JP4407149B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheet conveying apparatus and an image forming apparatus having a plurality of conveying units.
[0002]
[Prior art]
Image forming apparatuses such as printers and copiers include a feed roll that feeds a sheet taken out from a sheet storage tray to a conveyance path, a relay roll that relays the sheet in the conveyance path, and a registration roll that conveys the sheet with its leading edge aligned. It has a plurality of conveying members, and these conveying members cooperate to convey one sheet to an image forming position or a paper discharge tray.
A technique for improving sheet conveyance in a sheet conveyance apparatus or an image forming apparatus provided with a plurality of conveyance members is disclosed (for example, Patent Documents 1 to 3).
[0003]
[Patent Document 1]
JP-A-2-233433 [Patent Document 2]
JP-A-4-133070 [Patent Document 3]
Japanese Patent Laid-Open No. 5-270693
[Problems to be solved by the invention]
The present invention has been made from the above-described background, and maintains a transportability by transporting a sheet by a plurality of transporting means, and prevents the occurrence of wrinkles associated with the sheet transport, and this An object of the present invention is to provide an image forming apparatus.
[0005]
[Means for Solving the Problems]
[Sheet Conveying Device]
In order to achieve the above object, a sheet conveying apparatus according to the present invention is provided with a first conveying means disposed in a sheet conveying path and downstream of the first conveying means in the conveying path. When the size of the second transport unit, the third transport unit disposed downstream of the second transport unit in the transport path, and the sheet transported to the transport path is equal to or greater than a predetermined value, On condition that the conveyance of the sheet is started by the third conveying unit, the second conveying unit is switched from the driving state to the driven state, and the first conveying unit and the third conveying unit change the sheet. And the second conveying means is switched from the driven state to the driven state on condition that the trailing edge of the sheet has passed through the first conveying means, and the second conveying means and the third conveying means are switched. controls to convey the sheet by the conveying means, said If the size of the sheet to be conveyed to the sending passage is less than the predetermined value, the third even conveyance of the sheet is started by the conveying means, control for controlling so that the second transport means maintains the driving state Means.
[0007]
In addition, a sheet conveying apparatus according to the present invention includes a first conveying unit disposed in a sheet conveying path, and a second conveying unit disposed downstream of the first conveying unit in the conveying path. The third conveying means disposed downstream of the second conveying means in the conveying path, the first conveying means, and the third conveying means are conveying the same sheet The second conveying means is switched from the driven state to the driven state, and the second conveying means is switched from the driven state to the driven state on condition that the trailing edge of the sheet has passed through the first conveying means. Te, and a control unit that controls so as to convey the sheet by the second conveying means and the third conveying means.
[0010]
[Image forming apparatus]
The image forming apparatus according to the present invention includes a sheet storage unit that stores at least one sheet, a first transport unit that extracts a sheet from the sheet storage unit, and a sheet that is removed by the first transport unit. The second conveying means that conveys downstream of the conveying path, the third conveying means that conveys the leading edge of the sheet conveyed by the second conveying means, and the third conveying means that have been conveyed. If the size of the image forming means for forming an image on the sheet and the sheet conveyed to the conveying path is equal to or larger than a predetermined value, the third conveying means starts the conveyance of the sheet on the condition The second conveying means is switched from the driven state to the driven state, the sheet is conveyed by the first conveying means and the third conveying means, and the trailing edge of the sheet has passed through the first conveying means. As matter, said second transport means by switching from the driven state to the drive state, the control to convey the sheet by the second transport means and the third conveying means, the sheet is conveyed to the conveying path And a control unit that controls the second conveyance unit to maintain a driving state even when the conveyance of the sheet is started by the third conveyance unit when the size is less than the predetermined value .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 includes an image forming apparatus main body 12, an image forming unit 14 is mounted in the image forming apparatus main body 12, and a discharge unit 16 described later is provided on the upper portion of the image forming apparatus main body 12. In addition, for example, two-stage sheet feeding units 18 a and 18 b are disposed below the image forming apparatus main body 12. Further, below the image forming apparatus main body 12, two-stage sheet feeding units 18c and 18d that are detachably mounted as options are arranged. In the following description, when any of a plurality of components such as the paper feeding units 18a to 18d is not specified, it may be simply abbreviated as the paper feeding unit 18 or the like.
[0012]
Each sheet feeding unit 18 includes a sheet feeding unit main body 20 and a sheet feeding cassette 22 (sheet storing means) for storing sheets (sheets). The paper feed cassette 22 is slidably attached to the paper feed unit main body 20 and is pulled out in the front direction (right direction in FIG. 1). In addition, a pickup roll 24 is disposed in the upper part near the rear end of the paper feed cassette 22, and a feed roll 26 and a retard roll 28 that cooperate to prevent double feeding of sheets are disposed behind the pickup roll 24. Yes. Further, the optional paper feed units 18c and 18d are provided with a pair of turn rolls 30c and 30d, respectively.
The set of the pickup roll 24, the feed roll 26, and the retard roll 28 is an example of the first transport unit according to the present invention, and the turn roll 30 is an example of the second transport unit. Moreover, the registration roll 40 mentioned later is an example of the 3rd conveyance means which concerns on this invention.
[0013]
The conveyance path 36 is a sheet path from the pickup roll 24 d of the lowermost sheet feeding unit 18 d to the discharge port 38, and this conveyance path 36 is near the back surface (left side surface in FIG. 1) of the image forming apparatus main body 12. The lowermost sheet feeding unit 18d has a portion formed substantially vertically from the turn roll 30d to the fixing device 62 described later. A transfer device 56 and an image carrier 54 which will be described later are disposed on the upstream side of the fixing device 64 in the conveyance path 36, and a resist roll 40 is disposed on the upstream side of the transfer device 62 and the image carrier 54. Further, a discharge roll 42 is disposed in the vicinity of the discharge port 38 of the conveyance path 36.
[0014]
Therefore, the leading edge of the sheet conveyed from the sheet feeding unit 18 is temporarily stopped by the registration roll 40 in the conveyance path 36, and the sheet is further fed by the turn roll 30 or the like, so that the sheet bends and loops. Form and align the leading edge of the sheet. The sheet whose skew has been corrected in this manner is then sent from the registration roll 40 to the image forming means 14 at a predetermined timing to form an image, and is discharged to the discharge section 16 by the discharge roll 42.
[0015]
However, in the case of duplex printing, it is returned to the reverse path. That is, the front side of the discharge roll 42 is divided into two forks, and a switching claw 44 is provided at the divided portion, and an inversion path 46 is formed to return from the divided portion to the registration roll 40. The reversing path 46 is provided with conveying rolls 48a to 48c. In the case of double-sided printing, the switching claw 44 is switched to the side where the reversing path 46 is opened and the discharge roll 42 is in front of the trailing edge of the sheet. Thus, the discharge roll 42 is reversed, the recording medium is guided to the reverse path 46, and is discharged to the discharge portion 16 through the resist roll 40, the transfer device 62, the image carrier 54 and the fixing device 64.
[0016]
The discharge unit 16 includes an inclined unit 50 that is rotatable with respect to the image forming apparatus main body 12. The inclined portion 50 has a lower discharge port portion and is inclined so as to gradually increase in the front direction (right direction in FIG. 1), with the discharge port portion as a lower end and a higher tip as an upper end. The inclined portion 50 is supported by the image forming apparatus main body 12 so as to be rotatable around the lower end. As shown by a two-dot chain line in FIG. 1, when the inclined portion 50 is rotated upward to be opened, an opening portion 52 is formed, and a process cartridge 68 to be described later can be attached / detached through the opening portion 52. .
[0017]
The image forming means 14 is of, for example, an electrophotographic system, and includes an image carrier 54 made of a photosensitive member, a charging device 56 made of, for example, a charging roll that uniformly charges the image carrier 54, and charging by the charging device 56. An optical writing device 58 that writes a latent image on the image carrier 54 by light, a developing device 60 that visualizes the latent image of the image carrier 54 formed by the optical writing device 58 with a developer, and the developing device. A transfer device 62 composed of, for example, a transfer roll for transferring the developer image by the sheet 60 to the paper, a cleaning device 63 composed of, for example, a blade for cleaning the developer remaining on the image carrier 54, and the paper transferred by the transfer device 62 For example, a fixing device 64 composed of a pressure roll and a heating roll. The optical writing device 58 is composed of, for example, a scanning type laser exposure device, and is arranged in the vicinity of the front surface of the image forming apparatus main body 12 in parallel with the paper feeding unit 18 described above, and exposes the image carrier 54 across the developing device 60. . Further, the developing device 60 includes a developing roll 66 that faces the image carrier 54.
[0018]
The process cartridge 68 is obtained by integrating the image carrier 54, the charging device 56, the developing device 60, and the cleaning device 64. The process cartridge 68 is disposed immediately below the inclined portion 50 of the discharge portion 16 and is attached / detached via the opening portion 52 formed when the inclined portion 50 is opened as described above.
[0019]
[Paper transport mechanism]
In FIG. 2, the paper transport mechanism 70 of the image forming apparatus 10 is schematically shown. In addition to the pickup roll 24, feed roll 26, retard roll 28, turn roll 30, conveyance path 36, and registration roll 40, the sheet conveyance mechanism 70 (sheet conveyance device) includes a control unit 710 that controls a sheet conveyance process, A motor 720 that drives the roll 30 and the like, a clutch 730 that transmits a driving force of the motor 720, and a sensor 740 that detects a sheet conveyed by the conveyance path 36 are included. Note that, in this drawing, for the sake of simplicity, only the paper feeding unit 18a and the paper transport mechanism that transports the paper stacked on the paper feeding unit 18c are shown.
The control unit 710 includes a CPU (Central Processing Unit), a memory, an ASIC (Application Specific Integrated Circuit), and the like, and is disposed inside the image forming apparatus 10. The control unit 710 outputs a control signal to the motors 720a to 720d and the clutch 730 according to the length of the transported paper in the transport path direction to control the paper transport processing.
The motors 720a, 720b, and 720d supply rotational driving force to the pickup roll 24, the feed roll 26, the retard roll 28, and the registration roll 40 in accordance with a control signal from the control unit 710. Further, the motor 720 c supplies rotational driving force to the turn roll 30 via the clutch 730 in response to a control signal from the control unit 710.
The clutch 730 transmits the rotational driving force from the motor 720 c to the turn roll 30 in accordance with a control signal from the control unit 710.
The sensor 740 is a photo sensor, for example, and is disposed on the conveyance path 36 near the upstream side of the registration roll 40 and detects the presence or absence of a sheet conveyed to the registration roll 40.
[0020]
[Paper transport operation]
First, the operation of the sheet transport mechanism 70 when a sheet larger than a predetermined value (for example, B4 size or larger) is stored in the sheet feeding unit 18c will be described. FIG. 3 illustrates a time chart 810 of the paper transport mechanism 70 when the paper is B4 size or larger.
As illustrated in FIG. 3, the control unit 710 (FIG. 2) rotates the motor 720 c when the paper stored in the paper supply unit 18 c is requested, and further rotates the motor 720 c by inserting the clutch 730. The driving force is transmitted to the turn roll 30c. The turn roll 30c obtains a rotational driving force via the clutch 730 and enters a driving state (t1).
[0021]
Subsequently, the control unit 710 rotates the motor 720b. The pickup roll 24c, the feed roll 26c, and the retard roll 28c rotate by obtaining the rotational driving force of the motor 720b. The pick-up roll 24c takes out the paper from the paper feed cassette 22c, and the feed roll 26c and the retard roll 28c cooperate to handle the taken-out paper one by one toward the turn roll 30c in order to prevent double feeding. Transport (t2).
When the paper conveyed by the feed roll 26c and the retard roll 28c is further conveyed in the direction of the resist roll 40 by the turn roll 30c, the sensor 740 detects the leading edge of the conveyed paper, and the control unit 710 detects the leading edge. The detection signal “0” is output (t3).
When the front end detection signal “0” is input from the sensor 740, the control unit 710 rotates the motor 720d to rotate the registration roll 40 (t4). Subsequently, the control unit 710 disconnects the clutch 730 and stops supplying the rotational driving force to the turn roll 30. The turn roll 30 loses the positive driving force due to the separation of the rotational driving force, and switches from the driving state to the driven state (t5). That is, the turn roll 30 is rotated by being separated from the driving force, and is driven to rotate by the conveyed paper.
[0022]
The control unit 710 determines whether or not the trailing edge of the sheet has passed between the feed roll 26c and the retard roll 28c based on the timing at which the sensor 740 detects the leading edge of the sheet and the size of the sheet. When the trailing edge of the sheet passes between the feed roll 26c and the retard roll 28c, the motor 720b is controlled to stop the rotation of the pickup roll 24, the feed roll 26 and the retard roll 28 (t6), and the clutch 730 Is controlled to resume the supply of the rotational driving force to the turn roll 30 (t7).
[0023]
In this way, the sheet transport mechanism 70 switches the turn roll 30 to the driven state, thereby relaxing the loop generated between the registration roll 40 and the turn roll 30c and preventing the generation of wrinkles. That is, when the length of the transported paper in the transport path direction is larger than the predetermined value, the same paper is transported by the resist roll 40 and the turn roll 30c for a long time, and therefore the resist roll 40 and the turn roll 30c. Loops that occur between and may be fixed as wrinkles. Therefore, the paper transport mechanism 70 switches the turn roll 30 to the driven state, and disperses the loop generated between the registration roll 40 and the turn roll 30 between the registration roll 40 and the feed roll 26c. Relaxes the loop and prevents wrinkles. Further, after the trailing edge of the paper passes between the feed roll 26 and the retard roll 28, the paper transport mechanism 70 switches the turn roll 30 to the driving state again, so that high transportability can be maintained.
[0024]
Next, the operation of the sheet transport mechanism 70 when a sheet smaller than a predetermined value (for example, less than B4 size) is accommodated in the sheet feeding unit 18c will be described. FIG. 4 illustrates a time chart 820 of the paper transport mechanism 70 when the paper is smaller than the B4 size. In FIG. 4, the same reference numerals (t1 to t7) are attached to the same timing as in FIG.
The operation of the paper transport mechanism 70 illustrated in FIG. 4 is as follows. Even when the control unit 710 receives the leading edge detection signal “0” from the sensor 740 (t3), the rotational force is applied to the turn roll 30 without disengaging the clutch 730. 3 is different from FIG. 3 in that the driving state is maintained by continuing the supply (t5).
[0025]
As described above, when the length of the transported paper in the transport path direction is smaller than the predetermined value, the time during which the paper is transported while the loop is formed between the registration roll 40 and the turn roll 30c is short. Therefore, the paper transport mechanism 70 can maintain the high transportability by preventing the slip between the registration roll 40 and the paper while keeping the turn roll 30 in the driving state. In particular, in the embodiment in which the sheet is conveyed substantially vertically upward along the conveyance path 36 as in the present embodiment, if the sheet is conveyed by only one conveyance roll (registration roll 40 or the like), the load on the conveyance roll increases. Since the conveyance speed is not stable, it is desirable to always convey the sheet with two or more conveyance rolls as in this example. In addition, when the length of the sheet in the conveyance path direction is smaller than a predetermined value, the width direction may be small. Then, since the area which a sheet | seat applies to a roll becomes small, it is difficult to obtain sufficient conveyance force. Therefore, when a small-size sheet is conveyed, it is highly necessary to prevent the slip between the registration roll 40 and the sheet while keeping the turn roll 30 in the driving state.
[0026]
When a sheet stored in the sheet feeding unit 18a is requested, the control unit 710 controls the motors 720a and 720b to move the pickup roll 24a, the feed roll 26a, the retard roll 28a, and the registration roll 40. The paper stored in the paper feed cassette 22a in the driven state is conveyed toward the image forming means 14.
[0027]
As described above, in the image forming apparatus 10 according to the present embodiment, when the length of the transported paper in the transport path direction is larger than the predetermined value, the turn roll 30 is driven for a certain period during transport of the paper. To prevent the occurrence of wrinkles by relaxing the loop generated between the registration roll 40 and the turn roll 30, and when the length of the conveyed paper in the conveyance path direction is smaller than the predetermined value, The driving state of the turn roll 30 is maintained to prevent the slip between the registration roll 40 and the paper.
[0028]
[Modification]
Note that the paper transport mechanism 70 (FIG. 2) may drive the pickup roll 24, the feed roll 26, the retard roll 28, the turn roll 30 and the registration roll 40 by a stepping motor. In this case, the control unit 710 can switch the turn roll 30 to the driving state or the driven state depending on the presence / absence of a pulse signal output to the stepping motor, so the clutch 730 shown in FIG. 2 is not necessary.
In the above embodiment, the turn roll 30 is switched from the driving state to the driven state according to the length of the paper in the conveyance path direction, but may be switched according to the flexibility of the paper.
In the above-described embodiment, a mode in which three transport units (registration rolls 40, etc.) are simultaneously involved in paper transport has been described as a specific example. However, the present invention is not limited to this. The present invention can be applied to For example, when the same sheet is simultaneously transported by four or more transporting units, the sheet transporting mechanism 70 drives the transporting units at both ends that transport the sheet and drives the other transporting units to the driven state. .
[0029]
【The invention's effect】
As described above, according to the sheet conveying apparatus of the present invention, it is possible to prevent wrinkles due to sheet conveyance while maintaining the conveyance property by conveying the sheet with a plurality of conveying units.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an image forming apparatus 10 according to an embodiment of the present invention.
2 is a diagram schematically illustrating a sheet transport mechanism 70 of the image forming apparatus 10. FIG.
FIG. 3 is a time chart 810 for explaining the operation of the paper transport mechanism when the paper is longer than a predetermined value.
FIG. 4 is a time chart 820 for explaining the operation of the paper transport mechanism when the paper is shorter than a predetermined value.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming apparatus main body 14 Image forming means 18 Paper feed unit 22 Paper feed cassette 24 Pickup roll 26 Feed roll 28 Retard roll 30 Turn roll 40 Registration roll 710 Control unit 730 Clutch

Claims (3)

First conveying means disposed in a sheet conveying path;
Second transport means disposed downstream of the first transport means in the transport path;
Third conveying means disposed downstream of the second conveying means in the conveying path;
When the size of the sheet conveyed to the conveyance path is equal to or larger than a predetermined value, the second conveyance unit is moved from the driven state to the driven state on condition that the conveyance of the sheet is started by the third conveyance unit. And the second conveying means is driven on condition that the sheet is conveyed by the first conveying means and the third conveying means, and the trailing edge of the sheet has passed through the first conveying means. Switching from the state to the driving state, and controlling the sheet to be conveyed by the second conveying unit and the third conveying unit, and when the size of the sheet conveyed to the conveying path is less than a predetermined value, A sheet conveying apparatus comprising: a control unit that controls the second conveying unit to maintain a driving state even when the conveyance of the sheet is started by the third conveying unit. First conveying means disposed in a sheet conveying path;
Second transport means disposed downstream of the first transport means in the transport path;
Third conveying means disposed downstream of the second conveying means in the conveying path;
On the condition that the first conveying means and the third conveying means are conveying the same sheet, the second conveying means is switched from the driven state to the driven state, and the trailing edge of the sheet is the first sheet. Control means for switching the second conveying means from the driven state to the driving state on the condition that the sheet has passed the conveying means, and controlling the sheet to be conveyed by the second conveying means and the third conveying means. And a sheet conveying apparatus. Sheet storage means for storing at least one sheet;
First conveying means for taking out a sheet from the sheet accommodating means;
Second conveying means for conveying the sheet taken out by the first conveying means downstream of the conveying path;
Third conveying means for aligning and conveying the leading edge of the sheet conveyed by the second conveying means;
Image forming means for forming an image on the sheet conveyed by the third conveying means;
When the size of the sheet conveyed to the conveyance path is equal to or larger than a predetermined value, the second conveyance unit is changed from the driving state to the driven state on condition that the conveyance of the sheet is started by the third conveyance unit. The sheet is conveyed by the first conveying means and the third conveying means, and the second conveying means is driven on condition that the rear end of the sheet has passed through the first conveying means. When the sheet is conveyed by the second conveying unit and the third conveying unit so that the size of the sheet conveyed to the conveying path is less than a predetermined value. An image forming apparatus comprising: a control unit that controls the second conveying unit to maintain a driving state even when the conveyance of the sheet is started by the third conveying unit .

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