JPH0413264B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling paper feeding using a friction separation roller type paper feeding device.

As shown in FIG. 1, for example, a paper feeding device of a copying machine or the like presses against the top surface of a stack of paper sheets 1 placed on a paper feeding table, and rotates in the paper feeding direction shown by the arrow in the figure. A pick-up roller 2, which feeds paper by entraining it by friction, and a feed roller 3, which is located on the downstream side in the paper feeding direction and rotates in the paper feeding direction, are in pressure contact with each other across the paper path, and are in pressure contact with each other in the paper feeding direction. and a separation roller 4 to which a certain torque is applied in the opposite direction as shown by the dashed arrow in the figure.When there is no paper between this pair of rollers and when the paper is When only one sheet is fed, the separation roller 4 is driven by the feed roller 3 without slipping because the torque due to the frictional force with the feed roller 3 or the frictional force with the paper overcomes the above-mentioned constant torque, and the separation roller 4 is moved by the pick-up roller 2. Two or more sheets of paper are sent to roller pair 3,
4, the separation roller 3 rotates in the opposite direction to the paper feeding direction because the above-mentioned constant torque is greater than the frictional force between the sheets sandwiched between the roller pair. A so-called friction retard roller (Friction Retard Roller) pushes the second and subsequent sheets of paper back toward the paper feed tray, and only the one sheet of paper in contact with the feed roller 2 is guided by a guide 5 and fed toward the registration roller 6. ) Paper feeding devices are known to have various advantages.

In this type of paper feeding device, the pick-up roller 2 is normally driven via a gear (not shown) from a feed roller shaft 7 whose axis center is fixed relative to the machine frame, and is rotatably supported on the feed roller shaft 7. The arm 8 is pivotally supported at the free end of the arm 8, which presses against the upper surface of the paper bundle 1 at a predetermined height with a constant pressing force due to its own weight or a force such as a spring, and moves it along with the feed roller 3 in response to a paper feed signal. It is rotated by a predetermined angle in the direction of the arrow. Conventionally, in this type of paper feeder, the pick-up roller 2 is generally in pressure contact with the upper surface of the stack of sheets at all times during paper feeding.

Here, the paper feeding range of the conventional friction separation paper feeding device of this type will be explained.

First, as shown in FIG. 2, only one sheet of paper is sent out from the stack of sheets by the pick-up roller 2.
The conditions for conveying the material through the nip between the feed roller 3 and separation roller 4 are as follows.

The pressure force of the pick-up roller 2 on the paper is
P _A is the pressing force of the separation roller 4 against the feed roller 3, P _B is the weight of one sheet of paper, m,
If the coefficient of friction between each roller and the paper is μ _R and the coefficient of friction between the sheets is μ _P , then the paper being fed has a friction of μ _R P _B in the paper feeding direction by the feed roller 3, as shown in the figure. The pick-up roller 2 exerts a frictional force of μ _R P _A in the paper feeding direction, and the separation roller 4 exerts a constant return force in the return direction.
A frictional force μ _P ·(P _A +m) acts between T _A (value obtained by dividing the constant torque applied to the separation roller by its radius) and the second sheet of the paper stack. Therefore, the conditions for conveying paper in the paper feeding direction are μ _R・P _B + μ _R・P _A > T _A + μ _P (P _A + m) ∴P _B > T _A / μ _R − (μ _R − μ _P ) P _A /μ _R ... In the above equation, m is omitted because it is sufficiently small compared to P _A.

Next, as shown in FIG. 3, the pick-up roller 2 double-feeds two sheets of paper from the paper stack, and the lower paper separated by the feed roller 3 and separation roller 4 is one of the paper stacks. Think about the conditions for returning between the eyes and the third sheet of paper. 2
For the first sheet of paper, there is a feed roller 3 in the paper feeding direction.
The frictional force μ _P・P _B between the first sheet of paper and the first sheet of paper pressed against each other by the separation roller 4 with a pressure of P _B ,
Due to the pressing force P of the pick-up roller 2 and the weight of one sheet of paper, the frictional force μ _P (P _A +m) acting on the top surface and the frictional force μ _P (P _A +2m) between the top surface of the third sheet of paper are In the return direction, a force T _A is exerted by the separation roller 4.

Therefore, the conditions for the second sheet of paper to return to the paper stack are μ _P P _B + μ _P (P _A + m) + μ _P (P _A +2m) < T _A ∴P _B < T _A / μ _P − (2P _A + 3m) ... The above equation is shown in a graph in Figure 4 with P _B on the vertical axis and T _A on the horizontal axis. The illustrated straight line 1a shows the lower limit of the equation when μ _R is low, and the straight line 1b shows the lower limit of the equation when μ _R is high. Further, the straight line 2a shows the upper limit of the equation when μ _P is low, and the straight line 2b shows the lower limit of the equation when μ _P is high.

Therefore, P _B when using low friction paper,
The paper feeding range for the combination T _A is the range sandwiched between straight lines 1a and 2a on the right side of the intersection, and the paper feeding range when using high friction paper is the range between straight lines 1b and 2a.
The area to the right of the intersection of b is the range sandwiched between these. As is clear from the figure, the paper feeding range when using low-friction paper is quite wide, but the paper feeding range when using high-friction paper is quite narrow.

In view of the above-mentioned drawbacks of conventional paper feeding using the friction separation roller paper feeding method, the present invention provides a sufficiently wide paper feeding range not only when using low-friction paper but also when using high-friction paper. The purpose of the present invention is to provide a paper feed control method that can handle a wide range of paper types.

The purpose of this is to use the pick-up roller according to the present invention, when feeding high-friction paper, to hold the paper fed by the pick-up roller on top of the paper stack until the paper is clamped by a pair of rollers consisting of a feed roller and a separation roller. This is achieved by bringing the sheet into pressure contact with the paper bundle, removing pressure or separating it from the sheet bundle during separation and conveyance by the pair of rollers, and controlling it so that it is always in pressure contact with the top surface of the sheet bundle during low-friction paper feeding.

In other words, when separating and returning double-fed sheets, if the pick-up roller is separated from or pressure is removed from the top surface of the paper stack, P _A becomes zero in the above equation, so the second sheet is returned. The conditional expression for this is P _B < T _A / μ _P −3m ……. If this equation is shown graphically in FIG. 4, it will look like a straight line. Therefore, the paper feeding range of the paper feeding device according to the present invention when using high-friction paper is the range to the right of the intersection of the straight lines 1b and 1b, and that range is the same as that of the conventional device when using high-friction paper. It is considerably enlarged in comparison, and it becomes possible to stably separate and feed a wide range of paper types.

To control the paper feed pressure of the pick-up roller as described above, for example, the arm holding the pick-up roller is made to press the roller against the stack of sheets using a solenoid against a spring force, and the solenoid is turned on when the paper feed signal is turned on. The pick-up roller may be brought into pressure contact with the stack of sheets by force, and held for a predetermined timing, and the timing may be changed depending on the friction coefficient of the sheets.

Another embodiment in which control is performed using a cam is shown in FIGS. 5 and 6. In the figure, an arm 8 that pivotally supports the pick-up roller 2 at its tip supports a control lever 11 that is pivoted on a fulcrum 9 and whose tip is pulled downward by a spring 10. It is held near the tip. A pin 12 is installed between the fulcrum 9 of the control lever 11 and the protrusion tip holder of the arm 8,
This pin 12 engages with a cam surface of a cam portion 14 of a cam 13 that is rotatably supported on the feed roller shaft 7 and is pushed up.
is positioned. That is, when the pin 12 is engaged with the reference circle part of the cam part 14, the pick-up roller 2 is pressed against the upper surface of the paper bundle, and when it is engaged with the protrusion part of the cam part 14, the pick-up roller 2 is pressed against the top surface of the paper stack. Separated from bundle 1.

A ratchet 15 is fixed to the feed roller shaft 7 adjacent to the cam 13. On the surface of the cam 14 facing the ratchet 15, a claw 16 that can be engaged with and removed from the ratchet 15 is rotatably provided around a pin 17. protrudes from the outer circumferential surface of the
A first stopper 19 is provided on the protrusion of the pawl 16 in a detachable manner and is moved by a solenoid 18. During high-friction paper control, the first stopper 19 is moved to the position shown in FIG. The claw 16 is locked by coming into contact with the
6 and ratchet 15 are off. In this state, the cam protrusion engages with the pin 12, and the pick-up roller 2 is separated from the stack of sheets. When the paper feed signal is turned on, the solenoid 18 is energized and the first stopper 19 is activated.
When the pawl 16 is pulled and disengaged from the pawl 16, the pawl 16 engages with the ratchet 15, and the meshing cam 13 engages with the ratchet 1.
5, the pin 12 slides along the reference circle of the cam, and the pick-up roller 2 comes into contact with the stack of sheets. At a predetermined timing, the solenoid 18 is turned off and the first stopper 19 returns to its original position. After that, when the pawl 16 hits the first stopper 19, the pawl 16 and the ratchet 15 are disengaged, the cam 13 stops, and the pick-up roller 2 is held at a standby position spaced apart from the top surface of the paper stack.

When using paper with a low friction coefficient, switch lever 2.
0 in the direction of the arrow in the figure, the first stopper 1
9 is displaced to a position away from the pawl 16, and the pawl 16 engages with the ratchet 15, and the movement of the tip of the switching lever 20 causes the second stopper 22 to be displaced to the position indicated by the chain line in the figure, so that the tip touches the outer periphery of the cam 13. come into contact with the surface. The feed roller shaft 7 rotates in response to the paper feed signal, the cam 13 rotates due to the engagement between the ratchet 15 and the pawl 16, and when the pawl 16 comes into contact with the second stopper 22, the pawl 16 and the ratchet 15 are no longer engaged. The cam 14 comes off and stops with the reference circle portion of the cam 14 engaged with the pin 12, and the pick-up roller is held in a position where it is in pressure contact with the upper surface of the stack of sheets.

When the switching lever 20 is returned to its original position, the second stopper 22 is moved away from the outer peripheral surface of the cam 13 and moved to the first position.
The stopper 19 comes into contact with the outer peripheral surface of the cam, making the above-described control possible.

When the main switch is turned on to the machine, a control device (not shown) provides a drive for initialization before the paper feeding operation, and at this time the ratchet rotates, bringing the claw to the first stopper and entering the waiting state. .

As described above, according to the present invention, it is possible to expand the paper feeding range of the combination of the pressing force of the feed roller and the separation roller and the return force of the separation roller applied by the trim limiter, so that a wide range of paper types can be fed. It can be adapted to paper feeding, and stable separation and conveyance performance can be maintained over a long period of time even if the above-mentioned pressing force and torque change somewhat over time.

[Brief explanation of drawings]

FIG. 1 is a side view showing the general configuration of a friction separation roller paper feeding device to which the present invention is applied, and FIGS. 2 and 3 show the case in which one sheet of paper is conveyed in this device and the separated sheets, respectively. Fig. 4 is a schematic diagram showing the force applied to the paper when returning the paper, and Fig. 4 shows the paper feeding range in relation to the pressing force between the feed roller and separation roller and the torque applied to the separation roller by the conventional device and the device of the present invention. FIG. 5 is a side view showing an embodiment of the control device of the apparatus of the present invention, and FIG. 6 is a graph explaining - in FIG.
FIG. 1... Paper stack, 2... Pick-up roller, 3
... Feed roller, 4 ... Separation roller, 12-22 ... Control means.

Claims (1)

[Claims] 1. A pick-up roller that comes into contact with the top surface of a stack of sheets stacked on a paper feed table and rotates in the paper feeding direction to send out the paper that comes into contact with it by friction, and a feed roller that is located downstream of the roller in the paper feeding direction and rotates in the paper feeding direction. and a separation roller that pinches the paper path and presses against it and is applied with a constant torque in the opposite direction to the paper feeding direction. In a paper feeding control method using a friction separation roller paper feeding device that separates and conveys paper using the difference in frictional force, when the above-mentioned pick-up roller is used to feed high-friction paper, the paper fed by the pick-up roller is The paper is pressed against the paper stack until it is pinched by the roller pair consisting of the feed roller and the separation roller, and the pressure is removed or separated from the paper stack when the paper is separated and conveyed by the roller pair, and the paper is always kept in contact with the paper stack when low-friction paper is fed. A paper feed control method that controls the paper so that it is brought into pressure contact with the top surface of the bundle.