JPH08258331A - Image-forming apparatus - Google Patents

Abstract

PURPOSE: To prevent the waste of toner adhering to a photosensitive drum by setting a motor-driving means for delaying/starting a second motor by a time difference after each motor is started until the motor comes to rotate normally. CONSTITUTION: A laser light from a laser scanner unit 5 responding to an image signal from a host computer or an operation panel at an outer surface of a case forms an image on the surface of a photosensitive drum 2. The photosensitive drum 2 rotates in the clockwise direction. After the surface of the photosensitive drum is charged, for instance, at -500V by a charged part 4 to which -1000V is impressed, the drum is exposed by the laser scanner unit 5 correspondingly to the image signal. The laser light from a laser diode scans the photosensitive drum 2 from right to left at a constant speed in accordance with the rotation of a polygon mirror 21 by an optical system motor 24, whereby an electrostatic latent image is formed on the surface of the drum 2. The toner from a developing part 6 is adhered to the electrostatic latent image, turning the latent image to a visible image.

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 having an electrophotographic process mechanism.

[0002]

2. Description of the Related Art In an image forming apparatus of this type, for example, a laser printer, light from a polygon mirror of an optical scanning system driven by an optical system motor is driven by a transport system motor and is negatively charged by a charging section. The photosensitive drum of the transport system is irradiated with the electrostatic latent image on the surface of the photosensitive drum. Then, the electrostatic latent image is developed by applying toner to the electrostatic latent image in the developing section, and the toner image obtained by this development is transferred onto a transfer sheet transported by a transport system driven by a transport system motor to form an image on the transfer sheet. Forming (printing) is performed.

In such a laser printer, when the power is turned on or when a print start command is issued, the optical system motor and the transport system motor are started almost simultaneously after a predetermined time as shown in FIG. After the steady rotation is reached, printing operation such as formation of an electrostatic latent image on the surface of the photosensitive drum is performed.

[0004]

However, in general, the optical system motor and the transport system motor have different rotation speeds and output torques according to their purposes, so that the time from the start to the steady rotation is different. It is a thing. Therefore, in the image forming apparatus as described above, since the optical system motor and the transport system motor are started almost at the same time,
As shown in FIG. 5, the motors do not rotate to the steady rotation at the same timing, and the transport system motor that has a large output torque and reaches the steady rotation at a low rotation speed is an optical system motor that requires a small output torque and a high rotation speed. Steady rotation is reached before that.

Therefore, the time T from when the transport system motor reaches steady rotation until when the optical system motor reaches steady rotation.
In spite of the fact that the conveying drum motor rotates the photosensitive drum, the printing process such as the formation of an electrostatic latent image on the surface of the photosensitive drum is not started.

By the way, when the photosensitive drum starts to rotate, its surface is negatively charged by the charging portion regardless of the number of rotations. Further, the toner contained in the developing section is usually negatively charged, but some of them are positively charged. The positively charged toner adheres to the surface of the photosensitive drum when the photosensitive drum starts to rotate.

Therefore, the longer the time T during which the photoconductor drum is unnecessarily rotated by the transport system motor, the more positively charged toner that adheres to the photoconductor drum increases, and the toner is wasted. there were.

Therefore, the present invention intends to provide an image forming apparatus capable of saving the total amount of toner by preventing the waste of the toner adhering to the photosensitive drum as much as possible by eliminating the time during which the photosensitive drum is unnecessarily rotating normally. It is what

[0009]

SUMMARY OF THE INVENTION According to the present invention, light is emitted from an optical scanning system driven by a first motor to a photoconductor of a conveyance system driven by a second motor, and the surface of the photoconductor is exposed. In the image forming apparatus, an electrostatic latent image is formed, toner is attached to the electrostatic latent image to develop the latent image, and the toner image obtained by the development is transferred to the conveyed transfer paper to form an image. When driving the motor, the motor drive control means is provided for starting the first motor first and delaying the second motor by a delay of the time difference from the start of each motor to the steady rotation. is there.

[0010]

In the present invention having such a configuration, when driving each motor, the motor having a longer steady rotation arrival time from the start to the steady rotation is started first. After that, the other motor is started with a delay by the difference in the time required for steady rotation of each motor.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a laser printer will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a laser printer according to this embodiment, in which a photosensitive drum 2 is provided at a substantially central portion of a housing 1.
Has been arranged. The photosensitive drum 2 is a transport system motor 3
Is driven to rotate in one direction, that is, in the clockwise direction in the figure, around the photosensitive drum 2 as an electrophotographic process mechanism, which is a charging unit for uniformly negatively charging the photosensitive layer on the surface of the photosensitive drum 2. 4. A laser scanner unit 5, which irradiates the photosensitive layer charged by the charging unit 4 with laser light based on image information to form an electrostatic latent image,
A developing unit 6 that adheres toner to the electrostatic latent image formed on the photosensitive layer to develop the image, a transfer unit 7 that transfers the image developed by the developing unit 6 to a transfer sheet conveyed through a conveying path, and a photoconductor. A cleaning unit 8 that removes toner from the drum 2 and a charge eliminating unit 9 that removes electricity from the photosensitive drum 2 are arranged in order.

The developing section 6 is a container 6 containing toner.
a, a developing roller 6b that abuts the toner in the container on the photoconductor drum 2 to attach the toner while rotating, and an intermediate roller 6c that abuts on the developing roller 6b and rotates.

The transfer section 7 is located below the photosensitive drum 2, and a sheet is fed toward the transfer section 7 from a paper feed cassette 10 provided on one side of the housing 1 by a pickup roller 11. The sheets are conveyed one by one at a predetermined timing.

After the toner image on the photosensitive drum 2 is transferred by the transfer section 7, the conveyed sheet is discharged by the charge removing section 12 and then fixed by the fixing device 13.
Then, the fixed paper is discharged to the outside of the housing by the paper discharge rollers 14 and 14. Here, the drive motor 3 serves not only as a drive source for the photosensitive drum 2 but also as a drive source for the paper transport mechanism.

Further, inside the housing 1, a fan 15 for radiating internal heat to the outside, a power supply device 16, and a cover open switch 17 for detecting when the upper part of the housing 1 is opened and turning off the power. Etc. are provided.

The laser scanner unit 5 includes a laser diode 37, which will be described later, for generating a laser beam, a collimator lens (not shown) for correcting the laser beam from the oscillator into parallel light, and a laser beam from the lens for one scanning line. Rotating (driving) the polygon mirror 21, which is a rotating body having an octahedral mirror portion that reflects every minute, the f.theta. Lens 22, the mirror 23, and the polygon mirror 21.
The optical system motor 24 and so on.

During the image forming operation of the laser printer thus constructed, a laser scanner unit corresponding to an image signal from an externally connected host computer 47 described later or an operation panel provided on the outer surface of the housing. The laser light from 5 is imaged on the surface of the photosensitive drum 2. The photosensitive drum 2 rotates clockwise in the figure, and the surface thereof is negative by the charging unit 4 to which −1000 V is applied, for example.
Charged to 500V, then laser scanner unit 5
Thus, the exposure corresponding to the image signal is performed.

That is, the laser light generated from the laser diode 37 is scanned at a constant speed from the left to the right of the photosensitive drum 2 as the polygon mirror 21 is rotated by the optical system motor 24, thereby An electrostatic latent image is formed on the surface. The electrostatic latent image is visualized by the developing unit 6 attaching the toner contained in the container 6a.

FIG. 2 is a block diagram showing the configuration of the control unit of the laser printer. Reference numeral 31 is a CPU constituting the control unit main body.
(Central processing unit), 32 is a ROM (read only memory) in which program data or the like for the CPU 31 to control each unit is stored in advance, and 33 is for temporarily storing the data processed by the CPU 31. RAM (random access memory) where various memory areas of
34 is an I / O port.

The CPU 31, ROM 32, RAM 3
3 and the I / O port 34 are connected to each other via a bus line 35 such as an address bus, a data bus, a control bus or the like.

The charging section 4 is connected to the I / O port 34.
And a high-voltage power supply circuit 36 connected to the power supply device 16 that supplies a high voltage to the transfer unit 7, a laser diode drive circuit 38 that is provided in the laser scanner unit 5 and drives a laser diode 37 that oscillates a laser beam, and the transport system. A motor drive circuit 39 for driving and controlling the motor 3, and a motor drive circuit 41 for driving and controlling the optical system motor 24.
Is connected.

The I / O port 34 is also provided with a heater control circuit 43 for controlling the energization of the heat fixing device heater 42 of the fixing device 13 and a sensor for inputting various sensors 44 such as a paper detecting sensor for detecting the presence or absence of paper. A circuit 45 and an I / F (interface) 46 are connected. In the I / F 46,
A host computer 47 for communicating print data including output area information and various processing data is connected via a communication line.

When the power is turned on or the printing is started, the CPU 31 first starts the optical system motor 24, and then the predetermined time T
After a lapse of time, the transport system motor 3 is started (motor drive control means). Then, during the predetermined time T, the charging section 4, the drum bias, etc. are turned on.

The predetermined time T is set to the difference between the time required for the optical system motor 24 to reach steady rotation and the time for the transport system motor 3 to reach steady rotation. The predetermined time T differs depending on the torque of each motor and the required number of rotations.

For example, FIG. 3 shows an example of the control operation of the CPU 31 when the predetermined time T is set to about 3.1 seconds. That is, the CPU 31 first starts the optical system motor 24 to start the polygon mirror 21.

Thereafter, it is determined whether or not about 3 seconds have passed. When it is determined that 3 seconds have elapsed, the charging unit 4, the drum bias, etc. are turned on. Then, it is determined whether or not about 0.1 seconds has elapsed. When it is determined that 0.1 seconds have elapsed, the transport system motor 3 is started and the photosensitive drum 2 is started. Then, after about 1 second, the optical system motor 24 and the transport system motor 3 reach steady rotation almost at the same time.

In the present embodiment having such a configuration, when the power is turned on or the printing is started, the conveying system motor 3 is started after a predetermined time T has elapsed since the optical system motor 24 was started as shown in FIG. Then, the optical system motor 24 and the transport system motor 3 reach steady rotation almost at the same time. Then, from this time, irradiation of the laser beam onto the photosensitive drum 2 is started.

As a result, the photoconductor drum 2 is used as in the conventional case.
However, it is possible to eliminate wasteful time of steady rotation, and prevent positively charged toner from adhering to the photosensitive drum 2 as much as possible. Therefore, waste of toner can be prevented as much as possible, and the total amount of toner can be saved.

In this embodiment, the one applied to the laser printer has been described, but the present invention is not necessarily limited to this, and an optical system motor and a conveyance system motor are provided, each of which can be controlled independently, It can be applied to those that perform image formation in a photographic process. For example, it may be applied to a digital copying machine or the like.

[0031]

As described in detail above, according to the present invention, the time during which the photosensitive drum is unnecessarily rotating normally is eliminated by shifting the motor starting time so that the respective motors simultaneously reach stationary rotation. By doing so, it is possible to provide an image forming apparatus that can prevent the waste of toner as much as possible and save the total amount of toner.

[Brief description of drawings]

FIG. 1 is an overall sectional view showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a control unit in the embodiment.

3 is a flowchart showing a motor control operation performed by the CPU shown in FIG.

FIG. 4 is a timing chart showing driving states of an optical system motor and a conveyance system motor shown in FIG.

FIG. 5 is a timing chart showing driving states of an optical system motor and a conveyance system motor in a conventional laser printer.

[Explanation of symbols]

 2 ... Photosensitive drum (photosensitive member) 3 ... Conveying system motor (second motor) 5 ... Laser scanner unit (optical scanning system) 24 ... Optical system motor (first motor) 31 ... CPU

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H04N 1/29 G03G 21/00 372

Claims (1)

[Claims] 1. An optical scanning system driven by a first motor irradiates a photosensitive member of a conveyance system driven by a second motor with light to form an electrostatic latent image on the surface of the photosensitive member. In the image forming apparatus for adhering toner to this electrostatic latent image to develop it, and transferring the toner image obtained by this development to the transferred transfer paper to form an image, when driving each motor, the first The image forming apparatus is provided with a motor drive control means for starting the first motor and delaying the second motor by a delay of the time difference from the start of each motor until reaching the steady rotation. .