liquid crystal display or various indicators.

  The storage unit 54 stores, for example, print data DP and various setting information of the image forming apparatus 1. The storage unit 54 stores history data 541. The history data 541 is a record of the operation history of the image forming apparatus 1. Specifically, the history data 541 includes, for example, information on the cumulative number of printed sheets NT printed by the image forming apparatus 1 and the number of printed sheets N printed using the current fixing unit 30. The number N of prints is reset when the fixing unit 30 is replaced.

  The exposure control unit 55 controls the operation of the exposure head 22 based on an instruction from the image formation control unit 59.

  The voltage control unit 56 generates various voltages used in the image forming apparatus 1 based on instructions from the image formation control unit 59. Specifically, the voltage control unit 56 generates a charging voltage and a developing voltage used in the ID unit 20, a transfer voltage applied to the transfer roller 23, and the like.

  The motor control unit 57 controls the operation of the main motor used in the image forming apparatus 1 based on an instruction from the image formation control unit 59.

  The fixing unit 30 has a fixing motor 44. The fixing motor 44 supplies power to the fixing roller 32. The fixing motor 44 has a rotation unevenness detection unit 441. The rotation unevenness detection unit 441 generates an error signal when rotation unevenness occurs in the fixing motor 44.

  The fixing control unit 58 controls the operation of the fixing unit 30 based on an instruction from the image formation control unit 59 and a detection result of the temperature sensor 36 of the fixing unit 30. The fixing control unit 58 includes a heater control unit 581 and a fixing motor control unit 582. The heater control unit 581 controls the operation of the heater 38 of the fixing unit 30. The fixing motor control unit 582 controls the operation of the fixing motor 44. The fixing controller 58 also has a function of supplying the error signal to the image forming controller 59 when an error signal is received from the rotation unevenness detector 441 of the fixing motor 44.

  The image formation control unit 59 controls the operation of the image forming apparatus 1 by controlling the operation of each of these blocks. Specifically, for example, when the communication unit 51 of the image forming apparatus 1 receives the print data DP, the image formation control unit 59 uses the exposure control unit 55 and the voltage control unit 56 based on the print data DP. The motor control unit 57 and the fixing control unit 58 are instructed to perform an image forming operation. The image formation control unit 59 also has a function of stopping the processing being executed and displaying the error on the display unit 53 when an error signal is received from the fixing control unit 58. The function of the image formation control unit 59 may be realized by hardware or software, for example.

  When performing the image forming operation, the image forming apparatus 1 first performs the warm-up operation OP1 so that the belt temperature Tb reaches a predetermined target temperature Ttarget (for example, 170 [° C.]), and then performs the image forming operation. Perform OP2. In the warm-up operation OP1, the image formation control unit 59 and the fixing control unit 58 adjust the rotational speed R of the fixing roller 32 based on the belt temperature Tb and the number N of prints, as will be described later. As a result, the image forming apparatus 1 can reduce the possibility of noise being generated in the warm-up operation OP1, and can improve the quiet performance.

  Here, the ID unit 20 and the transfer roller 23 correspond to a specific example of “image forming unit” in the invention. The fixing belt 31 corresponds to a specific example of “belt” in the present invention. The pressure roller 43 corresponds to a specific example of “first roller” in the invention. The fixing roller 32 corresponds to a specific example of “second roller” in the invention. The pressure pad 33 corresponds to a specific example of “pressure contact member” in the present invention. The fixing motor 44 corresponds to a specific example of “motor” in the present invention. The heater 38 corresponds to a specific example of “heater” in the present invention. The image formation control unit 59 and the fixing control unit 58 correspond to a specific example of “a control unit” in the invention. The belt temperature Tb corresponds to a specific example of “fixing temperature” in the present invention. The number of printed sheets N corresponds to a specific example of “image forming number” in the present invention.

[Operation and Action]
Next, the operation and action of the image forming apparatus 1 according to the present embodiment will be described.

(Overview of overall operation)
First, an overview of the overall operation of the image forming apparatus 1 will be described with reference to FIGS. When the communication unit 51 of the image forming apparatus 1 receives the print data DP, the image formation control unit 59 performs processing based on the print data DP. The image formation control unit 59 controls the operations of the exposure control unit 55, the voltage control unit 56, the motor control unit 57, and the fixing control unit 58 based on the processing result. In the warm-up operation OP1, the fixing control unit 58 controls the operation of the fixing unit 30 so that the belt temperature Tb reaches a predetermined target temperature Ttarget. In the image forming operation OP2, the exposure control unit 55 controls the light emission operation of the exposure head 22, the voltage control unit 56 generates various voltages such as a charging voltage, a development voltage, and a transfer voltage, and the motor control unit 57 The operation of a main motor used in the image forming apparatus 1 is controlled, and the fixing control unit 58 controls the operation of the fixing unit 30. As a result, the recording medium 9 supplied from the medium tray 11 is conveyed along the conveyance path 10, the toner image generated by the ID unit 20 is transferred to the recording medium 9, and the toner image is transferred to the fixing unit 30. Fix on the recording medium 9. Then, the recording medium 9 on which the toner image is fixed is discharged to the discharge tray 19.

(Detailed operation)
When performing an image forming operation, the image forming apparatus 1 first performs a warm-up operation OP1 so that the belt temperature Tb reaches a predetermined target temperature Ttarget, and then performs an image forming operation OP2. In the warm-up operation OP1, the image formation control unit 59 and the fixing control unit 58 adjust the rotation speed R of the fixing roller 32 based on the belt temperature Tb and the number N of printed sheets. This operation will be described in detail below.

  FIG. 4 shows an example of the rotation speed R of the fixing roller 32. In this example, the rotation speed R of the fixing roller 32 is shown using ppm (page per minute) which is a unit of the printing speed.

  First, at timing t1, the communication unit 51 of the image forming apparatus 1 receives the print data DP, and during the period from timing t1 to t2, the image formation control unit 59 performs processing based on the print data DP.

  In the period from timing t2 to t4, the image forming apparatus 1 performs the warm-up operation OP1. Specifically, at timing t2, the heater control unit 581 of the fixing control unit 58 turns on the heater 38 based on an instruction from the image formation control unit 59, and the fixing motor control unit 582 of the fixing control unit 58 Based on an instruction from the formation control unit 59, the operation of the fixing motor 44 is started. As a result, the fixing roller 32 starts to rotate. At this time, the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 7.5 [ppm] in this example. The belt temperature Tb increases toward a target temperature Ttarget (for example, 170 [° C.]). At timing t3, when the belt temperature Tb reaches a predetermined threshold temperature Tth (for example, 150 [° C.]), the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 16 [ppm] in this example. Set to. At timing t4, when the belt temperature Tb reaches the target temperature Ttarget, the heater controller 581 of the fixing controller 58 temporarily turns off the heater 38, and the fixing motor controller 582 temporarily stops the operation of the fixing motor 44. As a result, the fixing roller 32 stops rotating.

  Next, during the period from timing t5 to t6, the image forming apparatus 1 performs the image forming operation OP2. At that time, at timing t5, the heater control unit 581 of the fixing control unit 58 turns on the heater 38, and the fixing motor control unit 582 of the fixing control unit 58 starts the operation of the fixing motor 44. As a result, the fixing roller 32 starts to rotate again. The heater controller 581 controls the operation of the heater 38 so that the belt temperature Tb maintains a predetermined temperature (for example, 180 [° C.]) necessary for the fixing operation. Further, the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 30 [ppm] in this example. That is, the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to a rotation speed corresponding to the printing speed of the image forming apparatus 1 in the image forming operation OP2. When the image forming apparatus 1 ends the image forming operation OP2 at timing t6, the fixing motor control unit 582 stops the operation of the fixing motor 44 at the subsequent timing t7. As a result, the fixing roller 32 stops rotating.

  As described above, in the image forming apparatus 1, the rotation speed R of the fixing roller 32 is adjusted in the warm-up operation OP1. At that time, the image formation control unit 59 and the fixing control unit 58 adjust the rotation speed R of the fixing roller 32 based on the belt temperature Tb and the number N of printed sheets.

  FIG. 5 shows the setting operation of the rotational speed R of the fixing roller 32 in the warm-up operation OP1. When the belt temperature Tb is lower than the predetermined threshold temperature Tth, the image formation control unit 59 and the fixing control unit 58 set the rotation speed R of the fixing roller 32 to 7.5 [ppm] and the belt temperature Tb. If the temperature is equal to or higher than the threshold temperature Tth, the rotation speed R is set to a speed corresponding to the number N of printed sheets. This operation will be described in detail below.

  First, the fixing control unit 58 checks whether the belt temperature Tb is lower than a predetermined threshold temperature Tth (for example, 150 [° C.]) (Tb <150 [° C.]) based on the detection result of the temperature sensor 36. (Step S101). When the belt temperature Tb is lower than the threshold temperature Tth (“Y” in step S101), the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 7.5 [ppm] (step S102). ), And proceeds to step S112.

  In step S101, when the belt temperature Tb is equal to or higher than the threshold temperature Tth (“N” in step S101), the image formation control unit 59 has the number N of printed sheets included in the history data 541 smaller than 300 sheets ( N <300 [sheets]) is checked (step S103). When the number of printed sheets N is less than 300 (“Y” in step S103), the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 7.5 [ppm] (step S104). Proceed to step S112.

  In step S103, when the number of printed sheets N is 300 or more (“N” in step S103), the image forming control unit 59 has the number of printed sheets N smaller than 5,000 (N <5,000 [ Sheet]) is checked (step S105). When the number of printed sheets N is less than 5,000 (“Y” in step S105), the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 10 [ppm] (step S106). Proceed to step S112.

  In step S105, when the number of printed sheets N is 5,000 or more (“N” in step S105), the image forming control unit 59 has the number of printed sheets N smaller than 50,000 (N <50, 000 [sheets]) (step S107). When the number N of printed sheets is less than 50,000 (“Y” in step S107), the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 12 [ppm] (step S108). Proceed to step S112.

  In step S107, when the number of printed sheets N is 50,000 or more (“N” in step S107), the image forming control unit 59 has the number of printed sheets N smaller than 80,000 (N <80, 000 [sheets]) (step S109). When the number of printed sheets N is less than 80,000 (“Y” in step S109), the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 14 [ppm] (step S110). Proceed to step S112.

  In step S109, when the number N of printed sheets is 80,000 or more (“N” in step S109), the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 16 [ppm] ( The process proceeds to step S111) and step S112.

  Next, the fixing control unit 58 checks whether or not the belt temperature Tb has reached a target temperature Ttarget (for example, 170 [° C.]) based on the detection result of the temperature sensor 36 (step S112). If the belt temperature Tb has not reached the target temperature Ttarget (“N” in step S112), the process returns to step S101, and the operations of steps S101 to S112 are repeated until the belt temperature Tb reaches the target temperature Ttarget.

  In step S112, when the belt temperature Tb has reached the target temperature Ttarget (“Y” in step S112), this flow ends. As a result, the image forming apparatus 1 ends the warm-up operation OP1.

  As described above, in the image forming apparatus 1, the rotation speed R of the fixing roller 32 is adjusted based on the belt temperature Tb and the number N of printed sheets in the warm-up operation OP1. Thereby, as will be described below using a comparative example and an experimental example, it is possible to reduce the possibility of noise being generated in the warm-up operation OP1, and to improve the quiet performance.

(Comparative example)
Next, an image forming apparatus 1R according to a comparative example will be described. The image forming apparatus 1R maintains the rotational speed R of the fixing roller 32 at a predetermined speed in the warm-up operation OP1. The image forming apparatus 1R includes a fixing control unit 58R and an image formation control unit 59R. The fixing controller 58R has a fixing motor controller 582R. Other configurations are the same as those in the present embodiment (FIG. 3).

  FIG. 6 shows the setting operation of the rotation speed R of the fixing roller 32 in the warm-up operation OP1 in the image forming apparatus 1R according to the comparative example. As in the case of the image forming apparatus 1 according to the present embodiment (FIG. 4), the communication unit 51 receives the print data DP at the timing t11, and the image formation control unit 59R performs this during the period from the timing t11 to t12. Processing is performed based on the print data DP. Then, during the period from timing t12 to t13, the image forming apparatus 1R performs the warm-up operation OP1. Specifically, at timing t12, the heater controller 581 turns on the heater 38 based on an instruction from the image formation controller 59R, and the fixing motor controller 582R is based on an instruction from the image formation controller 59. The operation of the fixing motor 44 is started. The fixing motor control unit 582R maintains the rotational speed R of the fixing roller 32 at 7.5 [ppm] in this example during the period from the timing t12 to t13. At timing t13, when the belt temperature Tb reaches the target temperature Ttarget, the heater control unit 581 temporarily turns off the heater 38, and the fixing motor control unit 582R temporarily stops the operation of the fixing motor 44. Thereafter, in the period from timing t14 to t15, the image forming apparatus 1R performs the image forming operation OP2 similarly to the image forming apparatus 1 according to the present embodiment. Thereafter, at timing t16, the fixing motor control unit 582R stops the operation of the fixing motor 44.

  Thus, when the warm-up operation OP1 is performed while the rotation speed R of the fixing roller 32 is maintained at a low speed (for example, 7.5 [ppm]), when the belt temperature Tb exceeds, for example, 150 [° C.]. In addition, abnormal noise may occur. In particular, as the number of printed sheets N increases, the friction coefficient μ between the inner peripheral surface of the fixing belt 31 and the pressure pad 33 increases, so that stick-slip occurs continuously, resulting in abnormal noise (noise). ) Occurs. Further, since the load of the fixing motor 44 changes in accordance with the stick-slip, the rotation unevenness occurs in the fixing motor 44. As a result, the fixing motor 44 may generate an error signal.

  FIG. 7 shows an example of an experimental result in the image forming apparatus 1R according to the comparative example. In this experiment, it was confirmed whether noise and uneven rotation occurred at various rotational speeds R while increasing the number of printed sheets N.

  For example, when the rotation speed R of the fixing roller 32 is set to 7.5 [ppm], noise and uneven rotation do not occur when the number of printed sheets N is 100. However, when the number of printed sheets N exceeds 500, noise occurs, and when the number of printed sheets N exceeds 10,000, uneven rotation occurs in the fixing motor 44.

  That is, as described above, the friction coefficient μ between the inner peripheral surface of the fixing belt 31 and the pressure pad 33 increases as the number of printed sheets N increases. As a result, as shown in FIG. 8, the load torque TL of the fixing motor 44 increases as the number of printed sheets N increases. Then, stick-slip is continuously generated, and noise and uneven rotation are generated.

  For example, when the rotation speed R of the fixing roller 32 is set to 10 [ppm], no noise or uneven rotation occurs when the number of printed sheets N is 5,000. However, when the number of printed sheets N exceeds 10,000, noise occurs, and when the number of printed sheets N exceeds 75,000, uneven rotation occurs in the fixing motor 44.

  Further, for example, when the rotational speed R of the fixing roller 32 is set to 12 [ppm], noise and uneven rotation do not occur when the number of printed sheets N is 50,000. However, noise occurs when the number of printed sheets N exceeds 75,000.

  Thus, as the rotation speed R of the fixing roller 32 is increased, noise and uneven rotation are less likely to occur. However, the faster the rotation speed R of the fixing roller 32, the easier the heat of the fixing belt 31 escapes to the pressure roller 43, so the time until the belt temperature Tb reaches the target temperature Ttarget becomes longer. . Therefore, in order to shorten the warm-up time, it is desirable to reduce the rotation speed R of the fixing roller 32.

(Experimental example)
Therefore, in order to reduce the warm-up time and make it difficult for noise and rotation unevenness to occur, first, in the image forming apparatus 1 according to the present embodiment, the rotation speed R of the fixing roller 32 is set to 7.5 [ppm]. After that, based on the belt temperature Tb and the number N of printed sheets, the rotational speed R of the fixing roller 32 is adjusted. Here, the rotational speed R before adjustment is defined as rotational speed R1 (7.5 ppm in this example), and the rotational speed R after adjustment is defined as rotational speed R2. The results of various experiments conducted to determine the threshold temperature Tth and the rotation speed R2 when the number of printed sheets N is 100,000 are shown below.

  FIG. 9 shows the conditions under which noise and uneven rotation occur. In this experiment, in the image forming apparatus 1, the rotation speed R2 of the fixing roller 32 is set to various speeds, and the threshold temperature Tth is set to various temperatures to check whether noise or uneven rotation occurs. ing. In this example, when the rotational speed R2 is set to 7.5 [ppm] or 10 [ppm], uneven rotation occurs regardless of the threshold temperature Tth, and the rotational speed R2 is set to 12 [ppm]. In this case, noise occurs regardless of the threshold temperature Tth. On the other hand, when the rotational speed R2 is set to 14 [ppm] or higher, noise is generated when the threshold temperature Tth is 160 [° C.] or higher, but noise is generated when the threshold temperature Tth is 155 [° C.] or lower. Does not occur. That is, when the belt temperature Tb increases in the warm-up operation OP1, for example, when the rotational speed R is changed from 7.5 [ppm] to 14 [ppm] at 155 [° C.], noise is generated. First, noise is generated when the rotational speed R is changed from 7.5 [ppm] to 14 [ppm] at 160 [° C.]. This result means that when the belt temperature Tb increases, noise starts to occur at a temperature higher than 155 [° C.] and lower than 160 [° C.].

  FIG. 10 shows a condition that the printing time becomes longer when the next print data DP is received after the image forming operation OP2 and before the image forming apparatus 1 enters the power saving state. In this experiment, the rotation speed R2 of the fixing roller 32 is set to various speeds, the threshold temperature Tth is set to various temperatures, and printing is performed from the reception timing of the print data DP to the end timing of the image forming operation OP2. Check the time. In this example, when the rotation speed R2 is set to 20 [ppm] or less, the printing time is shorter than 10 seconds regardless of the threshold temperature Tth, and when the rotation speed R2 is set to 23 [ppm] or more, the threshold is set. The printing time is longer than 10 seconds regardless of the temperature Tth. That is, the higher the rotational speed R2, the easier the heat of the fixing belt 31 escapes to the pressure roller 43, and the longer the printing time.

  FIG. 11 shows a condition for increasing the warm-up time. In this experiment, the rotation speed R2 of the fixing roller 32 is set to various speeds, the threshold temperature Tth is set to various temperatures, the warm-up time twu1 after power-on, and the return from the power save state The warm-up time twu2 is confirmed. In this example, the warm-up times twu1 and twu2 become longer as the rotational speed R2 is faster and the threshold temperature Tth is lower. That is, as the rotational speed R2 is increased, the heat of the fixing belt 31 easily escapes to the pressure roller 43, so that the warm-up times twu1 and twu2 become longer. Further, the lower the threshold temperature Tth, the larger the amount of temperature increase (Ttarget-Tth) to be raised while rotating the fixing roller 32 at a faster rotational speed R2, and the warm-up times twu1, twu2 become longer.

  FIG. 12 shows the experimental results in FIGS. In this example, for example, when the threshold temperature Tth is set to 140 [° C.], a favorable result is obtained by setting the rotation speed R2 of the fixing roller 32 to 14 [ppm], and the threshold temperature Tth is set to 145. When set to [° C.], the rotation speed R2 of the fixing roller 32 is set to 14 [ppm] or more and 18 [ppm] or less to obtain a favorable result, and the threshold temperature Tth is set to 150 [° C.] or 155 [° C. In the case of setting to [° C.], a favorable result is obtained by setting the rotation speed R2 of the fixing roller 32 to 14 [ppm] or more and 20 [ppm] or less.

  9 to 12 show experimental results when the number of printed sheets N is 100,000 as described above, and the same experiment is performed when the number of printed sheets N is less than 100,000. It can be carried out. When the number of printed sheets N is small, the range of conditions (range B in FIG. 12) shown in FIG. In the image forming apparatus 1 according to the present embodiment, the rotation speed R2 is set according to the number of printed sheets N, as shown in FIG.

  Thus, in the image forming apparatus 1, the rotational speed R of the fixing roller 32 is adjusted based on the belt temperature Tb. As a result, in the image forming apparatus 1, the rotation speed R of the fixing roller 32 can be increased before the belt temperature Tb reaches a temperature at which noise and uneven rotation occur, so that noise and uneven rotation are less likely to occur. As a result, quiet performance can be improved.

  Further, in the image forming apparatus 1, when the belt temperature Tb is low, the rotation speed R of the fixing roller 32 is slowed, so that the heat of the fixing belt 31 can be made difficult to escape to the pressure roller 43. Can be shortened.

  In the image forming apparatus 1, the rotation speed R of the fixing roller 32 is adjusted based on the number N of printed sheets in addition to the belt temperature Tb. As a result, the image forming apparatus 1 can reduce the rotational speed R when the number of printed sheets N is small, and can increase the rotational speed R when the number of printed sheets N is large. As a result, in the image forming apparatus 1, it is possible to effectively shorten the warm-up time and effectively improve the quiet performance.

[effect]
As described above, in this embodiment, since the rotation speed of the fixing roller is adjusted based on the belt temperature, the quiet performance can be improved.

  In this embodiment, when the belt temperature is low, the rotation speed of the fixing roller is slowed, so that the warm-up time can be shortened.

  In this embodiment, since the rotation speed of the fixing roller is adjusted based on the cumulative number of printed sheets in addition to the belt temperature, the warm-up time is effectively shortened and the quiet performance is effectively enhanced. Can do.

[Modification 1-1]
In the above embodiment, the information about the number N of prints printed using the current fixing unit 30 included in the history data 541 is used. However, the present invention is not limited to this, and is included in the history data 541. Various pieces of information related to the print amount so far can be used.

[Modification 1-2]
In the above embodiment, the rotational speed R is adjusted based on the belt temperature Tb and the number N of printed sheets, but the present invention is not limited to this. Below, this modification is demonstrated in detail.

  FIG. 13 illustrates a configuration example of the image forming apparatus 1B according to the present modification. The image forming apparatus 1B includes a fixing control unit 58B and an image formation control unit 59B. The fixing control unit 58B includes a motor current detection unit 583. The motor current detector 583 detects a motor current Im supplied to the fixing motor 44. The fixing controller 58B adjusts the rotational speed R of the fixing roller 32 based on the belt temperature Tb and the motor current Im. That is, in the image forming apparatus 1 according to the above-described embodiment, the image forming control unit 59 and the fixing control unit 58 adjust the rotational speed R of the fixing roller 32 based on the belt temperature Tb and the number N of prints. In the image forming apparatus 1B according to the modification, the fixing control unit 58B adjusts the rotational speed R of the fixing roller 32 based on the belt temperature Tb and the motor current Im. The image formation control unit 59B controls the operation of the image forming apparatus 1B.

  In this modification, the rotation speed R of the fixing roller 32 is adjusted based on the motor current Im instead of the number N of printed sheets. That is, as shown in FIG. 8, the load torque TL of the fixing motor 44 increases as the number N of printed sheets increases. As shown in FIG. 9, the motor current Im increases as the load torque TL increases. Therefore, the rotational speed R of the fixing roller 32 can be adjusted by using the motor current Im instead of the number N of printed sheets. In the following example, the fixing control unit 58B stores in advance the motor current Im (motor current Im0) when the number of printed sheets N is “0”, and the current difference ΔIm between the motor current Im and the motor current Im0. The rotational speed R of the fixing roller 32 is adjusted using (= Im-Im0).

  FIG. 15 shows the setting operation of the rotational speed R of the fixing roller 32 in the image forming apparatus 1B.

  First, the fixing controller 58B confirms whether the belt temperature Tb is lower than the threshold temperature Tth (for example, 150 [° C.]) (Tb <150 [° C.]) based on the detection result of the temperature sensor 36 (Tb <150 [° C.]). Step S101). When the belt temperature Tb is lower than the threshold temperature Tth (“Y” in step S101), the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 7.5 [ppm] (step S102). ), And proceeds to step S112.

  In step S101, when the belt temperature Tb is equal to or higher than the threshold temperature Tth (“N” in step S101), the fixing control unit 58B has a current difference ΔIm of 0 based on the detection result of the motor current detection unit 583. It is confirmed whether it is smaller than 15 [A] (ΔIm <0.15 [A]) (step S123). When the current difference ΔIm is smaller than 0.15 [A] (“Y” in step S123), the fixing motor control unit 582 sets the rotational speed R of the fixing roller 32 to 7.5 [ppm] ( The process proceeds to step S104) and step S112.

  Similarly, the fixing motor control unit 582 sets the rotational speed R of the fixing roller 32 to 10 [ppm] when the current difference ΔIm is smaller than 0.3 [A] (“Y” in step S125). If the current difference ΔIm is smaller than 0.5 [A] (“Y” in step S127), the rotation speed R of the fixing roller 32 is set to 12 [ppm] (step S108). When the current difference ΔIm is smaller than 0.75 [A] (“Y” in step S129), the rotational speed R of the fixing roller 32 is set to 14 [ppm] (step S110), and the current difference ΔIm is set. If it is 0.75 [A] or more (“N” in step S129), the rotation speed R of the fixing roller 32 is set to 16 [ppm] (step S111), and step S1. Proceed to 2.

  If the belt temperature Tb has not reached the target temperature Ttarget (“N” in step S112), the process returns to step S101, and these operations are repeated until the belt temperature Tb reaches the target temperature Ttarget.

  As described above, in the image forming apparatus 1B, the rotation speed R of the fixing roller 32 is adjusted based on the motor current Im. Therefore, the rotation speed R can be set according to the actual change state of the load torque TL. Therefore, the warm-up time can be shortened more effectively, and the quiet performance can be enhanced more effectively.

  In the image forming apparatus 1B according to the present modification, the fixing control unit 58B detects the motor current Im as shown in FIG. 13, but the present invention is not limited to this. For example, FIG. The fixing motor may detect the motor current Im as in the image forming apparatus 1C shown in FIG. The image forming apparatus 1C includes a fixing unit 30C and a fixing control unit 58C. The fixing unit 30C has a fixing motor 44C. The fixing motor 44 </ b> C has a motor current detection unit 442. The motor current detector 442 detects a motor current Im flowing through the fixing motor 44C. The fixing motor 44C supplies the detection result of the motor current detection unit 442 to the fixing control unit 58C. The fixing controller 58C has a function of adjusting the rotational speed R of the fixing roller 32 based on the belt temperature Tb and the motor current Im.

[Modification 1-3]
In the above embodiment, it is determined whether or not the rotation speed R of the fixing roller 32 is adjusted based on the belt temperature Tb. However, the present invention is not limited to this. In determining whether to adjust the rotational speed R, any parameter having a correlation with the belt temperature Tb can be used. Below, the example at the time of using the motor electric current Im is demonstrated.

  As illustrated in FIG. 13, the image forming apparatus 1 </ b> D according to this modification includes a fixing control unit 58 </ b> D and an image formation control unit 59. The fixing control unit 58D includes a motor current detection unit 583. The image forming control unit 59 and the fixing control unit 58D adjust the rotational speed R of the fixing roller 32 based on the motor current Im and the number N of printed sheets. That is, in the image forming apparatus 1 according to the above-described embodiment, the image forming control unit 59 and the fixing control unit 58 adjust the rotational speed R of the fixing roller 32 based on the belt temperature Tb and the number N of prints. In the image forming apparatus 1D according to the modification, the image forming control unit 59 and the fixing control unit 58D adjust the rotation speed R of the fixing roller 32 based on the motor current Im and the number N of printed sheets.

  In this modification, the rotational speed R of the fixing roller 32 is adjusted based on the motor current Im instead of the belt temperature Tb. That is, as shown in FIG. 17, in the warm-up operation OP1, the motor current Im decreases as the belt temperature Tb increases with time t. By the way, the motor current Im also changes when the number of printed sheets N increases as shown in FIGS. That is, as shown in FIG. 17, when the number of printed sheets N is small, the motor current Im is low, and when the number of printed sheets N is large, the motor current Im is high. Therefore, the fixing control unit 58D stores in advance the motor current Im (motor current Im2) at a low temperature at a predetermined frequency, and a current difference ΔIm2 (= | Im−Im2 |) between the motor current Im and the motor current Im2. ) And the rotational speed R of the fixing roller 32 is adjusted using the current difference ΔIm2.

  FIG. 18 shows the setting operation of the rotational speed R of the fixing roller 32 in the image forming apparatus 1D.

  First, based on the detection result of the motor current detection unit 583, the fixing control unit 58D has a current difference ΔIm2 smaller than a predetermined threshold current Ith (for example, a current difference ΔIM2 corresponding to 150 [° C.]) (ΔIm2 <Ith). ) Is checked (step S131). When the current difference ΔIm2 is smaller than the threshold current Ith (“Y” in step S131), the fixing motor control unit 582 sets the rotation speed R of the fixing roller 32 to 7.5 [ppm] (step S102). ), And proceeds to step S112.

  If the current difference ΔIm2 is greater than or equal to the threshold current Ith in step S131 (“N” in step S131), the image forming control unit 59 and the fixing control unit 58D are the same as those in the above embodiment (FIG. 5). Similarly, the rotation speed R of the fixing roller 32 is set according to the number of printed sheets N (steps S103 to S111), and the process proceeds to step S112.

  If the belt temperature Tb has not reached the target temperature Ttarget (“N” in step S112), the process returns to step S131, and these operations are repeated until the belt temperature Tb reaches the target temperature Ttarget.

  In the above, the present modification is applied to the image forming apparatus 1 (FIG. 5) according to the above-described embodiment. However, the present invention is not limited to this. For example, as illustrated in FIG. The present modification may be applied to the forming apparatus 1B (FIG. 15).

<2. Second Embodiment>
Next, the image forming apparatus 2 according to the second embodiment will be described. The image forming apparatus 2 adjusts the rotational speed R of the fixing roller 32 when uneven rotation occurs in the fixing motor 44. Note that components that are substantially the same as those of the image forming apparatus 1 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  As shown in FIG. 3, the image forming apparatus 2 includes a fixing control unit 68. The fixing control unit 68 adjusts the rotational speed R of the fixing roller 32 when uneven rotation occurs in the fixing motor 44.

  FIG. 20 shows the setting operation of the rotational speed R of the fixing roller 32 in the warm-up operation OP1 in the image forming apparatus 2. When the rotation unevenness does not occur, the image formation control unit 59 and the fixing control unit 68 maintain the rotation speed R of the fixing roller 32 at a predetermined speed (for example, 7.5 [ppm]), and the rotation unevenness occurs. In this case, the rotational speed R is adjusted based on the belt temperature Tb and the number N of printed sheets, and if the uneven rotation is not eliminated after the adjustment, the processing being executed is stopped. This operation will be described in detail below.

  First, the fixing control unit 68 checks whether or not the rotation unevenness occurs in the fixing motor 44 (step S201). Specifically, when the error signal is supplied from the fixing motor 44, the fixing control unit 68 determines that rotation unevenness has occurred in the fixing motor 44. When the rotation unevenness does not occur in the fixing motor 44 (“N” in step S201), the process proceeds to step S213.

  In step S201, when the rotation unevenness occurs in the fixing motor 44 ("Y" in step S201), the fixing control unit 68 determines that the belt temperature Tb is a predetermined threshold based on the detection result of the temperature sensor 36. It is confirmed whether the temperature is lower than Tth (for example, 150 [° C.]) (Tb <150 [° C.]) (step S202). If the belt temperature Tb is lower than the threshold temperature Tth (“Y” in step S202), the image formation control unit 59 stops the process being executed and causes the display unit 53 to display an error ( Step S212). Then, this flow ends. That is, in this case, since the rotation unevenness occurs in the fixing motor 44 even though the belt temperature Tb is low, the image formation control unit 59 determines that the operation state is not preferable for image formation. Cancel processing.

  In step S202, when the belt temperature Tb is equal to or higher than the threshold temperature Tth (“N” in step S202), the image formation control unit 59 has the number N of prints included in the history data 541 smaller than 300 ( N <300 [sheets]) is checked (step S203). When the number of printed sheets N is less than 300 (“Y” in step S203), the image formation control unit 59 stops the process being executed and causes the display unit 53 to display an error (step S212). ). Then, this flow ends. That is, in this case, since the rotation unevenness occurs in the fixing motor 44 even though the number of printed sheets N is small, the image formation control unit 59 determines that the operation state is not preferable for image formation. Cancel processing.

  In step S203, when the number of printed sheets N is 300 or more (“N” in step S203), the image forming control unit 59 and the fixing control unit 68 perform the image forming apparatus 1 according to the first embodiment. Similarly, the rotational speed R of the fixing roller 32 is set according to the number N of printed sheets (steps S204 to S210).

  Next, the fixing control unit 68 checks whether or not the rotation unevenness has been eliminated (step S211). If the rotation unevenness has not been eliminated (“N” in step S211), the image formation control unit 59 stops the process being executed and causes the display unit 53 to display an error (step S212). Then, this flow ends. In step S211, when the rotation unevenness is eliminated (“Y” in step S211), the process proceeds to step S213.

  Next, the fixing control unit 68 checks whether the belt temperature Tb has reached the target temperature Ttarget (for example, 170 [° C.]) based on the detection result of the temperature sensor 36 (step S213). If the belt temperature Tb has not reached the target temperature Ttarget (“N” in step S213), the process returns to step S201.

  In step S213, when the belt temperature Tb has reached the target temperature Ttarget (“Y” in step S213), this flow ends. As a result, the image forming apparatus 2 ends the warm-up operation OP1.

  As described above, in the image forming apparatus 2, in the warm-up operation OP1, when the rotation unevenness of the fixing motor 44 does not occur, the rotation speed R of the fixing roller 32 is set to a predetermined speed (for example, 7.5 [ppm]). maintain. Thereby, in the image forming apparatus 2, the heat of the fixing belt 31 can be made difficult to escape to the pressure roller 43, so that the warm-up time can be shortened.

  Further, in the image forming apparatus 2, when the rotation unevenness occurs in the fixing motor 44 in the warm-up operation OP 1, the rotation speed R of the fixing roller 32 is adjusted based on the belt temperature Tb and the number N of printed sheets. Therefore, the warm-up time can be shortened and the quiet performance can be improved.

  In addition, in the image forming apparatus 2, after the rotation speed R is adjusted based on the belt temperature Tb and the number N of printed sheets, if the rotation unevenness is not eliminated, the processing that is being executed is stopped. The possibility that an image is formed in an unfavorable state can be reduced, and the image quality can be improved.

  As described above, in this embodiment, when the rotation unevenness of the fixing motor does not occur, the rotation speed of the fixing roller is maintained at a predetermined speed, so that the warm-up time can be shortened.

  In this embodiment, when rotation unevenness occurs in the fixing motor, the rotation speed of the fixing roller is adjusted based on the belt temperature and the cumulative number of printed sheets, so the warm-up time is shortened and the quiet performance is achieved. Can be increased.

[Modification 2-1]
In the above embodiment, the information about the number N of prints printed using the current fixing unit 30 included in the history data 541 is used. However, the present invention is not limited to this, and is included in the history data 541. Various pieces of information related to the print amount so far can be used.

[Modification 2-2]
In the above embodiment, the rotational speed R of the fixing roller 32 is adjusted based on the belt temperature Tb and the number N of printed sheets. However, the present invention is not limited to this. Instead, for example, as shown in FIG. 21, the image forming apparatus 1B according to the modification of the first embodiment (FIGS. 13 and 15) is based on the belt temperature Tb and the motor current Im. The rotational speed R may be adjusted. The image forming apparatus 2B according to the present modification includes a fixing control unit 68B and an image formation control unit 59B. The fixing control unit 68B includes a motor current detection unit 583. The motor current detector 583 detects a motor current Im supplied to the fixing motor 44. The fixing controller 68B adjusts the rotational speed R of the fixing roller 32 based on the belt temperature Tb and the motor current Im. In this example, as in the case of the image forming apparatus 1B, the fixing control unit 68B stores in advance the motor current Im (motor current Im0) when the number of printed sheets N is “0”, and the motor current Im The rotational speed R of the fixing roller 32 is adjusted using a current difference ΔIm (= Im−Im0) with the motor current Im0.

  FIG. 21 shows the setting operation of the rotational speed R of the fixing roller 32 in the warm-up operation OP1 in the image forming apparatus 2B.

  First, the fixing control unit 68B checks whether or not the rotation unevenness occurs in the fixing motor 44 (step S201). When the rotation unevenness does not occur in the fixing motor 44 (“N” in step S201), the process proceeds to step S213.

  In step S201, when uneven rotation occurs in the fixing motor 44 (“Y” in step S201), the fixing control unit 68B determines that the belt temperature Tb is a predetermined threshold based on the detection result of the temperature sensor 36. It is confirmed whether the temperature is lower than Tth (for example, 150 [° C.]) (Tb <150 [° C.]) (step S202). If the belt temperature Tb is lower than the threshold temperature Tth (“Y” in step S202), the image forming control unit 59B stops the process being executed and causes the display unit 53 to display an error ( Step S212). Then, this flow ends.

  When the belt temperature Tb is equal to or higher than the threshold temperature Tth in step S202 (“N” in step S202), the fixing control unit 68B has a current difference ΔIm of 0 based on the detection result of the motor current detection unit 583. It is confirmed whether it is smaller than .15 [A] (ΔIm <0.15 [A]) (step S223). When the current difference ΔIm is smaller than 0.15 [A] (“Y” in step S223), the image formation control unit 59B stops the process being executed and displays an error on the display unit 53. (Step S212). Then, this flow ends.

  In step S223, when the current difference ΔIm is equal to or greater than 0.15 [A] (“N” in step S223), the fixing control unit 68B includes the image forming apparatus according to the modification of the first embodiment. Similarly to 1B (FIG. 15), the rotation speed R of the fixing roller 32 is set according to the current difference ΔIm. If the rotation unevenness has not been eliminated (“N” in step S211), the image formation control unit 59 stops the process being executed and causes the display unit 53 to display an error (step S212). ). Then, this flow ends. If the rotation unevenness is resolved (“Y” in step S211), the process proceeds to step S213.

  If the belt temperature Tb has not reached the target temperature Ttarget (“N” in step S213), the process returns to step S201, and these operations are repeated until the belt temperature Tb reaches the target temperature Ttarget.

  In the image forming apparatus 2B according to the present modification, the fixing control unit 68B detects the motor current Im. However, the present invention is not limited to this, and instead of this, for example, a modification of the first embodiment described above. Similarly to the image forming apparatus 1C (FIG. 16), the fixing motor may detect the motor current Im.

[Modification 2-3]
In the above embodiment, it is determined whether or not the rotation speed R of the fixing roller 32 is adjusted based on the belt temperature Tb when the rotation unevenness of the fixing motor 44 occurs. However, the present invention is not limited to this. Absent. In determining whether to adjust the rotational speed R, any parameter having a correlation with the belt temperature Tb can be used. For example, as shown in FIG. 22, when the rotation unevenness occurs in the fixing motor 44 as in the image forming apparatus 1D (FIGS. 13 and 19) according to the modification of the first embodiment, the motor current Whether or not to adjust the rotation speed R of the fixing roller 32 may be determined based on Im. The image forming apparatus 2D according to the present modification includes a fixing control unit 68D and an image formation control unit 59. The fixing control unit 68D includes a motor current detection unit 583. The image formation control unit 59 and the fixing control unit 68D adjust the rotational speed R of the fixing roller 32 based on the motor current Im and the number N of printed sheets. In this example, as in the case of the image forming apparatus 1D, the fixing control unit 68D stores the motor current Im (motor current Im2) at a low temperature in advance at a predetermined frequency, and the motor current Im and the motor current Im2 Current difference ΔIm2 (= | Im−Im2 |) is obtained, and the rotational speed R of the fixing roller 32 is adjusted using this current difference ΔIm2.

  FIG. 22 shows the setting operation of the rotational speed R of the fixing roller 32 in the image forming apparatus 2D.

  First, the fixing control unit 68D checks whether or not the rotation unevenness occurs in the fixing motor 44 (step S201). When the rotation unevenness does not occur in the fixing motor 44 (“N” in step S201), the process proceeds to step S213.

  In step S201, when uneven rotation occurs in the fixing motor 44 (“Y” in step S201), the fixing control unit 68D determines that the current difference ΔIm2 is a predetermined value based on the detection result of the motor current detecting unit 583. It is checked whether the threshold current Ith is smaller (ΔIm2 <Ith) (eg, current difference ΔIM2 corresponding to 150 [° C.]) (step S232). When the current difference ΔIm2 is smaller than the threshold current Ith (“Y” in step S232), the image formation control unit 59 stops the process being executed and causes the display unit 53 to display an error ( Step S212). Then, this flow ends.

  In step S232, when the current difference ΔIm2 is equal to or larger than the threshold current Ith (“N” in step S232), the fixing control unit 68D based on the detection result of the motor current detection unit 583, the image formation control unit 59. Confirms whether the print number N included in the history data 541 is less than 300 (N <300 [sheets]) (step S203). When the number of printed sheets N is less than 300 (“Y” in step S203), the image formation control unit 59 stops the process being executed and causes the display unit 53 to display an error (step S212). ). Then, this flow ends.

  In step S203, when the number of printed sheets N is 300 or more (“N” in step S203), the image forming control unit 59 and the fixing control unit 68 are similar to the image forming apparatus 2 according to the above embodiment. The rotation speed R of the fixing roller 32 is set according to the number N of printed sheets (steps S204 to S210). If the rotation unevenness has not been eliminated (“N” in step S211), the image formation control unit 59 stops the process being executed and causes the display unit 53 to display an error (step S212). ). Then, this flow ends. If the rotation unevenness is resolved (“Y” in step S211), the process proceeds to step S213.

  If the belt temperature Tb has not reached the target temperature Ttarget (“N” in step S213), the process returns to step S201, and these operations are repeated until the belt temperature Tb reaches the target temperature Ttarget.

  In the above, the present modification is applied to the image forming apparatus 2 (FIG. 20) according to the above-described embodiment. However, the present invention is not limited to this. For example, as illustrated in FIG. The present modification may be applied to the forming apparatus 2B (FIG. 21).

<3. Third Embodiment>
Next, an image forming apparatus 3 according to a third embodiment will be described. The image forming apparatus 3 adjusts the rotational speed R of the fixing roller 32 when the fluctuation amount of the motor current Im of the fixing motor 44 is equal to or larger than a predetermined amount. Note that components that are substantially the same as those of the image forming apparatus 2 according to the second embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  FIG. 24 illustrates an example of a control mechanism in the image forming apparatus 3. The image forming apparatus 3 includes a fixing control unit 78. The fixing controller 78 has a motor current detector 583. The motor current detector 583 detects a motor current Im supplied to the fixing motor 44. The fixing control unit 78 adjusts the rotational speed R of the fixing roller 32 when the fluctuation amount of the motor current Im of the fixing motor 44 is a predetermined amount or more. That is, in the image forming apparatus 2 according to the second embodiment, the rotation speed R of the fixing roller 32 is adjusted when the rotation unevenness occurs in the fixing motor 44. However, the image forming apparatus according to the present embodiment. 3, the fixing control unit 78 adjusts the rotational speed R of the fixing roller 32 when the fluctuation amount of the motor current Im of the fixing motor 44 is a predetermined amount or more.

  FIG. 25 shows the setting operation of the rotation speed R of the fixing roller 32 in the warm-up operation OP1 in the image forming apparatus 3. When the fluctuation amount of the motor current Im is smaller than a predetermined amount, the image formation control unit 59 and the fixing control unit 78 maintain the rotation speed R of the fixing roller 32 at a predetermined speed (for example, 7.5 [ppm]). If the fluctuation amount of the motor current Im is equal to or larger than the predetermined amount, the rotational speed R is adjusted based on the belt temperature Tb and the number N of printed sheets. Cancel the current process. This operation will be described in detail below.

  First, the fixing controller 78 checks whether or not the fluctuation of the motor current Im is large (step S241). Specifically, the fixing control unit 78 checks whether the fluctuation amount of the motor current Im is equal to or greater than a predetermined threshold based on the detection result of the motor current detection unit 583. By appropriately setting the predetermined threshold value, the fixing control unit 78 can detect uneven rotation of the fixing motor 44, a sign of occurrence of noise, a sign of occurrence of uneven rotation, and the like. In other words, for example, when the rotation unevenness occurs in the fixing motor 44, the motor current Im is fluctuated. Therefore, the fixing control unit 78 can detect the rotation unevenness based on the fluctuation of the motor current Im. . Further, for example, by setting the predetermined threshold value to a small value, it is possible to detect a sign of occurrence of noise or a sign of occurrence of rotation unevenness based on the fluctuation of the motor current Im. When the fluctuation of the motor current Im is small (“N” in step S241), the process proceeds to step S213.

  In step S241, when the fluctuation of the motor current Im is large (“Y” in step S241), the fixing controller 78 determines that the belt temperature Tb is a predetermined threshold temperature Tth (based on the detection result of the temperature sensor 36). For example, it is confirmed whether it is lower than 150 [° C.] (Tb <150 [° C.]) (step S202). If the belt temperature Tb is lower than the threshold temperature Tth (“Y” in step S202), the image formation control unit 59 stops the process being executed and causes the display unit 53 to display an error ( Step S212). Then, this flow ends.

  In step S203, when the belt temperature Tb is equal to or higher than the threshold temperature Tth (“N” in step S202), the image formation control unit 59 has the number N of printed sheets included in the history data 541 smaller than 300 ( N <300 [sheets]) is checked (step S203). When the number of printed sheets N is less than 300 (“Y” in step S203), the image formation control unit 59 stops the process being executed and causes the display unit 53 to display an error (step S212). ). Then, this flow ends.

  In step S203, when the number of printed sheets N is 300 or more (“N” in step S203), the image forming control unit 59 and the fixing control unit 78 perform the image forming apparatus 2 according to the second embodiment. Similarly, the rotational speed R of the fixing roller 32 is set according to the number N of printed sheets (steps S204 to S210).

  Next, the fixing controller 78 checks whether or not the fluctuation of the motor current Im has been eliminated (step S241). Specifically, the fixing control unit 78 checks whether the fluctuation amount of the motor current Im is smaller than a predetermined threshold based on the detection result of the motor current detection unit 583. When the fluctuation of the motor current Im has not been eliminated (“N” in step S251), the image formation control unit 59 stops the process being executed and causes the display unit 53 to display an error (step S51). S212). Then, this flow ends. If the fluctuation of the motor current Im is eliminated in step S251 ("Y" in step S251), the process proceeds to step S213.

  Next, the fixing control unit 78 checks whether or not the belt temperature Tb has reached a target temperature Ttarget (for example, 170 [° C.]) based on the detection result of the temperature sensor 36 (step S213). If the belt temperature Tb has not reached the target temperature Ttarget (“N” in step S213), the process returns to step S241.

  In step S213, when the belt temperature Tb has reached the target temperature Ttarget (“Y” in step S213), this flow ends. As a result, the image forming apparatus 3 ends the warm-up operation OP1.

  As described above, in the image forming apparatus 3, since the fluctuation amount of the motor current Im is detected in the warm-up operation OP1, it is possible to detect a sign that noise is generated or a sign that rotation unevenness occurs. . As a result, the image forming apparatus 3 can shorten the warm-up time and improve the quiet performance.

  As described above, in the present embodiment, since the amount of fluctuation of the motor current is detected, the warm-up time can be shortened and the quiet performance can be improved. Other effects are the same as those of the second embodiment.

[Modification 3]
Each modification of the second embodiment may be applied to the image forming apparatus 3 according to the above embodiment.

  The present technology has been described above with some embodiments and modifications. However, the present technology is not limited to these embodiments and the like, and various modifications are possible.

  For example, in each of the above-described embodiments and the like, a monochrome image is formed on the recording medium 9, but the present invention is not limited to this, and a color image may be formed.

  Further, for example, in each of the above-described embodiments, the present technology is applied to the image forming apparatus. However, the present invention is not limited to this, and instead, a multi-function having functions such as a copy, a facsimile, and a scanner. You may apply to a peripheral device.

  DESCRIPTION OF SYMBOLS 1,1B, 1C, 1D, 2,2B, 2D, 3 ... Image forming apparatus, 10 ... Conveyance path, 11 ... Medium tray, 12 ... Pickup roller, 13 ... Separation roller, 14 ... Registration roller, 15-17 ... Conveyance Roller, 18 ... discharge roller, 19 ... discharge tray, 20 ... ID (Image Drum) unit, 21 ... photoconductor, 22 ... exposure head, 23 ... transfer roller, 30, 30C ... fixing unit, 31 ... fixing belt, 32 ... Fixing roller 33 ... Pressure pad 34 ... Pad support part 35 ... Coil spring 36 ... Temperature sensor 37A, 37B ... Guide member 38 ... Heater 39 ... Heat transfer member 40 ... Heater support part 41 ... Coil spring, 42 ... support member, 43 ... pressure roller, 44, 44C ... fixing motor, 51 ... communication unit, 52 ... operation unit, 53 ... display unit, 54 ... storage unit, 55 ... exposure control unit, 56 ... electricity Pressure control unit, 57... Motor control unit, 58, 58B, 58C, 58D, 68, 78 .. fixing control unit, 59, 59B... Image formation control unit, 441. 541 ... History data, 581 ... Heater control unit, 582 ... Fixing motor control unit, Im ... Motor current, N ... Cumulative number of printed sheets, OP1 ... Warm-up operation, OP2 ... Image forming operation, R, R1, R2 ... Rotational speed , Tb: belt temperature, Ttarget: target temperature, Tth: threshold temperature, TL: load torque, NP: nip, ΔIm, ΔIm2: current difference.

Claims (21)

An image forming unit for forming a developer image on a recording medium;
An endless belt, a first roller disposed so as to contact the outer peripheral surface of the belt, and an inner peripheral surface of the belt, and disposed so as to be in pressure contact with the first roller across the belt. A fixing unit that fixes the developer image on the recording medium, the second roller and the pressure contact member, a motor that rotationally drives the second roller, and a heater;
In the preparatory operation for the fixing temperature of the fixing unit to reach a target temperature before the image forming unit forms the developer image, based on one or both of the fixing temperature and the motor current of the motor, An image forming apparatus comprising: a control unit that adjusts a rotation speed of the second roller. The image forming apparatus according to claim 1, wherein the control unit adjusts the rotation speed so as to increase the rotation speed based on one or both of the fixing temperature and the motor current. The fixing unit further includes a temperature sensor that detects the fixing temperature,
The image forming apparatus according to claim 1, wherein the control unit adjusts the rotation speed based on the fixing temperature. The image forming apparatus according to claim 3, wherein the controller adjusts the rotation speed when the fixing temperature is higher than a threshold temperature. A current sensor for detecting the motor current;
The image forming apparatus according to claim 1, wherein the control unit adjusts the rotation speed based on a temperature change amount of the motor current. The image forming apparatus according to claim 5, wherein the controller adjusts the rotational speed when an absolute value of the temperature change amount of the motor current is larger than a threshold value. A storage unit that stores history information indicating an operation history of the image forming unit;
The image forming apparatus according to claim 4, wherein the control unit adjusts the rotation speed based on the history information. The history information includes information on the number of images formed on the recording medium on which the image forming apparatus has formed an image using the fixing unit,
The image forming apparatus according to claim 7, wherein the control unit adjusts the rotation speed based on the number of image forming sheets. The controller sets the rotation speed to the first rotation speed when the number of image formations is the first number, and the second number of the image formations is greater than the first number. The image forming apparatus according to claim 8, wherein the rotation speed is set to a second rotation speed that is faster than the first rotation speed. A current sensor for detecting the motor current;
The image forming apparatus according to claim 4, wherein the control unit adjusts the rotational speed based on an amount of change in the motor current with time. The controller sets the rotational speed to the first rotational speed when the temporal variation is the first variation, and the second variation is greater than the first variation. The image forming apparatus according to claim 10, wherein the rotation speed is set to a second rotation speed that is faster than the first rotation speed. The fixing unit further includes a detection unit that detects a rotation operation of the motor,
The image forming apparatus according to claim 1, wherein the control unit adjusts the rotation speed when rotation unevenness occurs in the motor. The fixing unit further includes a temperature sensor that detects the fixing temperature,
The image forming apparatus according to claim 12, wherein the control unit adjusts the rotation speed based on the fixing temperature. The image forming apparatus according to claim 13, wherein the controller adjusts the rotation speed when the fixing temperature is higher than a threshold temperature. The image forming apparatus according to claim 14, wherein the controller ends the preparatory operation when rotation unevenness occurs in the motor and the fixing temperature is lower than the threshold temperature. A current sensor for detecting the motor current;
The image forming apparatus according to claim 12, wherein the control unit adjusts the rotational speed based on a temperature change amount of the motor current. The image forming apparatus according to claim 16, wherein the controller adjusts the rotation speed when an absolute value of the temperature change amount of the motor current is larger than a threshold value. The image forming apparatus according to claim 17, wherein the control unit ends the preparatory operation when rotation unevenness occurs in the motor and the absolute value of the temperature change amount is lower than the threshold value. 19. The image forming apparatus according to claim 12, wherein after the rotation speed is adjusted, the control unit ends the preparation operation when the rotation unevenness of the motor is not eliminated. 19. A current sensor for detecting the motor current;
The image forming apparatus according to claim 1, wherein the control unit adjusts the rotation speed based on a fluctuation amount of the motor current. The image forming apparatus according to claim 20, wherein the control unit adjusts the rotational speed when a fluctuation amount of the motor current is larger than a predetermined amount.

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