JP6668765B2 - Fixing device and image forming device - Google Patents

Description

  The present invention relates to a fixing device and an image forming device.

  In recent years, market demands for image forming apparatuses such as printers, copiers, facsimile machines, and the like for high quality, high speed, long life, and the like have become strong.

  In an image forming apparatus, an unfixed toner image is transferred to a recording material sheet, printing paper, photosensitive paper, electrostatic recording paper, or the like by an image transfer method or a direct method by an image forming process such as electrophotographic recording, electrostatic recording, or magnetic recording. It is formed on a recording medium. As a fixing device for fixing an unfixed toner image, a contact heating type fixing device such as a heat roller system, a film heating system, and an electromagnetic induction heating system is widely used (for example, see Patent Document 1).

  As shown in FIG. 12, in a fixing device 90 described in Patent Document 1, a pipe-shaped metal heat conductor 92 is provided inside an endless belt 91, and a metal heat conductor 93 in the metal heat conductor 92 is used. The endless belt 91 is heated via the intermediary belt 92. The fixing device 90 further includes a pressure roller 94. The pressure roller 94 contacts a metal heat conductor 92 via an endless belt 91 to form a nip portion N. The endless belt 91 moves in the circumferential direction by rotating with the rotation of the pressure roller 94. Then, the recording medium passing through the nip portion N is heated and pressed to perform the fixing process. With such a configuration, the entire endless belt 91 constituting the fixing device 90 can be warmed, so that the first print time from the heating standby state can be shortened, and the amount of heat during high-speed rotation can be reduced. It is possible to eliminate.

  However, in the above prior art, since the endless belt is indirectly heated via the metal heat conductor, the fixing belt is required to be true from the viewpoint of contact heat transfer of the heating unit and improvement of the separation property of the recording medium. The vehicle is running on a non-circular trajectory. For this reason, it is difficult to drive the fixing belt by attaching a gear or the like to the fixing belt side, and the driving mechanism becomes complicated. Further, since the inner surface of the endless belt slides while being pressed against a metal heat conductor or a nip forming member to be described later by a pressing force from a pressing roller, a driving load becomes relatively large. There is a tendency, and this tendency becomes particularly remarkable over time.

  Usually, when a fixing device having such a configuration is used, after providing a coating member / sheet having excellent slidability in the nip forming portion, the sliding load is further reduced by a lubricant such as oil or grease. Like that. However, parts wear and lubricant outflow over time are inevitable, and the driving load increases.

  Usually, a motor is used to drive the pressure roller via a gear, but an approximate unit usable life is determined based on a traveling distance (number of sheets passed) that reaches an allowable torque of the motor. However, this depends largely on the frequency of use, and the higher the duty mode in which the heat load of fixing is large, the shorter the possible travel distance tends to be.

  Conventional general maintenance services include setting a replacement life of a fixing unit based on the number of rotations (travel distance) of components inside the fixing unit and the number of sheets passed, and then replacing the fixing unit when the life is over. Was something. However, such a life setting is based on a high duty usage frequency from the viewpoint of guarantee. In the case of a fixing unit having a high duty cycle, the fixing heat load is relatively large, so that the wear of the fixing belt and the outflow of the lubricant become more remarkable, and the driving torque of the motor is greatly increased accordingly. On the other hand, most of the fixing units which are used at a low duty frequency have a small heat load, so that the wear of the parts is small, and the fixing unit is replaced with a sufficient margin up to the allowable torque of the drive motor. Since the replacement is performed before the end of the replacement life, the cost and the environment are not desirable.

  Further, in a fixing unit having a duty usage frequency as high as assumed in the setting of the replacement life, the driving torque of the motor for driving the pressure roller may exceed the allowable torque earlier than the set life. In such a case, there is a concern that a failure such as breakage of parts of the fixing unit occurs, the image forming apparatus is completely stopped, and it takes more time to repair.

  The present invention has been made in order to solve such a problem, and can be used up to the net replacement life regardless of the frequency of use, and prevent the entire device from stopping functioning due to failure due to replacement delay. It is an object of the present invention to provide a fixing device and an image forming apparatus that can prevent the occurrence of a problem.

In order to achieve the above object, a fixing device according to the present invention includes a rotatable fixing member, a heating source for heating the fixing member, and a temperature for adjusting a heating value of the heating source and controlling a temperature of the fixing member. A control unit, a pressing member forming a nip with the fixing member, a nip forming member facing the pressing member inside the fixing member to form the nip, and a nip forming member via the fixing member. A pressurizing and depressurizing means for pressurizing and depressurizing the pressurizing member, a driving means for driving the pressurizing member, and a driving load detecting means for detecting a driving load amount of the driving means; When the driving load amount detected by the detecting means exceeds a set value, the pressurizing and depressurizing means operates on the depressurizing side, and the pressurizing and depressurizing means moves to the depressurizing side according to the detection result of the driving load detecting means. The temperature control means. There and adjusting the heating value of the heating source on the side to raise the temperature of the fixing member.

  ADVANTAGE OF THE INVENTION According to the present invention, a fixing device and an image forming apparatus that can be used up to a net replacement life regardless of the frequency of use, and can prevent a functional stop of the entire apparatus due to a failure due to a delay in replacement. Can be provided.

1 is an overall configuration diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a partial cross-sectional view of the fixing device according to the first exemplary embodiment of the present invention. FIG. 3 is a block diagram of a control and drive system of the fixing device according to the first embodiment of the present invention. FIG. 2 is a schematic configuration diagram illustrating a normal state of a cam mechanism of the fixing device according to the first exemplary embodiment of the present invention. FIG. 2 is a schematic configuration diagram illustrating a pressure-removed state of a cam mechanism of the fixing device according to the first exemplary embodiment of the present invention. 6 is a graph illustrating a relationship between a pressing force and a driving load torque of the fixing device according to the first exemplary embodiment of the present invention. 5 is a graph illustrating a relationship between a pressing force and a nip width of the fixing device according to the first exemplary embodiment of the present invention. FIG. 9 is a partial cross-sectional view of a fixing device according to a second embodiment of the present invention. FIG. 11 is a partial cross-sectional view of a fixing device according to a third embodiment of the present invention. FIGS. 7A and 7B are schematic perspective views of a light shielding member of a fixing device according to a third embodiment of the present invention, wherein FIG. FIG. 10 is a development view of a light blocking member of a fixing device according to a third embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a fixing device of Patent Document 1.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First Embodiment)
First, the configuration will be described.
As shown in FIG. 1, the image forming apparatus 1 has an image forming unit 103 of a tandem type color printer. Four toner bottles 102Y, 102M, 102C, and 102K corresponding to respective colors (yellow, magenta, cyan, and black) are removably installed in a bottle storage unit 101 above the main body of the image forming apparatus 1. For this reason, these four toner bottles 102Y, 102M, 102C, and 102K can be replaced by a user or the like.

  An intermediate transfer unit 85 is provided below the bottle storage unit 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are provided in the image forming units 4Y, 4M, 4C, and 4K, respectively. A charging unit 75, a developing unit 76, a cleaning unit 77, a charge removing unit, and the like are provided around each of the photosensitive drums 5Y, 5M, 5C, and 5K. Then, on each of the photoconductor drums 5Y, 5M, 5C, and 5K, an image forming process (a charging process, an exposure process, a development process, a transfer process, and a cleaning process) is performed. An image of each color is formed on 5K.

  The photosensitive drums 5Y, 5M, 5C, and 5K are driven to rotate clockwise in FIG. 1 by a drive motor. Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging section 75 (this is a charging step). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser beam L emitted from the exposure unit 3, and an electrostatic latent image corresponding to each color is formed by exposure scanning at this position. (This is an exposure step).

  Thereafter, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach the positions facing the developing unit 76, where the electrostatic latent images are developed, and toner images of each color are formed. Is). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K. , 5C and 5K are transferred onto the intermediate transfer belt 78 (this is a first transfer step). At this time, untransferred toner slightly remains on the photosensitive drums 5Y, 5M, 5C, and 5K.

Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the position facing the cleaning unit 77, and the untransferred toner remaining on the photosensitive drums 5Y, 5M, 5C, and 5K at this position is removed by the cleaning unit. It is mechanically collected by a cleaning blade 77 (this is a cleaning step).
Finally, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach the positions facing the static elimination unit, and at this position, the residual potential on the photoconductor drums 5Y, 5M, 5C, and 5K is removed. Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

  Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 78 in a superimposed manner. Thus, a color image is formed on the intermediate transfer belt 78. Here, the intermediate transfer unit 85 includes four primary transfer bias rollers 79Y, 79M, 79C, 79K of the intermediate transfer belt 78, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning unit 80. Etc. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84, and is moved endlessly in the direction of the arrow in FIG.

  The four primary transfer bias rollers 79Y, 79M, 79C, and 79K respectively sandwich the intermediate transfer belt 78 between the photosensitive drums 5Y, 5M, 5C, and 5K to form primary transfer nips. Then, a transfer bias opposite to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. Then, the intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. Thus, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are primary-transferred onto the intermediate transfer belt 78 in a superimposed manner.

  Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and the secondary transfer roller 89 to form a secondary transfer nip. Then, the four color toner images formed on the intermediate transfer belt 78 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip. At this time, untransferred toner not transferred to the recording medium P remains on the intermediate transfer belt 78. Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. Then, at this position, the untransferred toner on the intermediate transfer belt 78 is collected. Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

  Here, the recording medium P conveyed to the position of the secondary transfer nip is conveyed from the paper supply unit 12 disposed below the main body via the paper supply roller 97 and the registration roller pair 98 and the like. It is. More specifically, a plurality of recording media P such as transfer papers are stored in the paper supply unit 12 in a stacked manner. When the paper feed roller 97 is driven to rotate in the counterclockwise direction in FIG. 1, the uppermost recording medium P is fed between the registration rollers 98.

  The recording medium P conveyed to the registration roller pair 98 temporarily stops at the position of the roller nip of the registration roller pair 98 whose rotation has been stopped. Then, the registration roller pair 98 is driven to rotate in synchronization with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. Thus, a desired color image is transferred onto the recording medium P.

  Thereafter, the recording medium P on which the color image has been transferred at the position of the secondary transfer nip is transported to the position of the fixing device 20. Then, at this position, the color image transferred to the surface is fixed on the recording medium P by the heat and pressure by the fixing belt 22 and the pressure roller 21. After that, the recording medium P is discharged to the outside of the apparatus via a pair of paper discharge rollers 99. The recording medium P having the transferred image discharged outside the apparatus by the discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image. Thus, a series of image forming processes in the image forming apparatus is completed.

  Next, the configuration of the fixing device 20 will be described in detail with reference to FIG.

  As shown in FIG. 2, the fixing device 20 includes a pressure rotating body (a pressure roller 21 in FIG. 2) and a fixing belt 22 in the device, and a heat source (a halogen heater in the example of FIG. 2) 23 As a result, the fixing belt 22 is directly heated by radiant heat from the inner peripheral side.

  At this time, inside the fixing belt 22 shown in FIG. 2, there is a nip forming member 24 that forms a nip portion N with the pressure roller 21 opposed to the fixing belt 22 via the fixing belt 22. (Indirectly via a sliding sheet not shown).

  In FIG. 2, the shape of the nip portion N is flat, but may be a concave shape or another shape (the concave shape of the nip portion N increases the discharge direction of the leading end of the recording medium P). This is closer to the pressure roller 21 and the separability is improved, so that the occurrence of jam is suppressed.)

  As shown in FIG. 2, the fixing belt 22 is a metal belt such as nickel or SUS or an endless belt (or film) using a resin material such as polyimide. The belt surface layer has a release layer 22b such as a PFA or PTFE layer, and has a release property so that toner does not adhere. An elastic layer 22c formed of a silicone rubber layer or the like is provided between the belt base material 22a and the release layer 22b. When the elastic layer 22c is not provided, the heat capacity is reduced and the fixing property is improved. This causes a problem that gloss unevenness (yuzu skin image) remains. In order to improve this, it is necessary to provide the elastic layer 22c of 100 [μm] or more. Due to the deformation of the elastic layer 22c, minute unevenness is absorbed, and the skin image of Yuzu is improved.

  A support member 25 (stay) for supporting the nip portion N is provided inside the fixing belt 22 to prevent the nip forming member 24 from being bent by the pressure of the pressure roller 21 and to provide a uniform nip in the axial direction. I am trying to get the width. The support member 25 is held and fixed by a holding member 26 (flange) at both ends in the rotation axis direction of the fixing belt 22 and is positioned. In addition, a reflection member 27 is provided between the heat source 23 and the support member 25, thereby suppressing unnecessary energy consumption due to the support member 25 being heated by radiant heat from the heat source 23 or the like. Here, the same effect can be obtained even if the surface of the support member 25 is heat-insulated or mirror-finished instead of having the reflection member 27.

  The heat source 23 may be a halogen heater as shown, but may be an IH (Induction Heating), a resistance heating element, a carbon heater, or the like.

  The pressure roller 21 has a core 28 covered with an elastic rubber layer 29, and has a release layer (PFA or PTFE layer) on its surface to obtain releasability. The pressure roller 21 is rotated by a driving force transmitted from a pressure roller driving device (see FIG. 3) 30 such as a motor provided in the image forming unit 103 via a reduction mechanism including a gear and the like. Further, the pressure roller 21 is pressed against the fixing belt 22 by a pressure depressurizing device 59 (see FIG. 4) as a cam mechanism, and the elastic rubber layer 29 is crushed and deformed so that a predetermined nip is formed. It has a width. The pressure roller 21 may be a hollow roller, and the pressure roller 21 may have a heating source such as a halogen heater. The elastic rubber layer 29 may be solid rubber, but if there is no heater inside the pressure roller 21, sponge rubber may be used. Sponge rubber is more preferable because it enhances heat insulation and makes it difficult to remove heat from the fixing belt.

  The fixing belt 22 is rotated by the pressure roller 21. In the case of FIG. 2, the pressure roller 21 is rotated by the pressure roller driving device 30, and the driving force is transmitted at the nip N, so that the fixing belt 22 is rotated. The fixing belt 22 rotates while being nipped by the nip portion N, and travels at both ends except the nip portion while being guided by the holding member 26 (flange).

  With the above-described configuration, the fixing device 20 can be inexpensive and can warm up quickly.

Next, a control / drive system of the image forming apparatus 1 according to the present embodiment will be described.
As shown in FIG. 3, the image forming apparatus 1 includes a main body control unit 51, a first sensor 55, a second sensor 56, a temperature sensor 57, a paper ejection sensor 58, and a heater driving device 60 (temperature control unit). ), A pressure roller driving device 30 (driving means), a driving load sensor 36 (driving load detecting means), a pressure depressurizing device 59 (pressure depressurizing means), and an alarm 62. I have.

  The main body control unit 51 performs a central processing unit (CPU) 52 that performs various operations for controlling the image forming unit 103, a read only memory (ROM) 53 that is a read-only memory, and a random access memory (RAM) for temporary storage. ) 54, and an input / output interface. The main body control unit 51 executes a control program stored in the ROM 53 while using the temporary storage function of the RAM 54.

  Specifically, the main body control unit 51 is configured such that a first sensor 55, a second sensor 56, a temperature sensor 57, a paper discharge sensor 58, and a drive load sensor 36 are electrically connected to an input side, and an output side. A pressure depressurizing device 59, a heater driving device 60, a pressure roller driving device 30, and an alarm 62, which will be described later, are electrically connected.

  The first sensor 55 is a known sensor that detects the first filler portion, and is disposed at a position where the first filler portion is detected when the contact roller moves to the first position. Here, the first position means a position where the amount of deformation that allows deformation of the fixing belt 22 can be detected, and is set to a position where the fixing temperature rise time is not significantly reduced.

  The second sensor 56 is a known sensor that detects the second filler portion, and is disposed at a position where the second filler portion is detected when the contact roller moves to the second position. Here, the second position means a position where the amount of deformation of the fixing belt 22 that cannot be deformed can be detected.

  The temperature sensor 57 is formed of a known thermistor or the like, and is provided to face the surface of the fixing belt 22. The temperature sensors 57 are disposed in the central region and the end region in the longitudinal direction of the fixing belt 22, detect the temperature of the fixing belt 22, and provide temperature information to the main body control unit 51. The main body controller 51 functions as a temperature controller that controls the temperature of the fixing belt 22 by controlling the power supplied to the heat source 23 via the heater driving device 60 based on the temperature information from the temperature sensor 57. .

  The paper discharge sensor 58 is provided in the paper discharge path on the discharge side of the nip portion N, detects the paper discharge information, and gives it to the main body controller 51.

  The alarm 62 issues an alarm signal or the like when the driving load of the pressure roller driving device 30 exceeds a set value. Here, the alarm signal and the like mean a buzzer sound, a lamp display, and the like.

  The heater driving device 60 is connected to an external power supply and the heat source 23, and controls electric power supplied from the power supply to the heat source 23 based on a control signal from the main body control unit 51. Therefore, the heat source 23 is controlled by the heater driving device 60 to have a desired lighting rate.

  The pressure roller driving device 30 includes a drive motor 32 for driving the pressure roller 21 to rotate, and a motor driver 34 for driving the drive motor 32. The drive motor 32 is a DC motor whose output torque is proportional to the drive current. The motor driver 34 supplies a drive current for driving the drive motor 32 to the drive motor 32 based on a control signal from the main body control unit 51.

  The driving load sensor 36 detects a driving load amount of the pressure roller driving device 30 and provides information on the driving load amount to the main body control unit 51. Specifically, the driving load sensor 36 is a current sensor that acquires the value of the driving current of the pressure roller driving device 30. The main body controller 51 can obtain information on the output torque, which is the drive load of the drive motor 32, from the value of the drive current. The drive load sensor 36 may have a configuration in which a torque converter is separately provided on a motor shaft or the like of the drive motor 32 instead of the current sensor.

  The main body control unit 51 operates the pressure depressurizing device 59 to the depressurizing side when the driving load amount of the pressing roller driving device 30 obtained from the driving load sensor 36 exceeds a predetermined value. , A control signal is sent to the pressure depressurizing device 59. At the same time, when the pressurizing and depressurizing device 59 is operated on the depressurizing side, the main body control unit 51 controls to increase the temperature of the fixing belt 22 via the heater driving device 60.

  As shown in FIG. 4, the pressure depressurizing device 59 is configured using a cam mechanism. The pressurizing / depressurizing device 59 is configured such that a cam plate 64 connected to a cam driving motor 63 as a driving source presses a cantilever-supported lever 65 so that the nip forming member 24 is fixed to the nip forming member 24 via the fixing belt 22. The pressure roller 21 is pressurized or depressurized. Here, an end of the lever 65 is connected to a housing of the image forming apparatus 1 via a spring member 66. Therefore, when pressed by the cam plate 64, the lever 65 presses the cam plate 64 against the spring member 66. Further, as shown in FIG. 5, when the pressing force from the cam plate 64 is lost, the lever 65 returns to the return position by the elastic restoring force accumulated in the spring member 66.

  In the normal state in which the recording medium P is conveyed and fixed, the driving load torque of the driving motor 32 of the pressure roller driving device 30 is equal to or less than a predetermined torque (or a driving current value corresponding thereto). In this case, the rotation stop position of the cam plate 64 is determined so that the pressing force applied from the pressure roller 21 to the nip forming member 24 via the fixing belt 22 becomes an appropriate pressing force. In the following description, it is assumed that the maximum pressure in the normal state and the nip width of the fixing device 20 obtained by the maximum pressure are 100% (FIGS. 6 and 7).

  As shown in FIG. 5, the depressurized state of the pressurizing / depressurizing device 59 is a mode to shift to when the predetermined drive load torque of the drive motor 32 is exceeded.

  FIG. 6 shows a relationship between the pressing force applied to the nip forming member 24 from the pressing roller 21 via the fixing belt 22 and the driving load torque output by the driving motor 32 of the pressing roller driving device 30. FIG. 7 shows the relationship between the pressing force and the nip width of the fixing device 20. As time passes, the drive load torque of the drive motor 32 gradually increases. Regarding the relationship between the pressing force and the nip width, from the new state to the time when the driving load torque is increased over time, the driving load torque is reduced from a low value to 100% at a pressing force of 100% (permissible of the pressing roller driving device 30). (A value set in consideration of torque or a margin). When the torque reaches 100%, if it is further rotated and driven at a pressing force of 100%, parts may be damaged. However, the driving load torque of the pressure roller driving device 30 may be reduced by rotating the cam plate 64 and removing the pressure. it can.

  However, when the pressing force is reduced, a decrease in the nip width cannot be avoided. Since the surface temperature of the fixing belt 22 is set with some allowance for cold offset (toner peeling), there is no concern about image defects unless a significant decrease in the nip width is used. In some cases, it is assumed that the allowable torque is greatly exceeded at a pressing force of 100%, so that the allowable torque may not be satisfied unless the pressing force is significantly reduced. In such a case, by adding the temperature correction of the fixing belt 22 according to the nip width, the power consumption is increased, but the image quality can be secured.

  Note that the depressurized state shown in FIG. 5 is a limited mode that shifts when the allowable torque is exceeded. When it is detected that the allowable torque has been exceeded in the normal state of the applied pressure of 100%, a display for prompting replacement is turned on on the monitor or a replacement instruction alarm is transmitted to a maintenance service person. good. Although torque over is a major factor in the unit life, the surface release layer of the fixing belt 22 and the pressure roller 21 also wears due to the conveyance of the recording medium. Jams and the like due to defects frequently occur. The mode of the decompression state is used as a temporary response means from when the replacement alarm is issued to when the replacement is performed.

  In the present embodiment, the drive load sensor 36 detects the drive load of the pressure roller driving device 30 that drives the pressure roller 21, and when the drive load exceeds a set value, the main body control unit 51 operates the pressure depressurizing device 59 on the depressurizing side. As a result, the machine can be used up to the net replacement life (torque life) irrespective of the frequency of use, and it is possible to prevent the machine from completely stopping due to a failure due to a delay in replacement.

  Further, in the present embodiment, when the main body controller 51 operates the pressurizing and depressurizing device 59 on the depressurizing side, the main controller 51 raises the temperature of the fixing belt 22 via the temperature control means such as the heater driving device 60. Control. As a result, when the pressure is released to reduce the driving load torque, the nip width is reduced. However, there is a concern that the power consumption may be slightly deteriorated by increasing the temperature of the fixing belt 22 according to the depressurized amount (the nip width reduced amount). In some cases, image quality troubles such as toner offset can be avoided.

  Further, in the present embodiment, a DC motor is used as the drive motor 32 of the pressure roller drive device 30, and the drive current value of the DC motor is used for detecting the drive load, so that an inexpensive machine can be provided. Since it is sufficient to detect the drive current value to grasp the load state, a separate torque converter or the like is not required, and an increase in the size of the device can be avoided.

  Further, in the present embodiment, the pressure depressurizing device 59 uses a cam mechanism, and the pressure depressurizing (depressurizing) amount can be adjusted steplessly by the surface shape of the cam plate 64, and the configuration can be simplified. .

  Further, in the present embodiment, when a drive current value corresponding to a value exceeding the allowable torque of the pressure roller driving device 30 is detected, an alarm signal is issued to visually prompt the exchange, or a service person is notified of the exchange. Or send. Thus, since the fixing device 20 is replaced before the failure, it is possible to prevent a trouble such as a complete stoppage of the machine due to a unit failure.

  Further, in the present embodiment, the fixing device 20 can be used up to near the net replacement life (allowable torque) of the pressure roller driving device 30, and the fixing device 20 having a usage frequency exceeding the assumed Duty is used before the failure. Therefore, the image forming apparatus 1 can be provided with low environmental load and high reliability.

(Second embodiment)
Next, a second embodiment of the present invention will be described.
As shown in FIG. 8, in the fixing device 120 according to the second embodiment of the present invention, the heat source 23 in the first embodiment shown in FIG. However, the difference is that the heat source 23 is constituted by three halogen heaters. The other configuration is the same, and the description is omitted. For example, in FIG. 8, the pressure roller driving device 30 (see FIG. 2) and the pressure reducing device 59 (see FIG. 4) are not shown.

  In the present embodiment, since the light emitting (heating) locations of the respective heat sources 23 are different, productivity can be ensured by selecting the heat sources 23 to be turned on according to various paper sizes.

(Third embodiment)
Next, a third embodiment of the present invention will be described.
As shown in FIG. 9, the fixing device 130 according to the third embodiment of the present invention has a configuration including a light shielding member 131 in addition to the configuration of the second embodiment shown in FIG. 9, the pressure roller driving device 30 (see FIG. 2) and the pressure reducing device 59 (see FIG. 4) are not shown.

As shown in FIG. 10, the shape of the light shielding member 131 is, for example, a three-stage shape provided with a light shielding area corresponding to each paper width for A3 paper passage and postcard paper passage. It has a stepped shape with two steps 132 and a second and third steps 134.
As shown in FIG. 11, as the shape of the light blocking member 131, for example, a step 132 between the first step and the second step according to the width of A3 paper, B4 paper, and postcard paper is used. The step 133 of the second step and the third step and the step 134 of the third step and the fourth step may have a stepped shape.

  The light shielding member 131 is arranged so as to rotate in a non-contact manner along the inside of the fixing belt 22, and has a function of rotating to a position corresponding to each paper width to shield an area unnecessary for heating.

  In the present embodiment, even when the recording medium P having a narrow paper width is continuously passed, the non-paper passing area does not become in an excessively high temperature state, and control such as lowering the productivity to cool the excessively high temperature area is performed. No need to do. Along with this, the number of halogen heaters can be reduced from three in the second embodiment shown in FIG. 8 to two, and energy saving can be achieved.

  As described above, according to the present invention, it is possible to use up the entire replacement life irrespective of the frequency of use, and to prevent a failure of the entire apparatus due to a failure due to a delay in replacement. This is useful for fixing apparatuses and image forming apparatuses in general.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 20, 120, 130 Fixing apparatus 21 Pressure roller (Pressure member)
22 Fixing belt (fixing member)
23 heat source (heating source)
24 Nip forming member 30 Pressure roller driving device (driving means)
32 Drive motor (drive means)
36 Drive load sensor (drive load detection means)
59 Pressure depressurizing device (Pressure depressurizing means)
60 heater driving device (temperature control means)
103 Image forming part N Nip part (nip)
P Recording medium

JP 2007-334205A

Claims (5)

A rotatable fixing member,
A heating source for heating the fixing member,
A temperature control unit that adjusts a heating value of the heating source and controls a temperature of the fixing member;
A pressure member forming a nip with the fixing member;
A nip forming member that faces the pressure member inside the fixing member and forms the nip;
Pressure depressurizing means for depressurizing the nip forming member and the pressing member via the fixing member;
Driving means for driving the pressure member,
A drive load detecting means for detecting a drive load amount of the driving means,
When the driving load amount detected by the driving load detecting means exceeds a set value, the pressurizing and depressurizing means operates on the depressurizing side ,
When the pressurizing and depressurizing means operates on the depressurizing side according to the detection result of the driving load detecting means, the temperature control means adjusts the heat generation amount of the heating source to the side that increases the temperature of the fixing member. Fixing device. DC motor is used as the drive means, the fixing device according to claim 1, wherein the driving load detecting means and detecting the drive load on the basis of the drive current value of the DC motor. The fixing device according to claim 1 or 2, characterized in that the cam mechanism is used as the pressurizing圧脱pressure means. The driving load when the detection means driving load amount detected exceeds a set value, the fixing device according to claim 1 to 3 any one, characterized in that an alarm signal. In an image forming apparatus including: an image forming unit that forms an image on a recording medium; and a fixing unit that performs a fixing process on the recording medium on which the image is formed by the image forming unit. an image forming apparatus comprising according to claim 1-4 that equipped with the fixing device according to any one.

Images