JPH06603B2 - High-speed paper transport device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-speed sheet conveying device used in a copying machine or the like.

“Prior Art” For example, when copying of a large number of original sheets is required, it requires a great deal of labor for the operator to set the original sheets one by one in the copying machine and perform the copying operation. . Therefore, a conveying device has been developed which can automatically feed the original sheets one by one onto the plan glass of the copying machine (Japanese Patent Laid-Open No. 56-56443).

As shown in FIG. 7, this device is placed on a plantain glass of a copying machine. A stack 2 for accommodating a manuscript sheet 1 and a stack 2 for pulling out the stack 2 one by one from the bottom are shown in the figure. A feeding belt 3 that is fed to the right, a conveying drum 6 and a pressing roller 7 that convey the original paper 1 pulled out in this way onto the platen glass 4, and a paper stop claw 8 that determines the stop position of the leading end of the original paper 1. And a drive roller 9 for advancing the document sheet 1 up to this point. Paper stop pawl 8 retracts the pawl ₈₁ after the original paper 1 on the platen glass 4 has finished copying. The original paper 1 is sent back to the stack 2 by the drive roller 9 and the forwarding roller 11.

According to such a principle, the original sheets 1 are sequentially conveyed onto the platen glass 4 and all the portions accommodated in the stack 2 can be automatically copied.

If the copying operation of the copying machine is speeded up by the improvement of its function, it is required that the transfer speed of the transfer device is also increased accordingly.

"Problems to be Solved by the Invention" However, if the transport speed of such a sheet transport device is increased, the following problems occur.

FIG. 8 is a partial vertical cross-sectional view when the original paper 1 is stopped at a normal position on the platen glass 4. The leading edge of the original sheet 1 is blocked by the sheet stop claw 8 and the conveyance is stopped at this position. However, when the original paper 1 is conveyed at high speed and collides against the paper stop claw 8, the front end of the original paper 1 may be bent or damaged by the impact. For this reason, when carrying a thin original paper which is weak against impact, it is necessary to reduce the carrying speed. On the contrary, in the case of conveyance of the manuscript paper 1 having a strong stiffness, as shown in FIG. 9, when the leading end of the manuscript paper 1 collides with the paper stopping claw 8, the paper becomes a bow and absorbs the energy, and the reaction causes the first motion. As shown in FIG. 10, when the leading edge of the sheet stopping claw 8 retreats by the width D, the sheet stops.

If the width D is in the range of several millimeters, there is no practical problem, but if it is several tens of millimeters, the deviation cannot be ignored. From this point of view, even if the manuscript paper is thick, it is not possible to speed up beyond a certain speed.

The present invention has been made in view of the above points, and an object of the present invention is to provide a high-speed sheet feeding device capable of feeding thin original sheets and thick original sheets at a higher speed without trouble. .

"Means for Solving Problems" In the present invention, (a) a conveyance motor as a conveyance means for conveying a sheet along a predetermined path, and (b) a voltage according to the rotation of the conveyance motor is generated. Rotation speed detection means,
(C) A paper stop claw that stops the leading edge of the sheet that is freely retracted in the above-described path and is conveyed in the appearance state, and (d) When the leading edge of the sheet reaches a predetermined position before the sheet stop claw. Paper leading edge position detecting means for detecting this,
(E) Absolute value for high-speed conveyance of the sheet until the first time elapses before the sheet leading edge position detecting means detects the sheet leading edge and before the sheet leading edge reaches the position of the sheet stop claw. Output the highest voltage, and for the low-speed conveyance of this paper from the first time has elapsed until the second time for the leading edge of the paper to reach the paper stop claw with a certain margin. A voltage switching means for outputting a non-zero voltage significantly lower than the absolute value and setting the voltage to zero after the second time has passed; and (f) the voltage output by the voltage switching means and the rotation speed detection. The high-speed sheet conveying apparatus is provided with a difference detecting means for obtaining a difference from the voltage output by the means, and (g) a motor drive control means for controlling the conveyance of the conveying motor according to the detected difference.

That is, in the present invention, a sheet leading edge position detecting means for detecting the leading edge of the sheet is provided at a predetermined position in front of the sheet stopping claw in the sheet conveying path of a copying machine or the like, and the speed at that time after the sheet is detected by this is detected. The sheet is conveyed at high speed until the first time elapses before it reaches the sheet stop claw as if the sheet was conveyed by. Further, the sheet is conveyed at a low speed after the lapse of the first time period, and the driving of the conveyance motor is stopped at the time point when the second time period has elapsed. The second time period continues from when the first time period elapses until after the sheet conveyed at a low speed reaches the sheet stop claw, where the leading edge of the sheet is accurately positioned.

(Explanation of Operation Principle) FIG. 1 is a block diagram for explaining the operation principle of the high-speed sheet conveying apparatus of the present invention.

Paper Fast conveying apparatus of the present invention, conveying outputs and the transfer mechanism 16 for conveying the document sheets at a high speed, the control signal 17 ₁ to be able to switch to two types of at least fast and slow the transport speed of the transport means Speed setting means 17 is provided.

According to the experiments conducted by the present inventors, when a document sheet having a predetermined standard thickness is used, the relationship between the conveyance speed and the amount of rebound after colliding with the sheet stopping claw is shown in FIG. became. In this figure, when the document sheet conveyance speed is 50 mm / sec or less per second, the amount of rebound is almost zero, and at about 200 mm / sec, it is about 3 mm. This amount of bounce can usually be ignored, but if it exceeds this, for example, 100
At 0 [mm / sec], it becomes about 30 [mm] or more, and a large deviation occurs at the copy position.

Therefore, in the high-speed sheet conveying apparatus of the present invention, for example, the conveying speed setting means 17 is designed so that the conveying speed of the conveying means is 1000 [mm / sec] at high speed and 50 [mm / sec] at low speed. . Or for controlling the conveying means at any rate in the two speed determining means 18 determines, and it outputs the selection signal 18 ₁ with respect to the conveying speed setting means 17.

3A, 3B and 3C are longitudinal sectional views of a main part of the high-speed sheet feeding device, showing the feeding states of original sheets at different times.

In FIG. 3, the one attached between the conveying roller 6 and the platen glass 4 is the sheet leading end position detecting means 19
Is. When the paper leading edge position detection means 19 detects the leading edge 1 ₀ of the original sheet 1, from which the detection signal 19 (first
(Fig.) Is output. Determining means 18 (Figure 1) deduces the subsequent movement of the tip 1 ₀ of the original sheet 1 from the conveying speed. Then, when the tip 1 ₀ has come to the position shown in FIG. 3 b, switches the transport speed to the low speed side. As a result, the document sheet 1 is substantially suddenly braked, and the impact at the time of colliding with the sheet stop claw 8 is alleviated.

(Explanation of Specific Block Diagram) FIG. 4 shows an embodiment of the high-speed sheet conveying apparatus of the present invention in which each block shown in FIG. 1 is embodied in more detail.

In this embodiment, the conveying means 16 is the conveying motor 12
, A tacho generator 22, a differential amplifier 23, a comparator 25, a triangular wave generator 24, and a drive circuit 26. The conveyance motor 21 is connected to the conveyance drum 6 and the conveyance roller 7 via a transmission mechanism (not shown), and these are rotated at a predetermined speed. The tachogenerator 22 is directly connected to the drive shaft of the carry motor 21, and sends a DC voltage proportional to the rotation speed thereof to the differential amplifier 23. The differential amplifier 23 sends a DC voltage corresponding to a difference signal between the differential amplifier 23 and the control signal 17 ₁ input to the other terminal thereof to the comparator 25. The comparator 25 compares this DC voltage with the output signal of the triangular wave generator 24 and supplies intermittent pulses to the drive circuit 26 at predetermined intervals.
The drive circuit 26 is composed of a switching transistor or the like, and supplies so-called PWN (pulse width control) system drive power to the carry motor 21 by the pulse thereof.

The conveying means 16, when the voltage of the control signal 17 ₁ for inputting thereto is increased, the drive circuit 26 supplies a large drive power to the conveying motor 21 in accordance with this, the conveying speed becomes faster. Furthermore, lowering the control signal 17 ₁ voltage, operate to transport motor 21 is slower reversed.

Next, the transport speed setting means 17 outputs a control signal of such two stages, and a changeover switch 27 having one circuit and three contacts, and two switches connected in series to each other to apply a voltage to this contact. Of resistors 28 ₁ and 28 ₂ . A constant voltage V [v] is applied to one end of the resistor 28 _1.
Is connected to one terminal 27 ₁ of the changeover switch 27. The connection point of the _two resistors 28 ₁ and 28 ₂ is connected to another terminal 27 ₂ of the changeover switch 27. One end of the resistor 28 ₂ are connected to ground, and the remaining terminals 27 ₃ of the switching switch 27.

Switching switch 27 may be a electromagnetic relay, also may be one which combined the transistor switch circuit, the selection signal 18 ₁ to be input from the determining unit 18 switches the connection of the switch.

Further, the judging means 18 is composed of a microprocessor, a memory in which its operation program is written, and its peripheral circuits, and this is indicated as CPU in the figure. In addition, the paper leading edge position detection means 19, and use a light reflection type, and outputs the coming leading edge of the original sheet 1 immediately below, a detection signal 19 ₁ captures the light reflected by the upper surface of the document sheet Works like.

(Specific Operation of Apparatus) The high-speed sheet conveying apparatus of this embodiment operates according to the flowchart shown in FIG. This operation will be described in comparison with FIG.

First, the transport motor 21 is started to transport the original paper 1 by the transport drum 6 (step). At this time, the switching switch 27 of the transport speed setting means 17 is in a state where the contact is connected to the terminal 27 ₁ , and the control signal 17 ₁ having the maximum voltage is output. The set speed in that case is 1000 [mm / sec].

Then, when the leading end 1 ₀ of the original sheet 1 passes directly below the paper leading edge position detection means 19, determination means 18 receives the detection signal 19 ₁ (step).

From this moment, the judging means 18 waits for 280 [msec] using the built-in timing device (step). Next to switch the selection signal 18 ₁ instructs the deceleration of the motor. By the selection signal 18 _1, the changeover switch 27 of the paper tip position detecting means 17 switches the contact point e to the terminal 27 _2. This control signal 17 ₁ output from the paper leading edge position detection means 17 is switched to a lower voltage.
Then 50 [m sec] while, after waiting (step), the decision circuit 18 switches the selection signal 18 ₁ again.
Thus, the change-over switch 27 of the paper tip position detecting means 17 switches the contacts to the terminals 27 _3, the control signal 17
Set ₁ to zero volts. This causes the transport motor 21 to stop rotating (step).

FIG. 6 is a graph showing the state of changes in the transport speed of the original sheet during this series of operations.

Before the front edge of the original paper is detected
sec], the original paper is conveyed at a speed of 1000 [mm / sec], and then speeded down to a speed of 50 [mm / sec]. Then, the leading edge of the document sheet collides with the sheet stop claw to stop the movement, but the conveyance motor stops about 30 [msec] later.
This is to prevent the document sheet from stopping before it collides with the sheet stopping claw.

When the document sheet conveyance speed is to be rapidly reduced in this way, it may be possible to reduce the rotation speed of the relatively lightweight drive roller 9 (FIG. 4) only.
By doing so, the weight is lighter than that of the transport drum 6, the inertia is small, and the falling speed can be made steep.

The transport speed setting means, a selection signal 18 ₁ to the output of the decision device 18 may be constituted by a direct digital-to-analog converter that changes analog voltage.

"Advantages of the Invention" The high-speed sheet conveying apparatus of the present invention having the above-described configuration can convey a sheet as fast as possible and can quickly stop the sheet at a predetermined position. In this case, the transport speed is reduced immediately before the sheet is stopped, so that the impact of the sheet colliding with the sheet stop claw does not damage the leading edge of the sheet. Further, the stop position shift due to the rebound of the paper does not occur.

As a result, it is possible to convey thin paper, which is weak against impact, at high speed, and also to stop thick paper that rebounds remarkably at an accurate position.

Further, in the present invention, the control voltage is switched and controlled in three steps by the voltage switching means, and the drive control of the carry motor is performed by using the difference from the voltage generated according to the rotation of the carry motor. By forming a feedback loop in this way to control the rotation of the carry motor, it is possible to stabilize the carry speed at each stage even when the load on the carry motor fluctuates. The leading end of the sheet can be reliably brought into contact with the sheet stopping claw, and the stopping position of the sheet can be set accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic structure of a high-speed sheet conveying apparatus according to the present invention, FIG. 2 is a graph showing the relationship between the sheet conveying speed and the amount of rebound, and FIGS. FIG. 4 is a longitudinal sectional view of the high-speed sheet conveying apparatus at different times, FIG. 4 is a block diagram showing a detailed embodiment of the high-speed sheet conveying apparatus of the present invention, FIG. 5 is a flowchart of its operation, and FIG. FIG. 7 is a longitudinal sectional view of a conventional sheet conveying apparatus, and FIGS. 8 to 10 are explanatory views of the sheet conveying operation. 8 ... Paper stop claw, 16 ... Conveying means, 17 ... Conveying speed setting means, 17 ₁ ...... Control signal, 18 …… Determining means, 18 ₁ …… Selecting signal, 19 …… Paper tip position detecting means, 19 ₁ ...... Detection signal.

Claims (1)

[Claims] 1. A carrying motor as a carrying means for carrying a sheet along a predetermined path, a rotation speed detecting means for generating a voltage according to the rotation of the carrying motor, and a carrying motor arranged so as to be retractable in the path. A paper stop claw that stops the front end of the paper in the appearance state, a paper front end position detection unit that detects when the front end of the paper reaches a predetermined position before the paper stop pawl, and the paper front end position Until the first time elapses after the detection means detects the leading edge of the sheet and before the leading edge of the sheet reaches the position of the sheet stop pawl, the highest absolute voltage is used for high-speed conveyance of the sheet. This is an absolute value for low-speed conveyance of the sheet during the period from the output and the second time when the leading edge of the sheet reaches the sheet stop claw with a predetermined margin after the first period has elapsed. Much lower than A voltage switching means for outputting a non-zero voltage and setting the voltage to zero after the second time has elapsed, and a difference detection for obtaining a difference between the voltage output by the voltage switching means and the voltage output by the rotation speed detecting means. And a motor drive control means for controlling the conveyance of the conveyance motor according to the detected difference.