JP2009180924A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which carries out both reduction in material cost and productivity while preventing occurrence of needless toner consumption when paper runs out. <P>SOLUTION: The image forming apparatus includes: a plurality of photoreceptor drums 2; a rotational transfer belt 9; a paper transfer unit 8 which is arranged more on the downstream side than a photoreceptor drum 2d on the most downstream side; a storing means 14 for the paper; and a toner image transporting path K3 extending from a toner image transferring position of the most downstream side photoreceptor drum 2d to the paper transfer unit 8, which is longer than paper supplying paths K1 and K2 extending from a leading tip of the paper which is stored in the top most position in the storing means 14 to the paper transfer unit 8. In addition, a transferring action for a toner image precedes a transporting action of paper in the image forming apparatus. The storing means 14 includes a main hopper 13 and an auxiliary hopper 12 arranged so that a paper supplying path is shorter than in the main hopper 13 by a prescribed length or more. Furthermore, a detection means for detecting the existence of the paper in the main hopper 13 and a hopper switching means for carrying out paper supply from the auxiliary hopper 12 when paper runs out are provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a plotter.

Conventionally, in a multicolor image forming apparatus such as a full-color printer or a spot color printer, a plurality of image carriers are provided along the traveling direction of a rotary transfer belt composed of an endless belt, and electrostatic latent images formed on the respective image carriers In addition, a tandem method is employed in which toners of different colors are adsorbed to form a toner image and sequentially transferred onto a transfer belt.
A tandem type image forming apparatus is known that feeds paper after a predetermined time has elapsed from the start of image formation on an image carrier due to the relationship between the length of a rotary transfer belt and the length of a paper feed path. . In the case of this apparatus, during continuous printing, since image formation is performed at regular intervals, paper feeding is generally performed at regular intervals.
However, if it is determined that there is no paper by the detection sensor that checks the presence or absence of paper at the start of image formation, image formation is naturally not performed, but there is only one remaining sheet, and two or more sheets are output. In this case, when the sheet runs out after the first image is formed, the already formed second toner image is discarded without being transferred to the sheet.

As a countermeasure to this toner waste problem, a detection sensor capable of accurately detecting the remaining amount of paper in the hopper is provided, and image formation is performed when an image corresponding to the last sheet of paper is formed. A technique for stopping processing and preventing wasteful toner consumption is disclosed (for example, see Patent Document 1).
As another measure, when there is no paper after the first image is formed, the plurality of image carriers and belt cleaners that are in contact with the transfer belt are separated from the transfer belt, so that the belt A technique is disclosed in which a toner image is left on, and paper feeding is resumed when a sheet is replenished in the hopper, and printing is started using the toner image on the belt (see, for example, Patent Document 2).

JP 2003-72984 A JP 2006-78613 A

However, the technique disclosed in Patent Document 1 has a problem in that productivity is reduced because processing related to image formation is stopped when image formation corresponding to the last sheet of paper is performed. Further, the detection sensor needs to accurately grasp the remaining amount of paper that is about to run out of paper, and there is a problem that application of the detection sensor leads to an increase in the cost of the image forming apparatus.
The technique of Patent Document 2 has a problem that productivity cannot be reduced because it is not possible to shift to the next image forming operation until paper is supplied to the paper hopper after paper is detected.
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus that does not cause wasteful consumption of toner when the paper runs out while achieving both cost reduction and high productivity. The purpose is to do.

The features of the present invention, which is a means for solving the above problems, are listed below.
An image forming apparatus according to the present invention includes a plurality of image carriers, a rotary transfer belt that sequentially contacts the plurality of image carriers, and onto which a toner image on the image carrier is transferred, and the plurality of image carriers. A transfer unit disposed on the downstream side of the most downstream image carrier and transferring the toner image transferred to the rotary transfer belt to paper; storage means for housing paper; and the plurality of image carriers. The toner image transport path from the toner image transfer position of the most downstream image carrier to the transfer means is a paper feed path from the leading edge of the uppermost sheet stored in the storage means to the transfer means. In an image forming apparatus that is longer and precedes the transfer operation of the toner image before the transport operation of the uppermost sheet from the storage means, the storage means has a main hopper and a main length longer than the length in the paper feed direction. Paper path is shorter than hopper An auxiliary hopper disposed on the main hopper, and detecting means for detecting the presence or absence of paper in the main hopper, and when the detection means detects that the paper has run out, paper is fed from the auxiliary hopper And hopper switching means for switching to.

In the image forming apparatus of the present invention, when the detection unit detects that there is a sheet during the paper feeding operation from the auxiliary hopper after the main hopper runs out of paper, the hopper switching unit Switching is performed so as to feed paper from the main hopper.
Further, in the image forming apparatus of the present invention, when the feeding operation from the auxiliary hopper exceeds a certain number, the hopper switching means switches from the feeding operation from the auxiliary hopper to the feeding operation from the main hopper. A warning lamp is lit to make a paper supply request to the auxiliary hopper.

  In the image forming apparatus as the means for solving the above problem, wasteful consumption of toner is not generated when the paper runs out while satisfying both cost saving and high productivity.

The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

First, an outline of a four-color full-color image forming apparatus will be described with reference to FIG. The image forming apparatus includes four image forming units 1 a, 1 b, 1 c, and 1 d arranged along the traveling direction of the rotary transfer belt 9. The image forming unit 1a includes a photosensitive drum 2a as an image carrier, a drum charger 3a, an exposure device 4a, a developing device 5a, a transfer device 6a, a cleaning device 7a, and the like. The image forming units 1b to 1d are also configured similarly to 1a. The image forming units 1a to 1d form images of different colors, for example, 1a is yellow, 1b is magenta, 1c is cyan, and 1d is black.
When the photosensitive drum 2a receives a start instruction signal for an image forming operation from the apparatus control unit, the photosensitive drum 2a starts rotating and continues rotating until the image forming operation ends. When the photosensitive drum 2a starts rotating, a high voltage is applied to the drum charger 3a, and negative charges are uniformly charged on the surface of the photosensitive drum 2a.

Then, an optical image including character data and graphic data converted into a dot image is emitted as laser light from the exposure device 4a and irradiated onto the surface of the photosensitive drum 2a. When the portion where the charge is reduced on the photosensitive drum 2a reaches the position facing the developing device 5a by the irradiation of the laser beam from the exposure device 4a, the portion where the charge is reduced on the photosensitive drum 2a is charged with a negative charge. The attracted toner is attracted to form a toner image.
When the toner image formed on the photosensitive drum 2a reaches the transfer device 6a, the toner image is transferred onto the rotary transfer belt 9 by the action of a high voltage applied to the transfer device 6a. Note that the toner remaining on the photosensitive drum 2a without being transferred to the rotary transfer belt 9 even after passing through the toner image transfer position is cleaned by the cleaning device 7a. The image forming apparatus prepares for the next image forming operation.

An image forming operation is similarly performed in the image forming unit 1b following the image forming unit 1a, and the toner image formed on the photosensitive drum 2b is applied to the rotary transfer belt 9 by the action of a high voltage applied to the transfer device 6b. Is transcribed.
At this time, the timing at which the image formed by the image forming unit 1a and transferred onto the rotary transfer belt 9 reaches the transfer device 6b and the toner image formed on the photosensitive drum 2b are transferred to the rotary transfer belt 9. By matching the transfer timing, the toner images formed by the image forming unit 1 a and the image forming unit 1 b overlap on the rotary transfer belt 9.
Similarly, a full color image is formed on the rotary transfer belt 9 by superimposing the toner images formed by the image forming units 1 c and 1 d on the rotary transfer belt 9.

A sheet transfer device 8 serving as transfer means is provided downstream of the most downstream photosensitive drum 2d among the plurality of photosensitive drums 2a, 2b, 2c, and 2d. The sheet transfer device 8 is a device for transferring the toner image transferred to the rotary transfer belt 9 to a sheet. At the same time when the full-color image reaches the paper transfer device 8, the paper P conveyed from the storage means 14 that stores the paper reaches the paper transfer device 8 and is rotated and transferred by the action of a high voltage applied to the paper transfer device 8. The full color image on the belt 9 is transferred onto the paper P. When the paper P is conveyed to the fixing device 10, the toner image on the paper is melted and fixed on the paper P. The storage means 14 includes a main hopper 13 and an auxiliary hopper 12 that is disposed so that the paper feed path is shorter than the main hopper 13 in the feed direction of the paper P. Here, the paper feed path refers to a path from the leading edge of the uppermost sheet stored in the storage unit 14 to the sheet transfer unit 8. A paper feed path from the main hopper 13 is indicated by K1 in the figure, and a paper feed path from the auxiliary hopper 12 is indicated by K2 in the figure. In addition, a toner image transport path from the toner image transfer position of the most downstream photosensitive drum 2d to the sheet transfer device 8 among the plurality of photosensitive drums 2a, 2b, 2c, and 2d is indicated by K3 in the figure.
On the other hand, after the full-color image passes through the paper transfer unit 8, toner that is not transferred adheres to the rotary transfer belt 9, and the toner is cleaned by the belt cleaning mechanism 11.
The image forming apparatus operates so that the transfer operation of the toner image precedes the transport operation of the uppermost sheet from the storage unit 14.

Next, the control and timing sequence of the paper feeding / conveying unit for image forming data will be described with reference to FIGS.
When the image forming apparatus receives image forming data transmitted at a cycle of T1 shown in FIG. 2, an image forming data receiving process 100 is started as shown in FIG. In the image formation data reception process 100, the main hopper paper feed signal on timing timer t1 is started in process 101, and then in process 102, it is determined whether or not the received data is the first page. If it is the first page, the image forming data receiving process 100 is terminated. If it is the second page or later, the auxiliary hopper paper feed signal on timing timer t2 is started in process 103, and the process is terminated.

Next, as shown in FIG. 2, the main hopper paper feed signal is turned on in response to the timeout of t1, and the main hopper paper feed process 105 shown in FIG. 5 is started. When the main hopper paper feed process 105 is activated, a paper empty check timer T3 is started in process 106. Further, the auxiliary hopper sheet feeding mode is checked in the process 107, and if the sheet feeding mode is the auxiliary hopper, the main hopper sheet feeding process 105 is ended as it is, but if the auxiliary hopper sheet feeding mode is not set, that is, the main hopper sheet feeding mode. In this case, after the main hopper paper feed signal is turned on in process 108, the main hopper paper feed process 105 is terminated.
Further, since the next page image data is received while the paper empty check timer T3 is started, the image data reception processing 100 is started, and the next page main hopper paper feed signal on timing timer t1 and The auxiliary hopper paper feed signal on timing timer t2 for the page is started.

Next, when the paper empty check timer T3 shown in FIG. 2 times out, as shown in FIG. 6, the paper check processing 110 is started, and in step 111, the presence or absence of paper in the main hopper is checked. At this time, when the main hopper is empty, that is, when the paper is out, in step 112, the auxiliary hopper paper feed mode is set and the paper check processing 110 is ended. If the main hopper is not empty in process 111, the auxiliary hopper paper feed timing timer t2 is stopped in process 113, the main hopper paper feed mode is set in process 114, and the paper check process 110 is terminated. .
Next, when the auxiliary hopper paper feed timing timer t2 times out, the auxiliary hopper paper feed process 120 shown in FIG. 7 is started. In process 121, the auxiliary hopper paper feed signal is turned on (see FIG. 2), and the auxiliary hopper paper feed process 120 ends.

In FIG. 2, the image data reception processing 100 is executed upon reception of image data on the third page, and the main hopper paper feed signal on timing timer t1 and the auxiliary hopper paper feed signal on timing timer t2 are started. When the main hopper paper feed signal ON timing timer t1 times out, the main hopper paper feed processing 105 shown in FIG. 5 is executed, and the paper empty check timer T3 (see FIG. 2) is started. In this case, since the judgment of processing 107 is not the auxiliary hopper paper feeding mode, the main hopper paper feeding signal is turned on in processing 108 and the main hopper paper feeding processing 105 is ended. Next, when the paper empty check timer T3 times out, the paper check process 110 shown in FIG. 6 is started, and the process 111 detects that the main hopper is out of paper, so the process proceeds to process 112 and the auxiliary hopper paper feed mode is set. Then, the paper check process 110 is completed. In this case, since the auxiliary hopper paper feed signal on timing timer t2 does not stop until the main hopper is determined not to be empty in the process 111 due to paper feed to the main hopper and the like, the time-out of t2 is not stopped. The auxiliary hopper paper feed process 120 is executed as an opportunity, the auxiliary hopper paper feed signal is turned on in process 121, and the auxiliary hopper paper feed process 120 ends.
By this series of flows, when the main hopper runs out of paper during feeding from the main hopper, the processing is switched to the feeding processing from the auxiliary hopper.

As detection means for detecting the presence or absence of paper in the main hopper, a simple means is preferable from the viewpoint of cost reduction, and it is only necessary to determine only the presence or absence of paper. For example, an optical sensor with low sensitivity can be used. Of course, as described in Patent Document 1, a light emitting element and a light receiving element are provided so as to sandwich a sheet set in the main hopper or the auxiliary hopper, and detection can be performed based on the amount of light received by the light receiving element. This method can detect not only the presence / absence of a sheet but also the remaining number of sheets, but the detection sensor becomes expensive.
As the hopper switching means for switching so as to feed paper from the auxiliary hopper when it is detected that the sheet is out of paper, for example, the feeding roller of the main hopper and the feeding roller of the auxiliary hopper are rotated. Known means including a stepping motor and a switch circuit using a transistor can be used. The hopper switching means of the present embodiment can perform switching from the main hopper to the auxiliary hopper and switching from the auxiliary hopper to the main hopper.

Next, when the detecting means detects that there is paper during the paper feeding operation from the auxiliary hopper after the main hopper runs out of paper, the hopper switching means switches to feed paper from the main hopper. Will be described.
In FIG. 3, the image data reception processing 100 shown in FIG. 4 is executed upon reception of image data on page N + 1, and a main hopper paper feed signal on timing timer t1 and an auxiliary hopper paper feed signal on timing timer. Start t2. When the main hopper paper feed signal on timing timer t1 times out, the main hopper paper feed process 105 shown in FIG. 5 is executed to start the paper empty check timer T3. In this case, since the determination in the process 107 is the auxiliary hopper paper feed mode, the main hopper paper feed process 105 is terminated. Next, when the paper empty check timer T3 times out, the paper check process 110 shown in FIG. 6 is started, and the process 111 detects the presence of paper in the main hopper. t2 is stopped, the main hopper paper feed mode is set in processing 114, and the paper check processing 110 is terminated.
By this series of flows, when paper is supplied to the main hopper during paper feeding from the auxiliary hopper, the processing is switched to paper feeding processing from the main hopper.

By performing the operation described above, even if it is detected that the main hopper is out of paper, the control is performed to switch the paper feed destination to the auxiliary hopper, so that the written image data is not wasted and the paper feed destination hopper is switched. Productivity is good because there is no waiting time. In other words, it is possible to provide an image forming apparatus that achieves both cost saving and high productivity and does not cause unnecessary toner consumption when the paper runs out.
In the image forming apparatus of the present embodiment, when the feeding operation from the auxiliary hopper exceeds a certain number, the hopper switching unit switches from the feeding operation from the auxiliary hopper to the feeding operation from the main hopper, At that time, a warning lamp may be lit to make a paper supply request to the auxiliary hopper. In this way, it is possible to prevent the auxiliary hopper from running out of paper.

  Further, in the present embodiment, the form using the two-stage sheet feeding cassette of the main hopper and the auxiliary hopper has been described, but the present invention may be applied to an image forming apparatus provided with three or more sheet feeding cassettes. For example, one of three paper feeding cassettes may be a main hopper and one may be an auxiliary hopper. Alternatively, one may be a main hopper, one may be an auxiliary hopper, and one may be a second auxiliary hopper that assists the auxiliary hopper as a main hopper. The relationship between the main hopper and the auxiliary hopper of the present invention may be included, and the present invention is not limited to the above embodiment.

FIG. 1 is an explanatory view showing an embodiment of the image forming apparatus of the present invention. FIG. 2 is a timing chart of the sheet feeding / conveying unit of the image forming apparatus of FIG. FIG. 3 is a timing chart of the sheet feeding / conveying unit of the image forming apparatus of FIG. FIG. 4 is an explanatory diagram showing a part of the operation flow of the sheet feeding / conveying section in the image forming apparatus of FIG. FIG. 5 is an explanatory diagram showing a part of the operation flow of the sheet feeding / conveying section in the image forming apparatus of FIG. FIG. 6 is an explanatory diagram showing a part of the operation flow of the sheet feeding / conveying section in the image forming apparatus of FIG. FIG. 7 is an explanatory diagram showing a part of the operation flow of the sheet feeding / conveying section in the image forming apparatus of FIG.

Explanation of symbols

1a, 1b, 1c, 1d Image forming unit 2a, 2b, 2c, 2d Photosensitive drum 3a, 3b, 3c, 3d Drum charger 4a, 4b, 4c, 4d Exposure device 5a, 5b, 5c, 5d Developer 6a, 6b , 6c, 6d Transfer device 7a, 7b, 7c, 7d Cleaning device 8 Paper transfer device 9 Rotating transfer belt 10 Fixing device 11 Belt cleaning mechanism 12 Auxiliary hopper 13 Main hopper 14 Storage means K1, K2 Paper feed path K3 Toner image conveyance path P paper

Claims (3)

A plurality of image carriers;
A rotary transfer belt that sequentially contacts the plurality of image carriers and to which a toner image on the image carrier is transferred;
A transfer unit disposed on the downstream side of the most downstream image carrier among the plurality of image carriers, and transferring the toner image transferred to the rotary transfer belt to a sheet;
Storage means for storing paper;
A toner image transport path from the toner image transfer position of the most downstream image carrier among the plurality of image carriers to the transfer unit is transferred from the leading edge of the uppermost sheet stored in the storage unit. In the image forming apparatus, which is longer than the paper feed path leading to the means, and precedes the transfer operation of the toner image prior to the transport operation of the uppermost sheet from the storage means,
The storage means includes a main hopper, and an auxiliary hopper arranged so that the paper feed path is shorter than the main hopper having a length equal to or longer than the length in the paper feeding direction,
Detection means for detecting the presence or absence of paper in the main hopper;
Hopper switching means for switching so as to feed paper from the auxiliary hopper when it is detected by the detection means that paper has run out;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
During the paper feeding operation from the auxiliary hopper after the main hopper runs out of paper, when the detecting means detects that there is paper, the hopper switching means performs switching so as to feed paper from the main hopper. An image forming apparatus. The image forming apparatus according to claim 2.
When the feeding operation from the auxiliary hopper exceeds a certain number of sheets, the hopper switching means switches from the feeding operation from the auxiliary hopper to the feeding operation from the main hopper, and warns to make a paper supply request to the auxiliary hopper. An image forming apparatus characterized in that a lamp is lit.

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