JP5448519B2 - Motor drive device and image forming apparatus - Google Patents

Description

  The present invention relates to a motor drive device and an image forming apparatus, and more particularly, to a motor drive device using a stepping motor, mainly to applications in the fields of image forming apparatuses, copiers, printers, and multifunction peripherals.

  The following proposals have been made as conventional techniques for a low power drive method of a stepping motor.

  For example, in Patent Document 1, a stepping motor is rotated by flowing a sufficient phase current that does not step out in advance, and a step-out point is detected by gradually lowering the phase current. It is disclosed to drive a motor by giving it to a driver.

  Further, for example, in Patent Document 2, when the motor drive current is increased, the motor drive current control signal is changed stepwise, and when the motor drive current control signal is decreased, the motor drive current control signal is gradually decreased. The structure to perform is disclosed.

  Further, for example, Patent Document 3 discloses that the current value is determined and optimized from the step-out detection of the step-out detection means when the current is reduced.

JP 05-146505 A JP 2004-180353 A Japanese Patent Laid-Open No. 11-215890

  In the conventional low power drive method for stepping motors, it takes time to gradually reduce the phase current from a state where a large margin is added to the phase current value for stable rotation, and a relatively large surplus of power is required. Has occurred and power loss has increased. Further, when the step-out point is found by lowering the phase current for each driving frequency of the motor, further time loss cannot be denied.

  The present invention has been made paying attention to the above points, and is intended to shorten the time required for detecting a step-out point, reduce power consumption, and obtain a stable motor rotation without step-out. Let it be an issue.

  In order to solve the above problems, the present invention comprises the following arrangement.

(1) Motor, drive means for driving the motor, detection means for detecting the rotational speed of the motor driven by the drive means, and switching for switching a current value for the drive means to drive the motor And a control means for controlling the switching of the current value of the switching means, wherein the control means uses the driving means as a first current value for the motor itself. A second current that is different from the first current value from the first current value by the switching means while driving the motor at the starting frequency and driving the motor at the self-starting frequency. controlled so as to switch to a value, in the plurality of sections of continuous when being the motor driving in the first current value, maximum times detected by said detecting means Speed and the first difference information between the minimum rotational speed, the plurality of sections of continuous when they are the motor driven by the second current value, and the maximum rotational speed and the minimum rotational speed detected by said detecting means Based on the second difference information , the current value after the second current value is controlled so that the motor does not step out, and the current value after the second current value is the first difference information. A motor drive device characterized by a value corresponding to a step-out current value obtained from the second difference information, the first current value, the second current value, and step-out point information under a predetermined condition .

( 2 ) An image forming apparatus comprising the motor driving device according to (1 ) .

  According to the present invention, it is possible to shorten the time required to detect a step-out point, reduce power consumption, and obtain stable motor rotation without step-out.

  Specifically, it is possible to predict a phase current value that can be stepped out from the output counter value of the encoder when the phase current is temporarily changed in the same time as in the prior art by the startup self-starting frequency drive at the time of motor startup. In particular, by predicting the out-of-step current for each job, it is possible to take into account the variation of load torque of the motor load system in each device, changes over time such as part life, and the influence of environmental characteristics. A system can be constructed.

  Furthermore, by giving a margin to the predicted phase current value that can be stepped out and calculating the phase current with a coefficient that takes into account the torque change due to the rotation speed of the motor, the excess current is reduced and stable. A motor drive device that does not step out can be provided.

The figure which shows the system configuration | structure of the motor drive device which concerns on Example 1. FIG. The figure explaining the detailed structure content of the motor drive device which concerns on Example 1. FIG. The figure which shows the internal circuit example of the REF voltage switching part which concerns on Example 1. FIG. The figure which shows the motor drive current pattern of each phase of the motor phase drive line at the time of driving a motor using the motor driver which concerns on Example 1. FIG. (A) The figure which shows the conventional electric current sequence, (b) The figure which shows the conventional motor rotational speed The graph which shows the motor rotational speed and motor torque which concern on Example 1. The figure which shows the motor drive current pattern of each phase of the motor phase drive line corresponding to the D section and E section of FIG. (A) The figure which shows the electric current sequence of Example 1, (b) The figure which shows the motor rotational speed of Example 1. (A) The figure which shows C part and D part of the electric current sequence of Fig.8 (a), (b) The figure which shows the phase current when the current sequence changes in C part 100% and D part 80%, (c ) Diagram showing logic output signal of motor phase angle output section (A) FIG. 8 (a) is a diagram showing the C part and D part of the current sequence, (b) is a diagram showing the logic output signal of the motor phase angle output unit, (c) by the sampling timing inside the motor phase angle detection unit The figure which shows the continuous count period when the logic output signal of the motor phase angle output unit is sampled Table illustrating count output values in the continuous count period of FIG. (A) The graph which plotted the torque ripple accompanying the motion of the motor by the difference in the phase current which concerns on Example 1, (b) The figure which shows the position of the rotor of the motor which concerns on Example 1. FIG. (A) The figure which plotted the numerical value which divided the period T for 1pps by the count output value of a motor phase angle detection part, (b) The figure which shows the torque ripple of FIG. 12 (a), (c) Motor phase angle output part Diagram showing the logic output signal The graph which shows the relationship between the phase electric current which concerns on Example 1, and the ratio (DELTA) T of a torque ripple (A) The figure which compares and shows the current sequence which concerns on Example 1, 2 and the current sequence which concerns on a prior art example, (b) The figure which shows the motor rotational speed which concerns on Example 1, 2. (A) FIG. 8 (a) is a diagram showing the C part and D part of the current sequence, (b) is a diagram showing the logic output signal of the motor phase angle output unit, (c) by the sampling timing inside the motor phase angle detection unit The figure which shows the continuous count period when the logic output signal of the motor phase angle output unit is sampled Table illustrating count output values in the continuous count period of FIG. FIG. 6 is a diagram illustrating an appearance of a printer that is an example of an image forming apparatus according to a second embodiment. FIG. 10 is a diagram illustrating a configuration of a printer that is an example of an image forming apparatus according to a second embodiment. 10 is a flowchart illustrating a change sequence of a motor phase current value in the image forming apparatus according to the second embodiment.

  The mode for carrying out the present invention will be described in detail below with reference to examples.

<System configuration of motor drive device>
FIG. 1 shows a system configuration of a motor driving apparatus according to an embodiment of the present invention.

  The motor 1 includes a stepping motor, but can be implemented by a DC motor or the like. The drive shaft of the motor 1 is attached with a disk on which a black radial line is printed on a transparent disk at regular intervals along the circumference. The width of the line on the disk is printed so as to match the width of the gap between the lines. The sensor unit 2 has a light emitting unit and a light receiving unit that are provided so as to sandwich the disk, and when the black portion on the disk comes to the position of the light receiving unit during motor rotation, the light to the light receiving unit is blocked, When the transparent part of the disc reaches the position of the light receiving part, light enters the light receiving part. The sensor unit 2 outputs a signal photoelectrically converted by the light receiving unit as an output electric signal 3. The motor phase angle output unit 4 that is a phase angle output means forms a waveform from the input of the output electric signal 3 of the sensor unit 2 and generates a high (transparent portion) and a low (black portion) (hereinafter referred to as “HI”, “HIGH”). A logic output signal 11 (denoted LOW). Here, the motor phase angle output unit 4 may be, for example, an encoder, a resolver, a frequency generator FG (Frequency generator) using a Hall element, or the like. The motor phase angle output unit 4 outputs the logic output signal 11 to the motor phase angle detection unit 5 serving as detection means.

  The motor phase angle detection unit 5 samples the logic output signal 11 with a high-speed clock, counts the number of consecutive logic levels, and uses the data bus signal line 12 to count the counted value to the arithmetic processing unit 6 that is a control means. Forward. Here, the arithmetic processing unit 6 has a configuration capable of performing a hard logic operation including a programmable semiconductor device including an CPU (Central Processing Unit) or a DSP (Digital Signal Processing Unit) or an ASIC (Application Specific Integrated Circuit).

  The arithmetic processing unit 6 performs an operation based on the count value obtained by counting the number of consecutive logical levels and the change point thereof. The calculation result of the calculation processing unit 6 is sent to the motor driver unit 8 as the driver means by the phase control signal 10 through the signal line 13 and the motor driver phase current instruction unit 7 as the phase current instruction means. Then, the switching instruction of the phase current 9 output by the motor driver unit 8 is performed.

<Detailed configuration of motor drive device>
A more detailed configuration will be described with reference to FIG.

  The motor driver phase current instruction unit 7 in FIG. 1 corresponds to the REF voltage switching unit 105, and the arithmetic processing unit 6 in FIG. 1 corresponds to the CPU 101, ROM 102, and RAM 103. The motor driver unit 8 in FIG. 1 corresponds to the motor driver 107.

  The CPU 101 is connected by a bus signal line 114 to a ROM 102 that stores program data for controlling the operation of the CPU 101 and a RAM 103 that temporarily stores data calculated by the CPU 101. The bus signal line 114 includes an address line, a data line, and a line for transmitting a control signal such as a chip select signal, a memory read signal, and a memory write signal. The CPU has a built-in counter and timer that counts according to the basic clock for driving the CPU 101 or according to the divided clock, and outputs a pattern of the phase excitation signal 111 and a sequential instruction to the REF voltage switching unit 105. Is used. The basic clock is supplied from the outside of the CPU 101 by a crystal resonator or a crystal vibrator.

  The motor 108 corresponds to the motor 1 in FIG. 1 and is a stepping motor. The motor driver 107 is connected to the motor phase drive line 109, and is composed of four lines of A phase, B phase, anti-A phase, and anti-B phase. The current directions of the A-phase line and the anti-A-phase line are opposite to each other, and the absolute values of the current values are approximately equal. Similarly, the current directions of the B phase and the anti-B phase are opposite, and the absolute values of the current values are approximately equal. The driving of the stepping motor itself may be full step, half step, or micro step.

  The motor driver 107 is a semiconductor IC device and uses a motor driving power source 106 as a phase excitation power source for the motor 108. The motor driver 107 has a reference signal input for changing the phase excitation current of the motor 108 in response to the REF signal 112 from the REF voltage switching unit 105. The motor driver 107 drives (drives) the motor phase drive line 109 of the motor 108 according to the instruction pattern in accordance with the input pattern instruction of the phase excitation signal 111 from the CPU 101.

  The REF voltage switching unit 105 changes the voltage of the REF signal line 112 stepwise by an instruction from the CPU 101 via the port line 113 by a program built in the ROM 102. Here, the port line 113 corresponds to the signal line 13 in FIG. 1, and the REF signal 112 corresponds to the signal line of the phase control signal 10 in FIG. Reference numeral 104 denotes a logic power source.

About the configuration of the REF voltage switching unit 105
FIG. 3 illustrates an internal circuit example of the REF voltage switching unit 105. In this example, the port line 113 corresponds to three lines 113-1, 113-2, and 113-3, and each port signal of 113-1, 113-2, and 113-3 is at a high level and each transistor. Drive. The potential of the REF signal 112 is determined by the state of each transistor and the voltage dividing ratio of the resistor 117, the resistor 118, the resistor 119, and the resistor 116 connected to the collector.

About motor drive current pattern
A motor drive current pattern flowing in the motor phase drive line 109 when the motor 108 is driven using the motor driver 107 is shown in FIG. FIG. 4 shows a half-step driving method as a representative driving method, and shows a case where the motor excitation current is not switched by the REF signal 112 by the REF voltage switching unit 105. The vertical axis represents the current value, and the motor driver 107 performs constant current control corresponding to the reference potential of the REF signal 112 to reach a current value of 100% in the positive direction and a current value of 100% in the negative direction.

  As described above, the A phase and the anti-A phase are in opposite phases. The B phase and the anti-B phase are opposite phases, but the A phase and the anti-A phase form current waveforms having different phases as shown in FIG. In addition, a, B, C, D part in a figure is mentioned later.

-Description of a conventional example for comparison with the present embodiment-
FIG. 5 is a diagram showing the relationship between a conventional current sequence and the rotational speed of the motor.
FIG. 5A shows a current sequence, and FIG. 5B shows a motor rotation speed.

  For example, according to a program in the ROM 102, the CPU 101 uses the phase excitation signal line 111 to drive the motor 108 to the motor driver 107. The motor phase drive line 109 is a phase A, anti-A phase, B phase, anti-B phase. Is controlled as shown in FIG. The CPU 101 performs the following control when starting to drive the motor 108. That is, 100 ms before the start of driving, the REF voltage switching unit switches the level of the REF signal 112 by the port line 113 in FIG. 2 or the port line 113-1, the port line 113-2, and the port line 113-3 in FIG. 105 is instructed. Then, the phase excitation current value is changed from the A part to the B part in FIG. In part B of FIG. 5, the drive with the excitation pattern of FIG. 4 is not performed, so the excitation is phase-fixed in a one-phase or half-step state, and the motor does not rotate and is in the hold (hereinafter referred to as HOLD) state. It is. Further, after a lapse of 100 ms, the motor 108 is rotated by the drive pattern shown in FIG. At this time, the time a in FIG. 4 is gradually changed from a large time to a small time (C portion in FIG. 5) in consideration of the influence of the load torque on the motor shaft and its inertia. The state becomes stable (D section in FIG. 5) at the determined target time.

  In FIG. 5, when the portion D has elapsed for 100 ms, the CPU 101 controls as follows according to the program in the ROM 102. That is, the CPU 101 controls the port line 113 of the CPU 101 so that the REF signal 112, which is the output voltage of the REF voltage switching unit 105, becomes approximately 75% when the D unit current value is 100%. In order to set the REF signal 112 to 75%, the CPU 101 sets the states of the port lines 113-1, 113-2, and 113-3 in FIG. 3 and the resistors 116, 117, 118, and 119 in advance. Control by value (E section in FIG. 5).

  The reason why the phase current value of the motor is increased when the motor is started as shown in FIG. 5 will be described with reference to FIG. FIG. 6 is a graph showing motor rotation speed and motor torque. As shown in FIG. 6, when pull-in (motor drive) (indicated by a broken line) is started at a motor rotation speed R1 pps (shown by a broken line) at a motor drive current of 75% (the motor phase excitation current is not changed), the torque that can be generated by the motor 108 is 6 Td points. Compared with the motor drive current 75% pull-out (indicated by a broken line) (Tb point), the generated torque value is considerably reduced. For this reason, there is a possibility that the motor 108 cannot be pulled in depending on the load to be rotated. Therefore, it is necessary to temporarily increase the motor drive current immediately before starting. 5 is a pull-out region where the inertia and rotation due to the load of the motor are stable, there is a problem of thermal destruction due to heat generation of the motor 108 and the motor driver 107 due to a high motor drive current value. The drive current value is lowered.

  7 represent current sequences of the respective phases of the motor phase drive line 109 of the motor 108 corresponding to the D and E parts in FIG.

<About this example>
In this embodiment, the current sequence of FIG. 5 is changed as shown in FIG. FIG. 8A is a diagram showing the current sequence of this embodiment, and FIG. 8B is a diagram showing the motor rotation speed.

  Control of the A part and the B part of FIG. 8 is the same as the description of the A part and the B part of FIG. In this embodiment, the rotation of the motor 108 is started at the maximum value of the self-starting frequency. The current at this time is assumed to be C part 100% (first current value).

  Further, rotation is performed at the self-starting frequency, and the phase current is reduced to a current value (second current value) of 80% as in the D part. Thereafter, in the E part, the rotational speed is gradually accelerated to the motor rotational speed of 100% of the target.

  The current X1% in FIG. 8A at this time is based on the detection result data from the motor phase angle detection unit 5 by the logic output signal 11 of the motor phase angle output unit 4 of the motor 108 during the period of the C part and the D part. CPU101 calculates.

  FIG. 9A shows a C part and a D part of the current sequence of FIG. FIG. 9B shows the phase current (A phase, anti-A phase, B phase, anti-B phase) when the current sequence is switched between C part 100% and D part 80%. Represents the relationship of the logic output signal 11 of the motor phase angle output unit 4.

  Further, FIG. 10 shows details of the K portion surrounded by an ellipse in FIG. FIG. 10A shows a C part and a D part of the current sequence shown in FIG. FIG. 10B shows the logic output signal 11 of the motor phase angle output unit 4. FIG. 10C illustrates continuous count periods a to q which are a plurality of continuous sections when the logic output signal 11 of the motor phase angle output unit is sampled at the sampling timing inside the motor phase angle detection unit 5. . The table of FIG. 11 illustrates count output values (transmitted to the CPU 101 via the data bus signal line 12 and hereinafter referred to as count output value 12) (see FIG. 2) in the continuous count periods a to q.

  FIG. 12 (a) plots the torque ripple accompanying the movement of the motor 108 due to the difference in phase current. FIG. 12B illustrates the position of the rotor of the motor 108. When driving the motor 108 at the self-starting frequency, the CPU 101 has at least two types, in this embodiment, 100% and 80% of the phase current values of the motor phase angle output unit 4 based on the time information from the phase angle output unit 4 and the torque ripple due to the phase current change. The phase current value out of phase is derived from the change in the ratio. 12A shows the torque generated in the rotor when the magnet of the magnetized rotor at the position aa of the motor 108 in FIG. 12B moves to the cc point in response to the switching of the phase excitation signal 111. FIG. Indicates. The torque generated at the point bb where the electrical angle is 0 is the largest at bb, the torque generated by the motor 108 is small at the rotation start point (apparently) point aa and the rotation end point cc, and the torque curve is shown in FIG. As shown in (a), it fluctuates and appears as a ripple. As for the torque value generated at each of the points aa to cc, the 100% phase current is larger than the 80% phase current value, and the ripple as a whole increases.

  FIG. 13A plots the numerical value (T / count value) obtained by dividing the period T for 1 pps by the count output value 12 of the motor phase angle detector 5. FIG. 13B shows the torque ripple of FIG. 12A and FIG. 13C shows the logic output signal 11 of the motor phase angle output unit 4. Here, the period T is a time when moving by one rotation angle. ΔC is the difference between the maximum value and the minimum value within the period T of a numerical value (T / count value) obtained by dividing the period T by the count output value 12 of the motor phase angle detector 5. As shown in FIGS. 13A and 13B, it can be seen that there is a correlation between the T / count value and the torque fluctuation.

  Immediately after changing the rotation speed of the motor 108, the count values of the periods T and a to q are unstable due to speed ripple. Therefore, it is necessary to use ΔC at a point where the rotation of the motor 108 is stable, and the CPU 101 can determine from the output of the motor phase angle detection unit 5 whether the rotation of the motor 108 is stable. Since the value obtained by multiplying the values of ΔC100% and ΔT100% in FIG. 13A and the value obtained by multiplying the values of ΔC80% and ΔT80% show close values, the motor phase angle detection unit when the current is changed The torque ripple ratio ΔT can be derived from the count output value 12 of 5. Here, as will be described with reference to FIG. 14, when the phase current value of the motor 108 during rotation driving is changed (decreased), even when there is no load (the motor is not incorporated in the device) Even when the motor is incorporated in the device, the step-out occurs when the torque ripple ratio ΔT is reached. Therefore, the torque when the phase current value is changed by the motor 108 when there is a load is obtained by changing the phase current value by the motor 108 when there is no load in advance, and obtaining the step-out point when stepping out. If the ratio of ripple is estimated, the out-of-step current under load can be estimated. As a result, the motor 108 can be driven with a current value with a margin of the step-out current by obtaining the step-out current according to the mechanical load of the device, and wasteful power consumption is avoided while avoiding the step-out. Can be prevented.

  For example, the case of FIG. 8 obtained from the output from the count output value 12 of the motor phase angle detector 5 in a state where a load is connected to the motor in the actual system will be described. In FIG. 8, the relationship between ΔC100% in part C and ΔC80% in part D can be represented as shown in FIG. 14 between ΔC80% −ΔC100% and torque ripple ratio ΔT. FIG. 14 is a graph showing the relationship between the phase current and the torque ripple ratio ΔT.

When ΔT (100% -A%) that steps out at no load from the ΔT characteristic (no load characteristic) in a no-load state in advance, the phase current 100% and the phase current 80% by the load system From ΔT, the step-out current due to the load system is
I = K1 × (phase current 100% −phase current 80%) × ΔT (100% −A%) / ΔT (100% −80%) + K2
It becomes.

A% represents the phase current value at the torque at which the motor steps out.
The values of K1 and K2 are values that represent the difference between when there is no load and when there is a system load, and need to be measured and determined in advance.
K1 is a coefficient having linearity indicating the slope of the current-torque characteristic when there is no load and when the system is loaded, and has a different value depending on the characteristics of the motor.
K2 is a difference of step-out current at no load and system load.

  The value converted from the value of ΔC to the count output value 12 of the motor phase angle detector 5 is used for ΔT.

ΔT (100% -A%) × ΔC (A% -100%) ≈ΔT (100% -80%) × ΔC (80% -100%)
Is subject to advance calculation,
ΔT (100% -80%) ≈K3 × ΔC (80% -100%)
ΔT (100% −A%) ≈K3 × ΔC (A% −100%)
Can be converted to

K3 is a coefficient, and the value depends on the values of the no-load characteristics ΔT (100% -80%) and ΔC (80% -100%) measured in advance. K3≈ΔT (100% -80%) / ΔC (80% -100) %)
Ask for.

The step-out current is
I = K1 × (phase current 100% −phase current 80%) × K3 × ΔC (A% −100%) / (K3 × ΔC (80% −100%)) + K2
And
I = K1 × (phase current 100% −phase current 80%) × ΔC (A% −100%) / ΔC (80% −100%) + K2
It becomes.

  The CPU 101 calculates the step-out current due to the load system in the C part and D part of the current sequence of FIG. 8A, and the reference current X3% on the acceleration sequence of the E part is determined. Further, a specific coefficient is added as a margin to the step-out current to reflect the phase current value on the acceleration sequence (X1%), and the CPU 101 instructs the REF voltage switching unit 105 to switch the REF signal 112.

Here, in the present embodiment, a current sequence for increasing the current value according to the motor rotation speed in the E part acceleration sequence is reflected by reflecting that the motor torque changes as shown in FIG. 6 according to the motor rotation speed. carry out. The amount of change in the motor rotational speed versus phase current value uses the slope of the motor drive current 100% pullout torque approximation line (thin solid line) in FIG. The Te point (drive speed TOP) (motor rotation speed R2pps) in FIG.
1− (Tf point torque−Te point torque) / (R2pps−R1pps) × Xpps
Xpps is the target frequency. Except for the target frequency Xpps, the measurement is performed based on the pre-measured characteristics of the motor at no load, and is stored as data in the ROM 102. In FIG. 8 (b), the motor rotation speed is increased to 100% in the F part and the G part, and the phase current of the motor is also X2% as shown in FIG. 8 (a).

  An embodiment in which the current sequence is reflected in the image forming apparatus is described with reference to FIG.

  C and D in FIG. 15 are drive regions at the self-starting frequency of the motor 108. When the motor 108 is driven, if the count output value 12 of FIG. 2 as phase information does not fall within a predetermined range, the current value is increased to a predetermined value of MAX within one motor step number. Increase the motor torque. Further, a sufficient torque margin with respect to the mechanical load can be taken and step-out can be prevented.

  This will be described with reference to FIG. FIG. 16A shows a C part and a D part of the current sequence shown in FIG. FIG. 16B shows the logic output signal 11 of the motor phase angle output unit 4. FIG. 10C illustrates the continuous count periods aa to qq when the logic output signal 11 of the motor phase angle output unit 4 is sampled at the sampling timing inside the motor phase angle detection unit 5. Part C in FIG. 16A starts self-starting with the phase current set to a predetermined phase current value (100%) as in part C in FIG. In the self-starting region after a plurality of hours have passed after passing the pull-in region and entering the pull-up region, the D portion in FIG. 16B reduces the phase current value to 80%. As an example, the count output value 12 at this time is shown in FIG. The count output value in the jj period of FIG. 16C shows about 4600. However, when the normal range of the count value is set in advance as 4420 to 4500, the jj period is out of the normal range.

  The zz period in FIG. 16C indicates that the count value of the count output value 12 in FIG. 2 has passed 4500. After the zz period has elapsed, the CPU 101 uses the port line 113 from the REF voltage switching unit 105 to the motor driver. The REF signal 112 to 107 is changed. As shown in FIG. 16A, in the self-starting frequency region of the D part, 80% is set with respect to 100% of the phase current in the rising self-starting frequency region of the C part. In FIG. 16, when the output from the motor phase angle detector 5 does not change even after the lapse of 4500 counts with the phase current set to 80%, the phase current is immediately changed to 110%. It shows how it is. Even when the output from the motor phase angle detector 5 is changed below the count value 4420 described above, the motor is obtained by instantly increasing the phase current to 110% and improving the torque margin at the time of the change. It is also possible to contribute to the stable operation.

  Furthermore, after the phase current of the motor 108 is increased to 110%, the count output value 12 from the motor phase angle detector 5 does not fall within the predetermined count value 4420-4500 range for a plurality of times. At this time, the following processing is also possible. That is, in such a case, it is possible to determine that the motor 108 is out of step, stop the apparatus, and perform processing such as warning. It is premised that the count value and the phase current REF value based on the count output value 12 from the motor phase angle detector 5 are determined in advance according to the operation of the apparatus.

  As described above, the present embodiment starts driving at the self-starting frequency of the motor, extracts a change in time from an output signal from an encoder or the like as phase angle output means when the current is changed, and estimates a step-out current. It is characterized by that.

  In addition, the numerical value and percentage which were described in the Example are an example for description.

  As described above, according to the present embodiment, it is possible to construct a motor drive system that is low in power and does not stably step out compared to the prior art.

  In the first embodiment, the configuration of the motor driving device has been described. In the second embodiment, the current sequence applied to the motor driving device described in the first embodiment is reflected in the system of the image forming apparatus. Here, FIG. 15A shows a current sequence in the image forming apparatus including the motor drive device of the first embodiment, and FIG. 15B is a diagram showing the motor rotation speed. FIG. 15A also shows the phase current of the conventional example for comparison with the phase current of the present embodiment, and the portion corresponding to the phase current reduction is shaded.

<Regarding Image Forming Apparatus to Which Motor Drive Device of Embodiment 1 is Applied>
18 and 19 show a configuration and an external view of a printer that is an example of an image forming apparatus using the motor drive device of this embodiment.

  A printer main body 600, which is an image forming apparatus, a main body substrate unit 76, and a paper transport cassette 601 are shown.

  When an image formation start signal is issued from, for example, a personal computer connected to the image forming apparatus or an operation unit (not shown) to perform a copying operation, the paper feeding operation is started from the selected cassette or manual feed tray. For example, the case where the paper is fed from the paper transport cassette 601 will be described. First, the recording medium P is sent out one by one from the cassette by the pickup roller. In this embodiment, the motor 108 described in the first embodiment is used for driving a pickup roller, for example. The recording medium P is guided between the paper feed guides 18 and conveyed to the registration rollers 19. At that time, the registration roller 19 is stopped, and the leading edge of the paper hits the nip portion of the registration roller 19. Here, the registration sensor 131 detects that the recording medium P has been conveyed to the registration roller 19. Thereafter, the registration roller 19 starts rotating based on a timing signal at which the image forming unit starts forming an image. The rotation timing is set so that the recording medium P and the toner image primarily transferred onto the intermediate transfer belt 80 from the image forming unit exactly coincide with each other in the secondary transfer region. The intermediate transfer belt 80 has moved in the direction of arrow A in the figure.

  On the other hand, when an image forming operation start signal is issued in the image forming unit, electrostatic latent images are formed on the photosensitive drums 2a to 2d of the respective colors. Note that the subscript a corresponds to yellow (Y), b corresponds to magenta (M), c corresponds to cyan (C), and d corresponds to black (BK). The image forming timing in the sub-scanning direction is determined and controlled in accordance with the distance between the image forming units in order from the photosensitive drum (Y in the case of FIG. 17) located upstream in the rotation direction of the intermediate transfer belt 80. Here, the sub-scanning direction is a moving direction of the photosensitive drums 2 a to 2 d and the intermediate transfer belt 80. Further, the writing timing in the main scanning direction of each of the photosensitive drums 2a to 2d is controlled by generating a pseudo BD sensor signal using one BD sensor signal (arranged in BK in this embodiment) by a circuit operation (not shown). To do. The main scanning direction is a direction perpendicular to the moving direction (rotating direction) of the photosensitive drums 2a to 2d and the intermediate transfer belt 80, and is a direction perpendicular to the sub-scanning direction.

  The formed electrostatic latent image is developed by the process described above. The toner image formed on the photosensitive drum 2a at the most upstream is primarily transferred to the intermediate transfer belt 80 in the primary transfer region 32a by the primary transfer charger 5a to which a high voltage is applied. The primarily transferred toner image is conveyed to the next primary transfer region 32b. In the primary transfer region 32, image formation is performed with a delay by a time during which the toner image is conveyed between the image forming portions by the timing signal described above. In the primary transfer area 32b, the next toner image (in this case, a magenta toner image) is transferred onto the previous image (in this case, a yellow toner image) by aligning the resist. Thereafter, the same process is repeated in the primary transfer regions 32 c and 32 d, and eventually, four color toner images are primarily transferred onto the intermediate transfer belt 80.

  Thereafter, when the recording medium P enters the secondary transfer region (secondary transfer roller 120) and contacts the intermediate transfer belt 80, a high voltage is applied to the secondary transfer roller 120 in accordance with the passing timing of the recording medium P. Then, the four color toner images formed on the intermediate transfer belt 80 by the above-described process are transferred onto the surface of the recording medium P. After the secondary transfer, the recording medium P is accurately guided to the nip portion of the fixing roller by the conveyance guide 34. The toner image is fixed on the surface of the recording medium P by the heat of the fixing film 16a and the pressure roller 16b and the pressure of the nip portion. Thereafter, the recording medium P is conveyed by the outer paper discharge roller 21, and the recording medium P is discharged to the outside of the apparatus to complete a series of image forming operations.

  In this embodiment, yellow, magenta, cyan, and black are arranged in this order from the upstream side, but this is determined by the characteristics of the apparatus and is not limited to this.

  Control of the motor, which is a feature of the present embodiment, is performed by the motor 108, the motor phase drive line 109, and the circuit configuration shown in FIG.

<Current sequence and motor rotation speed in image forming operation>
An embodiment will be described with reference to FIG. The operation when the same control as that in FIG. 8 described in the first embodiment is performed between jobs such as paper conveyance (shown as JOB) is as follows. That is, when an activation factor such as the next job is input in the I part of FIG. The CPU 101 switches the phase current between the C part and the D part, and detects the rotational speed of the motor 108 by the motor phase angle detection part 5 via the sensor part 2 and the motor phase angle output part 4. The CPU 101 introduces a step-out current based on the count output value 12 from the sensor unit 2, the motor phase angle output unit 4, and the motor phase angle detection unit 5, which can be called a speed detection system, adds a margin, and rotates the motor in the acceleration sequence of the E unit. Increase speed. In this way, the rotational speed of the motor 108 is increased to the required rotational speed. Since the conventional phase current has a torque margin at the TOP speed in advance at any speed, it is almost always determined by a value of 120% as shown in FIG. In the image forming apparatus of the present embodiment, as described in the first embodiment, a current sequence (hereinafter referred to as a step-out step) in which the motor 108 is accelerated by adding a margin to the step-out current obtained from the count values of the C and D portions. Operate according to current + margin + current sequence). Thus, the difference from the change in current according to the rotation speed of the motor 108 is the amount of phase current reduction shown in FIG. 15, and it can be clearly seen that this embodiment can contribute to the reduction of power. .

  FIG. 20 is a flowchart showing a change sequence of the excitation current (phase current) value of the motor in the image forming apparatus.

  FIG. 20 will be described together with the sequence of FIG. In part I of FIG. 15, the phase current is 50%, the excitation phase of the motor 108 is fixed (HOLD), and the motor is stopped. Here, when an activation factor such as a next job for image formation is input, the CPU 101, the ROM 102, and the RAM 103 start driving the motor according to a program described in advance in the ROM 102 (step 201 (hereinafter referred to as S201). That is, the CPU 101 increases the current value of the motor 108 to 100% in the portion C of FIG.15 (a), and the CPU 101 increases the current value of the motor 108 to 100% and at the same time, Driving the motor can be started by giving a motor phase drive signal.

  When the motor drive is started in S201, the output electric signal 3 from the encoder is changed in S202, and at the same time, the CPU 101 starts a count timer 1 (hereinafter simply referred to as timer 1), and outputs the encoder output (each change interval) during this period. Count. In S203, the CPU 101 refers to the value of the timer 1 and determines whether or not a predetermined time has elapsed. If the CPU 101 determines in S203 that the predetermined time has elapsed, the process proceeds to S204. In S204, the phase excitation current value of the motor 108 is lowered to 80%, the timer 2 is started, and the encoder output (each change interval) is counted. As described above, the section where the phase excitation current value is 100% is the C section in FIG. 15, and the section where 80% is the D section. The CPU 101 obtains the slope of the torque ripple ratio ΔT from the difference (ΔC100%, ΔC80%) between the lowest count value and the highest count value in each change interval of the 100% and 80% phase current values. Then, the CPU 101 derives a current value indicating the same value as ΔT (ΔC80% −ΔC100%) that is stepped out without load in advance (see FIG. 14).

  Further, in S205, the CPU 101 refers to the value of the timer 2 and determines whether or not a predetermined time has elapsed. When the CPU 101 determines in S205 that the predetermined time has elapsed, the process proceeds to S206. In FIG. 15, after a predetermined time has elapsed from the start of timer 2, the stage of part E is entered. In the stage of section E, that is, S206, the motor drive frequency is gradually changed from the self-starting frequency to a drive frequency necessary for operating as an actual system. The motor phase current value is changed to a value obtained by adding a margin and a speed margin to the calculated value of the step-out current. The margin is a value that takes into consideration in advance the torque variation of the motor itself, the variation intersection of the current value, and the variation of the mechanical load. In addition, since the torque of the motor 108 changes according to the speed, the speed margin is reflected in advance in the phase current of the motor 108 in consideration of this torque change, and the torque curve differs depending on each motor type. Thus, at a frequency equal to or higher than the self-starting frequency, the coefficient corresponding to the torque of the motor 108 measured in advance is multiplied.

  In step S207, the CPU 101 determines whether the motor speed has been changed or stopped. Here, in part F of FIG. 15, the motor rotation speed is constant and the phase current is also a constant value. However, in part G of FIG. 15, for example, the motor speed is changed due to an increase in speed as a system specification. Indicates that there may be cases.

  When the motor speed is changed, the process proceeds to S208. Since the torque of the motor 108 changes when the motor speed is changed, the speed margin is changed. In general, since the torque of the stepping motor decreases as it goes into the high-speed driving region, the phase current is increased in the G part of FIG. As described above, in S208, the motor phase current is controlled by the necessary amount according to the speed, so that the maximum mechanical load and the constant current of the conventional phase current for the maximum frequency in the current sequence shown in FIG. Compared with, phase current can be reduced. In FIG. 15A, the phase current reduction is shown by shading.

  On the other hand, if the CPU 101 determines in step S207 that the motor 108 has been stopped, a motor rotation stop process is performed in step S209.

  As described above, according to the present embodiment, it is possible to realize step-out-less stably with low power compared to the prior art.

DESCRIPTION OF SYMBOLS 1 Motor 2 Sensor part 4 Motor phase angle output part 5 Motor phase angle detection part (detection means)
6 Arithmetic processing part (control means)
7 Motor driver phase current indicator (switching means)
8 Motor driver (drive means)

Claims (8)

A motor,
Drive means for driving the motor;
Detecting means for detecting the rotational speed of the motor driven by the driving means;
Switching means for switching a current value for the driving means to drive the motor;
Control means for controlling switching of the current value of the switching means, and a motor drive device comprising:
The control means includes
The driving means starts driving the motor at the self-starting frequency of the motor with the current value as a first current value, and the switching means sets the current value while the motor is driving at the self-starting frequency. Control to switch from the first current value to a second current value different from the first current value,
In more sections of continuous when being the motor driving in the first current value, the first difference information between the maximum rotational speed and the minimum rotational speed detected by said detecting means,
In more sections of continuous when they are the motor driven by the second current value, the second difference information between the maximum rotational speed and the minimum rotational speed detected by said detecting means, based on,
Controlling the current value after the second current value so that the motor does not step out,
The current value after the second current value is a step-out current obtained from the first difference information, the second difference information, the first current value, the second current value, and step-out point information under a predetermined condition. A motor drive device characterized by having a value corresponding to the value . The plurality of consecutive sections correspond to a period for changing the phase current,
The motor driving apparatus according to claim 1, wherein the rotation speed is information indicating a ratio of time taken in each of the plurality of continuous sections with respect to the cycle. The step-out point information under the predetermined condition is calculated by changing the phase current in a no-load state in which the motor is not incorporated in a device,
The step-out current value is obtained by dividing a value obtained by multiplying the difference between the first current value and the second current value by the step-out point information by a difference between the second difference information and the first difference information. The motor driving apparatus according to claim 1, wherein the motor driving apparatus is determined based on the determination. Before SL motor, a motor driving apparatus according to any one of claims 1 to 3, characterized in that a stepping motor. Before Symbol detection means, an encoder, a resolver, or the motor driving apparatus according to any one of claims 1 to 4, characterized in that a frequency generator using a Hall element. Before SL control means, the motor driving apparatus according to any one of claims 1 to 5, characterized in that it has a hard logic operations possible configuration including a programmable semiconductor device or an ASIC including a CPU or DSP. Before SL control means, when the value of the result of the detection by said detecting means is no longer fall within the predetermined, it allowed switching the current value by said switching means, one step until the current value of the preset predetermined value The motor drive device according to any one of claims 1 to 6, wherein the motor drive device is raised. An image forming apparatus comprising: a motor driving device according to any one of claims 1 to 7.

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