JP2000056529A - Paper loop amount control device - Google Patents

Abstract

(57) Abstract: The present invention provides a low-cost paper loop amount control capable of forming a predetermined amount of loop in front of a conveying member and preventing occurrence of an abnormal image. Things. SOLUTION: A loop detection sensor 17 detects a loop of the sheet P, and transmits a driving force to a heating roller 12 based on detection information from the sensor 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling a loop amount of a sheet, and more particularly, to a fixing member when a sheet on which a toner image has been transferred by an image transfer member is conveyed to a fixing member and fixed by the fixing member. The present invention relates to a loop amount control device that can prevent a situation in which an abnormal image is transferred by pulling the sheet from the image transfer member side by forming a loop in the sheet in front of the loop.

[0002]

2. Description of the Related Art Generally, when a toner image is transferred to a sheet by an image transfer member such as a photosensitive drum or a transfer roller, the toner image is fixed on the sheet by a fixing member including a heating roller and a pressure roller. I have to. In such an apparatus, before the sheet fed from the nip between the photosensitive drum and the transfer roller is nipped by the nip between the heating roller and the pressure roller, a certain margin is provided for the sheet at the upstream portion of both rollers. After a loop is formed as a part, the toner image is fixed on a sheet by sandwiching the nip between a heating roller and a pressure roller.

In order to form a loop as described above, the linear speed of the heating roller is set to be lower than the linear speed of the photosensitive drum. Abnormalities such as the toner image not being able to be normally transferred to the paper by the photosensitive drum due to the paper being pulled too much by the roller and the pressure roller, or the toner image being rubbed by the paper being pulled too much by the heating roller and the pressure roller An image is prevented from being generated.

As this kind of loop amount control, for example,
Japanese Patent Application Laid-Open No. 1-267237 discloses a method in which the amount of a loop generated before a heating roller and a pressure roller is detected, and when the amount of a loop is large, fixing is performed. Since there is a risk that paper jams may occur on the transport path in front of the device, the linear velocity of the pressure roller is increased to reduce the loop that has become too large, and when the amount of loop is small, the pressure roller It is determined that the linear velocity is faster than that of the photosensitive drum, and the linear velocity of the pressure roller is reduced to prevent the transfer of paper from being poor due to the tension of the sheet.

[0005]

However, in such a conventional loop amount control device, two drive units are independently provided to make the linear speed of the pressure roller different from that of the photosensitive drum. Either a motor is required, or two transmissions for varying the driving force transmitted from the driving motor to the pressure roller in two stages, A and B, are required.
There is a problem that the cost of loop amount control increases.

When a registration roller is provided upstream of the photosensitive drum in the sheet conveying direction, the relationship between the linear velocity A of the registration roller, the linear velocity B of the photosensitive drum, and the linear velocity C of the pressure roller is determined. Since A>B> C is generally satisfied (because the registration roller desirably has a high linear velocity in order to quickly feed the sheet to the photosensitive drum), roll paper or A
When an image is formed on a long sheet of three sizes or the like, the linear velocity changes in the middle of the sheet.

In particular, as shown in FIG. 6, since the linear velocity of the heating roller is varied based on the magnitude of the loop amount, the characteristic values such as the fixing rate change within one sheet and the image quality is reduced. The problem of lowering has occurred. Further, since the linear velocity A of the registration roller is greater than the linear velocity B of the photosensitive drum, a loop is generated between the registration roller and the photosensitive drum, and a loop is formed on the transport path between the registration roller and the photosensitive drum. There is a possibility that a jam or the like may occur.

Accordingly, the first aspect of the present invention is to provide a low-cost paper loop amount control capable of forming a predetermined amount of loop in front of a conveying member and preventing occurrence of an abnormal image. It is an object. According to the second aspect of the present invention, when an image is formed on a long sheet, characteristic values such as a fixing rate are reliably prevented from changing within one sheet, thereby deteriorating image quality. It is an object of the present invention to provide a paper loop amount control capable of preventing the occurrence of a loop.

Further, according to the present invention, it is possible to prevent a loop from being formed on a transport path between an image transfer member and a transport member on the upstream side of the image transfer member, thereby preventing the image transfer member and the transport member from being looped. It is an object of the present invention to provide a loop amount control capable of preventing a jam or the like from occurring on a transport path between the loops.

[0010]

According to the first aspect of the present invention,
In order to solve the above problem, when a sheet on which a toner image has been transferred by an image transfer member is conveyed to a fixing member and is fixed by the fixing member, a loop is formed on the sheet on the front side of the fixing member. A loop detecting device for detecting a loop of the paper, and a control device for transmitting a driving force to the fixing member based on detection information of the loop detecting device. Features.

In this case, since the driving force is not transmitted to the fixing member when the sheet is fed from the image transfer member,
Since the sheet can be brought into contact with the fixing member to form a loop, and when the loop of the sheet becomes a predetermined size, the driving force is transmitted to the fixing member.
A loop can be reliably formed irrespective of the size and coefficient of friction of the paper, and the toner image cannot be normally transferred to the paper by the photoconductor drum due to the tension of the paper by the fixing member, or the paper can be formed by the fixing member. It is possible to prevent an abnormal image from being generated due to, for example, rubbing of the toner image due to excessive pulling.

Further, the driving force transmitted to the fixing device is turned on.
Since the size of the loop can be made constant by providing the control means for turning on / off, a complicated drive mechanism for changing the linear speed of the image transfer member and the fixing member as in the related art is unnecessary, and the loop amount control is performed. Can be prevented from increasing. According to a second aspect of the present invention, in order to solve the above-mentioned problem, in the first aspect of the present invention, the conveyance is performed at a timing at which the paper conveyed to the image transfer member is upstream of the image transfer member in the conveyance direction of the paper. Having members,
The control means controls the conveying member, the image transfer member, and the fixing member at the same linear velocity.

In this case, since the linear velocity of the conveying member, the image transfer member and the fixing member is the same, when an image is formed on a long sheet, the linear velocity changes in the middle of the sheet. Thus, it is possible to reliably prevent the image quality from deteriorating. Further, even when the conveying member, the image transfer member, and the fixing member have the same linear velocity, the loop can be reliably formed on the sheet by turning on / off the control unit.

According to a third aspect of the present invention, in order to solve the above-mentioned problem, in the first or second aspect of the present invention, a transport member side loop detecting means for detecting a loop generated on a sheet in front of the transport member. Wherein the control means transmits a driving force to the conveyance member based on the detection information of the conveyance member-side loop detection means, and controls the conveyance member and the image transfer member at the same linear velocity. .

In this case, since the driving force is not transmitted to the conveying member when the sheet reaches the conveying member, the sheet can contact the conveying member to form a loop, and
When the loop amount of the paper reaches a predetermined value, the transport member is driven to have the same linear velocity as the image transfer member, so that a loop occurs on the transport path between the image transfer member and the transport member. Can be prevented, and the occurrence of a jam or the like on the transport path between the image transfer member and the transport member can be prevented.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are diagrams showing one embodiment of the paper loop amount control according to the present invention. Note that this loop amount control is installed in an image forming apparatus such as a copying machine, a printer, and a facsimile machine.

First, the configuration will be described. 1 and 2, reference numeral 1 denotes a transport roller which is a driving side, and reference numeral 2 denotes a pressure transport roller which is a driven side which is slidably brought into contact with the transport roller 1; The transported paper is transported while being pinched.
The sheet P conveyed by the rollers 1 and 2 passes through guide plates 3 and 4, and is a driving roller (conveying member) 5 and a resist pressing roller (conveying member) that is in sliding contact with the roller 5. It is transported toward the transport member 6. These rollers 5 and 6 are adapted to take timing of the sheet P conveyed to the photosensitive drum (image transfer member) 7, and more specifically, when the sheet P is conveyed to the photosensitive drum 7. After being temporarily stopped, the pressure roller 6 is driven again at the same time as the image forming timing, and conveys the sheet P to the photosensitive drum 7 through the guide plate 8.

The photosensitive drum 7 carries a toner image corresponding to the image, and transfers the toner image together with the transfer roller 9 to a sheet P conveyed to the photosensitive drum 7. The paper P on which the toner image is transferred is guided by the guide plates 10 and 11 and is sandwiched between the heating roller 12 on the driving side and the fixing pressure roller 13 on the driven side which is slidably pressed against the heating roller 12. The sheet P is pressed by the fixing pressure roller 13 while being heated by a heater built in the heating roller 12, so that the toner image is fixed on the sheet P. In addition,
The heating roller 12 and the fixing pressure roller 13 constitute a fixing member.

As shown in FIG. 2, the transport roller 1, the registration roller 5, the photosensitive drum 7, and the heating roller 12 are driven by a drive motor 14. Further, the heating roller 12 has the fixing drive clutch 15 turned on / off.
As a result, the driving force from the driving motor 14 is transmitted or interrupted, and the registration roller 5 transmits or receives the driving force from the driving motor 14 when the registration driving clutch 16 is turned ON / OFF. The transport roller 1, the registration roller 5, the photosensitive drum 7, and the heating roller 12 are rotatably driven at the same linear speed by a drive motor 14.

On the other hand, the guide plate 10 is provided with a loop detection sensor (loop detection means) 17, which is constituted by a switch having a filler or the like which comes into direct contact with the paper, and is provided in front of the heating roller 12. When the loop portion of the paper P generated on the side contacts, it turns on and outputs this detection information to a CPU (Central Processing Unit) 18. The CPU 18 turns on the fixing drive clutch 15 based on the detection information from the detection sensor 17 and transmits the driving force of the drive motor 14 to the heating roller 12.

The guide plate 3 is provided with a loop detection sensor (transport member side loop detection means) 19. The loop detection sensor 19 is constituted by a switch having a filler or the like which comes into direct contact with the sheet, and a registration roller. When the loop portion of the sheet P generated on the front side of the sheet No. 5 comes into contact, it is turned on and outputs this detection information to the CPU 18. The CPU 18 turns on the registration drive clutch 16 based on the detection information from the detection sensor 19 to turn on the drive motor 14.
Is transmitted to the registration roller 5.

When the fixing drive clutch 15 is turned on and the registration roller 5 is rotated, and when the registration drive clutch 16 is turned on and the heating roller 12 is rotated, the registration roller 15 and the heating roller 12 It rotates at the same linear speed as. Note that the sensors 17 and 19 may be photo sensors or ultrasonic sensors for detecting the distance of the sheet P, and in this case, C
The PU 18 determines that the loop amount of the sheet P is a predetermined amount when the detection signal from the sensor reaches a certain value, and controls the clutches 15 and 16 to be turned on.

In this embodiment, the driving motor 14, the fixing driving clutch 15, the registration driving clutch 16 and the CP
U18 constitutes the control means. Also, in FIG.
21 is a PSU (Power Supply) for supplying power to the equipment.
Unit), 22 is a power pack, 23 is a memory in which a program for loop control processing or various data used in this device is stored, 24 is a drive motor 14, clutches 15, 16 and sensors
17, 19, CPU 18, PSU 21, power pack 22, memory
This is a bus connecting 23.

Next, the flowchart of FIG.
The loop amount control will be described based on the timing chart shown in FIG. First, the sheet conveyed from the sheet cassette is conveyed along the guide plates 3 and 4 while being pinched by the conveying roller 1 and the pressure conveying roller 2. At this time, since the registration drive clutch 16 is in the OFF state, the drive motor 14
No driving force is transmitted to the registration roller 5 from the above, and the registration roller 5 is stopped. For this reason, a loop is formed at the leading end of the sheet P that has reached the registration roller 5 and the registration pressure roller 6 in a region indicated by B in FIG.

Next, when the loop of the sheet P is detected by the loop detection sensor 19 (Yes in step S1),
The registration drive clutch 16 is turned on, and the registration roller 5 is driven by the drive motor 14 at the same linear speed as the linear speed of the photosensitive drum 7 (steps S2 and S3). Next, after the electrostatic latent image corresponding to the image signal is written on the photosensitive drum 7 and the toner image is written on the electrostatic latent image (step S4), the paper P is transferred between the photosensitive drum 7 and the transfer roller 9. The toner image that enters the nip and is carried on the photosensitive drum 7 is transferred onto the paper P (step S5).

Next, the paper P is conveyed along the guide plates 10 and 11 while being nipped by the photosensitive drum 7 and the transfer roller 9. At this time, the fixing drive clutch 15
In the state of F, the driving force is not transmitted from the driving motor 14 to the heating roller 12, and the heating roller 12 is stopped.
For this reason, a loop is formed at the leading end of the sheet P that has reached the heating roller 12 and the fixing pressure roller 13 in a region indicated by A in FIG. At this time, as shown in FIGS. 4 and 5, when the loop of the sheet P is detected by the loop detection sensor 17 (Yes in step S6), the fixing drive clutch 15 is turned on, and the heating roller 12 The drum 7 is driven at the same linear speed as the linear speed (steps S7 and S8). Therefore, the toner image is fixed on the sheet by the heating roller 12 and the pressure roller 13, and the sheet P on which the toner image has been fixed is discharged to a discharge tray (not shown) (step S9).

As described above, in this embodiment, when the sheet P is sent out from the photosensitive drum 7, the fixing drive clutch
Since the driving force is turned off and the driving force is not transmitted to the heating roller 12, the paper P can be brought into contact with the heating roller 12 and the fixing pressure roller 13 to form a loop, and the loop of the paper P can have a predetermined size. When this happens, the fixing drive clutch 15 is turned on to transmit the driving force to the heating roller 12, so that a loop can be reliably formed irrespective of the size of the sheet P, the friction coefficient, and the like. Heating roller
The toner image cannot be normally transferred to the paper P by the photoconductor drum 7 due to the paper P being pulled too much by the fixing pressure roller 13 and the toner P, and the paper P is pulled too much by the heating roller 12 and the fixing pressure roller 13. It is possible to prevent occurrence of an abnormal image due to rubbing of the image and the like.

Further, by providing a fixing drive clutch 15 for turning on / off the driving force transmitted to the fixing roller 12, the size of the loop can be made constant. This eliminates the need for a complicated drive mechanism for varying the linear speed of the motor, thereby preventing an increase in the cost of loop amount control. The drive motor 14
Controls the registration roller 5, the photosensitive drum 7, and the heating roller 12 at the same linear velocity, so that the long paper P
When an image is formed on the paper P, it is possible to reliably prevent the linear velocity from changing in the middle of the sheet P, and to prevent the image quality from deteriorating. Further, even when the registration roller 5, the photosensitive drum 7, and the heating roller 12 are set to the same linear velocity, the ON / OFF of the fixing drive clutch 15 or the registration drive clutch 16 reliably forms a loop on the sheet P. can do.

Further, when the sheet P arrives at the registration roller 5, the registration drive clutch 16 is turned off and no driving force is transmitted to the registration roller 5, so that the sheet P contacts the registration roller 5 and the registration pressure roller 6. To form a loop, and when the loop amount of the paper P reaches a predetermined value, the registration driving clutch 16
Is turned on to drive the registration roller 5 at the same linear speed as the photosensitive drum 7, so that a loop is generated between the guide plates 3 and 4 between the photosensitive drum 7 and the registration roller 5. Can be prevented, and the occurrence of a jam or the like between the guide plates 3 and 4 can be prevented.

[0030]

According to the present invention, the driving force is not transmitted to the fixing member when the sheet is sent out from the image transfer member, so that the sheet can be brought into contact with the fixing member to form a loop. Since the driving force is transmitted to the fixing member when the loop of the sheet has a predetermined size, the loop can be reliably formed irrespective of the size of the sheet and the friction coefficient. Prevents the toner image from being normally transferred to the sheet by the photosensitive drum due to excessive pulling of the sheet, and the occurrence of an abnormal image due to the toner image being rubbed by the fixing member pulling the sheet too much. be able to.

The driving force transmitted to the fixing device is turned on.
Since the size of the loop can be made constant by providing the control means for turning on / off, a complicated drive mechanism for changing the linear speed of the image transfer member and the fixing member as in the related art is unnecessary, and the loop amount control is performed. Can be prevented from increasing. According to the second aspect of the present invention, since the linear speed of the conveying member, the image transfer member and the fixing member is the same, when forming an image on a long sheet, the linear speed changes in the middle of the sheet. Can be reliably prevented, and the image quality can be prevented from deteriorating. Further, even when the conveying member, the image transfer member, and the fixing member have the same linear velocity, the control unit is turned on / off.
By performing F, a loop can be reliably formed on the sheet.

According to the third aspect of the present invention, since the driving force is not transmitted to the conveying member when the sheet reaches the conveying member, the sheet can contact the conveying member to form a loop, and When the loop amount becomes a predetermined value, the conveying member is driven to have the same linear velocity as the image transfer member, so that the occurrence of a loop on the conveying path between the image transfer member and the conveying member is prevented. Thus, it is possible to prevent the occurrence of a jam or the like on the transport path between the image transfer member and the transport member.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a loop amount control device according to the present invention, and is a schematic diagram thereof.

FIG. 2 is a block diagram illustrating a circuit configuration of a loop amount control device according to an embodiment.

FIG. 3 is a flowchart of loop amount control according to one embodiment.

FIG. 4 is a timing chart illustrating loop amount control when a sheet is conveyed to a heating roller according to one embodiment.

FIG. 5 is a timing chart illustrating a linear velocity of the heating roller when a sheet is conveyed to the heating roller according to the embodiment;

FIG. 6 is a timing chart showing conventional loop amount control when a sheet is conveyed to a heating roller.

[Explanation of symbols]

 5 Registration Roller (Conveying Member) 6 Resist Pressing Roller (Conveying Member) 7 Photoconductor Drum (Image Transfer Member) 12 Heating Roller (Fixing Member) 13 Fixing Pressurizing Roller (Fixing Member) 14 Drive Motor (Control Unit) 15 Fixing Drive clutch (control means) 16 Registration drive clutch (control means) 17 Loop detection sensor (loop detection means) 18 CPU (control means) 19 Loop detection sensor (transport member side loop detection means) P paper

Claims (3)

[Claims] When a sheet on which a toner image has been transferred by an image transfer member is conveyed to a fixing member and is fixed by the fixing member, the sheet is formed such that a loop is formed on the sheet in front of the fixing member. A loop amount control device, comprising: a loop detection unit configured to detect a loop of the sheet; and a control unit configured to transmit a driving force to the fixing member based on detection information of the loop detection unit. Loop amount control. 2. The image forming apparatus according to claim 1, further comprising a conveying member upstream of the image transfer member in a conveying direction of the sheet, the conveying member for setting a timing of conveying the sheet conveyed to the image transfer member, and the control unit controls the conveying member, the image transfer member, and the fixing device. 2. The loop amount control according to claim 1, wherein the members are controlled at the same linear velocity. 3. A transport member side loop detecting means for detecting a loop generated on a sheet in front of the transport member, wherein the control means controls the transport based on detection information of the transport member side loop detecting means. 3. The loop amount control according to claim 1, wherein a driving force is transmitted to the members, and the conveying member and the image transfer member are controlled at the same linear velocity.