Stepping motor control device, image forming device and program

Abstract

To easily prevent the occurrence of vibration and an increase in temperature.SOLUTION: A stepping motor control unit comprises: a stepping motor 510; FETs 632, 633, 634, 635 that energize the stepping motor 510 and detect a current value; shunt resistances 636, 637 and operational amplifiers 638, 639; comparators 621, 622 that determine that the detected current value reaches a preset current value; and an excitation control unit 623 that switches an energization pattern at an instructed period, performs comparator processing of turning off the energization to the stepping motor 510 according to results of determination made by the comparators 621, 622, performs current control period processing of turning on the energization to the stepping motor 510 according to a constant current control period timing, and according to a priority instruction to switch priority, sets the priority of the comparator processing and the priority of the current control period processing.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a stepping motor control device, an image forming apparatus, and a program. [Background technology]

[0002] Conventionally, a configuration is known in which a stepping motor is used in a drive unit of an image forming apparatus such as an MFP (Multifunction Peripheral) that forms an image on paper. Also known are a stepping motor control device that changes the chopping PMW (Pulse Width Modulation) frequency according to the speed of the stepping motor, and a stepping motor control device that changes the chopping PMW frequency according to a detected vibration value of a load system (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-298691 Summary of the Invention [Problem to be solved by the invention]

[0004] Although the stepping motor control device in the cited document 1 suppresses vibration, there is a demand for easily preventing vibration generation and temperature rise caused by the stepping motor. Also, the stepping motor control device in the cited document 1 that measures vibration needs to measure the vibration itself, which makes the process complicated.

[0005] An object of the present invention is to easily prevent the occurrence of vibrations and an increase in temperature. [Means for solving the problem]

[0006] In order to solve the above problems, the stepping motor control device of the invention described in claim 1 comprises: A stepping motor, A drive unit that energizes the stepping motor and detects a current value; a comparator for determining whether the detected current value has reached a set current value; a current conduction pattern switching control unit that switches the current conduction pattern at a specified cycle; a comparator processing control unit that performs comparator processing to turn off power supply to the stepping motor in response to a determination result of the comparator; Periodic current waveform maximum a current cycle control unit that performs current control cycle processing to turn on the power supply to the stepping motor in accordance with a cycle of constant current control that controls the amplitude to a constant value; a priority instruction unit that generates a priority instruction to prioritize the comparator process when a characteristic amount corresponding to a rotation speed of the stepping motor corresponds to a high rotation speed range of the rotation speed, and to prioritize the current control period process when the characteristic amount corresponds to a low rotation speed range of the rotation speed; a priority setting unit that sets priorities between the comparator process and the current control period process in response to the priority instruction. 、 The characteristic quantity is based on a clock signal, The priority instruction unit compares the characteristic amount with a predetermined threshold value indicating a characteristic amount at the boundary between the high rotation range and the low rotation range, and generates a priority instruction to prioritize the comparator process when the characteristic amount corresponds to the high rotation range side of the threshold value, and to prioritize the current control period process when the characteristic amount corresponds to the low rotation range side of the threshold value. .

[0008] Claim 2 The invention described in claim 1 In the stepping motor control device according to the The characteristic quantity is the number of rotations of the stepping motor, or a frequency or period corresponding to the number of rotations.

[0009] Claim 3 The invention described in claim 1 or 2 In the stepping motor control device according to the The priority instruction unit corrects the characteristic amount in accordance with an excitation method of the stepping motor, and compares the corrected characteristic amount with the threshold value.

[0010] Claim 4The invention described in claim 1 or 2 In the stepping motor control device according to the The priority instruction unit compares a characteristic amount corresponding to an excitation method of the stepping motor with the threshold value corresponding to the characteristic amount.

[0011] Claim 5 The invention described in claim 1 from 4 In the stepping motor control device according to any one of claims 1 to 5, The clock signal is an external clock signal input from outside the control means including the current supply pattern switching control section, or an internal clock signal generated within the control means.

[0012] Claim 6 The invention described in claim 1 from 5 In the stepping motor control device according to any one of claims 1 to 5, The priority instruction unit is disposed outside a control means including the energization pattern switching control unit, outputs an external clock signal as the clock signal, and compares a characteristic amount based on the external clock signal with the threshold value.

[0013] Claim 7 The invention described in claim 1 from 6 In the stepping motor control device according to any one of claims 1 to 5, The priority indicator determines the characteristic amount and the first priority as the threshold value. 3 Threshold and the 3 The first one on the high rotation side of the threshold 4 A threshold is compared with the characteristic quantity. 3 When the rotation speed corresponds to a lower rotation speed region side than the threshold value, the current control periodic process is prioritized, and the characteristic quantity is 4 When the rotation speed corresponds to a higher rotation range side than the threshold value, the priority instruction is generated so that the comparator process has a priority and has a hysteresis characteristic.

[0014] Claim 8The image forming apparatus of the present invention is A stepping motor, A drive unit that energizes the stepping motor and detects a current value; a comparator for determining whether the detected current value has reached a set current value; a current conduction pattern switching control unit that switches the current conduction pattern at a specified cycle; a comparator processing control unit that performs comparator processing to turn off power supply to the stepping motor in response to a determination result of the comparator; a current cycle control unit that performs current control cycle processing to turn on current supply to the stepping motor in accordance with a cycle of constant current control that controls a maximum amplitude of a periodic current waveform to a constant value; a priority instruction unit that generates a priority instruction to prioritize the comparator process when a characteristic amount corresponding to a rotation speed of the stepping motor corresponds to a high rotation speed range side of the rotation speed, and to prioritize the current control period process when the characteristic amount corresponds to a low rotation speed range side of the rotation speed; a priority setting unit that sets priorities between the comparator process and the current control period process in response to the priority instruction. A stepping motor control device; an image forming unit that forms an image on a sheet; a conveying unit that conveys the paper by rotating a roller by rotation of the stepping motor, The characteristic amount is an operation mode of the image forming apparatus in which the number of revolutions of the stepping motor is different.

[0015] Claim 9 The program of the invention described in A stepping motor, A drive unit that energizes the stepping motor and detects a current value; a comparator that determines whether the detected current value has reached a set current value, an energization pattern switching control unit that switches the energization pattern at a specified cycle; a comparator processing control unit that performs comparator processing to turn off power supply to the stepping motor in response to a determination result of the comparator; Periodic current waveform maximum a current cycle control unit that performs current control cycle processing to turn on current supply to the stepping motor in accordance with a cycle of constant current control that controls the amplitude to a constant value; The characteristic value corresponding to the rotation speed of the stepping motor is in a high rotation range of the rotation speed. side When the characteristic value corresponds to the low rotation speed range of the rotation speed, the comparator process is prioritized. side a priority instruction unit that generates a priority instruction for prioritizing the current control period processing when the current control period processing corresponds to the priority instruction; a priority setting unit that sets priorities between the comparator process and the current control cycle process in response to the priority instruction; Function as 、 The characteristic quantity is based on a clock signal, The priority instruction unit compares the characteristic amount with a predetermined threshold value indicating a characteristic amount at the boundary between the high rotation range and the low rotation range, and generates a priority instruction to prioritize the comparator process when the characteristic amount corresponds to the high rotation range side of the threshold value, and to prioritize the current control period process when the characteristic amount corresponds to the low rotation range side of the threshold value. . Effect of the Invention

[0016] According to the present invention, the occurrence of vibrations and an increase in temperature can be easily prevented. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a block diagram showing a functional configuration of the image forming apparatus. [Diagram 3] FIG. 4 is a circuit diagram of a stepping motor, a fuse, and a circuit board. [Figure 4] 11 is a timing chart showing the gate voltage of an A-phase FET, the gate voltage of an AB-phase FET, an A-phase current, and an AB-phase current. [Diagram 5] 1A is a diagram showing an A-phase current in a coil, a FET, and a shunt resistor, and FIG. 1B is a diagram showing an AB-phase current in a coil, a FET, and a shunt resistor. [Figure 6] 1 is a timing chart showing first to third interrupt patterns. [Figure 7] 13 is a timing chart showing fourth to sixth interrupt patterns. [Figure 8] 13 is a timing chart showing a seventh interrupt pattern. [Figure 9] 13 is a timing chart showing tenth to twelfth interrupt patterns. [Figure 10]1A is a diagram showing vibrations with respect to the rotation speed of a stepping motor when the priority of a current control periodic interrupt is higher than the priority of a comparator interrupt, and FIG. 1B is a diagram showing vibrations with respect to the rotation speed of a stepping motor when the priority of a comparator interrupt is higher than the priority of a current control periodic interrupt. [Figure 11] 1A is a graph showing the A-phase current of a stepping motor in the high rotation range against time, and FIG. 1B is a graph showing the A-phase current of a stepping motor in the low rotation range against time. [Figure 12] 1A is a diagram showing the current values ​​of the A-phase current and the AB-phase current with respect to time when the priority of the current control periodic interrupt is higher than the priority of the comparator interrupt, and FIG. 1B is a diagram showing the current values ​​of the A-phase current and the AB-phase current with respect to time when the priority of the comparator interrupt is higher than the priority of the current control periodic interrupt. [Figure 13] 1A is a diagram showing a correction value table, and FIG. 1B is a diagram showing a threshold value table. [Figure 14] 13 is a flowchart showing a first priority instruction process. [Figure 15] 13 is a flowchart showing a priority setting process. [Figure 16] FIG. 11 is a circuit diagram of a control unit according to a first modified example. [Figure 17] FIG. 13 is a diagram showing a threshold table of a second modified example. [Figure 18] FIG. 13 is a block diagram showing a control unit and a higher-level control unit of a third modified example. [Figure 19] 13 is a flowchart showing a second priority instruction process. [Figure 20] 13 is a flowchart showing a third priority instruction process. [Figure 21] 13 is a flowchart showing a fourth priority instruction process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention and first to fifth modified examples thereof will be described in detail in order with reference to the accompanying drawings. Note that the present invention is not limited to the illustrated examples.

[0019] (Embodiment) An embodiment of the present invention will be described with reference to Figures 1 to 15. First, the configuration of an image forming apparatus 1 of the present embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram of the image forming apparatus 1 of the present embodiment.

[0020] The image forming apparatus 1 of this embodiment is a multifunction machine that forms a color image on paper by electrophotography based on image data received from an external device. Note that the image forming apparatus 1 may be an image forming apparatus of another electrophotographic type, such as a printer, or an image forming apparatus of another image forming type, such as an inkjet type.

[0021] 1, image forming apparatus 1 includes, in order along the flow of paper from upstream to downstream (paper passing direction), a paper feeder 200, an image forming apparatus main body 100, a post-processing device 300, and a paper discharge tray T4. Based on image data received from an external device, image forming apparatus main body 100 forms a color toner image on paper supplied from a paper feed section 20 (described below), fixes the image by applying heat and pressure, and transports the paper after the image formation to post-processing device 300 at the downstream stage.

[0022] The sheet feeding device 200 includes a large-capacity sheet feeding tray (not shown), and obtains sheets from a sheet feeding tray instructed by a control unit 11 (described later) of the image forming apparatus main body 100 and conveys the sheets to the image forming apparatus main body 100 .

[0023] The post-processing device 300 includes a post-processing section 21 (not shown in FIG. 1) for performing post-processing on the paper. Examples of post-processing include stapling, punching, folding, and bookbinding. The post-processing device 300 performs post-processing on the paper after image formation, which is transported from the image forming apparatus main body 100, as necessary using the post-processing section 21, and discharges the paper, which may or may not have been subjected to post-processing, onto the paper output tray T4.

[0024] The paper discharge tray T4 is a tray on which paper conveyed from the post-processing device 300 after image formation (and post-processing) is placed.

[0025] As shown in FIG. 1, an image forming apparatus main body 100 includes an operation unit 12, a display unit 13, an image forming unit 17, a fixing unit 18, paper feed trays T1, T2, and T3, a conveying unit 19, and the like.

[0026] The operation unit 12 has a touch panel formed so as to cover the display screen of the display unit 13, and various operation buttons such as numeric buttons and a start button.

[0027] The display unit 13 is configured with a display panel such as an LCD (Liquid Crystal Display) or an EL (ElectroLuminescence) display, and displays various types of display information on the display screen of the display panel.

[0028] Image forming section 17 forms an image on paper supplied from paper supply section 20. Image forming section 17 has image forming units 17Y, 17M, 17C, and 17K for each color of yellow (Y), magenta (M), cyan (C), and black (K), an intermediate transfer belt 177, and a secondary transfer roller 178. Each of image forming units 17Y, 17M, 17C, and 17K has a photoconductor drum 171, a charging section 172, an exposure section 173, a developing section 174, a primary transfer roller 175, and a cleaning section 176.

[0029] Here, each part of the yellow image forming unit 17Y will be described. The photoconductor drum 171 is a rotating body on which a yellow toner image is formed. The charging section 172 uniformly charges the photoconductor drum 171. The exposure section 173 scans and exposes the surface of the photoconductor drum 171 with a beam such as a laser light based on the yellow component of image data related to image formation to form an electrostatic latent image. The development section 174 stores yellow toner and causes the yellow toner to adhere to the electrostatic latent image on the photoconductor drum 171 for development. The primary transfer roller 175 transfers the yellow toner image formed on the photoconductor drum 171 onto the intermediate transfer belt 177 (primary transfer). The cleaning section 176 removes the toner remaining on the photoconductor drum 171. The magenta, cyan, and black image forming units 17M, 17C, and 17K are similar to the yellow image forming unit 17Y, except for the colors (toners) they handle.

[0030] The intermediate transfer belt 177 is an endless belt onto which the toner images formed on the photoconductor drums 171 of the image forming units 17Y, 17M, 17C, and 17K are sequentially transferred. The secondary transfer roller 178 transfers the four-color toner images formed on the intermediate transfer belt 177 onto a sheet of paper (secondary transfer).

[0031] The fixing unit 18 conveys the paper on which the toner image has been formed by the image forming unit 17, and fixes the toner image onto the paper by applying heat and pressure.

[0032] The paper feed section 20 has paper feed trays T1, T2, and T3, a paper feed roller, and the like, and supplies paper to the image forming section 17. Each of the paper feed trays T1 to T3 stores paper of a predetermined paper type and size. The paper feed section 20 includes a paper feeder 200.

[0033] Conveyance section 19 is composed of transport rollers, registration rollers, etc. for transporting paper, and is disposed on a paper transport path from paper feed section 20, via image forming section 17 and fixing section 18, to post-processing device 300, and transports paper on the paper transport path. Conveyance section 19 also includes an inverting section that inverts paper on which an image has been formed by image forming section 17 and transported from fixing section 18, and transports the paper again to image forming section 17. Conveyance section 19 also includes a transport section for paper on the paper transport path transported from image forming apparatus main body 100, via post-processing device 300, to discharge tray T4.

[0034] The image forming apparatus 1 may be configured to include other components, such as a scanner that reads an original and generates image data.

[0035] Next, the internal functional configuration of the image forming apparatus 1 will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the functional configuration of the image forming apparatus 1.

[0036] 2, the image forming apparatus 1 includes a control unit 11, an operation unit 12, a display unit 13, a storage unit 14, a communication unit 15, an image processing unit 16, an image forming unit 17, a fixing unit 18, a conveyance control unit 19a, a conveyance unit 19, a paper feed unit 20, and a post-processing unit 21. Each unit of the image forming apparatus 1 in FIG. 2 except for the conveyance unit 19 is connected via a bus 22.

[0037] The control unit 11 is configured with a CPU (Central Processing Unit), a RAM (Random Access Memory), etc., and controls each part of the image forming apparatus 1. The control unit 11 reads out various programs stored in the storage unit 14, expands them in the RAM, and executes various processes in cooperation with the expanded programs and the CPU.

[0038] The operation unit 12 receives touch input and button press input from the user, and outputs the operation information to the control unit 11.

[0039] The display unit 13 displays display information on the display panel in accordance with the display information input from the control unit 11 .

[0040] The storage unit 14 is configured with a non-volatile storage device such as a hard disk drive (HDD), a solid state drive (SSD), or a flash memory, and stores various data such as image data and various programs.

[0041] The communication unit 15 transmits and receives data to and from an external device such as a PC (Personal Computer) connected via a communication network such as a LAN (Local Area Network). The control unit 11 transmits and receives data to and from the external device via the communication unit 15. For example, the communication unit 15 receives a print job including image data for printing from the external device.

[0042] The image processing unit 16 has, for example, a rasterization processing unit, a color conversion unit, a gradation correction unit, and a halftone processing unit, and in accordance with the control of the control unit 11, each of these units performs various image processing on image data for printing received from an external device via the communication unit 15 (stored in the memory unit 14).

[0043] The image forming unit 17, under the control of the control unit 11, forms an image on paper fed from the paper feeding unit 20 based on print image data received from an external device via the communication unit 15 (and image processed by the image processing unit 16).

[0044] The fixing unit 18, under the control of the control unit 11, applies heat and pressure to the paper on which the toner image has been formed by the image forming unit 17, thereby fixing the toner image to the paper.

[0045] The transport control unit 19a controls the transport unit 19 under the control of the control unit 11. The transport unit 19 transports the paper fed from the paper feed unit 20 to the paper output tray T4 under the control of the transport control unit 19a via the control unit 11. The paper feed unit 20 supplies the paper to the image forming unit 17 under the control of the control unit 11.

[0046] The post-processing section 21, under the control of the control section 11, performs various post-processing steps as necessary on the paper on which an image has been formed and fixed and which has been conveyed from the image forming apparatus main body 100, and discharges the paper onto the paper discharge tray T4.

[0047] Next, the configuration of the transport control unit 19a and the transport unit 19 will be described with reference to Fig. 3. Fig. 3 is a circuit diagram of a stepping motor 510, a fuse 520, and a substrate 600.

[0048] 3, a stepping motor 510 that drives the transport rollers of the transport unit 19, a fuse 520 connected to the stepping motor 510, and a substrate 600 of a unipolar stepping motor drive circuit that drives the stepping motor 510 will be described. The stepping motor 510 and the fuse 520 are included in the transport unit 19, and the substrate 600 is included in the transport control unit 19a. The stepping motor 510, the fuse 520, and the substrate 600 function as a stepping motor control device.

[0049] The stepping motor 510 is a two-phase unipolar stepping motor that drives the conveying rollers, registration rollers, etc. of the conveying unit 19, and has coils 511, 512, 513, and 514. One end of the coils 511, 512, 513, and 514 is connected to a power supply unit (24 [V]) of a driving power source via a fuse 520. This power supply unit is not limited to 24 [V], and may be 36 [V] or the like. The coils 511, 512 and the coils 513, 514 are each paired. The pairs are coupled so that when a current flows in the same direction (power supply → each coil terminal), the current flows in the opposite magnetic direction. For convenience, each pair is called an A-phase and a B-phase, and the terminals of the A-phase pair on the opposite side to the power supply unit of the coils are called the A-phase terminal and the AB-phase terminal, respectively, and the terminals of the B-phase pair on the opposite side to the power supply unit of the coils are called the B-phase terminal and the BB-phase terminal, respectively. Also, coil 511 corresponds to phase A, coil 512 paired with coil 511 corresponds to phase AB, coil 513 corresponds to phase B, and coil 514 paired with coil 513 corresponds to phase BB.

[0050] The excitation methods of the stepping motor 510 include 2-phase full step, 1-2 phase, W1-2 phase, 2W1-2 phase, and 4W1-2 phase. 2-phase full step is a method in which two phases are excited at a time at all times (2-phase excitation). 1-2 phase is a method in which the resolution is doubled by alternating between a method in which one phase is excited at a time at all times (1-phase excitation) and 2-phase excitation. W1-2 phase is a method in which one rotation is performed in four times the basic step number (the number of rotations in one full step). 2W1-2 phase is a method in which one rotation is performed in eight times the basic step number. 4W1-2 phase is a method in which one rotation is performed in 16 times the basic step number.

[0051] The substrate 600 has a control unit 610 as a control means, a pre-driver 631, FETs (Field effect transistors) 632, 633, 634, and 635, shunt resistors 636 and 637, and operational amplifiers 638 and 639. The pre-driver 631, the FETs 632, 633, 634, and 635, the shunt resistors 636 and 637, and the operational amplifiers 638 and 639 function as a driving unit.

[0052] The control unit 610 includes a CPU, a RAM, a ROM (Read Only Memory), and various circuit elements. The control unit 610 includes an excitation mode setting unit 611, an edge detection unit 612, a phase advance counter 613, a measurement unit 614 as a priority instruction unit, a current table storage unit 615, a current value calculation unit 616, an oscillator 617, a clock generation unit 618, D / A (Digital to Analog) converters 619 and 620, comparators 621 and 622, and an excitation control unit 623 as a current pattern switching control unit, a comparator processing control unit, a current cycle control unit, and a priority setting unit.

[0053] The pre-driver 631 is a driver circuit having four terminals connected to the excitation control unit 623 and four terminals connected to the gates of FETs 632, 633, 634, and 635. The FET 632 is a switching element having a drain connected to the terminal A of the coil 511, a source connected to a shunt resistor 636, and a diode that rectifies from the source to the drain. The FET 633 is a switching element having a drain connected to the terminal AB of the coil 512, a source connected to a shunt resistor 636, and a diode that rectifies from the source to the drain. The FET 634 is a switching element having a drain connected to the terminal B of the coil 513, a source connected to a shunt resistor 637, and a diode that rectifies from the source to the drain. The FET 635 is a switching element having a drain connected to the terminal BB of the coil 514, a source connected to a shunt resistor 637, and a diode that rectifies from the source to the drain.

[0054] The shunt resistor 636 is a resistor with a small resistance value for detecting a current between the terminals, with one end connected to the FETs 632 and 633 and the other end grounded. The shunt resistor 636 is a resistor with a small resistance value for detecting a current between the terminals, with one end connected to the FETs 634 and 635 and the other end grounded. The operational amplifier 638 has an input terminal connected to the sources of the FETs 632 and 633 and amplifies the voltage of the sources. The operational amplifier 639 has an input terminal connected to the sources of the FETs 634 and 635 and amplifies the voltage of the sources.

[0055] The control unit 610 receives the signals MODE, DIRECTION, an external clock signal CLOCK, a signal ENABLE, a supply voltage of 3.3V, a ground potential GND, and a voltage VREF from an external device such as the control unit 11. The signal MODE is a signal for the excitation method of the stepping motor 510. The signal DIRECTION is a signal for specifying the rotation direction of the stepping motor 510. The external clock signal CLOCK is a clock signal for driving the stepping motor 510 (for advancing the drive excitation pattern). The signal ENABLE is an ON / OFF signal for excitation of the stepping motor 510. The voltage VREF is a reference voltage for determining the value of the current to be passed through the stepping motor 510.

[0056] The excitation mode setting unit 611 outputs a setting signal for the excitation method of the stepping motor 510 in response to a signal MODE input from the outside. The edge detection unit 612 detects an edge for each cycle of an external clock signal CLOCK input from the outside, and outputs an edge detection signal as an external clock interrupt. The phase lead counter 613 generates a phase lead amount signal indicating a phase lead count value corresponding to the excitation method and rotation direction in response to a signal DIRECTION input from the outside, the excitation method setting signal input from the excitation mode setting unit 611, and the edge detection signal input from the edge detection unit 612.

[0057] The measurement unit 614 generates a priority instruction indicating the priority of a comparator interrupt INT1 and a current control period interrupt INT2 described later according to an edge detection signal input from the edge detection unit 612, an oscillation signal input from the oscillator 617, and a setting signal of an excitation method input from the excitation mode setting unit 611, and outputs the priority instruction to the excitation control unit 623. The measurement unit 614 includes a CPU, a RAM, and a ROM. In the measurement unit 614, a first priority instruction program for executing a first priority instruction process described later is stored in the ROM, and the CPU appropriately loads the first priority instruction program stored in the ROM in the RAM and executes the first priority instruction process in cooperation with the loaded first priority instruction program. The ROM of the measurement unit 614 stores a correction value table 71 and a threshold table 72 described later.

[0058] The current table storage unit 615 stores a preset current table. The current table is a table showing a current control pattern for the electrical angle of the stepping motor 510 according to the excitation method and the direction of rotation. For example, which of the A-phase FET 632 and the AB-phase FET 633 is turned on is determined by the electrical angle of the current control pattern (leading by an amount of lead angle that differs for each excitation mode according to the external clock signal CLOCK). The same applies to the B-phase and the BB-phase.

[0059] The current value calculation unit 616 reads out the current table from the current table memory unit 615, calculates the current value to be passed through the coils 511, 512, 513, and 514 of the stepping motor 510 based on the read current table, the voltage VREF input from outside, and the phase lead signal corresponding to the excitation method and rotation direction input from the phase lead counter 613, outputs the calculated current value signal to the excitation control unit 623, and generates a current setting reference voltage corresponding to the calculated current value and outputs it to the D / A converters 619 and 620.

[0060] The oscillator 617 generates an oscillation signal that is sufficiently faster than the external clock signal CLOCK and outputs it to the measurement unit 614 and the clock generation unit 618. The clock generation unit 618 generates and outputs an internal clock signal according to the oscillation signal input from the oscillator 617. The D / A converter 619 converts the digital current setting reference voltage input from the current value calculation unit 616 into an analog current setting reference voltage. The D / A converter 620 converts the digital current setting reference voltage input from the current value calculation unit 616 into an analog current setting reference voltage. The comparator 621 compares the voltage input from the operational amplifier 638 with the analog current setting reference voltage input from the D / A converter 619, and generates a comparator output signal indicating the comparison result. The comparator 622 compares the voltage input from the operational amplifier 639 with the analog current setting reference voltage input from the D / A converter 620, and generates a comparator output signal indicating the comparison result.

[0061] The excitation control unit 623 generates control signals for FETs 632, 633, 634, and 635 in response to the internal clock signal input from the clock generation unit 618, the signal ENABLE input from the outside, the current value signal input from the current value calculation unit 616, and the comparator output signals input from the comparators 621 and 622, and outputs these to the pre-driver 631 to turn the FETs 632, 633, 634, and 635 on / off.

[0062] The excitation control unit 623 includes a CPU, a RAM, and a ROM. In the excitation control unit 623, a priority setting program for executing a priority setting process described later is stored in the ROM, and the CPU appropriately loads the priority setting program stored in the ROM into the RAM and executes the priority setting process in cooperation with the loaded priority setting program.

[0063] Next, the operation of the stepping motor 510 and the board 600 of the image forming apparatus 1 will be described with reference to FIGS.

[0064] First, referring to Fig. 4 and Fig. 5, a current control (asynchronous rectification) in an excitation pattern for energizing the A-phase coil 511 will be described as an example of constant current control for keeping the current flowing through the coil of the stepping motor 510 constant. Fig. 4 is a timing chart showing the gate voltage of the A-phase FET 632, the gate voltage of the AB-phase FET 633, the A-phase current, and the AB-phase current. Fig. 5(a) is a diagram showing the A-phase current in the coils 511, 512, the FETs 632, 633, and the shunt resistor 636. Fig. 5(b) is a diagram showing the AB-phase current in the coils 511, 512, the FETs 632, 633, and the shunt resistor 636.

[0065] The excitation control unit 623 controls the on / off of the FETs 632, 633, 634, and 635 to control the current flowing through the stepping motor 510. Here, the current control of the A-phase coil 511 and the AB-phase coil 512 by the on / off control of the A-phase FET 632 and the AB-phase FET 633 will be described.

[0066] As shown in Fig. 4, first, the A-phase FET 632 is turned on at time t1 by the excitation control unit 623. By turning on the FET 632, the current value of the A-phase current flowing from the power supply unit to the ground unit via the A-phase coil 511, the drain-source of the FET 632, and the shunt resistor 636 increases over time, as shown in Fig. 5(a). At this time, the AB-phase FET 633 is turned off, and the AB-phase current flowing through the AB-phase coil 512 is 0 [A].

[0067] Then, at time t2, the voltage of the A-phase current becomes greater than the current setting reference voltage, so that the A-phase comparator 621 is turned on and an A-phase ON comparator output signal is output by the comparator 621. In response to the A-phase ON comparator output signal, the excitation control unit 623 turns off the A-phase FET 632.

[0068] 5B, an AB phase current is generated as a reverse current having the same magnitude as the A phase current at time t2, and flows from the ground to the power supply via the shunt resistor 636, the diode (asynchronous rectification) of the FET 633, and the coil 512. Then, with the FET 632 remaining off, the absolute value of the AB phase current decreases over time.

[0069] Then, the excitation control unit 623 turns on the A-phase FET 632 at time t3. In response to the A-phase FET 632 being turned on, the AB-phase current becomes 0 [A], and an A-phase current is generated as a forward current having the same magnitude as the AB-phase current at time t3. The time from time t1 to time t3 is set as a current control period. In this manner, the current is controlled to be constant. This current control similar to that from time t1 to t3 is repeated. The current control pattern for energizing the AB, B, and BB phases is also similar to the current control pattern for energizing the A phase described above.

[0070] Next, the types of interrupt processing performed by the excitation control unit 623 and interrupt patterns according to the priority of the interrupt will be described with reference to Fig. 6 to Fig. 9. Fig. 6 is a timing chart showing interrupt patterns IP1 to IP3. Fig. 7 is a timing chart showing interrupt patterns IP4 to IP6. Fig. 8 is a timing chart showing interrupt pattern IP7. Fig. 9 is a timing chart showing interrupt patterns IP10 to IP12.

[0071] An excitation control unit 623 including a CPU is used to control the current of the stepping motor 510. The processing of the excitation control unit 623 is implemented by software, but interrupt processing is used for timing-critical parts. There are three types of interrupt processing: an "external clock interrupt" that advances the excitation pattern according to an external clock signal CLOCK that indicates the rotation speed of the stepping motor 510; a "current control period interrupt" that turns on the FET for each current control period in current control; and a "comparator interrupt" that occurs when the comparators 621, 622 react when the set current value (the current detection amplifier voltage at) reaches the constant current control level (current setting reference voltage) in current control.

[0072] Depending on the priority of the interrupt processing, there are problems of vibration occurring in the high rotation range and temperature increase in the low rotation range, which are incompatible. Here, (1) the priority of the current control period interrupt is greater than the priority of the comparator interrupt, and (2) the priority of the comparator interrupt is greater than > The priority of current control periodic interrupts is explained in the following order: comparator interrupt processing is processing to turn off the FET in response to the occurrence of a comparator interrupt. current control periodic interrupt processing is processing to turn on the FET if the comparator is off when a current control periodic interrupt occurs.

[0073] (1) When the priority of the current control periodic interrupt is greater than the priority of the comparator interrupt, the following interrupt patterns IP1 to IP7 are generated for the interrupt operation depending on the occurrence timing of both interrupts. In (1), since the priority of the current control periodic interrupt is higher, when the current control periodic interrupt occurs, the comparator interrupt process is interrupted.

[0074] FIG. 6 shows a timing chart of the on / off voltage of the comparator, a timing chart of the on / off voltage of the FET, the comparator interrupt processing time (shown by hatching), and the current control period interrupt processing time (shown by shading), and the same is true for FIGS. 7 to 9.

[0075] As shown in Figure 6, in interrupt pattern IP1, the FET is turned off at time t11 due to a comparator interrupt (comparator on), and the FET is turned on at time t12 due to the occurrence of a current control periodic interrupt because the comparator is off. The comparator signal is a flag indicating that the comparator has reacted, and is reset by the comparator interrupt process. The FET goes on → off → on, so there is no problem with the timing.

[0076] In interrupt pattern IP2, the comparator interrupt process is interrupted by the occurrence of a current control period interrupt before the FET is turned off by the comparator interrupt, the FET continues to be on at time t21 because the comparator is off, the comparator interrupt process is resumed when the current control period interrupt process ends, and the FET is turned off at time t22. The FET goes on → continues to be on → off, there is a large delay in turning it off, and it does not turn on again.

[0077] In interrupt pattern IP3, the comparator interrupt process is interrupted by the occurrence of a current control period interrupt before the FET is turned off by the comparator interrupt, the FET is not turned on at time t31 because the comparator is on, the comparator interrupt process is resumed when the current control period interrupt process ends, and the FET is turned off at time t32. The FET goes from on to off, and just like the timing of interrupt pattern IP2, there is a large delay in turning it off and it does not turn on again.

[0078] As shown in Figure 7, in interrupt pattern IP4, the current control periodic interrupt occurs, and the comparator is turned on at time t41, so the FET is turned off. centre When the current control periodic interrupt process ends, the comparator interrupt process starts, and the FET is turned off at time t42. The FET goes from on to off, and although the off-time is delayed, this is an improvement over the interrupt patterns IP2 and IP3, and there is no re-on.

[0079] In interrupt pattern IP5, when a current control periodic interrupt occurs, the comparator turns off at time t51, so the FET continues to be on, and when the current control periodic interrupt process ends, the comparator interrupt process starts, and the FET is turned off at time t52. The FET goes on → continues to be on → off, and although the turning off is delayed, this is an improvement over interrupt pattern IP4, and there is no turning on again.

[0080] In interrupt pattern IP6, when a current control periodic interrupt occurs, the comparator turns off at time t61, so the FET continues to be on, and when the current control periodic interrupt process ends, the comparator interrupt process starts, and the FET is turned off at time t62. The FET goes on → continues to be on → off, and although the turning off is delayed, this is an improvement over interrupt pattern IP5, and there is no turning on again.

[0081] As shown in Figure 8, in interrupt pattern IP7, when a current control periodic interrupt occurs, the comparator turns off at time t71, so the FET continues to be on, and when the current control periodic interrupt process ends, the comparator interrupt process starts, and the FET is turned off at time t72. The FET goes from on to continuing on to off, so there is no problem with the timing.

[0082] The interrupt patterns IP2 to IP6 are not preferable because they cause a delay in the current control timing (especially the timing to turn off the FET). 、 The interrupt patterns IP2 and IP3 are the worst, and the order of interrupt patterns IP4, IP5, and IP6 shows improvement.

[0083] The current control difference between interruption pattern IP1 and interruption pattern IP2 is relatively large, and a slight difference in the timing of the current control cycle interrupt causes an abrupt transition. The most problematic point is that a slight difference in the timing of the current control cycle interrupt causes a discontinuous transition to either interruption pattern IP1 or interruption pattern IP2, and the fluctuation in current control causes vibrations in the output torque of the stepping motor 510.

[0084] In addition, the occurrence of interrupt patterns IP2 and IP3 can be suppressed by disabling the current control period interrupt within the comparator interrupt, but this has no effect on interrupt pattern IP4, and discontinuous changes between interrupt patterns IP1 and IP4 occur.

[0085] In addition, between the problem-free interrupt pattern IP7 and the problematic interrupt pattern IP6, the pattern changes continuously in accordance with the timing difference, and no discontinuous changes occur. Therefore, although there is a problem of bias in the current control value, this does not cause vibrations in the output torque of the stepping motor 510 due to fluctuations.

[0086] (2) Comparator interrupt priority > In the case of the priority of the current control periodic interrupt, the interrupt operation has the following interrupt patterns IP10 to IP12. Since the comparator interrupt has a higher priority, if a comparator interrupt occurs during the current control periodic interrupt processing, the current control periodic interrupt processing is interrupted.

[0087] 9, in interrupt pattern IP10, the FET is turned off at time t101 by the comparator interrupt, the current control period interrupt process starts when the comparator interrupt process ends, and the FET is turned on at time t102 because the comparator is off. The FET goes on → off → on, so there is no problem with the timing.

[0088] In interrupt pattern IP11, when a current control period interrupt occurs, the comparator is off at time t111 so the FET attempts to be turned on, but the current control period interrupt process is interrupted due to the comparator interrupt, the FET is turned off at time t112, and when the comparator interrupt process ends, the current control period interrupt process resumes and the FET is turned on at time t113. The FET goes on → off → on, and although it should remain off, it has turned on again, resulting in an NG operation. Although interrupt pattern IP11 is an abnormal operation, it can be suppressed by setting the period between the comparator level check and the FET on process as an interrupt prohibited section within the current control period interrupt process.

[0089] In interrupt pattern IP12, when a current control periodic interrupt occurs, the comparator is off at time t121 so the FET continues to be on, the current control periodic interrupt process is suspended when the comparator interrupt occurs, the FET is turned off at time t112, and the current control periodic interrupt process resumes when the comparator interrupt process ends. The FET goes from on to continuing on to off, so there is no problem with the timing.

[0090] The interrupt pattern IP11 can be suppressed by providing an interrupt prohibited section, so it essentially becomes interrupt patterns IP10 and IP12. In the interrupt patterns IP10 and IP12, even if there is a slight difference in timing between the two, there is no problem in terms of current control, so no vibration in the output torque of the stepping motor 510 due to fluctuations in current control occurs.

[0091] Next, the vibration characteristics and temperature characteristics of the stepping motor 510 will be described with reference to Figs. 10 to 12. Fig. 10(a) is a diagram showing vibration with respect to the rotation speed of the stepping motor 510 in the case where the priority of the current control period interrupt is higher than the priority of the comparator interrupt. Fig. 10(b) is a diagram showing vibration with respect to the rotation speed of the stepping motor 510 in the case where the priority of the comparator interrupt is higher than the priority of the current control period interrupt. Fig. 11(a) is a diagram showing the A-phase current in the high rotation range of the stepping motor 510 with respect to time. Fig. 11(b) is a diagram showing the A-phase current in the low rotation range of the stepping motor 510 with respect to time. Fig. 12(a) is a diagram showing the current values ​​of the A-phase current and the AB-phase current with respect to time in the case where the priority of the current control period interrupt is higher than the priority of the comparator interrupt. Fig. 12(b) is a diagram showing the current values ​​of the A-phase current and the AB-phase current with respect to time in the case where the priority of the comparator interrupt is higher than the priority of the current control period interrupt.

[0092] (1) When the priority of the current control period interrupt is greater than the priority of the comparator interrupt, the vibration [m / s 2 (2) When the priority of the comparator interrupt is greater than the priority of the current control period interrupt, the vibration [m / s rms (effective value)] characteristic of the stepping motor 510 with respect to the rotation speed [rpm] shown in FIG. 2 As can be seen from the characteristics of (rms) in (1), the portion with large absolute vibration values ​​is smaller than in (1), and the vibration caused by the above priority is suppressed.

[0093] The reason that vibration worsens at high rotation speeds is that at high rotation speeds, the delay in current rise caused by the inductance component of the coil (for example, A-phase coil 511) of stepping motor 510 causes the time to reach the current set value to become dominant, and the number of current control operations decreases, as shown in the characteristics of the A-phase current value at high rotation speeds of stepping motor 510 against time shown in Figure 11(a). At this time, if fluctuations occur in current control due to the high priority of the current control cycle interrupt, the current fluctuation = variation in the number of control operations is affected by "1 / number of operations", and so the impact is relatively large.

[0094] Conversely, in the low rotation range, as shown in the characteristic of the current value of the A-phase current in the low rotation range of the stepping motor 510 against time shown in Fig. 11(b), the number of current controls increases, so the effect of the fluctuation of "1 / number of times" becomes relatively small and is less likely to appear as output torque vibration of the stepping motor 510. The area within the distribution of the current values ​​in Fig. 11(a) and Fig. 11(b) contributes to the output torque. In the high rotation range of Fig. 11(a), the effect of interruption on the total area of ​​the distribution of one lump is small, while in the low rotation range of Fig. 11(b), the effect of interruption on the total area of ​​the distribution of one lump is large.

[0095] As described above, from the viewpoint of vibrations at high revolution ranges, the case (2) where the priority of the comparator interrupt is greater than the priority of the current control period interrupt is more preferable than the case (1) where the priority of the current control period interrupt is greater than the priority of the comparator interrupt. However, in the case of (2), the priority of the comparator interrupt is higher, so the current control period interrupt is interrupted, and as a result, the current control period is likely to be disrupted. Conversely, in the case of (1), the current control period interrupt has priority, so the current control period is less likely to be disrupted.

[0096] Figure 12(a) shows the characteristics of the A-phase current and the AB-phase current values ​​[A] versus time [μs] for case (1). Figure 12(b) shows the characteristics of the A-phase current and the AB-phase current values ​​[A] versus time [μs] for case (2). In Figures 12(a) and 12(b), the A-phase current value is shown by a solid line, and the AB-phase current value is shown by a dashed line.

[0097] In the graph of Figure 12(b), the comparator interrupt has a higher priority, so the current waveform in the case of a current control period interrupt, and the current control period is disrupted, resulting in a waveform in which the number of controls (the number of times the FET is turned on and off) increases in the latter half, and this waveform is longer (more control times) than the graph of Figure 12(a).

[0098] In this way, as the number of times the FET is turned on and off increases, the switching loss of the FET increases and the temperature of the FET rises. Also, the number of times the current is controlled per unit time is greater at lower speeds, which makes the FET temperature more likely to rise.

[0099] Next, the information stored in the ROM of the measurement unit 614 will be described with reference to Fig. 13. Fig. 13(a) is a diagram showing a correction value table 71. Fig. 13(b) is a diagram showing a threshold value table 72.

[0100] As shown in FIG. 13(a), the correction value table 71 stored in the ROM of the measurement unit 614 has items (columns) of excitation method and correction value. The item of excitation method is the type of excitation method of the stepping motor 510, for example, 2-phase full step, 1-2 phase excitation, W1-2 phase excitation, 2W1-2 phase excitation, and 4W1-2 phase excitation. The item of correction value is a correction value for correcting the frequency (or rotation speed) of the external clock signal to a constant value regardless of the excitation method. In FIG. 13(a), the correction value table 71 is described as having correction value example 1, correction value example 2, and correction value example 3 together, but it is sufficient to have at least one of them. Correction value example 1 is a correction value that corrects the frequencies [Hz] of all excitation methods to equivalent to 2-phase full step, and correction value example 2 is a correction value that corrects the frequencies [Hz] of all excitation methods to equivalent to 1-2 phase excitation full step. Correction value example 3 is a correction value for the rotation speed [rpm] of stepping motor 510 when using stepping motor 510 with a rotation angle of 1.8° per pulse in two-phase full step.

[0101] 13(b), the threshold table 72 stored in the ROM of the measurement unit 614 has items (columns) of correction value example and threshold. The correction value example item is each correction value example of the correction value table 71 (e.g., correction value example 1, correction value example 2, correction value example 3). The threshold item is a threshold of a characteristic amount for setting a priority corresponding to the correction value example. The threshold item is a threshold of frequency [Hz] in correction value example 1 and correction value example 2, and a threshold of rotation speed [rpm] in correction value example 3.

[0102] Next, the first priority instruction process executed by the measurement section 614 will be described with reference to Fig. 14. Fig. 14 is a flowchart showing the first priority instruction process.

[0103] As described above, the stepping motor 510 is controlled by the control unit 610 through software. When using interrupt processing for current control processing, which is a timing-critical process, (1) if the priority of the current control cycle interrupt is greater than the priority of the comparator interrupt, there is a problem that vibration occurs at high rotation speeds. > In the case of the current control periodic interrupt priority, there is a problem that the temperature of the FET becomes relatively high in the low rotation range. For this reason, it is preferable to switch the interrupt priority according to the rotation speed of the stepping motor 510.

[0104] However, it is not always necessary to obtain the rotation speed of the stepping motor 510, and the priority switching process may be performed using a value proportional to the rotation speed of the stepping motor 510. The first priority instruction process is a process for instructing a preferred priority between the comparator interrupt INT1 and the current control period interrupt INT2 according to the frequency of the external clock signal CLOCK corresponding to the rotation speed of the stepping motor 510.

[0105] In the image forming device 1, when the control unit 11 executes a printing process in response to operation information from a user via the operation unit 12, the control unit 11 starts to control the transport of paper by the transport unit 19, which triggers the measurement unit 614 to perform a first priority instruction process in accordance with a first priority instruction program stored in the internal ROM.

[0106] 14, first, the measurement unit 614 calculates the frequency of the external clock signal CLOCK by the following formula (11) in response to the edge detection signal input from the edge detection unit 612 and the oscillation signal input from the oscillator 617 (step S11). In step S11, the frequency of the external clock signal CLOCK is calculated from the value obtained by counting the period between edges of the external clock signal CLOCK by the oscillator 617 as a count clock, and the frequency of the external clock signal CLOCK = frequency of the oscillation signal ÷ number of counts between edges based on the edge detection signal ... (11) It is calculated as follows:

[0107] In step S11, the calculation may be performed from the number of external clock interrupts that occur within a certain period, for example, while a current control period interrupt occurs a predetermined number of times, using the following formula (12). Frequency of external clock signal CLOCK=number of external clock interrupts ÷ (current control period × predetermined number of times) (12)

[0108] Then, the measurement unit 614 reads the correction value table 71 from the internal ROM, and calculates a correction value for the frequency of the external clock signal CLOCK using the frequency of the external clock signal CLOCK calculated in step S11, the excitation method setting signal input from the excitation mode setting unit 611, and the correction value table 71 (step S12). Here, for example, a case where correction value example 1 is applied will be described. The correction value for the frequency of the external clock signal CLOCK is calculated using the following equation (13) using the correction value corresponding to the excitation method according to the excitation method setting signal in the correction value table 71. Correction value of the frequency of the external clock signal CLOCK = calculated frequency of the external clock signal CLOCK × correction value in the correction value table 71 ... (13)

[0109] Then, the measurement unit 614 reads the threshold table 72 from the internal ROM, and determines whether or not the correction value of the frequency of the external clock signal CLOCK calculated in step S12, the excitation method setting signal input from the excitation mode setting unit 611, and the threshold table 72 are equal to or greater than the threshold (first threshold) corresponding to the excitation method setting signal in the threshold table 72 (step S13). If the correction value of the frequency of the external clock signal CLOCK is equal to or greater than the first threshold (step S13; YES), the measurement unit 614 sets (2) the priority of the comparator interrupt INT1 > the priority of the current control period interrupt INT2, generates a priority instruction of (2) and outputs it to the excitation control unit 623 (step S14), and proceeds to step S11.

[0110] If the correction value of the frequency of the external clock signal CLOCK is less than the first threshold value (step S13; NO), the measurement unit 614 sets (1) the priority of the current control period interrupt INT2 > the priority of the comparator interrupt INT1, generates a priority instruction of (1) and outputs it to the excitation control unit 623 (step S15), and proceeds to step S11. The priority instruction (signal) may be defined logically, for example, by assigning (2) to 1 (high level) and (1) to 0 (low level).

[0111] In the above description, the frequency of the external clock signal CLOCK corresponding to the number of rotations of the stepping motor 510 is used to determine the priority of the interrupt, but the number of rotations according to the external clock signal CLOCK and the period of the external clock signal CLOCK may be used to set the priority of the interrupt. When the number of rotations corresponding to the external clock signal CLOCK is used, the number of rotations corresponding to the external clock signal CLOCK is calculated in step S11, a correction value of the number of rotations corresponding to the external clock signal CLOCK is calculated using a correction value of, for example, correction value example 3 in the correction value table 71 in step S12, and it is determined in step S13 whether the correction value of the number of rotations corresponding to the external clock signal CLOCK is equal to or greater than the threshold value of the number of rotations. When the period of the external clock signal CLOCK is used, the period of the external clock signal CLOCK is calculated in step S11, a correction value of the period of the external clock signal CLOCK is calculated in step S12, and it is determined in step S13 whether the period of the external clock signal CLOCK is equal to or less than the threshold value of the period.

[0112] As described above, the problems that occur change depending on whether the number of current control operations is relatively high or low. Therefore, it is desirable to switch the priority according to the rotation speed rather than the frequency of the external clock signal CLOCK. However, in a device equipped with multiple excitation methods, the external clock signal CLOCK, which determines the rotation speed depending on the excitation method, has the characteristic that it changes as a factor of 2 to the power of n. Therefore, when switching the priority, a different threshold value may be used for each excitation method.

[0113] Next, the priority setting process executed by the excitation control unit 623 will be described with reference to Fig. 15. Fig. 15 is a flowchart showing the priority setting process.

[0114] In the image forming apparatus 1, similarly to the above, when the control of the transport of the paper by the transport unit 19 is started, the excitation control unit 623 performs the priority setting process according to the priority setting program stored in the internal ROM.

[0115] 15, first, the excitation control unit 623 acquires the priority instruction input from the measurement unit 614 in response to steps S14 and S15 of the first priority instruction process (step S21). Then, the excitation control unit 623 determines whether the priority instruction input in step S21 is (2) the priority of the comparator interrupt INT1>the priority of the current control period interrupt INT2 (step S22).

[0116] If the priority of the comparator interrupt INT1 is higher than the priority of the current control period interrupt INT2 (step S22; YES), the excitation control unit 623 sets the priority of the comparator interrupt INT1 to the first priority and the priority of the current control period interrupt INT2 to the second priority (step S23), and proceeds to step S21. If the priority of the current control period interrupt INT2 is higher than the priority of the comparator interrupt INT1 (step S22; NO), the excitation control unit 623 sets the priority of the comparator interrupt INT1 to the second priority and the priority of the current control period interrupt INT2 to the first priority (step S24), and proceeds to step S21.

[0117] As described above, according to this embodiment, the image forming apparatus 1 (its stepping motor control device) includes the stepping motor 510, FETs 632, 633, 634, 635 which energize the stepping motor 510 and detect the current, shunt resistors 636, 637, operational amplifiers 638, 639, comparators 621, 622 which determine whether the detected current value has reached a set current value, and an excitation control unit 623 which switches the energization pattern at an instructed period, performs comparator interrupt processing as comparator processing which turns off the energization to the stepping motor 510 depending on the determination results of the comparators 621, 622, performs current control period interrupt processing as current control period processing which turns on the energization to the stepping motor 510 depending on the constant current control period timing, and sets the priority between the comparator interrupt processing and the current control period interrupt processing depending on a priority instruction which switches the priority.

[0118] For this reason, even if the stepping motor 510 is driven by the excitation control unit 623 of the control unit 610, which can be realized by an inexpensive CPU, without directly measuring the vibration of the stepping motor 510, it is possible to easily prevent the occurrence of vibration in the high rotation speed range and the temperature rise in the low rotation speed range of the driving speed of the stepping motor 510 in accordance with the priority instruction.

[0119] The image forming apparatus 1 also includes a measurement unit 614 that compares a characteristic amount based on the external clock signal CLOCK with a predetermined first threshold value and generates a priority instruction according to the comparison result. The characteristic amount based on the clock signal is a frequency corresponding to the rotation speed of the stepping motor 510. Therefore, without directly measuring the rotation speed of the stepping motor 510, it is possible to more easily prevent vibrations in the high rotation speed range and temperature rises in the low rotation speed range of the driving rotation speed of the stepping motor 510 according to the frequency of the external clock signal CLOCK.

[0120] Furthermore, the measurement unit 614 corrects the frequency of the external clock signal CLOCK in accordance with the excitation method of the stepping motor 510, and compares the corrected frequency with the first threshold value. Therefore, it is not necessary to prepare multiple threshold values ​​in accordance with the excitation method, and it is possible to easily compare the frequencies using one threshold value.

[0121] Moreover, the clock signal CLOCK for measuring the characteristic amount is an external clock signal CLOCK input from outside the control unit 610 including the excitation control unit 623. Therefore, it is possible to simplify the configuration of the control unit 610 without generating an internal clock signal CLOCK.

[0122] (First Modification) A first modification of the above embodiment will be described with reference to Fig. 16. Fig. 16 is a circuit diagram of control unit 610a.

[0123] In the above embodiment, it was assumed that an external clock signal CLOCK was input from outside to the control unit 610, but in this modified example, an equivalent clock signal is generated within the control unit itself (without an external clock signal).

[0124] In the device configuration of this modified example, image forming apparatus 1 is used in which control unit 610 of the above embodiment is replaced with control unit 610a shown in FIG. 16, and parts similar to those in the above embodiment are given the same reference numerals and their description is omitted.

[0125] The control unit 610a has an excitation mode setting unit 611, an edge detection unit 612, a phase advance counter 613, a current table memory unit 615, a current value calculation unit 616, an oscillator 617, a clock generation unit 618, D / A converters 619, 620, comparators 621, 622, an excitation control unit 623, an excitation mode period generation unit 624, a clock generation control unit 625, and a clock generation unit 626.

[0126] The excitation mode period generating unit 624 has a ROM, holds a period table in the ROM, generates a signal MODE, and outputs the period table and the signal MODE. The period table has a pattern of periods as setting values ​​that determine the internal clock signal to be generated.

[0127] The clock generation control unit 625 generates a priority instruction and outputs it to the excitation control unit 623, similar to the measurement unit 614 in the above embodiment, in accordance with the signal MODE (corresponding excitation method) input from the excitation mode period generation unit 624, the edge detection signal input from the edge detection unit 612, and the period (setting value) of the periodic table acquired from the excitation mode period generation unit 624.

[0128] In addition, when the externally input signal ENABLE is turned on, the clock generation control unit 625 obtains the period table from the excitation mode period generating unit 624 to obtain the period (set value) for the internal clock signal, and outputs the obtained period to the clock generating unit 626 to turn on the output of the internal clock signal.

[0129] The clock generation unit 626 generates and outputs an internal clock signal CLOCK in response to the period (set value) input from the clock generation control unit 625 and the oscillation signal input from the oscillator 617. The excitation mode setting unit 611 outputs a setting signal for the excitation method of the stepping motor 510 in response to the signal MODE input from the excitation mode period generation unit 624. The edge detection unit 612 detects an edge for each period of the internal clock signal CLOCK input from the clock generation unit 626, and outputs an edge detection signal as an internal clock interrupt.

[0130] Furthermore, in the internal clock interrupt, the clock generation control unit 625 acquires the next period (set value) of the periodic table acquired from the excitation mode period generation unit 624 (as part of the internal clock generation control), and outputs and sets it to the clock generation unit 626. After that, the period (set value) of the periodic table continues to be set in the clock generation unit 626 every time an edge is output, and when all the determined periods (set values) have been set from the table, the setting operation in the clock generation unit 626 ends, and thereafter the frequency of the internal clock signal CLOCK becomes constant (because the set value of the clock generation unit 626 does not change).

[0131] The clock generation control unit 625 is configured to use the frequency of the internal clock signal CLOCK corresponding to the rotation speed of the stepping motor 510, the rotation speed according to the internal clock signal CLOCK, or the period of the internal clock signal CLOCK to determine the priority of the interrupt.

[0132] As described above, according to this modification, the clock signal CLOCK for measuring the period as a characteristic amount is the internal clock signal CLOCK generated within the control unit 610. Therefore, it is possible to eliminate the configuration for generating the external clock signal CLOCK.

[0133] (Second Modification) A second modification of the above embodiment will be described with reference to Fig. 17. Fig. 17 is a diagram showing a threshold value table 73.

[0134] In the above embodiment, the correction value table 71 and the threshold value table 72 are used to correct (adjust) the frequency of the external clock signal CLOCK due to the excitation method, and then a uniform threshold value is used for judgment. However, it is also possible to use characteristic quantities such as the frequency of the external clock signal CLOCK as they are, without adjusting for differences due to the excitation method, and to change the threshold value for each excitation method.

[0135] The device configuration of this modified example is the image forming apparatus 1 of the above embodiment, but the ROM of the measurement unit 614 is stored with the threshold table 73 shown in FIG. 17 instead of the correction value table 71 and the threshold table 72.

[0136] The threshold table 73 has items (columns) of excitation method and threshold. The excitation method item is the type of excitation method of the stepping motor 510. The threshold item is a threshold of a characteristic amount for setting a priority corresponding to the excitation method. In the example of FIG. 17, the threshold of the threshold table 73 is a rotation speed [rpm] according to the external clock signal CLOCK corresponding to the rotation speed of the stepping motor 510. However, the threshold of the threshold table 73 may be a frequency or period of the external clock signal CLOCK corresponding to the rotation speed of the stepping motor 510.

[0137] As described above, according to this modification, the measurement unit 614 compares the rotation speed of the stepping motor 510 corresponding to the excitation method of the stepping motor 510 with the threshold value of the excitation method. Therefore, it is not necessary to correct the characteristic amount (rotation speed), and the comparison of the rotation speeds can be easily performed.

[0138] (Third Modification) A third modification of the above embodiment will be described with reference to Figures 18 and 19. Figure 18 is a block diagram showing a control unit 610b and a higher-level control unit 601 in this modification. Figure 19 is a flowchart showing a second priority instruction process.

[0139] In the above embodiment, the measurement unit 614 in the control unit 610 is configured to execute the first priority instruction process, but in this modified example, a control unit higher than the control unit 610 is configured to execute the first priority instruction process.

[0140] In the configuration of this modified example, control unit 610 of the above embodiment is replaced with control unit 610b shown in Fig. 16. The same parts as those in the above embodiment are denoted by the same reference numerals, and their description will be omitted. Control unit 610b has a configuration in which measurement unit 614 is deleted from control unit 610.

[0141] The substrate 600 also has a control unit 601 as a higher-level control unit of the control unit 610b. The control unit 601 has a CPU, RAM, ROM, etc., and stores in the ROM a second priority instruction program for executing a second priority instruction process described later, and a threshold table having a period of an external clock signal CLOCK corresponding to the excitation method.

[0142] The control unit 601 also includes clock generation hardware that generates an external clock signal CLOCK and outputs it to the control unit 610b. The control unit 601 on the upper side that supplies the external clock signal CLOCK already knows at what frequency (= number of rotations) the device should be driven, and therefore the control unit 601 issues a priority instruction.

[0143] Next, the operation of the image forming apparatus 1 will be described with reference to Fig. 19. In the image forming apparatus 1, the control unit 11 executes a print process in response to operation information from a user via the operation unit 12, and the control unit 601 executes a second priority instruction process in accordance with a second priority instruction program stored in the ROM, using the start of control of paper conveyance by the conveyance unit 19 as a trigger.

[0144] 19, first, the control unit 601 acquires the period of the external clock signal CLOCK of the excitation method to be output to the control unit 610b (step S31). Since the general clock generation hardware included in the control unit 601 generates the external clock signal CLOCK by setting a count value corresponding to the period, here, the period is used instead of the frequency.

[0145] Then, the control unit 601 reads out the threshold table from the internal ROM, and determines whether or not the period is less than the second threshold using the period according to the excitation method acquired in step S31 and the threshold of the period corresponding to the excitation method in the threshold table (second threshold) (step S32). If the period is less than the second threshold (step S32; YES), the control unit 601 sets (2) the priority of the comparator interrupt INT1 > the priority of the current control period interrupt INT2 (step S33). If the period is greater than or equal to the second threshold (step S32; NO), the control unit 601 sets (1) the priority of the current control period interrupt INT2 > the priority of the comparator interrupt INT1 (step S34).

[0146] Then, the control unit 601 generates a priority instruction of the priority set in step S33 or S34, outputs it to the control unit 610b (step S35), and outputs it to step S31. The control unit 610b receives the external clock signal CLOCK generated by the control unit 601, and also receives the priority instruction output from the control unit 601 in step S35 as an input to the excitation control unit 623.

[0147] The control unit 601 may be provided on a part other than the substrate 600 of the image forming apparatus 1 .

[0148] As described above, according to this modification, the control unit 601 is disposed outside the control unit 610b including the excitation control unit 623, outputs the external clock signal CLOCK, and compares the period of the external clock signal CLOCK as a characteristic amount with the second threshold value. This simplifies the configuration of the control unit 610b.

[0149] (Fourth Modification) A fourth modification of the above embodiment will be described with reference to Fig. 20. Fig. 20 is a flowchart showing the third priority instruction process.

[0150] In the above embodiment, the measurement unit 614 is configured to execute the first priority instruction process. Regarding the first threshold, if the frequency of the external clock signal CLOCK is near the first threshold, the priority may frequently change due to measurement error, causing the current control to be disturbed and causing vibration. Therefore, in this modified example, two thresholds are provided and the priority instruction process has a hysteresis characteristic, thereby preventing the occurrence of vibration.

[0151] As the device configuration of this modified example, the image forming device 1 similar to that of the above embodiment is used, and the same reference numerals are used for the same parts as those of the above embodiment, and the description thereof is omitted. However, instead of the first priority instruction program, a third priority instruction program for executing a third priority instruction process described later is stored in the ROM of the measurement unit 614. Also, the threshold table 72 stores a third threshold and a fourth threshold for the frequency of the external clock signal CLOCK according to the excitation method. The third threshold and the fourth threshold are thresholds that take into account the hysteresis characteristic, and the fourth threshold is greater than the third threshold. It is desirable that the error (hysteresis width) between the fourth threshold and the third threshold is larger than the measurement error.

[0152] Next, the operation of the image forming apparatus 1 will be described with reference to Fig. 20. In the image forming apparatus 1, the control unit 11 executes a print process in response to operation information from a user via the operation unit 12, and the control of the transport of the paper by the transport unit 19 is started, which serves as a trigger for the measurement unit 614 to execute a third priority instruction process in accordance with a third priority instruction program stored in the ROM.

[0153] As shown in Fig. 20, steps S41 and S42 are similar to steps S11 and S12 of the first priority instruction process in Fig. 14. Then, the measurement unit 614 determines whether the content of the currently set interrupt priority instruction is (2) the priority of the comparator interrupt INT1>the priority of the current control period interrupt INT2 (step S43).

[0154] If the priority of the comparator interrupt INT1 is currently greater than the priority of the current control period interrupt INT2 (step S43; YES), the measurement unit 614 reads the threshold table 72 from the internal ROM, and uses the correction value of the frequency of the external clock signal CLOCK calculated in step S42, the excitation method setting signal input from the excitation mode setting unit 611, and the third threshold value of the threshold table 72 to determine whether the correction value of the frequency of the external clock signal CLOCK is less than or equal to the third threshold value of the excitation method in the threshold table 72 (step S44).

[0155] If the correction value of the frequency of the external clock signal CLOCK is less than or equal to the third threshold (step S44; YES), the measurement unit 614 executes step S45 and proceeds to step S41. Step S45 is the same as step S15 in Fig. 14. If the correction value of the frequency of the external clock signal CLOCK is greater than or equal to the third threshold (step S44; NO), the process proceeds to step S41.

[0156] If the priority of the comparator interrupt INT1 is currently less than the priority of the current control period interrupt INT2 (step S43; NO), the measurement unit 614 reads the threshold table 72 from the internal ROM, and uses the correction value of the frequency of the external clock signal CLOCK calculated in step S42, the excitation method setting signal input from the excitation mode setting unit 611, and the fourth threshold value of the threshold table 72 to determine whether or not the correction value of the frequency of the external clock signal CLOCK is greater than or equal to the fourth threshold value of the excitation method in the threshold table 72 (step S46).

[0157] If the correction value of the frequency of the external clock signal CLOCK is equal to or greater than the fourth threshold (step S46; YES), the measurement unit 614 executes step S47 and proceeds to step S41. Step S47 is the same as step S14 in Fig. 14. If the correction value of the frequency of the external clock signal CLOCK is less than the fourth threshold (step S46; NO), the process proceeds to step S41.

[0158] As described above, according to this modification, the measurement unit compares the frequency of the external clock signal CLOCK as a characteristic quantity with two different third and fourth thresholds, and generates a priority instruction to have a hysteresis characteristic according to the comparison result. This makes it possible to prevent the occurrence of vibrations caused by frequent priority switching and disturbance of current control due to the use of a single threshold.

[0159] (Fifth Modification) A fifth modification of the above embodiment will be described with reference to Fig. 21. Fig. 21 is a flowchart showing the fourth priority instruction process.

[0160] In the third modified example, the control unit 601 above the control unit 610a knows the period (or frequency, number of rotations) of the external clock signal CLOCK to be driven, but in the conveying unit 19 of the image forming apparatus 1, the driving frequency of the stepping motor 510 is inevitably determined by the operation mode of the apparatus. Therefore, in this modified example, the priority of the interrupt is determined by the operation mode, not by information such as the period, frequency, or number of rotations of the external clock signal CLOCK.

[0161] As the device configuration of this modified example, similar to the third modified example, image forming apparatus 1 including control unit 601 and control unit 610b is used, and the same parts as those in the above embodiment are denoted by the same reference numerals and their description is omitted. However, control unit 601 stores in ROM a fourth priority instruction program for executing a fourth priority instruction process described later.

[0162] Next, the operation of the image forming apparatus 1 will be described with reference to Fig. 21. In the image forming apparatus 1, the control unit 11 executes a print process in response to operation information including an operation mode selection from a user via the operation unit 12, and control of paper transport by the transport unit 19 is started, which is used as a trigger to cause the control unit 601 to execute a fourth priority instruction process in accordance with a fourth priority instruction program stored in the ROM. Here, it is assumed that there are two operation modes: a plain paper print mode in which plain paper is printed as the paper, and a thick paper print mode in which thick paper is printed as the paper. Information on the operation mode selection may be included in the print job.

[0163] As shown in FIG. 21, first, the control unit 601 acquires the set operation mode from the control unit 11 (step S51). Then, the control unit 601 determines whether or not the operation mode acquired in step S51 is the plain paper print mode (step S52). If it is the plain paper print mode (step S52; YES), the control unit 601 executes step S53. If it is the thick paper print mode (step S52; NO), the control unit 601 executes step S54. Then, the control unit 601 executes step S55 and moves to step S51. Steps S53, S54, and S55 are similar to steps S33, S34, and S35 of the second priority instruction process in FIG. 19. In the thick paper print mode, the paper transport speed is slow (the rotation speed of the stepping motor 510 is low), so the priority instruction is (1), and in the plain paper print mode, the paper transport speed is fast (the rotation speed of the stepping motor 510 is high), so the priority instruction is (2).

[0164] According to this modification, image forming apparatus 1 includes control unit 610b, image forming unit 17 that forms an image on paper, transport unit 19 that transports paper by rotating transport rollers and the like with the rotation of stepping motor 510, and control unit 601 that generates priority instructions according to a plain paper print mode and a thick paper print mode as operation modes with different rotation speeds of stepping motor 510. Therefore, it is possible to more easily prevent vibrations and temperature rises according to the priority instructions corresponding to operation modes with different rotation speeds of stepping motor 510.

[0165] The above-described embodiment and each of the modifications are merely examples of the preferred stepping motor control device, image forming device, and program according to the present invention, and are not intended to be limiting. For example, at least two of the above-described embodiment and each of the modifications may be appropriately combined.

[0166] In the above embodiment and each modified example, the driving target of the stepping motor 510 is the transport roller that transports the paper in the transport unit 19, but the present invention is not limited to this. The driving target of the stepping motor may be a driving means of an image forming device, such as a driving means for the optical system of a scanner of the image forming device, or a driving means of a device other than the image forming device.

[0167] Furthermore, the detailed configurations and operations of the components constituting the data processing device 10 in the above embodiment may be modified as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0168] 1. Image forming device 100 Image forming apparatus body 11 Control section 12 Control section 13 Display section 14 Storage section 15 Communications Department 17 Image forming section 17Y, 17M, 17C, 17K Image forming unit 171 Photoconductor drum 172 Charging section 173 Exposure Section 174 Development Section 175 Primary transfer roller 176 Cleaning Department 177 Intermediate transfer belt 178 Secondary transfer roller 18 Fixing section 19a Transport control section 600 Substrates 610, 610a, 610b, 601 Control unit 611 Excitation mode setting section 612 Edge detection unit 613 Advance Counter 614 Measuring section 615 Current table storage unit 616 Current value calculation section 617 Oscillator 618 Clock Generation Unit 619,620 D / A Converter 621,622 Comparator 623 Excitation control section 624 Excitation mode period generator 625 Clock Generation Control Unit 626 Clock Generation Unit 631 Pre-driver 632,633,634,635 FET 636,637 Shunt resistor 638,639 Operational Amplifiers 19 Conveyor section 510 Stepping Motor 511,512,513,514 Coil 520 Fuse 20 Paper feed section T1, T2, T3 paper tray 200 Paper feeder 21 Post-processing section 300 Aftertreatment device 22 Bus T4 Output Tray

Claims

1. A stepping motor, A drive unit that energizes the stepping motor and detects a current value; a comparator for determining whether the detected current value has reached a set current value; a current conduction pattern switching control unit that switches the current conduction pattern at a specified cycle; a comparator processing control unit that performs comparator processing to turn off power supply to the stepping motor in response to a determination result of the comparator; a current cycle control unit that performs current control cycle processing to turn on current supply to the stepping motor in accordance with a cycle of constant current control that controls a maximum amplitude of a periodic current waveform to a constant value; a priority instruction unit that generates a priority instruction to prioritize the comparator process when a characteristic amount corresponding to a rotation speed of the stepping motor corresponds to a high rotation speed range of the rotation speed, and to prioritize the current control period process when the characteristic amount corresponds to a low rotation speed range of the rotation speed; a priority setting unit that sets a priority between the comparator process and the current control period process in response to the priority instruction, The characteristic quantity is based on a clock signal, The priority instruction unit compares the characteristic quantity with a predetermined threshold value indicating a characteristic quantity at the boundary between the high rotation range and the low rotation range, and generates a priority instruction to prioritize the comparator processing when the characteristic quantity corresponds to the high rotation range side of the threshold value, and to prioritize the current control period processing when the characteristic quantity corresponds to the low rotation range side of the threshold value.

2. The stepping motor control device according to claim 1 , wherein the characteristic amount is a rotation speed of the stepping motor, or a frequency or period corresponding to the rotation speed.

3. 3. The stepping motor control device according to claim 1, wherein the priority instruction unit corrects the characteristic amount in accordance with an excitation method of the stepping motor, and compares the corrected characteristic amount with the threshold value.

4. 3. The stepping motor control device according to claim 1, wherein the priority indicator compares a characteristic amount corresponding to an excitation method of the stepping motor with the threshold value corresponding to the characteristic amount.

5. 5. The stepping motor control device according to claim 1, wherein the clock signal is an external clock signal input from outside a control means including the current pattern switching control unit, or an internal clock signal generated within the control means.

6. 6. The stepping motor control device according to claim 1, wherein the priority instruction unit is disposed outside a control means including the current conduction pattern switching control unit, outputs an external clock signal as the clock signal, and compares a characteristic amount based on the external clock signal with the threshold value.

7. 7. The stepping motor control device according to claim 1, wherein the priority indication unit compares the characteristic quantity with a third threshold value as the threshold value and a fourth threshold value that is higher than the third threshold value and generates the priority indication so as to have a hysteresis characteristic by prioritizing the current control period processing when the characteristic quantity corresponds to a lower rotation range than the third threshold value and by prioritizing the comparator processing when the characteristic quantity corresponds to a higher rotation range than the fourth threshold value.

8. A stepping motor; A drive unit that energizes the stepping motor and detects a current value; a comparator for determining whether the detected current value has reached a set current value; a current conduction pattern switching control unit that switches the current conduction pattern at a specified cycle; a comparator processing control unit that performs comparator processing to turn off power supply to the stepping motor in response to a determination result of the comparator; a current cycle control unit that performs current control cycle processing to turn on current supply to the stepping motor in accordance with a cycle of constant current control that controls a maximum amplitude of a periodic current waveform to a constant value; a priority instruction unit that generates a priority instruction to prioritize the comparator process when a characteristic amount corresponding to a rotation speed of the stepping motor corresponds to a high rotation speed range side of the rotation speed, and to prioritize the current control period process when the characteristic amount corresponds to a low rotation speed range side of the rotation speed; a priority setting unit that sets a priority between the comparator process and the current control period process in response to the priority instruction; and an image forming unit that forms an image on a sheet; a conveying unit that conveys the paper by rotating a roller by rotation of the stepping motor, The characteristic amount is an operation mode of the image forming apparatus in which the number of revolutions of the stepping motor differs.

9. A stepping motor, A drive unit that energizes the stepping motor and detects a current value; a comparator that determines whether the detected current value has reached a set current value, an energization pattern switching control unit that switches the energization pattern at a specified cycle; a comparator processing control unit that performs comparator processing to turn off power supply to the stepping motor in response to a determination result of the comparator; a current cycle control unit that performs current control cycle processing to turn on current supply to the stepping motor in accordance with a cycle of constant current control that controls the maximum amplitude of a periodic current waveform to a constant value; a priority instruction unit that generates a priority instruction to prioritize the comparator process when a characteristic amount corresponding to a rotation speed of the stepping motor corresponds to a high rotation speed range side of the rotation speed, and to prioritize the current control period process when the characteristic amount corresponds to a low rotation speed range side of the rotation speed; a priority setting unit that sets priorities between the comparator process and the current control cycle process in response to the priority instruction; Function as a The characteristic quantity is based on a clock signal, The priority instruction unit is a program that compares the characteristic quantity with a predetermined threshold value that indicates the characteristic quantity at the boundary between the high rotation range and the low rotation range, and generates a priority instruction that prioritizes the comparator processing when the characteristic quantity corresponds to the high rotation range side of the threshold value, and prioritizes the current control period processing when the characteristic quantity corresponds to the low rotation range side of the threshold value.

Images