JP3000724B2 - Paper transport device for image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper transport device in an image forming apparatus such as an electronic copying machine, and more particularly, to a device such as an electronic copying machine in which paper is held by a transfer unit.
The present invention relates to an apparatus that feeds a sheet toward a transfer unit when a toner image formed on a photosensitive drum is transferred to a sheet to make a copy.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electronic copying machine, a plurality of sheet cassettes and sheet trays are arranged in a sheet feeding section of the apparatus, and sheets of different sizes are stored in such sheet storage devices. In addition, means for feeding a sheet of an appropriate size and making a copy in accordance with information such as the size of the document and the enlargement / reduction ratio is used. In the above-described image forming apparatus, when the paper feeding unit and the image forming apparatus are separated from each other, the paper transport speed is set to be high between the paper feeding unit and the image transfer unit, and The time required for transportation has been reduced. In the image transfer section, the paper is moved in synchronization with the speed of a device such as a photosensitive drum, so that the toner image is not disturbed when the toner image is transferred. For example,
In the conventional example as disclosed in Japanese Patent No. 86435, the paper transport mode described above is set.

In addition to a general electronic copying machine as described above, an apparatus such as a color electronic copying machine has a plurality of developing devices arranged to form a color toner image.
Means are used in which the color toner images are sequentially superimposed and transferred while the paper is held on a transfer drum or the like, and the paper is fixed through a fixing device to create a color copy. The color electronic copying machine is disclosed in, for example,
As disclosed in JP-A-107280 and the like, it is known to use a method in which a color toner image is transferred while the leading end of a sheet is held by a grip means provided on a transfer drum. In addition to the above-described conventional example, a method of transferring a color toner image in a state in which a sheet is electrostatically held on a transfer drum as shown in Japanese Utility Model Application Laid-Open No. 61-206970 or the like is disclosed. Things are also known.

In the color electronic copying machine shown in the above-mentioned conventional example, if the paper path connecting the paper feeding section and the image transfer section is long, the first copy command is output and the paper feeding apparatus is operated. In order to reduce the time required to feed the first sheet, it is necessary to shorten the time required to convey the sheet in the sheet path. Therefore, in a conventional electronic copying machine,
The paper transport speed in the paper path is set to a high speed, but the transport speed in the image transfer unit is set to match the peripheral speed of the photosensitive drum. On the other hand, a driving means for substantially synchronizing the driving speed of the registration roller is used.

[0005]

As described above, when the paper conveying speed in the paper path is set to a high speed, it is naturally necessary to increase the paper feeding speed in the paper feeding unit. However, from the viewpoint of the performance of the paper separating mechanism in the paper feeding unit, when the paper speed is low, the degree of double feeding is small, but when the paper is fed at high speed, the occurrence rate of double feeding is high. Is high. Also, if the paper is conveyed at a high speed in the paper path, the interval between the papers becomes narrower, and the paper can be continuously fed, thereby improving the efficiency of making a copy. If it is large, there is a problem that it is difficult to secure the interval between sheets.

[0006] The above-described conditions for transporting the paper in the paper path have been a serious problem in general electronic copiers and the like. However, even in a color electronic copier, when paper is sent out to a transfer drum. Is a problem that needs to be solved. That is, in order to feed the paper from the paper path to the transfer drum that carries the paper and hold the paper on the transfer drum, the paper is moved from the photosensitive drum to the image transfer unit from the photosensitive drum, It is necessary to set similar conditions. However, in the conventional color electronic copying machine, as seen in the above-described conventional example, there are few cases in which the conditions for transporting the paper in the paper path are strictly studied, and the variation in the paper feeding is small. Etc. have become major problems.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the paper transport apparatus. In particular, in an electronic copying machine, it is possible to exhibit good separation performance in a paper feeding section and to improve the performance in a paper path. It is an object of the present invention to provide a means capable of regulating the conveyance of a sheet and the feeding speed of a registration roller in a portion sent out to a transfer section.

[0008]

SUMMARY OF THE INVENTION The present invention relates to an image forming apparatus for transferring an image formed on a photoreceptor to paper. According to a first aspect of the present invention, in the image forming apparatus, the image forming apparatus conveys the paper fed by the paper feed roller in a paper path, and a paper feed roller for feeding paper stored in a paper feed cassette. A conveyance roller device, a registration roller provided immediately before a transfer unit that transfers an image to a sheet conveyed by the conveyance roller device, and a registration roller provided downstream of the conveyance roller device in the sheet conveyance direction and upstream of the registration roller in a sheet conveyance direction. A pre-registration roller, wherein the paper transport speed of the paper feed roller is V4, the paper transport speed of the transport roller device is V3,
When the paper conveyance speed of the registration roller is V1, V4 <
V3, V1 <V3, and the paper conveyance speed of the pre-registration roller is set to a first speed equal to the paper conveyance speed V3 of the conveyance roller device, and a second speed lower than the first speed. It is configured to be switchable in two stages with the sheet transport speed V2, and the relationship of V1 <V2 <V3 is satisfied, and the speed of the pre-registration roller is a first speed V3 until the leading edge of the sheet is regulated by the registration roller, A control means for switching to the second speed V2 after the paper loop is formed is provided.

As described above, by setting the paper transport speed in the paper feed unit, the transport speed in the paper path, and the speed in the cash register unit to appropriate speeds, the speed in the paper feed unit can be improved. Double feeding can be prevented by exhibiting good judgment performance. Further, by setting the transport speed in the paper path to be high, the first paper can be sent out to the image transfer section with the waiting time reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A sheet conveying device of an image forming apparatus according to the present invention will be described with reference to the illustrated example. The embodiment of the present invention shown in FIG. 1 shows a paper transport device that transports paper from a paper feed cassette 2 to a transfer drum 20 in a color electronic copying machine. In the paper transport device 1 shown in FIG. 1, a paper feed roller 3 and a separating device 4 are disposed with respect to a paper feed cassette 2 disposed in a paper feed unit, and the paper fed from the paper feed unit is provided. Is transported by the transport roller device 6 disposed in the paper path 5. Following the paper path 5, there is disposed a registration section paper path 10 configured as a curved path, and a pre-registration roller 15 is provided upstream of the registration section paper path 10.
, A registration roller 17 is disposed downstream. Further, the sheet fed by the registration roller 17 of the registration section paper path 10 is pressed toward the transfer drum 20 by the pressing roller 21, and is rotated while being electrostatically held on the transfer drum 20. The color toner image formed on the recording medium 25 is transferred.

A sensor S3 for detecting the passage of a sheet is disposed in the sheet path 5, and sensors S1 and S2 are disposed in the registration section sheet path 10, respectively. The operation of detecting the paper inside the printer is performed. The paper transport speed in the paper transport device 1 is:
The speed in the paper feeding unit is v4, the speed in the paper path 5 is v3, the speed of sending out from the registration roller 17 is v1, and the relationship between the speeds in each part is set as v4 <v3, v1 <v3. Further, in the portion of the paper path 10 of the registration unit, the pre-registration roller 15
The relation between the speed v2 of the registration roller and the speed v1 of the registration roller is represented by v1 <v
The number is set to 2 so that the paper in the paper path 10 in the cash register unit will not be pulled between the roller devices on both sides. The length La of the registration unit paper path 10 is set, for example, to a length substantially equal to the minimum size paper used in the image forming apparatus, and the leading end of the paper is nipped by the registration roller 17. , Pre-registration roller 15
, A loop is formed in the paper in the registration unit paper path 10, and the paper can be sent out to the next step in a state where the skew of the paper has been corrected.

When a sheet is conveyed in the sheet conveying apparatus 1 at the above-described speed and the sheet is supplied toward the transfer drum 20, the moving state of the sheet is shown in a timing chart of FIG. It is set as follows. The timing chart shown in FIG. 2 will be described with reference to each constituent member in FIG. 1.
The paper fed from the paper feed roller 3 and the separating device 4
Is sent out toward the paper path 5 at the speed v4. After the fed sheet is detected by the sensor S3 disposed in the sheet path 5, the sheet is moved within the sheet path 5 by a predetermined distance, and the transport roller device 6 disposed in the sheet path 5 is moved.
Then, the sheet is stopped in a state where the leading end of the sheet is nipped. Thereafter, at a predetermined timing, after the dispersion R of the paper feed is eliminated, the transport roller device 6 is driven at the speed v3, so that the transport roller device 6 arranged in the paper path 5 is formed. And the pre-registration roller 15 at the introduction portion of the registration section paper path 10, and is fed at high speed to the registration roller 17. Then, after the leading end of the sheet is nipped by the registration roller 17, the registration section paper path 10
Is stopped in a state in which a loop of a predetermined shape is formed.

The timing chart shown in FIG. 2 shows a case in which a large-size sheet is fed. For example, in a case where only one sheet is held on a transfer drum, the timing chart shown in FIG. Is set so that the distance between the first sheet and the second sheet is set relatively large. On the other hand, when two sheets are held on the transfer drum and the color toner image is sequentially transferred onto the two sheets held simultaneously on the transfer drum,
As shown in the timing chart of FIG. 3, the sheet is fed from the sheet feeding unit in a state where the interval between the first sheet and the second sheet is extremely narrow. Note that FIG. 2 and FIG.
In the example shown in the timing chart of
For example, two types of modes can be considered: a case where only one sheet of A3 size is held on the transfer drum, and a case where two sheets of A4 size are simultaneously held in a horizontal state.

In the state described above, the paper stopped in the paper path 10 of the registration unit is sent out by driving the registration roller 17 at a speed v1 in synchronization with the rotation of the transfer drum 20, and the transfer drum 20 is stopped. , And is electrostatically held by static electricity generated on the surface of the transfer drum. When the pressing roller 21 is pressed against the transfer drum 20, information from a unit for detecting the length of the sheet received in the sheet path or the size of the sheet output from the copying machine main body is used. Based on a signal or the like, a state is set in which the pressing roller 21 presses the sheet toward the transfer drum until the sheet is entirely held on the transfer drum. Each time the transfer drum 20 makes one rotation, the toner image formed on the photosensitive drum 25 is transferred to the sheet, and all the color toner images are transferred in a state of being superimposed on the sheet. Then, the sheet is transported to the fixing device, and a color copy is created.

In the paper transport apparatus 1, the pre-registration roller 15 arranged corresponding to the registration section paper path 10 is driven at high speed when paper is introduced from the paper path 5 into the registration section paper path 10, Is driven at a speed v1 to feed the paper from the registration unit paper path 10 toward the transfer drum, and is driven at a slightly higher speed than the speed v1. In order to drive the pre-registration roller 15 in the mode as described above, a driving device 27 as shown in FIG. 4 is used. The driving device 27 shown in FIG. 4 includes an input gear G1, an intermediate gear member, a high-speed gear G5, a low-speed gear G6, and a driving gear G7 provided on the shaft 16 of the pre-registration roller. The intermediate gear member includes a gear G2 that meshes with the input gear G1, and gears G3 and G4 that mesh with the high-speed and low-speed gears G5 and G6, respectively.
And each of the gears G3 and G4 is an intermediate gear G
The clutch means is arranged between the two shafts. And
In a state where the respective clutches are connected, driving for high-speed and low-speed gears is performed, and the roller shaft 16 is driven via the driving gear G7.

Accordingly, in the pre-registration roller 15 disposed at the entrance of the registration section paper path 10 according to the present invention, when the paper is introduced from the paper path 5 toward the registration section paper path 10, the high speed gear G5 is used. , The pre-registration roller shaft is driven, and the sheet is conveyed in the registration unit paper path 10 at the speed v3. Then, the sheet is conveyed at a high speed in the state where the leading end is nipped by the registration roller 17 until a slight additional feed is performed. Further, when the paper is temporarily stopped in the paper path 10 of the registration unit, and then the registration roller 17 is driven and sent out toward the transfer drum, the pre-registration roller 15 is driven at a low speed. In this case, the pre-registration roller 15 is driven at the speed v2 via the low-speed gear G6, and the feeding operation is continued while a loop is formed on the sheet in the registration unit sheet path 10. You. When the paper is conveyed in the paper path 10 in the register section, the paper is detected by a sensor provided in the paper conveyance device, and the control operation of driving each drive unit is performed according to a program set in the control device. To

In the paper transporting apparatus 1 shown in FIG. 1, the mechanism for driving the registration unit paper path 10 and the pressing roller is configured as shown in FIG. In FIG. 5, the registration section paper path 10 is configured as a curved path, the upper and lower guides 11 and 12 form a paper path, and an opening 13 is arranged at the entrance of the curved path. When the paper jams in the road, the paper can be removed from the opening 13. A pressing roller 21 for pressing the sheet against the transfer drum 20 is provided on a support bracket 22 that is swingable about a shaft 24 at a downstream portion of the registration unit sheet path 10. The guide plate 23 is arranged on the side of the bracket. Then, the pressing roller 21 is pressed against the transfer drum 20 for a predetermined time according to the length of the conveyed sheet,
The paper is held on the transfer drum.

In the apparatus shown in FIG. 5, a pressing roller driving device 30 as shown in FIG. 6 can be used to drive the pressing roller 21. In the pressing roller driving device 30 shown in FIG. 6, the swing arm 31 is disposed with respect to the support bracket 22 that supports the pressing roller 21, and the swing arm 31 is driven by the cam 35 to Is used to swing toward the transfer drum. Further, in order to control the swinging operation of the pressing roller 21, a clutch 40 is used,
An engagement claw 43 driven by a solenoid 42 is arranged for claw members 41 projecting outside the clutch 40. When swinging the pressing roller, the claw 43 of the solenoid 42 is separated from the clutch 40 and the clutch 4
0, the input gear 38 and the gear 37 are connected.
, The pressing roller is pressed against the transfer drum. An actuator member 33 is provided on the swing arm 31 so as to protrude therefrom.
7 is detected by a sensor (shown in FIG.
Is pressed by the information from the sensor S4.

Then, with the pressing roller 21 pressed against the transfer drum, the locking claw 43 is engaged with the claw member 41 of the clutch, and the cam 35 is stopped by rotating the cam 35 approximately ４ turn. The transfer drum is kept pressed. After that, when the timing at which the sheet is completely attached to the transfer drum is checked, the cam 35 is further rotated by １ ／ to separate the pressing roller from the transfer drum. Note that the time for driving the cam is set based on information such as the length of the paper, and the time for which the clutch is activated differs between large-size paper and small-size paper. To be. In the above-described embodiment, the information on the length of the paper may be, for example, information on the size when the size of the paper is selected, information on the length of the paper detected by the sensor, or the like.

In the paper transport apparatus of the present invention configured as described above, a driving device 45 for driving the registration roller 17 and the pressing roller 21 is configured as shown in FIG. In the example shown in FIG.
Through the clutch device 48 to drive the registration roller 17 from the gear device 47 and to drive the swing mechanism of the pressing roller 21 via the clutch 40. The same driving device 45 is used to drive the driving of the registration roller 17 and the mechanism for pressing the pressing roller toward the transfer drum, thereby causing the sheet to adhere to and support the transfer drum. You can do it.

The above-described embodiment of the present invention has been described as applied to an apparatus for transferring a color toner image in a color electronic copying machine in a state in which a sheet is held on a transfer drum. The paper transport mechanism in the transport device can be applied to a general electronic copying machine. Further, the configuration of the paper path in the cash register section and the state of transport of the paper in the paper path in the cash register section are not applied only to the color electronic copying machine. Further, the speed of the paper transport mode in the paper transport mechanism of the present invention can be arbitrarily changed according to the configuration of the electronic copying machine and other conditions.

[0022]

The image forming apparatus according to the present invention has the above-described configuration. In the sheet conveying device, as described above, the sheet conveying speed in the sheet feeding unit, the speed in the sheet path, and By setting the speed at the cash register unit to an appropriate speed, the separating performance at the paper feeding unit can be satisfactorily exhibited and double feeding can be prevented. In addition, by setting the transport speed in the paper path to be high, the first paper can be sent out to the image transfer unit with a reduced waiting time. Further, in the apparatus according to the present invention, after the paper is once stopped in the paper path, the paper can be sent out at a high speed toward the cash register with the interval from the preceding paper being set. The interval between sheets in a road can be set accurately.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a configuration of a sheet conveying device of the present invention.

FIG. 2 is a timing chart showing a state of conveyance of a large-sized sheet in the apparatus of the present invention.

FIG. 3 is a timing chart when a small-sized sheet is conveyed.

FIG. 4 is an explanatory diagram showing a configuration of a driving device for a pre-registration roller.

FIG. 5 is an explanatory diagram illustrating a paper path of a registration unit according to the present invention and a driving mechanism of a pressing roller in an upstream portion thereof.

FIG. 6 is a perspective view illustrating a configuration of a driving mechanism of a pressing roller.

FIG. 7 is an explanatory diagram of a driving device for a registration roller and a pressing roller.

[Explanation of symbols]

1 paper transport device, 2 paper cassette, 3
Paper feed roller, 5 paper path, 6 transport roller device,
10 cash register section paper path, 15 pre-registration roller,
17 registration roller, 20 transfer drum, 21
Press roller, 25 photosensitive drum, 27 drive gear device, 30 press roller drive device, 31 swing arm, 35 cam, 40/48 clutch,
45 Drive.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-243751 (JP, A) JP-A-62-13944 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65H 9/14 B65H 5/06

Claims (1)

(57) [Claims] 1. An image forming apparatus for transferring an image formed on a photoreceptor to a sheet, the image forming apparatus comprising: a sheet feeding roller for feeding a sheet housed in a sheet feeding cassette; A transport roller device that transports the fed paper in the paper path; a registration roller provided immediately before a transfer unit that transfers an image to the paper transported by the transport roller device; and a paper transport direction downstream from the transport roller device. A pre-registration roller provided upstream of the registration roller in the paper conveyance direction, wherein the paper conveyance speed of the paper supply roller is V4, the paper conveyance speed of the conveyance roller device is V3, and the paper conveyance speed of the registration roller is V1. At this time, the relations of V4 <V3 and V1 <V3 are satisfied, and the paper transport speed of the pre-registration roller is set to the paper transport speed V3 of the transport roller device. A first speed of the speed, 2 and the second sheet conveying speed V2 of slower than said first speed
The pre-registration roller speed is set to a first speed V3 until the leading edge of the sheet is regulated by the registration roller, and a loop of the sheet is formed. An image forming apparatus, comprising: control means for switching to a second speed V2 later.