JPH03279143A - Skew compensating mechanism for image forming device - Google Patents

Abstract

PURPOSE:To compensate a cut sheet for a skew by providing a sheet holding means between a top point of a slacking part of the cut sheet if the cut sheet slacks, and a transfer roller, and at a position where an outward slacking convex part can make contact with the sheet holding member so that the sheet holding member can follow up an inclination in the degree of slacking of the sheet. CONSTITUTION:In the case of a skew directing upward and rightward, after the right leading end part 18 of a sheet comes to a nip part 23 of a registration roller 15, a slacking 16 of the sheet occurs. In this phase, this slacking is pressed by a sheet holding member 20 so that a force for pushing the left leading end part 19 of the sheet into the nip part 23 of the registration roller 15 is effected, and accordingly, the leading end 17 of the sheet is compensated so as to set the sheet in parallel with the axis of the registration roller 15. The sheet holding member 20 is located at a position where a reaction force caused by the slacking 16 of the sheet acts upon the registration roller 15 between a position around the top point of the slacking 16 and a transfer roller 14, and the position is effectively set in an outward convex part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a skew correction mechanism for cut paper used in image forming apparatuses such as laser beam printers and copying machines.

[Background of the invention]

5 to 9, conventional examples will be explained using a laser beam printer as an example. The photosensitive drum 1 is charged by a charger 2, and a latent image is formed by a laser beam 3. Toner 12 is applied to the latent image by a developing device 4 to form a visible image. The cut paper 6 fed by the paper feed roller 9 is sent to the transfer section of the photosensitive drum 1 via the conveyance roller 14 and the registration roller 15, and the toner image on the photosensitive drum is transferred by the transfer corotron 5 to the cut paper. 6 transcribed. After the transfer, the cut paper 6 is neutralized by a peeling corotron 11 and peeled off from the photosensitive drum 1. Thereafter, the cut paper 6 is conveyed by a conveyor belt 7 and guided to a fixing device 8 where it is fixed. The toner remaining on the photosensitive drums 9 and 2 is cleaned and collected by a cleaner 13. Here, the cut paper 6 fed by the paper feed roller 9 is often skewed due to various reasons, regardless of the amount. If the toner image is transferred at the transfer section while being skewed, the toner image will be transferred obliquely relative to the cut paper 6.

Therefore, it is necessary to correct the paper skew at the transfer radical.

For example, when the cut sheet 6 is skewed upward to the right as shown in FIG. 6, the right leading edge 18 of the cut sheet 6 reaches the registration roller 15 first. The registration storage roller 15 can be driven intermittently, and when the leading edge 17 of the cut paper reaches the registration roller 15, the roller is generally stopped.

Therefore, as shown in FIG. 7, the right leading edge 18 of the cut paper 6 is delayed until the left leading edge 19 of the cut paper reaches the registration roller 15, which has been delayed by the dimension A.

This means that it is on standby at 15 registration rollers.

The left end 19 of the cut paper 6 is the registration roller 1
5, the cut paper 6 is further fed out by a predetermined amount by the conveyance roller 14, and
A slack 16 in the paper is formed before the end of the paper. (Fig. 8, 9
(Figure) In this state, the leading edge of the cut paper is corrected to be almost parallel to the registration roller 15.

Immediately after this, by driving the registration roller 15, the skew of the cut sheet is substantially corrected and the cut sheet is sent to the transfer section.

Also, there is a method that uses a paper leading edge stop member instead of the registration roller. (FIG. 11) This purpose is the same as that of the registration roller. However, the conventional example had the following problems.

In other words, taking the case of an upward skew to the right as an example, the right edge of the cut paper 6 first touches the registration roller 15.
After reaching this point, the left end of the cut paper 6 is also pushed into the contact area between the pair of rollers of the registration roller 15 (hereinafter referred to as the nip area 23) only by the pushing force from the conveyance roller 14. Since the right end of the cut paper 6 hits the nip portion 23 of the registration roller 15 first, a slack 16 occurs in the cut paper, and this slack 16
Therefore, the extrusion force from the conveyance roller 14 is not transmitted to the left edge 19 of the cut paper, and the skew correction rate (the rate at which the dimension before correction is corrected to the dimension A' after correction: A × 100%) ) had the problem of being low.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, reduce the skew of cut paper in printing devices such as laser beam printers and copying machines that use cut paper, and improve the reliability of the device. It is.

[Summary of the invention]

The present invention focuses on the fact that after the leading edge 17 of the cut paper hits the registration roller 15, the pushing force from the conveyance roller 14 is not transmitted to the leading edge of the paper due to the slack 16 of the paper, resulting in a small skew correction effect. The shape of the paper guide between the registration roller 15 and the transport roller 14 is devised so that the paper pushing force from the transport roller 14 is transmitted to the leading edge of the paper as much as possible to increase the skew correction effect.

[Embodiments of the invention]

Embodiments of the invention are shown in FIGS. 1-4. In the present invention, a paper holding member made of an elastic material such as a polyester film is provided between the conveyance roller 14 and the registration roller 15. Since the registration roller 15 is stopped after reaching , a slack 16 is generated in the paper. When the slack 16 exceeds a certain amount, the paper pressing member 20 comes into contact with the paper holding member 20, and when the slack 16 increases further, the cut paper 6 is forced in the direction of the arrow in FIG. 4 due to the reaction force from the paper holding member 20 made of an elastic body. receive.

Therefore, a force is applied to the leading edge 17 of the paper that pushes it into the nip 23 of the registration roller 15.For example, in the case of an upward skew to the right as shown in FIG. Registration roller 15
After reaching the nip 23 of the paper, a slack 16 is generated in the paper, but this slack is pushed by the paper pressing member 2o, and a force is applied to the left leading edge 19 of the paper to push it into the nip of the registration roller 15. The leading edge 17 of the paper is positioned at the third position relative to the axis of the registration roller 15.
It is corrected to be parallel as shown in the figure. The paper pressing member 20 is located at a position where a reaction force acts on the registration roller 15 side against the slack 16 of the paper, that is, between the vicinity of the apex of the paper slack 6 and between the conveyance rollers and an outward convex portion. The part (range B in Figure 10) is valid.

Note that since the paper pressing member is made of an elastic body, it has the following advantages compared to a rigid body.

When skew occurs, a difference occurs in the amount of slack on the left and right sides of the paper. (Figure 12 shows the slack on the right side of the paper, and Figure 13 shows the slack on the left side of the paper.) In the case of an upward skew to the right,
The amount of slack on the right side is larger, so there is no problem when the amount of skew is small, but when the amount of skew becomes large,
The difference in bulge between the left and right sheets also increases. At this time, if the paper pressing member is a rigid body, the side with the larger bulge will be pressed too much with a force exceeding a predetermined value as shown in FIG. This may cause local deformation of the paper, which may cause transfer failure in the printing section. By making this paper pressing member an elastic body, the above-mentioned problems can be prevented.

〔Effect of the invention〕

According to the present invention, the following effects can be achieved.

(1) Registration roller 1 forces the leading edge of the paper
Since the method of pushing into the nip portion 23 of No. 5 is used, it is possible to correct the skew regardless of the magnitude of the skew amount. For example, the conventional skew correction effect is, for example, 5 to 6
The skew of m could only be corrected to about 2 to 3 m (correction effectiveness: 50%), but with the present invention, it can be corrected to 0.5- or less (correction effect: 90% or more), significantly increasing the skew correction effect. be able to.

(2) Conventionally, overskew (exceeding the specified amount of skew for the device) would have caused the device to stop, but with the present invention, it is now possible to correct the skew to within the specified amount. Reliability (especially paper jam error rate) can be dramatically improved.

(3) Since the paper holding member is made of an elastic material, local deformation of the paper can be prevented.

[Brief explanation of drawings]

1 and 3 are plan views showing embodiments of the cut paper skew correction mechanism according to the present invention, and FIGS.
FIG. 4 is a side view of FIG. 3; 5@ is a side view of a laser beam printer, FIGS. 6 and 8 are plan views of a conventional cut paper skew correction mechanism, and FIGS. 7 and 9 are
9 is a side view of FIG. 8; FIG. Figure 10 is a side view showing how the paper sag, Figure 11 is a side view of the method using the paper leading edge and time stop member, Figure 12 shows the bulge on the right side of the paper, and Figure 13 shows the bulge on the left side of the paper. The side view shown in FIG. 14 is a side view when the paper pressing member is a rigid body. In the figure, 1 is a photoreceptor, 2 is a charger, 3 is a laser beam, 4 is a developer, 5 is a transfer corotron, 6 is cut paper, 7 is a conveyor belt, 8 is a fixing device, 9 is a paper feed roller, 11 is a 12 is a toner, 13 is a cleaning machine, 14 is a conveyance roller, 15 is a registration roller, 16 is a slack of paper, 17 is a cut paper leading edge, 18 is a cut paper right edge, 19 is a cut paper cloth edge, 20 is a peeling corotron Paper holding member, 21 is the upper paper guide, 22 is the lower paper guide, 23 is the nip portion, 24 is the paper leading edge stop member, 25 is the solenoid, A is the previous correction method, A' is the dimension after correction, B is the This is the effective paper holding range.

Claims (1)

[Claims] To correct the skew of cut paper that occurs in the paper feed section,
A conveying roller and an intermittently driven registration roller are provided between the paper feeding section and the printing section, and when the leading edge of the cut paper fed by the conveying roller reaches the registration roller, the registration roller is stopped, Furthermore, in a device that drives the registration roller to send the cut paper to the printing section after a predetermined amount of cut paper is fed out and a slack is formed in front of the registration roller, when the cut paper slack occurs. , a paper pressing member is provided between the vicinity of the apex of the slack portion and the conveyance roller, and at a position where the slack portion contacts the slack portion at an outwardly convex portion; A skew correction mechanism for an image forming apparatus, comprising an elastic body capable of following an increase in amount.