JP5831004B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly, to a fixing device using a heat roller fixing method and an image forming apparatus including the fixing device.

In an image forming apparatus such as a printer or a copying machine, a heat roller fixing method that is widely used as a fixing device for fixing a toner image on a recording sheet includes a pressure roller and a cylindrical heating roller.
A heat source such as a heater lamp is provided in the hollow portion of the heating roller, thereby heating the outer peripheral surface of the heating roller from the inner peripheral surface side. The pressure roller provided in parallel with the heating roller is pressed by the heating roller and forms a nip with the heating roller. Then, by passing a recording sheet on which an unfixed toner image is formed in the nip, fixing is performed by the action of heat energy conducted from the outer peripheral surface of the heating roller and pressure by the pressure roller.

  Generally, both ends of the heating roller are rotatably supported by metal rolling bearings. However, since a metal rolling bearing has high thermal conductivity, heat escapes through the bearing. That is, the heat that should be originally used for fixing the toner image is wasted, and the portion of the fixing device that does not need to be heated is also heated by conducting heat through the bearing.

In view of the recent demand for energy saving, it is conceivable that both ends of the heating roller are supported by synthetic resin plain bearings in order to effectively use the heat applied to the heating roller.
According to this, since the heating roller is supported by the synthetic resin sliding bearing having lower thermal conductivity than the metal rolling bearing, the heat wasted through the sliding bearing is reduced. More of the applied heat can be used for fixing the toner image, and the heat can be effectively used.

JP 7-104599 A

  By the way, in order to realize good heat fixing, the pressure roller is pressed against the heating roller with a large pressing force of, for example, 400 [N], and the sliding bearings at both ends of the heating roller receive the pressing force (radial load). . The plain bearing receives the radial load in a half circumference of the inner peripheral surface, but the load is concentrated in the central portion in the circumferential direction within the half circumference. In this state, since the heating roller rotates, the progress of wear of the central portion where the load is concentrated becomes faster than the other portions. As a result, the cross section of the inner peripheral surface of the slide bearing gradually distorts from a circular shape, and the smooth rotation of the heating roller is hindered.

  In view of the above-described problems, the present invention provides a fixing device that can reduce the distortion of the inner surface of the slide bearing as much as possible, and can ensure smooth rotation of the heating roller, and an image forming apparatus including the fixing device. With the goal.

In order to achieve the above object, a fixing device according to the present invention forms a nip portion by pressing a pressure member against a heating roller having a built-in heat source, and allows the toner on the recording sheet to pass through the nip portion. in the fixing device for fixing an image on the recording sheet, the heating roller is pivotally supported on the support via a slide bearing Rutotomoni, wherein the pressure member pressing state of pressing the heating roller the pressure member wherein A pressing / separating mechanism that switches to a separated state separated from the heating roller, and the slide bearing is rotated by a predetermined angle around its axis with respect to the support body, and a portion in the circumferential direction of the slide bearing is rotated before and after the rotation. and a rotating means for varying the rotating means, the pressing-spacing mechanism, the timing of switching to the separated state from the pressing state, especially that rotating the slide bearing To.

Further, the rotating means has a claw wheel formed of a tooth row formed in the circumferential direction of the outer peripheral surface of the slide bearing, and a claw meshing with the claw wheel, and the claw presses the pressure member. -It moves in conjunction with the separation operation to rotate the claw wheel.

In this case, the claw engages with the tooth row in accordance with the separation operation of the pressure member and rotates the claw wheel by a predetermined angle, and the claw gets over the tooth row with the pressing operation. After that, it is engaged with the dentition as a stopper.
Further, when the number of teeth formed on the ratchet wheel is T, and the rotation angle per rotation is t, where the number of teeth of the ratchet wheel is t, T and t are as follows. It is characterized in that it is large and T is indivisible by t.

Further, the present invention provides a fixing device that fixes a toner image on a recording sheet by forming a nip portion by pressing a pressure member against a heating roller having a built-in heat source and passing the nip portion through the nip portion. The heating roller is pivotally supported on a support via a slide bearing, and the slide bearing is rotated by a predetermined angle around its axis with respect to the support, so that a portion in the circumferential direction of the slide bearing is defined. Rotating means for making the difference before and after rotation, a pressing / separating mechanism for switching between a pressing state in which the pressing member is pressed against the heating roller and a separating state in which the pressing member is separated from the heating roller, and the nip portion Counting means for counting the number of recording sheets that have passed through, and the rotating means includes a motor, a power transmission mechanism for transmitting the power of the motor to the slide bearing, and the module. Control means for performing rotation control of the motor, and the control means is configured such that each time the number of sheets counted by the counting means is equal to or greater than a predetermined number and the pressure member is in the separated state, It is made to rotate.

Furthermore, the present invention provides a fixing device for fixing a toner image on a recording sheet to the recording sheet by forming a nip portion by pressing a pressure member against a heating roller incorporating a heat source, and passing the nip portion through the nip portion. The heating roller is pivotally supported by a support via a slide bearing, and is switched between a pressing state in which the pressing member is pressed against the heating roller and a separated state in which the pressing member is separated from the heating roller. When the pressing / separating mechanism and the pressurizing member are in the separated state, the sliding bearing is rotated by a predetermined angle around its axis with respect to the support, and a portion in the circumferential direction of the sliding bearing is rotated. Rotating means for making the front and rear different, and the rotating means includes a motor, a power transmission mechanism for transmitting the power of the motor to the slide bearing, and a control means for controlling the rotation of the motor. Wherein the said power transmission mechanism that includes a worm wheel made of teeth which are formed in the circumferential direction of the outer peripheral surface of the sliding bearing, a worm for rotating the worm wheel engaged said worm wheel and the teeth, the It is characterized by.

Further, the rotating means rotates the slide bearing so that a load concentration portion of the slide bearing where the radial load due to the pressing force of the pressurizing member acts most is different before and after the rotation. It is characterized by that.
In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus that forms an image on a recording sheet by an electrophotographic method, and as a fixing device for a toner image formed on the recording sheet, The above fixing device is provided.

  According to the fixing device having the above-described configuration, the sliding bearing is rotated by a predetermined angle around its axis with respect to the support body at a predetermined timing, so that the circumferential portion of the sliding bearing is different before and after the rotation. Therefore, the distortion of the inner surface of the slide bearing that occurs when the inner peripheral surface portion on which the radial load is most exerted is not changed can be reduced as much as possible, and the smooth rotation of the heating roller can be ensured.

1 is a diagram illustrating a schematic configuration of a tandem printer according to an embodiment. FIG. 2 is a front view of the fixing device according to the first embodiment, and shows a state where a pressure roller is pressed against a heating roller. FIG. 3 is a half cross-sectional view taken along the line EE in FIG. 2. FIG. 3 is a front view of the fixing device according to Embodiment 1 and shows a state in which a pressure roller is separated from a heating roller. FIG. 6 is a front view of a fixing device according to Embodiment 2 and shows a state where a pressure roller is pressed against a heating roller. 10 is a flowchart of a bearing intermittent rotation control program executed by a control unit of the fixing device according to the second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a fixing device and an image forming apparatus having the same according to the present invention will be described below with reference to the drawings.
<Embodiment 1>
FIG. 1 is a diagram showing a schematic configuration of a tandem printer 10 (hereinafter simply referred to as “printer 10”) according to the first embodiment. Although a printer is taken as an example here, the present invention can also be applied to an image forming apparatus such as a copying machine or a facsimile.

  As shown in FIG. 1, the printer 10 includes a transfer belt 14 that is horizontally installed in a housing 12 and travels in the direction of arrow A, and four image forming units 16 </ b> C that are arranged in the travel direction of the transfer belt 14. 16M, 16Y, 16K, primary transfer rollers 18C, 18M, 18Y, 18K provided corresponding to the respective image forming units, and secondary transfer unit 20, and each image forming unit 16C, 16M, 16Y, 16K. This is a so-called intermediate transfer type image forming apparatus in which the formed toner images of the respective color components are once transferred onto the transfer belt 14 and then transferred to the recording sheet S to form a color image.

  Each of the image forming units 20C, 22M, 22Y, and 20K has charging units 24C, 24M, 24Y, and 24K arranged around the photosensitive drums 22C, 22M, 22Y, and 22K, which are image carriers, and a developing unit. 26C, 26M, 26Y, and 26K. An exposure unit 28 is arranged below the image forming units 20C,..., 20K, and light-modulated laser beams LB are emitted toward the respective photosensitive drums 22C,. The surfaces of the photosensitive drums 22C,..., 22K rotated in the direction of arrow B are uniformly charged by the charging units 24C,. A latent image is formed, and the electrostatic latent image is developed into a toner image by the developing units 16C,. Each of the developing units 16C,..., 16K is sensitive to toners of C (cyan), M (magenta), Y (yellow), and K (black) corresponding to the light modulation color component of the laser light. Supplied to body drums 22C,.

The toner images formed on the photosensitive drums 22C,..., 22K travel by receiving the action of an electric field generated between the primary transfer rollers 18C,..., 18K and the photosensitive drums 22C,. The images are sequentially transferred onto the transfer belt 14.
On the other hand, the recording sheet S fed from the paper feed cassette 30 by the pickup roller 32 is moved to the secondary transfer unit 20 by the registration roller 34 in accordance with the timing when the toner image on the transfer belt 14 reaches the secondary transfer unit 20. It is conveyed. The secondary transfer unit 20 transfers the toner image superimposed on the transfer belt 14 onto the recording sheet S.

The toner image on the recording sheet S is fixed by the fixing device 36 and then discharged to the paper discharge tray 40 by the discharge roller 38.
The printer 10 has a control unit 42, and the control unit 42 has a configuration in which a ROM 46 and a RAM 48 are connected to a CPU 44. The CPU 44 executes various control programs stored in the ROM 46 so as to comprehensively control each unit and device described above to realize a smooth image forming operation.

2 shows a front view of the fixing device 36, and FIG. 3 shows a part of a half sectional view cut along the line EE in FIG.
The fixing device 36 includes a heating roller 50 and a pressure roller 52 that is a pressure member.
The heating roller 50 is formed by forming a release layer (not shown) on the outer peripheral surface of a metal cylindrical member, and a heater lamp 54 as a heat source is built in the hollow portion.

  Both ends of the heating roller 50 are reduced in diameter compared to the central portion through which the recording sheet S is passed (hereinafter, the reduced diameter end portion is referred to as a “reduced diameter portion 58”). The heat roller 50 is supported by a reduced diameter portion 58 supported by a metal support plate 62 as a support via a slide bearing 60. The other end of the heating roller 50 that does not appear in FIG. 3 is also pivotally supported by a support plate similar to the support plate 62 via a slide bearing similar to the slide bearing 60.

  The slide bearing 60 is a sleeve bearing having a flange portion 63. On the outer peripheral surface opposite to the flange portion 63, a tooth row is formed by forming a plurality of (in the present example, 56) teeth 64 at an equal pitch in the circumferential direction, thereby forming a ratchet wheel 66. Yes. The plain bearing 60 is made of polyacetal, fluororesin, nylon or other synthetic resin, and has heat insulation in the sense that its thermal conductivity is lower than that of stainless steel or other metals.

  The pressure roller 52 is formed by forming an elastic layer 70 made of silicone rubber or fluororesin on the outer peripheral surface of a metal cored bar 68. The cored bar 68 has a columnar shape as a whole, and has a reduced diameter portion 72 having a diameter reduced from the central portion at both ends of the central portion where the elastic layer 70 is formed. In the pressure roller 52, the reduced diameter portion 72 is pivotally supported on the swing plate 76 via a metal rolling bearing 74.

The swing plate 76 is a metal plate material having a uniform thickness in a direction perpendicular to the paper surface in FIG. The swing plate 76 is attached to a shaft 78 whose longitudinal direction is perpendicular to the paper surface. The swing plate 76 can swing around the axis of the shaft 78. The shaft 78 is fixed to a housing (not shown).
The other end of the claw 80 having one end formed in a bowl shape is attached to the swing plate 76 via a pin 82, and the claw 76 can be rotated around the axis of the pin 82. Yes. A hook-shaped end portion of the claw 80 (hereinafter referred to as “hook portion 80 </ b> A”) is engaged with any tooth 64 of the claw wheel 66.

A torsion coil spring 81 is stretched between the claw 80 and the swing plate 76. Due to the restoring force of the torsion coil spring 81, the claw 80 acts to rotate counterclockwise around the axis of the pin 82. Thus, the collar portion 80A is always in contact with the outer periphery of the claw wheel 66.
The swing plate 76 also has a strip-shaped lever portion 84 on the opposite side of the shaft 78 with the rolling bearing 74 interposed therebetween.

A tension coil spring 86 is stretched between the vicinity of the base portion of the lever portion 84 and the support plate 62. The restoring force of the tension coil spring 86 always acts on the swing plate 76 in the direction in which it is intended to rotate counterclockwise about the shaft 78.
A plate cam 88 is provided in the vicinity of the tip of the lever portion 84. The plate cam 88 is fixed to a camshaft 90 whose longitudinal direction is provided perpendicular to the paper surface. The camshaft 90 is rotated in the direction of arrow F from a motor (not shown) via a power transmission mechanism (not shown). Along with this, the plate cam 88 fixed integrally with the camshaft 90 also rotates around the axis of the camshaft 90.

  Note that the rolling roller bearing 74, the swing plate 76, the claw 80, the torsion coil spring 81, the tension coil spring 86, and the plate cam corresponding to the other end portion of the pressure roller 52 not shown in FIG. Members similar to 88 are provided in a similar manner. Further, the pressure roller 52 is rotated clockwise (in the direction of the arrow K) in FIG. 2 during image formation by power transmitted from a motor (not shown) via a power transmission mechanism (not shown).

  In the fixing device 36 configured as described above, the plate cam 88 is in the position shown in FIG. 2 while image formation is being performed. At this time, the pressure roller 52 is pressed against the heating roller 50 by the restoring force of the tension coil spring 86, and a part of the elastic layer 70 of the pressure roller 52 is elastically deformed to form a nip portion. Then, the heating roller 50 is rotated counterclockwise following the rotating pressure roller 52, and the recording sheet S on which an unfixed toner image is formed is passed through the nip portion, thereby the recording sheet. A toner image is fixed on S.

  Here, the pressure roller 52 presses the heating roller 50 with a force of, for example, 400 [N] by the tension coil springs 86 provided at both ends of the pressure roller 52. A radial load due to this pressing force acts on the slide bearing 60. The radial load acts on about a half circumference of the inner circumferential surface of the slide bearing 60, but also acts most heavily on the central portion in the circumferential direction within the half circumference. Hereinafter, the portion in the circumferential direction of the inner peripheral surface on which the radial load due to the pressing force of the pressure roller 52 acts most is referred to as a “load concentration portion”. For this reason, in the case where no care is taken, as described in the section “Problems to be solved by the invention”, the cross-sectional shape of the inner peripheral surface of the slide bearing gradually becomes distorted from a circular shape, and the heating roller is smooth. Rotation will be hindered.

  Therefore, the slide bearing 60 is rotated around the axis of the support plate 62 by a predetermined angle at a predetermined timing. In the first embodiment, the pressure roller 52 is heated by the pressing / separating mechanism including the support plate 62, the shaft 78, the swing plate 76, the tension coil spring 86, the plate cam 88, and the cam shaft 90 as main components. The slide bearing 60 is rotated at the timing when the pressure roller 52 is switched from the pressed state pressed against the roller 50 to the separated state separated from the heating roller 50.

  More specifically, when the plate cam 88 is rotated in the direction of arrow F in the state shown in FIG. 2, the lever portion 84 is pressed against the peripheral surface of the plate cam 88, and as shown in FIG. The entire moving plate 76 swings in the direction of arrow G. At this time, the claw 80 having one end connected to the swing plate 76 and the collar 80A at the other end engaged with the teeth 64 of the claw wheel 66 moves from the position indicated by the alternate long and short dash line. The wheel 66 is rotated in the direction of arrow J by a predetermined angle (in this example, three teeth).

  When the plate cam 88 is further rotated in the direction of the arrow F and returns to the state shown in FIG. 2, the collar portion 80A of the claw 80 gets over three teeth 64 of the claw wheel 66, and is shown in FIG. Return to position. At this time, the slide bearing 60 does not rotate due to the frictional force between the heating roller 50 and the support plate 62 caused by its own weight. When the heating roller 50 rotates following the pressure roller 52, the claw 80 serves as a stopper, and the sliding bearing 60 (claw wheel 66) is prevented from rotating together with the heating roller 50.

As described above, the sliding bearing 60 is intermittently rotated in accordance with the pressing / separating operation of the pressure roller 52, so that the load concentration portion is shifted little by little, so that the inner surface of the sliding bearing can be distorted. As much as possible, the smooth rotation of the heating roller 50 can be ensured.
Here, as described above, the claw wheel 66 has 56 teeth and is rotated by three teeth at a time. When 56 is divided by 3, there is a remainder of 2 (that is, it is not divisible), so that each time the hook wheel 66 is rotated, the teeth 64 with which the hook portion 80A of the claw 80 is engaged are shifted one by one. Therefore, even if the swinging width of the swinging plate 76 greatly exceeds the pitch (arrangement interval) of the teeth 64 of the claw wheel 66, the result is equivalent to the fact that the claw wheel 66 is sent little by little after all. Thus, the load concentration portion on the inner surface of the slide bearing can be changed as much as possible.

The pressure roller 52 is pressed against the heating roller 50 as shown in FIG. 2 during image formation, and is separated from the heating roller 50 as shown in FIG. 4 except during image formation. In the case where the pressure is constantly applied, if the image is not formed over a long period of time, the elastically deformed portion of the pressure roller 52 may not be completely restored to the original state. Become. On the other hand, in the present embodiment, as described above, the pressure roller 52 is separated from the heating roller 50 except when the image is being formed (that is, when the pressure roller 52 is not driven to rotate). Since the elastic deformation is not caused to occur in 52, it is possible to prevent the above-described problem from occurring when the pressure is constantly applied.
<Embodiment 2>
The printer according to the second embodiment has basically the same configuration as that of the printer 10 according to the first embodiment except that the rotation means of the slide bearing in the fixing device is mainly different. Therefore, in the drawings for describing the second embodiment, the same reference numerals are given to the components that are substantially the same as those of the first embodiment, and the description will be made with reference to different parts as necessary. To do.

FIG. 5 is a front view showing the fixing device 100 according to the second embodiment, which is drawn similarly to FIG.
The fixing device 100 includes a motor 102 and a worm 106 fitted to the output shaft 104 of the motor 102.
The sliding bearing 108 used in the fixing device 100 is a sleeve bearing having a flange portion 63 as in the sliding bearing 60 of the first embodiment. On the outer peripheral surface opposite to the flange portion 63, a tooth row in which a plurality of teeth 110 are formed at an equal pitch in the circumferential direction is formed, and the worm wheel 112 is configured. Note that the sliding bearing 108 is made of synthetic resin, as in the first embodiment.

The worm 106 meshes with the worm wheel 112, and the sliding bearing 108 is rotated by driving the motor 102 to rotate. According to this, unlike the first embodiment, the sliding bearing can be rotated at an arbitrary timing regardless of the pressing / separating operation of the pressure roller 52.
Further, in the fixing device 100, since the plate cam 88 is at the position indicated by the solid line in FIG. 5, the pressure roller 52 is pressing the heating roller 50, or the plate cam 88 is at the position indicated by the alternate long and short dash line. Therefore, a cam sensor 114 is provided for detecting whether the pressure roller 52 is separated from the heating roller 50. The cam sensor 114 has a light emitting element and a light receiving element (both not shown) arranged opposite to each other with a portion near the portion farthest from the cam shaft 90 of the plate cam 88 indicated by a solid line. When the emitted light from the light emitting element is blocked by the plate cam 88 and is not received by the light receiving element, it is determined that the pressure roller 52 is pressing the heating roller 50, and the light receiving element receives the emitted light. When it is determined, it is determined that the pressure roller 52 is separated from the heating roller 50.

In the printer according to the second embodiment, as shown in FIG. 1, a sheet detection sensor 116 that detects the passing recording sheet S is provided in the conveyance path of the recording sheet S immediately after the downstream side of the fixing device. .
The CPU 44 of the control unit 42 starts the motor 102 and rotates the slide bearing 108 intermittently at a predetermined timing based on the detection results of the cam sensor 114 and the sheet detection sensor 116. Specifically, the recording sheet S that has passed through the fixing device 100 (nip portion) is rotated when the number of recording sheets S exceeds a predetermined number (for example, 1000 sheets) and the pressure roller 52 is separated from the heating roller 50.

FIG. 6 shows a flowchart of a bearing intermittent rotation control program stored in the ROM 46. The program is activated when the printer switch is turned on.
When the CPU 44 serving as the control unit determines that the recording sheet S has passed the fixing device 100 (nip portion) based on the detection result of the sheet detection sensor 116 (YES in step S1), the value of the variable n is incremented by one. (Step S2). Therefore, Step S1 and Step S2 function as a counting unit that counts the number of recording sheets that have passed through the nip portion. It is determined whether or not the value of n that is the cumulative number of passing sheets is equal to or greater than a predetermined value N (for example, N = 1000) (step S3).

If n is less than N (NO in step S3), the process returns to step S1, and the recording process of the number of passing sheets S is repeated (steps S1 to S3).
If n is greater than or equal to N (YES in step S3), it is determined based on the detection result of the cam sensor 114 whether or not the pressure roller 52 is separated from the heating roller 50 (step S4).

If it is determined that they are not separated (NO in step S4), the process returns to step S1, and the processes in steps S1 to S4 are repeated until the pressure roller 52 is separated from the heating roller 50.
On the other hand, when it is determined that the pressure roller 52 is separated from the heating roller 50 (YES in step S4), the motor 102 is activated and the slide bearing 108 is rotated by a predetermined angle (for example, 5 degrees). Thereafter, after resetting n indicating the cumulative number of passing sheets of the recording sheet S (step S6), the process returns to step S1, and thereafter the processes of S1 to S6 are repeated.

  As described above, in the second embodiment, when the number of sheets passing through the fixing device 100 (nip portion) of the recording sheet S reaches the predetermined number N, the slip is performed when the pressure roller 52 is separated from the heating roller 50 for the first time. The bearing 108 is rotated. As a result, during the period from one rotation to the next rotation, the degree of wear occurring at the load concentration area on the inner surface of the slide bearing can be made the same every time, so wear in the circumferential direction of the inner surface of the slide bearing is possible. It can be made as uniform as possible, and as a result, distortion on the inner surface of the slide bearing is less likely to occur.

As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described form, and for example, the following form may be adopted.
(1) Although it is the rotation angle per time of the slide bearing, it is not limited to the above-described amount. In short, any angle other than an integral multiple of 360 degrees is acceptable. This is because the purpose is to change the load concentration portion on the inner surface of the slide bearing, and as a result of one rotation, it is not necessary to return to the same rotation position as before the one rotation. In other words, it is only necessary to change the load concentration portion before and after the rotation.

(2) In the first and second embodiments, the tooth is directly formed on the slide bearing to configure the claw wheel or the worm wheel. However, the present invention is not limited thereto, and the claw wheel or the worm wheel is manufactured separately. Alternatively, it may be integrally attached to the slide bearing. For example, what formed the tooth row | line | column in the circumferential direction at equal intervals on the outer periphery of a hollow disc may be fitted to the outer periphery of a slide bearing.
(3) In the first embodiment, the number of teeth of the ratchet wheel (hereinafter referred to as “total number of teeth”) is 56, and the number of teeth to be sent by the nail for one rotation of the slide bearing (hereinafter referred to as “ The total number of teeth and the number of feed teeth is not limited to the above number, but can be set arbitrarily (however, the total number of teeth is larger than the number of feed teeth). ). The number of feed dogs may be one, or two or four or more.

  In this case, as in the example described above, the total number of teeth may not be divisible by the number of feed teeth. In other words, when T is the total number of teeth and t is the number of feed teeth (T and t are positive integers, T> t), T and t are divisible by t. It doesn't matter if there is no relationship. By doing in this way, the effect mentioned above is acquired.

  The fixing device according to the present invention can be suitably used as a fixing device for fixing an unfixed toner image on a recording sheet to the recording sheet in an image forming apparatus such as a printer or a copying machine.

36,100 Fixing device 50 Heating roller 52 Pressure roller 54 Heater lamp 60,108 Slide bearing 62 Support plate 66 Claw wheel 76 Oscillating plate 78 Shaft 80 Claw 86 Tension coil spring 88 Plate cam 90 Camshaft 102 Motor 104 Output shaft 106 Worm 112 Worm wheel

Claims (8)

In a fixing device for fixing a toner image on a recording sheet to the recording sheet by forming a nip portion by pressing a pressure member against a heating roller incorporating a heat source, and passing the nip portion through the nip portion.
The heating roller is pivotally supported on the support via a slide bearing Rutotomoni,
A pressing / separating mechanism that switches between a pressing state in which the pressing member is pressed against the heating roller and a separating state in which the pressing member is separated from the heating roller;
The pre SL sliding bearing by a predetermined angle, rotates around its central axis relative to the support, and rotating means for varying the site in the circumferential direction of the sliding bearing in the front and rear pivot
Have
The fixing device , wherein the rotating means rotates the sliding bearing at a timing when the pressing / separating mechanism switches from the pressing state to the separating state . The rotating means is
A claw wheel comprising a tooth row formed in the circumferential direction of the outer peripheral surface of the sliding bearing;
A claw meshing with the claw wheel,
Have
The fixing device according to claim 1, wherein the pawl is moved in conjunction with the pressing-separating operation of the pressing member, wherein the rotating the ratchet wheel. The claw engages with the tooth row as the pressing member moves apart to rotate the claw wheel by a predetermined angle, and the claw moves over the tooth row along with the pressing operation and then stops. The fixing device according to claim 2 , wherein the fixing device engages with the tooth row. T number of teeth formed on the claw wheel,
T rotation angle per rotation is the number of teeth of the claw wheel,
If
The T and t, T is greater than t, and T is the fixing device according to claim 2 or 3, characterized in that a relationship is not divisible by t. In a fixing device for fixing a toner image on a recording sheet to the recording sheet by forming a nip portion by pressing a pressure member against a heating roller incorporating a heat source, and passing the nip portion through the nip portion.
The heating roller is pivotally supported on the support via a plain bearing,
The pre SL sliding bearing by a predetermined angle, rotates around its central axis relative to the support, and rotating means for varying the site in the circumferential direction of the sliding bearing in the front and rear pivot,
A pressing / separating mechanism that switches between a pressing state in which the pressing member is pressed against the heating roller and a separating state in which the pressing member is separated from the heating roller;
Counting means for counting the number of recording sheets passing through the nip portion;
Have
The rotation means includes a motor, a power transmission mechanism that transmits the power of the motor to the slide bearing, and a control means that performs rotation control of the motor,
The fixing device is characterized in that the control means rotates the slide bearing every time the number counted by the counting means is a predetermined number or more and the pressure member is in the separated state . In a fixing device for fixing a toner image on a recording sheet to the recording sheet by forming a nip portion by pressing a pressure member against a heating roller incorporating a heat source, and passing the nip portion through the nip portion.
The heating roller is pivotally supported on the support via a plain bearing,
A pressing / separating mechanism that switches between a pressing state in which the pressing member is pressed against the heating roller and a separating state in which the pressing member is separated from the heating roller;
When the pressure member is in the separated state, the sliding bearing is rotated by a predetermined angle around its axis with respect to the support body, and the rotation of the sliding bearing in the circumferential direction is changed before and after the rotation. Means and
Have
The rotation means includes a motor, a power transmission mechanism that transmits the power of the motor to the slide bearing, and a control means that performs rotation control of the motor,
The power transmission mechanism includes a worm wheel including a tooth row formed in a circumferential direction of the outer peripheral surface of the slide bearing;
A worm that meshes with the worm wheel and rotates the worm wheel;
A fixing device comprising: The rotating means rotates the slide bearing so that a load concentration portion of the slide bearing on which the radial load due to the pressing force of the pressurizing member acts most is different before and after the rotation. The fixing device according to any one of claims 1 to 6 , wherein the fixing device is characterized in that: An image forming apparatus for forming an image on a recording sheet by an electrophotographic method,
As a fixing device for toner image formed on a recording sheet, an image forming apparatus comprising the fixing device according to any one of claims 1-7.

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