JP3523707B2 - Image forming apparatus and driving method thereof - 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, and more particularly to
The present invention relates to an image forming apparatus including a laser scanning device such as a laser printer and a digital copying machine, and a driving method thereof.

[0002]

2. Description of the Related Art As an image forming apparatus, for example, a digital copying machine is provided with a scanner for reading an image of a document and an exposing device for exposing a peripheral surface of a photosensitive drum in accordance with image data of the read document. There is. This exposure apparatus has a laser light source that emits laser light according to image data, and a polygon mirror that continuously deflects the laser light emitted from the laser light source. It is driven to rotate.

The photosensitive drum is rotated at a predetermined speed by a drive system having a drive motor, a pulley, a belt and the like. Then, by scanning the peripheral surface of the photosensitive drum with laser light from the exposure device, an electrostatic latent image corresponding to the original is formed. This electrostatic latent image is developed by a developing device using a developer and transferred to copy paper.

In order to form a high quality and high resolution image, it is necessary to reduce a jitter image caused by vibration of the photosensitive drum, uneven rotation, and the like. Therefore, conventionally, a flywheel is provided on the rotary shaft of the drive system for rotating the photosensitive drum to reduce vibration and uneven rotation of the drive system including the drive motor, thereby preventing the occurrence of a jitter image.

[0005]

However, the flywheel is particularly effective in reducing the rotation unevenness in the high frequency region of the photosensitive drum, but it does not prevent the occurrence of a jitter image due to the vibration of the exposure apparatus. Can not. That is, the exposure apparatus vibrates under the influence of an internal vibration source such as a polygon motor and an external vibration source such as a drive motor of a drum drive system, but such vibration of the exposure apparatus cannot be reduced by the flywheel described above. . Then, the vibration of the exposure device adversely affects the laser light that exposes and scans the peripheral surface of the photoconductor drum and causes a jitter image.

The present invention has been made in view of the above points, and an object thereof is to provide an image forming apparatus and an image forming apparatus capable of improving an image defect due to occurrence of jitter and obtaining an image of high quality and high resolution. It is to provide a driving method.

[0007]

To achieve the above object, according to an aspect of the image forming apparatus according to the present invention, a drive motor for rotating the drum-shaped image carrier, rotation of the drive motor
A drive mechanism having a gear provided on a shaft for transmitting the drive force of the drive motor to the image carrier; a laser light source;
The laser light from the laser light source is deflected and
A rotatable scanning member for exposing and scanning the image carrier, and
An exposure unit having a scanning motor that rotationally drives the inspection member.
And is exposed and scanned by the laser beam by the scanning member.
And a means for forming a developer image from the image carrier.
It is Rotation frequency of the drive motor and number of teeth of the gear
The meshing frequency Hk of the drive mechanism and the rotation frequency Hp of the scanning motor that match the product of | Hp−HK |
/ HP is 0.2 or more, and the ratio between the mesh frequency and the rotation frequency of the scanning motor is set to a value that is not an integral multiple.

Further, the teeth provided on the rotary shaft of the drive motor
Through a drive mechanism having a car, the drive motor rotationally drives the drum-shaped image carrier, the scanning motor rotationally drives the scanning member, and the laser light from the scanning member causes the scanning member to rotate. In a driving method of an image forming apparatus for exposing and scanning an image carrier, the driving method according to the present invention is the above-mentioned driving motor.
Of the drive mechanism and the rotation frequency Hp of the scan motor, which are equal to the product of the rotation frequency of the gear and the number of teeth of the gear , | Hp-Hk | / Hp is 0.2 or more, and the engagement is The image carrier and the scanning member are driven by setting the ratio of the frequency and the rotation frequency of the scanning motor to a value that is not an integral multiple.

[0009]

In the image forming apparatus and the driving method configured as described above, the image carrier is rotationally driven by the driving motor through the driving mechanism, and the scanning member of the exposing means is rotationally driven by the scanning motor. The laser light from the laser light source is deflected by the rotating scanning member, and the image carrier is exposed and scanned to form an electrostatic latent image. At this time, vibrations of the driving mechanism, uneven rotation, and the like are transmitted to the exposing means. Therefore, when the meshing frequency of the driving mechanism and the rotating frequency of the scanning motor are close to each other, the vibration amplitude of the exposing means increases due to resonance.

Therefore, the meshing frequency HP and the rotation frequency HK are set so that | HP-HK | / HP becomes 0.2 or more, and these frequencies are provided with a certain difference to increase the vibration amplitude of the exposure means due to resonance. Is suppressed. Further, when the ratio of the mesh frequency to the rotation frequency of the scanning motor becomes an integral multiple, the vibration amplitude increases, so that the mesh frequency HP and the rotation frequency HK are set so that the ratio does not become an integral multiple.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which an image forming apparatus according to the present invention is applied to a digital copying machine will be described in detail below with reference to the drawings. As shown in FIG. 1, the digital copying machine includes an apparatus main body 10 in which a scanner 4 functioning as a reading unit and an image forming unit 6 functioning as an image forming unit, which will be described later, are provided. There is.

On the upper surface of the apparatus main body 10, there is provided a control panel (not shown) and an original placing table 12 made of transparent glass on which an object to be read, that is, an original D is placed. Further, an automatic document feeder 7 (hereinafter referred to as ADF) for automatically feeding a document onto the document table 12 is provided on the upper surface of the apparatus body 10. This ADF7
Is arranged so as to be openable and closable with respect to the document mounting table 12, and also functions as a document retainer that brings the document D mounted on the document mounting table 12 into close contact with the document mounting table 12.

The ADF 7 includes a document tray 8 on which a document D is set, an empty sensor 9 for detecting the presence or absence of the document, a pickup roller 14 for taking out the documents one by one from the document tray, and a paper feed roller 15 for conveying the taken out documents. ,
A pair of aligning rollers 16 for aligning the leading edge of the document and a conveyor belt 18 arranged so as to cover almost the entire document placing table 12 are provided. Then, the plurality of originals set on the original tray 8 face up, that is, the bottom page, that is,
The aligning rollers 16 are taken out in order from the last page.
After being aligned by, the sheet is conveyed to a predetermined position on the document placing table 12 by the conveying belt 18.

In the ADF 7, a reversing roller 20, a non-reversing sensor 21, a flapper 22, and a paper discharge roller 23 are arranged at the end opposite to the aligning roller pair 16 with the conveyor belt 18 interposed therebetween. The document D whose image information has been read by the scanner 4 described later is sent out from the document placing table 12 by the conveyor belt 18, and the reversing roller 20,
ADF 7 via flapper 21 and paper discharge roller 22
The document is discharged onto the document discharge unit 24 on the upper surface. When reading the back surface of the document D, by switching the flapper 22, the document D conveyed by the conveyor belt 18 is reversed by the reversing roller 20 and then moved again to a predetermined position on the document table 12 by the conveyor belt 18. Sent.

The scanner 4 provided in the apparatus body 10
Has a light source 25 such as a fluorescent lamp for illuminating the document D placed on the document table 12 and a first mirror 26 for deflecting the reflected light from the document D in a predetermined direction. The first mirror is attached to the first carriage 27 disposed below the document table 12. The first carriage 16 is movably arranged in parallel with the document table 12, and is reciprocated below the document table by a drive motor via a toothed belt (not shown).

A second carriage 28, which is movable in parallel with the original placing table, is disposed below the original placing table 12. The first carriage 2 is attached to the second carriage 28.
Second and third mirrors 30 and 31 for sequentially deflecting the reflected light from the document D deflected by 6 are attached at right angles to each other. The second carriage 28 is driven by the first carriage 27 by a toothed belt or the like that drives the first carriage 27, and at the same time, the original is placed at a speed half that of the first carriage. It is moved in parallel along the table 12.

Below the document table 12, an image forming lens 32 that focuses the reflected light from the third mirror 31 on the second carriage 28 and a reflected light that is focused by the image forming lens are received. And a CCD sensor 34 for performing photoelectric conversion. The imaging lens 32 is movably arranged in a plane including the optical axis of the light deflected by the third mirror 31 through a drive mechanism, and by moving itself, the reflected light is at a desired magnification. Form an image. Then, the CCD sensor 34
The incident reflected light is photoelectrically converted and an electric signal corresponding to the read document D is output.

On the other hand, the image forming section 6 is provided with a laser exposure device 40 which functions as an exposure means. The laser exposure device 40 includes a semiconductor laser 41 as a light source, a polygon mirror 36 as a scanning member that continuously deflects the laser light emitted from the semiconductor laser 41, and a polygon mirror that is rotationally driven at a predetermined rotational speed described later. A polygon motor 37 as a scanning motor, and an optical system 42 for deflecting the laser light from the polygon mirror and guiding it to a photosensitive drum described later.
And are equipped with. Laser exposure apparatus 4 having such a configuration
0 is fixed and supported by a support frame of the apparatus body 10 described later.

The semiconductor laser 41 is ON / OFF controlled according to image information of the document D read by the scanner 4 or facsimile transmission / reception document information, and this laser light is exposed through the polygon mirror 36 and the optical system 42. The electrostatic latent image is formed on the peripheral surface of the photosensitive drum by being directed toward the body drum and scanning the peripheral surface of the photosensitive drum.

The image forming unit 6 also has a rotatable photosensitive drum 44 as an image bearing member disposed substantially in the center of the apparatus main body 10, and the peripheral surface of the photosensitive drum from the laser exposure device 40. To expose a desired electrostatic latent image. Around the photosensitive drum 44, a charger 45 for charging the drum peripheral surface to a predetermined electric charge, and a toner as a developer for the electrostatic latent image formed on the peripheral surface of the photosensitive drum to supply a desired image. Developer 4 for developing with density
6. A transfer target material fed from a paper cassette, which will be described later, that is, a separation charger 47 for separating the copy paper P from the photoconductor drum is integrally provided, and the toner image formed on the photoconductor drum is transferred to the paper P. Transfer charger 48 for transferring the toner onto the peripheral surface of the photosensitive drum, a peeling claw 49 for peeling the copy sheet from the peripheral surface of the photosensitive drum, a cleaning device 50 for cleaning the toner remaining on the peripheral surface of the photosensitive drum, and a static eliminator for discharging the peripheral surface of the photosensitive drum 51 are arranged in order.

An upper cassette 52, a middle cassette 53, and a lower cassette 54, which can be pulled out from the main body of the apparatus, are arranged in the lower part of the main body 10 in a stacked state.
Copy papers of different sizes are loaded in each cassette. Large capacity feeders 5 beside these cassettes
5, a large-capacity feeder accommodates about 3000 sheets of frequently used copy paper, for example, A4 size copy paper. Further, above the large-capacity feeder 55, a paper feed cassette 57 also serving as a manual feed tray 56 is detachably attached.

In the apparatus main body 10, a conveying path 5 extending from each cassette and the large-capacity feeder 55 through a transfer portion located between the photosensitive drum 44 and the transfer charger 48.
8 is formed, and a fixing device 60 is provided at the end of the transport path. A discharge port 61 is formed on the side wall of the apparatus main body 10 facing the fixing device 60, and a discharge tray 62 is formed at the discharge port.
Is installed.

In the vicinity of the upper cassette 52, the middle cassette 53, the lower cassette 54, the paper feeding cassette 57, and the large-capacity feeder 55, the pickup roller 6 for taking out the sheets one by one from the cassette or the large-capacity feeder.
3 are provided respectively. Further, in the transport path 58,
A large number of paper feed roller pairs 6 that convey the copy paper P taken out by the pickup roller 63 through the conveyance path 58.
4 are provided.

A registration roller pair 65 is provided on the upstream side of the photosensitive drum 44 in the transport path 58. The registration roller pair 65 corrects the inclination of the copy sheet P taken out, aligns the leading edge of the toner image on the photoconductor drum 44 with the leading edge of the copy sheet P, and is the same as the moving speed of the peripheral surface of the photoconductor drum. The copy paper P is fed to the transfer unit at a speed. Before the registration roller pair 65, that is, on the side of the paper feed roller 64, a pre-aligning sensor 66 for detecting the arrival of the copy paper P is provided.

The copy sheets P taken out one by one from each cassette or the large-capacity feeder 55 by the pickup roller 63 are sent to the registration roller pair 65 by the paper feed roller pair 64. Then, the copy paper P is sent to the transfer unit after the leading edge of the copy paper P is aligned by the registration roller pair 65. At the transfer portion, the developer image formed on the photosensitive drum 44, that is, the toner image is transferred to the transfer charger 4
The image is transferred onto the sheet P by 8. The copy sheet P on which the toner image has been transferred is separated by the separation charger 47 and the separation claw 49.
Is peeled off from the peripheral surface of the photoconductor drum 44, and is conveyed to the fixing device 60 via the conveyance belt 67 forming a part of the conveyance path 52. Then, after the developer image is melted and fixed on the copy paper P by the fixing device 60, the copy paper P
Is discharged onto the discharge tray 62 through the discharge port 61 by the pair of paper feed rollers 68 and the pair of discharge rollers 69.

Below the transport path 58, the copy sheet P that has passed through the fixing device 60 is reversed and the registration roller pair 6 is again provided.
An automatic double-sided device 70 for sending to 5 is provided. The automatic double-sided device 70 has a temporary stacking unit 71 that temporarily stacks the copy sheets P, and a reversing path 72 that branches from the transport path 58 and reverses the copy sheets P that have passed through the fixing device 60 and guides them to the temporary stacking unit 71. And a pickup roller 73 for picking up the copy paper sheets P stacked in the temporary stacking unit one by one, and a paper feed roller 75 for feeding the taken-out paper sheets to the registration roller pair 65 through the transport path 74. Also, the transport path 5
A distribution gate 76 that selectively distributes the copy paper P to the discharge port 61 or the reversing path 72 is provided at a branch portion between the reversing path 72 and the reversing path 72.

When performing double-sided copying, the copy paper P that has passed through the fixing device 60 is guided to the reversing path 72 by the sorting gate 76, temporarily accumulated in the inverted state in the temporary accumulating section 71, and then picked up. The roller 73 and the paper feed roller pair 75 feed the resist roller pair 65 through the conveyance path 74. Then, the copy paper P is aligned by the pair of registration rollers 65 and then sent to the transfer portion again, and the toner image is transferred to the back surface of the copy paper P. After that, the copy paper P is discharged onto the paper discharge tray 62 via the conveyance path 58, the fixing device 60, and the paper discharge rollers 69.

2 to 4 show a part of the drive mechanism of the image forming section 6. The drive mechanism 80 includes a drive motor attached to a support frame 81 of the apparatus body 10,
It is composed of a plurality of gears, pulleys, and the like. More specifically, the oval-shaped opening 8 is formed in a part of the support frame 81.
2 is formed, and a mounting plate 83 having a U-shaped cross section is fixed to one surface of the support frame so as to face the opening 82. A main motor 84 that functions as a drive motor is attached to the mounting plate 83. Main motor 84
The rotary shaft of the above projects through the mounting plate 83 to the opening 82 side, and the gear 84a is cut at the projecting end. Instead of directly forming the gear on the rotary shaft, a separate gear may be attached to the rotary shaft.

A gear 86 having a pulley 86a and a gear 87 having a pulley 87a are attached to the rear surface of the mounting plate 83, and these gears 86 and 87 mesh with the gear 84a. And the main motor 84
Driving force is transmitted to the gears 86a and 87a via the gear 84a and distributed to the drum driving unit and other driving units.

The drum driving section is rotatably supported by the supporting frame 81 in a state of penetrating the supporting frame 81, and a pulley 90 fixed to the drum driving shaft on one side of the supporting frame. Further, it is provided with a flywheel 91 and a drive belt 92 which is stretched between pulleys 86a and 90. A tension pulley 94 urged toward the drive belt by a spring 93 is in rolling contact with the drive belt 92 in the middle thereof.

A coupling 96 for driving the drum is fixed to the end of the drum driving shaft 88 protruding to the other surface side of the support frame 81 via a spring 95. The rotary shaft 44a of the photosensitive drum 44 is attached to the coupling 96.
One end of is connected detachably. Therefore, the photosensitive drum 44 is rotationally driven by the main motor 84 via the drum drive shaft 88, the pulley 90, the drive belt 92, the pulley 86a and the gear 86.

The other drive parts are rotatably supported by the support frame 81 and located on the other surface side of the support frame, and the developing device drive gear 98 and the cleaning device drive gear 10 are provided.
0, and the fixing device drive gear 102. A pulley 98 is attached to the rotation shafts of these gears 98, 100, 102.
a, 100a, and 102a are fixed, and the drive belt 104 is stretched around these pulleys and the pulley 87a. The spring 10 is provided in the middle of the drive belt 104.
The tension pulley 106 urged toward the drive belt 104 by 5 is in rolling contact with the drive belt 104.

Therefore, the driving force of the main motor 84 is the gear 87, the pulley 87a, the drive belt 104, and the pulley 98.
a, 100a, 102a through the developing device drive gear 9
8, the cleaning device drive gear 100, and the fixing device drive gear 102, respectively, which are transmitted to the developing device 46, the toner recovery auger of the cleaning device 50, and the fixing device 6.
0 is driven respectively.

FIG. 5 schematically shows the control mechanism of the digital copying machine configured as described above. This control mechanism is roughly classified into a control panel unit 110 that controls the control panel 170, a scanner unit 120 that controls the scanner 4 that reads image information from the document D, and forms an image on the paper P based on the input image information. A printer unit 130 as an image forming unit, a scanner unit 4, and a memory editing unit 140 that processes image data supplied from an external device described later, such as a facsimile device, a hard disk device, or a known local area network (hereinafter, LAN). Of the control unit 110, the scanner unit 120, the printer unit 130, the memory editing unit 140, and the system unit 150. Belief in Main control unit 1 that controls the delivery of the issue
Equipped with 60.

The control panel section 110 includes a control panel CPU 111 and a control panel CPU1.
Read-only memory (hereinafter, RO
112, a random access memory (hereinafter, referred to as RAM) 113, and a priority card input unit 171.

The control panel CPU 111 uses the RO
Based on the data stored in the M112 and the RAM 113, detection of input by various switches and a touch panel provided on the control panel 170, display on the touch panel, and turning on and off of the LED are controlled.

The scanner unit 120 includes the scanner CPU 12
1. ROM 122 and RAM 1 including ROM 122 and RAM 123 connected to the scanner CPU 121
Scanner CP based on control data stored in 23
The CCD sensor 34 of the scanner 4 is controlled by U121.
To take in the image information of the document D as light / dark information of light and to energize a DC motor or the like (not shown) for moving the first carriage 27 and the second carriage 28 at a predetermined speed. A predetermined drive signal is output to the control unit 124.

Further, the scanner section 120 converts the analog image data output from the CCD sensor 34 into a known A / D format.
A / D conversion circuit 1 for converting into a digital signal by conversion
25, a shading correction circuit 126 for removing the influence of the individual error of the output of the CCD sensor 34 and the unevenness of the light quantity of the illumination lamp 25 from the image signal converted into the digital signal by the A / D conversion circuit 125, and the CCD A line memory 127 is provided for supplying the image information of the document D read by the sensor 34 to the memory editing unit 140 connected to the subsequent stage at a predetermined timing.
Under the control of the scanner CPU 121 based on the data of the ROM 122 and the RAM 123, the image information of the document D read by the CCD sensor 34 is converted into an electric signal, which is then binarized at a predetermined threshold level, and the memory editing unit connected to the subsequent stage. The data is output to a page memory 140 described later.

The scanner CPU 121 has an ADF
7 is also connected. The ADF 7 is a scanner CPU 1 based on control by a main control unit 160 described later.
The document D is fed under the control of 21. Also, the scanner C
The PU 121 outputs predetermined control data to the page memory of the memory editing unit 140 and holds image data used for image formation when edit data is input from a coordinate input device (not shown). An editor 128 for controlling the size of the memory area is connected.

The printer unit 130 includes the printer CPU 13
1 and a ROM 132 connected to the printer CPU 131
An image is formed on the paper P based on the image information read via the image reading unit 4 and the image data supplied from an external device described later, including the RAM 133.

The printer CPU 131 has a drive mechanism 80.
Motor control circuit for controlling the main motor 84, the polygon motor 37 of the laser exposure device 40, the drive motor of the automatic double-sided device 70, the large-capacity feeder (hereinafter referred to as LCF), the drive motor of the feeding mechanism of the paper feed cassette, and the like. Thirteen
4 and various sensors and switches such as a document position detection sensor that detects the position of the document D set on the document table 12, a paper empty switch, a lever switch that detects a jam of copy paper, and an aligning sensor 66. An input circuit 135 used for inputting an output signal is connected to a mechanism control unit 136 for energizing, for example, a sorting gate 76 of the automatic double-sided device 70 or a solenoid (not shown) included in the cleaning device 50. Has been done.

Further, the printer CPU 131 is provided with a voltage supply circuit 138 for applying a predetermined voltage to the charging charger, the developing device, the transfer / peeling charger, and the like, and the light intensity of the laser light emitted from the laser light source 41 of the laser exposure device 40. A laser drive circuit 139 for intensity modulation corresponding to image data supplied from a page memory described later is connected, and an image is formed on a copy sheet under the control of the printer CPU 131 based on the data of the ROM 132 and the RAM 133.

The memory editing unit 140 is a memory control CPU.
141 including a main CPU described later of the main control unit 160 and a system C described later of the system unit 150.
Image data supplied from the scanner unit 120 or an external device according to instructions from both the PU and the PU is converted into bitmap data used for intensity modulation of laser light emitted from the laser exposure device 32 of the printer unit 130. After that, it is temporarily stored in the page memory shown in the latter part.

In the memory control CPU 141, image data supplied from an external device via the system unit 150 and read via the scanner unit 120 are read out, and then the image processing unit of the main control unit 160, which will be described later, converts the image data into a predetermined format. An image editing unit 142 that edits the converted image data of the document D, a compression / expansion unit 143 that compresses or expands the input image data, and expands the input image data.
A page memory 145, which stores image data processed through the enlargement / reduction / rotation unit 144, the image editing unit 142, the compression / decompression unit 143, and the enlargement / reduction / rotation unit 144 that are reduced or rotated page by page. An address control unit 146 that manages addresses, a memory management control unit 147 that manages memory data, and processing such as compression / expansion and enlargement / reduction / rotation for image data taken in by the image editing unit 142 Is connected to an interrupt control unit 148 that gives an instruction.

The system section 150 includes a system CPU 151 for controlling the capture of image data supplied from other than the scanner section 120, and a facsimile apparatus 152 as an external apparatus connected to the system CPU 151, a hard disk apparatus 153, a computer (not shown), and Controls each of the LAN 154 to which a word processor or the like is connected, and the printer controller 155 that converts image data supplied via the facsimile 152, the hard disk device 153, and the LAN 154 from code data into image data in a format processable by a copying machine. By doing so, the image editing unit 142 of the memory editing unit 140 is made to input the image data.

The main control section 160 operates the digital copying machine, that is, the control panel section 110, the scanner section 120, the printer section 130, and the memory editing section 14.
0 and the CPU 121 of each of the system units 150,
Main CPU 1 for controlling 131, 141 and 151
It has 61.

The main CPU 161 has a ROM 162 in which initial data for operating the digital copying machine is stored, and each CPU 121, 131, 141.
And control 151 to control panel 11
0, the scanner unit 120, the printer unit 130, the memory editing unit 140, and the RAM 163 that holds various data input from the system unit 150, respectively.

Further, the main CPU 161 holds a printer font R which holds a printer font used for storing the code data input via the system section 150 in the page memory 145 of the memory editing section 140.
An image corresponding to the code data input via the system unit 150 is displayed on the OM 164 and an editing display device (not shown), and a control panel 170 is also provided.
Display font ROM 165 that holds a display font for displaying a predetermined image on the liquid crystal display / input panel, designation of a destination of image data read by the scanner unit 120, switching of image data supplied to the printer unit 130, and the like. And functions as a buffer memory for image data transferred between the line memory 127 of the scanner unit 120 and the page memory 145 of the memory editing unit 140 and between the page memory 145 and the laser exposure device 40. A data switching / buffer memory 166 for switching and an image processing unit 167 for masking or trimming the input image data are connected.

On the other hand, in the digital copying machine having the above construction, the rotation frequency Hp of the polygon motor 37 of the laser exposure device 40 and the meshing frequency Hk of the gear 84a provided on the main motor 84 of the drive mechanism 80, that is, the main motor 84. The product of the rotation frequency and the number of teeth of the gear 84a is set as follows in order to reduce the occurrence of a jitter image due to the rotation of the polygon motor 37 and the main motor 84.

That is, the main motor 84 of the drive mechanism 80.
Since the laser exposure apparatus 40 is attached to the support frame 81 of the apparatus body 10, the vibration of the main motor is transmitted to the laser exposure apparatus 40 via the support frame 81. Therefore, the vibration frequency of the main motor 84, that is, the meshing frequency Hk is determined by the polygon motor 37.
Of the laser exposure device 4 when the rotation frequency HP of
0 resonates and its vibration amplitude increases. In FIG. 6, the mesh frequency HK (385 Hz) is the rotation frequency HP (429H).
z) is a graph obtained by frequency analysis of vibration data of the laser exposure apparatus 40 in the case of approaching z).
It can be seen that the amplitude level (output level) in the inter-frequency band is increasing. When the amplitude level in the frequency band between both frequencies increases in this way, it becomes difficult to perform accurate exposure scanning by the laser exposure device 40, which adversely affects the formed image. Therefore, it is necessary that the mesh frequency HK and the rotation frequency HP have a certain difference.

However, even if there is a difference between the frequencies Hp and Hk, if the ratio of these frequencies is an integral multiple, the vibration amplitude of the laser exposure apparatus 40 will be the same as above due to the frequency components generated in the double period. Increase. In FIG. 7, the mesh frequency Hk is 215 Hz and the rotation frequency Hp is 42.
It is set to 9 Hz, these substantially integral multiple ratio, i.e., Hk: Hp ≒ 1: vibration data of the laser exposure device 40 when that is the 2 shows a result of frequency analysis. From this analysis result, it can be seen that the amplitude level increases at both the frequencies Hk and Hp.

Further, a DC motor is mainly used as the main motor 84 of the drive mechanism 80, and its rotation speed is about 20.
Although the speed is around 00 rpm, the polygon motor 37
The number of revolutions depends on the resolution and printing speed, but is about 4 to 15 times that of the main motor. Therefore, the meshing frequency of the gear 84a formed or attached to the rotation shaft of the main motor 84 is set to the laser exposure device 4
It greatly affects the vibration of 0.

In the digital copying machine of this embodiment, the copy speed is set to 38 copies / minute, and in order to realize this, the process speed, that is, the peripheral speed of the photosensitive drum 44 is set to 118 mm / second. There is. Also, the resolution is 40
In order to realize 0 dpi, the rotation speed of the polygon motor 37 is
It is set to 25,748 rpm.

The present inventor variously changes the number of rotations of the main motor 84 and the number of teeth of the gear 48a provided on the rotation shaft of the main motor, and the jitter generated in the formed image depends on the number of rotations and the number of teeth. Experiments were carried out to see if there was any change. FIG. 8 shows 11 kinds of combinations for which experiments were conducted. The number of revolutions of the main motor 84 in each combination,
The absolute value of the number of teeth of the gear 84a, the meshing frequency HK at that time, and the difference between the rotation frequency HP of the polygon motor 37 and the meshing frequency HK is calculated as the rotation frequency H of the polygon motor.
The value (| HP-HK | / HP) normalized by P is shown. However, an experiment was conducted by setting the rotation frequency HP of the polygon motor 37 constant at about 429 Hz and changing the reduction ratios so that the peripheral speed of the photosensitive drum 44 was constant.

FIG. 9 shows the measurement result of the jitter generated in the formed image in each combination. The evaluation value of the jitter is as follows.
The numerical value of the standard deviation (3σ) by the variation measurement of m) was used.

As can be seen from FIG. 9, when the standard deviation of the line-to-line variation of the 2-dot pair line is set to 20 μm, the value (│HP -HK │ / HP) normalized by the rotation frequency of the polygon motor 37 is obtained. By setting the number of rotations and the number of teeth so as to be 0.2 or more, the standard of the standard deviation can be satisfied. However, as described above, when the ratio of the rotation frequency HP of the polygon motor 37 to the meshing frequency HK is set to be an integral multiple, the jitter is deteriorated by the frequency component generated in the double cycle.

From the above, according to the present embodiment, the rotation speed of the main motor 84 and the number of teeth of the gear 84a are set so that the rotation frequency HP and the meshing frequency HK of the polygon motor 37 satisfy the following conditions. ing.

(1) | Hp-Hk | / Hp is set to 0.2 or more, and (2) the ratio of Hp and Hk is set to be an integer multiple. In the digital copying machine according to the embodiment, the rotation speed of the polygon motor 37 is set to 25,7 in consideration of the above conditions.
The rpm is 48 rpm, the rotation frequency is 429 Hz, the rotation speed of the main motor 84 is 2,000 rpm, and the number of teeth of the gear 84a provided on the rotation shaft of the main motor is 10 (combination "6" in FIG. 8). As a result, the mesh frequency Hk is 333.3 Hz, and the value of | Hp-Hk | / Hp is 0.
22, which satisfies the above condition (1). Also,
The ratio of the meshing frequency Hk and the polygon motor 37Hp is, Hk: Hp ≒ 1: not an integral multiple 1.28, the above conditions (2) is also satisfied.

FIG. 10 shows the frequency analysis result of the vibration of the laser exposure apparatus 40 when the meshing frequency HK satisfying the above conditions is set. The meshing frequency HK and the rotation are compared with those in FIGS. 6 and 7. It can be seen that the vibration amplitude is reduced at any of the frequencies HP and the increase of the amplitude level in the frequency band between these frequencies is suppressed. Also, when the jitter of the formed image was measured,
The variation in the distance between two dot pair lines could be maintained within the specified standard deviation of 20 μm.

As described above, according to the digital copying machine of the present embodiment, the mesh frequency HP and the rotation frequency HK.
Is set so that | HP-HK | / HP is 0.2 or more, and these frequencies are provided with a certain difference to suppress an increase in the vibration amplitude of the laser exposure apparatus due to resonance. Also, by setting the ratio of the mesh frequency to the rotation frequency of the polygon motor so that it is not an integer multiple,
This prevents an increase in the vibration amplitude of the laser exposure apparatus due to the frequency component generated in the double cycle.

As described above, by preventing the increase of the vibration of the laser exposure apparatus due to the vibration of the drive mechanism including the main motor, the occurrence of the jitter due to the vibration of the laser exposure apparatus on the writing side is reduced, and the formed image is reduced. The quality and resolution of can be improved.

The present invention is not limited to the above-described embodiments, but can be variously modified within the scope of the present invention. For example, although the configuration is such that the gear formed or attached to the rotation shaft of the main motor is used, the configuration is not limited to this.
Instead of the gear, a toothed pulley may be attached to the rotary shaft of the main motor to transmit the driving force via the toothed belt. Also in this case, the meshing frequency is determined by the rotation frequency of the main motor and the number of teeth of the toothed pulley.

Further, the motor for vibrating the laser exposure apparatus is not limited to the above-mentioned main motor, and, for example, a drive motor for driving the carriage of the scanner unit, a drive motor for the paper feed mechanism, and the like are also conceivable. With respect to the motor as well, the influence on the laser exposure apparatus can be reduced by setting the meshing frequency so as to satisfy the above condition.

The setting condition | HP-HK | / H
Since the numerical value of P is a value normalized by the rotation frequency of the polygon motor, even in a copying machine having a different rotation frequency of the polygon motor, it is possible to obtain the same effect as that of the present embodiment by satisfying the above setting conditions. it can.

The scanning member and the scanning motor are not limited to the combination of the polygon mirror and the polygon motor, but may be a combination of the galvano mirror and the motor for driving the galvano mirror.

[0066]

As described above in detail, according to the present invention, at least the meshing frequency HK of the drive system for driving the image carrier and the rotation frequency HP of the scanning motor of the exposing means are respectively | HP-HK |. / HP is 0.2 or more, and the ratio of the mesh frequency to the rotation frequency of the scanning motor is set so as not to be an integral multiple, thereby reducing the vibration of the exposure means and improving the image defect due to the occurrence of jitter. In addition, it is possible to provide an image forming apparatus and a driving method capable of obtaining high-quality and high-resolution images.

[Brief description of drawings]

FIG. 1 is a sectional view showing the entire digital copying machine according to an embodiment of the present invention.

FIG. 2 is a plan view showing a drive mechanism of the digital copying machine.

FIG. 3 is a front view of the drive mechanism.

FIG. 4 is a rear view of the drive mechanism.

FIG. 5 is a block diagram showing a configuration of a control system of the entire digital copying machine.

FIG. 6 is a graph showing a result of vibration frequency analysis of the laser exposure apparatus when the rotation frequency and the mesh frequency of the polygon motor of the laser exposure apparatus are close to each other.

FIG. 7 is a graph showing the results of vibration frequency analysis of the laser exposure apparatus when the ratio of the rotation frequency of the polygon motor of the laser exposure apparatus to the meshing frequency is set to an integral multiple.

FIG. 8 is a diagram showing each set value when an jitter generation state is tested by variously changing the number of rotations of the main motor of the digital copying machine and the number of teeth of the gear provided on the rotation shaft of the main motor. .

FIG. 9 is a graph showing the relationship between the absolute value of the difference between the rotation frequency HP of the polygon motor and the meshing frequency HK normalized by the rotation frequency HP of the polygon motor (| HP-HK | / HP) and the standard deviation. .

FIG. 10 is a graph showing the results of vibration frequency analysis of the laser exposure apparatus when the rotation frequency and mesh frequency of the polygon motor of the laser exposure apparatus are set to satisfy predetermined conditions.

[Explanation of Codes] 36 ... Polygon mirror, 37 ... Polygon motor, 40 ...
Laser exposure device, 44 ... Photosensitive drum, 80 ... Driving mechanism, 81 ... Support frame, 84 ... Main motor, 84
a, 86, 87 ... Gear, 86a, 87a, 90, 98
a, 100a, 102a ... pulley, 91 ... flywheel.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/00 G03G 15/00 107 G03G 15/00 550 G03G 15/04-15/056 G03G 13/04- 13/056 G03G 21/16-21/18 G02B 26/10-26/10 109

Claims (4)

(57) [Claims] 1. A drive motor for rotatably driving a drum-shaped image carrier, and a drive mechanism having a gear provided on a rotation shaft of the drive motor for transmitting a driving force of the drive motor to the image carrier. An exposure unit including a laser light source, a rotatable scanning member that deflects the laser light from the laser light source and exposes and scans the image carrier by the laser light, and a scanning motor that rotationally drives the scanning member, Means for forming a developer image from the image carrier that has been exposed and scanned with laser light by the scanning member, and a product of the rotational frequency of the drive motor and the number of teeth of the gear is provided.
The meshing frequency Hk of the drive mechanism and the rotation frequency Hp of the scanning motor that match are such that | Hp-HK | / HP is 0.2 or more, and the ratio of the meshing frequency to the rotation frequency of the scanning motor is an integer multiple. An image forming apparatus characterized by being set to respective values that do not satisfy the above. 2. A drive motor for rotationally driving a drum-shaped image carrier, a drive mechanism for transmitting the driving force of the drive motor to the image carrier, a laser light source, and a laser beam deflected from the laser light source. Exposure means having a rotatable scanning member that exposes and scans the image carrier with a laser beam, and a scanning motor that rotationally drives the scanning member, and the image carrier that is exposed and scanned with the laser beam by the scanning member. And a means for forming a developer image from the body, wherein the drive mechanism is driven according to the rotation of the gear and a gear provided on the rotation shaft of the drive motor, and transmits the driving force to the image carrier. The transmission frequency of the drive motor, and the meshing frequency Hk of the drive mechanism that matches the product of the rotation frequency of the drive motor and the number of teeth of the gear, and the rotation frequency Hp of the scan motor are | Hp-H An image forming apparatus, wherein k | / Hp is 0.2 or more, and the ratio between the mesh frequency and the scanning motor rotation frequency is set to a value that is not an integral multiple. 3. A drive motor for rotationally driving a drum-shaped image carrier, and a drive mechanism having a gear provided on a rotation shaft of the drive motor for transmitting a driving force of the drive motor to the image carrier. An exposure unit having a laser light source, a polygon mitter for deflecting the laser light from the laser light source to expose and scan the image carrier by the laser light, and a polygon motor for rotationally driving the polygon mirror; Means for forming a developer image from the image carrier exposed and scanned by the laser beam by means of the drive mechanism, and the meshing frequency Hk of the drive mechanism, which is equal to the product of the rotation frequency of the drive motor and the number of teeth of the gear, And the rotation frequency Hp of the polygon motor is such that | Hp−Hk | / Hp is 0.2 or more, and the ratio of the mesh frequency to the rotation frequency of the polygon motor is An image forming apparatus characterized by being set to the value which is not integer multiple. 4. A gear provided on a rotary shaft of a drive motor
Through the driving mechanism provided therein, the driving motor rotationally drives the drum-shaped image carrier, the scanning motor rotationally drives the scanning member, and the laser light from the scanning member exposes and scans the image carrier. In the driving method of the image forming apparatus, the product of the rotation frequency of the drive motor and the number of teeth of the gear is calculated.
The meshing frequency Hk of the drive mechanism and the rotation frequency Hp of the scanning motor that match each other are set to | Hp-Hk | / Hp
Is 0.2 or more, and the ratio of the mesh frequency to the rotation frequency of the scanning motor is set to a value that does not become an integral multiple, and the image carrier and the scanning member are driven. Device driving method.