JP2017129710A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus equipped with a fixing device using a belt realizes stable belt shift regulation. When the temperature of the fixing device becomes a predetermined value or less at the start of belt driving, an initial adjustment of the steering angle related to the belt shift control of the fixing device is automatically performed. [Selection] Figure 1A

Description

  The present invention relates to an image forming apparatus.

  In general, in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, an unfixed toner image is formed on a sheet-like recording material, and the toner image is heated and pressed by a fixing device on the recording material. It has become established.

  In order to increase the glossiness of the image and increase the speed of image formation, it is preferable to sufficiently melt the toner by widening the fixing nip portion (width in the recording material conveyance direction). Therefore, in recent years, a fixing device of a belt fixing method that can widen the fixing nip portion while reducing the size of the device as compared with the conventional roller fixing method has been put into practical use.

  In a belt nip type fixing device using a so-called endless belt such as a fixing belt or a pressure belt as a fixing member, an important problem is a belt shifting operation. When the belt is shifted, that is, while the belt is rotating, the belt moves toward the end of the belt in the longitudinal direction (width direction) and shifts away, so that the belt falls off from the belt running area (predetermined zone) or the belt end Problems such as contact with external parts occur.

  Further, if the reciprocating speed is too fast even if the belt is not displaced, there is a problem that the behavior of the recording material that is nipped and conveyed by the fixing nip is difficult to stabilize. This is because the recording material sandwiched at the fixing nip is affected by the reciprocating movement of the belt. The higher the speed of the belt in the reciprocating direction, the greater the amount of movement in the same recording material. Occur.

  With respect to these two problems, Patent Document 1 provides a means for detecting the belt shift position. Then, when it is detected that one end in the width direction of the belt has reached a predetermined position due to the deviation movement, the inclination direction of the belt is changed so that the movement direction of the belt is changed to the other end side in the belt width direction. Furthermore, a belt shift control method has been proposed in which the durability of fixing is predicted using the number of recording materials introduced to the fixing device, and the shift speed in the belt width direction is changed to prevent the belt from shifting.

Japanese Patent Laid-Open No. 5-100588

  The present invention is a further development of the above prior art. The object is to realize stable belt deviation regulation in an image forming apparatus equipped with a fixing device using a belt.

  In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention includes a printing unit that forms a toner image on a recording material, and a nip unit that heats the toner image formed on the recording material. A pair of rotating bodies, at least one of which is an endless belt, a support member that rotatably supports the endless belt, a driving unit of the rotating body, and a temperature detection unit that detects the temperature of the rotating body, A detection unit that detects that the endless belt has deviated from a predetermined zone in the width direction, and one end in the longitudinal direction of the support member according to the output of the detection unit so that the endless belt returns to the predetermined zone The endless belt is moved by selectively displacing the endless belt from a reference position to a first position and from the reference position to a second position opposite to the first position by a predetermined inclination amount. A displacement mechanism that reciprocates in the direction, a time measuring unit that measures a moving time between one end side and the other end side in the width direction of the endless belt detected by the detection unit, and the reciprocation timed by the time measuring unit. A tilt amount correcting unit that corrects the tilt amount so that the one-way time of movement approaches a predetermined value, a storage unit that stores the corrected tilt amount, and an tilt amount that returns the stored tilt amount to an initial value When the temperature detected by the temperature detection unit is equal to or lower than a predetermined value when the driving unit starts driving from the state where the rotating unit stops the rotating body, the inclination amount initialization unit sets the inclination amount. And a control unit for initialization.

  According to the present invention, stable belt shift regulation can be realized in an image forming apparatus equipped with a fixing device using a belt.

Steering angle initialization and adjustment flowchart (part 1) Steering angle initialization and adjustment flowchart (part 2) Steering angle adjustment flowchart (part 1) Steering angle adjustment flowchart (part 2) Configuration schematic diagram of image forming apparatus of embodiment Schematic diagram of the left side of the fixing device of the embodiment Cross-sectional schematic diagram of the device Explanatory drawing of the sensor unit on the heating belt unit side Explanatory drawing of the belt displacement mechanism on the heating belt unit side Illustration of steering operation of belt reciprocation control Illustration of belt position detection logic by sensor Block diagram of control system

[Example 1]
(Image forming part)
FIG. 3 is a schematic configuration diagram of an example of the image forming apparatus. The image forming apparatus 1 includes an image processing unit (printing unit) 210 for forming a toner image on a recording material (paper: hereinafter referred to as a sheet) S. In this embodiment, the image processing unit 210 includes four image forming units U (UY, UM, UC, UK) of yellow (Y), magenta (M), cyan (C), and black (K). .

  In each image forming unit U, the photosensitive drum (image carrier) 2 charged by the charging roller 3 is input to the CPU circuit unit (control unit) 200 from the external host device 23 via the external I / F processing unit 230. Laser light is exposed from the laser scanner 4 in accordance with the information. Thereby, an electrostatic latent image corresponding to the exposure pattern is formed on each photosensitive drum 2. The external host device 23 is a personal computer, an image reader, a facsimile, a network, or the like.

  The electrostatic latent image formed on each photosensitive drum 2 is developed as a toner image of each color using the toner of each color by the developing device 5. The formed toner images of respective colors are transferred onto the intermediate transfer belt 8 by the primary transfer roller 6 to form a full color toner image.

  On the other hand, the sheet S accommodated in the cassette 15 or 16 is conveyed on the conveyance path 17 by the feeding roller 11, the conveyance roller 12, and the registration roller 18, and the intermediate transfer belt 8 and the secondary transfer roller (transfer means) 14 are transferred. Is conveyed to a secondary transfer nip portion which is a pressure contact portion. The sheet S conveyed to the secondary transfer nip portion is secondarily transferred with the full color toner image, and is conveyed to the fixing device 100 through the conveyance path 19. The sheet S is heated and pressed by the fixing device 100 to be fixed with the toner image, and is discharged as a printed product to the discharge tray 21 by the discharge roller 20.

  The CPU circuit unit 200 controls all devices of the image forming apparatus 1 and sequence control of image forming operations (printing operations). Reference numeral 24 denotes an operation unit (user interface) for inputting various types of information to the CPU circuit unit 200, which has a display unit such as a liquid crystal touch panel and displays various types of information on the display unit by the CPU circuit unit 200. .

(Fixing device)
4 is a left side view of the fixing device 100, and FIG. 5 is a cross-sectional view of the same device. In this embodiment, the front surface of the fixing device 100 is a surface on the sheet entrance side, and the back surface is a surface on the sheet exit side. Left and right are left or right when the device is viewed from the front, the left side is the front side or one end side, and the right side is the back side or the other end side. Up and down is up or down in the direction of gravity. Upstream or downstream is upstream or downstream with respect to the conveyance direction (recording material conveyance direction) V of the sheet S.

  The fixing device 100 is a twin belt nip type and electromagnetic induction heating (IH) type image heating device. Broadly divided, it has a heating belt unit A, a pressure belt unit B, an IH heater (heater: induction heating coil) 135, and a housing 140 that accommodates these.

  The heating belt unit A has an endless heating belt (endless belt) 130 as a first rotating body. In addition, a plurality of support rollers (belt stretching rollers: support members) that rotatably support (suspend) the heating belt 130 from the inner surface side, here, a driving roller 131 and a tension roller 132 that applies tension to the belt are provided. Have. Moreover, it has the pad stay 137 formed, for example with stainless steel (SUS material). The IH heater 135 is a heating unit that dielectrically heats the heating belt 130 and includes the heating belt 13 induction heating coil (excitation coil).

  The heating belt 130 may be appropriately selected as long as it generates heat by the IH heater 135 and has heat resistance. For example, a magnetic metal layer such as a nickel metal layer or a stainless steel layer having a thickness of 75 μm, a width of 380 mm, and a circumferential length of 200 mm is coated with, for example, 300 μm of silicon rubber, and a surface layer is coated with a PFA tube.

  The drive roller 131 is a roller in which a heat-resistant silicon rubber elastic layer is integrally formed on a core metal surface layer having an outer diameter of φ18 made of solid stainless steel, for example. The tension roller 132 is a hollow roller formed of stainless steel, for example, with an outer diameter of about 20 mm and an inner diameter of about 18 mm.

  The tension roller 132 and the driving roller 131 are disposed substantially parallel to the upstream side and the downstream side in the sheet conveying direction V with a predetermined interval therebetween. The pad stay 137 is disposed between the tension roller 132 and the driving roller 131 so as to be close to the driving roller 131 and parallel to the driving roller 131. The heating belt 130 is stretched between the driving roller 131, the tension roller 132, and the pad stay 137 with a predetermined tension (for example, 200 N).

  The pressure belt unit B has an endless pressure belt (endless belt) 120 as a second rotating body. Further, a plurality of support rollers (belt stretching rollers: support members) that rotatably support (suspend) the pressure belt 120 from the inner surface side, here, the pressure roller 121 and a tension roller that applies tension to the belt 122. Moreover, it has the press pad 125 formed, for example with rubber | gum. The pressure pad 125 is covered with a sliding sheet 128. An oil application roller (lubricant application member) 126 is also provided.

  The pressure belt 120 may be appropriately selected as long as it has heat resistance. For example, a nickel metal layer having a thickness of 50 μm, a width of 380 mm, and a circumferential length of 200 mm is coated with, for example, a 300 μm-thick silicon rubber and a surface layer is coated with a PFA tube. The pressure roller 121 is a roller having an outer diameter of φ20 made of, for example, solid stainless steel. The tension roller 122 is a hollow roller made of stainless steel, for example, having an outer diameter of about 20 mm and an inner diameter of about 18 mm.

  The tension roller 122 and the pressure roller 121 are disposed substantially parallel to the upstream side and the downstream side in the sheet conveying direction V with a predetermined interval therebetween. The pressure pad 125 is disposed between the tension roller 122 and the pressure roller 121 so as to be close to the pressure roller 121 and parallel to the pressure roller 121. The oil application roller 126 is disposed between the pressure pad 125 and the tension roller 122 in parallel with the tension roller 122. The pressure belt 120 is stretched between the pressure roller 121, the tension roller 122, the pressure pad 125, and the oil application roller 126 with a predetermined tension (for example, 200 N).

  As shown in FIG. 6, the oil application roller 126 is rotatably supported by an arm 127 that is rotatably supported around a shaft portion 122 a of the tension roller 122. The arm 127 is rotationally biased by a biasing member (not shown) such as a spring in a direction in which the oil application roller 126 comes into contact with the inner surface of the pressure belt 120.

  The oil application roller 126 includes a heat-resistant aramid felt impregnated with a heat-resistant silicone oil having a viscosity of about 1000 CS as a lubricant so that a certain amount of oil is supplied (applied) to the inner surface of the pressure belt 120. It is configured. As a result, the frictional force between the inner surface of the pressure belt 120 and the sliding sheet 128 covering the pressure pad 125 is reduced, and the durability is improved. The heat-resistant silicone oil supplied to the inner surface of the pressure belt 120 is also applied to the surfaces of the pressure roller 121 and the tension roller 122 via the inner surface of the pressure belt 120.

  The pressure belt unit B is disposed below the heating belt unit A. The pressurizing unit B is pressed against the heating unit A with a predetermined pressing force by a pressurizing operation of a pressurizing mechanism which is not described here.

  In this pressure state, the driving roller 131 and the pressure roller 121 are pressed against each other with a predetermined pressing force with the heating belt 130 and the pressure belt 120 interposed therebetween. The driving roller 131 is one in which the elastic layer is elastically distorted by a predetermined amount by the pressure contact of the pressure roller 121. Further, the pad stay 137 and the pressure pad 125 are pressed against each other with a predetermined pressing force (for example, 400 N) with the heating belt 130 and the pressure belt 120 interposed therebetween. Accordingly, a wide nip portion (fixing nip portion) N in the sheet conveyance direction V is formed between the heating belt 130 and the pressure belt 120.

  Then, the driving force of the driving motor (driving unit) 163 controlled by the CPU circuit unit 200 is transmitted to the driving gear G attached to the shaft portion 131a of the driving roller 131, and the driving roller 131 is rotationally driven. As a result, the heating belt 130 circulates and rotates in the clockwise direction indicated by the arrow in FIG. In order to stably convey the sheet S, driving is reliably transmitted between the heating belt 130 and the driving roller 131. The pressure belt 120 on the pressure unit B side also rotates in a counterclockwise direction indicated by an arrow following the rotation of the heating belt 130 by the frictional force with the heating belt 130 in the nip portion N.

  Further, the heating belt 130 is heated by the IH heater 135, raised to a predetermined temperature, and temperature-controlled. Here, a thermistor sensor (temperature detection unit) 138 capable of detecting the temperature of the heating belt 130 is disposed on the heating belt 130, and can always detect the temperature of the heating belt 130.

  Detection temperature information (electrical information related to temperature) of the thermistor sensor 138 is input to the CPU circuit unit 200. The CPU circuit unit 200 supplies the IH heater 135 to the IH heater 135 based on the detected temperature information of the heating belt 130 input from the thermistor sensor 138 so that the temperature of the heating belt 130 heated by the IH heater 135 is maintained at a predetermined temperature. Control the power supply.

  In the image forming apparatus 1 of this embodiment, in order to shorten the heating time of the heating belt 130 during the printing operation, the fixing device 100 always has the exception of when the power is turned off and when an abnormal stop due to occurrence of a sheet jam (paper jam) occurs. It is assumed that the heating belt 130 is heated. At this time, the CPU circuit unit 200 controls the power supplied to the IH heater 135 so that the heating belt 130 becomes 150 ° C. regardless of the printing operation.

  Further, when the heating belt 130 is heated by the IH heater 135, the CPU circuit unit 200 always rotates the driving roller 131 in order to make the temperature distribution on the heating belt 130 uniform. In this embodiment, the driving roller 131 is rotated at a rotational speed of 300 mm / second during sheet conveyance (printing operation) and 50 mm / second during other times (non-printing and standby).

  During a printing operation, a sheet S carrying an unfixed toner image t is introduced from the entrance side to the fixing device 100, guided by a guide member (not shown), enters the nip portion N, and is nipped and conveyed. The As a result, the toner image t is fixed to the sheet S as a fixed image by heat and pressure. The sheet S exits the nip portion N and is discharged from the fixing device 100 from the exit side.

  As described above, in the present embodiment, at least one of the heating belt 130 and the pressure belt 120 forming the nip portion N for heating the toner image t on the sheet (on the recording material) is an endless belt. 1 and a second pair of rotating bodies.

(Belt shift control mechanism)
The heating belt 130 in the heating belt unit A has a phenomenon (belt shift) that moves so as to be deviated toward the front side (one end side) or the back side (the other end side) in the width direction orthogonal to the sheet conveying direction V in the rotation process. Occur. In addition, a phenomenon occurs in which the pressure belt 120 in the pressure belt unit B also moves toward the front side or the back side in the width direction orthogonal to the sheet conveying direction V during the rotation process. FIG. 8 shows a state in which the pressure belt 120 in the pressure belt unit B moves so as to be shifted toward the front side or the back side in the width direction W orthogonal to the sheet conveying direction V in the rotation process.

  In this embodiment, the belt shift movement is stabilized within a predetermined shift range (predetermined zone) by swing-type shift control (belt shift control: meandering control). Swing-type shift control is a method of tilting in the direction opposite to the belt shift direction using a tension roller as a steering member when it is detected that the belt position has moved a predetermined amount or more from the central portion in the width direction.

  By repeating the swing-type deviation control, the belt periodically moves from one side in the width direction (one direction in the width direction) to the other side (the other direction in the width direction). Can be controlled. That is, the belt is configured to be able to reciprocate in a direction W perpendicular to the conveyance direction V of the sheet S. A similar belt shift control mechanism (belt steering mechanism) is provided on each of the heating belt unit A side and the pressure belt unit B side, and the shift control of the heating belt 130 and the pressure belt 120 is independently performed in the same manner.

  Therefore, in the following, the belt shift control mechanism (belt reciprocation control means) on the pressure belt unit B side and the shift control of the pressure belt 120 will be described as a representative, and the belt shift control mechanism on the heating belt unit A side will be described. The explanation of the deviation control of the heating belt 130 is omitted.

  With reference to FIGS. 4 and 7, a support arm 154 is disposed on the side plate on the front side of the housing 140. The support arm 154 is supported by a shaft portion 121a on the front side of the pressure roller 121 via a bearing 154a, can rotate about the shaft portion 121a as a center (fulcrum), and extends to the sheet entrance side. A pin 159 is planted at the free end of the support arm 154.

  A movable bearing 153 is provided between the bearing 154a and the pin 159 of the support arm 154. The movable bearing 153 is fitted in a long slot along the length of the support arm 154 and has a degree of freedom to move along the slot. ing. A shaft portion 122a on the front side of the tension roller 122 is supported by the bearing 153. The bearing 153 is biased by a tension spring (biasing member) 156 in a direction in which the pressure belt 120 is tensioned. The tension belt 156 applies a tension of 20 kgf to the pressure belt 120.

  A shaft 160 is planted on the side plate on the front side of the housing 140 on the sheet entrance side. A worm wheel (helical gear) 157 a is rotatably supported on the shaft 160. A folk wheel (control arm) 152 having a U-shaped groove 152a is integrally provided on the worm wheel 157a. The pin 159 of the support arm 154 is engaged with and supported by the groove portion 152a of the fork plate 152. A stepping motor 155 is disposed on the side plate on the front side of the housing 140. A worm 157 fixed to the rotating shaft of the motor 155 meshes with the worm wheel 157a.

  When the stepping motor 155 is driven forward or reversely, the fork plate 152 is rotated upward or downward via the worm 157 and the worm wheel 157a. In conjunction with this, the support arm 154 rotates upward or downward about the shaft portion 121a. Accordingly, the shaft 122a on the near side of the tension roller 122 is moved upward or downward with the shaft 122a on the back side as a fulcrum (FIG. 8). As a result, the inclination of the tension roller 122 changes (the relative position between the pressure roller 121 and the tension roller 122 changes), thereby correcting the belt deviation.

  That is, the tension roller 122 functions as a steering roller that adjusts the meandering in the width direction (longitudinal direction) orthogonal to the moving direction of the pressure belt 120. Therefore, hereinafter, the tension roller 122 is referred to as a steering roller.

  Belt reciprocation control means for moving the pressure belt 120 in the width direction perpendicular to the sheet conveying direction V by the steering roller 122, fork plate (control arm) 152, worm wheel 157a, worm 157, stepping motor 155, etc. It is. That is, one end in the longitudinal direction of the steering roller 122 is located on the opposite side from the reference position 0 (FIG. 7) to the first position a and from the reference position 0 to the first position a so that the pressure belt 120 returns to a predetermined zone. The second position b is selectively displaced by predetermined inclination amounts α ° and β °, respectively. This is a displacement mechanism for reciprocating the pressure belt 120 in the width direction.

  Referring to FIGS. 5 and 6, the housing 140 is disposed near the end of the front side of the fixing device in the width direction perpendicular to the sheet conveying direction V of the pressure belt 120 below the pressure belt unit B. A sensor unit 150 is provided for detecting the belt end position. That is, the position detection means (detecting that the belt has deviated from a predetermined zone in the width direction) can be detected by the sensor unit 150 in the width direction of the pressure belt 120 toward the one end side and the other end side. Detection unit).

  The CPU circuit unit 200 detects the position of the end of the pressure belt 120 by the sensor unit 150, and changes the inclination of the steering roller 122 constituting the belt steering mechanism in accordance with the detection result to correct the belt deviation. . Thus, control is performed so that the pressure belt 120 is reciprocated between the near side (one end side) and the far side (the other end side) in the width direction. That is, the belt steering mechanism is controlled so that the pressure belt reciprocates within a predetermined zone in the width direction.

  In addition, the operation | movement of the belt deviation control in the near side using the sensor part 150 and the operation | movement of the same belt deviation control in the back | inner side are performed independently. That is, the sensor unit 150 is provided at both ends of the pressure belt 120 in the width direction, and the execution of the belt shift control operation on the one end side and the execution of the belt shift control operation on the other end side are independently performed. Done.

  Specifically, in the belt shift control, the end position of the pressure belt 120 is detected by the sensor unit 150. In response to the detection, the stepping motor 155 is driven at a predetermined rotational speed, and the pressure belt 120 is rotated in a state where the inclination of the steering roller 122 is changed. Thereby, deviation correction in the axial direction (width direction) of the belt is realized. Here, the amount of movement of the pressure belt 120 in the width direction can be controlled by changing the alignment of the steering roller 122.

  The sensor unit 150 is a belt position detection unit that detects the movement position of the pressure belt 120 in the belt width direction. The sensor unit 150 includes a sensor spring for operating the sensor arm 150d following the movement of the first and second sensors 150a and 150b, the sensor flag 150c as a flag member, the sensor arm 150d, and the pressure belt 120. 150e. The sensor flag 150c rotates around the fulcrum 150f in conjunction with the sensor arm 150d.

  Then, the sensor arm 150d, which is an arm member, is pressed against (contacted) with the front end surface 120a, which is one end side of the heating belt 120, with a force of 3 gf. As a result, the pressure belt 120 is combined with a combination of ON / OFF signals of the sensors 150a and 150b as flag detection means for optically detecting the sensor flag 150c, which is a flag member that rotates according to the position in the belt width direction. Detect the position in the width direction. The signal is OFF when the sensor flag 150c shields each of the first sensor 150a and the second sensor 150b, and is ON when the light is transmitted.

  FIG. 9 shows the relationship between the state of the pressure belt 120 being shifted and the states of the first and second sensors 150a and 150b. The pressure belt 120 reciprocates between a position where the first sensor 150a is ON and the second sensor 150b is OFF and a position where the first sensor 150a is OFF and the second sensor 150b is ON. The reciprocating control is performed so that the pressure belt 120 exists in the section. The distance of the section is set to ± 1.5 mm from the center position of the pressure belt 120 in the rotation axis direction.

  That is, the CPU circuit unit 200 controls the belt steering mechanism so that the pressure belt reciprocates within a predetermined zone in the width direction based on the detection logic of the first and second sensors 150a and 150b.

  When the pressure belt 120 moves closer to the front side, the sensor flag 150c operates via the sensor arm 150d that contacts the pressure belt 120. When the pressure belt 120 reaches a position of −1.5 mm or less on the near side, the first sensor 150a detects the sensor flag 150c, and the signal of the sensor 150a is turned off. Further, when the moving direction of the pressure belt 120 is reversed and reaches a position of +1.5 mm or more, the sensor flag 150c moves from the position detected by the first sensor 150a, and the signal of the first sensor 150a is It becomes ON. Accordingly, it is possible to detect whether the pressure belt 120 is closer to the back or closer to the front.

  In this embodiment, as shown in FIG. 8, the pressure belt 120 moves to the back side by tilting the steering roller 122 by α °, and moves to the near side by tilting β °. The values of the rear steering angle α ° and the front steering angle β ° (inclination amount: inclination angle) are variable by steering angle adjustment control, which will be described later, but in the initial state α °: 2.0 °, β °: The value is -2.0 ° (initial value). In the present embodiment, it is experimentally shown that the pressure belt 120 can always move to the back and front as long as the initial value described above is set, so that it is set as the initial value before the steering angle adjustment control. Has been.

(CPU circuit part)
FIG. 10 is a block diagram of a control system in the present embodiment. The CPU circuit unit 200 includes a CPU 201, a ROM 202, and a RAM 203.

  The CPU 201 is a control unit that performs control processing of the image forming apparatus 1 (FIG. 2). The ROM 202 is a storage unit that stores a program for the CPU 201 to operate. The RAM 203 is a storage unit used for the CPU 201 to temporarily store data. For example, the values of the above-mentioned back steering angle α ° and the front steering angle β ° are also stored in the RAM 203. A CPU circuit unit (control unit) 200 includes the CPU 201, the ROM 202, and the RAM 203.

  The fixing processing unit 220 is a circuit unit that controls the fixing device 100 in accordance with a control signal from the CPU 201. The fixing processing unit 220 includes a fixing temperature adjustment control unit 221, a roller control unit 222, an I / O control unit 223, and a timer unit 224.

  The fixing temperature adjustment control unit 221 controls power supply to the IH heater 135 and appropriately controls the temperature of the heating belt 130. The roller control unit 222 performs drive control of a motor connected to the drive roller 131 and the steering roller 122. The I / O control unit 223 includes a sensor signal reading unit 224, and performs control to read values of the pressure belt shift sensor unit 150 and the thermistor sensor 138 and notify the I / O control unit 223 of the values. The timer unit 224 is a clock function unit that measures time.

  The image processing unit (printing unit) 210 forms a toner image on the sheet S by an electrophotographic method in accordance with the image information transmitted from the external I / F processing unit 230 and the control signal from the CPU 201. The external I / F processing unit 230 transmits image information input from the external host device 23 to the CPU 201.

(Initial adjustment control of steering angle)
The steering angle initial adjustment control in this embodiment will be described with reference to FIGS. 1A and 1B. First, the CPU circuit unit (control unit) 200 determines whether or not the driving roller 131 is stopped in S1. As described above, the driving roller 131 of the fixing device 200 of the image forming apparatus 1 is always driven regardless of whether the image forming apparatus 1 is performing printing, non-printing, or standby. Accordingly, when the driving roller 131 stops, the image forming apparatus 1 is abnormally stopped due to sheet jam or the like, or the power of the image forming apparatus 1 is turned off for maintenance work of the fixing device 100 or the like. Is assumed.

  When the drive roller 131 is stopped, the CPU circuit unit 200 clears the front movement measurement start time TFstart and the back movement measurement start time TRstart to 0 in S2 and S3. These two values will be described in the steering angle adjustment control in FIGS. 2A and 2B described later.

  Next, the CPU circuit unit 200 stops accepting the printing operation (stops accepting JOB) in S4. This is because the printing operation of the image forming apparatus 1 is not possible because the driving roller 131 is stopped. Thereafter, the CPU circuit unit 200 determines whether or not the driving roller 131 has started rotating in S5. When the drive roller 131 is driven after being stopped, it is assumed that an abnormal state such as a sheet jam is released, or that the maintenance operation or the like is completed and the image forming apparatus 1 is turned on.

  After driving the driving roller 131, the process proceeds to S <b> 6, and the CPU circuit unit 200 acquires the temperature Ftemp of the heating belt 130 when the driving roller 131 starts driving from the thermistor sensor (temperature detection unit) 138. In S7, it is determined whether Ftemp exceeds 50 ° C.

  Ftemp does not exceed 50 ° C. (below a predetermined value) means that the temperature of the heating belt 130 is constantly controlled at 150 ° C., that is, the temperature has decreased by 100 ° C., that is, the fixing device 100 has been operating for a long time. It means no. At this time, the CPU circuit unit 200 and the fixing device 100 are judged to have undergone maintenance and other work such as component replacement, and the process proceeds to S9 in order to adjust the steering angle.

  If it exceeds 50 ° C., it can be determined that the adjustment of the steering angle is not necessary, so that the process proceeds to S8, the acceptance of the printing operation is permitted (JOB acceptance is permitted), and the sequence is terminated. Based on the determination in S7, it is possible to automatically determine that the pressure belt 120 has been maintained.

  For example, it is impossible to substitute this determination by having means for notifying the image forming apparatus 1 that the worker has performed maintenance work, and adjusting the steering angle depending on whether or not the means has been used (proceed to S9). There is no. However, in this case, there is a possibility that the steering angle cannot be adjusted when the operator forgets to notify that the maintenance work has been completed. In that respect, in S7, since the determination can be automatically made based on the temperature Ftemp, it is possible to prevent a notification mistake by a person.

  In S9 and S10, before adjusting the steering angle, the CPU circuit unit 200 sets initial values for the back steering angle α ° and the front steering angle β °. In S11, RFLG for determining whether or not the steering angle adjustment for the rearward control is completed is cleared to 0. In S12, FFLG for determining whether or not the steering angle adjustment for the frontward control is completed is cleared to 0.

  Next, the CPU circuit unit 200 starts measuring the steer angle adjustment time in S13. (Measured values are stored in Tadjust). Thereafter, the steering angle adjustment is started in S14. Details of the processing will be described later.

  In S15, both RFLG and FFLG become 1, that is, the CPU circuit unit 200 determines whether or not the adjustment of the rear steering angle α ° and the front steering angle β ° is completed, and determines that the adjustment is completed. , Go to S8. When the adjustment of the steering angle is not completed, the process proceeds to S16, and it is determined whether or not the adjustment time has elapsed for 600 seconds. This is a process for preventing the printing operation from starting until the adjustment operation continues. If the adjustment time has not passed 600 seconds, the process returns to S14 and the adjustment of the steering angle is continued.

  When the CPU circuit unit 200 determines in S15 and S16 that there is a possibility that maintenance or other work such as component replacement has been performed on the fixing device 100, the adjustment of the steering angle is currently attached to the image forming apparatus. It adjusts according to the fixing device 100 that is present. In addition, the printing operation is not performed until the adjustment is completed. Therefore, the rear steering angle α ° and the front steering angle β ° according to the fixing device 100 can be set, so that the pressure belt 120 is not displaced and an appropriate reciprocating speed with respect to the pressure belt 120 is obtained. It becomes possible to set.

(Steering angle adjustment control)
Next, the steering angle adjustment control in this embodiment will be described with reference to FIGS. 2A and 2B. First, in S21 and S22, the CPU circuit unit 200 determines whether or not the pressure belt 120 is closer to the back (YES in S21) or closer to the front (S22 is YES).

  If the pressure belt 120 is in the back, the process proceeds to S23 to acquire the current time Tend. Next, in S24, it is determined whether or not the belt back travel time measurement start time TRstart is zero.

  When TRstart is 0, it means that the drive roller 131 has stopped between the start of the belt back travel time measurement and the time when the pressure belt 120 actually approaches the back, and therefore the correct belt back travel time cannot be calculated. For this reason, if TRstart is 0, the process proceeds to S29 without adjusting the steering angle during the back movement. Then, the steering roller 122 is tilted to the front steering angle β °, the process proceeds to S30, the current time is stored in the belt front movement time measurement start time TFstart, and the process ends. The TFstart is stored for use in calculating the forward movement time performed in S32 described later.

  If TRstart is not 0, the process proceeds to S25, and the belt back travel time TRmove is calculated from the difference between TRstart and Tend. If TRmove does not exceed 50 seconds in S26, the process proceeds to S27 and α is subtracted by 0.1 °.

  In the present embodiment, when the driving roller 131 is rotated at 50 mm / second, if the offset time of the pressure belt 120 exceeds 50 seconds, the following can be experimentally confirmed. Yes. That is, it has been confirmed that the belt can be reciprocated while stabilizing the behavior when the pressure belt 120 passes the sheet (recording material) through the fixing nip portion N at 300 mm / second. Therefore, if TRmove exceeds 50 seconds in S26, RFLG is set to 1 in S28, and the process proceeds to S29.

  If the pressure belt 120 is closer to the front, the process proceeds to S31, and the current time Tend is acquired. Then, in the same way as when detecting the back, it is determined in S32 whether or not the belt front travel time measurement start time TFstart is zero.

  When TFstart is 0, it means that the driving roller 131 has stopped between the start of the belt back travel time measurement and the time when the pressure belt 120 actually approaches the front, and therefore the correct front belt travel time cannot be calculated. For this reason, when TFstart is 0, the steering angle is not adjusted at the time of the back movement, and the process proceeds to S37, the steering roller 122 is inclined to the back steering angle α, the process proceeds to S38, and the belt back movement time measurement start time TRstart is present. Save the time and exit.

  TRstart is stored for use in the calculation of the belt back travel time performed in S25 described above. In S32, the belt front movement time TFmove is calculated from the difference between TFstart and Tend. If TFmove does not exceed 50 seconds in S34, the process proceeds to S35 and α is added by 0.1 °. If TFmove exceeds 50 seconds in S34, 1 is set in FFLG in S36, and the process proceeds to S377.

  In this way, when the offset time of the pressure belt 120 is 50 seconds or less, the steering angle is changed until the desired belt reciprocation time is reached by decreasing the tilt angle setting value of the steering roller 122. be able to. Accordingly, an appropriate belt steering angle can be set regardless of the state of the fixing device 100.

  The configuration of the image forming apparatus 1 of the above embodiment is summarized as follows. A pair of rotators 130 in which at least one of the printing unit 210 that forms the toner image t on the sheet (recording material) S and the nip portion N for heating the toner image t formed on the sheet S is an endless belt. , 120. Support members 121 and 122 that rotatably support the endless belt 120, a driving unit 163 of the rotating body 130, and a temperature detection unit 138 that detects the temperature of the rotating body 130 are included.

  Moreover, it has the detection part 150 which detects that the endless belt 120 remove | deviated from the predetermined zone in the width direction. “And it has displacement mechanisms 122, 152, 157a, 157, 155 for reciprocating the endless belt 120 in the width direction so that the endless belt 120 returns into a predetermined zone. Accordingly, one end in the longitudinal direction of the support member 121 is selectively transferred from the reference position 0 to the first position a and from the reference position 0 to the second position b opposite to the first position a by predetermined inclination amounts α ° and β, respectively. The endless belt 120 is moved back and forth in the width direction.

  Moreover, it has the time measuring part 224 which time-measures the movement time between the one end side of the width direction of the endless belt 120 detected by the detection part 150, and the other end side. And it has the inclination amount correction | amendment part 200 which correct | amends the said inclination amount so that the one way time of the said reciprocating movement time-measured by the time measuring part 224 may become close to predetermined value. In addition, the storage unit 203 stores the corrected inclination amount and the inclination amount initialization unit (200) that returns the stored inclination amount to the initial value.

  When the drive unit 163 starts driving from the state where the rotating body is stopped, the tilt amount initialization unit initializes the tilt amount when the temperature detected by the temperature detection unit 138 is equal to or lower than a predetermined value. A control unit 200 is included.

  As described above, when the fixing device temperature is cooled to a predetermined value, that is, when it is assumed that maintenance work has occurred on the fixing device, the endless belt steering angle is automatically cleared and reset. To do. Accordingly, it is possible to suppress the behavior of the recording material that is nipped and conveyed at the nip portion, inadvertently offset the endless belt due to an operator's mistake.

  Further, the control unit 200 prevents the printing unit 210 from operating when the tilt amount initialization unit initializes the tilt amount. Then, when the correction of the tilt amount is completed by the displacement mechanism, or when a predetermined time has elapsed since the start of the correction of the tilt amount, the operation of the printing unit 210 is permitted.

  The endless belt 120 is suspended by a plurality of support members 121 and 122, and the displacement mechanism reciprocates the endless belt in the width direction by changing the alignment of at least one support member 122. A control target for controlling the tilt amount is an input pulse of the drive motor 163 that drives the support member of the displacement mechanism.

  The description of the belt shift control mechanism on the heating belt unit A side and the shift control of the heating belt 130 is omitted, but it is the same as the belt shift control mechanism and belt shift control of the pressure belt unit B described above. 4 and 5, 150A corresponds to the sensor unit 150 on the pressure belt unit B side. Reference numerals 154A, 153A, 156A, and 160A correspond to the support arm 154, the bearing 153, the tension spring 156, and the shaft 160 on the pressure belt unit B side. 152A, 157A, and 155A correspond to the fork plate 152, the worm 157, and the stepping motor 155 on the pressure belt unit B side.

(Other matters)
(1) Although the pressure belt 120 has been described in the above-described embodiment, the pressure belt 120 may be applied to the heating belt 130.

  (2) The first and second rotating bodies 130 and 120 constituting the nip portion N are not limited to the case where both are endless belts as in the apparatus 100 of the embodiment. An apparatus configuration in which one is an endless belt and the other is a roller may be employed.

  (3) The fixing device is not limited to use as a device that fixes an unfixed toner image t formed on the recording material S as a fixed image. It is also effective as an apparatus for adjusting the surface properties of an image, such as improving the glossiness of an image by heating and pressurizing a toner image once fixed or presupposed to the recording material S (also for such an apparatus). Called a fixing device).

  (4) The image forming apparatus is not limited to an image forming apparatus that forms a full-color image as in the embodiment, and may be an image forming apparatus that forms a monochrome image. In addition, the image forming apparatus can be implemented in various applications such as a copying machine, a FAX, and a multifunction machine having a plurality of these functions in addition to necessary equipment, equipment, and housing structure.

  1 .... Image forming device 210 ... Printing unit 100 ... Fusing device 200 ... Control unit S ... Recording material t ... Toner image N ... Nip part 130,120 ... At least one A pair of rotating bodies, which are endless belts, 121, 122... Support member, 163... Drive unit, 138 .. temperature detection unit, 150... Detection unit, 122, 152, 157a, 157, 155. , 0... Reference position, a... 1st position, b... 2nd position, 224.

Claims (7)

A printing unit for forming a toner image on a recording material;
A pair of rotating bodies, at least one of which is an endless belt, forming a nip portion for heating the toner image formed on the recording material;
A support member that rotatably supports the endless belt;
A driving unit of the rotating body;
A temperature detector for detecting the temperature of the rotating body;
A detection unit for detecting that the endless belt is out of a predetermined zone in the width direction;
The one end side in the longitudinal direction of the support member is set to the first position from the reference position and from the reference position to the opposite side of the first position in accordance with the output of the detection unit so that the endless belt returns to the predetermined zone. A displacement mechanism for selectively displacing each of the endless belts to a second position by a predetermined inclination amount to reciprocate the endless belt in the width direction;
A timing unit for measuring a moving time between one end side and the other end side in the width direction of the endless belt detected by the detection unit;
A tilt amount correcting unit that corrects the tilt amount so that the one-way time of the reciprocating movement timed by the time measuring unit is close to a predetermined value;
A storage unit for storing the corrected inclination amount;
An inclination amount initialization unit for returning the stored inclination amount to an initial value;
A control unit that initializes the amount of inclination by the amount of inclination initialization unit when the temperature detected by the temperature detection unit is equal to or lower than a predetermined value when the driving unit starts driving from the state where the rotating body is stopped. When,
An image forming apparatus comprising:   When the inclination amount is initialized by the inclination amount initialization unit, the control unit is configured not to operate the printing unit, and when the correction of the inclination amount is completed by the displacement mechanism, or the inclination amount The image forming apparatus according to claim 1, wherein the operation of the printing unit is permitted when a predetermined time has elapsed since the start of correction of the amount.   The endless belt is suspended by a plurality of support members, and the displacement mechanism reciprocates the endless belt in the width direction by changing alignment of at least one of the support members. Or the image forming apparatus according to 2;   4. The image forming apparatus according to claim 1, wherein an object to be controlled for controlling the amount of inclination is an input pulse of a drive motor that drives the support member of the displacement mechanism. 5. .   The image forming apparatus according to claim 1, wherein the detection unit is provided at both ends in the width direction.   The detection unit includes an arm member that contacts one end side in the width direction of the endless belt, a flag member that rotates around a fulcrum in conjunction with the arm member, and a flag detection unit that detects the flag member. The image forming apparatus according to claim 1, further comprising:   The image forming apparatus according to claim 6, wherein the flag detection unit is two optical detection units.