JP2018155850A - Image formation apparatus, control method and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus which can extend the time to the end of the service life of a fixation device more than that of a conventional technique.SOLUTION: A fixation device of an image formation apparatus includes: a first rotor 60; a second rotor 65; a biasing mechanism 64 which presses one of the first rotor 60 and second rotor 65 to the other; and a current sensor 96 (load detection unit) which detects the load of the rotation of at least one of the first rotor 60 and second rotor 65. The image formation apparatus further includes a control device 101 for controlling the fixation device. The control device 101 includes: a determination unit which determines whether or not the service life of the fixation device 51 comes to the end on the basis of the magnitude of the load detected by the current sensor 96; and a pressure control unit which controls a pressure-contact motor 94 so as to reduce the pressure-contact force of the first rotor 60 and second rotor 65 more than the time before the service life comes to the end when the determination unit determines that the service life comes to the end.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to control of an image forming apparatus, and more particularly to control of a fixing device provided in an electrophotographic image forming apparatus.

  An electrophotographic image forming apparatus is widely used. An electrophotographic image forming apparatus includes, as a printing process, a process for forming a toner image corresponding to an input image on a photoconductor, a process for primary transfer of the toner image on the photoconductor onto a transfer belt, The step of secondary transfer of the toner image to the paper and the step of fixing the toner image to the paper by the fixing device by heat are executed.

  The fixing device includes a rotating body such as a fixing roller and a pressure roller. Since the fixing device is a consumable item, it is necessary to perform maintenance such as predicting the life of the fixing device and replacing consumable parts at an appropriate time in order to provide users with stable and high-quality print images. is there.

  In the conventional determination of the life of the fixing device, a uniform travel distance is determined from a predetermined durability evaluation result and the like, and the travel distance is determined as the arrival time of the end of the life that requires maintenance. However, in this case, since the fixing device that can still be used has been determined to be at the end of its life, it is inefficient for the user's use. In view of this, for example, a technique has been proposed that can detect a change in the diameter of a rotating body and determine the life of the rotating body as disclosed in Patent Document 1.

JP 2007-127759 A

  However, in the above-described conventional fixing device, it is necessary to perform maintenance immediately after determining the end of the life of the fixing device, and it is not possible to secure time for maintenance, and as a result, the image forming apparatus cannot be used. There were problems such as time.

  The present disclosure has been made in order to solve the above-described problems, and an object in one aspect thereof is to provide an image forming apparatus capable of extending the time until the life of the fixing device reaches the conventional level. is there. Another object of the present invention is to provide a control method for an image forming apparatus that can extend the time until the life of the fixing device reaches the conventional level. Another object of the present invention is to provide a control program for an image forming apparatus that can extend the time until the life of the fixing device reaches the conventional level.

  According to an aspect, the image forming apparatus includes a fixing device for fixing the toner formed on the paper to the paper, and the fixing device is provided to face the first rotating body and the first rotating body. By pressing one of the second rotator and one of the first and second rotators against the other, pressure is applied to the paper passing between the first rotator and the second rotator, and toner is applied to the paper. And a load mechanism for detecting a load of rotation of at least one of the first rotating body and the second rotating body. The image forming apparatus further includes a control device for controlling the fixing device, and the control device determines whether or not the end of life of the fixing device has come based on the magnitude of the load detected by the load detection unit. When the determination unit for determining and the determination unit determine that the end of life has arrived, the contact pressure between the first rotating body and the second rotating body is reduced more than before the end of life has arrived. A pressure control unit for controlling the pressurizing mechanism.

  Preferably, the fixing device further includes a heating mechanism for heating at least one of the first rotating body and the second rotating body. When the determination unit determines that the end of life has arrived, the heating mechanism raises the temperature of the heating target more than before the end of life reaches.

  Preferably, the control device includes an estimation unit for estimating an amount of toner to be formed on the paper based on image information that defines a location where the toner should be attached on the paper. When the determination unit determines that the end of life has come, the heating mechanism increases the temperature of the heating target as the amount of toner estimated by the estimation unit increases.

  Preferably, the image forming apparatus further includes an adjustment mechanism for adjusting the amount of toner deposited on the paper. When the determination unit determines that the end of the life has come, the adjustment mechanism reduces the amount of toner adhering to the paper more than before the end of the life.

  Preferably, the fixing device further includes a rotation mechanism for rotationally driving at least one of the rotation objects of the first rotation body and the second rotation body. When the determination unit determines that the end of life has arrived, the rotation mechanism makes the rotation speed of the rotation target slower than before the end of life reaches.

  Preferably, a load detection part detects the fluctuation rate of the rotational torque in at least one of a 1st rotary body and a 2nd rotary body as a load. The determination unit determines that the end of life has come when the rate of change exceeds a predetermined threshold.

  Preferably, the pressure control unit further reduces the contact pressure as time passes after the contact pressure decreases.

  Preferably, the pressure control unit controls the pressurization mechanism so as to maintain the contact pressure after the decrease after the decrease of the contact pressure.

  Preferably, the image forming apparatus further includes a slip detection unit for detecting a slip state in which the sheet conveyance speed between the first rotating body and the second rotating body is lower than a predetermined conveyance speed. . A pressure control part raises the contact pressure after a fall, when a slip state is detected by the slip detection part.

  Preferably, the image forming apparatus includes an operation unit that allows a user to select the type of the paper, and the operation unit has a plurality of predetermined types when the end of the life is determined by the determination unit. It is configured to be able to accept the type of paper to be prohibited from printing from among the paper.

  According to another aspect, a fixing device control method for fixing toner formed on a sheet to the sheet is provided. The fixing device includes a first rotating body and a second rotating body provided to face the first rotating body, and the control method presses one of the first rotating body and the second rotating body to the other. Thus, pressure is applied to the sheet passing between the first rotating body and the second rotating body to fix the toner to the sheet, and a rotation load of at least one of the first rotating body and the second rotating body is detected. And determining whether the fixing device has reached the end of life based on the magnitude of the load detected in the detecting step, and determining that the end of life has arrived in the determining step If it is, the step of lowering the contact pressures of the first rotating body and the second rotating body than before the end of the service life is reached is included.

  According to still another aspect, there is provided a fixing device control program for fixing toner formed on a sheet to the sheet. The fixing device includes a first rotating body and a second rotating body provided to face the first rotating body, and the control program causes the fixing device to have one of the first rotating body and the second rotating body. By pressing against the other, pressure is applied to the paper passing between the first rotating body and the second rotating body to fix the toner to the paper, and rotation of at least one of the first rotating body and the second rotating body And the step of determining whether or not the end of life of the fixing device has come based on the magnitude of the load detected in the step of detecting, and the step of determining whether or not the end of life has come. When it is determined that the contact pressure of the first rotating body and the second rotating body is lower than before the end of the life comes, the step of reducing the contact pressure is executed.

  In one aspect, the time until the end of the life of the fixing device can be extended as compared with the conventional case. The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention taken in conjunction with the accompanying drawings.

1 is a diagram illustrating an outline of a fixing device according to a first embodiment. FIG. 3 is a diagram illustrating control of a fixing device. It is a graph which shows the rotational torque of a rotary motor, and the travel distance of a fixing belt. 1 is a diagram illustrating an internal structure of an image forming apparatus. 2 is a block diagram illustrating a hardware configuration of the image forming apparatus. FIG. 6 is a processing flow showing control processing of the fixing device. FIG. 10 is a block diagram illustrating a control function of a fixing device according to a second embodiment. 6 is a graph showing a relationship between toner melting time and pressure. FIG. 10 is a block diagram illustrating a control function of a fixing device according to a third embodiment. It is a block diagram which shows the control function of the fixing device in 4th Embodiment. FIG. 10 is a block diagram illustrating a control function of a fixing device according to a fifth embodiment. It is a figure which shows the paper sensor in 5th Embodiment. It is a figure which shows the detection method using a paper sensor. FIG. 10 is a block diagram illustrating a control function of a fixing device according to a sixth embodiment.

  Embodiments according to the present invention will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. Each embodiment and each modified example described below may be selectively combined as appropriate.

<First Embodiment>
[Fixing device 50]
With reference to FIG. 1, the fixing device 50 used in the fixing process of the toner image 32 will be described. An image forming apparatus including the fixing device 50 will be described later. FIG. 1 is a perspective view illustrating a general shape of the fixing device 50.

  As shown in FIG. 1, the fixing device 50 includes a fixing member 60 as a first rotating body and a pressure roller 65 as a second rotating body. The fixing member 60 includes a fixing roller 51, a cored bar 52, a fixing belt 53, and a heating roller 57. The fixing belt 53 is stretched around the fixing roller 51 and the heating roller 57. When the heating roller 57 is rotated by the rotation motor 66, the fixing belt 53 wound around the heating roller 57 travels along the rotation direction, and accordingly, the fixing roller 51 is also rotated in the same direction. Yes.

  The heating roller 57 has, for example, a cylindrical shape. A heater H as a heating mechanism is provided inside the heating roller 57. The number of heaters H is arbitrary. As an example, as schematically shown in FIG. 2, one heater H is provided inside the heating roller 57. The heater H is, for example, a halogen heater.

  The heater H heats the fixing member 60 and applies heat to the paper S passing through the contact portion between the fixing member 60 and the pressure roller 65. More specifically, the heater H transfers heat to the fixing belt 53 that contacts the heating roller 57 by heating the heating roller 57. The heated fixing belt 53 travels in the rotation direction to contact the fixing roller 51 and transmit heat to the sheet S being conveyed on the conveying path 41 (see FIG. 2). When the sheet S is heated, the toner image 32 on the sheet S is melted. As a result, the toner image 32 is easily fixed on the paper S.

  Here, the heater H may be configured to heat at least one of the fixing member 60 and the pressure roller 65. That is, the heating target by the heater H may be the pressure roller 65 instead of the fixing member 60. In this case, the heater H is provided inside the pressure roller 65. The fixing device 50 further includes a temperature detection sensor (not shown) configured with a thermistor or the like for measuring the temperature of the fixing member 60 heated by the heater H.

  The pressure roller 65 is provided so as to face the fixing member 60. The pressure roller 65 is urged so as to press the fixing member 60 by an urging mechanism 64 (see FIG. 2) using, for example, a spring. More specifically, the pressure roller 65 is configured to press the fixing roller 51 around which the fixing belt 53 is wound. As a result, the sheet S passing through the contact portion between the pressure roller 65 and the fixing member 60 is pressurized, and the toner image 32 formed on the sheet S is fixed to the sheet S. In the present embodiment, the pressure roller 65 is pressed against the fixing member 60 by the urging mechanism 64, but the fixing member 60 may be pressed against the pressure roller 65.

  The fixing roller 51 can have a cylindrical shape, for example. A cored bar 52 is provided inside the fixing roller 51 so as to extend in the cylinder axis direction. A pair of flat pressure contact levers 92 and annular pressure contact gears 93 are provided at both ends of the fixing roller 51 in the cylinder axis direction. The pressure contact lever 92 is engaged with the core metal 52, and a cutout 92a is formed in a part of the pressure contact lever 92, and the convex portion 93a of the pressure contact gear 93 is fitted into the cutout 92a. The lever 92 and the press contact gear 93 are configured to engage with each other.

  The rotation of a pressure contact motor 94 provided on one end side in the cylinder axis direction of the fixing roller 51 is transmitted to the pressure contact gear 93 by a plurality of transmission gears 97. That is, when the press contact motor 94 rotates, the transmission gears 97, 97,... Rotate, and the press contact gear 93 rotates accordingly. Here, the pressure contact motor 94 and the biasing mechanism 64 constitute a pressure mechanism 54 for pressing the pressure roller 65 against the fixing roller 51.

  Further, a pressure sensor 95 that detects the pressure received from the pressure roller 65 is provided on one end side of the fixing roller 51 in the cylinder axis direction. Here, as the pressure sensor 95, for example, a known pressure detection mechanism using a transmission type sensor and a light shielding member can be used. Thereby, the contact pressure between the fixing member 60 and the pressure roller 65 can be detected.

[Control of Fixing Device 50]
The control of the fixing device 50 will be described with reference to FIG. FIG. 2 is a schematic diagram illustrating the control of the fixing device 50.

  In the fixing device 50, the heating roller 57 is rotated in one direction by the rotary motor 66 as described above. As the rotation motor 66, for example, a control motor such as a servo motor can be used. Here, the rotation motor 66 is controlled by the rotation control unit 113 of the control device 101 provided in the image forming apparatus, and the current value flowing to the rotation motor is detected by the current sensor 96 (load detection unit). Thus, the rotational torque of the rotary motor 66 can be detected. In the present embodiment, the current sensor 96 detects the rotational torque of the rotary motor 66, but a known torque sensor may be configured to detect the rotational torque of the pressure roller 65, for example.

  The rotational torque generated by the rotary motor 66 increases as the fixing device 50 deteriorates over time. When the end of life comes to the fixing device 50, the fluctuation rate of the rotational torque changes rapidly. Here, the end of life is immediately before the end of life when the fixing device 50 cannot be used, and predetermined maintenance associated with aging, such as replacement of a worn rotating body or replenishment of lubricant, It is time to do. Then, when the fluctuation rate of the rotational torque exceeds a predetermined threshold, the determination unit 111 included in the control device 101 determines that the end of life of the fixing device 50 has come. Here, the variation rate means the amount of change in rotational torque per unit amount (time or travel distance). Since the determination unit 111 determines the end of life of the fixing device 50 based on the fluctuation rate, not the absolute value of the rotation torque, the determination unit 111 is provided between the rotation motor 66 and the rotation motor 66 and the heating roller 57. There is no need to consider individual differences in parts such as gears (not shown). As a result, the end of life of the fixing device 50 can be determined without depending on the components.

  When the determination unit 111 determines that the end of the life of the fixing device 50 has come, the pressure control unit 112 controls the pressure contact motor 94 so as to reduce the contact pressure between the fixing member 60 and the pressure roller 65. The pressure contact motor 94 is formed of, for example, a stepping motor, and rotates the transmission gear 97 to rotate the pressure contact gear 93 in a predetermined direction. As a result, as shown in FIG. 2B, the convex portion 93 a of the press contact gear 93 fitted in the cutout 92 a formed in the press contact lever 92 moves the press contact lever 92 in a direction away from the pressure roller 65. As a result, the cored bar 52 engaged with the pressure contact lever 92 moves the fixing roller 51 away from the pressure roller 65. As a result, the contact pressure between the fixing member 60 and the pressure roller 65 decreases. At this time, the pressure control unit 112 controls the pressure contact motor 94 based on the information detected by the pressure sensor 95.

  In the present embodiment, the contact pressure between the fixing member 60 and the pressure roller 65 is reduced by the fixing member 60 moving away from the pressure roller 65 by the rotation of the pressure contact motor 94. However, the pressure roller 65 may move in a direction away from the fixing member 60.

  With reference to FIG. 3, the effect by the above-mentioned contact pressure control is demonstrated. FIG. 3 is a graph showing the relationship between the travel distance of the fixing belt 53 of the fixing device 50 and the rotational torque of the rotary motor 66.

  In FIG. 3, the distance a indicates the end of life of the fixing device 50 uniformly determined based on a predetermined durability evaluation result or the like as a travel distance. The distance b indicates the end of life of the fixing device 50 determined by a sudden change in the fluctuation rate of the rotational torque as a travel distance. The distance c indicates the service life of the fixing device when the contact pressure control is not performed as a travel distance. The distance d indicates the service life of the fixing device 50 in the present embodiment as a travel distance.

  As shown in FIG. 3, when the end of life (distance b) at which the variation rate of the rotational torque changes abruptly is reached, when the contact pressure control is not performed (one-dot chain line), the rotational torque rapidly increases. . For this reason, the service life torque that is the limit on the durability performance of the fixing device 50 is reached immediately. As a result, before the maintenance is performed, the service life (distance c) is reached, resulting in problems such as downtime that cannot be used. However, when the contact pressure control is performed in this embodiment (solid line), the rotation of the fixing member 60 is performed by reducing the contact pressure between the fixing member 60 and the pressure roller 65 after the end of life (distance b) has been reached. As a result, the rotational torque can be reduced. As a result, the service life extends from the distance c to the distance d, and the fixing device 50 can be used for a longer period (a period from the distance c to the distance d). As a result, it is possible to secure a time from when the end of the life of the fixing device is determined to when the fixing device is maintained, thereby improving user convenience.

  Since the end of life (distance a) of the fixing device 50 determined based on a predetermined durability evaluation result is determined earlier than the actual end of life (distance b), the use efficiency is reduced. .

[Internal structure of image forming apparatus 100]
With reference to FIG. 4, the image forming apparatus 100 on which the above-described fixing device 50 is mounted will be described. FIG. 4 is a diagram illustrating an example of the internal structure of the image forming apparatus 100.

  FIG. 4 shows an image forming apparatus 100 as a color printer. Hereinafter, the image forming apparatus 100 as a color printer will be described, but the image forming apparatus 100 is not limited to a color printer. For example, the image forming apparatus 100 may be a monochrome printer, may be a fax machine, or may be a monochrome printer, a color printer, and a multifunction machine (MFP: Multi-Functional Peripheral).

  The image forming apparatus 100 includes image forming units 1Y, 1M, 1C, and 1K, an intermediate transfer belt 30, a primary transfer roller 31, a secondary transfer roller 33, a cassette 37, a driven roller 38, and a drive roller 39. A timing roller 40, a cleaning blade 42, a fixing device 50, and a control device 101.

  The image forming unit 1Y receives toner from the toner bottle 15Y and forms a yellow (Y) toner image. The image forming unit 1M receives the supply of toner from the toner bottle 15M and forms a magenta (M) toner image. The image forming unit 1C receives toner from the toner bottle 15C and forms a cyan (C) toner image. The image forming unit 1K receives toner from the toner bottle 15K and forms a black (BK) toner image.

  The image forming units 1Y, 1M, 1C, and 1K are arranged along the intermediate transfer belt 30 in the rotation direction of the intermediate transfer belt 30, respectively. Each of the image forming units 1Y, 1M, 1C, and 1K includes a photoconductor 10, a charger 11, an exposure unit 12, a developing unit 13, and a cleaning blade 17.

  The charger 11 uniformly charges the surface of the photoconductor 10. The exposure unit 12 irradiates the photoconductor 10 with laser light in accordance with a control signal from the control device 101, and exposes the surface of the photoconductor 10 according to the input image pattern. Thereby, an electrostatic latent image corresponding to the input image is formed on the photoreceptor 10.

  The developing device 13 applies a developing bias to the developing roller 14 while rotating the developing roller 14, and causes the toner to adhere to the surface of the developing roller 14. As a result, the toner is transferred from the developing roller 14 to the photoreceptor 10, and a toner image corresponding to the electrostatic latent image is developed on the surface of the photoreceptor 10.

  The photoconductor 10 and the intermediate transfer belt 30 are in contact with each other at a portion where the primary transfer roller 31 is provided. The primary transfer roller 31 has a roller shape and is configured to be rotatable. A transfer voltage having a polarity opposite to that of the toner image is applied to the primary transfer roller 31, whereby the toner image is transferred from the photoreceptor 10 to the intermediate transfer belt 30. A yellow (Y) toner image, a magenta (M) toner image, a cyan (C) toner image, and a black (BK) toner image are sequentially superimposed and transferred from the photoreceptor 10 to the intermediate transfer belt 30. As a result, a color toner image is formed on the intermediate transfer belt 30.

  The intermediate transfer belt 30 is wound around the driven roller 38 and the driving roller 39 in a stretched state. The drive roller 39 is connected to a motor (not shown). The motor is controlled by the control device 101, for example. As the motor control method, for example, PWM (Pulse Width Modulation) control is adopted. When the control device 101 controls the motor, the drive roller 39 rotates. The intermediate transfer belt 30 and the driven roller 38 rotate in conjunction with the drive roller 39. As a result, the toner image on the intermediate transfer belt 30 is conveyed to the secondary transfer roller 33.

  The cleaning blade 17 is in pressure contact with the photoreceptor 10. The cleaning blade 17 collects toner remaining on the surface of the photoconductor 10 after the transfer of the toner image from the photoconductor 10 to the intermediate transfer belt 30.

  A sheet S is set in the cassette 37. The sheets S are sent one by one from the cassette 37 to the secondary transfer roller 33 along the conveyance path 41 by the timing roller 40. The control device 101 controls the transfer voltage applied to the secondary transfer roller 33 in accordance with the timing at which the paper S is sent out.

  The secondary transfer roller 33 has a roller shape and is configured to be rotatable. The secondary transfer roller 33 applies a transfer voltage having a polarity opposite to that of the toner image to the sheet S being conveyed. As a result, the toner image is attracted from the intermediate transfer belt 30 to the secondary transfer roller 33, and the toner image on the intermediate transfer belt 30 is transferred. The conveyance timing of the sheet S to the secondary transfer roller 33 is controlled by the timing roller 40 in accordance with the position of the toner image on the intermediate transfer belt 30. As a result, the toner image on the intermediate transfer belt 30 is transferred to an appropriate position on the paper S.

  As described above, the fixing device 50 pressurizes and heats the sheet S passing between the fixing member 60 and the pressure roller 65. The fixing device 50 controls the degree of heating of the fixing member 60 and the contact pressure between the fixing member 60 and the pressure roller 65 in accordance with a control signal from the control device 101. The fixing device 50 heats and pressurizes the paper S, whereby the toner image is fixed on the paper S. Thereafter, the sheet S is discharged to the tray 48.

  The cleaning blade 42 is in pressure contact with the intermediate transfer belt 30. The cleaning blade 42 collects toner remaining on the surface of the intermediate transfer belt 30 after the transfer of the toner image from the intermediate transfer belt 30 to the paper S. The collected toner is conveyed by a conveying screw (not shown) and stored in a waste toner container (not shown).

[Hardware Configuration of Image Forming Apparatus 100]
An example of the hardware configuration of the image forming apparatus 100 will be described with reference to FIG. FIG. 5 is a block diagram illustrating a main hardware configuration of the image forming apparatus 100.

  As illustrated in FIG. 5, the image forming apparatus 100 includes a control device 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a network interface 104, an operation panel 107, and a storage device 120. Including.

  The control device 101 is configured by at least one integrated circuit, for example. The integrated circuit includes, for example, at least one CPU (Central Processing Unit), at least one ASIC (Application Specific Integrated Circuit), at least one FPGA (Field Programmable Gate Array), or a combination thereof.

  The control apparatus 101 controls the operation of the image forming apparatus 100 by executing various programs such as the control program 122 according to the present embodiment. The control device 101 reads the control program 122 from the storage device 120 to the RAM 103 based on receiving the execution instruction of the control program 122. The RAM 103 functions as a working memory and temporarily stores various data necessary for executing the control program 122.

  An antenna (not shown) or the like is connected to the network interface 104. The image forming apparatus 100 exchanges data with an external communication device via the antenna. The external communication device includes, for example, a mobile communication terminal such as a smartphone, a server, and the like. The image forming apparatus 100 may be configured to download the control program 122 from a server via an antenna.

  The operation panel 107 includes a display and a touch panel. The display and the touch panel are overlapped with each other, and the operation panel 107 receives, for example, a printing operation or a scanning operation for the image forming apparatus 100.

  The storage device 120 is a storage medium such as a hard disk or an external storage device. Storage device 120 stores control program 122 according to the present embodiment. The storage location of the control program 122 is not limited to the storage device 120, and may be stored in a storage area (for example, a cache) of the control device 101, a ROM 102, a RAM 103, an external device (for example, a server), or the like.

  The control program 122 may be provided by being incorporated in a part of an arbitrary program, not as a single program. In this case, the control process according to the present embodiment is realized in cooperation with an arbitrary program. Even such a program that does not include some modules does not depart from the spirit of the control program 122 according to the present embodiment. Furthermore, some or all of the functions provided by the control program 122 may be realized by dedicated hardware. Furthermore, the image forming apparatus 100 may be configured in the form of a so-called cloud service in which at least one server executes a part of the processing of the control program 122.

[Control Processing of Fixing Device 50]
The control process of the fixing device 50 will be described with reference to FIG. FIG. 6 is a process flow showing a control process of the fixing device 50.

  When the secondary transfer process in the image forming apparatus 100 is completed, the sheet S on which the toner image 32 is formed is conveyed to the fixing device 50. In step S <b> 1, when the sheet S is conveyed to the fixing device 50, the control device 101 of the image forming apparatus 100 drives the rotation motor 66 to rotate the heating roller 57 in a predetermined direction. When the heating roller 57 rotates in a predetermined direction, the fixing belt 53 wound around the heating roller 57 travels along the rotation direction of the heating roller 57. Accordingly, the fixing roller 51 around which the fixing belt 53 is wound also rotates in the same direction as the rotation of the heating roller 57. Since the pressure roller 65 is urged by the urging mechanism 64 so as to press the fixing member 60, the sheet conveyed on the conveyance path 41 formed between the fixing member 60 and the pressure roller 65. A pressure for fixing the toner image 32 is applied to S, and a fixing operation is performed.

  In step S <b> 2, the control device 101 detects the fluctuation rate of the rotational torque for the rotation of the rotary motor 66 based on the output value from the current sensor 96.

  In step S3, the control device 101 determines whether or not the variation rate of the rotational torque is equal to or greater than a predetermined threshold value. When control device 101 determines that the variation rate of the rotational torque is equal to or greater than a predetermined threshold (YES in step S3), control device 101 switches control to step S4. If not (NO in step S3), control device 101 switches control to step S5.

  Here, if the fluctuation rate of the rotational torque is less than the predetermined threshold (NO in step S3), the fixing operation is continued as it is. When the sheet S on the transport path 41 passes between the fixing member 60 and the pressure roller 65 and the fixing operation is completed, the rotation driving of the rotation motor 66 is stopped in step S5, and the fixing process is completed. .

  On the other hand, when the fluctuation rate of the rotational torque is equal to or greater than the predetermined threshold (YES in step S3), in step S4, the control device 101 determines that the end of life of the fixing device 50 has come as the determination unit 111, An input signal is transmitted to the pressure control unit 112. The pressure control unit 112 that has received the input signal controls the pressure contact motor 94 included in the pressure mechanism 54 to reduce the contact pressure between the fixing member 60 and the pressure roller 65. Then, returning to step S <b> 2 again, the control device 101 detects the fluctuation rate of the rotational torque of the rotary motor 66.

  Then, the control device 101 determines again whether or not the fluctuation rate of the rotational torque is greater than or equal to a predetermined threshold (step S3). Here, when the variation rate of the rotational torque is equal to or greater than the predetermined threshold value (step S3 / YES), the contact pressure is reduced again. At this time, the control device 101 reduces the contact pressure by the same magnitude as the previously reduced contact pressure based on the contact pressure value between the fixing member 60 and the pressure roller 65 obtained from the pressure sensor 95. The pressure contact motor 94 may be controlled so that the contact pressure is lowered, or the pressure contact motor 94 may be controlled so as to further reduce the contact pressure with time.

  In this embodiment, the image forming apparatus 100 is configured to return to step S2 after step S4 in FIG. 6, but the fixing operation is continued while maintaining the contact pressure reduced in step S4. When the fixing operation is completed, the drive of the rotary motor 66 may be stopped in S5.

<Second Embodiment>
[Overview]
The second embodiment is different from the first embodiment in that the control device 201 includes a heating control unit 114 that controls the heater H provided in the heating roller 57. In the second and subsequent embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will not be repeated.

[Details]
With reference to FIGS. 7 and 8, an image forming apparatus 200 according to the second embodiment will be described. FIG. 7 is a block diagram illustrating a function of performing control processing of the fixing device 50 according to the second embodiment. FIG. 8 is a graph showing the relationship between toner melting time and pressure.

  As shown in FIG. 7, the control device 201 in the second embodiment includes a heating control unit 114. In this embodiment, when the determination unit 211 determines that the end of life of the fixing device 50 has come based on the fluctuation rate of the rotational torque detected by the current sensor 96, the determination unit 211 determines the heating control unit 114. An input signal is sent to. Upon receiving the input signal, the heating control unit 114 controls the heater H provided in the heating roller 57 of the fixing device to increase the temperature of the heating roller 57 to be heated. Here, the heating control unit 114 controls the heating amount based on information from a temperature detection sensor (not shown) provided in the fixing device 50.

  As shown in FIG. 8, it can be read that the higher the pressure in the fixing operation and the higher the melting temperature of the toner, the more the fixing property is improved. That is, in the fixing device 50 according to the present embodiment, when the determination unit 211 determines that the end of life of the fixing device 50 has come to an end, the contact pressure between the fixing member 60 and the pressure roller 65 is reduced. The controller 114 heats the heating roller 57 to increase the temperature of the toner on the paper S conveyed between the fixing member 60 and the pressure roller 65 and maintain the fixing property. .

  Furthermore, in the present embodiment, the control device 201 may include an estimation unit 115 for estimating the amount of toner formed on the paper S based on image information 98 transmitted from the outside. Here, the outside refers to a scanner (not shown) provided in the image forming apparatus 200, for example, when using the copy function. Or, when using the printout function, it refers to the network interface 104, for example. However, it is not limited to these structures. The image information 98 defines a location where the toner should adhere to the paper S. The estimation unit 115 transmits an input signal to the heating control unit 114 so that the temperature of the heating roller 57 increases as the estimated toner amount increases. As a result, the heating roller 57 can be heated to a temperature corresponding to the toner amount, and the heating roller 57 can be appropriately heated to the extent necessary for the fixing operation.

<Third Embodiment>
[Overview]
In the third embodiment, the image forming apparatus 300 is different from the first embodiment in that the image forming apparatus 300 includes an adjustment unit 13a that adjusts the amount of toner on the paper S.

[Details]
With reference to FIG. 9, an image forming apparatus 300 according to the third embodiment will be described. FIG. 9 is a block diagram illustrating a function for performing control processing of the fixing device 50 according to the third embodiment.

  As shown in FIG. 9, the image forming apparatus 300 according to the third embodiment includes an adjustment unit 13 a that adjusts the amount of toner on the paper S. The adjusting unit 13a can be provided in the developing unit 13, for example, but may be provided outside the developing unit 13. In this embodiment, when the determination unit 311 determines that the end of life of the fixing device 50 has come based on the fluctuation rate of the rotational torque detected by the current sensor 96, the determination unit 311 sends the adjustment unit 13 a to the adjustment unit 13 a. Send the input signal. The adjustment unit 13a that has received the input signal reduces the amount of toner that adheres to the paper S more than before the end of the lifetime.

  With the above configuration, the amount of toner on the paper S is reduced, so that the toner can be fixed on the paper S at a pressure lower than the pressure before the end of the life of the fixing device 50. As a result, even after the contact pressure between the fixing member 60 and the pressure roller 65 is reduced, the fixing operation can be performed reliably.

<Fourth embodiment>
[Overview]
The fourth embodiment differs from the first embodiment in that the rotation control unit 413 controls the rotation motor 66 when the determination unit 411 determines that the end of life of the fixing device 50 has come. Different.

[Details]
An image forming apparatus 400 according to the fourth embodiment will be described with reference to FIG. FIG. 10 is a block diagram illustrating a function for performing control processing of the fixing device 50 according to the fourth embodiment.

  As shown in FIG. 10, in the fourth embodiment, when the determination unit 411 determines that the end of life of the fixing device 50 has come based on the fluctuation rate of the rotational torque detected by the current sensor 96. In addition, the determination unit 411 transmits an input signal to the rotation control unit 413. The rotation control unit 413 that has received the input signal controls the rotation motor 66 to slow down the rotation of the heating roller 57. As a result, the rotation speed of the fixing member 60 is decreased.

  With the above configuration, since the rotation speed of the fixing member 60 is slowed down, the sheet S transported on the transport path 41 takes a longer time than before the end of the life of the fixing device 50 arrives. 60 and the pressure roller 65 are conveyed. As a result, the time during which the sheet S is pressed becomes longer, and the fixing operation can be performed reliably even after the contact pressure between the fixing member 60 and the pressure roller 65 is lowered.

<Fifth embodiment>
[Overview]
In the fifth embodiment, the image forming apparatus 500 detects a slip sensor in which the transport speed of the paper S is in a slip state that is slower than a predetermined transport speed (slip detector). This is different from the first embodiment in that

[Details]
An image forming apparatus 500 according to the fifth embodiment will be described with reference to FIGS. FIG. 11 is a block diagram illustrating functions for performing control processing of the fixing device 50 according to the fifth embodiment. FIG. 12 is a diagram illustrating a sheet sensor 90 according to the fifth embodiment. FIG. 13 is a diagram illustrating a detection method using the paper sensor 90.

  As shown in FIG. 11, the image forming apparatus 100 according to the fifth embodiment includes a paper sensor 90 (slip detection unit). Specifically, as shown in FIG. 12, the first paper sensor 90 a and the second paper sensor 90 b are connected to the fixing member 60 with respect to the conveyance path 41 formed between the fixing member 60 and the pressure roller 65. It is provided so as to sandwich the contact portion with the pressure roller 65.

  As a result, as shown in FIG. 13, based on the time when the conveyance of the paper S is confirmed by the first paper sensor 90a and the time when the conveyance of the paper S is confirmed by the second paper sensor 90b. By measuring the passing time, the conveyance speed of the sheet S at the contact portion between the fixing member 60 and the pressure roller 65 can be obtained.

  When it is detected that the paper S is in a slip state in which the conveyance speed of the paper S is slower than a predetermined conveyance speed, the paper sensor 90 transmits an input signal to the pressure mechanism 54. The pressure mechanism 54 that has received the input signal controls the pressure contact motor 94 to improve the contact pressure between the fixing member 60 and the pressure roller 65.

  With the above configuration, when the determination unit 111 determines that the end of life has come to an end and the contact pressure between the fixing member 60 and the pressure roller 65 is reduced, the contact pressure is excessively reduced to cause slipping. A situation can be prevented from occurring.

<Sixth Embodiment>
[Overview]
In the sixth embodiment, the image forming apparatus 600 includes an operation panel 107 that can accept the type of paper to be prohibited from printing from a plurality of predetermined types of paper. This is different from the first embodiment.

[Details]
An image forming apparatus 600 according to the sixth embodiment will be described with reference to FIG. FIG. 14 is a block diagram illustrating a function for performing control processing of the fixing device 50 according to the sixth embodiment.

  As shown in FIG. 14, in the sixth embodiment, when the determination unit 611 determines that the end of life of the fixing device 50 has come based on the fluctuation rate of the rotational torque detected by the current sensor 96. In addition, the determination unit 611 transmits an input signal to the operation panel 107 provided in the image forming apparatus 600. The operation panel 107 that has transmitted the input signal can accept the type of paper to be prohibited from printing from a plurality of predetermined types of paper from the user.

  With the above configuration, it is not possible to use paper that requires particularly a contact pressure between the fixing member 60 and the pressure roller 65 in the fixing operation, for example, a thin paper having a low basis weight, and a paper jam due to a decrease in the contact pressure. Can be prevented from occurring.

  In addition, this indication is not limited to the said embodiment. For example, in the above embodiment, the current sensor 96 is configured to detect the torque fluctuation rate. However, for example, an absolute value of the torque may be detected. Even in this case, the same effect as that of the above embodiment can be obtained.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1C, 1K, 1M, 1Y Image forming unit, 10 photoconductor, 11 charger, 12 exposure unit, 13 developing unit, 13a adjustment unit, 14 developing roller, 15C, 15K, 15M, 15Y toner bottle, 17, 42 Cleaning blade , 30 Intermediate transfer belt, 31 Primary transfer roller, 32 Toner image, 33 Secondary transfer roller, 37 Cassette, 38 Driven roller, 39 Drive roller, 40 Timing roller, 41 Conveyance path, 48 tray, 50 Fixing device, 51 Fixing roller , 52 cored bar, 53 fixing belt, 54 pressure mechanism, 57 heating roller, 60 fixing member, 64 biasing mechanism, 65 pressure roller, 66 rotation motor, 90 sheet sensor, 90a first sheet sensor, 90b second sheet Sensor, 92 Pressing lever, 92a Cutout, 93 Pressing gear, 93a Convex part, 94 pressure contact motor, 95 pressure sensor, 96 current sensor, 97 transmission gear, 98 image information, 100, 200, 300, 400, 500, 600 image forming apparatus, 101, 201, 301, 401, 601 control apparatus, 102 ROM, 103 RAM, 104 network interface, 107 operation panel, 111, 211, 311, 411, 611 judgment unit, 112 pressure control unit, 113, 413 rotation control unit, 114 heating control unit, 115 estimation unit, 120 storage device 122 Control program.

Claims (12)

An image forming apparatus including a fixing device for fixing toner formed on a sheet to the sheet,
The fixing device includes:
A first rotating body;
A second rotating body provided to face the first rotating body;
By pressing one of the first rotating body and the second rotating body against the other, pressure is applied to the sheet passing between the first rotating body and the second rotating body, and the toner is applied to the sheet. A pressure mechanism for fixing;
A load detector for detecting a load of rotation of at least one of the first rotating body and the second rotating body,
The image forming apparatus further includes a control device for controlling the fixing device,
The control device includes:
A determination unit for determining whether or not the end of life of the fixing device has come based on the magnitude of the load detected by the load detection unit;
When the determination unit determines that the end of life has arrived, the pressurization is performed so that the contact pressure between the first rotating body and the second rotating body is lower than before the end of life has arrived. An image forming apparatus including a pressure control unit for controlling the mechanism. The fixing device further includes a heating mechanism for heating at least one heating target of the first rotating body and the second rotating body,
2. The image formation according to claim 1, wherein when the determination unit determines that the end of life has arrived, the heating mechanism raises the temperature of the heating target before the end of life reaches. apparatus. The control device further includes an estimation unit for estimating an amount of toner to be formed on the paper based on image information that defines a location where the toner should be adhered to the paper.
The heating mechanism increases the temperature of the heating target as the amount of toner estimated by the estimation unit increases when the determination unit determines that the end of life has come. The image forming apparatus described in 1. An adjustment mechanism for adjusting the amount of toner deposited on the paper;
The adjustment mechanism reduces the amount of toner adhering to the paper when the determination unit determines that the end of life has come, compared to before the end of life. The image forming apparatus according to any one of the above. The fixing device further includes a rotation mechanism for rotationally driving at least one rotation target of the first rotating body and the second rotating body,
5. The rotation mechanism according to claim 1, wherein when the determination unit determines that the end of life has arrived, the rotation mechanism makes the rotation speed of the rotation target slower than before the end of life reaches. The image forming apparatus according to claim 1. The load detector is
Detecting a variation rate of rotational torque in at least one of the first rotating body and the second rotating body as the load;
The image forming apparatus according to claim 1, wherein the determination unit determines that the end of life has arrived when the variation rate exceeds a predetermined threshold.   The image forming apparatus according to claim 1, wherein the pressure control unit further reduces the contact pressure as time passes after the contact pressure decreases.   The image forming apparatus according to claim 1, wherein the pressure control unit controls the pressurizing mechanism so as to maintain the contact pressure after the decrease after the decrease in the contact pressure. The image forming apparatus further includes a slip detection unit for detecting a slip state in which a transport speed of the paper between the first rotating body and the second rotating body is slower than a predetermined transport speed. Prepared,
The image forming apparatus according to claim 1, wherein the pressure control unit increases the contact pressure after the decrease when the slip detection unit detects the slip state. An operation unit that allows a user to select the type of paper;
The operation unit is configured to be able to accept a type of a sheet to be prohibited from printing from a plurality of predetermined types of sheets when it is determined by the determination unit that the end of life has come. The image forming apparatus according to any one of claims 1 to 9. A method of controlling a fixing device for fixing toner formed on a sheet to the sheet,
The fixing device includes:
A first rotating body;
A second rotating body provided opposite to the first rotating body,
The control method is:
By pressing one of the first rotating body and the second rotating body against the other, pressure is applied to the sheet passing between the first rotating body and the second rotating body, and the toner is applied to the sheet. Fixing, and
Detecting a rotation load of at least one of the first rotating body and the second rotating body;
Determining whether or not the end of life of the fixing device has come based on the magnitude of the load detected in the detecting step;
Lowering the contact pressure between the first rotating body and the second rotating body when it is determined in the determining step that the end of life has arrived, than before the end of life reaches. , Control method. A control program for a fixing device for fixing toner formed on a sheet to the sheet,
The fixing device includes:
A first rotating body;
A second rotating body provided opposite to the first rotating body,
The control program is stored in the fixing device.
By pressing one of the first rotating body and the second rotating body against the other, pressure is applied to the sheet passing between the first rotating body and the second rotating body, and the toner is applied to the sheet. Fixing, and
Detecting a rotation load of at least one of the first rotating body and the second rotating body;
Determining whether or not the end of life of the fixing device has come based on the magnitude of the load detected in the detecting step;
When it is determined in the determining step that the end of life has arrived, the step of lowering the contact pressure of the first rotating body and the second rotating body than before the end of life reaches is performed. Let the control program.

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