JPH06209595A - Constant speed drive method for rotating mechanism by stepping motor - Google Patents

Abstract

PURPOSE:To mate it possible to perform constant speed drive control by creating drive pulse period data for canceling irregularity in rotation and by inputting drive pulses at the period based on said data in response to each rotation phase of a motor. CONSTITUTION:When a rotation drum 21 is rotated by setting the drive pulses of a motor 23, irregularity in rotation of a reduction gear mechanism 22 and the motor 23 appears in superimposed state and a measuring instrument 7 saves the mean value of predetermined measured data by considering reproducibility. The measuring instrument 7 determines a control factor, calculates drive pulse period data(PD) by multiplying the control factor by the mean value and saves the data. Next, a switch 5 is operated and the measuring instrument 7 determines a value [Nos] corresponding to the smallest value of P-P value and sets [4*Nos] in ROM as the optimum offset value. Then, a rotating position where the rotation phase of the motor 23 becomes zero is detected and, from this position, the pulse period is sequentially set starting with [4*Nos]-th data at PD.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a rotary mechanism at a constant speed by a stepping motor (hereinafter referred to as “STEP motor”), which is an electrophotographic printer or copying machine. The present invention relates to a method for canceling minute and periodical rotation unevenness of a rotating mechanism, which is applied to constant speed drive control of a rotating mechanism using a STEP motor as a drive source such as the rotating drum mechanism in. 2. Description of the Related Art Conventionally, a structure as shown in FIG. 5 has been adopted in an electrophotographic color printer, in which a rotary drum 21 around which photosensitive paper is wound is provided with a speed reducing mechanism 22 such as a harmonic gear. Then, it is rotated by the STEP motor 23, and the printing process by the electrophotographic method is executed in the circulation process. A photosensitive paper 24a supplied from a photosensitive paper roll 24 is wound around the rotary drum 21 so as to be in close contact therewith, and in the course of its winding, the surface of the photosensitive paper 24a is charged by corona discharge of a charger 25. The laser emitting section 26
While scanning the laser beam output from the polygon mirror 27, the photosensitive paper 24a is passed through the optical system (lens, mirror) 28.
To form an electrostatic latent image by exposing the surface of the photosensitive paper 24a with a pre-wetting device 29, then develop with a toner developer 30 and squeeze 31 to roughly remove the toner developer 30. After that, the surface of the photosensitive paper 24a is dried by the heater 32 to fix the dye of the toner, and the static elimination lamp 33
Then, a series of processes for removing the charged electric charge is executed. In a color printer, the above process is repeated for each toner developer of yellow (Y) → magenta (M) → cyan (C) → black (B), and finally a color image is printed on the photosensitive material. The paper 24a is discharged. In the above color printer, in order to improve the quality of the color image, it is essential that the rotary drum 21 be rotated with high precision. In that case, in the development by the electrophotographic method, the development time is mainly determined by the laser power and the scanning resolution, and when the semiconductor laser is used as the light source, the rotary drum 21 cannot be rotated at a very high speed, for example,
The rotation is controlled for several tens of seconds per one rotation. Therefore, in this type of color printer, the STEP motor 23 having excellent controllability is used as a drive source, and the reduction mechanism 22 has a large reduction ratio to ensure effective use of the drive torque and high resolution. Has been realized, and high quality image printing is possible. However, as described above, the rotating drum 21 is moved by the STEP motor 23 via the speed reduction mechanism 22.
When driving the
There is a factor that causes periodical rotation unevenness unique to 22,
Further, the STEP motor 23 itself has periodical rotation unevenness, and minute and periodical rotation unevenness occurs in the rotating drum 21 in a state where they are superimposed. Actually, when measuring the uneven rotation of the rotary drum 21 for a certain color printer, the STEP motor
During one rotation of 23, the rotation speed of the rotary drum 21 changed for two cycles, and uneven rotation of about several percent occurred at the peak value. In a color printer having a high resolution, even if the periodical rotation unevenness of the rotary drum 21 is minute, a minute shade or color shift is generated in the recorded image, and as a result, the quality of the recorded image is improved. Will be lowered. By the way, when the rotational speed of the rotary drum 21 is measured, the above-mentioned uneven rotation has extremely good periodicity and reproducibility. Further, this tendency is not limited to the drive mechanism of the rotary drum 21 as described above, and similarly occurs when a general rotary mechanism is driven by the STEP motor. Therefore, the present invention focuses on the periodicity and reproducibility relating to the rotation unevenness of the rotating mechanism, and provides a method for canceling the rotation unevenness by controlling the cycle of the drive pulse for the STEP motor. It was created for the purpose of enabling stable constant speed driving and realizing high quality of a recorded image by applying it to the color printer or the like. The present invention provides a method of driving a rotating mechanism using a STEP motor as a drive source, wherein each rotation of the STEP motor is performed while the STEP motor is driven by a drive pulse having a constant cycle. Measures the rotation speed of the rotation mechanism in each phase, obtains and stores the drive pulse period data obtained by multiplying the rotation speed data of the rotation mechanism in each rotation phase by a constant coefficient, and corresponds to each rotation phase of the STEP motor. The present invention relates to a constant speed driving method for a rotating mechanism using a STEP motor, characterized in that driving pulses having a cycle based on the driving pulse cycle data are sequentially input. Further, in the above invention, it is necessary to associate each rotation phase of the STEP motor with a drive pulse having a period based on the drive pulse period data. In that case, an offset relating to the order of use of the drive pulse period data is required. While changing the value, measure the rotation speed of the rotating mechanism in the state where the drive pulse is sequentially input at a cycle based on the data,
An offset value that minimizes the change in the measured rotation speed of the rotating mechanism is set as an optimum offset value, and thereafter, a stepping motor is driven using the optimum offset value and the drive pulse cycle data. By doing so, it is possible to realize the constant speed drive of the rotating mechanism with the accurate correspondence set. In principle, the rotation speed of the STEP motor is inversely proportional to the drive pulse cycle. Therefore, when the rotation speed of the rotating mechanism has periodic unevenness while the STEP motor is being driven with the drive pulse of a constant cycle, the cycle of the driving pulse is increased in the rotation phase of the STEP motor where the rotation speed of the rotating mechanism increases. ST that increases the speed and, conversely, decreases the rotation speed of the rotating mechanism
By reducing the period of the drive pulse in the rotation phase of the EP motor, it is possible to cancel the rotation unevenness of the rotation mechanism. The drive pulse cycle data in the present invention has the meaning as correction data for canceling the rotation unevenness of the rotating mechanism, and the drive pulse cycle is set in accordance with the rotation phase of the STEP motor according to the data. In the future, open loop control that rotates the rotating mechanism at a constant speed becomes possible. In particular, if a constant coefficient to be multiplied is set to a value obtained by dividing the period of the drive pulse at the time of measurement by the target rotation speed, constant speed rotation control at the target rotation speed can be performed. In addition, the uneven rotation of the rotating mechanism is STEP
When one cycle or two or more cycles appear during one rotation of the motor, the drive pulse cycle data to be stored is set to one cycle or an integer cycle of the change of the data value based on good reproducibility of rotation unevenness, The drive pulse cycle data can be cyclically used in correspondence with each rotation phase of the stepping motor, and constant speed rotation control can be realized with a small amount of data. By the way, the drive pulse period data is
It is a group of data corresponding to the rotation phase of the STEP motor.Of course, when inputting a drive pulse to the STEP motor, it is necessary to set the drive pulse cycle based on each data in sequence while making the correspondence There is no. On the other hand, since the rotation unevenness of the rotating mechanism and the drive pulse cycle data have periodicity, the above-mentioned correspondence is automatically made by setting an optimum offset value related to the order of using the drive pulse cycle data. Therefore, the offset value of the rotation phase is changed to drive the STEP motor in a cycle based on the drive pulse cycle data, and the offset value when the change in the rotation speed of the rotating mechanism is the smallest is set as the optimum offset value. By adopting the method described above, the above-mentioned association can be rationalized. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of "a constant speed driving method of a rotating mechanism using a STEP motor" of the present invention will be described in detail below with reference to FIGS. This embodiment relates to constant speed driving of the rotary drum 21 of the color printer shown in FIG. 5, and FIG. 2 shows a system configuration diagram for carrying out the method. In FIG. 2, the rotary drum 21 is driven through a reduction mechanism 22 using a STEP motor 23 as a drive source, and the rotary drum 21 has a rotary shaft for detecting the start and end of various electrophotographic processes on the shaft. Encoder 1 is installed. Further, the drive control of the rotary drum 21 is performed by a microcomputer.
(Microcomputer) Based on the control signal of circuit 2, motor driver 3
Is executed by outputting a drive pulse to the STEP motor 23. Furthermore, in the color printer of this embodiment, STEP
A rotary encoder 4 is also attached to the shaft of the motor 23, and an 8-bit DIP switch 5 is connected to the microcomputer circuit 2. The rotary encoder 4 described above
Suffices to have a simple structure in which only the rotational position where the rotational phase of the STEP motor 23 becomes "0" is detected. Next, the procedure of the method for driving the rotary drum 21 at a constant speed according to this embodiment will be described with reference to the graph of FIG. 1 and the flowcharts of FIGS. First, the flowchart of FIG. 3 shows a procedure for creating drive pulse cycle data.
In this procedure, a tacho generator 6 for measurement is attached to the shaft of the rotary drum 21, and a measuring instrument 7 for measuring the output of the tacho generator 6 and the output of the encoder 4 is prepared. Then, when an instruction command is given to the microcomputer circuit 2, the microcomputer circuit 2 makes the motor driver 3
To start the STEP motor 23, and the rotary drum 21
The EP motor 23 rotates in synchronism with the rotation of the EP motor 23. In this case, the microcomputer circuit 2 drives the STEP motor 23 with the period of the drive pulse set to a constant value Tc (S1, S2). On the other hand, the measuring instrument 7 detects the rotation speed Vcz of the rotary drum 21 from the output of the tachogenerator 6 while referring to the output of the encoder 4 while the rotary drum 21 is rotating, and detects one rotation of the STEP motor 23. The rotation speed data Vcz (P) is saved (S3, S4). However, the STEP motor 23 in this case is 1
One rotation in 000 steps (step angle: 0.36 °), the reduction mechanism 22 has a reduction ratio of 1/100, and the STEP motor 23 has 100,000.
The rotary drum 21 is rotated once by inputting each driving pulse. Therefore, the rotation speed data Vcz (P) of the rotating drum 21 is 1 for the rotation phase of the STEP motor 23 of 0 to 360 ° (hereinafter, made dimensionless "0 to 999").
Saved as 000 time series data. By the way, when the drive pulse of the STEP motor 23 is set to a constant cycle Tc and the rotary drum 21 is rotated, the rotation unevenness as shown by the chain double-dashed line in the upper diagram of FIG. 1 occurs. This is due to uneven rotation unique to the speed reduction mechanism 22.
The rotation unevenness of the STEP motor 23 itself appears in a superimposed manner, but in this case, the rotation unevenness of two cycles occurs for one rotation of the STEP motor 23. Moreover, its periodicity and reproducibility appear in a very stable manner, and the STEP motor
Vcz (P): P = 0 to 999 can be detected as accurate cycle data from the measurement data during one rotation of 23. However, the detection of the data in this case does not necessarily have to be performed during one rotation of the STEP motor 23, and a method of rotating the STEP motor 23 a plurality of times and extracting the data for one rotation may be adopted. In the present embodiment, the above procedure is executed three times in consideration of confirmation of reproducibility,
The measuring instrument 7 measures the three measurement data Vc1 (P), Vc2 (P), Vc
3 (P): P = 0 to 999 is saved (S5 → S6 → S2), and the measurement data Vc1 (P), Vc2 (P), Vc3 (P) are added for each phase (P = 0 to 999). The calculation for averaging is performed, and the average value Vc (P): P = 0 to 999 is saved (S7). Next, the measuring instrument 7 obtains a control coefficient K (= Tc / Vs) when the target rotation speed of the rotary drum 21 is Vs, and the control coefficient K has the above-mentioned average value Vc (P). : P = 0 to 999
Drive pulse cycle data [Ts (P) = K · Vc (P): P
= 0 to 999] and save the data (S8). As is clear from the above formula, the drive pulse cycle data naturally has the same cycle as Vc (P), and has the respective cycle values in the waveform shown by the solid line in the lower diagram of FIG. .
Here, the drive pulse cycle data has significance as data for correcting uneven rotation of the rotary drum 21 and executing constant speed rotation control at the target rotation speed Vs. That is, ST
The rotation speed of the EP motor 23 is inversely proportional to the drive pulse cycle,
Further, since the rotary drum 21 rotates in synchronization with the rotation of the STEP motor 23, there is a relationship of [Tc / Ts (P) = Vs / Vc (P)], and the rotary drum 21 is rotated at the target rotation speed Vs. For S
The drive pulse cycle in each phase of the TEP motor 23 is Ts (P):
It should be controlled with P = 0 to 999. The driving pulse cycle data [Ts (P) = K · Vc (P): P = 0 to 999] obtained by the measuring instrument 7 is the microcomputer circuit.
It is written to ROM 2 (S9). In this embodiment, the drive pulse cycle data is written for two sets, and the cycle data for 2000 pulses is stored in the ROM as shown in the lower diagram of FIG. When the above-described procedure for creating the drive pulse period data is completed, the procedure for setting the optimum offset value shown in FIG. 4 is executed. First, by giving an instruction to the microcomputer circuit 2, the microcomputer circuit 2 activates the STEP motor 23, and the rotary encoder 4 detects a rotational position at which the rotational phase P of the STEP motor 23 becomes “0”. The motor 23 is temporarily stopped (S11 to S14). In this case, ST
Only the initial phase of the EP motor 23 is set, and the drive pulse cycle may use the above-mentioned constant cycle Tc. Next, when the DIP switch 5 is operated to set its value to N, the microcomputer circuit 2 sets [4 * N] as an offset value in the RAM (S15 to S17). Here, when an instruction is given to the microcomputer circuit 2, the microcomputer circuit 2 restarts the STEP motor 23 (S18), and the drive pulse cycle data [Ts (P): P = 0 to 999] stored in the ROM in advance. The drive pulse period for one rotation is set sequentially from the [4 * N] th period data of, and the drive pulse period data is used cyclically and continuously.
The STEP motor 23 is rotated (S19). On the other hand, the measuring instrument 7 detects the rotational speed Vc (N) of the rotary drum 21 from the tachogenerator 6 during its rotation, and the PP value of the rotational speed of the rotary drum 21 during 80 rotations of the STEP motor 23 [ ΔVc (N)]
Is saved (S19, S20). Further, the microcomputer circuit 2 stops the STEP motor 23 when the encoder 4 detects that the STEP motor 23 has rotated 80 times (S21). Then, the above procedure is performed by the DIP switch 5
It is repeatedly executed while changing N set in step 0 to 249, and the measuring instrument 7 changes the PP value [ΔVc (N): N = 0 to 24 each time.
9] is saved (S22 → S23 → S16). Further, the measuring instrument 7 is a value corresponding to the minimum value of the above PP value [ΔVc (N): N: 0 to 249].
[Nos] is calculated and [4 * Nos] is set as the optimum offset value in the ROM of the microcomputer circuit 2 (S24). When this optimum offset value [4 * Nos] is made to correspond to FIG. 1, the cycle of the rotation speed Vcp (two-dot chain line) of the rotary drum 21 shown in the above figure and the drive pulse shown in the following figure. It has the significance of matching the cycle of the cycle data [Ts (P) = K · Vc (P): P = 0 to 999]. Therefore, when the above procedure is completed and the normal printing operation is started, the tacho generator 6 and the measuring instrument 7 are removed, the STEP motor 23 is rotated, and the rotation phase P of the STEP motor 23 from the encoder 4 is set to "0". "Rotation position is detected, and from that position, it is stored in the ROM of the microcomputer circuit 2 at the 4th [4 *] in the drive pulse cycle data [Ts (P): P = 0 to 999].
Set the pulse cycle sequentially from the Nos] th data and cyclically use the drive pulse cycle data [Ts (P): P = 0 to 999] for S
When the TEP motor 23 is continuously driven, the rotary drum 21 can be rotated at a constant speed at the target rotation speed Vs. Specifically, Ts (4 * Nos-1) → Ts (4 * Nos) → Ts (4 * Nos + 1) → ・ ・
・ → Ts (999) → Ts (0) → Ts (1) → ・ ・ ・ → Ts (4 * Nos-2) cycle interrupts the CPU of the microcomputer circuit 2 and the STEP motor 23
Drive pulse will be output. As a result, the uneven rotation of the rotating drum 21 is canceled, and the rotating drum 21 rotates at the target rotation speed Vs at a constant speed as shown by the solid line in the upper part of FIG. It is possible to obtain a high quality recorded image.
In this case, strictly speaking, the rotation unevenness occurs when driven with the above-mentioned optimum offset value [4 * Nos], but since it is the rotation unevenness suppressed to the minimum, it is almost constant speed rotation state. Can be regarded as However, in the present embodiment, since the 8-bit DIP switch 5 is used when setting the optimum offset value, the resolution is in units of 4 steps, but if a DIP switch with a large number of bits is used, Fine adjustment is possible. By the way, in this embodiment, a dip switch
Although the optimum offset value is obtained while changing the offset value in step 5, the mounting angle of the encoder 4 is adjusted and the relationship between the rotation unevenness phase of the rotary drum 21 and the rotation phase of the STEP motor 23 is offset value in advance. If the system can be started without the need, a troublesome procedure for setting the optimum offset value becomes unnecessary, and it becomes unnecessary to provide the DIP switch 5. Also, operate the DIP switch 5 by 25
The work of repeating 0 times is very troublesome. Therefore, measuring instrument
If you prepare a program to execute the above-mentioned procedure for creating the drive pulse cycle data and the procedure for setting the optimum offset value in relation to the microcomputer circuit 2, the DIP switch 5 becomes unnecessary naturally and All steps can be performed automatically without intervention, and significant labor saving in adjustment work can be achieved. Further, in this embodiment, the encoder 4 which is not used in the ordinary color printer is added,
The phase of the STEP motor 23 and the phase of the rotating drum 21 always have a correspondence unless the stepping out of the STEP motor 23 occurs, and the encoder 4 can be omitted by detecting the phase of the STEP motor 23 from the encoder 1. It is possible. In this embodiment, the drive pulse cycle data for two revolutions of the STEP motor 23 is stored in the ROM of the microcomputer circuit 2. In principle, one cycle of data in the change of the data value is prepared. The same control can be performed by cyclically using the data for one cycle.
In this embodiment, the rotary drum 21 is driven through the speed reduction mechanism 22. However, if the step motor 1 step feed resolution is sufficiently secured, the rotary drum 21 is directly connected to the STEP motor. A step drive method can be adopted, and a timing belt method or the like can be adopted as a driving force transmitting means, but the constant speed drive control method according to the present embodiment is effective in any method. Besides, in the method according to the present embodiment, the rotation unevenness is measured by each color printer each time, but if the measurement result of the rotation unevenness is stable in lot units of the device, By storing the common cycle data in the ROM, it is possible to omit the measurement for each device. Further, the optimum offset value [4 * Nos] does not necessarily have to be stored in the ROM, and the set value of the DIP switch may be read when the device is started up. EFFECTS OF THE INVENTION The constant speed driving method of the rotating mechanism using the STEP motor according to the present invention has the following effects due to the above configuration. According to the invention of claim 1, when the rotating mechanism is driven by the STEP motor, attention is paid to the fact that the minute rotation unevenness generated in the rotating mechanism has extremely good periodicity and reproducibility. Since the drive pulse cycle data to be canceled is created and the drive pulse is input at the cycle based on the above data in correspondence with each rotation phase of the STEP motor, it is accurate by the open loop method of the rotating mechanism. Constant speed drive control becomes possible. In particular, by being applied to a rotating mechanism of an electrophotographic color printer or the like, high-quality image recording can be realized without uneven density or color shift. According to the second aspect of the present invention, constant speed drive control of the rotating mechanism is enabled with a small amount of drive pulse period data, and the memory capacity of the control circuit is saved. The invention of claim 3 provides a method for accurately obtaining an offset value for associating the drive pulse cycle data with the rotation phase of the STEP motor, and enables optimum constant speed drive control of the rotating mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a principle diagram according to an embodiment of a constant speed driving method of a rotating mechanism by a STEP motor of the present invention, a graph showing rotation unevenness of a rotating drum with respect to a rotation phase of the STEP motor, as well as
7 is a graph showing the contents of drive pulse cycle data and offset values with respect to the rotation phase of a STEP motor. FIG. 2 is a diagram showing a constant speed drive control system for a rotating drum in an electrophotographic color printer. FIG. 3 is a flowchart showing a procedure for creating drive pulse cycle data. FIG. 4 is a flowchart showing a procedure for setting an optimum offset value. FIG. 5 is a schematic configuration diagram centering on a rotating drum in an electrophotographic color printer. [Explanation of symbols] 1,4 ... Rotary encoder, 2 ... Microcomputer circuit, 3 ... Motor driver, 5 ... Dip switch, 6 ... Tachometer, 7 ... Measuring instrument, 21 ... Rotary drum, 22 ... Reduction mechanism, 23 ... STEP motor (stepping motor), 24 ... Photosensitive paper roll, 24a ... Photosensitive paper, 25 ... Charging device, 26 ... Laser emitting section, 27 ... Polygon mirror, 28 ... Optical system, 29 ... Prewetting device, 30 ... Toner developer , 31 ... Squeeze, 32 ... Heater, 33 ... Static elimination lamp, Nos ... Optimal offset value, P ... Motor rotation phase, Tc ... Constant drive pulse cycle, Ts (P):
P = 0 to 999 ... Drive pulse cycle data, Vc (P): P = 0 to 999, V
s ... The rotation speed of the rotating drum.

Claims (1)

Claim: What is claimed is: 1. A method for driving a rotating mechanism using a stepping motor as a drive source, wherein the stepping motor is driven by a drive pulse of a constant cycle, and the rotating mechanism in each rotation phase of the stepping motor is driven. The rotation speed is measured, and the drive pulse cycle data obtained by multiplying the rotation speed data of the rotation mechanism at each rotation phase by a constant coefficient is obtained and stored, and the drive is performed corresponding to each rotation phase of the stepping motor. A constant speed driving method for a rotating mechanism using a stepping motor, characterized in that driving pulses having a cycle based on pulse cycle data are sequentially input. 3. The drive pulse cycle data to be stored is one cycle or an integer cycle of a change in the data value thereof, and the drive pulse cycle data is cyclically used in correspondence with each rotation phase of the stepping motor. 2. A constant speed driving method for a rotating mechanism using a stepping motor according to claim 1, wherein drive pulses having a period based on the above are sequentially input. 2. A method of driving a rotating mechanism using a stepping motor as a drive source, wherein the rotational speed of the rotating mechanism for each rotation phase of the stepping motor is measured in a state where the stepping motor is driven by a drive pulse having a constant cycle, The drive pulse cycle data obtained by multiplying the rotation speed data of the rotating mechanism in each rotation phase by a constant coefficient is obtained and stored, and the drive pulse cycle data is based on the data while changing the offset value related to the use order of the drive pulse cycle data. The rotation speed of the rotation mechanism is measured in the state where the drive pulse is sequentially input at a cycle, and the offset value at which the change in the rotation speed of the rotation mechanism measured is the minimum value is set as the optimum offset value. It is possible to drive the stepping motor using the optimum offset value and the above drive pulse period data. A constant-speed driving method for a rotating mechanism using a characteristic stepping motor.