JP3269289B2 - Image forming device - Google Patents

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 laser beam printer for processing an image by a digital signal and obtaining a hard copy from the signal.

[0002]

2. Description of the Related Art An example of this type of image forming apparatus will be described with reference to FIG. This drawing shows a schematic view of a laser beam printer, in which a laser beam emitted from a laser emitting unit 11 is deflected by a rotating polygon mirror 12 rotating at high speed, and a lens 13
Scans on the photoreceptor 14 via the. The mission of such an apparatus is to perform high-speed processing. In particular, a drive motor of a rotary polygon mirror in an optical scanning system is required to have a short startup time and to save power. Therefore, in order to satisfy these demands, a method of extending the life of the apparatus and reducing power consumption by reducing the speed of the drive motor of the rotary polygon mirror during standby or stopping the rotation of the rotary polygon mirror during standby has been disclosed in Japanese Patent Application Laid-Open No. H11-157421. JP-A-62-237864, JP-B-4-4
No. 9688 and the like. However, in this case, there are disadvantages that the start-up time becomes longer and the copy time at the start of the copying operation becomes longer. Also, in a device equipped with a plurality of rotary polygon mirror devices, a method of monitoring the temperature of a fuser and sequentially starting up a drive motor of the rotary polygon mirror (see Japanese Patent Application Laid-Open No. 64-79759).
Further, Japanese Patent Laid-Open No. 62-161177 discloses a method of reducing the load on a power source by sequentially starting up each rotating polygon mirror with a predetermined time difference. In the method, the rise time difference of the drive motor of the rotary polygon mirror affects the operation time of the first copy (first copy) when the operation shifts from the standby state to the copy operation.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of reducing power consumption without sacrificing the operation time of the first copy.

[0004]

According to the present invention, there is provided an image forming apparatus having a plurality of optical scanning devices arranged from upstream to downstream of a paper transport path, a driving motor for rotating a rotary polygon mirror, and an image forming apparatus. Output a drive signal of the highest rotational speed to the rotary polygon mirror drive motor in the first optical scanning device arranged on the upstream side of the paper transport path when is in the standby state;
The rotary polygon mirror drive motor in the optical scanning device provided on the downstream side includes a control device for sequentially outputting a drive signal of a low rotation speed.

[0005]

When the image forming apparatus is in the standby state, the rotation speed of the drive motor of each rotary polygon mirror is set to be lower than a predetermined rotation speed required for writing, and to be gradually lower from the upstream to the downstream of the paper transport path. Power consumption is reduced without affecting the initial copy time.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG.
FIG. 2 is a schematic diagram of a tandem full-color copying machine which is an image forming apparatus shown in this embodiment, and FIG. 2 shows a timing of starting each rotary polygon mirror and a timing of writing on a sheet. The paper 50 is placed on the transport belt 55 and transported and moved in the direction of arrow A. At the time of movement, the image of the paper 50 is colored yellow by the first optical scanning device Y, magenta by the second optical scanning device M, cyan by the third optical scanning device C, and black by the fourth optical scanning device K. The paper is sequentially overwritten, and the paper on which the full-color copy has been completed is finally output. During this copy operation, the paper 50 is
It is not necessary that the drive motors of the rotary polygon mirrors of the respective colors simultaneously rise to the number of rotations required for the copy operation at the stage of reaching the optical scanning device Y. Therefore, this image forming apparatus is designed such that when the paper 50 reaches the lower part of the writing portion of each optical scanning device, the corresponding rotary polygon mirror rotates at a prescribed rotation, in this embodiment, the rotation speed N ₅ . It is controlled by a control device (not shown).

Next, control of the control device at the stage of the image forming apparatus will be described. Before the copy operation is started, the standby image forming apparatus is in a standby state during the copy operation. In the standby stage, the drive motor of the rotary polygon mirror rotates at a low speed.
The control of the rotation of each drive motor at this stage is as follows. Control of the drive motor of the first rotary polygon mirror Y: The drive motor of the rotary polygon mirror Y in the first optical scanning device disposed at the position where the sheet 50 first reaches when a copy operation is commanded is since the time the paper required for the movement is short, it must be reached in the copy operable rotational speed N ₅ in a short time. Therefore, the driving motor of the first rotation polygon mirror Y rotates at the highest rotational speed N ₄ from the beginning. Control of the drive motor of the second rotary polygon mirror M ... The drive motor of the rotary polygon mirror M in the second optical scanning device disposed at the position where the paper 50 reaches the second position is the first rotary polygon mirror. rotating a small rotational speed N ₃ than the rotational speed N ₄ of the Y drive motor. Control of drive motor of third rotary polygon mirror C ... The drive motor of rotary polygon mirror C in the third optical scanning device disposed at the position where paper 50 reaches the third position is the second rotary polygon mirror. rotate less at a rotational speed N ₂ than the rotational speed N ₃ of the M drive motor. Drive motor of the rotary polygon mirror K in the fourth optical scanning device 4 of the rotary polygonal mirror control ...... sheet 50 of the drive motor of K is disposed at a position to reach the end, at the lowest rotational speed N ₁ Rotate. That is, the number of rotations of the drive motor of each rotary polygon mirror in the standby state is as follows: the number of rotations N ₅ required for writing> the number of rotations N ₄ of the drive motor of the first rotary polygon mirror Y> the second number of rotary polygons. The rotation speed N ₃ of the drive motor of the mirror M> the rotation speed N ₂ of the drive motor of the third rotation polygon mirror C> the rotation speed N ₁ of the drive motor of the fourth rotation polygon mirror K is satisfied. It is controlled by the control device.

The copy is started at the copy command time t ₁ , and the paper 50 is moved to the first position at time t ₂ .
At the writing position by the optical scanning device Y at time t ₃
Writing position by the optical scanning apparatus, the write position by the third optical scanning device M at time t _4, and reaches the writing position by the fourth optical scanning device K at time t _5, each color write is performed.

As described above, in the drive motor of each rotary polygon mirror, the number of rotations can be set lower by the difference in the time required to reach the predetermined number of rotations required for writing. FIG. 7 shows the timing of starting the rotary polygon mirror and the timing of writing on a sheet in the embodiment.

[0010] In FIG. 7, the rotary polygon mirror M in the rotary polygon mirror Y and the second optical scanning device of the first optical scanning device, respectively, starting time (t ₂ over t _1), (t ₃ over t ₁ ), A rotation speed N ₆ capable of reaching a predetermined rotation speed,
Rotating at N _7. Now, when an image formation command is issued,
The rotating polygon mirrors Y and M are obtained by calculating the rotational acceleration (N ₅ −N ₆ ) / (t ₂
-T ₁ ) = (N ₅ −N ₇ ) / (t ₃ −t ₁ ), and the start is started. However, since the rotating polygon mirrors C and K in the second and third optical scanning devices have enough time to be able to start even from a stopped state, the rotation acceleration at the time of starting can be set low for each. In this case, when an image forming command is issued, the rotating polygon mirrors C and K start to be activated at rotational accelerations N ₅ / (t ₄ −t ₁ ) and N ₅ / (t ₅ −t ₁ ), respectively. . That is, the control device calculates the rotational acceleration of each drive motor up to the start of writing on the paper, the rotational acceleration of the drive motor of the first rotary polygon mirror Y = the rotational acceleration of the drive motor of the second rotary polygon mirror M> third. The driving command is output in the relation of the rotational acceleration of the driving motor of the rotating polygon mirror C> the rotational acceleration of the driving motor of the fourth rotating polygon mirror K.

Next, the drive mechanism of the polygon drive motor will be described (see FIGS. 3, 4 and 5). FIG. 3 is a block diagram of a driving circuit of the polygon motor. The driver circuit 60 operates according to an input voltage Vin from a power supply, and outputs Vout to each motor 100. In the image forming apparatus of the present invention, the input voltage Vin to the driver circuit at this time is kept low for a certain period. The image forming apparatus includes a conversion unit (not shown) that can change the voltage of the power supply, and converts the input voltage Vin to the driver circuit 60 into the set voltage VH and the voltage VL lower than the voltage VH. The device is switched on,
During operation of the device, the voltage is at the voltage VH. At startup,
The output voltage Vout output from the driver circuit 60 fluctuates. Then, it is constrained to a constant voltage Vc, and enters a standby state. At this time t ₀ , the voltage conversion means is operated to change the voltage Vin from the set voltage VH to a lower voltage VL.
Down to. At this time, the current does not change. This low voltage V
L is the voltage driving motor of the rotary polygon mirror to rotate at a rotational speed N _4, and about 12V approximately 10V. When a copy operation is instructed (time t ₁ ), the conversion means is operated, the input voltage Vin is switched to the normal voltage VH, and each drive motor is operated. Generally, in a rotary polygon mirror motor drive circuit, rotation is controlled by varying a drive voltage (or current) inside a driver circuit. Naturally, when the rotation speed is low as in the standby mode, the drive voltage (or current) is also low. However, since the input voltage to the drive circuit is usually constant, the power loss in the drive circuit in such a state is small. It will be the maximum.

On the other hand, according to the present invention, the input voltage at the time of standby is reduced to the voltage required for the number of revolutions at the time of standby, so that the copy time at the start of the copy operation is not affected, and the waste consumed in the drive circuit is reduced. Power can be reduced. In this embodiment, the voltage conversion is performed by the conversion means. However, a high-voltage power supply and a low-voltage power supply may be prepared and switched between the copy operation and the standby. In this image forming apparatus, the drive motor of each rotary polygon mirror is rotated at a lower rotation speed than that required for writing an image during standby, so that power consumption can be reduced during standby and noise and temperature rise of the device can be achieved. Can be prevented. Further, at the time of standby in which the rotation speed of the rotary polygon mirror is reduced, the power supply to the rotary polygon mirror drive circuit is set to a voltage lower than the voltage during normal operation, thereby reducing power consumption in the drive circuit.

In addition, by setting the rotation of the rotary polygon mirror in the standby mode to be higher in the order of operation timing, the start time at the start of the copy operation is not affected. In addition, a time interval required for the paper 50 placed on the belt 55 and conveyed to move between the optical scanning devices is provided, and the paper 50 is moved downstream from the first optical scanning device Y disposed on the upstream side. Since the drive motor of the rotary polygon mirror is sequentially started up to the fourth optical scanning device K disposed on the side, further power saving can be achieved.

[0014]

According to the image forming apparatus of the present invention, the number of revolutions of the driving motor of the rotary polygon mirror in the standby state is sequentially reduced from the first optical scanning apparatus, so that the power consumption in the standby state can be reduced. It can also be used as a countermeasure against noise and temperature rise during standby. Further, when the image formation command is input, the first copy time is not affected. further,
During standby, power consumption in the drive circuit can be reduced by lowering the power supply voltage input to the motor drive circuit of the rotary polygon mirror.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a tandem full-color copying machine

FIG. 2 is a timing chart for controlling the rotation of each rotating polygon mirror and writing an image.

FIG. 3 is a circuit block diagram of a drive motor.

FIG. 4 is a graph of an input voltage of a motor drive circuit.

FIG. 5 is a graph of output voltage.

FIG. 6 is a schematic diagram of an optical scanning device.

FIG. 7 is a timing chart for controlling the rotation of each rotating polygon mirror and writing an image in another embodiment.

[Explanation of symbols]

50 paper, 55 belt, 60 driver circuit,
100 motor, Y first optical scanning device, M second optical scanning device, C third optical scanning device, K
Fourth optical scanning device.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-145261 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 26/10 B41J 2/44

Claims (3)

(57) [Claims] 1. An optical scanning device, comprising: a rotary polygon mirror; and a drive motor for rotating the rotary polygon mirror, and scanning a photosensitive member by deflecting laser light from a laser emitting unit by the rotary polygon mirror. In an image forming apparatus having a plurality of first optical scanning devices disposed upstream from a transport path, a control unit for controlling rotation of the drive motor includes a sheet transport path when the image forming apparatus is in a standby state. The drive signal of the highest rotation number is output to the drive motor of the rotary polygon mirror of the first optical scanning device arranged on the upstream side, and the drive motor of the rotary polygon mirror of the optical scanning device arranged on the downstream side is output. An image forming apparatus which controls so as to sequentially output a drive signal of a lower rotation speed. 2. An optical scanning device, comprising: a rotary polygon mirror; and a drive motor for rotating the rotary polygon mirror, and scanning a photosensitive member by deflecting a laser beam from a laser emitting unit by the rotary polygon mirror. In the image forming apparatus, a plurality of which are arranged from the first optical scanning device upstream of the transport path toward the downstream, wherein the control unit for controlling the rotation of the drive motor includes a plurality of rotating surfaces when the image forming device is in a standby state. The drive motor of the mirror outputs a rotation drive signal of a lower rotation speed than a predetermined rotation speed required for writing, and when an image forming command is input, the drive motor of each rotary polygon mirror has a predetermined rotation speed. Outputs a rotation drive signal that accelerates the rotation speed,
The drive signal when the image forming command is input maximizes the acceleration of the rotational speed output to the drive motor of the rotary polygon mirror of the first optical scanning device arranged on the upstream side of the paper transport path,
An image forming apparatus, which controls so as to sequentially decrease the acceleration of a rotation speed output to a drive motor of a rotary polygon mirror disposed on a downstream side. 3. The voltage supply means for the drive motor includes switching means for switching between a normal supply voltage and a voltage lower than the normal supply voltage, and the control means controls the drive motor when the image forming apparatus is in a standby state. 3. The image forming apparatus according to claim 1, wherein the switching unit is controlled to switch a supply voltage to a low voltage.