JPH012954A - Sheet conveyance device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a sheet conveying device in an image forming apparatus such as a copying machine or a laser beam printer, and particularly relates to a sheet conveying device in an image forming apparatus such as a copying machine or a laser beam printer. The present invention relates to a sheet conveying device that can prevent image blurring caused by fluctuations in feed speed.

(B) Conventional technology Conventionally, as shown in FIGS. 3 and 4, a sheet conveying device such as a copying machine uses a first pair of conveying rollers 1°2 and a second pair of conveying rollers 3 and 4 to convey sheets. The paper is transported between the transport guide plates 5 to 8 and sent to the transfer section T.

Then, the toner image formed on the electrostatic photoreceptor drum 9 by a known electrophotographic process is transferred onto the sheet S at the transfer section T.

Here, when handling a jam such as a paper jam, as shown in FIG. 5, the conveyance guide plates 6 and 8 are rotated downward to remove the jammed paper. Since there is an unfixed toner image on the sheet, when removing the jammed paper, the second conveying roller pair 3, 4 and the guide plate 7,
5 becomes smeared with toner, and the smudge adheres to the subsequent printed image, deteriorating the image.

Therefore, conventionally, the pressure on the second pair of conveyance rollers is not released, and the first one-way clutch 10 is used to prevent rotation in the opposite direction. It is constructed so that it can be removed from below the drum 9 by rotating it.

Further, the second pair of conveyor rollers 3 and 4 are coupled together with the drum 9 to a motor M via a gear, and the first pair of conveyor rollers 1 and 2 are coupled to another motor M2 via a clutch 13. By making the drive systems independent from each other, it is possible to prevent the rotation of the drum 9 from being disturbed due to the on/off operation of the clutches, thereby preventing the rotation of the drum 9 from being disturbed.

Furthermore, when clearing a jam, when the second feed roller pair 3, 4 is rotated in the direction of the arrow as described above, the motor M, which is gear-coupled with the second roller pair, and the drum 9 rotate together. A large torque is required to rotate the pair of conveying rollers 3 and 4, which impairs the workability of jam removal. Therefore, motor M
When the second one-way clutch 11 is interposed between the first and second conveying roller pair 3, 4 and the second conveying roller pair 3, 4 is rotated in the direction of the arrow, the rotation is controlled by the motor M1 and the drum 9. It is configured so that it is not transmitted to

Conventionally, in the sheet conveyance device as described above, the circumferential speed of the first pair of conveying rollers and the second pair of conveying rollers is the same, or the circumferential speed of the first pair of transport rollers is set to a second pair of conveying rollers. By making the circumferential speed of the sheet S slightly faster than the circumferential speed of the second pair of conveying rollers, slack is generated in the sheets 1-3 during conveyance, and the conveying speed of the sheet S is determined only by the second pair of conveying rollers.
The speed at the transfer section T was kept constant, and this was considered to be the best means.

(I → The problem that the invention aims to solve However,
Even in the above-mentioned conventional technology, disturbances may occur in the sheet feeding speed below the transfer portion. In other words, when the first pair of conveying rollers is rotated at a constant speed or slightly faster than the second pair of conveying rollers, the sheet S does not always sag, especially when a thick sheet is used. Due to the rigidity of the sheet, even after the leading edge of the sheet is pinched by the second pair of conveying rollers, the sheet is conveyed at the conveying speed of the first pair of conveying rollers, and as a result, the second one-way clutch 11 is in an idling state. Become.

The second one-way clutch 11 shifts from a free state to a locked state at the moment the rear end of the sheet hs passes through the first pair of conveyor rollers, and the sheet S is moved by the second pair of conveyor rollers. He will have to be transported. Therefore, when this one-way clutch 11 shifts to the locked state, the second
The peripheral speed of the pair of conveying rollers momentarily becomes very slow or stops.

At this time, the sheet S may be out of synchronization with the drum 9, which is directly connected to the motor M1 and rotates at a constant circumferential speed, which may cause image blurring.

(5) Means for Solving the Problems The present invention aims to solve the above-mentioned problems, and it is an object of the present invention to solve the problems described above.
In the sheet conveying device including a pair of conveying rollers and a second pair of conveying rollers provided on the downstream side, a one-way clutch is provided so that the second pair of conveying rollers can freely rotate in the conveying direction of the sheet. The roller is connected to the drive input shaft via the roller, and is configured such that the circumferential speed of the first pair of conveying rollers is slightly slower than the circumferential speed of the second pair of conveying rollers. .

(E) Effect Based on the above-mentioned configuration, the circumferential speed of the second conveying roller pair is equal to the first
Since the circumferential speed of the conveying roller pair is slightly faster than the circumferential speed of the second conveying roller pair, the conveyed sheet is slightly accelerated at the moment it is nipped by the second conveying roller pair, and then is conveyed to the transfer section at a constant speed.

Further, the second one-way clutch is never in a free state and always transmits power to the second pair of transport rollers in a locked state.

(F) Examples Examples of the present invention will be described below with reference to the drawings.

Note that parts corresponding to those of the prior art described above are given the same reference numerals.

In FIG. 1, the second transport roller pair 3, 4 is configured to be driven by a drive motor M via a one-way clutch 11. As shown in FIG. Note that the one-way clutch 10 is provided to prevent the pair of transport rollers 3 and 4 from reversing during jam handling.

In this embodiment, the first. In each of the second general feed roller pairs, a metal roller is used as the upper roller 1, and neoprene rubber with a hardness of 55 to 65 degrees is used as the lower roller. Further, the roller diameter is 16.01111% of the diameter of the rubber roller 4 of the second conveyance roller pair, and 998% to 970% of the diameter of the rubber roller 2 of the first conveyance roller pair.
It was experimentally confirmed that synchronization blur can be effectively prevented when the value is within the range of . In addition, the first
It has also become clear that if the diameter of the conveying rubber roller 2 is made smaller, the acceleration of the sheet 1 conveying speed at the moment the trailing edge of the sheet passes through the first pair of conveying rollers 1 and 2 is too large, resulting in synchronization blur. Ta.

In addition, the image magnification of the front and rear of the sheet is within the range of the roller diameter that prevents synchronized blurring, and the circumferential speed of the first pair of conveyance rollers is slower than the circumferential speed of the second pair of conveyance rollers. In order to minimize the difference, in the embodiment, the diameter of the first conveying rubber roller 2 is the diameter 1 of the second conveying rubber roller 4.
The optimal value is 15.9 mm, which is 994% of 6.0 mm.

Note that, as shown in FIG. 2, in order to eliminate the adverse effect on the image magnification caused by the circumferential speed of the first pair of conveying rollers being smaller than the circumferential speed of the second pair of conveying rollers, the first pair of conveying rollers is One-way clutch 1 between 1, 2 and its drive morph M2
Set up 2 and see! - is held between the second pair of conveying rollers 3 and 4, the first pair of I-feeding rollers 1 and 2 are freed from the rotation of the drive motor M2 by the one-way clutch 12,
It may be configured so that it can rotate at the same circumferential speed as the second pair of conveyance rollers 3 and 4, thereby eliminating the influence on the image magnification.

Also, a clutch 1 that controls the drive of the first conveying roller pair
In the case where 3 can be turned on and off by an electromagnetic clutch such as a registration roller, the first pair of conveyor rollers 1 and 2 are moved when the sheet is sandwiched between the second pair of conveyor rollers 3 and 4. By turning off the drive of , tension is applied to the sheet between the first and second vR feed roller pair, and the same effect as that of reducing the diameter of the first conveying rubber roller 2 can be obtained.

In this case, the circumferential speed of the first (7) feed roller pair can be set arbitrarily.

Further, in the above-described embodiment, the circumferential speed was changed by changing the diameter of the rubber roller, but the same effect can be obtained by changing the angular speed of the roller, for example, by changing the gear ratio of the drive system.

(g) As described in detail of the invention, among the pair of conveying rollers provided on the sheet conveying path, each having an independent drive source, the downstream roller pair is made to be able to freely rotate only in the sheet conveying direction. , when the sheet with the unfixed image on it touches the upstream rollers and guide plate, these rollers,
This prevents the problem of the guide plate becoming dirty.
Furthermore, the circumferential speed of the upstream pair of conveyor rollers is slightly slower than that of the downstream pair of conveyor rollers, which may cause image blurring, especially when the trailing edge of the sheet is connected to the upstream conveyor roller when using a thick sheet. It is possible to effectively prevent blurring of both images when passing through the pair.

Therefore, even though the roller pairs have two independent drive sources, interference due to the difference in circumferential speed between them can be prevented, and the sheet can be conveyed in the same way as when conveyed by a single roller pair. Feed accuracy can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a sheet lifting device according to the present invention, Fig. 2 is a perspective view showing another embodiment, and Fig. 3 is a conventional sheet conveying device.
- A perspective view showing the conveying device, FIG. 4 is a side view of the main part showing the sheet collective feeding state, and FIG. 5 is a side view of the main part showing the state during jam processing. 1.2 First conveyance roller pair, 3,4・Second conveyance roller pair, 10.11・One-way clutch,
S, -1・.

Claims (3)

[Claims] (1) In a sheet conveying device including a first pair of conveying rollers provided on the upstream side of the sheet conveying path and a second pair of conveying rollers provided on the downstream side, the second pair of conveying rollers , coupled to the drive input shaft via a one-way clutch so as to freely rotate in the sheet conveying direction, and the circumferential speed of the first pair of conveying rollers is controlled by the second pair of conveying rollers.
A sheet conveying device characterized in that the peripheral speed of the pair of conveying rollers is slightly slower than that of the pair of conveying rollers. (2) The sheet conveyance device according to claim 1, wherein the second conveyance roller pair is driven at a circumferential speed equal to a required sheet conveyance speed. (3) The sheet according to claim 1, wherein the circumferential speed of the first pair of conveying rollers is 99.8 to 97.0% of the circumferential speed of the second pair of conveying rollers. Conveyance device.