JPH03118796A - Image forming device - Google Patents

Abstract

PURPOSE:To heighten the quality of images by driving and controlling stepping motors, varying the intervals of switching the excitation of the exciting windings of the stepping motors periodically in accordance with speed variation data stored in memory units, in time of rotating the stepping motors. CONSTITUTION:Drive units 71, 72 drive stepping motors 19, 22 by switching and exciting in a specified order a plurality of exciting windings provided on the stator sides of the stepping motors 19, 22 which rotate an image-carrying substance, and memory units 92, 93 store a plurality of speed variation data of the stepping motors 19, 22. And, the intervals of switching the excitation of the exciting windings of the stepping motors 19, 22 are periodically varied in accordance with the speed variation data stored in the memory units 92, 93, in time of rotating the stepping motors 19, 22. By such arrangement, a control unit 81 controls the drive units 71, 72.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus that forms an image on an image forming medium, such as a laser printer.

(Prior Art) Conventionally, image forming devices such as laser printers can be controlled by digital signals from a CPU, speed can be adjusted, highly accurate positioning is possible, and the direction of rotation can be changed freely. For this reason, stepping motors are used in photoreceptor drums and transfer drums.

However, since the stepping motor is structured so that rotational force is obtained through continuous step motion, speed fluctuations, that is, rotational irregularities occur, and in even worse cases, large vibrations are caused. These speed fluctuations (uneven rotation) and vibrations generated by the stepping motor appear as image blur and unevenness in the output image of the laser printer, adversely affecting image quality and even causing vibration.

Therefore, in order to reduce speed fluctuations (uneven rotation) and vibrations that adversely affect image quality, conventional methods have been to attach a dynamic damper to the rotor shaft or load shaft of a stepping motor, or to install a damping material in the middle of the torque transmission mechanism. Techniques are used to suppress the rotation by inserting a flyhole, or to smoothen the rotation by using a large flyhole. In addition, as an electrical "method," one step is divided into several 10 steps of several steraples by increasing and decreasing the applied current to different excitation phases in stages and shifting the excitation stop point of the rotor in stages. Attempts have also been made to reduce speed fluctuations (uneven rotation) and vibrations using a so-called microstep drive system.

However, the method of reducing speed fluctuations (rotational unevenness) and vibrations of the stepping motor by providing external additional elements not only increases the size and weight of the apparatus, but also has the problem that it is not possible to expect a significant improvement in image quality. Further, even if a microstep drive method is adopted for the stepping motor, if there are variations in torque characteristics between different excitation phases, it is not possible to expect a significant improvement in image quality.

Therefore, the drawbacks are that external additional elements are required, structural changes are required, and speed fluctuations of the stepping motor, that is, uneven rotation and vibration, cannot be easily and effectively reduced, and high image quality cannot be achieved. There is.

(Problems to be Solved by the Invention) As described above, it is not possible to easily and effectively reduce speed fluctuations, that is, uneven rotation and vibrations of a stepping motor, without requiring external additional elements or structural changes. This method eliminates the disadvantage of not being able to achieve high image quality, and can easily and effectively eliminate speed fluctuations, that is, uneven rotation, of a stepping motor without requiring external additional elements or structural changes. An object of the present invention is to provide an image forming apparatus capable of reducing noise and vibration and achieving high image quality.

[Structure of the Invention] (Means for Solving the Problems) An image forming apparatus of the present invention includes an image forming means for forming an electrostatic latent image on an image bearing member, and the image bearing member formed by the image forming means. A developing means for developing the above electrostatic latent image with a developer, a transfer means for transferring the developer image on the image carrier developed by the developing means to an image forming medium, and a stepping motor for rotating the image carrier. , a driving means for driving the stepping motor by switching and exciting a plurality of excitation windings provided on the stator side of the stepping motor in a predetermined order; a storage means for storing speed fluctuation data of the stepping motor; When rotating the stepping motor, the time interval for switching the excitation of the excitation winding of the stepping motor is periodically varied according to the speed fluctuation data stored in the storage means, It is composed of a control means for controlling the above-mentioned driving means.

The image forming apparatus of the present invention includes an image forming means for forming an electrostatic latent image on an image carrier, and a developing means for developing the electrostatic latent image on the image carrier formed by the image forming means with a developer. , the developer image on the image carrier developed by this developing means is applied
! 1IIJl! The stepping motor is driven by switching and exciting in a predetermined order a transfer means for transferring the image onto a forming medium, a stepping motor for rotating the image carrier, and a plurality of excitation windings provided on the stator side of the stepping motor. A plurality of speed fluctuation data of the driving means and the above-mentioned stepping motor fc! a storage means for storing speed fluctuation data; a selection means for selecting one of a plurality of speed fluctuation data stored in the storage means; and a selection means for selecting one of the plurality of speed fluctuation data stored in the storage means; The driving means is configured to control means for controlling the driving means by periodically varying the time interval at which excitation of the excitation winding of the stepping motor is switched in accordance with the speed fluctuation data obtained.

The image forming apparatus of the present invention includes an image forming means for forming an electrostatic latent image on an image carrier, and a developing means for developing the electrostatic latent image on the image carrier formed by the image forming means with a developer. , a transfer means for transferring the developer image on the image carrier developed by the developing means to an image forming medium, a stepping motor for rotating the image carrier, and a plurality of excitations provided on the stator side of the stepping motor. A driving means for driving the stepping motor by switching and exciting the windings in a predetermined order, a detecting means for detecting the amount of variation in the stepping motor driven by the driving means, and an amount of variation detected by the detecting means. storage means for storing as speed fluctuation data of the stepping motor, and when rotating the stepping motor, excitation of the excitation winding of the stepping motor according to the speed fluctuation data stored in the storage means; The control means is configured to control the driving means by periodically varying the switching time interval.

(Function) This invention forms an electrostatic latent image on an image carrier, develops the formed electrostatic latent image on the image carrier with a developer, and deposits the developed electrostatic latent image on the image carrier. In an apparatus for transferring a developer image to an image forming medium, the stepping motor is activated by switching and exciting a plurality of excitation windings provided on the stator side of the stepping motor that rotates the image carrier in a predetermined order. The stepping motor is driven by a driving means, a plurality of speed fluctuation data of the stepping motor is stored in a storage means, and when the stepping motor is rotated, the speed fluctuation data of the stepping motor is The time interval for switching the excitation of the excitation winding is periodically varied.

Further, this invention forms an electrostatic latent image on an image carrier,
The formed electrostatic latent image on the image carrier is developed with a developer, and the developed developer image on the image carrier is transferred to an image forming medium, in which the image carrier is rotated. The stepping motor is driven by a driving means by switching and exciting a plurality of excitation windings provided on the stator side of the stepping motor in a predetermined order, and the speed fluctuation data of the stepping motor is stored in a storage means, When one of the plurality of speed fluctuation data stored in the storage means is selected by the selection means and the stepping motor is rotated, the speed fluctuation data selected by the selection means and read from the storage means is selected. Accordingly, the time interval for switching the excitation of the excitation winding of the stepping motor is periodically varied.

The present invention also provides a method for forming an electrostatic latent image on an image bearing member, developing the formed electrostatic latent image on the image bearing member with a developer, and developing the developed electrostatic latent image on the image bearing member. In an apparatus for transferring an agent image to an image forming medium, a plurality of excitation windings provided on the stator side of a stepping motor that rotates the image carrier are switched and excited in a predetermined order,
The stepping motor is driven by a driving means, the amount of fluctuation of the stepping motor driven by the driving means is detected, the detected amount of fluctuation is stored in the storage means as speed fluctuation data of the stepping motor, and the stepping motor is driven by the stepping motor. When the motor is rotated, the time interval for switching the excitation of the excitation winding of the stepping motor is periodically varied according to the speed fluctuation data stored in the storage means. be.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view schematically showing the internal structure of a laser printer as an image forming apparatus of the present invention. This laser printer 1 is sequentially supplied with image data separated into dots for each color component from an external host or document reading device (not shown). A laser printer 1 sequentially exposes image data for each color component to an optical system 3 using a laser beam 2.
The photosensitive drum 4 is charged in advance through a mirror lens, etc.
to form an electrostatic latent image. The photosensitive drum 4 is
By absorbing the first color toner from the developing device 5A, the electrostatic latent image formed by the laser beam 2 is visualized to form a toner image.

On the other hand, a gripper 7 provided on the transfer drum 6 as a rotating body grips the transfer paper (image forming medium) P stored in the paper feed cassette 8a s 8 b, and transfers the gripped transfer paper. The paper P is attached to the outer peripheral surface of the transfer drum 6. The photosensitive drum 4 and the transfer drum 6 (facing each other while maintaining contact at the horizontal point A, arrows B and C, respectively)
The first color toner image formed on the photosensitive drum 4 is transferred onto the transfer paper P by rotating at the same peripheral speed in the same direction. When the transfer of the first color to the transfer paper P is completed, the photosensitive drum 4 and the transfer drum 6 are separated from the contact state with an interval of 2 to 3 m+s, and the transfer drum 6 is moved when the toner image is transferred. It is rotated in the opposite direction to the rotated direction F by a predetermined amount ff1 (the length of the toner image). When the transfer drum 6 is reversely rotated by a predetermined amount, the initial position of the transfer paper P is opposite to the photoreceptor drum 4 at point A. Further, while rotating the photosensitive drum 4 in the direction B, it is similarly set to a position where transfer can be resumed when the initial position reaches point A. In this way, the second, third, and fourth color toner images are sequentially transferred onto the transfer paper P. When the transfer is completed, the transfer paper P is peeled off from the transfer drum 6 and sent to a fixing device 9, where it is fixed and discharged onto a collection tray 10.

The exposure optical system 3 is provided on the upper part of the laser printer 1, and as shown in FIGS. 1 and 2, a semiconductor laser oscillator 4
0, a high-speed rotating motor 11, a polygon mirror 12, an optical lens 13, a reflective mirror 14, and a protective glass 15. The exposure optical system 3 receives a laser beam 2 according to image data oscillated from a semiconductor laser oscillator 40.
For example, the beam is shaped and input by a beam shaping optical system (not shown) consisting of a cylindrical lens or the like. Also,
The laser beam 2 is deflected by a polygon mirror 12 that is rotationally driven by a high-speed rotary motor 11 using an air bearing that is driven and controlled by a motor drive circuit 87 that will be described later. Then, the deflected laser beam 2 passes through the optical lens 13 and is reflected by the mirror 14,
A spot image is formed at the exposure position on the photoreceptor drum 4 through the protective glass 15 at the required resolution, and scanning exposure is performed.

As shown in FIG. 2, a laser beam receiving element 41 is provided on the entire side of the photosensitive drum 4 outside the image forming area of the scanning line scanned by the laser beam 2. As shown in FIG. This laser light receiving element 41 detects the laser light 2 prior to each scan, and outputs this detection signal to a horizontal synchronizing signal generating circuit 88, which will be described later.

As shown in FIG. 1, around the photosensitive drum 4,
Along the rotational direction B, a charger 16 that charges the drum surface, and developing devices 58 to 5D for each color.

a transfer drum 6 that rotates with transfer paper P attached to the drum surface;
A cleaner 17 and an erasing and neutralizing lamp 18 are provided.

The photosensitive drum 4 is constantly rotationally driven by a stepping motor 19, and the drum surface is charged by a charger 16 provided opposite to the drum surface.

The laser beam 2 is spot-imaged at the exposure position of the drum surface of the charged photoconductor drum 4 via the protective mirror 15, and the electrostatic charge is removed in accordance with the laser beam 2. A latent image is formed. When the photoreceptor drum 4 on which this electrostatic latent image has been formed is rotated in the direction of arrow B to the developing position E, it comes into contact with the developing device 5A, and yellow toner is supplied to the photoreceptor drum 4 through the developing sleeve 5a. and is absorbed.

In addition to this developing device 5A, a developing device 5B has a developing sleeve 5b containing magenta toner, a developing device 5C has a developing sleeve 5c containing cyan toner, and a developing device has a developing sleeve 5d containing black toner. 5
D are provided adjacent to each other. These developing devices 58 to 5D are moved by a moving mechanism (not shown) so that each time the transfer of each color to the transfer paper P attached to the transfer drum 6 is completed, the developing devices 5A to 5D are moved to the photosensitive drum 4 one after another. is moved to the development position ESF, G%H. For example, a toner image formed with the first color yellow toner is transferred to the transfer paper P attached to the transfer drum 6 at the transfer position A of the photoreceptor drum 4, but after the transfer is completed, Before the transfer of the second color starts, the developing device 5B for magenta, which is the second color, is moved to the developing position F of the photoreceptor drum 4.
Move it to the point.

The photoreceptor drum 4, on which a toner image is formed by adsorbing toner of one color in the developing device, continues to rotate, and the toner image is transferred to the transfer paper P attached to the transfer drum 6 at the transfer position A. transcribe. After the transfer at the transfer position A, the photoreceptor drum 4 continues to rotate further in the direction of arrow B, and the cleaner 17 provided opposite to the photoreceptor drum 4 cleans the surface of the photoreceptor drum 4. The toner is removed, and the remaining potential on the surface of the photoreceptor drum 4 is further removed by the erasing charge removal lamp 18.

As shown in FIG. 2, the photosensitive drum 4 includes a pulley 42 connected to the drive shaft 19a of the stepping motor 19, which receives the rotational force from the stepping motor 19.
The rotational shaft 4a of the photosensitive drum 4 is transmitted via the timing belt 43 to a pulley 44 connected thereto. Further, the stepping motor 19 is provided with an encoder 45 for detecting rotational speed and rotational fluctuation on the drive shaft 19a.
is connected to. This encoder 45 outputs a pulse signal according to the rotation speed of the stepping motor 19, and when the rotation speed of one stepping motor is slow, the time interval between the output pulses is wide.
(longer), and when it is faster, it is 1, and the time interval between the output pulses becomes narrower (shorter).

Further, as shown in FIG. 1, the transfer drum 6 is provided with a gripper 7 fixedly provided in a part thereof for holding the transfer paper P, and this gripper 7 is connected to the paper feed rollers 20a and 20a.
A sensor 21 is provided for detecting that the transfer paper P supplied by the transfer paper P is held. The transfer drum 6 is rotated by the stepping motor 22 to rotate the photosensitive drum 4.
While the toner image formed thereon is being transferred to the transfer paper P, it rotates in the direction of arrow C, and when the transfer is completed, the photosensitive drum 4 is rotated in the opposite direction to the direction of arrow C by the distance of the toner image. Also, around the transfer drum 6, in addition to the photoreceptor drum 4, a movable guide plate 23, a guide 24, and a transfer drum cleaner 25 are provided.
is installed.

As shown in FIG. 2, the rotational force from the stepping motor 22 is applied to the transfer drum 6 via a boot 946 connected to the drive shaft 22a of the stepping motor 22 and a timing belt 47. Rotating shaft 6a
is transmitted to a pulley 48 connected thereto. Furthermore, an encoder 49 for detecting rotation speed and rotation fluctuation is connected to the drive shaft 22a of the stepping motor 22. This encoder 49 outputs a pulse signal according to the rotational speed of the stepping motor 22. When the rotational speed of the stepping motor 22 is slow, the time interval between the output pulses becomes wider (longer), and when the rotational speed is faster, the time interval between the output pulses becomes wider (longer). , the time interval between the output pulses becomes narrower (shorter).

A gripper 7 provided at the end of the transfer drum 6 grips the transfer paper P stored in the paper feed cassette 8a (8b) by rotating the paper feed roller 20a (20b).
One by one, conveyance roller 26a (26b), conveyance guide 27
a (27b), which holds the leading edge of the transfer paper P when it is supplied via the conveyance roller 28; Subsequently, by applying a bias voltage to the transfer drum 6, the transfer paper P
is attached to the transfer drum 6. Further, when the transfer paper P is held by the gripper 7, a sensor 21 provided at the end of the drum detects that the transfer paper P is held, and outputs a detection signal to a control circuit 81, which will be described later. The transfer drum 6 with the transfer paper P attached rotates in the direction of arrow B to the transfer position A of the photoreceptor drum 4, and when the leading edge of the transfer paper P reaches the transfer position A of the photoreceptor drum 4, The stepping motor 22 is rotated in response to a pulse signal output from a control circuit 81 to the drive circuit 71, which will be described later. The transfer drum 6 transfers the toner image formed on the photoreceptor drum 4 onto the transfer paper P while rotating together with the photoreceptor drum 4 .

When the rear end of the transfer paper P passes the transfer position A of the photosensitive drum 4 and the transfer is completed, the control circuit 81 excites the eccentric cam solenoid 83, which will be described later, to drive the eccentric cam 29a. The photosensitive drum 4 and the transfer drum 6 are spaced apart from each other by a distance of 2 to 3 cm. When this separation is completed, the control circuit 81 outputs a pulse signal to the stepping motor 22 so that the transfer drum 6
is rotated by the size of the transfer paper P in the direction opposite to the direction of arrow C. This series of operations is repeated until full-color transfer, in which four colors are superimposed and transferred, is completed.

When the toner images of all colors have been transferred, the movable guide plate 23, which has one end rotatably supported and the other end movable toward and away from the surface of the transfer drum 6, is moved by a signal from the control circuit 81. , for example, several cIII from the 6th surface of the transfer drum.
It moves from the M position (23a) in the direction 23b and comes into contact with the transfer drum 6.

As a result, the transfer paper P adhering to the transfer drum 6 is peeled off by the movable guide plate 23 and guided to the fixing device 9 via the guide roller 30.
and the pressure roller 32. The conveyed transfer paper P has a toner image heated and fixed onto the transfer paper P by a heat roller 31 and a pressure roller 32, and then is further conveyed by a paper discharge roller 33 and discharged onto the collection tray 10.

The cooling fan 34 cools waste heat discharged from the heat roller 31 and the like of the fixing device 9 to prevent the temperature inside the laser printer 1 from becoming high.

The eccentric cam 29a controls the contact between the photosensitive drum 4 and the transfer drum 6, or the separation of the photosensitive drum 4 and the transfer drum 6 by about 2 to 3 degrees.

This eccentric cam 29a is provided on one side of the laser printer 1 between the cooling fan 34 and the fixing device 9, and when a solenoid (not shown) is energized by a control signal from a control circuit 81, which will be described later, the eccentric cam 29a is Points connecting the cooling fan 34 and the fixing device 9, the photosensitive drum 4 and the transfer drum 6, and the lower sides of the developing devices 5A to 5D from the point of the cam 29a (
(indicated by a dotted chain line in the figure) are separated by rotating about a point 29b as a fulcrum. As a result, the photosensitive drum 4 and the transfer drum 6 are spaced apart from each other by about 2 to 3 degrees.

Next, the configuration of the stepping motor 19 (22) and its drive circuit 71 (72) will be explained using FIGS. 3 to 6. That is, the stepping motor 19 (
22) is composed of a rotor 51 and a stator 52. The rotor 51 is connected to a mass-balanced rotating load (not shown).

As shown in FIG. 3, the rotor 51 includes a shaft 53 made of a non-magnetic material, a permanent magnet 54 attached to the outer periphery of the shaft 53 and magnetized in the axial direction, and both ends of the permanent magnet 54. It is composed of toothed cups 55a and 55b made of a magnetic material and each mounted in a cap shape from the side. Gear cutter cup 55a.

55b, in this example, there are 5 at equal pitches in the circumferential direction.
08 small m56 is formed. Note that the small teeth 56 on the gear cup 55a side and the small teeth 5 on the gear cup 55b side
6 and is provided with a phase difference of 172 pitches in the circumferential direction. On the other hand, the stator 52, as shown in FIG.
A stator core 57 arranged to surround the rotor 51, ten salient stator poles 58 protruding from the inner surface of the stator core 57, and small teeth 59 provided at equal pitches at the tips of these salient stator poles 58. and an excitation winding 60 wound around the stator salient poles 50. The excitation windings 60 are connected in series or in parallel with each other attached to the stator salient poles 58 facing each other, thereby dividing the excitation windings 60 into five excitation phases a, bSc, and dSe.
It has a phase composition.

As shown in FIG. 5, the drive circuit 71 (72) connects both ends of excitation windings constituting each excitation phase to power supply lines 63 and 64 via power transistors 61 and 62, respectively, and connects the excitation windings located diagonally. By sequentially turning on and off the power transistors, a positive or negative current is caused to flow through the excitation windings of each phase, and a magnetic field is generated between the stator 52 and the rotor 51.

Further, the drive circuit 71 (72) drives the sixth
As shown in a typical excitation sequence in the figure, power transistors 61.6 and 61.6
The base signal is configured to output a base signal that controls the on/off state of the 2.

In this example, 10 steps are repeated.

Furthermore, power supply to the power supply line 63 is controlled by an excitation signal from the timing signal generation circuit 90 (91).

The drive circuit 72 also includes a control circuit 81 which will be described later.
When a reversal signal is supplied from , it outputs a base signal that turns on and off the power transistors 61 and 62 in order to cause excitation current to flow through the excitation windings of each phase in a reverse sequence different from that shown in Fig. 6. It looks like this.

2 and 7 are block diagrams of main parts of the electric circuit of the laser printer 1 explained in FIG. 1. That is,
A control circuit 81 that performs various controls and calculations, a printer interface 82, and an image data processing circuit 83
, test pattern signal generator 84, selection circuit 85, laser drive circuit 86, motor drive circuit 87, horizontal synchronization signal generation circuit 88, control panel 89, timing signal generation circuit 90, 91, memory circuit 92, 93, drive circuit 9
4.

The printer interface 82 outputs various commands supplied from the host (not shown) via the system bus to the control circuit 81, outputs the status from the control circuit 81 to the host via the system bus, and also outputs the status from the host to the image bus. It receives image data supplied via the receiving image data processing circuit 83 and outputs it to the received image data processing circuit 83.

The image data processing circuit 83 is the printer interface 8
It stores one page of image data supplied from 2, converts the stored image data (parallel data) into serial image data, and outputs the serial image data to the selection circuit 85. The test pattern signal generator 84 generates serial image data of a test pattern in which rotational unevenness is noticeable according to instructions from the control circuit 81, and outputs it to the selection circuit 85.

The selection circuit 85 operates according to instructions from the control circuit 81.
When printing image data from the host, the image data supplied from the image data processing circuit 83 is output to the laser drive circuit 86, and when printing a test pattern, the image data supplied from the test pattern signal generator 84 is output. It outputs data to the laser drive circuit 86.

The laser drive circuit 86 drives the semiconductor laser oscillator 40 according to the image data supplied from the selection circuit 85, and causes the semiconductor laser oscillator 40 to generate laser light.

The motor drive circuit 87 rotates the high-speed rotation motor 11 at high speed according to instructions from the control circuit 81.

The horizontal synchronization signal generation circuit 88 generates a horizontal synchronization signal necessary as a reference position (timing) when writing an electrostatic image on the photoreceptor drum 4 with a laser beam.

The control panel 89 is operated by the operator and is used to instruct print start, output test pattern, set speed fluctuation data to the storage circuit 92.93, and select speed fluctuation data to the storage circuit 92.93. Instructions (rotation mode switching instructions), etc. are given.

The drive circuit 94 drives the eccentric cam 29a by exciting a solenoid (not shown), and the photosensitive drum 4 and the transfer drum 6 are moved by 2 to 3 +wm depending on the amount of eccentricity.
The transfer drum 6 is spaced apart from the transfer drum 6 by a certain distance to enable the transfer drum 6 to be reversed.

The timing signal generation circuit 90 includes a control circuit 81
The output of the excitation signal to the drive circuit 71 is controlled by the start/stop signal from A pulse is generated at a timing corresponding to the timing, and is output to the drive circuit 71.

The timing signal generation circuit 91 is a control circuit 81
The output of the excitation signal to the drive circuit 72 is controlled by the start/stop signal from The storage circuit 92, which generates pulses at timing and outputs them to the drive circuit 72, stores excitation switching timing data as speed fluctuation data for reducing speed fluctuations of the stepping motor 19, that is, rotational unevenness. Yes, address from control circuit 81 (upper bit)
and the address (lower bits) from the timing signal generation circuit 90 to output excitation switching timing data to the timing signal generation circuit 90. It stores excitation switching timing data as speed fluctuation data for reducing rotational unevenness, and the address (upper bit) from the control circuit 81
The excitation switching timing data of the address specified by the address (lower bit) from the timing signal generation circuit 91 is output to the timing signal generation circuit 91.

Further, the memory circuits 92 and 93 are supplied with a write signal from the control circuit 81, and the encoder 4
When the excitation switching timing data and address obtained by calculating the encoded data detected by 5.49 are supplied, the excitation switching timing data is stored at the address.

The memory circuit 92 stores, for example, the stepping motor 1.
9 is rotated at 1500 pps, a variable pulse rate for periodically varying the time interval for switching excitation is stored as speed variation data (excitation switching timing data).

Assuming that the pulse rate fluctuates by ±10% in 10 pulse cycles, the address rOJ
excitation switching timing data r9000J, switching time "
600 μs” is stored, and excitation switching timing data r940.600 μs is stored at address “1”. OJ, switching time “627μs
” is stored, excitation switching timing data r9800J and switching time “653 μs” are stored at address “2”, and excitation switching timing data “102” is stored at address “3”.
00", switching time "680 μS" are stored, excitation switching timing data "10600" and switching time "707 μs" are stored at address "4", and excitation switching timing data "11000" and switching time "11000" are stored at address "5". 7
33μs” is stored, excitation switching timing data r10600J and switching time “707μs” are stored at address “6”.
is stored, excitation switching timing data "10200" and switching time "680 μs" are stored at address "7", and excitation switching timing data "980" is stored at address "8".
0” and switching time “654 μS” are stored, and the address “
Excitation switching timing data r9400J and switching time "627 μs" are stored in "9". As a result, 1/
This is the same as excitation being switched every 1500 seconds (666.7 μS) (average value).

The memory circuit 93 also includes, for example, the stepping motor 2.
Excitation switching timing data for No. 2 is stored.

The excitation switching timing data stored in the storage circuits 92 and 93 may be set in advance at the time of manufacture, or may be set by the operator. Encoder 45.49 if preset during manufacturing
It is not necessary to have one. When set by the operator, the excitation switching timing data obtained by calculating the encoded data detected by the encoders 45 and 49 is set, or the excitation switching timing data is set by the encoder 45.
Instead of using 5.49, one of a plurality of excitation switching timing data strings having different excitation switching timings in the storage circuit 92.9B may be selected based on the output example (actual print example).

For example, a case where excitation switching timing data obtained by calculating encoded data detected by the encoder 45 is set in the storage circuit 92 will be described. In other words, when no image forming operation is performed, such as during adjustment or immediately after turning on the power, or when the control panel 8
When instructed by the operator from 9, a start signal from the control circuit 81 causes the timing signal generation circuit 90 to send pulses at a predetermined timing to the drive circuit 71.
Output to. For example, the oscillation frequency of the oscillator 90 is 15M
In the case of H2, a pulse is output every 1/1500 (666,7 μs). Thereby, the drive circuit 71 rotates the stepping motor 19 in accordance with the pulse. At this time, the stepping motor 19 is rotated without consideration of speed fluctuations, that is, rotational unevenness. An encoded output from the encoder 45 (a signal of approximately 200 pulses is output from the encoder 45 for one pulse of the stepping motor 19) obtained by the rotation including this speed variation is output to the control circuit 81. The control circuit 81 creates excitation switching timing data for each pulse of the stepping motor 19 according to the number of pulses from the encoder 45, and outputs the address and excitation switching timing data to the storage circuit 92. As a result, the storage circuit 92 stores an excitation switching timing data string having a period of 10 pulses as shown in FIG. 8, which reduces speed fluctuations, that is, uneven rotation of the stepping motor 19. Also,
The excitation switching timing data of the storage circuit 93 for the stepping motor 22 is also stored in accordance with the encode output from the encoder 49 in the same manner as in the storage circuit 92 described above.

Further, a case will be described in which one of a plurality of excitation switching timing data strings having different excitation switching timings in the storage circuit 92 is selected based on their output examples (actual print examples). In this case, the storage circuit 92 stores excitation switching timing data strings having different excitation switching timings from "1 to 10" as shown in FIG. 9(a), and these excitation switching timing data strings are converted into pulse rates. An example is shown in FIG. 9(b).

That is, when instructed by the operator from the control panel 89, the control circuit 81
21: Output the selection signal of the rlJ excitation switching timing data string. As a result, the timing pulse generation circuit 9
The stepping motor 19 is rotated by outputting a pulse corresponding to the excitation switching timing data string of "1" from "0" to the drive circuit 71. Further, the control circuit 81 generates a test pattern from the test pattern signal generator 84, and sends the test pattern to the selection circuit 85.
The signal is outputted to the laser drive circuit 86 via. This results in
A laser drive circuit 86 causes the semiconductor laser oscillator 40 to generate laser light corresponding to the test pattern. After exposure and transfer, a test pattern is printed on the transfer paper P and the paper is discharged. Furthermore, printing of test patterns corresponding to the other excitation switching timing data strings "2 to 10" is performed in the same manner as described above. As a result, the 10th
When test patterns such as those shown in Figures (a) and (b) are printed, Figure 10 (a) shows that the speed fluctuations have been canceled out, that is, the pitch is equal to the pitch P, and there is no unevenness in the image. Figure 10(b) shows the one that includes speed fluctuations, that is, the dense pitch part of the one-dot line and P
The image has unevenness in which m1n and the coarse portion Pmax appear. As a result, the operator confirms the printing quality of the printed test pattern, and then instructs the operator to select the one that provides the most accurate printing (reducing speed fluctuations, that is, rotational unevenness) using the control panel 89. For example, it instructs to select the excitation switching timing data string corresponding to the print shown in FIG. 10(a). Thereafter, when the stepping motor 19 is rotated, the selected excitation switching timing data string is output from the storage circuit 92.

Note that when printing test patterns for a plurality of excitation switching timing data strings in the storage circuit 92, the stepping motor 22 is driven with pulses at regular intervals. Thereafter, the selection of the excitation switching timing data string of the memory circuit 93 for the stepping motor 22 operates in the same manner as the selection of the memory circuit 92 described above.

Regarding the timing signal generation circuit 90 (91),
This will be explained in detail using FIG. 11. The timing signal generation circuit 90 includes an oscillation circuit 100, a counter 101, a comparison circuit 102, and a counter 103. The oscillation circuit 100 generates a clock determined by the frequency of the oscillator 90a and outputs it to the counter 101. The counter 101 counts clocks from the oscillation circuit 100, is reset by pulses from the comparison circuit 102, and starts/stops counting in response to start/stop signals from the control circuit 81. The comparison circuit 102 compares the count number of the counter 101 and the speed fluctuation data (excitation switching timing data) from the storage circuit 92, and outputs a pulse when they match. The counter 103 counts the number of output pulses from the comparison circuit 102,
The counting operation is started/stopped in response to a start/stop signal from the control circuit 81. The count number of the counter 103 is outputted to the storage circuit 92 as an address.

For example, now the stepping motor 19 is connected to the memory circuit 9.
1500pps according to the excitation switching timing data of 2.
We will explain the case where it is rotated by . That is, the start signal from the control circuit 81 is sent to the counter 101.
103.

This start signal is output to the drive circuit 71 as an excitation signal. At this time, the counter 101 starts counting according to the clock from the oscillation circuit 100. Further, the counter 103 is "0", and the address "0" is the memory circuit 9.
Output to 2. Then, the memory circuit 92 has the address “0”.
” is output to the comparator circuit 102.

Then, when the count value of the counter 101 reaches r9000J (when 600 μs has elapsed), a pulse as a coincidence signal is outputted from the comparison circuit 102 to the drive circuit 71. As a result, the drive circuit 71 rotates the stepping motor 19 by one pulse. Further, the counter 101 is reset by a pulse from the comparison circuit 102, starts counting from "O", the counter 103 counts up, and the count content "1" is outputted to the storage circuit 92 as an address. Then, the storage circuit 92 outputs excitation switching timing data r9400J of address “1” to the comparison circuit 102. Thereafter, every time a pulse is output from the comparison circuit 102, the excitation switching timing data of the corresponding address in the storage circuit 92 is read out, and when the time corresponding to this excitation switching timing data has elapsed,
The next pulse is output from comparison circuit 102. As a result, the comparison circuit 1
A pulse is output from 02.

Therefore, since the excitation timing of each excitation layer a, b, c, d, and e is controlled in consideration of the speed fluctuation of the stepping motor 19, the speed fluctuation is canceled out and the stepping motor 19 rotates smoothly.

FIG. 12 <a> shows the excitation switching timing when the stepping motor 19 is driven to rotate at a constant speed. In accordance with this switching timing, the excitation of the excitation windings constituting each phase is switched. In this drive circuit 71, the time interval of excitation switching timing is set to Δt 1n~ with Δt as a reference.
It is varied between Δt wax. The reciprocal of this time interval is the pulse rate, and 1. This pulse rate is 12th
As shown in Figure (b), it fluctuates in a sinusoidal manner with a period T.

If there is no inherent speed fluctuation in the stepping motor 19, the stepping motor 19 rotates with speed fluctuations at a period T as shown in FIG. 12(b). However, normal stepping motors always have inherent speed fluctuations. In this drive device 71, the period T is made to match the speed fluctuation period specific to the stepping motor, and the time interval of the excitation switching timing, that is, the pulse rate is changed so as to be almost inverted. Therefore, assuming that the amplitude is set appropriately, the speed fluctuations inherent to the stepping motor can be canceled out by the speed fluctuations accompanying pulse rate fluctuations, and the rotor 51 can be rotated smoothly.

Further, in the case of the stepping motor 22, as in the case of the stepping motor 19, speed fluctuations inherent to the stepping motor can be canceled out and the stepping motor 22 can be rotated smoothly.

Next, the operation of this image forming apparatus with the above configuration will be explained.

First, image data separated into each color component is supplied from the host to the printer interface 82 via the image bus, and designation information such as the size of the transfer paper P and the transfer density, that is, various commands, are supplied from the host to the printer interface 82. be done. Then, various commands supplied to the printer interface 82 are supplied to the control circuit 81. The control circuit 81 controls the motor drive circuit 87 to rotate the high-speed rotation motor 11 at high speed,
The stepping motor 19 is rotated by controlling the drive circuit 71 via the timing signal generation circuit 90, and the stepping motor 22 is rotated by controlling the drive circuit 72 via the timing signal generation circuit 91.

Further, the image data supplied to the printer interface 82 is converted into serial image data by the image data processing circuit 83 and then output to the laser drive circuit 86 via the selection circuit 85. As a result, the laser drive circuit 86
drives the semiconductor laser oscillator 40 according to the image data supplied from the selection circuit 85, and causes the semiconductor laser oscillator 40 to generate laser light. Laser light 2 oscillated from this semiconductor laser oscillator 40 is shaped by a shaping optical system and deflected by a polygon mirror 12. The deflected laser beam 2 passes through the optical lens 13, is reflected by the mirror 14, passes through the protective glass 15, and is spot-imaged at point D on the drum surface of the photoreceptor drum 4 with the required resolution. Scanning exposure is performed. The photosensitive drum 4 is charged in advance by a charger 16, and is neutralized by the laser beam 2 irradiated through the protective glass 15, thereby forming an electrostatic latent image corresponding to the image of the document. The photosensitive drum 4 on which the electrostatic latent image is formed comes into contact with the developing sleeve 5a carrying yellow toner contained in the developing device 5A at the developing position E. Due to this contact, the yellow toner is attracted to the electrostatic latent image on the photoreceptor drum 4, and a toner image is formed.

The photosensitive drum 4 on which the toner image is formed is transferred to the transfer drum 6.
continues to rotate while maintaining contact with the

While this photosensitive drum 4 continues to rotate, the paper feed roller 20a (20b) is driven, and the paper feed cassette 8a (
8b), the leading edge of the transfer paper P stored in the transfer drum 6
is supplied to the gripper 7. The supplied transfer paper P is
By applying a bias voltage, it adheres to the surface of the transfer drum 6 and is held by the gripper 7 of the transfer drum 6.

When the transfer paper P is held by the gripper 7, the sensor 21 detects that the transfer paper P is held and outputs a detection signal to the control circuit 81. The transfer drum 6 rotates along with the transfer paper P held by the gripper 7 while maintaining contact with the photoreceptor drum 4 in the direction of arrow B until the toner image is at the transfer position A on the photoreceptor drum 4. Continue to do so.

Then, the toner image on the photosensitive drum 4 is transferred onto the transfer paper P of the transfer drum 6 by rotating the photosensitive drum 4 and the transfer drum 6 while maintaining a contact state. In this manner, when the transfer of the first color onto the transfer paper P is completed, the control circuit 81 outputs a stop signal to the timing signal generation circuit 91, thereby causing the drive circuit 7
The output of the pulse signal to 1 is stopped. As a result, the driving of the stepping motor 22 by the drive circuit 71 is stopped, and the transfer drum 6 is also stopped.

Next, the control circuit 81 controls the drive circuit 94 and excites a solenoid (not shown) to adjust the eccentricity of the eccentric cam 29a to the photosensitive drum 4 and the transfer drum 6.
and the distance between them is approximately 2 to B + am. Then, the control circuit 81 controls the drive circuit 72 via the timing signal generation circuit 91, so that the transfer drum 6 rotates in a direction opposite to the rotation direction in which the toner image was transferred from the photoreceptor drum 4. stepping motor 22
, the transfer drum 6 rotates in the opposite direction by the length of the toner image. On the other hand, after the photosensitive drum 4 has been transferred to the transfer drum 6, a cleaner 17 removes the toner adhering to the surface, and an erasing and neutralizing lamp 18 eliminates static electricity from the surface of the drum.

The transfer of the second color magenta toner image is also performed in the same manner as above in the transfer process described above.

By repeating such an operation for each color, a full-color image is obtained by completing overlapping transfer using toner of each of the four colors from the yellow developing device 5D to black. Next, the control circuit 81 outputs a drive signal to a driver (not shown) to move the movable guide plate 23 from the transfer drum 6 by about 2 to 3 cm.
It is rotated from a distant point 23a to a point 23b and brought into contact with the transfer drum 6. Then, when the gripper 7 faces the paper feeding position, it stops rotating.

As a result, the transfer paper P on which the full-color toner image has been transferred is peeled off from the transfer drum 6 by the movable guide plate 23 and guided between the heat roller 31 and pressure roller 32 of the fixing device 9, where the toner image is fixed. Paper ejection roller 33.
33 and discharged onto the collection tray 10.

As described above, the pulses that are output to the drive circuit that drives the stepping motor are output at time intervals that correspond to the variable speed data stored in the storage circuit. In other words, the pulse rate of the pulses output from the timing signal generation circuit to the drive circuit is controlled so that the speed of the stepping motor does not fluctuate. If excitation switching is performed based on pulses whose pulse rate is controlled, the stepping motor rotates smoothly. If such a smoothly rotating stepping motor is used to rotate the photoreceptor drum or transfer drum, pitch unevenness (jitter) in the sub-scanning direction of the output image, which conventionally occurs due to speed fluctuations, that is, rotational unevenness and vibration, of the stepping motor can be eliminated. ) That is, it is possible to reduce stripes or lines that appear in the main scanning direction, and also to reduce noise.

In addition, by setting the excitation switching timing data of the memory circuit using encoded data from the encoder, there is no need to investigate the speed fluctuations of each stepping motor in advance, and the optimum pulse rate selected by the device itself can be used. By rotating the stepping motor, it is possible to improve the quality of the output image.

In addition, it is possible to print test patterns for a plurality of excitation switching timing data strings stored in the memory circuit, and to select the excitation switching timing data string with the most accurate printing from the printed contents. It is possible to easily reduce speed fluctuations, that is, rotational unevenness and vibrations, and it is possible to improve the quality of the output image.

Furthermore, although the above embodiment describes the case where the application is applied to a color copying machine, the application is not limited to a color copying machine, but can be applied to a device that reads an original and transfers an image, such as a facsimile machine or a monochrome copying machine. It is also possible to do so.

[Effects of the Invention] As explained above, according to the present invention, speed fluctuations, that is, uneven rotation, and vibrations of a stepping motor can be easily and effectively eliminated without requiring external additional elements or structural changes. Accordingly, it is possible to provide an image forming apparatus that can reduce the amount of noise and achieve high image quality.

[Brief explanation of drawings]

The figures show one embodiment of the present invention, in which Fig. 1 is a cross-sectional view schematically showing the internal structure of a color copying machine, and Fig. 2 is a schematic structure of an exposure optical system and a part of an electric circuit. Figure 3 is a longitudinal sectional view of the stepping motor rotor, Figure 4 is a plan view of the stator incorporating the stepping motor rotor, Figure 5 is a configuration diagram of the stepping motor drive circuit, and Figure 6 is a diagram showing the blocks. 5 is a diagram showing the operation sequence of the drive circuit in FIG. 5, FIG. 7 is a block diagram showing a schematic configuration of a part of the electric circuit, and FIG. 8 is a storage example of excitation switching timing data stored in the storage circuit. 9(a) and 12(a) are diagrams showing examples of the pulse output of the timing signal generation circuit, FIG. 9(b) and FIG. 12(b).
) is a diagram showing an example of converting pulse output to pulse rate,
FIGS. 10(a) and 10(b) are diagrams showing examples of printed test patterns, and FIG. 11 is a diagram showing the configuration of a timing signal generation circuit. 1... Laser printer, 3... Exposure optical system, 4...
- Photosensitive drum (image carrier), 5A, 5B, 5C. 5D... Developing device (developing means), 6... Transfer drum (
holding means), 7...Gripper 19, 22...Stepping motor, 45.49...Encoder, 71.
72... Drive circuit, 81... Control circuit (control means), 89... Control panel, 90.91
...Timing signal generation circuit, 92.93...Storage circuit, P...Transfer paper (image forming medium). Figure 3

Claims (3)

[Claims] (1) An image forming means for forming an electrostatic latent image on the image carrier; a developing means for developing the electrostatic latent image on the image carrier formed by the image forming means with a developer; A transfer means for transferring the developer image on the image carrier developed by the means to an image forming medium, a stepping motor for rotating the image carrier, and a plurality of excitation windings provided on the stator side of the stepping motor. a driving means for driving the stepping motor by switching and exciting wires in a predetermined order; a storage means for storing speed fluctuation data of the stepping motor; and a storage means for storing speed fluctuation data in the storage means when rotating the stepping motor. control means for controlling the drive means by periodically varying the time interval at which excitation of the excitation winding of the stepping motor is switched according to speed fluctuation data that has been set; An image forming apparatus characterized by: (2) an image forming means for forming an electrostatic latent image on the image carrier; a developing means for developing the electrostatic latent image on the image carrier formed by the image forming means with a developer; A transfer means for transferring the developer image on the image carrier developed by the means to an image forming medium, a stepping motor for rotating the image carrier, and a plurality of excitation windings provided on the stator side of the stepping motor. a driving means for driving the stepping motor by switching and exciting lines in a predetermined order; a storage means for storing a plurality of speed fluctuation data of the stepping motor; and a plurality of speed fluctuation data stored in the storage means. selection means for selecting one of the above, and excitation of the excitation winding of the stepping motor according to the speed fluctuation data selected by the selection means and read from the storage means when rotating the stepping motor; An image forming apparatus comprising: a control means for controlling the driving means by periodically varying the time interval at which the driving means is switched. (3) an image forming means for forming an electrostatic latent image on the image carrier; a developing means for developing the electrostatic latent image on the image carrier formed by the image forming means with a developer; A transfer means for transferring the developer image on the image carrier developed by the means to an image forming medium, a stepping motor for rotating the image carrier, and a plurality of excitation windings provided on the stator side of the stepping motor. a driving means for driving the stepping motor by switching and exciting wires in a predetermined order; a detecting means for detecting the amount of variation in the stepping motor driven by the driving means; and a variation detected by the detecting means. storage means for storing the amount as speed fluctuation data of the stepping motor; and when the stepping motor is rotated, the excitation winding of the stepping motor is excited according to the speed fluctuation data stored in the storage means. An image forming apparatus comprising: a control means for controlling the driving means by periodically varying the time interval at which the driving means is switched.