KR100644674B1 - Paper feeding apparatus of image forming apparatus - Google Patents

Abstract

Disclosed is a paper feeding apparatus of an image forming apparatus. A paper feeding device of the disclosed image forming apparatus is provided at a lower side of the pickup roller and has a feeding prevention member having a feeding prevention portion for preventing the feeding of paper conveyed by the pickup roller. It is fixed to the member, characterized in that the portion in contact with the back of the sheet to be conveyed is rotatably installed.

According to the present invention, unlike the conventional invention, when the contact surface that contacts the paper is worn out of the anti-feeding part, it can be used by rotating it in a predetermined direction, thereby improving the replacement cycle and life of the non-feeding part. In addition, it is possible to minimize the entry gap between the pickup roller and the feed prevention member to prevent the case of entering a plurality of sheets. In addition, by providing a friction preventing portion at the entrance of the paper to minimize the friction with the paper to enter can improve the paper feed performance.

Description

Paper feeding apparatus of image forming apparatus

1 is a view schematically showing a conventional paper feeder.

2 is a schematic cross-sectional view of an image forming apparatus according to a preferred embodiment of the present invention.

3 is a perspective view showing a paper feeding device of the image forming apparatus according to the preferred embodiment of the present invention.

4 is a perspective view illustrating the pickup roller and the anti-feeding member of the paper feeding device illustrated in FIG. 3.

5 is a perspective view illustrating in detail a portion of the paper feeding prevention part of the paper feeding device illustrated in FIG. 3.

FIG. 6 is a perspective view showing an embodiment of the feeding prevention member of the paper feeding device illustrated in FIG. 3.

FIG. 7 is a perspective view illustrating another embodiment of the feeding prevention member of the paper feeding device illustrated in FIG. 3.

FIG. 8 is a perspective view illustrating a pickup roller of the paper feeding device illustrated in FIG. 3.

9 and 10 are plan views showing examples of the pickup roller surface pattern.

11 and 12 are enlarged cross-sectional views of a part of the pickup roller of FIG. 8, showing a state in contact with a state before contacting the paper.

<Description of the symbols for the main parts of the drawings>

100 ... Frame 110 (110C, 110M, 110Y, 110K) ... Current cartridge

120 ... Return belt 121,122,123,124 ... Support roller

140 ... Transfer Roller 130 (130C, 130M, 130Y, 130K) ... Exposure

150 ... seat 160 ... print unit

172 Pickup rollers 173

173b..vertical wall 173c ..

200 ... Anti-friction 201a..Roller

201b..Inclined plane 203 ...

204 ... Suppression belt 205 ... Suppression belt

206.Bias section 207.Support roller section

207a, 207b ... axis 208 ... elastic member

210 ... friction member 220 ... contact surface of pick-up roller

272 ... hole

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, to a paper feeding apparatus of an image forming apparatus capable of preventing paper feeding and improving the life of the feeding sheet.

In general, an image forming apparatus such as a printer or a copying machine includes a sheet feeding apparatus for picking up sheets of paper loaded in a paper cassette and supplying them to a printing unit installed inside the image forming apparatus. 1 shows an example of a conventional paper feeder.

Referring to FIG. 1, a conventional paper feeder includes a paper feed cassette 71 in which paper is loaded, a pick-up roller 72 which pulls out paper from the paper feed cassette 71, and a paper feed prevention mechanism. A transport prevention member 73 is provided.

The paper feeding cassette 71 includes a knock-up plate 71a on which paper is loaded, and an elastic member (not shown) for elastically biasing the knock-up plate 71a upward. The sheets stacked on the knockup plate 71a are conveyed one by one by the pickup roller 72. The upper surface of the knock-up plate 71a is provided with a friction member 10 at a position facing the pick-up roller 72 to prevent the conveyance of paper. The friction member 10 provides a frictional force on the back surface of the last sheet at least larger than the frictional force between the sheets to prevent feeding.

The anti-feeding member 73 is provided below the pick-up roller 72 and has a feed-transfer prevention part 4 for preventing the conveying of paper conveyed by the pick-up roller 72. The conveyance preventing part 4 is attached to one side of the conveyance preventing member 73, and prevents the conveyance of the paper conveyed by the pickup roller 72. The anti-feeding unit 4 provides a frictional resistance to the back surface of the paper conveyed by the pickup roller 72 so that only the uppermost paper is conveyed. That is, even if a plurality of sheets of paper are conveyed by the pickup roller 72, the other sheets of paper are kept in progress by the feeding prevention unit 4, and only the sheets stacked on the upper side of the knock-up plate 71a are conveyed. As the paper is conveyed, the surface abrasion of the conveyance prevention part 4 also progresses. If the surface of the transport prevention part 4 is worn to a certain degree or more, the transport prevention part 4 can no longer perform the function of preventing the transport of the paper. That is, when the surface of the transport prevention portion 4 in contact with the paper is worn, it is no longer possible to provide a frictional resistance to the back surface of the paper, so the wear rate of the paper increases as the surface of the transport prevention portion 4 is worn out. Done.

In addition, in order to prevent the feeding of the paper, the entry portion 70 entering between the pickup roller 72 and the feeding prevention portion 4 is configured at intervals of about 1 mm to 1.5 mm. Curls are formed at the leading end of the paper conveyed from the knock-up plate 71a by the pickup roller 72. If the interval of the entry portion 70 is large, the leading end of the curled paper easily enters the entry portion 70, but the frequency of paper feeding increases. On the contrary, when the interval of the entry portion 70 is small, the frequency of occurrence of feeding of the paper is lowered, but the occurrence of paper jams at the leading edge of the paper caught by the feeding prevention member 73 is increased. 73) the friction with the paper is increased, the feeding performance is lowered.

As described above, according to the related art, as the surface of the feeding prevention portion 4 in contact with the paper wears out, the feeding rate of the feeding paper increases. In addition, minimizing the interval of the entry portion 70, but the rate of paper feed is reduced, but the frequency of the paper caught on the feed prevention member 73 increases according to the shape of the leading end of the paper. In addition, when the gap is minimized, the friction between the lower surface of the paper to be conveyed and the anti-feeding member 73 is increased to lower the paper feeding force.

 SUMMARY OF THE INVENTION The present invention has been made to improve the above problems, and an object of the present invention is to provide a paper feeder for an image forming apparatus that can improve the replacement cycle or life of the heavy feed prevention unit. In addition, an object of the present invention is to provide a paper feeder of the image forming apparatus that can minimize the gap between the entry portion and prevent paper jams or paper feed force drop. It is also an object of the present invention to provide a paper feeder of an image forming apparatus having a paper feed preventing portion whose paper feed preventing function is maintained longer than before.

The paper feeding apparatus of the image forming apparatus according to the present invention includes a paper feed cassette including a knock-up plate on which paper is loaded and an elastic member for biasing the knock-up plate upward, and a pickup for pressing and transferring the paper loaded on the knock-up plate. A paper feeding device of an image forming apparatus, comprising: a feeding member having a roller and a feeding prevention portion provided below the pickup roller to prevent feeding of the paper conveyed by the pickup roller. Being fixed to the prevention member, the portion in contact with the back of the paper to be conveyed is characterized in that it is installed rotatably.

In the sheet feeding apparatus of the image forming apparatus according to the present invention, the feeding member is rotatably installed in a belt shape, the feeding member is in contact with the back of the sheet to prevent the feeding of the sheet; A bias part installed to be in contact with the inside of the anti-feed belt so as to bias the inside of the anti-feed belt so as not to rotate; It is characterized by including.

A paper feeding device for an image forming apparatus according to the present invention, wherein the bias unit comprises: a pair of support rollers installed to be in contact with the inside of the anti-feed belt; An elastic member for biasing the pair of support roller parts in opposite directions; It is characterized by including.

The paper feeding apparatus of the image forming apparatus according to the present invention includes: a friction preventing portion provided in the anti-feeding member, the friction preventing portion being provided on the side where the leading end of the sheet enters to reduce friction with the sheet; It is characterized by further comprising.

In the paper feeding apparatus of the image forming apparatus according to the present invention, the friction preventing portion is provided with a roller.

Hereinafter, a sheet feeding apparatus of an image forming apparatus according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this process, the thickness of the lines or the size of the components shown in the drawings are exaggerated for quick understanding of the description. In addition, the image forming apparatus equipped with the paper feeding apparatus will be described first for a quick understanding of the description, and then the paper feeding apparatus of the image forming apparatus according to the present invention will be described. Although the image forming apparatus of this embodiment is described using an electrophotographic image forming apparatus as an example, the present invention is not limited to the electrophotographic image forming apparatus.

2 is a schematic cross-sectional view of an image forming apparatus according to a preferred embodiment of the present invention.

Referring to FIG. 2, the image forming apparatus includes a printing unit 160 for printing an image on paper S by an electrophotographic process, and a paper feeding device 170 for feeding paper S to the printing unit 160. It is provided.

The printing unit 160 includes four toners each containing toners of different colors, for example, C: cyan, M: magenta, Y: yellow, and black: K. The developing cartridge 110C, 110M, 110Y, 110K, the conveyance belt 120, the exposure part 130C, 130M, 130Y, 130K), the transfer roller 140, and the fixing part 150 are included.

The conveyance belt 120 is supported by a plurality of support rollers 121, 122, 123, and 124 to circulate. The conveyance belt 120 in this embodiment is installed in the vertical direction. Each of the exposure units 130C, 130M, 130Y, and 130K is configured to generate light corresponding to image information of cyan, magenta, yellow, and black colors. The photosensitive drum 111 of each of the developing cartridges 110C, 110M, 110Y, and 110K is irradiated according to the signal.

Each developing cartridge 110C, 110M, 110Y, 110K includes a photosensitive drum 111, a developing roller 112, a charging roller 113, a supply roller 114, a regulating member 116, and a cleaning member. 118 and the storage unit 119. The photosensitive drum 111 is installed to expose a portion of its outer circumferential surface and rotates in a predetermined direction, and a photoconductive material layer is coated on the outer circumference of the metal drum.

A charging bias voltage is applied to the charging roller 113 in order to charge the outer circumference of the photosensitive drum 111 to a uniform potential. Instead of the charging roller 113, a corona discharger (not shown) may be employed. The developing roller 112 attaches toner to its outer circumference and supplies the toner to the photosensitive drum 111. The developing roller 112 contains solid powder toner, and supplies these toners to the electrostatic latent image formed on the photosensitive drum 111 to develop the toner image. A developing bias voltage for supplying these toners to the photosensitive drum 111 is applied to the developing roller 112.

On the outside of the developing roller 112, a supply roller 114 for attaching toner to the developing roller 112, and a toner layer regulating member 116 for regulating the amount of toner attached to the developing roller 112, the frame 100 ) Is installed.

Each developing cartridge 110C, 110M, 110Y, 110K may further include an agitator (not shown) for transferring the toner contained therein to the feed roller 114 and / or the developing roller 112.

The developing cartridges 110C, 110M, 110Y, and 110K of the present embodiment have an opening 117 that forms a passage so that light scanned by the exposure units 130C, 130M, 130Y, and 130K can be irradiated to the photosensitive drum 111. It is provided. The outer circumferential surface exposed to the outer circumference of the photosensitive drum 111 faces the conveyance belt 120.

Four transfer rollers 140 are disposed at positions facing the photosensitive drums 111 of each of the developing cartridges 110C, 110M, 110Y, and 110K with the conveyance belt 120 interposed therebetween. In this embodiment, the transfer roller 140 is applied with a transfer bias voltage having a polarity opposite to that of the toner image so that the toner image developed on the photosensitive drum 111 is transferred to the paper S. FIG. The toner image is transferred to the paper S by the electrostatic force acting between the photosensitive drum 111 and the transfer roller 140.

The fixing unit 150 includes a heating roller 151 and a pressure roller 152 to fix the toner image on the paper S by applying heat and pressure to the toner image transferred to the paper S. The heating roller 151 is installed so as to be opposed to the pressure roller 152 in the axial direction as a heat source for permanently fixing the toner image. The pressure roller 152 is installed to face the heating roller 151 to apply a high pressure to the paper S to fix the toner image onto the paper S.

The discharge roller 176 discharges the paper S on which the fixing is completed, out of the electrophotographic image forming apparatus. The paper S discharged from the discharge roller 176 along the paper transfer path 180 from the printing unit 160 is loaded in the loading unit 190.

In addition, the image forming apparatus includes a paper feeding device 170 provided below the paper S to feed the paper S to the printing unit 160. The paper feeding device 170 includes a paper feed cassette 171 in which the paper S is loaded, a pick-up roller 172 which pulls out the paper S from the paper cassette 171, and a paper S. A heavy feed preventing member 173 is provided to prevent a heavy feed. One side of the image forming apparatus may additionally include a multi-purpose feeder (MPF) for mounting the paper (S). MPF is mainly used to transport OHP paper or non-standard paper (S).

The paper feeding cassette 171 is an example of a stacking means in which the paper S is loaded. The paper cassette 171 elastically biases the knock-up plate 171a on which the paper S is loaded and the knock-up plate 171a upward. An elastic member 171b is provided.

The paper S loaded on the knock-up plate 171a is conveyed one by one by the pickup roller 172 which will be described later. Since a plurality of sheets S loaded on the knockup plate 171a may be picked up at once, a friction member 210 may be provided on the upper surface of the knockup plate 171a at a position facing the pickup roller 172. It is preferable to be. The friction member 210 provides a frictional force greater than at least the frictional force between the papers S on the back surface of the last sheet S to prevent feeding.

The elastic member 171b elastically biases the paper S loaded on the knockup plate 171a toward the pickup roller 172. That is, the paper S loaded on the knock-up plate 171a is in contact with the pickup roller 172 by the elastic member 171b, and is conveyed one by one by the pickup roller 172.

3 is a perspective view showing a paper feeding device of the image forming apparatus according to a preferred embodiment of the present invention, Figure 4 is a perspective view showing the pickup roller and the anti-feeding member of the paper feeding device shown in Figure 3, Figure 5 3 is a perspective view illustrating in detail a portion of the sheet feeding prevention part of the sheet feeding apparatus shown in FIG. 3, and FIG. 6 is a perspective view illustrating an embodiment of the sheet feeding preventing member of the sheet feeding apparatus illustrated in FIG. 3. 7 is a perspective view showing another embodiment of the feeding prevention member of the paper feeding device shown in FIG. 3.

3 to 6, the anti-feeding member 173 is provided at the lower side of the pickup roller 172 and the anti-feeding unit 204 for preventing the feeding of the paper S transported by the pickup roller 172 and In addition, the front end portion of the paper (S) is provided on the side is provided with a friction preventing portion 200 to reduce the friction with the paper (S) entering. In the present embodiment, the anti-feeding member 173 is rotatably installed around one point 173a, and has a coupling groove 173c to which the vertical wall 173b and the non-feeding unit 204 to be described later are coupled. It is elastically biased toward the pickup roller 172 by an elastic member (not shown). In addition, in the accompanying drawings, the anti-feeding member 173 is provided with the anti-feeding unit 204 and the anti-friction unit 200, but on the contrary, only the anti-feeding unit 204 is provided on the anti-feeding member 173. It may be.

The anti-feeding unit 204 is fixedly installed at one side of the anti-feeding member 173, and the part contacting the rear surface of the conveyed paper S is rotatably installed and is conveyed by the pickup roller 172. Prevents S's feeding. The anti-feeding unit 204 provides frictional resistance to the back surface of the paper S to be transferred to the printing unit 160 by the pickup roller 172 so that only the uppermost paper S is transferred. That is, even if several sheets of paper S are conveyed by the pick-up roller 172, the other sheets of paper are blocked by the feeding prevention unit 204, and only the paper S loaded on the uppermost side of the knock-up plate 171a. It is transferred to the printing unit 160. In order to perform this separation, the anti-feeding unit 204 should have at least a frictional force with the paper S than a frictional force between the papers S.

Referring to FIG. 5, the anti-feeding unit 204 includes a non-feeding belt 205 and a bias unit 206.

The anti-feed belt 205 is rotatably installed in a belt shape, and is in contact with the rear surface of the paper S to prevent the feeding of the paper S. When the surface in contact with the paper S in the anti-conveyor belt 205 is worn by continuous printing operation, the anti-feed belt 205 is rotated with a predetermined force so that the non-wearing surface is in contact with the paper S. By configuring the anti-feed belt 205 as described above, it is possible to extend the life of the product.

The bias unit 206 is installed to be in contact with the inside of the anti-feed belt 205 to bias the inside of the anti-feed belt 205 outward so that the anti-feed belt 205 is not rotated while the paper S is being conveyed. . The bias portion 206 is provided with a pair of support roller portions 207 installed to contact the inside of the anti-feed belt 205 and an elastic member 208 for biasing the pair of support roller portions 207 in opposite directions. ).

The shafts 207a and 207b provided in each of the pair of supporting roller parts 207 are slidably coupled to the coupling groove 173c provided in the vertical wall 173b of the heavy transport prevention member 173, thereby preventing the heavy transport. 204 is fixed to the anti-feed member 173.

The elastic member 208 is coupled to the shafts 207a and 207b to elastically bias the pair of support roller parts 207 in opposite directions, that is, away from each other. At this time, the elastic force of the elastic member 208 for biasing the support roller portion 207 is preferably greater than the friction force applied to the anti-feed belt 205 by the paper (S) to be conveyed. Otherwise, since the conveyance prevention belt 205 is rotated by the paper S to be conveyed, the conveyance prevention belt 205 cannot properly perform the conveyance prevention function of the paper S.

In the present embodiment, the elastic member 208 is installed at both ends of the shafts 207a and 207b, but the present invention is not limited thereto, and various modifications may be made, such as being integrally installed with the support roller unit 207.

The separation action of the paper S by the transport prevention portion 204 is more efficient as the gap between the pickup roller 172 and the transport prevention portion 204 is narrower. Further, in order to prevent the feeding of the paper S, the interval between the entry portions into which the paper S enters between the pickup roller 172 and the feeding prevention portion 204 may be smaller. That is, in order to prevent the paper S from being fed, minimizing the gap between the pickup roller 172 and the feed prevention portion 204 where the paper S enters prevents the paper S from entering multiple sheets. can do.

However, when the distance between the pickup roller 172 and the drop prevention portion 204 is narrowed, the front end of the paper S to be caught is caught by the drop prevention member 173 and cannot enter the entry portion. That is, when the distance between the entry portions into which the paper S enters is too narrow, the front end portion of the sheet S entering may be caught by the non-feeding member 173, thereby preventing entry. Therefore, minimizing the gap between the pickup roller 172 and the anti-feeding unit 204 causes friction between the paper S and the anti-feeding member 173 to enter, so as to minimize the friction, the anti-feeding member ( An antifriction unit 200 is provided at 173.

The anti-friction unit 200 is provided at the side where the front end of the paper S conveyed by the pick-up roller 172 enters, and the paper S is caught by the feed prevention member 173 to prevent the pick-up roller 172 from being fed. Preventing entry between sections 204 is prevented. In addition, the friction preventing unit 200 reduces the friction with the paper (S) entering. It is preferable that the anti-friction part 200 is provided with the roller 201a (refer FIG. 6), or the inclined surface 201b (refer FIG. 7).

Referring to FIG. 6, the friction preventing part 200 includes a roller 201a. The roller 201a is rotatably installed about the shaft 202 in the groove 203 provided in the anti-feed member 173. That is, the roller 201a is installed to be freely rotated in the transport prevention member 173 so that the front end of the paper S conveyed by the pickup roller 172 is caught by the transport prevention member 173 or the transport prevention unit 204 is provided. To prevent them from entering. The roller 201a is preferably configured to be integral with the shaft 202.

Referring to FIG. 7, the friction preventing unit 200 may include an inclined surface 201b. The inclined surface 201b is formed to be inclined downward toward the knock-up plate 171a. The paper S conveyed by the pick-up roller 172 is guided by the inclined surface 201b and conveyed toward the middle feed prevention unit 204. Therefore, the paper S, which enters between the pickup roller 172 and the middle feed preventing unit 204, is minimized in friction with the anti-feeding member 173 by the anti-friction unit 200, and thus the paper feeding capacity is improved.

In the present embodiment, the anti-feeding part 204 is installed on the vertical wall 173b provided in the anti-feeding member 173, but the present invention is not limited thereto, and the anti-feeding part 204 may be installed in the main body frame. Various modifications are possible.

FIG. 8 is a perspective view illustrating a pickup roller of the sheet feeding apparatus shown in FIG. 3, FIGS. 9 and 10 are plan views illustrating an embodiment of a pickup roller surface pattern, and FIGS. 11 and 12 are a part of the pickup roller of FIG. 8. Is an enlarged cross-sectional view showing a state in contact with a state before contacting the paper.

Pick-up roller 172 is installed on the upper side of the knock-up plate (171a) is rotated while pressing the upper surface of the paper (S) by the paper S from the knock-up plate (171a) through the anti-friction portion 200 to prevent heavy feeding Transfer to section 204.

Referring to FIG. 8, a plurality of holes 272 are formed in the contact surface 220 of the pickup roller 172 in contact with the paper S to improve pickup performance. In addition, each of the holes 272 may be arranged in various ways to improve pickup performance. For example, the holes 272 may be distributed in a regular pattern over the entire surface of the pickup roller 172 as shown in FIGS. 9 and 10. Specifically, in FIG. 9, the holes 272 are vertically arranged in parallel with the conveying direction of the paper S indicated by the arrows, and in FIG. 10, the holes 272 are conveyed in the conveying direction of the paper S indicated by the arrows. It is arranged zigzag with respect to the species. 9 and 10, the holes 272 may be distributed in an irregular pattern over the entire surface of the pickup roller 172. In addition, the pickup roller 172 may have a wavy surface pattern to increase the friction of the surface.

Referring to FIG. 11, each of the holes 272 extends in the direction toward the shaft 265, which is the center of rotation of the pickup roller 172. When the paper S loaded on the knock-up plate 171a is not in contact with the pickup roller 172, the pickup roller 172 and the holes 272 formed on the surface thereof retain their original shape, and the hole 272 The internal pressure Pin and the external pressure Patm remain the same. When printing starts and the knock-up plate 171a is raised to contact the lower end of the pickup roller 172, the lower end of the pickup roller 172 pressed by the paper S as shown in FIG. 12. Is modified so that its inner diameter extends from D1 to D2. Since the above change occurs instantaneously, it can be assumed to be an adiabatic change process, and the expansion of the inner diameter of the hole 272 causes the volume expansion inside the hole 272. Therefore, according to the known thermodynamic law, the pressure Pin inside the hole 272 will be smaller than the external pressure Patm, and the paper S is attracted to the lower end of the pickup roller 172 by this pressure difference. It can be seen that the force will be generated.

The pickup roller 172 is preferably made of a material having a Poisson's ratio of 0.1 or more and 0.49 or less. Poisson's ratio means the ratio between the transverse and longitudinal deformation of the material when stress is applied to the material. If the Poisson's ratio is less than 0.1, the pickup roller 172 is hard and the change in the inner diameter of the hole 272 is performed. If the Poisson's ratio is greater than 0.49, the pickup roller 172 may recede and be deformed in a direction in which the hole 272 inner diameter is reduced.

Pick-up roller 172 is preferably made of EPDM in order to increase the friction force with the paper (S). That is, the surface of the pickup roller 172 in contact with the paper S is preferably made of EPDM. However, in addition to the EPDM, NR-based, NBR-based, urethane-based, or silicone-based rubber may also be used as the material of the pickup roller 172.

The feed roller 174 feeds the paper S drawn out from the paper feed cassette 171 by the pickup roller 172 toward the printing unit 160. The paper S conveyed as described above passes through the printing unit 160, at which time the toner image is transferred to the paper S. FIG. The toner image transferred to the paper S is fixed to the paper S via the fixing unit 150, and discharged out of the image forming apparatus by the delivery roller 176.

Hereinafter, an operation of a paper feeder and an image forming apparatus having the same according to a preferred embodiment of the present invention will be described.

The color image information is a mixture of information corresponding to cyan (C), magenta (M), yellow (Y), and black (K) colors, respectively. In this embodiment, a color image is formed by transferring a toner image of each color in the order of cyan (C), magenta (M), yellow (Y), and black (K) to the paper S and then fixing it.

When the paper cassette 171 is mounted in the image forming apparatus after the paper S is loaded in the paper cassette 171, the following image forming process proceeds.

The photosensitive drums 111 of each of the developing cartridges 110C, 110M, 110Y, and 110K are charged at a uniform potential by the charging bias voltage applied to the charging roller 113. The four exposure units 130C, 130M, 130Y, and 130K respectively emit light corresponding to the image information of cyan, magenta, yellow, and black colors through the openings 117 of each of the developing cartridges 110C, 110M, 110Y, and 110K. The photosensitive drum 111 is irradiated. When light is irradiated, only the irradiated portion is selectively discharged to lower the potential, and the output pattern formed by the potential difference is an electrostatic latent image.

On the other hand, the toner is supplied to the developing roller 112 to which the developing bias voltage is applied by the supply roller 114. The toner adhered to the outer circumference of the developing roller 112 is thinned to a uniform thickness by the toner layer regulating member 116. At this time, the toner is charged while being rubbed by the developing roller 112 and the toner layer regulating member 116. The toner attached to the outer circumference of the developing roller 112 is attached to the electrostatic latent image formed on the outer circumference of the photosensitive drum 111. The toners of the developing cartridges 110C, 110M, 110Y, and 110K are respectively cyan and magenta. Toner images of yellow and black colors are formed.

The paper S is withdrawn from the paper feed cassette 171 by the pickup roller 172, is conveyed through a predetermined paper feed path, and then discharged out of the image forming apparatus by the discharge roller 176.

Pick-up roller 172 is rotated while pressing the upper surface of the paper (S) loaded on the knock-up plate (171a) by rotating the paper (S) from the knock-up plate (171a) through the anti-friction portion 200 through the anti-feeding portion ( 204). The papers S transferred to the anti-feeding unit 204 are blocked by the anti-feeding unit 204 so that only the uppermost paper S is transferred to the feed roller 174. At this time, the surface state of the contact surface 220 of the pick-up roller 172 and the transport prevention belt 205 of the transport prevention portion 204 in order to maintain a constant separation force of the paper (S) by the transport prevention portion 204 at all times. Wear should be minimized.

However, the contact surface 220 of the pick-up roller 172 and the anti-conveying belt 205 of the anti-feeding unit 204 have parts with a certain life, so they should be replaced periodically according to the usage amount. However, if the component is configured to have the configuration as described above, when the portion of the anti-feed belt 205 in contact with the paper S is worn, the non-wear surface is rotated by rotating the non-feed belt 205. Can be adjusted in contact with Therefore, since the surface of the unused conveyance prevention belt 205 is located on the contact surface 220 of the pickup roller 172, the separation force of the paper S by the transport prevention portion 204 can be kept constant. In addition, during feeding of the paper S, the feeding prevention belt 205 is not rotated by the biasing force of the elastic member 208, so that feeding of the paper S can be efficiently prevented.

The paper S that has passed through the conveyance prevention part 204 is drawn into the conveyance belt 120 by a feed roller 174. The paper S is attached to the surface of the conveyance belt 120 by an electrostatic force and conveyed at the same speed as the traveling linear velocity of the conveyance belt 1201. For example, the paper S is adapted to a point where the tip of the cyan color toner image formed on the outer circumferential surface of the photosensitive drum 111 of the developing cartridge 110C reaches the transfer nip facing the transfer roller 140. The tip of the reaches the transfer nip.

When a transfer bias voltage is applied to the transfer roller 140, the toner image formed on the photosensitive drum 111 is transferred to the paper S. As the paper S is transported, the toner images of magenta (M), yellow (Y), and black (K) colors formed on the photosensitive drums 111 of the developing cartridges 110M, 110Y, and 110K are sequentially loaded with the paper S. ) Is superimposed, and a color toner image is formed on the paper (S).

The toner remaining on the outer circumferential surface of the photosensitive drum 111 after the transfer is removed by a cleaning member (not shown). The fixing unit 150 applies heat and pressure to the color toner image formed on the paper after transfer to fix the toner image to the paper. The paper S is discharged out of the image forming apparatus by the discharge roller 176. The paper S discharged from the discharge roller 176 along the paper transfer path 180 is loaded in the stacking unit 190.

According to the configuration as described above, the present invention can be used by rotating in a predetermined direction when the contact surface that is in contact with the paper (S) of the non-feeding portion 204 is worn, unlike the prior invention. In addition, the interval between the pickup roller 172 and the middle feed preventing member 173 can be minimized, and the paper feeding performance of the paper S by the pickup roller 172 can be improved.

As described above, the paper feeder of the image forming apparatus according to the present invention can be used by rotating the contact surface in contact with the paper in the predetermined direction when worn out of the feed prevention portion, to improve the replacement cycle and life of the feed prevention portion Can be. In addition, it is possible to minimize the entry gap between the pickup roller and the feed prevention member to prevent the case of entering a plurality of sheets. In addition, by providing a friction preventing portion at the entrance of the paper to minimize the friction with the paper to enter can improve the paper feed performance.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and various modifications and equivalent other embodiments are possible to those skilled in the art. Will understand. Therefore, the true technical protection scope of the present invention will be defined by the claims below.

Claims (5)

A paper feed cassette including a knock-up plate on which paper is loaded and an elastic member for biasing the knock-up plate upward; A paper feeder of an image forming apparatus, comprising: a feed feed preventing member having a feed feed preventing portion for preventing feed of the paper conveyed by a roller, The congestion prevention unit, And a portion fixed to the conveyance preventing member, the portion of which is brought into contact with the rear surface of the paper to be conveyed by being rotated when worn, so as to be replaced. The method of claim 1, The congestion prevention unit, It is rotatably installed in a belt shape, the contact belt to prevent contacting the back of the paper to prevent the conveying of the paper; A bias part installed to be in contact with the inside of the anti-feed belt so as to bias the inside of the anti-feed belt so as not to rotate; Paper feeder of the image forming apparatus comprising a. The method of claim 2, The bias unit, A pair of support rollers installed to be in contact with the inner conveyance prevention belt; An elastic member for biasing the pair of support roller parts in opposite directions; Paper feeder of the image forming apparatus, characterized in that provided. The method according to any one of claims 1 to 3, An anti-friction portion provided on the anti-feeding member, the anti-friction portion provided on a side where the leading end of the paper enters to reduce friction with the paper entering; The paper feeder of the image forming apparatus, further comprising. The method of claim 4, wherein And the friction preventing portion comprises a roller.

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