JPH0449148A - Paper feeder for image forming device - Google Patents

Abstract

PURPOSE:To correct a diagonal feed of a sheet so as to make paired conveying rollers always drive-rotatable by providing an openable/closable shutter for temporarily closing a sheet conveying path between a feed roller and the paired conveying rollers and forming a loop in a sheet separated by a separating means. CONSTITUTION:A plurality of sheets S are fed into a nip part 45 between a feed roller 21 and a separating pad 22 through friction force between an intermediate plate 20 and the feed roller 21 by drive-rotating the feed roller 21 in a direction A. Here the sheets S are separated into sheet by sheet. When the sheet S, whose point end collides against a lever 42, is turned in a left direction to a point (a) by further conveying the sheet S in the downstream, the feed roller 21 is drive-rotated till the point end of the sheet S is brought into contact with a shutter 27 by actuating a paper feed sensor 29, and a diagonal feed is corrected by forming a loop in the sheet S. Next, a sheet conveying path 41 is opened by turning the shutter 27 in a direction D. The point end of the sheet S is advanced into a nip part 35 of paired conveying rollers 26 of always drive-rotating a lower roller 47, and the sheet S is conveyed to a sensitive drum by the paired conveying rollers 26.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a paper feeding device included in an image forming apparatus such as a copying machine or a laser beam printer.

(B) Conventional Technology As a typical paper feeding device for an image forming apparatus such as a copying machine, there is a system shown in FIGS. 11 and 12.

The paper feeding device shown in FIG. 11 is of a type that includes a feeding roller 1, a separation means (separation pad in this case) 2, and a pair of conveyance rollers (registration rollers) 3. In this paper feeding device, when the feeding roller 1 is driven to rotate, the sheets S (not shown) stacked on the paper feeding tray 5 are moved between the middle plate 6 of the paper feeding tray 5 and the feeding roller 1. The friction force causes the paper to be fed into the nip 7 between the feed roller 1 and the separation pad 2. Here, the frictional force between the separation pad 2 and the sheet S μm,
The relationship between the frictional force μ2 between the sheets S and the frictional force μ3 between the feeding roller 1 and the sheet S is μ3〉μm〉μ2
Since the sheet S is set to
sent out. This separated and sent out sheet S
is transported until its tip enters the nip 9 of the transport roller pair 3 whose rotation is stopped. The feeding roller 1 stops rotating after a predetermined period of time. When the leading edge of the sheet S enters the nip portion 9 of the transport roller pair 3, a loop is formed in the sheet S, and the skew of the sheet S is corrected by this loop. Then, the pair of conveying rollers 3 is driven to rotate in synchronization with the start of writing an image on the photosensitive drum 10, and conveys the sheet S to the photosensitive drum 10. Note that the toner image transfer, fixing, and
Explanation regarding discharge, etc. will be omitted.

The paper feeding device shown in FIG. 12 includes a pair of slip rollers (feeding rollers) 11, a registration shutter 12, and a pair of conveyance rollers 13. Since this paper feeding device does not have a 1-separation means, the sheet S (not shown) is separated by 1
Paper is manually fed one by one. Sheet S on paper feed tray 15
When manually feeding the sheet S, the sheet S passes through the slip roller pair 11.
Fed by. And the resist shutter 12
When the feeding of the sheet S is blocked, a slip occurs between the slip roller pair 11 and the sheet S, and at the same time, the leading edge of the sheet S comes into contact with the registration shutter 12, so that the skewness of the sheet S is corrected. . And photosensitive drum 1
When the registration shutter 12 retreats from the sheet conveyance path 16 in synchronization with the start of image writing on WI, the sheet S is again conveyed by the pair of slip rollers 11, and then by the pair of conveyor rollers that are constantly rotating. 13 to the photosensitive drum 10. It should be noted that a description of the subsequent transfer, fixing, discharge, etc. of the toner image will be omitted here.

(c) Problem to be solved by the invention However, in the case of the paper feeding device shown in FIG. A clutch (spring clutch) is required to connect and disconnect, which increases costs.

Moreover, this clutch had the disadvantage of slipping and making strange noises due to variations in the quality of Grease.

Further, in the case of the sheet feeding device shown in FIG. 12, since it does not have a means for separating the sheets hs, there is a drawback that the sheets S must be manually fed one by one.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides a paper feeding device for an image forming apparatus that is capable of feeding sheets in a stacked state5 and eliminates the need for a clutch for a pair of transport rollers. The purpose is to

(d) Means for Solving the Problems In order to achieve the above object, the present invention provides a feeding roller (21) for feeding stacked sheets (S), as shown in FIG. 1, for example. , separating means (2) for separating the sheets (S) fed by the feeding roller (21) one by one.
2) and a pair of conveying rollers (26) that conveys the sheet S) separated by the separating means (22).

In the present invention, the sheet conveying path (4) is temporarily disposed between the feeding roller (21) and the conveying roller pair (26).
1) is provided with an openable/closable shutter (27) that closes the sheet (S) and forms a loop in the sheet (S) separated by the separating means (22).

Further, when the sheet (S) separated by the separating means (22) is prevented from being conveyed by the shutter (27), the feeding roller (21) temporarily stops rotating and the shutter (27) ) is about to open the sheet conveying path (41) at a predetermined timing, the feeding roller (21) is again driven to rotate for a predetermined period of time.

Furthermore, the shutter (27) is connected to the transport roller pair (
26) in the vicinity of the nip portion (35).

(f) Effect According to the above configuration, the shutter (27) disposed upstream of the pair of conveying rollers (26) allows the separation means (22
) can correct the skew of the separated sheet (S). Therefore, there is no need to correct the skew of the sheet (S) in the pair of conveying rollers (26) disposed downstream of the shutter (27), and the pair of conveying rollers can be driven to rotate at all times.

In addition, when the shutter (27) is about to open the sheet conveyance path (41), the feeding roller (21) is rotated for a predetermined period of time, so that even if the sheet has not formed a loop, the leading edge of the sheet is removed by the shutter (27). will surely enter the nip portion (35) of the conveying roller pair (26).

Furthermore, if the shutter (27) is placed near the nip (35) of the pair of transport rollers (26), the shutter (27)
Even if the resulting loop amount of the sheet (S) is small, the leading edge of the sheet (S) will surely enter the nip portion (35) of the pair of conveying rollers (26).

Note that the above reference numerals in parentheses are used to refer to the drawings, and do not limit the answer structure.

(f) Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows a longitudinal sectional front view of a paper feeding device 17 according to the present invention, and FIG. 2 shows a longitudinal sectional front view of the entire image forming apparatus (copying machine) 19 equipped with the same paper feeding device 17. It is something.

The paper feeding device 17 includes an intermediate plate 20, a feeding roller 21, a separation pad 22, an upper paper feeding guide 23, and a lower paper feeding guide 25.
, a pair of transport rollers 26 , a shutter 27 , and a paper feed sensor 29 .

The middle plate 20 is attached to the apparatus main body 31 of the image forming apparatus 19 so as to be swingable in the vertical direction about a support shaft 30, and
A push-up spring (coil spring), not shown, allows
It is always in contact with the feeding roller 21 with a predetermined pressure.

When the feed roller 21 receives a paper feed start signal from a controller (not shown) that controls the entire apparatus main body 31 of the image forming apparatus 19, a paper feed clutch (not shown) is turned on.
By turning N, the rotational force of the main motor (not shown), which is already rotating, is transmitted and the motor is rotated in the six directions of the arrows.

The separation vat 22 is attached to the main body 31 of the apparatus so as to be able to swing vertically around a support shaft 32, and is always connected to the feeding roller 21 by a push-up spring (coil spring) 33.
It is in contact with a predetermined pressure.

The paper feed upper guide 23 has a mountain-shaped cross section in the conveyance direction, and is arranged from the feed roller 21 to the conveyance roller pair 26 . Further, the paper feed lower guide 25 is inclined to become higher toward the downstream side, and the paper feed lower guide 25 is inclined to become higher toward the downstream side.
1 to the conveying roller pair 26.

When the main motor rotates, the conveyance roller pair 26 is constantly driven to rotate by receiving the rotational force of the main motor.

The shutter 27 is rotatably fitted onto the lower roller shaft 36 of the pair of conveying rollers 26 in order to bring it close to the nip portion 35 of the pair of conveying rollers 26 . In this case, the shutter 27
As shown in FIG. 5, the conveyor rollers 26 are divided along the axis into a detail 36 between each pair of transport rollers 26 and a shaft portion 36 on both sides. This shutter 27 is rotated by a link 39 attached to the device main body 31 so as to be swingable in the vertical direction about a support shaft 37 . The link 39 swings in the vertical direction when an arm 40 provided on the support shaft 37 receives rotational force from the main motor. In the state shown in FIG. 1, the shutter 27 is closing the sheet conveyance path 41 consisting of the upper paper feed guide 23 and the lower paper feed guide 25 (see FIG. 4(a)). In this state, the arm 40- When rotated in the direction of arrow B, the link 39 moves upward in the direction of arrow C, which causes the shutter 27 to rotate in the direction of the arrow and opens the sheet conveyance path 41 (see FIG. 4(b)).

The paper feed sensor 29 is located upstream of the shutter 27.
Sheet S separated by separation pad 22 or separation pad 2
2. It detects that it has been fed to a predetermined position downstream. This paper feed sensor 29 consists of a light emitting element and a light receiving element and is attached to the main body 31gR of the apparatus. When a lever 42 rotatably attached to the upper paper feed guide 23 rotates in the direction of arrow E due to a collision with the sheet S, the light emitted from the light emitting element is blocked, which is detected by the light receiving element or the controller. It is designed to output a signal. In this case, if the detection signal is emitted from the light receiving element when the lever 42 is rotated to point a, then the distance from point a to the shutter 27 is L. Therefore, in this case, the controller moves the feed roller 21 to the paper feed sensor, assuming that the time required for conveying the sheet S a distance by the paper feed roller 21 after the paper feed sensor 29 outputs the paper feed signal is in seconds. After the paper feed signal from 29 is input, the sheet S is rotated for seconds to convey the sheet S until the leading edge of the sheet S comes into contact with the shutter 27.

Next, the paper feeding operation of the paper feeding device 17 will be described.

The sheets S loaded on the paper feed tray 43 are transported by the feed roller 2
1 is rotated, the frictional force between the intermediate plate 20 and the feeding roller 21 causes a plurality of sheets to be fed into the nip portion 45 between the feeding roller 21 and the separation pad 22, as shown in FIG. 3(a). Here, the separation pad 22 is in contact with the feeding roller 21 by the pushing up force (F) of the pushing up spring 33, and the friction force μ between the separation pad 22 and the sheet S, F, and the friction force between the sheets S Since the relationship between the frictional force μ2F of
As shown in b), the sheets are separated one by one at the nip portion 45.

Then, the sea)-3 separated by the separation pad 22
The paper continues to be transported downstream by the feeding roller 21. During this conveyance process, the leading edge of the sheet S collides with the lever 42, causing the lever 42 to rotate to the left. lever 42a
When it is turned on and rotated, the paper feed sensor 29 outputs a paper feed signal to the controller. As a result, the feeding roller 21 is driven to rotate until the leading edge of the sheet S contacts the shutter 27. In this case, after the paper feed sensor 29 outputs a paper feed signal, the feed roller 21 is driven to rotate for a time required to convey the distance IIL between point a and the shutter 27, or As shown in FIG. 6, when the rotation is driven for j+a seconds for the distance +11L+a, the sheet S is separated by the separation pad 22 and its tip or shutter 2
Even if it skews before it comes into contact with point 7, it can be corrected.

When the leading edge of the sheet S contacts the shutter 27, a loop is formed in the sheet S.

Here, the distance between the nip portion 45 of the feeding roller 21 and the separation pad 22 and the shutter 27 is the length of the smallest size sheet S used in the paper feeding direction (here, 85 mm).
) is set as below. For this reason, if the sheet S is plain paper or thin paper, a loop may be formed, or if the sheet S is sturdy such as thick paper, postcards, business cards, etc., the tip of the sheet S may come into contact with the shutter 27. rear,
Although the feeding roller 21 is rotationally driven during the time t+a during which a loop is formed, only a small number of loops are formed. This is due to the force F3 forming the loop or the feeding roller 21
This is because slipping occurs between the thick sheet S and the feeding roller 21 because it is larger than the conveyance force μ3F (F, >μ3F). However, if the sheet S is skewed, the feeding roller 21 will act as a slip roller if the sheet S is thick, so that the skew can be corrected.

As described above, when the sheet S is conveyed until the leading edge contacts the shutter 27 and a loop is formed in the sheet S, the shutter 27 starts writing an image on the photosensitive drum 46. In this case, the distance ρ between the shutter 27 and the nip portion 35 of the pair of conveying rollers 26 is set to 2.5+aln. There is. Therefore, the amount of the loop formed between the shutter 27 and the feeding roller 21 is only 2.5 mm + α, and even with stiff sheets S such as postcards, there is less curl (2.5 mm).
It can enter the nip portion 35 of the pair of conveying rollers 26 at (10). Then, by reducing the distance Iβ,
The leading edge of the sheet S moves from the shutter 27 to the transport roller pair 26
It is possible to prevent the sheet S from being skewed before it enters the nip portion 35 of the sheet S.

When the shutter 27 opens the sheet conveyance path 41, at the same time, the feed roller 21 is driven to rotate for the time required to convey the sheet S a distance of 1llI2. As a result, the leading edge of the sheet S enters the nip portion 35 of the pair of transport rollers 26. In this case, the sheet S is conveyed by the conveying force of the feeding roller 21, so even if the sheet S cannot be looped due to deterioration of the frictional force of the feeding roller 21, or the sheet S is too stiff and cannot be looped, the sheet S can be reliably transported. The tip of the tip is in the nip portion 3 of the pair of conveyor rollers 26.
Enter 5.

When the leading edge of the sheet S enters the nip portion 35 of the conveying roller pair 26 whose lower roller 47 is always rotationally driven, the sheet S is conveyed to the photosensitive tram 46 by the conveying roller pair 26 . In this case, since the feeding roller 21 has stopped rotating and is in a driven state because it has a clutch, it does not place a large load on the pair of conveying rollers 26. Here, the sheet S or conveyance roller pair 26
A description of the transfer, fixing, discharge, etc. of the toner image performed after the toner image is conveyed by the toner image will be omitted.

The paper feeding device 17 of the above embodiment employs a separation means using a separation pad 22, or a separation means using a feed roller 49, a reverse roller 50, and a pickup roller 51 as shown in FIG. It can also be adopted. This separating means is set so that the relationship between the frictional force μ4F between the feed roller 49 and the sheet S and the frictional force μ5F between the reverse roller 50 and the sheet S is μ4F·〉μ,F. Multiple sheets S are picked up by the pickup roller 51.
is fed through a nip 52 between a foot roller 49 and a reverse roller 50, and a plurality of sheets S are separated one by one by the foot roller 49 rotating in the sheet conveyance direction and the reverse roller 50 rotating in the opposite direction. .

Further, as shown in FIG. 8, the shutter 27 for opening and closing the sheet conveyance path 41 is attached to the main body 31 of the apparatus above the upper paper feed guide 23 so as to be able to swing vertically about a support shaft 52. A shutter 53 may also be used. The shutter 53 is designed to rotate in the vertical direction when the support shaft 52 rotates in response to the rotational force of the main motor, and when it moves downward, it closes the sheet conveyance path 41 as shown.

When using such a shutter 53, as shown in FIG. 9, the shaft 56 of the upper roller 55 on the driven side is also divided for each divided transport roller pair 26, A shutter 53 is arranged between 56 and 56. Moreover, in this case, the upper roller 55, as shown in FIG.
It is disposed in an opening 57 formed in the paper feeding upper guide 23, and its shaft 56 is elastically supported by a coil shaft 59.

(G) As described in detail of the invention, the sheet feeding device of the image forming apparatus of the present invention temporarily closes the sheet conveying path between the feeding roller and the pair of conveying rollers, and separates the sheet by the separating means. Since an openable/closable shutter is provided to form a loop in the separated sheets, the shutter can correct the skew of the sheets separated by the separation means. Therefore, there is no need to correct the skew in the pair of conveying rollers, and therefore, the pair of conveying rollers that are constantly driven to rotate can be used, and a clutch is not necessary.

Furthermore, when the sheet separated by the separation means is blocked from being conveyed by the shutter, the feed roller temporarily stops rotating, and when the shutter attempts to open the sheet conveyance path at a predetermined timing, the feed roller stops rotating. After the sheet was rotated again for a predetermined period of time, loops were not formed on the shutter due to a decrease in the conveying force (frictional force) of the feeding roller, and some sheets were stiff and strong, such as cardboard, making it difficult to form loops on the shutter. The leading edge of the sheet will surely enter the nip between the pair of conveying rollers.

Furthermore, by arranging the shutter near the nip between the pair of conveyor rollers, even if the amount of sheet looping caused by the shutter is small, the leading edge of the sheet will surely enter the nip between the pair of conveyor rollers. This makes it possible to feed paper such as postcards and cardboard, which are strong and difficult to obtain a sufficient amount of loop.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view showing a paper feeding device according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional front view of an image forming apparatus (copying machine) equipped with the same paper feeding device, and FIG. b) is a vertical cross-sectional front view illustrating the process of separating sheets by the feeding roller and separation pad of the paper feeding device; FIGS. 4(a) and 4(b)
5 is a front view illustrating the opening and closing operation of the shutter of the paper feeding device, FIG. 5 is a perspective view showing the arrangement of the shutter, and FIG. A time chart showing the operation, FIG. 7 is a longitudinal sectional front view showing another example of the structure of the separating means provided in the paper feeding device, and FIG. 8 shows another example of the structure of the shutter provided in the same paper feeding device. 9 is a perspective view showing the arrangement of the shutter, and FIG. 10 is a perspective view showing the mounting structure of the upper roller of the conveying roller pair when using the shutter,
FIGS. 11 and 12 are longitudinal sectional front views showing a paper feeding device of a conventional image forming apparatus, respectively. 21... Feeding roller 22... Separation pad (separation means) 26... Conveyance roller pair 27.53.
...Shutter 35...Nip portion, 41...Sheet conveyance path 49...Feet roller (feed roller) 50...Reverse roller (separation means)
S... Sheet

Claims (1)

[Scope of Claims] 1. A feeding roller that feeds stacked sheets; a separating means that separates the sheets fed by the feeding roller one by one; and a separating means that separates the sheets separated by the separating means. A sheet feeding device of an image forming apparatus, comprising: a pair of conveying rollers for conveying; and a sheet conveying path is temporarily closed between the feeding roller and the pair of conveying rollers, and the sheet separated by the separating means is separated. 1. A paper feeding device for an image forming apparatus, comprising an openable and closable shutter that forms a loop. 2. When the sheet separated by the separating means is prevented from being conveyed by the shutter, the feeding roller temporarily stops rotating, and when the shutter attempts to open the sheet conveying path at a predetermined timing; 2. A paper feeding device for an image forming apparatus according to claim 1, wherein the feeding roller is rotated again for a predetermined period of time. 3. The paper feeding device for an image forming apparatus according to claim 1, wherein the shutter is disposed near a nip portion between the pair of conveying rollers.