JP2001022147A - Multicolor image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the color slurring of respective colors in a multicolor image forming device with simple constitution at low cost. SOLUTION: A Y(yellow) motor 40a is started, an interval between pulses outputted from a speed information detecting means (magnetic pattern 45 and MR sensor 41) is measured by a timer unit and the rotating speed information of the motor 40a is arithmetically calculated. A difference on the periphery of a rotating body between the cycle of rotating speed fluctuation per one rotation of the rotating body and that in the case of performing ideal rotating motion is detected as irregular rotation information. Next, an M(magenta) motor 40b is driven and the difference on the periphery of the rotating body between the cycle of the rotating speed fluctuation per one rotation of the rotating body and that in the case of performing the ideal rotating motion is detected as the irregular rotation information. Succeedingly, the relative difference of irregular rotation between the motors 40a and 40b is compared. Whether the relative difference is equal to or under a fixed value is judged. When it is equal to or above a certain fixed value and positive, the motor 40b is accelerated for a fixed time, and when it is negative, the motor 40b is decelerated for the fixed time so as to make the relative difference of the irregular rotation of the motors 40a and 40b equal to or under the fixed value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus such as a copying machine or a printer, and more particularly to a multicolor image forming apparatus for forming a multicolor image. is there.

[0002]

2. Description of the Related Art FIG. 10 shows four colors, that is, yellow Y,
1 shows a color printer as a multicolor image forming apparatus including image forming units for magenta M, cyan C, and black BK.
The color printer includes a photosensitive drum (image carrier) 1a, 1b, 1c, 1 as a rotating body on which an electrostatic latent image is formed.
d, a rotation drive mechanism 6a, 6b, 6c, 6d including a motor as a drive source for driving each of the photosensitive drums 1a to 1d, forming an electrostatic latent image on the photosensitive drums 1a to 1d by performing exposure in accordance with an image signal Laser scanners 2a, 2b, 2
c, 2d, an endless transport belt 3 also serving as a transfer belt for sequentially transporting the transfer material to the image forming units of the respective colors, and a drive roller connected to driving means including a motor and gears (not shown) to drive the transport belt 3 And a fixing device 5 for melting and fixing the toner image transferred to the recording material.

When the data to be printed is sent from the computer to the printer, and the image formation according to the printer engine system is completed and the printer becomes ready for printing, the recording material sheets are supplied from the paper cassette and reach the transport belt 3. Then, the paper is sequentially conveyed to the image forming units of each color by the conveyance belt 3. The image signals of the respective colors are transmitted to the respective laser scanners 2 in synchronism with the sheet conveyance by the conveyance belt 3.
a to 2d, an electrostatic latent image is formed on the photosensitive drums 1a to 1d, developed with toner by a developing unit (not shown), and transferred onto a sheet at a transfer unit.

In FIG. 10, images are sequentially formed on a sheet in the order of Y, M, C, and BK. Thereafter, the toner image is separated from the transport belt 3, and the toner image is fixed on the paper by heat in the fixing device 5, and is discharged to the outside.

The photosensitive drums 1a to 1d of each color are driven by a motor, for example, a DC brushless motor. However, due to the effects of torque ripple of the motor, eccentricity and pitch error of the gear, eccentricity of the rotating shaft, and the like, FIG. As shown in FIG. Therefore, as shown in FIG. 11B, the laser scan position of each color has an error in a sine curve shape with respect to the ideal scan position, resulting in color misregistration when finally transferred to a sheet, deteriorating the image quality.

In order to prevent such color misregistration, as a conventional device, for example, there is a device using a flywheel to suppress the rotation unevenness of a rotating body.

Alternatively, as disclosed in Japanese Patent Application Laid-Open No. 9-146329, a color misregistration detection pattern is formed on a rotating body, and the color misregistration detection pattern is detected by pattern detection means. There is a method of controlling the motor according to the result.

[0008] Alternatively, there is a method in which a rotary encoder is provided on a shaft of a rotating body and a motor is controlled based on a detection result.

[0009]

However, the above conventional example has the following disadvantages.

In the method using a flywheel, it is necessary to use a flywheel of several tens of kilograms in order to obtain a sufficient suppression effect, which has led to an increase in size and cost of the apparatus.

Further, in the method using the color misregistration detecting pattern and the pattern detecting means for detecting the color misregistration detecting pattern, not only the toner is excessively consumed, but also the deterioration of the photosensitive member and the increase of waste toner are caused. In addition, time is required to execute a series of image forming processes, and furthermore, a pattern detection unit is required, which results in a decrease in apparatus quality and an increase in cost.

In the method using a rotary encoder provided on a rotating body, a high-precision encoder and high mechanical accuracy are required in order to obtain a sufficient suppression effect, resulting in an increase in the cost of the apparatus.

Accordingly, it is an object of the present invention to provide a multicolor image forming apparatus which can prevent the occurrence of color misregistration with a simple configuration and at low cost.

[0014]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A driving source, and a rotating body driven by the driving source, in a multicolor image forming apparatus provided for each color, provided in the driving source, speed information detecting means for detecting speed information of the driving source, Means for detecting rotation unevenness information of the rotating body from the speed information, and driving for controlling the drive source such that a relative difference between the rotation unevenness of the rotating body of the reference color and the rotation unevenness of the other color is minimized. And a source control unit.

It is preferable that the means for detecting the rotation unevenness information detects a period of a rotation speed fluctuation per rotation of the rotating body and a speed difference from a reference rotation speed. It is preferable that the rotation unevenness information detecting means or the driving source control means is constituted by a DSP. Preferably, the driving source is a motor, and the rotating body is an image carrier.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multicolor image forming apparatus according to the present invention will be described in more detail with reference to the drawings. In the following embodiment, the present invention is described as being embodied in the multicolor image forming apparatus shown in FIG. Therefore, description of the overall configuration and functions of the multicolor image forming apparatus will be omitted, and only the features of the present invention will be described.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a schematic configuration relating to a control system of a printer which is the present multicolor image forming apparatus. As shown in FIG. 1, a printer 10 includes a printer control unit 11 for controlling each device in the printer, a power supply 12 for supplying power to each device in the printer, and sensors 13 for detecting the status of each unit in the printer. A motor 15 as a drive source of each device in the printer, a motor control unit 14 for controlling the motors 15 according to an instruction of the printer control unit 11, a display unit 16 for notifying a user of the operation status of the printer, and the printer 10. A communication controller 17 for controlling communication with a host computer 18 is provided. Then, data and the like to be printed on the printer are transferred from the host computer 18.

FIGS. 2 and 3 show the structure of the main part according to the present invention.

As shown in FIG. 2, a photosensitive drum 1 serving as an image carrier has a DC brushless motor 40 as a drive source.
The photosensitive drum 1 is driven by a gear 46 fixed to the drive shaft 40s and a gear 47 fixed to the rotation shaft 1s of the photosensitive drum 1. The gear ratio is 8: 240.

DSP (Digital Signal)
A processor / digital signal processor 20 is included in the motor control unit 14 and controls phase switching based on a rotor position signal from the DC brushless motor 40.
The start and stop control of the motor by the control signal from the printer control unit 11 is compared with the speed signal from the printer control unit 11 and the output of the speed information detecting means, and the speed control, that is, the motor control according to the present invention is performed.

FIG. 4 is a block diagram of the DSP 20. As shown in FIG. 4, the DSP 20 includes a program controller 21 and a MAC 2 for performing a product-sum operation as an arithmetic unit.
3, an ALU 22 for performing addition, subtraction and logical operations, a data memory 24, a program memory 25, and a data memory bus 2.
6, program memory bus 27, serial port 28,
A timer 29 and an I / O port 30 are provided.

As described above, the memory is used as the data memory 24.
And a program memory 25, the bus is also separated into a data memory bus 26 and a program memory bus 27, and a MAC 23 that performs multiplication and addition in one machine cycle is provided, thereby enabling high-speed operation.

In FIG. 3, a DC brushless motor 40
Has a coil 43 and a rotor 44 in which three phases U, V and W are star-connected. Further, three Hall elements 42 for detecting the magnetic poles of the rotor 44 as position detecting means of the rotor 44.
, The output of which is connected to the DSP 20. In addition, the magnetic pattern 4 provided on the circumference of the rotor 44
5 and an MR sensor 41, and its output is also connected to the DSP 20.

The driver 30 for driving the DC brushless motor 40 includes three high-side transistors 31 and three low-side transistors 32, and U, V,
Connected to W.

The DSP 20 specifies the position of the rotor 44 based on the rotor position signals HU, HV, HW generated by the Hall element 42, and generates a phase switching signal. Phase switching signal U
U, UV, UW, LU, LV, and LW control the transistors 31 and 32 of the driver 30 on and off to sequentially switch the phase to be excited and rotate the rotor.

Further, the DSP 20 compares the rotation speed target value with the rotation speed information, and generates and outputs a PWM signal. PWM
The signals are ANDed by the phase switching signals UU, UV, UW and the AND gate 33 to chop the drive current,
The rotation speed of the motor 40 is controlled.

The rotation drive mechanism 6 (6a) of the photosensitive drum 1
6d), the motor shaft 40s and the photosensitive drum rotating shaft 1s generate rotation unevenness during driving. For example, motor shaft 40s
When the motor 40 is driven at 10 rps and the gear ratio of the photosensitive drum rotating shaft 1s is 8: 240, the frequency component is
FIG. 5 shows the uneven rotation of the motor shaft 40s, and FIG. 6 shows the uneven rotation of the photosensitive drum rotating shaft 1s.

As described above, in the photosensitive drum rotating shaft 1s, the rotation unevenness due to the gear pitch and the rotation unevenness due to the periodic load fluctuation due to the eccentricity of the rotating shaft occur, and appear as banding in the image. At this time, as can be seen from FIGS. 5 and 6, the rotation unevenness of the photosensitive drum rotating shaft 1s is
It can be detected on the motor shaft 40s side.

Next, the operation of this circuit will be described with reference to the flowchart of FIG. 7 and the waveform diagrams of the signals shown in FIG.
In the present embodiment, the present invention is applied to a case where the dominant rotational unevenness frequencies of the respective photosensitive drums are the same.

When the rotation of the motor is instructed by the printer control unit 11, the DSP 20 first activates the Y motor 40a for yellow as a reference color (step 1), and sets the interval of the pulse output by the speed information detecting means to the timer unit. 29, and a Y motor 40 as shown in FIG.
The rotation speed information a is calculated (step 2). When the Y motor 40a reaches the target rotation speed (step 3), the rotation speed information is subjected to FFT calculation, and as rotation unevenness information shown in FIG. Is detected on the periphery of the rotating body between the case where the rotational movement is ideal and the case where the ideal rotational movement is performed (step 4).

Next, the M motor 40b is driven (step 5), and as in the case of steps 1 to 4, the period of the rotation speed fluctuation per rotation of the rotating body and the ideal rotational movement are obtained as the rotation unevenness information. (Steps 6 to 8).

Next, as shown in FIGS. 8C and 8D, the relative difference between the rotational unevenness of the Y motor 40a and the M motor 40b is compared at a certain timing (step 9), and the relative difference is fixed at a certain value. Determine if: (Step 10). If the relative difference is greater than a certain value and the relative difference is positive, the M motor 40b is accelerated for a certain time (step 12), and if negative, it is decelerated for a certain time (step 13), as shown in FIG. The relative difference between the rotation unevenness of the Y motor 40a and the M motor 40b is set to a certain value or less (step 11).

Hereinafter, the C motor 40c and the BK motor 40d
Rotation unevenness of the Y motor 40a in the same manner as the above operation.
Is controlled so that the relative difference from the rotation non-uniformity is equal to or less than a certain value.

As described above, according to this embodiment, the occurrence of color misregistration can be prevented with a simple configuration and at low cost.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 9 is a flowchart for explaining the operation of this circuit.

When the rotation of the motor is instructed by the printer control unit 11, the DSP 20 first drives the Y motor 40a (step 1), measures the interval output by the speed information detecting means by the timer unit 29, and 40a
Is calculated (step 2). Y motor 4
When 0a reaches the target rotation speed (step 3),
The rotation speed information is subjected to FFT calculation to obtain rotation unevenness information (step 4).

Next, the M motor 40b is driven to extract the uneven rotation frequency in the same manner as in steps 1 to 5 (steps 5 to 8). Subsequently, the absolute value of the relative difference between the rotational unevenness of the Y motor 40a and the M motor 40b is added over one rotation of the photosensitive drum (step 9). Next, a comparison is made with the minimum value of the calculation result up to the previous time (step 10), and if not, the speed of the M motor 40b is reduced for a certain period of time (step 11), and the calculation is performed. The calculation is performed until the relative difference is minimized.
Is driven normally (step 12).

Hereinafter, the C motor 40c and the BK motor 40d
Rotation unevenness of the Y motor 40a in the same manner as the above operation.
Is controlled so that the relative difference between the rotation unevennesses of the two is minimized.

As described above, according to this embodiment, similarly to the above embodiment, it is possible to prevent the occurrence of color misregistration with a simple configuration and at low cost.

[0041]

As is apparent from the above description, according to the multicolor image forming apparatus of the present invention, the speed information detecting means provided in the driving source for detecting the speed information of the driving source, Means for detecting rotation unevenness information of the rotator from, and means for controlling the drive source such that the relative difference between the rotation unevenness of the rotator of the reference color and the rotation unevenness of the other color is minimized. As a result, color shift can be prevented at low cost,
High quality multicolor images can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control system according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a main part of the control system according to the first embodiment.

FIG. 3 is a motor rotation control circuit according to the first embodiment.

FIG. 4 is a block diagram showing a main part of the control system of the first embodiment.

FIG. 5 is an explanatory diagram of a frequency component of uneven rotation of a motor shaft in the first embodiment.

FIG. 6 is an explanatory diagram of a rotational unevenness frequency component of a drum shaft in the first embodiment.

FIG. 7 is a flowchart for explaining the operation of the first embodiment.

FIG. 8 is a waveform chart showing signals in the first embodiment.

FIG. 9 is a flowchart for explaining the operation of the second embodiment.

FIG. 10 is a schematic configuration diagram illustrating an example of a conventional multicolor image forming apparatus in which the present invention is embodied.

FIGS. 11A and 11B are explanatory diagrams showing rotation unevenness of a motor (a) and an error (b) of a laser scan position.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier / rotating body) 20 DSP (rotation unevenness information detecting means / driving source control means) 40 Motor (driving source) 41 MR sensor 45 Magnetic pattern

Claims (4)

[Claims] 1. A multicolor image forming apparatus provided with a driving source and a rotating body driven by the driving source for each color, wherein a speed provided in the driving source and detecting speed information of the driving source is provided. Information detecting means, means for detecting the rotation unevenness information of the rotating body from the speed information, and the driving so that the relative difference between the rotation unevenness of the rotating body of the reference color and the rotation unevenness of the other color is minimized. And a drive source control means for controlling a source. 2. The apparatus according to claim 1, wherein the means for detecting the rotation unevenness information detects a period of a rotation speed fluctuation per rotation of the rotating body and a speed difference with respect to a reference rotation speed. Color image forming apparatus. 3. The multicolor image forming apparatus according to claim 1, wherein the rotation unevenness information detecting unit or the driving source control unit is configured by a DSP. 4. The multicolor image forming apparatus according to claim 1, wherein said driving source is a motor, and said rotating body is an image carrier.