JPH0649538B2 - Paper feeder - Google Patents

Description

The present invention relates to improvements in an automatic document feeder and the like used in electronic copying machines and the like.

[Conventional technology]

An electronic copier exposes a charged drum to light according to document information, then forms a visible toner image on the electrostatic latent image formed on the drum surface, and transfers the toner visible image to recording paper. It is a device that makes you sick. In recent years, this type of electronic copying machine has been widely used for information copying in all fields of industry. In addition to the automatic copying of the number of copies, recent electronic copying machines are commercially available that have a zoom function for enlarging / reducing images. 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. 7 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]

In the case of this type of conventional document feeder, a drive source (motor)
It was not possible to correctly stop the copy paper at the stopper point S because of the inertia, the difference in the paper used as the manuscript, the difference in the usage environment in which the electronic copying machine is installed, and the like.

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

[Means for solving problems]

This object is achieved by the following technical means a or b.

(A) A stopper S which is a stop position of the trailing edge of the document on the document table
A trailing edge detection sensor for detecting the trailing edge of the document at the entrance of the document table at a fixed distance a from the stopper S, an automatic document feeding motor to which an encoder is connected, and a pulse signal from the encoder. ADF that is a control unit for counting
A motor control device and a drive unit that operates the forward and reverse rotation amounts of the motor according to a command from the control device are provided, and after the sensor detects the trailing edge of the document, the sensor position is longer than the constant distance a as a base point. The set distance a + b is sent by the pulse signal of the encoder to generate a signal for ending the forward rotation, and the signal is sent from the base point to a position at another set distance a + c longer than the set distance a + b by the pulse signal of the encoder, The position there is set as the generation point of the reverse rotation signal for starting the reverse rotation, and the normal rotation amount due to the inertia after the generation of the reverse rotation signal is detected and added by the pulse signal of the encoder and corrected, and the total encoder pulse signal value in the positive direction Then, a signal value of a value obtained by subtracting the set pulse signal value of the encoder corresponding to the constant distance a from the signal value is calculated by the control device, and The motor is driven as an encoder pulse signal value of the reverse rotation amount, the paper feeding device for a document, characterized in that as allowed to stop the trailing edge of the document to the stopper S.

(B) The set distance a + b and the other set distance a + c have the same size, and the generation point of the signal for ending the forward rotation and the generation point of the reverse rotation signal for starting the reverse rotation are the same. A paper feeder for the document described.

〔Example〕

Hereinafter, embodiments 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 figure is a so-called switchback 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. 7 are designated by the same reference numerals. The paper tray 5 is
It is provided on the opposite side of the conventional example shown in FIG. In the figure, 11 and 12 are rollers around which the belt 13 is wound.
11 is driven by an automatic document feeding motor (hereinafter referred to as an ADF motor) 14. Reference numeral 15 is an encoder for detecting the rotation speed and rotation direction of the ADF motor 14, and 16 is the encoder
The motor control device receives the 15 detection clock pulses and the reference clock pulse for driving the ADF motor 14 and drives the ADF motor 14.

Transmission of power from the ADF motor 14 to the roller 11 may be performed by using a belt as shown in the figure, or by using 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 passage of light by teeth of the gear. As the motor control device 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. 2 and the flow charts shown in FIGS.

In FIG. 2, (a) is a diagram showing a rotation detection signal of the ADF motor 14 by the encoder 15, and (b) is a diagram showing an operation signal to the ADF motor 14.

The original 6 placed on the paper feed table 5 is moved by the paper feed roller 7
Only one sheet is sent onto the document table 8. At this time, the motor control device 16 sets the ADF motor 14 to the St in the flowchart of FIG.
As shown in ep1, the driving is started and rotated in the arrow direction shown in FIG. As a result, the document sheet 17 sent out on 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.

As shown in FIG. 1, when the trailing edge of the document 6 passes through the trailing edge detection sensor 20 located at a distance a behind the stopper S as shown in Step 2 of FIG. 3, the forward rotation starts from that point.
The reference clock pulse value to be turned off is set as in Step 3, and it is counted up as in Step 4, and when the trailing edge of the original 17 reaches the point B at the distance b in front of the stopper S, the normal rotation is performed. ADF motor 4 sends a signal to turn off the drive signal as in Step 5 and immediately drive it in reverse.
However, it is preferable that the timer is set as Step 6 at that point and the set time ends at Step 7, and the semiconductor relay switched during this time causes the semiconductor relay to switch to the point C in the distance c in front of the stopper S. When the trailing edge of the document 17 is reached, in step 8, a start signal for driving in the reverse direction is given to the ADF motor 14. However, the ADF 14 that has been rotating in the forward direction cannot rotate instantaneously due to inertia, and continues rotating in the forward direction for a while. However, the rotation speed of the encoder becomes gentle as shown in FIG. 2 (a). Then, at time t ₂ , the rotation of the ADF motor 14 is stopped, but the situation is confirmed by the increase of the pulse width by the encoder. ADF motor in time t _{1 1}
The period T from the application of the reverse rotation signal to 4 until the motor stops at time t ₂ is a so-called braking period. During this braking period, the document 17 moves in the forward direction.

That is, the points B and C may be the same as in the former case, or may be provided separately as in the latter case.

Although until time t ₂ is the document 17 has moved forward will initiate a substantial reversal from this point. Step here
If the interrupts from Step 8-1 to Step 8-4 shown in the flowchart of FIG. 4 are entered during the process from Step 8 to Step 9, the trailing edge of the original will move to the stopper position S more precisely in the case of ultra-high speed orientation. It will come to a stop. That is, the reverse signal
The number of clock pulses p ₄ until the forward movement is completed at time t ₂ after being inserted at point C (time t ₁ ) of 8 is monitored in Step 8-2, and is output in Step 8-3. If the number of pulses is reversed, the trailing edge of the original 6 can reach point C again. However, since there is inertia, the reverse signal is OF
Number of clock pulses timing back to F is selected in Step8-4 the place less than p _4, thereby intermittently driving signals to reach the p _4.

The trailing edge of the document 17 which has been returned to the point C in this way must be further returned to the stopper S point. The distance c between them is divided into N, and the number of clock pulses returning between each c / N is set to Ste.
p10-1, CONT1, Step11-1, CONT2 ..., Step12-
At 1, set CONT N as shown in FIG. 4 by setting an interrupt, and each setting counter is cleared as shown in FIG.

That is, when the trailing edge of the document 17 reaches point C in Step 10,
In order to clear CONT1, the paper is moved by the clock pulse corresponding to the reference value I = c / N.
The driving signal is driven to 2 and is driven for the reference clock pulse corresponding to the length of c / N. When this is cleared, the driving signal is driven for the reference clock pulse corresponding to the next c / N. Is repeated, and this is repeated N times in Step 13 below.
When CONT N is cleared and the drive signal has been applied N times, the stopper S and the trailing edge of the original 17 coincide with each other, the positioning is completed, and Step 14 ends.

Of course, when the A4 version is operated at a normal high speed of about 60 sheets / minute, even if it is reversed until the encoder counts up without causing such an interrupt, there is almost no problem in practical use. With no accuracy, the trailing edge of the original document stands still at point S.

The above is the method of the present invention in which the document is fed in the forward direction and reversed in the middle, and the trailing edge of the document is abutted against the stopper S for positioning, but as shown in FIG.
It is an application example of the present invention that the tip of 17 is abutted against a stopper S'set in the front for positioning.

That is, when the effective length of the document table is 1, the leading edge of the document 17 is located at a distance l + a behind the stopper S '.
When passing through 20 ', a clock pulse value for turning the forward rotation OFF is set with the time point as a base point, which counts up and the leading edge of the original paper is set to B'point which is a distance b'before the stopper S'. When the normal rotation signal is reached and the normal rotation signal is turned off, the normal set clock pulse number becomes close to the count up by the inertia, and the leading end stops near the point C '. And
Until the point C'is reached, a drive signal is added and the counter is cleared as in the first embodiment to reach the point C '.

Even if the distance from the point C'to the point S'is kept as it is so that the tip reaches the point S ', fairly stable positioning can be achieved, but preferably the following means is further adopted. This allows more precise positioning.

The tip clearing the point C'is divided into N'distances c'from the point C'to the point S '. The number of clock pulses corresponding to each distance is set to CONT 1 ', CONT 2' ..., CONT N '.

The tip, which has reached the point C'and has already cleared the counter up to that point, has a distance of the reference clock pulse I'according to the applied drive signal. The drive is turned off by clearing the number of clock pulses corresponding to, but N'number of drive signals are sequentially added, and CONT 1 ', CONT corresponding to the standard II' ... standard N '.
2 ', ..., CONT N'are cleared and the leading edge of the original 6 is abutted against the stopper S'to complete the positioning of the original.

The above operation is performed by configuring the circuit of the drive control mechanism shown in FIG.

〔effect〕

Multiple (forward and reverse) drive signals are added to the paper feed of the paper feeding device to perform reversal while applying the reverse rotation braking action, so the speed at the time of positioning is held low and accurate paper feeding positioning can be performed. Therefore, the obstacles such as the breakage of the paper due to the abrupt contact with the reference stopper are eliminated, and the stable and accurate positioning of the paper feed is achieved, and the practical effect to the document feeder of the copying machine is particularly great.

[Brief description of drawings]

 FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of each part, FIGS. 3 and 4 are flowcharts thereof, and FIG. 5 is a circuit diagram of a drive control mechanism thereof. FIG. 7 is a block diagram of an application example of the present invention, and FIG. 7 is a block diagram of a conventional device. 1 ... Electronic copying machine main body 2,3 ... Paper feed cassette 4 ... Paper discharge tray 5 ... Paper feed tray 6 ... Loaded originals 17 ... Original paper 7 ... Paper feed roller 8 ... Original tray 11 , 12 ...... Roller 13 …… Belt 14 …… ADF motor 15 …… Encoder 16 …… ADF motor control device S, S ′ …… Positioning stopper 20 …… Rear end detection sensor 20 ′ …… Front end detection sensor

Claims (2)

[Claims] 1. A stopper S which is a stop position of a rear end of a document on a platen, and a rear end detection sensor which detects a paper rear end of a document located at an entrance of the platen at a constant distance a from the stopper S. An automatic document feeding motor to which an encoder is connected, an ADF motor control device that is a control unit that counts the pulse signal of the encoder, and a drive unit that operates the forward and reverse rotation amounts of the motor according to commands from the control device. After the sensor detects the trailing edge of the document, a preset distance a + b longer than the fixed distance a is sent by a pulse signal of the encoder with the sensor position as a base point to generate a signal for ending the forward rotation. A point of generation of a reverse rotation signal for starting reverse rotation at that position after sending by a pulse signal of an encoder to a position at another set distance a + c longer than the set distance a + b Then, the normal rotation amount due to the inertia after the generation of the reverse rotation signal is detected and added by the pulse signal of the encoder and corrected to obtain the total encoder pulse signal value in the positive direction, and the encoder value corresponding to the constant distance a from the signal value. A signal value of a value obtained by subtracting the set pulse signal value is calculated by the control device, and the value is used as the encoder pulse signal value of the reverse rotation amount to drive the motor so that the stopper S stops the trailing edge of the document. A paper feeding device for original documents. 2. The set distance a + b and the different set distance a
2. The paper feeding device for a document according to claim 1, wherein + c has the same size, and the generation point of the signal for ending the forward rotation and the generation point of the reverse rotation signal for starting the reverse rotation are the same. .