JP7141597B2 - Sheet conveying device and image forming device - Google Patents

Description

The present invention relates to a sheet conveying device and an image forming apparatus.

Conventionally, a sheet conveying member that conveys the sheet toward a registration conveying member that conveys the sheet after the leading edge of the sheet being conveyed collides with the sheet, a detection unit that detects the sheet conveyed by the sheet conveying member, and a detection unit. A known sheet conveying apparatus includes a calculating means for calculating the sheet length, which is the length of the sheet in the conveying direction, based on the detection result of (1).

For example, Japanese Patent Application Laid-Open No. 2002-200000 discloses that a detection means is provided immediately upstream of a registration conveying member, and the calculation means calculates the sheet length using the time from when the detection means detects the arrival of the sheet to when the detection means detects the passage of the sheet. An image forming apparatus having a configuration of a sheet conveying device to be calculated is described. In this image forming apparatus, when the input sheet length information differs from the sheet length calculated by the calculator, the sheet conveying member and the resist conveying member stop conveying the sheet.

However, in the image forming apparatus described in Japanese Patent Application Laid-Open No. 2002-200011, in which the sheet length is calculated using a detection means arranged near the resist conveying member, the length from the accommodation unit that accommodates the sheet to the resist conveying member When the conveying distance is long, the following problems may occur.
In other words, the length of the sheet is unknown until the detection means located near the registration conveying member detects the passage of the sheet. Therefore, even if it is found that the input sheet length is different from the calculated sheet length and the transport is stopped, there are cases where a plurality of sheets already exist in the transport path from the storage unit to the detection means. The sheets existing in the transport path are often discarded after the transport is stopped, and if a plurality of sheets exist in the transport path when the transport is stopped, the sheets are wasted.

In order to solve such a problem, a configuration is conceivable in which a detecting means is arranged at a position on the upstream side in the conveying direction away from the resist conveying member, and the sheet length is calculated based on the detection result of this detecting means. However, if the detection means at a position distant from the registration conveying member is used, the sheet length cannot be calculated appropriately.

In order to solve the above-described problems, the present invention provides a sheet conveying member that conveys the sheet toward a registration conveying member that conveys the sheet after the leading edge of the conveyed sheet collides with the sheet, and the sheet conveying member. A sheet conveying apparatus comprising: detecting means for detecting a sheet to be conveyed; and calculating means for calculating a sheet length, which is the length of the sheet in the conveying direction, based on the detection result of the detecting means, wherein the calculating means comprises: The sheet length is calculated based on the time from when the sheet is detected by the detecting means to when the sheet is no longer detected. When the detecting means stops detecting the sheet during the abutting period until the conveying member starts conveying, the calculating means calculates the abutment period and a predetermined period after the resist conveying member starts conveying. between and when the detection result of the detection means is not used for calculating the sheet length and the detection means continues to detect the sheet during the abutment period, the calculation means After the registration conveying member starts to be conveyed, the detection result of the detecting means is used for calculating the sheet length .

According to the present invention, it is possible to appropriately calculate the sheet length with the configuration in which the sheet length is calculated based on the detection result of the detection means located upstream of the registration conveying member. be.

4 is a timing chart of the printer according to the invention; 1 is a schematic configuration diagram of a copier according to the present embodiment; FIG. FIG. 2 is a block diagram of the main configuration of the control system of the paper feeding unit of the printer; FIG. 11 is an explanatory view schematically showing a transport path for feeding paper from the second additional paper feed tray; FIG. 11 is an explanatory diagram of a state in which a sheet fed from a second additional sheet feeding tray collides with a pair of registration rollers, and bending is formed near the leading edge of the sheet; 10 is a timing chart when the length of the sheet in the transport direction is sufficiently short with respect to the distance from the second additional transport sensor to the pair of registration rollers in the transport path; FIG. 10 is a schematic diagram showing a state in which the trailing edge of the sheet is positioned at the detection position of the second extension feeding sensor when the sheet fed from the second extension sheet feeding tray stops being conveyed; FIG. 8 is a timing chart when a sheet that can be in the state shown in FIG. 7 is fed; FIG. 11 is an explanatory diagram of a state in which a sheet slightly longer than the distance "L1" is fed, the sheet strikes against the registration roller, and the sheet is flexed to stop the conveyance; FIG. 10 is an explanatory diagram of a state in which the sheet is no longer bent from the state of FIG. 9 ; FIG. 11 is an explanatory diagram of a state in which sheet conveyance is resumed from the state in FIG. 10; FIG. 12 is a timing chart in the case where a sheet that can be in the states shown in FIGS. 9 to 11 is fed and the mask period is set as the conveyance stop period; FIG. 10 is a flowchart showing an outline from the start of paper feeding to the determination of size mismatch in a configuration in which a paper detection sensor is used to measure the length of paper; 4 is a flow chart for judging signs of deterioration and end of service life of a conveying roller pair; 6 is a flow chart of control for measuring the paper size and detecting a transport failure; FIG. 10 is a schematic configuration diagram of an image reading apparatus according to a modification;

An embodiment of an image forming apparatus having a configuration of a sheet conveying device according to the present invention will be described below.
FIG. 2 is a schematic configuration diagram of a copier 200 including the printer 100, which is the image forming apparatus of this embodiment.
A copier 200 shown in FIG. 2 is a multifunction machine having functions such as a copier, a printer, a facsimile machine, and a scanner. or output in a predetermined data format.

As shown in FIG. 2, the copier 200 includes a printer 100, and above the printer 100, a scanner 90 and an ADF 80, which is an automatic document feeder. The scanner 90 and the ADF 80 constitute an image reading device 300 as a whole.

The printer 100 includes a main housing portion 1 having an image forming portion 10 and an additional paper feeding portion 500 attached below the main housing portion 1 .
As shown in FIG. 2, the main body housing 1 includes a main paper feeding section 30 having a main paper feeding tray 31, a main paper feeding roller 11, and a main paper feeding separation roller 34 below the image forming section 10. Prepare.

The extension sheet feeder 500 includes three extension sheet feeders 50, ie, a first extension sheet feeder 50a, a second extension sheet feeder 50b, and a third extension sheet feeder 50c in order from the top. Since the three additional paper feeders 50 (a, b, c) have the same configuration, they are members of the first to third additional paper feeders 50 indicated by the reference numerals in FIG. The suffixes “a”, “b” and “c” indicating that are omitted as appropriate.
The three additional paper feeders 50 each include an additional paper feed tray 70 , an additional paper feed roller 51 , and an additional paper feed separation roller 74 .

The main paper feed tray 31 is arranged so as to be able to be pulled out on the front side of the apparatus (on the right side in FIG. 2) with respect to the main body housing portion 1, and the additional paper feed tray 70 is attached to the housing of the additional paper feed device 50. With respect to the body, it is arranged so that it can be pulled out on the front side of the apparatus (right side in FIG. 2).
The main body unit 1 includes a manual feed tray 3 and a manual feed roller 17 on the front side of the printer 100 (on the right side in FIG. 2) to constitute a manual feed unit.

The image forming unit 10 includes a photoreceptor 2 as a latent image carrier, an image forming unit 7 that forms a toner image on the surface of the photoreceptor 2, and a toner image on the surface of the photoreceptor 2 that is transferred onto a sheet of paper P. and a fixing device 5 for fixing the toner image transferred onto the paper P onto the paper P.

When an image is formed by the printer 100 , a latent image is formed on the surface of the photoreceptor 2 by the exposing means provided in the image forming section 7 , and a latent image is formed on the surface of the photoreceptor 2 by the developing device provided in the image forming section 7 . is developed to form a toner image on the surface of the photoreceptor 2 .
On the other hand, the sheets conveyed one by one by the paper feed rollers (11, 51, 17) from the stack of paper stacked in the main paper feed tray 31, the additional paper feed tray 70, or the manual paper feed tray 3 are transferred to the registration roller pair. 13 is transported.
Then, the registration roller pair 13 is rotationally driven so as to coincide with the timing when the toner image on the surface of the photoreceptor 2 reaches the transfer nip, which is the portion opposed to the transfer roller 14, and the toner image on the surface of the photoreceptor 2 is transferred at the transfer nip. A toner image is transferred onto the surface of the paper. The fixing device 5 heats and presses the paper P onto which the toner image has been transferred so that the toner image is fixed.

Of the paper P that has passed through the fixing device 5, the paper P on which an image is not formed on the back side passes through the post-fixing transport nip between the post-fixing transport roller 4 and the post-fixing reversing transport roller 8, and is shown by the solid line in FIG. It is guided by the pre-ejection branch claw 6 at the position indicated by . Then, it is discharged to the paper discharge tray 19 from the paper discharge nip formed by the first paper discharge roller 16a and the second paper discharge roller 16b.

After passing through the fixing device 5, the paper P on which an image is formed on the back side passes through the post-fixing transport nip between the post-fixing transport roller 4 and the post-fixing reversing transport roller 8, and reaches the position indicated by the dashed line in FIG. It is guided by the pre-ejection branch claw 6 at the . Then, the paper P is protruded from the paper discharge nip formed by the second paper discharge roller 16b and the third paper discharge roller 16c except for a part of the rear end side in the transport direction. After that, when the trailing edge of the paper P passes the position of the pre-ejection branching claw 6, the pre-ejection bifurcation claw 6 moves to the position indicated by the solid line, and the rotation direction of the second paper ejection roller 16b and the third paper ejection roller 16c. is the opposite. As a result, the paper P passes through the reverse transport nip between the post-fixing reverse transport roller 8 and the reverse transport roller 9 and is transported to a position where it hits the registration roller pair 13 through the reverse transport path. After that, an image is formed on the back side by the same process as the image formation on the front side, and the image is transferred from the paper ejection nip formed by the first paper ejection roller 16a and the second paper ejection roller 16b to the paper ejection tray 19. Ejected.

As shown in FIG. 2, a registration sensor 20 for detecting the presence or absence of the paper P within the detection range is provided in the vicinity of the upstream side of the pair of registration rollers 13 in the main body housing 1 in the conveying direction. In addition, a pre-relay sensor 35 for detecting the presence or absence of the paper P within the detection range is provided near the upstream side of the relay roller pair 12 in the main body casing 1 in the conveying direction. Further, a post-fixing sensor 21 is provided between the fixing roller pair 15 and the post-fixing conveying roller 4 to detect the presence or absence of the paper P within the detection range.
The additional paper feeding device 50 includes an additional conveying roller pair 52 that is a sheet conveying member, and an additional conveying sensor 53 that is arranged near the upstream side of the additional conveying roller pair 52 in the conveying direction and detects the presence or absence of the paper P within the detection range. Prepare.

The leading edge of the sheet P conveyed by the relay roller pair 12 and the additional conveying roller pair 52, which are sheet conveying members, abuts against the registration roller pair 13, and the leading edge of the sheet P is temporarily stopped. Thereafter, the sheet P is conveyed toward the image forming section 10 on the downstream side in the conveying direction at a predetermined timing.

The printer 100 has a configuration in which the additional paper feeders 50, which are option banks, can be stacked in multiple layers, and the number and types of the additional paper feeders 50 (different numbers of sheets that can be set in the additional paper feed tray 70) can be selected.
The skew of the paper P before the toner image is transferred is corrected by abutting the fed paper P against the pair of registration rollers 13 arranged in the main body housing portion 1 of the printer 100 . More specifically, a skew correction method is adopted in which the paper P abuts against the registration roller pair 13 in a non-rotating state to warp the paper P. As shown in FIG.

The bending of the paper P at the registration roller pair 13 is caused by the intermediate roller pair 12, which is a roller pair that conveys the paper P one upstream from the registration roller pair 13 while the registration roller pair 13 is stopped. Created by continuing transport. In the printer 100, the relay roller pair 12 is temporarily stopped before the registration roller pair 13 starts rotating. After the relay roller pair 12 stops, the relay roller pair 12 and the registration roller pair 13 start rotating, thereby restarting the transport of the paper P and feeding the paper P toward the image forming section 10 .

The detection result of the registration sensor 20 is used to adjust the amount of bending of the paper P (hereinafter referred to as "amount of bending") during skew correction. Based on the distance from the detection position of the registration sensor 20 to the registration roller pair 13 and the desired deflection amount, the transport amount of the paper P after the leading edge of the paper P passes the registration sensor 20 is calculated. Based on the calculated transport amount, the timing for stopping the rotation of the relay roller pair 12 after the registration sensor 20 detects that the leading edge of the paper P has passed is calculated.

The additional paper feeding device 50 includes an additional transport roller pair 52 that is a transport roller pair for transporting the paper P transported from the additional paper feeding tray 70 to the main body housing portion 1 . Furthermore, in order to convey the paper P fed from the additional paper feeding device 50 to the position of the registration sensor 20 , the body housing section 1 of the printer 100 is provided with a relay roller pair 12 .

In the printer 100 , the user sets the paper P to be used using an external device such as a personal computer or the operation panel 102 . The additional paper feeding device 50 has an additional transport sensor that detects the length of the paper P to confirm whether the paper P loaded in the additional paper feeding tray 70 matches the paper P set by the user. 53.

FIG. 3 is a block diagram of the main configuration of the control system of the paper feeding unit of the printer 100. As shown in FIG.
In FIG. 3, the body transport motor 22 is a drive source that rotationally drives the body feed roller 11, the relay roller pair 12, and the registration roller pair 13 by turning ON each of the clutches (23, 24, and 25). be. Further, the additional paper feeding motors 122 provided in each of the three additional paper feeding devices 50 rotate the additional paper feeding rollers 51 and the additional conveying roller pairs 52 by turning on the respective clutches (123 and 124). It is a driving source that makes

Next, conveyance of sheets from the main sheet feeding section 30 and the additional sheet feeding device 50 will be described.

When paper is fed from the main body paper feeding unit 30, the main body control unit 101 starts driving the main body conveying motor 22 and turns the main body relay clutch 24 to "ON". The two rollers of the relay roller pair 12 start rotating in the direction in which the paper P is conveyed by turning the main body relay clutch 24 to "ON". By turning on the main body paper feed clutch 23 at a predetermined timing, the main body paper feed roller 11 starts to rotate counterclockwise in FIG.

One sheet of paper P is fed from the paper stack by the rotation of the main body paper feed roller 11 provided facing the paper stack of the paper P stacked on the main body paper feed tray 31 . The fed sheet P is transported by the relay roller pair 12 , passes through the transport path 18 after the relay nip, and hits the registration roller pair 13 . Next, the registration clutch 25 is turned "ON", and the registration roller pair 13 is driven to convey the sheet P. Then, the toner image on the photosensitive member 2 is transferred to the paper P at the transfer nip where the transfer roller 14 is arranged, and the toner image is fixed on the paper P by the fixing device 5 having the fixing roller pair 15 . After that, the paper P is discharged to the paper discharge tray 19 by the paper discharge rollers (16a, 16b).

When paper is fed from the additional paper feeding device 50, the body control unit 101 transmits a paper feed command to the additional paper feeding control unit 501 of the additional paper feeding device 50 on which the paper P to be fed is stacked. Further, the body control unit 101 starts driving the body conveying motor 22 .
Upon receiving the paper feed command, the additional paper feed control unit 501 starts driving the additional paper feed motor 122 and turns the additional transport clutch 124 to "ON". The two rollers of the pair of additional conveying rollers 52 start rotating in the direction in which the paper P is conveyed by turning the additional conveying clutch 124 to "ON". By turning the additional paper feed clutch 123 "ON" at a predetermined timing, the additional paper feed roller 51 starts to rotate counterclockwise in FIG.

One sheet of paper P is fed from the bundle of paper P loaded on the additional paper feed tray 70 by rotation of an additional paper feed roller 51 provided facing the bundle of paper P. The fed paper P is conveyed by an additional conveying roller pair 52 provided in the additional paper feeding device 50 . At this time, after a predetermined time has passed since the additional transport sensor 53 arranged near the upstream side of the additional transport roller pair 52 in the transport direction detects that the leading edge of the paper P has passed, the main body control unit 101 performs the main body relay The clutch 24 is turned "ON". Then, before the leading edge of the paper P reaches the relay roller pair 12, the rotation of the relay roller pair 12 is started. The paper P conveyed by the additional conveying roller pair 52 passes through the main body paper feeding section passage conveying path 33 provided in the main body paper feeding tray 31 and is conveyed downstream in the paper feeding direction by the relay roller pair 12 .

The additional sheet feeding device 50 is provided with an additional sheet feeding device passing transport path 73 so as to be on the same straight line as the main body sheet feeding section passing transporting path 33, and is configured such that an identically shaped additional sheet feeding device 50 can be added below. It's becoming
The printer 100 shown in FIG. 2 includes a plurality (three) of additional paper feeders 50 having the same shape. The paper P fed from the additional paper feeding device 50 added below passes through the additional paper feeding device passing transport path 73 of the additional paper feeding device 50 above the additional paper feeding device 50 in which the paper P was accommodated. pass through. Then, it is conveyed from the additional paper feeder passing conveying path 73 to the main body paper feeding section passing conveying path 33, passes through the main body paper feeding section passing conveying path 33, is conveyed downstream in the paper feeding direction by the intermediate roller pair 12, and is registered. It abuts on the roller pair 13 . After hitting the registration roller pair 13, the operation is the same as in the case of feeding from the main body feeding section 30 described above.

When paper is fed from one of the additional paper feeders 50 in which another additional paper feeder 50 is arranged on the downstream side in the conveying direction of the paper P, the other additional paper feeder located downstream is used. It rotates the additional conveying roller pair 52 of the paper device 50 . As a result, the paper P fed from the additional paper feeding device 50 located on the upstream side is transported toward the main paper feeding section passage transport path 33 .

In this embodiment, the length of the paper P is calculated using one of the plurality of paper detection sensors (35, 53a, 53b and 53c). Specifically, the length of the paper P is calculated based on the time from when the leading edge of the paper P reaches the detection position of the paper detection sensor to when the trailing edge of the paper P leaves the detection position. As for the sensor output of the paper detection sensor, when the leading edge of the paper P passes the detection position of the paper detection sensor, the paper P exists at the detection position, so the sensor output changes from "OFF" to "ON". . On the other hand, when the trailing edge of the paper P passes the detection position of the paper detection sensor, the paper P does not exist at the detection position, so the sensor output changes from "ON" to "OFF". For this reason, the sensor output of the paper detection sensor changes from "OFF" to "ON" until it changes to "OFF". can be calculated.

In the printer 100 of this embodiment, the length of the paper P fed from each of the paper feed trays (31, 70a, 70b, and 70c) in the transport direction is detected by the paper detection sensor (35, 35, 53a, 53b and 53c).
Specifically, the paper P fed from the main body paper feed tray 31 passes through the detection range of the main body pre-relay sensor 35 based on the time from when the leading edge passes until the trailing edge passes, and on the transport speed. , the length in the transport direction is calculated.
Similarly, the length of the paper P fed from the first extension paper feeding tray 70a in the transportation direction is calculated based on the detection result of the first extension transportation sensor 53a. In addition, the length of the sheet P fed from the second extension sheet feeding tray 70b in the transport direction is calculated based on the detection result of the second extension sheet feeding sensor 53b. Further, the length of the paper P fed from the third extension paper feed tray 70c in the transport direction is calculated based on the detection result of the third extension transport sensor 53c.

In the printer 100, the length of the paper P set in each of the paper feed trays (31, 70a, 70b, and 70c) is input in advance to the storage section of the body control section 101. FIG. By selecting a paper feed tray to be used for paper feeding according to user settings, the body control unit 101 can acquire information on the length of the paper P to be conveyed.
When the length of the paper P calculated using the paper detection sensors (35, 53a, 53b, and 53c) does not match the length of the paper P set by the user, the body control unit 101 performs the feeding operation and the image processing. Stop the forming action. Furthermore, a warning is displayed on the external device and the operation panel 102 to notify that the size of the paper P is not appropriate.

The printer 100 has an operation panel 102 and a communication unit with the above-described external device as an input unit for inputting the size of the paper P to be fed for printing. When the size of the paper P input to be fed differs from the size of the paper P calculated based on the detection result of the paper detection sensor, the size of the paper P input to be fed differs from the actual size. It is notified that the size of the paper sheet P being fed to is different from that of the sheet P.

The three additional paper feeders 50 are paper feeders having a sensor (53) that detects the paper P to be conveyed, and the paper P set in the paper feed tray (70) by the user and the paper P set on the system. It has a configuration as a paper feeding device capable of detecting a size mismatch with the paper P that is present. In addition, the main housing unit 1 of the printer 100 is also a paper feeder having a sensor (35) that detects the paper P to be conveyed, and the paper P set in the paper feed tray (31) by the user and the It has a configuration as a paper feeding device capable of detecting size mismatch with the set paper P. - 特許庁

The paper detection sensors (35, 53a, 53b and 53c) use optical sensors, for example. As the optical sensor, a reflective optical sensor that includes a light emitting unit that emits light toward the transport path of the paper P and a light receiving unit that receives the light emitted from the light emitting unit and reflected by the paper P can be used. Further, as the optical sensor, a transmissive optical sensor having a light-emitting portion, a light-receiving portion, and an actuator that moves in contact with the paper P being conveyed can be used.

As such a transmissive photosensor, the following can be used. That is, when the paper P does not exist at the detection position, the actuator is positioned at the initial position and blocks the light from the light emitting section to the light receiving section. On the other hand, when the paper P exists at the detection position, the position of the actuator changes, light reaches the light receiving section from the light emitting section, and the output from the light receiving section changes. The presence or absence of the paper P at the detection position can be detected from the change in this output. Any sensor other than the optical sensor may be used as long as it can detect the presence or absence of the paper P at the detection position.

The paper detection sensor that uses the detection result in the transport path to calculate the length of the paper P is not limited to the sensor positioned most upstream in the transport path. For example, the lengths of the paper P fed from the additional paper feed tray 70 and the paper P fed from the main paper feed tray 31 are calculated based on the detection result of the main body pre-relay sensor 35 or the registration sensor 20. It is good also as a structure which carries out.

However, in a configuration such as the printer 100 in which the additional paper feeding devices 50 are stacked in multiple stages, the distance from the paper feeding tray (additional paper feeding tray 70) containing the paper P to be fed to the paper detection sensor is long. With such a configuration, when a sheet P having a short length in the transport direction is fed, it is detected that the length of the sheet P is not appropriate based on the detection result of the paper detection sensor, and the feeding operation and image formation are performed. Even if the operation is stopped, a plurality of sheets P may be fed from the paper feed tray. At this time, the paper P fed from the paper feed tray and remaining in the paper transport path when the apparatus is stopped may be discarded as jammed paper, leading to wastage of the paper P.

On the other hand, in the printer 100 of this embodiment, the length of the paper P in the transport direction is calculated using the detection result of the sensor positioned most upstream in the transport path. As a result, the number of sheets P left in the paper transport path can be minimized (approximately 1 to 2 sheets) when it is detected that the length is not appropriate and the apparatus is stopped. Then, by notifying the user that the length of the paper P calculated using the sensor does not match the length of the paper P that has been set, the user can receive the paper P It is possible to notify that the paper P has been set incorrectly, and waste of the paper P can be prevented.

When the apparatus is stopped, the number of sheets of paper P left in the paper transport path can be reduced when the position of the sensor is not limited to the most upstream sensor of the transport path, but when the position of the sensor is on the upstream side of the transport path. For example, the length of the paper P fed from the second additional paper feed tray 70b or the third additional paper feed tray 70c in the conveying direction is calculated using the first additional conveyance sensor 53a of the first additional paper feeder 50a. may In this case, it is possible to reduce the number of sheets of paper P left in the paper transport path when the apparatus is stopped, rather than using the detection results of the main body pre-relay sensor 35 and the registration sensor 20 in the main body housing 1. .

However, when the length of the paper P is calculated using a sensor positioned upstream of the pair of registration rollers 13 in the transport path to some extent in the transport direction, the following problem may arise. That is, if the distance from the detection position of the paper detection sensor to the registration roller pair 13 is close to the length of the paper P to be fed, the trailing edge of the paper P stops at or near the detection position of the paper detection sensor. However, the passage of the trailing edge could not be detected properly.
This problem will be described below with reference to the drawings. First, referring to FIGS. 4 to 6, a case where the length of the sheet P in the transport direction is sufficiently short and the above problem does not occur will be described.

FIG. 4 is an explanatory view schematically showing the transport path when the paper P is fed from the second additional paper feed tray 70b.
Specifically, from the upstream side (right side in FIG. 4) in the conveying direction indicated by the arrow "α" in FIG. 53b, a second additional conveying roller pair 52b and a first additional conveying roller pair 52a. Furthermore, the relay roller pair 12, registration sensor 20, and registration roller pair 13 are shown on the downstream side (left side in FIG. 4).
FIG. 5 is an explanatory diagram of a state in which the paper P fed from the second additional paper feed tray 70b collides with the pair of registration rollers 13, and a bend Pd is formed in the vicinity of the leading edge of the paper P. As shown in FIG.
4 and 5 show that the length of the paper P in the transport direction with respect to the distance from the second additional transport sensor 53b to the registration roller pair 13 in the transport path (distance "L1" in FIGS. 4 and 5) is It is explanatory drawing in case it is sufficiently short.

FIG. 6 is a timing chart of the printer 100 when the length of the paper P in the transport direction is sufficiently short with respect to the distance from the second additional transport sensor 53b to the registration roller pair 13 in the transport path.

When the paper P accommodated in the second additional paper feed tray 70b is selected and the print start button is pressed (or a print start command is input from an external device), the main body control unit 101 starts the first additional paper feed. A paper feed signal is issued to the second additional paper feed control unit 501b via the paper control unit 501a. Upon receiving the paper feed signal, the second additional paper feed control unit 501b starts driving the second additional paper feed motor 122b. At this time, the first extension sheet feeding controller 501a also starts driving the first extension sheet feeding motor 122a.

Next, the second extension feeding control unit 501b turns the second extension conveying clutch 124b to "ON" ("T1" in FIG. 6), so that the second extension conveying roller pair 52b starts rotating. At this time, the first extension feeding control unit 501a also turns the first extension conveying clutch 124a "ON", so that the first extension conveying roller pair 52a also starts to rotate.

Next, the second additional paper feeding control unit 501b turns the second additional paper feeding clutch 123b to "ON" to start feeding the paper P from the second additional paper feeding tray 70b. When the leading edge of the fed paper P reaches the detection position of the second extension transport sensor 53b, the sensor output of the second extension transport sensor 53b is turned "ON" ("Tp1" in FIG. 6). After passing the detection position of the second extension transport sensor 53b, the sheet P passes through the second extension transport nip of the second extension transport roller pair 52b, and the first extension paper feeder passage transport path of the first extension paper feeder 50a. 73a to pass through the first additional conveying nip of the first additional conveying roller pair 52a.

After passing through the first additional conveying nip, the sheet P passes through the relay nip of the relay roller pair 12 through the main body paper feeding section passage conveying path 33 . Here, after the sensor output of the second additional conveying sensor 53b is turned "ON", the main body relay clutch 24 is turned "ON" at a timing before the timing at which the leading edge of the sheet P reaches the relay nip. (“T2” in FIG. 6). As a result, when the leading edge of the paper P reaches the relay nip, the relay roller pair 12 is rotating, and the paper P that has reached the relay nip can be transported toward the registration nip.

If the paper P is sufficiently short with respect to the distance "L1", the trailing edge of the paper P reaches the second position before the leading edge of the paper P reaches the detection position of the registration sensor 20 ("T3" in FIG. 6). It passes through the detection position of the additional transport sensor 53b (“Te1” in FIG. 6). At this time, a time difference ( (“Ts1”)), the length of the sheet P in the transport direction can be calculated. Specifically, the length of the paper P can be obtained from the product of the time difference (“Ts1” in FIG. 6) and the transport speed of the paper P described above.

When the leading edge of the sheet P transported from the relay nip to the registration nip reaches the detection position of the registration sensor 20, the sensor output of the registration sensor 20 is turned "ON"("T3" in FIG. 6). After the sensor output of the registration sensor 20 is turned "ON", the conveyance of the paper P is stopped ("T4" in FIG. 6) after a predetermined leading edge positioning conveyance period ("Ta" in FIG. 6) has elapsed. ). In the leading edge positioning transport period Ta, the paper P is transported by the distance ("L2" in FIGS. 4 and 5) from the registration sensor 20 to the registration nip, and further by the amount of deflection Pd of a certain amount. This is the period required for transportation.
Skew correction can be performed by forming a constant deflection Pd on the sheet P that has hit the registration nip during the leading edge positioning transport period Ta.
In the present embodiment, the distance "L2" is "12.1 [mm]", and the amount of transport that forms the deflection Pd (hereinafter also referred to as "amount of deflection") is "0 [mm] to 10 [mm]". can be set between, but not limited to these values.

After the sensor output of the registration sensor 20 is turned "ON", the body control unit 101 issues a transport stop signal after the leading edge positioning transport period Ta has elapsed. As a result, the body relay clutch 24 is turned "OFF" ("T4" in FIG. 6), and the first additional transport clutch 124a and the second additional transport clutch 124b are also turned "OFF". Here, the first extension conveying clutch 124a and the second extension conveying clutch 124b are turned "OFF" from the main body control section 101 via the first extension sheet feeding control section 501a and the second extension sheet feeding control section 501b. Therefore, as shown in FIG. 6, after the main relay clutch 24 is turned "OFF", the second additional transport clutch 124b is turned "OFF" with a delay of a predetermined delay period. In the printer 100 of this embodiment, this delay period was "46 [ms]".

Delay in communication from the main body control unit 101 occurs in the additional transport clutches 124 (a to c) arranged in the additional paper feeders 50 (a to c). For this reason, the transport members (52a to 52c) of the additional paper feeding devices 50 (a to c) are delayed in transport start timing with respect to the transport members (12, 13) in the main body housing portion 1. FIG. On the other hand, the conveying members (52a-52c) of the additional sheet feeding devices 50(a-c) are provided with one-way clutches. As a result, in a state in which one sheet of paper P straddles the inside of the main body casing 1 and the inside of the additional paper feeding device 50, the conveying member of the additional paper feeding device 50 is moved relative to the conveying member inside the main body casing 1. Even if the start of transportation is delayed, the transportation member of the additional paper feeding device 50 can rotate along with the paper P pulled on the main body side.

After the transportation is stopped, the body relay clutch 24, the registration clutch 25, the first additional transportation clutch 124a, and the second additional transportation clutch 124b are turned ON so as to coincide with the timing when the toner image on the surface of the photoreceptor 2 reaches the transfer nip. ” (“T5” in FIG. 6). As a result, conveyance of the paper P by each roller pair (52b, 52a, 12, 13) is resumed, and the toner image on the surface of the photoreceptor 2 is transferred onto the surface of the paper at the transfer nip.
As in the case of stopping the transport, transmission of the transport restart signal to the first additional transport clutch 124a and the second additional transport clutch 124b is delayed. Therefore, as shown in FIG. 6, after the main relay clutch 24 is turned "ON", the second additional transport clutch 124b is turned "ON" with a delay of a predetermined delay period.

When the paper P is sufficiently short with respect to the distance "L1", as shown in FIG. After passing the detection position. Therefore, during the transport suspension period ("Tb" in FIG. 6) from the timing of stopping transport ("T4" in FIG. 6) to the timing of restarting transport ("T5" in FIG. 6), the second The sensor output of the second additional transport sensor 53b remains "ON". For this reason, the time difference ( (“Ts2”)), the length of the paper P in the transport direction is longer than the actual length. Therefore, if there is a transport stop period Tb while the sensor output of the second additional transport sensor 53b remains "ON", the value obtained by subtracting the transport stop period Tb from the above-described time difference ("Ts2" in FIG. 6) and the transport speed of the paper P, the length of the paper P is obtained.

"W" in FIG. 5 indicates the paper interval, and the length of the paper P can be obtained from the product of the time difference between "Te1" and "Tp2" in FIG. 6 and the transport speed of the paper P. can. In this embodiment, the sheet interval W is set to be "25 [mm]", but it is not limited to this.

Next, referring to FIGS. 7 and 8, the trailing edge Pe of the paper P that can occur when the distance from the detection position of the paper detection sensor to the registration roller pair 13 is close to the length of the paper P to be fed. Describe the problem of not being able to properly detect passage.
FIG. 7 is a schematic diagram showing a state in which the trailing edge Pe of the sheet P is positioned at the detection position of the second extension feeding sensor 53b when the transportation of the sheet P fed from the second extension sheet feeding tray 70b is stopped. is.
FIG. 8 is a timing chart when feeding the paper P that can be in the state shown in FIG.

As shown in FIG. 7, when the trailing edge Pe of the paper P whose transportation is stopped in a state where the leading edge is abutted against the registration roller pair 13 to form the deflection Pd, is positioned at the detection position of the second additional transportation sensor 53b. The sensor output of the second additional transfer sensor 53b may become unstable as shown in FIG. Specifically, in the timing chart shown in FIG. 8, after the transport of the paper P is stopped ("T4" in FIG. 6), the second addition The sensor output of the transport sensor 53b is in a state of repeating "ON" and "OFF". This is because the trailing edge Pe of the sheet P is positioned at the detection position of the second extension conveying sensor 53b, and a slight movement of the sheet P causes the second extension conveying sensor 53b to detect the sheet P, or not to detect it. This is because it becomes a state.

As shown in FIG. 8, when the sensor output of the second additional conveying sensor 53b repeats "ON" and "OFF" and the sensor output is reflected in the control, the control unit (101 or 501b) The length of P cannot be calculated. As a result, the control unit (101 or 501b) determines that there is a problem with the transport of the paper P, and restarts the apparatus even though there is no paper jam or transport failure, and no problem other than the sensor output has occurred. It may stop.

As a configuration for preventing such a problem, it is conceivable to perform mask control in which the sensor output of the second additional transport sensor 53b is ignored during the transport stop period Tb and a mask period not reflected in the control is set.
Mask control is performed in which the sensor output of the second additional transport sensor 53b is not reflected in the control, with the transport stop period Tb as the mask period MT. As a result, even if the trailing edge Pe of the paper P is positioned at the detection position of the second additional conveying sensor 53b and the sensor output repeats "ON" and "OFF", the unstable sensor output is reflected in the control. not. Therefore, the control unit (101 or 501b) does not determine whether or not there is a problem with the paper P transport. As a result, it is possible to prevent the control unit (101 or 501b) from stopping the apparatus when there is no paper jam or conveyance failure.

In the example shown in FIG. 8, the paper is fed based on the time difference (“Ts1” in FIG. 8) from the timing “Tp1” to the timing when the sensor output of the second additional conveying sensor 53b immediately after the end of the mask period MT becomes “OFF”. The length of P in the transport direction can be calculated. Specifically, the length of the paper P can be obtained from the product of the value obtained by subtracting the transport stop period Tb (=MT) from the above-described time difference (“Ts1” in FIG. 8) and the transport speed of the paper P. can.
Further, when the sensor output of the second additional transport sensor 53b is already "OFF" at the end of the mask period MT, the time difference from the timing "Tp1" to the end of the mask period MT ("T5" in FIG. 8) The length of the paper P in the transport direction can be calculated based on. Specifically, the value obtained by subtracting the transport stop period Tb (=MT) from the above-described time difference (the time from “Tp1” to “T5” in FIG. 8) and the transport speed of the paper P are calculated. length can be obtained.

However, even if the mask control is performed with the transport stop period Tb as the mask period, the second extension transport sensor 53b again detects the passage of the trailing edge Pe of the paper P, causing a problem. something happened.
This defect will be described below.

FIG. 9 illustrates a state in which a sheet P whose length in the transport direction is slightly longer than the distance "L1" is fed, and the sheet P abuts against the pair of registration rollers 13 to form a bend Pd and stop transport. It is a diagram. FIG. 10 is an explanatory diagram of a state in which the bending Pd is eliminated due to the stiffness (rigidity) of the sheet P from the state of FIG. FIG. 11 is an explanatory diagram of a state in which the transport of the paper P is restarted from the state of FIG.
FIG. 12 is a timing chart in the case of feeding the paper P that can be in the states shown in FIGS. 9 to 11 and using the mask period MT as the conveyance stop period Tb.

Even if the paper P is longer than the distance "L1", if the leading edge of the paper P reaches the registration nip and is further conveyed to form the deflection Pd, as shown in FIG. The trailing edge Pe of the sheet may pass the detection position of the second additional conveying sensor 53b. This is because although the length of the paper P is longer than the distance "L", the trailing edge Pe of the paper P is detected by the second additional transportation sensor 53b during leading edge positioning (during the leading edge positioning transportation period Ta). This is the case where the detection position is passed. In this case, as shown in FIG. 12, the sensor output of the second additional transport sensor 53b becomes "OFF" before the timing ("T4" in FIG. 12) at which the transport of the paper P is stopped.

After that, the transportation is stopped (“T4” in FIG. 12) to enter the transportation stop period Tb. Since the portion of the sheet P having the flexure Pd is elastically deformed, a restoring force acts on the sheet P to extend the flexure Pd and restore the state before the deformation. For this reason, when a sheet P having a large restoring force, such as a sheet P having high rigidity (strong stiffness), hits the resist nip, the bending Pd may disappear due to the restoring force during the transport stop period Tb.

When the paper P is stretched so as to eliminate the flexure Pd, the distance from the leading end to the trailing end of the paper P in the conveying path returns to its original length by the flexure Pd, and the distance from the leading end to the trailing end of the paper P returns. may be longer than the distance "L1". At this time, the leading edge of the paper P hits the registration nip and cannot move downstream in the transport direction. It reaches the upstream side and becomes the state shown in FIG.
At this time, as shown in FIG. 12, the sensor output of the second additional transport sensor 53b changes from "OFF" to "ON" during the transport stop period Tb.
That is, when the roller pair (52b, 52a and 12) cannot hold the deflection Pd of the paper P after the leading edge positioning is completed, the trailing edge Pe of the paper P returns to the upstream side in the transportation direction by the deflection amount, and the second additional transportation is performed. It will be detected again by the sensor 53b.

As a configuration for preventing the trailing edge Pe of the paper P from returning to the upstream side in the transport direction, increasing the nip pressure of the roller pair (52b, 52a and 12) on the upstream side of the registration roller pair 13 can be considered. However, in the registration nip, a correction called skew correction is performed to return the inclination of the sheet P. FIG. Therefore, if the nip pressure of the pair of rollers (52b, 52a, and 12) nipping the paper P that has reached the registration nip is too high, the paper P cannot be rotated so as to return the skew, and the skew is corrected. I can't do it. In the registration nip, it is desired not only to align the leading edge of the paper P but also to perform skew correction. be. As a result of the nip pressure being relaxed, the trailing edge Pe of the paper P may return to the upstream side in the transport direction due to the force that attempts to restore the deflection Pd.

Next, when the transport is restarted, as shown in FIG. 11, the trailing edge Pe of the paper P again passes the detection position of the second additional transport sensor 53b. Therefore, as shown in FIG. 12, the sensor output of the second additional transport sensor 53b changes from "ON" to "OFF" immediately after the transport stop period Tb has passed.
When such a change occurs in the sensor output, in the control without providing the mask period MT, the sensor output becomes "OFF" before the conveyance is stopped, so that the trailing edge Pe of the paper P is detected by the second extension conveyance sensor 53b. Determine that the position has been passed. Next, when the sensor output changes from "OFF" to "ON" after the transportation is stopped, the control unit (101 or 501b) recognizes that the leading edge of the new paper P has passed the detection position, and Start paper length measurement to measure the length. After that, immediately after the conveyance stop period Tb has passed, the sensor output turns "OFF", so that it is recognized that the trailing edge of the new sheet P has passed the detection position. At this time, since the time from when the leading edge passes the detection position to when the trailing edge passes the detection position is very short, the control unit (101 or 501b) cannot measure the paper length, determines that there is a transport error, and restarts the apparatus. Stop.

On the other hand, as shown in FIG. 12, when the mask period MT is set to the conveyance stop period Tb, the sensor output becomes "OFF" before the start of the mask period MT. is determined to have passed the detection position. Next, the sensor output changes to "ON" during the mask period MT, and the paper P that has passed the detection position once is detected again, but this change is ignored. Next, the mask period MT ends with the end of the transport stop period Tb, and the sensor output is acquired, but the sensor output is already "ON". Therefore, the control unit (101 or 501b) recognizes that the leading edge of the new paper P has passed the detection position at the timing when the mask period MT ends, and starts paper length measurement for measuring the length of the paper P. do. However, immediately after that, the sensor output becomes "OFF", so that it is recognized that the trailing edge of the new sheet P has passed the detection position. At this time, since the time from when the leading edge passes the detection position to when the trailing edge passes the detection position is very short, the control unit (101 or 501b) cannot measure the paper length, determines that there is a transport error, and restarts the apparatus. Stop.

Next, specific examples of states in which the behavior of the sheet P shown in FIGS. 9 to 11 may occur will be described.
For example, the distance "L1" is set to 295 [mm], the distance "L2" is set to 12.1 [mm], and the distance from the second additional conveying sensor 53b to the second additional conveying nip ( "L3") is 2.0 [mm]. Also, during the leading edge positioning transport period Ta from when the registration sensor 20 detects the leading edge of the paper P (“T3” in FIG. 12) to when the transportation is stopped (“T4” in FIG. 12), 22.1 Convey by [mm]. Then, when an A4 sheet of paper P is fed in the vertical direction (length 297 [mm]), the behavior of the paper sheet P described with reference to FIGS. 9 to 11 may occur.

When the paper P is conveyed by 22.1 [mm] during the leading edge positioning conveyance period Ta, first, the registration sensor 20 detects the leading edge of the paper P, and then the paper P is conveyed by 12.1 [mm]. reaches the resist nip. Further, by conveying by 10 [mm], the deflection Pd is formed, and the trailing edge Pe of the paper P reaches a position 8 [mm] downstream in the conveying direction from the detection position of the second additional conveying sensor 53b. Then, the state shown in FIG. 9 is reached and the transport is stopped (T4). When the trailing edge Pe of the paper P passes through the detection position, the sensor output of the second additional transport sensor 53b becomes "OFF".
In the control shown in FIG. 12, the mask period MT is started at the same time as the transportation is stopped.

During this mask period MT, the warping Pd of the paper P returns to a flat state, so that the trailing edge Pe of the paper P moves backward by 10 [mm] corresponding to the warping amount. At this time, since the length of the paper P is 297 [mm] and the distance "L1" is 295 [mm], the trailing edge Pe of the paper P is moved to the first position by the difference of 2.0 [mm]. It moves to a position on the upstream side in the conveying direction from the detection position of the second additional conveying sensor 53b, and the state shown in FIG. 10 is reached.
After that, when the mask control is canceled at the same time as the transport is restarted by the registration control, the sensor output is turned "ON" because the paper P already exists at the detection position of the second additional transport sensor 53b. It recognizes that a new sheet has been conveyed. However, since the trailing edge of the paper P passes the detection position after 2 [mm] of transport (the state shown in FIG. 11), the sensor output of the second additional transport sensor 53b becomes "OFF". At this time, the length of the paper P that has passed the detection position after the mask control is calculated as 2 [mm], which is inappropriate as the length of the paper P. It is determined that there is a problem with the transportation of the At this time, the apparatus is stopped even though there is no paper jam or conveyance failure and no problem other than the sensor output occurs.

The distance from the additional feeding sensor 53 to the registration nip depends on the number of stages of the additional paper feeding device 50 and other additional paper feeding device 50 located downstream of the additional paper feeding device 50 accommodating the paper P to be fed in the conveying direction. It changes depending on the vertical dimension of Therefore, the states shown in FIGS. 9 to 11 may or may not occur depending on the above-described number of stages and the vertical dimension of the other downstream additional paper feeder 50. When the paper feeder 50 has only one stage, the distance from the additional transport sensor 53 of the additional paper feeder 50 to the registration nip is sufficiently shorter than the length of the A4 paper, resulting in the states shown in FIGS. It didn't work.

In addition, when the number of stages of the extension sheet feeding device 50 is set to multiple stages and feeding is performed from the second stage extension sheet feeding device 50 (second extension sheet feeding device 50b), the first stage extension sheet feeding device 50 (first Depending on the height dimension of the additional sheet feeding device 50a), the states shown in FIGS. 9 to 11 may occur.
More specifically, the additional paper feeder 50 can be selected between one that can accommodate 250 sheets of paper P and one that can accommodate 500 sheets of paper P. The states shown in FIGS. 9 to 11 did not occur even when the sheets were fed from the additional sheet feeding device 50 in the second stage. In this case, the trouble of detecting the trailing edge Pe of the same sheet P multiple times does not occur.

On the other hand, when a 500-sheet storage device (having a larger height dimension and a longer transport path than a 250-sheet storage device) is used as the first-stage additional sheet feeding device 50, the second-stage extension When the paper was fed from the paper feeding device 50, the states shown in FIGS. 9 to 11 were sometimes encountered. In this case, the trouble of detecting the trailing edge Pe of the same sheet P multiple times may occur.

Next, control for measuring the length of the paper P of the printer 100 according to the present invention will be described.
FIG. 1 is a timing chart of the printer 100 according to the present invention, in the case of feeding the paper P that can be in the states shown in FIGS. It is a timing chart when

The timing chart shown in FIG. 1 differs from the timing chart shown in FIG. 12 only in the mask period MT, so the description of common points will be omitted.
In the timing chart shown in FIG. 1, at a predetermined timing (after "dT1" in FIG. 1 after the registration sensor 20 detects the leading edge of the paper P (T3) during the leading edge positioning transport period Ta), the mask period Start MT. Further, after the conveyance stop period Tb has passed, the mask period MT is set at a predetermined timing (after the passage of "dT2" in FIG. 1 from the restart of conveyance (T5)) before the leading edge of the next sheet P reaches the detection position. finish.

In the timing chart shown in FIG. 1, the sensor output of the second additional transport sensor 53b changes from "ON" to "OFF" during the mask period MT. Therefore, the control unit (101 or 501b) does not recognize that the trailing edge Pe of the paper P has passed the detection position of the second additional transport sensor 53b before the start of the mask period MT. At the end of the mask period MT, the sensor output of the second additional transport sensor 53b is already "OFF", so at this time the trailing edge Pe of the paper P passes the detection position of the second additional transport sensor 53b. paper length measurement.

In the configuration of the timing chart shown in FIG. 1, the time difference (“Ts1” in FIG. 1) between the timing when the leading edge of the paper P passes the detection position (“Tp1” in FIG. 1) and the timing when the mask period MT ends (“Ts1” in FIG. ), the length of the sheet P in the transport direction can be calculated. Specifically, the length of the paper P can be obtained from the product of the value obtained by subtracting the transport stop period Tb from the above-described time difference (“Ts1” in FIG. 1) and the transport speed of the paper P.
In this control, when the trailing edge Pe of the paper P passes the detection position during the mask period MT, the paper length is calculated on the assumption that the trailing edge Pe has passed the detection position at the timing when the mask period MT ends. . Specifically, when the trailing edge Pe passes the detection position immediately after the start of the mask period MT and when the trailing edge Pe passes the detection position just before the end of the mask period MT, the calculated length is the same. The transport time during the mask period MT is the sum of "dT1" and "dT2" in FIG. This is not a problem in paper length measurement for determining whether paper P of an appropriate size is being conveyed.

“dT1” for determining the start timing of the mask period MT is preferably shorter than the time required for the leading edge of the paper P to reach the registration nip after passing through the position detected by the registration sensor 20 . That is, it is preferable that "dT1" is shorter than the time during which the paper P is conveyed by the distance "L2" after the sensor output of the registration sensor 20 is turned "ON". As a result, the mask period MT can be started before the sheet P reaches the registration roller pair 13, which is a resist conveying member, and before the leading edge of the sheet P begins to be bent Pd. Therefore, the trailing edge Pe of the paper P, which has passed the detection position before the start of the mask period MT, can be prevented from passing the detection position toward the upstream side during the mask period MT.

Since the distance from the registration sensor 20 to the registration nip differs depending on the model, the value of "dT1" differs depending on the model. In the printer 100 of this embodiment, the value of "dT1" is set so that the transport distance of the paper P during the time "dT1" is 7 [mm].
Since the distance from the detection position of the registration sensor 20 to the registration nip is 12.1 [mm], the mask period MT is started before the leading edge of the paper P reaches the registration nip, that is, before the bending Pd starts to form. can be realized.

The time “dT2” from the restart of transport to the end of the mask period MT is set to the following value. That is, in the sheet P whose trailing edge Pe has passed the detection position of the second additional conveying sensor 53b during the mask period MT, even if the bending (Pd) is extended and the trailing edge Pe is located upstream of the detection position, It is a value that is not detected. Specifically, in the present embodiment, the transport amount that forms the deflection Pd can be set between "0 [mm] to 10 [mm]". The maximum value of the distance that the trailing end of is returned to the upstream side is "10 [mm]". Therefore, in the printer 100 of this embodiment, the value of "dT2" is set so that the transport distance of the paper P during the time "dT2" is "10 [mm]". The value of "dT2" is not limited to this value, and is set according to the value of the transport amount that forms the deflection Pd.

Further, if the trailing edge Pe of the preceding sheet of paper P passes the detection position of the sensor during the mask period MT, and the leading edge of the succeeding sheet of paper P further passes, the trailing edge Pe of the preceding sheet of paper P passes through. can no longer be detected. Therefore, in the present embodiment, the transport distance of the paper P between "dT1" and "dT2", which is the transport time between the mask periods MT, is set to be less than the "paper gap W".
In this embodiment, the transport distance between "dT1" is "7 [mm]" and the transport distance between "dT2" is "10 [mm]". The transport distance between the two is "17 [mm]", which is less than the paper spacing W (=25 [mm]).

Let La be the conveying distance (the conveying distance between "Ta" in FIG. 1) from the detection of the leading edge of the sheet by the registration sensor 20 until the conveying is stopped. The distance “La” is the sum of the distance “L2” and the amount of deflection, and the amount of deflection can be set between “0 [mm] to 10 [mm]”. The value is "22.1 [mm]". Also, the length of the paper P is assumed to be "Lp".
The length over which the rear end Pe moves upstream when the flexure Pd extends is the length of contraction due to the flexure Pd, which is "La-L2".
The conditions under which the trailing edge Pe of the sheet P that has once passed the detection position of the second additional transport sensor 53b can return to the upstream side of the detection position due to the extension of the flexure Pd are "Lp−L1>0", In addition, "Lp-L1<La-L2" is established.

In the printer 100 of the present embodiment, when conveying an A4 sheet in the vertical direction (297 [mm]) so that the amount of deflection is "10 [mm]", "Lp" = 297 [mm], "L1" = 295 [mm], “La”=22.1 [mm], and “L2”=12.1 [mm]. In this case, "Lp-L1"=2.0 [mm], which satisfies the condition "Lp-L1>0". Further, since "La-L2"=10 [mm] (amount of deflection), the condition "Lp-L1<La-L2" is satisfied.

When the present inventors confirmed with an actual machine, the design value of "L1" is 299 [mm], and the amount of deflection of A4 paper in the vertical direction (297 [mm]) is "10 [mm]". Also, when the paper P is conveyed to , the trailing edge Pe of the paper P may be detected again. In this case, "Lp-L1"=-2.0 [mm], which does not satisfy the condition "Lp-L1>0". However, the above "Lp-L1 >0” condition is satisfied.

In the printer 100, the time from when the second additional transport sensor 53b is turned "ON" ("Tp1" in FIG. 1) to when the main relay clutch 24 is turned "ON" ("T2" in FIG. 1) is , the conveying distance at that time is set to be 10 mm. The conveying distance from "Tp1" to "T2" in FIG. 1 is not limited to "10 mm". is set so that the relay roller pair 12 rotates before reaching .

The timing chart shown in FIG. 1 includes a portion (“β” in FIG. 1) in which the second additional transport clutch 124b is temporarily turned “OFF” and immediately turned “ON” after transport is restarted. In this portion, when the space W between the preceding paper P and the succeeding paper P is jammed, the paper space W is fixed ("25 [mm]" in this embodiment). The roller pair 52b is stopped for a short period of time to temporarily stop the transport of the succeeding paper P.

A printer 100 having a configuration for conveying a sheet of paper P inside the device and having a function as a sheet conveying device includes an image forming unit 10, a main body paper feeding unit 30 as a paper feeding unit for supplying the paper P, An additional paper feeding unit 500 is provided. The main body control unit 101 of the printer 100 receives the size information of the paper P set in the main paper feed tray 31 of the main paper feed unit 30 and the additional paper feed tray 70 of each additional paper feed device 50 in the additional paper feed unit 500. and information on the length of the paper P in the transport direction (paper length). Further, the additional paper feeding control unit 501 of each additional paper feeding device 50 has size information of the paper P set in each additional paper feeding tray 70, and the length of the paper P in the transport direction (paper It also has information on

The printer 100 also includes a relay roller pair 12 and an additional transport roller pair 52 as transport means for transporting the paper P supplied from the main body paper feeding unit 30 or the additional paper feeding device 50 toward the image forming unit 10 . Further, as detection means for detecting the presence or absence of the paper P at the detection position in the paper P conveyance path, the pre-main body relay sensor 35 and the additional conveyance sensor 53, which are paper detection sensors, are provided. Then, the body control unit 101 can calculate the sheet length of the transported sheet P based on the detection result of the body pre-relay sensor 35 or the additional transport sensor 53 .

Further, during the leading edge position adjustment of the leading edge position of the paper P that has collided with the registration roller pair 13 provided on the upstream side of the image forming section 10 to a desired position, the sensor output of the paper detection sensor described above is turned "OFF". If not, mask control is started. This mask control is control in which the sensor output of the additional transport sensor 53 during the predetermined mask period MT is not used for the paper length measurement. Then, after the end of the mask period MT, which is a certain period of time ("Tb"+"dT2" in FIG. 1) after the leading edge positioning operation is completed ("T4" in FIG. 1), the paper detection sensor paper length is measured based on the sensor output.

When the trailing edge Pe of the paper P is detected during the positioning of the leading edge by the registration roller pair 13 and the trailing edge Pe is positioned near the paper detection sensor that uses the detection result to calculate the paper length, the detection position of the sensor is determined. trailing edge noise may occur in which the trailing edge Pe returns to the detection position after passing through once. With respect to such trailing edge noise, when the trailing edge Pe of the sheet of paper P passes the detection position of the paper detection sensor during leading edge positioning, that is, when the sensor output becomes "OFF", the above mask The sensor output of the paper detection sensor is not used for calculating the paper length until the period MT ends. As a result, the influence of trailing edge noise can be suppressed, and the sheet length can be appropriately measured regardless of the state of the trailing edge Pe of the sheet P during leading edge positioning.

In the configuration for controlling the timing chart shown in FIG. 1, the mask period MT is started at a predetermined timing after a certain period of time has passed since the registration sensor 20 was turned "ON" and before the transportation is stopped, and after the transportation is restarted. After a certain period of time has elapsed, the mask period MT ends. With such a configuration, the length of the paper P in the transport direction can be calculated without any problem even if the paper P performs the operations shown in FIGS. Therefore, regardless of the number of stages of the additional paper feeder 50 and the vertical dimension of the other additional paper feeder 50 positioned downstream in the transport direction from the additional paper feeder 50 accommodating the paper P to be fed, It is possible to determine whether or not the length of the paper P in the transport direction is appropriate.

In the printer 100, depending on whether or not the sensor output changes until the timing of resuming paper feeding (“T5” in FIG. 1), the additional conveying sensor 53 is detected between the resumption of paper feeding and the end of the mask period MT. may be configured to determine whether or not to use the sensor output. Specifically, while the trailing edge Pe of the paper P detected by the registration sensor 20, which is a detecting means installed on the upstream side of the registration roller pair 13, does not pass the detection position of the paper detection sensors (53, 35), , continue to check changes in the sensor output of the paper detection sensor. If the sensor output changes until the paper feed restart timing ("T5" in FIG. 1), the sensor output of the additional transport sensor 53 is used for paper length measurement until the above-described mask period MT ends. Control not to use. On the other hand, if the sensor output does not change until the timing of resuming paper feeding ("T5" in FIG. 1), the sensor output of the additional transport sensor 53 from the resumption of paper feeding to the end of the mask period MT is used for paper length measurement.

In this control, if the sensor output does not change from the start timing of the mask period MT to the timing of resuming paper feeding (“T5” in FIG. 1) and mask control is not necessary, then after resuming paper feeding Immediately, the sensor output of the additional transport sensor 53 can be used for paper length measurement. As a result, when performing mask control, the passage of the trailing edge Pe can be detected during the period ("dT2" in FIG. 1) in which the passage of the trailing edge Pe cannot be detected, so the length of the paper P can be calculated more accurately. It becomes possible to

As a method for calculating the length of the paper P, a plurality of paper detection sensors are arranged in the transport direction of the paper feed tray, and the paper detection sensors that detect the paper P and the paper detection sensors that do not detect the paper P are used. A method of calculating the length of the paper P based on the position of the boundary is conceivable. However, if an attempt is made to be able to detect paper P of any length, the number of paper detection sensors will increase, leading to increased cost and increased size. In order to reduce the number of paper detection sensors, the paper detection sensors must be arranged only at positions corresponding to the frequently used standard size paper P, and the length of the irregular size paper P must be reduced. cannot be detected. On the other hand, in the printer 100 of the present embodiment, based on the time from detecting the passage of the leading edge of the sheet P to detecting the passage of the trailing edge Pe by a certain sheet detection sensor, and the conveying speed, The length of the paper P is calculated. Therefore, since the length of the paper P can be calculated regardless of the size of the paper P, the size of the paper P set in each of the paper feed trays (31, 70a, 70b, and 70c) is irregular size. Even if there is, it becomes possible to deal with it.

Also, the timing at which the trailing edge Pe of the paper P passes the paper detection sensor can be detected appropriately, and the length of the paper P can be calculated accurately. Therefore, even if the paper P is of an irregular size, it is possible to accurately determine whether or not the set size of the paper P matches the size of the paper P being conveyed. It can also handle the paper P of .

Further, the additional transport sensor 53 has a function as a transport failure detection sensor that detects whether or not a transport failure such as a paper jam has occurred in the paper P fed from the additional paper feed tray 70 . Specifically, after the additional paper feed clutch 123 is turned "ON", the additional paper feed roller 51 starts to rotate, and the additional transport sensor 53 detects the passage of the leading edge of the paper P within a predetermined period of time. check whether it did. If the passage of the leading edge of the paper P is not detected within a predetermined period of time, it means that a paper jam or other transport failure has occurred in the transport path of the paper P between the additional paper feed tray 70 and the additional transport sensor 53. can be detected. By notifying the external device or the operation panel 102 of the occurrence of the transport failure based on the detection result, the transport failure, which is different from the problem that the length of the sheet P is not appropriate, is generated. The user can be informed of this.
The length of the paper P is calculated based on the detection result of the additional transport sensor 53, which is a sensor for detecting defective transport, and the noise countermeasures against the trailing edge noise are implemented by mask control. It is possible to take countermeasures against rear end noise.

FIG. 13 is a flow chart for measuring the length of the paper P using the paper detection sensor (one of 35, 53a, 53b, and 53c), and is a flow chart showing an outline from the start of paper feeding to the determination of size mismatch. is.
Using one of the paper detection sensors as a paper length measurement sensor, the length of the paper P is measured (calculated by the controller) based on the detection result.

After the start of paper feeding, when the passage of the leading edge of the paper P is detected by the corresponding paper detection sensor (35 or 53) ("Yes" in S11), the control unit (101 or 501) starts measuring the paper length ( S12). After that, when the passage of the trailing edge Pe of the paper P is detected by the paper detection sensor, the paper length measurement is completed ("Yes" in S13), and the measured (calculated) length of the paper P and the set length of the paper P are detected. It is determined whether or not the difference between the two is within a specified value (S14). If the value is within the specified value ("Yes" in S14), paper feeding is continued (S15). S16).

FIG. 14 is a flowchart for judging signs of deterioration and end of service life of the pair of conveying rollers applicable to the printer 100 of the present embodiment.
The paper detection sensor (one of 35, 53a, 53b and 53c) is assumed to be a paper length measurement sensor A. FIG. Further, any one of the paper detection sensors (35, 53a, 53b), the registration sensor 20, and the post-fixing sensor 21 located downstream of the paper length measurement sensor A in the transport direction is assumed to be a paper length measurement sensor B. By comparing the paper size measured by the paper length measuring sensor A and the paper size measured by the paper length measuring sensor B, it is possible to determine signs of deterioration and end of life of the transport roller pair.

After the start of paper feeding, when the paper length measuring sensor A detects the passage of the leading edge of the paper P ("Yes" in S21), the controller (101 or 501) starts measuring the paper length A (S22). Next, when the sheet length measurement sensor B detects the passage of the leading edge of the sheet P ("Yes" in S23), the control section (101 or 501) starts measuring the sheet length B (S24). Thereafter, when the passage of the trailing edge Pe of the paper P is detected by the paper length measurement sensor A, the measurement of the paper length A is completed ("Yes" in S25). Further, when the passage of the trailing edge Pe of the paper P is detected by the paper length measurement sensor B, the measurement of the paper length B is completed ("Yes" in S26). If the difference between the paper length A and the paper length B is less than the predetermined amount ("No" in S27), the measurement is terminated (S28), and the difference between the paper length A and the paper length B is equal to or greater than the predetermined amount. If so ("Yes" in S27), a display warning about the life of the roller pair is displayed (S29). This warning display is displayed on an external device or the operation panel 102 as notification means.

FIG. 15 is a flow chart of control for measuring the paper size and detecting a transport failure.
After the start of paper feeding, when the passage of the leading edge of the paper P is detected by the corresponding paper detection sensor (35 or 53) ("Yes" in S31, "Tp1" in FIG. 1), the controller (101 or 501) , the paper length measurement is started (S32). Next, when the registration sensor 20 detects the passage of the leading edge of the paper P ("Yes" in S33, "T3" in FIG. 1), leading edge positioning is started (S34, "Ta" in FIG. 1). When the positioning of the leading edge is completed ("Yes" in S35, "T4" in FIG. 1), registration is restarted (conveyance is restarted) (S36, after "T5" in FIG. 1).

After restarting registration, when the paper detection sensor detects passage of the trailing edge Pe of the paper P (at the end of "MT" in FIG. 1), the paper length measurement is completed ("Yes" in S37). Then, it is determined whether or not the difference between the measured (calculated) length of the paper P and the set length of the paper P is equal to or greater than a predetermined amount (S38). If the amount is equal to or greater than the predetermined amount ("Yes" in S38), it is determined that the sizes do not match, and paper feeding is stopped (S39). If the amount is less than the predetermined amount ("No" in S38), paper feeding is continued (S40), and it is determined whether or not a paper feeding failure will occur. If no paper feed failure has occurred ("No" in S41), paper feeding is continued (S42). occurrence), the sheet feeding is stopped (S43), and the external device and the operation panel 102 are notified to that effect.
Poor paper feeding includes non-feeding of the paper P, in which the paper P is not conveyed to the paper detection sensor, and accompanying feeding, in which a plurality of papers P are continuously conveyed while partially overlapping each other. .

In a configuration in which mask control is not performed or a configuration in which mask control is performed in which the mask period MT is set only during the transport stop period Tb, the re-detection of the trailing edge Pe causes the apparatus to be restarted even though there are no problems other than the sensor output. It may stop. On the other hand, in the printer 100 of the present embodiment that performs the mask control shown in FIG. 1, the re-detection of the trailing edge Pe is prevented, and it is erroneously detected that the transport failure has occurred even though the transport failure has not occurred. can be prevented. As a result, more accurate conveyance failure detection (JAM detection) can be performed, and the user can be notified of this.

The above-described printer 100 includes a multistage paper feed tray, and a paper detection sensor (main body pre-relay sensor 35 or pre-relay sensor 35 or The length of the paper P is calculated based on the detection result of the additional conveyance sensor 53). In addition, mask control is used to prevent a paper length calculation error caused by trailing edge noise that may occur during positioning of the leading edge of the sheet P by the pair of registration rollers 13 provided on the upstream side of the image forming section 10 .

A sheet conveying apparatus having a configuration for preventing calculation failure of the sheet length by performing such mask control is not limited to the sheet feeding section that conveys the sheet P as the recording medium. It is applicable to other sheet conveying devices as long as it has a registration conveying member (registration roller) that conveys the sheet to the downstream side at a predetermined timing after the sheet collides.

[Modification]
Hereinafter, as a modified example, a configuration in which the configuration of the sheet conveying device according to the present invention is applied to the ADF 80 will be described.
FIG. 16 is a schematic configuration diagram of an image reading device 300 according to a modification.
The image reading device 300 is configured to be switchable between a flatbed scanner mode (placed document reading mode) and a DF scanner mode (conveyed document reading mode).

The flatbed scanner mode is executed when a document is placed on the flatbed contact glass 113 at the top of the scanner 90 and a reading start request operation such as pressing a copy start button is performed, and the image of the placed document is displayed. Read operation mode. While moving the image reading unit 116 in the moving reading area 111 directly below the flatbed contact glass 113 , the image surface of the document is irradiated with light. The image of the document is read by converting the reflected light from the image surface of the document into an image signal.
The DF scanner mode is an operation mode in which the image reading unit 116 is stopped in the stop reading area 112 immediately below the DF contact glass 114 to read the conveyed document image.

When the image reading device 300 is in the DF scanner mode, the ADF 80 separates the document sheets one by one from the document sheet bundle stacked on the document placement tray 121 (document placement table) and conveys them into the document transport path 182 . and transported along the document transport path 182 . During the transport, the document sheet partially faces the upper surface of the DF contact glass 114 sequentially from the upstream portion in the transport direction.

The ADF 80 is attached to the upper rear portion (rear side portion) of the scanner 90 via an opening/closing mechanism such as a hinge. Further, the ADF 80 can take an open position in which the flatbed contact glass 113 is opened with respect to the scanner 90 and a closed position in which the original on the flatbed contact glass 113 can be pressed.

The image reading unit 116 may be a CCD module, a CIS module, or the like, as long as it can read the image on the front side of the document by repeatedly line-scanning it at a predetermined image reading position. A fixed image reading unit fixed to the stationary reading area 112 and a moving reading unit that moves along the flatbed contact glass 113 in the moving reading area 111 may be provided.

Left and right movable side guide plates 183 are attached to the document placement tray 121 for positioning the document sheet set on the ADF 80 in the sheet width direction orthogonal to the sheet feeding direction. These side guide plates 183 can be relatively moved toward and away from each other so that the center of the document tray 121 and the document sheet in the width direction are aligned. However, the side guide plate 183 may be arranged so that one edge of the document sheet is brought into contact with one edge of the document tray 121 and only the other edge is movable.

The ADF 80 is covered with a cover 138 that can be opened and closed at least above. Further, a main guide portion forming the document transport path 182 of the ADF 80 is formed by ribs or the like formed on the cover 138 . The ADF 80 includes a call roller 184 for picking up the document sheet set on the document tray 121 in the feeding direction, and a feed roller 184 for sending the document called in the feeding direction by the call roller 184 toward the document conveying path 182 . A roller 125 and a separation pad 143 are provided.

The ADF 80 has a transport section 127 that transports the document fed into the document transport path 182 by the feed roller 125 onto the DF contact glass 114 in an image-readable posture, and transports the document after image reading to the discharge port 136 . I have.

The transport unit 127 reverses the document sheet separated and transported by the feed roller 125 or the like so as to be folded back along the document transport path 182 . Feed the original sheet. For such document transport, a first transport roller pair 128 and a second transport roller pair 129 are provided on the upstream side of the DF contact glass 114 in the document transport path 182 to detect the leading edge of the document sheet in the transport direction. A document registration sensor 131 is provided. A document feeding detection sensor 154 is provided between the feed roller 125 and the first conveying roller pair 128 , and a document registration roller pair 150 is provided between the document registration sensor 131 and the DF contact glass 114 .

The original sheet separated by the feed rollers 125 and the like is conveyed by the first conveying roller pair 128 and the second conveying roller pair 129 to a position where it abuts against the original document registration roller pair 150 . Then, after a predetermined timing has elapsed from the timing at which the document registration sensor 131 detects the leading edge of the document sheet, the document registration roller pair 150 is rotationally driven. As a result, the document sheet is conveyed by the document registration roller pair 150 so as to pass over the DF contact glass 114 . Then, when the document sheet passes over the DF contact glass 114, the image reading unit 116 reads the image of the lower surface (front surface) of the document sheet in a timely manner.

When it is required to read the image of the back side of the document sheet (the side that becomes the top side when passing through the DF contact glass 114), the back side image is read by the back side image reading module 135 (second image reading department).
After reading, the document is discharged to the document discharge tray 139 .

On the downstream side of the DF contact glass 114 in the document transport path 182, there is provided a reading exit roller pair 132 for transporting the image-read document on the front side to the back image reading module 135 side. On the downstream side of the reading exit roller pair 132, there are a white guide member 133 facing the back image reading module 135, and a document discharge roller pair 137 positioned downstream from the back image reading module 135 and the white guide member 133. are provided respectively.

The white guide member 133 has a guide function to move the conveyed document along the back side image reading module 135, and has a white reference surface for shading correction arranged to face the back side image reading module 135 in the entire main scanning direction. have.

In the ADF 80 shown in FIG. 16, the transport direction of the document sheet is determined based on the time from when the document feed detection sensor 154 detects the leading edge of the document sheet to when the trailing edge of the document sheet is detected and the transport speed of the document sheet. can be calculated. The ADF 80 of the modified example is configured to calculate the length of the document sheet based on the detection result of the document feeding detection sensor 154, and the document sheet is brought into contact with the document registration roller pair 150 to form a bend at the leading edge of the document sheet. This is a configuration in which transportation is restarted after In such a configuration, control similar to the control described with reference to FIG. 1 of the printer 100 described above is performed. As a result, even if the trailing edge of the document sheet that hits against the document registration roller pair 150 is located near the document feed detection sensor 154, the document feed detection sensor 154 can prevent the trailing edge from being detected again. The length of the sheet can be properly calculated.

In the above-described embodiment, the sheet conveying member is formed of two roller members, but the sheet conveying member is not limited to two roller members. For example, a configuration in which a conveying nip is formed by a belt member and a roller member may be used.

The "sheet" conveyed by the sheet conveying apparatus according to the present invention includes paper, coated paper, OHP sheet, label paper, film, fabric, and the like. In addition, "sheets" include resin sheets, front and back protective paper, metal sheets, metal foils such as copper foils, electronic circuit board materials that have been plated, special films, plastic films, prepregs, and electronic circuit boards. Including sheets for A prepreg is a sheet-like material in which carbon fibers or the like are impregnated with a resin in advance. As an example of prepreg, a fibrous reinforcing material such as carbon fiber or glass cloth is impregnated with a thermosetting resin mixed with additives such as a curing agent and a coloring agent, and then heated or dried to a semi-cured state. sheet-like reinforced plastic molding compound.

In addition, an "image forming apparatus" having a structure of a sheet conveying device applies developer and ink to media such as paper, OHP sheet, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramics. image forming apparatus. Further, "image formation" includes not only imparting meaningful images such as characters and figures to the medium, but also imparting meaningless images such as patterns to the medium.

What has been described above is only an example, and each of the following aspects has a unique effect.

(Aspect 1)
A sheet conveying member such as a second additional conveying roller pair 52b that conveys the sheet toward a registration conveying member such as the registration roller pair 13 that conveys the sheet after the front end of the sheet such as the sheet P that is conveyed collides; Detecting means such as a second additional conveying sensor 53b for detecting a sheet such as the paper P conveyed by the conveying member; In the second additional paper feeding device 50b or the sheet conveying device such as the printer 100 including a calculating means such as the additional paper feeding control section 501b, the calculating means stops detecting the sheet after the detecting means detects the sheet. The length of the sheet is calculated based on the time (Ts1, etc.) until the sheet reaches the resist conveying member, and the abutment period (from timing "T3" until the resist conveying member starts conveying) When the detecting means stops detecting the sheet (the sensor output of the second additional conveying sensor 53b) during the period from the timing at which the sheet P is conveyed by the distance "L2" to the timing "T5" is changed from "ON" to "OFF"), the calculation means determines the interval between the abutment period and a predetermined period ("dT2" in FIG. 1) after the start of conveyance of the resist conveying member (mask period The period included in MT) is characterized in that the detection result of the detection means is not used for calculating the sheet length.

As a result of extensive studies by the inventors of the present invention, it has been found that when the sheet length is close to the distance from the detection means that uses the detection result to calculate the sheet length, the sheet length can be appropriately determined. I found that there are things that cannot be calculated. This is considered to be due to the following reasons.
That is, if the sheet continues to be conveyed by the sheet conveying member after it hits the resist conveying member and before being conveyed by the resist conveying member, the sheet is flexed (flexure Pd or the like) in the vicinity of the leading end of the sheet. Since the flexed portion of the sheet is elastically deformed, a restoring force acts on the sheet to extend the flexure and restore the state before the flexure is formed. If the sheet is stiff, the restoring force is large, and the bending of the sheet that is in contact with the resist conveying member may be extended. At this time, the leading edge of the sheet striking the registration conveying member cannot move downstream in the conveying direction, and the trailing edge of the sheet moves upstream in the conveying direction.
When the trailing edge of the sheet passes the detection position of the detection means after such deflection begins to be formed and the deflection is extended, the trailing edge of the sheet that has passed the detection position again moves further in the conveying direction than the detection position. move upstream. As a result of this movement, the detecting means detects the sheet, and when the registration conveying member starts conveying the sheet, the trailing edge of the sheet immediately passes the detecting position and the detecting means stops detecting the sheet. In such a case, the time from when the detecting means detects the sheet until it stops detecting it becomes very short, and the detection result is as if a sheet with a very short length has passed the detection position of the detecting means. Length cannot be calculated properly.

In mode 1, when the detecting means stops detecting the sheet during the abutting period, control is performed so that the detection result of the detecting means during the abutting period is not used for calculating the sheet length.
Before the abutment period, that is, before the leading edge hits the resist conveying member, the sheet that has passed the detection position of the detection means then bends. never move upstream. In this case, even if a phenomenon occurs in which the flexure of the sheet is elongated, the sheet whose trailing edge has passed the detection position will not be detected again by the detection means.
On the other hand, the sheet whose trailing edge has passed the detection position of the detecting means during the abutment period thereafter bends and when the bending extends, the trailing edge reaches the upstream side of the detection position and is again detected by the detecting means. be done. After that, when the registration conveying member starts conveying, the trailing edge passes the detection position again, and the detecting means stops detecting the sheet. In mode 1, since the detection result of the detection means is not used for calculating the sheet length between the abutment period and the predetermined period, the predetermined period is defined as a period including the timing when the trailing edge passes the detection position again. Then, it is recognized that the detecting means continues to detect the sheet until a predetermined period of time elapses. After that, the detecting means after the lapse of the predetermined period is used to calculate the sheet length. The length of the sheet is calculated assuming that the edge has passed the detection position of the detection means.
As a result, even if a phenomenon occurs in which the flexure of the sheet, which has formed the flexure due to contact with the registration conveying member, is extended, the sheet length is not affected by the detecting means again detecting the sheet whose trailing end has been detected by the detecting means. can be prevented from occurring.
Further, when the sheet whose trailing edge has passed the detection position of the detection means during the abutment period forms a flexure and then maintains the flexure, the detection means will not detect the sheet again. In this case, in mode 1, based on the sheet detection state of the detection means before the start of the abutment period and the sheet non-detection state of the detection means after the predetermined period has passed, when the predetermined period has passed, The sheet length is calculated assuming that the trailing edge of the sheet has passed the detection position of the detection means.
In such control, an error in the sheet length occurs, at maximum, by an error corresponding to the sheet conveying amount during the combination of the abutment period and the predetermined period. However, since this error is sufficiently short with respect to the sheet length, it does not pose a problem in the control of calculating the sheet length in order to determine whether or not the sheet of an appropriate length is being conveyed. The length can be calculated properly.

When the sheet conveying device of the present invention is an additional sheet feeding device such as the second additional sheet feeding device 50b in the above-described embodiment, the sheet conveying device does not have a resist conveying member and conveys the sheet toward the resist conveying member. It becomes a device to Further, when the sheet conveying device of the present invention is an image forming apparatus such as the printer 100 in the above-described embodiment, the sheet conveying device includes a resist conveying member, and the sheet conveying member arranged on the upstream side in the conveying direction causes the resist. It becomes a device that conveys the sheet toward the conveying member. Also in the case where the sheet conveying device of the present invention is a document conveying device like the modified ADF 80 described above, the sheet conveying device includes a resist conveying member, and the sheet conveying member arranged on the upstream side in the conveying direction performs resist conveying. It becomes a device that conveys a sheet toward a member.

(Aspect 2)
In Aspect 1, a pre-registration detecting means such as a registration sensor 20 for detecting a sheet heading toward the resist conveying member is provided on the upstream side of the conveying direction of the resist conveying member. (timing "T3", etc.), a predetermined timing until the sheet reaches the resist conveying member (timing after "dT1" has elapsed from "T3", starting timing of the mask period MT, etc.) to the abutment period (such as during the mask period MT), the calculation means calculates the detection result of the detection means from a predetermined timing to the end of the predetermined period as It is characterized in that it is not used for calculating the sheet length.
According to this, control is performed so that the detection result of the detection means is not used for calculating the sheet length from a predetermined timing until the sheet reaches the registration conveying member. For this reason, even if the timing at which the sheet reaches the registration conveying member is slightly earlier, the control is performed so that the detection result of the sheet whose trailing end has passed the detection position after the bending starts is not used for calculating the sheet length. realizable.

(Aspect 3)
In mode 1 or 2, when the detecting means continues to detect the sheet during the abutting period, the calculating means calculates the detection result of the detecting means as the length of the sheet after the registration conveying member starts to be conveyed. It is characterized by being used for calculation.
According to this, the sheet whose trailing edge has not passed the detection position during the abutting period will not be detected again by the detection means due to the extension of the flexure. Therefore, by using the detection result of the detection means for calculating the sheet length after the registration conveyance member starts to be conveyed, the detection result of the detection means can be used to calculate the sheet length after a predetermined period of time ("dT2" or the like) has elapsed. can be used to calculate the sheet length more accurately.

(Aspect 4)
In any one of modes 1 to 3, a plurality of detecting means (53a to 53c, 35, 20 and 21, etc.) are provided in the sheet conveying path, and the calculating means is the sheet conveying path among the plurality of detecting means. It is characterized in that the sheet length is calculated based on the detection results of detection means (53a to 53c, 35, etc.) located on the most upstream side in the conveying direction.
According to this, it is possible to calculate the sheet length while the number of conveyed sheets subsequent to the sheet whose length is being calculated is small.

(Aspect 5)
In any one of the modes 1 to 4, the value of information about the length of the sheet acquired before being transported by the sheet transporting member (information about the size of the sheet P input from an external device or the operation panel 102, etc.); It is characterized by comprising a notification means such as a communication unit for communicating with an external device or an operation panel 102 or the like for notifying when the value of the sheet length calculated by the calculation means does not match.
According to this, it is possible to inform the user that the length of the sheet being conveyed is not appropriate. Furthermore, in the case of providing the configuration of Mode 4, it is possible to notify the user of a state in which the length of the conveyed sheets is not appropriate (such as a setting error state), even when the minimum number of sheets is conveyed.

(Aspect 6)
In any one of modes 1 to 5, a plurality of detection means (53a to 53c, 35, 20 and 21, etc.) are provided in the sheet conveying path, and one of the plurality of detection means (53a to A control unit (101) for comparing the sheet length calculated based on the detection result of the other detection means (53a, 53b, 35, 20 or 21) with the sheet length calculated based on the detection result of the other detection means (53a, 53b, 35, 20 or 21). or 501) or the like.
According to this, when the difference in sheet length compared by the comparing means is large, the members (52a to 52c, 12, 13, or the members 52a to 52c, 12, 13 or 4 and 8) that convey the sheet located downstream of each detecting means It can be determined that one of the pair of rollers is prone to slip due to deterioration. Therefore, it is possible to predict that the member for conveying the sheet is approaching the end of its life due to deterioration over time, and it is possible to perform maintenance before frequent paper jams occur due to deterioration. .

(Aspect 7)
In any one of modes 1 to 6, the apparatus is characterized in that, when a sheet transport defect is detected, a transport defect occurrence notification means such as a communication unit for communicating with an external device and an operation panel 102 or the like is provided to notify the occurrence of the sheet transport defect. and
According to this, when it is detected whether or not a conveyance failure has occurred based on the detection result of the detection means, when the trailing edge of the sheet passes through a plurality of detection positions due to the extension of the flexure, the conveyance error occurs. It is possible to prevent the determination of a transport defect in a state in which no defect has occurred. Therefore, it is possible to more accurately detect the occurrence of a transport failure.

(Aspect 8)
In an image forming apparatus such as a printer 100 including an image forming means such as an image forming unit 10 for forming an image on a sheet such as a sheet of paper P to be conveyed, any one of the aspects 1 to 7 is used as a configuration for conveying the sheet. It is characterized by having such a configuration of the sheet conveying device (additional sheet feeding device 50 or main body sheet feeding section 30 or the like).
According to this, it is possible to appropriately calculate the length of the sheet on which the image is to be formed, and to prevent the image from being formed on the sheet having an inappropriate length.

1 Main Body Housing 2 Photoreceptor 3 Manual Feed Tray 4 Post-Fixing Conveyance Roller 5 Fixing Device 6 Pre-Ejection Diverting Claw 7 Imaging Section 8 Post-Fixing Reversing Conveying Roller 9 Reversing Conveying Roller 10 Image Forming Section 11 Main Body Feeding Roller 12 Relay roller pair 13 Registration roller pair 14 Transfer roller 15 Fixing roller pair 16a First paper discharge roller 16b Second paper discharge roller 16c Third paper discharge roller 17 Manual feed roller 18 Post-relay nip transport path 19 Paper discharge tray 20 Registration sensor 21 Post-fixing sensor 22 Main body conveying motor 23 Main body paper feed clutch 24 Main body relay clutch 25 Registration clutch 30 Main body paper feed section 31 Main body paper feed tray 33 Main body paper feed section passage conveyance path 34 Main body paper feed separation roller 35 Main body pre-relay sensor 50 Extension paper feeder 50a First extension paper feeder 50b Second extension paper feeder 50c Third extension paper feeder 51 Extension paper feed roller 51b Second extension paper feed roller 52 Extension transport roller pair 52a First extension transport roller pair 52b Second extension transport roller pair 53 Extension transport sensor 53a First extension transport sensor 53b Second extension transport sensor 53c Third extension transport sensor 70 Extension paper feed tray 70a First extension paper feed tray 70b Second extension paper feed tray 70c Third Additional paper feed tray 73 Additional paper feeder passage transport path 73a First additional paper feeder passage transport path 74 Additional paper feed separation roller 90 Scanner 100 Printer 101 Main body control unit 102 Operation panel 111 Moving reading area 112 Stop reading area 113 Flatbed Contact glass 114 Contact glass 116 Image reading unit 121 Document placing tray 122 Extension paper feeding motor 122a First extension feeding motor 122b Second extension feeding motor 123 Extension feeding clutch 123b Second extension feeding clutch 124 Extension transport clutch 124a First additional conveying clutch 124b Second additional conveying clutch 125 Feed roller 127 Conveying unit 128 First conveying roller pair 129 Second conveying roller pair 131 Document registration sensor 132 Reading exit roller pair 133 White guide member 135 Back image reading module 136 Exit 137 Document discharge roller pair 138 Cover 139 Document discharge tray 143 Separation pad 150 Document registration roller pair 154 Document feed detection sensor 182 Document transport path 183 Side guide plate 184 Call roller 200 Copier 300 Image reader 500 Additional paper feed section 501 additional paper feed controller 5 01a First additional paper feed control unit 501b Second additional paper feed control unit MT Mask period P Paper Pe Rear end Ta Leading edge positioning transport period Tb Transport stop period W Between sheets

Patent No. 5358607

Claims (7)

a sheet conveying member for conveying the sheet toward a resist conveying member for conveying the sheet after the leading edge of the conveyed sheet collides with the sheet;
a detecting means for detecting the sheet conveyed by the sheet conveying member;
A sheet conveying apparatus comprising: calculating means for calculating the sheet length, which is the length of the sheet in the conveying direction, based on the detection result of the detecting means,
The calculating means calculates the sheet length based on the time from when the detecting means detects the sheet until when the sheet is no longer detected,
When the detecting means stops detecting the sheet during the abutment period from when the sheet reaches the resist conveying member to when the resist conveying member starts conveying,
The calculating means does not use the detection result of the detecting means for calculating the sheet length between the abutment period and a predetermined period after the start of conveyance of the resist conveying member,
When the detecting means continues to detect the sheet during the abutting period,
The sheet conveying apparatus , wherein the calculating means uses the detection result of the detecting means for calculating the sheet length after the registration conveying member starts to convey. In the sheet conveying device of claim 1,
pre-registration detecting means for detecting the sheet heading toward the resist conveying member on the upstream side of the resist conveying member in the conveying direction;
The calculation means performs the detection during a period from a predetermined timing after the pre-registration detection means detects the sheet until the sheet reaches the registration conveying member until the end of the abutment period. If the means no longer detect the sheet,
The sheet conveying apparatus, wherein the calculation means does not use the detection result of the detection means during the period from the predetermined timing to the end of the predetermined period for calculating the sheet length . In the sheet conveying device according to claim 1 or 2 ,
A plurality of the detection means are provided on the sheet conveying path,
The calculating means calculates the sheet length based on the detection result of the detecting means positioned most upstream in the conveying direction of the sheet in the conveying path among the plurality of detecting means. Sheet conveying device. The sheet conveying device according to any one of claims 1 to 3 ,
a notification means for notifying a fact when the value of information on the length of the sheet acquired before being conveyed by the sheet conveying member and the value of the length of the sheet calculated by the calculation means do not match each other; A sheet conveying device characterized by: The sheet conveying device according to any one of claims 1 to 4 ,
A plurality of the detection means are provided on the sheet conveying path,
A comparison means for comparing the sheet length calculated based on the detection result of one of the plurality of detection means and the sheet length calculated based on the detection results of the other detection means. A sheet conveying device characterized by: The sheet conveying device according to any one of claims 1 to 5 ,
A sheet conveying apparatus comprising: a conveying defect occurrence notification unit that notifies the occurrence of a conveying defect of the sheet when the sheet conveying defect is detected. In an image forming apparatus comprising an image forming means for forming an image on a conveyed sheet,
An image forming apparatus comprising the configuration of the sheet conveying device according to any one of claims 1 to 6 as a configuration for conveying the sheet.

Images