JPH01231751A - Printing device - Google Patents

Abstract

PURPOSE:To prevent the accumulation of stain on a conveying means and prevent the staining of the back of as well as the excessive tension of a printing medium by changing the feeding speed of each conveying means of a discharging portion and forcedly forming a slip condition in the feeding of the printing medium. CONSTITUTION:The diameters of transmission gears 52 and a fixing gear 53, the diameters of conveying gears 54, 56 and transmission gears 55, and the diameters of transmission gears 57 and a conveying gear 58 are made equal respectively and made smaller in this order. Also, the diameter of a conveying roller 30 is made smaller than the diameters of conveying rollers 31, 32 and, due to the relation of the size of diameters among these gears and rollers, the feed speed of a fixing roller 27a and the conveying rollers 30, 31, 32 gets larger in this order. Hence, the feed speed of the conveying rollers 30, 31, 32 gets higher toward a discharging direction. Thereby, forced slip condition can be formed by each roller 30-32. Then, a conveying force is varied so as to prevent the excessive tensile force of a sheet of paper. That is, by reducing the spring force of springs 30c, 31c, 32c in this order, the pinching forces of pinch rollers 30a, 31a, 32a are reduced in this order, reducing a conveying force in the discharging direction.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figure 4) Means for solving the problem to be solved by the invention (Figure 1) Working example (a) 1 Description of the embodiment (Figs. 2 and 3) (b) Description of other embodiments Effects of the invention [Summary] When the printed medium is discharged and conveyed after printing is completed, it is possible to prevent stains on the printed medium by the conveyance system. Regarding the printing device for preventing dirt from accumulating on the conveying means and preventing the occurrence of back dirt on the printing medium, a printing section that forms a visible image on the printing medium while feeding the printing medium is provided. and a discharge section having a plurality of conveying means disposed in contact with each other to convey the print medium on which the visible image is formed, and the feed speed of the discharge section is faster than the feed speed of the printing section. In the printing apparatus, the feeding speed of each conveyance means is decreased as it goes in the discharge direction, and the conveyance force of each conveyance means is made smaller as it goes in the discharge direction.

[Industrial application field]

The present invention relates to a printing apparatus for preventing a printed medium from being stained by a conveyance system when the printed medium is discharged and conveyed after printing is completed.

Printing devices are widely used in printers, copiers, facsimile machines, and the like.

Among such printing apparatuses, there are those that print using a liquid or solid colored printing material, such as a thermal transfer method, an inkjet method, and an electrophotographic method.

In particular when using colored printing materials, the printing material from the printing medium conveyed to the transport system adheres, staining the printing medium and deteriorating the print quality.

This phenomenon becomes particularly noticeable when the conveyance system is relatively long, and there is a need for a technique to effectively prevent the generation of dirty print media.

[Conventional technology]

FIG. 4 is an explanatory diagram of the prior art.

The paper feeding section 1 takes out the cut paper PP from the paper cassette IO with a pick roller 11, feeds it with a feeding roller I2, and synchronizes with writing on the photosensitive drum 20 of the printing section 2. The cut paper PP is fed to the printing section 2 by.

In the printing section 2, the developed image on the photosensitive drum 20 is transferred onto the cut paper PP by the transfer device 24, and is thermally fixed while being fed by the fixing device 27.

In the discharge section 3, the printed cut paper PP is discharged by a combination of conveyance rollers 30, 31, and 32 and pinch rollers 30a, 31a, and 32a.

In an electrophotographic printing apparatus using such printing material (toner), when the fixing process is a heating method, the fixing device 27
Cant paper stretches due to heat and moisture, making it prone to wrinkles.

To prevent the occurrence of wrinkles, the feeding speed of the paper in the fixing device 27 (■) must be adjusted. Faster speed ■ 1 and strength P, which is weaker than the paper conveyance force P0 in the fixing device 27 and does not tear the paper
′? :*The paper is transported by the feeding section 3 and tension is applied to the paper.

Further, in an apparatus in which the image forming process of the printing section 2 is slow, the conveying speed of the discharge section 3 is increased in order to improve the stackability of sheets.

The conveyance speed v1 of the discharge section 3 is the conveyance speed V1 of the printing section 2.
0, but the speed and conveyance force of each conveyance roller 30 to 32 in the discharge section 3 were constant at V+ and P+.

[Problem to be solved by the invention]

By the way, in the discharge section 3, the pinch rollers 30a, 3
1a and 32a are not forcedly driven, so paper PP
When the paper PP is pinched, it rotates according to the speed of the paper, and when there is no paper PP, it rotates according to the speed of the conveyance rollers 30 to 32.

Since the pinch rollers 30a to 32a press against the image forming surface of the paper PP, they are contaminated by the paper PP.

When there is no paper PP, the pinch rollers 30a to 32a are pressed against the transport rollers 30 to 32, so the dirt is transferred to the transport rollers 30 to 32.

Therefore, by conveying the paper PP, the pinch roller 30a
32a and the transport rollers 30 to 32 will both become dirty.

This stain causes a problem in the prior art in that the back side of the paper is stained.

For example, the paper length is 2. If longer than 'Czt, then 1
Each roller 30 to 32.30a is
-32a becomes dirty.

In this state, when the leading edge of the second sheet reaches the conveyance roller 30, V,>V. , p, < p, the conveyance roller 30 slips on the back side of the paper and rubs dirt on the conveyance roller 30 on the back side of the second sheet, but the amount of dirt caused by only the first sheet of paper is small. Therefore, stains on the paper are not noticeable.

In addition, since the amount of dirt is small, dirt accumulation is eliminated with one slip.

However, since the paper conveyance speed of the subsequent conveyance rollers 31 and 32 is the same as the conveyance speed of the preceding conveyance roller 30 (1), no slipping occurs.

Therefore, when a large number of printed sheets are conveyed, their stains accumulate.

If a sheet longer than 12 is conveyed in this state, the conveyance rollers 31 and 32 will slip due to vo<Vl, rubbing dirt accumulated on the back of the paper, making the dirt on the back of the paper more noticeable. , leading to deterioration of print quality.

When a large amount of dirt accumulates, there is a tendency for the number of sheets of paper with back dirt to increase.

SUMMARY OF THE INVENTION An object of the present invention is to provide a printing apparatus that can prevent dirt from accumulating on a conveyance means and prevent dirt from forming on the back of a printing medium.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention.

The present invention includes a printing unit 2 that forms a visible image on the print medium PP while feeding the print medium PP, and a conveyance unit 30 that contacts and conveys the print medium PP on which the visible image has been formed for ejection.
In a printing apparatus having a discharge section 3 in which a plurality of transport means 32 are arranged, and the feed speed (Iltffi feed) of the discharge section 3 is faster than the feed speed of the printing section 2, the feed speed of each conveyance means 30 to 32 is V2, V3 is made faster as it goes in the discharge direction, and the conveying forces P and -P of each of the conveyance means 30 to 32 are made smaller as it goes in the discharge direction.

[Effect]

In the present invention, in the discharge section 3, each conveyance means 30 to 32
The feed speed V2, (2) is increased toward the discharge exit, and the conveying forces P, , Pg, and P3 are decreased toward the discharge exit.

With this setting, each conveying means 3 is used for each sheet conveyed.
At 0 to 32, slipping occurs and dirt does not accumulate.

At this time, the reason why the conveying force is small is to prevent the printing medium PP from being pulled and torn by changing the feeding speed.

Therefore, even if a longer sheet of paper is conveyed, the amount of dirt is drastically reduced and does not pose a practical problem.

〔Example〕

(a) Description of an Embodiment FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a block diagram of essential parts of an embodiment of the present invention, showing an electrophotographic laser printer.

In the figure, the same parts as those shown in FIGS. 1 and 6 are indicated by the same symbols, and 13 is a feeding (standby) roller, which carries the cut PP fed by the feeding roller 12. 15 is a feeding path through which the paper PP is fed from the paper cassette 10 to the feeding roller (referred to as a standby roller) 13;
Reference numeral 16 denotes an insertion port for manually inserting a printing medium such as paper into the feeding path 15 and the standby roller 13 from the outside.

21 is a charger that charges the photosensitive drum 20; 22 is an optical unit that scans laser light from a laser light source modulated by a video signal and irradiates the photosensitive drum 20 to expose an image; It is something.

23 is a developing device, in which a paddle roller 230 rotates counterclockwise to agitate the toner and carrier of the developer, forms a magnetic brush of the developer on a developing roller 231 rotating clockwise, and a blade 232 keeps the developer constant. High, photosensitive drum 2
0 electrostatic latent image is developed, the developer regulated by the blade 232 is returned to the paddle roller 230 by the channel plate 233, and the consumed toner is replenished by the toner replenisher 234.

25 is a static eliminator that eliminates static from the photosensitive drum 20 after transfer; 26 is a cleaning unit that removes static electricity from the photosensitive drum 20 after transfer;
27 is the above-mentioned fixing device, which thermally fixes the paper after transfer, and includes a heat roller 27a and a facing roller 27b.

Reference numeral 33 denotes a discharge path, which guides the paper PP from the printing unit 2 (fixing device 27) to the discharge roller 31, and 4 denotes a paper discharge stacker, which stores the discharged paper.

30b to 32b are levers, each of which supports a pinch roller 30a to 32a at one end and is rotatable;
32c is a spring, and levers 30b to 3
2b, the pinch rollers 30a to 32a are connected to the conveyance roller 3.
This is for pressing 0 to 32.

50 is a transport motor, which serves as a drive motor for the paper transport system; 51a and 51b are reduction gears (gears);
A large-diameter gear 51b meshes with a small-diameter gear 51a provided on the shaft of the drive motor 50 to reduce the speed. 52 is a transmission gear that transmits the rotation of the gear 51b using three gears. 53 is a fixing gear. This gear is provided on the shaft of the fixing roller 27a, meshes with the transmission gear 52, and transfers the fixing roller 2
7a is rotated.

54 is a first conveyance gear, which is provided on the shaft of the first conveyance roller 30, meshes with the reduction gear 51b, and rotates the first conveyance roller 3o; 55 is a transmission gear;
The rotation of the gear 54 is transmitted by five gears, and 56 is a second conveyance gear, which is provided on the shaft of the second conveyance roller 31 and meshes with the transmission gear 55 to transmit the rotation of the second conveyance roller 31.
It rotates.

57 is a transmission gear, which controls the rotation of the second conveyance gear 56 by 3
58 is a third conveyance roller, which is provided on the shaft of the third conveyance roller (discharge roller) 32, meshes with the transmission gear 57, and rotates the third conveyance roller 32. It is.

In this example, the rotation of one conveyance motor 5o is transmitted by a gear transmission mechanism 52, 55, 57, and the fixing roller 27a
Four rollers, ie, conveyance rollers 30, 31, and 32, are rotationally driven.

The following procedure is used to change the conveyance speed.

First, the diameters of the transmission gear 52 and fixing gear 53 are the same ro(
The diameters of the first and second conveyance gears 54, 56 and the transmission gear 55 are the same r+ (number of teeth n+), and the diameters of the transmission gear 57 and the third conveyance gear 58 are the same rz. (Number of teeth n
z).

Then, these are given the following magnitude relationship.

".> r 1 > r z (= no > n
1 > n z ) · · (1) Furthermore, the diameter R1 of the first conveyance roller 3o and the second and third conveyance rollers 31.3
2 and the diameter R2, RI < R2------
・ (2).

Depending on the size relationship of the gears and the size relationship of the roller diameters, the feed speed v0 of the fixing roller 27a, the feed speed v2 of the first conveyance roller 30, the feed speed v2 of the second conveyance roller 3I, and the third conveyance roller v3. The relationship is vo<Vl<Vz<V3 --- (3).

Therefore, the further the conveyance rollers 3o, 31.3
2, the feed speed becomes faster.

With this, 1. A forced slip condition is created on each roller 30.31.32.

Next, to prevent the tensile force of the paper PP from becoming excessive,
Change the conveying force as follows.

That is, if the spring forces of each spring 30c, 31C, 32c are r, , r, , f, then the relationship between these spring forces is (,>12> r, -----(4)).

As a result, the pinch force of each of the pinch rollers 30a to 30c becomes P, -P, B, P, >P, >P3- (5), and the conveying force becomes smaller as it moves toward the discharge direction.

In this way, when the paper PP is discharged and conveyed, slippage occurs on each roller 30.31.32, and the roller 30.31.
．． 32 prevents dirt from accumulating, and this also prevents excessive tension from being applied to the paper PP.

In this example, it can be realized with one drive system by setting the gear and roller diameter, only one drive motor is required, and synchronization of conveyance is easy.

In this laser printer, the path from the lower paper cassette 10 to the upper paper discharge stacker 4 is formed in the shape of an S.
A configuration is adopted in which a paper discharge stacker 4, a printing section 2, and a paper cassette 10 are stacked in this order from the top.

Therefore, the device can be made smaller and requires a slightly larger installation area than paper.

Also, since the paper PP printed in the printing unit 2 is reversed in the discharge unit 3 and discharged to the discharge stacker 4, the paper PP printed by the discharge unit 2 is
In this case, sheets of paper having a printing surface on the lower side of the figure are stored in page order from the bottom.

Therefore, when printing multiple pages, the paper output stacker 4
9, where the sheets are arranged in page order.

(b) Description of other embodiments In the above embodiments, the contact-type conveyance means was explained using conveyance rollers, but it is also possible to use a contact-type conveyance means such as a conveyor belt, and the number of conveyance means is limited to three. In short, it can be applied to two or more things.

Furthermore, although the drive of the conveyance system has been explained using the gear mechanism shown in FIG. 3, a belt transmission system or other type of transmission may be applied, and the number of motors is not limited to one.

Furthermore, although a laser printer has been described as an example of a printing device, the present invention can be applied to other well-known devices such as electrophotographic devices and thermal transfer devices, and is not limited to printers, but may also be a copying machine or the like.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, the feed speed of each conveyance means in the discharge section is changed and a slip state is forcibly formed with respect to the conveyance of the print medium, so that dirt does not accumulate on the conveyance means. This has the effect of preventing stains on the back of the print medium without causing any damage.

Further, even if the feed speed is changed in this way, since the conveyance force is changed, there is no risk of excessive tension being applied to the print medium, and tearing of the print medium can also be prevented.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is a block diagram of essential parts of an embodiment of the present invention, and FIG. 4 is an explanatory diagram of the prior art. In the figure, 2-printing section, 3...-discharging section, 30-32
- Conveyance rollers (conveyance means).

Claims (1)

[Claims] (1) A printing unit (2) that forms a visible image on the print medium while feeding the print medium, and a conveyance unit (30 to 30) that contacts and conveys the print medium on which the visible image has been formed for ejection. 32) in which a plurality of discharge parts (
3), in which the feeding speed of the discharge section (3) is faster than the feeding speed of the printing section (2), each of the conveying means (30 to 3
2) A printing apparatus characterized in that the feeding speed of item 2) is increased toward the discharge direction, and the conveyance force of each conveyance means (30 to 32) is decreased toward the discharge direction.