JPS63113564A - Laser beam printer - Google Patents

Abstract

PURPOSE:To prevent a shift of an image, and to record a distinct image by providing a common frequency signal generating means for supplying a common reference frequency signal to plural PLL control means. CONSTITUTION:A reference frequency signal generated from a reference signal oscillator 73 consisting of a crystal oscillator, etc. is supplied to each PLL control part 81 of a scanner control part 75, a photosensitive drum control part 76, a fixing roller control part 77, and a belt control part 78, through a frequency divider 74. Each PLL control part compares signals which are divided into frequencies corresponding to each driving speed of a scanner, a photosensitive drum, a carrying belt, and a fixing roller from a common reference frequency signal, and frequency signals which are fed back from encoders 57, 63, 67 and 72, and executes a rotational control. In such a way, a variance of the reference frequency for driving each member is prevented and a shift of an image is eliminated, and a distinct image can be recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a laser beam printer having a plurality of image carriers, a plurality of laser units, a recording paper transport means, and a fixing device.

(Prior Art) Conventionally, this type of clothing includes the following. In other words, images corresponding to each color are exposed on four photosensitive drums corresponding to each color of cyan, magenta, yellow, and black by scanning a laser beam emitted from a light source with a rotating polygon mirror to form an electrostatic latent image. is formed, and this electrostatic latent image is developed using a developer corresponding to each color of cyan, magenta, yellow, and black. The developed images of each color formed on this photosensitive drum are sequentially transferred onto a recording paper conveyed by a conveyor belt, and then the images of each color transferred onto the recording paper are heated and pressed by a fixing roller of a fixing device to be fixed. do. Incidentally, each of the photosensitive drums is driven by a separate drive motor. Each of these motors is driven by a reference frequency from a separate reference oscillator, and is PLL-controlled by detecting the speed of the photosensitive drum with an encoder.

Further, the rotating polygon mirrors that scan images corresponding to the respective colors are driven by drive motors that are PLL-controlled by different reference oscillators. Furthermore, the conveyor belt is driven by a reference frequency from a reference oscillator different from the above.
It is driven by a drive motor that is controlled by LL. Meanwhile, the fusing roller is similarly driven by a motor that is PLL controlled by its own reference oscillator.

(Problems to be Solved by the Invention) However, this prior art has the following problems. That is, in the case of the above-mentioned apparatus, each photosensitive drum, each rotating polygon mirror, conveyance belt, and fixing roller are driven and controlled by reference frequencies from different reference oscillators. By the way, since there are inevitably variations in the reference frequency of each reference oscillator, variations occur in the rotational speed of each photosensitive drum, which causes a shift in the image transferred onto the recording paper conveyed by the conveyor belt, resulting in color misregistration. In addition, if there is a discrepancy between the rotational speeds of the conveyor belt and the fixing roller, when the fixing roller fixes the image on the recording paper, some of the fixing rollers, which have a large conveying force, may still be in the transfer process. There was a problem in that when a certain recording paper was pulled, the transfer of the image would be misaligned and the quality of the image would be degraded. Furthermore, since a large number of reference oscillators are required to drive each photosensitive drum, each rotating polygon mirror, conveyance belt, and fixing roller, there is also the problem of high cost.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the prior art described above, and its purpose is to provide a laser beam printer that can prevent image shift and record clear images at a low cost. It is about providing.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides rotation of a rotating polyhedron that irradiates each image carrier with each laser beam emitted from a plurality of laser units; In a laser beam printer in which a plurality of PLL control means respectively control the rotation of an image carrier, the rotation of a conveying means for conveying recording paper, and the rotation of a fixing roller of a fixing device, the plurality of PL
The L control means is configured to include common frequency signal generation means for supplying a common reference frequency signal to the L control means.

(Function) In the present invention, by providing a common reference signal generation means that supplies a common reference frequency to a plurality of PLL control means, variations in the driving speed of each control means are eliminated, and the reference signal generation means You only need one.

(Example) The present invention will be explained below based on illustrated embodiments.

FIG. 1 is a sectional view illustrating an example of a four-drum laser beam printer. In FIG. 6, 21 is the main body of the device;
Reference numeral 22 denotes a paper feed cassette, into which recording paper 24 is fed by driving a paper feed roller 23 .

A laser unit 41c forms a latent image on a cyan photosensitive drum 45c according to color image data. 41s
is a laser unit that forms a latent image on the magenta photosensitive drum 45M according to color image data. 41Y is a laser unit that forms a latent image on the yellow photosensitive drum 45Y according to color image data. 4te is a laser unit that forms a latent image on a black photosensitive drum 4581 according to color image data * 42Cr42
M, 42y, and 428L are toner hoppers filled with cyan, magenta, yellow, and black toners. A conveyance belt 43 serves as a conveyance means and conveys the recording paper 24. 44C.

44M, 44y, and 44B1 are transfer chargers that transfer toner images onto the recording paper 24 being conveyed. Note that each laser unit 41c, 418 . 41y, 41B
L has a polygon mirror (rotating polygon mirror) to be described later, and horizontally scans the laser beam in the main scanning direction.

Uniformly charged photosensitive drums 45C, 45,.

45Y and 45BL have a laser unit 41c.

41M, 41v, and 41BL emit laser light that turns on and off depending on the color image signal, and latent images are formed on the photosensitive drums 45c, 45M, 45Y, and 4581, and each toner hopper 42c+42M
It is developed and visualized using cyan, magenta, yellow, and black toners filled in +42Y and 428L. A recording paper 24 on which the toner image is conveyed
Transfer charger 44C, 44M on top? 44Y, 44B
Press L to transfer. Next, the recording paper 24 on which the toner image is fixed by the fixing device 34 and the color image is formed thereon is discharged onto a paper discharge tray 35 .

FIG. 2 is a perspective view of the laser beam printer shown in FIG. 1, and the same members as in FIG. 1 are given the same reference numerals.

In this figure, 51c, 51M, 51y
.

51B is a polygon mirror, and each laser unit 41c
, 41M, 41y, 418L are transmitted through f/θ lenses 52c, 52. .

Photosensitive drum 45C via 52Y and 52BL.

Uniformly scan at 45%, 45y, and 45et.

53c, 53M, 53Y, 538L are mirrors, and each laser unit 41c + 41MI
41 Y 1418 [Beam detect signal generation unit that receives the laser beam emitted from before the image writing position) (BD signal generation unit)) 54c
.

54M, 54Y, and 54BL are scanned. Note that each photosensitive drum 45c, 45M, 45y,
45BL are arranged at regular intervals. 55 is a recording medium, which is sequentially conveyed in the direction of the arrow to form a color image e 56 Cl 56 s + 56 y
+ 568 L is the scanner motor and polygon mirror 51c.

51M, 51Y, and 51BL are rotated at a constant speed.

Figure 3 shows scanner motors 56C and 56M.

56Y and 5681 are explanatory diagrams showing the drive mechanisms.

Scanner motor 56C, 56N, 56y.

A Hall element 57 for detecting the rotation of the scanner motor is disposed at 56aL, and feeds back the detected frequency signal to a PLL control section to be described later.

FIG. 4 shows a drive mechanism for a conveyor belt that conveys recording paper. The conveyor belt 43 is driven by a drive motor 60 via a drive roller 61 , and the speed of the belt 43 is detected by an encoder 63 via a pickup roller 62 . The frequency signal detected by this encoder 63 is fed back to a PLL control section, which will be described later.

FIG. 5 shows the drive mechanism of the photosensitive drum. Photosensitive drums 45c, 45s, 45Y.

The photosensitive drum 45B is driven by a drive motor 64 and driven through driven rollers 65 and 66, and the rotational speed of the photosensitive drum is detected by an encoder 67 connected to the central axis of the drum, and the detected frequency signal will be described later. pLI
Feedback is provided to the JIIi department.

FIG. 6 shows a drive mechanism for the fixing roller. The fixing roller 68 is driven by a drive motor 69 through a driven gear 70.71, and the speed of the fixing roller 68 is detected by an encoder 72 provided coaxially with the motor 69.

The detected frequency is fed back to a PLL control section, which will be described later.

FIG. 7 shows the drive control system. A reference frequency signal generated by a reference signal oscillator 73 consisting of a crystal oscillator or the like passes through a frequency divider 74 to a scanner control section 75, a photosensitive drum control section 76, a fixing roller control section 77, and a belt control section 78.
The signal is supplied to each PLL control section 81 of. Each PLL control section receives a signal whose frequency is divided from a common reference frequency signal into a frequency corresponding to each drive speed of the scanner, photosensitive drum, conveyor belt, and fixing roller, and the encoders 57 and 63.

The rotation is controlled by comparing the frequency signal fed back from 67 and 72.

In this way, in this embodiment, the photosensitive drum, scanner, conveyor belt, and fixing roller are controlled by PLL using a reference frequency signal from a common reference frequency oscillator, so that variations in the reference frequency for driving each member can be prevented. This can prevent the images of each color transferred to the recording paper from becoming blurred or
It is possible to prevent the recording paper from being pulled by the fixing roller and record clear images.

(Effects of the Invention) The present invention has the above-described structure and operation, and can prevent uneven rotation of the scanner, photosensitive drum, feeding means, and fixing means, and can record clear images without color shift. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a laser beam printer according to the present invention, FIG. 2 is a perspective view showing an image exposure section, FIG. 3 is an explanatory view showing the drive mechanism of the scanner motor, and FIG. FIG. 5 is a perspective view showing the drive mechanism of the conveyor belt, FIG. 5 is a perspective view showing the drive mechanism of the photosensitive drum, FIG. 6 is a sectional view showing the drive mechanism of the fixing roller, and FIG. 7 is a block diagram showing the control system. This is a diagram.
Explanation of transfer code 24...Recording paper 41...Laser unit, unit 45...Photosensitive drum 56...Scanner motor 57...Hall element 60...Drive motor 63
...Encoder 64...Drive motor 67...
・Encoder 69...Drive motor 72...Encoder 73...Reference signal oscillator 81...P
LL control section Fig. 4 Fig. 5 Fig. 6 N"il Fig. 7 "-1

Claims (1)

[Claims] The rotation of a rotating polyhedron that irradiates each image carrier with each laser beam emitted from a plurality of laser units, the rotation of each image carrier, the rotation of a conveying means that conveys recording paper, and the fixing roller of a fixing device. What is claimed is: 1. A laser beam printer in which a plurality of PLL control means respectively control the rotation of the laser beam printer, comprising a common frequency signal generation means for supplying a common reference frequency signal to the plurality of PLL control means.