JP4291608B2 - Fixing device and image forming apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is used in electrophotographic copying machines, printers, facsimiles, and the like.Induction heating, etc.To fix the toner image on the recording mediumFixing deviceAnd an image forming apparatus using the same.
[0002]
[Prior art]
  Conventionally, in induction heating fixing devices, in order to enable quick start by preventing heat loss from the heating member to the pressure member, pressure is applied based on temperature information detected in the vicinity of the heating member or pressure member. There has been known one in which the nip width is changed by changing the pressure contact force between the member and the heating member (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
  JP 2000-206825 A
[0004]
[Problems to be solved by the invention]
  However, the above-described conventional induction heating fixing device uses a pressure roller shaft to reduce the pressure contact force between the fixing sleeve and the pressure roller and change the nip width by light pressure when energization of the coil is started. There is a configuration in which a pressing force changing means such as a spring or a cam that moves up and down is provided on the opposite side of the fixing sleeve with respect to the pressure roller.
[0005]
  The present invention solves this problem, and it is possible to downsize the configuration of the pressure contact force changing means and smoothly perform the pressure contact and separation of the heating roller at the time of initialization.Fixing deviceAn object of the present invention is to provide an image forming apparatus using the same.
[0006]
[Means for Solving the Problems]
  The present invention fixesRotating bodyAnd this fixingRotating bodyPressurized againstRotating bodyWhen,Heating means for partially heating the surface facing the fixing rotator, a drive source capable of forward / reverse rotation, and one of the fixing rotator and the pressure rotator as a drive rotator as the drive A drive transmission means for transmitting a driving force for rotating the drive rotator in a predetermined direction regardless of whether the source is forward rotation or reverse rotation, and an interval between the pressure rotator and the fixing rotator by reverse rotation of the drive source Pressure contact state switching means for changing the pressure contact state between the rotating bodies between a pressurized state and a light pressure state by changingThe drive transmission means comprises:A path for transmitting the driving force includes a first transmission path when the drive source is rotating forward and a second transmission path when the drive source is rotating backward, and these transmission paths have a predetermined direction to the drive rotating body. A common drive transmission member for transmitting the driving force of the intermediate drive transmission member, and an intermediate drive transmission member for reversing the direction of the driving force when the drive source is reversely rotated and transmitting it to the common drive transmission member in the second transmission path Was providedThe fixing device is characterized in that.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
  The first aspect of the present invention is fixing.Rotating bodyAnd this fixingRotating bodyPressurized againstRotating bodyWhen,Heating means for partially heating the surface facing the fixing rotator, a drive source capable of forward / reverse rotation, and one of the fixing rotator and the pressure rotator as a drive rotator as the drive A drive transmission means for transmitting a driving force for rotating the drive rotator in a predetermined direction regardless of whether the source is forward rotation or reverse rotation, and an interval between the pressure rotator and the fixing rotator by reverse rotation of the drive source Pressure contact state switching means for changing the pressure contact state between the rotating bodies between a pressurized state and a light pressure state by changingThe drive transmission means comprises:A path for transmitting the driving force includes a first transmission path when the drive source is rotating forward and a second transmission path when the drive source is rotating backward, and these transmission paths have a predetermined direction to the drive rotating body. A common drive transmission member for transmitting the driving force of the intermediate drive transmission member, and an intermediate drive transmission member for reversing the direction of the driving force when the drive source is reversely rotated and transmitting it to the common drive transmission member in the second transmission path Was providedThe fixing device is characterized in that.
[0008]
  According to the present invention,Rotating bodyJust reverse the drive source ofFixing rotating body and pressure rotating bodyChange the interval betweenRotating bodyCan smoothly switch between pressurization and light pressurization,Rotating bodyEven if the drive source ofRotating bodyThe rotation direction can be fixed in one direction without stopping the rotation.
[0009]
  Of the present inventionAccording to a second aspect, the fixing device according to the first aspect includes control means for controlling forward / reverse rotation of the drive source at the time of initialization of the device.It is.
[0010]
  According to the present invention, during initialization processing, etc.Rotating bodyWith the driving sourceRotating bodyInterval can be changed, and without increasing the size of the entire device,Rotating bodyIt is possible to smoothly switch between pressurization and light pressurization.
[0011]
  According to a third aspect of the present invention, in the fixing device according to the second aspect, the control means includes the fixing unit.Rotating bodyAnd pressurizationRotating bodyThe drive source is controlled based on the output from the detecting means for detecting whether the pressure is between the pressurized state or the light pressure state.
[0012]
  According to the present invention,Rotating bodyThe forward / reverse rotation of the drive source can be easily controlled based on the state of the pressure contact state switching means.
[0013]
  Of the present inventionThe fourth aspect is the fixing device according to the third aspect.The detecting means comprises a pair of sensors for detecting a light pressure state and a pressurized state.
[0014]
  According to the present invention, a pair of sensor outputsRotating bodyThe forward / reverse rotation of the drive source can be reliably controlled.
  According to a fifth aspect of the present invention, there is provided an image forming apparatus including a fixing device for fixing a toner image held on a recording medium, wherein the fixing device is, ConstantArrivalRotating bodyAnd this fixingRotating bodyPressurized againstRotating bodyWhen,Heating means for partially heating the surface facing the fixing rotator, a drive source capable of forward / reverse rotation, and one of the fixing rotator and the pressure rotator as a drive rotator as the drive A drive transmission means for transmitting a driving force for rotating the drive rotator in a predetermined direction regardless of whether the source is forward rotation or reverse rotation, and an interval between the pressure rotator and the fixing rotator by reverse rotation of the drive source Pressure contact state switching means for changing the pressure contact state between the rotating bodies between a pressurized state and a light pressure state by changingThe drive transmission means comprises:A path for transmitting the driving force includes a first transmission path when the drive source is rotating forward and a second transmission path when the drive source is rotating backward, and these transmission paths have a predetermined direction to the drive rotating body. A common drive transmission member for transmitting the driving force of the intermediate drive transmission member, and an intermediate drive transmission member for reversing the direction of the driving force when the drive source is reversely rotated and transmitting it to the common drive transmission member in the second transmission path Was providedAn image forming apparatus characterized by the above.
[0015]
  According to the present invention,Rotating bodyJust reverse the drive source and fixRotating bodyAnd pressurizationRotating bodyChange the interval betweenRotating bodyCan smoothly switch between pressurization and light pressurization,Rotating bodyEven if the drive source ofRotating bodyThe rotation direction can be fixed in one direction without stopping the rotation.
[0016]
  Of the present inventionAccording to a sixth aspect, in the image forming apparatus according to the fifth aspect, there is provided control means for controlling forward / reverse rotation of the drive source at the time of initialization of the apparatus.An image forming apparatus including the image forming apparatus.
[0017]
  According to the present invention, during initialization processing, etc.Rotating bodyWith the driving sourceRotating bodyInterval can be changed, and without increasing the size of the entire device,Rotating bodyIt is possible to smoothly switch between pressurization and light pressurization.
[0018]
  According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the control means is the fixing unit.Rotating bodyAnd pressurizationRotating bodyThe drive source is controlled based on the output from the detecting means for detecting whether the pressure is between the pressurized state or the light pressure state.
[0019]
  According to the present invention,Rotating bodyThe forward / reverse rotation of the driving source can be easily controlled based on the state of the pressure contact state switching means.
[0020]
  Of the present inventionThe eighth aspect is the seventh aspect.In the image forming apparatus, the detection unit includes a pair of sensors that detect a light pressure state and a pressure state.
[0021]
  According to the present invention, a pair of sensor outputsRotating bodyThe forward / reverse rotation of the drive source can be reliably controlled.
[0022]
  Hereinafter, the present inventionFixing deviceAn embodiment of a multifunction machine to which the image forming apparatus is applied will be specifically described with reference to the drawings.
[0023]
  FIG. 1 is an overall configuration diagram of a multifunction peripheral according to the present embodiment. The multifunction machine shown in FIG. 1 includes a process unit including a developing device 101 and a photoreceptor 102 and an induction heating type fixing unit 103 inside the apparatus main body 100.
[0024]
  A paper feed cassette 104 (a three-stage cassette is shown in the figure) is detachably provided at the lower part of the apparatus main body 100, and an automatic paper feeder (ADF) 105 is installed at the upper end of the apparatus main body 100. ing. The reading surface of the reading unit 106 is disposed so as to face the lower surface of the automatic paper feeder 105.
[0025]
  In addition, the apparatus main body 100 is provided with a paper feed mechanism that discharges the paper fed from the paper feed cassette 104 to the outside of the apparatus after passing through the process unit and the fixing unit 103. A pickup roller 111 is provided in the vicinity of the paper feed port of the paper feed cassette 104, and the paper taken out by the pickup roller 111 is fed to the paper path by the paper feed roller 112. Resistor et al. 113 is provided in front of the developing device 101 on the paper path. The paper transport speed is controlled in synchronism with the image forming operation on the photosensitive member 102 for the paper conveyed to the Registror et al. 113. The paper that has passed through the fixing unit 103 is discharged onto the tray 107 by the paper discharge roller 114. However, in the case of double-sided copying that forms an image on both sides of the paper, the paper discharge roller 114 is reversed after passing through the fixing unit 103. The sheet is rotated and fed to the back paper path 115 and returned to the position of the registration roller 113 through the back paper path 115 again.
[0026]
  In such a multi-function peripheral, the original fed onto the reading surface by the automatic paper feeder 105 is optically scanned by the reading unit 106, converted into image data, and output to an LSU (not shown). While the developing device 101 uniformly deposits toner on the surface of the developing roller, the LSU forms a latent image based on the image data on the photoconductor 102, thereby forming a toner image on the photoconductor 102. The sheet is fed there by Regrow et al. 113, and the toner image is transferred from the photoreceptor 102 to the sheet. When the sheet on which the toner image has been transferred passes between the fixing roller 116 and the pressure roller 117 by the fixing unit 103, the toner is melted by the heat of the fixing roller 116 and fixed on the sheet.
[0027]
  In the case of a multi-function peripheral, image data received by a FAX unit (not shown) may be output to the LSU. When a network printer function is installed, the image data supplied from the printer engine is LSU. May be output.
[0028]
  FIG. 2 is a cross-sectional view of the fixing unit 103. The fixing unit 103 is disposed in a state where the fixing roller 116 and the pressure roller 117 are in pressure contact with each other. The pressure roller 117 is driven and the fixing roller 116 is rotated around the pressure roller 117. The IH unit 120 is installed so as to cover approximately half of the outer peripheral surface of the fixing roller 116 opposite to the paper path along the axial direction.
[0029]
  The IH unit 120 includes a core including a center core 121, side cores 122 and 123, and an arch core 124, and an induction heating coil 125 is wound around the core. The induction heating type fixing unit 103 causes Joule heat to be generated on the heat generating belt 126 on the surface of the fixing roller 116 facing the IH unit 120 by reversing the direction of the current flowing through the induction heating coil 125 at a high frequency. Heat. The heat generating belt 126 has a structure in which SUS304, Cu plating, an elastic layer, and a release layer are laminated from the roller axis side to the surface, but the structure of the heat generating belt is limited to this. It is not a thing.
[0030]
  FIG. 3 is a perspective view in which the fixing roller 116, the pressure roller 117, and the cam mechanism are extracted. The main cam mechanism 200 is installed at one end of the fixing roller 116 and the pressure roller 117 arranged in parallel, and the sub cam mechanism 300 is installed at the other end.Fixing roller 116Both ends thereof are fixed to the unit main body (fixed side) of the fixing unit 103 via bearings. on the other hand,Pressure roller 117Both ends thereof are held by the rotating arm 201 of the main cam mechanism 200 and the rotating arm 301 of the sub cam mechanism 300 via bearings. The main cam mechanism 200 is provided with a motor 202 as a drive source, and the driving force by the motor 202 is configured to be transmitted to the opposite sub cam mechanism 300 via the drive transmission member 203.
[0031]
  The configuration of the main cam mechanism 200 will be described. First, a structure for switching the pressure contact state between the fixing roller 116 and the pressure roller 117 will be described with reference to FIGS. The rotation arm 201 has a rotation shaft 231 that serves as a rotation fulcrum of the arm itself at the lower end portion, and has an intermediate portion.Fixing roller 116It has a roller holding part 232 opened to the side. The roller holder 232 hasPressure roller 117One end of the is rotatably held. On the other hand, a protrusion 233 for hooking a hook is formed on the upper end of the rotating arm 201. From this protrusion 233Fixing roller 116A cam 234 is installed approximately horizontally to the side by a predetermined distance. A protrusion 235 for hooking the hook at an eccentric position is formed on the side surface of the cam 234. A spring 236 is stretched between the protrusion 235 provided at the eccentric position of the cam 234 and the protrusion 233 provided at the upper end of the rotating arm 201. That is, as shown in FIG. 4A, when the cam 234 rotates and the eccentric position (projection 235) comes to the position farthest from the upper end of the rotating arm 201,Pressure roller 117IsFixing roller 116Is pressed with the greatest force (pressurized state). Also, as shown in FIG. 4B, when the cam 234 rotates and the eccentric position (projection 235) comes to the position closest to the upper end of the rotating arm 201,Pressure roller 117IsFixing roller 116Is pressed with the smallest force (light pressure state). Each time the cam 234 makes one rotation, the pressure state and the light pressure state are repeated. Note that a similar cam mechanism is also provided in the auxiliary cam mechanism 300 that holds the other end portions of the fixing roller 116 and the pressure roller 117 as described later.
[0032]
  Next, a structure that always rotates the pressure roller 117 forward regardless of whether the motor 202 rotates forward or backward will be described with reference to FIG.
[0033]
  In the mechanism shown in FIG. 5, a forward rotation gear 211 and a reverse rotation gear 212 are attached to a rotation shaft 210 that is coaxial with the rotation shaft of the motor 202. The forward rotation gear 211 has a built-in one-way clutch that rotates idly when the rotation shaft 210 rotates reversely, and rotates (forward rotation) when the rotation shaft 210 rotates forward (rotation in the direction B). Rotate), it will turn idle. The reverse gear 212 has a built-in one-way clutch that rotates idly when the rotating shaft 210 rotates in the forward direction, and rotates (reverses) when the rotating shaft 210 rotates in the reverse direction (rotation in the b direction). When it is rotated, it turns idle. A first gear 213 constituting a double gear meshes with the forward rotation gear 211. A pressure roller gear 215 meshes with a gear 214 provided coaxially on the rotation shaft of the double gear. The pressure roller gear 215 is a gear fixed coaxially with the rotation axis of the pressure roller 117. Therefore, when the motor 202 rotates normally, the rotation force in the normal rotation direction is transmitted from the normal rotation gear 211 to the first gear 213, the gear 214, and the pressure roller gear 215, and the pressure roller 117 rotates normally.
[0034]
  On the other hand, the first intermediate gear 216 is engaged with the reverse gear 212, and the second gear 217 of the double gear is engaged with the first intermediate gear 216. By transmitting the rotation of the reverse gear 212 (rotation in the direction B) to the second gear 217 via the first intermediate gear 216, the double gear (the second gear 217) has a forward rotation direction (rotation in the direction B). The rotational force in the forward rotation direction is transmitted to the pressure roller gear 215, and the pressure roller 117 rotates in the forward direction.
[0035]
  As described above, the pressure roller 117 rotates forward both when the motor 202 rotates forward and when it rotates backward. In the present embodiment, the light pressure state is achieved by switching the rotation direction of the motor 202 to reverse the rotation. Note that if the rotation of the pressure roller 117 is stopped when the rotation direction of the motor 202 is reversed, the heating belt 126 may be unevenly heated, which may cause a fixing failure. Therefore, the pressure roller 117 is rotated during the period in which the motor 202 is reversely rotated. In addition, when the rotation of the motor 202 is reversed, it is not necessary to stop the rotation of the pressure roller 117 and the fixing roller 116, so that the rotation direction of the roller can be fixed in one direction, and mechanical stress is reduced. There are advantages you can do.
[0036]
  Next, how the driving force of the motor 202 is transmitted to the cam 234 will be described. The reverse gear 212 is connected to the second intermediate gear 218 via the first intermediate gear 216 and further connected to the third intermediate gear 219. The cam gear 220 meshes with the third intermediate gear 219. A return prevention plate 221 is concentrically fixed to the cam gear 220. A cam 234 is concentrically fixed to the return preventing plate 221.
[0037]
  Therefore, when the motor 202 is rotated in the reverse direction, the rotational force of the reverse rotation gear 212 is transmitted to the cam gear 220 via the first, second, and third intermediate gears 216, 218, and 219, and returns together with the cam gear 220. The prevention plate 221 and the cam 234 rotate. On the other hand, when the motor 202 is rotated in the forward direction, the reverse gear 212 is idled so that the rotational force in the forward direction is not transmitted to the return preventing plate 221 and the cam 234.
[0038]
  Further, as shown in FIG. 5, a lock mechanism is provided by a return prevention plate 221 or the like. Notches 222 and 223 are formed on both sides facing each other across a straight line connecting a point (P) on the return prevention plate 221 corresponding to the eccentric position of the cam 234 and the rotation center of the return prevention plate 221. Immediately before the eccentric position (P) of the cam 234 is farthest from the upper end of the rotating arm 201 (the state shown in FIG. 4A), the lock member 224 fits into the notch 223 and the eccentric position (P). Is configured so that the lock member 224 fits into the notch 222 when it is closest to the upper end of the rotating arm 201 (the state shown in FIG. 4B). It is assumed that the lock member 224 is always urged counterclockwise. As a result, even if a return force is applied to the cam 234 from the drive source side, the lock member 224 abuts against the notches 222 and 223 so as to block the rotation in the return direction, so that the cam 234 rotates. Therefore, it is possible to prevent a problem that the interval between the rollers changes.
[0039]
  Although the above description is for the main cam mechanism 200, the sub cam mechanism 300 operates in the same manner in synchronization with the main cam mechanism 200. That is, as shown in FIG. 3, one end of the drive transmission member 203 is inserted into the center of the gear 225 connected to the cam gear 220 in the main cam mechanism 200, and the other end of the drive transmission member 203 is connected to the cam gear in the sub cam mechanism 300. It is inserted in the center of a gear 303 connected to 302. A return prevention plate and a cam are fixed to the cam gear 302. The rotation arm 301, the spring 304, the return prevention plate, the cam and the lock mechanism (such as the lock member 305) provided in the sub cam mechanism 300 are configured in the same manner as the main cam mechanism 200 and are synchronized with the main cam mechanism 200. Works.
[0040]
  In the present embodiment, the sub cam mechanism 300 includes detection means for detecting the pressure contact state. FIG. 6 is a perspective view of the detecting means viewed from the two directions in FIG. The sensor A rotating plate 310 and the sensor B rotating plate 311 are concentrically joined so as to sandwich a return preventing plate having the same shape as the return preventing plate 221 shown in FIGS. A cam having the same shape as the cam 234 is fixed to the sensor B rotating plate 311. The sensor A rotating plate 310 has a perfect circular outer shape, and has notches 310a and 310b at two positions on the outer periphery and facing each other across the rotation center. In the sensor B rotating plate 311, half of the outer periphery forms a long diameter part 311 a and the other half forms a short diameter part 311 b. A light shielding sensor A is provided for the sensor A rotating plate 310. The light shielding sensor A detects the notches 310a and 310b of the sensor A rotating plate 310. Further, a light shielding sensor B is provided for the sensor B rotating plate 311. The light shielding sensor B detects the boundary between the long diameter portion 311a and the short diameter portion 311b of the sensor B rotating plate 311. Immediately before the light shielding sensor A detects one notch 310a or 310b, the light shielding sensor A and the light shielding sensor B are detected so that the light shielding sensor B simultaneously detects one boundary (boundary between the long diameter portion 311a and the short diameter portion 311b). The relative rotation angle is adjusted.
[0041]
  Next, a specific operation of the present embodiment configured as described above will be described with reference to FIG.
[0042]
  First, the relationship between the output signals (transmission and light shielding) of the light shielding sensors A and B and the pressure contact state between the fixing roller 116 and the pressure roller 117 will be described. In the present embodiment, the output signals of the light shielding sensors A and B are both (transmission and transmission) in the light pressure state, the output signal of the light shielding sensor A is transmitted in the pressure state, and the light shielding sensor B The output signal is set to be shielded from light.
[0043]
  The drive control of the motor 202 and the IH unit 120 is performed by a control unit (not shown). Output signals of the light shielding sensors A and B are input to the control unit. The control unit performs initialization when the power is turned on or when returning from the standby mode (power saving mode). First, it is confirmed that the light shielding sensors A and B are both in the (transmission, transmission) position. As described above, when the output signals of the light shielding sensors A and B are (transmission, transmission), it means that the light pressure state shown in FIG.
[0044]
  Upon confirming that the control unit is in the light pressure state, the control unit outputs a temperature increase operation command (energization command) to the IH unit 120 and then issues a forward rotation command to the motor 202. When the motor 202 rotates in the forward direction, the pressure roller 117 rotates in the forward direction and the fixing roller 116 that is in pressure contact with the pressure roller 117 in a light pressure state rotates. Further, since the normal rotation of the motor 202 is not transmitted to the cam gear 220 by the main cam mechanism 200, the cam 234 of the main cam mechanism 200 does not rotate. In addition, since the cam gear 220 of the main cam mechanism 200 does not rotate, the rotational force is not transmitted to the sub gear mechanism 300 connected via the drive transmission member 203, so the cam of the sub gear mechanism 300 does not rotate. Therefore, since the cam does not rotate while the motor 202 is rotating forward, the initial light pressure state is maintained.
[0045]
  When a predetermined time elapses after the temperature raising operation by the IH unit 120 is started, the heat generating belt 126 reaches the fixing temperature, so that the control unit completes the temperature raising operation for the IH unit 120 and starts through-down. Then, in order to start the fixing operation, an operation of switching from the light pressure state shown in FIG. 4B to the pressure state shown in FIG. 4A is started. That is, the reverse rotation command is output after the motor 202 is stopped. When the motor 202 rotates in the reverse direction, the rotation in the reverse direction is converted into the rotation in the normal direction by the main cam mechanism 200 and is transmitted to the pressure roller 117. As a result, the fixing roller 116 that is in pressure contact with the pressure roller 117 also rotates forward.
[0046]
  On the other hand, the reverse rotation of the motor 202 is transmitted to the cam gear 220 by the main cam mechanism 200 and rotates in the direction of the arrow C as shown in FIG. This rotation is also transmitted to the cam of the auxiliary cam mechanism 300 via the drive transmission member 203. As shown in FIG. 7, when rotation of the cam 234 or the like starts, the output signal of the light shielding sensor A changes from transmission to light shielding, and the output signal of the light shielding sensor B remains transmissive.
[0047]
  When the cam 234 and the like rotate 180 degrees from the light pressure state shown in FIG. 4B, the pressure state shown in FIG. As shown in FIG. 7, immediately before the cam 234 and the like rotate 180 degrees, the output signal of the light shielding sensor B changes from transmission to light shielding. At this time, the control unit starts a stop operation of the motor 202 and controls the motor 202 to stop completely at the timing when the output signal of the light shielding sensor A changes from light shielding to transmission. As a result, the fixing roller 116 comes into pressure contact with the pressure roller 117 in a pressurized state. That is, the fixing roller 116 is pressed against the recording paper with a pressure capable of fixing the toner.
[0048]
  When the control unit confirms that the output signal of the light shielding sensor A changes from light shielding to transmission and the output signal of the optical sensor B is light shielding, the control unit starts the fixing operation. A normal rotation command is issued to the motor 202, and an energization command is issued to the IH unit 120. At this timing, a recording operation is executed, and a recording sheet on which a toner image is formed is sent to the fixing unit 103 and passes between the pressure roller 117 and the fixing roller 116 in a pressurized state. During the passage, the toner is melted by the heat from the heat generating belt 126 of the fixing roller 116, and the melted toner is fixed to the recording paper by the pressure between the rollers. When printing continuously, the forward rotation of the motor 202 and the induction heating operation by the IH unit 120 are continued as they are.
[0049]
  When the fixing operation is completed, the control unit changes the pressure contact state between the pressure roller 117 and the fixing roller 116 from the pressure state to the light pressure state. As shown in FIG. 7, for the IH unit 120, the fixing operation is completed and through-down is started, while a stop command is issued to the motor 202, and after the motor 202 is stopped, a reverse rotation command is issued to the motor 202. .
[0050]
  When the motor 202 is reversed, the cam 234 and the like rotate, and the sensor A rotating plate 310 and the sensor B rotating plate 311 rotate in conjunction with the cam 234 and the like. The output signal of the light shielding sensor B changes from light shielding to transmission just before the rotation starts 180 degrees. The control unit starts the stop operation of the motor 202 at this timing. Then, when the output signal of the light shielding sensor A changes from light shielding to transmission, the motor 202 is completely stopped. As a result, the pressure contact state between the pressure roller 117 and the fixing roller 116 changes to a light pressure state shown in FIG. This state is the standby mode. When the recording operation is started again, the procedure shown in FIG. 7 is repeated.
[0051]
  Thus, according to the present embodiment,Pressure roller 117The distance between the fixing roller 116 and the pressure roller 117 can be changed using the drive source (motor 202), and the pressure contact state between the rollers can be smoothly switched without increasing the size of the entire apparatus. Also,Pressure roller 117It is possible to change the distance between the fixing roller 116 and the pressure roller 117 only by reversing the motor 202 that is the driving source of the motor, and to smoothly switch between the pressure between the rollers and the light pressure.
[0052]
  In the above explanation,Pressure roller 117On the movable sideFixing roller 116Although it is a configuration to press against,Fixing roller 116On the movable sidePressure roller 117It is good also as a structure made to press-contact with.
[0053]
【The invention's effect】
  As described in detail above, according to the present invention, at the time of initialization, etc.Rotating bodyJust reverse the drive source ofRotating bodyCan smoothly switch between pressurization and light pressurization,Rotating bodyEven if the drive source ofRotating bodyAs the rotation direction can be fixed in one direction without stopping the rotation, mechanical stress can be reduced,Rotating bodyUneven heating caused by stopping the rotation of the toner, and thus fixing failure can be prevented.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a multifunction peripheral according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a fixing unit provided in the multifunction machine shown in FIG.
FIG. 3 is a perspective view showing a roller and a drive mechanism extracted from the fixing unit shown in FIG. 2;
FIG. 4A is a schematic side view of the cam mechanism in a pressurized state.
  (B) Schematic side view of cam mechanism in light pressure state
FIG. 5 is a perspective view showing the configuration of the main cam mechanism.
FIG. 6 is a perspective view showing the configuration of the auxiliary cam mechanism.
FIG. 7 is a timing chart showing the relationship among the fixing operation, the rotation direction of the motor, and the sensor state in the embodiment.
[Explanation of sign]
  100 Main unit
  101 Developer
  102 photoconductor
  103 Fixing unit
  116 fixing roller
  117Pressure roller
  120 IH units
  126 Heating belt
  200 Main cam mechanism
  201, 301 Rotating arm
  202 motor
  236 cam
  234 Spring
  300 Secondary cam mechanism
  310 Sensor A rotating plate
  311 Sensor B rotating plate

Claims (8)

A fixing rotator, and a pressure rotating body pressed against the fixing rotary member, a heating means for heating the fixing rotary body and the facing surfaces partially, with a reversible drive source, and the fixing rotator the Drive transmission means for transmitting a driving force for rotating the drive rotator in a predetermined direction when one of the pressure rotators is a drive rotator and the drive source is rotating forward or reverse; and Pressure contact state switching means for changing a pressure contact state between the rotating bodies between a pressure state and a light pressure state by changing a distance between the pressure rotating body and the fixing rotating body by reversing a drive source ;
The drive transmission means includes a first transmission path when the drive source is forward rotating and a second transmission path when the drive source is reverse rotation as a path for transmitting the driving force. A common drive transmission member for transmitting a driving force in a predetermined direction to the drive rotating body;
Further, the fixing device is characterized in that the second transmission path is provided with an intermediate drive transmission member for reversing the direction of the drive force when the drive source is reversely rotated and transmitting it to the common drive transmission member .   2. The fixing device according to claim 1, further comprising control means for controlling forward / reverse rotation of the drive source when the device is initialized. The control means controls the drive source based on an output from a detection means for detecting whether the space between the fixing rotator and the pressure rotator is in a pressurized state or a light pressure state. The fixing device according to claim 2, wherein:   The fixing device according to claim 3, wherein the detection unit includes a pair of sensors that detect a light pressure state and a pressure state. An image forming apparatus having a fixing device for fixing a toner image held on the recording medium, the fixing device includes a constant wear rotating body, a pressure rotating body pressed against the fixing rotary member, said fixing A heating means for partially heating the surface facing the rotator, a drive source capable of forward and reverse rotation, and one of the fixing rotator and the pressure rotator as a drive rotator, In both cases of forward rotation and reverse rotation, the drive transmission means for transmitting the driving force for rotating the drive rotator in a predetermined direction, and the interval between the pressure rotator and the fixing rotator is changed by the reverse rotation of the drive source. Pressure contact state switching means for switching the pressure contact state between the rotating bodies to a pressurized state and a light pressure state ,
The drive transmission means includes a first transmission path when the drive source is forward rotating and a second transmission path when the drive source is reverse rotation as a path for transmitting the driving force. A common drive transmission member for transmitting a driving force in a predetermined direction to the drive rotating body;
Further, the second transmission path is provided with an intermediate drive transmission member that reverses the direction of the drive force when the drive source is reversely rotated and transmits it to the common drive transmission member .   6. The image forming apparatus according to claim 5, further comprising control means for controlling normal rotation and reverse rotation of the drive source when the apparatus is initialized. The control means controls the drive source based on an output from a detection means for detecting whether the space between the fixing rotator and the pressure rotator is in a pressurized state or a light pressure state. The image forming apparatus according to claim 6.   The image forming apparatus according to claim 7, wherein the detection unit includes a pair of sensors that detect a light pressure state and a pressure state.

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