JP2017223826A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to fix an edge scratch caused by a recording sheet while avoiding an increase in size of the device.SOLUTION: The present invention provides a fixing device comprising a fixing belt 53 that heats a recording sheet P carrying an unfixed toner image to fix it, and a pressure roller 51 that is in pressure contact with the fixing belt 53 to form a nip part N, the fixing device including motors for driving 54 and 55 that set the fixing belt 53 and pressure roller 51 independently to rotate the fixing belt 53 or the pressure roller 51 or both of them in the regular/reverse direction, and polishing control means C2 that polishes the surface of the fixing belt 53 by rotating, with the motors for driving 54 and 55, the fixing belt 53 and pressure roller 51 in the regular direction or the reverse direction with a difference in linear velocity therebetween at a predetermined timing while the recording sheet P is not fed.SELECTED DRAWING: Figure 3

Description

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

  In general, an image forming apparatus using an electrophotographic process technique forms an electrostatic latent image by irradiating a charged photoconductor with laser light. Then, a toner image is formed by supplying toner from the developing device to the photoreceptor on which the electrostatic latent image is formed. Thereafter, the toner image is transferred onto a recording paper, and then fixed by heating and pressurizing to form an image on the recording paper.

  By the way, when the recording paper is passed through the fixing nip portion, scratches due to paper passing, paper dust, and dirt of offset toner are generated on the surface of the fixing surface, and the surface of the fixing surface is gradually roughened. As a main cause of scratches generated on the surface of the member on the fixing surface side, burrs generated at both ends of the recording paper can be mentioned.

  The burr described above is formed by cutting the recording paper, and is generated as a cutter cutting trace. When passing through the fixing nip with the recording paper having burrs, it is known that burrs generated at both ends of the recording paper cause paper edge scratches parallel to the conveyance direction of the recording paper on the member surface on the fixing surface side. It has been.

  If a recording sheet having a width larger than the width of the recording sheet that has passed through is passed, if an image is present at a location where there is a scratch on the paper edge, a difference in gloss between that portion and the other portion will occur, and the vertical streaks will appear in the image. Uneven gloss appears.

  Focusing on the above-described problems, there are configurations disclosed in Patent Documents 1 to 3, respectively, in an attempt to repair the scratches on the surface of the member on the fixing surface side. Japanese Patent Application Laid-Open No. 2004-133867 discloses a control for moving a fixing surface side member or a pressure surface side member or both in the recording paper width direction orthogonal to the recording paper conveyance direction, and a fixing surface side member and a pressure surface side. A configuration is disclosed in which these members are rotated at different peripheral speeds.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a configuration in which the fixing nip width is narrowed and the fixing surface side member and the pressure surface side member are rotated at different peripheral speeds. Further, Patent Document 3 discloses a configuration in which an abrasive member is brought into contact with a member on the fixing surface side and the rotation speed of the abrasive member is controlled to increase according to the situation.

  However, the configuration disclosed in Patent Document 1 described above requires a mechanism for moving in the recording paper width direction orthogonal to the recording paper conveyance direction. Further, the configuration disclosed in Patent Document 2 requires a mechanism for increasing and decreasing the pressure in the control for narrowing the fixing nip width. That is, in any case, there is a risk of increasing the cost and size of the apparatus. Furthermore, since the polishing mode is forward rotation, it may not be repaired depending on the level of scratches on the paper edge.

  Further, the configuration disclosed in Patent Document 3 requires a mechanism for bringing the abrasive member into contact with the fixing surface side member, and there is a concern that the cost and size of the apparatus may be increased as described above.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device capable of repairing an edge flaw of a fixing member due to recording paper while avoiding an increase in size of the device.

  In order to solve the above problems, the present invention described in claim 1 is directed to a fixing member that heats and fixes a recording paper carrying an unfixed toner image, and a pressure that presses against the fixing member to form a nip portion. In the fixing device including a member, the fixing member and the pressure member are made independent of each other, and the fixing member and / or the pressure member or both are rotated forward and backward, and the recording paper is not passed. A polishing control means is provided that polishes the surface of the fixing member by rotating the fixing member and the pressing member forward or backward with a linear velocity difference by the driving source at a predetermined timing in a paper state. ing.

  According to the present invention, the edge flaw of the fixing member due to the recording paper can be repaired while avoiding the enlargement of the apparatus.

1 is a front view showing a schematic configuration of an entire image forming apparatus using a fixing device according to an embodiment of the present invention. It is explanatory drawing which shows a mode that the wide solid image was fixed to the recording paper. FIG. 2 is an enlarged view showing a main configuration of a fixing device according to an embodiment of the present invention. It is a flowchart which shows the content of the grinding | polishing control in a fixing device same as the above. FIG. 10 is a front view illustrating a schematic configuration of a fixing device according to a conventional example.

  Hereinafter, a fixing device and an image forming apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a front view showing a schematic configuration of an entire image forming apparatus using a fixing device according to an embodiment of the present invention. In this embodiment, a tandem color copying machine will be described as an example of the image forming apparatus.

  As shown in FIG. 1, a tandem color copier (hereinafter simply referred to as “copier”) A according to an example includes an exposure device 15, an image forming device 20, an intermediate transfer belt 25, a fixing device B, and a paper feeding unit. In this configuration, 30 is appropriately disposed in the main body 9.

  The exposure device 15 is for forming an electrostatic latent image on each photosensitive drum 13 of the image forming device 20 described later. The image forming apparatus 20 includes four image forming units 21Y, 21M, 21C, and 21K of yellow, magenta, cyan, and black arranged in parallel along a conveyance direction α of an intermediate transfer belt 25 described later. .

  In each of the image forming units 21Y, 21M, 21C, and 21K, a developing machine 10, a charging unit 11, and a cleaning unit 12 are arranged around the photosensitive drum 13. The developing machine 10 develops an electrostatic latent image formed on the photosensitive drum 13, the charging unit 11 charges the photosensitive drum 13, and the cleaning unit 12 is the photosensitive drum 13. The upper untransferred toner is collected. In FIG. 1, only the photosensitive drum 13, the charging unit 11, the developing device 10, and the cleaning unit 12 included in the black image forming unit 21 </ b> K are denoted by reference numerals, and the other image forming units 21 </ b> Y, 21 </ b> M, and 21 </ b> C are provided. Is omitted.

  The intermediate transfer belt 25 is stretched around three rollers 25a, 25b, and 26 so that the toner image is transferred to the intermediate transfer belt 25, and is rotated and conveyed in the conveyance direction α. A belt cleaning unit 27 for cleaning the intermediate transfer belt 25 is disposed at the left end of the intermediate transfer belt 25 in the figure.

  A secondary transfer bias roller 28 for transferring the toner image on the intermediate transfer belt 25 onto the recording paper P is disposed facing the roller 26. The paper feed unit 30 has storage cassettes 31 and 31 for storing the recording paper P, and the recording paper P stored in each of the storage cassettes 31 and 31 is sent toward the transport path 32. Paper feeding rollers 33 and 33 for feeding are arranged close to each other.

  A fixing device B, which will be described in detail later, is disposed at the end of the conveyance path 32, and the recording paper P on which the toner image is fixed is conveyed downstream of the conveyance path 32 of the fixing device B. Transport rollers 34 and 34 are arranged.

  According to the above-described copying machine A, based on image data generated by reading an image to be fixed by an image reading unit (not shown), colors (magenta, yellow, yellow) corresponding to each photosensitive drum 13 such as each image forming unit 21Y. Cyan and black) toner images are formed. Then, the toner images of the respective colors are transferred to the intermediate transfer belt 25 so as to overlap each other, and conveyed toward the secondary transfer bias roller 28 while moving in the conveyance direction α.

  On the other hand, the recording paper P accommodated in the paper supply unit 30 is fed from the paper supply rollers 33 and 33 toward the transport path 32, and then is recorded by the secondary transfer bias roller 28 at a predetermined timing. A toner image is transferred on top. The recording paper P carrying the toner image is heated and pressed by the fixing roller 50 and the pressure roller 51 of the fixing device B, which will be described in detail later, so that the toner image is fixed on the recording paper P. Then, the recording paper P sent out from the fixing device B is discharged to the outside by the transport rollers 34 and 34, but is transported toward the lower side of the fixing device B at the time of duplex printing.

  Next, the problem to be solved by the present invention will be described with reference to FIG. FIG. 2 is an explanatory diagram showing a state in which a wide range of solid images are fixed on the recording paper. On the recording paper P shown in FIG. 2, when a wide solid image 40 is fixed, two glossy lines 41, 41 are generated in the transport direction α. That is, when recording paper P of the same size is continuously passed, burrs at cut portions attached to both ends of the recording paper P damage the surface of the fixing member (paper edge scratch).

  As the above state continues, the portion of the fixing member that contacts the edge portion of the recording paper P is clearly marked with a vertical stripe. If a wide solid image 40 is fixed on the recording paper P larger than the size with the paper edge scratched in this state, the portion corresponding to the vertical stripe-shaped scratched portion is fixed differently from the other portions, and the vertical portion is fixed. Striped gloss unevenness.

  Next, details of the fixing device B according to the embodiment of the present invention will be described. FIG. 3 is an enlarged front view showing a main configuration of the fixing device B according to the embodiment of the present invention. 3 includes a fixing roller 50, a heating roller 52, a fixing belt 53 as a fixing member, and a pressure roller 51 as a pressure member.

The heating roller 52 has a built-in heater 52a for fixing unfixed toner on the recording paper P.
The fixing belt 53 is for heating and fixing the recording paper P carrying an unfixed toner image, and is stretched between the heating roller 52 and the fixing roller 50. The pressure roller 51 is in pressure contact with the fixing roller 50 via the fixing belt 53 to form a nip portion N.

  In the present embodiment, the pressure roller 51 is provided with a drive motor 54 that is a drive source for driving the pressure roller 51 forward and backward, and the fixing roller 50 is provided with the fixing roller 50 forward and backward. A driving motor 55 that is a driving source for rotational driving is connected to each other. The pressure roller 51 is connected to a driving motor for driving the pressure roller 51 in a forward rotation, and the fixing roller 50 is connected to a driving motor for rotating the fixing roller 50 in a forward and reverse direction. May be. Furthermore, a configuration may be adopted in which both the pressure roller 51 and the fixing roller 50 are connected to a driving motor that rotates forward and backward independently of each other.

  That is, the fixing belt 53 and the pressure roller 51 may be made independent from each other, and the fixing belt 53 and / or the pressure roller 51 may be rotated forward and backward. The fixing roller 53 and the pressure roller 51 are independent from each other, and are not limited to the configuration in which the driving motor is connected to the pressure roller 51 and the fixing roller 50, respectively. It is good also as a structure which provided the single drive source for rotating both forward and backward.

  By the way, the drive motors 54 and 55 are connected to the output side of the control unit C, respectively. The control unit C is provided with a storage unit CM, and necessary setting values are stored in advance in the storage unit CM.

  The control unit C is a control center of the fixing device B, and implements the following functions by executing predetermined programs. A cumulative number determination function for determining whether or not the cumulative number of recording sheets P passing through the nip portion N has reached a predetermined number. This function is referred to as “cumulative number determination means C1”. The “cumulative number” is a number set corresponding to the difference in the type and thickness of the recording paper P, and is stored in advance in the storage unit CM as a set value. In the present embodiment, a sensor (not shown) is arranged in the vicinity of the nip portion N, and the cumulative number of recording paper P is counted for each type and thickness of the recording paper P through the sensor. It is not limited to.

  The fixing member is caused to rotate forward or backward with a linear velocity difference between the fixing member (fixing belt) 53 and the pressure member (pressure roller) 51 at a predetermined timing when the recording paper P is not passed. A function of polishing the surface of the (fixing belt 53). This function is referred to as “polishing control means C2.” “Predetermined timing” is when the cumulative number of sheets of recording paper P passing through the nip portion N reaches a predetermined number. “Forward rotation or forward / reverse rotation” is stored in advance in the storage unit CM as a set value corresponding to the difference in the type and thickness of the recording paper P. Details will be described later. The “linear velocity difference” is stored in advance as a setting value in the storage unit CM in accordance with the difference in the type and thickness of the recording paper P.

FIG. 4 is a flowchart showing the details of the polishing control in the fixing device B described above.
Step 1 (abbreviated as “S1” in the figure): When paper feeding is started, the process proceeds to Step 2.
Step 2: When passing paper, the cumulative number of papers passed by size of the recording paper P, the type of recording paper P set on the copier A side (for example, plain paper, other materials), and thickness (thin paper, plain paper) , Thick paper) The operation of acquiring another cumulative number of sheets is started.
Step 3: Each polishing mode corresponding to the difference in the type and thickness of the recording paper P is detected, and the process proceeds to Step 4.
Step 4: The detection value (cumulative sheet passing number) acquired in step 3 is compared with the preset setting value (sheet passing number) of the polishing mode, and it is determined that the detection value exceeds the set value. If so, go to Step 5. On the other hand, if it is determined that the detected value is equal to or less than the set value, the process proceeds to step 7 to end the operation.

Step 5: Since the detected value exceeds the set value, a predetermined polishing mode (polishing operation) is executed at a predetermined timing, and the process proceeds to Step 6.
Step 6: After initializing the detection value, the process proceeds to Step 7 to finish the operation.

  Details of the polishing mode in step 5 will be described. When the paper edge scratch described above occurs on the surface of the fixing member (fixing belt 53) and the recording paper P having a larger width in the transport direction α than the occurrence site is passed, vertical stripe-like gloss unevenness occurs. At this time, even if the fixing roller 50 and the pressure roller 51 are idled at the same speed, the paper edge scratch of the fixing belt 53 is not repaired.

  In this case, it is known that the paper edge scratch can be repaired by rotating the fixing roller 50 and the pressure roller 51 with a linear speed difference. However, if the rotating speed is always rotated, the fixing roller 50 or the pressure roller 51 may be shortened. Therefore, it is preferable to activate a polishing mode that repairs a paper edge flaw only when necessary in consideration of the life of the fixing roller 50 and the pressure roller 51. In addition, depending on the level of the paper edge scratch, there are cases where it cannot be repaired by rotation in the same direction, and the structure can be driven forward and backward. This is because the polishing level is higher in forward / reverse rotation driving than in forward rotation.

  The operation timing of the polishing mode is basically performed when the number of accumulated sheets is counted for each size of the recording sheet P and reaches a predetermined number in the non-sheet passing state. However, the predetermined number varies depending on the type and thickness of the recording paper P. Therefore, the type information (material difference) and thickness information (thin paper, plain paper, thick paper) of the recording paper P are stored in advance, and the setting value of the polishing mode is determined according to the difference of the recording paper P. . It should be noted that the setting value should be larger for thin paper with a small edge burr on the recording paper P, and the setting value should be shorter for thick paper with a large edge burr.

  The rotation direction of the polishing mode may be set according to the type and thickness of the recording paper P. For example, in the case of thin paper with few edge burrs, polishing by forward rotation is performed, and in the case of thick paper with large edge burrs, polishing by forward and reverse rotation is performed. Since the forward and reverse rotations have higher polishing ability, paper edge scratches are more effective for repair.

  The linear velocity difference in the polishing mode may be set corresponding to the difference in the type and thickness of the recording paper P. In the case of thin paper with little edge burrs, it is not necessary to give a great difference in linear velocity, and in the case of thick paper with large edge burrs, it is preferable to increase the linear velocity difference. However, it is necessary to be careful because the effect of repairing the scratches on the paper edge is lost if the linear velocity difference is too great. Experimentally, it has been found that the setting of the linear velocity ratio of 1: 1.2 to 1.5 has the highest polishing effect.

  It is preferable to use a combination of the number of operating sheets, the rotational direction, and the linear velocity difference corresponding to the difference in the number of sheets to be passed, the type of recording paper P, and the thickness, which are the operating conditions of the polishing mode. When paper edge scratches occur at the earliest stage, the cumulative number of sheets passed until operation is small, the rotation direction is forward / reverse rotation, and the linear velocity difference is preferably large. On the other hand, in the case of thin paper in which paper edge scratches are unlikely to occur, it is preferable that the cumulative number of sheets passed until operation is increased, the rotation direction is set to forward rotation, and the linear velocity difference is decreased.

  For comparison with the above polishing mode, a conventional fixing device will be described with reference to FIG. FIG. 5 is a front view illustrating a schematic configuration of a conventional fixing device. A conventional fixing device includes a fixing belt 100, a fixing roller 101, a pressure roller 102, and a heating roller 103 with a built-in heater 104. Further, a refreshing roller 105 for polishing the surface of the fixing belt 100 and a counter roller 106 are disposed on a part of the fixing belt 100.

  In the conventional fixing device, since the surface of the fixing belt 100 is always polished by the refresh roller 105, the life of the fixing belt 100 is shortened. In addition, the mechanical part for polishing increases the cost and the demerit of increasing the size of the fixing device itself occurs. On the other hand, the fixing device B of the present invention described above can be applied to any of the roller fixing method, the fixing belt method, and other fixing methods while avoiding an increase in the size of the fixing device B itself. can do.

  According to the fixing device B and the copying machine A according to the above-described embodiment, the following effects can be obtained. With the minimum configuration of providing a drive motor, the rotation direction and linear velocity difference between the fixing member (fixing belt) and the pressure member (pressure roller) can be provided. As a result, it is possible to repair the paper edge scratches, reduce the cost, and prevent the apparatus itself from becoming large.

  By performing surface polishing of the fixing member (fixing belt) at a timing when a predetermined cumulative number of sheets has passed, paper edge scratches can be repaired without shortening the life of the fixing member. Efficiently because polishing timing is set according to each recording paper in accordance with the time until the paper edge scratches occur due to the type and thickness of the recording paper, and the depth of the scratches differing Paper edge scratches can be repaired.

  Depending on the type and thickness of the recording paper, the rotation direction of the fixing member and the pressure member can be set forward and backward according to the difference in the depth of the paper edge scratch, and the paper edge scratch can be repaired without shortening the life of the fixing member. it can.

  The difference in linear velocity between the fixing member and the pressure member can be set according to the depth of the paper edge flaw which varies depending on the type and thickness of the recording paper, and the paper edge flaw can be repaired efficiently.

  Even if the fixing member has a roller shape or a belt shape, the scratches on the paper edge can be repaired. If the copying machine has a fixing surface side, a rotation direction of the pressure member, and a fixing device that gives a difference in linear velocity, a paper edge scratch can be repaired.

  In the above-described embodiment, the belt-shaped fixing belt is shown as an example of the fixing member. However, the fixing member is not limited to the fixing belt, and may be a roller-shaped fixing roller.

9 Main body 10 Developing machine 11 Charging unit 20 Image forming devices 21Y, 21M, 21C, 21K Each image forming unit 26 Roller 28 Secondary transfer bias roller 31 Housing cassette 32 Conveying path 40 Solid image 50 Fixing roller 51 Pressure roller (Pressurizing) Element)
52a heater 53 fixing belt (fixing member)
54 Driving motor 100 Fixing belt 105 Refresh roller C Control unit CM Storage unit N Nip unit P Recording paper α Conveying direction

JP 2014-232215 A JP 2014-228789 A Japanese Patent Laying-Open No. 2015-87738

Claims (8)

In a fixing device comprising: a fixing member that heats and fixes a recording paper carrying an unfixed toner image; and a pressure member that presses against the fixing member to form a nip portion;
A driving source for making the fixing member and the pressure member independent from each other and rotating the fixing member or the pressure member or both forward and backward;
The surface of the fixing member is polished by rotating the fixing member and the pressing member forward or backward with a linear velocity difference by the driving source at a predetermined timing when the recording paper is not passed. A fixing device comprising a polishing control means.   The fixing device according to claim 1, wherein the predetermined timing is when the cumulative number of recording sheets passing through the nip portion reaches a predetermined number.   The fixing device according to claim 2, wherein the predetermined number of sheets is preset according to a difference in a type and a thickness of the recording paper.   4. The fixing device according to claim 2, wherein the rotation direction of the fixing member and the pressure member is set in advance corresponding to the difference in the type and thickness of the recording paper.   The fixing device according to claim 1, wherein the linear velocity difference is set in advance in accordance with a difference in the type and thickness of the recording paper.   The fixing device according to claim 1, wherein the fixing member is a fixing belt, and the pressing member is in pressure contact with the fixing belt.   The fixing device according to claim 1, wherein the fixing member is a fixing roller, and the pressure member is in pressure contact with the fixing roller. An image forming apparatus comprising the fixing device according to claim 1.