JP3065894B2 - Curl straightening mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curl correcting mechanism for correcting a curl of a recording medium generated when a fixing process is performed in a fixing device of an electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, as a fixing device used in an electrophotographic apparatus, a fixing device having a structure in which a heating roller and a pressure roller are arranged in a state where their outer peripheral surfaces are pressed against each other is widely known. .

When the fixing process is performed by such a fixing device, the outer peripheral surface of the heating roller is harder than the outer peripheral surface of the pressing roller, so that the heating roller bites into the pressing roller. Is higher than the surface temperature of the pressure roller, the recording medium passing between the heating roller and the pressure roller curls in a direction in which the heating roller side becomes concave. When such a curl occurs in the recording medium, it causes a jam during conveyance in the electrophotographic apparatus, or the stacking property after the sheet is discharged out of the electrophotographic apparatus is reduced.

Therefore, various curl correcting mechanisms for correcting such curls have been proposed and put into practical use. For example, as disclosed in Japanese Patent Application Laid-Open No. 4-56980, A pair of upper and lower linear discharge guide plates (guide members) extending in a direction coinciding with the tangential direction at the contact point between the heating roller and the pressure roller is provided downstream of the fixing device along the line. There is something. The curl correcting mechanism guides the curled recording medium between the guide members when passing through the fixing device, corrects the curl by bringing the curled recording medium into contact with the guide member, and removes the curled recording medium. It is to return to a flat state. Note that the recording medium immediately after passing through the fixing device is extremely hot, and is in a state in which the recording medium is likely to have a habit. By bringing the recording medium into contact with a linearly arranged guide member, the curl of the recording medium is reduced. Correction can be performed easily.

[0005]

However, the state of curl becomes remarkable, and the amount of curl (the height from the curled recording medium 8 to the top of the curved portion of the recording medium when the curled recording medium 8 is placed on a flat surface) If the distance between the pair of guide members is larger than the distance between the pair of guide members, there is a disadvantage that the curled recording medium comes into contact with the leading end of the guide member facing the fixing device to cause a jam.

If the gap between the guide members is widened on the side facing the fixing device, it is possible to prevent the curled recording medium from contacting the leading end of the guide member and causing a jam. However, in such a case, since a portion in which a pair of guide members are opposed in parallel is required to have a predetermined size in order to perform the curl correction, the size of the guide member extending to the downstream side in the transport direction of the recording medium is long. Become
It becomes difficult to reduce the size and weight of the electrophotographic apparatus.

Therefore, according to the present invention, even if a recording medium has a significant curl, the correction can be performed, and there is no need to increase the size of the guide member for correcting the curl. An object of the present invention is to provide a curl correcting mechanism capable of preventing a recording medium from being jammed.

[0008]

According to the first aspect of the present invention,
A pair of linear guide members facing each other substantially in parallel at a predetermined interval are provided on the downstream side of the fixing device along the conveying direction of the recording medium, and the guide device guides the recording medium curled at the time of fixing processing by the fixing device. In a curl correcting mechanism configured to correct curl by passing between members, at least one of the guide members is formed such that an entrance-side end of the guide member facing the fixing device is opposed to the other guide member. A position in which the entrance end of the guide member is largely separated from the other guide member until the leading end of the recording medium enters between the guide members. The guide member is rotated to guide the guide member to a position where the guide members face each other in parallel after the leading end of the recording medium enters between the guide members. A rotation mechanism for rotating the timber provided coupled to the guide member.

According to a second aspect of the present invention, in the first aspect of the present invention, an interval between the guide member connected to the rotating mechanism and the other guide member is gradually expanded at an entrance end facing the fixing device. A slanted portion is provided that is inclined in the direction of the angle.

[0010]

According to the first aspect of the present invention, the guide member connected to the rotation mechanism is rotated by the rotation mechanism, and the end of the rotated guide member facing the fixing device at the entrance side is connected to the other guide member. By separating the recording medium from the pair of guide members, the curled recording medium can smoothly enter between the pair of guide members, and even if the recording medium is significantly curled, the recording medium contacts the end of the guide member. Can prevent the occurrence of jams,
After the leading end of the recording medium enters between the guide members, the guide member is rotated by the rotation mechanism so that the pair of guide members face each other in parallel, so that the curl correction can be performed. Since this can be used for curl correction, the size of the guide member can be reduced.

According to a second aspect of the present invention, as described above, when the end of the guide member connected to the rotating mechanism, which is opposite to the fixing device, on the entrance side is rotated to a position where it is separated from the other guide member. In this case, the ends of the pair of guide members facing the fixing device can be very far apart from each other. Therefore, even when a recording medium having significant curl has entered the guide members, It is possible to reliably prevent the occurrence of a jam due to contact with the end.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional front view showing a fixing device 1 and its surrounding structure in an electrophotographic apparatus. The fixing device 1 includes a heating roller 2, a pressure roller 3, and a heating roller 2 whose outer peripheral surfaces are pressed against each other. A halogen lamp 4 provided inside, a thermistor 5 for measuring the temperature of the outer peripheral surface of the heating roller 2, an oil supply roller 6 for supplying oil to the outer peripheral surface of the heating roller 2, a toner adhered to the outer peripheral surface of the heating roller 2, etc. It comprises a cleaning roller 7 to be removed, a peeling claw 9 for peeling the recording medium 8 having undergone the fixing process from the heating roller 2, and the like. The outer peripheral portions of the heating roller 2 and the pressing roller 3 are formed of an elastic body such as silicon rubber, and the rubber hardness of the heating roller 2 is higher than the rubber hardness of the pressing roller 3.

A pair of upper and lower linear guide members 10a and 10b are provided on the downstream side of the fixing device 1 along the conveying direction of the recording medium 8 and are opposed to each other substantially in parallel at a predetermined interval. The position is fixed, and the lower guide member 10b is held rotatably in the vertical direction about a fulcrum 11 provided at the end opposite to the side facing the fixing device 1. The guide member 10a is fixed by:
The fixing is performed by inserting a screw (not shown) into a fixing hole 12 formed in the guide member 10a and screwing the screw to frames 13 located on both sides of the fixing device 1. On the other hand, the holding of the guide member 10 b is performed by rotatably inserting the fulcrum 11 into the holding hole 14 formed in the frame 13. Further, the frame 13 is provided with a stopper 15 for restricting the guide member 10b from rotating above the curl correction position shown by the two-dot chain line.

Next, protrusions 16 are provided on both sides of the guide member 10b at a substantially central portion along the conveying direction of the recording medium 8.
a, 16b are formed, a substantially U-shaped arm 17 is attached to these projections 16a, 16b, and the guide member 10b is urged downward between one projection 16a and the stud 18 attached to the frame 13. A spring 19 is stretched. The arm 17 is connected to a solenoid 20 for turning the guide member 10b upward when energized. The solenoid 20, the arm 17, and the spring 19 constitute a rotation mechanism 21 that rotates the guide member 10 b in the vertical direction with the fulcrum 11 as a fulcrum. The leading end of the recording medium 8 is attached to the guide member 10a by the guide members 10a and 10b.
The sensor 22 for detecting the intrusion into the gap and the peeling claw 9 are attached.

In such a configuration, the recording medium 8 holding the unfixed toner image is conveyed toward the nip between the heating roller 2 and the pressure roller 3, and heat and pressure are applied when passing through the nip. Then, the toner image is fixed on the recording medium 8. At the time of this fixing, the rubber hardness of the heating roller 2 is higher than the rubber hardness of the pressing roller 3 and the temperature at the time of fixing is higher in the heating roller 2 than in the pressing roller 3. No. 8 is apt to cause curl in which the side in contact with the heating roller 2 is concave.

After passing through the nip between the heating roller 2 and the pressure roller 3 in the fixing device 1, the recording medium 8 on which the fixing process has been completed enters between the guide members 10a and 10b, and the guide members 10a and 10b. The recording medium 8 that has passed through the gap is discharged to a paper discharge unit (not shown). Note that the recording medium 8 during the fixing process may be in a state of being stuck to the outer peripheral surface of the heating roller 2 and the releasability from the heating roller 2 may be reduced. The separation can be reliably performed by the peeling nail 9.

Next, the recording medium 8 on which the fixing process has been completed enters between the guide members 10a and 10b. At this time, power is not supplied to the solenoid 20, and the guide member 10b is attached with the spring 19. The guide member 10b is rotated to the lower position shown by the solid line by the force, and the end of the guide member 10b on the entrance side facing the fixing device 1 is separated from the other guide member 10b. For this reason,
Even if the recording medium 8 has a significant curl during the fixing process, the convex side of the curl enters the space between the guide members 10a and 10b without abutting against the end of the guide member 10b. Therefore, even when the recording medium 8 is significantly curled, it is possible to prevent the recording medium 8 from contacting the end of the guide member 10b and causing a jam.

The leading end of the recording medium 8 has guide members 10a,
10b, the recording medium 8 is moved to the sensor 22.
Is detected, and a control unit (not shown) energizes the solenoid 20 based on the detection result from the sensor 22. When the solenoid 20 is energized, the guide member 10b rotates to the curl correction position indicated by the two-dot chain line, and the guide members 10a and 10b face each other at a predetermined interval in a parallel state. Therefore, the curled recording medium 8 comes into contact with the guide members 10a and 10b when passing between the guide members 10a and 10b opposed in a parallel state. Since the recording medium 8 in the high temperature state immediately after the fixing process is in a state in which the recording medium 8 is likely to have a habit, a straight guide member facing the curled recording medium 8 immediately after the fixing process is opposed in parallel. Curling can be corrected by transporting the sheet while making contact with 10a and 10b.

In the curl correction, the guide members 10a and 10b are opposed to each other in parallel and contribute to the curl correction.
And the dimensions from the fixing device 1 to the rear ends of the guide members 10a and 10b can be shortened, and the size of the electrophotographic apparatus can be reduced.

Here, the relationship between the length (member length) of the parallel opposing linear portions of the guide members 10a and 10b and the curl amount of the recording medium 8 after passing through the guide members 10a and 10b is examined. The experimental results will be described based on Table 1. The distance between the guide members 10a and 10b is 12
mm. If the curl amount is 30 mm or less, it is assumed that the curl has been properly corrected.

[0021]

[Table 1]

As can be seen from Table 1, the member length is 40 m
It can be seen that curl correction is favorably performed by setting m or more. Similar experiments were performed by changing the distance between the guide members 10a and 10b to 3 mm, 6 mm, and 9 mm, and almost the same results were obtained.

When the recording medium 8 advances between the guide members 10a and 10b and the sensor 22 detects the rear end of the recording medium 8 and a predetermined time has elapsed, the control unit cuts off the power supply to the solenoid 20. I do. Then, the guide member 10
b rotates to the lower position shown by the solid line by the urging force of the spring 19, and the guide member 10b waits at the rotation position until the next recording medium 8 enters between the guide members 10a and 10b.

In this embodiment, the rotating mechanism 21
Although the solenoid 20 has been described as an example of the drive unit, a cam or a motor may be used instead of the solenoid 20.

Next, a second embodiment of the present invention will be described with reference to FIG. 1 to 4 are denoted by the same reference numerals, and description thereof will be omitted.
In the present embodiment, the guide member 10 b
Is formed at an end on the side facing the fixing device 1 in such a manner as to be inclined so as to gradually widen the interval with the guide member 10a.

In such a configuration, by forming the oblique portion 23, the distance between the ends of the guide members 10a and 10b facing the fixing device 1 is very large. Therefore, even when the recording medium 8 entering between the guide members 10a and 10b is significantly curled, the recording medium 8 contacts the end of the guide member 10b on the side facing the fixing device 1. Therefore, it is possible to more reliably prevent a jam from occurring.

[0027]

According to the first aspect of the present invention, as described above, at least one guide member is turned in a direction in which the entrance end of the guide member facing the fixing device comes into contact with or separates from the other guide member. The guide member is movably provided, and the guide member is rotated to a position where the entrance end of the guide member is largely separated from the other guide member until the leading end of the recording medium enters between the guide members. After the leading end of the guide member enters between the guide members, a rotation mechanism for rotating the guide member to a position where the guide members face each other in parallel is provided in connection with the guide member. Is rotated by the rotation mechanism, and the end of the rotated guide member facing the fixing device is separated from the other guide member, so that the curled recording medium is removed by a pair of guides. Even if the recording medium can smoothly enter between the members and has a significant curl, it can be prevented from causing a jam by contacting the end of the guide member. The curl correction can be performed by rotating the guide member by the rotating mechanism after the leading end portion of the guide member enters between the guide members so that the pair of guide members face each other in parallel.
Since the entire guide member can be used for curl correction, the size of the guide member can be reduced.

According to the second aspect of the present invention, as described above, the guide member connected to the rotating mechanism is inclined at the inlet side end facing the fixing device so as to gradually widen the interval with the other guide member. When the guide member to which the rotating mechanism is connected is rotated to the position where the entrance-side end facing the fixing device is separated from the other guide member, a pair of guides is provided. The end of the member facing the fixing device can be made very far apart, so that even when the recording medium is significantly curled, the recording medium contacts the end of the guide member when entering between the guide members. It is possible to reliably prevent the occurrence of a jam.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a guide member and a rotation mechanism.

FIG. 3 is an enlarged front view showing a part of a guide member.

FIG. 4 is an enlarged side view showing an arrangement state of a guide member.

FIG. 5 is a longitudinal sectional front view showing a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing apparatus 2 Heating roller 3 Pressure roller 8 Recording medium 10a, 10b Guide member 21 Rotation mechanism 23 Oblique part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-64-53978 (JP, A) JP-A-5-338894 (JP, A) JP-A-6-175526 (JP, A) JP-A-6-175526 100219 (JP, A) Fully open sho 56-66952 (JP, U) Fully open sho 60-120461 (JP, U) Fully open sho 57-1997058 (JP, U) (58) Field surveyed (Int. ^7, DB name) G03G 13/20 G03G 15/00 510 - 534 G03G 15/20

Claims (2)

(57) [Claims] A pair of linear guide members which are substantially parallel to each other at a predetermined interval and are provided downstream of the fixing device along a conveying direction of the recording medium; In a curl correcting mechanism configured to correct a curl by passing a recording medium between the guide members, at least one of the guide members is formed such that an entrance-side end of the guide member facing the fixing device has the other end. The guide member is rotatably provided in a direction of coming into contact with and separating from the guide member, and until the leading end of the recording medium enters between the guide members, the entrance-side end of the guide member with respect to the other guide member. The guide member is rotated to a position where the guide members are largely separated from each other, and a position where the guide members face each other in parallel after the leading end of the recording medium enters between the guide members. A curl correcting mechanism, wherein a rotating mechanism for rotating the guide member is provided in connection with the guide member. 2. An oblique portion that is inclined at a direction to gradually widen the interval with the other guide member at an entrance side end of the guide member connected to the rotating mechanism facing the fixing device. The curl correcting mechanism according to claim 1, wherein