JPS60167836A - Friction-separation paper feeder - Google Patents

Abstract

PURPOSE:To prevent occurrence of a jam due to misfeeding by disposing a solenoid clutch between a driving gear and a driving source of a reverse roller, and controlling the solenoid clutch in such a manner that a sheet to be fed is not brought back to the reverse roller in a friction-separation paper feeder. CONSTITUTION:A reverse roller driving gear 24 is driven by a driving source through a solenoid clutch 26. That is, registration rollers 4a, 4b, a feed roller 2 and the reverse roller driving gear 24 are started and stopped independently from each other by respective solenoid clutches. Accordingly, there is provided control means for controlling the solenoid clutch 26 in such a manner that at the time of feeding a sheet to a photoreceptor 15 with the registration rollers 4a, 4b, the driving of the reverse roller 3 is started during the time at least the leading end of a sheet is completely nipped by the registration rollers 4a, 4b and then the leading end of the sheet reaches the photoreceptor 15.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a friction separation paper feeding device used in an electrophotographic recording device such as a copying machine.

As shown in FIG. 1, a conventional paper feeding device for a copying machine, facsimile, etc. Pickup roller 1 that presses and rotates according to the paper feed signal
The feed roller 2 located on the downstream side of the feed roller 2 rotates in the paper feeding direction, and is in pressure contact with the feed roller 2 across the paper path, and the torque limiter 11 applies torque in the opposite direction to the paper feeding direction. It has a reverse roller 6 that can rotate in any direction, and the difference between the coefficient of friction between the roller and the paper and the coefficient of friction between the sheets, the torque of the reverse roller 3 due to these frictional forces, and a torque limiter. When a sheet of paper is fed between the feed roller 2 and the reverse roller 5, this is registered to feed the paper to the photoreceptor at a predetermined timing by using the difference in torque caused by The paper is fed to the roller pair 4a, 4b, and the feed roller 2
When two or more sheets of paper are fed between the feed roller 2 and the reverse roller 2, they are separated and only the one sheet in contact with the feed roller 2 is transferred to the registration roller pair 4 (4a, 4b).
) A friction separation paper feeding device is known.

In the illustrated paper feeding device, as shown in the timing diagram of FIG. 2, the pickup roller 1,
The feed roller 2, reverse roller 6, and registration ports to 4 start rotating at the same time, and the pickup roller 1 transfers the paper to the feed roller 2 and reverse roller 3.
After a period of time Pl (number of pulses) in which the sheet is sufficiently fed, the pickup roller 1 stops and retreats from the upper surface of the sheet bundle 10. Next, the paper is passed through the guide plates 6a, 6 by the feed roller 2.
b. A paper sensor 5 is provided immediately upstream of the registration roller 4, and when the leading edge of the paper is detected by this sensor, the reverse roller 3 and the registration roller 4 are stopped. However, the feed roller 2 is set in advance to continue rotating for Pz (pulse) time and feed the paper after the paper sensor 5 detects the leading edge of the paper. During this time, the leading edge of the paper collides with the stationary registration roller 4, and as shown by the two-dot chain line in FIG.
A sufficient slack is formed along the line. After a Pz (pulse) time after the paper feed signal is output, the registration roller 4 starts rotating and conveys the paper to the photoreceptor 15.

Now, in the conventional friction separation paper feeding device having the above configuration, the drive shaft 2 of the reverse roller 6 is driven by the rotation of the registration roller 4a via the gear train 20.21°22, and the rotation of the drive shaft 23 is driven by the rotation of the registration roller 4a. The torque was transmitted to the reverse roller via gears 24, 25 and a torque limiter 11. Therefore, after a pH time has elapsed since the paper feed signal, the registration roller 4 starts rotating and at the same time the torque limiter 11 is activated, and a predetermined torque is applied to the reverse roller.

Incidentally, the amount of paper fed by the feed roller 2 is determined by the feeding time P2 (pulse) after the paper sensor 5 detects the paper. As shown in FIG. 1, the distance from the nip between the feed roller 2 and the reverse roller 3 to the nip between the color registration rollers 4a and 4b is to1, and the distance from the paper sensor 5 to the registration rollers 4a and 4b is tl, and the distance from the paper sensor 5 to the registration rollers 4a and 4b is tl, and the paper sensor If △L is the paper conveyance distance per pulse of pulse number P2 from when 5 detects the leading edge of the paper until the feed roller 2 stops, then the paper length from the feed roller 2 to the registration l/-john roller is is given by the following equation.

L = P2 Slips occur when being transported. In particular, it is known that when the difference in the friction coefficient between the front and back sides of a sheet of paper that has been copied for 1 m per side in double-sided copying increases, the above-mentioned slip increases, and experimental verification results show that the slip rate is approximately 30%. Applying this to equation (1) above, we get
L'” P 2 X△t X 0.7 + (to
-tz) ----(2) Therefore, the amount of paper slack is determined by L'-1Q.

Stable conveyance by the registration rollers 4 can be obtained by increasing the amount of slack in the paper with a certain margin, but in reality, the slip rate is affected by the shape of the guide plate O, etc. For tall paper, etc., there is almost no slack in the amount of slack, so when the registration roller fully feeds the paper, as mentioned above, if torque is applied to the reverse roller B at the same time in the opposite paper feeding direction, this will cause the registration There is a drawback that the paper that has been bent by the rollers 4 is pulled back before it is securely gripped by the registration rollers, and a non-feed jam is likely to occur.

Objective: The present invention eliminates the above-mentioned drawbacks of the conventional frictional separation paper feeding device having the above-mentioned structure. It is an object of the present invention to provide a friction separation paper feeding device that is less likely to cause a non-feeding jam due to being pulled back by a reverse roller even when feeding a small amount of paper.

Configuration The present invention will now be described in detail based on embodiments shown in the drawings.

FIG. 6 is a diagram showing an embodiment of the present invention, and the same members as those in the device shown in FIG. 1 are given the same reference numerals and will be explained.

In the device of this embodiment, the reverse roller drive gear 24 is not driven by the rotation of the registration roller 4a being transmitted by a gear train as in the device shown in FIG. 1, but by a drive source via an electromagnetic clutch 26. It is meant to be driven. That is, the registration roller 4, the feed roller 2, and the reverse roller drive gear 24 are started and stopped independently of each other according to the timing chart shown in FIG. 4 by electromagnetic clutches provided respectively.

Therefore, when the paper feed signal is turned on, the pickup roller 1, feed roller 2, and reverse roller 4 start rotating at the same time, but the reverse roller 6 is rotated by an independent electromagnetic clutch 26, so l/sist = John roller 4 is rotated. There's no need. Then, the registration roller 4 was turned on after P3 (pulse) time after the paper feed signal was turned on.
By turning on the electromagnetic clutch 26 after , P4 (pulse) time, the drive timing of the reverse roller 5 is controlled to be delayed by 24 hours from the start of drive of the registration roller 4. When the reverse roller 6 starts driving, at least the paper is connected to the registration roller pair 4.
It is preferable to do this during the period from when the paper is held in its grip until the leading edge of the paper reaches the photoreceptor 15. If the leading edge of the paper is
If torque is applied to the reverse roller 3 while the toner image on the photoreceptor has been completely transferred, the paper conveyance speed will change and jitter etc. will occur, which is undesirable.

Effects As described above, according to the present invention, the paper fed to the photoreceptor by the registration roller can be pulled back by the reverse roller even under adverse conditions such as when there is a large difference in the coefficient of friction between the front and back sides of the paper. Paper can be reliably fed to the photoreceptor without any problems.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventional friction separation paper feeding device.
FIG. 2 is a timing chart of each roller, etc., FIG. 2 is a sectional view showing an embodiment of the present invention, and FIG. 4 is a timing chart of each roller, etc. 1...Pickup roller 2...Feed roller 3...Reverse rollers 4a, 4b...Registration roller 10...
Paper bundle 11...Torque limiter 15...Photoreceptor 24...Reverse roller drive gear 26...Electromagnetic clutch Fig. 1 Fig. 2

Claims (1)

[Claims] A feed roller rotates in the paper feeding direction, and a torque limiter presses against the feed roller across the paper path, and a torque limiter applies a constant torque in the opposite direction to the paper feeding direction. A pair of rollers consisting of a reverse roller that can also rotate is used to separate the double feeds and feed the sheets one by one to the registration rollers, and the sheets are fed to the photoreceptor by the registration rollers at a predetermined timing. In a friction separation paper feeding device for an electrophotographic recording device that produces paper, a clutch independent from the registration roller is provided between the drive gear of the reverse roller and the drive source of the device, and the registration roller is connected to the photoreceptor. When feeding paper, the electromagnetic clutch is controlled so as to start driving the reverse roller at least between the time when the leading edge of the paper is completely gripped by the registration roller and before the leading edge of the paper is bent by the photoreceptor. A paper feeding device characterized by being provided with a control means.