JP3140153B2 - Control method of sheet conveying device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a sheet conveying apparatus for conveying a sheet by a pair of rollers driven by a stepping motor used in various apparatuses including an image forming apparatus such as a laser printer, a copying machine, and a facsimile machine. About.

[0002]

2. Description of the Related Art In a sheet conveying apparatus as described above,
When driving a stepping motor, drive is started in a slow-up manner to prevent step-out (a state in which the movement of the rotor does not follow the command pulse signal) when the motor starts, and in a slow-down manner when the motor stops. Stopping is being done.

[0003] Here, the slow-up drive system is a drive system in which the motor starts to operate at a speed within the self-starting frequency range and gradually accelerates to a target frequency speed. This is a driving method in which the motor is stopped after the speed is reduced to a speed within the self-starting frequency range.

[0004]

However, in the above-described conventional sheet conveying apparatus, the sheet conveyed by a pair of rollers driven by a stepping motor is conveyed by another conveying means located downstream of the pair of rollers. When the stepping motor is started, there is no need to use the conveying force of the roller pair, so there is a case where the current supply to the stepping motor is stopped. There is a problem that the conveyed sheet cannot be performed.

When a sheet is conveyed by two pairs of rollers, a linear speed difference may occur due to abrasion of the rollers or adhesion of dust. If the speed is higher than the sheet conveying speed by the roller pair, the sheet is slack between the roller pairs.For example, if there is an image reading unit such as a scanner between the respective roller pairs or an image forming unit such as a printer. , Poor image reading quality due to sagging sheets,
There is also a problem that a desired image quality cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its first object to make it possible to smoothly stop driving of a stepping motor without hindering sheet conveyance. It is a second object of the present invention to be able to smoothly restart the driving of the stepping motor without hindering the sheet transportability. A third object is to prevent the sheet from sagging between each pair of rollers.

[0007]

In order to achieve the above object, the present invention provides a sheet conveying apparatus for conveying a sheet by a pair of rollers driven by a stepping motor. After the point at which the conveyance is started by another conveyance means located on the downstream side, the current supply to the stepping motor is instantly cut off and the roller pair is rotated.
When the roller pair is rotating,
When transporting the next sheet by re-driving the pair,
The stepping motor rotates at a speed corresponding to the specified transport speed.
Provided is a method for controlling a sheet conveying device that immediately supplies a current .

[0008] Further , the roller pair is brought into a rotating state.
After a predetermined period of time has passed, the rear end of the sheet
Just before passing through the
The present invention also provides a method for controlling a sheet conveying device that immediately supplies a rotating current corresponding to the conveying speed of the sheet.

[0009]

According to the control method of the sheet conveying apparatus according to the present invention, when the sheet conveyed by the roller pair is started to be conveyed by another conveying means located on the downstream side, the current is supplied to the stepping motor. Since the roller pair is cut off so as to rotate, the brake phenomenon of the sheet during conveyance when the driving of the stepping motor is stopped can be reliably avoided.

Further, in a state in which the rollers are rotated together, if for transporting the following sheet by the re-driving of the roller pair is supplied immediately rotary current corresponding to a predetermined conveying speed in the stepping motor since the brake phenomena conveyance in the sheet at the time of re-driving the stepping motor
Can be reliably avoided.

Further, when the succeeding sheet is conveyed at a narrow sheet interval, it is considered that the re-driving of the roller pair may not be in time . After passing, the trailing edge of the sheet
Immediately before passing through the pair of rollers , if a rotating current corresponding to a predetermined conveyance speed is immediately supplied to the stepping motor, even if the sheet is continuously fed with a short sheet interval, Stable transport can be performed without causing slack.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 2 is a schematic configuration diagram of a sheet conveying apparatus according to an embodiment of the present invention. This sheet conveying device is configured to convey a sheet 34 by a pair of rollers 32 driven by a stepping motor 31 and a pair of rollers 33 located downstream thereof.

The pair of rollers 32 is a pair of rollers having a function of correcting the registration of the sheet, and is stopped by stopping the driving of the stepping motor 31 when the registration sensor 35 detects the leading edge of the following sheet. Here, in the normal control, after the trailing end of the preceding sheet is sent out from the roller pair 32, the roller pair 32 is stopped by a slow down drive of the stepping motor 31 as shown in FIG. It is common to wait for the next sheet to arrive.

However, when the sheet is conveyed efficiently with a very small sheet interval, the trailing edge of the preceding sheet leaves the roller pair 32 and then the leading edge of the succeeding sheet reaches the roller pair 32. Because the time to do it is short,
As shown in FIG. 4, there is no time to stop the roller pair 32 by reliably performing the slow-down drive and the slow-up drive, and the registration correction cannot be performed.

In order to stop the roller pair 32 immediately after the trailing edge of the sheet leaves the roller pair 32, the driving of the roller pair 32 is started when the sheet is started to be conveyed by the roller pair 33 located downstream thereof. It is a solution to stop and bring it into a swiveling state. However, if the roller pair 32 is stopped by slowdown drive at this time, the sheet being conveyed is braked, and convey cannot be performed properly.

Therefore, in this embodiment, the roller pair 33, which is a conveying means located downstream of the roller pair 32 driven by the stepping motor 31, has a sufficiently strong conveying force. When the roller pair 32 can be rotated when the driving force of the stepping motor 31 is not transmitted, the sheet conveyed by the roller pair 32 is conveyed by the roller pair 33 located downstream of the roller pair 32. After that, as shown in FIG. 1, the current supply to the stepping motor 1 is cut off instantaneously to bring the roller pair 32 into a rotating state.

Accordingly, the brake is not applied to the sheet being conveyed, and the sheet can be stably conveyed. Further, since the roller pair 32 stops immediately after the trailing edge of the sheet leaves the roller pair 32, even when the sheet is conveyed with a small sheet interval, there is a time margin for stopping the roller pair 32. Registration correction can be performed.

The present invention is not limited to the above-described sheet conveying apparatus that conveys a sheet with the sheet interval as small as possible, and can be applied to a sheet conveying apparatus that conveys a sheet at a normal sheet interval. When a linear velocity difference occurs between the roller pair located on the upstream side and the roller pair located on the downstream side due to wear of the roller pair, the sheet is slackened by rotating the roller pair on the upstream side. (Which occurs when the linear velocity of the upstream roller pair is high) and the phenomenon of applying a brake to the sheet being conveyed (which occurs when the linear velocity of the upstream roller pair is low) can be avoided.

On the other hand, a plurality of sheets are continuously
2 and 33, the roller pair 3
After the third sheet is brought into the rotating state, it may be necessary to restart the sheet for continuous feeding of the next sheet. In such a case, when the operation is started by the slow-up drive, a brake is applied to the sheet, and the transportability is deteriorated.

Here, when the pair of rollers 32 is rotating, the rotor of the stepping motor 31 is also rotating at a speed corresponding to the rotation. Therefore, when the stepping motor 31 is restarted, it is necessary to perform a slow-up drive. However, even if a rotation current corresponding to the transport speed is immediately supplied, the rotation can be started stably. This is shown in FIG.

The sheet conveyed from the upstream is detected by the registration sensor 35, and the roller pair 32 is driven at a predetermined timing. At this time, the stepping motor 3
No. 1 needs to perform slow-up driving as before. Then, the sheet is carried by the pair of rollers 32 and transported downstream, and the transport is further started by the pair of rollers 33. At this time, when the drive to the roller pair 32 is stopped and the current supply to the stepping motor 31 is cut off, the roller pair 2
Is in a rotating state.

When it is necessary to drive the roller pair 32 again from this state, performing the slow-up drive as normally performed would hinder the sheet conveyance. In this embodiment, as shown in FIG. Stepping motor 31
Is restarted, a rotating current corresponding to the transport speed is supplied to the stepping motor 31 immediately. Thereby, stable sheet conveyance can be performed without applying a brake to the sheet.

FIG. 6 is an explanatory view showing a conveying operation by a sheet conveying apparatus according to another embodiment of the present invention in comparison with a conventional conveying operation, and the same parts as those in FIG. 2 are denoted by the same reference numerals. In the sheet conveying apparatus, an image reading sensor 36 is disposed between a pair of rollers 32 driven by a stepping motor 31 and a pair of rollers 33 driven by a driving unit (not shown) located downstream of the pair. Also,
A sensor 37 is arranged immediately before the roller pair 32 so that the position immediately before the rear end of the sheet passes through the roller pair 32 can be determined.

FIG. 3A shows a state where the acceleration is completed in advance by a slow-up drive to a predetermined transport speed, the first sheet reaches the roller pair 32 rotating at a constant speed, and the transport is started. Is shown. 3B illustrates a state where the first sheet is continuously conveyed by the roller pair 32 and the leading end of the sheet reaches the roller pair 33. FIG.

FIG. 3C shows that when the sheet is continuously conveyed by the two roller pairs 32 and 33, the roller pair 32 has a higher rotational speed, so that the sheet is slackened. This is a defect caused by abrasion of the roller, adhesion of dust, and the like. In this case, the image reading by the image reading sensor 36 cannot be performed accurately.
Take the measures described in.

In (c '), after the sheet is nipped by the pair of rollers 33 and the conveyance is started, the current supply to the stepping motor 31 is cut off to bring the pair of rollers 32 into a rotating state. As a result, the sheet does not sag, so that the image can be accurately read by the image reading sensor 36.

However, as shown in FIG.
When the first sheet has been conveyed at a very narrow interval with respect to the trailing edge of the preceding first sheet, the stepping motor 3
If 1 is driven again, it will not be in time for the second sheet to be sent subsequently. This is because the stepping motor 31 is started by the slow-up drive, so that it takes some time to reach a predetermined transport speed.

Therefore, a countermeasure as shown in (d ') is taken. That is, just before the rear end of the first sheet passes through the roller pair 32, as described above, the stepping motor 3
Then, the current supply to the roller pair 1 is cut on, and the roller pair 32 is driven again. As a result, the roller pair 32 can be driven instantaneously at a predetermined number of rotations, and it is possible to make a sufficient time for the arrival of the succeeding second sheet.

FIG. 7 is a timing chart showing the relationship between the presence / absence of a sheet at each of the roller pairs 32 and 33, the drive current of the stepping motor 32, and the output of the sensor 37 in the transport operation by the sheet transport apparatus of FIG.

Thus, at least two roller pairs 3
When one sheet is being conveyed by the rollers 2 and 33 at the same time, the current supply of the stepping motor 31 is cut off to make the roller pair 32 rotate, and the rear end of the first sheet is After reaching the position immediately before passing through, the current supply to the stepping motor 31 is instantly cut-on, and the roller pair 32 is immediately rotated at a predetermined conveying speed. The occurrence of slack can be prevented.

In this embodiment, the sensor 37 is provided immediately before the roller pair 32 in order to know the position immediately before the rear end of each sheet passes through the roller pair 32. However, other means may be used. No problem.

FIG. 8 is an overall configuration diagram showing an embodiment in which the present invention is applied to a sheet conveying device of a laser printer.
In this laser printer, a duplex unit 2 and a paper feed unit 3 as peripheral devices are integrally incorporated in a table 5 and connected to a printer main body 1 as an image forming apparatus main body, and a paper discharge unit 4 is mounted on an upper portion. Have been.

When the image forming process is started, the photosensitive drum 8 provided in the printer main body 1 is driven to rotate in a direction indicated by an arrow by a drive motor (not shown), and its surface is charged by a charging charger 9 provided above the photosensitive drum. Are uniformly charged.

The laser beam modulated according to the image data by the optical writing unit 10 is irradiated while being irradiated in the axial direction of the photosensitive drum 8 while being main-scanned, and an electrostatic latent image is formed on the surface. A toner is attached to the electrostatic latent image by the developing unit 11 and developed to visualize the electrostatic latent image.

On the other hand, each of the paper feed rollers 15 from one of the two upper and lower paper feed trays 6 and 7 provided in the printer body 1 or the paper feed unit 3 provided in the table 5 is provided.
Transfer paper (sheet) (not shown) is selectively fed by rotation of any of a, 15b, and 15c, and the transfer paper is transferred via a pair of transport rollers 30 to a pair of registration rollers 16 located near the photosensitive drum 8. Stops in the state of being pinched. The stop timing is determined according to the output of the registration sensor RS.

Then, in synchronization with the rotation of the photosensitive drum 8 carrying the toner image, the registration roller pair 16
Also starts rotating at a predetermined timing, and sends out the transfer paper to a position facing the photosensitive drum 8 and the transfer / separation unit 17 provided thereunder. As a result, the toner image on the photosensitive drum 8 is transferred to the transfer paper by the action of the transfer charger of the transfer / separation unit 17, and the transfer paper is separated from the photosensitive drum 8, and the fixing device is conveyed by the transport belt 18. 19, the transferred image is heated and fixed.

Thereafter, the path of the printed transfer paper is selected by the switching operation of the pair of paper path switching claws 20 and 21, and the openable and closable discharge stacker 22 at the rear of the printer main body 1 and the discharge unit 4 at the upper part. Alternatively, it is selectively discharged to one of the lower duplex units 2. Reference numerals 23 and 24 denote transport rollers on the printer body 1 side and the paper discharge unit 4 side.
Reference numerals a and 25b denote discharge rollers for discharging the transfer paper from the discharge unit 4 to the lower tray 4a and the upper tray 4b, respectively.

After the toner image is transferred onto the transfer paper, the toner remaining on the photosensitive drum 8 is removed by the cleaning unit 14. Further, the residual potential of the photosensitive drum 8 is discharged by the discharge lamp 26. In this way, the photosensitive drum 8 is initialized and proceeds to the charging of the image forming process for the next page, and the same operation is repeated.

The printer main body 1 further includes a controller 27 for controlling the entire laser printer and processing of print data, and an engine driver 28 for controlling the printer engine constituting the image forming unit. ,
And a power supply unit 29 and the like.

FIG. 9 is a block circuit diagram showing a portion of the laser printer according to the present invention. In this figure, reference numeral 41 denotes a stepping motor control unit (hereinafter, simply referred to as a "control unit") using a microcomputer mounted on the engine driver of FIG. 8, and controls the rotation of the stepping motor 43 in accordance with the output of the registration sensor RS. R that stores a CPU and a program corresponding to the control
It has an OM, a work RAM, and the like. Reference numeral 42 denotes a stepping motor drive circuit, and reference numeral 43 denotes, for example, a four-phase stepping motor, which is used as a drive source for driving the registration roller pair 16 in this embodiment.

In this embodiment, after the transfer paper conveyed by the registration roller pair 16 driven by the stepping motor 43 is started to be conveyed by the conveyer belt 18 which is a conveyer, the stepper motor controller 41
Cuts off the current supply to the stepping motor 43 via the drive circuit 42 to make the registration roller pair 16 rotate, and then, when the registration roller pair 16 is stopped, registration correction is performed on the next transfer sheet to be transferred. At a predetermined timing, the registration roller pair 16 is driven again by the slow-up driving of the stepping motor 43, and the registration-corrected transfer paper is transported.

Therefore, according to this embodiment, the same effects as those of the first embodiment can be obtained. Although the embodiment in which the present invention is applied to the sheet conveying device of the laser printer has been described above, the present invention is not limited to this, and is applicable to the sheet conveying device of various devices including an image forming device such as a copying machine and a facsimile device. It is.

[0043]

As described above, according to the control method of the sheet conveying apparatus of the first aspect, the driving of the stepping motor can be stopped smoothly, and at that time, the pair of rollers driven by the stepping motor can be stopped. The brake is not applied to the sheet conveyance by the other conveyance means located on the downstream side thereof, and at the same time, the roller pair driven by the stepping motor can be stopped immediately after the sheet is separated.

[0044] According to the control method of the sheet conveying device,
Smooth restart of stepping motor drive
Since it is, prevents the brake is applied to the sheet conveyance in accordance with another conveying means located this time in the roller pair is driven by a stepping motor also downstream thereof,
The sheet can always be stably conveyed.

According to the control method of the sheet conveying apparatus of the second aspect , even when the sheets are continuously fed with a short sheet interval, the sheet is slack between the roller pairs. No more.

[Brief description of the drawings]

FIG. 1 is a timing chart showing an operation example in a case where a stepping motor 31 in the sheet conveying apparatus of FIG. 2 is stopped by cutoff of current supply.

FIG. 2 is a schematic configuration diagram of a sheet conveying apparatus according to an embodiment of the present invention.

FIG. 3 is a timing chart showing an operation example in a case where the stepping motor 31 in the sheet conveying device of FIG. 2 is stopped by slowdown driving.

FIG. 4 is a timing chart showing another operation example in the case where the stepping motor 31 in the sheet conveying device of FIG. 2 is stopped by slowdown driving.

FIG. 5 is a timing chart showing an operation example in a case where the stepping motor 31 in the sheet conveying apparatus of FIG. 2 is stopped by cut-off of current supply and re-driven by cut-on of current supply.

FIG. 6 is an explanatory diagram showing a conveyance operation by a sheet conveyance device according to another embodiment of the present invention in comparison with a conventional conveyance operation.

7 is a timing chart showing an operation example in the case where the stepping motor 31 in the sheet conveying apparatus in FIG. 6 is stopped by cutting off the current supply and is re-driven by cutting on the current supply.

FIG. 8 is an overall configuration diagram showing an embodiment in which the present invention is applied to a sheet conveying device of a laser printer.

FIG. 9 is a block circuit diagram showing a portion related to the present invention of the laser printer of FIG. 8;

[Explanation of symbols]

16 registration roller pair 18 conveyance belt 30 conveyance roller pair 31, 43 stepping motor 32, 33 roller pair 34 sheet 35, RS registration sensor 36 image reading sensor 37 sensor 41 stepping motor control unit 42 drive circuit

Continuation of the front page (56) References JP-A-2-86950 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) B65H 5/06

Claims (2)

(57) [Claims] 1. A rotor driven by a stepping motor.
In a sheet transport device that transports sheets by roller pairs
The sheet conveyed by the pair of rollers is positioned below the pair of rollers.
By other transport means located on the upstream sideTransportStarted
TimeLaterSupply current to the stepping motor.Instant
SometimesCut off to rotate the roller pairAnd While the roller pair is rotating, the roller pair
When the next sheet is conveyed by re-driving the
Rotational current corresponding to the specified transport speed for the stepping motor
Supply instantly Control of sheet conveying device
Your way. 2. A rotor driven by a stepping motor.
In a sheet transport device that transports sheets by roller pairs
The sheet conveyed by the pair of rollers is positioned below the pair of rollers.
By other transport means located on the upstream sideTransportStarted
TimeLaterSupply current to the stepping motor.Instant
SometimesCut off to rotate the roller pairAnd A predetermined time has passed since the pair of rollers entered the rotating state
Immediately before the trailing edge of the sheet passes through the roller pair.
Corresponding to a predetermined conveying speed to the stepping motor.
Supply instantaneous rotating current Sheet transport characterized by the following:
A control method of the feeding device.