JP4574528B2 - Image forming apparatus and paper feed control method - Google Patents

Description

  The present invention relates to an image forming apparatus and a sheet feeding control method, and more particularly to an image forming apparatus that forms an image according to an electrophotographic method and a sheet feeding control method applied to the apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus according to an electrophotographic method for visualizing image data stored in a memory by fixing toner on a recording medium, as represented by a laser beam printer or a copying apparatus, Widely used due to its quietness.

  For image formation in such an image forming apparatus, for example, a visible image is formed with a toner on a recording medium through each process of a known electrophotographic method disclosed in Patent Document 1, and finally the toner image is formed. The fixing is performed on the recording medium.

  FIG. 7 is a side sectional view showing a schematic configuration of an image forming apparatus 400 employing a conventional electrophotographic system.

  As shown in FIG. 7, a charging roller 402 for uniformly charging the surface of the photosensitive drum 400 is provided above the photosensitive drum 401 carrying the electrostatic latent image so as to contact the surface. . Further, the light beam 403 is irradiated by the light emitting means on the charged surface on the downstream side in the rotation direction of the photosensitive drum 401 from the contact position of the charging roller 402. The light emitting means includes a semiconductor laser 404 that emits laser light and a collimator lens 405 that polarizes the laser light into parallel light. Further, the light emitting means includes a polygon mirror 406 that deflects the beam light 403 so as to scan the surface of the photosensitive drum 401, and an optical lens 408 that adjusts the beam light 403 so as to form a spot on the surface. The polygon mirror 406 is controlled at a constant speed by the scanner motor 407.

  Further, an electrostatic latent image is formed on the surface of the photosensitive drum 401 by irradiating the beam light 403 according to the image data. This electrostatic latent image is developed as a toner image by a developing device 409 disposed so as to contact the photosensitive drum 401 further downstream in the rotation direction of the photosensitive drum 401 than the irradiation position of the beam light 403. This toner image is transferred onto the recording paper P as a transfer material by a transfer roller 410 disposed so as to face the photosensitive drum 401.

  The recording paper P is stored in the recording paper cassette 500 on the upstream side (lower side in FIG. 7) of the photosensitive drum 401, but can be fed manually. A paper feed roller 411 is disposed at the end of the recording paper cassette 500. The paper feed roller 411 swings up and down while rotating, picks up the recording paper P in the recording paper cassette 500, and only one uppermost paper of the recording paper P loaded by the feed retard roller 418 is transported. It is sent to. A registration roller 412 is provided in the conveyance path between the paper supply roller 411 and the transfer roller 410 to synchronize skew feeding correction of the recording paper P, image formation on the photosensitive drum 411, and recording paper conveyance. ing. The registration roller 412 feeds the recording paper P to the transfer position described above at a predetermined timing. The conveyance path on the upstream side of the paper supply roller 411, the registration roller 412, and the photosensitive drum 401 constitutes a paper supply unit of the image forming apparatus 400.

  A registration paper presence / absence detection sensor 413 is provided between the registration roller 412 and the paper feed roller 411 so that the presence / absence of the recording paper P can be detected.

  The recording paper P to which the toner image has been transferred is further conveyed to a fixing device on the downstream side (left side in FIG. 7) of the photosensitive drum 401. The fixing device includes a fixing roller 414 having a fixing heater (not shown) therein and a pressure roller 415 disposed so as to be in pressure contact with the fixing roller 414. Then, the recording paper P conveyed from the transfer unit is heated while being pressed by the pressure contact portion between the fixing roller 414 and the pressure roller 415, thereby fixing the toner image on the recording paper P to the recording paper P. A discharge paper presence / absence detection sensor 416 for confirming that the recording paper P is conveyed from the press contact portion is disposed on the downstream side of the press contact portion. Further, a paper discharge roller 417 is disposed on the downstream side of the paper discharge presence / absence detection sensor 416, and the paper discharge roller 417 discharges the recording paper P on which the image is fixed.

  As shown in FIG. 7, the image forming apparatus 400 has optional sheet feeding units 700 a and 700 b connected to the sheet feeding unit. The recording paper P is stored in the paper cassettes 701a and 701b inside the optional paper feeding units 700a and 700b, respectively. When a print signal is transmitted to the image forming apparatus 400 in a state where the paper feed location designation from the controller (not shown) is set to the optional paper feed unit, the paper feed rollers 702a and 702b swing up and down while rotating. Then, the recording paper P is picked up. Then, only one sheet of recording paper is fed into the image forming apparatus 400 by the feed retard rollers 703a and 703b. A predetermined image is formed and fixed on the fed recording paper P by the above-described image forming operation, and is discharged. Note that the driving force is supplied to the sheet feeding rollers 702a and 702b by a motor in the image forming apparatus 400.

  When continuous image formation is performed in the image forming apparatus 400, the feeding start timing of the subsequent recording paper is set as follows in order to keep the interval of the recording paper constant.

  Here, the distance from the registration sheet presence / absence detection sensor 413 to the leading end of the recording cassette 500, 701a, or 701b in which the recording sheet P is stored is L, the length of the sheet is Plen, and the interval between the recording sheet and the recording sheet. Is Pitvl and the paper transport speed is V. Also, the time from when the paper feed roller is driven until the recording paper P actually starts to move is defined as Tpick. The time (T) from the feeding of the preceding paper to the start of feeding of the next recording paper is expressed by equation (1) after the leading edge of the preceding paper is detected by the registration paper presence / absence detection sensor. .

T = (Plen + Pitvl-L) / V-Tpick (1)
In recent years, laser beam printers capable of connecting a plurality of optional paper feeding units have been sold, and a mode in which an arbitrary number of optional paper feeding units are connected in a stack according to the user's selection has become normal. As described above, the multi-stage option sheet feeding units 700a and 700b are mounted, and the longer the transport path on the upstream side, the larger the value of “L” in Expression (1), and T in Expression (1) becomes smaller. Negative value. This means that an image forming operation at a physically target interval becomes impossible.

  In order to solve this problem, it has been proposed that the paper feed start timing is performed after a predetermined time from feeding the preceding paper. That is, the time (T) from the feeding of the preceding paper to the start of feeding the next recording paper is expressed by the equation (2) from the start of feeding the preceding paper.

T = (Plen + Pitvl) / V-Tpick (2)
As a result, the recording paper can be conveyed at a constant interval even if the value of “L” becomes large due to the configuration of the paper feeding unit.
JP-A-10-114121

  However, in the above-described conventional example, when the paper feed unit including the main body paper feed port and the multi-stage optional paper feed unit provides more paper feed locations, the paper feed location on the downstream side of the transport path and the upstream side. The difference in the transport distance between the paper feeding locations increases. For this reason, there is a problem that the paper interval cannot be kept constant when the paper feeding location is switched from the downstream side to the upstream side.

  Further, when the sheet is fed from the upstream sheet feeding position, the distance to the sensor on the transport path that first passes is increased. For this reason, it is necessary to set the determination time until a paper feed failure is detected and a paper feed retry operation is performed, and the time until a paper feed failure is determined and a jam is determined as long as the upstream paper feed position. No longer. This leads to a problem of complicated control relating to paper feeding.

  The present invention has been made in view of the above-described conventional example. Even if a plurality of paper feed units are connected and paper is fed from any unit, and even if image formation is continuously performed while switching units, the present invention is suitable. It is an object of the present invention to provide an image forming apparatus and a sheet feeding control method capable of performing sheet feeding control.

  In order to achieve the above object, the image forming apparatus of the present invention has the following configuration.

That is, a plurality of paper feeding units loaded with recording media can be connected, the recording media supplied from the plurality of paper feeding units are transported through a common transport path, and an image is transferred to the transported recording media. An image forming apparatus to form, wherein the image is formed with a plurality of sensors that are provided in the common conveyance path and detect a recording medium supplied from each of the plurality of paper feeding units to the common conveyance path. A designation unit that designates a sheet feeding unit that supplies a recording medium to be recorded, and a sensor that first detects a recording medium supplied from any of the plurality of sheet feeding units to the common conveyance path among the plurality of sensors. selecting means for selecting as a reference sensor, when the image is formed on the plurality of recording media continuously, to determine whether switching is feeding unit supplying a recording medium used for image forming A determination unit, a reference sensor when said discriminating means thus sheet feed unit is determined to switches is selected by the selecting means before switching the paper feed unit, the selection after the paper feed unit is switched Adjusting means for adjusting the supply timing of the recording medium based on the distance in the common conveyance path with the reference sensor selected by the means .

According to another invention, a plurality of paper feeding units loaded with recording media can be connected, and the recording media supplied from the plurality of paper feeding units are supplied via a common conveyance path. A sheet feeding control method for an image forming apparatus for forming an image on a recording medium, comprising: a designation step for designating a sheet feeding unit that supplies a recording medium on which an image is formed; and the common conveyance path, Among the plurality of sensors that detect the recording medium supplied from each of the plurality of paper feeding units to the common conveyance path, the recording medium supplied from any of the plurality of paper feeding units to the common conveyance path Whether to switch to the paper feed unit that supplies the recording medium used for image formation when selecting the sensor to be detected first as the reference sensor, and when forming images on a plurality of recording media continuously no A determination step of determining a reference sensor selected in the selection step before the sheet feed unit is switched, the common conveying path of the reference sensor selected in the selecting step after the paper feed unit is switched And an adjusting step for adjusting the supply timing of the recording medium based on the distance in the paper feed control method.

  Therefore, according to the present invention, in a configuration in which a plurality of paper feeding units are connected, there is an effect that it is possible to appropriately control the paper feeding of the recording medium regardless of the paper feeding unit.

  Hereinafter, preferred embodiments of the present invention will be described more specifically and in detail with reference to the accompanying drawings.

  FIG. 1 is a side sectional view showing a schematic configuration of a sheet feeding portion of an image forming apparatus for forming an image according to an electrophotographic system which is a typical embodiment of the present invention.

  The image forming unit and the fixing unit of this apparatus have the same configuration as the conventional example described in FIG. Accordingly, the constituent elements other than the sheet feeding unit will be referred to using the same reference numerals as those described in FIG.

  Further, this apparatus has a configuration capable of connecting a multi-stage type paper feed option having a sensor for detecting a recording paper on a paper feed conveyance path, and is connected with a four-stage paper feed unit as shown in the figure. Of these four paper feed units, the paper feed unit 100a at the top is a standard paper feed unit. Optional paper supply units 100b, 100c, and 100d are sequentially connected below the paper supply unit 100a.

  The paper feed unit 100a includes a paper cassette 101a, a paper feed roller 102a, a transport path sensor 103a, a feed roller 104a, and a retard roller 105a. The conveyance path sensor 103a is a conveyance path sensor that first passes when a sheet is conveyed from the paper supply unit 100b.

  The paper feeding units 100b to 100d include paper cassettes 101b to 101d, paper feeding rollers 102b to 102d, conveyance path sensors 103b to 103d, feed rollers 104b to 104d, and retard rollers 105b to 105d, respectively. Each of the conveyance path sensors 103b to 103d is a conveyance path sensor that first passes when a sheet is fed from a sheet feeding unit connected directly below the conveyance path sensors 103b to 103d. Accordingly, the conveyance path sensor 103d is a sensor on the conveyance path that first passes when a sheet is fed from a sheet feeding unit connected further below (upstream as a conveyance path) of the optional sheet feeding unit 100d. Note that the transport path sensor 103 that first passes when the paper is fed from the paper feed unit 100 a is the transport path sensor 103.

  In addition, conveyance rollers 106, 106a, 106b, 106c, and 106d are provided in the conveyance path, and these rollers operate when a main motor (not shown) in the image forming apparatus is driven and a clutch is connected.

  FIG. 2 is a block diagram showing a control configuration for executing conveyance control of the image forming apparatus shown in FIG.

  In FIG. 2, reference numeral 501 denotes a CPU that controls the image forming apparatus, 502 denotes a main motor that is a drive source of the image forming apparatus, and 503 denotes a clutch that switches on / off of transmission of driving force to the conveyance roller. Further, reference numerals 504a to 504d respectively denote sheet feeding solenoids for driving the sheet feeding rollers 102a to 102d of the sheet feeding units 100a to 100d, and 505b to d are sub CPUs for controlling optional sheet feeding units.

  As shown in FIG. 2, the CPU 501 and the sub CPUs 505 b to d are connected by three signal lines representing a command (CMD) / status (STS) / clock (CLK), and information is transmitted using three-wire serial communication. Give and receive.

  Further, the CPU 501 and the sub CPUs 505b to 505d are connected in series in order, but these connection methods are not limited to the configuration described here. For example, a mode in which the CPU 501 directly controls the actuators and sensors of the optional paper feed cassette without using a sub CPU is also conceivable.

  A broken line shown in FIG. 2 represents a transmission path of the conveyance driving force. When the main motor 502 is driven, the conveyance roller 412 is driven. At the same time, by turning on the clutch 503, the transport rollers 106a to 106d, the feed rollers 104a to 104d, and the retard rollers 105a to 105d are driven. Further, by turning on the paper feed solenoids 504a, 504b, 504c, and 504d, the paper feed rollers 102a to 102d of the paper feed units 100a to 100d are driven.

  Next, an embodiment relating to sheet conveyance control of an image forming apparatus having a sheet feeding unit having the above configuration will be described.

  A method for generating paper feed timing according to this embodiment will be described below.

  The paper feed timing when images are continuously formed from the same paper feed position is determined as follows.

  The distance from the first transport path sensor 103, 103a-c to the recording paper leading edge of the paper cassette 101a-d in which the recording paper P is stored is L1, the paper length is Plen, and the distance between the recording paper and the recording paper Is Pitvl and the paper transport speed is V. Let Tpick be the time from when the paper feed roller is driven until the recording paper P actually starts to move.

  The time (T) from the feeding of the preceding recording sheet to the start of feeding the next recording sheet is detected by the equation (3) after the leading end of the preceding recording sheet is detected by the transport path sensor first. ).

T = (Plen + Pitvl-L1) / V-Tpick (3)
When the paper feed position is switched from the upstream paper feed position to the downstream paper feed position, the time (T) is the downstream paper feed position from the transport path sensor that first passes with respect to the upstream paper feed position. If the distance to the transport path sensor that first passes is Lchg, it is expressed by equation (4).

T = (Plen + Pitvl-L1 + Lchg) / V-Tpick (4)
Conversely, when the paper feed position is switched from the downstream paper feed position to the upstream paper feed position, the time (T) is determined from the transport path sensor that first passes through the downstream paper feed position to the upstream paper feed position. If the distance from the paper position to the transport path sensor that first passes through is Lchg, it is expressed by equation (5).

T = (Plen + Pitvl-L1-Lchg) / V-Tpick (5)
Next, the generation of the paper feed timing when the image formation is performed continuously while specifically switching the paper feed position will be described with reference to a flowchart.

  FIG. 3 is a flowchart showing sheet feeding timing control according to this embodiment.

  Here, it is assumed that six recording sheets are fed in the order of paper feed unit 100a → paper feed unit 100a → paper feed unit 100c → paper feed unit 100b → paper feed unit 100d → paper feed unit 100a. Assume that the CPU 501 has already instructed the sheet feeding order for six sheets.

  First, in step S201, the CPU 501 waits for a print instruction. When a print instruction in which the paper feed position is specified as the paper feed unit 100a is received, the process proceeds to step S202. Next, in step S202, the paper feed timing generation reference sensor is used as the transport path sensor 103 in accordance with the paper feed position. Further, the paper feed roller 102a of the paper feed unit 100a is driven.

  In step S204, it waits for the paper feed timing generation reference sensor to detect the leading edge of the paper. Here, when the leading edge of the sheet is detected, the process proceeds to step S205, and the feeding position of the second recording sheet is determined. The second recording paper feed unit is also the paper feed unit 100a, and there is no switching of the paper feed port. Accordingly, in step S205, it is determined that there is no paper feed port switching, and the process proceeds to step S206, where the paper feed timing is generated according to equation (3). Thereafter, the process proceeds to step S209 to wait for the paper feed timing.

  Thereafter, when the paper feed timing is reached, the process returns to step S202, and the paper feed timing generation reference sensor is set as the transport path sensor 103 in accordance with the paper feed position. Thereafter, the processes of steps S203 to S205 described above are executed.

  Now, the third recording sheet is fed from the sheet feeding unit 100c. In this case, the paper feed port is changed to the upstream side with respect to the conveyance path. Therefore, the process proceeds to step S207 based on the determination in step S205, and the sheet feeding timing is generated with the distance between the conveyance path sensor 103 and the conveyance path sensor 103b as Lchg according to the equation (5). Thereafter, the process proceeds to step S209 to wait for the paper feed timing.

  Thereafter, when the paper feed timing comes, the process returns to step S202, and the paper feed timing generation reference sensor is set as the transport path sensor 103b in accordance with the paper feed position. Thereafter, the processes of steps S203 to S205 described above are executed.

  The fourth recording sheet is fed from the sheet feeding unit 100b. In this case, the paper feed port is changed to the downstream side with respect to the transport path. Therefore, the process proceeds to step S208 based on the determination in step S205, and the sheet feeding timing is generated with the distance between the conveyance path sensor 103a and the conveyance path sensor 103b as Lchg according to the equation (4). Thereafter, the process proceeds to step S209 to wait for the paper feed timing.

  Thereafter, when the paper feed timing is reached, the process returns to step S202, and the paper feed timing generation reference sensor is set as the transport path sensor 103a in accordance with the paper feed position. Thereafter, the processes of steps S203 to S205 described above are executed.

  The fifth recording sheet is fed from the sheet feeding unit 100d. In this case, the paper feed port is changed to the upstream side of the transport path again. Accordingly, the process proceeds to step S207 based on the determination in step S205, and the sheet feeding timing is generated with the distance between the conveyance path sensor 103a and the conveyance path sensor 103c as Lchg according to the equation (5). Thereafter, the process proceeds to step S209 to wait for the paper feed timing.

  Thereafter, when the paper feed timing is reached, the process returns to step S202, and the paper feed timing generation reference sensor is set as the transport path sensor 103c in accordance with the paper feed position. Thereafter, the processes of steps S203 to S205 described above are executed.

  The sixth recording sheet is fed from the sheet feeding unit 100a. In this case, the paper feed port is changed to the downstream side of the transport path again. Accordingly, the process proceeds to step S208 based on the determination in step S205, and the sheet feeding timing is generated with the distance between the conveyance path sensor 103 and the conveyance path sensor 103c as Lchg according to the equation (4). Thereafter, the process proceeds to step S209 to wait for the paper feed timing.

  Thereafter, when the paper feed timing is reached, the process returns to step S202, and the paper feed timing generation reference sensor is set as the transport path sensor 103 in accordance with the paper feed position. In step S203, the paper feed roller 102a of the paper feed unit 100a is driven.

  The recording paper conveyance control in the embodiment described above will be described as follows from the viewpoint of signal control.

  FIG. 4 is a time chart of signals related to recording paper conveyance control.

  In this example of the time chart, two sheets of recording paper are fed and conveyed from the paper feeding unit 100a, and then one sheet of recording paper is fed and conveyed from the paper feeding unit 100b. The control when switching to the side is shown.

As shown in FIG. 4, the recording sheet in the sheet cassette 101a is driven paper feed solenoid 504a of the paper feeding units 100a at the timing of t = T ₆₁ is transported one transport path sensor at the timing of t = T ₆₂ The recording paper reaches 103. Here, based on equation (3) to generate a paper feed timing of the next recording sheet, and drives the paper feed solenoid 504a at the timing of t = T _63. Accordingly, the recording sheet in the sheet cassette 101a is conveyed one sheet, the recording paper conveying path sensor 103 at the timing of t = T ₆₄ reaches.

Since the next recording sheet is fed from the paper feeding unit 100b located upstream of the formula (5) to generate a sheet feeding timing based on, the paper feeding solenoid 504b of the sheet feeding unit 100b at the timing of t = T ₆₅ Drive. Accordingly, the recording sheet in the sheet cassette 101b is conveyed one sheet, the recording paper conveying path sensor 103a at the timing of t = T ₆₆ reaches.

  When the recording sheet is fed at the timing generated as described above, the sheet interval in the registration sheet presence / absence sensor 413 in the main body of the image forming apparatus is constant regardless of switching of the sheet feeding unit as shown in FIG. To be kept.

  Therefore, according to the embodiment described above, even when a plurality of paper feeding units having different paper transport distances from each to a predetermined sensor in the apparatus are mounted and recording paper is fed from these units, the feeding of the recording paper is possible. The interval can be controlled to be the same.

  As a result, optimal paper supply can be realized.

  In this embodiment, the paper feed control when the paper feed operation fails will be described.

  The distance from the first transport path sensor 103, 103a-c to the leading edge of the recording paper in the paper cassette 101a-d in which the recording paper P is stored is L1, the paper transport speed is V, and the paper feed roller is driven. Let Tpick be the time until the recording paper P actually starts to move.

  Here, assuming that the time from when the recording paper originally reaches the sensor to the time when it is determined that the paper feeding has failed is the maximum time (TE) from when the preceding recording paper is fed until it is determined that the paper feeding has failed. Is represented by Formula (6).

TE = L1 / V + Tpick + Terr (6)
In this embodiment, the optimum sensor for each paper feed unit is used for judgment of paper feed failure, so that the value of L1 in equation (6) is kept within a certain range, and the judgment of paper feed failure by the paper feed unit is made. I try to align the accuracy.

  Next, a method for determining a paper feed failure when image formation is continuously performed while switching the paper feed unit will be described with reference to a flowchart.

  FIG. 5 is a flowchart showing a paper feed control process that can cope with a paper feed failure situation.

  First, in step S301, the designated paper feeding unit is determined, and it is determined whether it is the timing when paper can be fed. Here, if it is not the timing when paper can be fed, it waits for the timing when paper can be fed. On the other hand, if it is the timing when paper feeding is possible, the process proceeds to step S302, and the paper feeding operation failure determination sensor is set as a conveyance path sensor corresponding to the paper feeding position. In step S303, the timing at which it is determined that the paper feed has failed according to the paper feed position is calculated based on equation (6).

  In step S304, a timer required for the paper feeding operation is started. In step S305, the paper feeding roller of the designated paper feeding unit is driven. In step S306, the elapsed time by the timer is compared with the paper feed failure determination timing calculated in step S303. If it is determined that the elapsed time has not reached the paper feed failure determination timing, the process proceeds to step S307, and has the recording paper been transported to the transport path sensor set as the paper feed operation failure determination sensor? Find out.

  If it is determined that the recording sheet has not reached the conveyance path sensor, the process returns to step S306. On the other hand, if it is determined that the sheet has reached the conveyance path sensor, the process proceeds to step S308 to clear the sheet feeding failure number counter. In step S309, it is checked whether a recording sheet to be fed next is designated. If it is determined that the recording paper to be fed is not designated, the paper feeding operation is terminated. On the other hand, if it is determined that there is the designation, the process returns to step S301.

  If it is determined in step S306 that the elapsed time of the timer has reached the paper feed failure determination timing, the process proceeds to step S310, and the paper feed failure number counter is updated. In step S311, the paper feed failure number counter is compared with a predetermined threshold value. If the count value exceeds the threshold value, the process proceeds to step S312, where it is determined that the recording paper is jammed, and the paper feeding operation is terminated. On the other hand, if the count value is less than or equal to the threshold value, the process returns to step S304 to perform paper feed retry.

  The recording paper conveyance control in the embodiment described above will be described as follows from the viewpoint of signal control.

  FIG. 6 is a time chart of signals related to recording paper conveyance control.

  In this example of the time chart, one sheet of recording paper is fed from the paper feeding unit 100a, but the first time feeding fails and retry is performed, and then one sheet of recording paper is fed from the paper feeding unit 100b. Again, the first time represents the control when the paper feed fails and a retry is performed.

As shown in FIG. 6, the maximum time (TE) until the paper reaches the transport path sensor 103 that first passes by driving the paper supply solenoid 504 a of the paper supply unit 100 a at the timing of t = T ₇₁ is an expression. Calculate according to (6). Then, it is monitored whether or not the sheet reaches the conveyance path sensor 103 by the calculated timing. In this case, since the recording paper to the timing of t = T ₇₂ does not reach the conveying path sensor 103, drives the paper feed solenoid 504a again the sheet feeding unit 100a.

In this case, since the paper reaches the transport path sensor 103 within the maximum time (TE) until the recording paper arrives at the transport path sensor 103 that passes through the first time calculated above, the error determination is terminated. Then, the paper feed timing from the paper feed unit 100b at the timing of t = T ₇₃ is generated based on equation (5).

Further, by driving the paper feed solenoid 504b of the sheet feeding unit 100b at the timing of t = T _74, in turn a reference sensor for calculating the maximum time until the sensor reaches switched the transport path sensor 103a. Then, according to the equation (6), the maximum time (TE) until the recording paper reaches the transport path sensor 103a that first passes is calculated, and whether the recording paper reaches the transport path sensor 103a by the calculated timing. Monitor whether. In this case, since the recording paper to the timing of t = T ₇₅ does not reach the conveying path sensor 103a, and drives the paper feed solenoid 504b again the paper feed unit 101b.

  In this case, since the paper reaches the transport path sensor 103a within the maximum time (TE) until the recording paper arrives at the transport path sensor 103a that passes through the first time calculated above, the error determination is terminated.

By performing time monitoring in this way, even if the paper feeding unit for feeding the recording paper is different, feeding including retry from t = T ₇₁ to t = T ₇₃ and t = T ₇₄ to t = T _{76 is performed.} Paper time can be kept constant.

  According to the embodiment described above, an optimum sensor is used for judging the paper feed failure according to the paper feed unit, and the maximum time until the recording paper reaches the sensor is monitored. Regardless of the paper feed unit, the paper feed time including the retry can be made constant.

1 is a side cross-sectional view illustrating a schematic configuration of a sheet feeding unit of an image forming apparatus that forms an image according to an electrophotographic system that is a representative embodiment of the present invention. FIG. 2 is a block diagram illustrating a control configuration that executes conveyance control of the image forming apparatus illustrated in FIG. 1. It is a flowchart which shows the paper feed timing control according to Example 1 of this invention. It is a time chart of the signal which concerns on the recording paper conveyance control according to Example 1 of this invention. It is a flowchart which shows the paper feed control process which can respond also to the condition of the paper feed failure according to Example 2 of this invention. It is a time chart of the signal which concerns on the recording paper conveyance control according to Example 2 of this invention. It is a sectional side view showing a schematic configuration of an image forming apparatus that performs image formation according to a conventional electrophotographic system.

Explanation of symbols

101a, 101b, 101c, 101d Paper cassettes 102a, 102b, 102c, 102d Paper feed rollers 103, 103a, 103b, 103c, 103d Conveyance path sensors

Claims (7)

A plurality of paper feeding units loaded with recording media can be connected, the recording media supplied from the plurality of paper feeding units are conveyed through a common conveyance path, and an image is formed on the conveyed recording medium. An image forming apparatus,
A plurality of sensors that are provided in the common conveyance path and detect recording media supplied from the plurality of paper feeding units to the common conveyance path;
Designating means for designating a paper feed unit for supplying a recording medium on which an image is formed;
A selection unit that selects, as a reference sensor, a sensor that first detects a recording medium supplied from any of the plurality of paper feeding units to the common conveyance path among the plurality of sensors;
A discriminating means for discriminating whether or not a paper feed unit for supplying a recording medium used for image formation is switched when an image is continuously formed on a plurality of recording media ;
A reference sensor selected by the selecting means before switching the sheet feeding unit when it is determined that switches said the determining means thus sheet feeding unit is selected by the selection means after the sheet feed unit is switched an image forming apparatus, comprising an adjustment means for adjusting the supply timing of the common recording medium based on the distance in the transport path of the reference sensor that. The determining means determines whether the paper feed unit switches to a paper feed unit located upstream or to a paper feed unit located downstream relative to the recording medium transport direction in the common transport path. The image forming apparatus according to claim 1, wherein discrimination is performed. Supply means for supplying a recording medium from the plurality of paper supply units onto the common conveyance path;
The image forming apparatus according to claim 1, further comprising a transport unit configured to transport the recording medium supplied by the supply unit in the common transport path. The adjusting means, imaging according to any one of claims 1 to 3, characterized in that the spacing between the plurality of recording medium in the common transport path to adjust the feed timing to be the same apparatus. The adjusting means adjusts the supply timing to be earlier than the supply timing before the paper feed unit is switched when the discrimination means determines that the paper feed unit is switched to the paper feed unit located upstream. And
When the determining means determines that the paper feed unit is switched to a paper feed unit located downstream, the supply timing is adjusted to be later than the supply timing before the paper feed unit is switched. The image forming apparatus according to claim 2. A plurality of paper feeding units loaded with recording media can be connected, recording media supplied from the plurality of paper feeding units are supplied through a common conveyance path, and an image is formed on the supplied recording media. A paper feed control method for an image forming apparatus,
A designation step for designating a paper feeding unit for supplying a recording medium on which an image is formed;
Among the plurality of sensors that are provided in the common transport path and detect the recording medium supplied from each of the plurality of paper feed units to the common transport path, the common from any of the plurality of paper feed units A selection step of selecting, as a reference sensor, a sensor that first detects the recording medium supplied to the conveyance path;
A determination step of determining whether or not to switch to a paper feeding unit that supplies a recording medium used for image formation when images are continuously formed on a plurality of recording media ;
A recording medium based on a distance in the common conveyance path between the reference sensor selected in the selection step before the paper feed unit is switched and the reference sensor selected in the selection step after the paper feed unit is switched. An adjustment step of adjusting the supply timing of the paper. The Determination process, the paper feed unit, the recording medium conveying direction in the common transport path, whether switching to the sheet feeding unit located upstream, or whether the switching to the paper feed unit located downstream The paper feed control method according to claim 6 , further comprising a step of discriminating.

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