JPS63171748A - Sheet conveyor - Google Patents

Abstract

PURPOSE:To let a sheet tip positively come into contact with a sheet stopping means as well as to make it skew compensation so as to be accurately performed, by making a sheet conveying means so as to change its pressing force according to the progress of a sheet, in case of a sheet conveyor available for a copying machine or the like. CONSTITUTION:A sheet conveyor 5 is constituted of a conveying roller pair 1 consisting of a drive roller 1a and a pressing roller 1b, a variable pressure means 7 energizing this pressing roller 1b, a guide pair 2 guiding a sheet S and a resist roller pair 3. The sheet S is conveyed to the conveying roller pair 1 and the conveyed the resist roller pair 3 through between the paired guides 2. At this time, a solenoid 10 is turned to ON by a signal of a sheet position detecting means, rotating a pressure arm 9 counterclockwise via a spring 11, pressing the roller 1b to the roller 1a, and the conveying roller pair 1 conveys the sheet S. In just before a tip of the sheet S is reached to the resist roller pair 3, the solenoid 10 is turned to OFF whereby pressing force of the roller 1b is reduced, so that the sheet is conveyed as being slipped, thus skew compensation is performed.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a sheet conveying device used in an image forming apparatus (hereinafter referred to as a “copying machine”) such as a copying machine and a laser beam printer. This relates to C+-m bag feeding (2) that performs line correction and synchronous conveyance.

(B) Conventional technology Conventionally, in a copying machine that forms an image on a sheet, in order to prevent image misalignment, it is necessary to accurately align the sheet and the image. Several types of sheet transport devices have been put into practical use.

For example, as shown in FIG. 2, there is a pair of conveying rollers 1' consisting of an upper roller 1'a and a lower roller 1'b that convey the sheet S, an upper guide plate 2'a and a lower guide plate that guide the sheet S. A guide pair 2' consisting of 2'b and an upper roller 3a
In the sheet conveyance device 5a, which is constituted by a pair of registration rollers 3 consisting of a pair of registration rollers 3 and a lower roller 3b, the sheet S is conveyed by a pair of conveyance rollers 1' and stops when its leading end abuts against the pair of registration rollers 3. Then, the conveying roller pair 1'
The sheet S further rotates to form a loop in the sheet 1-3, and the sheet S enters through this loop and is pushed into the nip N between the upper roller 3a and the lower roller 3b of the registration roller pair 3, and the skew correction is performed. It is done. And registration roller pair 3
starts rotating in synchronization with the operation timing of a copying section (not shown), and the rate S is conveyed by the pair of registration rollers 3 in synchronization with the image on the copying section.

(/→ Problem to be Solved by the Invention By the way, in the sheet conveying device 5a described above, the sheet S is transferred to the pair of registration rollers 3.
It may not be fed into the nip N accurately. For example, as shown in FIG. 3, the lower roller 3 whose outer periphery is made of rubber is faster than the upper roller 3a which is a metal roller.
When the lower roller 3b comes into contact with the nip N, the leading edge of the sheet S may not enter the nip N because the lower roller 3b has a large friction coefficient. As a result, a paper jam occurs in which the feeding timing of the sheet S is shifted.

To solve this problem, as shown in FIG. 4, a slip roller pair 6 consisting of a slip roller 6a and a drive roller 6C, which are rotatable about a central axis 6b, is proposed.
A sheet conveying device 5b has been devised which includes a guide plate 2 for regulating the vertical direction of the sheet S. Then, the sheet conveyance device i5b presses the slip roller 6a against the drive roller 6c under its own weight to convey the sheet S so that it comes into contact with the nip N of the pair of registration rollers 3. Further, the slip roller pair 6 reliably contacts the nip N while slipping the sheet S.

However, since the slip roller pair 6 has only a weak conveyance force, the conveyance roller pair 1' must be placed at a position shorter than the shortest paper length from the registration roller pair 3, which increases the number of shafts to be driven. This requires extra driving force and increases costs.

(f) Means for solving the problem The present invention aims to solve the above-mentioned problems, and the sheet pressing means is configured so that the pressing force changes according to the progress of the sheet. The sheet is conveyed by pressing the sheet pressing means against the sheet conveying means with a predetermined force until the leading edge of the sheet contacts the sheet stopping means, and when the leading edge of the sheet contacts the sheet stopping means, the sheet pressing means The sheet is characterized in that the pressing force is reduced so that the sheet slips while applying a conveying force to the sheet.

(e) Operation Based on the above structure, the sheet is conveyed by the sheet conveying means and the sheet pressing means that presses with a predetermined force until the leading edge of the sheet abuts the sheet stopping means, and then the sheet leading edge contacts the sheet stopping means. When the sheet contacts the sheet pressing means, the pressing force of the sheet pressing means becomes low, and the sheet conveying means causes the sheet to come into contact with the sheet stopping means while slipping.

(F) Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the sheet conveying device 5 includes a driving roller 1a whose outer periphery is covered with a friction material such as rubber and driven by a WJAwb means (not shown), and a pressing roller 1b which presses the sheet S onto the roller 1a. A pair of conveyor rollers 1,
A pressure changing means 7 that urges the pressure roller 1b upward, a guide pair 2 that guides the sheet S, and an upper roller 3a and a lower roller 3.
Registration roller 3 that synchronously conveys the sheet S with b
It is made up of. The voltage transformation means 7 is -
@A is supported by the apparatus main body (not shown) and has a curved portion B in the center portion that engages with the shaft IC of the pressure roller 1b, and the other pressure arm 9 is shown as @C. It has a spring 11 that connects the solenoid 10 which is actuated by a detection signal from the seat position detection means, and the solenoid 1
0 turns ON and OFF, the pressure arm 9 is rotated via the spring 11, and the pressure roller 1 is rotated to the drive roller 1a.
It is configured to adjust the pressing force for pressing b.

Since the present embodiment has the above-described configuration, the sheet hs is separated one by one from the sheet storage section by the paper feed section (both not shown) and transported to the transport roller pair 1, and then transported to the transport roller pair 1. It is held between pair 1 and conveyed between pair 2 of guides to pair of registration rollers 3. At this time, solenoid 10
In response to the detection signal from the sheet position detection means, ONI rotates the pressure arm 9 counterclockwise via the lever spring 11 and strongly presses the pressure roller 1b against the drive roller 1a. The sheet S is conveyed by the conveying force.

Then, immediately before the leading edge of the sheet S reaches the nip between the pair of registration rollers 3, the solenoid 10 is turned off by the detection signal of the sheet position detection means, and the pressing force of the pressing roller 1b against the driving roller la is reduced. As a result, the sheet S is conveyed while slipping by the drive roller 1a and is pushed into the nip of the pair of registration rollers 3 to perform skew correction (see FIG. 1 (bl)). The solenoid 10 is turned on by a detection signal from the sheet position detection means to start feeding the sheet sJi!m in synchronization with the image (not shown), and the pressing roller 1
(b) is strongly pressed against the driving roller 1a, thereby F) the conveying roller pair 1 conveys the rear part of the sheet S with a strong conveying force.

Next, the sheet S has an image copied thereon by the copying section, is conveyed to a fixing section (not shown), further has the image fixed thereon, and is ejected from the main body of the copying machine.

In the above embodiment, the drive roller 1a continues to slip until the registration roller pair 3 starts rotating, but the drive roller 1a is removed after a predetermined period of time after the sheet S reaches the nip of the registration roller pair 3. By stopping the driving roller 1a, wear of the driving roller 1a can be reduced.

Further, in the above embodiment, the solenoid 10 was used as the drive source for the voltage transformation means 7, but as shown in FIG. In addition, if the arm 13, one end of which is supported by the apparatus main body, is used as the drive source for the voltage transformation means 7', the cost can be reduced because the solenoid 10 is not used.

Furthermore, in the above-mentioned embodiment, the pressing force of the pressing roller 1b on the driving roller 1a was adjusted by the pressure changing means 7, but as shown in FIG.
A pair of conveying rollers 1' consisting of a pressing roller l'b rotatably supported by a spring 15 fixed at both ends to the apparatus body starts conveying the sheet S from a point E. The pair of rollers 1' conveys the sheet S to the pair of registration rollers 3 with a strong conveyance force from point E to point F, and slips the sheet S from point F to point G to the nip of the pair of registration rollers 3. Corrects skew by coming into contact with. Next, the conveying roller pair 1' moves the sheet S from point G to point H with a strong conveying force.
The sheet S is conveyed, and the pressing force is weakened from point H to point E to allow movement of the sheet S. When the transport roller pair 1' is configured in this way, no lifting means is used, so the apparatus can be simplified and costs can be reduced.

Further, in the above embodiment, the registration roller pair 3 is used as the sheet stopping means, but the present invention is not limited to this, and a stopper 17 whose driving source is a solenoid 16 as shown in FIG. 7 may be used.

Further, in the above embodiment, the pressing roller 1b is used as the sheet pressing means, but the seventh embodiment is not limited to this.
As shown in the figure, a pressing plate 1 whose one end is supported by the device body
9 may also be used.

Further, in the last embodiment described above, the driving roller 1a was used as the sheet conveying means, but as shown in FIG. 8(a), the driving roller 20a and the driven roller 2. A conveyor belt 20 wound around Ob may also be used.

Furthermore, when a conveyor belt is used as a sheet conveyance means, a conveyor belt 21 whose thickness is partially changed and a pressing roller 1 whose both ends are supported by springs 15 fixed to the main body of the apparatus are used.
The pressure-transforming means may be omitted by changing the pressing force, that is, the conveying force (see Fig. 8fbl). The pressure may be varied (see Figure 8 (cl)).

(G) Effects of the Invention As explained above, according to the present invention, the sheet pressing means is configured so that the pressing force changes according to the advance of the sheet. It must be possible to reliably contact the sheet stop means and perform skew correction accurately.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a sheet conveying device according to the present invention, FIGS. 2 to 4 are front views showing a conventional example, and FIGS. 5 to 8 are front views showing other embodiments. 1 a, 1' a, l'a, 20... sheet feeding means, 1 b, 1' b, l'b... sheet pressing means, 3.17... sheet stopping means,
5, 5a, 5b, 5c ・Sheet conveyance device, S
...Sheet.

Claims (2)

[Claims] (1) A sheet conveying means for conveying a sheet, a sheet pressing means for pressing the sheet against the sheet conveying means, and a sheet stopping means for temporarily stopping the sheet, the sheet being conveyed by the sheet conveying means and the sheet pressing means. In the sheet conveying device, in which the sheet contacts the sheet stopping means to correct skew, and the sheet stopping means releases at a predetermined timing, the pressing force of the sheet pressing means changes according to the progress of the sheet. The sheet is conveyed by pressing the sheet pressing means against the sheet conveying means with a predetermined force until the leading edge of the sheet contacts the sheet stopping means, and the sheet is conveyed by pressing the sheet pressing means against the sheet conveying means until the leading edge of the sheet contacts the sheet stopping means. 1. A sheet conveying device characterized in that when the sheet comes into contact with the sheet, the pressing force of the sheet pressing means decreases, and the sheet slips while applying a conveying force to the sheet. (2) The sheet conveying device according to claim 1, wherein the pressing force of the sheet pressing means is controlled by the amount of movement of the sheet conveying means.