JPH1179474A - Paper sheet feeding device of image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper sheet feeding device of an image forming device capable of suppressing wrinkles from being produced without lowering a skew correction capability in a resister. SOLUTION: Even if the distortion of a paper sheet P occurs by a skew, the paper sheet P is freed by the separation of the rollers forming a pair of intermediate feeding rollers 4a so as to release a grip force to the paper sheet P, and returned in the arrow direction of C by an amount of distortion. Therefore wrinkles are prevented from occurring. Also a deflection generating time is set at (a), a separation timing (b) is set at 0<b<a, and a separation timing (c) is set at 0<c<a and b+c<a. By this, the distortion of the paper sheet P can be eliminated securely without subjecting to those affections such as a reduction in deflection due to a linear velocity difference between the pair of intermediate feeding rollers 4a and a pair of register rollers 4b. In addition, because the separation of the pair of intermediate feeding rollers 4a is completed without transmitting a load on a paper sheet feeding part to the pair of register rollers 4b, there is no effect on images.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device for an image forming apparatus such as a copying machine.

[0002]

2. Description of the Related Art In current image forming apparatuses such as copier printers and facsimile machines, high quality of output images is required, and therefore, particularly, skew due to skew of paper is improved. Is desired.

However, under the present circumstances, when the sheet fed from the sheet feeding device skews, the sheet whose skew has been corrected by the intermediate conveyance roller and the registration roller is stressed by the intermediate conveyance roller and the registration roller, and is subjected to the stress by the registration roller. There is a problem that wrinkles occur. In order to reduce the occurrence of wrinkles, a technique has been proposed in which the end of the registration roller is cut to reduce the diameter, and the shape of the rollers is reduced to a dumpling shape, thereby reducing the occurrence of paper wrinkles. This causes a phenomenon that the skew correction ability of the resist is reduced. Also, Japanese Patent Application Laid-Open No. Hei 7-261573 proposes a technique of providing a registration roller conveyance force canceling mechanism to eliminate the influence on an image. The same applies to this technique.

An object of the present invention is to provide a paper feeder of an image forming apparatus capable of suppressing generation of wrinkles without deteriorating the skew correction ability at a resist in view of the above-mentioned conventional problems.

[0005]

According to a first aspect of the present invention, there is provided a sheet feeding device for an image forming apparatus, comprising: a sheet separating unit, an intermediate conveying roller pair, and a registration roller pair. In the sheet feeding device of the image forming apparatus having the above-mentioned structure, the image forming apparatus further includes a unit for moving a roller forming the intermediate conveying roller pair toward and away from the roller.

According to a second aspect of the present invention, the initial separation timing of the pair of intermediate conveyance rollers by the contacting / separating means is performed before the sheet is deflected by the registration.

According to a third aspect of the present invention, the driving side roller of the intermediate transport roller pair is driven when the intermediate transport roller pair is separated by the contact / separation means.

According to a fourth aspect of the present invention, the intermediate transport roller pair is contacted and separated a plurality of times by the contacting / separating means.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing an entire example of an electrophotographic printing machine to which a sheet feeding device according to the present invention is installed. The printing apparatus 1 mainly includes a paper feed cassette 2, a paper separating unit 3, a paper feed unit 4, an image forming unit 5, a fixing unit 6, and a paper discharging unit 7.

The printing paper P fed from the paper feeding cassette 2
Are transported one by one by the paper separating unit 3 and sent to the registration roller pair 4b by the intermediate transport roller pair 4a. The registration roller pair 4b sends out the sheet P to the image forming unit 5 in synchronization with the optical writing 5a. Thereafter, the paper P passes through the fixing unit 6 and is discharged to the paper discharge unit 7, and printing is completed.

The pair of intermediate transport rollers 4a has a high paper transport force so as not to transmit the load of the sheet separating section 3 to the pair of registration rollers 4b, and is always driven to rotate when the pair of registration rollers 4b is driven.

In the drawing, 5b is a developing device, 5c is a photoreceptor,
5d is a transfer device, and 5e is a cleaning device.

FIG. 2 is a cross-sectional view showing the entire sheet feeding / conveying section 4. The printing paper P stored in the paper feeding cassette 2 is fed one by one by the paper separating unit 3 and sent to the intermediate transport roller pair 4a. The intermediate transport roller pair 4a sends the sheet P further to the registration roller pair 4b. At this time, paper P
Is detected by the registration sensor 4c and the distance from the detection position to the nip of the pair of registration rollers 4b is added to the distance from the end of the sheet P until the tip of the sheet P strikes the pair of registration rollers 4b to generate a deflection for skew correction. During this distance, the intermediate transport roller pair 4a is driven and then stopped. Thereafter, the registration roller pair 4b is activated in synchronization with the image on the photoconductor 5c, and at the same time, the intermediate conveyance roller pair 4b is activated.
a also sends out the paper P (see the timing chart of FIG. 3). In the figure, 3a indicates a paper feed roller, and 4d indicates a grip sensor.

Next, the details of an example of the contact / separation mechanism for the intermediate conveying roller pair 4a will be described with reference to FIG. The driven roller 42, which is in contact with the driving roller 41, is supported by an arm lever 44 that rotates about a rotation fulcrum 43, and a solenoid actuator 45 is connected to the opposite end. When the contact / separation solenoid 46 sucks (in the direction of arrow A in the figure), the driven roller 42 supported by the arm lever 44 rotates about the rotation fulcrum 43 in the direction of arrow B in the figure to rotate the drive roller 41. Separate from. By this operation, the paper P is released from the gripping force of the intermediate transport roller pair 4a and becomes free. In the drawing, reference numeral 47 denotes a pressure spring for bringing the driven roller 42 into contact with the drive roller 41.

Next, the process of generating wrinkles by the registration roller pair 4b will be described with reference to FIGS. The sheet P skewed and conveyed from the sheet feeding unit is conveyed to the registration roller pair 4b by the intermediate conveyance roller pair 4a in that posture (FIG. 5). Since the leading end of the sheet P abuts on the registration roller pair 4b and is fed by the amount of deflection generated by the intermediate conveying roller pair 4a, only the leading end of the sheet P follows the alignment of the registration roller pair 4b (FIG. 6), and the intermediate conveying roller pair 4a. The paper P is distorted D between the pair of registration rollers 4b. When the sheet P is conveyed in this state, the distortion D of the sheet P is pressed by the registration roller pair 4b to form wrinkles S (see FIG. 7). In the present embodiment, even if the paper P is distorted as shown in FIG.
The roller forming the intermediate transport roller pair 4a is separated from the paper P
Is released, the paper P becomes free and returns in the direction of the arrow C by the amount of the distortion D, thereby preventing the occurrence of wrinkles.

Next, the separation timing of the intermediate conveying roller pair 4a will be described with reference to FIG. When the deflection generation time is a, the separation timing b is 0 <b <a, and the separation time c is
By setting 0 <c <a and b + c <a, the distortion of the sheet P can be surely eliminated without being affected by a decrease in deflection due to a difference in linear speed between the intermediate conveyance roller pair 4a and the registration roller pair 4b. Apply the load on the paper section to the registration roller pair 4
Since the separation of the pair of intermediate transport rollers 4a is completed without transmitting the signal to b, there is no adverse effect on images and the like. When the driven roller 42 of the intermediate conveying roller pair 4a is separated from the driven roller 42, the driving roller 41 is rotationally driven (d portion), so that the driven roller 42
Can be prevented from being braked on the paper P at the time of contact. Further, in order to separate the intermediate transport roller pair 4a again after an arbitrary time, the effect of the portion e in the drawing in which the contact / separation solenoid 46 is operated is further improved for the large-size paper P. The timing at this time is desirably performed after the trailing edge of the sheet has passed through the sheet feeding unit, because the registration roller 4b does not receive the sheet feeding load.

[0017]

As described above, in the sheet feeding device of the image forming apparatus according to the first aspect, since the pair of intermediate conveyance rollers can be moved toward and away from the registration roller, the sheet conveyance direction with respect to the registration rollers is skewed. Even if it is displaced, the intermediate transport roller pair is separated to release the gripping force on the sheet, and the intermediate transport roller pair becomes free, so that stress on the sheet is eliminated and wrinkles can be prevented.

According to a second aspect of the present invention, as described above, the separation timing of the intermediate conveyance roller is adjusted by causing the leading edge of the sheet to hit the resist, generating a deflection for skew correction, and By synchronizing with the writing start timing, and after the registration roller is started, the paper is separated for a time shorter than the time during which the deflection of the paper is eliminated, and in addition to the above-described common effects, the generation of wrinkles due to skew is further improved. There is an effect that the conveyance can be performed effectively and the conveyance can always be performed stably without generating the speed unevenness and the load impact when the paper is conveyed by the registration rollers.

According to a third aspect of the present invention, in addition to the above-described common effects, the sheet feeding device of the image forming apparatus drives the driving side of the intermediate conveying roller pair when the driven roller is separated from the driven roller. There is an effect that the braking action on the sheet at the time of contact is eliminated, and the sheet can always be stably conveyed without generating speed unevenness and load impact when the sheet is conveyed by the pair of registration rollers.

According to the fourth aspect of the present invention, the sheet feeding device of the image forming apparatus performs the contact and separation of the intermediate conveyance roller not only at the time of starting the registration at the leading end of the sheet but also during the sheet conveyance. In addition to the above-described common effects, there is an effect that wrinkles can be prevented even for large-size paper and long paper.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an entire example of an electrophotographic printing machine to which a paper feeding device according to the present invention is installed.

FIG. 2 is a cross-sectional view showing the entire sheet feeding and conveying unit of the apparatus shown in FIG.

FIG. 3 is a timing chart of the operation of the sheet feeding and conveying unit in FIG. 2;

FIG. 4 is a side view of an example of a mechanism for contacting / separating an intermediate conveying roller pair.

FIG. 5 is a plan view showing a process of generating wrinkles by a pair of registration rollers.

FIG. 6 is a plan view showing a process of generating wrinkles by a pair of registration rollers.

FIG. 7 is a plan view showing a process of generating wrinkles by a pair of registration rollers.

FIG. 8 is a timing chart showing separation timing of a pair of intermediate conveyance rollers.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 printing device 2 paper feed cassette 3 paper separation unit 3a paper feed roller 4 paper feed transport unit 4a intermediate transport roller pair 4b registration roller pair 4c resist sensor 4d grip sensor 5 image forming unit 5a optical writing 5b developing device 5c photoconductor 5d transfer Apparatus 5e Cleaning device 6 Fixing unit 7 Discharge unit 41 Drive roller 42 Follower roller 43 Rotating fulcrum 44 Arm lever 45 Solenoid actuator 46 Contacting / separating solenoid 47 Pressure spring P Paper S Wrinkle

Claims (4)

[Claims] 1. An image forming apparatus comprising a sheet separating unit, an intermediate conveying roller pair, and a registration roller pair, the image forming apparatus comprising: a unit configured to move a roller forming the intermediate conveying roller pair toward and away from the roller. Paper feeder for the device. 2. The sheet feeding device according to claim 1, wherein an initial separation timing of the pair of intermediate conveyance rollers by the contact / separation unit is performed before the sheet is deflected by registration. 3. The sheet feeding device of the image forming apparatus according to claim 1, wherein a driving-side roller of the pair of intermediate transport rollers is driven when the pair of intermediate transport rollers is separated by the contact / separation unit. 4. The sheet feeding device for an image forming apparatus according to claim 1, wherein the contact and separation of the intermediate conveyance roller pair by the contact and separation means is performed a plurality of times.