JP2008090233A - Speed regulator and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speed regulator and an image forming apparatus reducing oscillating factors in a rotating body, as well as, carrying out stable driving control, even in a state when an abnormal state exists in an encoder. <P>SOLUTION: The speed regulator monitors a phase in which the abnormal state in the encoder has occurred, discriminates the type of error in the encoder, based on detected abnormal state and the information of the phase in which the abnormality has occurred, selects the best method from a plurality of encoder data compensation methods incorporated beforehand for the types of discriminated abnormal states, and executes the encoder data compensation method selected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotation speed control device in a rotating body drive system and an image forming apparatus having the rotation speed control device.

  In copying machines, printers, and the like that use an electrophotographic process, it is known that fluctuations in the speed of a rotating body such as a photosensitive drum cause degradation of images.

  Here, an image forming apparatus using an electrophotographic process will be described as a suitable example for explaining the present invention.

  FIG. 7 is a schematic configuration diagram of the image forming apparatus. The image forming unit includes a photosensitive member 701 (corresponding to the rotating member 101), a developing unit 706, a cleaner 707, a charging unit 708, a primary transfer roller 709, and a laser optical system 710. A color image is formed on an intermediate transfer belt 711 driven by an intermediate transfer roller 702. In this embodiment, images of respective colors of Y (yellow), M (magenta), C (cyan), and K (black) are formed.

  The image forming operation of this apparatus is controlled by the system controller 720, and the color image supplied from the image reading apparatus 721 or the image processing apparatus 722 is supplied to the image forming section for each color. The rotating body (photosensitive drum) 101 in each image forming unit is formed with an optical semiconductor layer whose electrical characteristics change when irradiated with light, and rotates at a constant speed during the image forming operation. Done.

  (1) Charging: The optical semiconductor layer of the rotating body 101 is uniformly charged by the charger 708.

  (2) Laser exposure: An image pattern (electrostatic latent image) is irradiated to the photosensitive drum 701 by the laser optical system 710 (broken line portion B).

  (3) Development: A toner is attached to the electrostatic latent image by the developing unit 706.

  (4) Primary transfer: The image is transferred onto the intermediate transfer belt 711 by the primary transfer roller 709.

  The operations (1) to (4) are performed in each image forming unit.

  (5) Secondary transfer: The toner image on the intermediate transfer belt 711 is transferred to the recording paper by the secondary transfer unit 712.

  (6) Fixing: The fixing device 713 heats and presses the recording paper to fix the toner on the recording paper and is discharged out of the apparatus.

  (7) Cleaning: Toner remaining on the drum without being transferred onto the transfer belt is cleaned by a cleaner 707.

  As described above, the toner images formed by the image forming units are formed on the intermediate transfer belt so as to overlap each other.

  Therefore, if the rotation speed of the transfer belt when a toner image of a certain color is formed and the rotation speed of the transfer belt when the next toner image is formed do not match, the respective toner images are shifted. In other words, so-called color misregistration occurs, and the speed fluctuation of the photoconductor causes image deterioration such as density unevenness when a halftone image is formed.

  Therefore, with respect to the rotational speed fluctuation correction control method of the rotating body, the position deviation and the speed deviation are calculated by performing a predetermined filter processing calculation based on the encoder data, and the detected data is A method of performing correction driving based on this has been proposed.

  In addition to the above examples, various control methods have been proposed for the speed control method of the rotating body, but the basic control method is generally a method of detecting the speed with an encoder installed on the shaft of the rotating body. It is.

As shown in FIG. 6, the encoder speed detection method is such that a code wheel on which a slit pattern of a predetermined interval set (printed) is engraved (printed) is installed on the rotating body axis, and is placed on the circumference of the code wheel. A method of measuring the input time interval of the slit pattern with an installed detection element (hereinafter referred to as an encoder) and detecting the speed fluctuation from the detected time fluctuation is common. Therefore, when an abnormal state occurs in the encoder or the code wheel, for example, the detection time interval may be out of the predetermined range due to adhesion of foreign matter to the code wheel or application of electric noise to the detection electric signal. In the case of an image forming apparatus, in which the correction driving of the rotating body does not normally operate, an abnormal state is detected, and rotation is stopped when the abnormality reaches a predetermined number of times. A method of stopping the image forming operation has been proposed (see Patent Document 1).
JP 2004-205717 A

  However, in the above method, when the frequency of the abnormal state is large with respect to the encoder, the stop frequency or stop time of the rotating body becomes long. In addition, when the rotating body speed control method described in the conventional example is adopted in the image forming apparatus, the downtime of the apparatus becomes long, and there is a high possibility that the reliability for the user is impaired.

  The encoder itself has become more sensitive to electrical noise, as the required detection resolution is further improved, foreign matter is more likely to adhere to the code wheel, as the speed correction control of the rotating body increases. There are problems, and in order to completely remove these, it is assumed that the encoder is increased in circuit size, mounting surface, and cost.

A rotation driving means for driving based on a supplied clock signal, an encoder for digitally detecting the speed of the rotating body, and a home position sensor for detecting a predetermined reference position of the rotating body,
In a rotating body speed control apparatus having control means for driving the rotating body drive means to correct the speed fluctuation based on the speed fluctuation data detected by the encoder,
In the encoder, when an abnormal signal is detected, the type of abnormality is determined based on the phase of the rotating body when the abnormality is detected,
If the signal (detection value) is abnormal for a predetermined number of times in the same phase, it is determined that the encoder is mechanically abnormal (attachment of foreign matter, slit deformation), and data is interpolated in the abnormal area. To perform correction control drive,
If the abnormal signal is input irregularly, it is determined as an electric noise error, and the detection data is replaced with preset data, and the correction driving is continued.

Therefore, in order to solve the above problem, the present invention monitors the phase where the abnormal state of the encoder has occurred, and determines the type of error of the encoder based on the detected abnormal state and the phase information where the abnormal state has occurred. Determining, selecting an optimal method from a plurality of encoder data correction methods incorporated in advance for the determined abnormal state type, and executing the selected encoder data correction method,
It is possible to provide a speed control device and an image forming apparatus that perform stable drive control while reducing the vibration factor of the rotating body even in a state where an abnormal state of the encoder exists.

  Embodiments of a rotating body speed control device according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram and a control block diagram showing a drive transmission system for explaining a speed control device in the present embodiment.

1. Control Configuration and Control Flow of the Present Invention In FIG. 1, reference numeral 101 denotes a rotating body, and 102 denotes a gear mounted on the same axis as the rotating body 101. Reference numeral 103 denotes a motor which is a rotating body driving means, which drives the rotating body 101 via the gear 102 at a predetermined gear ratio. In this embodiment, the motor 103 is described using a stepping motor. A motor driver 104 outputs a phase signal (pulse signal) necessary for driving to the stepping motor 103. Reference numerals 105 and 106 denote encoders A and B that detect the angular velocity of the rotating body 101, have a predetermined resolution, and are disposed so as to face each other. Reference numeral 107 denotes a code wheel installed on the same axis as the rotating body 101, on which a slit pattern that can be detected by the encoder is formed. Reference numeral 108 denotes a home position sensor that detects the reference phase of the rotating body.

  Reference numeral 109 denotes a control unit that calculates and drives a drive pulse of the motor 103 based on angular velocity fluctuation data detected by the encoders 105 and 106.

  FIG. 2 shows a timing chart of angular velocity detection by the encoder. Reference numeral 201 denotes a basic clock on which the control unit 108 itself operates, and describes a count value for each clock. Reference numeral 202 denotes an encoder input, which is signal edge e_n (n is an integer) according to the input at the slit interval of the code wheel. At this time, since the slits are equally spaced Θ, the count value e_n_Data obtained by counting the input time interval of the signal edge e_n by the basic clock becomes digital data of the speed variation of the rotating body 101.

  Actually, the angular velocity on the rotating body axis is calculated from the detection data e_n_Data_A by the encoder A105 and the detection data e_n_Data_B by the encoder B based on the following equation in order to cancel out the speed difference due to the eccentric component of the code wheel 107.

e_n_Data = (e_n_Data_A + e_n_Data_B) / 2 Equation 1
In FIG. 3, the control schematic diagram (flowchart) of this invention is shown.

  When driving of the rotating body 101 is started, the angular velocity fluctuation is detected by first measuring the slit input interval (time) of the code wheel 107 by the encoders 105 and 106 based on the above-described method, and the detected angular velocity fluctuation data. Is detected as data as shown in FIG. 4 (S301).

  In the data, the horizontal axis indicates the number of encoder inputs, and the vertical axis indicates the speed fluctuation level (calculated based on Equation 1). As shown in the figure, the speed fluctuation data of the rotating body rotates with various factor frequencies.

  According to the author's experiment, the speed fluctuation factor of the rotating body often has the same level of vibration level constantly during one rotation of the rotating body, and there is data that exceeds a preset predetermined range. It is considered that an error state has occurred (details of the error state will be described later in 2.1 and 2.2).

Then, during rotation driving of the rotating body (any Nth rotation, N is an integer), it is always determined whether or not the encoder data is in an error state (S302). If no error has occurred, the error count value is set. Clear (S303)
Continue rotating.

  If it is determined that an error has occurred, the phase where the error has occurred (encoder input count value) is stored with reference to the phase where the home position sensor signal is input, and the error count of the generated phase is incremented (S304). ).

  At this time, a determination is made on the count value of the error count (S304). If the error count is “1”, it is determined that electrical noise has been applied (S305), and data correction is performed when electrical noise occurs. Processing (S306: details will be described later in 2.1) is performed. If the error count is greater than “1”, it means that an error has occurred at the same phase during multiple rotations, and it is determined that this is a physical error due to foreign matter adhering to the code wheel (S307). Data correction processing when an error occurs is performed (S308: details will be described later in 2.2). Then, the error count value is cleared, the phase where the error processing has been performed is stored and stored (S309), and the normal correction rotation operation is continued.

2. Details of Error Generation and Correction Processing at the Time of Generation 2.1 Data Correction Processing at the Time of Electric Noise Generation The data correction processing at the time of electric noise generation (FIG. 3: S306) will be described with reference to FIG.

  When it can be determined as electrical noise, it can be defined as a case where data outside a predetermined range in which encoder data is preset is detected irregularly regardless of the phase of the rotating body. Therefore, in the control flowchart of FIG. 3, it is determined as an electrical noise error when no error is repeatedly detected at the same phase.

  In this case, since the detected encoder data is not a signal for detecting the actual speed of the rotating body, the data is ignored and the data is replaced with a preset target value of the encoder data (S401).

  When the error occurs, there is a high possibility that the number of samples in one revolution of the encoder is “deviation” during the rotation. Therefore, during the rotation, a phase check is performed at the input of the home position sensor (S402). If there is a deviation, a process for returning the encoder detection phase to the home position reference value is performed (S403).

2.2 Data Correction Processing When Physical Noise (Foreign Object Adhesion) Occurs With reference to FIG. 5, data correction processing when physical noise occurs (FIG. 3: 308) will be described.

  As a main factor of physical noise, there is foreign matter adhesion to the slit of the code wheel as shown in FIG. In this case, since the detected encoder data is outside the predetermined range, that is, the phase where the error is detected is detected at the same phase every rotation, the phase where the error has occurred is the same as shown in FIG. If it is determined (FIG. 3: S304), it is determined as a physical error.

  In this case, the detected encoder data is assumed to greatly exceed a predetermined range. Therefore, at this time, the correction drive drives the rotating body based on a preset target value, and based on the data at both ends of the area where the encoder input is not detected within a predetermined time, the data of the area is Interpolation calculation is performed (S501).

  Examples of the interpolation method include linear interpolation of both end data, or interpolation based on a sine wave profile of the rotation frequency of the rotating body. The interpolation method does not limit the present invention.

  When the error occurs, it is highly possible that the number of samples per rotation of the encoder is “deviation” during the rotation, as in the case of the electrical noise described in 2.1. The phase check is performed at the input of the home position sensor (S502), and if there is a deviation, the encoder detection phase is returned to the home position reference value (S503). 3: The error correction phase is stored and stored as shown in S309, and the correction rotation drive is continued.

As described above, according to the present invention, the phase where the abnormal state of the encoder has occurred is monitored, and the type of the encoder error is determined based on the detected abnormal state and the phase information where the abnormal state has occurred. Then, by selecting an optimal method from a plurality of encoder data correction methods incorporated in advance for the determined abnormal state type, and executing the selected encoder data correction method,
It is possible to provide a speed control device and an image forming apparatus that perform stable drive control while reducing the vibration factor of the rotating body even in a state where an abnormal state of the encoder exists.

The schematic block diagram of the rotary body speed control apparatus which is this invention. Speed data detection method using an encoder. The control flowchart at the time of the encoder data error which is this invention. 5 is a control flowchart of error processing when electrical noise occurs in the encoder according to the present invention. The error processing control flowchart at the time of the physical noise generation | occurrence | production to the encoder which is this invention. The block diagram which shows the physical noise generation | occurrence | production state to a code wheel. 1 is a configuration diagram of an image forming apparatus including a rotating body speed control device according to the present invention.

Claims (7)

A rotation driving means for driving based on a supplied clock signal, an encoder for digitally detecting the speed of the rotating body, and a home position sensor for detecting a predetermined reference position of the rotating body,
In a rotating body speed control apparatus having control means for driving the rotating body drive means to correct the speed fluctuation based on the speed fluctuation data detected by the encoder,
In the encoder, when an abnormal signal is detected, the type of abnormality is determined based on the phase of the rotating body when the abnormality is detected,
If the signal (detection value) is abnormal for a predetermined number of times in the same phase, it is determined that the encoder is mechanically abnormal (attachment of foreign matter, slit deformation), and data is interpolated in the abnormal area. To perform correction control drive,
A rotating body speed control device characterized in that if an irregular signal is input irregularly, it is determined as an electric noise error, and detection data is replaced with preset data and correction driving is continued.   2. The rotating body speed control apparatus according to claim 1, wherein the data that is determined to be abnormal for the encoder is performed on the encoder data after low-pass filter computation on the encoder data. Body speed control device.   2. The rotating body speed control apparatus according to claim 1, wherein the abnormal signal in the encoder is a case where a signal outside a predetermined range set in advance is input.   2. The rotating body speed control apparatus according to claim 1, wherein in the case of a mechanical abnormality of the encoder, a method of interpolating data in the abnormal area is based on a vibration rotational frequency profile of the rotating body. A rotating body speed control device characterized by being calculated.   2. The rotating body speed control device according to claim 1, wherein the rotation driving of the rotating body is stopped when the number of abnormalities detected in one rotation of the rotating body is a predetermined number or more. .   2. An image forming apparatus according to claim 1, wherein the rotating member speed control device according to claim 1 is used for rotating the photosensitive member.   2. An image forming apparatus according to claim 1, wherein the rotating body speed control device according to claim 1 is used for rotating the transfer body in an electrophotographic image forming apparatus.

Images