JPH0664371B2 - Automatic document feeder - Google Patents

Description

TECHNICAL FIELD The present invention relates to an automatic document feeder used in an electronic copying machine or the like.

(Prior Art) An electronic copying machine exposes a charged drum on an electrostatic latent image formed on the surface of a drum after exposing the charged drum to light according to document information. Is a device for transferring the image onto recording paper. In recent years, this type of electronic copying machine has been widely used for information copying in all fields of industry. In addition, recent electronic copying machines are commercially available that have a zoom function for enlarging / reducing images in addition to automatic copying of the number of copies. Furthermore, an electronic copying machine with an automatic document feeder, which can sequentially send a plurality of documents to a document table and make a copy, has also appeared.

FIG. 3 is a diagram showing a conventional example of an automatic document feeder.
In the figure, 1 is an electronic copying machine main body, 2 and 3 are paper feed cassettes loaded with copy papers corresponding to the sizes of copy papers (for example, A4, B5, etc.), and 4 is a tray for receiving the copied copy papers. It is a paper plate. Reference numeral 5 is a paper feed tray on which a plurality of originals 6 are placed, 7 is a paper feed roller for feeding the originals one by one to the original table 8, and 9 is an original cover.

The originals 6 placed on the paper feed tray 5 are fed one by one by a paper feed roller 7 rotated by a drive source (not shown), and conveyed in an arrow direction by a conveying mechanism (not shown). Positioning is performed by stopping at the stopper point S.

(Problems to be Solved by the Invention) Conventionally, in the case of this type of document feeder, due to the inertia of the drive source (motor), the difference in the paper used as the document, the environment in which the electronic copying machine is installed, etc. , The frictional force between each original and the platen glass is different, which causes variations in the paper feed, and the stopper point S must be correct.
I couldn't stop the manuscript paper.

That is, the stopper point S may not be reached, or conversely, the stopper may be too strongly struck and the document may be deformed.

Recently, a drive source has a motor capable of rotating in the forward and reverse directions, and the motor sequentially feeds the original onto the platen glass, and thereafter, the original is reversely fed by a reference amount and stopped at a stopper S point. There is a feeder. However, in the past, this reference amount was obtained by driving the motor for a certain period of time, and the frictional force with the platen glass of each original was different, which caused variations in paper feeding and The document could not be stopped at the stopper point S.

The present invention has been made in view of such points,
It is an object of the present invention to realize an automatic document feeder that can always accurately position a document sheet on a document table.

The present invention, which solves the above-mentioned problems, has a motor capable of forward and reverse rotation, and sequentially feeds a document to a document table by the motor,
Then, in the automatic document feeder configured to reversely feed the document by a reference amount and position it at a stopper point, a motor drive circuit for generating a signal for controlling the rotation direction of the motor, A rotation detection unit that generates a rotation detection signal of the motor, and a period from when the reverse rotation signal generated from the motor drive circuit is applied to the motor until the motor actually reverses, that is, a braking period is based on the rotation detection signal. Braking period determining means, a moving amount calculating means for calculating the moving amount of the document during the braking period determined immediately before the reverse rotation start by the braking period determining means, and the calculated moving amount as the reference. And a correction means for adding the amount to the above amount to obtain the reverse feed amount.

That is, since the original document feeding amount of the automatic document feeder is proportional to the rotation amount of the motor, the motor rotation amount is detected based on the motor rotation detection signal during the period from when the reverse rotation signal is applied to the motor to when the motor actually reverses. The amount of extra movement of the document during the so-called braking period when stopped can be obtained.

Then, when the document is fed backward (at the time of abutting), the obtained movement amount when the motor is stopped is added to the predetermined reference backward feeding amount, and the backward feeding that considers the moving amount is realized. To do.

If feedback of such movement amount is not performed as in the conventional case, the amount of contact with the stopper (abutting plate) will not reach the stopper, or if the product is fed backward with a uniform margin. Causes problems such as deformation of the original due to too strong abutment,
According to the present invention, the abutting amount (abutting speed) of a document is always constant, and accurate and stable positioning can be performed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The apparatus shown in the drawing is a so-called swing-back type automatic document feeder which sequentially feeds a document to a document table by a motor and then reversely feeds the document by a predetermined amount to position the document. The same parts as those in FIG. 3 are designated by the same reference numerals. Paper tray 5
Is provided on the opposite side of the conventional example shown in FIG. In the figure, 11 and 12 are rollers around which a belt 13 is wound, and the roller 11 is an automatic document feeding motor (hereinafter referred to as ADF).
It is driven by a motor 14). Reference numeral 15 is an encoder for detecting the rotation speed and rotation direction of the ADF motor 14,
Reference numeral 16 is a motor drive circuit that drives the ADF motor 14 by receiving the detection clock of the encoder 15 and the reference clock for driving the ADF motor 14.

The transmission of the power from the ADF motor 14 to the roller 11 may use a belt as shown in the figure, or a gear mechanism. The encoder 15 is composed of, for example, a gear directly connected to the rotation shaft of the ADF motor 14, and a photo sensor that interrupts the passage of light by the teeth of the gear.
As the motor drive circuit 16, for example, a microcomputer is used because it is necessary to perform arithmetic processing. The operation of the apparatus thus configured will be described in detail with reference to the timing chart shown in FIG.

In FIG. 2, (a) is the ADF by the encoder 15.
A rotation detection signal of the motor 14, (B) is the ADF motor 14
It is a figure which shows operation | movement.

The document 6 placed on the paper feed tray 5 is moved by the paper feed roller 7
Only one sheet is sent onto the document table 8. At this time, the motor drive circuit 16 drives the ADF motor 14 to rotate it in the arrow direction. As a result, the document sheet 17 sent out onto the document table is pressed between the belt 13 and the document table 8, and when the belt 13 moves in the arrow direction, it moves in the same direction. Here, the direction indicated by the arrow in the figure is defined as the forward direction.

Next, the motor drive circuit 16 displays the time t ₁ ((b) in FIG. 2).
To the ADF motor 14
Give to. However, the ADF motor 14, which has been rotating in the forward direction until then, cannot instantaneously rotate in the reverse direction due to inertia, and continues to rotate in the forward direction for a while. However, the rotation speed becomes gentle as shown in FIG. At time _{t 2, the} rotation of the ADF motor 14 is stopped. A period T from application of the reverse rotation signal to the ADF motor 14 at time t ₁ to stop of the motor at time t ₂ is a so-called braking period. Even during this braking period, the document 17 moves in the forward direction. The movement amount during the braking period T needs to be corrected when the document is moved in the reverse direction.

After being temporarily stopped at time t ₂ , the ADF motor 14 is stopped.
Starts rotating in the opposite direction this time. At the same time, the pulse detected by the encoder 15 increases as shown in FIG. Then, when the ADF motor 14 rotates in the reverse direction, the roller 11 also rotates in the reverse direction, the original 17 is pressed against the belt 13, and this time moves in the opposite direction. When the motor drive circuit 16 moves the document 17 by a predetermined amount, the ADF
A stop signal is sent to the motor 14 at time t ₃ to stop the motor.

By the way, since the output of the encoder 15 and the reference clock are given to the motor drive circuit 16, the motor drive circuit 16 starts the time from the time t ₁ when the reverse rotation signal is given to the ADF motor 14 to the time when the ADF motor 14 is turned on. The time T until the vehicle stops at t ₂ can be obtained. Since the stop of the ADF motor 14 can be known from the fact that the output of the encoder 15 has stopped changing, the time T can be obtained by counting the number of reference clocks from t ₁ to t _2. it can. When the time T is obtained,
The motor drive circuit 16 can obtain the distance that the document 17 has moved in the forward direction within the time T (the above-described braking period T) by calculation.

The distance traveled by the original 17 in the forward direction during the braking period is Δx
Then, when moving in the opposite direction, if Δx is added, the distance moved by the document within the braking period can be corrected. Therefore, the motor drive circuit 16 is actually AD
From time t ₂ when the F motor 14 starts to rotate in reverse, time t _{2 at} which a stop signal is given to the ADF motor 14 and time corresponding to the correction distance is added to give an actual motor stop signal t
_I will decide ₃ . By performing such control, the swing-back type document feeder used in the present invention can be positioned extremely accurately. That is, manuscript 1
The end of 7 can always be brought to the stopper point S. As a result, it is possible to obtain a copy image in which the image position does not shift.

(Effects of the Invention) As described in detail above, according to the present invention, the distance a document moves in the forward direction from when the reverse rotation signal is applied to the ADF motor until when the ADF motor is stopped is corrected during the backward movement. As a result, the original can always be set to the correct position as an initial setting, which has a large practical effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of each section, and FIG. 3 is a diagram showing a structural example of a conventional device. DESCRIPTION OF SYMBOLS 1 ... Electronic copying machine main body, 2, 3 ... Paper feeding cassette 4 ... Paper ejection tray 5, 5 ... Paper feeding tray 6, 17 ... Original, 7 ... Paper feeding roller 8 ... Original plate, 9 ... Original cover 11, 12 ... Roller , 13 ... Belt 14 ... ADF motor, 15 ... Encoder 16 ... Motor drive circuit

Claims (1)

[Claims] 1. A motor having a reversible motor, wherein the motor sequentially feeds a document to a document table, and thereafter,
An automatic document feeder configured to reversely feed the document by a reference amount and position it at a stopper point, a motor drive circuit for generating a signal for controlling a rotation direction of the motor, and rotation detection of the motor. A rotation detection unit that generates a signal, a period from when the reverse rotation signal generated from the motor drive circuit is applied to the motor until the motor actually reverses,
That is, a braking period determining unit that determines a braking period based on the rotation detection signal, and a movement amount calculating unit that calculates a moving amount of the document during the braking period determined immediately before the reverse rotation start by the braking period determination unit, An automatic document feeder, which comprises a correction unit that adds the calculated movement amount to the reference amount to obtain a reverse feed amount.