JP2000284556A - Recording sheet supply device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always steadily supply recording sheets to a carrying path at regular intervals by determining, for each sheet based on measured time, a standby period from the time of the detection of the recording sheet by a recording sheet detection means to the time of the supply of the following recording sheet by a pickup mechanism. SOLUTION: In the case recording paper of K page is fed out to a carrying path 10 after the drive of a pickup mechanism 4, a top sensor 11 changes from an off-condition to an on-condition when the leading end of the recording paper of K page reaches the top sensor 11. In order to determine the timing of paper feed for the following page (K+1 page), the value of a timer (Time n) obtained when the pickup mechanism 4 is driven and the value of the timer obtained when the top sensor 11 detects the recording paper are set as Tstn and T1n, respectively. A value obtained by subtracting (T1n-Tstn) from a value found by dividing the sum of a page length and a page gap by the speed of carrying is set as Twn. Then, after the top sensor 11 is turned on, the pickup mechanism 4 is driven following standby for a period of only Twn, and the following page is supplied to the carrying path 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conveying device for conveying a recording sheet in an image forming apparatus such as a printer.

[0002]

2. Description of the Related Art In an image forming apparatus (such as a printer) for forming an image on a recording sheet such as a recording paper or an OHP film,
The recording sheets are stored in a cassette in a stacked state. A pickup mechanism is provided to supply the recording sheets in the cassette one by one to a predetermined conveyance path in the image forming apparatus.

In general, the pickup mechanism has a pickup roller (a cylindrical type or a D-shaped cross section) that comes into contact with the uppermost recording sheet in the cassette. The pickup roller is configured to rotate while contacting the upper surface of the recording sheet on its outer peripheral surface, and to send the recording sheet to a transport path. In order to ensure that the recording sheet and the pickup roller are in contact with each other, the stacked recording sheets are urged (by a spring or the like provided at the bottom of the cassette) in a direction in which the recording sheet comes into contact with the pickup roller.

When image formation is continuously performed on a plurality of pages, the pickup roller is rotated to supply the uppermost recording sheet to the conveyance path, and after waiting for a certain period of time, the pickup roller is rotated again and the next recording sheet is rotated. Is supplied to the transport path. This “standby time” is a value obtained from the dimensions of the apparatus.

[0005]

However, when the stacking amount of the recording sheet is small and large, the compression state of the spring member pressing the recording sheet against the pickup roller is different. Frictional force changes. When the frictional force changes, the time from when the pickup mechanism is operated to when the recording sheet is actually supplied to the transport path changes little by little. for that reason,
In the configuration in which the recording sheet is supplied after waiting for a certain time as described above, stable continuous supply of the recording sheet cannot be maintained for a long time.

The present invention has been made in view of the above circumstances, and has as its object to provide a recording sheet supply apparatus capable of supplying recording sheets to a conveyance path at regular intervals in a stable state.

[0007]

In order to solve the above-mentioned problems, a recording sheet supply apparatus of an image forming apparatus according to the present invention comprises a storage unit for storing recording sheets and a recording sheet stacked on the storage unit. A pickup mechanism that supplies the recording sheet to the path, a recording sheet detection unit that detects passage of the recording sheet in the conveyance path, and a time period from when the pickup mechanism operates until the recording sheet is detected by the recording sheet detection unit. And measuring means. The standby time from when the recording sheet detecting means detects the recording sheet to when the pickup mechanism supplies the next recording sheet is determined one by one based on the time measured by the measuring means. Is what you do.

As described above, according to the present invention, the time from when the pickup mechanism operates to when the recording sheet is detected by the recording sheet detecting means is actually measured, and the supply of the next recording sheet is performed based on the actually measured value. Timing is decided.
Therefore, even if the timing from when the pickup mechanism operates to when the recording sheet is sent to the conveyance path changes due to a change in the frictional force between the recording sheet and the roller, the interval between the recording sheets sent to the conveyance path changes. Nothing to do.

More specifically, the waiting time T from when the recording sheet detecting means detects the recording sheet to when the pickup mechanism supplies the next recording sheet is determined by T = BA. Here, A is the measured time, and B is a time conversion value obtained by dividing the total of the page length of the recording sheet and the page interval to be provided by the transport speed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to embodiments. FIG. 1 is a diagram illustrating a basic configuration of an electrophotographic printer (hereinafter, printer 1) according to an embodiment. The printer 1 has a housing 18 having a substantially rectangular parallelepiped shape. Although a recording sheet is used as the recording sheet, an OHP film or the like may be used. Is a recording paper cassette 5 in which recording paper is laminated.
Are housed in a cassette mounting portion 19 at the bottom of the housing 18.

A transport path 10 through which the recording paper is transported extends from the lower right to the upper left of the housing 18 in the drawing. The recording paper sent out from the recording paper cassette 5 (by the pickup mechanism 4 described later) is transported along the transport path 10 from lower right to upper left in the figure. Along the transport path 10,
A process unit 6 for transferring a toner image to recording paper and a fixing device 7 for fixing the transferred toner image to recording paper are provided.

The process unit 6 uniformly charges the outer peripheral surface of the photosensitive drum 61, irradiates the outer peripheral surface with a laser beam to form an electrostatic latent image, and adsorbs toner powder on the electrostatic latent image. And transfer the toner image to recording paper. Since the configuration of the process unit 6 is known, a detailed description thereof will be omitted. Note that a transfer roller 62 for bringing the recording paper conveyed through the conveyance path into close contact with the photosensitive drum 61 and transferring the toner image on the drum to the recording paper is disposed opposite to the photosensitive drum 61. The photosensitive drum 61 and the transfer roller 62 are a transfer unit 60.

A scanning optical device 8 is arranged above the process unit 6 for irradiating the outer peripheral surface of the photosensitive drum 61 with a laser beam. The fixing device 7 includes a pair of rollers (fixing roller pair 70) including a heat roller 71 having a built-in heat source and a transfer roller 72 for pressing a recording sheet against the heat roller 71. Since the configurations of the scanning optical device 8 and the fixing device 7 are both publicly known, detailed description thereof is omitted.

In order to convey the recording paper along the transport path 10, three transport roller pairs 14, 1 are provided along the transport path 10.
5 and 16 are provided. These transport rollers 14, 1
The motors 5 and 16 are rotationally driven by a motor M (not shown) (always during printing control). The recording paper supplied to the conveyance path 10 is sequentially conveyed by three pairs of conveyance rollers 14, 15, 16, a transfer unit 60 and a fixing roller pair 70, and a discharge port 18 a formed at the upper left of the housing 18 in FIG. Is discharged from The recording paper discharged from the discharge port 18a falls as it is and is stacked on the mounting table 18b (image side downward).

The transport path 10 is provided with a top sensor 11 and a paper discharge sensor 12 for detecting the passage of the recording paper.
The top sensor 11 is arranged on the upstream side in the transport direction of the transfer unit 60, and is pivoted by the leading end of the recording sheet to fall down.
1a and a photo sensor (not shown) for detecting the tilting of the swing lever 11a. The paper ejection sensor 12
The swing lever 12a is disposed downstream of the fixing roller pair 70 and is pushed down by the leading edge of the recording paper to fall down, and includes a photo sensor (not shown) for detecting the fall down of the swing lever 12a.

The pickup mechanism 4 for feeding the recording paper in the cassette 5 to the transport path 10 has a pickup roller 40 which is a roller having a substantially D-shaped cross section (a so-called D roller). The pickup roller 40 is arranged such that its arc-shaped outer peripheral portion is in contact with the upper surface of the uppermost recording sheet in the cassette 5. Note that the bottom plate 51 of the cassette 5 is configured to be swingable so that the uppermost recording sheet in the cassette 5 can be in contact with the arc-shaped outer peripheral portion of the pickup roller 40. It is biased upward. The upper limit position of the recording paper stacked on the bottom plate 51 is regulated by a stopper 53 fixed to a side wall (a front side or a back side in the figure) of the cassette 5.

As shown in FIG.
The pickup roller 40 is not in contact with the recording paper when the circular arc-shaped outer peripheral portion is facing the opposite side to the recording paper. In this state, the recording paper is in contact with the stopper 53. When the pickup roller 40 rotates counterclockwise in the drawing, the arc-shaped outer peripheral portion of the pickup roller 40 comes into contact with the surface of the uppermost recording sheet. Then, the recording paper is fed to the right side in the figure and fed to the transport path 10 by the frictional force between the roller surface and the recording paper.

The recording paper sent to the transport path 10 is further transported along the transport path 10 by a pair of transport rollers 14 that are constantly rotating during printing control. After supplying one sheet of recording paper to the conveyance path 10, the pickup roller 40 stops with its arc-shaped outer peripheral portion facing upward as shown in FIG. 1, and waits until the next page is fed.

FIGS. 2A to 2C are diagrams showing the operation of the pickup mechanism 4. FIG. FIG. 3 is a sectional view of the pickup mechanism 4. As shown in FIG. 3, a ring 43 with a gear and a stopper ring 44 are coaxially attached to a rotation shaft 42 of the pickup roller 40. The geared ring 43 is slidably attached to the rotating shaft 42 and has gear teeth on the outer periphery. On the other hand, the stopper ring 44 is fixed to the rotating shaft 42 and has a projection 45 on the outer periphery.

The geared ring 43 is driven to rotate by the motor M via a gear train (not shown). The geared ring 43 and the stopper ring 44 are engaged while sliding via a coil spring 43a. That is, when the rotation of the stopper ring 44 is not locked (by any stopper means), the stopper ring 44 (and the pickup roller 40) rotates following the geared ring 43. On the other hand, if the rotation of the stopper ring 44 is locked, the stopper ring 44 (and the pickup roller 4
0) does not rotate, and only the geared ring 43 idles.

The protrusion 45 of the ring 44 has a solenoid 4
6 is driven by the stopper plate 47 shown in FIG.
Are engaged as shown in FIG. When the solenoid 46 is turned on, the stopper plate 47 moves away from the outer peripheral surface of the stopper ring 44. Thereby, FIG. 2 (B)
, The stopper ring 44 (and the pickup roller 40) rotates counterclockwise. Solenoid 46
Turns on for a short time (for example, 100 msec),
To return to the off state, the stopper plate 47 again contacts the outer periphery of the stopper ring 44 as shown in FIG. When the stopper ring 44 makes one rotation in this state (that is, when the pickup roller 40 makes one rotation), the protrusion of the ring 44 comes into contact with the stopper plate 47 again. Thus, the pickup roller 40 stops just after making one rotation per one operation of the solenoid 46.

FIG. 4 is a block diagram showing a control system of the printer 1. Instruction information from an external device such as a personal computer is transmitted to the controller 100 of the printer 1. Various commands and image information are transmitted from the controller 100 to the printer engine 110. Also, printer engine 1
From the printer 10 to the controller 100, status information on the printer side and horizontal and vertical synchronization signals are transmitted.

The printer engine 110 includes a pickup mechanism 4 (solenoid 46), a top sensor 11 and a paper ejection sensor 12, a transport motor M, a scanning optical device 8 (a laser irradiating device and a scanning mirror rotating device, etc.), and a process power supply unit 6 ( (A high-voltage power supply to a charger, a developing device, and a transfer unit).

Next, the transfer device of the embodiment will be described. FIG. 5 is a timing chart of the transfer device. For example, it is assumed that the pickup mechanism 4 is driven to send the K-th page of the recording sheet to the transport path 10. When the leading edge of the K-th page of the recording paper reaches the top sensor 11, the top sensor 11 changes from off to on. Note that the timer in this embodiment is based on software timekeeping processing in the printer engine.

In order to determine the paper feed timing of the next page (K + 1 page), the value of the timer (Time n) when the pickup mechanism 4 is driven is set to Tst n, and the top sensor 11 detects the recording paper. Set the value of the timer at the time of execution to Tin. Then, a value obtained by subtracting (Tin-Tstn) from a value obtained by dividing the total of the page length and the page gap (a predetermined interval provided between pages) by the transport speed is set as Twn. After the top sensor 11 is turned on, after waiting for a time Twn, the pickup mechanism 4 is driven to supply the next page to the transport path 10.

As described above, in this embodiment, the time from when the pickup mechanism 4 operates to when the recording paper is detected by the top sensor 11 is actually measured, and the next recording paper is fed based on the actually measured value. Timing is decided. Therefore, due to the change in the frictional force between the recording paper and the pickup roller 40, the recording paper is transferred to the conveyance path 1 after the operation of the pickup mechanism.
Even if the timing until the recording paper is fed to 0 changes, the interval between the recording paper fed to the conveyance path 10 can be kept constant.

The transfer bias in the transfer unit 60 of the process unit 6 is turned on a predetermined time Txon after the recording paper reaches the top sensor 11 (upstream from the transfer unit). The predetermined time Txon is a value (time conversion value) obtained by dividing the distance between the top sensor 11 and the transfer unit by the transport speed. The transfer bias is such that the rear end of the recording paper is the top sensor 11.
Is turned off after a predetermined time Txoff (= Txon). Although not shown in the timing chart,
The control such as the rotation of the scanning optical device 8 and the photosensitive drum 61 is also performed based on the on / off timing of the top sensor 11.

As described above, the control system of this embodiment can perform parallel processing of up to four pages, but in the example of FIG. 5, parallel processing of two pages is performed (that is, the K-th page). (The (K + 1) th page is being fed during the processing).

The following is a flowchart (FIGS. 6 to 27)
The transport device according to the embodiment will be described in detail with reference to FIG.

FIG. 6 is a flowchart showing a main routine of the printer engine 110. After the power of the printer 1 is turned on, a start process is performed. Specifically, a flag PageActive n (n = 0, 1, 2, 3) described later is set to 0 (prohibited).
And set NextPage n (n = 0, 1, 2, 3) to 1 (permitted)
And clear the timers Time and Time p described later (S
2). Next, the timer starts counting (S
4) The timer interrupt is permitted (S6), and communication with the controller is enabled so that data can be received (S8).

When the start process is completed, the process enters a loop of a command receiving process (S10) and a status transmitting process (S12). In the command reception process, it is checked whether a command signal has been received from the controller. In the status transmission process, information on the printer side, such as a print completion signal and an error signal, is transmitted to the controller.

The command receiving process (S10) and the status transmitting process (S12) include steps S14 and S14.
The print sequence control (S18) is continued via S16. Steps S14 and S16 are periodically executed in parallel with the loop of the command receiving process (S10) and the status control process (S12) to control the print sequence (S18).
Is to execute. Time is a variable that is sequentially incremented by a timer interrupt, and the latest Time value is stored in Time p (S16). Therefore, only when Time is incremented by a timer interrupt, the result of step S14 is NO, and the result of step S1 is NO.
8 print sequence control is performed. That is, the print sequence control (S18) is executed every time a timer interrupt occurs.

FIG. 7 shows the command receiving process in step S10. In the command receiving process, it is checked whether a command from the controller has been received (S1).
00), if a command has been received, it is checked whether the command is a print command (S10).
2). Then, a “page control permission” process (S110) for initializing the memory area for the print sequence is performed. or,
When a command other than the print command is received, other command control is performed (S104).

Here, the page control permission subroutine of step S110 called in the command receiving process of FIG. 7 will be described with reference to FIG. In the control system of this embodiment, four sets of parameters can be set to enable printing control of up to four pages. The number indicating which set of parameters is n (n =
0, 1, 2, 3). In the page control permission process of FIG. 8 executed after receiving the print command, a number n of 0, 1, 2, or 3 is assigned to the page to be printed. The number n is incremented by 1 starting with ntop (S400, S406). However, after n = 3, n =
0. For example, when ntop is 0, n = 0 → 1 →
Numbers are assigned in the order of 2 → 3. And
The print control of the page corresponding to the assigned number n (hereinafter, simply referred to as page n) is permitted. Specifically, PageActive n, which is a flag for permitting printing of page n, is set to 1 (S412).

However, if there is a page currently being printed, it is necessary to assign a "next number" to the page to be printed. Then, while incrementing n, it is checked whether PageActive n has already become 1 for each n (S402, S404, S406, S408, S4).
10), initialize and use parameters of page n for which PageActive is not set to 1 yet.

If the parameter clear has not been completed after four rounds of the loop from steps S402 to S410, the parameter Resp indicating a negative response is set to 0 (S41).
6). On the other hand, if the parameter clear is completed normally, the parameter Resp indicating an affirmative response is set to 1 (S41).
4). After returning to the command receiving process of FIG. 7, if Resp is 1, an affirmative response (S114) is performed, and if Resp is 0, a negative response (S116) is performed.

Step S4 of the page control permission process of FIG.
12, a timer Time n set for each page, a waiting time Tw n until the supply of the subsequent page, a comparison variable Tcomp n used for a plurality of purposes, and a flag NextPage n for inhibiting the printing control of the next page. Set to 0 (prohibited). Also, a flag PageActive n for permitting printing of page n is set to 1 (printing permitted). Furthermore, a parameter Tpagelength n described later
Is a value obtained by dividing the page length (length of the recording paper in the transport direction) by a predetermined transport speed set in advance (that is, a time conversion value of the length of one page of the recording paper).

If the page to be printed is the first page (print start page), it is necessary to perform a starting operation for starting the polygon mirror and the like of the scanning optical device. On the other hand, if it is a page to be printed continuously from the previous page, it is not necessary to perform the start-up operation. Therefore, it is determined in the parameter clear processing (S412) whether the print start page is in the middle of continuous printing.

That is, when the process has passed through steps S402 and S404 at one time (i = 0), it is determined that the page is a print start page, and a sequence described later is started from the start-up process (sequence # 0). In other cases (i> 0), it is determined that continuous printing is being performed, and the sequence is started from the sheet feeding process (sequence # 1) without performing the startup process. The start-up process and the sheet feeding process (sequences # 0 and # 1) will be described later.

FIG. 9 shows a status transmission routine of step S12. In the status transmission routine, it is checked whether there is a status to be transmitted, such as completion of printing or occurrence of an error (S120), and the status is transmitted to the controller (S1).
22).

FIG. 10 shows the print sequence control in step S18. In the print sequence control, print control of the page set in the command receiving process is executed. That is, based on the value of PageActive n set in the command reception process, it is determined which page n corresponds to which page is being processed (S134), and print control of that page is executed (S136). Steps S130 and S13
Numeral 8 is for increasing n by 1 from ntop. Steps S140 and S142 are for setting n = 0 after n = 3. The variable i and step S132 are for returning to the main routine (FIG. 6) after making four rounds of the loop (steps S132 to S142).

FIG. 11 shows a control routine for page n in S136 in the print sequence (FIG. 10). As described above, since the print sequence control (FIG. 10) is executed every time a timer interrupt occurs, the control of page n in FIG. 11 is also executed every time a timer interrupt occurs. Therefore, Time n (S) is incremented each time the print control of page n is executed.
150) functions as a timer dedicated to page n.

In step S152, the sequence # 0
The processing of # 10 (or # 1 to # 10) is performed. Each time one process of the sequence is completed, it is checked whether a standby time Twn described later has elapsed (S154), and the standby time Tw is checked.
Is passed, print control for the next page is permitted (S156). Then, returning to the print sequence control of FIG. 10, after n is incremented, page control is started again.

Here, the relationship between print sequence control and individual processing will be described with reference to the schematic diagram of FIG.
In FIG. 12, ntop is assumed to be 0. Regardless of whether or not a command has been received from the controller, the loop in FIG. 10 (steps S132 to S142) is repeatedly executed. However, when the command has not been received yet,
“Control of page n (step S136 in FIG. 10)” is skipped (passed through).

When the first print command is received from the controller, the command reception process permits print control of the page corresponding to n = 0. In the print sequence control, the control of page n (S136 in FIG. 10) is executed, and the activation process of sequence # 0 is performed.

When n = 1, 2, 3, the control of page n is skipped. When n = 0 again, the control proceeds to page n. This time, the process proceeds to sequence # 1, which is one sequence ahead of the previous sequence # 0, and the pickup mechanism is driven. After the completion of sequence # 1, FIG.
It returns to the control of page n of 1.

As described above, until the next command is received, only the sequence for n = 0 is processed in numerical order (sequence # 1 → # 2 → # 3...).

When a print command is newly received from the controller, the print control of the page corresponding to n = 1 is permitted in the command receiving process. In this case, in the print sequence control, after performing the print control of the page of n = 0 (for example, sequence # 7), the print control of the page of n = 1 is performed. Since the printer has already been started, sequence # 1 (paper feed processing) is executed instead of sequence # 0.

At this time, if the “prohibition of printing control of the page next to the n = 0 page” set at the time of receiving the first command is not released, the sequence # 1 is performed without driving the pickup mechanism 4. Then, the process returns to the control routine for page n. On the other hand, if "control prohibition of the page next to the page of n = 0" has already been released, the pickup mechanism 4 is driven to feed a new page.

As described above, in the control system of this embodiment,
n = 0, 1, 2, 3. . . Since the sequence is sequentially executed one by one while repeating the above, it is possible to perform the parallel control of a plurality of pages (for example, the trailing edge detection check of the first page and the sheet feeding of the second page).

Next, the specific processing contents of the sequence will be described. The sequence # 0 in FIG. 13 is a start-up process executed only in the case of a print start page. In this start-up process, the start-up sequence of the printer, that is, processes such as the start of rotation of the polygon mirror of the scanning optical device 8, the start of rotation of the (constantly rotating) transport rollers 14, 15, 16 and the charging of the photosensitive drum of the process unit 6, (S15)
8). Thereafter, the sequence number SQn is increased by 1 (S159).

Sequence # 1 in FIG. 14 is a paper feed process for driving the pickup mechanism 4 to feed the recording paper to the transport path 10. First, the value of the parameter NextPage n-1 is checked to determine whether control of page n is prohibited (S160). The symbol n-1 is set to 3 when n is 0.

If the control of page n is not prohibited, the current time Time n is stored as Tst n, and the pickup mechanism 4 is simultaneously driven (S162, S16).
4). Specifically, the above-described solenoid 46 is driven to release the lock of the pickup roller 40 by the stopper plate 47, and the motor M is started to drive the pickup roller through rotation.

Further, after the paper is fed, the recording paper is
In consideration of the reference time Ttop (constant value) required to reach 1, the “longest scheduled time” at which the leading edge of the recording paper reaches the top sensor 11 is stored as Tcomp n (S166). still,
The longest scheduled time is set slightly longer in consideration of a margin value. At the end of sequence # 1, sequence number S
Qn is increased by 1 (S168).

Sequence # 2 in FIG. 15 is a leading edge detection process for detecting the leading edge of the recording paper. In the leading edge detection process, it is detected whether or not the top sensor 11 is actually turned on before the scheduled time at which the leading edge of the recording paper reaches the top sensor 11 (S170, S172). If the top sensor 11 is not turned on even at the longest scheduled time, an error process (S171) is performed. When the top sensor 11 is turned on,
It is stored as the time Tin (S174).

Then, "the leading edge of the recording paper is
The waiting time Twn from the time when the recording paper of the next page is fed until the next page is reached is determined according to the following formula (S178).
Tw n = Tlength n + Tgap n- (Ti n-Tst n) where Ti n-Ts
tn is the time from when the paper is fed to when the recording paper reaches the top sensor 11. Tlength n is a time conversion value (fixed value) obtained by dividing the page length by the conveyance speed, and Tgap n is a time conversion value (fixed value) obtained by dividing the gap length provided between pages by the conveyance speed. It is.

The standby time Twn set here is used in step S154 of the above-described page n control (FIG. 11). That is, every time one process of the sequence is completed,
It is checked whether the waiting time Twn has elapsed (S15).
4) If the waiting time Twn has elapsed, the printing control of the next page is permitted (S156). At this time, if a command from the controller has been received, the next page is fed as shown in FIG.

Thereafter, a vertical synchronization signal is transmitted to the controller (S180). Further, the transfer start time (Tin + Txon) is set to Tcompn based on the time (constant value determined by the apparatus size) Txon required for the recording paper that has passed the top sensor 11 to reach the transfer unit 60 (S182). At the end of the leading edge detection processing, the sequence number SQn is incremented by one (S184).

Sequence # 3 in FIG. 16 is a process for turning on the transfer bias in the transfer unit 60 of the process unit 6. In sequence # 2, the transfer bias is turned on at the scheduled time when the recording paper reaches the transfer section R (S190, S190).
192). Then, the recording paper is transferred from the transfer section to the paper ejection sensor 12.
, Based on the time Tpout (a constant value determined by the device size) required to reach the maximum time (Tin)
+ Tpout) is set to Tcomp n (S194). At the end of the transfer bias on process, the sequence number SQn is increased by 1 (S196).

Sequence # 4 in FIG. 17 is a recording paper discharge check process for checking whether the recording paper has normally reached the discharge sensor 12 (without causing a paper jam or the like). In this sequence # 4, the recording paper is
The paper discharge sensor 12 is checked until the longest scheduled time to reach (S200).

FIG. 18 shows the sheet discharge sensor check process called in step S200. In the paper discharge sensor check process of FIG.
Before the longest scheduled time (Tcomp n = Ti n + Tpout) reaching 2 is reached, it is checked whether the paper discharge sensor 12 is actually turned on (S300, S302). If the paper discharge sensor 12 is not turned on even at the longest scheduled time, an error process (S304) is performed. If the paper ejection sensor 12 is turned on as scheduled, the longest scheduled paper ejection sensor 12 to be turned off is based on the value (Tlength × m) obtained by multiplying the time conversion value Tlength of the page length by a predetermined margin m (> 1). Time (Ti n +
(Tlength × m)) is set to Tcomp n (S306).
This value is used in sequence # 9 described later. At the end of the sheet discharge sensor check processing, the sequence number SQn is increased by 3 (S308).

When the paper discharge sensor check processing is completed, the rear end detection processing is called in step S202 of sequence # 4 (FIG. 17). The trailing edge detection processing shown in FIG. 19 is for setting the time when the transfer bias should be turned off. Specifically, after detecting that the trailing edge of the recording paper has passed the top sensor 11 (that is, the top sensor 11 has changed from on to off) (S310), the time of the distance between the top sensor 11 and the transfer unit R is determined. Based on the converted value Txoff, the scheduled time (Ti n + Txof) at which the rear end of the recording paper passes the transfer portion R
f) is set to Tcompsub n (S312). At the end of the trailing edge detection processing, the sequence number SQn is incremented by 1 (S314).

The sequence after the sequence # 4 is branched into two types depending on whether the page length is longer or shorter than the distance between the top sensor 11 and the paper discharge sensor 12 (the distance between the sensors). As shown in FIG. 20A, if the page length is shorter than the sensor-to-sensor distance, the trailing edge of the recording paper reaches the top sensor 11 before the leading edge of the recording paper reaches the paper ejection sensor 12.
(That is, the top sensor 11 is turned off before the paper discharge sensor 12 is turned on). In this case, S308 of the sheet ejection sensor check processing (FIG. 18) is skipped, and S314 of the trailing edge detection processing (FIG. 19) is executed, so that the next sequence to be executed is "sequence # 5".

On the other hand, as shown in FIG. 20B, if the page length is longer than the distance between the sensors, when the leading edge of the recording paper reaches the paper ejection sensor 12, the trailing edge of the recording paper extends to the top sensor 11. (That is, the top sensor 11 remains on when the paper discharge sensor 12 turns on). In this case, S308 of the sheet discharge sensor check process (FIG. 18) is executed, and S314 of the trailing edge detection process (FIG. 19) is skipped. Therefore, the sequence to proceed to next is “sequence # 7”.

First, sequences # 5 and # 6 executed when the page length is shorter than the inter-sensor distance will be described. Sequence # 5 shown in FIG. 21 is a process for turning off the transfer bias. In sequence # 5, the above-described sheet ejection sensor check processing (FIG. 18) is executed (S21).
0) Then, the transfer bias off process of FIG. 22 is executed (S212). The reason for repeating the above-described sheet discharge sensor check processing is that the leading edge of the recording sheet has not yet reached the sheet discharge sensor 12 in the situation where sequence # 5 is executed.

In the transfer bias-off process shown in FIG. 22, the scheduled time at which the trailing edge of the recording paper passes the transfer portion R (Tcomps
Then, the transfer bias of the transfer unit of the process unit is turned off (S320, S322). Then, the sequence number SQn is increased by 1 (S3
24).

In the sequence # 6 shown in FIG. 23, the above-described sheet ejection sensor check processing is executed (S220). Since sequence # 6 includes only S220, the paper discharge sensor 12
Until is turned on or the scheduled time is reached, the sheet discharge sensor check processing is repeatedly executed. When the paper ejection sensor 12 is turned on, the time conversion value Tl of the page length is used as described above.
ength multiplied by a predetermined margin m (> 1) (Tlength
× m), the scheduled time at which the paper discharge sensor 12 is turned off is set to Tcomp n. At the end of the sheet discharge sensor check processing, the sequence number SQn is increased by 3, and the sequence to proceed to next is sequence # 9. Sequence # 9 will be described later.

Next, sequences # 7 and # 8 executed when the page length is longer than the inter-sensor distance will be described. In the sequence # 7 shown in FIG. 24, the above-described rear end detection processing (FIG. 19) is executed (S230). The reason for repeating the trailing edge detection process is that the trailing edge of the recording paper has not yet reached the top sensor 11 in the situation where sequence # 7 is executed. Since the sequence # 7 includes only S230, the rear end detection process is repeatedly executed until the top sensor 11 is turned off. When the top sensor 11 is turned off, the sequence number SQn is increased by one, and the sequence to proceed to next is sequence # 8.

In the sequence # 8 shown in FIG. 25, the above-described transfer bias off processing (FIG. 22) is executed (S24).
0). As described above, in the transfer bias off process, the transfer bias is turned off at the scheduled time when the rear end of the recording paper passes the transfer portion R, and the sequence number SQn is increased by one.

In the case of passing through sequences # 5 and # 6,
When the sequence # 7 or # 8 is passed, the sequence #
9 is performed. The sequence # 9 shown in FIG. 26 is a process of checking whether the paper discharge sensor 12 is actually turned off by the longest scheduled time at which the paper discharge sensor is turned off (set to Tcomp n) (S250, S250). S252).
If the discharge sensor 12 is not turned off by the longest scheduled time,
Error processing is performed (S254). Then, the paper ejection sensor 1
The scheduled discharge time is set to Tcomp n based on the time Texit (a fixed value determined by the distance from the paper discharge port to the paper discharge sensor) required for the recording paper that has passed through No. 2 to be completely discharged from the paper discharge port (S256). ). Then, the sequence SQn is set to 1
(S258).

In sequence # 10 of FIG. 27, it is determined whether to print the next page. Specifically, n + 1
Check PageActive n corresponding to (S260, 2
62, 264, 266). When performing the print control of the next page, return PageActiven to 0, and then return to the control routine for page n (FIG. 11). On the other hand, if the next page is not to be printed, the printer waits until the printed recording paper is scheduled to be completely discharged from the paper discharge port 18a (set to Tcomp n) and stops the printer (S268). , S
270). Finally, PageActive n is set to 0, and ntop is incremented (S272).

Finally, the features of this embodiment will be summarized. In sequence # 2 in FIG. 15, the time from when a certain page is fed to when it reaches the top sensor (Ti n-Tst
n) is measured, and based on the measured value, the waiting time Tw from the detection of the certain page by the top sensor to the supply of the next page is determined as follows (S1).
76). Twn = Tlengthn + Tgapn- (Tin-Tstn) where Tlengthn is a value obtained by dividing the page length by the transport speed (so-called time conversion value), and Tgapn is a gap provided between pages. This value is obtained by dividing the length by the transport speed.

With this configuration, even if a large number of images are continuously formed, the interval between the recording sheets does not change. In particular, even when the time from when the pickup roller 40 is activated to when the recording sheet is actually fed to the transport path changes due to the change in the frictional force acting between the pickup roller 40 and the recording sheet. Thus, the interval between the pages sent to the transport path can be kept constant, and the continuous supply of the recording paper can be always stabilized.

[0074]

As described above, according to the recording paper supply device of the image forming apparatus of the present invention, the time from when the pickup mechanism picks up the recording paper to when the recording paper is detected by the recording paper detecting means. Since the time is actually measured and the timing of supplying the next recording paper is determined based on the measured value, the interval between the recording papers can be kept constant even if image formation is continued with continuous paper.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a basic configuration of a printer according to an embodiment.

FIG. 2 is a diagram illustrating an operation of a pickup mechanism.

FIG. 3 is a sectional view showing a structure of a pickup mechanism.

FIG. 4 is a block diagram illustrating a control system of the printer in FIG. 1;

FIG. 5 is a timing chart showing the operation of the printer of FIG.

FIG. 6 is a flowchart showing a main flow.

FIG. 7 is a flowchart illustrating a command receiving process.

FIG. 8 is a page control permission routine.

FIG. 9 is a flowchart showing a status receiving process.

FIG. 10 is a flowchart illustrating print sequence control.

FIG. 11 is a flowchart showing page control.

FIG. 12 is a schematic diagram showing the progress of a sequence.

FIG. 13 is a flowchart showing a sequence # 0.

FIG. 14 is a flowchart showing a sequence # 1.

FIG. 15 is a flowchart showing a sequence # 2.

FIG. 16 is a flowchart showing a sequence # 3.

FIG. 17 is a flowchart showing a sequence # 4.

FIG. 18 is a flowchart illustrating a sheet ejection sensor check process.

FIG. 19 is a flowchart illustrating a trailing edge detection process.

FIG. 20 is a schematic diagram illustrating a relationship between a page length and a distance between sensors.

FIG. 21 is a flowchart showing a sequence # 5.

FIG. 22 is a flowchart illustrating a transfer bias off process.

FIG. 23 is a flowchart showing a sequence # 6.

FIG. 24 is a flowchart showing a sequence # 7.

FIG. 25 is a flowchart showing a sequence # 8.

FIG. 26 is a flowchart showing a sequence # 9.

FIG. 27 is a flowchart showing a sequence # 10.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer 4 Pickup mechanism 6 Process unit 10 Transport path 11 Top sensor 12 Discharge sensor 40 Pickup roller 46 Solenoid 60 Transfer part

Continued on the front page F term (reference) 2C058 AB15 AB23 AC08 AE02 AE09 AE13 AF17 AF20 AF23 AF25 GA14 GB03 GB08 GB14 GB31 GB49 GC06 GE21 2H072 AA03 AA09 AA16 AA29 AB10 AB18 AB19 AB20 BA02 BA12 BA20 CA01 CA02

Claims (7)

[Claims] An image forming apparatus for forming an image on a recording sheet while conveying the recording sheet along a predetermined conveyance path, comprising: a storage unit for storing the recording sheet; and a recording sheet stacked on the storage unit. A pickup mechanism for feeding the recording sheet to the conveyance path one by one; a recording sheet detection means provided in the conveyance path for detecting passage of a recording sheet; and a recording sheet detection means for detecting the passage of the recording sheet after the operation of the pickup mechanism. Measuring means for measuring the time until it is detected, and, the standby time from when the recording sheet detecting means detects a recording sheet until the pickup mechanism supplies the next recording sheet, A recording sheet supply device for an image forming apparatus, comprising: a control unit that determines one sheet at a time based on the time measured by the measurement unit. 2. A method according to claim 1, wherein the time measured by said measuring means is A, and the time conversion value obtained by dividing the total of the page length of the recording sheet and the page interval to be provided by B is B. 2. The standby time T from when the sheet detecting means detects the leading edge of the recording sheet to when the pickup mechanism supplies the next recording sheet is determined by T = BA. Recording sheet supply device of the image forming apparatus. 3. The recording sheet feeding device according to claim 1, wherein the pickup mechanism has a sheet feeding roller having a D-shaped cross section. 4. The recording sheet supply device according to claim 3, wherein the sheet feeding roller makes one rotation after the elapse of the standby time to feed the recording sheet to the conveyance path. . 5. The transport path is provided with a constantly rotating transport roller that transports a recording sheet supplied to the transport path by the paper feed roller. A recording sheet supply device for an image forming apparatus according to any one of the above. 6. The recording sheet supply apparatus according to claim 1, wherein said image forming apparatus is a printer using an electrophotographic method. 7. The recording sheet detecting means includes a swing lever which falls down on the leading end of the recording sheet, and a photo sensor which detects the fall of the swing lever.
The recording sheet supply device for an image forming apparatus according to claim 1, wherein: