JP2002003046A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of being miniaturized and simplified and capable of reducing part cost. SOLUTION: This image forming device is provided with a driving motor 23 for conveying paper sheets P, a pair of paper discharge rollers 14, 15 for pinching and conveying the paper sheet P on which an image is formed, a torque limiter 21 for transmitting drive in the normal rotating direction from the driving motor 23 to the paper sheet discharge rollers 14, 15 to specified torque, an electromagnetic clutch 19 for switching connection and disconnection in drive in the reversal rotating direction from the driving motor 23 to the paper sheet discharge rollers 14, 15, a first paper sheet passing path in which the paper sheet advances to a paper sheet discharge tray 17 outside the machine in normal rotational drive of the paper sheet discharge rollers 14, 15, a second paper sheet passing path in which the paper sheet P again advances to an image forming part in reversal drive of the paper sheet discharge rollers 14, 15, and a control means for making the electromagnetic clutch 19 into the off-state when the paper sheet P is conveyed to the first paper sheet passing path and for making the electromagnetic clutch 19 into the on-state when the paper sheet is conveyed to the second paper sheet passing path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image on paper, such as an electrophotographic printer, a copying machine, and a printing machine.

[0002]

2. Description of the Related Art An image forming apparatus having an automatic double-sided printing function for printing on both sides of a sheet is conventionally known. The basic configuration of an image forming apparatus having the automatic double-sided printing function is to supply one side of a sheet to a transfer section of a toner image, switch back the sheet, and print a toner image on the other side.

A switchback device for transporting a sheet on which an image is formed on one side of the sheet to an image forming unit again has two drive clutches arranged in parallel in a drive transmission unit from a sheet transport drive motor to a transport roller. By controlling ON / OFF of each clutch, the drive in the forward rotation direction and the reverse rotation direction can be selectively transmitted to the transport roller. By providing such a switchback device, it is possible to automatically perform sheet discharge outside the apparatus and switchback to the image forming unit.

As an example of an electrophotographic printer compatible with automatic double-sided printing, Japanese Patent Application No. 10-169640 (JP-A-2000-2000)
No. 7191). In the switchback device according to this application, a switchback-dedicated paper passage path and a transport roller are provided to perform switchback of a sheet.

[0005]

However, when two drive clutches are provided, there is a problem that the drive clutches are generally expensive and the structure becomes large.

Further, in the configuration described in Japanese Patent Application No. 10-169640, since a paper passage path dedicated to switchback and a transport roller are required, the apparatus becomes large, the configuration becomes complicated, and the cost increases. There's a problem.

An object of the present invention is to provide an image forming apparatus capable of reducing the size and simplification of the apparatus and reducing the cost of parts.

[0008]

According to the present invention, there is provided a drive motor for driving the conveyance of a sheet, a pair of discharge rollers for pinching and conveying the sheet on which an image has been formed, and a drive motor for driving the sheet from the drive motor to the discharge roller. A torque limiter for transmitting the drive in the forward rotation direction to a predetermined torque, a drive clutch for switching between connection and release in the reverse rotation direction drive from the drive motor to the discharge roller, and a drive clutch for forward rotation drive of the discharge roller. A first paper passing path in which the paper is directed to a paper output tray outside the machine,
When the paper discharge roller is driven to rotate in reverse, the driving clutch is turned off when the paper is conveyed again to the image forming section and the second paper is conveyed to the first paper passing path. Control means for turning on the drive clutch when the paper is conveyed to the paper passing path.

According to the present invention, there is provided an image forming apparatus capable of reducing the size and simplification of the apparatus and reducing the cost of parts.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to a first aspect of the present invention is directed to a driving motor for driving the conveyance of a sheet, a pair of sheet discharging rollers for pinching and conveying the sheet on which an image has been formed, and a driving motor from the driving motor to the sheet discharging roller. A torque limiter for transmitting the drive in the forward direction to a predetermined torque, a drive clutch for switching between connection and release in the reverse direction drive from the drive motor to the discharge roller, and A first sheet passing path toward the outer sheet ejection tray, a second sheet passing path toward the image forming section when the sheet ejection rollers are driven in reverse, and a sheet conveying sheet to the first sheet passing path. Is an image forming apparatus having a drive clutch in an off state and a control means for turning on the drive clutch when the sheet is conveyed to the second paper passing path. Set the limiter mechanism By configuring the switchback mechanism combined, it has the effect of miniaturization of parts cost reduction and the device can be realized.

According to a second aspect of the present invention, the torque limiter includes a gear G-1 fixed on the shaft of the paper discharge roller, a gear G-2 rotatably disposed coaxially, and a coaxially rotatable gear G-2. And a coil-shaped spring for pressing the gear G-2 against the gear G-1, and the drive transmission is performed by the frictional force generated on the press-contact surface of the gear G-1 and the gear G-2. Claim 1
The image forming apparatus of (1) has an effect that the cost of parts can be reduced by incorporating the torque limiter into the switchback mechanism.

According to a third aspect of the present invention, the drive clutch includes a drive shaft rotatably provided, a gear G-3 fixed on the drive shaft, and a gear coaxially rotatably disposed. G-4, and a clutch for connecting and disconnecting the gear G-4 to and from the drive shaft. The gear G-3 is arranged so as to be able to transmit rotation to the gear G-1, and the gear G-4 is a drive source gear and Gear G
-2, and at least one idle gear G-5 is connected between the gear G-3 and the gear G-1 or between the gear G-4 and the gear G in order to reverse the drive rotation direction.
3. The image forming apparatus according to claim 2, wherein the image forming apparatus has an effect that the arrangement of the gears can reduce the size and cost of the reversing drive device.

According to a fourth aspect of the present invention, in a device for forming an image on a sheet, a pair of sheet discharges which sandwich and convey an image-formed sheet located at an upper portion of a main body and conveyed from below in a substantially horizontal direction. Rollers, drive means capable of switching the paper discharge rollers in forward and reverse directions, two paper discharge ports provided on both sides of the paper discharge rollers for discharging paper outside the machine, and a forward rotation direction of the paper discharge rollers. In the mode in which the sheet is disposed in the discharge tray through the first discharge port and the paper discharge tray disposed adjacent to the first discharge port located on the side, the drive unit is driven to rotate forward. And a control unit for performing a normal rotation drive and then a reverse rotation drive to switch back the paper in a mode in which the paper is discharged out of the apparatus from the other second paper discharge port. No need for a dedicated paper path and switch rollers for switchback. Has the effect that it is reduced in size and simplified and the component cost of the apparatus.

According to a fifth aspect of the present invention, there is provided a sheet insertion port connected to an image forming section provided below the second sheet discharge port;
5. The image forming apparatus according to claim 4, further comprising a transport unit detachably provided in the image forming apparatus for transporting the sheet discharged from the second sheet discharge port to the sheet insertion port. This has the effect that paper can be inserted into a detachable transport unit or other optional equipment without increasing the size and complexity of the forming apparatus body.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth aspect, there is provided a storage tray detachably provided in the image forming apparatus in proximity to the second sheet discharge port. There is an effect that printed paper can be sorted into two groups without increasing the size and cost of the apparatus.

Hereinafter, embodiments of the present invention will be described.

FIG. 1 is a schematic diagram of an entire image forming apparatus using an electrophotographic laser beam printer according to an embodiment of the present invention as an example. In the present embodiment,
An electrophotographic laser beam printer will be described as an example.

In FIG. 1, an exposing unit 2 is disposed in a main body 1 of the image forming apparatus, and image forming units for yellow, magenta, cyan, and black are disposed. The yellow image forming unit includes a photosensitive drum 3-1 on which an electrostatic latent image is formed by a laser beam from the exposure device 2, and a charger 5-1 for charging the photosensitive drum 3-1. A developing unit 4-1 for adhering toner to the photosensitive drum 3-1 to visualize the electrostatic latent image; and a photosensitive drum 3-transferred after transferring the toner image to an intermediate transfer belt (described later) 8. 1
And a cleaner 6-1 for removing the residual toner. The other color magenta, cyan, and black image formations have the same configuration, and include the photosensitive drums 3-2, 3-3, 3-4, the chargers 5-2, respectively.
5-3, 5-4, developing units 4-2, 4-3, 4-4, and cleaners 6-2, 6-3, 6-4. Further, an intermediate transfer belt 8 is disposed so as to be able to run along each image forming unit, and the transfer opposing rollers 7-1, 7-2, 7-3, 7-4 are arranged.

Here, toner images of four colors are superposedly formed on the intermediate transfer belt 8 by the photosensitive drums 3-1 to 3-4.
Transports the paper P. The toner image on the intermediate transfer belt 8 is transferred to the conveyed sheet P by the transfer roller 12, and the toner image is fixed when the sheet P passes through the fixing device 13. The sheet P exiting the fixing device 13 is discharged from the first discharge port 31 to the discharge tray 17 outside the apparatus by a pair of discharge rollers 14 and 15. Note that the residual toner on the intermediate transfer belt 8 after the transfer to the paper P is completed is removed by the cleaning unit 9.

A second discharge port 32 is provided to the left of the discharge roller 14. The discharge roller 14 is selectively driven in the forward and reverse directions by a drive / rotation switching mechanism described in detail later. During double-sided printing, the sheet P on which an image has been formed on one side is switched back and the second discharge is performed. Paper is fed from the paper port 32 to the duplex unit 18.

The duplex unit 18 is configured to be detachably attached to the image forming apparatus as an option.
2 is conveyed to the image forming unit, that is, the insertion opening 33 connected to the transfer roller 12, the toner image is transferred to the other side of the paper P, and after fixing by the fixing device 13, the paper is discharged. The paper is discharged from the first paper discharge port 31 to the paper discharge tray 17 outside the apparatus by the rollers 14 and 15.

FIG. 2 is a configuration diagram of a sheet discharge section reversing device according to an embodiment of the present invention.

In FIG. 2, the discharge roller 14 is formed as a plurality of rubber driving rollers 14-1, 14-2, 14-3, and 14-4 on a shaft 14-5 connected to the reversing device driving section D. Have been. The other discharge roller 15 is driven by driven rollers 15-1, 15-2,
15-3 and 15-4. The driving rollers 14-1 to 14-4 and the driven rollers 15-1
The paper P is nipped and conveyed by the nips of 15 to 15-4.

FIG. 3 is an explanatory diagram of the operation when the reversing device of FIG. 2 performs the forward rotation driving, and FIG. 4 is an explanatory diagram of the operation when the reversing device of FIG. 2 performs the reverse driving. The reversing device driving unit D that selectively drives in the reversing and reversing directions will be described.

A gear G-1 which is non-rotatably fixed and a gear G-2 which is rotatably disposed coaxially are mounted on the shaft 14-5 of the paper discharge roller 14, and are coaxially provided. The gear G-2 is turned into the gear G-
1 is pressed. That is, the gear G-2 and the gear G
-1 disc-shaped friction plates G-1a, G
-2a are integrally provided, and these friction plates G-1a, G-2
a is pressed by a spring 26. Gear G-2
Rotates, the friction plate G-2a and the friction plate G
The rotational driving torque T1 is transmitted by the frictional force generated between −1a. That is, the drive transmittable torque of the torque limiter 21 in the above configuration is the above-described torque T1. On the other hand, the drive shaft 20 rotatably provided in parallel with the shaft 14-5 of the paper discharge roller is provided with a gear G-3 fixed non-rotatably and a rotatable gear G-4. Further, an electromagnetic clutch 19 for connecting and disconnecting the gear G-4 to and from the drive shaft 20 is provided coaxially with the drive shaft 20 as a drive clutch. The gear G-3 transmits the rotation to the gear G-1 via the idle gear G-5, and the gear G-4 rotates to the gear train and the gear G-2 for transmitting the drive from the drive motor (not shown). Can be transmitted.

From the drive motor, the rotational drive in the direction of the arrow is always transmitted to the gear G-4.
Is given a rotational drive in the direction of the arrow. Discharge roller 14
, The electromagnetic clutch 19 is off (drive is released), and the drive shaft 20 is freely rotatable with the gear G-4. Friction plate G-2a and friction plate G-1a
The rotational driving torque T1 due to the frictional force generated therebetween is set to be larger than the rotational torque T2 sufficient to convey the paper P. Therefore, when the gear G-1 is driven to rotate in the direction of the arrow, the sheet discharge roller 14 is driven to rotate in the forward direction, which is the same direction as the arrow. Gear G-5 and Gear G-3
Rotates in the direction of the arrow and the direction of the arrow, respectively, due to the rotation in the direction of the gear G-1.

On the other hand, as shown in FIG. 4, also at the time of reversing, the drive motor drives the gear G-4 to rotate in the direction of the arrow.
In response, the gear G-2 is given a rotational drive in the direction of the arrow. In the mode in which the discharge roller 14 is driven to rotate in the reverse direction, the electromagnetic clutch 19 is on (drive-coupled).
The drive shaft 20 is connected to the gear G-4. Drive shaft 20
The gear G-3, which is non-rotatably fixed above, is driven to rotate in the direction of the arrow 'in the same direction as the arrow of the gear G-4. Since the gear G-5 and the gear G-1 are connected to the gear G-3, the gears G-5 and G-1 are respectively driven to rotate in the directions indicated by arrows 'and'. Since the gear G-1 is fixed to the shaft 14-5 of the paper discharge roller, the paper discharge roller 14 is driven to rotate in the reverse direction in the same direction as the arrow G 'of the gear G-1.

Since the driving coupling force of the electromagnetic clutch 19 is larger than the transmission torque T1 of the torque limiter 21, the gear G-
2 and the friction plate G-2a, G-1a of the gear G-1, slip occurs, and the driving rotation of the gear G-2 in the direction of the arrow is not transmitted to the gear G-1. As described above, the discharge roller 14 rotates in the normal direction when the electromagnetic clutch 19 provided in the reversing device driving unit D is turned off (released), and rotates in the reverse direction when turned on (coupled).

FIG. 5 is a control circuit diagram for driving a paper discharge roller according to an embodiment of the present invention.

The paper sensor 22 in the circuit diagram is arranged near the upstream side of the paper discharge roller 14 (see FIG. 1), and is turned on when the paper P is passing. The ON / OFF signal of the paper sensor 22 is transmitted through the I / O 27 to C
It is input to PU30. The CPU 30 turns on / off the electromagnetic clutch 19 via the I / O 28 and the drive circuit 24, and drives the drive motor 23 via the I / O 29 and the drive circuit 25.
On / off.

FIG. 6 is a control flowchart for driving the paper discharge roller in one embodiment of the present invention. Since the electromagnetic clutch 19 switches between normal rotation and reverse rotation of the paper discharge roller 14, only the drive control routine of the electromagnetic clutch 19 is shown here. The following explanation is
9 is a control flow when the drive motor 23 is in an on state in a print operation mode.

Steps 1-2: The reversal drive of the paper discharge roller 14 of the present embodiment is performed on the paper P on which the first side is fixed by the fixing unit 13 in the duplex mode in the duplex mode. Perform identification.

Steps 3 and 4: When the leading end of the sheet P passes through the sheet sensor 22, an ON signal is input from the sheet sensor 22 to the CPU 30, and the timer Tp starts.

Steps 5-6: When the timer Tp reaches the predetermined time T0, the electromagnetic clutch 19 is turned on, and the rotation of the paper discharge roller 14 switches from normal rotation to reverse rotation. The time from when the leading end of the sheet P passes through the sheet sensor 22 to when the trailing end passes through the branch point 34 (see FIG. 1) of the sheet passing path is T0. After a predetermined time T0 has elapsed from the timer Tp, the discharge roller 1
By the reversing drive of No. 4, the sheet P is conveyed toward the duplex unit 18 through the second sheet ejection port 32 with the front end and the rear end reversed.

Steps 7 and 8: When the rear end of the sheet P passes through the sheet sensor 22, an off signal is input from the sheet sensor 22 to the CPU 30, and the electromagnetic clutch 19 is turned off, so that the rotation of the sheet discharging roller 14 is reversed. To forward rotation.

Step 9: While the first-side printing in the double-sided mode is continued, the discharge roller 14 waits until the next sheet P arrives while maintaining the normal rotation (→ Step).
p 3). When the first-side printing in the double-sided mode is completed, since there is no drive switching of the paper discharge roller 14 between normal rotation and reverse rotation, the process returns to the main routine (not shown) for performing normal control.

FIG. 7 is a schematic view of an entire image forming apparatus using an electrophotographic laser beam printer as an example according to a second embodiment of the present invention.

As shown, a storage tray 41 is arranged on the side of the main body 1 in place of the double-sided unit 18, and the other configuration is the same as that described with reference to FIGS.

In this configuration, as described above, the rotational drive of the discharge roller 14 is switched between normal rotation and reverse rotation by the on / off control of the electromagnetic clutch 19, so that the paper P on which the printing process has been completed is used. Accordingly, the sheet can be sorted into the discharge tray 17 and the storage tray 41.

[0040]

According to the first aspect of the present invention, one drive clutch is used to solve the conventional problem that the drive clutch is generally expensive and the configuration becomes large when two drive clutches are provided. By configuring the switchback mechanism by combining the inexpensive torque limiter mechanism and the inexpensive torque limiter mechanism, it is possible to reduce the cost of parts and downsize the device. In addition, by using two clutches as one, it is possible to simplify electric components and reduce costs.

According to the second aspect of the present invention, the cost of parts can be reduced by incorporating the torque limiter configuration into the switchback mechanism. Further, by incorporating a torque limiter into the paper discharge roller that performs normal rotation and reverse rotation, the size of the apparatus can be reduced.

According to the third aspect of the invention, by arranging the gears, it is possible to reduce the size of the reversing drive device and reduce the cost of parts.

According to the fourth aspect of the present invention, the paper is switched back by the standard paper discharge tray, and the paper discharge rollers are selectively driven in both the normal rotation and the reverse rotation. Switchback transport is performed.
This eliminates the need for a switchback-dedicated paper passage path and transport rollers, and makes it possible to reduce the size and simplification of the apparatus and reduce the cost of parts.

According to the fifth aspect of the present invention, the second discharge port is provided adjacent to the side of the discharge transport roller opposite to the tray, and the transport roller is driven in both forward and reverse directions. Thus, paper can be inserted into a detachable double-sided unit or other optional devices without increasing the size and complexity of the image forming apparatus main body.

According to the sixth aspect of the present invention, it is possible to selectively transfer the paper to the two storage trays without adding a dedicated device for switching the paper passing path, so that the size of the device is increased. In addition, the printed paper can be sorted into two groups without increasing the cost.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an image forming apparatus as an example of an electrophotographic laser beam printer according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a paper discharge unit reversing device according to an embodiment of the present invention.

FIG. 3 is an operation explanatory diagram when the reversing device of FIG. 2 performs forward rotation driving.

FIG. 4 is an operation explanatory diagram when the inverting device in FIG. 2 performs inversion driving.

FIG. 5 is a control circuit diagram for driving a paper discharge roller according to the embodiment of the present invention.

FIG. 6 is a control flowchart for driving a discharge roller according to the embodiment of the present invention;

FIG. 7 is an overall schematic diagram of an image forming apparatus as an example of an electrophotographic laser beam printer according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body 1 2 Exposure device 3-1, 3-2,3-3,3-4 Photoconductor drum 4-1, 4-2,4-3,4-4 Developing part 5-1, 5-2,5 -3, 5-4 Charger 6-1, 6-2, 6-3, 6-4 Cleaner 7-1, 7-2, 7-3, 7-4 Transfer facing roller 8 Intermediate transfer belt 9 Cleaning unit 10 Paper cassette 11 Paper feed roller 12 Transfer roller 13 Fixing device 14, 15 Discharge roller 14-1, 14-2, 14-3, 14-4 Driving roller 15-1, 15-2, 15-3, 15-4 Driven roller 14-5 shaft 17 paper discharge tray 18 double-sided unit 19 electromagnetic clutch (drive clutch) 20 drive shaft 21 torque limiter 22 paper sensor 23 drive motor 24, 25 drive circuit 26 spring 27, 28, 29 I / O 30 CPU 31 First paper discharge port 32 Second Inserting the sheet discharge outlet 33 outlet 34 branch point 41 accommodating tray D inversion device driver P sheet G-1, G-2, G-3, G-4 gear G-1a, G-2a friction plate G-5 idle gear

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/00 106 G03G 15/00 106 550 550 (72) Inventor Seiichi Kitagawa 1006 Kadoma, Kazuma, Kadoma, Osaka Address Matsushita Electric Industrial Co., Ltd. F-term (reference) 2H028 BA06 BA09 BA16 BB02 BB04 2H071 BA03 BA13 CA05 DA21 DA24 DA31 EA18 3F049 AA10 DA11 DA12 EA01 EA17 LA02 LA06 LA07 LB03 3F053 BA03 BA14 BA13 LA03 LA03 LA07 EA05

Claims (6)

[Claims] A drive motor that drives the paper to be transported; a pair of paper discharge rollers that sandwich and transport the paper on which an image has been formed; and a predetermined torque that drives the drive motor to the paper discharge roller in the normal rotation direction. A drive limiter that switches between connection and disengagement in a reverse rotation direction from the drive motor to the paper discharge roller; and a paper discharge outside the machine when the paper discharge roller is driven forward. A first sheet passing path toward the tray, a second sheet passing path toward the image forming section when the sheet discharge rollers are driven in reverse, and a state in which the sheet is conveyed to the first sheet passing path. And control means for turning on the drive clutch when the sheet is conveyed to the second paper passing path by turning off the drive clutch. 2. A gear G-1 fixed on a shaft of the discharge roller, a gear G-2 rotatably disposed coaxially, and a gear G-2 coaxially rotatable. To gear G-
2. An image forming apparatus according to claim 1, wherein said image forming apparatus comprises a coil-shaped spring that presses said gear G-1 and said gear G-1 and said gear G-2. . 3. The drive clutch, comprising: a drive shaft rotatably provided; a gear G-3 fixed on the drive shaft;
A gear G-4 rotatably arranged on the same axis as the gear G-
4 is connected to and released from the drive shaft, the gear G-3 is arranged to be capable of transmitting rotation to the gear G-1, and the gear G-4 is a drive source gear and the gear G-. 2, and at least one idle gear G-5 is connected between the gear G-3 and the gear G-1 or between the gear G-4 and the gear G-4 in order to reverse the drive rotation direction. 3. The image forming apparatus according to claim 2, wherein the image forming apparatus is disposed between the gears G-2. 4. An apparatus for forming an image on a sheet, comprising: a pair of sheet discharging rollers for holding an image-formed sheet, which is located at an upper portion of a main body and conveyed from below, in a substantially horizontal direction; Drive means for switching the rollers in the forward and reverse directions, two discharge ports provided on both sides of the discharge roller for discharging the paper outside the machine, and a forward rotation side of the discharge roller. In a mode in which a sheet is disposed adjacent to a first paper discharge port located in a paper discharge tray and the paper is passed through the first paper discharge port and stored in a paper discharge tray, the drive unit is driven to rotate forward. An image forming apparatus comprising: a control unit that performs initial forward drive and then reversely drives to switch back a sheet in a mode in which the sheet is discharged outside the apparatus from the other second sheet discharge port. 5. A sheet insertion port connected to an image forming section provided below the second sheet ejection port, and the sheet ejected from the second sheet ejection port is transported to the sheet insertion port. The image forming apparatus according to claim 4, further comprising a transport unit detachably provided in the image forming apparatus. 6. The image forming apparatus according to claim 4, further comprising a storage tray that is provided in said image forming apparatus so as to be detachable and close to said second paper discharge port.