JP2000118749A - Picture image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten FCOT(First Copy Out Time) without causing the inconvenience of a picture image due to the fluctuation of rotation speed of a motor and causing an error in motor rotation. SOLUTION: Whether the number of revolutions of a motor is within a region of the number of normal rotation or not is monitored by an encoder 22, an f/V converter 23, a specified rotation number voltage generation part 26, and a comparator 27. When a signal indicating that the rotation of the motor is out of the region of the number of normal rotation is generated from the comparator 27, the signal is neglected if the time of the signal generation is within the time determined in advance from the start of the rotation of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, and more particularly to an image forming apparatus for forming an image on a conveyed sheet.

[0002]

2. Description of the Related Art In an electrophotographic copying machine, a sheet stored in a sheet cassette is fed by driving a motor, conveyed to an image forming section, and forms an image on the sheet. That is, after developing the latent image formed on the photoconductor drum with toner, the toner image on the photoconductor drum is transferred onto paper, and the toner image is fixed on the paper by a fixing device. The motor used for paper feeding is called a main motor, and is commonly used for driving a photosensitive drum, a fixing device, and a paper discharging mechanism in addition to a paper feeding mechanism.

Conventionally, there has been a method of monitoring the number of rotations of such a motor and, when the number of rotations falls outside a predetermined number of rotations range, setting an error state as a motor rotation failure. This is to prevent the rotation speed of the photosensitive drum from changing due to the rotation of the motor, thereby preventing a latent image formed on the photosensitive drum from expanding and contracting in the drum rotation direction.

In general, the rotation speed of a motor starts rotating from a stopped state and does not become constant until a certain time elapses, but gradually converges to a constant rotation speed while increasing or decreasing the rotation speed. It is something that goes.

A conventional copier monitors the number of rotations of a motor, and starts latent image formation and sheet feeding after the unstable region is completed and the number of rotations is stabilized.

Further, the time from when the copy start button is pressed until the copy sheet is discharged (First Copy O
In order to shorten the ut Time (hereinafter, FCOT), means for increasing the sheet conveyance speed to a position just before the image transfer unit is adopted.

[0007]

However, when the latent image formation and the sheet feeding operation are started after the rotation of the motor is stabilized, the time required to escape from the unstable region is added to the FCOT. . Further, if paper is fed in an unstable region to shorten FCOT, the rotation speed may deviate from a predetermined rotation speed region at a stage before the rotation speed converges. At this time, an abnormal motor rotation error is output. There was a problem that it would.

SUMMARY OF THE INVENTION The present invention has been made in view of such a background, and an object of the present invention is to reduce an FCOT without causing a problem of an image due to a fluctuation in a rotation speed of a motor and without causing a motor rotation error. An object of the present invention is to provide an image forming apparatus that can be shortened.

[0009]

According to the present invention, there is provided an image forming apparatus for conveying a sheet from a sheet tray to an image forming section to form an image on the sheet. It has a paper means, and starts the operation of the paper supply means in an initial rotation unstable region of a motor for conveying the paper.

More specifically, a motor rotation speed detecting means for monitoring whether or not the rotation speed of the motor is within a normal rotation speed region, and the motor rotation speed deviating from the normal rotation speed region from the motor rotation speed detecting device. Error generating means for generating an error when a signal indicating that the motor rotation is out of the normal rotation speed area within a predetermined time from the start of rotation of the motor. If the indicated signal is generated, the signal is ignored.

In other words, the motor rotation speed detecting means for monitoring whether or not the rotation speed of the motor is within the normal rotation speed region, and the motor rotation speed deviates from the normal rotation speed region from the motor rotation speed detection means. Error generating means for generating an error when a signal indicating that the motor rotation is normal within a predetermined time from the start of sheet feeding at the time of forming the first image. When a signal indicating that the signal is out of the rotation speed range is generated, the signal is ignored.

More specifically, the sheet conveyed from the sheet tray is once conveyed to a predetermined position on a conveyance path, and then is made to stand by at this position. A sheet feeding mechanism for conveying the sheet to the image forming section, wherein the sheet is conveyed from the sheet tray to a standby position within an initial rotation unstable region of the motor;

As described above, according to the present invention, the FCOT can be shortened by utilizing the initial rotation unstable region of the motor for transporting the sheet within a range where no problem occurs in image formation.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 schematically shows the internal structure of an electrophotographic copying machine as an example of an image forming apparatus according to the present invention.

Inside the copier 100, a reading optical system 64 is located below the platen glass 62. The reading optical system 64 reciprocates to scan a document. The optical image read by the reading optical system 64 forms an electrostatic latent image on a photosensitive drum (image forming unit) 65 via an optical system including a lens system 60. This electrostatic latent image is developed by the developing unit 63 with toner. Further, in the transfer section 77, the toner image is transferred onto the conveyed paper. The transferred toner image on the sheet is heated and fixed by the fixing device 68 and is discharged onto a sheet discharge tray 70.
The power of each of these mechanisms is obtained by the main motor 75.

A sheet as a recording medium is selected from one of a plurality of sheet trays 13, a manual tray 74, and a roll sheet feeding section 17, and is temporarily moved to a position of a sheet leading edge sensor (registration sensor) 66 prior to image formation. Paper is fed and waits here. The waiting sheet is conveyed toward a transfer unit 77 by a registration (registration) roller 76 at a predetermined timing. The rotation of the registration roller 76 is performed by transmitting the rotation of the main motor 75 via a registration clutch (not shown).

The copying machine 100 is provided with an operation panel (not shown) for man-machine interface with the user. The operation panel includes a display (LCD) for presenting various information to the user, Indicator indicating current paper feed position, paper selection key for selecting paper feed position (paper tray 13, manual feed tray 74, roll paper feed unit 17), start key for starting copying, copy Numeric keys and the like for designating the number of sheets are arranged.

In this embodiment, a DC brushless motor is used as the main motor 75, and the rotation speed of the motor is controlled by PLL control (Phase L).
ock Loop). FIG. 2 shows a block diagram of the control device according to the present embodiment.

In FIG. 2, the main motor 75 is shown as a motor unit 20. This motor unit 20
It is driven by the device control unit 30 including the CPU 31. The motor unit 20 includes a motor unit 21, a frequency / voltage (f / V) converter 23, a first comparison unit 24, a drive unit 25, a specified rotation speed voltage generation unit 26, and a second comparison unit 2.
7, a motor unit 21, an f / V converter 23, and a comparison unit 2.
4. The drive unit 25 and the specified rotation speed voltage generation unit 26 constitute a PLL control unit. The motor unit 21 includes a rotor, a stator, and a drive coil (none of which are shown), and also has a built-in encoder 22 that generates a pulse signal having a frequency corresponding to the rotation speed of the rotor.

The drive section 25 drives / stops the motor section 21 in response to an ON / OFF signal from the apparatus control section 30. Motor unit 21 driven by drive unit 25
Is converted into a pulse signal by the encoder 22. This pulse signal is converted by the f / V converter 23 into a corresponding analog voltage. Specified rotation speed voltage generator 26
Is a reference voltage (specified rotation speed voltage) Vref corresponding to a rotation speed preset (specification) in the motor unit 20.
Occurs. This reference voltage Vref and the f / V converter 2
The comparison unit 24 compares the analog voltage Vo from the control unit 3 with the analog voltage Vo, and feeds back the comparison result to the drive unit 25 so that the rotation speed of the motor unit 21 is controlled to match the specified rotation speed.

The second comparing section 27 determines whether or not the analog-converted voltage Vo is within a specified voltage range (Vref ± α), so that the motor rotation speed falls within the normal rotation speed region. A rotation speed detection signal 35 indicating whether or not there is is output. For this purpose, the specified rotation speed voltage generation unit 2
It is determined whether the absolute value of the difference between the reference voltage Vref and the voltage Vo from No. 6 is within a predetermined value (2α).

Although not shown, the device control section 30 is provided with time measuring means such as a timer.

FIG. 3 is a timing chart showing the rotation characteristics of the motor according to the present embodiment, together with the signal waveforms of various parts.

"Motor rotation speed change" in FIG. 3 indicates a change in motor rotation speed until the rotation speed falls within a specified normal rotation speed region after the motor starts to be driven from a stopped state. As can be seen from the figure, it takes a certain time after the start of motor driving until the motor rotation speed falls within the normal rotation speed region.

The “paper feed ON signal” 33 is transmitted to the apparatus control unit 30.
For starting a sheet feeding operation, which is started by the sheet feeding mechanism, and starts conveying the sheet. In this embodiment, when the motor rotation speed first enters the normal rotation speed region (t1), the paper feed O
The N signal 33 turns ON. Specifically, when the paper feed ON signal 33 is turned on, a paper feed clutch (not shown) is turned on. The paper is pulled out from the paper tray 13 by turning on the paper feed clutch, and the conveyance is started. After the completion of feeding one sheet, the feed ON signal 33 is turned OFF.

The "rotational speed detection signal" 35 is a signal output from the comparing unit 27 and indicating whether or not the rotational speed of the motor is within the normal rotational speed range. , A High signal is output, and if it is out of the area, Lo signal is output.
It outputs a w signal. In the example of FIG. 3, even after the motor rotation speed once enters the normal rotation speed region, the motor rotation speed rises from the upper limit of the normal rotation speed region between time t2 and t3, and becomes normal between time t4 and t5. Since the rotation speed is lower than the lower limit of the rotation speed region, the rotation speed detection signal 35
Is at the Low level.

The "motor drive signal" 32 is a control signal for driving the motor, which is given from the device control unit 30 to the drive unit 25. In FIG. 3, it is turned on at time t0.

The registration sensor signal 36 is a detection signal of the leading edge of the sheet output from the registration sensor 66 shown in FIG. In the example of FIG. 3, after the sheet feeding is started at time t1, the position of the registration sensor 66 (standby position) is reached at time t6, at which point the registration sensor signal 36 becomes High level.
The sheet waits at this position. The device control unit 30 can recognize that the sheet is at the standby position based on the registration sensor signal 36.

The registration clutch ON signal 34 is a signal output from the apparatus control unit 30 for driving the registration roller 76. By driving the registration rollers 76, the sheet is conveyed toward the transfer unit 77. The waiting time is from time t6 to t9.

ΔT is a rotation error non-detection period which is a predetermined time from the start of rotation of the motor, and corresponds to a time between time points t0 and t7 in the figure. During this time, even if the rotation speed detection signal 35 becomes Low level, it is not determined as an error. In the case of the present embodiment, the predetermined time ΔT from the start of the motor operation is 1 sec. However,
This time can vary depending on the characteristics of the motor used.

Conventionally, the sheet feeding is started at time t7, but in the present embodiment, the sheet feeding is started at time t1 in an area where the motor speed is still unstable. As a result, the time for the first copy can be reduced. Note that the rotation speed detection signal 35 is ignored during the first ΔT so that a motor rotation error does not occur during the use of the unstable region. Further, at the time of copying the second and subsequent sheets, the motor continues to rotate, and since there is no unstable area in a normal state, the suppression of the motor rotation error is released.

Next, according to the timing chart of FIG.
The operation of the copying machine according to the present embodiment will be described. First,
When the copy start key is pressed, the motor drive signal 32 rises, and the operation of the motor is started (time t0). After that, the motor rotation speed detection signal 35 is monitored,
The paper feeding operation is started at the first rising time (that is, after the motor rotation speed enters the normal rotation speed region) (time t
1). At this time, the rotation of the motor repeatedly increases and decreases (controls the rotation speed), and may gradually move out of the normal rotation speed region until it gradually converges within the normal rotation speed region (time points t2 to t).
3 and time points t4 to t5). However, only at the time of feeding the first sheet after the start of motor driving, the motor is determined to be in the initial rotation unstable region at the start of the motor and is not regarded as an error. That is, during the rotation error non-detection period ΔT, which is a predetermined time from the start of rotation of the motor, the rotation speed detection signal 35
This is ignored even if becomes a low level. When the leading edge of the sheet reaches the position of the registration sensor 66, the registration sensor signal 36 becomes High level (time t6). Then, at time t8
, The paper feed ON signal 33 returns to the low level, and then at time t9, the registration clutch ON signal 34 goes to the high level. The timing of the time point t9 corresponds to the reading of the document, the formation of a latent image, and the rotation of the
Is determined.

Even after the leading edge of the sheet reaches the standby position at time t6, slack is formed at the leading edge of the sheet until the time point t8 when the sheet feed ON signal 33 is at the high level. When ejected, the skewed state of the document (if any) is corrected.

Conventionally, paper feeding is started after the motor rotation has entered the normal rotation speed region. In contrast, in the present invention, an unstable region of the motor rotation is used for paper conveyance within a range that does not affect the copied image. By doing so, FCOT can be shortened.

FIG. 4 shows the device control unit 3 according to this embodiment.
5 shows a flowchart of a control operation of 0. First, when the copy start button is pressed, the motor is driven (motor O).
N) is started (S11, time point t0). At the same time as the driving of this motor, the monitoring of the rotation speed is started (S1).
2) Wait until the rotation speed of the motor reaches the normal rotation speed region (S14), and after reaching the normal rotation speed region (S13, Yes), start feeding (S15, time point t1). Thereafter, when the number of rotations is out of the normal region (S16, Yes), it is first determined whether the copy operation is the first copy (S17), and if it is the second copy or later, an error message is displayed. To stop the operation (S18). If the first sheet is being operated, the elapse of time from the start of sheet feeding is determined (S19), and if the predetermined time has elapsed (S1).
9, Yes), an error message is displayed, and the operation is stopped (S18). Here, the starting point of the “predetermined time” is paper feed O
This is the time when the N signal 33 rises. In the description of FIG.
The calculation is started from the rising time point t0 of the motor drive signal 32, but in any case, it is important whether the current time point is before or after the time point t7. In this example, the sheet feeding start time is determined as the starting point of the timing by determining the sheet feeding number first.

In step S19, the paper feed ON signal 33
(S1)
9, No), it is determined that the motor is in the initial rotation unstable region, and the copy operation is continued without displaying an error (S2).
0).

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the details of the above embodiments, and various modifications and changes can be made. For example, in the example of FIG. 3, the time point t7 is described as being between the time points t6 and t8, but the position of the time point t7 is not particularly limited to between the two time points.

[0039]

As described above, according to the present invention, a motor rotation speed higher than the motor rotation speed in an initially unstable region of the motor rotation is not detected as an error, and this unstable region is used for the sheet feeding operation. FCOT can be shortened.

[0040]

[Brief description of the drawings]

FIG. 1 is a view schematically showing an internal structure of an electrophotographic copying machine as an example of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram of a control device according to the embodiment of the present invention.

FIG. 3 is a timing chart showing rotation characteristics of the motor according to the embodiment of the present invention, together with signal waveforms of respective parts.

FIG. 4 is a flowchart of a control operation of the control device according to the embodiment of the present invention.

[Explanation of symbols]

13: paper cassette, 21: motor unit, 23: f / V converter, 24, 27: comparison unit, 25: drive unit, 26 ...
Specified rotational speed voltage generator, 30 ... device controller, 31 ... CP
U, 33: paper feed ON signal, 34: registration clutch ON signal, 35: rotation speed detection signal, 63: developing unit, 64: reading optical system, 66: registration sensor, 68: fixing device, 75 ...
Main motor, 76: registration roller, 77: transfer unit, 10
0: Copy machine.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masatoshi Tanabe 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H027 DA16 DA38 DE07 DE09 ED17 3F343 FA02 FB02 JA01 LA04 LA16 LC09 LD10 MA04 MA14 MA15 MA42 MA45 MB04 MB14 MB15 MC08 MC09 MC28

Claims (4)

[Claims] An image forming apparatus for conveying a sheet from a sheet tray to an image forming unit to form an image on the sheet, comprising: a sheet feeding unit for feeding the sheet from the sheet tray; An image forming apparatus, wherein the operation of the sheet feeding means is started in an unstable region where the motor is initially rotated. 2. A motor rotation speed detecting means for monitoring whether the rotation speed of the motor is within a normal rotation speed region, and detecting that the motor rotation has deviated from the normal rotation speed region from the motor rotation speed detection device. Error generating means for generating an error when a signal indicating the error is generated, wherein the error generating means outputs a signal indicating that the motor rotation has deviated from the normal rotation speed region within a predetermined time from the start of rotation of the motor. 2. The image forming apparatus according to claim 1, wherein the signal is ignored when the signal is generated. 3. A motor rotation speed detecting means for monitoring whether or not the rotation speed of the motor is within a normal rotation speed region, and detecting that the motor rotation has deviated from the normal rotation speed region from the motor rotation speed detecting device. Error generating means for generating an error when a signal indicating the error is generated, the error generating means controlling the motor rotation within a normal rotation speed range within a predetermined time from the start of sheet feeding at the time of forming the first image. 2. The image forming apparatus according to claim 1, wherein when a signal indicating that the image is out of the range is generated, the signal is ignored. 4. The method according to claim 1, wherein the sheet conveyed from the sheet tray is once conveyed to a predetermined position on a conveyance path, and then is made to stand by at this position. 2. A paper feed mechanism for conveying the paper from the paper tray to a standby position, wherein the paper is conveyed within an unstable area where the motor is initially rotated.
The image forming apparatus as described in the above.