JP2698440B2 - Automatic document feeder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic document feeder mounted on a copying machine or the like for automatically setting a document at a predetermined position. The present invention relates to an automatic document feeder that transports a document by a transport belt.

<Prior Art> An automatic document feeder including a mechanism for transporting a document by a transport belt is known.

In this type of automatic document feeder, in order to accurately align the trailing edge of the document with a reference line provided at the set position,
After the original is slightly overrun from the set position, the transport belt is driven in the reverse direction to switch back the original, and the end of the original collides with a projection provided at the reference line position. There is something.

<Problems to be solved by the invention> However, when a document is transported by a transport belt,
The contact ratio between the transport belt and the transport path surface (for example, contact glass) changes depending on the size and type of the document. Usually, the surface of the conveyor belt is roughened to increase the coefficient of friction. Therefore, when a small-sized document is transported, the contact area between the transport belt and the transport path surface is large, and a large force is required to drive the transport belt. Conversely, the contact area between the conveyance belt and the conveyance path surface decreases as the size of the document is conveyed, and the driving force can be reduced. As described above, the difference in the document size causes a change in load of a driving unit for driving the transport belt, for example, a motor.

Similarly, the type of the document, for example, a difference in paper quality or thickness also causes a change in motor load.

Therefore, if the size or type of the document changes, the overrun amount when the set position is overrun varies, and when the document is switched back, the rear end of the document does not collide with the protrusion and does not stop accurately on the reference line. There was something.

SUMMARY OF THE INVENTION The present invention has been made to solve such a drawback, and has as its object to provide an automatic document feeder capable of accurately setting a document at a predetermined position.

<Means for Solving the Problems> The present invention is an automatic document feeder that conveys a document set at a predetermined position by a conveyance belt,
Pulse output means for outputting a pulse in conjunction with driving of the conveyor belt, and driving the conveyor belt in a first direction by a predetermined amount and then driving the conveyor belt in a second direction opposite to the first direction for a certain time Belt driving means, a pulse counting means for counting the number of pulses output from the pulse output means within a certain time during which the conveyor belt is driven in the second direction, and a reference value for counting the pulse counting means. And automatic driving means for driving the conveying belt in the second direction by a predetermined number of pulses after the lapse of the predetermined time based on the output of the comparing means. It is a sending device.

<Operation> When the size or type of the document changes, the driving amount varies even if the conveying belt is driven in the second direction for a certain period of time.

Therefore, the above-described variation due to the type and size of the document is detected by counting the number of pulses output from the pulse output unit, and based on the detection result, the transport belt is further driven by a further fixed amount in the second direction. The document edge is made to coincide with a predetermined reference line.

<Embodiment> FIG. 3 is a schematic sectional view for explaining the configuration of an automatic document feeder according to an embodiment of the present invention.

The automatic document feeder 1 is mounted on the upper surface of a copying machine main body 2 and includes a paper feed unit 3, a belt transport unit 4, and a reversing unit 5.

The paper feed unit 3 includes a document set table 6, a document set detection switch 7 for detecting that a document has been set on the document set table 6, a forward feed roller 8 for feeding out a document,
A pair of a feed roller 9 and a reversing roller 10 for feeding a document one by one while preventing double feed, and a pair of registration rollers 11 for feeding the document to the belt transport unit 4 at a constant timing.
And a document detection sensor 12 for detecting a document sent to the belt transport unit 4.

The belt transport unit 4 is provided with 13 documents. The document 13 has a protruding edge having a step with the surface of the contact glass 14 arranged on the upper surface of the copying machine main body 2, and this edge forms a reference line 15 when the document is set on the contact glass 14. Has formed.

The belt transport unit 4 further includes a transport belt 16, a pulse output switch 17 that outputs a pulse in conjunction with the drive of the transport belt 16, and a discharge tray 18 disposed above the transport belt 16. ing. The paper discharge tray 18 is a tray from which a document having a single-sided copy is discharged.

The reversing unit 5 includes a conveyance switch 19 for detecting a document sent from the belt conveyance unit 4, a document reversing roller 20, and a reversing unit for reversing the document reversed by the document reversing roller 20 to the belt conveyance unit 4. Further, a document detection sensor 21 for detecting the leading edge of the document and a paper discharge tray 22 are provided. The paper discharge tray 22 is a tray from which a document whose front and back sides have been copied is discharged. In addition, a switching claw (not shown) is disposed in association with the reversing roller 20, and the destination of the document is switched by the switching claw.

FIG. 4 is a block diagram showing a part of the electrical configuration of the control unit of the automatic document feeder 1 according to this embodiment. FIG. 4 shows only a portion necessary for a control operation which is a feature of this embodiment described later.

The electrical configuration includes a CPU 23 as the control center and a CPU 23
And a belt motor 25 to which a drive control signal from the CPU 23 is given. Also, CP
The output of the document detection sensor 12 and the output of the pulse output switch 17 are supplied to U23.

The memory 24 has a CPRUN area, C
A PSET area, a timer 1 area, a timer 2 area, a timer 3 area, and a counter area are included.

FIG. 1 is a diagram showing the contents of drive control of the belt motor 27 in the automatic document feeder 1 having the configuration shown in FIGS. FIG. 2 shows a conventional belt motor drive control content for comparison with the control content of FIG.

Further, FIG. 5 shows a flowchart of the control operation executed by the CPU 23 of FIG. The flowchart of FIG. 5 is for executing the control contents shown in FIG.

Next, a control operation which is a feature of the automatic document feeder 1 according to this embodiment will be described with reference to FIGS. 1 to 4 in accordance with the flow of FIG.

When the feeding of the document is started by the paper feeding unit 3 and the document fed to the belt transport unit 4 is detected by the document detection sensor 12, a detection output is given to the CPU 23. Depending on the CPU23
Gives a forward drive signal to the belt motor 25 (step S
1) The belt motor 25 is rotated forward, and the belt motor 25 causes the transport belt 16 to transport the document from the paper feeding unit 3 to the reversing unit 5.

The CPU 23 provides the forward rotation drive signal to the belt motor 25, and at the same time, decrements the count value preset in the CPRUN area of the memory 24 (step S23).
2) Belt motor 2 until the count value becomes "0"
Turn 5 forward. When the count value becomes "0" (step S3), the timer 1 is started (step S4). Timer 1 has a predetermined time, for example,
This timer measures 10 msec. Until the timer 1 times out, the CPU 23 brakes the belt motor 25 (steps S5 and S6).

Further, the CPU 23 counts the number of pulses X given from the pulse output switch 17 while applying a brake to the belt motor 25 (step S7).

When the timer 1 times out, the CPU 23 gives an inversion drive signal to the belt motor 25 (step S8), and starts the timer 2 (step S9). The timer 2 measures a predetermined time, for example, 25 msec. And CPU23
Counts the number of pulses X given from the pulse output switch 17 until the timer 2 times out (step
S11).

That is, the number of pulses X output from the pulse output switch 17 is counted during the total time Tmsec of the output time of the brake signal to the belt motor 25 and the output time of the inverted drive signal output subsequently thereto in FIG. .

As described above, when the inversion drive signal is given to the belt motor 25, the inversion drive signal is managed by time, and the pulse output from the pulse output switch 17 output within that time (including the brake signal output time in this embodiment). The feature of this embodiment is that the number X is counted.

 Such control has the following merits.

That is, as shown in FIG. 1, when a forward drive signal is output to the belt motor 25, a brake signal is applied, and when a reverse drive signal is applied, the transport belt 16 driven by the belt motor 25 is driven by the belt motor 25. It does not stop or reverse without a time lag for each signal given to 25, it stops while having a certain time lag,
Invert. The time lag differs depending on the size and type of the document conveyed by the conveyance belt 16.
This is because, as described above, when the size of the document changes, the force required to drive the transport belt 16 changes.

Therefore, the document conveyed by the conveyance belt 16 is reversed (moves in the first movement direction in which the document moves in the direction from the sheet feeding unit 3 to the reversing unit 5 in FIG. 3) (in FIG. The stop position A of the rear end of the original in the case of (the second movement direction) varies depending on the original size and the original type.

When the stop position A varies, as in the conventional control shown in FIG. 2, when the reverse drive signal is given to the belt motor 25 based on the number of pulse outputs, the document is stopped. It was not possible to cope with the variation in the position, and the document could not be finally stopped so that the trailing edge of the document coincided with the reference line 15.

Therefore, in this embodiment, when the inversion drive signal is given to the belt motor 25, it is managed by time, and the pulse output switch 17 gives the movement amount of the actual movement of the conveyor belt 16 within that time. It was made to grasp by the number of pulses.

That is, the actual amount of movement of the transport belt 16, that is, the variation of the stop position A can be detected based on the number of pulses output within the fixed time T (the total time of the timer 1 and the timer 2). Specifically, when the document size is small, since the contact area between the transport belt 16 and the contact glass 14 is large, the moving amount of the transport belt 16 is small, and the stop position A is shifted leftward in FIG. However, when the document size is large, the stop position A is shifted rightward. The shift amount is proportional to the number of pulses given from the pulse output switch 17.

Therefore, in step S12 in FIG. 5, the CPU 23
A difference between the counted number of pulses X and a reference value N set in advance by an experiment or the like is obtained, and the difference is used as a corrected pulse number X ', which is added to CPSET to calculate CPSET' (step S1).
3).

Then, after the timer 2 expires, the belt motor 25
The inversion drive signal is successively applied to each time, and the value of CPSET 'is decremented every time a pulse is supplied from the pulse output switch 17 during that time, and when CPSET' reaches "0" (steps S14 and S15). ), Start the timer 3 (step S16).

As described above, the inversion drive signal is continuously supplied to the belt motor 25 by the amount in consideration of the variation of the stop position A in steps S14 and S15. It can be removed. Then, the brake signal is transmitted to the belt motor 25 for a predetermined time set by the timer 3, for example, 20 msec.
(Steps S17 and S18), and the belt motor 25 is turned off (step S19).

In step S12, normally, the time set by the timer 2 is set so that X> N. Therefore, when the timer 2 times out, the correction amount always remains, and CPSET 'does not become a negative value.

In the brake control in step S5 and step S17, it is preferable that both terminals of the belt motor 25 be grounded and short-circuited because a higher control force can be obtained than opening both terminals.

<Effects of the Invention> Since the present invention is configured as described above, it is possible to reliably set a document at a predetermined set position even if the size and type of the document are different.

Further, when the document is switched back by the transport belt, the transport belt does not transport the document more than necessary, so that there is no fear that the document edge is bent.

Furthermore, since it is not necessary to newly add an element or the like to the conventional device, the present invention can be realized without increasing the cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing a control operation which is a feature of the apparatus according to one embodiment of the present invention. FIG. 2 is a diagram showing a control operation of a conventional device for comparison with FIG. FIG. 3 is a schematic sectional view showing the structure of one embodiment of the present invention. FIG. 4 is a block diagram showing a partial configuration of an electric circuit necessary for a control operation in one embodiment of the present invention. FIG. 5 is a flowchart showing a control operation in one embodiment of the present invention. In the figure, 1... Automatic document feeder, 2... Copying machine body, 3... Paper feeding unit, 4... Belt transporting unit, 5... Reversing unit, 10. Wire, 16 ... Conveyer belt, 17 ... Pulse output switch, 23 ... CPU, 24 ...
... memory, 25 ... belt motor.

Claims (1)

(57) [Claims] 1. An automatic document feeder for conveying a document to be set at a predetermined position by a conveyance belt, comprising: pulse output means for outputting a pulse in conjunction with driving of the conveyance belt; Belt driving means for driving the transport belt in a second direction opposite to the first direction for a predetermined time after driving the transport belt in the first direction; and a pulse within a predetermined time during which the transport belt is driven in the second direction. Pulse counting means for counting the number of pulses output from the output means; comparing means for comparing the count value of the pulse counting means with a predetermined reference value; based on the output of the comparing means, after the elapse of the predetermined time, And a drive amount correcting means for continuously driving the transport belt in the second direction by a predetermined number of pulses.