JP2000330447A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten first printing time and to prevent a problem such as image failure by altering a speed at which paper is carried according to an increase in the detected number of revolutions of a rotary polygon mirror. SOLUTION: Upon receiving a print instruction, a printer main body starts to drive a main motor for driving the paper transport system of a printer and a scanner motor for writing an image with a laser beam. The number of revolutions of the scanner motor is monitored until it exceeds, for example, 50% of the rated number of revolutions. In order to measure time needed to start up the rotation of the scanner motor, a timer is started. When it exceeds 50% of the rated number of revolutions, the timer is stopped, and the indication of the timer at that time is stored into a parameter T. Then the feed of paper is started and in the case where the build up time T needed for the scanner motor to reach 50% to 80% of the rated number of revolutions is longer than predetermined time T0, the number of revolutions of the main motor is decreased by, for example, 10% in order to delay the transport of the paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduction in the time (first print time) from the start of the printing operation of the first sheet to the completion of discharge in an image forming apparatus.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing a configuration of a conventional laser printer 100.

[0003] A conventional laser printer 100 is known as an image forming apparatus for performing printing by scanning a laser beam.

A conventional laser printer 100 includes a laser printer main body 101, a TOP sensor 102, a conveying roller 103, a stacked paper 104, and a paper feeding roller 10.
5, an optional paper supply unit 106, a photosensitive drum 107, a scanner unit 108, and a fixing device 109.
, A roller 111, and a registration sensor 113.

[0005] The TOP sensor 102 is a sensor for detecting the timing of starting image formation, and starts image formation when the leading edge of the sheet is detected. The transport roller 103 for transporting the fed paper has a clutch mechanism and can stop the rotation of the roller to stop the paper.

The loaded paper 104 is fed to the paper feed roller 10
5 feeds and conveys the sheets one by one.

The registration sensor 113 is a sensor for detecting that the fed paper has reached the rollers 103. The scanner unit 108 scans a laser beam to write image data.

The toner image formed on the photosensitive drum 107 is transferred to a sheet, fixed by a fixing device 109, and discharged to a tray 102. The paper discharge sensor 104 detects that the paper has been discharged, and the roller 111 is the last roller in the paper transport path.

FIG. 6 is a timing chart showing the operation in the above conventional example.

The / PRNT signal is a signal input from the outside to the printer, and issues a print instruction by setting this signal to "L" level. Upon receiving the print instruction, the printer outputs a MON signal and starts driving the main motor of the paper transport system (T201). At the same time, S
By outputting the CNON signal, the rotation of the scanner motor of the scanner unit 108 also starts. When the rotation of the main motor is stabilized, the FEED signal is output, the sheet feeding roller 105 is rotated, and the sheet feeding is started (T202). After the fed sheet reaches the registration sensor 113 (T203), at a position where the leading end of the sheet does not reach the TOP sensor 102, the clutch is disengaged and the sheet conveyance is stopped (T2).
04).

The SCNRDY signal is monitored and waited until the number of rotations of the scanner motor reaches a value required for image formation. When the scanner motor starts rotating at a predetermined number of revolutions, the clutch is engaged and the transport roller I03 is rotated to start paper transport (T205). TOP sensor 1
When the leading edge of the sheet is detected in 02, a / TOP signal is output to start the image forming operation (T206). Then, the sheet is discharged to the tray 112 through the fixing device 109.

As described above, the paper feed is started almost simultaneously with the activation of the scanner motor, and the paper is stopped immediately before the TOP sensor. Control can be performed with less loss. As a result, a fast first print time can be realized.

However, some of the cheaper products do not have the clutch mechanism on the transport roller 103. In such a product, once the paper feeding and conveyance have been started, the paper conveyance cannot be stopped halfway.

FIG. 7 is a timing chart showing the control in the conventional example.

When a print instruction is received by the / PRNT signal, a MON signal and a SCONN signal are output.
Start rotation of main motor and scanner motor (T3
01). Then, SCNRDY is monitored and waited until the scanner motor reaches a predetermined number of revolutions required for image formation.
When it is detected that the rotation speed of the scanner motor has risen to the predetermined rotation speed, the FEED signal is output, and paper feeding is started (T302). When the top end of the sheet is detected by the TOP sensor 102, a / TOP signal is output to start image formation.

[0016]

However, in the above-mentioned conventional laser printer, there is a problem that the first print time is delayed since the sheet feeding is started only after the scanner motor has risen to the rated value.

In particular, there is a problem that the first print time becomes longer as the distance from the paper feed port to the TOP sensor 102 or the image forming section becomes longer as in the optional paper feeder 106.

[0018]

SUMMARY OF THE INVENTION The present invention relates to an image forming apparatus for forming an image by an electrophotographic method using a laser beam, and a rotary polygon mirror for rotating and driving a rotary polygon mirror for deflecting and scanning the laser beam. Driving means, rotation number detecting means for detecting the rotation number of the rotating polygon mirror, rotation state monitoring means for detecting and monitoring the rising state of the rotation number of the rotating polygon mirror, and controlling the conveyance speed of the fed paper. A sheet conveyance control unit for controlling the rotation of the rotating polygon mirror, and before the rotation speed of the rotary polygon mirror reaches a predetermined rotation speed for forming an image, starts feeding of the paper, and the rotation detected by the rotation state monitoring unit. The image forming apparatus is characterized in that a conveying speed of a sheet conveyed by the sheet conveying control means is changed in accordance with a rising state of the number.

[0019]

[First Embodiment] The configuration of a laser printer according to a first embodiment of the present invention is the same as the configuration shown in FIG.

FIG. 1 is a flowchart showing the control operation in the above embodiment.

FIG. 2 is a timing chart showing the operation of the above embodiment.

In the above embodiment, the printer main body 101
Receives a print instruction (S1), and starts driving a main motor for driving the paper transport system of the printer and a scanner motor for writing an image with a laser beam (S2). At the same time, the fixing heater starts to be heated to a temperature at which the toner image can be fixed. However, since the fixing heater is not directly related to the control in the above embodiment, the description thereof is omitted.

The rotation speed of the scanner motor is monitored, and for example, in the above-described embodiment, the process waits until the rotation speed exceeds 50% of the rated rotation speed (S3). A timer is started to measure the rise time of the rotation of the scanner motor (S4). And
If it exceeds 80% of the rated speed (S5), the timer is stopped, and the timer value at this time is stored in a variable T (S6).

At the start of paper feeding (S7),
Rise time T from 50% to 80% of scanner motor
Is longer than the predetermined time T0 (S
8) In order to delay the sheet conveyance, the number of rotations of the main motor is reduced by, for example, 10%. The time T0 will be described later.

The TOP sensor 102 monitors the arrival of the leading edge of the sheet. If the top sensor 102 detects the arrival (S10), the rotational speed of the main motor is returned to the original speed (S11). And T
An OP signal is output (S12), and an image forming process is performed (S12).
13).

Next, the time T0 will be described.

FIG. 3 is a diagram showing the rise time of the scanner motor in the above embodiment.

In FIG. 3, the horizontal axis represents time, and the vertical axis represents the percentage of the rotation speed of the scanner motor when the rated rotation speed of the scanner motor is 100%.

The two curves in FIG. 3 show the rise characteristics from the stop state of the scanner motor to the rated rotation speed.
One that shows a rising characteristic like curve a and one that shows curve b
It shows that some of them have a rising characteristic as shown in FIG.

It is not limited to the scanner motor.
Generally, the rising characteristics of the motor vary as shown in FIG. Motor speed from 50% to 8
The time t1 required to reach 0% and the number of rotations from 80% to 1
The measurement is performed in combination with a time t2 until the image reaches 00% (accurately, a time until the image is stabilized so as not to cause an image defect even when writing of the image is started), and data of variation is collected.

Here, the time required for paper feeding when the paper feeding speed at the time of paper feeding is the same as the paper feeding speed at the time of image formation (from the start of paper feeding to the output of the / TOP signal). Time), T3
And Then, the longer the time t1 until the rotation speed reaches 50% to 80%, the longer the time t2 until the rotation speed reaches 80% to 100%. Therefore, the rotation speed increases from 80% to 100%. The time t2 from the start of sheet feeding until the output of the / TOP signal is T
The rising characteristics of the motor that are equal to 3 are determined from the collected data, and the time t1 (the number of rotations is reduced from 50% to 8%) in the determined rising characteristics of the motor.
The time required to reach 0%) is defined as T0.

When the paper transport speed during paper feeding is the same as the paper transport speed during image formation,
(Time t until the number of rotations reaches 80% to 100%
2) The condition of ≤ (time T3 required for sheet feeding) must be satisfied. If the above condition is not satisfied, t2> T
If the number is 3, since the rotation of the scanner motor is not yet stable when image formation is started, an image defect such as distortion of a printed image may occur. Therefore, in the above-described embodiment, when t2> T3, the paper feeding time T
3 ′ is made longer than the time t2.

That is, when printing, the time until the number of rotations of the scanner motor reaches 50% to 80% is measured, and when the measured time is later than T0 predetermined by the above method. In this case, the paper transport speed of paper feed is reduced.

By controlling as described above, FIG.
Is controlled as shown in the timing chart of FIG.

When a print instruction is received by the / PRNT signal, a MON signal and a SCONN signal are output.
The main motor and the scanner motor start rotating (T5
01). Then, when the rotation speed of the scanner motor becomes 50% (T502), it exceeds 80% (T503).
The time t until is measured.

At the time when the value exceeds 80%, a FEED signal is output to start feeding the sheet. At this time, if the time t is equal to or longer than the time T0, the rotation speed of the main motor is reduced by, for example, 10%.

When the leading edge of the sheet is detected by the TOP sensor,
A TOP signal is output to start image formation (T50).
5). Regardless of whether the rise of the scanner motor is early or late, the scanner motor rotates at the rated speed by the time the / TOP signal is output, and the SCNRDY signal is "H" (T504 <T505).

In the above embodiment, the section in which the paper transport speed is reduced is the / TOP signal output (T505) from the start of sheet feeding (T503), but the present invention is not limited to this section. For example, from the start of sheet feeding (T503) until the scanner motor rotates at the rated speed and stabilizes (T50).
4).

In the above embodiment, when the rise of the scanner motor is slow, the number of rotations of the main motor for driving the paper transport system is reduced so that the paper transport time is controlled to be longer than usual. are doing. As a result, when the rise time of the scanner motor is a normal time, the first print time can be shortened, and even if the rise of the scanner motor is slow, printing can be performed without causing an error or an image defect.

[Second Embodiment] FIG. 4 is a flowchart showing the operation of the second embodiment of the present invention.

The flowchart shown in FIG. 4 is basically the same as the flowchart shown in FIG.
The difference from the flowchart shown in FIG. 1 is that 0 and S21 are added.

Step S6 will be explained. The time T required to rise to 50% to 80% of the rated rotation speed of the scanner motor is measured up to step 408, and sheet feeding is started (S
7). Then, it is determined whether or not the measured time T is longer than a predetermined time T0 (S8). Drop (S9). Time T
0 is the time determined in the same manner as in the first embodiment.

Conversely, if the measured time T is shorter than the predetermined time T4 (S20), the rotation speed of the paper transport main motor is increased to increase the paper transport speed (S21). For example, in the second embodiment, the speed is increased by 10%.

Here, assuming that the time required from the start of sheet feeding to the output of the / TOP signal is T5 while the rotation speed of the main motor is increased, the time from 80% to 100% is equal to T3. The rise time from 50% to 80% at this time is defined as T4.

In the second embodiment, when the rise of the scanner motor is slow, the rotation speed of the main motor for driving the paper transport system is reduced, and when the rise of the scanner motor is earlier than the standard time. The number of rotations of the main motor was increased. As a result, when the rise time of the scanner motor is a normal time, the first print time can be shortened, and even if the rise of the scanner motor is slow, printing can be performed without causing an error or an image defect.

Further, when the scanner motor rises faster than the standard product, the first print time is further shortened. This means that even if the characteristics of the scanner motor are improved,
The first print time can be improved only by a simple change such as replacement of the scanner unit.

[0047]

According to the present invention, the first print time can be shortened to the last minute, and even if it takes a long time to start up the scanner motor due to variations or the like, there is no problem such as image defects. To play.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a control operation according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the embodiment.

FIG. 3 is a diagram showing a rise time of a scanner motor in the embodiment.

FIG. 4 is a flowchart showing the operation of the second embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a conventional laser printer 100.

FIG. 6 is a timing chart showing an operation in the conventional example.

FIG. 7 is a timing chart showing control in the conventional example.

[Explanation of symbols]

 100 laser printer, 101 laser printer main body, 102 TOP sensor, 103 transport roller, 104 paper, 105 paper feed roller, 106 optional paper feed unit, 107 photoconductor drum, 108 scanner unit, 109: fixing device, 113: resist sensor.

Claims (7)

[Claims] 1. An image forming apparatus for forming an image by an electrophotographic method using a laser beam, comprising: a rotating polygon mirror driving means for rotating a rotating polygon mirror for deflecting and scanning the laser beam; Rotation number detection means for detecting the rotation number of the rotating polygon mirror; rotation state monitoring means for detecting and monitoring the rising state of the rotation number of the rotating polygon mirror; sheet transport control means for controlling the transport speed of the fed sheet;
Before the rotation number of the rotary polygon mirror reaches a predetermined rotation number for performing image formation, feeding of the paper is started, and according to a rising state of the rotation number detected by the rotation state monitoring unit. An image forming apparatus that changes a conveyance speed of a sheet conveyed by the sheet conveyance control means. 2. The method according to claim 1, wherein the rotation state monitoring means measures a time required to reach a second predetermined rotation number from a first predetermined rotation number. An image forming apparatus characterized in that when the time is longer than a predetermined time, the conveying speed of the conveyed paper is reduced. 3. The paper transporting device according to claim 1, wherein the rotation state monitoring unit detects a rotation speed of the rotary polygon mirror after a predetermined time has elapsed from when the rotation speed reaches the first predetermined rotation speed. The image forming apparatus is characterized in that the control means is means for reducing the transport speed of the transported paper when the detected rotation speed is lower than a second predetermined rotation speed. 4. The apparatus according to claim 1, wherein the rotation state monitoring means is a means for measuring a time required for the rotation speed to reach a second predetermined rotation speed from a first predetermined rotation speed. An image forming apparatus, wherein when the time is shorter than a predetermined time, the conveying speed of the conveyed paper is increased. 5. The paper transporting device according to claim 1, wherein the rotation state monitoring means detects a rotation number of the rotary polygon mirror after a predetermined time has elapsed from when the rotation number reaches a first predetermined rotation number. The image forming apparatus is characterized in that the control means is means for increasing the conveying speed of the conveyed sheet when the rotation speed detected by the detection means is higher than a second predetermined rotation speed. 6. The image forming apparatus according to claim 1, wherein, when the transport speed of the sheet is changed, the original transport speed is restored when image formation is started. 7. The method according to claim 2, wherein, when the transport speed of the sheet is reduced, when the rotation speed of the rotary polygon mirror reaches a predetermined rotation speed for performing image formation,
An image forming apparatus for returning to an original conveying speed.