JP2021135339A - Image forming apparatus - Google Patents

Abstract

To allow improvement in productivity without increasing the conveyance speed of a sheet.SOLUTION: An image forming apparatus 1 comprises: a sheet detection sensor (paper feeding sensor 146C) for sheet-to-sheet interval adjustment that is provided at a position separated toward the upstream in a sheet conveyance direction from a registration roller pair 191 by a length obtained by adding a predetermined sheet-to-sheet distance to the length in the sheet conveyance direction of a preset paper size (A4 size); and a control unit 100 that, even when a preceding sheet P1 stops at the registration roller pair 191, does not stop feeding of a subsequent sheet P2 at that time, and when a leading end of the subsequent sheet P2 is detected to have reached a detection position of the paper feeding sensor 146C, stops the feeding of the subsequent sheet P2 to reduce an interval between a rear end of the preceding sheet P1 and the leading end of the subsequent sheet P2.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus, and more particularly to control when continuously transporting paper.

Patent Document 1 below describes a technique for accurately generating the deflection of the paper at the position of the resist roller by adjusting the transport speed of the paper. Further, Patent Document 2 below describes a technique for controlling the drive timing and the stop timing of the transport rollers provided in each of the paper feed units with high accuracy.

Further, Patent Document 3 below describes a technique for preventing the occurrence of so-called hollowing out, which is erroneous detection that there is no paper even though the paper has passed over the resist sensor. Then, Patent Document 4 below describes a technique for preventing a decrease in the productivity of the apparatus due to a decrease in the transfer speed due to aged deterioration of the rollers involved in the paper transfer.

JP-A-2018-193141 Japanese Unexamined Patent Publication No. 2015-102564 Japanese Unexamined Patent Publication No. 2019-066504 Japanese Unexamined Patent Publication No. 2003-095460

In recent years, image forming devices such as copiers and multifunction devices have been required to improve the number of image forming sheets per unit time. That is, improvement in productivity is required. The above-mentioned Patent Documents 1 to 4 describe techniques for more appropriately controlling the transfer of paper, and by using these techniques, the transfer speed of the paper can be increased and the number of images formed per unit time can be increased. It will be possible to increase it. However, if the transport speed is increased, the amount of heat given to the paper at the fixing portion is reduced, which may cause fixing failure. To solve this problem, the amount of heat at the fixing portion may be increased, but if the amount of heat is increased, the power consumption increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the productivity of image formation without increasing the paper transport speed or the amount of heat at the fixing portion.

The image forming apparatus according to one aspect of the present invention conveys a paper feeding unit having a paper feed cassette for accommodating paper, an image forming unit for forming an image on the paper, and paper fed from the paper feed cassette. The image along the transport path, the transport section provided in the transport path, and the transport section for transporting the paper from the paper feed cassette toward the image forming position where the image is formed by the image forming section, and the transport path. A pair of resist rollers provided on the upstream side of the forming position in the paper conveying direction for stopping the conveyed paper and re-delivering the paper to the image forming position, and a pair of papers that have reached the registration roller pair. A control unit that temporarily stops and adjusts the timing of transporting the paper to the image forming position to restart the feeding of the paper to the image forming position, and a preset length of the paper size in the paper transport direction are set in advance. The length obtained by adding the paper-to-paper distances, which is set to be shorter than the paper-to-paper distance required to achieve the target number of images to be formed per unit time, in the paper transport direction from the resist roller pair. A paper detection sensor for adjusting paper spacing provided at a position on the upstream side of the paper is provided, and the control unit further follows the paper at this point when the paper is stopped by the resist roller pair. When the paper detection sensor detects that the tip of the succeeding paper has reached the detection position of the paper by the paper detection sensor without stopping the paper feeding of the succeeding paper at the paper feed unit or the transport unit. In addition, when the paper feed unit or the transport unit stops the paper feed of the succeeding paper and the transport of the preceding paper is restarted by the registration roller pair, the paper feed of the succeeding paper is performed by the paper feed unit or the paper feed unit or the above. It is restarted by the transport unit.

Conventionally, when a plurality of sheets are continuously fed into the transport path, when the preceding paper is stopped by the resist roller pair, the feeding of the succeeding paper following the preceding paper is stopped at that time.

According to the present invention, even if the preceding paper is stopped by the pair of resist rollers, the paper feeding of the succeeding paper is not stopped at that time, the paper feeding of the succeeding paper is continued for a while, and the succeeding paper is placed at the detection position of the paper detection sensor. Since the paper is stopped when the tip reaches, the distance between the preceding paper and the succeeding paper is reduced to a paper-to-paper distance shorter than the paper-to-paper distance required to achieve the target number of image formations per unit time. Therefore, since the distance between the preceding paper and the succeeding paper is narrower than before, in order to achieve the number of images formed per unit time without increasing the paper transport speed or the amount of heat at the fixing portion. The required time can be shortened and productivity can be improved.

It is a schematic partial front view which shows the structure of the image forming apparatus which concerns on one Embodiment of this invention. It is a figure for demonstrating the positional relationship between a pair of resist rollers and a paper feed sensor which is a paper detection sensor. It is a functional block diagram which shows schematic the main internal structure of the image forming apparatus which concerns on 1st Embodiment. It is a flowchart which shows an example of the processing performed by the control unit in the image forming apparatus which concerns on 1st Embodiment. It is a functional block diagram which shows schematic the main internal structure of the image forming apparatus which concerns on 2nd Embodiment.

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic partial front view showing the structure of the image forming apparatus according to the first embodiment of the present invention. The image forming apparatus 1 is a multifunction device having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function, and includes an image forming unit 12, a paper feeding unit 14, and a conveying unit 19. It is composed of.

The image forming unit 12 includes an intermediate transfer unit 120, a photoconductor drum 121 for black, magenta, cyan, and yellow, and a secondary transfer roller 210. The intermediate transfer unit 120 includes an intermediate transfer belt 125, a driving roller 125A, a driven roller 125B, and a primary transfer roller 126 on which a toner image is transferred on the outer peripheral surface thereof.

The intermediate transfer belt 125 is stretched between the drive roller 125A and the driven roller 125B, and is driven by the drive roller 125A in a state of being in contact with the peripheral surface of the photoconductor drum 121, while synchronizing with the photoconductor drum 121. Run endlessly.

The toner images of each color (black, magenta, cyan, yellow) transferred on the intermediate transfer belt 125 are superposed on the intermediate transfer belt 125 by adjusting the transfer timing to obtain a color toner image.

The secondary transfer roller 210 transfers a color toner image formed on the surface of the intermediate transfer belt 125 from the paper feed unit 14 to the transfer path 190 at the nip portion N1 with the drive roller 125A sandwiching the intermediate transfer belt 125. It is transferred to the paper P that has been conveyed through the paper P.

The transport unit 19 is a resist provided along the transport path 190 and the transport path 190 on the upstream side in the paper transport direction with respect to the nip portion N1 (that is, the image forming position where the image is formed by the image forming unit 12). The roller pair 191 and the resist sensor 192 provided on the upstream side of the resist roller pair 191 in the paper transport direction, the intermediate roller pair 193 provided between the resist roller pair 191 and the paper feed unit 14, and the intermediate roller. It is provided with an intermediate sensor 194 provided on the upstream side in the paper transport direction with respect to the pair 193.

The resist roller pair 191 is for stopping the paper P conveyed by the nip portion N2 formed by the resist roller pair 191 and retransmitting the paper P to the nip portion N1. The resist sensor 192 is provided to adjust the stop timing of the paper P.

The intermediate roller pair 193 is for transporting the paper P toward the resist roller pair 191. The intermediate sensor 194 is provided to detect a paper jam.

The resist sensor 192, the intermediate sensor 194, and the paper feed sensors 146A to 146C described later are known to include, for example, a light emitting element and a light receiving element for detecting the reflected light from the paper P of the light emitted from the light emitting element. It consists of a reflective photoelectric sensor and detects the front edge and the rear edge of the paper P.

The paper feed unit 14 includes a plurality of paper feed cassettes 141A to 141C (hereinafter, also simply referred to as “paper feed cassette 141”). The paper cassettes 141A to 141C are referred to as a pickup roller 142, a feed roller 143, a retard roller 144 arranged to face the feed roller 143, and a transport roller pair 145A to 145C (hereinafter, also simply referred to as "convey roller pair 145"). ) And the paper feed sensors 146A to 146C (hereinafter, also simply referred to as “paper feed sensor 146”).

The pickup roller 142 is for picking up the paper P housed in the paper feed cassette 141. The feed roller 143 and the retard roller 144 are for separating the sheets P picked up by the pickup roller 142 one by one and transporting them toward the transport roller pair 145.

The transport roller pair 145 is for transporting the paper P toward the resist roller pair 191. Each of the paper feed sensors 146 is arranged on the downstream side in the paper transport direction from the transport roller pair 145, detects the paper P passing through the transport roller pair 145, and determines the completion of paper feed from the paper feed cassette 141. It is provided.

When the paper P housed in the paper feed cassette 141 is continuously fed, generally, when the rear end of the preceding paper P (preceding paper P1) passes through the paper feed sensor 146, it continues to the preceding paper P1. The pickup of the succeeding paper P2 is started. This control is performed by the control unit 100 (see FIG. 3), which will be described later.

When the paper P housed in the first-stage paper cassette 141A, which is the uppermost stage, is continuously fed, the distance from the paper cassette 141A to the resist roller vs. 191 is short, so that the tip of the preceding paper is resisted. Even when the roller pair 191 is reached, the rear end generally remains in the paper cassette 141A. Therefore, when the tip of the preceding paper reaches the resist roller pair 191, the succeeding paper is not yet fed from the paper feed cassette 141A.

Similarly, when the paper P housed in the second-stage paper feed cassette 141B is continuously fed, the distance from the paper feed cassette 141B to the resist roller vs. 191 is short, so that the tip of the preceding paper is When the resist roller pair 191 is reached, the subsequent paper is not yet fed from the paper cassette 141B.

However, when the paper P housed in the third-stage paper feed cassette 141C is continuously fed, the distance from the paper feed cassette 141C to the resist roller vs. 191 is long, so that the rear end of the preceding paper is After exiting the paper feed cassette 141C and passing through the detection position of the paper feed sensor 146C (that is, after the start of paper feeding of the succeeding paper), the tip of the preceding paper reaches the resist roller pair 191. Therefore, as shown in FIG. 1, the succeeding paper P2 is fed before the tip of the preceding paper P1 reaches the resist roller pair 191.

If the preceding paper P1 is stopped but the succeeding paper P2 continues to be fed without stopping, the succeeding paper P2 may overlap with the preceding paper P1 and a paper jam may occur. Therefore, conventionally, the preceding paper P1 When was stopped, the succeeding paper P2 was also stopped.

By the way, the paper feeding speed when the paper P housed in the paper feed cassette 141 is fed into the transport path 190 is often slightly slower than the transport speed in the transport path 190. There are two main reasons for this.

One is that the pickup roller 142 is not a pair of rollers, so that the carrying force is weak. The other is that the feed roller 143 and the retard roller 144 are paired, but since the paper P needs to be separated one by one, the retard roller 144 is braked, which becomes a load. This is because the speed drops.

When the paper feeding speed becomes slower than the conveying speed, the distance (distance between papers) between the rear end of the preceding paper P1 and the front end of the succeeding paper P2 increases. As the distance between papers increases, the number of images formed per unit time decreases, which may reduce productivity.

For example, consider a control that satisfies an image formation of 50 sheets / min with a paper P having a transport speed of 288 mm / sec and an A4 size (length in the paper transport direction of 297 mm). In order to satisfy 50 sheets / min, it is necessary to form an image once every 1.2 seconds and to convey the paper P accordingly. To achieve this, the inter-paper distance is 48.6 mm (= 288 mm / sec x 1.2 sec-297 mm. This inter-paper distance is the inter-paper distance required to achieve the target number of images formed per unit time. Example) It is necessary to keep it within. Here, if the distance between the papers increases and exceeds 48.6 mm, the transport of the paper P will be delayed with respect to the timing of image formation, and the productivity will decrease.

Although it is possible to prevent a decrease in productivity by increasing the transport speed of the paper P, as explained in the item of "Problems to be Solved by the Invention", the fixing portion 13 (see FIG. 3) described later will be used. It is necessary to increase the amount of heating, which increases power consumption. In this embodiment, the productivity of image formation is improved by reducing the distance between papers without increasing the transport speed (the power consumption for fixing is not increased). However, if the distance between the papers is too small, the preceding paper P1 and the succeeding paper P2 may overlap each other, causing a paper jam.

FIG. 2 is a diagram for explaining the positional relationship between the resist roller pair 191 and the paper feed sensor 146C provided in the third stage paper feed cassette 141C. The paper feed sensor 146C has a length (297 mm) obtained by adding a predetermined paper-to-paper distance D to a preset paper size (for example, A4 size most frequently used in the business scene) in the paper transport direction. Only L is provided at a position separated from the resist roller pair 191 (nip portion N2 formed by the nip portion N2) on the upstream side in the paper transport direction.

The predetermined inter-paper distance D is obtained from the distance between the rear end of the preceding paper P1 and the front end of the succeeding paper P2, which is generated when the succeeding paper P2 is fed from the paper feed cassette 141C, which is calculated in advance. Is also set short. For example, the predetermined paper-to-paper distance D is set to 10 mm. The paper-to-paper distance D is a length obtained by adding a predetermined paper-to-paper distance to a preset paper size in the paper transport direction within the scope of the patent claim, and is a target image per unit time. This is an example of a length set shorter than the paper-to-paper distance required to achieve the number of sheets to be formed. The paper feed sensor 146C is an example of a paper detection sensor for adjusting paper spacing within the scope of claims.

FIG. 3 is a functional block diagram schematically showing a main internal configuration of the image forming apparatus according to the first embodiment. The image forming apparatus 1 includes a control unit 10, a document feeding unit 6, a document reading unit 5, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, an operation unit 47, and a conveying unit 19. ..

The document feeding unit 6 is configured to be openable and closable on the upper surface of the document reading unit 5 by a hinge or the like shown in the drawing. Functions as a holding cover.

A case where the document reading operation is performed by the image forming apparatus 1 will be described. The document reading unit 5 optically reads the image of the document supplied to the document reading unit 5 by the document feeding unit 6 or the document placed on the platen glass, and generates image data. The image data generated by the document reading unit 5 is stored in an image memory or the like (not shown).

A case where the image forming operation is performed by the image forming apparatus 1 will be described. The image forming unit 12 feeds paper from the paper feeding unit 14 based on the image data generated by the document reading operation, the image data stored in the image memory or the like, the image data received from the computer connected to the network, and the like. Then, a toner image is formed on the paper P as a recording medium conveyed through the transfer path 190 of the transfer unit 19.

The fixing unit 13 heats and pressurizes the paper P on which the toner image is formed by the image forming unit 12 to fix the toner image on the paper P, and the paper P subjected to the fixing treatment is ejected (not shown). It is discharged to the tray.

As shown in FIG. 1, the paper feed unit 14 includes a paper feed sensor 146, and the transport unit 19 includes a resist sensor 192 and an intermediate sensor 194. Then, the detection signal indicating the detection result by the paper feed sensor 146, the resist sensor 192, and the intermediate sensor 194 is output to the control unit 10.

The operation unit 47 receives instructions such as an image formation operation execution instruction from the operator for various operations and processes that can be executed by the image forming apparatus 1. The operation unit 47 includes a display unit 473 that displays operation guidance and the like to the operator. Further, the operation unit 47 receives an input of an instruction from the user based on an operation (touch operation) by the user on the operation screen displayed on the display unit 473 via the touch panel of the display unit 473.

The display unit 473 is composed of an LCD (Liquid Crystal Display) or the like. The display unit 473 includes a touch panel. When the operator touches a button or key displayed on the screen, the touch panel receives an instruction associated with the touched position.

The control unit 10 includes a processor, a RAM (Random Access Memory), a ROM (Read Only Memory), and a dedicated hardware circuit. The processor is, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), an MPU (Micro Processing Unit), or the like. The control unit 10 includes a control unit 100.

The control unit 10 functions as a control unit 100 by operating the processor according to a control program stored in an HDD (Hard Disk Drive) or an SSD (Solid State Drive). However, the control unit 100 can be configured by a hardware circuit, regardless of the operation according to the control program by the control unit 10. Hereinafter, the same applies to each embodiment unless otherwise specified.

The control unit 100 controls the overall operation of the image forming apparatus 1. The control unit 100 is connected to a document feeding unit 6, a document reading unit 5, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, an operation unit 47, and a transport unit 19, and performs drive control and the like of each of these units. ..

For example, the control unit 100 forms an image on the paper P by controlling the paper feeding unit 14, the conveying unit 19, the image forming unit 12, and the like. Specifically, the control unit 100 causes the pickup roller 142 to pick up the paper P stored in the paper feed cassette 141 by controlling the motor, the clutch, etc., which are the drive sources of the paper feed unit 14, and picks up the paper P. The paper P is separated one by one by the feed roller 143 and the retard roller 144, and is sent out to the transport path 190 by the transport roller pair 145.

Further, the control unit 100 uses the intermediate roller pair 193 to direct the paper P supplied to the transport path 190 toward the resist roller pair 191 by controlling the motor, the clutch, etc., which are the drive sources of the transport unit 19. The paper P is conveyed toward the nip portion N1 of the image forming portion 12 by using the resist roller pair 191.

Further, when the control unit 100 detects that the tip of the paper P has reached the detection position of the resist sensor 192 based on the detection signal obtained from the resist sensor 192, the resist roller pair 191 is set and registered in advance. The time for the paper P to reach the resist roller pair 191 is calculated based on the distance between the paper P and the resist sensor 192 and the transport speed of the paper P.

Then, based on the calculated time, the control unit 100 determines the intermediate roller pair 193 and the transport roller pair 145A at the timing when a small amount of deflection is generated in the paper P after the tip of the paper P reaches the resist roller pair 191. By stopping the rotation of 145B, the paper P is temporarily stopped by the resist roller pair 191 and then the resist roller pair 191 is transferred to the paper P at the timing of transferring the image formed on the intermediate transfer belt 125 to the paper P. The paper P is rotated and conveyed toward the nip portion N1.

Generally, when the preceding paper P (preceding paper P1) is stopped by the resist roller pair 191, control is performed to stop the succeeding paper P2 at that time, but in the present embodiment, the control unit 100 controls the succeeding paper P2. P2 is not stopped by the transport unit 19 or the paper feed unit 14 (at least one of them; the same applies hereinafter), the paper feed of the subsequent paper P2 is continued by the transport unit 19 or the paper feed unit 14, and the paper feed sensor 146C is at the detection position. When it is detected that the tip of the succeeding paper P2 has reached, the conveying unit 19 or the paper feeding unit 14 temporarily stops the feeding of the succeeding paper P2, and the resist roller pair 191 adjusts the feeding of the preceding paper P1 in accordance with the above timing. When the feeding is restarted, the feeding unit 19 or the paper feeding unit 14 restarts the feeding of the succeeding paper P2.

However, control is performed when paper of a paper size having a different length from the preset paper size (A4 size is taken as an example here) and the length in the paper transport direction are continuously fed into the transport path 190. When the preceding paper P1 stops at the resist roller pair 191, the unit 100 stops the feeding of the succeeding paper P2 at that time. For example, the control unit 100 detects the paper size from the paper size indicated by the paper size designation instruction used for image formation, which is input to the operation unit 47 by the user when the user inputs the execution instruction of the image forming operation. ..

Next, an example of the processing performed by the control unit 10 in the image forming apparatus 1 according to the first embodiment will be described with reference to the flowchart shown in FIG. This process is a process performed by the control unit 100 when A4 size paper is continuously fed from the third-stage paper cassette 141C.

The control unit 100 determines whether or not the tip of the paper P has reached the detection position of the resist sensor 192 based on the detection signal from the resist sensor 192 (S1), and the detection signal from the resist sensor 192 detects the paper. When, it is determined that the tip of the paper P has reached the detection position of the resist sensor 192, and in this case (YES in S1), after the tip of the paper P reaches the resist roller pair 191 as described above, the paper By stopping the rotation of the intermediate roller pair 193 and the transport roller pairs 145A and 145B at the timing when a small amount of deflection is generated in P, the paper P (preceding paper P1) is stopped by the resist roller pair 191 (S2).

Subsequently, the control unit 100 detects the paper feed sensor 146C at the tip of the succeeding paper P2 following the preceding paper P1 based on the detection signal from the paper feed sensor 146C that serves as a paper detection sensor for paper spacing adjustment. It is determined whether or not the position has been reached (S3), and when the detection signal from the paper feed sensor 146C indicates paper detection, it is determined that the tip of the subsequent paper P2 has reached the detection position of the paper feed sensor 146C. In this case (YES in S3), the subsequent paper P2 is stopped by stopping the pickup roller 142, the feed roller 143, the retard roller 144, or the transport roller pair 145C (at least one or more; the same applies hereinafter). ).

Subsequently, the control unit 100 rotates the resist rollers 191 and the intermediate rollers 193 and the transport rollers 145A and 145B in accordance with the timing of transferring the image formed on the intermediate transfer belt 125 to the preceding paper P1. , The transport of the preceding paper P1 is restarted (S5), and the pickup roller 142, the feed roller 143, the retard roller 144, or the transport roller pair 145C is rotated to restart the feeding of the succeeding paper P2 (S6). After this, the process ends.

According to the first embodiment, even if the transfer of the preceding paper P1 is stopped at the resist roller pair 191, the feeding of the succeeding paper P2 is not stopped at this point, and the feeding of the succeeding paper P2 is continued for a while. Since the paper feed sensor 146C, which acts as a paper detection sensor, stops when the tip of the succeeding paper P2 reaches the detection position, the distance between the preceding paper and the succeeding paper achieves the target number of image formations per unit time. It shrinks to a paper-to-paper distance that is shorter than the conventional paper-to-paper distance required to do so. Therefore, since the distance between the preceding paper P1 and the succeeding paper P2 is narrower than in the conventional case, the unit time is not required to increase the conveying speed of the paper P or increase the heating amount in the fixing portion 13. The time required to achieve the number of images formed per image can be shortened, and productivity can be improved.

Further, since the paper feed sensor 146C is also used as a paper detection sensor for adjusting the space between the preceding sheets P1 and the following sheets P2, the apparatus can be simplified.

By the way, the paper cassette 141 may be provided as standard equipment in the main body of the image forming apparatus 1 in advance, or may be provided as an optional device. In particular, the lower third-stage paper cassette 141C (that is, the paper cassette having a longer distance from the resist roller vs. 191) is often an optional device.

FIG. 5 is a functional block diagram schematically showing a main internal configuration of the image forming apparatus according to the second embodiment. The image forming apparatus according to the second embodiment includes a communication unit 31 for transmitting and receiving information between the image forming apparatus according to the first embodiment shown in FIG. 3 and an optional device provided in the apparatus main body. The difference is that the third-stage paper cassette 141C is an optional device.

When the paper cassette 141C is an optional device, information transmission / reception between the control unit 10 and the paper cassette 141C is performed by serial communication instead of parallel communication. Therefore, even if the paper detection sensor is newly added to the paper feed cassette 141C, it is not necessary to provide the dedicated input / output port in the device main body of the image forming apparatus 1, so that the number of input / output ports does not increase and the device It has the advantage of avoiding the complication of. Of course, as described above, the paper feed sensor 146C may be used as the paper detection sensor.

However, since the reception of the detection signal (on / off signal) from the sensor provided on the paper cassette 141C and the transmission of the instruction signal indicating the on / off instruction of the motor, the clutch, etc. are performed by serial communication, communication is performed. There is a possibility that a delay will occur, the control timing will be deviated, and the distance between the preceding paper P1 and the succeeding paper P2 will vary.

For example, when the control unit 10 on the device main body side of the image forming apparatus 1 and the paper feed cassette 141C, which is an optional device, communicate with each other in a communication cycle of 10 msec, the control unit 10 recognizes the information from the paper feed cassette 141C. If there is a maximum delay of 10 msec and a maximum delay of 10 msec occurs before the on / off instructions for the motor, clutch, etc. are transmitted to the paper cassette 141C, a total delay of 20 msec will occur. There can also be. Therefore, the stop of the succeeding paper P2 is delayed by a maximum of 20 msec (= 0.02 sec), and when the transport speed is 288 mm / sec, the control unit 100 tells the control unit 100 that the paper feed sensor 146C is at the detection position and the tip of the succeeding paper P2 is at the detection position. Even if the transport of the succeeding paper P2 is stopped when the paper arrives, the distance between the rear end of the preceding paper P1 and the front end of the succeeding paper P2 is not the ideal 10 mm, but a maximum of 5.76 mm (= 288 mm / sec). × 0.02 sec) Subsequent paper P2 may stop only at shorter intervals.

Therefore, in the second embodiment, in consideration of the above delay time, even if the control unit 100 restarts the conveying of the preceding paper P1 (S5 shown in FIG. 4), at that time, the succeeding paper P2 is fed. The communication unit 31 waits for a preset communication delay time (communication cycle (for example, 10 mmsec) or maximum delay time (for example, 20 msec)) according to the communication cycle (10 msec) with the optional device without restarting. A signal instructing the resumption of paper feeding of the succeeding paper P2 is transmitted to the paper feed cassette 141C via. As a result, it is possible to eliminate the shortened gap and extend the paper spacing to bring it closer to the ideal distance, and prevent the gap between the rear end of the preceding paper P1 and the front end of the succeeding paper P2 from becoming too tight. ..

Further, as another embodiment, when a communication retry occurs due to electrical noise or the like, the control unit 100 calculates the communication delay time required for the retry, and further sets the communication delay time to the standby time. In addition, a signal instructing the resumption of paper feeding of the succeeding paper P2 may be transmitted to the paper feed cassette 141C via the communication unit 31.

Further, in the above embodiment, the case where the paper detection sensor (paper feed sensor 146C) is provided at the position corresponding to the A4 size is described, but as yet another embodiment, the transport corresponding to each of the different paper sizes is described. The paper detection sensor may be provided at the position of the road 190.

The present invention is not limited to the configuration of the above embodiment, and various modifications are possible. Further, in the above embodiment, a multifunction device is used as an embodiment of the image forming apparatus according to the present invention, but this is only an example, and has, for example, a copy function, a printer function, and a facsimile function. Other image forming devices may be used.

Further, the configurations and treatments shown in the above embodiments with reference to FIGS. 1 to 5 are merely one embodiment of the present invention, and the present invention is not intended to be limited to the configurations and treatments.

1 Image forming device 12 Image forming unit 14 Paper feeding unit 19 Transfer unit 31 Communication unit 100 Control unit 141 Paper feed cassette 146 Paper feed sensor 190 Transport path 191 Resist roller pair

Claims (5)

A paper feed unit with a paper feed cassette for storing paper,
An image forming part that forms an image on paper,
A transport path for transporting paper fed from the paper cassette and
A transport unit provided in the transport path and transports paper from the paper feed cassette toward an image forming position where an image is formed in the image forming portion.
A pair of resist rollers provided along the transport path on the upstream side of the image forming position in the paper transport direction for stopping the conveyed paper and re-transporting the paper to the image-forming position.
A control unit that temporarily stops the paper that has reached the resist roller pair, adjusts the timing of transporting the paper to the image forming position, and restarts the transport of the paper to the image forming position.
The length is the sum of the length of the preset paper size in the paper transport direction and the predetermined paper-to-paper distance, which is larger than the paper-to-paper distance required to achieve the target number of images to be formed per unit time. It is provided with a paper detection sensor for adjusting the paper spacing, which is provided at a position separated from the registration roller pair on the upstream side in the paper transport direction by a short set length.
Further, when the paper is stopped by the resist roller pair, the control unit does not stop the paper feeding of the subsequent paper following the paper at the paper feeding unit or the conveying unit, but by the paper detection sensor. When the paper detection sensor detects that the tip of the succeeding paper has reached the detection position of the paper, the paper feed unit or the transport unit stops the paper feed of the succeeding paper, and the preceding paper An image forming apparatus that restarts the feeding of the subsequent paper by the feeding unit or the conveying unit when the feeding is restarted by the resist roller pair. The paper feed unit has a paper feed sensor that detects the completion of paper feed from the paper feed cassette.
The image forming apparatus according to claim 1, wherein the paper feed sensor is also used as the paper detection sensor. In addition to being further equipped with a communication unit that sends and receives information to and from the optional device installed in the device body,
The paper cassette is equipped as the optional device, and the paper cassette is provided.
Even if the control unit restarts the transfer of the preceding paper by the resist roller pair, at this point, the control unit does not restart the feeding of the succeeding paper to the paper feeding unit or the conveying unit, and communicates with the optional device. A request for transmitting a signal instructing the resumption of paper feeding of the subsequent paper to the paper feeding unit or the conveying unit via the communication unit after waiting for a communication delay time set in advance according to the cycle. The image forming apparatus according to claim 1 or 2. When continuously feeding paper having a paper size different from the preset paper size and the length in the paper transport direction into the transport path by the paper feed unit,
The image according to any one of claims 1 to 3, wherein when the preceding paper is stopped by the resist roller pair, the control unit stops the feeding of the following paper by the feeding unit at this point. Forming device. The image forming apparatus according to any one of claims 1 to 3, wherein the paper detection sensor is provided at a position in the transport path corresponding to each of the different paper sizes.

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