JP3930329B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine or a printer.
[0002]
[Prior art and problems to be solved by the invention]
A conventional general image forming apparatus such as a copying machine or a printer is shown in FIG. In the figure, 1 is an optical unit, 2 is a process cartridge unit (PCU), 3 is a developing unit, 4 is a transfer belt, 5 is a registration roller, 6 is a straight paper feed tray, 7a is a first paper feed tray, and 7b is a second paper feed tray. A sheet feeding tray, 8 is a duplex conveying unit, 9 is a duplex reversing unit, 10 is a fixing belt, 11 is a pressure roller, 12 is a toner bottle, and 13 is a sheet discharge tray.
[0003]
In such an image forming apparatus, generally, as shown in FIG. 2, a plurality of paper feed trays 7a and 7b provided in the apparatus main body for accommodating several different sizes of paper, and these paper feed trays Paper feed rollers 15a to 15c for feeding paper from 7a and 7b to a paper conveyance path provided in the apparatus main body, and pickup rollers 14a to 14c for moving paper from the paper feed trays 7a and 7b to paper feed rollers 15a to 15c In addition, a paper feeding device including reverse rollers 16a to 16c for handling paper and feeding paper one by one is used.
[0004]
The sheet fed from such a sheet feeding device is transferred to the conveyance rollers 17a, 17b, and 18 provided on the conveyance path, and is transferred to the image forming unit (optical unit 1 to transfer belt 4) downstream in the sheet conveyance direction. Delivered. Then, the sheet skew is corrected by the registration roller 5 positioned on the upstream side in the sheet conveyance direction of the image forming unit, and the image formed by the image forming unit is correctly transferred to the sheet.
[0005]
Here, the paper is transported by the transport rollers 17a, 17b, and 18 until it abuts against the registration roller 5, and from that state, only a small amount of the transport rollers 17a, 17b, and 18 is driven to form the paper P as shown in FIG. Tarmi is generated and conveyed to the image forming unit with the leading edge of the paper P aligned with the registration roller 5. Note that FIG. 3A is when the main body is fed, and FIG. 3B is when the straight sheet is fed.
[0006]
In the image forming unit, image information is irradiated from the optical unit 1 to the photosensitive drum 2 to form a toner image using an electrophotographic method, and the image is transferred onto a sheet by the transfer belt 4. The image-transferred paper is fixed with the image passing between the fixing belt 10 and the pressure roller 11 on the downstream side, and is sent to a post-processing device such as a paper discharge tray 13 or a double-side reversing unit 9, a finisher (not shown), and a 4-bin print post. It is conveyed.
[0007]
In such an image forming apparatus, the sheet feeding tray is generally arranged below the image forming unit as in the example shown in FIG. 1 from the viewpoint of minimizing the overall size of the apparatus. For this reason, the sheet conveyance path that continues from the sheet feeder to the image forming unit via the registration roller 5 is greatly curved. However, since paper such as thick paper and OHP is stronger than plain paper and the surface of the paper is easily damaged, it is not preferable to carry it on a curved conveyance path.
[0008]
For this reason, it is common to provide a paper feeding device (6, 14c to 16c) that can transport the paper along a straighter transport path, in addition to the transport path. Unlike the sheet feeding device in the apparatus main body, this straight sheet feeding device is generally arranged along the extension line in the conveyance direction on the upstream side in the sheet conveyance direction to the image forming unit.
[0009]
As shown in FIG. 4, the main body sheet feeding device 21 includes sheet feeding trays 7 a and 7 b, roller groups 14 a and 14 b to 17 a and 17 b for the sheet feeding trays 7 a and 7 b, and a common conveyance roller 18. The main body paper feeder 21 is driven by a stepping motor 19a. Each of the paper feed rollers 15a and 15b is provided with a clutch 20a. The pickup rollers 14a and 14b and the reverse rollers 16a and 16b operate in synchronization with the paper feed rollers 15a and 15b, respectively. These pickup rollers 14a and 14b and paper feed rollers 15a and 15b rotate in the transport direction of the paper P to perform a paper feeding operation, but the reverse rollers 16a and 16b are always driven to rotate in the direction opposite to the transport direction of the paper P. It takes the action of returning the paper P to the paper feed trays 7a and 7b. The reverse rollers 16a and 16b have a torque limiter (not shown), and rotate in the rotation direction of the paper feed rollers 15a and 15b when there is no paper P and when there is one paper P. When there are two or more sheets P, the sheet P is set so as to rotate in the original rotation direction. The clutch 20a connected to the paper feed rollers 15a and 15b is connected from the start of paper feed, and cuts immediately before the paper P passes the position of the paper feed rollers 15a and 15b, thereby improving the paper separation performance. Yes.
[0010]
In the straight sheet feeder 22, a driving force is obtained from the DC motor 19b, and a sheet feeding operation is performed by the clutch 20b connected to the sheet feeding roller 15c. The roller configuration of the straight sheet feeder 22 is the same as that of the main body sheet feeder 21, and the functions and operations thereof are also the same. The paper P transported by the straight paper feeder 22 is transported until it abuts against the registration roller 5 and performs the same paper leading edge correction operation as described above. When this correction operation is performed, the clutch 20b for the paper feed roller 15c of the straight paper feeder 22 is disconnected immediately before the paper P passes the position of the paper feed roller 15c, and between the registration roller 5 and the paper feed roller 15c. The pulling of the paper P occurs abruptly (see FIG. 5).
[0011]
For this reason, the shock of clutch disconnection affects the image forming unit via the paper P, resulting in image distortion. Further, as shown in the figure, when the drive source of the straight sheet feeder 22 is the same motor as the drive source of the registration roller 5, the shock as described above directly affects the rotation of the registration roller 5 through the drive system. The influence on the department is great.
[0012]
In order to avoid such a problem, a transport roller is added between the straight sheet feeding device 22 and the registration roller 5, or the driving source of the straight sheet feeding device 22 is completely different from that for driving a dedicated motor or registration roller. Need to be obtained from the drive source. However, the addition of a conveyance roller and the addition of a dedicated motor are directly related to the increase in cost and apparatus size of the image forming apparatus, and are not easy. In addition, when driving from another drive source, the torque limiter load applied to the reverse roller 16c of the straight sheet feeder 22 is applied to the drive source. Therefore, it is essential to increase the torque of the motor as the drive source. Become.
[0013]
An object of the present invention is to provide an image forming apparatus capable of solving the problems related to the conventional paper feeding and conveyance.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention is a straight sheet feeder provided with a sheet feed table for stacking and holding sheets, and a sheet feed roller for feeding sheets from the sheet feed table, and a sheet A plurality of main body sheet feeding devices, a sheet feeding roller that feeds a sheet from the sheet feeding tray, a conveyance roller that conveys the sheet fed by the sheet feeding roller, and the straight sheet feeding device and connected to said main body feeding device, at the time of unidirectional rotation to drive the main body feeding device, the image forming apparatus Ru provided with a reversible drive device that drives the straight sheet feeding device at the time of the other direction rotation, the paper type for conveying the paper feed by the straight sheet feeding device, and wherein the Rukoto such as an individually settable by the control of the drive device the drive speed of the straight sheet feeding apparatus.
[0015]
According to a second aspect of the present invention, in order to achieve the above object, in the image forming apparatus according to the first aspect, a junction point downstream of the conveyance path of the main body sheet feeding apparatus and the conveyance path from the straight sheet feeding apparatus. A first sheet detection device that detects the presence or absence of a sheet is arranged near the upstream of the conveyance path, and a second detection unit detects the presence or absence of the sheet downstream of the straight sheet feeding path and upstream of the merging point. A sheet detection device is provided.
[0016]
According to a third aspect of the present invention, in order to achieve the above object, in the image forming apparatus of the first or second aspect, the drive device is smoothly slowed down during the drive switching operation of the straight sheet feeder. It is characterized by controlling as it goes.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the following description, common parts are denoted by common reference numerals, and redundant description is omitted.
FIG. 6 shows an embodiment of an image forming apparatus according to the present invention. However, the parts other than those around the sheet feeder are omitted. As shown in the drawing, the pickup rollers 14a to 14c, the feed rollers 15a to 15c, the reverse rollers 16a to 16c, and the transport rollers 15a to 15c constituting the main body sheet feeding device 21 and the straight sheet feeding device 22 are the same as the conventional apparatus. It is.
[0019]
The drive system from the stepping motor 19a, which is a paper feed drive motor for driving the main body paper feed device 21, has the same configuration as that of the conventional device, but is straightened by the gear 23, timing belt, and gear 24 connected to the drive gear of the transport roller 18. The driving force is transmitted to the driving gear of the paper feeding roller 15c of the paper feeding device 21.
[0020]
As shown in FIG. 7, the gear 23 obtains a driving force from the main body paper feed driving system via the one-way clutch 25. Thus, only the main body paper feeding device 21 is driven when the paper feeding drive system rotates in the forward direction, and the driving force is transmitted to the straight paper feeding device 22 only when the main body paper feeding device 21 rotates in the reverse direction. The main body paper feeding device 21 and the straight paper feeding device 22 can be controlled by the control of the stepping motor 19a as a source. Since the one-way clutch 25 is interposed, the load torque generated in the straight sheet feeding device 22 is not added to the driving of the main body sheet feeding device 21, so that the sheet feeding motor 19a has a conventional device. It is not necessary to use a torque-up product.
[0021]
In the conventional apparatus, since the driving force is obtained from the DC motor 19b that normally rotates and is controlled only by ON / OFF of the clutch connected to the paper feed roller, the rotational speed during operation is constant. It is advantageous in that the operation of the paper feeding device 22 can be performed by the control of the stepping motor 19a.
[0022]
In the present embodiment, the transport rollers 17a, 17b, and 18 constituting the main body paper feeding device 21 are reversed when the straight paper feeding device 22 is driven. For this reason, when the paper is alternately fed from the two paper feeding devices 21 and 22, the paper fed from the main body paper feeding device 21 needs to be in a place that is not affected by the transport rollers 17a, 17b, and 18. .
[0023]
Therefore, as shown in FIG. 8, the one-way clutch 25 that does not rotate when the conveyance rollers 17a, 17b, and 18 are driven in reverse rotation, and the conveyance path from the straight sheet feeder 22 downstream of the conveyance path of the main body sheet feeder 21 A sheet presence / absence detection device 27 provided upstream from the junction 28 and a sheet presence / absence detection device 26 provided downstream of the conveyance path of the straight sheet feeder 22 and upstream of the junction are provided. For each paper feeding device 21, 22, the paper to be transported next before feeding by the other paper feeding device is transported in advance to the detection device 26 or the paper detection device position of the detection device 27 provided on each transport path. Thus, the sheet interval can be shortened, that is, the product time of the image forming apparatus can be shortened.
[0024]
The operation of the straight sheet feeder of the present embodiment will be described with reference to FIG. The stepping motor 19a starts reverse driving, the drive is transmitted to the straight paper feeder 22 by the gear 23, and the paper feeding operation is started (t1), the leading edge of the paper P hits the registration roller 5 (t2), and a predetermined The motor drive speed is set to v1 until the sag occurs (t3). Here, by setting the motor drive speed v1 and the image forming unit conveyance speed vp to have a relationship of v1 >> vp, the time required from the start of paper feeding to the start of image formation can be shortened. The product time of the image forming apparatus can be shortened. The driving speed of the straight sheet feeder is between the time when the registration roller 5 starts conveying the sheet P in synchronization with the start of image formation (t3) in the image forming unit and the trailing edge of the sheet passes the sheet feeding roller (t4). Drive at a speed v2 (= vp + Δv) slightly faster than vp. This is because the reverse rollers 16a to 16c constituting the paper feeding devices 21 and 22 always act on the paper P in the returning direction, so that a minute slip occurs between the paper feeding rollers 15a to 15c and the paper P. This is to compensate for the slow feeding speed. Further, since the degree of the phenomenon varies depending on the friction coefficient of the surface of the paper P and the thickness of the paper P, an optimal value of Δv is prepared in advance according to the type of the paper P, and the paper to be passed through By changing the driving speed according to the type of P, it becomes possible to obtain a stable conveyance performance regardless of the type of paper. Further, the sheet P is conveyed from the registration roller 5 to the image forming unit, and before the trailing end of the sheet P passes through the positions of the sheet feeding rollers 15a to 15c, the driving of the straight sheet feeder 22 is started, that is, the sheet feeding is performed. When the driving of the apparatus 21 is stopped, the stepping motor is controlled as indicated by t4 ′ → t4 in FIG. 9, and the sheet feeding roller 15c of the straight sheet feeding apparatus 22 is continuously stopped. Thereby, it is possible to avoid a shock due to a discontinuous change in driving due to the clutch being turned off.
[0025]
【The invention's effect】
In the image forming apparatus according to the first aspect, as described above, since the drive of the straight sheet feeding device is obtained from the main body sheet feeding device drive system via the gear provided with the one-way clutch, By rotating the system forward and backward, it is possible to control the two sheet feeding apparatuses, the straight sheet feeding apparatus and the main body sheet feeding apparatus, without affecting each other, and the drive speed of the straight sheet feeding apparatus is set to be variable. it is possible, it is possible to perform appropriate transport depending on the type of paper, there is an effect that is Ru can be reduced the influence to the image forming unit.
[0026]
In the image forming apparatus according to claim 2, as described above, the operation of the main body sheet feeding device and the straight sheet feeding device does not affect the operation of the other, and means for detecting the position of the sheet conveyed from each device. In addition to the above-described common effect, the productivity can be improved.
[0027]
In the image forming apparatus according to the third aspect, as described above, since the drive-off operation of the straight sheet feeder is smoothly performed, the influence on the image forming unit can be reduced in addition to the above-described common effect. There is an effect.
[Brief description of the drawings]
FIG. 1 is a conceptual cross-sectional view showing an image forming apparatus such as a conventional general copying machine or printer.
2 is a conceptual cross-sectional view of a sheet feeding device portion of the image forming apparatus of FIG.
FIG. 3 is a conceptual cross-sectional view showing the same sheet feeding form.
FIG. 4 is a conceptual cross-sectional view (A) showing a detailed configuration of the paper feeding device and perspective views (B, C) showing a paper feeding operation.
FIG. 5 is a conceptual cross-sectional view showing the same sheet feeding form.
FIG. 6 is a conceptual cross-sectional view showing a detailed configuration of an apparatus according to an embodiment of the present invention.
7 is a plan view showing a driving force transmission mechanism of the embodiment device shown in FIG. 6;
FIG. 8 is a conceptual cross-sectional view showing an enlarged configuration around the registration roller.
FIG. 9 is a time chart of the same operation.
[Explanation of symbols]
1 Optical unit 2 Process cartridge unit (PCU)
3 Development Unit 4 Transfer Belt 5 Registration Roller 6 Straight Feed Tray 7a First Feed Tray 7b Second Feed Tray 8 Duplex Transport Unit 9 Duplex Inversion Unit 10 Fixing Belt 11 Pressure Roller 12 Toner Bottle 13 Discharge Tray 14a 14c Pickup rollers 15a to 15c Paper feed rollers 16a to 16c Reverse rollers 17a, 17b, 18 Transport rollers 19a Stepping motor 19b DC motor 20a Clutch 20b Clutch 21 Main body paper feeder 22 Straight paper feeder 23, 24 Gear 25 One-way clutch 26, 27 Paper detection device P Paper

Claims (3)

A sheet feeding table for stacking and holding sheets, a straight sheet feeding device including a sheet feeding roller for feeding sheets from the sheet feeding table, a sheet feeding tray for storing sheets, and a sheet feeding roller for feeding sheets from the sheet feeding tray; A plurality of main body sheet feeders, each of which is connected to the straight sheet feeder unit and the main body sheet feeder unit, and the main body sheet feeder unit when rotating in one direction; driven, in the image forming apparatus Ru provided with a reversible drive device that drives the straight sheet feeding device at the time of the other direction rotation, the paper type for conveying the paper feed by the straight sheet feeding device, the driving of the straight sheet feeding apparatus an image forming apparatus comprising Rukoto such as an individually settable by the control of the drive speed. The image forming apparatus according to claim 1, the first sheet detection for detecting the presence or absence of the conveying path upstream near the paper from the confluence of the conveying path from the conveying path downstream and in the straight sheet feeding device of the main feeder An image forming apparatus comprising: a second sheet detecting device that detects the presence / absence of a sheet downstream of a transport path of the straight sheet feeder and upstream of the transport path from the merging point.   3. The image forming apparatus according to claim 1, wherein the drive device is controlled to smoothly slow down when the drive switching operation of the straight sheet feeding device is performed. 4.

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