JPS62232258A - Picture forming device - Google Patents

Abstract

PURPOSE:To obtain a reproduced picture with high quality by providing a control means controlling a drive means in each step operation of a recording medium. CONSTITUTION:When,e.g., a terminal 41a is switched to a terminal 41c by a distributing circuit 22a, an output of an exciting coil 45a is lowered gradually and an output of an exciting coil 45c is increased gradually. As a result, a step motor is driven smoothly in each step operation. Thus, the step operation of the step motor without vibration is attained and a photosensitive drum 7 is in step ooperation smoothly. Thus, the vibratioin caused by the step operation of the photosensitive drum is prevented and the reproduced picture with high picture quality without recording blur is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an image forming apparatus that forms an image on a recording medium such as a photoreceptor.

[Prior art]

FIG. 4 is a schematic diagram illustrating a conventional laser exposure operation. In the figure, reference numeral 51 denotes a photosensitive drum, which is rotated in the direction of arrow a by a driving means (not shown).

52 and 53 are laser beams that are scanned in the direction of the arrow to perform exposure. When a copy command is issued, the photosensitive drum 51 is controlled by a driving means to always rotate at a constant speed.

However, when forming a latent image on the surface of the photoreceptor drum 51, when the laser beam 52 is scanned on the photoreceptor drum 51, as shown in FIG. Since the photosensitive drum 51 is rotating in the direction of the arrow a, it is scanned in the direction of the arrow and the laser beam 5
2, like the laser beam 53, its locus is inclined at a predetermined angle, so the photoreceptor drum 5
There was a problem in that an accurate latent image could not be formed on 1.

〔the purpose〕

The aim of the invention is to eliminate the above-mentioned drawbacks.

Another object of the present invention is to provide an image forming apparatus capable of producing high quality reproduced images.

A further object of the present invention is to provide an image forming apparatus that can form excellent images with a simple apparatus configuration.

Another object of the present invention is to improve a recording device that records images using a beam.

A further object of the present invention is to provide an image forming apparatus capable of forming stable images.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a perspective view illustrating a laser scanning operation of an image forming apparatus according to an embodiment of the present invention. Reference numeral 1 denotes a manual terminal to which a video signal (image information) 1a is input manually. 2 is a video amplifier that amplifies the video signal. 3 is a semiconductor laser, and 4 is a collimator lens, which shapes the laser beam. A scanner motor 5 rotates the polygon mirror 5a at high speed. Reference numeral 6 denotes an f.theta. lens which adjusts the optical path length of the laser beam reflected by the polygon mirror 5a and evenly focuses the laser beam onto the photoreceptor drum 7.

Reference numeral 8 denotes a drum drive device, which is composed of a stepping motor. 9 is a laser beam detector (beam detector),
It is provided at the writing start position of the laser beam scanned in the width direction A of the photosensitive drum 7, detects the laser beam, and outputs a print synchronization signal (BD signal) 9a. The laser beam detector 9 is composed of, for example, a photodiode. 10
is an amplifier that amplifies the print synchronization signal 9a. A waveform shaping circuit 11 shapes the amplified print synchronization signal 9a into a pulse signal of a predetermined width, and outputs a drive pulse signal +1a for driving the drum drive device 8 from the output port 12. Reference numeral 13 denotes a fixing device drive unit for fixing the transfer paper onto which the toner image has been transferred, and is composed of a fixing roller, a stepping motor, etc. (not shown).

Incidentally, as is well known, image data is read out from an unillustrated laser or the like in synchronization with the BD signal 9a and applied to the semiconductor laser.

Next, the operation of the image forming apparatus shown in FIG. 1 will be explained with reference to FIG.

FIG. 2 shows an example of a drive circuit showing an embodiment of the present invention, 21 is an AND gate, and a drive pulse signal 11a,
An AND operation is performed between the drum drive device 8 and the signal 13a that enables the fuser drive unit 13 to be driven. 22a and 22b are distribution circuits that specify the phases of the stepping motors of the drum drive device 8 and the fixing device drive unit 13. Note that the distribution circuit can be configured with a simple changeover switch or the like. 23a.

Reference numeral 23b is an excitation circuit that excites the phases designated by the distribution circuits 22a and 22b, and causes the stepping motors of the drum drive device 8 and the fixing device drive unit 13 to operate in predetermined steps. When the video signal 1a having image information after the step operation of the photosensitive drum is input to the human powered boat 1 in synchronization with the BD signal 9a, it is amplified by the video amplifier 2 and then drives the semiconductor laser 3. The laser beam emitted from the semiconductor laser 3 is shaped by a collimator lens 4 and then passed through a polygon mirror 5 which is rotated by a scanner motor 5.
It is deflected by a, passes through an f/θ lens 6, and horizontally scans the surface of the photoreceptor drum 7. As a result, the photoconductor tram 7 came to rest.
An electrostatic latent image of one line is formed by the beam above.

By repeating the above operations, an image for one screen can be formed on the photoreceptor drum.

At this time, the writing start position of the laser beam transmitted through the f/θ lens 6 is detected by the laser beam detector 9,
A print synchronization signal 9a is output.

This print synchronization signal 9a is amplified by an amplifier 10, and a drive pulse signal 11a whose pulse width is adjusted by a waveform shaping circuit 11 is sent from an output port 12 to an AND gate 21. The AND gate 21 uses this drive pulse signal 11a, the drum drive device 8, and the fuser drive unit 1.
3 with the signal 13a that enables driving, and when both are manually operated, a pulse signal is output to the distribution circuits 22a, 22b, and each time a pulse signal is output to the distribution circuits 22a, 22b, the excitation circuit is 23a and 23b excite predetermined phases of the stepping motors of the fixing unit drive unit 13 and the drum drive device 8.

That is, each time the drive pulse signal 11a is output, the photosensitive drum 7 moves in steps by a predetermined amount, and the stepping motor of the fixing unit drive unit 13 is also driven, so that the fixing roller and the like move in steps. Note that the laser beam is forcibly turned on to ensure that the laser beam is incident on the laser beam detector 9. Thus, in this example, the photoreceptor is rotated by a predetermined amount before the laser beam enters the image area.

FIG. 3 is a sectional view showing an example of a laser beam printer to which the present invention is applied, and the same parts as in FIG. 1 are given the same reference numerals.

In this figure, 31 is the main body of the laser beam printer. A scanning unit 32 includes a scanner motor 5, a polygon mirror 5a, an f/θ lens 6, a scanning mirror 32a, and the like. 33 is a developing unit,
Filled with developer (toner). Reference numeral 34 denotes a paper feed cassette, into which the stored recording paper P is fed by a paper feed roller 35 . Feed rollers 36a and 36b feed the recording paper P to the photosensitive drum 7. A transfer charger 37 transfers a toner image onto the recording paper P by, for example, corona discharge. 3
A transport guide 8 guides the recording paper P separated from the photosensitive drum 7 to the fixing device 39 . 40 is a paper ejection tray on which recording paper P is loaded.

The image forming operation is based on a known electrophotographic method, so a description thereof will be omitted.

FIG. 5 is a diagram showing in more detail a part of the excitation circuit 23a and the drum driving device @8 shown in FIG. 2. FIG. 5 shows the circuit configuration for driving the stepping motor. 45a to 45d are excitation coils in the step motor, 43a to transistors, 47a and 47d, respectively.
is a switching transistor for adjusting the supplied power by controlling the energization period of the energized excitation coils 45a to 45d.

In addition, the diodes 48a to 48d and the Zener diode 49 are connected to an excitation changeover switch (transistor) 43a.
~43d forms a circuit for absorbing the back electromotive force of the coil that occurs when the coil is cut off. Similarly, diodes 48a and 46b are connected to excitation coils 45a to 45 when switching transistors 47a and 47b are cut off.
This is a circuit for releasing the energy stored in d.

Further, the terminals 41a to 41d are for manually inputting the output from the distribution circuit 22a, and the signals inputted from the distribution circuit 22a through the terminals 41a to 41d are amplified by amplifiers 44a to 44d, respectively, and then switched. The transistors 43a to 43d are manually powered. Further, the current control output 52 from the distribution circuit is connected to the capacitor 51.
A and the inverter 42 are applied to the capacitor 51b, and also to one terminal of the comparators 40a and 40b. A triangular wave signal, which is the output of the triangular wave generating circuit 50, is input to the other terminals of the comparators 4a and 40b.

In this example, a triangular wave signal is used to perform the step operation smoothly. Explain the operation. Distribution circuit 22a
For example, when the terminal 41a is selected and the switching transistor 43a is turned on, the exciting coil 45a is energized. Next, for example, when the terminal 41c is selected, both the switching transistors 43a and 43c are turned on.

At this time, the current control output 52 changes from high level to low level. Then, the output voltage of the capacitor 51a gradually decreases, and the output of the comparator 40a also gradually decreases. Conversely, the output voltage of the capacitor 51b gradually increases, and the output of the comparator 40b also gradually increases.

That is, when the distribution circuit 22a switches the selection from the terminal 41a to the terminal 41c, for example, the exciting coil 45a
The output of the excitation coil 45c gradually decreases, and the output of the exciting coil 45c gradually increases. Repeat the above operation for each terminal. *As a result, the step motor can rotate smoothly during each step operation.

By using the circuit configuration as shown in FIG.
The step motor is capable of performing a smooth step motion without vibration, and is capable of causing the photosensitive drum 7 to perform a smooth step motion. Therefore, it is possible to prevent vibrations that occur during the step operation of the photosensitive drum, so that high-quality reproduced images without recording blur can be obtained.

(Effects) As explained above, according to the present invention, high-quality reproduced images can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view illustrating the operation of an image forming apparatus showing an embodiment of the present invention, FIG. 2 is a drive circuit block diagram showing an embodiment of the present invention, and FIG. 3 is a laser to which the present invention is applied. A sectional view of the beam printer, FIG. 4 is a schematic diagram explaining conventional laser beam scanning, and FIG. 5 is a diagram showing in detail a part of the excitation circuit 23a and drum drive device 8 shown in FIG. 2. . In the figure, 1 is a human-powered boat, 2 is a video amplifier, 3 is a semiconductor laser, 4 is a coupling lens, 5 is a scanning motor, 5a is a polygon mirror, 6 is an f/theta lens, 7 is a photosensitive drum, and 8 is a drum drive 9 is a laser beam detector, 9a is a print synchronization signal, 10 is an amplifier, 11 is a waveform shaping circuit, lla is a drive pulse signal, 12 is an output port, 21 is an AND gate,
22a and 22b are distribution circuits, and 23a and 23b are excitation circuits.

Claims (1)

[Scope of Claims] A recording medium, a beam irradiation means for irradiating a beam to form an image on the recording medium, a beam position detection means for detecting a scanning position of the beam, and a detection of the beam position detection means. An image forming apparatus comprising: a drive means for causing the recording medium to move in steps based on an output; and a control means for controlling the drive means during each step motion of the recording medium.